pmacs/docs/generated-buffer-immutability-framing.md

# Generated-buffer immutability

**APPROVED and MERGED as PR #188** (`main` @ `27b1185`, 2026-07-29).
Stage 1 implementation is PR #191.

**Revision 7 — answers review round 6 on `55c3061`, authored against
canonical `githubsucks/main` @ `64883eb` and integrated through
`5e186c7`, 2026-07-29.** #193 landed after revision 7's first push at
`34041a4`; `64883eb..5e186c7` changes only `TEST_IMPROVEMENT.md` and
`docs/active-work.md`, so the source readings and citations below
survive. This revision changes the quarantine state machine, five
acceptance classifications and the cross-machine ledger because the
reviewed design did not contain every route it claimed to contain.

## Revision 7

**Answers review round 6 on `55c3061` — four P1, one P2. All five
confirmed. Two of revision 6's "total" sweeps were not total: snapshot
publication had a third path, quarantine was installed only by one
caller and was not itself a write refusal, and the acceptance audit
reversed its own definition for two of the six relabels.**

| finding | the decision |
|---|---|
| **P1-1** — quarantine misses the explicit-initial-target snapshot | Confirmed. `initial_target_snapshot` (`src/daemon.rs:1873-1897`) is a third production CRDT snapshot exporter, distinct from the legacy no-target `send_buffer_snapshots` loop and `export_buffer_snapshot`. It feeds `InstanceMessage::BufferSnapshot` directly at `:1996-2029`. It becomes the third snapshot guard, and criterion 16c drives an explicit-initial-target attach rather than treating the legacy loop as all attach traffic. |
| **P1-2** — ordinary edits can construct `Diverged` without installing quarantine | Confirmed. Revision 6 said the flag was set by the generated cleanup arm even though `apply_edit` and `apply_edit_skip_intercepts` reach the same classifier and map its outcome back to `Result`. Quarantine now installs at the **common divergence-detection point**, before any caller maps the outcome. The generated cleanup observes an already-poisoned buffer; it does not own the poison. Criterion 16c gains an ordinary-apply half. |
| **P1-3** — a quarantined buffer accepts another owner-generated write | Confirmed. `read_only` cannot be the guard because `{ generated = true }` exists to bypass it. `crdt_quarantined` becomes preflight exit 0 and is rechecked by `apply_generated_edit`; a distinct `CrdtQuarantined` refusal prevents the owner from compounding the divergence. New criterion 16d drives the second write. |
| **P1-4** — `docs/active-work.md` still carries revision 5's classifier and an obsolete integration checkpoint | Confirmed. The lane advances from `300cbc4` to the actual `64883eb` integration (`76cfaac`) and replaces the delete→insert-classifier recovery text with revision 7's common poison, three snapshot guards, queue guard and generated-write refusal. A recovered Stage 2 can no longer implement a decision the framing withdrew. |
| **P2-5** — sweep G's pre-image audit is still wrong | Confirmed. Criterion 5(a) passed on the base as written; 15a and 22 failed on the base; and the reasons revision 6 gave for moving 16 and 16b to `[mutation]` are precisely why their assertions fail on the base. Criterion 5 now asserts the exact rope error before the lift, making it `[main, and also fix-shape]`; 15a, 16, 16b and 22 carry dual `main` + mutation classifications. Q#GB14 is corrected to distinguish “some refusal” from the full error source. |

**Containment sweep, revision 7.** Start from the state transition rather
than from its current callers:

1. Any local-edit CRDT mutation followed by an error before the rope
   mutation calls the common poison helper.
2. Poison sets `crdt_quarantined = true` and `read_only = true` before
   `GeneratedOutcome` is mapped by any public API.
3. Three snapshot exporters refuse publication:
   `initial_target_snapshot`, `send_buffer_snapshots` and
   `export_buffer_snapshot`.
4. `queue_daemon_origin_crdt_op` refuses later deltas.
5. Both generated preflight and authoritative apply refuse every later
   owner write.

Criterion 16c pins 1–4 across generated and ordinary entry points;
criterion 16d pins 5. The flag is monotonic in this arc. Repair remains a
separate lane.

**Acceptance arithmetic after the new criterion:** revision 6 audited
41 criteria (Stage 1: 17; Stage 2: 24). Criterion 16d raises Stage 2 to
25 and the current total to **42**; the five corrected classifications
change labels, not that count.

## Revision 6

**Revision 6 — scouted against canonical `githubsucks/main` @ `64883eb`,
merged into this branch at `76cfaac`, 2026-07-29.** Both SHAs were
measured in this worktree at the moment of writing (`git rev-parse
githubsucks/main`, `git rev-parse HEAD`), not carried forward from a
briefing. Every count and every pre-image below is **a reading at
`76cfaac`, not a constant**; the base has moved four times while this
document has been open and will move again.

> **Numbering note.** The review that this revision answers asked for
> "revision 5". The document at the reviewed commit `cab3404` was
> **already** revision 5 (written by `238fd04`, closing review round 4),
> so this is **revision 6**. Recorded rather than silently renumbered,
> because two documents disagreeing about which revision is live is the
> failure this arc's cross-lane boundary exists to prevent.

**Answers review round 5 on `cab3404` — five P1, two P2. All seven
confirmed. It withdraws two of revision 5's decisions, corrects one
assertion revision 5 made about containment, and reclassifies six
criteria.**

| finding | the decision |
|---|---|
| **P1-1** — Stage 1 criterion 5 is impossible | Confirmed. `begin_edit` (`src/buffer.rs:724`) and `apply_edit` (`:772`) each call `ensure_writable()` as their **first** statement, so once the rope is locked an ordinary edit *necessarily* returns `ReadOnly` and no intercept runs. **The named-error requirement is dropped from the ordinary path and moved behind a Rust-side lift**, where the intercept genuinely is the guard. The wider error-precedence change is considered and rejected. **Consequence revisions 1–5 all missed:** after adoption the intercept is unreachable on the ordinary path **including in the shipped precedent** — `terminal.lua`'s intercept has been dead since #178. Criterion 5 splits into (a) refused-and-unchanged and (b) refused-by-the-intercept-under-a-lift, which is where the original bite survives. |
| **P1-2** — `Diverged` misses another post-mutation failure | Confirmed, **and revision 5 got three of seven cases wrong, not one.** `export_updates_since` (`src/buffer.rs:1173`) runs after *every* successful CRDT mutation, for all three op shapes. Revision 5's "delete→insert classifier" maps all three of those to `Rejected`, whose cleanup **restores a fresh buffer to writable while the CRDT and rope disagree** — reintroducing the exact harm round 4's P1-3 withdrew the four-variant fallback to prevent. Replaced by a `crdt_mutated` flag carried out of the routing function, which is **total by construction** rather than an enumeration that a future failure point can escape. |
| **P1-3** — `read_only` does not contain a divergent CRDT | Confirmed; revision 5's "strongest available containment" was simply wrong. Neither outbound snapshot path reads `read_only` (`src/daemon.rs:2563-2578`, `:2693-2708`) — and neither can, since `read_only` is a statement about *inbound* mutation. New **`crdt_quarantined`** flag with **three** consumers: both export sites and `queue_daemon_origin_crdt_op`, the third of which the review did not name. Repair stays deferred, and the cost of quarantine (the buffer stops collaborating) is stated rather than buried. |
| **P1-4** — `AppliedThenFailed` leaves later views stale | Confirmed. Revision 5 fixed the fan-out *after* the borrow drops and left the loop *inside* it broken. **The review named one broadcast site; sweep F found four**, and two of the three it did not name are load-bearing for this arc specifically: `src/buffer.rs:1250` is the arm every `NoOp` takes — including Q#GB5's `ensure_slot` lock — and `:1033` is how a locked buffer's write reaches a replica at all. All four adopt continue-and-retain-first-error. Criterion 15a gains a `RecordingView` **after** `FailingView`. |
| **P1-5** — Q#GB6 omits the selection anchor | Confirmed, and it is the only one of the three coordinates that **panics**: `Window::region` (`src/window.rs:472-479`) clamps neither endpoint, and `region_bytes` (`src/editor_core.rs:4184-4191`) hands the result to `Rope::slice`, which asserts at `src/rope.rs:145`. #191 reproduced it. The rule is **clamp-or-clear**, in **both** clamp sites, for every affected window — and it is not invented here: `src/terminal/view.rs:715-721` already solved the identical problem for `TerminalSelection`, `collapsed_by_clamp` and all. New criterion 8c. Also found: a stale anchor reaches the **presence broadcast** (`src/presence.rs:122-123`), not only the local slice. |
| **P2-6** — four criteria have incorrect `main` pre-images | Confirmed, **and there are six.** 15, 16, 16b, 17, 18 and 21 all pass at the base. Relabelled to `[mutation]` / `[fix-shape]` with a table stating, per criterion, what the base actually does. None is weakened — each already carried its falsifying mutation. |
| **P2-7** — a rejected generated edit can still unfold | Confirmed. A `generated_preflight` runs §3.4's exits 1–4 under a read-only borrow **before** the unfold; `apply_generated_edit` still re-checks all four, because the borrow is released between and `Buffer` stays the only authority. Dropping the unfold and narrowing the contract were both considered and rejected. New criterion 22, with a second half on the identity-protected refusal so it pins the preflight rather than one hoisted check. |

**Sweep F — every recovery or containment mechanism in the document,
audited for failure points it does not enumerate (obligation 1).** The
review is right that P1-2, P1-3 and P1-4 are one class. **10 mechanisms
examined, 4 broken — all four are the review's — and within them three
exits the review did not name.**

| # | mechanism | verdict |
|---|---|---|
| 1 | `Diverged` classifier | **BROKEN** — enumerated 1 of 3 failure points; now flag-based and total |
| 2 | `Diverged` containment via `read_only` | **BROKEN** — 2 export paths, **plus `queue_daemon_origin_crdt_op` (not named by the review)** |
| 3 | `AppliedThenFailed` view notification | **BROKEN** — **4 broadcast sites, review named 1** |
| 4 | Q#GB6's coordinate clamp | **BROKEN** — 3rd coordinate; **and it also reaches presence, not named by the review** |
| 5 | `Rejected` restore-entry-state | clean — exits 1–4 plus CRDT-untouched, and total once `crdt_mutated` is the discriminator |
| 6 | `NoOp` cleanup | clean — one exit (`src/buffer.rs:1245`) |
| 7 | `generated_preflight` (new) | clean by construction — evaluates the same four predicates `apply_generated_edit` does |
| 8 | `clear_history` across modes | clean — `if let Some(crdt)` guard covers both |
| 9 | `identity_protected` write refusal | clean — single exit |
| 10 | Q#GB12's revision guard going near-dead | clean — names its residual writer (a future Rust-side one) |

**Sweep G — every criterion's pre-image re-derived by asking what the
BASE does (obligation 2).** Re-derived at `76cfaac`; see the table above
criterion 15. **41 criteria audited across both stages, 6 mislabelled,
all relabelled.** The arithmetic, since a count asserted without one is
what this sweep exists to catch: Stage 1 has **14** top-level entries of
which `13` is a split header carrying no assertions, plus **4** lettered
sub-criteria (`8b`, `8c`, `13a`, `13b`) — 14 − 1 + 4 = **17**. Stage 2
has **25** entries of which `10` is "Coverage, not a criterion" —
25 − 1 = **24**. 17 + 24 = **41**. The rule, now stated for the third
time and applied by
construction rather than by inspection: *a criterion's pre-image is a
fact about the base, established by running it there.* Because the base
moves, §6's labels carry the commit they were derived at.

**Re-measured at `76cfaac` (obligation: paste the output).**

```
$ git rev-parse --short HEAD; git rev-parse --short githubsucks/main
76cfaac
64883eb
$ grep -rn 'describe\.buffer' builtin/ --include='*.lua' | wc -l
14
$ grep -rn bypass_intercept builtin | wc -l
21
$ grep -rn --include='*.lua' add_intercept . --exclude-dir=target | wc -l
17
$ grep -rn "is_modified()" src/ pmacs-gpu/ | wc -l
26
$ grep -rn "mark_clean()" src/ | wc -l
6
$ grep -c "dispatch_idle_for" tests/terminal_copy_mode_acceptance.rs
0
```

All unchanged. **Verified rather than assumed:** `git diff --stat
300cbc4..64883eb` touches only `docs/` and `scripts/bite` — **no product
code** — which is why the source citations below survive the base move.

**Citation audit, revision 6.** PR #187 moved four source files, and a
sweep of every citation in this document into them found **15 stale
instances across 9 distinct citations**, all corrected here:
`editor_core.rs` `:1814`→`1836`, `:1843`→`1865`, `:1841-1842`→`1863-1864`,
`:1853-1857`→`1875-1879` (×3), `:2575`→`2597`, `:1945`→`1967`;
`editor.rs` `:1436,1984,2128,2163`→`1472,2356,2500,2535`, `:3704`→`4129`
(×2); `daemon.rs` `:2976`→`3167`; `semantic_render.rs` `:1347`→`1716`
(×2). The tell was internal: revision 6's new text cited
`editor_core.rs:1836` and `:1865` for the same two functions that older
text still cited as `:1814` and `:1843`. **A citation is a reading too**,
and this document had not been re-reading them.

**`scripts/bite` now has a positive control** (`main` @ `64883eb`), so
every "falsify by …" below can be executed rather than asserted: exit 0
is a real bite, **exit 3 is `NO CONTROL`** — the named tests did not pass
on the working tree, or none ran — exit 1 is vacuous, exit 4 is
`INCONCLUSIVE (MIXED)`, and the swapped run is labelled
`OK (assertion)` or `OK (COMPILE)`. **Prefer `OK (assertion)`**; treat
`OK (COMPILE)` as a prompt to narrow the swap. Criteria whose bite is a
one-line mutation of a Rust file are directly `bite`-able; the Lua-side
ones swap the `builtin/` file.

Revision 5's decisions and its answers to review round 4 remain below as
history. Where its live design said "delete→insert classifier" or called
`read_only` containment, revision 6 supersedes it explicitly.

## Revision 5

**Answers review round 4 on `d98d0b3` — four P1, one P2. All five
findings are confirmed. This revision removes one proposed public
capability, makes one transaction outcome larger, and makes the CRDT
fault seam mandatory rather than leaving a fallback for implementation
time.**

| finding | the decision |
|---|---|
| **P1-1** — `AppliedThenFailed` loses the `Edit`, so the binding cannot fan out a mutation before returning `Err` | Confirmed. `AppliedThenFailed` becomes `{ edit: Edit, error: BufferError }`; `apply_generated_edit` returns the outcome rather than collapsing it to `Result` inside `Buffer`. After the registry borrow drops, the binding fans out `Applied`, `NoOp`, **and `AppliedThenFailed`**. The last arm then surfaces its error. That preserves the window-cache and replica-mirror invariant even when a `View::on_edit` failure occurs after the rope swap. The Rust return type of `set_generated_contents` changes with the internal transaction; its Lua name and call signature do not. New criterion 15a pins both the window and CRDT directions. |
| **P1-2** — criterion 15 probes the edit flag while `read_only` masks it | Confirmed. `begin_edit` calls `ensure_writable` before it checks `editing_in_progress`, while `AppliedThenFailed` deliberately relocks. The old follow-up therefore returned `ReadOnly` for both the correct and broken implementations. Criterion 15 now performs the same Rust-side lift already used by criteria 4, 16b and 17 before issuing the ordinary edit; only then can its outcome distinguish the cleared flag from `ConcurrentEdit`. |
| **P1-3** — the four-variant fallback maps divergence to `Rejected` and restores a fresh buffer to writable | Confirmed. The fallback is withdrawn. A CRDT delete-success/insert-failure must be `Diverged`, must leave the buffer locked, and must surface distinctly. Criterion 16c is reclassified as a `crdt`-only fault-injection unit test: Stage 2 extracts a private delete→insert classifier whose production closures call loro and whose test closures force delete `Ok` / insert `Err`. There is no implementation-time choice to weaken containment because staging is inconvenient. |
| **P1-4** — `identity_protected` is not generated-lock provenance | Confirmed. Q#GB7 now chooses the fallback it previously named: **this arc ships no `unlock_generated` at all.** `identity_protected` remains, but only as a monotonic terminal-identity guard in the write direction; it is never described as proof that the generated primitive installed a lock. The proposed setter becomes a crate-private, one-way `mark_identity_protected()` so “set once” is enforced rather than documentary. A future wdired door stays with dired Stage 3 and must frame the provenance/ownership transition it actually needs. |
| **P2-5** — Stage 2 still instructs implementation to build revision 3's rejected shared registry | Confirmed. The staging checklist now matches Q#GB18 exactly: `compile.lua` answers from `slot_for_buffer`, `default.lua` answers from `search_panel_owns`, and each capture site consults the other through a guarded optional predicate. No owner registers buffers with the other, and no teardown work is introduced. |

**Reachability recheck for the changed criteria.** Criterion 15 now
crosses the post-failure lock only by a Rust-side lift, so the next edit
can actually reach the flag it asserts. Criterion 15a drives the same
valid `FailingView` mutation through the production Lua finisher and
observes its window and replica consumers. Criterion 16c drives the
otherwise-unconstructible second-op failure through the private
delete→insert classifier. Criterion 13 is deliberately structural
because revision 5's decision is the absence of a capability. None
passes merely by failing before the mechanism under test.

Revision 4's measurements and its answers to review round 3 remain
below as history. Where its live design said “bounded unlock” or offered
the four-variant CRDT fallback, revision 5 supersedes it explicitly
rather than silently smoothing the reversal over.

## Revision 4

**Answers review round 3 on `8e032d7` — three P1, two P2 — and two sweeps
the review asked for by class. It withdraws three of revision 3's own
decisions. All five findings are confirmed; none is re-litigated.**

| finding | the decision |
|---|---|
| **P1-1** — the revision predicate is wrong in two directions | Confirmed, **and it is wrong in three.** §3.4 is rewritten around an **explicit `GeneratedOutcome`** reported by the apply instead of a predicate inferred from `revision`: five variants, each with its own cleanup, tabulated. Direction A (successful no-op) is fixed by restating the invariant as a property of the **buffer** — *a generated-locked buffer carries no history* — so `NoOp` clears, which needs no reference to `revision` and is therefore mode-independent. Direction B (CRDT mid-transaction) gets its own `Diverged` variant that **clears nothing and surfaces**, because clearing would destroy the last local record of the pre-edit rope. **Third direction, found while fixing the other two and not reported by the review:** revision 3's unconditional relock **locked a fresh buffer that was never successfully written** — a mid-codepoint generated insert on a writable `*scratch*` returned `Err` *and* left it read-only. `Rejected` now restores the entry value. |
| **P1-2** — criteria 15-16 never enter the transaction | Confirmed, and the contradiction was internal: revision 3 argued in §3.4 that pre-validation makes an invalid range cost nothing, then used an invalid range to test the post-apply cleanup. Both criteria are rewritten around a **valid** write that fails at the `on_edit` broadcast, staged with a Rust-side `FailingView` (`pmacs::view::View` is `pub`, `src/view.rs:221`; `Buffer::attach_view` is `pub`). Criterion 16 splits into relock-on-failure **and** no-lock-on-refusal, which §3.4 now answers differently. New 16b and 16c cover the two P1-1 directions. **Rule adopted: every criterion names the exit it drives the implementation to, and that exit must be inside the mechanism under test.** |
| **P1-3** — provenance invalidates the lift-and-restore seam | Confirmed. **Q#GB15's `generated_lock` is withdrawn.** The defect is not the rule's details but that a *derived* fact must be maintained by every mutation of what it derives from, and `set_read_only` is `pub`. Replaced by **`identity_protected`** — a property of what the buffer *is*, set once by `TerminalSession::open`, **never written by `set_read_only`**. `tests/terminal_copy_mode_acceptance.rs:578-584`'s lift/upgrade/restore cycle is transparent to it, so Q#GB12 and Stage 2 criterion 4 need no change. The `crdt`-gated terminal suite is now named explicitly in §10. |
| **P2-4** — search registration adds a hard dependency on `compile.lua` | Confirmed. Revision 3 replaced an existing *guarded, optional* dependency (`default.lua:991-994`'s triple check) with an unguarded call. Q#GB18 is rewritten to **symmetric guarded optionality**: each module answers for its own buffers and consults the other through the guard shape already in the tree. That also removes the teardown obligation revision 3's registry introduced. New Stage 2 criterion 21 pins the minimal harness. |
| **P2-5** — fold criterion 13 contradicts its classification | Confirmed. If dired folds successfully on `main`, asserting `false` **fails** on `main`, so `[fix-shape]` was the wrong label. Split into **13a `[main]`** (the behaviour change, falsifiable by revert) and **13b `[mutation]`** (the status string, whose pre-image cannot be `main` because on `main` the call succeeds and sets no status). |

**Sweep D — rules spanning the v0.1/CRDT boundary or the
fresh-lock/existing-lock boundary (obligation 1).** The review is right
that P1-1 and P1-3 are one class: *a rule derived from one mechanism and
applied to a second that does not share its ordering.* **13 rules
examined, 3 broken, 1 verified that looked at risk.**

| # | rule | boundary | verdict |
|---|---|---|---|
| 1 | cleanup keyed on `revision` | v0.1 / CRDT | **BROKEN** — P1-1 |
| 2 | `clear_history` clears whichever history exists | v0.1 / CRDT | clean — reads both, `src/buffer.rs:558-566` |
| 3 | Q#GB4's O(1) clear argument | v0.1 / CRDT | clean — in CRDT mode `self.undo` is bypassed entirely (`:1268-1272`), so the "at most one entry" premise is vacuously true rather than wrong |
| 4 | Stage 2 criterion 4 asserts `Err(NothingToUndo)` | v0.1 / CRDT | **verified, not assumed** — `undo_crdt_mode` returns `BufferError::NothingToUndo` when the manager reports nothing undone (`src/buffer.rs:1374-1376`), so the same assertion is correct in both modes |
| 5 | §3.3 "CRDT behaviour: nothing new" | v0.1 / CRDT | corrected — true except for `Diverged`; §3.4 now says so |
| 6 | Q#GB10's `mark_clean` | neither | clean — `is_modified` is mode-independent |
| 7 | Q#GB6's coordinate clamp | neither | clean |
| 8 | criterion 10's coverage rule | v0.1 / CRDT | tightened — it now names which criteria are irreducibly single-configuration |
| 9 | refuse "someone else's lock" by provenance | fresh / existing lock | **BROKEN** — P1-3 |
| 10 | relock unconditionally | fresh / existing lock | **BROKEN** — found here, not reported; a refusal locked a buffer nobody wrote |
| 11 | Q#GB5's empty `set_generated_contents` in `ensure_slot` | fresh / existing lock | clean **only because** Q#GB13 makes the buffer fresh by construction — and it is also the concrete caller that made P1-1 direction A load-bearing rather than theoretical; the dependency now runs both ways and is stated in Q#GB5 |
| 12 | `unlock_generated`'s refusal | fresh / existing lock | follows 9; fixed with it |
| 13 | Q#GB2's `generated` implies bypass | neither | clean |

**Sweep E — every criterion added in revisions 3 and 4, audited for
whether the state it asserts is reachable by the operation it performs
(obligation 2).** This is the vacuous-criterion class, which this arc has
now shipped **twice** — revision 2's Stage 2 criteria 3-5, then revision
3's 15-16. **19 criteria audited, 3 defects, all fixed here.**

| criterion | reachable by its own operation? |
|---|---|
| S1-6 (round-trip, 3 halves) | yes — and (c) is what makes (b) non-vacuous |
| S1-11 (disambiguated panel keys) | yes — foreign buffer first, panel opens as `<2>` |
| S1-12 (`q`-target not inverted) | yes — needs the two-panel sequence, which is why it is separate from 11 |
| S1-13 (fold) | **MISCLASSIFIED** — P2-5; split into 13a/13b |
| S1-14 (structural) | n/a |
| S2-6 (four surfaces) | yes |
| S2-13 (unlock, 3 halves) | yes — the terminal half needs a real terminal, which the copy-mode suite already opens |
| S2-14 (refuse a foreign lock) | yes — fails on `main` |
| S2-15 (flag cleared on error) | **VACUOUS** — P1-2; rewritten around `FailingView` |
| S2-16 (relock on error) | **VACUOUS** — P1-2; rewritten and split |
| S2-17 (invalid range keeps history) | yes — and it is the one criterion for which exit 4 *is* the mechanism under test, so it stays as written |
| S2-18 (re-entrant refused) | yes — phase 2 of `run_managed_edit` releases the borrow (`src/lua_bindings/mod.rs:1477-1487`), so the inner call reaches the buffer and finds the flag set |
| S2-19 (`is_generated_buffer` disambiguated) | yes |
| S2-20 (structural) | n/a |
| **new in rev 4:** 13a, 13b, 16 (2nd half), 16b, 16c, 21 | each names its exit; 16c carries an explicit caveat that its staging recipe is **not** verified here, with the four-variant fallback rather than a criterion that passes by never reaching its path |

**Re-measured at `7586905` (obligation: paste the output).** Every count
in this document, re-run in this worktree:

```
$ grep -rn 'describe\.buffer' builtin/ --include='*.lua' | wc -l
14
$ grep -rn bypass_intercept builtin | wc -l
21
$ grep -rn --include='*.lua' add_intercept . --exclude-dir=target | wc -l
17
$ grep -rn "is_modified()" src/ pmacs-gpu/ | wc -l
26
$ grep -rn "mark_clean()" src/ | wc -l
6
$ grep -c "dispatch_idle_for" tests/terminal_copy_mode_acceptance.rs
0
```

All unchanged from revision 3's readings, which were taken at `ad41cf1`;
#189 adds no Lua and no tests. The **276 CRDT-dark** figure is
deliberately still not re-quoted — see §10.

---

**Revision 3 — scouted against canonical `githubsucks/main` @ `7586905`,
2026-07-28. Every claim below about pmacs was executed or read at a named
line, not recalled.** The reproductions in §0 and §2 are transcripts of
throwaway probes run in this worktree at `ad41cf1` and deleted before each
commit; nothing between `ad41cf1` and `7586905` touches a file they
measure (#189 edits `COHERENCE.md` only), so they still describe the base.
The counts in §1 and §2.10 are whole greps with the arithmetic shown,
never `| head`.

