BranchExists returns true before the generated branch is writable, so waitForBranch didn't help and a 2.5s retry budget was too short (branch became writable ~30s post-generate under load in live testing). Drop waitForBranch; let upsertRetry be the gate — retry the write on the transient "branch does not exist" not-found for up to 60s, early-exit on success. Once the first write lands the branch is writable and the rest succeed immediately. Refs #42. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>