gitea_mcp_server.py

@@ -2445,6 +2445,20 @@ def _evaluate_issue_lock_recovery(
             descendant_sha=local_head,
         )
 
+    # #871: the inverse of the #768 descendant relation — the *remote* head may
+    # have advanced past the local/recorded head via a sanctioned merge-based
+    # branch sync (``gitea_update_pr_branch_by_merge``) while the local worktree
+    # stayed put. Observe that provenance server-side so the assessor can prove
+    # it and nothing else. Probed only when the heads differ; never from any
+    # caller-supplied value.
+    sync_provenance: dict | None = None
+    if remote_head and local_head and remote_head != local_head:
+        sync_provenance = issue_lock_worktree.read_merge_sync_provenance(
+            worktree_path,
+            prior_head_sha=local_head,
+            synced_head_sha=remote_head,
+        )
+
     # #772: with no remote branch there is no head to measure against, so the
     # base the branch was cut from is observed instead. Probed only in that
     # case, so the published path's evidence is untouched (#772 AC8).
@@ -2487,6 +2501,7 @@ def _evaluate_issue_lock_recovery(
         remote_branch_exists=remote_branch_exists,
         recorded_base_sha=recorded_base,
         base_ancestry=base_ancestry,
+        sync_provenance=sync_provenance,
     )
 
 
@@ -18889,10 +18904,59 @@ def gitea_update_pr_branch_by_merge(
         prepared_verdict_head_sha=live_pr_head,
     )
 
-    return {
-        "success": True,
+    # #871: the remote head is now advanced; the durable linked-issue lock must
+    # be advanced with it, or a later dead-session recovery can never prove
+    # ownership at the new head. This runs AFTER the successful remote update, so
+    # a failure here is a *partial* lifecycle failure — the remote moved but the
+    # durable state did not — and must never be reported as a full success.
+    claimant = _work_lease_claimant(h)
+    matched_issue = ownership.get("matched_issue")
+    synced_at = datetime.now(timezone.utc).strftime("%Y-%m-%dT%H:%M:%SZ")
+    lock_refresh: dict = {
+        "refreshed": False,
+        "reasons": ["durable lock head refresh was not attempted"],
+    }
+    if new_head and matched_issue and source_branch and (wt or None):
+        try:
+            lock_refresh = issue_lock_store.apply_durable_lock_head_refresh(
+                remote=remote,
+                org=o,
+                repo=r,
+                issue_number=int(matched_issue),
+                branch_name=source_branch,
+                worktree_path=wt,
+                pr_number=pr_number,
+                identity=claimant.get("username"),
+                profile=claimant.get("profile"),
+                current_pid=os.getpid(),
+                expected_old_head=live_pr_head,
+                new_head=new_head,
+                synced_at=synced_at,
+                base_head=live_base_head,
+            )
+        except Exception as exc:
+            lock_refresh = {
+                "refreshed": False,
+                "reasons": [
+                    f"durable lock head refresh raised (fail closed): {_redact(str(exc))}"
+                ],
+            }
+    else:
+        lock_refresh = {
+            "refreshed": False,
+            "reasons": [
+                "durable lock head refresh could not run: missing new head, "
+                "linked issue, source branch, or worktree binding"
+            ],
+        }
+
+    durable_refreshed = bool(lock_refresh.get("refreshed"))
+    base_result = {
         "performed": True,
         "mutation_allowed": True,
+        "durable_lock_refreshed": durable_refreshed,
+        "durable_lock_refresh": lock_refresh,
+        "fully_synchronized": durable_refreshed,
         "style": "merge",
         "force_push": False,
         "rebase": False,
@@ -18914,19 +18978,37 @@ def gitea_update_pr_branch_by_merge(
         "prepared_verdict_invalidated": transition.get(
             "prepared_verdict_invalidated"
         ),
-        "recommended_next_action": transition.get(
-            "recommended_next_action",
-            pr_sync_status.ACTION_FRESH_REVIEW_REQUIRED,
-        ),
         "transition": transition,
         "role_kind": role,
         "profile_name": profile.get("profile_name"),
         "worktree_path": wt or None,
-        "reasons": list(transition.get("reasons") or []) + [
-            "update-by-merge completed via native Gitea API (style=merge only)"
-        ],
     }
 
+    if durable_refreshed:
+        base_result["success"] = True
+        base_result["recommended_next_action"] = transition.get(
+            "recommended_next_action",
+            pr_sync_status.ACTION_FRESH_REVIEW_REQUIRED,
+        )
+        base_result["reasons"] = list(transition.get("reasons") or []) + [
+            "update-by-merge completed via native Gitea API (style=merge only)",
+            f"durable linked-issue lock #{matched_issue} head refreshed to "
+            f"{new_head} (verified by read-after-write)",
+        ]
+        return base_result
+
+    # Partial lifecycle failure: the remote advanced but the durable lock did
+    # not. Do NOT report a fully successful synchronization (#871).
+    base_result["success"] = False
+    base_result["partial_lifecycle_failure"] = True
+    base_result["recommended_next_action"] = pr_sync_status.ACTION_BLOCKED
+    base_result["reasons"] = list(lock_refresh.get("reasons") or []) + [
+        f"PARTIAL LIFECYCLE FAILURE: PR #{pr_number} remote head advanced to "
+        f"{new_head} but the durable linked-issue lock head was not refreshed; "
+        "the synchronization is NOT complete",
+    ]
+    return base_result
+
 
