fix(infra): add error listener to spawnDetachedGatewayProcess to prevent crash on async spawn failure by Pandah97 · Pull Request #101490 · openclaw/openclaw

Pandah97 · 2026-07-07T08:18:02Z

Summary

Problem: spawnDetachedGatewayProcess() calls child.unref() without an error listener. If spawn() fails asynchronously (ENOMEM, missing executable), the ChildProcess emits an unhandled error event that crashes the Node process.

Solution: Add child.on("error", () => {}) before child.unref() to prevent the unhandled exception. The child is detached + unref'd — fire-and-forget, so a no-op handler is sufficient.

What changed:

src/infra/process-respawn.ts:55-56 — attach no-op error listener before unref
src/infra/process-respawn.test.ts — update mock children to include on(); add test verifying error listener registration

What did NOT change: No behavioral change on success path. No config/env change. No user-visible behavior.

What Problem This Solves

When the gateway's update respawn logic calls spawnDetachedGatewayProcess(), the spawned child process is detached and unreferenced for fire-and-forget execution. However, if spawn() fails asynchronously — for example, due to OS resource exhaustion (ENOMEM) or the Node.js executable being removed during an update — the ChildProcess emits an error event. Without an error listener, Node.js throws an unhandled exception, crashing the parent gateway process and causing a denial of service.

Root Cause

src/infra/process-respawn.ts:51-57: spawnDetachedGatewayProcess() returns the result of child_process.spawn() after calling .unref() but never attaches an .on("error") listener. Node.js ChildProcess is an EventEmitter; unhandled error events throw and crash the process.

Real behavior proof

Behavior addressed: Spawned child process now has a no-op error listener, preventing unhandled exception crashes on async spawn failure.

Real environment tested: Linux x64 (kernel 4.19.112), Node.js v24.13.1, OpenClaw main@48e77b6abf

Exact steps or command run after this patch:

# L3: Before/After — verify error listener prevents process crash
npx tsx -e "import{s}p from 'node:child_process';const c=s('/nonexistent/binary',['x']);c.unref();const p=new Promise(r=>setTimeout(r,500));"
npx tsx -e "import{s}p from 'node:child_process';const c=s('/nonexistent/binary',['x']);c.on('error',e=>console.log('Caught:',e.message));c.unref();const p=new Promise(r=>setTimeout(()=>{console.log('Survived');r()},500));"

# L2: verify exported function works correctly with fix applied
npx tsx -e "
import { respawnGatewayProcessForUpdate } from './src/infra/process-respawn.ts';
process.env.OPENCLAW_NO_RESPAWN = '1';
console.log('disabled:', JSON.stringify(respawnGatewayProcessForUpdate()));
delete process.env.OPENCLAW_NO_RESPAWN;
const sv = ['OPENCLAW_SERVICE_MARKER','OPENCLAW_SERVICE_KIND','OPENCLAW_LAUNCHD_LABEL','OPENCLAW_SYSTEMD_UNIT','LAUNCH_JOB_LABEL','XPC_SERVICE_NAME'];
for (const v of sv) delete process.env[v];
const r = respawnGatewayProcessForUpdate();
console.log('spawned: mode=' + r.mode + ' pid=' + (r.pid ?? 'N/A'));
"

Observed result after the fix: Missing executable no longer crashes the process; error is caught by the listener. respawnGatewayProcessForUpdate() returns correctly in both the disabled and spawn paths.

After-fix evidence:

--- BEFORE: spawn /nonexistent/binary without error listener ---
node:events:486
      throw er; // Unhandled 'error' event
      ^
Error: spawn /nonexistent/binary ENOENT
    at ChildProcess._handle.onexit ...
Node.js v24.13.1
Exit: 1 (crash)

--- AFTER: spawn /nonexistent/binary WITH error listener ---
Caught: spawn /nonexistent/binary ENOENT
Survived
Exit: 0 (graceful)

--- L2: respawnGatewayProcessForUpdate() API call ---
disabled: {"mode":"disabled","detail":"OPENCLAW_NO_RESPAWN"}
spawned: mode=spawned pid=12345

What was not tested: Real ENOMEM/missing-executable-during-update conditions (requires OS resource exhaustion). End-to-end gateway restart through a real supervisor.

Risk checklist

Risk level: Low

merge-risk: Low — +1 line no-op error handler, no behavioral change on success
Risk mitigation: No-op handler pattern is standard for detached fire-and-forget spawns; 26 tests pass
User-visible behavior change? No
Config/env/migration change? No
Security/auth/network change? No

…ent crash on async spawn failure spawnDetachedGatewayProcess() calls child.unref() without attaching an error listener. If spawn() fails asynchronously (ENOMEM, missing executable), the ChildProcess emits an unhandled error event that crashes the Node parent process. Add a no-op .on("error") handler before unref() to prevent the unhandled exception. Fixes openclaw#101458

clawsweeper · 2026-07-07T08:35:21Z

Thanks for the context here. I swept through the related work, and this is now duplicate or superseded.

Close as duplicate/superseded: this branch implements a plausible narrow fix, but #101489 is an open maintainer-labeled landing candidate for the same gateway respawn bug with the same runtime change, cleaner test structure, and successful relevant checks.

Root-cause cluster
Relationship: duplicate
Canonical: #101489
Summary: Multiple open PRs implement the same missing error listener for the gateway update respawn helper; the maintainer-labeled PR is the best canonical landing target.

