diff --git a/frontend/src/views/SettingsView.vue b/frontend/src/views/SettingsView.vue
index 73fa61c..5ecaa00 100644
--- a/frontend/src/views/SettingsView.vue
+++ b/frontend/src/views/SettingsView.vue
@@ -96,6 +96,7 @@ const kbToolRuleThreshold = ref("0.68");
 // And the prompt boundary is a third query shape again — the operator's own
 // prose rather than anything a tool produced (#3852).
 const kbPromptRuleThreshold = ref("0.72");
+const kbReportPrefThreshold = ref("0.72");
 // Near-duplicate report floors, one per record kind (services/dedup.py).
 // Snippets are single-chunk, so their floor sits below the 0.90 write-time
 // gate and catches what it lets through. Notes/tasks are scored at chunk
@@ -171,6 +172,7 @@ async function saveKbInject() {
   // Bash call, so a fallback of 0 would put a rule in front of every command.
   const trT = Math.min(1, Math.max(0, Number(kbToolRuleThreshold.value) || 0.68));
   const prT = Math.min(1, Math.max(0, Number(kbPromptRuleThreshold.value) || 0.72));
+  const rpT = Math.min(1, Math.max(0, Number(kbReportPrefThreshold.value) || 0.72));
   kbInjectThreshold.value = String(t);
   kbInjectTopK.value = String(k);
   kbDupThresholdSnippet.value = String(dupSnip);
@@ -181,6 +183,7 @@ async function saveKbInject() {
   kbRuleHintThreshold.value = String(rhT);
   kbToolRuleThreshold.value = String(trT);
   kbPromptRuleThreshold.value = String(prT);
+  kbReportPrefThreshold.value = String(rpT);
   savingKbInject.value = true;
   kbInjectSaved.value = false;
   try {
@@ -202,6 +205,12 @@ async function saveKbInject() {
       // queries are different shapes. Moving one must not move the others.
       kb_toolrule_threshold: String(trT),
       kb_promptrule_threshold: String(prT),
+      // A SIXTH, and the one that most needed its own key: this arm's query
+      // is a fixed string, so its score is a constant for a given corpus.
+      // While it borrowed the prompt bar, tuning prose silently retuned it —
+      // and a constant that lands under the bar is a dead arm, not a quiet
+      // one (#3860).
+      kb_reportpref_threshold: String(rpT),
       kb_duplicate_threshold_snippet: String(dupSnip),
       kb_duplicate_threshold_note: String(dupNote),
       kb_duplicate_threshold_task: String(dupTask),
@@ -657,6 +666,9 @@ onMounted(async () => {
   if (allSettings.kb_promptrule_threshold !== undefined) {
     kbPromptRuleThreshold.value = allSettings.kb_promptrule_threshold;
   }
+  if (allSettings.kb_reportpref_threshold !== undefined) {
+    kbReportPrefThreshold.value = allSettings.kb_reportpref_threshold;
+  }
   if (allSettings.kb_writepath_threshold !== undefined) {
     kbWritePathThreshold.value = allSettings.kb_writepath_threshold;
   }
@@ -1568,6 +1580,28 @@ async function deleteUser(userId: number) {
             not a command or a file — which is why it carries its own number.
           </p>
         </div>
+        <div class="field">
+          <label for="kb-reportpref-threshold">Completion-report confidence threshold (0–1)</label>
+          <input
+            id="kb-reportpref-threshold"
+            v-model="kbReportPrefThreshold"
+            type="number"
+            min="0"
+            max="1"
+            step="0.01"
+            class="fs-input input"
+            style="max-width: 8rem"
+          />
+          <p class="field-hint">
+            The bar for a <em>preference about how a completion report should be
+            written</em>, looked up when a task closes. Unlike every other bar
+            here, the question this arm asks never changes — so its score is
+            fixed by your preferences alone, and it will either always find one
+            or never find one. If you have written a preference for report shape
+            and it is not arriving, lower this; there is no run of calls that
+            will reveal the problem on its own.
+          </p>
+        </div>
         <!-- A design system belongs to a PROJECT, and the picker for it lives on
              the project. There was a setting here that designated the system
              this install's own interface was built from; it only ever described
diff --git a/plugin/.claude-plugin/plugin.json b/plugin/.claude-plugin/plugin.json
index 2b8533f..3aa5c75 100644
--- a/plugin/.claude-plugin/plugin.json
+++ b/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": "2026.09.16.1232",
+  "version": "2026.09.16.2102",
   "author": {
     "name": "Bryan Van Deusen"
   },
diff --git a/plugin/hooks/hooks.json b/plugin/hooks/hooks.json
index ff1d27b..6907f98 100644
--- a/plugin/hooks/hooks.json
+++ b/plugin/hooks/hooks.json
@@ -53,6 +53,15 @@
             "command": "bash \"${CLAUDE_PLUGIN_ROOT}/hooks/scribe_after_write.sh\""
           }
         ]
+      },
+      {
+        "matcher": "mcp__.*__get_rule",
+        "hooks": [
+          {
+            "type": "command",
+            "command": "bash \"${CLAUDE_PLUGIN_ROOT}/hooks/scribe_record_opened.sh\""
+          }
+        ]
       }
     ],
     "PreCompact": [
diff --git a/plugin/hooks/scribe_autoinject.sh b/plugin/hooks/scribe_autoinject.sh
index 956d8a2..b61aac6 100755
--- a/plugin/hooks/scribe_autoinject.sh
+++ b/plugin/hooks/scribe_autoinject.sh
@@ -100,6 +100,8 @@ if [ -n "$session_id" ]; then
   # stops holding what it was told. scribe_rules_live carries the reasoning.
   rule_seen=$(scribe_rules_live "$rulefile")
   [ -n "$rule_seen" ] && exclude_q="${exclude_q}&exclude_rule_ids=${rule_seen}"
+  # What the session actually OPENED, as against what it was shown (#4100).
+  exclude_q="${exclude_q}$(scribe_held_query "$rule_state_dir/${safe_sid}.opened.ids")"
 fi
 
 body=$(curl -fsS --max-time 5 \
diff --git a/plugin/hooks/scribe_defs.sh b/plugin/hooks/scribe_defs.sh
index 4d75438..0331abe 100644
--- a/plugin/hooks/scribe_defs.sh
+++ b/plugin/hooks/scribe_defs.sh
@@ -289,6 +289,25 @@ scribe_rules_append() {
   awk -v ts="$now" 'NF { print $1 "\t" ts }' >> "$f" 2>/dev/null || true
 }
 
+# The OPENED ledger's contribution to a rule arm's query string (#4100).
+#
+# TWO LEDGERS, BECAUSE THEY RECORD TWO DIFFERENT FACTS. `.rules.ids` holds
+# every id an arm has NAMED; `.opened.ids` holds the ids the session actually
+# read, written by scribe_record_opened.sh from the `get_rule` call itself.
+# Named is not read: the injected line is a teaser, and one skimmed past
+# leaves nothing behind — least of all across a compaction. Sending both lets
+# the server tell a reader who opened a rule from one who was only shown it,
+# instead of telling them both the same untrue thing.
+#
+# Same reader as the naming ledger on purpose, so ageing, the last-entry-wins
+# rule and the bare-id format are defined once and cannot drift apart.
+scribe_held_query() {
+  local ids
+  ids=$(scribe_rules_live "$1")
+  [ -n "$ids" ] && printf '&held_rule_ids=%s' "$ids"
+  return 0
+}
+
 # ---------------------------------------------------------------------------
 # WHICH PROJECT IS THIS DIRECTORY'S? (#4085)
 #
diff --git a/plugin/hooks/scribe_prior_art.sh b/plugin/hooks/scribe_prior_art.sh
index db2081f..af4eda6 100755
--- a/plugin/hooks/scribe_prior_art.sh
+++ b/plugin/hooks/scribe_prior_art.sh
@@ -207,6 +207,8 @@ if [ -n "$session_id" ]; then
   # this arm's sibling hook reads the same rule file through the same helper.
   rule_seen=$(scribe_rules_live "$rulefile")
   [ -n "$rule_seen" ] && rule_exclude_q="&exclude_rule_ids=${rule_seen}"
+  # What the session actually OPENED, as against what it was shown (#4100).
+  rule_exclude_q="${rule_exclude_q}$(scribe_held_query "$state_dir/${safe_sid}.opened.ids")"
 fi
 
