feat(plugin): the seam that erases the evidence is where the unresolved rules get named (#4216)

Step 5 of milestone 419. The milestone's subject is that a rule read and
ignored is arithmetically identical to a rule read and followed, and the
compaction is where that identity becomes permanent — the turns holding the
evidence are summarised away, and the unjudged thing survives as nothing.

WHY THIS IS ASSEMBLED IN THE HOOK. `rule_usage_events` has no session column;
it is per user over a window. A session-scoped answer therefore cannot be
asked of the server, and has to be built where a session is a thing that
exists. Four ledgers four hooks already write:

  .rules.ids      an arm NAMED the rule
  .opened.ids     the session called get_rule      (#4100)
  .acted.ids      the session called rule_outcome  (new here)
  .checkpoint.ids the rule HELD an act             (#4214)

Every one is an observed tool call. Nothing asks the model what it followed —
milestone 386 ruled that out, because a model asked "did you apply rule 156?"
says yes. Two subtractions: named-minus-opened is the arm talking to nobody,
opened-minus-acted is the milestone's whole subject.

PreCompact stdout is the compaction's custom instructions (#3680), not a
message to the model, so the readout does not say "you slipped" — it says
which ids must be carried through, which is the one thing a summary can do
about an unjudged finding.

SILENT WHEN NOTHING HAPPENED, and the accusations are conditional on having
members. "0 rules unresolved" on every compaction is how a readout teaches
its reader to skip it. Traffic is still reported, because the static
instructions already ask for it in prose; these lines are the measured
version.

scribe_record_outcome.sh is the third ledger's writer, matched on
mcp__.*__rule_outcome and mirroring scribe_record_opened.sh: TMPDIR only,
silent, exit 0 on every path. A PostToolUse hook that spoke would put a line
after every rule_outcome call and give recording an outcome a cost.

Also: check_plugin.py skipped the new hook for want of a smoke event, which
would have left the newest of the three ledgers as the only one the plugin
lane never runs. Added, mirroring its sibling.

tests/test_precompact_hook.py now isolates TMPDIR — the hook reads session
ledgers from there, so without isolation a test would see whatever this real
session had accumulated.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01821k5B3Ysecp9fNYs92Kuy

plugin/.claude-plugin/plugin.json

@@ -1,7 +1,7 @@
 {
   "name": "scribe",
   "description": "Scribe for Claude Code: connects the scribe MCP server, adds the hooks that deliver live project state and relevant records at the right moment, ships the shared client-neutral Scribe skills (using-scribe, writing-plans, reporting-back, systematic-debugging, verification, brainstorming, reusing-code, shape-accounting), and syncs your saved Scribe Processes as skills (/scribe:sync).",
-  "version": "2026.09.21.0442",
+  "version": "2026.09.21.0452",
   "author": {
     "name": "Bryan Van Deusen"
   },

plugin/hooks/hooks.json

@@ -62,6 +62,15 @@
             "command": "bash \"${CLAUDE_PLUGIN_ROOT}/hooks/scribe_record_opened.sh\""
           }
         ]
+      },
+      {
+        "matcher": "mcp__.*__rule_outcome",
+        "hooks": [
+          {
+            "type": "command",
+            "command": "bash \"${CLAUDE_PLUGIN_ROOT}/hooks/scribe_record_outcome.sh\""
+          }
+        ]
       }
     ],
     "PreCompact": [

