From c1e816741dbc19f3cb6a7649c5f33a8b8750bc6a Mon Sep 17 00:00:00 2001
From: Gabriel Brown <gbrown@ksensetech.com>
Date: Fri, 10 Jul 2026 18:45:10 -0400
Subject: [PATCH] fix(worker): marked-command survives tail-exec; kill script
 excludes itself

---
 apps/agent-worker/src/runtime/docker.ts       | 65 ++++++++++++++++---
 .../tests/unit/box-process-kill.test.ts       | 46 ++++++++++++-
 ...-07-10-spoon-phase2-runtime-unification.md | 39 +++++++++--
 3 files changed, 132 insertions(+), 18 deletions(-)

diff --git a/apps/agent-worker/src/runtime/docker.ts b/apps/agent-worker/src/runtime/docker.ts
index c1181ba..e390c9b 100644
--- a/apps/agent-worker/src/runtime/docker.ts
+++ b/apps/agent-worker/src/runtime/docker.ts
@@ -393,28 +393,75 @@ export const ensureUserContainer = async (args: {
 
 const shellQuote = (value: string) => `'${value.replaceAll("'", "'\\''")}'`;
 
+// The marker is embedded literally into a `# comment` line and into a `pgrep`
+// pattern, so it must not contain shell metacharacters or a newline (either could
+// break out of the comment or the pattern). Callers generate it, but validate
+// defensively so a malformed marker fails loudly instead of silently corrupting
+// the script.
+const MARKER_PATTERN = /^[A-Za-z0-9_-]+$/;
+const assertMarker = (marker: string) => {
+  if (!MARKER_PATTERN.test(marker)) {
+    throw new Error(
+      `Invalid process marker ${JSON.stringify(marker)}: must match ${String(MARKER_PATTERN)}.`,
+    );
+  }
+};
+
 // Wraps a CLI argv so the process runs as a new session/process-group leader whose
 // bash parent carries the marker in its argv (matchable by `pgrep -f`). We do NOT
-// `exec` (bash must survive so the marker stays visible); stdout/stderr fds are
-// inherited by the CLI so streaming still works.
+// `exec` the CLI: bash tail-exec's a final simple command, which would replace the
+// marker-carrying bash with the CLI and make `pgrep -f <marker>` miss the running
+// turn. Keeping a trailing `rc=$?; exit "$rc"` after the CLI means the CLI is no
+// longer the script's final statement, so bash survives as the group leader while
+// still propagating the CLI's exit code (downstream `normalizeRunResult` relies on
+// it — a bare trailing `wait` would mask a non-zero CLI failure as 0). The CLI runs
+// in the same process group as this bash, so the kill helper's group signal reaches
+// it. stdout/stderr fds are inherited by the CLI so streaming still works.
 export const buildMarkedCommand = (
   marker: string,
   command: string[],
 ): string[] => {
-  const script = `# ${marker}\nexec 0</dev/null\n${command.map(shellQuote).join(' ')}`;
+  assertMarker(marker);
+  const script = [
+    `# ${marker}`,
+    'exec 0</dev/null',
+    command.map(shellQuote).join(' '),
+    'rc=$?',
+    'exit "$rc"',
+  ].join('\n');
   return ['setsid', 'bash', '-lc', script];
 };
 
 // Kills every process group whose bash parent matches the marker, TERM then KILL.
-// The negative pid (`-"$pid"`) targets the whole process group, so the CLI and any
-// children it spawned die together.
-export const buildKillScript = (marker: string): string =>
-  [
+// The negative pid (`kill -TERM -"$pgid"`) targets the whole process group, so the
+// CLI and any children it spawned die together.
+//
+// pgrep self-match: this kill script runs via `bash -lc <script>`, whose OWN argv
+// contains the marker literal, so `pgrep -f <marker>` matches the kill script (and
+// its command-substitution subshells) too. Left unguarded it would `kill -TERM` its
+// own process group and die on iteration one, leaking the real target. So we compute
+// this script's pgid up front and skip any match sharing it, killing only the
+// target's process group.
+export const buildKillScript = (marker: string): string => {
+  assertMarker(marker);
+  return [
+    `self_pgid=$(ps -o pgid= -p $$ | tr -d ' ')`,
     `pids=$(pgrep -f ${shellQuote(marker)} || true)`,
-    `for pid in $pids; do kill -TERM -"$pid" 2>/dev/null || true; done`,
+    `for pid in $pids; do`,
+    `  pgid=$(ps -o pgid= -p "$pid" | tr -d ' ')`,
+    `  [ -z "$pgid" ] && continue`,
+    `  [ "$pgid" = "$self_pgid" ] && continue`,
+    `  kill -TERM -"$pgid" 2>/dev/null || true`,
+    `done`,
     `sleep 2`,
-    `for pid in $pids; do kill -KILL -"$pid" 2>/dev/null || true; done`,
+    `for pid in $pids; do`,
+    `  pgid=$(ps -o pgid= -p "$pid" | tr -d ' ')`,
+    `  [ -z "$pgid" ] && continue`,
+    `  [ "$pgid" = "$self_pgid" ] && continue`,
+    `  kill -KILL -"$pgid" 2>/dev/null || true`,
+    `done`,
   ].join('\n');
+};
 
