feat(codex): ship the compaction hook as a plugin-provided hook

The compaction re-injection hook previously required users to hand-merge
an example into user-level ~/.codex/hooks.json — which renders in the
Codex hooks UI as an anonymous, unattributed "Hook 1" and puts the
install burden on every user. Restore the plugin-provided delivery this
repo used before "Remove Codex hooks" (640ce6c0): the Codex manifest
points hooks at hooks/hooks-codex.json, which runs session-start-codex
via ${PLUGIN_ROOT}/hooks/run-hook.cmd with matcher "compact".

Unlike the removed hook, this one never fires at session start — Codex
surfaces skills natively there, which is why the old startup-injecting
hook was removed. The matcher plus the script's own source gate restrict
it to post-compaction re-starts. The explicit manifest pointer also
keeps suppressing Codex's hooks/hooks.json auto-discovery fallback,
which the previous empty-object declaration existed for (7d8d3d4b).

The Codex portal archive now ships hooks/hooks-codex.json,
hooks/run-hook.cmd, and hooks/session-start-codex; other-harness hook
files stay excluded.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

.codex-plugin/plugin.json

@@ -21,7 +21,7 @@
     "workflow"
   ],
   "skills": "./skills/",
-  "hooks": {},
+  "hooks": "./hooks/hooks-codex.json",
   "interface": {
     "displayName": "Superpowers",
     "shortDescription": "Planning, TDD, debugging, and delivery workflows for coding agents",

README.md

@@ -98,6 +98,22 @@ Superpowers is available via the [official Codex plugin marketplace](https://git
 
 - Select `Install Plugin`.
 
+#### Codex: compaction re-injection hook
+
+Codex compacts long sessions, replacing the transcript with a summary that
+drops Superpowers' skill instructions mid-run — long autonomous workflows
+(like subagent-driven-development) then drift back to harness defaults.
+Claude Code re-injects the bootstrap after every compaction; the plugin ships
+a SessionStart hook (`hooks/hooks-codex.json`) that restores the same
+behavior on Codex (0.145+). It fires only on post-compaction re-starts
+(`source: "compact"`) and is silent at normal session start.
+
+The hook installs with the plugin — no configuration needed. Codex asks you
+to review and trust it once, the first time it loads after install or update.
+Headless automation (CI, eval harnesses) must pass
+`--dangerously-bypass-hook-trust` instead, because untrusted hooks are
+skipped silently.
+
 ### Cursor
 
 - In Cursor Agent chat, install from marketplace:

docs/porting-to-a-new-harness.md

@@ -237,10 +237,12 @@ nesting differ per harness**.
 - Manifests: `.cursor-plugin/plugin.json` is the Shape A manifest example that
   points the harness at `./skills/` and the right `hooks-*.json`. Claude Code's
   `.claude-plugin/plugin.json` sets neither field — it auto-discovers `skills/`
-  and `hooks/hooks.json` by convention. Do **not** copy Codex's
-  `.codex-plugin/plugin.json` for Shape A: it declares an empty `hooks` object
-  specifically to suppress Codex's `hooks/hooks.json` auto-discovery, because
-  Codex surfaces skills natively and runs no session-start hook.
+  and `hooks/hooks.json` by convention. Codex's `.codex-plugin/plugin.json`
+  points `hooks` at `./hooks/hooks-codex.json` — a compaction-only hook, not a
+  bootstrap injector: Codex surfaces skills natively at session start, so its
+  hook fires only on post-compaction re-starts. The explicit pointer also
+  suppresses Codex's `hooks/hooks.json` auto-discovery fallback, which would
+  otherwise run the Claude Code hook.
 