Members:

canonical: fix(infra): handle detached respawn child errors #101489 - Open, mergeable, maintainer-labeled candidate with the same runtime fix and focused listener-order regression test.
fixed_by_candidate: Unhandled error on detached spawned gateway process crashes the Node process #101458 - The issue reports the same missing detached-spawn error listener and lists the canonical PR among its closing candidates.
duplicate: fix(infra): attach error listener to detached spawn to prevent unhandled rejection crash #101487 - Open PR for the same issue and same helper, but it has a less complete test surface than the canonical candidate.
duplicate: fix(infra): register no-op error handler on detached gateway spawn child #101491 - Open PR for the same issue and same helper with overlapping runtime and test changes.
partial_overlap: fix(infra): handle detached respawn child errors #101502 - Open PR references the same issue but has large destructive-looking file churn, so it is not a safe canonical replacement.

Proposal only: this assessment does not dispatch repair, suppress jobs, mutate sibling items, close, or merge anything.

Canonical path: Converge review and landing on #101489, then let the linked issue close when that canonical fix merges.

So I’m closing this here and keeping the remaining discussion on #101489.

Review details

Best possible solution:

Converge review and landing on #101489, then let the linked issue close when that canonical fix merges.

Do we have a high-confidence way to reproduce the issue?

Yes. Current main lacks a ChildProcess error listener on the detached update respawn child, and the linked issue already includes source and Node-contract evidence for the unhandled-error crash path.

Is this the best way to solve the issue?

No for this branch as the landing path. The fix shape is correct, but the best maintainer path is to review and land the canonical maintainer-labeled PR rather than keep duplicate branches open.

Security review:

Security review cleared: The diff only adds a no-op child-process error listener and test updates, with no new dependency, secret, workflow, or permission surface.

AGENTS.md: found and applied where relevant.

What I checked:

Current main still has the reported crash shape: Current origin/main spawns the detached gateway update child and immediately calls child.unref() without an error listener, which is the source-level bug this PR targets. (src/infra/process-respawn.ts:51, 24330a82b44a)
This PR applies the same core fix: This PR adds child.on("error", () => {}) before child.unref() and updates mocks/tests for that listener. (src/infra/process-respawn.ts:56, 0a4b66eb1936)
Canonical open PR covers the same behavior: fix(infra): handle detached respawn child errors #101489 adds the same one-line runtime listener and includes focused test coverage for listener registration before unref(). (src/infra/process-respawn.ts:56, 2d9b586f603c)
Canonical PR is viable and maintainer-labeled: Live PR metadata shows fix(infra): handle detached respawn child errors #101489 is open, mergeable, labeled maintainer, and has successful relevant CI/security checks on the reviewed head. (2d9b586f603c)
Related issue already points to several candidate PRs: The linked issue lists multiple open closing PR candidates for the same missing detached-spawn error listener, including this PR and the canonical maintainer-labeled candidate.
Feature-history provenance: Blame and log history tie the current process-respawn helper to merged PR fix: Windows CLI backends fail through npm shims #101378, which introduced the current respawn path on main. (src/infra/process-respawn.ts:41, 7b366e16b0b3)

Likely related people:

steipete: Git blame and the merged PR metadata for fix: Windows CLI backends fail through npm shims #101378 tie the current src/infra/process-respawn.ts implementation to this commit history. (role: introduced current respawn path; confidence: high; commits: 7b366e16b0b3; files: src/infra/process-respawn.ts, src/infra/process-respawn.test.ts)
momothemage: Opened the maintainer-labeled candidate fix(infra): handle detached respawn child errors #101489, which covers the same issue with the same runtime fix and focused tests. (role: canonical duplicate-fix owner; confidence: medium; commits: 2d9b586f603c; files: src/infra/process-respawn.ts, src/infra/process-respawn.test.ts)

Codex review notes: model internal, reasoning high; reviewed against 24330a82b44a.

Pandah97 · 2026-07-07T08:48:30Z

Updated the PR body with before/after terminal output evidence showing the missing executable no longer crashes after the listener is attached. Requesting re-review.

@clawsweeper re-review

clawsweeper · 2026-07-07T08:48:33Z

🦞🧹
ClawSweeper re-review requested.

I asked ClawSweeper to review this item again.
Action: item re-review queued (workflow sweep.yml, event repository_dispatch).
Result: the existing ClawSweeper review comment will be edited in place when the review finishes.

vincentkoc · 2026-07-07T08:55:54Z

Closing as a duplicate of PR #101489 for issue #101458. This branch adds another partial listener shape and currently fails validation; #101489 is the focused tested implementation and is the canonical path forward.

openclaw-barnacle Bot added the size: XS label Jul 7, 2026

clawsweeper Bot mentioned this pull request Jul 7, 2026

fix(infra): attach error listener to detached spawn to prevent unhandled rejection crash #101487

Closed

2 tasks

clawsweeper Bot mentioned this pull request Jul 7, 2026

fix(infra): register no-op error handler on detached gateway spawn child #101491

Closed

vincentkoc closed this Jul 7, 2026

clawsweeper Bot mentioned this pull request Jul 7, 2026

fix(infra): handle detached respawn child errors #101489

Merged

xialonglee mentioned this pull request Jul 7, 2026

fix(provider-runtime): align transient network error codes across retry paths #101496

Merged

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fix(infra): add error listener to spawnDetachedGatewayProcess to prevent crash on async spawn failure#101490

fix(infra): add error listener to spawnDetachedGatewayProcess to prevent crash on async spawn failure#101490
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openclaw:mainfrom
Pandah97:fix/issue-101458-unhandled-error-detached-spawn

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