plugin/hooks/scribe_defs.sh

@@ -525,6 +525,98 @@ scribe_contract_block() {
   return 0
 }
 
+# ── The session slippage readout (#4216, milestone 419) ───────────────────
+#
+# WHAT IT ANSWERS, AND WHY IT CANNOT BE ASKED OF THE SERVER. Which rules fired
+# this session, which changed an action, which did not. `rule_usage_events`
+# carries no session column — it is per user over a window — so a
+# session-scoped answer has to be assembled where a session is a thing that
+# exists. That is here, from ledgers four hooks already write:
+#
+#   .rules.ids      an arm NAMED the rule           (a teaser was shown)
+#   .opened.ids     the session called get_rule     (#4100, an observed event)
+#   .acted.ids      the session called rule_outcome (#4216)
+#   .checkpoint.ids the rule HELD an act            (#4214, the strongest)
+#
+# EVERY LINE IS AN OBSERVED TOOL CALL. Nothing here asks the model what it
+# followed — milestone 386 ruled that out, and rightly: a model asked "did you
+# apply rule 156?" will say yes. These four files record what HAPPENED.
+#
+# THE SUBTRACTIONS ARE THE POINT. Named-minus-opened is the arm talking to
+# nobody; opened-minus-acted is the milestone's whole subject, a rule read and
+# then indistinguishable from one that worked. Neither is an accusation — a
+# rule may be read and correctly judged not to apply — which is why the lines
+# below ask for the leftovers to be CARRIED, not explained.
+scribe_ledger_ids() {
+  # Live ids from one ledger as space-separated words, for set arithmetic.
+  # Aged through scribe_rules_live so a rule named two hours ago does not read
+  # as something this context still holds; a bare-id ledger (the checkpoint
+  # one) simply has no stamps and survives the ageing unchanged.
+  local f="$1"
+  [ -n "$f" ] && [ -f "$f" ] || return 0
+  scribe_rules_live "$f" | tr ',' ' '
+}
+
+scribe_slippage_lines() {
+  # $1 state dir, $2 sanitised session id.
+  #
+  # SILENT ONLY WHEN NO RULE TOUCHED THE SESSION AT ALL. Traffic that did
+  # happen is always reported, because "which rules governed this work" is
+  # what the static instructions above already ask the summariser to preserve
+  # in prose — these lines are the measured version of that, and they are
+  # three short lines.
+  #
+  # What is conditional is the ACCUSATION. Each subtraction prints only when
+  # it has members, so a session that opened everything it was shown and
+  # resolved everything it opened gets the traffic and no more. "0 rules
+  # unresolved" on every compaction is how a readout teaches its reader to
+  # skip it.
+  local dir="$1" sid="$2" named opened acted held
+  [ -n "$dir" ] && [ -n "$sid" ] || return 0
+  named=$(scribe_ledger_ids "$dir/${sid}.rules.ids")
+  opened=$(scribe_ledger_ids "$dir/${sid}.opened.ids")
+  acted=$(scribe_ledger_ids "$dir/${sid}.acted.ids")
+  held=$(scribe_ledger_ids "$dir/${sid}.checkpoint.ids")
+  [ -n "$named$opened" ] || return 0
+
+  local unread unresolved
+  unread=$(scribe_ids_minus "$named" "$opened")
+  unresolved=$(scribe_ids_minus "$opened" "$acted")
+
+  printf -- '- This session'"'"'s rule traffic, from what actually happened rather than from recollection:\n'
+  [ -n "$opened" ]     && printf -- '  read: %s\n' "$opened"
+  [ -n "$held" ]       && printf -- '  held an act before it ran: %s\n' "$held"
+  [ -n "$unread" ]     && printf -- '  named by an arm and never opened: %s\n' "$unread"
+  if [ -n "$unresolved" ]; then
+    printf -- '  READ WITH NO OUTCOME RECORDED: %s. Carry these over as outstanding. A rule read and left unresolved looks exactly like one that worked, and the summary is where that difference is lost for good — say `rule_outcome(id, "applied")`, or `rule_outcome(id, "departed", why=...)` where you deliberately went another way.\n' "$unresolved"
+  fi
+  return 0
+}
+
+scribe_ids_minus() {
+  # Set difference over two space-separated id lists, order preserved. Written
+  # as one awk pass rather than a nested shell loop because the ledgers can
+  # hold a few dozen ids by the end of a long session and this runs inside the
+  # compaction path, where a slow hook delays the thing it is decorating.
+  local a="$1" b="$2"
+  [ -n "$a" ] || return 0
+  awk -v a="$a" -v b="$b" '
+    BEGIN {
+      n = split(b, drop, " ")
+      for (i = 1; i <= n; i++) if (drop[i] != "") skip[drop[i]] = 1
+      m = split(a, keep, " ")
+      out = ""
+      for (i = 1; i <= m; i++) {
+        id = keep[i]
+        if (id == "" || (id in skip) || (id in done)) continue
+        done[id] = 1
+        out = out (out == "" ? "" : " ") id
+      }
+      if (out != "") print out
+    }
+  ' </dev/null 2>/dev/null
+}
+
 scribe_local_dups() {
   local root="$1" rel="$2" kind name pat hits count label files
   while IFS=$'\t' read -r kind name; do

plugin/hooks/scribe_precompact_preserve.sh

@@ -46,11 +46,22 @@
 # text is the receipt. (Auto-compaction suppresses that notification.)
 set -uo pipefail
 