 # Not `|| exit 0`: an unreachable instance must not discard a local finding
diff --git a/plugin/hooks/scribe_record_opened.sh b/plugin/hooks/scribe_record_opened.sh
new file mode 100644
index 0000000..f41c7b2
--- /dev/null
+++ b/plugin/hooks/scribe_record_opened.sh
@@ -0,0 +1,76 @@
+#!/usr/bin/env bash
+# Scribe — record that this session OPENED a rule, not merely saw it named (#4100).
+#
+# WHAT THIS CLOSES
+#
+# The rule arms keep a ledger of every id they have NAMED, and the injected
+# line used to tell the reader "You saw it earlier this session". That claim
+# was never checked. The line those arms emit is a TEASER — title, trigger,
+# `get_rule(N)` — so a session can be named a rule twenty times and never read
+# one word of it, and after a compaction the teaser is summarised away leaving
+# nothing at all. The server was asserting something about the reader's
+# context that it had no way to know.
+#
+# This is the observable half. PostToolUse fires for MCP tools (the event's own
+# output schema carries `updatedMCPToolOutput`, which would be meaningless
+# otherwise), so the `get_rule` CALL can be watched directly.
+#
+# WHY THIS IS NOT THE SELF-REPORT MILESTONE 386 REJECTED
+#
+# 386 ruled out asking the session whether it holds a rule, because a model
+# asked "do you still hold rule 156?" will say yes and the answer is
+# unverifiable self-report. That objection is about ASKING. This asks nobody:
+# a tool call happened or it did not, and the harness reports it either way.
+# Recording what a session DID is a different kind of evidence from believing
+# what it says about itself.
+#
+# WHAT IT DELIBERATELY DOES NOT DO
+#
+# It does not prove the rule is still in context — nothing can, and a
+# compaction can drop it moments later. That is why `.opened.ids` ages exactly
+# like `.rules.ids` and is cleared on the same events (#3749): both ledgers
+# describe a context that no longer exists once the context is destroyed. The
+# claim it supports is only ever "you opened this, pull it again if you no
+# longer hold it", which stays true in every case and carries its own remedy.
+#
+# EXIT 0, ALWAYS. This decorates a ledger; a bookkeeping failure must never
+# turn a successful tool call into a hook error. Worst case the id is missed
+# and the reader is offered a rule it already read — the cost of a wrong guess
+# here is one extra line, in the direction that shows more rather than less.
+set -uo pipefail
+
+event=$(cat 2>/dev/null || true)
+[ -n "$event" ] || exit 0
+
+# No jq, no ledger — and no complaint. Every other hook degrades the same way
+# rather than printing a tooling error in front of the operator's work (#4107
+# tracks making that dependency honest; this is not the place to diverge).
+command -v jq >/dev/null 2>&1 || exit 0
+
+session_id=$(printf '%s' "$event" | jq -r '.session_id // empty' 2>/dev/null) || session_id=""
+[ -n "$session_id" ] || exit 0
+
+# The matcher in hooks.json already narrows to the get_rule tools, but the
+# server segment of an MCP tool name varies with how the plugin was installed,
+# so the id is read from whichever field is actually present rather than from
+# an assumed tool name. An event that carries none simply records nothing.
+rule_id=$(printf '%s' "$event" \
+  | jq -r '(.tool_input.rule_id // empty) | tostring' 2>/dev/null) || rule_id=""
+rule_id=$(printf '%s' "$rule_id" | tr -cd '0-9')
+[ -n "$rule_id" ] || exit 0
+
+# The same directory the naming ledger uses. One session keeps its state in one
+# place, and the prior-art name is kept for the reason scribe_tool_rules.sh
+# gives: renaming it would orphan every live session's state for a cosmetic
+# gain.
+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._-' '_')
+
+# shellcheck source=plugin/hooks/scribe_defs.sh
+. "$(dirname "${BASH_SOURCE[0]}")/scribe_defs.sh"
+
+# Stamped and append-only, exactly like the naming ledger — so the same reader
+# (`scribe_rules_live`) ages both, and the last entry for an id wins.
+printf '%s\n' "$rule_id" | scribe_rules_append "$state_dir/${safe_sid}.opened.ids"
+exit 0
diff --git a/plugin/hooks/scribe_session_context.sh b/plugin/hooks/scribe_session_context.sh
index 85aa216..5d0da25 100755
--- a/plugin/hooks/scribe_session_context.sh
+++ b/plugin/hooks/scribe_session_context.sh
@@ -105,6 +105,13 @@ case "$source" in
       # Best-effort, like every other filesystem touch in these hooks: a ledger
       # that cannot be removed costs a repeated exclusion, never a session.
       rm -f "${TMPDIR:-/tmp}/scribe-priorart/${safe_sid}.rules.ids" 2>/dev/null || true
+      # BOTH ledgers, for one reason (#4100). `.opened.ids` records what the
+      # session read; a compaction is exactly the event that takes it away
+      # again. Clearing the naming ledger while keeping this one would leave
+      # the surfacing arms telling a freshly-summarised session "you opened
+      # it earlier" about a rule that is no longer anywhere in its context —
+      # a more confident version of the claim this milestone removed.
+      rm -f "${TMPDIR:-/tmp}/scribe-priorart/${safe_sid}.opened.ids" 2>/dev/null || true
     fi
     ;;
 esac
diff --git a/plugin/hooks/scribe_tool_rules.sh b/plugin/hooks/scribe_tool_rules.sh
index 3262460..1995aaa 100644
--- a/plugin/hooks/scribe_tool_rules.sh
+++ b/plugin/hooks/scribe_tool_rules.sh
@@ -87,6 +87,8 @@ if [ -n "$session_id" ]; then
   # session is still holding. scribe_rules_live carries the reasoning.
   rule_seen=$(scribe_rules_live "$rulefile")
   [ -n "$rule_seen" ] && rule_exclude_q="&exclude_rule_ids=${rule_seen}"
+  # What the session actually OPENED, as against what it was shown (#4100).
+  rule_exclude_q="${rule_exclude_q}$(scribe_held_query "$state_dir/${safe_sid}.opened.ids")"
 fi
 
 # `|| exit 0` here, unlike the prior-art hook: there is no local arm whose
diff --git a/scripts/check_plugin.py b/scripts/check_plugin.py
index 9e82042..b1df3cf 100755
--- a/scripts/check_plugin.py
+++ b/scripts/check_plugin.py
@@ -345,13 +345,43 @@ SMOKE_EVENTS: dict[str, str] = {
         {"session_id": "smoke", "transcript_path": "/nonexistent/smoke.jsonl",
          "cwd": ".", "hook_event_name": "Stop", "stop_hook_active": False}
     ),
+    # The PreCompact preserver (#3680). Its whole contract is the inverse of
+    # every other hook's: it must exit 0 AND print, because stdout is what
+    # becomes the summarizer's custom instructions. A silent success here is
+    # the failure mode, and it would look like every other hook's success.
+    "scribe_precompact_preserve.sh": json.dumps(
+        {"session_id": "smoke", "cwd": ".", "hook_event_name": "PreCompact",
+         "trigger": "manual", "custom_instructions": None}
+    ),
+    # The opened-ledger recorder (#4100). It writes to TMPDIR and prints
+    # nothing — a PostToolUse hook that emitted output would put a line in
+    # front of every get_rule call, which is the opposite of its purpose. The
+    # smoke case is a well-formed open: it must exit 0 and stay silent.
+    "scribe_record_opened.sh": json.dumps(
+        {"session_id": "smoke", "cwd": ".",
+         "tool_name": "mcp__scribe__get_rule", "tool_input": {"rule_id": 1},
+         "tool_response": {}}
+    ),
     # The shared library is sourced, never run; executed bare it defines
     # functions and exits — silent by construction.
     "scribe_defs.sh": "",
 }
 
-# The one hook that legitimately produces output with no credentials.
-STATIC_FLOOR = "scribe_session_context.sh"
+# The hooks that legitimately produce output with NO credentials, each for its
+# own reason — named per hook rather than shared, because "this one is allowed
+# to speak" is exactly the kind of exemption that quietly grows to cover a hook
+# that is merely leaking.
+STATIC_EMITTERS = {
+    # The two-tier SessionStart design: the bundled static tier ships whatever
+    # the instance does, and that floor is the whole point of the split.
+    "scribe_session_context.sh": "static floor present",
+    # PreCompact's contract is INVERTED (#3680). Its stdout becomes the
+    # summarizer's custom instructions, and what must survive a summary is
+    # known without asking anything — so it needs no instance, and silence is
+    # the failure mode rather than the success one. Read as a generic hook it
+    # would look like a leak; it is the opposite.
+    "scribe_precompact_preserve.sh": "preservation instructions present",
+}
 # The hooks that say so when a configured instance does not answer (#2932).
 OUTAGE_SPEAKERS = {"scribe_prior_art.sh", "scribe_after_write.sh"}
 OUTAGE_LINE = "> Scribe did not answer the prior-art check"
@@ -398,14 +428,13 @@ def check_fail_open() -> None:
                      f"a recall aid may never fail the operator's action")
                 continue
             out = proc.stdout.strip()
-            if script.name == STATIC_FLOOR:
-                # Emits its bundled static tier regardless; that floor is the
-                # whole point of the two-tier design.
+            if script.name in STATIC_EMITTERS:
+                what = STATIC_EMITTERS[script.name]
                 if not out:
-                    fail(f"{rel} [{label}]: emitted nothing — the static "
-                         f"behavioural floor must survive having no credentials")
+                    fail(f"{rel} [{label}]: emitted nothing — this hook's "
+                         f"output must survive having no credentials ({what})")
                 else:
-                    ok(f"{rel} [{label}]: exit 0, static floor present")
+                    ok(f"{rel} [{label}]: exit 0, {what}")
             elif out and label == "unreachable" and script.name in OUTAGE_SPEAKERS:
                 # The only thing allowed here is the outage line itself.
                 try:
diff --git a/src/scribe/mcp/tools/rulebooks.py b/src/scribe/mcp/tools/rulebooks.py
index 630201f..e193ce8 100644
--- a/src/scribe/mcp/tools/rulebooks.py
+++ b/src/scribe/mcp/tools/rulebooks.py
@@ -246,7 +246,7 @@ async def get_rule(rule_id: int) -> dict:
 
