docs(evidence): D0a executed --- the source hypothesis is eliminated

Ten runs under the approved contract: counterbalanced A B B A A B B A A
B, N = 5 per endpoint, clean detached worktrees at 7599661 and 724b785,
isolated target directories, the gate's build-crdt precondition then its
sweep-crdt command, dirty=0 verified per run. Zero voids, zero splits.

A (7599661) uniform-red. B (724b785) uniform-red. By the approved
endpoint table that is the both-endpoints-uniform-same row: the
difference is NOT captured by those two commits.

What it settles:

  - No bisect of 7599661..724b785 is justified, and none will run.
    7599661 passed inside sweep-crdt on 08-15 and fails 5/5 clean today,
    so the interval cannot contain the transition.
  - The onset window is demoted --- still a true observation, but not
    reachable by source.
  - A RELIABLE REPRODUCTION now exists: 10/10 today across two commits
    at ~4 minutes per run. This is D0a's most useful product, because
    D1/D2 no longer depend on catching a rare event.

What it does not settle: anything about the mechanism. One cheap
negative on "what else changed" --- no package activity in the window per
pacman.log, nearest on 08-18 --- and it is not pursued further, because
with a reproduction in hand direct measurement dominates archaeology.

A's three extra failing binaries are recorded rather than swept up:
a54_real_daemon_real_pty_and_headless_gpu_render..., a v21/v20 row
expected to differ at that older commit, and m6_1_pty_mode_lifecycle.
Two of the three are process/PTY-spawn rows, the same family as the
target. None affect classification, which reads only the two target
copies.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016bqGA6s9tTUFzYpbeW3tai

docs/active-work.md

@@ -270,7 +270,7 @@ hazard in a shape that looks committed. **A documented error message
 that never appears is worse than no documentation**, because the reader
 waits for a signal that is not coming.
 
-## GPU launcher / probe SIGINT teardown — FRAMING APPROVED, diagnostics not started
+## GPU launcher / probe SIGINT teardown — D0a DONE, mechanism unknown
 
 **Written with the branch's FIRST commit**, per the standing correction
 from #171 and #215.
@@ -285,6 +285,19 @@ from #171 and #215.
   rather than guessing. Revisions 1, 2 and 3 were each rejected on
   findings, all upheld; run provenance lives in
   `docs/probe-sigint-evidence.md`.
+- **D0a EXECUTED 2026-08-19 — verdict: difference NOT captured by the
+  two commits.** 10 runs, counterbalanced, N=5 per endpoint, clean
+  detached worktrees with isolated target dirs, `dirty=0` per run, zero
+  voids, zero splits. **A (`7599661`) uniform-red; B (`724b785`)
+  uniform-red.** So `7599661`, which passed inside `sweep-crdt` on
+  08-15, fails 5/5 clean today: **the source hypothesis is eliminated
+  and no bisect will run.** The onset window is demoted to a true but
+  unreachable-by-source observation. No package activity in the window
+  (`pacman.log`), which is a cheap negative and not pursued further.
+- **The useful product is a RELIABLE REPRODUCTION** — 10/10 across two
+  commits at ~4 min/run. D1/D2 no longer wait on a rare event and are
+  the next step. Per-run provenance in `docs/probe-sigint-evidence.md`
+  §D0a and `/home/jeans/build/pmacs-gate-targets/d0a/results.tsv`.
 - **Why it exists.** `ctrl_c_on_launcher_group_does_not_reach_spawned_daemon`
   fails in gate stage `sweep-crdt` with "child did not exit within 5s".
   **Pre-existing on `main`** — `72da24a` fails it in a clean worktree

docs/gpu-probe-sigint-framing.md

@@ -1,6 +1,8 @@
 # GPU launcher / probe SIGINT teardown — framing
 
-Revision 9. Status: **approved 2026-08-19 at `15c25ec`. No implementation.**
+Revision 9, approved 2026-08-19 at `15c25ec`.
+Status: **D0a EXECUTED — see §4b. No fix implemented; mechanism still
+unknown.**
 
 Revisions 1 and 2 were each rejected on five findings. Every correction
 is recorded in place rather than quietly rewritten, because three of
@@ -267,6 +269,32 @@ rule; a bare difference decides nothing.)
 move**, as endpoint reproduction — which is a decision procedure, not a
 prediction.
 
+## 4b. D0a result — the source hypothesis is eliminated
+
+Executed 2026-08-19 under the approved contract: 10 runs,
+counterbalanced `A B B A A B B A A B`, N = 5 per endpoint, clean
+detached worktrees, isolated target directories, `dirty=0` verified per
+run. **Zero voids, zero splits.**
+
+**A (`7599661`) uniform-red. B (`724b785`) uniform-red.** By the
+endpoint table this is *both endpoints uniform the same way*: the
+difference is **not captured by those two commits**.
+
+- **No bisect of `7599661..724b785` is justified, and none will run.**
+  `7599661` passed inside `sweep-crdt` on 08-15 and fails 5/5 clean
+  today, so the interval cannot contain the transition.
+- **The onset window is demoted.** Still a true observation, but not
+  reachable by source.
+- **A reliable reproduction now exists** — 10/10 today across two
+  commits, ~4 minutes per run. This is D0a's most useful product:
+  **D1/D2 no longer wait on a rare event.**
+- One cheap negative on "what else changed": **no package activity in
+  the window** (`/var/log/pacman.log`, 08-15 19:57 → 08-16 06:33;
+  nearest 08-18). Not pursued further — with a reproduction in hand,
+  direct measurement dominates archaeology.
+
+Per-run provenance: `docs/probe-sigint-evidence.md` §D0a.
+
 ## 5. Two retracted claims, both mine, kept as warnings
 