-# Drain the event so the caller never sees a broken pipe. Nothing in it changes
-# what we emit: the instruction is the same whether the operator typed
-# `/compact` or the session hit its limit, and it composes with any custom
-# instructions they gave, which are merged ahead of ours.
-cat >/dev/null 2>&1 || true
+# shellcheck source=plugin/hooks/scribe_defs.sh
+. "$(dirname "${BASH_SOURCE[0]}")/scribe_defs.sh"
+
+# THE EVENT IS NOW READ, where it used to be drained. The old comment here said
+# nothing in it changes what we emit, and that was true while every line was
+# static. It stopped being true at #4216: the slippage readout below is
+# specific to THIS session, and `session_id` is the key to the ledgers that
+# hold it. The instruction is still the same whether the operator typed
+# `/compact` or the session hit its limit — what varies is the measurement
+# appended to it.
+event=$(cat 2>/dev/null || true)
+session_id=""
+if [ -n "$event" ]; then
+  event_flat=$(printf '%s' "$event" | scribe_json_flat 2>/dev/null || true)
+  session_id=$(scribe_json_pick "$event_flat" '.session_id' 2>/dev/null || true)
+fi
 
 cat <<'EOF'
 Preserve the following literally in the summary — copied through, not
@@ -71,4 +82,29 @@ paraphrased or counted:
 Everything else here can be recovered from the repository or from Scribe. These
 cannot: they are this session's only copy.
 EOF
+
+# ── The slippage readout (#4216, milestone 419) ───────────────────────────
+#
+# WHY IT BELONGS HERE RATHER THAN IN A REPLY. A rule read and left unresolved
+# is invisible by construction: it looks exactly like a rule that worked. The
+# compaction is where that invisibility becomes permanent — the turns holding
+# the evidence are summarised away, and an unjudged thing that survives as
+# nothing is how a decision quietly becomes nobody's.
+#
+# STDOUT HERE IS THE SUMMARISER'S INSTRUCTIONS, not a message to the model
+# (the header records how that was established). So this does not say "you
+# slipped"; it says WHICH ids must be carried through, which is the one thing
+# the summary can do about it. The next turn then reads them in the summary
+# with the work still attached.
+#
+# SILENT WHEN THERE IS NOTHING TO SAY. A session that opened everything it was
+# shown gets no extra lines. "0 rules unresolved" on every compaction is how a
+# readout teaches its reader to skip it.
+if [ -n "$session_id" ]; then
+  safe_sid=$(printf '%s' "$session_id" | tr -c 'A-Za-z0-9._-' '_')
+  slippage=$(scribe_slippage_lines "${TMPDIR:-/tmp}/scribe-priorart" "$safe_sid" 2>/dev/null || true)
+  if [ -n "$slippage" ]; then
+    printf '\n%s\n' "$slippage"
+  fi
+fi
 exit 0