## Revision history

**Revision 3 answers five review findings on PR #188 @ `516bd35` — three
P1, two P2 — and one sweep the review asked for by class. It also
withdraws one of revision 2's own decisions, reports four defects the
review did not name, and says where it thinks the review is wrong.**

| finding | the decision |
|---|---|
| **P1-1** — the proposed route cannot write to a locked buffer | Confirmed and **worse than stated: the review's first repair option cannot work.** `run_bypass_edit` calls `begin_edit`, whose *first* statement is `ensure_writable()` (`src/buffer.rs:724-735`) — but **reordering `begin_edit`'s two checks does not help**, because both checks are unconditional and both `return Err`; the reorder only changes which error a doubly-failing call reports. Any path that admits a generated write must not call `ensure_writable` **at all**, so the design space is one option, not two. **Q#GB3 is reversed**: generated writes get their **own** `run_buffer_edit` arm and never touch `begin_edit`. The whole transaction — refusal, re-entrancy gate, unlock, write, relock, history, flag clear — becomes a single `&mut Buffer` method with no exit path a caller can miss (new §3.4, new **Q#GB17**). |
| **P1-2** — disambiguation is not carried through name-based identity | Confirmed. The census is new §2.10: **19 units across 14 grep lines**, classified by reading each enclosing function. Two sites are genuinely **broken** by disambiguation, and between them they have **six** downstream consumers, not the three the review named — `listview.open`'s own never-capture-a-panel guard is the fourth listview consumer, and it fails *silently and inverted*, capturing a panel as its own `q` target. New **Q#GB18** routes both by owned `BufferId`. Five further sites are the correct use of a name lookup and are named so a reviewer does not re-derive them. |
| **P1-3** — `unlock_generated` is an unrestricted clear | Confirmed, and the review's second half is decisive: the binding does not achieve its stated purpose. **Revision 2's Q#GB7 is withdrawn as written.** The capability survives only bounded by **lock provenance** (new **Q#GB15**), moves from Stage 1 to **Stage 2**, and its justification narrows from "brick escape" to "the closure of the capability `{ generated = true }` adds". Stage 1 ships no unlock because Stage 1 adds no lock capability `main` does not already expose. |
| **P2-4** — Stage 1 criterion 6 passes through the side-window gate | Confirmed, **and the framing cited the wrong precedent.** `tests/terminal_copy_mode_acceptance.rs`'s `acc16` — which revision 2 named as the model — has **no** `is_side` assertion (`grep -c dispatch_idle_for tests/terminal_copy_mode_acceptance.rs` = 0; it goes through `state.dispatch_idle()`). The test that gets it right is `tests/dired_acceptance.rs:969`. The criterion is rewritten to carry **both** halves — the document-window premise *and* `acc16`'s positive control — because `dispatch_idle_for` has **six** ways to return false and the review named one. |
| **P2-5** — the path-backed refusal is tested only through the wrapper | Confirmed. Stage 2 criterion 6 now exercises **all four** surfaces — the wrapper plus each of `insert` / `delete` / `replace` with `{ generated = true }` — with the misplacement as the explicit bite. |

**Sweep C — "a mechanism was assumed to compose with an existing guard
without reading the guard" (obligation 3).** Findings 1 and 3 are both
that shape. Sweeping the rest of the framing for it found **two more, both
in the shipped primitive, and both unframed anywhere**:

1. **`Buffer::set_generated_contents` lifts a lock it did not install.**
   It sets `read_only = false` unconditionally (`src/buffer.rs:546`), so
   `pmacs.buffer.set_generated_contents(term_buf, "junk")` on a **live
   terminal identity buffer** — whose `read_only` was set by
   `src/terminal/session.rs:305` for reasons that have nothing to do with
   this arc — overwrites its contents and re-locks it as if the primitive
   owned it. This ships today. Q#GB15's provenance field closes it in the
   **write** direction as well as the unlock direction, which is what
   makes a second field worth its cost rather than a one-off for Q#GB7.
2. **`read_only` is also the fold subsystem's "is this a document
   buffer" test.** `document_bytes` (`src/lua_bindings/fold.rs:310-318`)
   returns `None` for any `read_only` buffer, so `pmacs.fold.fold`
   answers `false` with the status `fold rejected: not a document buffer`
   — and `tests/folding_acceptance.rs:570-590` pins exactly that. Locking
   five buffer families therefore **silently disables fold creation** on
   all five. This directly contradicts Q#GB3's own stated rationale
   ("folding a `*compilation*` buffer is possible, so changing this would
   be a silent behaviour change to a pinned seam"): revision 2 preserved
   the *unfold-on-edit* seam while the lock it recommends kills the
   *fold-creation* seam. New **Q#GB16**.

Two further defects found while answering the review, neither of them of
that shape and neither named by the review:

3. **§1.5's correction has landed and this document was about to
   re-assert it.** PR #189 (`main` @ `7586905`, merged after revision 2
   was pushed) corrects `COHERENCE.md` §14's listview consumer list to
   exactly the three call sites §1.5 measured, and moves the row from ✓ to
   ◐. §1.5, §8 and §9's "correction owed" are rewritten from *owed* to
   *landed*. A merged correction must be removed, not restated.
4. **`*help*` has two independent writers, one of them Rust, and §1.4
   named only the Lua one.** `src/help.rs:354-372` `replace_help_buffer`
   does its own `find_by_name(HELP_BUFFER_NAME)`-or-create, writes
   delete-all + insert-all through `Buffer::apply_edit`, and calls
   `mark_clean()` (`:381`) — while `builtin/commands/default.lua:1229-1246`
   does the same thing in Lua and does **not** mark clean. Two owners, two
   copies of the name constant across the FFI boundary, one buffer. It is
   a **fifth** writer mechanism, and it is a reason Q#GB9's deferral of
   Class C is right rather than merely convenient.

**Revision 2 answered five review findings on PR #188 @ `9101bf5` — three
P1, two P2 — and two sweeps the review asked for by class rather than by
item. Nothing was silently rewritten; each change is attributed below.**

| finding | what it changed |
|---|---|
| **P1-1** — three Stage 2 criteria are non-discriminating | Stage 2 criteria 3, 4 and 5 rewritten (§6). All three **passed on the pre-image**: ordinary edits are already refused by the existing intercept, and `Buffer::undo` checks `read_only` *before* it looks at history (`src/buffer.rs:1302`), so "undo returns false" passes against an implementation that locks and never clears. The new wording uses a **bypass write** or Rust-side `Buffer::is_read_only()` to prove locking, and **lifts the lock inside a Rust test** before asserting `NothingToUndo` / `can_undo() == false` to prove clearing. Confirmed against the tree. |
| **P1-2** — staging omits the ownership prerequisite | New §2.8 (measured), new **Q#GB13**, amended **Q#GB5**, and staging changes in §5: ownership-by-handle is now a **prerequisite of the stage that locks each writer**, not a follow-up. Confirmed and materially worse than the review stated — §2.8 measures that a *failed* `pmacs.compile.run` already leaves a foreign buffer permanently un-editable today, and that `M-x buffer.undo` is currently the **only** way to recover a clobbered one. This arc removes that accidental safety net, which is exactly why it cannot ship without ownership. |
| **P1-3** — `mark_clean` can suppress recovery | New §2.9 and a rewritten **Q#GB10**. **Revision 1 was wrong**: it claimed `is_modified` "drives only the mode-line indicator and the buffer-list column". It is also read by `src/autosave.rs:363` — the skip that decides whether a crash-recovery slot is written — and `src/desktop.rs:302`. The rule chosen and framed: **a generated write refuses a buffer that has a `file_path`**, which bounds the contents clobber and the lock as well as the flag. |
| **P2-4** — Q#GB6 conflates byte extent with line extent | **Q#GB6** rewritten. `win.view_top` is a **line index** (`src/window.rs:373-374`) bounded by `TextView::line_count`; `win.cursor` is a byte position bounded by `Buffer::len`. The clamp is now per-coordinate and ungated, matching `rebuild_views_for`'s own shape (`src/editor_core.rs:1875-1879`), and §6 gains a longer-in-bytes / fewer-in-lines pin. |
| **P2-5** — the CRDT-dark count was knowingly stale | **Re-measured at `ad41cf1`: 276 dark** (3,251 vs 3,527), with the command shown in §10. Revision 1 quoted **264**, which `docs/active-work.md:107-115` explicitly labels historical with "the number moves with every merge and must be re-measured, not quoted". |

**Sweep A — every criterion re-audited against its pre-image, not only
3–5.** Two results beyond the cited items. First, **eight criteria pass
on `main` by design** and their bites name a *non-`main`* pre-image; that
is legitimate (`docs/agent-handoff.md` §5: "bite against every pre-image
the fix could plausibly have taken"), but revision 1 did not say so, and
an unlabelled always-green criterion is indistinguishable from a vacuous
one. §6 now carries a **pre-image column for every criterion**. Second,
**Stage 1 criterion 7's stated bite was wrong**: a "partial conversion"
that keeps a `bypass_intercept` write beside the primitive does not
produce a stale paint, it **raises** at the bypass write (§2.4,
measured), so the criterion could never have failed the way it claimed.
Restated as an explicit mutation bite.

**Sweep B — "a capability was made public without bounding who may use it
on what."** Two results beyond P1-2 and P1-3. First, the pathless rule
bounds *what* but not *who*: any Lua, including a third-party package,
can still permanently lock `*scratch*` — pathless, the default buffer,
and the quit target of five different code paths. Second, and decisive,
**the two halves of the protection are not symmetric**: the intercept is
removable (`remove_intercept`, `src/lua_bindings/mod.rs:3433`, used by
the REPL at `repl/init.lua:325-327`) and the rope lock is one-way from
Lua. That falsifies revision 1's stated reason for deferring the unlock
("a binding whose only consumer does not exist yet cannot be pinned"):
the brick scenario **is** a consumer and **is** pinnable. **Q#GB7 is
upgraded from "name it, do not build it" to "ship the unlock in Stage
1."**

> **Revision 3 keeps sweep B's observation and reverses its conclusion**
> (review P1-3). The asymmetry is real. The brick scenario is not a
> *recovery* consumer — by the time anyone reaches for the unlock,
> `set_generated_contents` has already cleared the history — and the
> `*scratch*` exposure it turns on is one `main` already ships, since
> `set_generated_contents` is already public. Sweep B also stopped one
> step short: an unbounded clear of `read_only` is a strictly larger
> capability than the arc adds, because the same flag protects live
> terminal identity buffers. Q#GB7 now lands in **Stage 2**, bounded by
> Q#GB15's provenance.

**Revision 1** — initial framing: the confirmed bug, the classified
census, the primitive decision, staging, and acceptance.

This closes the class-wide half of the invariant `Buffer::set_generated_contents`
opened in terminal copy mode (#178) and that `docs/agent-handoff.md` §4 and
`COHERENCE.md` §14 both record as unfinished: **four writer mechanisms across
five buffer families still pair an erroring intercept with `bypass_intercept`
writes over a writable rope, and every one of them is emptied by undo.**

Two things the arc turns out NOT to be, both discovered by measurement:

- It is **not** "compile is the urgent one". `compile.lua` and the
  `*search-results*` panel rebind all seven undo chords to a no-op
  (`compile.lua:219`, `builtin/commands/default.lua:855`), so reaching
  them needs `M-x`. **`dired.lua` and `listview.lua` rebind nothing**, so
  a bare `C-/` empties them. The cheap half is also the exposed half.
- It is **not** a Lua-only change. Two of the four mechanisms write
  incrementally and cannot use the shipped primitive at all, and a
  buffer the shipped primitive has locked **refuses `bypass_intercept`
  writes** (§2.4, measured) — so partial adoption is impossible and a
  new Rust primitive is required.
- **Added in revision 2:** it is **not** safe to lock these buffers
  before fixing who owns them. Three of the five writers adopt any
  buffer that shares their name (§2.8, measured), and the only thing
  that currently recovers a clobbered user buffer is `M-x buffer.undo`
  — this arc's bug. Ownership is a prerequisite, not a follow-up
  (Q#GB13).
- **Added in revision 3:** and fixing ownership is **not** free, because
  fixing it changes what buffers are *called*. Five sites in `builtin/`
  recover a buffer's identity from its name; two of them break (§2.10),
  and one of those two — `listview.open`'s own `q`-target guard — breaks
  **inverted and silently**, producing exactly the failure its comment
  says it prevents. Q#GB18.
- **Added in revision 3:** `read_only` is **not** this arc's flag. It
  carries three unrelated authorities (§2.11), so a capability defined
  over it reaches all three — which is why revision 5 removes the unlock
  rather than pretending `identity_protected` is provenance (Q#GB7),
  why the lock silently disables fold creation (Q#GB16), and why the
  *shipped* primitive can already overwrite a live terminal's identity
  buffer (Q#GB15).

---

## 0. The bug, reproduced

`Buffer::undo` (`src/buffer.rs:1301`) gates on `ensure_writable()`
(`src/buffer.rs:568`) and nothing else. `ensure_writable` reads the Rust
`read_only` field; it never consults the intercept chain. The
`pmacs.buffer.add_intercept(buf, function() error(name .. " is read-only") end)`
idiom therefore protects the *edit* path and leaves the *history* path
wide open, while the owner's own `bypass_intercept` paint lands on the
undo stack for undo to pop.

The user-reachable chain, verified end to end:

`M-x buffer.undo` → `cmd { name = "buffer.undo" }`
(`builtin/commands/default.lua:179`) → `ed.undo()` → `EditorCore::undo`
(`src/editor_core.rs:2597`) → `Buffer::undo` → `ensure_writable`. The
chords `C-/ C-_ C-4 C-x u` are bound globally
(`builtin/keymaps/default.lua:126-136`) and the menu carries it too
(`builtin/menus/default.lua:141`). **No buffer-local rebinding removes
the command**, which is what `compile.lua`'s own comment already admits
("command/menu undo stays dispatchable", `compile.lua:236`).

### 0.1 Measured transcripts

Every line below is probe output from `ad41cf1`.

**listview panel, plain `C-/` through `dispatch_key`** — no rebinding
exists, so this is the whole distance from a keystroke to an empty panel:

```
listview BEFORE   = "H\nrow-one\nrow-two"
listview after C-/ = ""
```

**listview panel, ordinary edit** — the intercept works, which is exactly
why the idiom reads as safe:

```
listview ORDINARY EDIT = false | intercept rejected the edit:
  builtin/runtime/listview.lua:102: *probe-panel* is read-only
```

**dired listing, one `buffer.undo`:**

```
dired BEFORE  = "/tmp/.tmpEJlp9i:\n  -rw-r--r--  1 2026-07-28 17:42 alpha.txt\n  -rw-r--r--  1 2026-07-28 17:42 beta.txt"
dired AFTER 1 = ""
```

**`*shell-command*`, `M-x buffer.undo` through the real minibuffer** (`M-x`,
typed `buffer.undo`, RET):

```
shell BEFORE = "$ printf ...\nDirectory: ...\n\none\ntwo\n\n[shell exited with code 0]\n"
shell after M-x buffer.undo
             = "$ printf ...\nDirectory: ...\n\none\ntwo\n\n[output desynced by external edit]\n"
```

**Read that one carefully — it is the single most important measurement in
this document.** The Q#CM2 revision guard *noticed* and appended its
desync marker. It did **not** prevent anything: the run's exit status is
gone for good, and the buffer is still non-empty. Any acceptance
criterion phrased as "the buffer is not empty" **passes with the bug
live**. See §5, Stage 2 criterion 1.

Driven programmatically to the end, the same buffer empties completely:

```
shell AFTER 1 undo  = "... one\ntwo\n"          (exit marker gone)
shell AFTER 13 undos = ""
```

**`*search-results*`:**

```
search BEFORE = "Searching for: fn main\n\n"
search AFTER  = ""
```

### 0.2 The fix already in the tree, and what it proves

`terminal.lua` is the adopter and the precedent. `render_snapshot`
(`terminal.lua:320-337`) calls `pmacs.buffer.set_generated_contents`, and
the comment at `:322-336` documents this exact defect in these exact
terms. `claim_snapshot` (`:339-396`) keeps the erroring intercept **and**
`set_round_trip_input`, and `:351-366` states the layering that this
framing must preserve at every adopter:

> rope-level read-only protects the daemon copy, round-trip input
> protects the replica copy — and neither substitutes for the other.

A locked buffer measured at `ad41cf1`:

```
bypass write after lock            = false | buffer `*probe*` (id BufferId(4)) is read-only
M-x buffer.undo after lock leaves  = "header\n"
```

---

## 1. The census, with its arithmetic

### 1.1 `bypass_intercept` — 21 grep hits, 16 write sites

`grep -rn bypass_intercept builtin` returns **21** lines. Five of them
are prose in comments, not calls:

| file:line | what it is |
|---|---|
| `compile.lua:265` | comment above `ensure_slot`'s intercept |
| `terminal.lua:304` | comment in `unique_snapshot_name` |
| `terminal.lua:324` | comment in `render_snapshot` (the round-2 note) |
| `dired.lua:478` | comment above `claim_handle` |
| `listview.lua:9` | module header |

21 − 5 = **16 actual write call sites**, and the per-file arithmetic is
9 + 4 + 1 + 2 + 0 = 16:

| file | writes | lines |
|---|---|---|
| `compile.lua` | 9 | 319, 443, 454, 465, 506, 512, 642, 794, 798 |
| `builtin/commands/default.lua` | 4 | 827, 849, 1005, 1007 |
| `dired.lua` | 1 | 371 |
| `listview.lua` | 2 | 60, 61 |
| `terminal.lua` | **0** | — (it adopted the primitive) |

**Two corrections to the counts this lane was briefed with.** `compile.lua`
has **9** write sites, not 10 — the tenth hit is the comment at `:265`.
`terminal.lua`'s two hits are **both comments**; it performs no
`bypass_intercept` write at all, which is the correct state for an
adopter and is worth stating because the raw grep count reads as though
it still does.

### 1.2 `add_intercept` — 17 Lua sites, 6 production

`grep -rn --include='*.lua' add_intercept . --exclude-dir=target`
returns **17** lines: **6** in `builtin/`, **11** under `tests/fixtures/`.
One of the eleven (`tests/fixtures/pmacs-mcp-prompts/init.lua:84`) is a
doc comment, so the fixture *call* count is 10; 6 + 10 = 16 calls across
17 lines. The six production sites:

| site | buffer(s) | shape |
|---|---|---|
| `terminal.lua:367` | terminal copy snapshot | blanket read-only — **adopted** |
| `dired.lua:509` | every dired buffer | blanket read-only |
| `listview.lua:101` | every listview panel | blanket read-only |
| `compile.lua:266` | `*compilation*`, `*shell-command*` | blanket read-only |
| `builtin/commands/default.lua:869` | `*search-results*` | blanket read-only |
| `builtin/packages/repl/init.lua:187` | REPL buffers | **filtering** — §2.5 |

### 1.3 `set_read_only` — zero Lua callers, and no Lua binding

`grep -rn set_read_only builtin tests` returns 5 hits, **all Rust test
code** (`tests/folding_acceptance.rs:587`,
`tests/vterm_stage1_acceptance.rs:139,175`,
`tests/terminal_copy_mode_acceptance.rs:582,584`). The stronger fact:
the Lua binding table registers `"add_intercept"` and no
`"set_read_only"` / `"is_read_only"` at all
(`src/lua_bindings/mod.rs:3409` is the only match in the neighbourhood).
Lua *cannot* set `read_only` today. That matters for Q#GB7.

### 1.4 The classification, by writer mechanism

**Class A — erroring intercept + `bypass_intercept` writes over a
writable rope. This is the bug.**

1. **`terminal.lua`** — copy-mode snapshot. **ADOPTED** (`:336`). Fixed.
2. **`dired.lua`** — every dired buffer. One write, in `paint`
   (`:369-372`): `handle.buf:replace(0, handle.buf:len(), text, {bypass_intercept=true})`.
   A whole-buffer replace already. **Convertible with the shipped
   primitive.**
3. **`listview.lua`** — `*references*`, `*outline*`, `*lsp-help*` (the
   three production `listview.open` callers, all in `lsp.lua`:2056, 2102,
   2513). One writer, `render` (`:50-62`): delete-all then insert-all,
   which is a whole-buffer replace spelled in two ops.
   **Convertible.**
4. **`compile.lua`** — `*compilation*` and `*shell-command*`, both via
   `ensure_slot` (`:258`). Nine writes across five enclosing functions,
   and they are genuinely incremental:

   | enclosing function | line | shape |
   |---|---|---|
   | `resync` (`:309`) | 319 | append desync marker at end |
   | `emit_text` (`:432`) | 443 | append remainder at end |
   | `emit_text` | 454 | append `"\n"` at end |
   | `emit_text` | 465 | **positional `replace`** (CR overwrite) |
   | `apply_events` (`:480`) | 506 | **targeted delete** (erase-to-eol) |
   | `apply_events` | 512 | **targeted delete** (erase-line) |
   | `emit_text_raw` (`:639`) | 642 | append marker at end |
   | `start_run` (`:746`) | 794 | delete-all (run reset) |
   | `start_run` | 798 | insert header (run reset) |

   **NOT convertible.** `emit_text` is a terminal emulator: it tracks
   `slot.out_pos` / `slot.line_start` / `slot.parse_line_start` as byte
   anchors, reads `buf:slice(pos, len)` between writes, and settles
   `slot.expected_rev = buf:revision()` afterwards. A whole-buffer
   replace destroys every one of those anchors.
5. **`builtin/commands/default.lua`** — the independent `*search-results*`
   panel (`ensure_search_panel`, `:857`). Four writes across three
   enclosing functions:

   | enclosing function | line | shape |
   |---|---|---|
   | `search_panel_resync` (`:821`) | 827 | append desync marker |
   | `search_panel_append` (`:844`) | 849 | append match batch |
   | `pmacs.project.search` (`:982`) | 1005 | delete-all (query reset) |
   | `pmacs.project.search` | 1007 | insert header (query reset) |

   **NOT convertible**, for the same reason at smaller scale: the append
   path carries `p.next_row` / `p.expected_rev` bookkeeping.

   **Do not read `ensure_slot` as covering this panel.** It serves
   `*compilation*` and `*shell-command*` only; `*search-results*` has its
   own intercept, its own round-trip mark, its own resync and its own
   writes, and `compile.lua` names it only inside the
   `is_generated_buffer` predicate (`:216`).

**Class B — filtering intercept, deliberately partly editable.**

6. **`builtin/packages/repl/init.lua:187`** — see §2.5. Shares the root
   cause, does not share the remedy. **Out of this arc.**

**Class C — generated, but nothing ever claimed they were protected.**
Keying the inventory on `bypass_intercept` misses these entirely,
because an unprotected buffer needs no bypass:

7. **`*buffer-list*`** — `render_list` (`default.lua:387`) writes with
   plain `buf:delete(0, len)` / `buf:insert(0, body)` (`:403-404`). No
   intercept, no round-trip mark. Whole-replace shape.
8. **`*help*` — TWO independent writers, one Lua and one Rust.
   Corrected in revision 3; revision 2 named only the first.**
   - `show_help_text` (`default.lua:1239`), plain delete-all +
     insert-all (`:1245-1246`), no intercept, **no `mark_clean`**.
   - `replace_help_buffer` (`src/help.rs:354-383`) — `find_by_name(
     HELP_BUFFER_NAME)`-or-create (`:358-360`), delete-all + insert-all
     through `Buffer::apply_edit` (`:365`, `:372` — the
     intercept-*running* path, not the skip path), then
     `Buffer::mark_clean()` (`:381`) with the comment "The help buffer
     is regenerated content".

   The name constant is declared twice, independently, on either side of
   the FFI boundary: `src/help.rs:38` (`pub const HELP_BUFFER_NAME`) and
   `builtin/commands/default.lua:1226`. Neither writer knows about the
   other; they differ on `mark_clean` and on which write primitive they
   use. **Two owners for one buffer is why Class C's deferral (Q#GB9) is
   correct rather than merely convenient** — "make `*help*` immutable"
   is not a conversion, it is first a decision about who owns it.
9. **`*workers*`** — a **Rust** writer, `workers_buffer::render`
   (`src/workers_buffer.rs:65`), using `Buffer::apply_edit` (not the
   skip-intercepts path), delete-all + insert-all, then
   `Buffer::mark_clean()` (`:95`). Its fan-out is a fourth mechanism:
   `queue_generated_buffer_edits` + `rebuild_generated_buffer_views`
   (`src/lua_bindings/mod.rs:7142-7145`).

Class C is a **different defect** — nothing is defeated, because nothing
was claimed. It is named here so the inventory is complete and so a
future reviewer does not re-derive it; §4 keeps it out of this arc.

**Revision 3's correction to the inventory's headline number.** This
document, `docs/agent-handoff.md` §4 and `COHERENCE.md` §14 all say
**four writer mechanisms**. Counting `src/help.rs:354` — a distinct
mechanism by every criterion the others are counted by (its own
find-or-create, its own write primitive, its own clean-marking policy)
— the honest figure across Classes A and C is **five**, over seven
buffer families. The four-row table in the handoff is keyed on
`bypass_intercept` and structurally cannot see it. Carried to the PR
body; the handoff is not this lane's file to edit mid-flight.

### 1.5 The `COHERENCE.md` §14 correction — LANDED, not owed

**Revision 3 rewrites this section from a claim into a record, because
the correction merged while revision 2 was open.**

Revision 1 and 2 recorded that §14's "references, outline, buffer-list,
and project-search all use listview" was wrong: `pmacs.listview.open`
has **three** production callers, all in `lsp.lua` — `*references*`
(`:2056`), `*outline*` (`:2102`), `*lsp-help*` (`:2513`) — while
`*buffer-list*` is hand-rolled in `default.lua` (`render_list`, `:387`)
and `*search-results*` is the independent grep panel.

**PR #189 landed exactly that correction** (`main` @ `7586905`,
`0dd0bf2`): §14's List bullet now names the three `lsp.lua` call sites,
the scorecard row moves from ✓ to ◐, and the §6 picker/panel
parenthetical gains `*lsp-help*`. Nothing is owed. This section survives
only so a reader of the earlier revisions does not go looking for a
correction that is already in the tree, and so the *reason* stays
recorded: the miscount came from counting the `compile.lua` and
`dired.lua` comments that cite "the listview idiom" as adoptions. Those
comments are imitators, and what they imitate is the
erroring-intercept-over-a-writable-rope pattern this document exists to
fix.