 **Claim A — "mechanism located".** Reported the launcher blocked in

docs/probe-sigint-evidence.md

@@ -157,6 +157,69 @@ source/environment interaction, or a fix before `7599661` followed by a
 regression before `724b785`. And an ancestor outside the interval is
 irrelevant to whether the interval contains a regression.
 
+## D0a — EXECUTED 2026-08-19. Verdict: difference NOT captured
+
+Ten runs, counterbalanced `A B B A A B B A A B`, N = 5 per endpoint,
+**zero voids, zero splits**. Endpoints checked out detached and clean
+in dedicated worktrees (`pmacs-d0a-A`, `pmacs-d0a-B`), each with its own
+target directory, each run performing the gate's `build-crdt`
+precondition then the `sweep-crdt` command. `dirty=0` verified per run.
+
+| run | endpoint | HEAD | class | ctrl_c ok/failed | red bins | log |
+|---|---|---|---|---|---|---|
+| A#1 | A | `7599661` | **red** | 0 / 2 | 3 | `d0a/A-1.log` |
+| B#1 | B | `724b785` | **red** | 0 / 2 | 2 | `d0a/B-1.log` |
+| B#2 | B | `724b785` | **red** | 0 / 2 | 2 | `d0a/B-2.log` |
+| A#2 | A | `7599661` | **red** | 0 / 2 | 4 | `d0a/A-2.log` |
+| A#3 | A | `7599661` | **red** | 0 / 2 | 3 | `d0a/A-3.log` |
+| B#3 | B | `724b785` | **red** | 0 / 2 | 2 | `d0a/B-3.log` |
+| B#4 | B | `724b785` | **red** | 0 / 2 | 2 | `d0a/B-4.log` |
+| A#4 | A | `7599661` | **red** | 0 / 2 | 3 | `d0a/A-4.log` |
+| A#5 | A | `7599661` | **red** | 0 / 2 | 3 | `d0a/A-5.log` |
+| B#5 | B | `724b785` | **red** | 0 / 2 | 2 | `d0a/B-5.log` |
+
+Full per-run provenance — timestamp, HEAD, dirty count, exit, both copy
+results, unrelated red-bin count, Cargo suffixes, `uptime`, `free`,
+`/tmp` usage, leaked-daemon count, log digest — is in
+`/home/jeans/build/pmacs-gate-targets/d0a/results.tsv`.
+
+**Endpoint verdicts: A uniform-red, B uniform-red.** By the approved
+table this is the *both endpoints uniform the same way* row:
+
+> **the difference is not captured by those two commits** under current
+> conditions, and the question becomes what else changed across the
+> window.
+
+### What this settles
+
+- **The source hypothesis is eliminated for this interval.** `7599661`
+  passed inside `sweep-crdt` on 08-15 and now fails **5/5** clean. No
+  bisect of `7599661..724b785` is justified, and none will be run.
+- **The onset window is demoted as a lead.** It remains a true
+  observation, but since neither endpoint reproduces the old green, the
+  window cannot be probed by source at all.
+- **A reliable reproduction now exists.** 10/10 today, on two different
+  commits, at ~4 minutes per run. **This is the most useful thing D0a
+  produced**: the mechanism diagnostics D1/D2 no longer depend on a
+  rare event, and can proceed immediately.
+- **A's three extra failures are recorded, not swept up**:
+  `a54_real_daemon_real_pty_and_headless_gpu_render_one_panel_hosted_terminal`,
+  `one_daemon_serves_a_v21_panel_session_and_a_shipped_v20_client`, and
+  `m6_1_pty_mode_lifecycle_started_then_exited`. The v21/v20 row is
+  expected to differ at that older commit; the other two are
+  process/PTY-spawn rows, the same family as the target. They do not
+  affect classification, which reads only the two target copies.
+
+### What it does not settle
+
+Nothing about the mechanism. "What else changed across the window" has
+one cheap negative result so far: **no package activity in the window**
+(`/var/log/pacman.log` shows nothing between 08-15 19:57 and 08-16
+06:33; nearest is 08-18). The `1.88` rust toolchain directory has mtime
+08-15 22:39, inside the window, but the gate builds with `1.95.0`.
+Neither is pursued further, because with a reliable reproduction in
+hand **direct measurement (D1/D2) dominates archaeology**.
+
 ## D0 — re-run the matrix with captured provenance
 
 Before any §4 row is relied on for a conclusion, re-run the reductions