 > **A hook *system* is not a session-start *event*.** A harness can have a
 > `hooks.json` mechanism — and even contain the literal string `SessionStart` in
@@ -785,7 +787,7 @@ Use this as the live index; when in doubt, read the files, not this table.
 | Harness | Entry point | Bootstrap mechanism | Tool mapping | Tests | Distribution |
 |---|---|---|---|---|---|
 | Claude Code | `.claude-plugin/plugin.json` + `hooks/hooks.json` | shell hook → `hooks/session-start` (`hookSpecificOutput.additionalContext`) | native `Skill` tool; no adapter file needed | `tests/hooks/` | marketplace |
-| Codex | `.codex-plugin/plugin.json` (declares empty `hooks`) | native skill discovery (no session-start hook) | `references/codex-tools.md` | `tests/codex/`, `tests/codex-plugin-sync/` | fork sync (`scripts/sync-to-codex-plugin.sh`) |
+| Codex | `.codex-plugin/plugin.json` + `hooks/hooks-codex.json` | native skill discovery at startup; shell hook → `hooks/session-start-codex` re-injects after compaction only | `references/codex-tools.md` | `tests/codex/`, `tests/codex-plugin-sync/` | fork sync (`scripts/sync-to-codex-plugin.sh`) |
 | Cursor | `.cursor-plugin/plugin.json` + `hooks/hooks-cursor.json` | shell hook → `hooks/session-start` (`additional_context`) | none needed (Claude Code–compatible tool surface) | `tests/hooks/` | hand-authored |
 | Copilot CLI | (shares Claude Code hook path; `COPILOT_CLI` env) | shell hook → `hooks/session-start` (`additionalContext`) | none needed (Claude Code–compatible tool surface) | `tests/hooks/` | — |
 | Gemini CLI | `gemini-extension.json` + `GEMINI.md` | instructions file `@`-includes bootstrap + mapping | `references/gemini-tools.md` | — | `gemini extensions install` |

hooks/hooks-codex.json

@@ -0,0 +1,17 @@
+{
+  "hooks": {
+    "SessionStart": [
+      {
+        "matcher": "compact",
+        "hooks": [
+          {
+            "type": "command",
+            "command": "\"${PLUGIN_ROOT}/hooks/run-hook.cmd\" session-start-codex",
+            "async": false,
+            "timeout": 30
+          }
+        ]
+      }
+    ]
+  }
+}

hooks/session-start-codex

@@ -0,0 +1,56 @@
+#!/usr/bin/env bash
+# Codex SessionStart hook for the superpowers plugin.
+#
+# Codex re-fires SessionStart with source:"compact" after every context
+# compaction (verified on codex-cli 0.145.0). Compaction replaces the live
+# context with a summary, which sheds the using-superpowers bootstrap and any
+# active skill's instructions — the measured cause of mid-session dispatch
+# drift in long multi-agent runs. This hook re-injects the bootstrap at
+# exactly that moment, restoring the same re-injection Claude Code performs
+# via its "startup|clear|compact" SessionStart matcher.
+#
+# On source:"startup" it emits nothing: the native Codex plugin path owns
+# session-start injection, and duplicating it here would recreate the
+# redundancy that led to the original session-start-codex hook's removal.
+#
+# Codex injects raw hook stdout into the model's context (verified with
+# sentinel probes), so output is plain text — not the JSON envelopes other
+# harnesses require of hooks/session-start.
+#
+# A hook failure must never break a session: every path fails open to empty
+# output and exit 0.
+
+set -u
+
+payload="$(cat 2>/dev/null || true)"
+
+# Act only on post-compaction re-fires. Tolerate arbitrary whitespace around
+# the JSON colon; anything unparseable falls through to a silent no-op.
+if ! printf '%s' "$payload" | grep -qE '"source"[[:space:]]*:[[:space:]]*"compact"'; then
+    exit 0
+fi
+
+SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd)"
+PLUGIN_ROOT="$(cd "${SCRIPT_DIR}/.." && pwd)"
+
+using_superpowers_content="$(cat "${PLUGIN_ROOT}/skills/using-superpowers/SKILL.md" 2>/dev/null)" || using_superpowers_content=""
+if [ -z "$using_superpowers_content" ]; then
+    exit 0
+fi
+
+# printf instead of heredocs throughout: heredocs hang on bash 5.3+.
+# See: https://github.com/obra/superpowers/issues/571
+printf '%s\n' "<EXTREMELY_IMPORTANT>"
+printf '%s\n\n' "You have superpowers."
+printf '%s\n\n' "**Below is the full content of your 'superpowers:using-superpowers' skill - your introduction to using skills. For all other skills, use the 'Skill' tool:**"
+printf '%s\n' "$using_superpowers_content"
+printf '%s\n\n' "</EXTREMELY_IMPORTANT>"
+printf '%s\n' "<CONTEXT_RESTORED>"
+printf '%s\n' "Your context was just summarized (compacted). The summary preserves your progress but not your working instructions — the files are authoritative."
+printf '%s\n' ""
+printf '%s\n' "Before your next tool call:"
+printf '%s\n' "- Re-read the SKILL.md of any skill you are mid-way through executing. If you are executing subagent-driven-development, re-read skills/subagent-driven-development/SKILL.md."
+printf '%s\n' "- On Codex, also re-read skills/using-superpowers/references/codex-tools.md and follow its dispatch rules on every spawn_agent call."
+printf '%s\n' "</CONTEXT_RESTORED>"
+
+exit 0

