diff --git a/.github/workflows/ci-stable.yml b/.github/workflows/ci-stable.yml
index 80d1200..3213470 100644
--- a/.github/workflows/ci-stable.yml
+++ b/.github/workflows/ci-stable.yml
@@ -140,16 +140,25 @@ jobs:
                   raw = resp.read()
                   return json.loads(raw) if raw else None
 
+          # Delete any pre-existing release branch (from a prior partial run)
+          # so the bump always starts from main's HEAD. Avoids STALE_DATA from
+          # createCommitOnBranch and prevents stacking multiple bump commits.
+          # Any open PR on the stale branch gets auto-closed when the branch
+          # is deleted, which is fine — we always open a fresh PR below.
           try:
-              api(
-                  f"repos/{repo}/git/refs",
-                  method="POST",
-                  body={"ref": f"refs/heads/{branch}", "sha": head_oid},
-              )
+              api(f"repos/{repo}/git/refs/heads/{branch}", method="DELETE")
+              print(f"deleted stale branch: {branch}")
           except urllib.error.HTTPError as error:
-              if error.code != 422:  # 422 = ref already exists; OK to reuse
+              if error.code not in (404, 422):  # ref doesn't exist; nothing to clean
                   raise
 
+          api(
+              f"repos/{repo}/git/refs",
+              method="POST",
+              body={"ref": f"refs/heads/{branch}", "sha": head_oid},
+          )
+          expected_oid = head_oid
+
           def b64(path: str) -> str:
               with open(path, "rb") as fp:
                   return base64.b64encode(fp.read()).decode("ascii")
@@ -173,7 +182,7 @@ jobs:
                       "message": {
                           "headline": f"Bump version to v{version} [skip ci]",
                       },
-                      "expectedHeadOid": head_oid,
+                      "expectedHeadOid": expected_oid,
                       "fileChanges": {
                           "additions": [
                               {"path": "stable.toml", "contents": b64("stable.toml")},