---

## 2. Ground truth (measured, not recalled)

### 2.1 What the shipped primitive is

`Buffer::set_generated_contents` (`src/buffer.rs:545`, doc comment
`:507-544`): lift `read_only`, `apply_edit_skip_intercepts` a **single
whole-buffer** `EditOp::Replace`, `clear_history()` (the **call** is
`:553`; `:559` is the definition — a revision-2 miscitation), re-assert
`read_only`, **return the `Edit`**. The Lua binding
(`src/lua_bindings/mod.rs:3079-3095`) fans that `Edit` out via
`notify_buffer_edit_to_windows` (`:1573`) *after* dropping the registry
borrow, because the fan-out re-enters the core.

`clear_history` clears whichever history the buffer has: the v0.1
`undo`/`redo` stacks, and in CRDT mode `CrdtState::clear_undo_history`
(`src/crdt.rs:507`), which rebinds a fresh `UndoManager` to the same doc
because loro exposes no `clear`.

### 2.2 Why history clearing is load-bearing

The doc comment's reason is retention, not tidiness: `read_only`
guarantees the pushed entries can never be popped, so a periodically
refreshed panel accumulates full rope clones nothing will ever release.
CRDT mode has the identical retention inside loro's `UndoManager`.

### 2.3 Why a bare lock is not the answer

`ensure_writable` guards the bypass path too
(`apply_edit_skip_intercepts`, `src/buffer.rs:1055-1056`). Locking a
generated buffer without giving its owner a door refuses the refresh the
buffer exists for. That is why the *pairing* is the primitive and why
there is deliberately no Lua `set_read_only` today.

### 2.4 Partial adoption is impossible — measured

This is the fact that decides the design. Once `set_generated_contents`
has locked a buffer, a subsequent owner write through `bypass_intercept`
is refused:

```
bypass write after lock = false | buffer `*probe*` (id BufferId(4)) is read-only
```

So compile **cannot** convert its run reset (`start_run:794,798`) to the
shipped primitive and keep `bypass_intercept` for streaming: the first
append after the reset raises. The streaming owner needs a write path
that *itself* carries authority. Reads are unaffected — `buf:slice`,
`buf:len` and `buf:revision` all work on a locked buffer, which is what
makes an op-level solution viable at all.

### 2.5 The REPL: same root cause, different remedy — measured

`builtin/packages/repl/init.lua:187` installs
`function(op) return repl._intercept(h, op) end` — a **filtering** policy
(`repl._intercept`, `:686-726`): reject edits wholly inside the
history/prompt region, **truncate** edits that straddle the boundary,
pass edits in the input region. Its own writes use a `_self_write` flag
(`with_self_write`, `:111-116`) rather than `bypass_intercept`, and it
has real teardown (`remove_intercept`, `:325-327`).

Does it share the bug? **Yes — measured — and I am not asserting the
comfortable answer:**

```
repl BEFORE                 = "line one\nline two\n> "
repl ordinary edit at pos 0 = false | REPL: history/prompt region is read-only
                                      (insert at 0; input region begins at 20)
repl AFTER 1 buffer.undo    = "line one\nline two\n"
repl bookkeeping after undo = _history_end=18 / _prompt_end=20  (rope is 18 bytes)
```

Undo deleted the prompt the intercept had just refused to let anyone
touch, and left `_prompt_end` pointing two bytes past the end of the
rope. The marks (`_history_end_mark`, `_prompt_end_mark`) adjust with the
rope, but `_blocks[i].start_byte` are plain integers maintained by hand
in `drop_oldest_block` (`:643-656`) and do not.

**But the remedy cannot be rope-level `read_only`**: the input region
must accept ordinary user edits, which is the whole point of a REPL. The
REPL needs either an undo that consults the intercept chain, or
mark-anchored blocks. Both are different work. **Q#GB8: out of this arc,
named deferral, with its measurement recorded above so the next lane does
not have to rediscover it.**

### 2.6 A pre-existing defect in the shipped primitive — measured

`notify_buffer_edit` (`src/editor_core.rs:1836`) updates each window's
`TextView` and overlays. It does **not** clamp `win.cursor` or
`win.view_top`. Only `rebuild_views_for` (`:1865`) does, and its doc
comment says so explicitly (`:1863-1864`). `set_generated_contents`'s
binding calls the former.

```
cursor before = 29, len = 30
cursor after set_generated_contents(G, 'x\n') = 29, len = 2
row0 after shrink = "x"          (paint did not crash)
cursor after C-p  = 29           (motion did not recover it)
```

A shrinking generated write leaves the window cursor 27 bytes past the
end of the buffer, indefinitely. **This ships today in terminal copy
mode** — refresh a snapshot to a shorter one with the point low in the
buffer and this is the state — and every adopter inherits it.

**The two coordinates fail on different axes** (review P2-4). `cursor` is
a byte position (`src/window.rs:366-367`) bounded by `Buffer::len()`;
`view_top` is a **line index** (`:373-374`, "First buffer *line* shown at
the top") bounded by `TextView::line_count()` (`src/text_view.rs:67`).
The transcript above is the byte case. The line case is **not measured**
— staging it needs a scrolled window — but it is available from the types
alone: a write that grows in bytes while collapsing lines invalidates
`view_top` on a write no byte-length comparison calls a shrink.
`rebuild_views_for` already clamps each against its own bound
(`src/editor_core.rs:1875-1879`); the clamp added to
`notify_buffer_edit` must do the same. Q#GB6.

### 2.7 What `buffer.after-edit` does and does not do

`buf:insert` / `buf:delete` / `buf:replace` do **not** fire
`buffer.after-edit`; the dispatcher and daemon do
(`src/editor.rs:1472,2356,2500,2535`, `src/daemon.rs:3167`).
`compile.lua:714` already relies on this ("hook edits don't re-fire the
hook"). Consequence for §3: a generated write does not run arbitrary Lua,
so the *fan-out* is not a re-entrancy hazard — but a scoped primitive's
**callback body** still is, because it is arbitrary owner Lua.

### 2.8 Three writers adopt any buffer that shares their name — measured

**The invariant already exists in this codebase; three writers simply do
not honour it.** `terminal.lua:300-305` states it verbatim:

> `pmacs.buffer.create` takes any caller-chosen name, so a foreign buffer
> may already be called `*terminal-copy: sh*` [...] **found-by-name is NOT
> adoption**: ownership means "this buffer is in the handle table above",
> exactly as in dired.

`dired.lua:476-504` implements the same rule: `claim_handle` looks up its
**handle table** first, and on a name collision disambiguates
`<2>`…`<99>` (`NAME_VARIANT_LIMIT`, `:474`) or raises. Three writers
instead adopt:

| writer | line | code |
|---|---|---|
| `listview.ensure_panel` | `listview.lua:95` | `find_buffer_by_name(name) or pmacs.buffer.create(name)` |
| `compile.ensure_slot` | `compile.lua:263` | `buffer_named(name) or pmacs.buffer.create(name)` |
| `ensure_search_panel` | `default.lua:861-868` | name scan over `pmacs.buffer.list()`, then `buf or create` |

Measured at `ad41cf1`, a user buffer named `*references*` and then a
references panel:

```
foreign BEFORE               = "my precious notes"
foreign AFTER listview.open  = "H\nr1"
buffers named *references*ish = 1              (no disambiguation happened)
ordinary edit to MINE now    = false | intercept rejected the edit:
                               listview.lua:102: *references* is read-only
```

The user's buffer is clobbered **and left permanently un-editable**,
because `ensure_panel` installs an erroring intercept whose handle it
discards.

**Compile is worse, and it is worse on a path that fails.**
`pmacs.compile.run` calls `ensure_slot` (`compile.lua:1090`) *before*
`start_run` validates `opts.display` (`:752-757`). Measured:

```
compile.run('true', { display = 'bogus' })
  = false | compile.lua:754: compile.run: unknown display "bogus"
foreign *compilation* contents after the FAILED call = "my precious notes"
ordinary edit to MINE after the FAILED call
  = false | intercept rejected the edit: compile.lua:267: *compilation* is read-only
```

A call that **raised and did nothing else** left the user's buffer
uneditable. Q#GB5's revision-1 recommendation — an empty
`set_generated_contents` at the end of `ensure_slot` — would make that
same failing call **empty the buffer and lock the rope**. Q#GB5 is
amended accordingly.

**Why this is a prerequisite and not a follow-up.** Today the clobber is
recoverable, and the thing that recovers it is *this arc's bug*:

```
after clobber = "H\nr1"
after undo 1  = ""
after undo 2  = "my precious notes"
```

`M-x buffer.undo` is currently the only way back. After adoption the rope
is `read_only`, the history is cleared by the same call that wrote, and
§1.3 measured that **no Lua binding can clear `read_only`**. The arc
therefore converts a recoverable clobber into an unrecoverable one, and
it removes the accidental safety net in the same commit that removes the
need for it. Q#GB13.

**Dired needs none of this work** — it already disambiguates — which is
why it is the cheaper of Stage 1's two adopters despite being the newer
one.

### 2.9 `is_modified` reaches autosave and desktop persistence — a revision-1 error

**Revision 1 stated that the flag "drives only the mode-line indicator
and the buffer-list column". That is wrong**, and it was wrong because
the sweep was `grep -rn '\.modified' builtin` plus a narrow `src` path
rather than `grep -rn 'is_modified' src`. The full sweep finds two more
consumers, both load-bearing:

- **`src/autosave.rs:359-364`** — the per-buffer skip:
  `let Some(path) = buf.file_path() else { continue };` then
  `if !buf.is_modified() { continue; }`. A clean buffer gets **no
  crash-recovery slot written**.
- **`src/desktop.rs:298-303`** — `SavedBuffer { path, modified: b.is_modified() }`,
  again only for buffers with a `file_path`.

Both gate on `file_path()` being `Some` before they read the flag. That
is the fact Q#GB10's revised rule turns on.

**Revision 3: the sweep was under-run a second time, and the arithmetic
is stated here so it is not under-run a third.** `grep -rn 'is_modified()'
src/ pmacs-gpu/` returns 26 lines. Removing the accessor definition and
the 18 `src/buffer.rs` unit-test assertions leaves **7 production
consumers**:

| consumer | load-bearing? |
|---|---|
| `src/autosave.rs:363` | **yes** — the crash-recovery skip (§2.9 above) |
| `src/desktop.rs:302` | **yes** — the persisted `SavedBuffer.modified` |
| `src/editor.rs:4129` | no — the TUI mode-line `*` |
| `src/semantic_render.rs:1716` | no — the **semantic frontend's** statusline payload |
| `src/help.rs:131` | no — the `Modified:` line of describe-buffer text |
| `src/instance_buffer.rs:401` | no — an assertion, not a read |
| `src/lua_bindings/mod.rs:1262`, `:6359` | no — `buf:is_modified()` and `describe.buffer().modified`, which `default.lua:395` renders |

Revision 1 said two consumers; revision 2 said four; the true figure is
**seven, of which two are load-bearing**. Both new ones
(`semantic_render.rs:1716`, `help.rs:131`) are display, so **Q#GB10's
conclusion is unchanged** — but the conclusion was reached twice from an
incomplete count, and only the arithmetic makes that visible.

Also found in the same sweep, and reused below: `mark_clean()` has six
callers (`grep -rn 'mark_clean()' src/`, minus the definition).
`src/instance_buffer.rs:95,114`, `src/workers_buffer.rs:76,95` and
`src/help.rs:381` are all **generated-buffer writers that already mark
clean**; `src/editor_core.rs:1967` is the save path. So the convention
Q#GB10 adopts is established by **three** Rust writers, not the one
revision 1 cited.

### 2.10 The name-based identity census, with its arithmetic

Review P1-2 named two consumers. This is the whole set, and the
classification comes from reading each enclosing function, never from the
grep line.

**Scope.** A site is in scope when a *disambiguated* name would change
its answer: it either (i) recovers a buffer's identity by comparing that
buffer's name against an expected value, or (ii) keys a table by a buffer
name. `pmacs.describe.buffer(id).name` is the **only** Lua surface that
yields a buffer's name — `buffer_info_table`
(`src/lua_bindings/mod.rs:6352-6364`) sets `name`, `length`, `modified`,
`view_count` and nothing else, and no other binding exposes it — so
`grep -rn 'describe\.buffer' builtin/ --include='*.lua'` is a complete
frontier for `builtin/`.

**The arithmetic.** That grep returns **14** lines. Five of them are the
bodies of shared helpers rather than decisions:

| helper | file:line | callers |
|---|---|---|
| `buffer_name` | `terminal.lua:276` | 1 (`:293`) |
| `buffer_named` | `terminal.lua:283` | 2 (`:308`, `:311`) |
| `buffer_named` | `dired.lua:196` | 3 (`:491`, `:495`, `:914`) |
| `buffer_named` | `compile.lua:194` | 2 (`:263`, `:1052`) |
| `find_buffer_by_name` | `listview.lua:32` | 2 (`:95`, `:190`) |

14 − 5 helper bodies = **9 direct sites**; the five helpers expand to
1 + 2 + 3 + 2 + 2 = **10 call sites**; 9 + 10 = **19 units**, and the
five classes below partition them 2 + 3 + 2 + 5 + 7 = **19**.

**Class 1 — BROKEN by disambiguation. In scope for this arc (Q#GB18).**

1. **`listview.lua:42-44`, `panel_for_current_buffer`.** `panels` is
   written `panels[name] = p` at `:97` with the **requested** name and
   read `return panels[d.name]` at `:44` with the **actual** name. A
   panel created as `*references*<2>` can never resolve its own record.
   **Four consumers, not the three the review named:**

   | consumer | line | what breaks |
   |---|---|---|
   | `listview.visit` (RET/SPC) | `:150` | returns early; RET does nothing |
   | `listview.refresh` (`g`) | `:161` | returns early; `g` does nothing |
   | `listview.quit` (`q`) | `:177` | returns early; `q` does nothing |
   | `listview.open`'s capture guard | `:118-123` | **fails inverted, and silently** |

   The fourth is the one worth reading twice. `listview.open` captures
   the return target with
   `if active and not panel_for_current_buffer() then p.prev = active end`,
   and the comment above it states the intent: "never another panel
   (chained panels would trap `q` in a loop; restore targets the last
   real buffer)". When `panel_for_current_buffer()` cannot recognise a
   disambiguated panel it returns `nil`, the guard reads as "the current
   buffer is not a panel", and the panel is captured as its own `q`
   target — **exactly the loop the guard exists to prevent**, produced by
   the guard. The other three fail closed and visibly; this one fails
   open and quietly, which is why it needs its own criterion rather than
   riding on the other three.

2. **`compile.lua:214-216`, `pmacs.compile.is_generated_buffer`.**
   `return d.name == COMPILATION or d.name == SHELL_OUT or d.name ==
   SEARCH_RESULTS`. **Two consumers**, both the Q#CM11
   never-capture-a-generated-buffer `q`-target discipline:
   `compile.lua:762` (compile's own capture) and
   `default.lua:993-994` (the search panel's). A disambiguated
   `*compilation*<2>` is not recognised, so it gets captured as a `q`
   target and `q` returns the user to a generated buffer.

   Note that `compile.lua:232`'s `slot.name == COMPILATION` is **not** in
   this class and needs no change: `slot.name` is the record's own field,
   set from the module constant `ensure_slot` was called with, and never
   from a buffer's actual name.

   Note also that `slots` (`compile.lua:185`) is **not** broken by
   disambiguation, unlike `panels`: it is keyed by the module constant at
   both write (`:262`) and read (`:259`, `:923`, `:1104`), and the only
   buffer→slot direction is `slot_for_buffer` (`:200-206`), which
   compares `slot.buf == buf` by id. Compile got this half right and
   listview did not; the census is what makes that visible, and it means
   Q#GB18's compile work is one predicate, not a table rewrite.

**Class 2 — the find-by-name adoption Q#GB13 already removes.** In scope,
already framed. `listview.lua:95` (Stage 1), `compile.lua:263` (Stage 2),
`default.lua:863` (Stage 2). **3 sites.**

**Class 3 — the same adoption defect in Class C families.** Out of arc
(Q#GB9), named so it is not re-derived: `default.lua:380`
(`find_list_buffer`, `*buffer-list*`) and `default.lua:1231`
(`find_or_create_help_buffer`, `*help*`). **2 sites.** The Rust-side
instance of the same shape, `src/help.rs:358-360`, is outside this
census's `builtin/` frontier and is recorded in §1.4 instead.

**Class 4 — collision probes: the CORRECT use of a name lookup.**
`dired.lua:491`, `:495` (`claim_handle`'s `<2>`…`<99>` walk);
`terminal.lua:308`, `:311` (`unique_snapshot_name`); `terminal.lua:293`
(`snapshot_base_name`, which *derives* a new name from a name and
recovers no identity). **5 sites.** These are the shape Q#GB13 asks the
other three writers to adopt, so they are the reference implementation,
not debt.

**Class 5 — correct by construction; a disambiguated name does not change
the answer.** **7 sites.**

- `default.lua:391` — `render_list` prints `d.name` in a column. Display.
- `default.lua:604` — `switch-to-buffer` matches the name the **user
  typed**, sourced from the same registry that would show a
  disambiguated name. Correct precisely because it is name-based.
- The five `*scratch*` fallbacks — `default.lua:581`, `:1145`,
  `listview.lua:190`, `compile.lua:1052`, `dired.lua:914`. `*scratch*` is
  an unowned shared buffer that no writer in this arc disambiguates, so
  its name **is** its identity.

**One flag on Class 5, carried rather than fixed.** Those five
`*scratch*` fallbacks are five independent copies of one find-or-create,
and they are correct only while `*scratch*` stays unowned and
undisambiguated. If a future lane gives `*scratch*` an owner — a
plausible move, since it is the quit target of all five paths — all five
break together and nothing in the tree connects them. Named in §8.

### 2.11 `read_only` is one boolean serving three policies

Revision 2 treated `read_only` as this arc's flag. It is not, and both
review P1-3 and sweep C turn on that.

| policy | who sets or reads it | what it means there |
|---|---|---|
| **generated lock** | `Buffer::set_generated_contents` (`src/buffer.rs:546`, `:554`) | "the owner's write path is the only writer" |
| **terminal identity** | `src/terminal/session.rs:305`, at `TerminalSession::open` | "the host may not edit this at all — not by edit, not by undo, not by remote CRDT import" |
| **"is this a document buffer?"** | `document_bytes` (`src/lua_bindings/fold.rs:310-318`), **reading** it | Q#FD11's foldability test |

`Buffer::set_read_only`'s own doc comment (`src/buffer.rs:496-502`)
describes only the second, and the third is a *reader* that was written
when the second was the only writer —
`tests/folding_acceptance.rs:570-573` says so in as many words:
"terminals are read-only, so a read-only buffer is not foldable."

Six paths gate on the flag through `ensure_writable`
(`src/buffer.rs:568`): `begin_edit` (`:725`), `apply_edit` (`:773`),
`apply_remote_crdt_op` (`:845`), `apply_edit_skip_intercepts` (`:1056`),
`undo` (`:1302`), `redo` (`:1410`). That breadth is the point of the flag
and is not in question. What is in question is that a single boolean
carries three unrelated *authorities*, so a capability defined over it —
in either direction — necessarily reaches all three. Q#GB15 and Q#GB16
are the two consequences.

---

## 3. The primitive decision (Q#GB1)

**The question this arc exists to answer: what write primitive do
`compile.lua` and the search panel need?**

### 3.1 Recommendation

**`Buffer::apply_generated_edit(op: EditOp) -> GeneratedOutcome`
— one authorized op at a time — exposed to Lua as a new option key on
the mutators that already exist:**

```lua
buf:insert(pos, text,   { generated = true })
buf:delete(start, end_, { generated = true })
buf:replace(s, e, text, { generated = true })
```

Semantics, per call, entirely inside one `with_registry_mut` and one
`&mut Buffer` method — the exact ordering, including every error path, is
§3.4, which revision 3 adds because review P1-1 showed revision 2 had no
workable one. The binding then fans every outcome that carries an
`Edit` out through `notify_buffer_edit_to_windows` after the borrow has
dropped: `Applied` and `NoOp` before returning success, and
`AppliedThenFailed` **before returning its error**. Revision 5 makes that
third arm explicit because collapsing the outcome to `Result` inside
`Buffer` discarded the only value capable of updating window caches and
replica mirrors.

`Buffer::set_generated_contents(bytes)` is reimplemented as
`apply_generated_edit(Replace { range: 0..len, bytes })`. **Its Lua name
and call signature stay fixed; its Rust return changes from
`Result<Edit, BufferError>` to `GeneratedOutcome`**, and its direct Rust
tests match on the outcome. The change is required: a wrapper that
collapses `AppliedThenFailed` to `Err` before the binding sees it loses
the applied `Edit` and cannot satisfy the fan-out contract. It becomes
the whole-buffer spelling of one primitive rather than a second
primitive.

**One sentence for why it wins: it is the only candidate in which the
buffer is never observably unlocked, because the lift and the re-assert
happen inside a single registry borrow with no Lua in between — so there
is no flag to clear on an error path, no yield to defend against, and
nothing for a reviewer to audit site by site.**

### 3.2 Why the alternatives lose

**A. `append_generated_contents` — provably insufficient.** `compile.lua`
does a positional `replace` at `emit_text:465` (the CR overwrite that
makes progress bars work) and two targeted `delete`s at
`apply_events:506,512` (erase-to-eol, erase-line). Append cannot express
any of the three. Dead on the census.

**B. Scoped `with_generated_writes(buf, fn)` — the pattern this project
has already been burned by.** It is the cheapest on history (one
`clear_history` per scope instead of one per op) and that is its only
real advantage. Against it:

- **The unlocked interval is the callback's whole duration, and the
  callback is arbitrary owner Lua.** Drawn loosely around `start_run`
  (`compile.lua:746`), the scope spans `pmacs.window.switch_buffer(buf)`
  and `pcall(pmacs.process.spawn, spec)` — the buffer would be writable
  across a process spawn. Drawn tightly, compile needs four separate
  scopes (`start_run`'s reset, `resync`, `feed_bytes`, `finish_run`), each
  needing its own audit for what the body reaches.
- **Correctness reduces to "a flag cleared on every exit."** That is the
  exact shape `docs/agent-handoff.md` §5 and #155 record as a repeat
  offender, and the REPL already had to defend its own version of it:
  `with_self_write` (`repl/init.lua:111-116`) wraps in `pcall`
  specifically because "a single failed write would leave the bypass on
  for every subsequent user edit". Adding a second instance of a pattern
  the tree already documents as fragile is a poor trade for one saved
  `clear_history` per batch.
- **Yield is an error here, which helps but does not rescue it.** A Lua
  callback that yields across the Rust boundary raises
  `attempt to yield across C-call boundary` (observed in this worktree
  while probing `pmacs.dired.open`), so a yielding body surfaces as
  `Err` — but the relock must still run on that path, which is the same
  obligation.
- It is strictly harder to review: a per-site scope audit versus a
  mechanical option-key change at 16 call sites.

**C. Standalone `generated_edit(buf, op)`.** Identical semantics to the
recommendation, worse ergonomics: it re-implements the three-op argument
parsing that `buf:insert/delete/replace` already own, and turns adoption
from an option-key change into a rewrite of 16 call sites. Recommended
only if the user objects to `{ generated = true }` sitting beside
`{ bypass_intercept = true }` in the same options table.

**D. Make `Buffer::undo`/`redo` consult the intercept chain.** This would
fix all six families at once, including the REPL, and it deserves an
explicit rejection rather than silence. Against it: (i) there is no
`EditOp` to hand the chain — v0.1 undo is a whole-rope swap
(`src/buffer.rs:1327-1328`) and CRDT undo is materialize-and-replace
(`undo_crdt_mode`, `:1365`), so the chain would have to be given a
synthetic op it was never designed to see; (ii) it changes behaviour for
every intercept in the tree, including the *transforming* ones
(auto-pair, lean-input, the REPL's truncation) which have no business
rewriting an undo; (iii) an erroring intercept becomes a new Lua-raise
failure path out of `EditorCore::undo`, which today cannot fail that way.
It may still be the right answer **for the REPL specifically** — recorded
in Q#GB8's deferral, not adopted here.

### 3.3 The four questions the recommendation must answer

**How many `Edit`s are fanned out, and when?** One per generated op that
reaches an `Edit`, immediately, by the binding. That includes
`AppliedThenFailed`: the rope and CRDT have already changed, so the
binding fans its carried `Edit` out and only then returns the carried
error. `compile.lua`'s
`emit_text` fast path emits one insert for a whole output batch, so a
typical `feed_bytes` produces one to three ops; a CR-heavy progress bar
produces more. Successful calls retain today's fan-out cardinality; the
new failure arm adds the notification that today's early `Err` loses,
because that error can follow a real mutation.

**Per-op or per-scope history clearing?** Per op, and it is cheap by
construction: because `read_only` is re-asserted immediately, **at most
one** v0.1 undo entry can exist when the clear runs and the redo stack is
always empty, so the v0.1 clear is O(1). In CRDT mode the clear rebinds
a fresh `UndoManager` (`CrdtState::clear_undo_history`), and
`create_undo_manager` (`src/crdt.rs:154`) is `UndoManager::new(doc)` plus
`set_max_undo_steps` — a subscription registration, not a document copy,
so it is O(1) in document size too. **Measurement obligation, not a
claim:** Stage 2 must show a streaming compile run does not regress
against the existing compile-mode timings in both configurations. If it
does, the escape hatch is to suppress recording rather than clear it —
recorded as a named deferral rather than designed speculatively.

**CRDT-mode behaviour?** Identical to `set_generated_contents` today on
success, and corrected on the post-apply error path. The `Edit` carries
`crdt_op` when the buffer is CRDT-backed, and
`notify_buffer_edit_to_windows` queues it via
`queue_daemon_origin_crdt_op` (`src/lua_bindings/mod.rs:1582`) so replica
mirrors import the owner's write. `AppliedThenFailed` must carry that
same `Edit`; returning its error before notification would leave the
authoritative CRDT changed while every replica missed the op. History
clearing goes to loro's `UndoManager`.

