flake: TestRefreshToken/RefreshRetries #1550

CI Run (original): https://github.com/coder/coder/actions/runs/26556543979
Job: test-go-pg (windows-2022)
Commit: ca7f07142e83ddb6c9acbeeaca7c6d11a67affe6 (author: Ethan)

Failure:

=== FAIL: coderd/externalauth TestRefreshToken/RefreshRetries (0.01s)
    externalauth_test.go:210:
        Error:       Not equal:
                     expected: 2
                     actual  : 1

New occurrence (2026-06-04):
CI Run: https://github.com/coder/coder/actions/runs/26933139214
Job: https://github.com/coder/coder/actions/runs/26933139214/job/79456825080
Commit: becc858fa85182ed55a45d1a317bc7e60da8f8bb (author: Ethan)
Failure:

=== FAIL: coderd/externalauth TestRefreshToken/RefreshRetries (0.00s)
    externalauth_test.go:210:
        Error:       Not equal:
                     expected: 2
                     actual  : 1

Root cause classification: Flaky test (refresh retry count mismatch).

Notes:

• The subtest expects exactly one IDP refresh attempt per RefreshToken call when RefreshRetryTimeout is set to time.Nanosecond, but the observed refreshCount was lower than totalRefreshes.
• No data race, panic, or OOM indicators in the job logs (no "WARNING: DATA RACE", "panic:", or OOM signals).

Assignment analysis:

• git log --oneline -10 --follow coderd/externalauth/externalauth_test.go
  • 58f6b9c4d0 "fix(coderd/externalauth): retry transient refresh failures with backoff" (Kyle Carberry / @kylecarbs)
    This commit most recently modified the RefreshToken retry behavior and the RefreshRetries subtest. Assigning to @kylecarbs for triage.

Related issues searched (none found):

• "TestRefreshToken", "RefreshRetries", "externalauth", "externalauth_test.go" in coder/internal

Reproduction (if needed):

• go test ./coderd/externalauth -run TestRefreshToken/RefreshRetries -count=1