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

@@ -0,0 +1,15 @@
+<!-- board-roll: 1 entry rolled from BOARD.md -->
+
+### **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
 
@@ -53,37 +53,34 @@
 4. Hygiene + conformance harness
    Cross-cutting retirements: flat-file tracking, 3 MACP islands, silent MOSAIC BYPASS.
 
-## Dogfood evidence captured this session (live failure classes, not hypotheticals)
+## Dogfood evidence — live failure classes, not hypotheticals
 
-- **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.
-- **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).
-- **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-4 / P-LIFECYCLE + hygiene — a dispatched agent silently IGNORED an in-message context reset.**
-  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.
+> Newest first. Oldest entries roll to `BOARD-LEDGER.md` via `board-roll.sh` when this file
+> exceeds its 8 KB cap. Keystone detail is duplicated in `TASKS.md` §1a, so rolling loses nothing.
 
-- **D-6 / P-QUEUE-001 — the mandated queue guard returned PASS on an UNKNOWN state, live, today.**
-  Running the required `ci-queue-wait.sh --purpose push` before pushing produced
-  `state=unknown ... exit 0` — the exact defect at `ci-queue-wait.sh:282-288` that PR #1023 is parked
-  on. It also evaluated `branch=main` rather than the branch being pushed. The mission's own required
-  pre-push gate passed me on an indeterminate result. Third independent live instance of the class.
-- **D-5 / P-QUEUE-001 + P-CONFORMANCE-001 — KEYSTONE: an inert gate that erased its own evidence.**
-  Merged PR #868 (`b79336a8`) shipped a file that FAILS `pnpm format:check` ⇒ the CI format gate did
-  not block. An unrelated later PR (#872) then reformatted that file via its own `lint-staged`, so
-  `main` went green again and nobody learned the gate had failed to fire. Verified blob-level under the
-  repo's own config. **Detection must be per-merge-commit against that commit's own tree** — a "is main
-  green today" check reports all-clear on this exact defect. Binding on RM-02/RM-55. Full chain in
-  `TASKS.md` §1a. NOT quiet-patched, by Mos's ruling: patching the symptom destroys the signal.
+<!-- 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.
+
+### **D-6 / P-QUEUE-001 — the mandated queue guard returned PASS on an UNKNOWN state, live, today.**
+
+Running the required `ci-queue-wait.sh --purpose push` before pushing produced `state=unknown ... exit 0` — the exact defect at `ci-queue-wait.sh:282-288` that PR #1023 is parked on. It also evaluated `branch=main` rather than the branch being pushed. The mission's own required pre-push gate passed me on an indeterminate result. Third independent live instance of the class.
+
+### **D-5 / P-QUEUE-001 + P-CONFORMANCE-001 — KEYSTONE: an inert gate that erased its own evidence.**
+
+Merged PR #868 (`b79336a8`) shipped a file that FAILS `pnpm format:check` ⇒ the CI format gate did not block. An unrelated later PR (#872) then reformatted that file via its own `lint-staged`, so `main` went green again and nobody learned the gate had failed to fire. Verified blob-level under the repo's own config. **Detection must be per-merge-commit against that commit's own tree** — a "is main green today" check reports all-clear on this exact defect. Binding on RM-02/RM-55. Full chain in `TASKS.md` §1a. NOT quiet-patched, by Mos's ruling: patching the symptom destroys the signal.
+
+### **D-4 / P-LIFECYCLE + hygiene — a dispatched agent silently IGNORED an in-message context reset.**
+
+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.
+
+<!-- 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**
@@ -116,6 +157,27 @@ tmux-session GC.
 **Added to RM-01 as acceptance criteria:** heavy build artifacts (node_modules, package stores, build
 output) must land on the main disk in the worktree, never on the shared 30 G `/tmp`.
 
+**Resolution, and the part that is actually the finding.** Mos verified the attribution independently
+(mtimes, no process or `lsof` holding either path, no live session maps) and reaped both as lead
+coordinator: `/tmp` went to 79%, 6.0 G free. But note _how_ it was resolved — **a human-authority seat
+did it by hand, because the authority exists and the reaper does not.** That gap is the finding, not
+the disk usage.
+
+Two doctrine points fall out, both binding on RM-50:
+
+1. **The fix is not "agents should tidy up."** Asking each seat to clean its own scratch is
+   `instructions are not enforcement` (D-4) wearing a different hat. A deterministic reaper must own
+   it — same conclusion the north star reaches for every other class in this mission.
+2. **Refusing to unilaterally delete another session's scratch was correct, and the resolution is not
+   "be braver about deleting."** An agent guessing that someone else's state is garbage is exactly the
+   unreviewed destructive act the Constitution forbids. The resolution is that _ownership and liveness
+   become mechanically decidable_, so reaping is a determination rather than a judgement call.
+
+**Reaper requirements for RM-50:** liveness determined mechanically (process/`lsof`/session-map, not
+mtime alone); an age threshold; a dry-run that reports what it would reap and why; and an audit event
+per reap. Never a heuristic sweep — that would reintroduce the P-WORKFLOW-001 auto-sync failure in a
+more destructive form.
+
 **The self-erasure is the important part.** An inert gate that is masked by unrelated downstream
 commits produces no lasting artifact, which is precisely why this class survives for months. Detection
 cannot rely on "is `main` currently red" — it must be per-merge-commit.
@@ -237,7 +299,7 @@ spread is itself information, and X1 says we calibrate on real merged PRs.
 
 | id    | task                                                                                                                                                 | src                   | depends_on                 | est (S/O)        | tier   |
 | ----- | ---------------------------------------------------------------------------------------------------------------------------------------------------- | --------------------- | -------------------------- | ---------------- | ------ |
-| RM-50 | One roster-owned socket/host; quarantine unmanaged; stale-session GC                                                                                 | O+S                   | RM-04                      | 14K / 150K       | sonnet |
+| RM-50 | One roster-owned socket/host; quarantine unmanaged; **deterministic reaper for stale sessions AND dead-session disk scratch** (D-7)                  | O+S+live              | RM-04                      | 14K / 150K       | sonnet |
 | RM-51 | Auto-sync **allowlist** (never auto-stage unknown paths) + worktree/lease isolation                                                                  | O+S                   | RM-02                      | 8K / 110K        | sonnet |
 | RM-52 | Retire the Python controller + duplicate MACP islands (3 → 1)                                                                                        | O+S                   | RM-26, RM-27, RM-25, RM-28 | 14K / 110K       | codex  |
 | RM-53 | Flat-file orchestration → DB hard cutover, with rehearsed rollback artifact                                                                          | O+S                   | RM-27, RM-30, RM-34, RM-29 | (in S-10) / 200K | opus   |