scripts/package-codex-plugin.sh

@@ -40,8 +40,9 @@ Options:
   -h, --help               Show this help.
 
 The archive is rootless: .codex-plugin/, assets/, skills/, README.md, LICENSE,
-and CODE_OF_CONDUCT.md sit at the archive root. Source-only repo files, hooks, tests,
-docs, and other harness manifests are intentionally not shipped.
+CODE_OF_CONDUCT.md, and the Codex SessionStart hook (hooks/hooks-codex.json plus
+its two scripts) sit at the archive root. Source-only repo files, other-harness
+hooks, tests, docs, and other harness manifests are intentionally not shipped.
 EOF
 }
 
@@ -238,6 +239,9 @@ git -C "$REPO_ROOT" -c tar.umask=0022 archive --format=tar "$REF" -- \
   LICENSE \
   README.md \
   assets \
+  hooks/hooks-codex.json \
+  hooks/run-hook.cmd \
+  hooks/session-start-codex \
   skills \
   | tar -xpf - -C "$STAGE"
 
@@ -333,7 +337,7 @@ esac
 
 unexpected_paths="$(
   printf '%s\n' "$archive_paths" |
-    grep -E '(^superpowers/|^\.agents/|^hooks/|package\.json$|^\.git|^\.pytest_cache|^\.ruff_cache|^scripts/|^tests/|^docs/|^evals/|^lib/|^\.claude|^\.cursor|^\.kimi|^\.opencode|^\.pi|^AGENTS\.md$|^CLAUDE\.md$|^GEMINI\.md$|^RELEASE-NOTES\.md$|^CHANGELOG\.md$)' || true
+    grep -E '(^superpowers/|^\.agents/|^hooks/hooks\.json$|^hooks/hooks-cursor\.json$|^hooks/session-start$|package\.json$|^\.git|^\.pytest_cache|^\.ruff_cache|^scripts/|^tests/|^docs/|^evals/|^lib/|^\.claude|^\.cursor|^\.kimi|^\.opencode|^\.pi|^AGENTS\.md$|^CLAUDE\.md$|^GEMINI\.md$|^RELEASE-NOTES\.md$|^CHANGELOG\.md$)' || true
 )"
 if [[ -n "$unexpected_paths" ]]; then
   printf '%s\n' "$unexpected_paths" | sed 's/^/  /' >&2