**How do the returned edits reach the fan-out without a live registry
borrow?** By construction, extending #178's shape: `run_bypass_edit`
(`src/lua_bindings/mod.rs:1445`) closes its `with_registry_mut` before
returning, and the mutator bindings call
`notify_buffer_edit_to_windows` afterwards. `run_generated_edit` (§3.4)
occupies the same position and closes its borrow the same way, but
returns the whole `GeneratedOutcome`. A binding-level finisher handles
it:

```rust
match run_generated_edit(lua, id, op) {
    Applied(edit) | NoOp(edit) => {
        notify_buffer_edit_to_windows(lua, id, &edit);
        Ok(edit)
    }
    AppliedThenFailed { edit, error } => {
        notify_buffer_edit_to_windows(lua, id, &edit);
        Err(error.into())
    }
    Rejected(error) => Err(error.into()),
    Diverged(error) => {
        surface_divergence(lua, &error);
        Err(error.into())
    }
}
```

The helper is shared by the three mutators and the
`set_generated_contents` binding so one of the four cannot forget the
failure fan-out.

### 3.4 The transaction, and why revision 2 had none (review P1-1)

**Revision 3 adds this section. It is the substance of P1-1 and it
reverses Q#GB3.**

**The defect, confirmed at line level.** Revision 2's Q#GB3 routed
generated writes "through `run_buffer_edit`'s bypass arm". That arm is
`run_bypass_edit` (`src/lua_bindings/mod.rs:1445-1454`), whose first act
on the buffer is `buf.begin_edit()`, and `begin_edit`'s first statement
is `self.ensure_writable()?` (`src/buffer.rs:724-725`). A generated write
must pass **while `read_only` is set** — that is the entire point — so
every generated write after the first would be refused, and for compile,
whose Q#GB5 lock is installed during `ensure_slot`, even the first
streaming write would be refused. As written, revision 2's design was
dead on arrival at every buffer it governs.

**The review offers two repair options; one of them cannot work, and
saying so is the first design decision.** The suggestion to reorder
`begin_edit`'s two checks does not repair anything:

```rust
pub fn begin_edit(&mut self) -> Result<(), BufferError> {
    self.ensure_writable()?;                       // src/buffer.rs:725
    if self.editing_in_progress { return Err(ConcurrentEdit { .. }); }
    self.editing_in_progress = true;
    Ok(())
}
```

Both checks are unconditional and both `return Err`. Reordering changes
only **which** error a call that fails both reports; a locked buffer is
still refused, one line later. It is also not free: at least one shipped
test asserts on the *text* of that error
(`tests/dired_acceptance.rs:999`, `status(&s).contains("read-only")`),
and `BufferError::ReadOnly` and `ConcurrentEdit` render differently
(`src/buffer.rs:1794`, `:1824-1831`). **Any path that admits a generated
write must not reach `ensure_writable` at all.** So there is one option,
not two: a separate entry point. Recorded as a disagreement with the
review rather than complied with silently.

**Where the concurrency gate lives.** Inside `Buffer`, in the generated
path itself, duplicating `begin_edit`'s **second** check and not its
first. It is **not** exposed as a public `begin_generated_edit`: making
it a public pair would recreate at the binding layer the exact
"a flag cleared on every exit" shape §3.2 rejects candidate B for. One
method, one exit set, nothing for a caller to forget.

**What that does to the `ConcurrentEdit` contract.** Nothing observable,
and the contract is still needed. Two directions:

- **Inward** (something re-enters *during* a generated write): impossible
  by construction, and this is worth stating because it is what makes the
  transaction safe to hold across a single borrow. `apply_edit_skip_intercepts`
  runs `View::on_edit`, never `View::intercept_edit`
  (`src/buffer.rs:1055-1060`), and `LuaInterceptView`
  (`src/lua_bindings/mod.rs:1755-1798`) implements **only**
  `intercept_edit` — it inherits `View::on_edit`'s default no-op body
  (`src/view.rs:252-254`). Of the seven production `on_edit`
  implementations (`grep -rn 'fn on_edit' src/`: `text_view.rs:150`,
  `fold.rs:274`, `overlay.rs:248`, `syntax.rs:1637`, plus test doubles)
  none calls into Lua. **A generated write runs no Lua**, so nothing can
  re-enter it.
- **Outward** (a generated write issued *from inside* a managed edit on
  the same buffer): entirely possible — a Lua intercept body on buffer X
  calling `X:insert(pos, s, { generated = true })` — and it must still
  fail. `run_managed_edit` phase 2 runs that body with the registry
  borrow released and its `InterceptContext` already snapshotted
  (`src/lua_bindings/mod.rs:1477-1487`); a generated write landing in
  between would leave phase 3 applying an op computed against a rope that
  no longer exists. So the generated path sets and clears
  `editing_in_progress` exactly as `begin_edit`/`end_edit` do, and this
  case surfaces `BufferError::ConcurrentEdit` unchanged.

**Cleanup is driven by an explicit outcome, NOT by inferring one from
`revision`. Rewritten in revision 4 (review round 3, P1-1); revision 3's
predicate was wrong in three directions and this section says so before
it says anything else.**

Revision 3 wrote `if self.revision() != rev_before { clear_history(); … }`
and argued the predicate was *exact* because `revision` bumps after the
undo push and before the `on_edit` broadcast. **That argument is sound
for the v0.1 undo stack and does not extend past it.** Three failures:

1. **A successful no-op keeps history that the contract says cannot
   exist.** An empty buffer can carry substantial undo history — insert,
   then delete back to empty. `set_generated_contents("")` then takes
   the no-op arm (`src/buffer.rs:1245-1253`), returns `Ok`, never bumps
   `revision`, so revision 3 skipped **both** the clear and
   `mark_clean`: the buffer ends locked, **modified**, and carrying
   poppable history that a later Rust-side lift can re-expose. Shipped
   `set_generated_contents` clears unconditionally (`:551-553`), so
   revision 3's predicate was a **regression of an existing contract**,
   not a refinement of one. And it lands on a path this document
   *prescribes*: Q#GB5's `ensure_slot` lock is exactly
   `set_generated_contents(slot.buf, "")`.
2. **CRDT mutation happens upstream of `revision` entirely.**
   `apply_to_crdt_then_normalize_bytes` runs **before** the rope edit
   (`src/buffer.rs:1194-1201`), and for `EditOp::Replace` it is two ops —
   `crdt.delete`, then `crdt.insert` (`:1140-1163`). The code's own
   comment states the hazard: if the delete succeeds and the insert
   fails, "the CRDT is mid-transaction (range deleted but replacement
   not inserted) and the rope is unchanged. This is an invariant
   violation." In that state `revision` has **not** advanced, so revision
   3's predicate neither clears the CRDT's history nor notices the
   `rope ≡ CRDT projection` divergence — in precisely the case that most
   needs both.
3. **Found while fixing the other two: revision 3's unconditional relock
   locks a buffer nobody wrote to.** `b:insert(mid_codepoint, "x",
   { generated = true })` on a *fresh, writable* `*scratch*` is rejected
   by the CRDT after the unlock, and revision 3 then set
   `read_only = true` on the way out. The caller gets an error **and** a
   locked buffer it never successfully wrote. Not reported by the review;
   same class as the other two (a rule derived for one case applied to a
   case whose ordering differs).

**The outcome value.** `run_rope_edit_and_broadcast` reports what it
actually did instead of leaving its caller to guess. This is a real
signature change and not a free one — see the cost note below.

```rust
/// What a generated write did, reported by the apply rather than
/// inferred by its caller. The variant, not `revision`, selects cleanup.
pub enum GeneratedOutcome {
    /// The rope changed and an undo entry exists.
    Applied(Edit),
    /// A semantic no-op: rope unchanged, no undo entry pushed. The call
    /// SUCCEEDED, so the buffer is now a generated buffer.
    NoOp(Edit),
    /// Failed with rope, CRDT and history exactly as they were. This also
    /// includes a deliberate no-op whose `on_edit` notification failed:
    /// view side effects may have run, but no buffer/CRDT mutation exists
    /// to fan out.
    Rejected(BufferError),
    /// The rope changed and a later stage failed. The Edit must survive so
    /// windows and replica mirrors observe the mutation before the error.
    AppliedThenFailed { edit: Edit, error: BufferError },
    /// CRDT only: the CRDT was mutated and the rope was not.
    /// `rope ≡ CRDT projection` no longer holds. See the staging rule
    /// below — this is NOT "delete succeeded, insert failed".
    Diverged(BufferError),
}
```

**Revision 6 (round 5, P1-2): `Diverged` is selected by whether the CRDT
was MUTATED, not by which of two ops failed.** Revision 5 specified a
"delete→insert classifier", which recognises exactly one failure point.
The CRDT routing has **three**, and the third is shared by every op
shape: `export_updates_since` runs after *every* successful CRDT mutation
and before the rope is touched (`src/buffer.rs:1173`), and it returns
`Result`. So:

| op | failure point | CRDT state | revision 5 said | correct |
|---|---|---|---|---|
| `Replace` | `crdt.delete` fails | untouched | `Rejected` | `Rejected` |
| `Replace` | `crdt.insert` fails after delete | **mutated** | `Diverged` | `Diverged` |
| `Replace` | **`export_updates_since` fails** | **mutated** | **`Rejected`** ✗ | `Diverged` |
| `Insert` | `crdt.insert` fails | untouched | `Rejected` | `Rejected` |
| `Insert` | **`export_updates_since` fails** | **mutated** | **`Rejected`** ✗ | `Diverged` |
| `Delete` | `crdt.delete` fails | untouched | `Rejected` | `Rejected` |
| `Delete` | **`export_updates_since` fails** | **mutated** | **`Rejected`** ✗ | `Diverged` |

Revision 5 got **three of seven** rows wrong, and each wrong row applies
`Rejected`'s cleanup — which **restores a fresh buffer to writable while
the CRDT and rope disagree**. That is the same harm P1-3 of round 4
withdrew the four-variant fallback to prevent, reintroduced through a
classifier that was too specific.

**The rule, stated so it cannot miss a future failure point.** The
routing function tracks one `bool`:

```rust
let mut crdt_mutated = false;
// ... immediately after EACH successful crdt.insert / crdt.delete:
crdt_mutated = true;
// ... and every `?` becomes an explicit map that carries the flag out:
//     Err(e) => return Err((e, crdt_mutated)),
```

`apply_to_crdt_then_normalize_bytes` returns
`Result<CrdtRoutingResult, (BufferError, bool)>`, and the caller maps
`(e, false) → Rejected(e)`. `(e, true)` goes through one common
`quarantine_divergence(e)` helper, which sets `crdt_quarantined = true`
and `read_only = true` **before** returning `Diverged(e)`. **The
classifier and containment are therefore total by construction**: any
failure added later anywhere downstream of a successful CRDT op is
classified and poisoned without anyone remembering which public caller
reaches it. That property is the point — revision 5's classifier was
correct for the cases it enumerated and wrong because enumeration was
the wrong mechanism.

```rust
fn quarantine_divergence(&mut self, error: BufferError) -> GeneratedOutcome {
    self.crdt_quarantined = true;
    self.read_only = true;
    GeneratedOutcome::Diverged(error)
}
```

`run_rope_edit_and_broadcast` returns this richer outcome.
`apply_edit` and `apply_edit_skip_intercepts` map it back to their
existing `Result<Edit, BufferError>` API, preserving ordinary callers'
surface **after the common helper has installed quarantine**; the
generated path retains it through cleanup and the borrow-free binding
finisher. The enum is public because the existing public
`set_generated_contents` method and the new `apply_generated_edit` method
return it; their Rust docs state that a higher layer that owns window or
replica state must fan out every edit-bearing variant before handling its
success/error.

That mapping deliberately does **not** claim to repair the same
post-apply notification loss for every ordinary Rust edit API. Their
public `Result<Edit, BufferError>` surface cannot carry both the edit and
the later view error, and changing all of those callers is broader than
generated-buffer immutability. The pre-existing ordinary path is named
in §8 rather than hidden by the helper refactor.

**`AppliedThenFailed` must also finish the BUFFER-attached broadcast, not
only the window and replica fan-out. New in revision 6 (round 5,
P1-4).** Revision 5 solved the fan-out that happens *after* the registry
borrow drops — windows and replica mirrors — and left the loop that
happens *inside* it broken. `on_edit` broadcasting stops at the first
error:

```rust
// src/buffer.rs:1286-1288
for (_, view) in views.iter_mut() {
    view.on_edit(self, &edit)?;          // <- returns on the FIRST Err
}
```

Buffer-attached views run in **attach order**, and the erroring one is
rarely last: `SyntaxHighlightView`, `ParseView`, `FoldStoreTranslator`,
`BufferStyleSpanTranslator` and `DiagnosticView` all maintain byte
offsets in `on_edit`. Any of them sitting *after* the failing view keeps
**pre-edit offsets over a post-edit rope** — the same stale-index class
`docs/agent-handoff.md` §4 records for the window `TextView`, one layer
down. Revision 5's fan-out cannot reach them; they are not windows.

**The decision: continue the broadcast and retain the first error.**

```rust
let mut first_err = None;
for (_, view) in views.iter_mut() {
    if let Err(e) = view.on_edit(self, &edit)
        && first_err.is_none()
    {
        first_err = Some(e);
    }
}
```

**FOUR broadcast sites, not one. The review named one; sweep F found the
other three, and every one of them is reached by this arc.** Measured:

```
$ grep -n "view.on_edit(self, &edit)?" src/buffer.rs
1033:            view.on_edit(self, &edit)?;
1250:                view.on_edit(self, &edit)?;
1288:            view.on_edit(self, &edit)?;
$ grep -n "view.on_edit(self, edit)?" src/buffer.rs
1543:                view.on_edit(self, edit)?;
```

| site | enclosing fn | who reaches it |
|---|---|---|
| `:1288` | `run_rope_edit_and_broadcast` | `apply_edit`, `apply_edit_skip_intercepts` — **the one the review named** |
| `:1250` | `run_rope_edit_and_broadcast`, **the no-op early-return arm** | every `NoOp` outcome — including **Q#GB5's `ensure_slot` lock**, which is exactly `set_generated_contents(buf, "")` |
| `:1033` | `run_remote_rope_stages` | `apply_remote_crdt_op` — a **replica importing the owner's write** |
| `:1543` | `broadcast_on_edit` | **`undo` and `redo`** — the command this whole arc exists because of |

Two of the three the review did not name are load-bearing for this arc
specifically. `:1250` is the path `NoOp` takes, and §3.4 treats `NoOp` as
a **success** that leaves the buffer generated-locked — but a view
erroring there today both strands the later views *and* converts the
success into an `Err`. `:1033` is how a locked generated buffer's write
reaches a replica at all, so a strand there is a mirror that paints from
stale offsets on the frontend the round-trip mark exists to protect.

**All four change**, to the same continue-and-retain-first-error shape. A
fix applied to one, or to two, would leave the same rope with different
broadcast semantics depending on which entry point wrote to it — the
defect class that has now produced five findings across four rounds.

**Why this changes the shipped path for ordinary edits too, deliberately.**
The alternative is a generated-only broadcast variant, which would give
one rope two broadcast semantics depending on who wrote to it. That is
the *exact* defect class that has now cost this arc four review findings
across three rounds — a rule derived for one mechanism and applied to a
second whose ordering differs. Continuing is also strictly better on its
own terms: no caller benefits from a view being skipped, and a view that
errors already cannot veto the rope mutation, which happened three stages
earlier. **Blast radius, named:** `apply_edit`, `apply_edit_skip_intercepts`,
`undo`, `redo`. The observable change is that a *later* view now sees an
edit it previously missed; no error is swallowed, because the first is
retained and returned.

**The cleanup each variant triggers.** `entry` is the `read_only` value
observed on entry.

| outcome | history | `mark_clean` | `read_only` after | binding action |
|---|---|---|---|---|
| `Applied` | **cleared** | yes | `true` | fan out `Edit`, then `Ok` |
| `NoOp` | **cleared** | yes | `true` | fan out `Edit`, then `Ok` |
| `Rejected` | untouched | no | **restored to `entry`** | `Err`, no fan-out |
| `AppliedThenFailed` | **cleared** | **no** | `true` | **fan out carried `Edit`, then `Err`** |
| `Diverged` | **untouched** | no | `true` | distinct surfaced `Err`, no rope `Edit` |

`editing_in_progress` is cleared on **all five**, unconditionally.

**Why `NoOp` clears — the rule that replaces revision 3's.** The
invariant is a property of the **buffer**, not of the write: *a buffer
that is generated-locked carries no history.* Every outcome that leaves
the buffer generated-locked therefore clears, and `NoOp` leaves it
locked because the call succeeded. `Rejected` is the only success-shaped
exception and it is not one — the buffer is not newly generated, so
there is nothing for the invariant to apply to. Stated this way the rule
needs no reference to `revision` at all, which is what makes it
mode-independent.

**Why `Rejected` restores rather than relocks.** Revision 3's "relock
unconditionally" was justified by "the contract is *leave it genuinely
immutable*" — true of a write that **happened**. A refusal is not a
write. Restoring the entry value keeps the refusal total: a fresh buffer
stays writable, an already-generated buffer stays locked, and no caller
can lock a buffer by failing to write to it.

**Why `Diverged` must surface rather than be cleaned.** This is the
variant the review specifically asks about, and the honest answer is
that **this arc cannot fix it**:

- The rope is intact and the CRDT is not. Nothing local reconstructs the
  deleted range — loro exposes no rollback at this seam, and the
  `export_updates_since` that would name the delta runs after both ops.
- The rope still contains the pre-edit bytes, but the CRDT UndoManager is
  the only existing **CRDT-native inverse record** for the successful
  delete. Clearing it would discard the one operation a later repair
  lane might use to reconcile the document. So `Diverged` clears
  nothing; this arc does not invoke that undo automatically.
- The common poison helper sets `read_only = true`, which stops ordinary
  local edits and remote imports. It does **not** stop an owner-generated
  write — that path exists to cross the lock — so quarantine is also exit
  0 of the generated preflight and authoritative apply below.
- It returns a **distinct** `BufferError` variant rather than reusing
  `CrdtRejected`, and the Lua binding surfaces it via
  `pmacs.editor.set_status` rather than swallowing it. A caller must be
  able to tell "your op was refused, nothing happened" from "this
  buffer's CRDT and rope no longer agree."

**`read_only` does NOT contain a divergent CRDT, and revision 5 asserted
that it did. Corrected in revisions 6 and 7.** Three outbound snapshot
paths do not consult `read_only` — they read `crdt_state()` and export
directly:

- **explicit initial target**, `initial_target_snapshot` at
  `src/daemon.rs:1873-1897`, whose bytes become the new session's
  `InstanceMessage::BufferSnapshot` at `:1996-2029`;
- **legacy no-target attach**, `send_buffer_snapshots` at
  `src/daemon.rs:2544-2586`: `buf.crdt_state()` then
  `crdt.export_snapshot()`;
- **buffer-follow**, `export_buffer_snapshot` at
  `src/daemon.rs:2693-2708`: `registry.get(buffer_id)` →
  `buf.crdt_state()?` → `crdt.export_snapshot()`.

None reads `read_only`, and none can — `read_only` means "no ordinary
local edits or remote imports", which is a statement about *inbound*
mutation. A replica attaching after the divergence therefore receives
**the divergent CRDT** as its authoritative document, while every daemon
window still paints the **old rope**. The explicit-initial-target route
is the normal modern attach path; the legacy loop is not a proxy for it.
The lock contains exactly the direction that was already safe and none
of the direction that was not.

**The fix: a quarantine flag installed at common divergence detection.**
`Buffer` gains one more private field, set by
`quarantine_divergence` before the outcome reaches either a generated or
ordinary public API, and never cleared by this arc:

```rust
/// Set when a CRDT mutation landed without its rope counterpart.
/// While true this buffer's CRDT must not be published: it no longer
/// projects to what any window shows.
crdt_quarantined: bool,
```

Five gates:

1. `initial_target_snapshot` returns a named `Err` before export. Its
   caller already sends `InitialTargetFailure`, unregisters the
   provisional frontend view and returns without publishing a snapshot.
2. `send_buffer_snapshots` already `continue`s on missing CRDT state and
   export failure; quarantine takes the same `continue`, with its own log
   line.
3. `export_buffer_snapshot` already returns `Option`; quarantine returns
   `None`, with its own log line.
4. `queue_daemon_origin_crdt_op` must not queue ops from a quarantined
   buffer, for the same reason — a delta on top of a divergent document
   propagates the divergence rather than the edit.
5. `generated_preflight` and `apply_generated_edit` both return the new
   `CrdtQuarantined` refusal. The first prevents an interactive unfold;
   the second is authoritative after the borrow boundary.

**Why quarantine rather than immediate repair.** Repair means either
invoking the CRDT's own undo of the landed op or re-deriving the document
from the rope, and both are decisions about *which side wins* that this
arc has no standing to make: the rope is what the user is looking at, the
CRDT is what replicas already hold, and if any replica has already
received the divergent snapshot the answer changes again. Quarantine is
the minimal correct action — it stops the divergence spreading and leaves
every input a repair lane would need intact. **Repair stays deferred
(§8), and revision 6 does not claim otherwise.**

**What quarantine costs, stated:** a buffer that hits `Diverged` stops
collaborating **and stops accepting owner refreshes**. Replicas attaching
later see no snapshot for it and continue to show whatever they had. An
explicit-initial-target attach fails rather than opening the wrong bytes.
That is a visible degradation, and it is the correct one — the
alternative is silent disagreement between what the user sees and what a
replica edits, or a later owner write compounding a state no longer
described by one rope.

**Scope, stated plainly: `Diverged` is a PRE-EXISTING hazard this arc
exposes, not one it creates.** `apply_edit` and
`apply_edit_skip_intercepts` reach the same two-op replace today and
report it as an ordinary `CrdtRejected`; nothing in the tree
distinguishes it. Making it a named variant is this arc's contribution;
**repairing the divergence is not, and is recorded in §8 as its own
lane.** Splitting a CRDT `Replace` into a single transactional op, or
reconciling the two, is loro-level work with no bearing on generated
buffers specifically.

**The ordering, with every exit path named.** The method returns the
outcome intact; only the borrow-free binding finisher above converts it
to Lua success/error after performing any required fan-out.

```rust
pub fn apply_generated_edit(&mut self, op: EditOp<'_>) -> GeneratedOutcome {
    // (0) A prior CRDT-only mutation poisoned this buffer. Generated
    // writes cross read_only, so the quarantine needs its own refusal.
    if self.crdt_quarantined {
        return Rejected(CrdtQuarantined { .. });
    }
    // (1) Q#GB10: path-backed refusal. Before any state change.
    if self.file_path.is_some() {
        return Rejected(GeneratedWriteOnFileBuffer { .. });
    }
    // (2) Q#GB15: this buffer's read_only is an identity protection.
    if self.identity_protected { return Rejected(ReadOnly { .. }); }
    // (3) re-entrancy gate — begin_edit's SECOND check, not its first.
    if self.editing_in_progress { return Rejected(ConcurrentEdit { .. }); }
    // (4) bounds pre-validation, so an invalid range costs nothing.
    if let Err(error) = self.validate_op_bounds(&op) {
        return Rejected(error);
    }

    let entry_read_only = self.read_only;
    self.editing_in_progress = true;
    self.read_only = false;                       // the ONLY unlocked interval
    let outcome = self.apply_generated_inner(op); // -> GeneratedOutcome
    match &outcome {                              // (5) per-variant cleanup
        Applied(_) | NoOp(_) => {
            self.read_only = true;
            self.clear_history();
            self.mark_clean();
        }
        AppliedThenFailed { .. } => {
            self.read_only = true;
            self.clear_history();
        }
        // The common detector installed both lock and quarantine before
        // this outcome crossed any public API.
        Diverged(_)          => {
            debug_assert!(self.read_only && self.crdt_quarantined);
        }
        Rejected(_)          => { self.read_only = entry_read_only; }
    }
    self.editing_in_progress = false;             // (6) unconditional, all paths
    outcome                                         // binding owns fan-out + conversion
}
```

| exit | when | `read_only` after | `editing_in_progress` | history | contents |
|---|---|---|---|---|---|
| (0) | CRDT already quarantined | unchanged (`true`) | unchanged | **untouched** | untouched |
| (1) | `file_path` is `Some` | unchanged | unchanged (`false`) | **untouched** | untouched |
| (2) | identity-protected (terminal) | unchanged (`true`) | unchanged | **untouched** | untouched |
| (3) | re-entrant on the same buffer | unchanged | unchanged (`true`, the outer edit's) | **untouched** | untouched |
| (4) | range out of bounds | unchanged | unchanged (`false`) | **untouched** | untouched |
| `Rejected` | mid-codepoint position, CRDT | **restored to entry** | `false` | **untouched** | untouched |
| `AppliedThenFailed` | a view rejected `on_edit` | `true` | `false` | **cleared** | **mutated; carried `Edit` must fan out** |
| `Diverged` | any error after CRDT mutation | `true`, quarantine set | `false` | **untouched** | rope untouched, **CRDT diverged** |
| `NoOp` | empty write over an empty rope | `true` | `false` | **cleared** | unchanged |
| `Applied` | the ordinary case | `true` | `false` | **cleared** | replaced |

**Why `end_edit` cannot be skipped.** It is line (6), unconditional and
outside the `match`, in the same function as line (3) that set it — there
is no caller who could return early past it, which is the whole reason
the transaction is one `Buffer` method rather than a binding-level pair.
Review round 2's P1-1 is right that a leaked `editing_in_progress` wedges
the buffer for **every** later edit (`begin_edit` `:726-731` and
`apply_edit` `:774-779` both refuse), and shipped
`set_generated_contents` avoids that hazard today only by never setting
the flag at all — which is also why it has no re-entrancy gate today, a
gap this closes.

**What bounds pre-validation is still for.** It is no longer load-bearing
for history (the `Rejected` variant covers that) but it is kept, for one
reason: it moves the most common caller error out of the unlocked
interval entirely, so an out-of-range op cannot even transiently unlock a
buffer. **It is not a substitute for the criteria** — review round 3's
P1-2 is exactly the trap of pinning the transaction through the one path
that never enters it (§6, Stage 2 criteria 15-16).

