Allow specifying base branch for PRs in Copilot Cloud (do not force default branch)

[Shreeyak]

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Product Feedback

Copilot Feature Area

Copilot in GitHub

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Currently, Copilot Cloud always creates pull requests from and into the repository’s default branch (usually main). Many teams—including mine—use a different branch (e.g., dev) for active development, and only use main for releases.

Problem:
There is no way to tell Copilot Cloud (or Copilot Agents) to use a different base branch for PRs at creation time, without changing the repo’s default branch. This causes friction and extra manual work to retarget PRs after creation.

I almost never create a PR directly into main. It's always into my custom dev branch.

Request:
Please add a way to specify the base branch for PRs when using Copilot Cloud—either via prompt, UI, or a project config file. This would make Copilot Cloud much more usable for teams with non-main development flows.

Impact:

Reduces manual PR retargeting
Supports common Git workflows (feature → dev → main)
Makes Copilot Cloud more flexible for real-world teams

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