 export const killBoxProcessesByMarker = async (args: {
   containerName: string;
diff --git a/apps/agent-worker/tests/unit/box-process-kill.test.ts b/apps/agent-worker/tests/unit/box-process-kill.test.ts
index 573e1d1..0d67a43 100644
--- a/apps/agent-worker/tests/unit/box-process-kill.test.ts
+++ b/apps/agent-worker/tests/unit/box-process-kill.test.ts
@@ -22,14 +22,54 @@ describe('in-box process-group marker + kill helpers', () => {
     expect(argv[2]).toBe('-lc');
     const script = argv[3] ?? '';
     expect(script).toContain('# spoon-turn-abc');
-    expect(script.split('\n').at(-1)).toBe("'codex' 'exec' '--json' 'hi'");
+    expect(script).toContain("'codex' 'exec' '--json' 'hi'");
+  });
+
+  test('buildMarkedCommand keeps a trailing exit after the CLI so bash survives tail-exec while propagating the exit code (C1 guard)', async () => {
+    const { buildMarkedCommand } = await loadDocker();
+    const script = buildMarkedCommand('spoon-turn-abc', ['codex', 'run'])[3] ?? '';
+    // The CLI must NOT be the final simple command (bash would tail-exec it,
+    // replacing the marker-carrying bash). The exit code must still propagate.
+    expect(script).toContain("'codex' 'run'\nrc=$?\nexit \"$rc\"");
+    expect(script.split('\n').at(-1)).toBe('exit "$rc"');
+    expect(script.split('\n').at(-1)).not.toBe("'codex' 'run'");
+  });
+
+  test('buildMarkedCommand rejects a marker that could break out of the comment', async () => {
+    const { buildMarkedCommand } = await loadDocker();
+    expect(() => buildMarkedCommand('bad\nmarker', ['codex'])).toThrow();
   });
 