**Cost, stated rather than buried — and revision 4's outcome enum is the
larger half of it.** `run_rope_edit_and_broadcast` must distinguish
`Rejected` from `Diverged`, and today it cannot: both surface as
`Err(CrdtRejected)` because `apply_to_crdt_then_normalize_bytes` uses a
bare `?` on the second op (`src/buffer.rs:1155-1163`). Distinguishing
them means that function reporting whether **any** CRDT mutation landed
before the error, including an error from `export_updates_since`. That
is a real change to a shipped CRDT path, it is in Stage 2's scope, and it
is the reason `Diverged` is a *named* variant rather than a note — a
variant nothing can construct is not a design.

**Revision 5 withdraws revision 4's four-variant fallback.** Folding
`Diverged` into `Rejected` would apply `Rejected`'s cleanup: on a fresh
writable buffer it restores `entry_read_only = false`, leaving a buffer
whose CRDT and rope already disagree open to further writes. That
directly contradicts the containment argument above.

**Revision 6 keeps that withdrawal and widens the seam it rests on
(round 5, P1-2).** Revision 5 specified "a private delete→insert
classifier that accepts the two operations as closures". Two operations
is one too few: `export_updates_since` is a third fallible stage that
runs after *every* successful CRDT mutation, so a two-closure seam
cannot construct three of the seven cases in §3.4's table — the three
where revision 5's classification was itself wrong. The seam is instead
**the `crdt_mutated` flag** described in §3.4, and the injectable
closures are the CRDT primitives **and** the export. Production supplies
the loro calls; `#[cfg(feature = "crdt")]` unit tests force a successful
delete followed by insert failure, and separately force export failure after successful
`Insert`, `Delete` and `Replace` mutations. The tests make every
post-mutation failure class constructible without adding a public
fault-injection API, and `cargo test --lib --features crdt` is their
gate. If that extraction proves larger than expected, Stage 2 stops for
review; it does not silently weaken the approved cleanup table.

`validate_op_bounds` is a new
private helper duplicating the bounds arithmetic `Rope::insert` /
`delete` / `replace` already perform (`RopeError::OutOfBounds`,
`src/rope.rs:371-383`). It is O(1) and it is duplication; the alternative
is a dry run, and there isn't one. Named in §7 as a bet.

---

## 4. Decisions

*Reading order note: Q#GB15–18 are new in revision 3 and sit **between
Q#GB7 and Q#GB8** rather than at the end, because each descends directly
from the decision above it — Q#GB15 and Q#GB16 are the two consequences
of §2.11's finding that `read_only` is not this arc's flag, and Q#GB17
and Q#GB18 are what review P1-1 and P1-2 turned into decisions. The
numbering is chronological; the placement is topical.*

**Q#GB1 — The streaming primitive.** `Buffer::apply_generated_edit(op)`,
exposed as `{ generated = true }` on the three Lua mutators.
`set_generated_contents` becomes its whole-buffer wrapper, keeping name,
**Lua** signature and behavioral tests; its Rust return becomes
`GeneratedOutcome` so a failed-but-applied edit survives to the fan-out.
Rationale and rejected alternatives: §3.

**Q#GB2 — `generated` is additive; `bypass_intercept` stays.** Seven
call sites outside `builtin/` depend on `bypass_intercept`, including
`tests/folding_stage2_acceptance.rs:1296-1315`, which pins that a bypass
edit still triggers the Q#FD19 interactive unfold. Redefining the
existing key would silently change that pinned seam. `generated = true`
implies bypass; passing both is legal and `generated` wins (it is
strictly stronger); passing `generated` on a buffer with no intercept is
legal (Class C would use it if it ever adopts).

**Q#GB3 — A generated write gets its OWN `run_buffer_edit` arm. Reversed
in revision 3 (review P1-1).**

Revision 2 said "a generated write goes through `run_buffer_edit`'s
bypass arm". **That is unimplementable** — the bypass arm is
`run_bypass_edit`, which calls `begin_edit`, which calls
`ensure_writable` first (§3.4). `run_buffer_edit`
(`src/lua_bindings/mod.rs:1353-1374`) grows a third arm **and becomes the
single owner of post-borrow fan-out**. The three mutator bodies remove
their separate `notify_buffer_edit_to_windows` calls, preventing the
generated success arm from notifying twice:

```rust
if generated {
    // (round 5, P2-7) Refusals decide BEFORE the unfold, so a rejected
    // attempt cannot leave a visible side effect behind. See below.
    generated_preflight(lua, id, &op)?;
    unfold_before_interactive_lua_edit(lua, id, edit_start_of(&op));
    let outcome = run_generated_edit(lua, id, op); // no begin_edit; §3.4
    finish_generated_outcome(lua, id, outcome)     // fan-out, then Ok/Err
} else if bypass_intercept {
    unfold_before_interactive_lua_edit(lua, id, edit_start_of(&op));
    let edit = run_bypass_edit(lua, id, op)?;
    notify_buffer_edit_to_windows(lua, id, &edit);
    Ok(edit)
} else {
    let edit = run_managed_edit(lua, id, op)?;
    notify_buffer_edit_to_windows(lua, id, &edit);
    Ok(edit)
}
```

**The refusal preflight, and why revisions 5 and 6 needed one.**
Revisions 3–5 unfolded *before* calling `run_generated_edit`, while four
refusals — path-backed, identity-protected, re-entrant, out-of-bounds —
were decided **inside** `apply_generated_edit`, one registry borrow
later. So an **interactive** generated attempt on a folded, file-backed
buffer would **open the fold** and then report that nothing was touched.
Revision 7 adds a fifth refusal: a prior CRDT divergence. It must run
before the unfold for the same reason, and it is more important than the
other four because another generated write can compound the poisoned
state. §3.4's contract says exits 0–4 are "before any state change"; a
fold is state, and it is the state the user can see.

`generated_preflight` is a **read-only** `with_registry` borrow that
evaluates §3.4's exits 0–4 against `&Buffer` and returns their errors
verbatim. All five are decidable without mutation, so nothing is lost by
asking early.

**`apply_generated_edit` still re-checks all five, and that is not
redundancy to remove.** The borrow is released between the preflight and
the apply, so the preflight is an *optimization of the error path*, not
an authority. `Buffer` remains the only authority — which is the same
reason §3.4 keeps the whole transaction in one method. The cost is that
five cheap predicates run twice on the refusal path and once-plus-once on
the success path; the alternative is an unfold that survives a refusal.

**Considered and rejected: drop the unfold from the generated arm.** That
would make refusals safe by removing the behaviour entirely, but Q#GB3
keeps the unfold deliberately — an interactive `M-x compile` into a
folded `*compilation*` should reveal what it wrote — and removing it
would be a silent behaviour change to the pinned Q#FD19 seam. Narrowing
the contract instead ("before any state change *except folds*") was also
rejected: it makes the contract unfalsifiable exactly where a user can
see it.

**Note the asymmetry this leaves, deliberately.** The `bypass_intercept`
arm still unfolds before a write that can fail — but its only refusal is
`ensure_writable`, which is pre-existing behaviour on a pre-existing
path, and widening the preflight to it would change a shipped seam this
lane does not own. Named rather than silently fixed.

`run_generated_edit` mirrors `run_bypass_edit`'s borrow shape but returns
the single transaction's whole outcome rather than calling `begin_edit`
+ `apply_edit_skip_intercepts`. `finish_generated_outcome` is the match
in §3.3 and is also used by the `set_generated_contents` binding.
`begin_edit` stays byte-identical, so no ordinary edit's error precedence
changes.

**What revision 2 got right and revision 3 keeps: the unfold seam.** The
generated arm still calls `unfold_before_interactive_lua_edit` at the
same point the bypass arm does, and for the same reason — the guard
already requires `InteractiveCommandOrigin::current()` to be `Some`
(`src/lua_bindings/mod.rs:1424-1429`), which is false for the
`process.after-tick` pump and true for `M-x compile`, and the op is
applied verbatim so the site is known up front (the round-5 F1
distinction the comment at `:1359-1367` records). Keeping it is the
no-change option.

**But revision 2's stated *reason* for keeping it is now known to be
half-false, and Q#GB16 is the consequence.** Revision 2 wrote "folding a
`*compilation*` buffer is possible, so changing this would be a silent
behaviour change to a pinned seam". Folding a `*compilation*` buffer is
possible **only until this arc locks it**: `pmacs.fold.fold` refuses
every `read_only` buffer at `src/lua_bindings/fold.rs:313`. So the arc
preserves the unfold-on-edit seam while silently killing the
fold-creation seam that feeds it. The unfold arm stays because it costs
nothing and because `FoldRegistry::unfold_containing` is registry-side
and unaffected by the lock; the *reason* is corrected here so a reviewer
does not inherit revision 2's version of it.

**Q#GB4 — History cleared per op, with a measurement obligation.** §3.3.
Deferred optimization: suppress recording instead of clearing.

**Q#GB5 — The lock-at-creation gap, and who closes it.** A
`{ generated = true }` write locks the buffer *after* its first call, so
between `pmacs.buffer.create(name)` and the owner's first generated write
the rope is writable. `dired.lua` (`claim_handle` → `paint`),
`listview.lua` (`ensure_panel` → `render`) and the search panel
(`ensure_search_panel` → the header write in `pmacs.project.search`) all
write synchronously in the same call, so the window is not observable.
**`compile.lua`'s `ensure_slot` (`:258-282`) does not** — it creates
`*compilation*` and returns, leaving it empty and writable until
`start_run`. Recommendation: `ensure_slot` ends with
`pmacs.buffer.set_generated_contents(slot.buf, "")`, using the shipped
primitive; no third surface is needed.

**Amended in revision 2 (review P1-2), and the amendment is a hard
ordering constraint, not a caveat.** `ensure_slot` is
`buffer_named(name) or create` (`compile.lua:263`), and
`pmacs.compile.run` calls it **before** `start_run` validates
`opts.display` (`:1090` vs `:752-757`). §2.8 measures that a
`display = "bogus"` call today raises *and still leaves a foreign
`*compilation*` permanently un-editable*; with the empty write placed at
the end of `ensure_slot` that same failing call would **empty the buffer
and lock the rope**, unrecoverably. So the lock may only be installed
once **Q#GB13's ownership rule guarantees `slot.buf` is a buffer compile
created**. With ownership in place the buffer is provably fresh and the
placement in `ensure_slot` is correct; without it, no placement is.

**Revision 4: this recommendation is also the concrete caller that made
P1-1 direction A load-bearing, and the dependency runs both ways.**
`set_generated_contents(slot.buf, "")` on a buffer that is already empty
is a **semantic no-op** — it takes `src/buffer.rs:1245-1253`'s early
return. Under revision 3's `revision`-keyed cleanup that call would have
locked the slot while leaving any pre-existing history intact and the
buffer marked modified, which is the opposite of what "lock it at
creation" is for. §3.4's `NoOp` variant clears unconditionally, so the
recommendation is sound again. Stated here rather than only in §3.4
because a reader reaching Q#GB5 first should not have to derive it: **the
correctness of this placement depends on two decisions in other
sections** — Q#GB13's freshness guarantee and §3.4's `NoOp` cleanup —
and criterion 16b is what pins the second.

**Q#GB6 — Clamp each window coordinate against its OWN post-edit bound.**
§2.6 measures a shipped defect: a shrinking generated write leaves
`win.cursor` past the end of the rope, and neither paint nor `C-p`
recovers it. Recommendation: clamp in `EditorCore::notify_buffer_edit`
— a **clamp**, not a call to `rebuild_views_for`, because a rebuild is
O(buffer length) and would run per streaming op.

**Revised in revision 2 (review P2-4). Revision 1 said "clamp when the
buffer shrank", which conflates two different extents.** The two
coordinates are bounded by different things:

- **`win.cursor` is a byte position** (`src/window.rs:366-367`, "Byte
  position of this window's cursor"), bounded by `Buffer::len()`.
- **`win.view_top` is a line index** (`src/window.rs:373-374`, "First
  buffer **line** shown at the top of this window's viewport"), bounded
  by `TextView::line_count()` (`src/text_view.rs:67`).

A replacement can **grow in bytes while collapsing many lines into one**
— `"a\nb\nc\nd\ne\nf\n"` (12 bytes, 7 lines) replaced by a single
80-byte line — leaving `view_top` invalid on a write that a byte-length
comparison calls a *growth*. So the trigger cannot be "the buffer
shrank": the clamp runs **unconditionally**, each coordinate against its
own bound, exactly as `rebuild_views_for` already does
(`src/editor_core.rs:1875-1879`, which clamps `cursor` against `len` and
`view_top` against `line_count().saturating_sub(1)`).

**Argued from the types and from `rebuild_views_for`'s existing shape,
not measured** — unlike §2.6's cursor case, the `view_top` case needs a
scrolled window to stage and was not staged. §6 Stage 1 criterion 8b is
what turns the argument into a pin.

**A THIRD window coordinate, and it crashes rather than dangles. New in
revision 6 (round 5, P1-5).** Every window also owns an optional
`Selection`, and `Selection::anchor` is a **byte position**
(`src/window.rs:120-130`, "Where the selection began"). Revisions 1–5
listed two coordinates and there are three.

The anchor is worse than the other two because nothing downstream
tolerates it being out of range. `EditorCore::region_bytes`
(`src/editor_core.rs:4184-4191`) does:

```rust
let (lo, hi) = self.active_region()?;              // Window::region(), :472-479
let mut out = vec![0u8; (hi - lo) as usize];
buf.snapshot_rope().slice(lo, hi, &mut out);
```

and `Rope::slice` asserts its bounds — `debug_assert!(end <= self.len())`
at `src/rope.rs:145`. `Window::region` (`src/window.rs:472-479`) returns
`(anchor, cursor)` in canonical order with **no clamping of either**. So
a stale anchor is not a cosmetic dangle: **#191 reproduced the crash** —
select bytes 0..30 in a generated buffer, let the owner rewrite it to two
bytes, press copy, panic at `src/rope.rs:145`. A shrinking refresh under
a live selection is not an exotic sequence; it is `g` on a listview panel
with a region marked.

**The rule: clamp-or-clear, per window, in BOTH functions.** For every
window whose `buffer_id` matches — the `windows.values_mut()` loop that
both functions already run:

1. `win.cursor` → clamp to `len`.
2. `win.view_top` → clamp to `line_count().saturating_sub(1)`.
3. `win.selection` → clamp `anchor` to `len`; **then, if the clamp
   collapsed the selection — `anchor == cursor` afterwards and at least
   one endpoint actually moved — set `selection = None`.**

**Rule 3 is not invented here; it is the tree's own answer to the same
question.** `src/terminal/view.rs:715-721` normalizes the terminal's
selection against a shrinking scrollback and does exactly this:

```rust
state.selection = state.selection.and_then(|selection| {
    let anchor = clamp_or_clear(&rows, selection.anchor)?;
    let head = clamp_or_clear(&rows, selection.head)?;
    let collapsed_by_clamp =
        anchor == head && (anchor != selection.anchor || head != selection.head);
    (!collapsed_by_clamp).then_some(TerminalSelection { anchor, head })
});
```

The terminal subsystem solved this for `TerminalSelection` and the window
`Selection` never got the same treatment. Adopting the same rule rather
than a fresh one is the point: a bare clamp would leave a zero-width
"active but empty" selection that `Selection`'s own doc says is legal
(`src/window.rs:123-126`) but that the user never asked for, and
`collapsed_by_clamp` is precisely the distinction between "the selection
survived, shortened" and "the selection's content is gone".

**Both functions, because they have different callers and neither
subsumes the other:**

- **`notify_buffer_edit`** (`src/editor_core.rs:1836-1850`) clamps
  **nothing** today — it only forwards `on_edit` to `text_view` and
  overlays. This is the function a generated write reaches, so this is
  where the crash is fixed.
- **`rebuild_views_for`** (`src/editor_core.rs:1865-1882`) already clamps
  `cursor` and `view_top` and **does not touch `selection`**. It serves
  the `*help*` and `*buffer-list*` rewrites, which are Class C and shrink
  wholesale. The same crash is reachable there today, independently of
  this arc.

**Blast radius of a stale anchor beyond the crash**, so the fix is not
undersold: `Window::region` also feeds the presence broadcast
(`src/presence.rs:122-123`, `SelectionSnapshot`), so an out-of-range
anchor is published to peers as well as sliced locally.

Recommended for **Stage 1**, because Stage 1's adopters refresh shrinking
panels constantly and because it fixes terminal copy mode retroactively.
**The selection half is not optional within that**: it is the only one of
the three that panics, and it is reproducible today. Alternative if the
user prefers a narrower Stage 1: its own lane, in which case Stage 1 must
say so out loud rather than inherit it silently.

**Cross-lane note.** Per the boundary in §9b, this rule is #188's to
specify and #191's to implement, and both must describe the same rule.
The text above is the specification; #191 adopts it rather than restating
it.

**Q#GB7 — No unlock ships in this arc. Revision 5 chooses the fallback
revision 4 named (review round 4, P1-4).**

Revision 2 recommended `pmacs.buffer.unlock_generated(buf)` — a one-way
clear of `read_only`, shipped in Stage 1 — on the strength of sweep B's
finding that the two halves of the protection are asymmetric: the
intercept half is removable (`remove_intercept`,
`src/lua_bindings/mod.rs:3433`, used by the REPL at
`repl/init.lua:325-327`) while the rope half is one-way from Lua. That
observation stands. **The capability revision 2 derived from it does
not**, on two independent counts, both of which the review is right
about.

**First: an unbounded clear of `read_only` is not a generated-buffer
capability at all.** §2.11 measures that the flag serves three unrelated
policies. `unlock_generated` as revision 2 wrote it — "clears `read_only`
and nothing else" — would let any Lua caller disable a **live terminal
identity buffer**'s protection (`src/terminal/session.rs:305`), which
this arc never locked, whose owner set it to refuse host edits, undo,
redo **and remote CRDT imports** alike, and which is Lua-reachable
(`pmacs.terminal.open` returns its id;
`pmacs.terminal.is_terminal(buf)` exists at
`src/lua_bindings/mod.rs:8858-8867`). That is a strictly larger capability
than the one the arc adds, granted by accident.

**Second: it does not achieve its own stated purpose.** Revision 2 sold
it as the escape from an accidentally bricked `*scratch*`. It is not:
by the time anyone reaches for it, `set_generated_contents` has already
replaced the contents **and cleared the history** (§3.4). Unlocking
returns writability to a buffer whose data is gone. The recovery
scenario that justified moving this from a deferral to Stage 1 work was
never a recovery.

**Revision 4's proposed bound was not provenance.** It refused only
when `identity_protected` was true. That proves “this is not a declared
terminal identity buffer”; it does **not** prove “the generated-write
primitive installed this lock.” As revision 4 itself admitted,
`unlock_generated` could therefore release any non-identity-protected
Rust lock, including one a future owner installed for an unrelated
reason. The live Q#GB7 text simultaneously promised to refuse exactly
those locks. Both statements cannot be the approved contract.

**The decision: remove the capability, not the promise.** Neither stage
adds `pmacs.buffer.unlock_generated`, and Q#GB15's field is used only to
refuse generated writes to intrinsic identity buffers. There is no Lua
clear of `read_only`.

This leaves the standing asymmetry visible rather than pretending to
close it: `remove_intercept` is exposed while `set_read_only` is not
(`src/lua_bindings/mod.rs:3072-3078` and
`docs/agent-handoff.md` §4). That asymmetry is deliberate today because
the rope lock protects more than generated buffers. A safe inverse needs
a lock-kind/provenance representation, or an owner-specific transition
whose preconditions prove the caller owns the state. Neither is required
to stop undo destroying generated output, and neither should be smuggled
into this arc for an escape that cannot restore the overwritten data.

The future concrete consumer remains wdired in dired Stage 3. That lane
must frame the transition it needs—generated listing to editable rename
surface—against its own owner handle and lifecycle. It may choose the
eventual `read_only` policy enum; it does not inherit a general-purpose
unlock from here.

**What Stage 1 loses, and why that is correct.** Nothing. Stage 1 adopts
`set_generated_contents`, which is **already public on `main`**, on two
more buffers. It therefore adds no brick capability the tree does not
already ship, and revision 2's argument that Stage 1 needed an escape
hatch applied equally to `main` — which is a sign the argument was about
the shipped primitive, not about Stage 1. The `*scratch*` exposure sweep
B found is real, and it is real **today**; it is recorded in §8 as a
pre-existing hazard this arc neither creates nor closes.

**Q#GB15 — `read_only` gains an intrinsic-identity guard, not a
provenance companion. New in revision 3, narrowed in revision 5
(review P1-3, sweep C; review round 4 P1-4).**

**Revision 4 replaces revision 3's `generated_lock` with an intrinsic
`identity_protected`, because review round 3's P1-3 showed provenance
cannot be inferred from the flag's history.**

Revision 3 proposed `generated_lock: bool`, meaning "this buffer's
`read_only` was set by a generated write", maintained by a third rule:
*every* `set_read_only` call clears it. That rule breaks a seam this very
document prescribes. `tests/terminal_copy_mode_acceptance.rs:578-584`
does exactly this cycle, with a comment explaining why:

```rust
// `read_only` refuses the upgrade's own bookkeeping path the same
// way it refuses everything else, so lift it around the upgrade.
buffer.set_read_only(false);
buffer.upgrade_to_crdt(2).expect("upgrade");
buffer.set_read_only(true);
```

Under revision 3's rule the final `true` yields
`read_only && !generated_lock`, so the **next owner refresh** of that
snapshot is refused as someone else's lock. Q#GB12 and Stage 2
criterion 4 prescribe the same lift-and-restore idiom, so revision 3
invalidated its own test strategy. The defect is not the rule's details;
it is that a *derived* fact has to be maintained correctly by every
mutation of the thing it is derived from, and `set_read_only` is `pub`
with callers this document does not control.

**The fix is to stop deriving it.** `Buffer` gains one private field that
is a property of **what the buffer is**, not of who last locked it:

```rust
/// Whether this buffer's read-only state is an intrinsic identity
/// protection rather than an ordinary lock. Marked once during owner setup,
/// by an owner that means "the host may not edit this at all"; never
/// derived from `read_only` and never changed by `set_read_only`.
identity_protected: bool,
```

Two rules maintain it, and `set_read_only` is not one of them:

1. `Buffer::mark_identity_protected()` — a new **crate-private,
   monotonic** method that can only set the field to `true`, called once
   by `TerminalSession::open` beside its existing `set_read_only(true)`
   (`src/terminal/session.rs:305`). There is no “false” operation and no
   Lua surface, so “set once” is enforced rather than a caller convention.
2. `apply_generated_edit` refuses iff `identity_protected` (§3.4 exit 2).
   It never writes the field.

**The lift-and-restore seam is now unaffected**, because
`identity_protected` is `false` for a snapshot buffer and stays `false`
through any number of `set_read_only` cycles. Q#GB12's prescription and
Stage 2 criterion 4 need no change, which is the test that the rule is
right.

**Why declaration beats inference, stated as a rule rather than as a
patch.** Inference required every mutation of `read_only` to maintain a
derived fact; P1-3 is the proof that it does not. Declaration is sound
for the one question this field now answers: *may an owner-authorized
generated write ever edit this buffer?* Terminal identity says no,
independently of temporary `read_only` lifts. It is deliberately **not**
used to answer who installed an ordinary lock; Q#GB7 no longer asks it
to.

**Rule 1's refusal is the half revision 2 did not have, and it closes a
hole in the SHIPPED primitive** (sweep C item 1).
`Buffer::set_generated_contents` today does `self.read_only = false`
unconditionally (`src/buffer.rs:546`), so
`pmacs.buffer.set_generated_contents(term_buf, "junk")` on a live
terminal identity buffer overwrites its contents and re-locks it as
though the primitive owned it. Nothing in the tree refuses that, and no
test covers it. That write-direction hole is the field's sole purpose.

**The alternatives, and why not.**

- *A registry-side set of generated-locked ids, held as Lua app-data.*
  This would exist only to resurrect Q#GB7: a second source of truth that
  can drift from the flag, plus a pruning obligation on buffer removal —
  the shape the terminal-config lane records as "`prune` **reacts** to
  buffer removal". Rejected along with the unlock.
- *Replacing `read_only: bool` with an enum.* Cleaner in principle,
  and it would let §2.11's third policy (`document_bytes`) ask the
  question it actually means. It also churns `ensure_writable`, all six
  gated paths, `is_read_only`'s seven callers and the public
  `set_read_only` signature — a refactor this arc would be smuggling.
  Named as the right eventual shape in §8, not adopted.

**Cost, stated:** one bool per buffer; one new crate-private monotonic
method with exactly one production caller; **no invariant to maintain
against `set_read_only`**, because the field is never derived from it;
and one new refusal that changes shipped `set_generated_contents`
behaviour, so it lands in Stage 2 with the rest of Q#GB10's changes to
that function, not in Stage 1.

**Q#GB16 — The lock silently disables fold creation on every buffer it
touches. New in revision 3 (sweep C item 2).**

`document_bytes` (`src/lua_bindings/fold.rs:310-318`) is Q#FD11's
"normal document buffer" guard and it is spelled `if buffer.is_read_only()
{ return Ok(None); }`. Its two consumers are `pmacs.fold.fold`
(`:67-70`, which then sets the status `fold rejected: not a document
buffer` and returns `false`) and `pmacs.fold.unfold`'s
normalize-an-arbitrary-range fallback (`:108`).
`tests/folding_acceptance.rs:570-590`
(`read_only_buffer_is_rejected`) pins the behaviour, and its comment
records the intent the guard was written with: "terminals are read-only,
so a read-only buffer is not foldable."

So the moment Stage 1 locks dired listings and listview panels, and
Stage 2 locks `*compilation*`, `*shell-command*` and `*search-results*`,
**`pmacs.fold.fold` starts answering `false` on all five families** —
with a status message that is now false ("not a document buffer"), on a
seam nothing in this arc's acceptance would notice, and against a guard
whose author meant "terminal", not "generated".

**Recommendation: name it, do not silently accept it, and do not fix it
here.** Three options, with the recommendation being (a):

- **(a) Accept, and pin the acceptance.** A generated buffer arguably
  *should not* be foldable — its contents are replaced wholesale and any
  stored fold range is invalidated on every refresh anyway. Then the
  change is intended, and Stage 1 owes **an explicit criterion asserting
  it**, plus the status string corrected to say `read-only`, not "not a
  document buffer". Cheap, honest, and it converts a silent behaviour
  change into a stated one.
- **(b) Preserve foldability** by changing the guard to
  the intrinsic `identity_protected` predicate rather than the broad
  `read_only` predicate. Available once Q#GB15 lands, but it edits a
  pinned Q#FD11 seam for a use case nobody has asked for.
- **(c) Do nothing and say nothing.** Rejected: this is exactly the
  defect class the review's findings 1 and 3 are instances of.

