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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"stream: `pipeTo` with `preventCancel` can hit `ERR_INTERNAL_ASSERTION` if destination errors before deferred write","articleBody":"### Version\n\nv24.16.0\n\n### Platform\n\n```text\nLinux n37-114-192 5.15.120.bsk.3-amd64 #5.15.120.bsk.3 SMP Debian 5.15.120.bsk.3 Fri Dec 8 12:41:09 UTC x86_64 GNU/Linux\n```\n\n### Subsystem\n\nstream\n\n### What steps will reproduce the bug?\n\n```js\nconst { ReadableStream, WritableStream } = require(\"node:stream/web\");\n\nlet sourceController;\nlet destController;\n\nconst source = new ReadableStream({\n  start(controller) {\n    sourceController = controller;\n  },\n});\n\nconst dest = new WritableStream({\n  start(controller) {\n    destController = controller;\n  },\n  write() {},\n});\n\nsource.pipeTo(dest, { preventCancel: true }).catch((err) =\u003e {\n  console.log(\"pipeTo rejected:\", err.name, err.message);\n});\n\nsetImmediate(() =\u003e {\n  destController.error(new Error(\"destination errored\"));\n  sourceController.enqueue(\"chunk\");\n});\n```\n\n### How often does it reproduce? Is there a required condition?\n\nAlways.\n\n### What is the expected behavior? Why is that the expected behavior?\n\n`pipeTo()` should reject with the destination error, like v24.14.1 does:\n\n```\npipeTo rejected: Error destination errored\n```\n\n### What do you see instead?\n\n```\nnode:internal/assert:11\n    throw new ERR_INTERNAL_ASSERTION(message);\n          ^\n\nError [ERR_INTERNAL_ASSERTION]: This is caused by either a bug in Node.js or incorrect usage of Node.js internals.\nPlease open an issue with this stack trace at https://github.com/nodejs/node/issues\n\n    at assert (node:internal/assert:11:11)\n    at writableStreamDefaultWriterWrite (node:internal/webstreams/writablestream:982:3)\n    at node:internal/webstreams/readablestream:1677:33\n    at process.processTicksAndRejections (node:internal/process/task_queues:104:5) {\n  code: 'ERR_INTERNAL_ASSERTION'\n}\n\nNode.js v24.16.0\n```\n\n### Additional information\n\nThe error starts to occur in v24.15.0. This lines up strongly with https://github.com/nodejs/node/pull/61800.","author":{"url":"https://github.com/colinaaa","@type":"Person","name":"colinaaa"},"datePublished":"2026-06-03T11:06:52.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":0},"url":"https://github.com/63732/node/issues/63732"}