skills/subagent-driven-development/scripts/review-package

@@ -73,5 +73,9 @@ if [ -z "${CLAUDECODE:-}" ] && [ -f "$hints_file" ]; then
   hint_line=$(grep "^${hint_key}:" "$hints_file" | head -1 | cut -d: -f2- | sed 's/^ *//') || true
   if [ -n "$hint_line" ]; then
     echo "$hint_line"
+    footer_line=$(grep "^footer:" "$hints_file" | head -1 | cut -d: -f2- | sed 's/^ *//') || true
+    if [ -n "$footer_line" ]; then
+      echo "$footer_line"
+    fi
   fi
 fi

skills/subagent-driven-development/scripts/task-brief

@@ -52,5 +52,9 @@ if [ -z "${CLAUDECODE:-}" ] && [ -f "$hints_file" ]; then
   hint_line=$(grep "^implementer:" "$hints_file" | head -1 | cut -d: -f2- | sed 's/^ *//') || true
   if [ -n "$hint_line" ]; then
     echo "$hint_line"
+    footer_line=$(grep "^footer:" "$hints_file" | head -1 | cut -d: -f2- | sed 's/^ *//') || true
+    if [ -n "$footer_line" ]; then
+      echo "$footer_line"
+    fi
   fi
 fi

skills/using-superpowers/references/codex-dispatch.hints

@@ -5,6 +5,10 @@
 # Model names track Codex's spawn_agent allowlist (currently gpt-5.6-sol
 # and gpt-5.6-terra) — update this file when the allowlist changes.
 # Format: <role>: <line printed verbatim>
+# The footer line prints after every role line: prevention alone does not
+# cure drift — in instrumented runs, reprinted hints did not heal an
+# already-broken dispatch pattern until the text named the drift directly.
+footer: If any spawn this session omitted these params or used fork_turns "all", you have drifted — re-read references/codex-tools.md before dispatching again.
 implementer: dispatch (spawn_agent): fork_turns=none model=gpt-5.6-terra reasoning_effort=high
 task-review: dispatch (spawn_agent): fork_turns=none model=gpt-5.6-terra reasoning_effort=high
 fix-review: dispatch (spawn_agent): fork_turns=none model=gpt-5.6-terra reasoning_effort=medium

skills/using-superpowers/references/codex-tools.md

@@ -19,7 +19,9 @@ If your `spawn_agent` schema has `model` and `reasoning_effort`
 parameters (Codex 0.145+), set both on every dispatch: task-brief and
 review-package print a `dispatch:` hint line with the exact values —
 copy it onto the call verbatim, every time, even late in a long
-session. Those hints are the Model Selection mapping on Codex:
+session. The hints print at those scripts' boundaries; every other
+spawn — ad-hoc fan-outs included — follows the same table without a
+printed reminder. Those hints are the Model Selection mapping on Codex:
 reviewer tier never exceeds implementer tier, no fix round gets an
 effort bump, and rounds 4-5's "more capable model" means a fresh
 implementer at the same tier — needing more is a BLOCKED escalation
@@ -34,6 +36,21 @@ your model and effort with no override — role files in
 partner before starting a plan of more than a few tasks, and offer a
 lower-effort session instead.
 
+## Compaction sheds these instructions
+
+Context compaction replaces your transcript with a summary that keeps
+your progress but not your working instructions — the first
+post-compaction dispatch is where routing drift starts, and once one
+bare spawn lands, the broken pattern becomes its own precedent. The
+plugin ships a compaction re-injection hook (`hooks/hooks-codex.json`,
+Codex 0.145+) that restores the bootstrap after every compaction; it
+needs one-time trust approval, so if you never see a
+`<CONTEXT_RESTORED>` block after a compaction, tell your human partner
+the hook may be untrusted or unsupported on this version. Without it,
+the printed `dispatch:` hints are your only re-grounding — treat every
+one you see as authoritative, especially right after a summary appears
+in your context.
+
 ## Environment Detection
 
