docs(remediation): sharpen D-8 — the conformance harness must itself be conformance-tested

Per Mos. Two requirements, both load-bearing:

RM-02: the gate registry must SELF-VERIFY that every registered case demonstrably
runs and demonstrably fails on a known-bad input. Presence in the registry is not
evidence. A check is not trusted until it has been shown to fail. This is mutation
testing / negative control at the registry level — the conformance harness must
itself be conformance-tested. RM-55 inherits the same recursion: the harness must be
observed red before its green means anything.

Reviewer disclosure: rev-974 could have silently substituted a working fixture and
reported AC2 PASS, and nothing would have caught it. The 'if a check is unrunnable,
say so rather than silently substituting' clause is what makes a PASS mean anything,
and must appear in every reviewer brief this mission issues.

Co-Authored-By: Claude Opus 5 (1M context) <[email protected]>

docs/remediation/BOARD-LEDGER.md

@@ -3,3 +3,13 @@
 ### **D-1 / P-ACTIVATION + hygiene — committed `.npmrc` hard-pins `store-dir=/root/.local/share/pnpm/store`.**
 
 Correct for the CI container (runs as root), fatal for EVERY non-root local checkout: `EACCES` on `/root/.local/share/pnpm/store/v10/server/server.json`. A committed config that only works on one runtime is exactly the activation-skew class. Fix candidate: make store-dir env-overridable, not hardcoded.
+
+<!-- board-roll: 2 entries rolled from BOARD.md -->
+
+### **D-3 / P-FLEET-001 — the seats running this mission are UNMANAGED.** `mos-remediation`, `rev-974`,
+
+`planner-opus`, `planner-sol` appear in NO roster (`~/.config/mosaic/fleet/roster.yaml`, `agents/`). Planners run on socket `default`; the roster declares `mosaic-fleet`. This is the exact "one roster-owned socket/host + quarantine unmanaged + stale GC" failure P-FLEET-001 indicts — observed on the remediation mission's own fleet. Prerequisite for INBOX identity-addressing.
+
+### **D-2 / hygiene — husky `prepare` fails `EPERM` copying into root-owned `.husky/_/`.** Repo working
+
+tree has root-owned dirs (`.husky/`, repo root) under a non-root agent. Worked around with the intended `HUSKY=0` escape hatch (does NOT disable the existing pre-commit/pre-push hooks).

docs/remediation/BOARD.md

@@ -1,6 +1,6 @@
 # mos-remediation — LIVE BOARD (keep < 8 KB)
 
-**Phase:** PLANNING COMPLETE — reconciled backlog landed; 3 decisions block dispatch.
+**Phase:** EXECUTING — first PR merged; RM-01 in flight; all 3 decisions ruled.
 **Updated:** 2026-07-31 (mos-remediation orchestrator; seat active on `mosaic-fleet`).
 
 ## Head
@@ -16,14 +16,14 @@
 
 ## In-flight
 
-| Task                                              | Owner           | State                                                 |
-| ------------------------------------------------- | --------------- | ----------------------------------------------------- |
-| PR #1026 `remediation/mission-setup` (docs-only)  | mos-remediation | OPEN, stacked on #1025; retarget to main after merge  |
-| PR #1025 `fix/hygiene-inert-format-gate`          | rev-974         | OPEN; ACs pre-registered 22:12:26Z; review DISPATCHED |
-| DECISION-1 wire-in point (charter change)         | Mos / Jason     | ESCALATED — both planners reject the charter's target |
-| DECISION-2 rollback artifact + availability trade | Jason           | ESCALATED                                             |
-| DECISION-3 RM-03 vs parked PR #1023 ownership     | Mos             | ESCALATED                                             |
-| RM-01 reproducible checkout (unblocks everything) | unassigned      | READY TO DISPATCH                                     |
+| Task                                              | Owner           | State                                                              |
+| ------------------------------------------------- | --------------- | ------------------------------------------------------------------ |
+| PR #1026 docs (mission record + backlog)          | mos-remediation | OPEN, retargeted to main, rebased; diff verified docs-only         |
+| PR #1025 hygiene                                  | —               | **MERGED** 52414605; rev-974 APPROVE + CI #2158 8/8 terminal-green |
+| DECISION-1 wire-in point (charter change)         | Mos / Jason     | ESCALATED — both planners reject the charter's target              |
+| DECISION-2 rollback artifact + availability trade | Jason           | ESCALATED                                                          |
+| DECISION-3 RM-03 vs parked PR #1023 ownership     | Mos             | ESCALATED                                                          |
+| RM-01 reproducible checkout (unblocks everything) | unassigned      | READY TO DISPATCH                                                  |
 
 ## Fleet seats
 
@@ -60,6 +60,10 @@
 
 <!-- BOARD-ROLL:START -->
 
+### **D-8 / P-CONFORMANCE-001 — a PRE-REGISTERED acceptance check that was not runnable as written.**
+
+PR #1025 AC2's fixture `mkdir -p apps/*/venv/lib` creates a literal `apps/*/venv/lib` dir when the glob is unmatched — it did not test what it claimed. rev-974 ran it exactly as written, caught it, re-ran the intended assertion at an explicit path, and **disclosed** rather than silently substituting a working fixture and reporting PASS. **Pre-registration protects a check from being retrofitted to the implementation; it does not make the check correct.** An unverified gate appeared inside the mechanism built to catch unverified gates. Hard requirement on RM-02: the registry must self-verify that every registered case runs AND can fail — presence is not evidence.
+
 ### **D-7 / P-FLEET-001 — stale-GC-on-disk: shared 30G /tmp hit 100% ENOSPC, degrading two seats.**
 