Under (a) the only code change is the status string; the substance is
the criterion. Stage 1, because Stage 1 is where the first three
families get locked.

**Q#GB17 — The transaction shape.** §3.4. One `&mut Buffer` method, its
own `run_buffer_edit` arm, `begin_edit` untouched, ten named exits, and
cleanup driven by an explicit `GeneratedOutcome` — **not** by
inferring one from `revision`, which revision 3 did and which was wrong
in three directions (§3.4). New in revision 3 (review
P1-1).

**Q#GB18 — Route the two broken identity consumers by owned `BufferId`.
New in revision 3 (review P1-2).**

§2.10's census finds exactly two sites that a disambiguated name breaks,
with six downstream consumers between them. Q#GB13 removes the
*adoption*; this removes the *recognition* that adoption was hiding.

**`listview.lua` (Stage 1, with Q#GB13's ownership fix).** `panels`
becomes a list of records rather than a name-keyed map, with two
lookups instead of one:

- `panel_for_requested_name(name)` — matches `p.requested_name`, the
  `spec.name` the caller asked for. Stable across disambiguation, so
  repeated `listview.open{ name = "*references*" }` finds the same panel.
- `panel_for_buffer(buf)` — scans `p.buffer == buf`. This is what
  `listview.visit`, `listview.refresh`, `listview.quit` and
  `listview.open`'s capture guard use.

The list-and-scan shape is deliberate and is dired's, for the reason
`dired.lua:123-127` already records: two `BufferIdLua` values for the same
buffer are **distinct userdata**, so `panels[buf]` would miss even for the
same buffer;
`handle_for_buffer` (`dired.lua:142-148`) compares with `==` instead, and
`compile.lua`'s `slot_for_buffer` (`:200-206`) does the same. Three
existing implementations of one shape; listview adopts it rather than
inventing a fourth.

**And listview needs dired's *other* half too, which is easy to miss.**
`grep -n on_removed builtin/runtime/listview.lua` returns **nothing** —
listview registers no buffer-removal callback, unlike compile
(`:277-279`) and the search panel (`default.lua:876-883`). Today that is
harmless because `ensure_panel` re-checks `p.buffer:is_valid()` on every
`open` (`:93-94`) and a name-keyed map holds at most one entry per name.
A **list** does not self-limit: kill and reopen `*references*` ten times
and a naive list holds ten records, nine of them dead, and
`panel_for_buffer`'s scan walks all of them. So the list must compact on
scan, exactly as `dired.lua:132-140`'s `live_handles()` does. Naming it
here because "swap a map for a list" reads like a one-line change and is
not.

**`compile.lua` and the search panel (Stage 2, with Q#GB13's ownership
fix). Rewritten in revision 4 (review round 3, P2-4).**

`is_generated_buffer` stops comparing names. Its two owners are in
different files (`compile.lua`'s `slots`, `default.lua`'s
`search_panel`), so the predicate needs a seam — and **revision 3 chose
the wrong one.**

Revision 3 had `ensure_search_panel` call
`pmacs.compile._register_generated_buffer(p.buf)`. That converts an
existing *guarded, optional* dependency into a hard one.
`default.lua:991-994` currently reads:

```lua
if cur
  and not (pmacs.compile
    and pmacs.compile.is_generated_buffer
    and pmacs.compile.is_generated_buffer(cur))
then
```

— a triple check, and it exists for a reason. `default.lua` is loaded by
`LuaHost::attach_editor` (`src/lua.rs:250-251`), while `compile.lua` is
loaded much later in `EditorState::new`'s runtime sequence
(`src/editor.rs:704`). `LuaHost` is `pub` and **nine existing test files
build one directly**, so a harness that has `pmacs.project.search` and no
`pmacs.compile` is not hypothetical — it is reachable with the pattern
those nine already use. A hard call to `pmacs.compile._register_…` inside
`ensure_search_panel` raises there.

**The decision: symmetric guarded optionality, not a shared registry.**
Each module answers for **its own** buffers, and each capture site ORs
the two through the guard shape that already exists:

- `compile.lua` — `is_generated_buffer(buf)` becomes
  `slot_for_buffer(buf) ~= nil`, which is already id-based (`:200-206`).
  It answers for `*compilation*` and `*shell-command*` **only**, which is
  the truthful scope and matches §1.4's warning not to read `ensure_slot`
  as covering the grep panel.
- `default.lua` — a local `search_panel_owns(buf)`, i.e.
  `search_panel ~= nil and search_panel.buf == buf`, exposed as
  `pmacs.project._is_search_panel` for the other direction.
- Each capture site checks its own predicate directly and the other
  module's **through the existing optional guard**:
  - `default.lua:991-994` keeps its triple check verbatim and gains
    `and not search_panel_owns(cur)`;
  - `compile.lua:762` gains the mirror-image guard,
    `and not (pmacs.project and pmacs.project._is_search_panel and
    pmacs.project._is_search_panel(cur))`.

**Three things this buys over revision 3's registry**, all of them
consequences of nobody owning a list of somebody else's buffers:

1. **No load-order constraint in either direction**, and no new one to
   document beside the three `src/editor.rs` already carries.
2. **No teardown obligation.** Revision 3's registry needed
   `on_removed`-driven unregistration, and a registry that only grows is
   the defect the terminal-config lane records as "`prune` **reacts** to
   buffer removal". Each owner's own table already tracks its own
   liveness (`slot_for_buffer` scans `slots`, `search_panel_owns` reads
   one field), so there is nothing to prune.
3. **Each predicate is answerable by the module that knows the answer**,
   so neither can go stale relative to the other.

**Cost:** the guard shape is written twice rather than once. That is the
existing pattern, and duplicating a four-line guard is cheaper than a
cross-module registry with a lifetime.

**This needs its own pin, because no ordinary test reaches it** — every
`EditorState::new` loads both modules. §6 Stage 2 criterion 21 builds a
`LuaHost`, calls `attach_editor`, and drives search with no
`pmacs.compile` present.

Alternative considered and rejected: leave `is_generated_buffer`
name-based and simply never disambiguate compile's buffers. Rejected
because Q#GB13's whole argument is that a foreign `*compilation*` must
not be adopted, and refusing to adopt without disambiguating means
raising — which turns a name collision into a failed `M-x compile`.

**Q#GB8 — The REPL is out of this arc.** §2.5. Same root cause, different
remedy, its own lane. Its measured exposure is recorded above so the next
scout starts from evidence.

**Q#GB9 — Class C is out of this arc.** `*buffer-list*`, `*help*` and
`*workers*` are generated but were never claimed to be protected, so
nothing about them is *defeated*. Making them immutable is a product
decision about `COHERENCE.md` §14's list and output-channel primitives,
not a bug fix, and it should not ride a bug-fix arc. `*workers*`
additionally writes from Rust with its own fan-out pair and already
`mark_clean`s, so it is not a like-for-like conversion.

**Q#GB10 — Refuse a generated write on a path-backed buffer; then, and
only then, mark clean.** Rewritten in revision 2 (review P1-3).

`set_generated_contents` leaves `is_modified = true` (measured), so every
adopter shows `*` in the mode line (`src/editor.rs:4129`) and in
`*buffer-list*` (`default.lua:395`). `workers_buffer::render` calls
`Buffer::mark_clean()` (`src/workers_buffer.rs:95`) and
`instance_buffer.rs:401` asserts the same for its own rendered buffer,
so marking clean is the established convention for a generated buffer.

**Revision 1's justification was wrong.** It said the flag "drives only
the mode-line indicator and the buffer-list column". §2.9 measures two
more consumers: `src/autosave.rs:363`, the skip that decides whether a
crash-recovery slot is written, and `src/desktop.rs:302`. Since
`{ generated = true }` is public Lua on any buffer id, a caller could
replace a **file-backed** buffer's contents, mark it clean, and suppress
autosave recovery for it.

**The rule, stated explicitly rather than left implicit:
`Buffer::apply_generated_edit` (and therefore `set_generated_contents`)
returns an error for a buffer whose `file_path()` is `Some`.** Then
`mark_clean` is unconditionally safe, because **both** consumers gate on
`file_path()` before they read the flag (`autosave.rs:359-364`,
`desktop.rs:298-303`).

Why refuse rather than the alternative "retain modified state for
path-backed buffers": the flag rule fixes only the flag. A generated
write on a file buffer would still **replace its contents and lock its
rope**, and §1.3 measured that Lua cannot unlock. Refusing bounds all
three harms with one rule, and it is the narrower capability.

**Verified non-breaking.** None of the six generated families is
path-backed: they are all `pmacs.buffer.create`d, and no builtin Lua sets
a buffer path — `grep -rn "set_path\|set_buffer_path" builtin` finds no
call sites (only a comment in `dired.lua:42` and `lsp.lua`'s own
`active_buffer_path` local). Path binding happens Rust-side in
`from_file` / `find_file` only.

**This changes shipped `set_generated_contents` behaviour** — both the
new refusal and `mark_clean` — and therefore the terminal snapshot, so it
belongs in Stage 2 alongside the reimplementation, not smuggled into
Stage 1.

**Q#GB11 — Staging.** §5.

**Q#GB12 — The revision guard becomes near-dead, and three tests break.**
After Stage 2, an external edit to `*compilation*` or `*search-results*`
is refused at the rope, so the Q#CM2 desync machinery (`check_rev`
`compile.lua:332`, `resync` `:309`, `search_panel_check_rev`
`default.lua:832`) can essentially no longer fire. Recommendation: **keep
it** — it is cheap, and a future Rust-side writer could still mutate the
buffer — but say so, and do not delete its tests. Three compile
acceptance tests inject intruder edits through `bypass_intercept`
(`tests/compile_mode_acceptance.rs:1040`, `:1106`, `:1305`) and **will be
refused** after conversion; they must lift `read_only` Rust-side first,
exactly as `tests/terminal_copy_mode_acceptance.rs:582-584` already does.
That is a concrete, verified integration cost of Stage 2, not a surprise
to discover during implementation.

**Revision 4: the lift-and-restore idiom this prescribes was briefly
invalidated by revision 3's own Q#GB15, and is now safe again.** Revision
3's `generated_lock` was cleared by every `set_read_only` call, so the
restoring `set_read_only(true)` would have left the buffer looking like
someone else's lock and the next owner refresh would have been refused
(review round 3, P1-3). Q#GB15's `identity_protected` is never written by
`set_read_only`, so the cycle is transparent and **this prescription,
Stage 2 criterion 4 and `acc16e` all need no change**. The seam is
`crdt`-gated, so §10 now names
`--test terminal_copy_mode_acceptance --features crdt` explicitly: a
default-feature sweep never compiles `acc16e` and proves nothing about
it.

**Q#GB13 — Ownership by handle is a prerequisite, not a follow-up.** New
in revision 2 (review P1-2). `listview.ensure_panel` (`listview.lua:95`),
`compile.ensure_slot` (`compile.lua:263`) and `ensure_search_panel`
(`default.lua:861-868`) adopt any buffer that shares their name. §2.8
measures the consequence today (a clobbered, permanently un-editable user
buffer — and, for compile, from a call that *raised*), and measures that
`M-x buffer.undo` is currently the **only** recovery. Locking the rope
removes that recovery, so the rule must land in the same stage as the
lock.

Recommendation: adopt the rule the tree already states at
`terminal.lua:300-305` and implements at `dired.lua:476-504` —
**ownership means "this buffer is in my handle table"**, a name collision
disambiguates `<2>`…`<99>`, and exhausting the limit raises rather than
adopting. Three writers, one shape, each in the stage that locks it:
listview in Stage 1, compile and search in Stage 2. Dired and terminal
already comply.

Alternative considered and rejected: a standalone Stage 0 that fixes all
three at once. Rejected because each writer's ownership fix is only
load-bearing for the stage that locks that writer, and a lone ownership
PR reads as unmotivated churn without the lock that makes it urgent. If
the user prefers the standalone shape, the acceptance criteria in §6 move
with it unchanged.

**Revision 3: Q#GB13 is only half the work, and revision 2 shipped the
half that is visible.** Disambiguating a name is not free — it changes
what a buffer is *called*, and five sites in `builtin/` recover identity
from what a buffer is called. Two of them break (§2.10 Class 1) and are
Q#GB18's. Stated as an ordering constraint so it cannot be split across
PRs: **within each stage, Q#GB18's routing change must land in the same
PR as Q#GB13's disambiguation for the same writer.** Disambiguate first
and you ship a listview panel whose `RET`, `g` and `q` are dead and whose
`q`-target capture is inverted; route first and you have written a
lookup nothing yet exercises.

**Q#GB14 — The lock is not observable from Lua, and the pins depend on
it.** New in revision 2, out of P1-1's fix. `describe.buffer` returns
`name`, `length`, `modified`, `view_count` and nothing else
(`buffer_info_table`, `src/lua_bindings/mod.rs:6352-6364`), so no Lua
assertion can read `read_only` directly. Two discriminators are
available and both are used in §6: a **`bypass_intercept` write**, which
lands on `main` and raises `` buffer `X` (id BufferId(n)) is read-only ``
once the rope is locked (measured, §2.4), and **Rust-side
`Buffer::is_read_only()`** (`src/buffer.rs:494`, already `pub`).
Recommendation: use both, and do **not** add a Lua surface for it — the
acceptance suites are Rust and need no new public API. Optional and
separable: adding `read_only` to `buffer_info_table` would be a
read-only introspection field with no new capability, useful if
Lua-level pins are ever wanted; it is not required by this arc.

---

## 5. Staging

**The proposed cut is endorsed, with two amendments.** The argument for
it is not the obvious one.

### Stage 1 — `generated-buffer-immutability-stage1`

`dired.lua` and `listview.lua` adopt `pmacs.buffer.set_generated_contents`.

- **Prerequisite, in this PR, before the lock (Q#GB13):**
  `listview.ensure_panel` (`listview.lua:95`) stops adopting a
  same-named foreign buffer. Ownership is the handle table (`panels`);
  a name collision disambiguates `<2>`…`<99>` and raises at the limit,
  matching `dired.lua:486-504`. **`dired.lua` needs no ownership work**
  — it already complies, which is why it is the cheaper of the two
  adopters.
- **In the SAME PR as that disambiguation (Q#GB18):** `panels` becomes a
  compacting list; `panel_for_current_buffer` is replaced by
  `panel_for_buffer(buf)` scanning `p.buffer == buf`, and
  `ensure_panel` looks up by `p.requested_name`. Four consumers move
  with it, including `listview.open`'s capture guard (`:118-123`).
  Ordering constraint, not a preference — see Q#GB13.
- `listview.lua:50-62` — `render`'s delete-all + insert-all becomes one
  `set_generated_contents(buf, body)`.
- `dired.lua:369-372` — `paint`'s whole-buffer replace becomes one
  `set_generated_contents(handle.buf, text)`.
- Both keep their erroring intercept (named error, per the layering at
  `terminal.lua:351-366`) and both keep `set_round_trip_input`.
- Plus Q#GB6's per-coordinate clamp, if approved.
- Plus **Q#GB16's fold decision** — under recommendation (a), the
  `fold.rs:68` status string, and the criterion that makes the change
  stated rather than silent.

**Revision 3 removed `unlock_generated` from Stage 1; revision 5 removes
it from the arc** (Q#GB7). Revision 2 put it here as "the escape from a
bricked buffer"; the escape does not recover anything (the history is
already cleared), and the brick it escapes is one `main` already ships,
since `set_generated_contents` is already public. Stage 1 adds no lock
capability that does not already exist, so it needs no door. Revision
4's attempt to restore the capability in Stage 2 used
`identity_protected` as though “not terminal identity” proved “generated
lock”; it does not. No stage adds the binding.

**Revision 2 grew Stage 1 by two prerequisites and one reversal.** The
ownership rule is load-bearing for the lock rather than adjacent to it,
and it stays. The unlock does not, per the paragraph above. Stage 1
is still **not** a pure-Lua change — Q#GB6's clamp is Rust, and under
Q#GB16(a) so is a status string — so revision 1's "pure Lua" claim stays
withdrawn.

**Why this cut, and why Stage 1 is not merely "the cheap half":** it is
the *worse-exposure* half. `compile.lua:219` and
`builtin/commands/default.lua:855` rebind all seven undo chords to
`compile.undo-noop`; `dired.lua` and `listview.lua` rebind **nothing** —
`grep -n 'C-/\|C-_\|C-x u\|undo' builtin/runtime/dired.lua builtin/runtime/listview.lua`
returns zero binding lines. Measured, a bare `C-/` empties a listview
panel and a dired listing. Stage 1 closes the only two families
reachable without `M-x`.

**Why the cut is safe under every candidate primitive:** a whole-buffer
replace is expressible in all of A–C, and under the recommendation
`set_generated_contents` keeps its **Lua** name and signature as
`apply_generated_edit`'s wrapper. Stage 1 is therefore not rework under
any Q#GB1 outcome — which is the decisive argument for cutting here
rather than shipping one large PR.

**The honest objection, and the answer.** A reviewer could call Stage 1
churn: two call sites converted to a primitive Stage 2 then rewrites.
Stage 2 rewrites the primitive's *implementation*, not its callers; the
diff at `dired.lua:371` and `listview.lua:60-61` is written once.

### Stage 2 — `generated-buffer-immutability-stage2`

- **Prerequisite, in this PR, before the lock (Q#GB13):**
  `compile.ensure_slot` (`compile.lua:263`) and `ensure_search_panel`
  (`default.lua:861-868`) stop adopting same-named foreign buffers, same
  shape as Stage 1's listview fix.
- **In the SAME PR as that disambiguation (Q#GB18):**
  `pmacs.compile.is_generated_buffer` (`compile.lua:212-217`) stops
  comparing names and answers only
  `slot_for_buffer(buf) ~= nil`; `default.lua` adds local
  `search_panel_owns(buf)` and exposes
  `pmacs.project._is_search_panel`. Each capture site ORs its own
  predicate with the other module's predicate through the guarded
  optional call shape Q#GB18 specifies. **No owner registers ids with
  the other and no new removal callback work exists.**
- `Buffer::apply_generated_edit` (§3.4) + the `{ generated = true }`
  option + its own `run_buffer_edit` arm + `set_generated_contents`
  reimplemented over it (Q#GB17, Q#GB3).
- Q#GB10's path-backed refusal **and** `mark_clean` — one rule, both
  halves, since the refusal is what makes the flag change safe.
- **Q#GB15's `identity_protected` field** and its write-direction
  refusal. `mark_identity_protected()` is crate-private and monotonic;
  `TerminalSession::open` is its only production caller. Q#GB7 adds no
  unlock surface.
- Conversion of all 13 remaining write sites (`compile.lua` 9,
  `builtin/commands/default.lua` 4).
- Q#GB5's `ensure_slot` lock, which is only placeable once ownership
  lands.
- The three `compile_mode_acceptance` intruder tests updated per Q#GB12.

All the new Rust and all the review risk in one PR, which is the point of
the cut.

**Amendments to the briefed cut:**

1. **Q#GB13 (ownership) is a prerequisite of the stage that locks each
   writer**, not a follow-up and not a separate PR. §2.8 is the
   argument: this arc removes the only recovery a clobbered buffer
   currently has.
2. **Q#GB18 (identity routing) rides in the same PR as Q#GB13 for the
   same writer**, per the ordering constraint under Q#GB13. New in
   revision 3.
3. **Q#GB7 (unlock) is removed from both stages.** Revision 1 deferred
   it; revision 2 built it in Stage 1; revision 3 moved it to Stage 2;
   revision 4 replaced its provenance with an identity exclusion and
   thereby made it general again. Revision 5 chooses no unlock. The
   reversals are recorded rather than smoothed over because the reason
   moved three times and the next reader needs to know which decision is
   live.
4. **Q#GB10 (path refusal + `mark_clean`) lands in Stage 2**, because it
   edits `set_generated_contents` itself and therefore changes the
   already-shipped terminal snapshot. **Stage 1 is not pure Lua**
   (Q#GB6's clamp, and Q#GB16's status string), which revision 1
   claimed and revision 2 withdrew; the withdrawal stands for a
   different reason than revision 2 gave.

**Where the REPL lands: neither stage.** Q#GB8.

---

## 6. Acceptance, with the pre-image each criterion must fail against

`M-x buffer.undo` is the user-reachable trigger and **needs no keymap**.
A criterion that only exercises the intercept, or only the chords, proves
nothing — that is precisely what `compile.lua`'s idiom already achieves
and what this bug already defeats.

**Revision 2 re-audited every criterion, not only the three the review
named (sweep A).** Each now carries an explicit pre-image class, because
an unlabelled always-green criterion is indistinguishable from a vacuous
one. Labels may be combined where separate assertions have independent
pre-images; each label must be justified by the assertion that bites it:

| class | meaning |
|---|---|
| **`main`** | fails on canonical base `64883eb` (integration tree `76cfaac`). A regression pin in the ordinary sense. |
| **fix-shape** | its assertion **passes on `main` by design** and fails against a specific *wrong implementation*, named in the criterion. Legitimate per `docs/agent-handoff.md` §5 ("bite against every pre-image the fix could plausibly have taken"), where `acc 6` deliberately passes on `main`. |
| **mutation** | its assertion passes on `main` and fails against a named one-line mutation of the fix. In a combined criterion, a different assertion supplies the `main` bite. |
| **structural** | no behavioural pre-image. Rides **alongside** the others, never instead — a structural comparison of two authorities does not catch a misrouted consumer. |

**Q#GB14: the lock is not observable from Lua.** `describe.buffer`
carries no `read_only` field, so every "is it locked" assertion below
uses a **`bypass_intercept` write** (lands on `main`, raises
`` buffer `X` (id BufferId(n)) is read-only `` once locked) or Rust-side
`Buffer::is_read_only()`. An *ordinary* edit is not a discriminator: the
fact that it was **refused** passes both before and after adoption. Its
**full error source is** a discriminator: the base reaches the intercept,
while an adopted buffer reaches `ensure_writable` first. Criteria that
need only prove the lock use a bypass write or Rust state; criterion 5
deliberately asserts both sources on opposite sides of a Rust lift.

### Stage 1

1. **[`main`] `C-/` cannot empty a listview panel.** Driven by
   `dispatch_key`, not a Lua call. *Bite:* measured — `"H\nrow-one\nrow-two"`
   → `""`.
2. **[`main`] `M-x buffer.undo` cannot empty a listview panel**, driven
   through the real minibuffer (`M-x`, type `buffer.undo`, RET), not
   `pmacs.command.invoke`. *Bite:* same empty result; and a chord-only
   fix passes 1 and fails this.
3. **[`main`] `C-/` and `M-x buffer.undo` cannot empty a dired listing.**
   *Bite:* measured — one undo takes the listing to `""`.
4. **[fix-shape] The owner's own refresh still works after the lock** —
   `g` on a listview panel and on a dired buffer renders *new* content.
   *Bite:* a naive `set_read_only(true)` at creation passes 1–3 and fails
   here; that is the failure mode `src/buffer.rs:521-524` exists to
   prevent. Assert the new content appears, not that the call did not
   raise.
5. **[`main`, and also fix-shape] An ordinary edit reaches the rope
   lock, and the intercept survives behind it. REWRITTEN in revision 6
   (round 5, P1-1), with the pre-image corrected in revision 7 — the old
   criterion was impossible, and this document is where that gets
   settled, not #191.**

   **Why the old one could not pass.** It required the *intercept's*
   message on an ordinary edit after adoption. Both entry points check
   the lock before any intercept runs: `begin_edit` (`src/buffer.rs:724`)
   and `apply_edit` (`src/buffer.rs:772`) each call `ensure_writable()`
   as their **first** statement, and the chain runs later, in
   `apply_edit_inner`. Once the rope is locked an ordinary edit
   **necessarily** returns `BufferError::ReadOnly`; the intercept cannot
   run, so no test can observe its text. #191 reached this independently
   and measured the actual message.

   **The consequence revisions 1–5 all missed: after adoption the
   intercept is UNREACHABLE on the ordinary path — including in the
   shipped precedent.** `terminal.lua`'s `claim_snapshot` keeps its
   erroring intercept beside the rope lock (`:339-396`), and that
   intercept has been dead since #178 landed. This document has been
   telling two more adopters to preserve it *and* to assert its message.

   **So why keep the intercept at all?** Because it is the guard that
   remains **whenever the lock is lifted**, and this document prescribes
   lifting it: Q#GB12's intruder-test conversion, criteria 4, 15, 16b and
   17's Rust-side lifts, and — if dired Stage 3 ever ships a wdired mode
   swap — the editable window. During any such window the intercept is
   the only thing refusing an ordinary edit. That is a real role, and it
   is testable.

   **The criterion, in two halves:**

   - **(a) [`main`] An ordinary edit is refused BY THE ROPE LOCK**,
     asserted on the exact `BufferError::ReadOnly` text
     `` buffer `X` (id BufferId(n)) is read-only ``, and the buffer text
     is byte-identical. Driven through `dispatch_key`. The base fails
     this assertion because its ordinary path reaches the intercept and
     reports `intercept rejected the edit: … is read-only`.
   - **(b) [fix-shape] With the lock lifted Rust-side, an ordinary edit
     is refused BY THE INTERCEPT**, asserted on the message text:
     `intercept rejected the edit: … is read-only`, not
     `` buffer `X` (id BufferId(n)) is read-only ``. Restore the lock
     afterwards.

   *Bite:* (a) pins the new guard's precedence and fails on the base;
   (b) is where the old criterion's intercept bite survives. An adopter
   that deletes the intercept and relies on the rope alone passes 1–4
   and (a), and fails (b). The layering at `terminal.lua:351-366` is
   preserved by (b); what revisions 1–5 got wrong was believing the
   ordinary path could see it.