 Skills that create worktrees or finish branches should detect their

tests/claude-code/test-sdd-workspace.sh

@@ -175,9 +175,16 @@ PLAN
         echo "    got: $brief_hint"
     fi
 
+    if [[ "$brief_hint" == *"you have drifted"* ]]; then
+        pass "task-brief prints the drift-cure footer after the hint"
+    else
+        fail "task-brief prints the drift-cure footer after the hint"
+        echo "    got: $brief_hint"
+    fi
+
     local rp_hint
     rp_hint="$(cd "$repo" && env -u CLAUDECODE "$SDD_SCRIPTS/review-package" plan-a.md HEAD~1 HEAD)"
-    if [[ "$rp_hint" == *"dispatch (spawn_agent): fork_turns=none model=gpt-5.6-terra reasoning_effort=high"* ]]; then
+    if [[ "$rp_hint" == *"dispatch (spawn_agent): fork_turns=none model=gpt-5.6-terra reasoning_effort=high"* && "$rp_hint" == *"you have drifted"* ]]; then
         pass "review-package relays the default-role hint off Claude Code"
     else
         fail "review-package relays the default-role hint off Claude Code"

tests/codex/test-marketplace-manifest.sh

@@ -52,24 +52,36 @@ if not plugin_manifest.exists():
 manifest = json.loads(plugin_manifest.read_text(encoding="utf-8"))
 assert_equal(manifest.get("name"), plugin.get("name"), "plugin manifest name")
 
-# Codex auto-discovers a plugin's hooks/hooks.json whenever the Codex manifest
-# has no `hooks` field: load_plugin_hooks falls back to a hardcoded
-# DEFAULT_HOOKS_CONFIG_FILE = "hooks/hooks.json" and registers it. That file is
-# the Claude Code SessionStart hook, it is tracked in this repo, and this
-# marketplace installs the whole repo root (source url "./"), so on Codex the
-# fallback re-registers the SessionStart hook and its install-time trust prompt.
-# Declaring an empty inline hooks object ({}) parses as an empty inline hook set
-# and suppresses the auto-discovery. An absent field, an empty array ([]), and
-# an empty inline list all collapse back to the fallback, so the value must be
-# exactly an empty object.
+# The Codex manifest must declare its hooks explicitly. An absent field makes
+# load_plugin_hooks fall back to a hardcoded DEFAULT_HOOKS_CONFIG_FILE =
+# "hooks/hooks.json" — the Claude Code SessionStart hook, which injects the
+# bootstrap at startup and must not run on Codex. The explicit pointer both
+# registers the Codex compaction re-injection hook and overrides that fallback.
 hooks_config = repo_root / "hooks" / "hooks.json"
 if not hooks_config.exists():
     raise AssertionError("hooks/hooks.json must exist (Claude Code SessionStart hook)")
 
 assert_equal(
     manifest.get("hooks"),
-    {},
-    "Codex manifest must declare empty hooks {} to suppress hooks/hooks.json auto-discovery",
+    "./hooks/hooks-codex.json",
+    "Codex manifest must point hooks at the Codex hook config (an absent field "
+    "falls back to auto-discovering the Claude Code hooks/hooks.json)",
+)
+
+codex_hooks_path = repo_root / "hooks" / "hooks-codex.json"
+if not codex_hooks_path.exists():
+    raise AssertionError("hooks/hooks-codex.json must exist (Codex manifest points at it)")
+
+codex_hooks = json.loads(codex_hooks_path.read_text(encoding="utf-8"))
+session_start = codex_hooks["hooks"]["SessionStart"]
+assert_equal(len(session_start), 1, "Codex SessionStart hook group count")
+assert_equal(session_start[0].get("matcher"), "compact", "Codex hook matcher")
+entry = session_start[0]["hooks"][0]
+assert_equal(entry.get("type"), "command", "Codex hook type")
+command = entry.get("command", "")
+if "${PLUGIN_ROOT}" not in command or not command.endswith("session-start-codex"):
+    raise AssertionError(
+        f"Codex hook command must run session-start-codex via ${{PLUGIN_ROOT}}: {command!r}"
     )
 
 print("Codex marketplace manifest looks good")

