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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"`subprocess.kill('SIGWINCH')` forcefully terminates subprocesses on Windows","articleBody":"### Version\n\nCurrent `main` by source inspection. This appears to affect releases since https://github.com/nodejs/node/pull/55514.\n\n### Platform\n\nMicrosoft Windows. The behavior is in the `_WIN32` path in `src/process_wrap.cc`.\n\n### Subsystem\n\nchild_process\n\n### What steps will reproduce the bug?\n\nRun this on Windows:\n\n```js\n// test.mjs\nimport {spawn} from 'node:child_process';\n\nconst subprocess = spawn(process.execPath, ['-e', 'setInterval(() => {}, 1000)']);\n\nsubprocess.on('error', error => {\n\tconsole.log('error', error.code);\n});\n\nsubprocess.on('exit', (exitCode, signalCode) => {\n\tconsole.log('exit', {exitCode, signalCode});\n});\n\nconsole.log('kill returned:', subprocess.kill('SIGWINCH'));\n\nsetTimeout(() => {\n\tconsole.log('still running:', !subprocess.killed && subprocess.exitCode === undefined && subprocess.signalCode === undefined);\n\tsubprocess.kill('SIGKILL');\n}, 1000);\n```\n\n### How often does it reproduce? Is there a required condition?\n\nAlways on Windows.\n\n### What is the expected behavior? Why is that the expected behavior?\n\n`SIGWINCH` should not forcefully terminate the subprocess on Windows.\n\nBefore https://github.com/nodejs/node/pull/55514, unsupported signals such as `SIGWINCH` reached libuv and returned `UV_ENOSYS`. In JavaScript, `ChildProcess.prototype.kill()` handles `UV_ENOSYS` by throwing an `ErrnoException`.\n\nThat behavior was safer for `SIGWINCH`: it did not terminate the subprocess.\n\n### What do you see instead?\n\nSince https://github.com/nodejs/node/pull/55514, `src/process_wrap.cc` remaps every Windows signal other than `SIGKILL`, `SIGTERM`, `SIGINT`, `SIGQUIT`, and `0` to `SIGKILL` before calling libuv:\n\n```cpp\n#ifdef _WIN32\n    if (signal != SIGKILL && signal != SIGTERM && signal != SIGINT &&\n        signal != SIGQUIT && signal != 0) {\n      signal = SIGKILL;\n    }\n#endif\n    int err = uv_process_kill(&wrap->process_, signal);\n```\n\nThe current vendored libuv Windows implementation only forcefully terminates for `SIGQUIT`, `SIGTERM`, `SIGKILL`, and `SIGINT`, treats `0` as a health check, and returns `UV_ENOSYS` for unsuported signals:\n\n```c\n    default:\n      /* Unsupported signal. */\n      return UV_ENOSYS;\n```\n\nBecause Node now remaps `SIGWINCH` before libuv sees it, `subprocess.kill('SIGWINCH')` terminates the subprocess as if `SIGKILL` had been sent.\n\nThis is surprising because `SIGWINCH` is not a termination signal. Users forwarding terminal resize notifications can accidentally kill a child process on Windows.\n\n### Additional information\n\nIt was already commented here: https://github.com/nodejs/node/issues/42923#issuecomment-3448792053 but it was ignored.\n\nPossible fix: exempt `SIGWINCH` from the Windows remapping in `src/process_wrap.cc`, so it keeps the previous unsupported-signal behavior instead of becoming `SIGKILL`.\n","author":{"url":"https://github.com/sindresorhus","@type":"Person","name":"sindresorhus"},"datePublished":"2026-07-06T13:39:47Z","url":"https://github.com/nodejs/node/issues/64324"}