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

Generated-buffer immutability

PROPOSED — needs explicit user approval before implementation. DO NOT implement, DO NOT merge.

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:1853-1857), 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 the unlock needed provenance (Q#GB15), why the lock silently disables fold creation (Q#GB16), and why the shipped primitive can already overwrite a live terminal's identity buffer.

---

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:2575) → 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:1814) updates each window's TextView and overlays. It does not clamp win.cursor or win.view_top. Only rebuild_views_for (:1843) does, and its doc comment says so explicitly (:1841-1842). 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:1853-1857); 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:1436,1984,2128,2163, src/daemon.rs:2976). 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:3704	no — the TUI mode-line *
src/semantic_render.rs:1347	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:1347, 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:1945 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) -> Result<Edit, BufferError> — one authorized op at a time — exposed to Lua as a new option key on the mutators that already exist:

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 the Edit out through the notify_buffer_edit_to_windows call it already makes (src/lua_bindings/mod.rs:1291, :1302, :1322), after the borrow has dropped.

Buffer::set_generated_contents(bytes) is reimplemented as apply_generated_edit(Replace { range: 0..len, bytes }). It keeps its name, its signature, its doc comment and its tests — 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 deletes 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 Edits are fanned out, and when? One per generated op, immediately, by the binding that already does it. 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. This is exactly today's fan-out count — the conversion changes authority, not cardinality.

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. 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. History clearing goes to loro's UndoManager. Nothing new.

How do the returned edits reach the fan-out without a live registry borrow? By construction, unchanged since #178: 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.

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:

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.

The ordering, with every exit path named. n marks the numbered exits; each row states the buffer state a caller observes afterwards.

pub fn apply_generated_edit(&mut self, op: EditOp<'_>) -> Result<Edit, BufferError> {
    // (1) Q#GB10: path-backed refusal. Before any state change.
    if self.file_path.is_some() { return Err(GeneratedWriteOnFileBuffer { .. }); }
    // (2) Q#GB15: refuse a lock this primitive did not install.
    if self.read_only && !self.generated_lock { return Err(ReadOnly { .. }); }
    // (3) re-entrancy gate — begin_edit's SECOND check, not its first.
    if self.editing_in_progress { return Err(ConcurrentEdit { .. }); }
    // (4) bounds pre-validation, so an invalid range costs nothing.
    self.validate_op_bounds(&op)?;

    self.editing_in_progress = true;
    let rev_before = self.revision();
    self.read_only = false;                       // the ONLY unlocked interval
    let result = self.apply_edit_skip_intercepts(op);
    self.read_only = true;                        // (5) relock, unconditional
    self.generated_lock = true;
    if self.revision() != rev_before {            // (6) history, iff an edit landed
        self.clear_history();
        if result.is_ok() { self.mark_clean(); }  // (7) Q#GB10's flag
    }
    self.editing_in_progress = false;             // (8) unconditional
    result
}

exit	when	read_only after	editing_in_progress after	history	contents
(1)	file_path is Some	unchanged	unchanged (false)	untouched	untouched
(2)	someone else's lock (terminal identity)	unchanged (true)	unchanged	untouched	untouched
(3)	re-entrant on the same buffer	unchanged	unchanged (true, owned by the outer edit)	untouched	untouched
(4)	range out of bounds	unchanged	unchanged (false)	untouched	untouched
Err from CRDT	mid-codepoint position, CRDT mode	true	false	untouched	untouched (src/buffer.rs:1843-1844: "the CRDT op is attempted before the rope mutation, so this error leaves the rope unchanged")
Err from on_edit	a view rejected the broadcast	true	false	cleared	mutated
Ok, no-op	empty insert / empty range	true	false	untouched	unchanged
Ok	the ordinary case	true	false	cleared	replaced

Why the relock is unconditional and not "restore what it was." The primitive's contract is leave it genuinely immutable, so the post-state is true on every path past (4), exactly as shipped set_generated_contents already does (src/buffer.rs:554). Restoring a saved prior value would let a first write on a fresh buffer leave it writable.