   **Recorded consequence, not this arc's to fix:** `terminal.lua`'s
   intercept is likewise reachable only under a lift. Whether a
   permanently-unreachable-on-the-ordinary-path guard should stay is a
   question for whoever owns the layering; §8 carries it.
6. **[fix-shape] `set_round_trip_input` is still set on both — asserted
   so that only the round-trip mark can make it pass. Rewritten in
   revision 3 (review P2-4), and the cited precedent was wrong.**

   `dispatch_idle_for` (`src/editor.rs:1126-1155`) returns `false` for
   **six** independent reasons, only one of which is the round-trip
   mark: a pending chord or terminal escape on that frontend
   (`:1130`), an active minibuffer, an active search, an active
   query-replace, an open menu (`:1135-1138`), a focused **side** window
   and `core.buffer_round_trips(window.buffer_id)` — both on `:1153`.
   A criterion that only asserts `!dispatch_idle_for(..)` is satisfied by
   any of the six.

   **Revision 2 named the wrong model.** It cited
   `tests/terminal_copy_mode_acceptance.rs` "criterion 16", but that file
   contains **zero** `dispatch_idle_for` references — `acc16`
   (`:321-339`) goes through `state.dispatch_idle()` and asserts no
   `is_side` premise. The test that gets the side-window half right is
   `tests/dired_acceptance.rs:969-1013`, which asserts
   `!window.is_side()` as an explicit fixture premise (`:975-989`,
   commented "A document window, deliberately: the panel arm of the same
   gate would otherwise be what makes this pass") **before** asserting
   `!s.dispatch_idle_for(FrontendId::LOCAL)`.

   **Both halves are required, because neither test has both.** The
   criterion asserts, for each of the dired and listview adopters:

   - **(a) the document-window premise**, `!window.is_side()` on the
     focused window, asserted as a premise so a fixture that later
     displays in a panel fails loudly rather than passing vacuously —
     `dired_acceptance.rs:975-989`'s shape verbatim;
   - **(b) `!dispatch_idle_for(FrontendId::LOCAL)` while the panel is
     focused**;
   - **(c) the positive control** — switch the same window to a plain
     `pmacs.buffer.create("*plain*")` and require `dispatch_idle_for` to
     become **`true`**. This is `acc16:332-337`'s half, and it is what
     rules out the other five clauses in one assertion: a stuck
     minibuffer, a pending chord, an open menu or an active search would
     keep the gate `false` across the buffer switch, so (c) failing is
     the signal that (b) passed for the wrong reason.

   *Bite:* delete the `set_round_trip_input` call in `listview.lua:106`
   / `dired.lua:516` and criteria 1–5 all still pass; only this fails,
   at (b). Falsify (a) by displaying the panel in a side window: (b) then
   passes with the round-trip mark deleted, which is the whole of P2-4.
   Falsify (c) by leaving a minibuffer open in the fixture: (b) passes
   and (c) fails. A daemon-side refusal does nothing for a replica's own
   mirror, which is why this is pinned through `dispatch_idle_for` and
   not through `read_only`.

   **Note what this criterion is NOT.** `dired_acceptance.rs:999`'s
   `status(&s).contains("read-only")` passes both before and after
   adoption, because `BufferError::ReadOnly` and the intercept's own
   message both contain that substring — the trap `docs/dired-stage2-framing.md`
   §3.1 hands to this lane. Criterion 5 is where the distinction is
   asserted, on the *full* message text; this one must not be counted as
   coverage of the adoption.
7. **[mutation] A refresh reaches the window, not just the rope** —
   pinned by **painting** a shrinking render (many rows → one) and
   asserting row 1 is empty, for each adopter. **Revision 2 corrected
   this criterion's bite (sweep A).** Revision 1 claimed it caught a
   "partial conversion" that kept a `bypass_intercept` write beside the
   primitive; that is wrong — such a conversion **raises** at the bypass
   write (§2.4, measured) and never reaches a stale paint. The real bite
   is the one-line mutation *delete the `notify_buffer_edit_to_windows`
   call in the `set_generated_contents` binding*
   (`src/lua_bindings/mod.rs:3092`), which a reviewer can perform.
8. **[`main`] Cursor clamp (Q#GB6).** After a shrinking refresh,
   `pmacs.editor.cursor() <= buf:len()` and `C-p` moves. *Bite:* measured
   on `ad41cf1` — cursor 29, len 2, `C-p` leaves it at 29. Fails on
   `main` today, including for terminal copy mode.
   **8b. [`main`] `view_top` clamp, on a LONGER buffer (Q#GB6, review
   P2-4).** With a window scrolled so `view_top` sits on line 5, replace
   `"a\nb\nc\nd\ne\nf\n"` (12 bytes, 7 lines) with a single line **longer
   than 12 bytes**, then require `view_top < TextView::line_count()`.
   *Bite:* a clamp gated on "the buffer shrank" passes 8 and fails 8b,
   which is the whole of P2-4. Unlike 8, this case is argued from the
   types and from `rebuild_views_for`'s existing clamp
   (`src/editor_core.rs:1865-1882`), **not measured** — staging it needs
   a scrolled window.

   **8c. [`main`] Selection-anchor clamp-or-clear, in BOTH clamp sites.
   New in revision 6 (round 5, P1-5). This is the only one of the three
   coordinates that PANICS, and #191 reproduced it.** Select bytes 0..30
   in a generated buffer, have the owner refresh it to two bytes, then
   invoke copy (`region_bytes`). Require: no panic; and either a valid
   region within the new extent, or **no selection at all** where the
   clamp collapsed it, per Q#GB6 rule 3.

   Assert it **twice**, once per site, because they have different
   callers and neither subsumes the other: through
   `notify_buffer_edit` (the generated-write path, which clamps nothing
   today) and through `rebuild_views_for` (the `*help*` /
   `*buffer-list*` rewrite path, which clamps `cursor` and `view_top`
   and **not** `selection`).

   *Bite:* measured by #191 — panic at `src/rope.rs:145`,
   `debug_assert!(end <= self.len())`, reached from
   `region_bytes` (`src/editor_core.rs:4184-4191`) via
   `Window::region` (`src/window.rs:472-479`), which clamps neither
   endpoint. Falsify the clear half by clamping only: the selection then
   survives as a zero-width region that the user never asked for, which
   is what `src/terminal/view.rs:715-721`'s `collapsed_by_clamp` exists
   to prevent for the terminal's own selection type. **Assert the
   produced region, not merely that the call returned** — "did not
   panic" is satisfied by clearing the selection unconditionally, which
   would be a different bug.
9. **[`main`] A foreign buffer named `*references*` is never adopted
   (Q#GB13).** Create a plain buffer of that name with user text, then
   open the references panel. Assert **both** halves: the user's bytes
   survive **and** an ordinary edit to the user's buffer still lands;
   and the panel appears under a disambiguated name. *Bite:* measured —
   `"my precious notes"` → `"H\nr1"`, one buffer not two, and the user's
   buffer is left permanently un-editable. The second half is what fails
   if adoption is merely made "safe" by skipping the render.
10. **[fix-shape] The disambiguation limit raises rather than adopting**,
    matching `dired.lua:493-503` / `terminal.lua:309-315`. *Bite:* an
    implementation that falls back to adoption once the limit is
    exhausted passes 9 and fails this.
11. **[`main`] A disambiguated listview panel still answers `RET`, `g`
    and `q` (Q#GB18, review P1-2).** Continue criterion 9's fixture: with
    a foreign `*references*` in place, open the references panel — it
    appears as `*references*<2>` — then, **through `dispatch_key`**,
    press `g`, `RET` and `q` in turn and assert the *content produced* by
    each: `g` re-renders (the `on_refresh` rows appear), `RET` fires
    `on_visit` (assert the visited item, via a probe that records it),
    and `q` restores the previous buffer. *Bite:* this is the criterion
    that fails against **Q#GB13 landed without Q#GB18** — disambiguation
    alone leaves `panel_for_current_buffer` looking up
    `panels["*references*<2>"]`, which was stored under
    `"*references*"`, so all three commands return early and do nothing.
    Assert what each command produced, not that it did not raise: every
    one of the three fails *silently*, so a "no error" assertion passes
    against the bug.
12. **[`main`] The `q`-target capture is not inverted (Q#GB18).** The
    fourth consumer, and it needs its own criterion because it fails
    **open** rather than closed. With a disambiguated panel focused, open
    a **second** panel (`*outline*`) and assert the second panel's `q`
    returns to the buffer that was current *before the first panel*, not
    to the first panel. *Bite:* with `panel_for_current_buffer` unable to
    recognise `*references*<2>`, `listview.open`'s guard at `:118-123`
    reads "the current buffer is not a panel" and captures the panel as
    `p.prev` — the chained-panel `q` loop the guard's own comment says it
    exists to prevent. Criterion 11 passes with this bug live, because
    each command works in isolation; only the two-panel sequence shows
    it.
13. **Q#GB16's fold change — SPLIT into two criteria in revision 4
    (review round 3, P2-5), because revision 3's single criterion
    contradicted its own classification.** Revision 3 labelled it
    `[fix-shape]` and then wrote that the first half "passes on `main`
    ... a dired buffer ... folds fine". If folding succeeds on `main`,
    an assertion that it returns `false` **fails** on `main` — which is
    a `main` pre-image, the opposite label. The two halves have different
    pre-images and belong apart.

    **13a. [`main`] A locked generated buffer is not foldable.** On a
    Stage 1 dired listing, `pmacs.fold.fold(buf, range)` returns
    `false`. *Bite:* this **fails on `main`**, where the same call
    returns `true` — verifiable by revert, and `scripts/bite` reports it.
    It is a regression pin *for the intended change*: the point is to
    make sweep C's silent behaviour change into a stated one, so the
    criterion asserts the new behaviour and the bite is that the old
    behaviour is different.

    **13b. [mutation] …and the refusal says why.** The status after 13a's
    call names the read-only lock, not `not a document buffer`. *Bite:*
    the falsifying mutation is reverting `fold.rs:68`'s string; that is
    the shape that ships if 13a is written alone — correct behaviour,
    false explanation. It cannot share 13a's `main` pre-image because on
    `main` the call succeeds and sets no status at all.
14. **[structural] No `bypass_intercept` write remains in `dired.lua` or
    `listview.lua`**; `listview.ensure_panel` contains no find-by-name
    adoption; and **no `panels[` subscript remains keyed by a name
    derived from `describe.buffer`** — the Q#GB18 half. Rides alongside
    1–13, never instead: a structural comparison of two authorities does
    not catch a misrouted consumer, which is why 11 and 12 assert through
    `dispatch_key`.

**Moved out of Stage 1 in revision 3 and removed in revision 5:** the
unlock criterion. Revision 2's Stage 1 criterion 11 pinned
`unlock_generated`; revision 3 moved it to Stage 2, revision 4's
identity exclusion failed to bound it by generated-lock provenance, and
Q#GB7 now ships no binding in either stage.

### Stage 2

1. **[`main`] `M-x buffer.undo` cannot destroy `*compilation*` /
   `*shell-command*` / `*search-results*` content — and the criterion
   must assert the *exit marker survives*, not that the buffer is
   non-empty.** *Bite, and this is the whole point:* measured, the result
   of `M-x buffer.undo` on `*shell-command*` is
   `[shell exited with code 0]` replaced by
   `[output desynced by external edit]`. The buffer is still non-empty,
   so a "not empty" assertion **passes with the bug live**. The revision
   guard *marks* the corruption; it does not prevent it.
2. **[fix-shape] A streaming run's incremental writes still land**,
   including CR overwrite semantics (a progress-bar fixture) and
   erase-to-eol. Assert the produced content, not the absence of an
   error. *Bite:* the tempting half-conversion — reset via
   `set_generated_contents`, stream via `bypass_intercept` — raises
   `is read-only` at the first append (§2.4, measured).
3. **[`main`] The rope is locked BETWEEN batches, not only after the
   run.** Mid-run, after one output batch has landed and before the
   next, a **`bypass_intercept`** write must be refused and
   `Buffer::is_read_only()` must be `true`. **Rewritten in revision 2
   (review P1-1).** Revision 1 said "attempt an ordinary edit and require
   the refusal", which **passes on `main`** — the intercept refuses
   ordinary edits today whether or not the rope is locked. A bypass write
   is the discriminator: it lands on `main` (`compile.lua` performs nine
   of them) and raises once the rope is locked. *Bite:* a scope-shaped
   implementation that unlocks for a whole run passes 1 and 2 and fails
   this. A state predicate, not a geometric readout.
4. **[`main`, and also fix-shape] History is discarded per generated
   write, asserted past the lock.** In a Rust acceptance test, after N
   batches: `buffer.set_read_only(false)`, then assert `buffer.undo()`
   is `Err(BufferError::NothingToUndo)` and — under `--features crdt` —
   that the CRDT reports `can_undo() == false`; restore the lock.
   **Rewritten in revision 2 (review P1-1).** `Buffer::undo` calls
   `ensure_writable()` **first** (`src/buffer.rs:1302`) and returns
   `ReadOnly` before it ever looks at the stacks, so revision 1's
   "`buf:undo()` returns false" **passes against an implementation that
   locks the rope and never clears history**. Lifting the lock inside the
   test is what makes the assertion about history rather than about the
   lock. `tests/terminal_copy_mode_acceptance.rs:582-584` is the existing
   precedent for a Rust-side lift. This criterion fails on `main` (where
   history accumulates) *and* against the locks-but-never-clears
   implementation, which is the strongest pairing available.
5. **[`main`] `ensure_slot` leaves `*compilation*` locked before any
   run (Q#GB5).** Create the slot without running anything, then require
   a **`bypass_intercept`** write to be refused and `is_read_only()` to
   be `true`. **Rewritten in revision 2 (review P1-1):** revision 1's
   "attempt an ordinary edit; without the explicit lock it lands"
   **passes on `main`**, because `ensure_slot` installs the erroring
   intercept at `compile.lua:266` at creation time.
6. **[`main`] A generated write on a path-backed buffer is refused —
   on ALL FOUR surfaces, not just the legacy wrapper (Q#GB10; rewritten
   in revision 3 for review P2-5).** Open a file, then, against its
   buffer, exercise each of:

   | surface | call |
   |---|---|
   | the wrapper | `pmacs.buffer.set_generated_contents(b, "x")` |
   | insert | `b:insert(0, "x", { generated = true })` |
   | delete | `b:delete(0, 1, { generated = true })` |
   | replace | `b:replace(0, b:len(), "x", { generated = true })` |

   Each must error, and after each the buffer's contents, `is_read_only()`
   and `is_modified` must all be unchanged (§3.4 exit 1: nothing is
   touched). Second half, once: after an ordinary edit, autosave still
   queues that buffer.

   *Bite, and this is exactly P2-5's point:* a guard placed on
   `Buffer::set_generated_contents` rather than on
   `Buffer::apply_generated_edit` **passes the wrapper row and fails the
   other three**, while the newly public surface could still replace a
   file buffer's contents, lock its rope and — with `mark_clean` — make
   `autosave.rs:363` skip it, so a crash loses the user's edits with
   **no recovery slot**. Reverting the guard to the wrapper is the
   one-line mutation that falsifies this. Assert the autosave queue, not
   just the flag: asserting a value was stored is not asserting anything
   reads it.
7. **[`main`] `mark_clean` (Q#GB10).**
   `pmacs.describe.buffer(b).modified` is `false` after a generated
   write on a pathless buffer. *Bite:* measures `true` on `ad41cf1`.
8. **[`main`] Foreign buffers named `*compilation*`, `*shell-command*`
   and `*search-results*` are never adopted (Q#GB13)** — same two-halved
   shape as Stage 1 criterion 9, plus the limit criterion of 10. *Bite:*
   measured on `ad41cf1` for `*compilation*`.
9. **[`main`] A FAILED `pmacs.compile.run` leaves a foreign
   `*compilation*` untouched AND editable.** Call it with
   `display = "bogus"` against a pre-existing foreign buffer of that
   name. *Bite:* measured — today the call raises at
   `compile.lua:754`, the contents survive, and the user's buffer is
   nonetheless left permanently un-editable (`ensure_slot` ran first and
   installed an intercept it discarded the handle for). With Q#GB5's
   lock placed naively it would additionally be **emptied and locked**.
   This is the criterion that pins the ordering constraint, and it fails
   on `main` today for the intercept half alone.
10. **Coverage, not a criterion: both configurations** — default and
    `--features crdt` — for criteria 1–5 and for the §3.4 transaction
    criteria 15, 15a, 16 (first half), 16b and 18. CI never enables the
    feature, so CRDT must not be the only home of any of them.

    **Three are irreducibly `crdt`-only and must say so rather than be
    quietly written once** (revision 4): criterion 16's *second* half
    (the `Rejected` refusal needs a mid-codepoint position, which only
    loro rejects), **16c** (`Diverged` has no default-feature analogue at
    all), and Stage 2 criterion 4's `can_undo() == false` half. Each is
    paired with a default-configuration sibling that exercises the same
    cleanup arm through a non-CRDT failure — criterion 15's `FailingView`
    is the default-feature route into `AppliedThenFailed`, and 16b's
    empty write is the default-feature route into `NoOp` — so **no
    cleanup arm of §3.4 is reachable only under `crdt`** except
    `Diverged`, which by construction cannot be. That pairing is the
    point of the rule; naming which criteria are single-configuration is
    what keeps it checkable.
11. **[structural] Zero `bypass_intercept` writes remain** in
    `compile.lua` and in `default.lua`'s search panel (comments
    excepted; §1.1's arithmetic is the reference), and neither
    `ensure_slot` nor `ensure_search_panel` contains a find-by-name
    adoption.
12. **[fix-shape] The three intruder tests still assert what they were
    written to assert** after being converted to a Rust-side `read_only`
    lift (Q#GB12), rather than being deleted or weakened. *Bite:* a
    conversion that drops the intruder edit entirely leaves the desync
    machinery unpinned while the suite stays green.

**New in revision 3 — the transaction and the identity guard. Revision
5 removes the attempted bounded unlock.**

13. **[structural] No Lua unlock surface is added (Q#GB7).** There is no
    `pmacs.buffer.unlock_generated`, no exposed `set_read_only`, and no
    binding that clears `read_only` without performing an
    owner-authorized generated write. *Bite:* adding the revision 4
    binding fails this structural assertion even if it refuses terminal
    identity buffers; `identity_protected == false` is not proof that the
    generated primitive installed the lock.
14. **[`main`] A generated write REFUSES a terminal identity buffer
    (Q#GB15; sweep C item 1).** Open a real terminal; call
    `pmacs.buffer.set_generated_contents(term_buf, "junk")` and each of
    the three `{ generated = true }` mutators against it. Every one must
    error, and the terminal's contents must be **byte-identical**
    afterwards. *Bite:* this **fails on `main` today** — shipped
    `set_generated_contents` does `self.read_only = false`
    unconditionally (`src/buffer.rs:546`), overwrites the buffer and
    re-locks it, and nothing in the tree refuses it. It is the pin for a
    hole that predates this arc, which is why it is a `main` pre-image
    rather than a mutation bite. Falsify by deleting §3.4's exit 2.
**Criteria 15-16 were VACUOUS in revision 3 and are rewritten. Review
round 3, P1-2, is right and the diagnosis is worth stating because it is
the second time this arc has shipped a criterion that passes with the bug
restored.** Both used an out-of-bounds op. Bounds validation is §3.4 exit
4 — **before** `editing_in_progress` is set and **before** the internal lift —
so the operation never enters the transaction the criteria claim to test,
and an implementation that omits *both* the flag clear and the error-path
relock passes both. Worse, revision 3 argued *in the same document* that
pre-validation makes an invalid range cost nothing; the design decision
and the test strategy contradicted each other in adjacent sections. **The
rule this yields: a criterion must name the exit it drives the
implementation to, and that exit must be inside the mechanism under
test.** Every criterion below names its exit.

**Pre-image relabels, revisions 6 and 7 (rounds 5 and 6, P2-6/P2-5).
The classification error was larger than revision 6 recorded.** The
test in every case is: *run this criterion's assertions against the
canonical base, `64883eb`; do they fail?*

| criterion | what the base actually does | was | now |
|---|---|---|---|
| 15 | `{ generated = true }` is an **unknown option key** on `main` — `parse_bypass_intercept` reads only `bypass_intercept`, so the call is an ordinary managed edit, and `run_managed_edit` clears the flag before phase 3. The follow-up edit lands. **Passes.** | `[main]` | `[mutation]` |
| 16 | the generated option is ignored, so the valid failing edit never installs the generated lock: the first half's `is_read_only() == true` assertion **fails**. The refusal half still describes a mutation after implementation. | `[main]` | [`main` + mutation] |
| 16b | an empty write on `main` is an ordinary managed no-op: it clears undo history and locks, but never calls `mark_clean`, so `modified == false` **fails**. Revision 3's cleanup predicate remains a separate post-fix mutation bite. | `[main]` | [`main` + mutation] |
| 17 | invalid-range rejection **already** preserves history on `main`, because no `clear_history` runs on that path at all. **Passes.** | `[main]` | `[mutation]` |
| 18 | `begin_edit` **already** rejects same-buffer re-entry (`src/buffer.rs:726-731`). **Passes.** | `[main]` | `[fix-shape]` |
| 21 | search **already** consults `pmacs.compile` through the optional triple guard (`default.lua:991-994`). **Passes.** | `[main]` | `[fix-shape]` |

Revision 7 also corrects three classifications outside revision 6's
six-row list. Criterion 5(a) now asserts the adopted rope error, so it
really fails on the base. Criterion 15a fails on the base because the
ordinary managed-edit error prevents the external window and replica
fanout; restoring stop-at-first-error after implementation is its
separate mutation bite. Criterion 22 fails on the base because
`generated` is ignored and the file edit lands; moving preflight below
the unfold remains its separate mutation bite.

None of the criteria is weakened by the relabel. What changes is that
the document no longer claims a `main` pass or failure it does not have,
which is what `scripts/bite` would have contradicted. **The rule,
restated for the third time and now applied by construction: a
criterion's pre-image is a fact about the base, established by running it
there — not an inference from what the fix is for.**

15. **[mutation] `editing_in_progress` is cleared on a failure that
    ENTERS the transaction (Q#GB17; §3.4 `AppliedThenFailed`).** Attach
    a Rust-side `FailingView` — `pmacs::view::View` is `pub`
    (`src/view.rs:221`, `src/lib.rs:141`) and `Buffer::attach_view` is
    `pub`, so a test crate can implement one whose `on_edit` returns
    `Err(BufferError::Intercepted { .. })` — then perform a **valid**
    generated write. It fails at the broadcast, *after* the rope swap.
    Then **lift `read_only` Rust-side** and require an ordinary edit on
    the same buffer to report the `FailingView`'s message, **not**
    `is already being edited`.
    *Bite:* an implementation that returns from the `match` without
    reaching §3.4's line (6) leaves the flag set, and `begin_edit`
    (`:726-731`) and `apply_edit` (`:774-779`) then refuse **every**
    later writable edit to that buffer for the rest of the session.
    Without the lift, `ensure_writable` runs before the flag check and
    both the correct and broken implementations report `ReadOnly`, which
    was revision 4's non-discriminating form. Falsify by
    moving the flag clear inside the `Applied | NoOp` arm. Assert the
    *next* edit's outcome, not the failing call's — the failing call
    reports the same error either way, which is the whole reason this
    criterion is about the buffer's state afterwards. Restore
    `read_only` after the probe so criterion 16 begins from the specified
    post-failure state.
15a. **[`main` + mutation; both configurations] `AppliedThenFailed` fans
    out its carried `Edit` before surfacing the error (Q#GB17; review
    round 4, P1-1).** Display the test buffer in a real window, attach the same
    `FailingView`, and issue a valid shrinking generated replace through
    the Lua binding. The call returns the view's error, but painting the
    window must show the new shorter contents with no stale-line panic.
    Under `--features crdt`, attach a replica mirror before the call and
    require it to import the owner's `crdt_op` despite the Lua error.
    *Bite:* deleting only the `AppliedThenFailed` arm's
    `notify_buffer_edit_to_windows` call leaves criteria 15 and 16 green
    — buffer cleanup is correct — while the window keeps stale line
    ranges and the replica never receives an operation that already
    changed the authoritative CRDT. This criterion fails that mutation
    in both directions.

