Failure due to GH_HOST not configured when fetching PR

[dsyme]

Here's another GH_HOST problem

The trigger was this comment:fsprojects/FSharp.Control.AsyncSeq#302 (comment)

The run is here: https://github.com/fsprojects/FSharp.Control.AsyncSeq/actions/runs/23929188570/job/69792652319#step:13:93

There are two issues in the failing part of the run.  First this - this is not actually a fork PR. That's maybe unrelated to the overall failure

Warning: ⚠️ Fork PR detected - gh pr checkout will fetch from fork repository

But then there's this:

/usr/bin/gh pr checkout 302
none of the git remotes configured for this repository correspond to the GH_HOST environment variable. Try adding a matching remote or unsetting the variable
❌ Checkout Error Details
Error: ERR_API: Failed to checkout PR branch: The process '/usr/bin/gh' failed with exit code 1

[lpcox]

Triage

Investigated the root cause. This is a two-bug interaction in gh-aw — neither gh-aw-firewall nor gh-aw-mcpg are involved.

Bug 1: False fork PR detection → #24218

detectForkPR() in pr_helpers.cjs uses head.repo.fork === true to detect fork PRs. But this flag indicates whether the repository itself is a fork of another repo, not whether the PR is cross-repo. For same-repo PRs in forked repositories (common in OSS), this produces a false positive, causing the checkout strategy to use gh pr checkout instead of the fast git fetch path.

Bug 2: Stale GH_HOST not cleared → #24217

configure_gh_for_ghe.sh exits early for github.com without unsetting GH_HOST. If GH_HOST has a stale/wrong value, it persists and causes gh pr checkout to fail with "none of the git remotes correspond to the GH_HOST environment variable".

Why both bugs are needed to trigger the failure

• Bug 1 forces the use of gh pr checkout (which depends on GH_HOST) instead of git fetch (which doesn't)
• Bug 2 leaves a stale GH_HOST that causes gh pr checkout to fail

No changes needed in other repos

• gh-aw-firewall: The DIFC proxy sets GH_HOST=localhost:18443 during agent execution, but this happens after the PR checkout step, so it's not involved.
• gh-aw-mcpg: Not involved in PR checkout or GH_HOST configuration.