Why end_edit cannot be skipped. It is line (8), unconditional, and it is 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 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.

History: the exact rule, and why it is not the shipped one. Shipped set_generated_contents calls clear_history() unconditionally, including on failure (src/buffer.rs:551-553, with a comment defending it). That is defensible for a whole-buffer replace of a buffer whose history the primitive owns. It stops being defensible once { generated = true } is public on any pathless buffer: a caller who passes a bad range to *scratch* would destroy a user's undo history via a call that changed nothing. Review P1-1 asks for the ordering; it is:

• Pre-validate bounds (4), so the common failure — an out-of-range op — is a pure refusal that touches neither the lock, the history, nor the flag. This is what makes the destructive-clear concern moot for every reachable caller error.
• Clear iff the revision advanced (6), which is exact rather than approximate. self.revision is bumped in the state-update stage (src/buffer.rs:1284) after the rope swap and the undo push and before the on_edit broadcast (:1286-1289), and the no-op arm returns early without bumping it (:1245-1253). So "revision advanced" is true exactly when an undo entry was pushed — including on the one failure mode that mutates before erroring (a view rejecting the broadcast), which is the case shipped code's unconditional clear exists for, and false on every refusal.
• mark_clean only on Ok (7). A half-applied write is not a clean buffer, and Q#GB10's safety argument (both load-bearing consumers gate on file_path) is about whether the flag may be cleared at all, not about clearing it over a failure.

Cost, stated rather than buried. 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, signature and tests. 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:

if generated {
    unfold_before_interactive_lua_edit(lua, id, edit_start_of(&op));
    run_generated_edit(lua, id, op)          // no begin_edit; §3.4
} else if bypass_intercept {
    unfold_before_interactive_lua_edit(lua, id, edit_start_of(&op));
    run_bypass_edit(lua, id, op)
} else {
    run_managed_edit(lua, id, op)
}

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.

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:1853-1857, 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.

Recommended for Stage 1, because Stage 1's adopters refresh shrinking panels constantly and because it fixes terminal copy mode retroactively. 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.

Q#GB7 — The unlock survives ONLY bounded by lock provenance, and it moves to Stage 2. Revision 3 withdraws revision 2's recommendation (review P1-3).

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.

The decision. The capability survives, bounded by lock provenance (Q#GB15), and:

• pmacs.buffer.unlock_generated(buf) refuses any buffer whose lock this arc's primitive did not install — terminal identity buffers, and anything a future Rust owner locks for its own reasons. It is not a clear of read_only; it is the inverse of apply_generated_edit's lock, and it can undo only what the same public API did.
• It moves to Stage 2, with Q#GB15, because it is meaningless without the provenance the same field provides and because Stage 2 is where the lock capability actually widens.
• Its claim narrows. It is the closure of the capability { generated = true } adds — not a recovery mechanism. The honest statement of what it buys: after a mistaken generated write, the buffer becomes writable again; its former contents do not come back.

On the standing asymmetry the review asks this to address directly (remove_intercept is exposed; set_read_only deliberately is not, src/lua_bindings/mod.rs:3072-3078 and docs/agent-handoff.md §4). A provenance-bounded unlock_generated does not breach that policy, and the reason is precise rather than rhetorical: it can only reach a lock that a public Lua call installed, so it adds no reachable state that { generated = true } did not already make reachable. A set_read_only(buf, true) would add the "lock with no door" state the invariant exists to forbid; a set_read_only(buf, false) would reach locks Lua never set. This reaches neither. If that argument does not persuade, the fallback is to ship no unlock at all and let dired Stage 3 frame its own door — which costs this arc nothing, because Stage 3 is not built.

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 a provenance companion. New in revision 3 (review P1-3, sweep C).

