doc: create ai-guidelines and include to CONTRIBUTING

CONTRIBUTING.md

@@ -19,6 +19,7 @@ works.
 * [Code of Conduct](#code-of-conduct)
 * [Issues](#issues)
 * [Pull Requests](#pull-requests)
+* [AI Use Policy and Guidelines](#ai-use-policy-and-guidelines)
 * [Developer's Certificate of Origin 1.1](#developers-certificate-of-origin-11)
 
 ## [Code of Conduct](./doc/contributing/code-of-conduct.md)
@@ -47,6 +48,15 @@ dependencies, and tools contained in the `nodejs/node` repository.
 * [Reviewing Pull Requests](./doc/contributing/pull-requests.md#reviewing-pull-requests)
 * [Notes](./doc/contributing/pull-requests.md#notes)
 
+## [AI Use Policy and Guidelines](./doc/contributing/ai-guidelines.md)
+
+Node.js expects contributors to understand and take full responsibility for
+every change they propose. Pull requests consisting of AI-generated code the
+contributor has not personally understood, tested, and verified will be closed
+without review.
+
+See [details on our AI use policy and guidelines](./doc/contributing/ai-guidelines.md).
+
 ## Developer's Certificate of Origin 1.1
 
 ```text

doc/contributing/ai-guidelines.md

@@ -0,0 +1,57 @@
+# AI use policy and guidelines
+
+* [Core principle](#core-principle)
+* [Using AI for code contributions](#using-ai-for-code-contributions)
+* [Using AI for communication](#using-ai-for-communication)
+
+## Core principle
+
+Node.js expects contributors to understand and take full responsibility for
+every change they propose. The answer to "Why is X an improvement?" should
+never be "I'm not sure. The AI did it."
+
+Pull requests that consist of AI-generated code the contributor has not
+personally understood, tested, and verified waste collaborator time and
+will be closed without review.
+
+## Using AI for code contributions
+
+AI tools may assist contributors, but must not replace contributor judgment.
+When using AI as a coding assistant:
+
+* **Understand the codebase first.** Do not skip familiarizing yourself with
+  the relevant subsystem. LLMs frequently produce inaccurate descriptions of
+  Node.js internals — always verify against the actual source.
+
+* **Own every line you submit.** You are responsible for all code in your
+  pull request, regardless of how it was generated. Be prepared to explain
+  any change in detail during review.
+
+* **Keep logical commits.** Structure commits coherently even when an LLM
+  generates multiple changes at once. Follow the existing
+  [commit message guidelines][].
+
+* **Test thoroughly.** AI-generated code must pass the full test suite and
+  any manually written tests relevant to the change. Do not rely on the LLM
+  to assess correctness.
+
+* **Edit generated comments critically.** LLM-produced comments are often
+  verbose or inaccurate. Remove comments that simply restate what the code
+  does; add comments only where the logic is non-obvious.
+
+## Using AI for communication
+
+Node.js values concise, precise communication that respects collaborator time.
+
+* **Do not post AI-generated messages** in pull requests, issues, or the
+  project's communication channels.
+* **Verify accuracy** of any LLM-generated content before including it in a
+  PR description or comment.
+* **Complete pull request templates fully** rather than replacing them with
+  LLM-generated summaries.
+* **Link to primary sources** — code, documentation, specifications — rather
+  than quoting LLM answers.
+* Grammar and spell-check tools are acceptable when they improve clarity and
+  conciseness.
+
+[commit message guidelines]: ./pull-requests.md#commit-message-guidelines