 ~5.2G was session scratch dead 8-9 days (this session's own footprint: 88K). Same missing capability as orphaned-tmux-session GC, applied to disk — not a quota or discipline problem. Resolved manually by Mos (lead coordinator) after independent verification; `/tmp` now 79%. **The gap IS the finding:** the authority to reap exists, the deterministic reaper does not. Folded into RM-50 with explicit requirements (mechanical liveness, age threshold, dry-run, audit event per reap — never a heuristic sweep). Refusing to unilaterally delete another session's scratch was correct doctrine; the fix is a reaper, not braver agents.
@@ -76,14 +80,6 @@ Merged PR #868 (`b79336a8`) shipped a file that FAILS `pnpm format:check` ⇒ th
 
 planner-sol was at 64.3%/372k; the brief asked it to reset first; it began work on dirty context anyway. Only an out-of-band `/new` driven by the orchestrator guaranteed clean state. Confirms the postmortem thesis: **instructions are not enforcement.** Reset must be a mechanical pre-dispatch step, not a request.
 
-### **D-3 / P-FLEET-001 — the seats running this mission are UNMANAGED.** `mos-remediation`, `rev-974`,
-
-`planner-opus`, `planner-sol` appear in NO roster (`~/.config/mosaic/fleet/roster.yaml`, `agents/`). Planners run on socket `default`; the roster declares `mosaic-fleet`. This is the exact "one roster-owned socket/host + quarantine unmanaged + stale GC" failure P-FLEET-001 indicts — observed on the remediation mission's own fleet. Prerequisite for INBOX identity-addressing.
-
-### **D-2 / hygiene — husky `prepare` fails `EPERM` copying into root-owned `.husky/_/`.** Repo working
-
-tree has root-owned dirs (`.husky/`, repo root) under a non-root agent. Worked around with the intended `HUSKY=0` escape hatch (does NOT disable the existing pre-commit/pre-push hooks).
-
 <!-- BOARD-ROLL:END -->
 
 ## Decisions log

docs/remediation/TASKS.md

@@ -93,6 +93,47 @@ and must not be cited as merge evidence. Rely on reviewer clearance + real CI.
 Three independent live instances in a single session — format gate, agent context reset, queue guard —
 is the class confirmed, not anecdote.
 
+### D-8 — a PRE-REGISTERED acceptance check that was not runnable as written
+
+On PR #1025 the author (me) pre-registered AC2 with the fixture snippet `mkdir -p apps/*/venv/lib`.
+In bash, when no `venv` exists the glob is unmatched and passes through literally, creating a
+directory named `apps/*/venv/lib` rather than one per workspace. The check as written did not test
+what it claimed to test.
+
+`rev-974` ran it **exactly as written**, observed the wrong behaviour, then re-ran the intended
+assertion at an explicit path — **and said so in the review** rather than silently substituting a
+working fixture and reporting PASS.
+
+Two things this establishes:
+
+1. **The instruction "do not adjust a check to fit the diff; if it is unrunnable, say so explicitly"
+   worked.** A silent substitution here would have produced a green AC2 that proved nothing, on the
+   exact task whose subject is gates that appear to work. The disclosure is what made the PASS
+   meaningful.
+2. **Pre-registration does not confer correctness.** A pre-registered check is protected from being
+   retrofitted to the implementation; it is not protected from being _wrong when written_. This is a
+   small instance of the mission's own class — an unverified gate — occurring inside the mechanism
+   built to catch unverified gates.
+
+**Requirement on RM-02 (non-negotiable, sharpened by Mos).** The registry must **self-verify** that
+every registered case demonstrably **runs** and demonstrably **fails on a known-bad input**.
+Presence in the registry is **not** evidence. **A check is not trusted until it has been shown to
+fail.** This is mutation testing / negative control applied _at the registry level_ — meaning
+**the conformance harness must itself be conformance-tested.** A registered case that cannot fail, or
+cannot run, is exactly as inert as an unregistered one, and the registry check must detect that
+itself rather than assume it.
+
+**Requirement on RM-55.** The same recursion applies to the harness: it must be observed red before
+its green is worth anything (OPUS R-063 AC1 already states this; D-8 is the empirical case for it).
+
+**Second, equally load-bearing lesson — reviewer disclosure is what makes a review trustworthy.**
+rev-974 could have silently swapped in a working fixture and reported `AC2 PASS`. Nothing in the
+process would have caught it, and the resulting green would have certified nothing — on the very task
+whose subject is gates that only appear to work. The brief's instruction — _"do not adjust a check to
+fit the diff; if it is genuinely unrunnable as specified, say so explicitly and explain why rather
+than silently substituting your own"_ — is therefore not boilerplate. It is the clause that makes a
+PASS mean something, and it must appear in **every** reviewer brief this mission issues.
+
 ### D-7 — shared-tmpfs contention → cascading ENOSPC (live incident, 2026-07-31)
 
 The shared 30 G `/tmp` hit **100% ENOSPC** mid-session. It broke tool calls in **two different seats**