Update PR-linking guidance to prevent cross-repo issues from auto-closing (#37534)

* Initial plan

* Update PR-linking guidance to prevent cross-repo issue auto-close

Co-authored-by: wadepickett <10985336+wadepickett@users.noreply.github.com>

* Use MM/DD/YYYY slash format for ms.date per metadata guidance

Co-authored-by: wadepickett <10985336+wadepickett@users.noreply.github.com>

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: wadepickett <10985336+wadepickett@users.noreply.github.com>

Author: Copilot

.github/PULL_REQUEST_TEMPLATE.md

@@ -3,11 +3,20 @@
 <!--
 # Instructions
 
-When creating a new PR, please reference the issue number if there is one:
+When creating a new PR, reference the originating issue on the first line of the description:
 
-Fixes #Issue_Number
+* Issue in this repository (dotnet/AspNetCore.Docs): use a closing keyword so GitHub auto-closes the issue when this PR is merged:
 
-The "Fixes #nnn" syntax in the PR description allows GitHub to automatically close the issue when this PR is merged.
+  Fixes #Issue_Number
+
+* Issue in another repository: use a non-closing, fully-qualified reference so it links without closing the other repository's issue:
+
+  Contributes to owner/repo#Issue_Number
+
+Notes:
+
+* If this PR only partially addresses an issue in this repository, use "Contributes to #Issue_Number" instead of "Fixes" so the issue stays open.
+* Never use a bare "#Issue_Number" for an issue in another repository; the bare form resolves to an issue of that number in this repository and links to the wrong issue. Always use the "owner/repo#Issue_Number" form for cross-repository references.
 
 NOTE: This is a comment; please type your descriptions above or below it.
 -->

.github/copilot-instructions.md

@@ -1,7 +1,7 @@
 ---
 author: tdykstra
 ms.author: wpickett
-ms.date: 10-16-2025
+ms.date: 08/25/2026
 ---
 
 # Copilot Instructions for `dotnet/AspNetCore.Docs`
@@ -157,7 +157,13 @@ When working on an issue:
   * [ ] When significantly updating, revise the introductory paragraph to match the new scope and content.
 
 ### 6. PR Description Requirements
-* [ ] ALWAYS include "Fixes #[issue-number]" in the PR description, at the first line of the description to link back to the original issue
+* [ ] On the first line of the PR description, reference the originating issue:
+  * [ ] Issue in this repository (`dotnet/AspNetCore.Docs`): use a closing keyword: `Fixes #[issue-number]`
+  * [ ] Issue in another repository: use a non-closing, fully-qualified reference so it links without closing: `Contributes to [owner]/[repo]#[issue-number]`
+* [ ] Exceptions to the above defaults:
+  * [ ] If this PR only partially addresses an issue in this repository, use `Contributes to #[issue-number]` instead of `Fixes`, so the issue stays open.
+  * [ ] Only use a closing keyword for an issue in another repository when a maintainer explicitly asks for it, and then use the fully-qualified form: `Fixes [owner]/[repo]#[issue-number]`.
+* [ ] Never use a bare `#[issue-number]` for an issue in another repository; the bare form resolves to an issue of that number in this repository and links to the wrong issue. Always use the `[owner]/[repo]#[issue-number]` form for cross-repository references.
 * [ ] Include a clear summary of changes made
 * [ ] List all files that were modified with brief descriptions