 @mcp.tool()
 def gitea_assess_conflict_fix_push(

issue_lock_recovery.py

@@ -85,6 +85,12 @@ HEAD_RELATION_STRICT_DESCENDANT = "strict_descendant"
 # #772: an unpublished claim has no recorded head to compare against at all, so
 # its head is measured against the base the branch was cut from instead.
 HEAD_RELATION_DESCENDS_FROM_BASE = "descends_from_recorded_base"
+# #871: the remote/PR head advanced *past* the recorded head via a sanctioned
+# merge-based branch synchronization (``gitea_update_pr_branch_by_merge``) while
+# the local worktree stayed at the recorded head. This is the inverse of the
+# #768 descendant relation — here the *remote* strictly descends the local head,
+# and only because a base was merged into the branch, proven server-side.
+HEAD_RELATION_REMOTE_MERGE_SYNCED = "remote_merge_synced"
 
 # Which body of evidence a recovery was decided on (#772 AC10). These are not
 # interchangeable: a published claim proves ownership against a remote/PR head,
@@ -266,6 +272,70 @@ def _assess_base_descendancy(
     ]
 
 
+def _assess_remote_merge_synced(
+    sync_provenance: Mapping[str, Any] | None,
+    *,
+    recorded_head: str,
+    remote_head: str,
+) -> tuple[bool, list[str]]:
+    """Did ``remote_head`` advance past ``recorded_head`` via a sanctioned
+    merge-based branch sync (#871)?
+
+    ``sync_provenance`` is the server-side git observation from
+    ``issue_lock_worktree.read_merge_sync_provenance``. Its own
+    ``prior_head_sha`` / ``synced_head_sha`` are re-checked against the heads
+    this assessment is actually reasoning about, so an observation taken for some
+    other pair of commits — stale, mismatched, or hand-built — can never
+    authorize recovery. This is the inverse of ``_assess_strict_descendant``: the
+    recorded head is the ancestor and the *remote* head is the descendant, and it
+    is accepted only because the remote head is a base-into-branch merge that
+    preserved the branch mainline back to the recorded head.
+
+    Returns ``(proven, notes)``. Notes name the exact missing element so a
+    refused caller sees why, never a bare "unproven".
+    """
+    if not isinstance(sync_provenance, Mapping):
+        return False, [
+            "no server-derived merge-sync provenance observation was available; a "
+            "remote head ahead of the recorded head cannot be accepted"
+        ]
+
+    probe_prior = _text(sync_provenance.get("prior_head_sha"))
+    probe_synced = _text(sync_provenance.get("synced_head_sha"))
+    if probe_prior != recorded_head or probe_synced != remote_head:
+        return False, [
+            f"merge-sync observation covers {probe_prior or 'unknown'} -> "
+            f"{probe_synced or 'unknown'}, not the heads under assessment "
+            f"({recorded_head} -> {remote_head})"
+        ]
+    if not sync_provenance.get("probe_ok"):
+        return False, (
+            list(sync_provenance.get("reasons") or [])
+            or ["merge-sync provenance probe did not complete; provenance unproven"]
+        )
+    if not sync_provenance.get("prior_is_ancestor"):
+        return False, [
+            f"recorded head {recorded_head} is not an ancestor of remote head "
+            f"{remote_head}; a rewritten or force-moved head cannot be recovered"
+        ]
+    if not sync_provenance.get("is_merge_sync"):
+        return False, (
+            list(sync_provenance.get("reasons") or [])
+            or [
+                f"remote head {remote_head} is not a sanctioned merge-based sync "
+                f"of the base into the branch above {recorded_head}"
+            ]
+        )
+
+    proof = _text(sync_provenance.get("proof")) or (
+        f"{remote_head} merged the base into the branch above {recorded_head}"
+    )
+    return True, [
+        f"remote head {remote_head} advanced past recorded head {recorded_head} "
+        f"via a sanctioned merge-based branch sync ({proof})"
+    ]
+
+
 def assess_dead_session_lock_recovery(
     existing_lock: Mapping[str, Any] | None,
     *,
@@ -290,6 +360,7 @@ def assess_dead_session_lock_recovery(
     remote_branch_exists: bool | None = None,
     recorded_base_sha: str | None = None,
     base_ancestry: Mapping[str, Any] | None = None,
+    sync_provenance: Mapping[str, Any] | None = None,
 ) -> dict[str, Any]:
     """Decide whether a dead-session author lock may be natively recovered.
 
