docs: clarify contribution responsibilities and PR limits

AGENTS.md

@@ -4,6 +4,32 @@ CodeIgniter 4 is a mature open-source PHP framework. Framework production
 code lives in `system/`; its tests mirror that structure under
 `tests/system/`.
 
+## Before opening a pull request
+
+Do not open a pull request unless the applicable pre-submission requirements
+in [CONTRIBUTING.md](CONTRIBUTING.md) and
+[Sending a Pull Request](contributing/pull_request.md) are met.
+
+- A human contributor must have reviewed and understood the complete diff
+  and taken responsibility for the submission. Agent review and passing
+  checks do not replace this human review.
+- Verify the target branch, commit signing, relevant tests, and required
+  documentation. Follow the focused validation policy below. Do not run
+  the full CI matrix locally.
+- Remind the user of the applicable open pull request limit before
+  submission. Check the contributor's open pull requests, including
+  drafts, when possible. If the limit or a maintainer-approved exemption
+  cannot be verified, clearly tell the user rather than claiming it has
+  been checked.
+- If a requirement is unmet or cannot be verified, do not open the pull
+  request. Tell the user which requirements remain unmet or unverified
+  and what is needed before submission. Continue preparing the changes
+  and completing any checks that can be performed. An unverified PR
+  limit or exemption alone does not block submission; a known limit
+  violation without an exemption does.
+- Report the checks performed, their results, and any validation left
+  to CI. Do not claim that checks passed unless they were actually run.
+
 ## Before making changes
 
 Consult the relevant sections of:

CONTRIBUTING.md

@@ -3,4 +3,42 @@
 CodeIgniter is a community driven project and accepts contributions of
 code and documentation from the community.
 
-If you'd like to contribute, please read the [Contributing to CodeIgniter](./contributing/README.md).
+## Responsibility for Contributions
+
+AI-assisted contributions are welcome, but contributors remain responsible
+for everything they submit.
+
+Before opening a pull request, you must:
+
+- Review and understand all proposed changes.
+- Explain the problem being addressed and why the proposed solution is appropriate.
+- Verify the changes, run relevant tests, and describe what you tested,
+  including any limitations.
+- Be prepared to answer review questions and revise your contribution.
+
+These requirements apply regardless of the tools used. AI-generated
+explanations and passing CI checks do not replace your own review.
+
+Automated submissions without meaningful human review are not accepted.
+Project-approved automation, such as dependency update bots, is exempt
+from this submission requirement.
+
+Maintainers may close pull requests without detailed code review when
+the problem is unclear, the changes have not been adequately verified,
+or the contributor cannot explain them.
+
+We do not require AI tool disclosures, prompts, or chat histories.
+
+## Open Pull Request Limit
+
+Contributors without write access may have up to three pull requests
+open in this repository at the same time, including drafts.
+Maintainers may grant exceptions to trusted contributors.
+
+Please address feedback on your existing pull requests before opening
+additional ones.
+
+## Further Guidance
+
+For detailed contribution instructions, please read
+[Contributing to CodeIgniter](./contributing/README.md).

contributing/README.md

@@ -12,6 +12,8 @@ specifically interested in at any point in time. Join the discussion for those i
 if you want to take the lead on one of them.
 
 - [Contributor Covenant Code of Conduct](../CODE_OF_CONDUCT.md)
+- [Responsibility for Contributions](../CONTRIBUTING.md#responsibility-for-contributions)
+- [Open Pull Request Limit](../CONTRIBUTING.md#open-pull-request-limit)
 - [Reporting a Bug](./bug_report.md)
 - [Sending a Pull Request](./pull_request.md)
 - [Configuring Upstream and Rebasing](./workflow.md#configuring-upstream-and-rebasing)

contributing/pull_request.md

@@ -2,6 +2,10 @@
 
 ## Contributions
 
+Before opening a pull request, read
+[Responsibility for Contributions](../CONTRIBUTING.md#responsibility-for-contributions)
+and the [Open Pull Request Limit](../CONTRIBUTING.md#open-pull-request-limit).
+
 We expect the following in all Pull Requests (PRs).
 - PRs must be sent to the [appropriate branch](#branching)
 - All git commits must be [GPG-signed](#signing)