Buffer gains one private field beside read_only:

/// Whether this buffer's `read_only` flag was set by a generated write.
/// Invariant: `generated_lock` implies `read_only`.
generated_lock: bool,

Three rules maintain it, and all three are in Buffer:

1. apply_generated_edit sets both on success (§3.4 line 5) and refuses a buffer that is read_only with generated_lock == false (§3.4 exit 2).
2. unlock_generated refuses unless generated_lock, then clears both.
3. Buffer::set_read_only(v) — the existing Rust setter, whose callers are terminal/session.rs:305 and test code — clears generated_lock whenever it is called, in either direction. That is what keeps the invariant true without asking six existing call sites to think about it.

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. It is why the field earns its cost in both directions rather than existing only to make Q#GB7 safe.

The alternatives, and why not.

• A registry-side set of generated-locked ids, held as Lua app-data. 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". A field on the buffer cannot drift from the buffer.
• 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 invariant (generated_lock ⇒ read_only) that rule 3 exists to maintain; 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 read_only && !generated_lock. 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, eight named exits, and history cleared iff the revision advanced. 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 (Stage 2, with Q#GB13's ownership fix). 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:

• compile keeps an owner-registered id list; ensure_slot adds slot.buf, and ensure_search_panel calls pmacs.compile._register_generated_buffer(p.buf);
• is_generated_buffer(buf) becomes a == scan of that list;
• teardown is an obligation, not an afterthought: all three owners already register pmacs.buffer.on_removed (compile.lua:277-279, default.lua:876-883), so the same callbacks unregister. A registry that only grows is the defect the terminal-config lane records as "prune reacts to buffer removal"; naming it here is what keeps it from being rediscovered in review.

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_cleans, 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:3704) 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.created, 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.

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 removes unlock_generated from Stage 1 (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. The capability re-appears in Stage 2, bounded by Q#GB15's provenance.

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 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 scans an owner-registered id list, with registration in ensure_slot and ensure_search_panel and unregistration in the on_removed callbacks both already have.
• 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 generated_lock field, its write-direction refusal, and pmacs.buffer.unlock_generated bounded by it (Q#GB7). All three edit set_generated_contents or the flag it sets, so they belong with the reimplementation.
• 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) moves to Stage 2, bounded by Q#GB15. Revision 1 deferred it; revision 2 built it in Stage 1 on an argument review P1-3 falsified; revision 3 lands it in Stage 2 with the provenance that makes it a bounded capability rather than a general one. The two reversals are recorded rather than smoothed over because the reason moved twice and the next reader needs to know which reason 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:

class	meaning
main	fails on ad41cf1. A regression pin in the ordinary sense.
fix-shape	passes on main by design; 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	passes on main; fails against a named one-line mutation of the fix.
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 intercept refuses it either way.

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. [fix-shape] An ordinary edit is refused by the INTERCEPT, not by the rope — assert on the message text, which distinguishes them. Measured, both forms: the intercept produces intercept rejected the edit: ... listview.lua:102: *probe-panel* is read-only; the rope produces buffer `*probe*` (id BufferId(4)) is read-only. Bite: an adopter that deletes the intercept and relies on the rope passes 1–4 and fails this. The layering at terminal.lua:351-366 requires the named error to survive.

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:1853-1857), not measured — staging it needs a scrolled window.

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. [fix-shape] A locked generated buffer is not foldable, and says so accurately (Q#GB16). On a locked dired listing: pmacs.fold.fold(buf, range) returns false and the status names the read-only lock rather than not a document buffer. Bite: the first half passes on main for the wrong reason before the lock — a dired buffer is a perfectly ordinary document buffer today and folds fine, so the pre-image for the first half is after Stage 1's lock; that is precisely the silent behaviour change sweep C found, and the criterion's job is to make it stated. The second half is the discriminator: it fails against a Stage 1 that locks the buffer and leaves fold.rs:68's message alone, which is the shape that would ship without this criterion. Falsify by reverting the status string.