 
 async def create_rule(
-    topic_id: int, title: str, statement: str, when_to_apply: str = "",
+    topic_id: int, title: str, statement: str, when_to_apply: str,
     why: str = "", how_to_apply: str = "", order_index: int = 0,
     arose_from_id: int = 0, verify_with: str = "", expires_when: str = "",
     system_ids: list[int] | None = None, force: bool = False,
@@ -344,10 +344,14 @@ async def create_rule(
         when_to_apply: WHEN this rule fires — the trigger, not the
             instruction. State the moment or the material: "before any git
             push", "when adding a value to a CHECK-gated column", "when a
-            release is being cut". Write it even though the parameter is
-            optional: it is how the rule is found
-            when it matters, and a rule nobody can place is a rule nobody
-            applies.
+            release is being cut". REQUIRED, and not as ceremony: nothing is
+            preloaded, so this is the whole of how the rule is found when it
+            matters — and it is half of what the rule is EMBEDDED as, so a
+            rule without one is not merely hard to find, it is stored in a
+            different shape from every rule it competes with. Name the SYMPTOM
+            — the words someone would type while stuck — rather than the
+            category: "the CI job passed locally and fails on the runner with
+            a permission error" retrieves; "when touching CI config" does not.
             This field is also the rule's RETRIEVAL SURFACE — it and the
             statement are what a search is matched against, so it should
             carry the SYMPTOM, not just the situation: the words someone
@@ -411,7 +415,7 @@ async def create_rule(
 
 
 async def create_project_rule(
-    project_id: int, statement: str, title: str = "", when_to_apply: str = "",
+    project_id: int, statement: str, when_to_apply: str, title: str = "",
     why: str = "", how_to_apply: str = "", order_index: int = 0,
     arose_from_id: int = 0, verify_with: str = "", expires_when: str = "",
     system_ids: list[int] | None = None, force: bool = False,
diff --git a/src/scribe/routes/plugin.py b/src/scribe/routes/plugin.py
index ee9e6e6..d5d58c0 100644
--- a/src/scribe/routes/plugin.py
+++ b/src/scribe/routes/plugin.py
@@ -100,6 +100,13 @@ async def autoinject_retrieve():
                              purpose: one session keeps ONE rule ledger, so a
                              rule named by any arm is not re-announced by
                              another. Ages out (#3751), so salience decays.
+        held_rule_ids      — comma-separated rule ids the session actually
+            (opt)            OPENED, observed from the `get_rule` call itself
+                             rather than claimed. A rule on exclude_rule_ids
+                             was NAMED; a rule here was READ, and the two say
+                             different things about what the reader holds —
+                             so they get different lines (#4100). Shares the
+                             ledger directory and the same clear-on-compact.
 
     TWO ARMS, TWO SETS OF GATES. Rules ride the same hook and the same query
     but nothing else: the notes menu can be disabled, thresholded and top-k'd
@@ -116,9 +123,10 @@ async def autoinject_retrieve():
     project_id, _repo, _unbound = await _project_scope()
     exclude_ids = _int_list(request.args.get("exclude_ids"))
     exclude_rule_ids = _int_list(request.args.get("exclude_rule_ids"))
+    held_rule_ids = _int_list(request.args.get("held_rule_ids"))
 
     rules = await plugin_ctx_svc.build_prompt_rule_hint(
-        g.user.id, q, project_id=project_id, exclude_rule_ids=exclude_rule_ids
+        g.user.id, q, project_id=project_id, exclude_rule_ids=exclude_rule_ids, held_rule_ids=held_rule_ids
     )
     result = await plugin_ctx_svc.build_autoinject_hint(
         g.user.id, q, project_id=project_id, exclude_ids=exclude_ids
@@ -157,14 +165,20 @@ async def pre_tool_rules():
                                   ledger on purpose: one session keeps one
                                   list, so a rule named by either arm is not
                                   re-offered by the other.
+        held_rule_ids (opt)     — rule ids the session actually OPENED, as
+                                  against merely named. Named and read are
+                                  different claims about the reader's
+                                  context, so they get different lines
+                                  (#4100).
     """
     tool = (request.args.get("tool") or "tool").strip()
     command = request.args.get("command") or ""
     project_id, _repo, _unbound = await _project_scope()
     exclude_rule_ids = _int_list(request.args.get("exclude_rule_ids"))
+    held_rule_ids = _int_list(request.args.get("held_rule_ids"))
     result = await plugin_ctx_svc.build_tool_rule_hint(
         g.user.id, tool, command,
-        project_id=project_id, exclude_rule_ids=exclude_rule_ids,
+        project_id=project_id, exclude_rule_ids=exclude_rule_ids, held_rule_ids=held_rule_ids,
     )
     return jsonify(result)
 
@@ -202,6 +216,9 @@ async def write_path_prior_art():
                              above, and for the same reason: a rule named
                              twenty turns ago should not be re-offered on
                              every subsequent write.
+        held_rule_ids (opt)  — RULE ids the session actually OPENED, as
+                             against merely named; drives the third
+                             reference wording (#4100).
         exclude_derive (opt) — comma-separated derive keys (a derive group id
                              or `canon:<snippet_id>`) already named this
                              session by the ledger arm (#2900); its own
@@ -225,6 +242,7 @@ async def write_path_prior_art():
         p.strip() for p in (request.args.get("exclude_derive") or "").split(",") if p.strip()
     ]
     exclude_rule_ids = _int_list(request.args.get("exclude_rule_ids"))
+    held_rule_ids = _int_list(request.args.get("held_rule_ids"))
     shapes = _parse_shapes(request.args.get("shapes") or "")
     api_key = getattr(g, "api_key", None)
     may_stamp = api_key is None or getattr(api_key, "scope", "") == "write"
@@ -235,7 +253,7 @@ async def write_path_prior_art():
         stamp_shapes=shapes if may_stamp else None,
         repo_key=repo_bindings_svc.normalize_repo_key(repo) if repo else "",
         exclude_derive=exclude_derive,
-        exclude_rule_ids=exclude_rule_ids,
+        exclude_rule_ids=exclude_rule_ids, held_rule_ids=held_rule_ids,
     )
     return jsonify(result)
 
diff --git a/src/scribe/routes/rulebooks.py b/src/scribe/routes/rulebooks.py
index b94ef57..e9e2bc4 100644
--- a/src/scribe/routes/rulebooks.py
+++ b/src/scribe/routes/rulebooks.py
@@ -345,6 +345,15 @@ async def create_project_rule(project_id: int):
     statement = (data.get("statement") or "").strip()
     if not statement:
         return jsonify({"error": "statement is required"}), 400
+    # Checked here as well as in the service, only for the STATUS CODE: the
+    # service raises ValueError, which this route maps to 404 for "project not
+    # found", and a missing trigger is a 400. The service stays the guard —
+    # this is the door telling the truth about whose mistake it was.
+    if not (data.get("when_to_apply") or "").strip():
+        return jsonify({
+            "error": "when_to_apply is required: a rule with no trigger never "
+                     "surfaces at the moment it applies."
+        }), 400
     title = (data.get("title") or "").strip() or statement.split(".")[0][:50]
     try:
         rule = await rulebooks_svc.create_project_rule(
diff --git a/src/scribe/services/plugin_context.py b/src/scribe/services/plugin_context.py
index acea2bb..b992354 100644
--- a/src/scribe/services/plugin_context.py
+++ b/src/scribe/services/plugin_context.py
@@ -471,6 +471,25 @@ PROMPTRULE_DEFAULT_THRESHOLD = 0.72
 # at all, where the act arms never face it because a command is one thing.
 PROMPTRULE_LIMIT = 3
 
+# THE COMPLETION-REPORT ARM'S OWN BAR (services/reply_preferences.py).
+#
+# It borrowed PROMPTRULE_THRESHOLD_KEY when it shipped, which made the two
+# arms one dial: an operator lowering the bar for their own prose moved this
+# one with it, silently. That contradicts the rule every other bar here
+# follows — one number cannot serve arms whose queries are different shapes —
+# and this arm's query is the most different of all. The others score an
+# operator's prose or a session's code, both of which vary per call; this one
+# scores a FIXED string (`COMPLETION_QUERY`) against rule triggers, so its
+# score for a given corpus is a constant. A constant that lands under the bar
+# is not a quiet arm, it is a dead one, and nothing about the prose arm's
+# traffic would ever reveal it.
+#
+# Kept at the prose arm's starting value rather than tuned: the split is what
+# makes the two independently movable, and a default is a product decision
+# that this install's corpus cannot settle (rule 115).
+REPORTPREF_THRESHOLD_KEY = "kb_reportpref_threshold"
+REPORTPREF_DEFAULT_THRESHOLD = 0.72
+
 
 def _slugify(text: str) -> str:
     """kebab-case slug for a skill directory name (a-z0-9 + single hyphens)."""
@@ -908,6 +927,7 @@ async def build_prompt_rule_hint(
     *,
     project_id: int = 0,
     exclude_rule_ids: list[int] | None = None,
+    held_rule_ids: list[int] | None = None,
 ) -> dict:
     """Rules and preferences that may apply to what the operator just asked.
 