    **Revision 6 (round 5, P1-4): the fixture must place a RECORDING
    view AFTER `FailingView` in attach order.** As written, 15a observes
    only the window and replica consumers, which are fanned out *after*
    the borrow drops — so it cannot see the buffer-attached views that
    `on_edit`'s stop-at-first-error loop skips. Attach order is
    `FailingView`, then a `RecordingView` whose `on_edit` appends the
    `Edit` it received; assert the recorder **saw the edit**. *Bite for
    this half:* on the base, the ordinary managed-edit failure prevents
    the later window and replica fanout as well as the recorder, which
    is the `main` bite. Against the completed implementation, restoring
    `view.on_edit(self, &edit)?` leaves the later window and replica
    assertions green but the recorder's log **empty**; that is the
    independent mutation bite. Falsify by restoring the `?`.
16. **[`main` + mutation] A generated write relocks on that same failure,
    and does NOT lock on a refusal (Q#GB17). Two halves, because §3.4
    gives them opposite answers and revision 3 gave them the same one.**
    - *Relock on `AppliedThenFailed`:* after criterion 15's failing
      write, `Buffer::is_read_only()` is `true` and a
      `bypass_intercept` write raises. *Bite:* the base treats
      `generated` as an unknown option and never installs the generated
      lock, so `is_read_only() == true` fails. After implementation,
      deleting `self.read_only = true` from the `AppliedThenFailed` arm
      recreates the same visible failure.
    - *No lock on `Rejected`:* on a **fresh, writable** pathless buffer
      under `--features crdt`, a mid-codepoint generated insert is
      refused; afterwards `is_read_only()` must still be **`false`** and
      an ordinary edit must land. *Bite:* **revision 3's own design fails
      this** — it relocked unconditionally, so a caller got an error and
      a locked buffer it never wrote. Falsify by replacing
      `self.read_only = entry_read_only` with `= true`. This half is
      `crdt`-only, so criterion 10's coverage rule names it explicitly.
16b. **[`main` + mutation] A successful no-op still discharges the
    invariant (Q#GB17; §3.4 `NoOp`). New in revision 4 (P1-1 direction
    A).** On a pathless buffer, insert text and delete it back to empty so the rope
    is empty **and the undo stack is not**; then call
    `set_generated_contents(b, "")`. Afterwards: `is_read_only()` is
    `true`, `describe.buffer(b).modified` is `false`, and — after a
    Rust-side lift — `buffer.undo()` returns `Err(NothingToUndo)`.
    *Bite:* the shipped whole-buffer wrapper clears history and locks,
    but does not mark clean, so the base fails `modified == false`.
    Independently, **revision 3's predicate fails all three.** The no-op arm
    (`src/buffer.rs:1245-1253`) returns `Ok` without bumping `revision`,
    so revision 3 skipped the clear and the `mark_clean` and left a
    locked, modified buffer with poppable history. Falsify by restoring
    `if self.revision() != rev_before`. This is not a hypothetical path:
    Q#GB5 prescribes exactly this call in `ensure_slot`.
16c. **[fault-injection, `crdt`-only] A CRDT mid-transaction failure is
    distinguishable and contained (Q#GB17; §3.4 `Diverged`). New in
    revision 4, made stageable and mandatory in revision 5, and made
    total in revisions 6 and 7.** This criterion has four required
    halves:

    - **Total classification.** In `src/buffer.rs` unit tests, drive the
      injectable CRDT-routing seam with (1) delete `Ok` + insert `Err`
      and (2) delete `Ok` + `export_updates_since` `Err`. Both must
      return `Diverged`; the seam carries a `crdt_mutated` flag rather
      than enumerating operation shapes. The export failure must also be
      exercised after each successful `Insert`, `Delete` and `Replace`
      shape, because export runs after all three. *Bite:* revision 5
      classifies three of those seven cases as `Rejected`, restoring a
      fresh buffer to writable while CRDT and rope disagree.
    - **Common poison before API mapping.** Drive one injected
      `Diverged` through `apply_generated_edit`, and a second through an
      ordinary `apply_edit`/skip-intercepts mapper. In both cases require
      `crdt_quarantined == true` and `read_only == true` **before** the
      outer API converts the outcome to its public error. The generated
      path surfaces a distinct error, not `CrdtRejected`; history is not
      cleared. *Bite:* setting quarantine only in generated cleanup
      leaves the pre-existing ordinary CRDT path divergent and
      publishable.
    - **All three snapshot routes refuse publication.** After forcing
      `Diverged`, require: an explicit-initial-target attach calls
      `initial_target_snapshot`, yields `InitialTargetFailure`, removes
      its provisional view and publishes no `BufferSnapshot`; a legacy
      no-target attach skips the buffer in `send_buffer_snapshots`; and
      `export_buffer_snapshot(&editor, buffer_id)` returns `None`.
      *Bite:* deleting any one guard still publishes the divergent CRDT
      through that route. The explicit-target assertion is independent
      of the legacy loop: it is the ordinary modern attach path.
    - **No delta is queued.** Call `queue_daemon_origin_crdt_op` for the
      quarantined buffer and require the pending-op collection to remain
      unchanged. *Bite:* a snapshot guard without the queue guard still
      propagates a delta based on a document the owner no longer paints.

    Assert the **absence of publication**, not merely that a flag was
    stored. Folding `Diverged` into `Rejected` must fail on the lock
    post-state as well as the discriminant. `cargo test --lib --features
    crdt` is the explicit gate. No public fault-injection API is added,
    and there is no four-variant fallback.
16d. **[mutation; `crdt`-only] A quarantined buffer refuses the owner's
    next generated write before CRDT mutation (Q#GB17; §3.4 exit 0). New
    in revision 7.** After criterion 16c forces `Diverged`, snapshot the
    rope, CRDT state, revision and undo history, then issue a
    bounds-valid generated insert and a bounds-valid generated replace.
    Both return the distinct `CrdtQuarantined` refusal; all four
    observations remain unchanged and no daemon-origin op is
    queued. This is the direct `Buffer::apply_generated_edit` assertion
    that pins the authoritative re-check.

    Separately, in an `editor_core` unit fixture, mark a folded buffer
    quarantined through a `#[cfg(test)]` helper and invoke a generated
    Lua mutator through the real interactive `run_buffer_edit` path.
    Require `CrdtQuarantined` and the same fold range still present. This
    pins `generated_preflight` before the unfold; it adds no production
    fault-injection API. *Bite:* deleting exit 0, or checking quarantine
    only in the preflight, lets an owner refresh cross `read_only` and
    compound the divergence. Checking it only in the authoritative apply
    preserves bytes but opens the fold first.
17. **[mutation] An invalid-range generated write does NOT destroy undo
    history (Q#GB17).** On a pathless buffer with two ordinary edits
    already on the stack, call `b:delete(0, b:len() + 1000,
    { generated = true })`; require the error, then lift `read_only`
    Rust-side and require `buffer.undo()` to **succeed** and restore the
    prior contents. *Bite:* this fails against the shipped ordering
    transplanted verbatim — `set_generated_contents` calls
    `clear_history()` **unconditionally** (`src/buffer.rs:551-553`), so a
    call that changed nothing would wipe the user's history. It is the
    concrete cost review P1-1 asks the ordering to state, and pre-
    validation (§3.4 exit 4) is what pays it.
18. **[fix-shape] A re-entrant generated write is refused (Q#GB17).** From
    inside an `add_intercept` body on buffer X, call
    `X:insert(0, "x", { generated = true })`; require
    `ConcurrentEdit`, and require the outer edit to complete normally
    afterwards. *Bite:* omit the gate and the inner write mutates the
    rope while `run_managed_edit` phase 3 is holding an op computed
    against the pre-edit `InterceptContext`
    (`src/lua_bindings/mod.rs:1477-1487`); the visible symptom is the
    outer edit landing at the wrong offset, so **assert the resulting
    text**, not the error.
19. **[`main`] `is_generated_buffer` recognises a disambiguated buffer
    (Q#GB18).** With a foreign `*compilation*` in place, run
    `M-x compile`; the run lands in `*compilation*<2>`. From inside that
    buffer, run `M-x compile` again (the `g`-recompile path) and require
    the `q` target still to be the user's original buffer — not
    `*compilation*<2>`. *Bite:* with `is_generated_buffer` still
    comparing names, `compile.lua:762`'s guard reads the disambiguated
    buffer as "not generated" and re-captures it, so `q` returns the
    user into a compilation buffer. Assert where `q` lands, not whether
    the predicate returned a boolean.
20. **[structural] Zero name comparisons remain in the Class 1 sites.**
    `pmacs.compile.is_generated_buffer` contains no `d.name ==`, and
    `listview.lua` contains no `panels[d.name]`. Rides alongside 11–19,
    never instead.
22. **[`main` + mutation] A REFUSED generated write leaves the fold
    closed (Q#GB3; round 5, P2-7). New in revision 6; pre-image corrected
    in revision 7.** Fold a region of a
    **file-backed** buffer, then, from inside an interactive command so
    `InteractiveCommandOrigin::current()` is `Some`, attempt
    `b:replace(s, e, "x", { generated = true })` on it. Q#GB10 refuses
    it. Require: the error, **and** `#pmacs.fold.folds(b) == 1` with the
    same range still stored.
    *Bite:* the base ignores `generated`, so the file-backed edit lands;
    that is the `main` bite. After implementation, **revision 5's
    ordering also fails this:** it called
    `unfold_before_interactive_lua_edit` before `run_generated_edit`, so
    the fold opened and then the write was refused — a visible side
    effect from an operation whose contract says "before any state
    change". Falsify by moving `generated_preflight` back below the
    unfold. Assert the fold **count and range**, not just that the call
    errored: the error is identical on the mutation either way, which is
    exactly why this needs a state assertion rather than an outcome
    assertion.

    Repeat once with the **identity-protected** refusal (a terminal
    identity buffer) so the criterion pins the preflight rather than
    Q#GB10's path check specifically — a preflight that hoists only the
    `file_path` test passes the first half and fails this one.
21. **[fix-shape] Search works with no `pmacs.compile` present (Q#GB18;
    review round 3, P2-4). New in revision 4.** Build a `LuaHost`
    directly, call `attach_editor`, and — with `compile.lua` never
    loaded — run `pmacs.project.search`. It must not raise, and the
    `q` target must be the buffer that was current before the search.
    Then assert the harness premise explicitly: `pmacs.compile == nil`,
    so a fixture that later gains the runtime sequence fails loudly
    rather than passing as an ordinary editor test.
    *Bite:* **revision 3's design fails this at the first search** —
    `ensure_search_panel` called `pmacs.compile._register_generated_buffer`
    unguarded, and `pmacs.compile` is nil here. Falsify by replacing the
    symmetric guard with a direct call. This configuration is reachable
    with the pattern nine existing test files already use (`LuaHost` is
    `pub`; `default.lua` loads at `src/lua.rs:250-251`, `compile.lua` at
    `src/editor.rs:704`), and **no ordinary acceptance test reaches it**,
    because every `EditorState::new` loads both — which is exactly why
    the guard it defends was invisible enough for revision 3 to remove.

---

## 7. Bets

- **That a per-op `clear_history` is not a throughput problem.** Argued
  from `create_undo_manager` being `UndoManager::new(doc)` (O(1) in
  document size) and from at most one v0.1 entry existing per clear.
  **Measured in Stage 2, not asserted here.**
- **That converting compile's nine sites does not disturb its byte
  anchors.** The conversion changes *authority*, not op shape, position
  or count — `emit_text`'s `slot.out_pos` arithmetic is untouched. The
  bet is that nothing else in the module reads `read_only` indirectly;
  criteria 2 and 3 are what test it.
- **That `{ generated = true }` sitting beside `{ bypass_intercept = true }`
  is clearer than replacing it.** Q#GB2.
- **That duplicating the rope's bounds arithmetic in
  `validate_op_bounds` is worth what it buys** (§3.4). The alternative to
  a pre-check is a dry run, and `Rope` offers none; the cost is one O(1)
  helper that must stay in step with `Rope::insert` / `delete` /
  `replace`'s own bounds rules (`src/rope.rs:174-230`). What it buys is
  criterion 17 — an invalid range that costs no history. If the user
  prefers no duplication, the fallback is to accept the shipped
  unconditional clear and **drop criterion 17**, which should be a
  stated trade rather than a silent one.
- **That one extra `bool` on `Buffer` is the right size for terminal
  identity protection** (Q#GB15), rather than the enum §2.11's three
  policies really want. It is deliberately not lock provenance and
  enables no unlock. The bet is that the enum is a separable refactor;
  if it is not, the field becomes churn the refactor has to undo.

## 8. Deferred (named)

- **The REPL's undo exposure** (Q#GB8), with the §2.5 measurement.
- **Class C: `*buffer-list*`, `*help*`, `*workers*`** (Q#GB9), and
  specifically **`*help*`'s two independent owners** (§1.4) — a Rust
  writer at `src/help.rs:354` and a Lua writer at `default.lua:1239`,
  disagreeing on `mark_clean`, each with its own copy of the name
  constant. Whoever takes Class C decides who owns `*help*` before they
  decide what it writes with.
- **The CRDT `Replace` mid-transaction divergence** (§3.4's `Diverged`).
  `EditOp::Replace` is two loro ops — `crdt.delete` then `crdt.insert`
  (`src/buffer.rs:1140-1163`) — and if the first succeeds and the second
  fails, "the CRDT is mid-transaction ... and the rope is unchanged.
  This is an invariant violation", in the code's own words. **This arc
  names the state and contains it; it does not repair it.** Repair means
  either a single transactional splice or a reconciliation pass, both
  loro-level work with no bearing on generated buffers specifically. It
  reaches `apply_edit` and `apply_edit_skip_intercepts` today and is
  reported as an ordinary `CrdtRejected`, so nothing in the tree
  currently distinguishes it — which is the smaller half this arc does
  fix. Named here so the next lane starts from the citation rather than
  the symptom.
- **Suppress-rather-than-clear history recording**, if Stage 2's
  measurement says the per-op clear costs anything.
- **`read_only` in `describe.buffer`** (Q#GB14) — separable, no new
  capability, not required by this arc.
- **Replacing `read_only: bool` with a policy/provenance enum**
  (Q#GB15's rejected alternative). It is the shape §2.11's three
  policies actually want, and it would let `document_bytes` ask the
  question it means instead of the question the flag happens to answer
  (Q#GB16). Rejected here as a refactor this arc would be smuggling;
  named as the right eventual shape.
- **Ordinary edit fan-out after a post-apply `View::on_edit` error.**
  The richer internal outcome makes the pre-existing loss explicit, but
  `apply_edit` and `apply_edit_skip_intercepts` keep their public
  `Result<Edit, BufferError>` surface in this arc. Generated bindings
  retain and fan out the edit; generalizing that contract across every
  Rust and Lua edit caller is separate work.
- **The five `*scratch*` find-or-create copies** (§2.10 Class 5) —
  `default.lua:581`, `:1145`, `listview.lua:190`, `compile.lua:1052`,
  `dired.lua:914`. Correct only while `*scratch*` stays unowned and
  undisambiguated; nothing in the tree connects them, so a future lane
  that gives `*scratch*` an owner breaks all five at once.
- **`*scratch*` can be permanently locked by any Lua caller today.**
  Sweep B (revision 2) found this and revision 2 treated it as a reason
  to ship an unlock. It is a **pre-existing** exposure:
  `pmacs.buffer.set_generated_contents` is already public on `main` and
  already locks any buffer id it is handed. This arc neither creates it
  nor closes it, and revision 5 deliberately adds no unlock because
  `identity_protected` cannot prove who installed the lock. Recorded as
  a standing hazard rather than as this arc's work, which is the
  correction revision 3 began and revision 5 completes.
- **`docs/agent-handoff.md` §4's inventory is keyed by
  `bypass_intercept`** and therefore misses Class C, and its headline
  "four writer mechanisms" is **five** once `src/help.rs:354` is counted
  (§1.4). Not this lane's file to edit mid-flight; carried in the PR
  body.
- **Removed from this list in revision 3: `COHERENCE.md` §14's listview
  consumer list.** PR #189 landed the correction (§1.5). A merged
  correction is removed, not relabelled.
- **Wdired's generated→editable transition.** Revision 1 deferred it,
  revision 2 made a general unlock Stage 1 work, revision 3 moved that
  capability to Stage 2, and revision 5 removes it. The **wdired
  consumer** stays deferred to dired Stage 3, which must frame an
  owner-specific transition or the eventual policy enum rather than
  inheriting a Lua clear of `read_only`.

## 9. Coherence impact (`COHERENCE.md` §20)

**Section served: §14 Coherent Workbench Primitives**, and specifically
its **Output channel** bullet, which is where this caveat is already
recorded ("*four writer mechanisms have not yet adopted it and remain
emptiable*"). This arc discharges that entry for Class A and replaces its
"a streaming variant of the primitive that does not exist yet" with one
that does. §14's list-primitive bullet is touched too: listview is called
"the strongest coherence asset in the UI layer", and it is currently
emptiable by one keystroke.

- **Priority 5 (finish the workbench convergence)** is the priority this
  serves. It is a correctness debt inside an existing primitive rather
  than a new primitive, so it is wiring, not model.
- **§14 consistency, added in revision 2:** Q#GB13 makes three writers
  honour an ownership rule the tree already states (`terminal.lua:300-305`)
  and already implements twice (dired, terminal). That is §14's thesis
  applied to a discipline rather than a view — five generated-buffer
  owners converging on one identity rule instead of three of them
  inventing find-by-name.
- **§6 interaction islands — none added.** No new keymap scope, no new
  dispatch shadow, no new precedence rung. The count stays at six. This
  arc deliberately does **not** add undo-chord rebindings anywhere; the
  measured point of the bug is that rebinding chords was never the fix.
- **§11 configuration registry — no new settings**, no adoption change.
- **§2 golden journey** — step 6 (compile) and the dired/browse steps are
  touched only in the sense that their buffers stop being destructible.
  No journey step opens or closes.
- **Background-work attribution — unchanged.** `compile.lua`'s process
  pump and the grep stream keep their existing ownership.
- **Protocol — no change.** Nothing new crosses the wire; the fan-out
  reuses `queue_daemon_origin_crdt_op`.
- **§14 correction — LANDED, not owed.** PR #189 (`main` @ `7586905`)
  corrected the listview consumer list and moved the scorecard row from
  ✓ to ◐ (§1.5). What remains owed on merge is the **handoff §4 table**,
  whose four-row inventory is keyed by `bypass_intercept`, therefore
  misses Class C, and undercounts the mechanisms by one (`src/help.rs`,
  §1.4).

## 9b. Cross-lane boundaries

**Four lanes touch adjacent ground. The boundaries below are settled
elsewhere and are recorded verbatim rather than re-decided here.**

**#188 → #191 — the acceptance-contract boundary. Added in revision 6:**

> #188 (framing) owns the **acceptance contract**. #191 (Stage 1
> implementation) may not restate, narrow, or reclassify a criterion —
> it adopts what the framing says. Where an implementation found a
> criterion impossible, the framing is revised and re-approved first;
> the implementation then follows. The **selection-anchor clamp** is
> Q#GB6's to specify and #191's to implement, and both must describe the
> same rule.

**What that boundary has already had to settle, twice, in this
revision.** Both are cases where #191 was right about the tree and wrong
about who decides:

1. **Stage 1 criterion 5 was impossible** (round 5, P1-1). #191 reached
   that independently and **restated the criterion locally** — which is
   exactly what the boundary forbids, and which left #191's tests and
   ledger describing a contract this document did not carry. Criterion 5
   is settled *here*, in revision 6; #191 adopts the (a)/(b) split rather
   than its local restatement. The same applies to the criterion 7
   divergence #191's review found.
2. **The selection anchor** (round 5, P1-5). #191 reproduced the panic;
   Q#GB6 in this revision is the specification, including the
   clamp-or-clear rule and the two clamp sites. #191 implements that
   text. If implementation finds it wrong, the correction lands here
   first.

**Why this boundary is worth its overhead.** A framing and its
implementation disagreeing about a criterion is not caught by either
lane's gates — both are green against their own description. It is
caught only by a reviewer holding the two documents side by side, which
is what happened, and only after the divergence had reached #191's tests
*and* its ledger entry.

**#186 / #171 — recorded, not this lane's:**

> #186 owns the urgent **pre-filesystem refusal** for synchronous
> `apply_resource_op`. #171 later owns **full post-delete lifecycle
> reconciliation**, including the **async race where a buffer becomes
> modified after dired dispatch**.

**#171 → #188: Q#DR25 is deferred INTO this lane, and revision 3 is the
first revision to say so.** Revisions 1 and 2 of this document never
mentioned Q#DR25, #171, or dired Stage 2 at all — a gap, since the other
lane had already handed the work over. Read against `#171` revision 7
(`fd7ae37`, pushed 2026-07-28), which is that document's current state:

- #171 §3.1 and its Q#DR25 entry state that dired's listing becoming a
  genuinely immutable generated buffer is **"not Stage 2's decision to
  make"**, that it is **"owned by the `generated-buffer-immutability`
  lane"**, and that **"Stage 2 does not implement it, does not gate on
  it, and carries no acceptance for it."** This document's Stage 1
  claims exactly that work (`dired.lua:369-372` adopting
  `set_generated_contents`), so the claim is live and the two documents
  agree.
- **Neither ordering creates a conflict**, per #171 §3.1: Stage 2b
  changes `paint`'s *callers*, this lane changes `paint` itself. If this
  lane lands first, Stage 2b rebases onto a `paint` that already writes
  through the primitive; if Stage 2b lands first, this lane adopts a
  `paint` with more callers and needs no change to them.
- **One inherited fact this lane must not lose**, recorded in #171 §3.1
  as "a trap for that lane's acceptance":
  `tests/dired_acceptance.rs:969`'s
  `dired_buffer_is_read_only_and_round_trips_input` asserts
  `status(&s).contains("read-only")`, and `BufferError::ReadOnly` renders
  as ``buffer `{name}` (id {id:?}) is read-only`` — so **that test passes
  both before and after the adoption** and is not coverage of it. It is
  cited in Stage 1 criterion 6 as the model for the *document-window
  premise* only; the note at the end of that criterion says so
  explicitly.
- **One difference worth flagging, not a conflict.** #171 revision 5's
  withdrawn plan had dired's `paint` adopt the primitive *"dropping the
  erroring intercept"*. This document keeps the intercept at both
  adopters, per the layering `terminal.lua:351-366` states. Since rev 6
  withdrew the decision from #171 entirely, this lane owns it and there
  is nothing to reconcile — but a reader who finds rev 5's phrasing
  should know it was superseded, not contradicted.

## 10. Verification plan

Full gate suite per `CLAUDE.md` for **each** PR separately:

```
cargo fmt --check
cargo clippy --workspace --all-targets -- -D warnings   # own step
cargo test --lib
cargo test --lib --features crdt
cargo test --test <the touched acceptance suites>
cargo test --test m4_acceptance -- --skip basedpyright
PMACS_REQUIRE_GPU=1 cargo test -p pmacs-gpu
git diff --check
```

Plus, per stage:

- **Stage 1** — `cargo test --test dired_acceptance` and
  `--test listview_acceptance` (the suite exists; `tests/listview_acceptance.rs`),
  plus `--test terminal_copy_mode_acceptance` if Q#GB6 lands, since the
  clamp changes the shipped snapshot path. **Plus
  `--test folding_acceptance`**, added in revision 3: Q#GB16 touches
  `src/lua_bindings/fold.rs` and `read_only_buffer_is_rejected`
  (`tests/folding_acceptance.rs:570`) pins the guard the lock now reaches.
  **Stage 1 touches Rust** (Q#GB6's clamp; Q#GB16's status string), so
  `cargo test --lib` and `--lib --features crdt` are load-bearing for it
  rather than formalities.
- **Stage 2** — `cargo test --test compile_mode_acceptance` **and**
  `--test compile_mode_crdt_acceptance`, plus
  `--test terminal_copy_mode_acceptance` (the `set_generated_contents`
  reimplementation, `mark_clean`, **and Q#GB15's write-direction refusal**
  all reach it), plus `--test vterm_stage1_acceptance` — added in
  revision 3, because `tests/vterm_stage1_acceptance.rs:139,175,290` are
  the shipped assertions about a terminal identity buffer's `read_only`
  and Q#GB15 changes what may touch it. **The search panel has no suite
  of its own** — `grep -rln 'search-results' tests/` returns only
  `compile_mode_acceptance.rs` and `m4_acceptance.rs`, so Stage 2's
  search-panel criteria need a new home rather than an existing one to
  extend.
- **Run the `crdt`-gated terminal suite explicitly, as its own step.
  Added in revision 4 (review round 3, P1-3).**

  ```
  cargo test --test terminal_copy_mode_acceptance --features crdt
  ```

  This is **not** covered by any other line in the gate list.
  `acc16e_a_refresh_queues_the_owners_write_for_replica_mirrors` is
  `#[cfg(feature = "crdt")]` (`tests/terminal_copy_mode_acceptance.rs:567`),
  and it is the shipped consumer of the lift-and-restore idiom that
  revision 3's `generated_lock` would have broken. A default-feature run
  of the same suite **never compiles it**, so a green sweep proves
  nothing about the seam P1-3 is about. Judge it by whether the test
  count includes `acc16e`, not by the verdict alone.
- **Stage 2 additionally needs a `crdt` run of whatever suite hosts the
  §3.4 transaction criteria**, for criterion 15a's replica half and
  criterion 16's second half. Criteria 16c and 16d live principally in
  `cargo test --lib --features crdt` because the common `crdt_mutated`
  routing seam and quarantine state are unit-test fault seams, not
  public acceptance inputs. Their explicit-target, legacy-attach,
  buffer-follow, queue and interactive-preflight halves may live in the
  corresponding in-crate modules; no production fault-injection API is
  added. Same reasoning, same failure mode.
- **Run `scripts/bite` on every criterion expressible as a test today,
  and read its new exit codes** (`main` @ `64883eb`, PR #192). Exit **0**
  is a real bite; **1** is vacuous; **3 is `NO CONTROL`** — the named
  tests did not pass on the working tree, or **none ran**, which is the
  filter-matches-nothing case that used to read as success; **4** is
  `INCONCLUSIVE (MIXED)`. The swapped run is labelled `OK (assertion)` or
  `OK (COMPILE)`. **Prefer `OK (assertion)`** and treat `OK (COMPILE)` as
  a prompt to narrow the swap to a file that builds both ways — a
  compile break proves the swap changed something, not that the test
  discriminates. Every "falsify by …" in §6 names a one-file change
  precisely so it can be run through this rather than asserted.
- **Run `scripts/bite` on every criterion expressible as a test today.**
  Stage 1 criteria 1–3, 5(a), 8 and 9 and Stage 2 criteria 1, 7, 8, 9,
  14, 15a, 16, 16b and 22 have `main` pre-images and can be falsified
  against the base. Criteria 15a, 16, 16b and 22 also name independent
  post-fix mutations; do not substitute the base run for those mutation
  runs. Every remaining criterion is fix-shape, structural or mutation
  coverage and names that bite inline. A criterion whose bite cannot be
  stated as one of those is not finished.
- **Do not gate any new test on `#[cfg(feature = "crdt")]` unless it
  genuinely needs CRDT.** CI never enables the feature — measured at
  `ad41cf1`, **276 tests are dark** as a result:

  ```
  cargo test --all-targets --no-default-features --features lua54 -- --list \
    | grep -c ': test$'          # 3251   (CI's exact flags)
  cargo test --all-targets --no-default-features --features lua54,crdt -- --list \
    | grep -c ': test$'          # 3527
  ```

  3,527 − 3,251 = **276**. **Revision 3 deliberately does NOT re-quote
  this at `7586905`.** The base moved (#189, `COHERENCE.md` only, which
  adds no tests), so the reading is very probably unchanged — but "very
  probably unchanged" is the reasoning the ledger warns against, and a
  framing doc is not the authority for this number in any case. Treat
  276 as a reading taken at `ad41cf1`, not as a constant. **Re-measured
  in revision 2 (review P2-5).**
  Revision 1 quoted **264**, which `docs/active-work.md:107-115` labels
  historical (#168's reading at `1b6a084`) and explicitly warns against:
  "the number moves with every merge and must be re-measured, not
  quoted." The ledger's own most recent figure is 273 at `74301d1`; this
  arc's base is later, and the number should be re-measured again rather
  than quoted from here.
- **Judge the touched suites by elapsed time as well as verdict** where
  they reach for a sibling binary (`docs/agent-handoff.md` §5).
- Commit before gating: `cargo fmt` after a commit splits the worktree
  from the branch and `git diff --check` will not catch it.