feat(hooks): Stop guard blocking the execution-mode menu

Mechanical fix for the 4×-recurring execution-mode menu ask (kaizen 2026-06-10).
A Stop hook reads the transcript and, if the final assistant message presents the
"subagent-driven vs inline — which approach?" menu, blocks the turn and tells the
model to proceed subagent-driven (boma's standing preference). Fails open,
respects stop_hook_active (no loop), tight match signature (no false positives on
meta-discussion). Pipe-tested across 5 scenarios. Activates next session
(settings watcher only tracks files present at session start).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

.claude/hooks/guard-execution-mode-menu.sh

@@ -0,0 +1,46 @@
+#!/usr/bin/env bash
+#
+# Stop guard: block ending the turn when the assistant's final message presents the
+# execution-mode menu. The writing-plans / subagent-driven-development skills script a
+# "Subagent-Driven vs Inline Execution — which approach?" menu at the plan→execution
+# handoff. boma's standing preference (docs/FRICTION.md + the
+# always-subagent-driven-execution memory) is to NEVER present it and proceed
+# subagent-driven. Prose reminders failed four times (06-05/06/09/10); this is the
+# mechanical guard recorded by the 2026-06-10 kaizen review.
+#
+# Fails OPEN: any parse/read problem → allow the stop. Respects stop_hook_active so a
+# block can never loop. The match signature is deliberately tight ("inline execution"
+# AND "which approach"/"two execution options") so it fires on the actual menu, not on
+# meta-discussion of it.
+#
+set -uo pipefail
+
+input=$(cat 2>/dev/null) || exit 0
+
+# Loop guard: if we already blocked once for this stop, let it through.
+active=$(printf '%s' "$input" | jq -r '.stop_hook_active // false' 2>/dev/null) || exit 0
+[ "$active" = "true" ] && exit 0
+
+transcript=$(printf '%s' "$input" | jq -r '.transcript_path // empty' 2>/dev/null) || exit 0
+[ -z "$transcript" ] || [ ! -r "$transcript" ] && exit 0
+
+# Last assistant message's text blocks, joined.
+text=$(jq -rs '
+  ([ .[] | select(.type=="assistant") ] | last) as $a
+  | ($a.message.content // [])
+  | if type=="array" then [ .[] | select(.type=="text") | .text ] | join("\n")
+    elif type=="string" then .
+    else "" end
+' "$transcript" 2>/dev/null) || exit 0
+
+low="${text,,}"
+
+if [[ "$low" == *"inline execution"* \
+   && ( "$low" == *"which approach"* || "$low" == *"two execution options"* ) ]]; then
+  cat <<'JSON'
+{"decision":"block","reason":"Execution-mode menu detected in your final message. boma standing preference (docs/FRICTION.md + always-subagent-driven-execution memory): never present the subagent-driven-vs-inline menu. Drop the menu and proceed with subagent-driven execution directly (superpowers:subagent-driven-development)."}
+JSON
+  exit 0
+fi
+
+exit 0

.claude/settings.json

@@ -56,6 +56,18 @@
           }
         ]
       }
+    ],
+    "Stop": [
+      {
+        "hooks": [
+          {
+            "type": "command",
+            "command": "bash \"${CLAUDE_PROJECT_DIR:-.}/.claude/hooks/guard-execution-mode-menu.sh\"",
+            "timeout": 10,
+            "statusMessage": "Checking for execution-mode menu"
+          }
+        ]
+      }
     ]
   }
 }