plugin/hooks/scribe_record_outcome.sh

@@ -0,0 +1,57 @@
+#!/usr/bin/env bash
+# Scribe — record that this session said what a rule DID, not merely that it
+# read one (#4216, milestone 419).
+#
+# THE THIRD LEDGER, AND WHY THE TWO THAT EXIST ARE NOT ENOUGH.
+#
+# `.rules.ids` says a rule was NAMED. `.opened.ids` says it was READ (#4100 —
+# a PostToolUse hook watches the `get_rule` call, so it is a recorded event
+# rather than a model's claim about its own context). Neither can say what
+# happened next, and that is the whole of what milestone 419 is about: a rule
+# read and followed and a rule read and forgotten leave identical traces.
+#
+# `rule_outcome` (#4212) is the call that closes that gap, and the server
+# records it. But the server's row carries no session — `rule_usage_events` is
+# per user over a window — so a SESSION-scoped readout cannot be asked of it.
+# The question "which rules changed something in THIS session" has to be
+# answered where a session is a thing that exists, which is here.
+#
+# SAME EVIDENCE CLASS AS `.opened.ids`, deliberately. A tool call happened or
+# it did not, and the harness reports it either way; nothing here asks the
+# model whether it followed anything. That is the distinction milestone 386
+# drew when it ruled out self-report, and this stays on the right side of it.
+#
+# WHAT IT CANNOT SAY: that the rule was followed WELL, or that `applied` was
+# honest. It records that an outcome was declared. The value of that is not the
+# claim itself — it is that the absence of one becomes visible, which is the
+# state nothing could previously name.
+#
+# EXIT 0, ALWAYS. This decorates a ledger; a bookkeeping failure must never
+# turn a successful tool call into a hook error.
+set -uo pipefail
+
+# shellcheck source=plugin/hooks/scribe_defs.sh
+. "$(dirname "${BASH_SOURCE[0]}")/scribe_defs.sh"
+
+event=$(cat 2>/dev/null || true)
+[ -n "$event" ] || exit 0
+
+event_flat=$(printf '%s' "$event" | scribe_json_flat)
+session_id=$(scribe_json_pick "$event_flat" '.session_id')
+[ -n "$session_id" ] || exit 0
+
+# The matcher in hooks.json narrows to the rule_outcome tools, but the server
+# segment of an MCP tool name varies with how the plugin was installed, so the
+# id is read from the field rather than from an assumed tool name — the same
+# reasoning scribe_record_opened.sh gives.
+rule_id=$(scribe_json_pick "$event_flat" '.tool_input.rule_id')
+rule_id=$(printf '%s' "$rule_id" | tr -cd '0-9')
+[ -n "$rule_id" ] || exit 0
+
+state_dir="${TMPDIR:-/tmp}/scribe-priorart"
+mkdir -p "$state_dir" 2>/dev/null || true
+safe_sid=$(printf '%s' "$session_id" | tr -c 'A-Za-z0-9._-' '_')
+
+# Stamped and append-only like its two siblings, so one reader ages them all.
+printf '%s\n' "$rule_id" | scribe_rules_append "$state_dir/${safe_sid}.acted.ids"
+exit 0

scripts/check_plugin.py

@@ -375,6 +375,17 @@ SMOKE_EVENTS: dict[str, str] = {
          "tool_name": "mcp__scribe__get_rule", "tool_input": {"rule_id": 1},
          "tool_response": {}}
     ),
+    # The acted-ledger recorder (#4216). Same shape and same reasoning as its
+    # sibling above: TMPDIR only, and silent, because a PostToolUse hook that
+    # spoke would put a line after every rule_outcome call and turn recording
+    # an outcome into something with a cost. A skip here would have left the
+    # newest of the three ledgers as the only hook the lane never runs.
+    "scribe_record_outcome.sh": json.dumps(
+        {"session_id": "smoke", "cwd": ".",
+         "tool_name": "mcp__scribe__rule_outcome",
+         "tool_input": {"rule_id": 1, "outcome": "applied"},
+         "tool_response": {}}
+    ),
     # The shared library is sourced, never run; executed bare it defines
     # functions and exits — silent by construction.
     "scribe_defs.sh": "",

tests/test_precompact_hook.py

@@ -29,6 +29,8 @@ correct beside every other hook in this directory and would inject nothing.
 from __future__ import annotations
 
 import json
+import tempfile
+import os
 import shutil
 import subprocess
 from pathlib import Path
@@ -44,11 +46,22 @@ EVENT = {"session_id": "s1", "transcript_path": "/tmp/t.jsonl", "cwd": "/repo",
          "custom_instructions": None}
 
