René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"AbortSignal.any() stops following a timeout signal once a listener is added to the timeout and removed, so the composite never aborts after a GC","articleBody":"### Version\n\nv26.10.0 and v26.11.1.\n\n### Platform\n\nLinux arm64.\n\n### Subsystem\n\nlib (abortcontroller)\n\n### What steps will reproduce the bug?\n\nRun `node --expose-gc repro.mjs`:\n\n```js\n// node --expose-gc e1.mjs\nconst sleep = ms => new Promise(resolve => setTimeout(resolve, ms));\nfor (const touch of [false, true]) {\n  const composite = (() => {\n    const timeout = AbortSignal.timeout(100);\n    const made = AbortSignal.any([timeout]);\n    if (touch) {\n      const listener = () => {};\n      timeout.addEventListener(\"abort\", listener);\n      timeout.removeEventListener(\"abort\", listener);\n    }\n    return made;\n  })();\n  composite.addEventListener(\"abort\", () => {});\n  await sleep(10);\n  globalThis.gc();\n  await sleep(300);\n  console.log(`listener added and removed on the timeout: ${touch}; composite aborted: ${composite.aborted}`);\n}\n```\n\n### How often does it reproduce? Is there a required condition?\n\nAlways: 3 of 3 runs on each version. The timeout must have had a listener that was then removed, and a garbage collection must run before it fires.\n\n### What is the expected behavior? Why is that the expected behavior?\n\n`listener added and removed on the timeout: true; composite aborted: true`. A composite aborts when one of its sources does, whatever listeners came and went on the source.\n\n### What do you see instead?\n\n`composite aborted: false`: the timeout is collected before it fires, so the composite never aborts.\n\n### Additional information\n\n#57867 keeps a timeout that `AbortSignal.any()` follows in `gcPersistentSignals`. Removing the timeout's last abort listener seems to delete it from that set while a composite still follows it. We hit this in code that hands a timeout to `AbortSignal.any()` and also waits on the timeout itself, for example with `timers/promises`' `setTimeout(ms, value, { signal })`, which adds a listener and removes it.\n","author":{"url":"https://github.com/rinarakaki","@type":"Person","name":"rinarakaki"},"datePublished":"2026-10-08T17:28:25Z","url":"https://github.com/nodejs/node/issues/66610"}