`gitea_update_pr_branch_by_merge` advanced a PR's remote head but never
advanced the linked durable issue lock's recorded head. After the owning
session died the drifted lock became unrecoverable and no further
synchronization was possible (PR #866 / issue #855).
Write-side (prevents future drift):
- issue_lock_store.assess/apply_durable_lock_head_refresh: on a successful
sync, CAS-refresh the durable lock's recorded head from the exact expected
PR head to the resulting head, re-verifying repo/issue/branch/worktree/
identity/profile/live-session ownership, with read-after-write verification.
- gitea_update_pr_branch_by_merge now refreshes the lock after the remote
advance and reports a PARTIAL LIFECYCLE FAILURE (success=False) when the
refresh fails, instead of falsely reporting a full synchronization.
Read-side (recovers already-drifted locks):
- issue_lock_worktree.read_merge_sync_provenance: server-side git observation
proving a remote head is a sanctioned base-into-branch merge that preserved
the branch mainline back to the recorded head.
- issue_lock_recovery: new HEAD_RELATION_REMOTE_MERGE_SYNCED accepts a
dead-session lock whose recorded head is a strict merge-sync ancestor of the
live PR head — and only that. Rewrites, rebases, force-pushes, non-ancestor
heads, dirty worktrees, live/competing owners, and wrong repo/issue/branch/
identity/profile all stay protected.
No existing exact-head, branch-protection, parity, workspace, identity, role,
or mutation-safety gate is weakened. All provenance is server-derived; nothing
is reachable from an MCP caller.
Tests: tests/test_issue_871_durable_lock_head_refresh.py (32 cases) covering
first/second sync, CAS, ownership, partial-failure, merge-sync recovery
happy-path and every fail-closed branch. Full suite: 4789 passed, 13 pre-
existing baseline failures unchanged.
Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>
Claude-Session: https://claude.ai/code/session_01FZPyVh2DGczQrDxtqwGH5p