 
-def _run(event: dict) -> subprocess.CompletedProcess:
+def _run(event: dict, tmpdir: str | None = None) -> subprocess.CompletedProcess:
+    """Run the hook with its ledger directory ISOLATED.
+
+    The hook reads this session's rule ledgers since #4216, and they live under
+    `$TMPDIR/scribe-priorart`. Without an override these tests would read the
+    machine's real /tmp: on a developer box mid-session that is not empty, and
+    the output would depend on what some other session happened to leave
+    behind. None of the assertions below would fail on it today, which is
+    exactly why it is worth closing now rather than after it starts flaking.
+    """
     if shutil.which("bash") is None:
         pytest.skip("bash not installed")
+    env = dict(os.environ)
+    env["TMPDIR"] = tmpdir or tempfile.mkdtemp()
     return subprocess.run(["bash", str(HOOK)], input=json.dumps(event),
-                          capture_output=True, text=True, timeout=30)
+                          capture_output=True, text=True, timeout=30, env=env)
 
 
 def _code() -> str:
@@ -115,9 +128,11 @@ def test_it_never_blocks_the_compaction():
     assert "decision" not in code, "a block decision would skip the compaction"
     assert "exit 2" not in code
     # A truncated or absent event must not turn into a non-zero exit either.
+    env = dict(os.environ)
+    env["TMPDIR"] = tempfile.mkdtemp()
     for event in ("", "not json", "{}"):
         out = subprocess.run(["bash", str(HOOK)], input=event,
-                             capture_output=True, text=True, timeout=30)
+                             capture_output=True, text=True, timeout=30, env=env)
         assert out.returncode == 0, f"{event!r} → {out.returncode}: {out.stderr}"
 
 

