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§1.8. Skill frontmatter hook registers AFTER first invoke. SessionStart + once:true does not fire. Self-block during own load is impossible.
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Based on SOC occupation classification
Mac Cowork で、plugin-level SessionStart hook(host 側)から $CLAUDE_PLUGIN_DATA に書いた値が「別の chat session を跨いで」残るかを検証する probe。書き込み＆読み戻しは hook(persist.sh)側で行い、その結果は SessionStart の stdout として context に出る。この skill body は対比用に「VM Bash 側から DATA が見えるか／hook が書いたファイルを読めるか」を確認する。
Surfaces UPE_PROBE_* marker lines to test whether the plugin-level UserPromptExpansion hook fires on Cowork. Invoking this skill via slash is itself the trigger; compares against UserPromptSubmit and SessionStart controls.
Triggers the plugin-level PreToolUse hooks by running a sentinel bash command, to test (via session export) whether Cowork runs PreToolUse hook commands through cmd.exe or a POSIX shell, and whether the inline block pattern actually blocks the bash tool.
Surfaces the EXEC_* marker lines emitted by the plugin-level SessionStart hooks, which run hook commands in EXEC FORM (args present). Used to test whether exec form resolves ${CLAUDE_PLUGIN_ROOT} to a real path and exports it as an env var on Cowork, where shell form (§2.1/§2.2) failed both.
Shows what skill-body CLAUDE_PLUGIN_ROOT and friends substitute to on Mac Cowork, whether the VM Bash tool can use that path, and whether the Read tool can read a bundled file at that host path.
Proves whether a skill frontmatter PreToolUse Bash hook fires on Cowork by emitting only a block decision (no echo). A marked bash should be blocked even though no frontmatter stdout surfaces.
| name | 08-frontmatter-timing |
| description | §1.8. Skill frontmatter hook registers AFTER first invoke. SessionStart + once:true does not fire. Self-block during own load is impossible. |
| user-invocable | true |
| hooks | {"SessionStart":[{"matcher":"startup|resume|clear|compact","hooks":[{"type":"command","once":true,"command":"echo \"[08-FM-SESSIONSTART unexpected fire] $(date -Iseconds)\" >> \"$CLAUDE_PROJECT_DIR/findings/${VERIFIER_VERSION_DIR:-v-unknown}/${CLAUDE_SESSION_ID:-no-sid}/probe.log\" 2>/dev/null"}]}],"PreToolUse":[{"matcher":"Bash","hooks":[{"type":"command","command":"echo \"[08-FM-PreToolUse fired] $(date -Iseconds)\" >> \"$CLAUDE_PROJECT_DIR/findings/${VERIFIER_VERSION_DIR:-v-unknown}/${CLAUDE_SESSION_ID:-no-sid}/probe.log\" 2>/dev/null"}]}]} |
§1.8 — skill frontmatter SessionStart + once:true は不発、PreToolUse は invoke 後の bash で発火。
proj="${CLAUDE_PROJECT_DIR:-$PWD}"
ver="${VERIFIER_VERSION_DIR:-v-unknown}"
sid="${CLAUDE_SESSION_ID:-no-sid}"
out_dir="$proj/findings/$ver/$sid"
mkdir -p "$out_dir"
printf '[08-BODY %s] tag=alive-check\n' "$(date -Iseconds)" | tee -a "$out_dir/probe.log"
echo
echo "=== probe.log (SessionStart canary entries should be absent) ==="
grep -E "08-FM-SESSIONSTART|08-FM-PreToolUse" "$out_dir/probe.log" 2>&1 || echo "(no 08-FM lines)"
echo
echo "=== hooks.log (plugin-level session-start should be present) ==="
grep -c "tag=session-start" "$out_dir/hooks.log" 2>&1 || echo "0"
完了して exit、./scripts/assert.sh 08。