@@ -966,6 +986,7 @@ async def build_prompt_rule_hint(
         duration_ms = (time.perf_counter() - t0) * 1000.0
 
         already = set(exclude_rule_ids or [])
+        held = set(held_rule_ids or [])
         fresh = [(score, rule) for score, rule in hits if rule.id not in already]
 
         # BEFORE the early return, for the reason both sibling arms spell out
@@ -1001,7 +1022,10 @@ async def build_prompt_rule_hint(
             return out
 
         lines = [
-            _rule_hint_line(rule, where="to this request", seen=rule.id in already)
+            _rule_hint_line(
+                rule, where="to this request",
+                seen=rule.id in already, held=rule.id in held,
+            )
             for _score, rule in hits
         ]
         # FRESH-ONLY (#3752). A reference is a rendering decision, not a
@@ -1278,7 +1302,9 @@ def _rule_band(hits: list) -> list:
     return [(s, r) for s, r in hits if s >= top - _RULEHINT_BAND]
 
 
-def _rule_hint_line(rule, *, where: str, seen: bool, compact: bool = False) -> str:
+def _rule_hint_line(
+    rule, *, where: str, seen: bool, held: bool = False, compact: bool = False,
+) -> str:
     """One rule hint line — both arms, both tails, both kinds (#3750, #3849).
 
     THREE INDEPENDENT AXES SINCE #3851. `compact` joins `kind` and `seen`, and
@@ -1361,13 +1387,37 @@ def _rule_hint_line(rule, *, where: str, seen: bool, compact: bool = False) -> s
         "for how this has been done before" if preference
         else "before deciding it does not apply"
     )
-    tail = (
-        f"You saw it earlier this session; pull it with get_rule({rule.id}) "
-        "if you no longer hold it."
-        if seen else
-        f"Read it with get_rule({rule.id}) {reason}; it is not in this "
-        "session's loaded set."
-    )
+    # THREE STATES, BECAUSE TWO OF THEM WERE BEING TOLD THE SAME LIE (#4100).
+    #
+    # `seen` means an arm NAMED this rule earlier. It does not mean the session
+    # read it — the line is a teaser, and a teaser skimmed past leaves nothing
+    # behind, least of all after a compaction summarises the turn it arrived
+    # in. "You saw it earlier this session" asserted something about the
+    # reader's context that the server had no way to know.
+    #
+    # `held` is the observable half: a PostToolUse hook watches for the
+    # `get_rule` call itself, so this is a recorded EVENT rather than a claim.
+    # That distinction is what keeps the non-goal above intact — the objection
+    # was to asking a model about its own context, not to noticing what it did.
+    #
+    # The middle state is the honest one and the one that was missing: named,
+    # not opened. It gets the full invitation, because a session that skipped
+    # the teaser is in almost the same position as one that never saw it.
+    if held:
+        tail = (
+            f"You opened it earlier this session; pull it with "
+            f"get_rule({rule.id}) again if you no longer hold it."
+        )
+    elif seen:
+        tail = (
+            f"Mentioned earlier this session but not opened — read it with "
+            f"get_rule({rule.id}) {reason}."
+        )
+    else:
+        tail = (
+            f"Read it with get_rule({rule.id}) {reason}; it is not in this "
+            "session's loaded set."
+        )
     if compact:
         # THE TRIGGER GOES; THE TAIL STAYS. Only one of the two is expensive \u2014
         # a trigger runs 300-400 characters after #3855, the tail about 100 \u2014
@@ -1402,6 +1452,7 @@ async def build_write_path_hint(
     repo_key: str = "",
     exclude_derive: list[str] | None = None,
     exclude_rule_ids: list[int] | None = None,
+    held_rule_ids: list[int] | None = None,
 ) -> dict:
     """Prior-art hint for the plugin's PreToolUse hook on Write/Edit.
 
@@ -1823,6 +1874,7 @@ async def build_write_path_hint(
     rule_ids: list[int] = []
     try:
         already = set(exclude_rule_ids or [])
+        held = set(held_rule_ids or [])
         # Timed like the notes arm above. Without this the rule row was the one
         # source in the whole readout reporting a null p90_duration_ms (#3311)
         # — a gap that reads as "this surface is somehow not measurable" rather
@@ -1848,6 +1900,7 @@ async def build_write_path_hint(
             lines.append(
                 _rule_hint_line(
                     rule, where="here", seen=rule.id in already,
+                    held=rule.id in held,
                     compact=idx > 0,
                 )
             )
@@ -1938,6 +1991,7 @@ async def build_tool_rule_hint(
     *,
     project_id: int = 0,
     exclude_rule_ids: list[int] | None = None,
+    held_rule_ids: list[int] | None = None,
 ) -> dict:
     """Standing rules that may apply to the ACTION about to be taken (#3476).
 
@@ -1992,6 +2046,7 @@ async def build_tool_rule_hint(
         duration_ms = (time.perf_counter() - t0) * 1000.0
 
         already = set(exclude_rule_ids or [])
+        held = set(held_rule_ids or [])
         # Band first, dedup second — see the sibling arm for why that order is
         # load-bearing rather than incidental.
         kept = _rule_band(hits)
@@ -2029,6 +2084,7 @@ async def build_tool_rule_hint(
             _rule_hint_line(
                 rule, where=f"to this {tool_name} call",
                 seen=rule.id in already,
+                held=rule.id in held,
                 # Rank decides volume (#3851): the ranker's best guess gets the
                 # trigger, the rest get cited.
                 compact=idx > 0,
diff --git a/src/scribe/services/reply_preferences.py b/src/scribe/services/reply_preferences.py
index 92082b4..fd04b5d 100644
--- a/src/scribe/services/reply_preferences.py
+++ b/src/scribe/services/reply_preferences.py
@@ -34,14 +34,26 @@ delivery entirely in retrieval, as 394 decided, and leaves an operator nothing
 new to learn: a preference reaches the completion report the same way every
 other record reaches its moment.
 
-THE BAR IS THE PROMPT ARM'S, AND IT IS NOT YET EARNED HERE
+THE BAR IS ITS OWN, AND THE FIRST READING EARNED IT (#3860)
 
-A fixed query against triggers is a different score distribution from an
-operator's message against the same documents. Starting at the prompt arm's
-setting is the value with evidence behind it, and an operator's tuning of that
-bar reaches this too. Every call logs under its own source,
-`report_preference`, so step 6 can read this surface's near misses apart from
-the prompt arm's before anyone moves the number.
+This borrowed the prompt arm's key when it shipped, on the argument that a
+fixed query against triggers is a different score distribution from an
+operator's message against the same documents — true, and the reason the two
+could not stay one dial. Five days of traffic settled it.
+
+What the readout said: 69 calls, 69 declines, every one naming the SAME record
+at the SAME score (rule 77 at 0.7194 against a 0.72 bar). That constancy is
+the signature of this arm — `COMPLETION_QUERY` never varies, so for a given
+corpus its best score is a constant, and a constant sitting under the bar is a
+dead arm rather than a quiet one. The record it kept declining was about
+reading a REQUEST, not about the shape of a report, so the decline was right
+and the arm is healthy: this install simply has no completion-report
+preference on file.
+
+The bar stayed at 0.72, and the key moved out (REPORTPREF_THRESHOLD_KEY) so
+that staying is a decision rather than a side effect of what the prose arm is
+set to. A surface whose score cannot vary is the one surface where a borrowed
+bar can be wrong forever without a single call looking unusual.
 """
 from __future__ import annotations
 