tests/test_session_slippage_readout.py

@@ -0,0 +1,255 @@
+"""Which rules fired this session, which changed an action, which did not (#4216).
+
+WHY THIS CANNOT BE ASKED OF THE SERVER
+
+`rule_usage_events` has no session column — it is per user over a window — so
+a SESSION-scoped answer has to be assembled where a session is a thing that
+exists. That is the plugin, from four ledgers four hooks already write:
+
+    .rules.ids      an arm NAMED the rule           (a teaser was shown)
+    .opened.ids     the session called get_rule     (#4100)
+    .acted.ids      the session called rule_outcome (#4216, new here)
+    .checkpoint.ids the rule HELD an act            (#4214)
+
+EVERY LINE IS AN OBSERVED TOOL CALL. Nothing asks the model what it followed;
+milestone 386 ruled that out because a model asked "did you apply rule 156?"
+will say yes. These record what happened.
+
+WHY THE COMPACTION SEAM
+
+A rule read and left unresolved is invisible by construction — it looks
+exactly like a rule that worked. The compaction is where that invisibility
+becomes permanent: the turns holding the evidence are summarised away, and an
+unjudged thing that survives as nothing is how a decision quietly becomes
+nobody's. A PreCompact hook's stdout becomes the summariser's instructions
+(#3680), so this does not say "you slipped" — it says which ids must be
+carried through, which is the one thing a summary can do about it.
+
+WHAT IS PINNED: the arithmetic, and which conditions produce which lines. NOT
+pinned: the wording.
+"""
+from __future__ import annotations
+
+import json
+import os
+import shutil
+import subprocess
+import time
+from pathlib import Path
+
+import pytest
+
+ROOT = Path(__file__).resolve().parents[1]
+HOOKS = ROOT / "plugin" / "hooks"
+DEFS = HOOKS / "scribe_defs.sh"
+PRECOMPACT = HOOKS / "scribe_precompact_preserve.sh"
+RECORDER = HOOKS / "scribe_record_outcome.sh"
+HOOKS_JSON = HOOKS / "hooks.json"
+
+
+def _need(*tools):
+    for t in tools:
+        if shutil.which(t) is None:
+            pytest.skip(f"hook runtime tool {t!r} not installed")
+
+
+def sh(script: str) -> str:
+    _need("bash", "awk")
+    r = subprocess.run(
+        ["bash", "-c", f'set -uo pipefail\n. "{DEFS}"\n{script}'],
+        capture_output=True, text=True, timeout=30,
+    )
+    assert r.returncode == 0, f"exit {r.returncode}: {r.stderr}"
+    return r.stdout
+
+
+def ledgers(tmp_path, *, named=(), opened=(), acted=(), held=()) -> Path:
+    """The four ledgers, written the way the hooks write them."""
+    d = tmp_path / "scribe-priorart"
+    d.mkdir(parents=True, exist_ok=True)
+    now = int(time.time())
+    for name, ids in (("rules", named), ("opened", opened), ("acted", acted)):
+        if ids:
+            (d / f"s.{name}.ids").write_text(
+                "".join(f"{i}\t{now}\n" for i in ids)
+            )
+    if held:
+        # The checkpoint ledger is bare ids — it records that something
+        # HAPPENED rather than what the context still holds, so it carries no
+        # stamp and never ages (#4214).
+        (d / "s.checkpoint.ids").write_text("".join(f"{i}\n" for i in held))
+    return d
+
+
+def readout(d: Path) -> str:
+    return sh(f'scribe_slippage_lines "{d}" "s"')
+
+
+# ── The arithmetic ────────────────────────────────────────────────────────
+
+def minus(a: str, b: str) -> str:
+    return sh(f'scribe_ids_minus "{a}" "{b}"').strip()
+
+
+def test_the_difference_keeps_order_and_drops_members():
+    assert minus("1 9 34 156 173", "9 34 156") == "1 173"
+
+
+def test_an_empty_difference_prints_nothing():
+    assert minus("9 34", "9 34") == ""
+
+
+def test_an_empty_minuend_is_not_an_error():
+    assert minus("", "9") == ""
+
+
+def test_a_repeated_id_is_counted_once():
+    """The ledgers are append-only, so the same rule can appear many times."""
+    assert minus("9 9 34 9", "") == "9 34"
+
+
+# ── What the readout says ─────────────────────────────────────────────────
+
+def test_the_readout_names_what_was_read(tmp_path):
+    out = readout(ledgers(tmp_path, named=[1, 9], opened=[9]))
+    assert "read: 9" in out
+
+
+def test_a_rule_named_and_never_opened_is_named_as_such(tmp_path):
+    """The arm talking to nobody. Not an accusation — a teaser skimmed past
+    leaves nothing behind — but it is the number that says whether the arm is
+    earning its place."""
+    out = readout(ledgers(tmp_path, named=[1, 9, 173], opened=[9]))
+    assert "never opened" in out
+    line = next(ln for ln in out.splitlines() if "never opened" in ln)
+    assert "1" in line and "173" in line
+    assert " 9" not in line.split(":")[1], "an opened rule is not also unread"
+
+
+def test_a_rule_read_with_no_outcome_is_the_headline(tmp_path):
+    """THE MILESTONE'S WHOLE SUBJECT. Read and unresolved is arithmetically
+    identical to read and followed, and this is the only place that difference
+    gets carried across the seam."""
+    out = readout(ledgers(tmp_path, named=[9, 34], opened=[9, 34], acted=[34]))
+    assert "READ WITH NO OUTCOME RECORDED" in out
+    line = next(ln for ln in out.splitlines() if "NO OUTCOME" in ln)
+    assert "9" in line