   test('buildKillScript TERM-then-KILLs every group matching the marker', async () => {
     const { buildKillScript } = await loadDocker();
     const script = buildKillScript('spoon-turn-abc');
     expect(script).toContain("pgrep -f 'spoon-turn-abc'");
-    expect(script).toContain('kill -TERM -"$pid"');
-    expect(script).toContain('kill -KILL -"$pid"');
+    expect(script).toContain('kill -TERM -"$pgid"');
+    expect(script).toContain('kill -KILL -"$pgid"');
+  });
+
+  test('buildKillScript excludes its own process group so it does not kill itself (C2 guard)', async () => {
+    const { buildKillScript } = await loadDocker();
+    const script = buildKillScript('spoon-turn-abc');
+    // Computes its own pgid and skips any match sharing it (the kill script's
+    // own bash + its command-substitution subshells all carry the marker).
+    expect(script).toContain('self_pgid=$(ps -o pgid= -p $$ | tr -d \' \')');
+    expect(script).toContain('[ "$pgid" = "$self_pgid" ] && continue');
+  });
+
+  test('buildKillScript escalates TERM -> KILL with a sleep 2 in between (order matters)', async () => {
+    const { buildKillScript } = await loadDocker();
+    const script = buildKillScript('spoon-turn-abc');
+    const termIdx = script.indexOf('kill -TERM -"$pgid"');
+    const sleepIdx = script.indexOf('\nsleep 2\n');
+    const killIdx = script.indexOf('kill -KILL -"$pgid"');
+    expect(termIdx).toBeGreaterThanOrEqual(0);
+    expect(sleepIdx).toBeGreaterThan(termIdx);
+    expect(killIdx).toBeGreaterThan(sleepIdx);
+  });
+
+  test('buildKillScript rejects a marker that could break out of the pgrep pattern', async () => {
+    const { buildKillScript } = await loadDocker();
+    expect(() => buildKillScript('bad\nmarker')).toThrow();
   });
 });
diff --git a/docs/superpowers/plans/2026-07-10-spoon-phase2-runtime-unification.md b/docs/superpowers/plans/2026-07-10-spoon-phase2-runtime-unification.md
index d7f58b3..02dd5ff 100644
--- a/docs/superpowers/plans/2026-07-10-spoon-phase2-runtime-unification.md
+++ b/docs/superpowers/plans/2026-07-10-spoon-phase2-runtime-unification.md
@@ -131,23 +131,50 @@ export const getAdapter = (name: AgentRuntimeName): AgentRuntime => {
 ```ts
 // Wraps a CLI argv so the process runs as a new session/process-group leader whose
 // bash parent carries the marker in its argv (matchable by `pgrep -f`). We do NOT
-// `exec` (bash must survive so the marker stays visible); stdout/stderr fds are
-// inherited by the CLI so streaming still works.
+// `exec` the CLI: bash tail-exec's a final simple command, so an `exec`-or-trailing
+// CLI would replace the marker-carrying bash and `pgrep -f <marker>` would miss the
+// running turn. Keep a trailing `rc=$?; exit "$rc"` so the CLI is no longer the final
+// statement (bash survives as group leader) while still propagating its exit code
+// (downstream `normalizeRunResult` relies on it; a bare `wait` would mask failures).
 export const buildMarkedCommand = (marker: string, command: string[]): string[] => {
-  const script = `# ${marker}\nexec 0</dev/null\n${command.map(shellQuote).join(' ')}`;
+  // assertMarker(marker) — reject anything but /^[A-Za-z0-9_-]+$/ so a newline can't
+  // break out of the `# comment` line.
+  const script = [
+    `# ${marker}`,
+    'exec 0</dev/null',
+    command.map(shellQuote).join(' '),
+    'rc=$?',
+    'exit "$rc"',
+  ].join('\n');
   return ['setsid', 'bash', '-lc', script];
 };
 
 // Kills every process group whose bash parent matches the marker, TERM then KILL.
+// pgrep self-match: the kill script runs via `bash -lc <script>` whose own argv holds
+// the marker literal, so pgrep matches the kill script (and its command-substitution
+// subshells) too. Exclude its own pgid or it SIGTERMs itself on iteration one and
+// leaks the target; kill the TARGET's pgid instead.
 export const killBoxProcessesByMarker = async (args: {
   containerName: string;
   marker: string;
 }): Promise<void> => {
+  // assertMarker(args.marker) — same /^[A-Za-z0-9_-]+$/ guard for the pgrep pattern.
   const script = [
+    `self_pgid=$(ps -o pgid= -p $$ | tr -d ' ')`,
     `pids=$(pgrep -f ${shellQuote(args.marker)} || true)`,
-    `for pid in $pids; do kill -TERM -"$pid" 2>/dev/null || true; done`,
+    `for pid in $pids; do`,
+    `  pgid=$(ps -o pgid= -p "$pid" | tr -d ' ')`,
+    `  [ -z "$pgid" ] && continue`,
+    `  [ "$pgid" = "$self_pgid" ] && continue`,
+    `  kill -TERM -"$pgid" 2>/dev/null || true`,
+    `done`,
     `sleep 2`,
-    `for pid in $pids; do kill -KILL -"$pid" 2>/dev/null || true; done`,
+    `for pid in $pids; do`,
+    `  pgid=$(ps -o pgid= -p "$pid" | tr -d ' ')`,
+    `  [ -z "$pgid" ] && continue`,
+    `  [ "$pgid" = "$self_pgid" ] && continue`,
+    `  kill -KILL -"$pgid" 2>/dev/null || true`,
+    `done`,
   ].join('\n');
   await execa(containerRuntime(), ['exec', args.containerName, 'bash', '-lc', script], {
     reject: false, stdin: 'ignore',
@@ -159,7 +186,7 @@ Add a local `const shellQuote = (v: string) => `'${v.replaceAll("'", "'\\''")}'`
 *Consumes:* `execa`, `containerRuntime()` (already in file).
 
 **Steps:**
-- [ ] Write failing `apps/agent-worker/tests/unit/box-process-kill.test.ts`: import `buildMarkedCommand`. Assert `buildMarkedCommand('spoon-turn-abc', ['codex', 'exec', '--json', 'hi'])` returns `['setsid', 'bash', '-lc', expect.stringContaining('# spoon-turn-abc')]` and the script's last line contains `codex exec --json 'hi'`. (Do not unit-test `killBoxProcessesByMarker` end-to-end — it shells out; assert only the argv via a spy if you refactor it to a pure `buildKillScript(marker)` helper. **Recommended:** extract `export const buildKillScript = (marker: string): string` and test it contains `pgrep -f 'spoon-turn-abc'`, `kill -TERM -"$pid"`, and `kill -KILL -"$pid"`.)
+- [ ] Write failing `apps/agent-worker/tests/unit/box-process-kill.test.ts`: import `buildMarkedCommand`. Assert `buildMarkedCommand('spoon-turn-abc', ['codex', 'exec', '--json', 'hi'])` returns `['setsid', 'bash', '-lc', expect.stringContaining('# spoon-turn-abc')]` and the script's last line contains `codex exec --json 'hi'`. (Do not unit-test `killBoxProcessesByMarker` end-to-end — it shells out; assert only the argv via a spy if you refactor it to a pure `buildKillScript(marker)` helper. **Recommended:** extract `export const buildKillScript = (marker: string): string` and test it contains `pgrep -f 'spoon-turn-abc'`, `kill -TERM -"$pgid"`, and `kill -KILL -"$pgid"`, plus the self-pgid exclusion (`[ "$pgid" = "$self_pgid" ] && continue`).)
 - [ ] Run `bun run test:unit` → FAIL.
 - [ ] Implement `buildMarkedCommand`, `buildKillScript`, and `killBoxProcessesByMarker` in `docker.ts`.
 - [ ] Run `bun run test:unit` → PASS. `bun run typecheck` → PASS.