fix(6855): the fence keeps its files where no compaction sweeps them, and builds id lists under mawk

The project a session entered now lives in grimoire-fence, which the
compaction clear never visits, and session end removes it. Arrays of ids
in a tool's input were sent as [,"3","4"] under mawk, which creates an
array element as soon as it is assigned to.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

plugin/.claude-plugin/plugin.json

@@ -1,7 +1,7 @@
 {
   "name": "grimoire",
   "description": "Grimoire for Claude Code: connects the grimoire MCP server, adds the hooks that deliver live project state and relevant records at the right moment, ships the shared client-neutral Grimoire skills (using-grimoire, writing-plans, reporting-back, systematic-debugging, verification, brainstorming, reusing-code, shape-accounting, family-canon), and syncs your saved Grimoire Processes as skills (/grimoire:sync).",
-  "version": "2026.11.05.0245",
+  "version": "2026.11.05.0251",
   "author": {
     "name": "Bryan Van Deusen"
   },

plugin/hooks/grimoire_project_fence.sh

@@ -51,7 +51,9 @@ session_id=$(grimoire_json_pick "$event_flat" '.session_id')
 tool_name=$(grimoire_json_pick "$event_flat" '.tool_name')
 hook_event=$(grimoire_json_pick "$event_flat" '.hook_event_name')
 cwd=$(grimoire_json_pick "$event_flat" '.cwd')
-state_dir="${TMPDIR:-/tmp}/grimoire-priorart"
+# Its own directory, which no compaction sweeps: the project a session
+# entered stays its project for the whole session.
+state_dir="${TMPDIR:-/tmp}/grimoire-fence"
 safe_sid=$(printf '%s' "${session_id:-none}" | tr -c 'A-Za-z0-9._-' '_')
 entered_file="$state_dir/${safe_sid}.entered"
 
@@ -135,7 +137,11 @@ fence_tool_input() {
     }
     $2 ~ /^\.tool_input\.[A-Za-z_]+\[[0-9]+\]$/ && $3 != "null" && length($3) <= 200 {
       k = substr($2, 13); sub(/\[.*$/, "", k); add(k)
-      arr[k] = (k in arr) ? arr[k] ",\"" $3 "\"" : "\"" $3 "\""
+      # Tested before assigning: mawk creates arr[k] as soon as it is the
+      # target, so the test inside the assignment would always be true.
+      item = "\"" $3 "\""
+      if (k in arr) item = arr[k] "," item
+      arr[k] = item
     }
     END {
       printf "{"

plugin/hooks/grimoire_session_end.sh

@@ -31,11 +31,13 @@ event_flat=$(printf '%s' "$event" | grimoire_json_flat)
 session_id=$(grimoire_json_pick "$event_flat" '.session_id')
 [ -n "$session_id" ] || exit 0
 
-# The moment arm's per-session files (its tool cache and the acts ledger)
-# describe a session that is over, on any exit — a clear
-# included, since the next conversation is a new session id.
+# The moment arm's per-session files (its tool cache and the acts ledger) and
+# the fence's (the project the session entered, its outage marker) describe a
+# session that is over, on any exit — a clear included, since the next
+# conversation is a new session id.
 safe_sid=$(printf '%s' "$session_id" | tr -c 'A-Za-z0-9._-' '_')
-rm -f "${TMPDIR:-/tmp}/grimoire-moment/${safe_sid}".* 2>/dev/null || true
+rm -f "${TMPDIR:-/tmp}/grimoire-moment/${safe_sid}".* \
+      "${TMPDIR:-/tmp}/grimoire-fence/${safe_sid}".* 2>/dev/null || true
 
 reason=$(grimoire_json_pick "$event_flat" '.reason')
 [ "$reason" = "clear" ] && exit 0

tests/test_project_fence.py

@@ -190,3 +190,25 @@ def test_an_unanswered_check_lets_the_act_through_and_says_so_once(tmp_path):
     ctx = json.loads(first)["hookSpecificOutput"]["additionalContext"]
     assert ctx.startswith("> Grimoire did not answer the project fence check")
     assert _run(tmp_path, 1, _edit(other / "b.py", home), home) == ""
+
+
+def test_the_entered_project_outlives_a_compaction_and_ends_with_the_session(tmp_path):
+    # A compaction loses the context, not the session: the project it entered
+    # stays its project. Session end clears it.
+    loose = tmp_path / "loose"
+    loose.mkdir()
+    _run(tmp_path, 1, {"hook_event_name": "PostToolUse", "cwd": str(loose),
+                       "tool_name": "mcp__plugin_grimoire_grimoire__enter_project",
+                       "tool_input": {"project_id": 7}}, loose)
+    entered = tmp_path / "tmp" / "grimoire-fence" / "s-fence.entered"
+    assert entered.read_text() == "7"
+
+    env = {"PATH": os.environ["PATH"], "TMPDIR": str(tmp_path / "tmp"), "HOME": str(tmp_path)}
+    hooks = HOOK.parent
+    for hook, event in (("grimoire_session_context.sh", {"source": "compact"}),
+                        ("grimoire_session_end.sh", {"reason": "other"})):
+        subprocess.run(["bash", str(hooks / hook)], input=json.dumps({"session_id": "s-fence", **event}),
+                       capture_output=True, text=True, env=env, timeout=60, check=True)
+        if hook == "grimoire_session_context.sh":
+            assert entered.exists(), "a compaction cleared the project the session entered"
+    assert not entered.exists()