+    assert "rule_outcome" in line, "a finding with no remedy is a complaint"
+
+
+def test_a_rule_that_held_an_act_is_reported_separately(tmp_path):
+    """The strongest evidence a rule changed something: it stopped a call
+    before it ran (#4214). Kept apart from `read` because reading a rule and
+    having it alter what you did are different claims."""
+    out = readout(ledgers(tmp_path, named=[156], opened=[156], held=[156]))
+    assert "held an act" in out and "156" in out
+
+
+def test_a_session_that_resolved_everything_makes_no_accusation(tmp_path):
+    """Traffic is always reported — it is what the static instructions above
+    already ask for in prose. The SUBTRACTIONS are conditional, so a clean
+    session gets no scolding. '0 rules unresolved' on every compaction is how
+    a readout teaches its reader to skip it."""
+    out = readout(ledgers(tmp_path, named=[7], opened=[7], acted=[7]))
+    assert "read: 7" in out
+    assert "NO OUTCOME" not in out
+    assert "never opened" not in out
+
+
+def test_a_session_no_rule_touched_says_nothing_at_all(tmp_path):
+    """Rule 115's reasoning: a fresh install must not be told something is
+    wrong when the truth is that nothing has happened yet."""
+    d = tmp_path / "scribe-priorart"
+    d.mkdir(parents=True)
+    assert readout(d).strip() == ""
+
+
+# ── The hook that carries it ──────────────────────────────────────────────
+
+def run_precompact(event: dict, tmpdir: Path) -> subprocess.CompletedProcess:
+    _need("bash")
+    env = dict(os.environ)
+    env["TMPDIR"] = str(tmpdir)
+    return subprocess.run(["bash", str(PRECOMPACT)], input=json.dumps(event),
+                          capture_output=True, text=True, timeout=30, env=env)
+
+
+def test_the_compaction_hook_appends_the_readout(tmp_path):
+    ledgers(tmp_path, named=[1, 9], opened=[9], acted=[])
+    r = run_precompact({"session_id": "s", "trigger": "manual"}, tmp_path)
+    assert r.returncode == 0
+    assert "Preserve the following literally" in r.stdout, "static half intact"
+    assert "READ WITH NO OUTCOME RECORDED" in r.stdout
+
+
+def test_the_compaction_hook_still_exits_zero_with_no_session(tmp_path):
+    """An event with no session_id has no ledgers to read. The static
+    instructions still go out — they are the part that matters most, and
+    losing them because a measurement was unavailable would be the worse
+    trade."""
+    r = run_precompact({"trigger": "auto"}, tmp_path)
+    assert r.returncode == 0
+    assert "Preserve the following literally" in r.stdout
+
+
+def test_the_compaction_hook_never_emits_a_json_envelope(tmp_path):
+    """Regression guard on the change that added the readout: for PreCompact
+    the envelope is pasted into the summariser's prompt rather than
+    unwrapped."""
+    ledgers(tmp_path, named=[1], opened=[1])
+    r = run_precompact({"session_id": "s", "trigger": "manual"}, tmp_path)
+    assert not r.stdout.lstrip().startswith("{")
+
+
+# ── The recorder that makes `acted` mean anything ─────────────────────────
+
+def run_recorder(event: dict, tmpdir: Path) -> subprocess.CompletedProcess:
+    _need("bash")
+    env = {"PATH": os.environ["PATH"], "HOME": str(tmpdir), "TMPDIR": str(tmpdir)}
+    return subprocess.run(["bash", str(RECORDER)], input=json.dumps(event),
+                          capture_output=True, text=True, timeout=30, env=env)
+
+
+def test_declaring_an_outcome_is_recorded(tmp_path):
+    r = run_recorder(
+        {"session_id": "s", "tool_input": {"rule_id": 156, "outcome": "applied"}},
+        tmp_path,
+    )
+    assert r.returncode == 0
+    assert (tmp_path / "scribe-priorart" / "s.acted.ids").read_text().startswith("156\t")
+
+
+def test_the_entry_is_stamped_like_its_siblings(tmp_path):
+    """One reader ages all three ledgers, so all three carry a timestamp."""
+    run_recorder({"session_id": "s", "tool_input": {"rule_id": 9}}, tmp_path)
+    line = (tmp_path / "scribe-priorart" / "s.acted.ids").read_text().strip()
+    assert "\t" in line and line.split("\t")[1].isdigit()
+
+
+@pytest.mark.parametrize("event", [
+    {}, {"session_id": "s"}, {"tool_input": {"rule_id": 9}},
+    {"session_id": "s", "tool_input": {"rule_id": "not-a-number"}},
+])
+def test_an_unusable_event_records_nothing_and_still_exits_zero(event, tmp_path):
+    """A bookkeeping failure must never turn a successful tool call into a
+    hook error."""
+    r = run_recorder(event, tmp_path)
+    assert r.returncode == 0
+    assert not (tmp_path / "scribe-priorart" / "s.acted.ids").exists()
+
+
+def test_the_recorder_is_registered_on_the_rule_outcome_tool():
+    """A ledger nothing writes to reads as 'nothing was acted on', which is
+    the exact false finding this milestone exists to avoid producing."""
+    cfg = json.loads(HOOKS_JSON.read_text())
+    entries = cfg["hooks"]["PostToolUse"]
+    assert any(
+        "rule_outcome" in e.get("matcher", "")
+        and any("scribe_record_outcome.sh" in h["command"] for h in e["hooks"])
+        for e in entries
+    )
+
+
+def test_the_recorder_is_shell_valid():
+    _need("bash")
+    subprocess.run(["bash", "-n", str(RECORDER)], check=True)