Tagging copilot in an existing PR doesn't work #179975
Replies: 4 comments 3 replies
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Hello there. This actually isn’t expected behaviour. Copilot Coding Agent is supposed to respond to an @copilot mention on an existing pull request by starting a task and opening a child pull request that uses the existing PR’s branch as its base. Since it already works for you when you start a task from the agents panel or by assigning an issue, your org and repo are most likely configured correctly. Make sure your @copilot message is a submitted top-level comment or review (not just a draft), that the PR is in a repository where Copilot Coding Agent is enabled, and that the repository isn’t using managed user accounts, where some Copilot features are restricted. After you post the comment, check the agents panel or your Copilot task list to see whether a task briefly starts and then fails. If you still see only the reaction and no new task or child PR, this is likely a bug rather than a configuration problem, so I believe the next step is to open a ticket with GitHub Support and include a link to one of the affected PRs and the time of your @copilot comment so they can look at the logs. Hope this helps! |
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Right now, Copilot Coding Agent can’t reliably trigger a task from comments on an existing PR. What does work
Both of these create a fresh task context that Copilot controls end-to-end, which is why they behave normally. What doesn’t work (by design, currently)
CCA doesn’t yet support taking over an already-open PR and treating it as a task. It won’t create a task, won’t open a working branch, and won’t push commits. The system reacts to the mention but cannot act on it. WorkaroundIf you need Copilot to modify the code:
This gives it the controlled environment it expects. Bottom lineYour repo isn’t misconfigured. This scenario just isn’t supported yet. |
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This behavior suggests there might be a specific configuration or permission issue that's blocking CCA from operating on existing PRs, even though it works for new tasks. Here are the most likely reasons:
Quick Debugging Steps: Try the @copilot mention on a different, simpler PR in the same repo to isolate the issue The fact that you get the "👀" reaction confirms CCA is receiving the trigger, but something is preventing the execution phase. This is likely a permissions or policy barrier rather than a complete feature failure. |
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I figured this out, but it still seems like a bug, and I still opened a support ticket with GitHub. We use repository Rulesets to restrict every one of our commit messages. We require all of our commit messages to match a given RegEx pattern. In order to get CCA working, I have added I did some testing, temporarily disabled my Ruleset, and now CCA works just fine when assigning from an existing PR. |
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Copilot Feature Area
Copilot Coding Agent
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For a given repo, CCA works fine in 2 out of 3 scenarios. For example, if I manually create a brand new Coding Agent task through the Agent panel, then it works fine. CCA will open a new branch, make its commits, and then open a draft PR. Also, it works fine when I assign an Issue to CCA, it is able to do what it needs to do.
However, on that same repo, if I go to an existing Pull Request, tag
@copilotand then ask it to make updates, then this does NOT work. Copilot reacts to my comment with the eyes emoji. But, then after that nothings happens. CCA does not open a branch, it does not start a new CCA task.I'm not sure why, as normal CCA tasks works fine, just not from an existing PR.
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