@@ -50,8 +62,8 @@ import time
 
 from scribe.services.embeddings import semantic_search_rules
 from scribe.services.plugin_context import (
-    PROMPTRULE_DEFAULT_THRESHOLD,
-    PROMPTRULE_THRESHOLD_KEY,
+    REPORTPREF_DEFAULT_THRESHOLD,
+    REPORTPREF_THRESHOLD_KEY,
 )
 from scribe.services.retrieval_telemetry import record_retrieval
 from scribe.services.rule_usage import record_rule_surfaced
@@ -79,9 +91,9 @@ LIMIT = 3
 async def _threshold(user_id: int) -> float:
     try:
         value = float(await get_setting(
-            user_id, PROMPTRULE_THRESHOLD_KEY, str(PROMPTRULE_DEFAULT_THRESHOLD)))
+            user_id, REPORTPREF_THRESHOLD_KEY, str(REPORTPREF_DEFAULT_THRESHOLD)))
     except (TypeError, ValueError):
-        value = PROMPTRULE_DEFAULT_THRESHOLD
+        value = REPORTPREF_DEFAULT_THRESHOLD
     return min(1.0, max(0.0, value))
 
 
diff --git a/src/scribe/services/rulebooks.py b/src/scribe/services/rulebooks.py
index 57b0849..9c60f47 100644
--- a/src/scribe/services/rulebooks.py
+++ b/src/scribe/services/rulebooks.py
@@ -457,12 +457,44 @@ async def rule_detail(user_id: int, rule: Rule, system_ids: list[int] | None = N
     return data
 
 
+def _require_trigger(when_to_apply: str | None) -> None:
+    """A rule without a trigger is not a quiet rule — it is an unreachable one.
+
+    Nothing is preloaded, so `when_to_apply` is the whole of how a rule
+    arrives. It is also what the record is EMBEDDED as: `rule_document` builds
+    `{title} — {trigger}` / `When to apply: {trigger}\\n\\n{statement}`, with
+    the trigger appearing twice so that purpose dominates a short vector. Drop
+    it and the document silently changes shape to title + statement, so the
+    same score means something different for that rule than for its
+    neighbours — and every bar and every rank in the system assumes one shape.
+
+    ENFORCED IN THE SERVICE, so both doors are covered: the MCP tools and the
+    frontend's fast path (`routes/rulebooks.py`) both land here, and a guard
+    written in one of them would leave the other able to create a rule that
+    never fires.
+
+    Deliberately NOT following `arose_from_id`, which the human door exempts
+    itself from on the stated grounds that provenance is about auditing what
+    the AGENT changed. That reasoning does not reach this field: a missing
+    trigger is not a missing explanation, it is a rule that does not work, and
+    it fails an operator exactly as badly as it fails a session.
+    """
+    if not (when_to_apply or "").strip():
+        raise ValueError(
+            "when_to_apply is required: a rule with no trigger never surfaces "
+            "at the moment it applies. Name that moment in the words a session "
+            "would actually be producing then — the command, the error, the "
+            "half-formed ask — not the category it belongs to."
+        )
+
+
 async def create_rule(
     topic_id: int, user_id: int, title: str, statement: str,
     why: str = "", how_to_apply: str = "", order_index: int = 0,
     when_to_apply: str = "", arose_from_id: int = 0,
     verify_with: str = "", expires_when: str = "", kind: str = "rule",
 ) -> Rule:
+    _require_trigger(when_to_apply)
     async with async_session() as session:
         await _assert_topic_owned(session, topic_id, user_id)
         rule = Rule(
@@ -498,6 +530,7 @@ async def create_project_rule(
     rule in a rulebook topic is global. Topic_id is left NULL — the CHECK
     constraint enforces exactly-one of (topic_id, project_id).
     """
+    _require_trigger(when_to_apply)
     async with async_session() as session:
         await _assert_project_owned(session, project_id, user_id)
         rule = Rule(
@@ -651,6 +684,17 @@ async def update_rule(
             "verify_with", "expires_when",
         }
         check_before = rule.verify_with
+        # A create-time guard is worth nothing if an edit can undo it, and
+        # both doors can: `clear=["when_to_apply"]` from the MCP side, and a
+        # emptied form input normalised to None from the REST side. Checked
+        # AFTER the mutation instead, so it covers every route to an empty
+        # trigger including ones added later.
+        #
+        # Asked as "did this edit REMOVE a trigger", not "does one exist":
+        # a rule predating the guard has none, and refusing to save it would
+        # make the record permanently unfixable — freezing the exact rules
+        # that most need the edit.
+        trigger_before = (rule.when_to_apply or "").strip()
         # Captured BEFORE anything is written, and as plain values — this has
         # to survive the mutation below. A rule's history is the only record
         # of what it used to say; the edit itself destroys that.
@@ -677,6 +721,13 @@ async def update_rule(
         # rule wrongly vouched for costs the thing the sweep exists to catch.
         if rule.verify_with != check_before:
             rule.verified_at = None
+        if trigger_before and not (rule.when_to_apply or "").strip():
+            raise ValueError(
+                "when_to_apply cannot be cleared: it is how this rule arrives, "
+                "and it is half of what the rule is embedded as. Replace the "
+                "trigger with a better one rather than removing it — a rule "
+                "with none is not a quieter rule, it is an unreachable one."
+            )
         # Same session as the edit, so the two commit together. The snapshot
         # holds the OLD verify_with — the check that was in force when that
         # wording was written — which is why it is taken before the loop and
diff --git a/tests/test_integration_embedding_yields_to_delete.py b/tests/test_integration_embedding_yields_to_delete.py
index be17d73..265b44e 100644
--- a/tests/test_integration_embedding_yields_to_delete.py
+++ b/tests/test_integration_embedding_yields_to_delete.py
@@ -77,6 +77,7 @@ async def seeded():
     rule = await rulebooks_svc.create_rule(
         topic.id, uid, "A rule with vectors",
         "Something for the embedder to index.",
+        when_to_apply="when the moment this fixture stands in for arises",
     )
     async with async_session() as s:
         note = Note(user_id=uid, title="A note with vectors", body="Body text.")
diff --git a/tests/test_integration_rule_verification.py b/tests/test_integration_rule_verification.py
index 3d5ee78..9e94f52 100644
--- a/tests/test_integration_rule_verification.py
+++ b/tests/test_integration_rule_verification.py
@@ -48,6 +48,7 @@ async def constraint():
         "Write every `run:` step in POSIX sh.",
         verify_with="read the workflow's shell setting",
         expires_when="the runner can be given a bash shell",
+        when_to_apply="when the moment this fixture stands in for arises",
     )
     async with async_session() as s:
         row = await s.get(Rule, rule.id)
@@ -154,14 +155,17 @@ async def rulebook_of_three():
     topic = await rulebooks_svc.create_topic(book.id, uid, "mixed")
     decision = await rulebooks_svc.create_rule(
         topic.id, uid, "dev is home", "Work directly on dev.",
+        when_to_apply="when the moment this fixture stands in for arises",
     )
     never = await rulebooks_svc.create_rule(
         topic.id, uid, "The runner has no bash", "Use POSIX sh.",
         verify_with="read the workflow's shell setting",
+        when_to_apply="when the moment this fixture stands in for arises",
     )
     stale = await rulebooks_svc.create_rule(
         topic.id, uid, "Bumps need a dashboard tick", "Tick it first.",
         verify_with="cat CI-runner/renovate/config.js",
+        when_to_apply="when the moment this fixture stands in for arises",
     )
     async with async_session() as s:
         row = await s.get(Rule, stale.id)
diff --git a/tests/test_integration_rule_versions.py b/tests/test_integration_rule_versions.py
index 83cc28e..9b40533 100644
--- a/tests/test_integration_rule_versions.py
+++ b/tests/test_integration_rule_versions.py
@@ -61,6 +61,7 @@ async def constraint():
         "Write every `run:` step in POSIX sh.",
         why="the image ships no bash",
         verify_with="read the workflow's shell setting",
+        when_to_apply="when the moment this fixture stands in for arises",
     )
 
     return {"uid": uid, "rule_id": rule.id}
@@ -259,6 +260,7 @@ async def test_a_version_cannot_be_read_through_a_DIFFERENT_rule(constraint):
         topic_id = rule.topic_id
     sibling = await rulebooks_svc.create_rule(
         topic_id, constraint["uid"], "A different rule", "Unrelated.",
+        when_to_apply="when the moment this fixture stands in for arises",
     )
 
     assert await rulebooks_svc.get_rule_version(
diff --git a/tests/test_mcp_tool_rulebooks.py b/tests/test_mcp_tool_rulebooks.py
index 6899261..202a30b 100644
--- a/tests/test_mcp_tool_rulebooks.py
+++ b/tests/test_mcp_tool_rulebooks.py
@@ -63,6 +63,7 @@ async def test_create_rule_passes_required_fields():
         from scribe.mcp.tools.rulebooks import create_rule
         await create_rule(
             topic_id=10, title="dev is home", statement="Work directly on dev",
+            when_to_apply="when the moment this fixture stands in for arises",
         )
     kwargs = mock.call_args.kwargs
     assert kwargs["user_id"] == 7
@@ -79,7 +80,7 @@ async def test_create_rule_blocked_by_duplicate_gate():
                AsyncMock(return_value=dup)), \
          patch("scribe.mcp.tools.rulebooks.rulebooks_svc.create_rule", create_mock):
         from scribe.mcp.tools.rulebooks import create_rule
-        out = await create_rule(topic_id=10, title="dev is home", statement="x")
+        out = await create_rule(topic_id=10, title="dev is home", statement="x", when_to_apply="when the moment this fixture stands in for arises")
     assert out["duplicate"] is True
     assert out["existing_id"] == 47
     assert "update_rule" in out["message"]
@@ -94,7 +95,7 @@ async def test_create_rule_force_bypasses_duplicate_gate():
                AsyncMock(return_value=fake_rule(id=5, title="r", statement="s", topic_id=10))), \
          _plain_detail():
         from scribe.mcp.tools.rulebooks import create_rule
-        out = await create_rule(topic_id=10, title="dev is home", statement="x", force=True)
+        out = await create_rule(topic_id=10, title="dev is home", statement="x", force=True, when_to_apply="when the moment this fixture stands in for arises")
     assert out["id"] == 5
     find_mock.assert_not_called()
 