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: the unlock criterion. Revision 2's Stage 1 criterion 11 pinned unlock_generated; Q#GB7 moves the capability to Stage 2, so the criterion moves with it (Stage 2 criterion 13) and grows the negative terminal-identity half review P1-3 asks for.

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 15–18, the §3.4 transaction criteria. CRDT must not be the only home of any of them; CI never enables the feature. Two of the transaction's error paths are CRDT-only in origin (the mid-codepoint CrdtRejected row of §3.4's table has no default-feature analogue), so the default configuration is the one at risk of leaving them unexercised, not the CRDT one — the usual asymmetry runs the other way and this is the exception.

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, the provenance, and the bounded unlock.

13. [main] The unlock is real, is narrow, and refuses a lock it did not install (Q#GB7 + Q#GB15; review P1-3). Three halves, and the third is the one revision 2 lacked.

    • Real: on a plain pathless buffer with no intercept, a generated write locks it (a bypass_intercept write raises), unlock_generated releases it (a bypass write lands), and an ordinary edit then lands too.
    • Narrow: on a listview panel, after unlock_generated an ordinary edit is still refused by the intercept, asserted on the full message text per Stage 1 criterion 5.
    • Negative terminal identity, the criterion review P1-3 asks for: open a real terminal, take its identity buffer id, and require pmacs.buffer.unlock_generated(term_buf) to error, with Buffer::is_read_only() still true afterwards and an ordinary edit still refused. Assert the post-state, not the error alone.

    Bite: a no-op unlock fails the first half; an unlock that also tears down the intercept — "unprotect" rather than "unlock" — fails the second; and revision 2's unlock_generated as written passes the first two and fails the third, which is the whole finding. Falsify the third by deleting the generated_lock check.

14. [main] A generated write REFUSES a buffer someone else locked (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.

15. [main] editing_in_progress is cleared on the ERROR path (Q#GB17; review P1-1). Drive a generated write to a failure — the cheapest reachable one is §3.4 exit 4, an out-of-bounds range — then require that an ordinary edit on the same buffer afterwards reports the intercept's message, not is already being edited. Bite: an implementation that sets the flag and returns early on the invalid-range path leaves it set, and begin_edit (:726-731) and apply_edit (:774-779) then refuse every later edit to that buffer for the rest of the session. Falsify by moving the flag clear above the error return. Assert the next edit's outcome, not the failing call's — the failing call reports the same error either way, which is why this criterion is about the buffer's state afterwards.

16. [main] A generated write RELOCKS on the error path (Q#GB17). After the same failure, Buffer::is_read_only() must be true and a bypass_intercept write must raise. Bite: an implementation that unlocks before validating and returns without relocking leaves the buffer writable and every criterion about undo silently stops applying. §3.4 orders validation before the unlock so this particular path cannot arise, and the criterion is what pins that ordering rather than trusting it.

17. [main] 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. [main] 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.

---

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 lock provenance (Q#GB15), rather than the enum §2.11's three policies really want. 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.
• 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 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.
• 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 — Q#GB15's provenance bounds who may unlock, not who may lock. Recorded as a standing hazard rather than as this arc's work, which is the correction revision 3 makes to sweep B's conclusion.
• 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.
• Returned to this list in revision 3: wdired's unlock. Revision 1 deferred it, revision 2 made it Stage 1 work, and revision 3 lands the capability in Stage 2 (Q#GB7 + Q#GB15) while the wdired consumer itself stays deferred to dired Stage 3, which is not framed.

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

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

#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 scripts/bite on every criterion expressible as a test today. Stage 1 criteria 1–3, 8, 9 and Stage 2 criteria 1, 7, 8, 9, 14 have main pre-images and can be falsified by revert; the rest are fix-shape or mutation bites and each names its mutation inline. A criterion whose bite cannot be stated as either 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.