tests/codex/test-package-codex-plugin.sh

@@ -141,7 +141,7 @@ tar_extracted="$TEST_ROOT/tar-extracted"
 write_metadata_fixture "$metadata_source"
 
 source_hooks="$(python3 -c 'import json; print(json.load(open("'"$REPO_ROOT"'/.codex-plugin/plugin.json")).get("hooks"))')"
-assert_equals "$source_hooks" "{}" "source Codex manifest suppresses local hook auto-discovery"
+assert_equals "$source_hooks" "./hooks/hooks-codex.json" "source Codex manifest declares the Codex hook config"
 
 if output="$("$SCRIPT_UNDER_TEST" --allow-dirty --metadata-source "$metadata_source" --output "$archive" 2>&1)"; then
   pass "package script exits successfully"
@@ -163,10 +163,13 @@ assert_contains "$output" "SHA-256:" "reports archive checksum"
 extract_archive "$archive" "$extracted"
 
 archive_paths="$(list_archive "$archive" | normalize_archive_paths)"
-unexpected_pattern='(^superpowers/|^\.agents/|^hooks/|package\.json$|^\.git|^\.pytest_cache|^\.ruff_cache|^scripts/|^tests/|^docs/|^evals/|^lib/|^\.claude|^\.cursor|^\.kimi|^\.opencode|^\.pi|^AGENTS\.md$|^CLAUDE\.md$|^GEMINI\.md$|^RELEASE-NOTES\.md$|^CHANGELOG\.md$)'
+unexpected_pattern='(^superpowers/|^\.agents/|^hooks/hooks\.json$|^hooks/hooks-cursor\.json$|^hooks/session-start$|package\.json$|^\.git|^\.pytest_cache|^\.ruff_cache|^scripts/|^tests/|^docs/|^evals/|^lib/|^\.claude|^\.cursor|^\.kimi|^\.opencode|^\.pi|^AGENTS\.md$|^CLAUDE\.md$|^GEMINI\.md$|^RELEASE-NOTES\.md$|^CHANGELOG\.md$)'
 assert_not_matches "$archive_paths" "$unexpected_pattern" "archive excludes source-only paths"
 assert_contains "$archive_paths" ".codex-plugin/plugin.json" "archive includes Codex manifest"
 assert_contains "$archive_paths" "skills/brainstorming/SKILL.md" "archive includes skills"
+assert_contains "$archive_paths" "hooks/hooks-codex.json" "archive includes Codex hook config"
+assert_contains "$archive_paths" "hooks/session-start-codex" "archive includes Codex hook script"
+assert_contains "$archive_paths" "hooks/run-hook.cmd" "archive includes hook runner"
 assert_contains "$archive_paths" "skills/brainstorming/agents/openai.yaml" "archive includes OpenAI skill metadata"
 assert_contains "$archive_paths" "assets/app-icon.png" "archive includes app icon"
 assert_contains "$archive_paths" "assets/superpowers-small.svg" "archive includes composer icon"