@@ -248,6 +249,7 @@ async def test_create_project_rule_passes_required_fields():
             project_id=42,
             statement="Always run migrations through alembic, not raw SQL.",
             why="audit trail",
+            when_to_apply="when the moment this fixture stands in for arises",
         )
     kwargs = mock.call_args.kwargs
     assert kwargs["user_id"] == 7
@@ -265,6 +267,7 @@ async def test_create_project_rule_derives_title_from_statement():
         await create_project_rule(
             project_id=42,
             statement="Avoid auto-generated docstrings. Reviewers find them noise.",
+            when_to_apply="when the moment this fixture stands in for arises",
         )
     kwargs = mock.call_args.kwargs
     # Title should be derived from the first sentence, capped at 50 chars
@@ -281,6 +284,7 @@ async def test_create_project_rule_uses_explicit_title_when_given():
             project_id=42,
             statement="anything",
             title="no auto-docstrings",
+            when_to_apply="when the moment this fixture stands in for arises",
         )
     kwargs = mock.call_args.kwargs
     assert kwargs["title"] == "no auto-docstrings"
diff --git a/tests/test_preference_write_path.py b/tests/test_preference_write_path.py
index 8ed4b27..f7ac662 100644
--- a/tests/test_preference_write_path.py
+++ b/tests/test_preference_write_path.py
@@ -9,7 +9,7 @@ a rule binds should have agreed to be bound.
 A preference inverts it. The operator's framing: *"preferences are rules that
 scribe can and should update during use."* A preference that asks every time
 never drifts, and drifting is the whole feature. Reaching one through
-`create_rule(kind=...)` would mean reading it through the gate's prose, and
+`create_rule(kind=..., when_to_apply="when the moment this fixture stands in for arises")` would mean reading it through the gate's prose, and
 the caller would hesitate over exactly the act this kind exists to make
 routine.
 
diff --git a/tests/test_rule_hint_band.py b/tests/test_rule_hint_band.py
index c86ffdd..dc0d0b4 100644
--- a/tests/test_rule_hint_band.py
+++ b/tests/test_rule_hint_band.py
@@ -149,16 +149,29 @@ def test_shortening_a_line_does_not_decide_what_it_says_about_holding():
     precisely because the session may no longer HOLD what it was told — and
     the tail is the entire difference a reader can act on.
 
-    `compact` and `seen` are independent axes. How much room a line gets is a
-    fact about its rank; whether the session holds it is a fact about the
-    ledger; and neither may be allowed to answer the other's question.
+    `compact` and the ledger are independent axes. How much room a line gets is
+    a fact about its rank; what the session holds is a fact about the ledger;
+    and neither may be allowed to answer the other's question.
+
+    THREE STATES SINCE #4100, so this checks three. The axis grew and the test
+    grew with it — pinning only two would leave the compact branch free to
+    collapse the new middle state into either neighbour, which is the same
+    regression this was written for with one more place to hide.
     """
     rule = fake_rule(id=4, title="dev is home", when_to_apply=_TRIGGER)
-    seen = _rule_hint_line(rule, where="here", seen=True, compact=True)
     fresh = _rule_hint_line(rule, where="here", seen=False, compact=True)
-    assert seen != fresh
-    assert "no longer hold it" in seen
+    named = _rule_hint_line(rule, where="here", seen=True, compact=True)
+    held = _rule_hint_line(rule, where="here", seen=True, held=True, compact=True)
+
+    assert len({fresh, named, held}) == 3, (
+        "the compact branch collapsed two holding states into one line"
+    )
     assert "not in this session's loaded set" in fresh
+    assert "not opened" in named
+    assert "no longer hold it" in held
+    # The claim that most needs to survive shortening: a line the session never
+    # opened must not imply it did, however little room the line was given.
+    assert "no longer hold it" not in named
 
 
 def test_a_compact_line_is_materially_shorter_than_a_full_one():
diff --git a/tests/test_rule_opened_ledger.py b/tests/test_rule_opened_ledger.py
new file mode 100644
index 0000000..3c7c765
--- /dev/null
+++ b/tests/test_rule_opened_ledger.py
@@ -0,0 +1,166 @@
+"""Named is not read: the ledger's third state (#4100).
+
+WHY THIS EXISTS
+
+Milestone 386 made a repeat REFERENCED rather than withheld, and the line it
+chose says "You saw it earlier this session". That claim was never checked.
+The arms emit a TEASER — title, trigger, `get_rule(N)` — so a session can be
+shown a rule twenty times and never read a word of it, and a compaction
+summarises the teaser away leaving nothing at all. The server was asserting
+something about the reader's context it had no way to know.
+
+`.opened.ids` is the observable half, written by a PostToolUse hook from the
+`get_rule` call itself. That is why this is not the self-report 386 rejected:
+the objection was to ASKING a model about its own context, and a tool call is
+an event the harness reports whether anyone asks or not.
+
+WHAT THIS PINS
+
+The three states and their three lines, the hook that records an open, and the
+fact that BOTH ledgers die together on a compaction — a session told "you
+opened it earlier" about a rule that was just summarised out of its context
+would be a more confident version of the bug this removes.
+"""
+from __future__ import annotations
+
+import json
+import os
+import re
+import shutil
+import subprocess
+from pathlib import Path
+from unittest.mock import MagicMock
+
+import pytest
+
+from scribe.services.plugin_context import _rule_hint_line
+
+ROOT = Path(__file__).resolve().parents[1]
+HOOKS = ROOT / "plugin" / "hooks"
+RECORDER = HOOKS / "scribe_record_opened.sh"
+
+
+def _rule(rid=156, kind="rule"):
+    return MagicMock(id=rid, kind=kind, title="A wait with no deadline is a bug",
+                     when_to_apply="crossing a process boundary")
+
+
+# ── the three lines ────────────────────────────────────────────────────────
+
+def test_a_rule_never_surfaced_is_offered_as_new():
+    line = _rule_hint_line(_rule(), where="here", seen=False, held=False)
+    assert "not in this session's loaded set" in line
+
+
+def test_a_rule_named_but_not_opened_says_so_and_still_invites():
+    """The state that did not exist. It must NOT claim the reader saw it, and
+    must still carry the pull pointer — a session that skipped the teaser is
+    in nearly the position of one that was never shown it."""
+    line = _rule_hint_line(_rule(), where="here", seen=True, held=False)
+    assert "not opened" in line
+    assert "get_rule(156)" in line
+    assert "You saw it earlier" not in line, (
+        "the middle state is claiming the reader read something they did not"
+    )
+
+
+def test_a_rule_the_session_opened_is_described_as_opened():
+    line = _rule_hint_line(_rule(), where="here", seen=True, held=True)
+    assert "opened it earlier" in line
+    assert "get_rule(156)" in line
+
+
+def test_the_three_states_produce_three_different_lines():
+    """Guard against a refactor collapsing two branches: each state has to be
+    distinguishable, or the distinction this milestone bought is gone while
+    every individual assertion above still passes."""
+    lines = {
+        _rule_hint_line(_rule(), where="here", seen=s, held=h)
+        for s, h in ((False, False), (True, False), (True, True))
+    }
+    assert len(lines) == 3
+
+
+def test_held_outranks_seen_regardless_of_kind():
+    """`kind` moves the head and the ledger moves the tail; #3497's history is
+    the two being reasoned about together and one of them being forgotten."""
+    for kind in ("rule", "preference"):
+        line = _rule_hint_line(_rule(kind=kind), where="here", seen=True, held=True)
+        assert "opened it earlier" in line
+
+
+# ── the recorder ───────────────────────────────────────────────────────────
+
+def _run_recorder(event: dict, tmp: Path) -> Path:
+    for tool in ("bash", "jq"):
+        if shutil.which(tool) is None:
+            pytest.skip(f"hook runtime tool {tool!r} not installed")
+    env = {"PATH": os.environ["PATH"], "HOME": str(tmp), "TMPDIR": str(tmp)}
+    out = subprocess.run(["bash", str(RECORDER)], input=json.dumps(event),
+                         capture_output=True, text=True, env=env, timeout=30)
+    assert out.returncode == 0, out.stderr
+    return tmp / "scribe-priorart" / "s1.opened.ids"
+
+
+def test_opening_a_rule_is_recorded(tmp_path):
+    led = _run_recorder(
+        {"session_id": "s1", "tool_name": "mcp__scribe__get_rule",
+         "tool_input": {"rule_id": 156}}, tmp_path)
+    assert led.exists()
+    assert led.read_text().split("\t")[0] == "156"
+
+
+def test_the_entry_is_stamped_so_it_ages_like_the_naming_ledger(tmp_path):
+    """Both ledgers are read by `scribe_rules_live`, which ages on that stamp.
+    An unstamped entry never expires — bounded, but it would mean an opened
+    rule stays 'opened' for a session's whole life."""
+    led = _run_recorder(
+        {"session_id": "s1", "tool_name": "mcp__scribe__get_rule",
+         "tool_input": {"rule_id": 9}}, tmp_path)
+    parts = led.read_text().strip().split("\t")
+    assert len(parts) == 2 and parts[1].isdigit()
+
+
+@pytest.mark.parametrize("event", [
+    {"session_id": "s1", "tool_name": "mcp__scribe__get_rule", "tool_input": {}},
+    {"session_id": "s1", "tool_name": "mcp__scribe__get_rule",
+     "tool_input": {"rule_id": "../../etc"}},
+    {"tool_name": "mcp__scribe__get_rule", "tool_input": {"rule_id": 5}},
+])
+def test_an_event_with_nothing_usable_records_nothing_and_still_exits_zero(event, tmp_path):
+    """A hook that fails a tool call over bookkeeping is worse than one that
+    misses an id: the cost of a miss is one extra line, in the direction that
+    shows more rather than less."""
+    led = _run_recorder(event, tmp_path)
+    assert not led.exists()
+
+
+# ── the two ledgers stay in step ───────────────────────────────────────────
+
+def test_a_compaction_clears_both_ledgers():
+    """The one that would be worst to get wrong. `.opened.ids` describes a
+    context the compaction just destroyed, so keeping it while clearing the
+    naming ledger would have the arms telling a freshly-summarised session
+    "you opened it earlier" about a rule now nowhere in its context.
+    """
+    sh = (HOOKS / "scribe_session_context.sh").read_text()
+    block = sh.split("case \"$source\" in")[1].split("esac")[0]
+    assert "compact|clear)" in block
+    for led in (".rules.ids", ".opened.ids"):
+        assert re.search(rf"rm -f .*{re.escape(led)}", block), (
+            f"{led} survives a compaction that destroyed what it describes"
+        )
+
+
+def test_the_recorder_is_registered_on_the_get_rule_tool():
+    hooks = json.loads((HOOKS / "hooks.json").read_text())["hooks"]
+    posts = hooks["PostToolUse"]
+    mine = [b for b in posts
+            if any("scribe_record_opened.sh" in h["command"] for h in b["hooks"])]
+    assert len(mine) == 1, "the opened-recorder is not registered exactly once"
+    # An MCP tool's server segment varies with how the plugin was installed, so
+    # the matcher must not pin one spelling of it.
+    matcher = mine[0]["matcher"]
+    assert re.fullmatch(matcher, "mcp__plugin_scribe_scribe__get_rule"), matcher
+    assert re.fullmatch(matcher, "mcp__scribe__get_rule"), matcher
+    assert not re.fullmatch(matcher, "Bash"), matcher
diff --git a/tests/test_rule_trigger_required.py b/tests/test_rule_trigger_required.py
new file mode 100644
index 0000000..be48654
--- /dev/null
+++ b/tests/test_rule_trigger_required.py
@@ -0,0 +1,119 @@
+"""A rule cannot be created, or edited into, having no trigger (#4099).
+
+WHY THIS EXISTS
+
+`when_to_apply` is not metadata. `rule_document` embeds a rule as
+`{title} — {trigger}` / `When to apply: {trigger}\n\n{statement}`, with the
+trigger appearing TWICE so purpose dominates a short vector — the shape note
+2485 measured. Drop the trigger and the document silently becomes title +
+statement: a DIFFERENT shape, ranked against a corpus it does not match, with
+nothing to report it. Every bar and every rank in the system assumes one shape.
+
+`create_preference` has always refused an empty trigger. `create_rule` and
+`create_project_rule` defaulted it to `""` — so the shape was enforced for the
+record kind that merely guides and optional for the kind that binds.
+
+WHAT THIS PINS
+
+The guard lives in the SERVICE, because both doors reach it: the MCP tools and
+the frontend's fast path in `routes/rulebooks.py`. A guard written in either
+one alone would leave the other able to create a rule that never fires, which
+is the failure mode this whole change exists to remove.
+
+These call the service directly and assert on the refusal, so an empty guard
+cannot make them pass by accident (rule 167).
+"""
+from __future__ import annotations
+
+import re
+
+import pytest
+
+from scribe.services import rulebooks as rulebooks_svc
+
+TRIGGER_RE = re.compile(r"when_to_apply", re.I)
+
+
+@pytest.mark.parametrize("blank", ["", "   ", "\n\t "])
+def test_a_rulebook_rule_needs_a_trigger(blank):
+    """Whitespace is not a trigger — it embeds exactly like an empty one."""
+    with pytest.raises(ValueError, match=TRIGGER_RE):
+        rulebooks_svc._require_trigger(blank)
+
+
+def test_a_real_trigger_passes():
+    """The guard has to let the normal case through, or the parametrised
+    refusals above would pass for a guard that rejects everything."""
+    assert rulebooks_svc._require_trigger("before any git push") is None
+
+
+@pytest.mark.asyncio
+async def test_create_rule_refuses_before_it_touches_the_database():
+    """The guard runs ahead of the ownership check, so a missing trigger is
+    reported as such rather than as whatever the session lookup says. A bogus
+    topic_id proves no database was reached: were the guard absent, this would
+    fail on the topic instead, with a different message."""
+    with pytest.raises(ValueError, match=TRIGGER_RE):
+        await rulebooks_svc.create_rule(
+            topic_id=999_999, user_id=1, title="t", statement="s",
+        )
+
+
+@pytest.mark.asyncio
+async def test_create_project_rule_refuses_too():
+    """The second door into the same defect. Named separately because the two
+    functions are separate code paths that have drifted apart before."""
+    with pytest.raises(ValueError, match=TRIGGER_RE):
+        await rulebooks_svc.create_project_rule(
+            project_id=999_999, user_id=1, title="t", statement="s",
+        )
+
+
+def test_both_creators_actually_call_the_guard():
+    """Structural, and deliberately not satisfied by the behavioural tests
+    above: those would still pass if a future edit inlined a second copy of
+    the check. One definition is the point — a rule shape enforced in two
+    places is a rule shape that will be enforced differently in two places."""
+    import inspect
+
+    for fn in (rulebooks_svc.create_rule, rulebooks_svc.create_project_rule):
+        src = inspect.getsource(fn)
+        assert "_require_trigger(when_to_apply)" in src, (
+            f"{fn.__name__} no longer delegates to the shared guard"
+        )
+
+
+def test_update_cannot_empty_a_trigger_that_exists():
+    """The create guard is worth nothing if an edit can undo it, and both
+    doors can try: `clear=['when_to_apply']` from the MCP side and an emptied
+    form input from the REST side.
+
+    Asserted on the source because the check sits mid-transaction, after the
+    mutation and before the commit — reaching it needs a database. What must
+    not silently vanish is the pairing: the before-value captured, and the
+    raise that reads it.
+    """
+    import inspect
+
+    src = inspect.getsource(rulebooks_svc.update_rule)
+    assert "trigger_before" in src, "the pre-edit trigger is no longer captured"
+    assert re.search(r"if trigger_before and not", src), (
+        "update_rule no longer refuses to empty an existing trigger"
+    )
+
+
+def test_a_rule_that_never_had_one_is_still_editable():
+    """The deliberate asymmetry, and the reason the check asks 'did this edit
+    REMOVE a trigger' rather than 'does one exist'.
+
+    A rule predating the guard has no trigger. Refusing to save it would
+    freeze exactly the records that most need fixing — the unreachable ones —
+    so the guard must not fire when there was nothing to remove.
+    """
+    import inspect
+
+    src = inspect.getsource(rulebooks_svc.update_rule)
+    assert "trigger_before and not" in src, (
+        "the guard no longer keys on the BEFORE value, so a legacy rule with "
+        "no trigger can no longer be edited at all"
+    )
diff --git a/tests/test_rule_usage_wiring.py b/tests/test_rule_usage_wiring.py
index d589587..6b383d6 100644
--- a/tests/test_rule_usage_wiring.py
+++ b/tests/test_rule_usage_wiring.py
@@ -747,7 +747,18 @@ def test_the_hook_and_the_route_agree_on_every_parameter_name():
     # repo and `project_id=` where a `.scribe` marker names the project. Both
     # halves are one contract with the route, so both are pinned.
     assert "scribe_scope_query" in hook, "hook no longer asks for a project scope"
+    # `held_rule_ids` joins them for the same reason (#4100): the OPENED ledger
+    # is read by a shared helper so its ageing and format cannot drift from the
+    # naming ledger's, which means the key is spelled in defs rather than here.
+    assert "scribe_held_query" in hook, "hook no longer sends the opened ledger"
     assert set(re.findall(r"printf '([a-z_]+)=", defs)) == {"repo", "project_id"}
+    # Spelled with its own leading `&` because it is APPENDED to a query that
+    # already has a scope key, where the two above are alternatives that open
+    # one. Asserted separately for that reason: a scope key and a ledger key
+    # are different contracts that happen to share a file.
+    assert "printf '&held_rule_ids=" in defs, (
+        "the opened ledger's query key is no longer spelled in the helper"
+    )
 