tests/hooks/test-session-start-codex.sh

@@ -0,0 +1,115 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd)"
+REPO_ROOT="$(cd "$SCRIPT_DIR/../.." && pwd)"
+HOOK_UNDER_TEST="$REPO_ROOT/hooks/session-start-codex"
+CONFIG_UNDER_TEST="$REPO_ROOT/hooks/hooks-codex.json"
+
+FAILURES=0
+
+pass() {
+    echo "  [PASS] $1"
+}
+
+fail() {
+    echo "  [FAIL] $1"
+    FAILURES=$((FAILURES + 1))
+}
+
+# run_hook <stdin-payload> — echoes hook stdout; fails the calling test on
+# non-zero exit. env -i mirrors the codex hook executor's clean environment.
+run_hook() {
+    printf '%s' "$1" | env -i PATH="${PATH:-}" bash "$HOOK_UNDER_TEST"
+}
+
+echo "Codex SessionStart hook tests"
+
+startup_payload='{"session_id":"s","hook_event_name":"SessionStart","model":"gpt-5.6-terra","source":"startup"}'
+if output="$(run_hook "$startup_payload")" && [ -z "$output" ]; then
+    pass "source=startup emits nothing and exits 0"
+else
+    fail "source=startup emits nothing and exits 0"
+    printf '%s\n' "$output" | head -3 | sed 's/^/    /'
+fi
+
+compact_payload='{"session_id":"s","hook_event_name":"SessionStart","model":"gpt-5.6-terra","source":"compact"}'
+if output="$(run_hook "$compact_payload")"; then
+    ok=1
+    for needle in \
+        "<EXTREMELY_IMPORTANT>" \
+        "You have superpowers." \
+        "name: using-superpowers" \
+        "<CONTEXT_RESTORED>" \
+        "subagent-driven-development/SKILL.md" \
+        "references/codex-tools.md"; do
+        if [[ "$output" != *"$needle"* ]]; then
+            ok=0
+            echo "    missing: $needle"
+        fi
+    done
+    if [ "$ok" -eq 1 ]; then
+        pass "source=compact emits bootstrap plus re-read addendum"
+    else
+        fail "source=compact emits bootstrap plus re-read addendum"
+    fi
+else
+    fail "source=compact emits bootstrap plus re-read addendum (hook exited non-zero)"
+fi
+
+# Whitespace-tolerant source matching (serializers vary).
+spaced_payload='{"hook_event_name":"SessionStart", "source" : "compact"}'
+if output="$(run_hook "$spaced_payload")" && [[ "$output" == *"<CONTEXT_RESTORED>"* ]]; then
+    pass "whitespace around the source key still triggers injection"
+else
+    fail "whitespace around the source key still triggers injection"
+fi
+
+if output="$(printf '' | env -i PATH="${PATH:-}" bash "$HOOK_UNDER_TEST")" && [ -z "$output" ]; then
+    pass "empty stdin fails open to no output, exit 0"
+else
+    fail "empty stdin fails open to no output, exit 0"
+fi
+
+if output="$(run_hook 'not json at all {{{')" && [ -z "$output" ]; then
+    pass "garbage stdin fails open to no output, exit 0"
+else
+    fail "garbage stdin fails open to no output, exit 0"
+fi
+
+# A compact mention inside some other field must not trigger injection.
+decoy_payload='{"hook_event_name":"SessionStart","source":"startup","cwd":"/tmp/compact"}'
+if output="$(run_hook "$decoy_payload")" && [ -z "$output" ]; then
+    pass "compact appearing outside the source field does not trigger"
+else
+    fail "compact appearing outside the source field does not trigger"
+fi
+
+if node -e '
+const config = JSON.parse(require("fs").readFileSync(process.argv[1], "utf8"));
+const group = config.hooks.SessionStart[0];
+if (group.matcher !== "compact") {
+  console.error(`hook matcher is ${JSON.stringify(group.matcher)}, expected "compact"`);
+  process.exit(1);
+}
+const entry = group.hooks[0];
+if (entry.type !== "command") {
+  console.error(`hook type is ${JSON.stringify(entry.type)}, expected "command"`);
+  process.exit(1);
+}
+if (!entry.command.includes("${PLUGIN_ROOT}") || !/run-hook\.cmd" session-start-codex$/.test(entry.command)) {
+  console.error(`unexpected command shape: ${entry.command}`);
+  process.exit(1);
+}
+' "$CONFIG_UNDER_TEST"; then
+    pass "hooks-codex.json runs session-start-codex via \${PLUGIN_ROOT} on compact"
+else
+    fail "hooks-codex.json runs session-start-codex via \${PLUGIN_ROOT} on compact"
+fi
+
+if [[ "$FAILURES" -gt 0 ]]; then
+    echo "STATUS: FAILED ($FAILURES failure(s))"
+    exit 1
+fi
+
+echo "STATUS: PASSED"