     # Both scope keys are read by the shared _project_scope() helper, not inline.
     assert "_project_scope()" in handler
@@ -756,6 +767,11 @@ def test_the_hook_and_the_route_agree_on_every_parameter_name():
         assert f'request.args.get("{arg}"' in scope, (
             f"the hooks can send {arg!r} and the route never reads it"
         )
+    # Read by the handler itself, not the scope helper — it is about what the
+    # reader holds, not about which project the work belongs to.
+    assert 'request.args.get("held_rule_ids")' in handler, (
+        "the hook sends held_rule_ids and the route never reads it"
+    )
     for arg in ("tool", "command", "exclude_rule_ids"):
         assert f'request.args.get("{arg}")' in handler, (
             f"the hook sends {arg!r} and the route never reads it"
@@ -1130,7 +1146,14 @@ _HELD = fake_rule(
     when_to_apply="writing any call that crosses a process boundary",
 )
 _FRESH_TAIL = "not in this session's loaded set"
-_SEEN_TAIL = "You saw it earlier this session"
+# `seen` WITHOUT `held` is the middle state since #4100: an arm named this rule
+# earlier, and the session never opened it. Every test below drives the arms
+# with `exclude_rule_ids` alone — the naming ledger — so this is the tail they
+# produce, and it is the one that used to claim "You saw it earlier this
+# session" about a teaser nobody had read.
+_SEEN_TAIL = "Mentioned earlier this session but not opened"
+# The third state, reached only when the opened ledger names the rule too.
+_HELD_TAIL = "You opened it earlier this session"
 
 
 @pytest.mark.parametrize(("source", "run"), _ARMS, ids=["write_path", "pre_tool", "prompt"])
@@ -1183,6 +1206,12 @@ async def test_the_two_tails_are_distinguishable_and_say_the_true_one(source, ru
         f"in its loaded set"
     )
     assert fresh_ctx != seen_ctx, "the two tails collapsed into one"
+    # Neither call named an OPENED ledger, so neither may claim the session
+    # read anything (#4100). Catches `held` defaulting true, which would make
+    # every repeat assert the strongest of the three claims on no evidence.
+    assert _HELD_TAIL not in fresh_ctx and _HELD_TAIL not in seen_ctx, (
+        f"{source} said the session had opened a rule it was only shown"
+    )
 
 
 # ── the third axis: KIND (milestone 399) ────────────────────────────────
diff --git a/tests/test_services_reply_preferences.py b/tests/test_services_reply_preferences.py
index 4c2e428..185233b 100644
--- a/tests/test_services_reply_preferences.py
+++ b/tests/test_services_reply_preferences.py
@@ -73,6 +73,46 @@ def test_it_is_a_ranked_source():
     assert not is_ambient("report_preference")
 
 
+def test_its_bar_is_its_own_key_not_the_prompt_arm_s(monkeypatch):
+    """Regression on the coupling #3860 found (and on the fix being real).
+
+    This arm shipped reading PROMPTRULE_THRESHOLD_KEY, so an operator tuning
+    the bar for their own prose moved this one with it and was never told.
+    That is worse here than anywhere else: every other arm scores a query that
+    varies per call, while COMPLETION_QUERY is fixed — so this arm's score for
+    a given corpus is a CONSTANT, and a constant that lands under the bar is a
+    dead arm rather than a quiet one. No amount of traffic reveals it.
+
+    Asserted on the key the lookup actually asks for, which is the thing that
+    broke, rather than on the constant being defined somewhere.
+    """
+    import asyncio
+
+    from scribe.services import plugin_context
+    from scribe.services.reply_preferences import completion_preferences
+
+    asked: list[str] = []
+
+    async def get_setting(user_id, key, default):
+        asked.append(key)
+        return default
+
+    async def search(user_id, query, **kw):
+        kw["report"].update({"searched": True})
+        return []
+
+    with patch(f"{M}.get_setting", AsyncMock(side_effect=get_setting)), \
+         patch(f"{M}.semantic_search_rules", AsyncMock(side_effect=search)), \
+         patch(f"{M}.record_retrieval"):
+        asyncio.run(completion_preferences(7))
+
+    assert asked == [plugin_context.REPORTPREF_THRESHOLD_KEY]
+    assert plugin_context.REPORTPREF_THRESHOLD_KEY != plugin_context.PROMPTRULE_THRESHOLD_KEY, (
+        "the two keys are the same string again, so the settings form has one "
+        "dial driving two arms — which is the defect, whatever the value is"
+    )
+
+
 def test_the_query_assumes_no_particular_domain():
     from scribe.services.reply_preferences import COMPLETION_QUERY
 
diff --git a/tests/test_services_rulebooks.py b/tests/test_services_rulebooks.py
index f701f28..46c2224 100644
--- a/tests/test_services_rulebooks.py
+++ b/tests/test_services_rulebooks.py
@@ -141,6 +141,7 @@ async def test_create_rule_requires_owned_topic():
         with pytest.raises(ValueError, match="topic .* not found"):
             await create_rule(
                 topic_id=999, user_id=7, title="x", statement="y",
+                when_to_apply="when the moment this fixture stands in for arises",
             )
 
 
diff --git a/tests/test_settings_defaults_agree.py b/tests/test_settings_defaults_agree.py
index ffb6917..390abf7 100644
--- a/tests/test_settings_defaults_agree.py
+++ b/tests/test_settings_defaults_agree.py
@@ -50,6 +50,7 @@ _PAIRS = (
     ("plugin_context.py", "RULEHINT_DEFAULT_THRESHOLD", "kbRuleHintThreshold"),
     ("plugin_context.py", "TOOLRULE_DEFAULT_THRESHOLD", "kbToolRuleThreshold"),
     ("plugin_context.py", "PROMPTRULE_DEFAULT_THRESHOLD", "kbPromptRuleThreshold"),
+    ("plugin_context.py", "REPORTPREF_DEFAULT_THRESHOLD", "kbReportPrefThreshold"),
     # The plan gate (milestone 415): it blocks a create, so a form showing a
     # looser bar than the one in force would be the more misleading drift.
     ("dedup.py", "PLAN_MATCH_DEFAULT_THRESHOLD", "kbPlanMatchThreshold"),
diff --git a/tests/test_write_path_trigger.py b/tests/test_write_path_trigger.py
index 84af7cd..a9e8044 100644
--- a/tests/test_write_path_trigger.py
+++ b/tests/test_write_path_trigger.py
@@ -938,8 +938,16 @@ def test_route_reads_every_arg_the_hook_sends():
     # whichever of `repo=` / `project_id=` scribe_scope_query picks, so the hook
     # splices in its output and the helper is the other half of the contract.
     assert "scribe_scope_query" in hook, "hook no longer asks for a project scope"
+    # Same arrangement for the OPENED ledger (#4100): spelled once in the
+    # helper so its ageing and format cannot drift from the naming ledger's.
+    assert "scribe_held_query" in hook, "hook no longer sends the opened ledger"
     defs = (HOOK.parent / "scribe_defs.sh").read_text()
     assert set(re.findall(r"printf '([a-z_]+)=", defs)) == {"repo", "project_id"}
+    # Its own leading `&` — it is appended to a query that already carries a
+    # scope key, rather than being one of the alternatives that opens one.
+    assert "printf '&held_rule_ids=" in defs, (
+        "the opened ledger's query key is no longer spelled in the helper"
+    )
 
 
 def test_route_resolves_repo_to_a_project_not_to_a_location_filter():