@@ -469,19 +540,39 @@ def assess_dead_session_lock_recovery(
                     head_relation = HEAD_RELATION_STRICT_DESCENDANT
                     ancestry_proof = notes[0] if notes else None
                 else:
-                    reasons.append(
-                        f"local head {local_head} does not match remote branch head "
-                        f"{remote_head}"
+                    # #871: the reverse relation — the remote head advanced past
+                    # the recorded/local head via a sanctioned merge-based branch
+                    # sync while the local worktree stayed put. Accepted only on
+                    # server-proven merge-sync provenance, never a caller claim.
+                    synced, sync_notes = _assess_remote_merge_synced(
+                        sync_provenance,
+                        recorded_head=local_head,
+                        remote_head=remote_head,
                     )
-                    reasons.extend(notes)
+                    if synced:
+                        head_relation = HEAD_RELATION_REMOTE_MERGE_SYNCED
+                        ancestry_proof = sync_notes[0] if sync_notes else None
+                    else:
+                        reasons.append(
+                            f"local head {local_head} does not match remote branch "
+                            f"head {remote_head}"
+                        )
+                        reasons.extend(notes)
+                        reasons.extend(sync_notes)
     evidence["recorded_base"] = recorded_base or None
     evidence["local_head"] = local_head or None
     evidence["remote_head"] = remote_head or None
     # ``recorded_head`` is the head recovery is being measured against;
     # ``accepted_head`` is the head this recovery actually adopts. They differ
     # only in the descendant case, and downstream gates need both (#768 AC2/AC7).
+    # #871: in the merge-sync case the branch/PR already carries the synced
+    # remote head, so that is the head recovery adopts; the local worktree stays
+    # at the ancestor recorded head.
     evidence["recorded_head"] = remote_head or None
-    evidence["accepted_head"] = local_head or None
+    if head_relation == HEAD_RELATION_REMOTE_MERGE_SYNCED:
+        evidence["accepted_head"] = remote_head or None
+    else:
+        evidence["accepted_head"] = local_head or None
     evidence["head_relation"] = head_relation
     evidence["ancestry_proof"] = ancestry_proof
 
@@ -493,12 +584,17 @@ def assess_dead_session_lock_recovery(
         # contradictory; re-stating it as a head mismatch would only obscure why.
         if not unpublished and local_head and pr_head != local_head:
             # A descendant recovery has not been published yet, so the open PR
-            # legitimately still points at the recorded head. Any other
-            # disagreement is a real mismatch.
+            # legitimately still points at the recorded head. A merge-sync
+            # recovery's PR legitimately sits at the advanced remote head. Any
+            # other disagreement is a real mismatch.
             if not (
                 head_relation == HEAD_RELATION_STRICT_DESCENDANT
                 and remote_head
                 and pr_head == remote_head
+            ) and not (
+                head_relation == HEAD_RELATION_REMOTE_MERGE_SYNCED
+                and remote_head
+                and pr_head == remote_head
             ):
                 reasons.append(
                     f"open PR #{pr_number} head {pr_head} does not match local head "
@@ -619,7 +715,11 @@ def assess_dead_session_lock_recovery(
         )
     if (
         head_relation
-        in (HEAD_RELATION_STRICT_DESCENDANT, HEAD_RELATION_DESCENDS_FROM_BASE)
+        in (
+            HEAD_RELATION_STRICT_DESCENDANT,
+            HEAD_RELATION_DESCENDS_FROM_BASE,
+            HEAD_RELATION_REMOTE_MERGE_SYNCED,
+        )
         and ancestry_proof
     ):
         proof.append(ancestry_proof)
@@ -697,6 +797,16 @@ def owning_pr_recovery_evidence(
             return None
         if accepted_head != local_head:
             return None
+    elif relation == HEAD_RELATION_REMOTE_MERGE_SYNCED:
+        # #871: the PR already sits at the advanced remote head; the local
+        # worktree is the ancestor the merge preserved. The head the open PR
+        # shows and the head recovery adopts are both the synced remote head.
+        if not remote_head or pr_head != remote_head:
+            return None
+        if accepted_head != remote_head:
+            return None
+        if not local_head or local_head == remote_head:
+            return None
     else:
         return None
     try:
@@ -765,6 +875,18 @@ def recovered_owning_pr_from_lock(
             return None
         if not accepted_head or accepted_head == recorded_head:
             return None
+    elif relation == HEAD_RELATION_REMOTE_MERGE_SYNCED:
+        # #871: PR sits at the advanced remote head, which is both the recorded
+        # measured-against head and the adopted head; the local worktree is the
+        # ancestor the merge preserved.
+        remote_head = _text(record.get("remote_head"))
+        local_head = _text(record.get("local_head"))
+        if not remote_head or pr_head != remote_head:
+            return None
+        if accepted_head and accepted_head != remote_head:
+            return None
+        if not local_head or local_head == remote_head:
+            return None
     else:
         return None
     try:

issue_lock_store.py

@@ -737,4 +737,308 @@ def format_lock_proof(
         parts.append("lock released")
     elif released is False:
         parts.append("lock retained")
-    return "; ".join(parts)
+    return "; ".join(parts)
+
+
+# ── #871: durable linked-issue lock head refresh after branch synchronization ──
+_FULL_SHA_RE = re.compile(r"^[0-9a-f]{40}$", re.IGNORECASE)
+
+# Provenance recorded on the lock when the head is refreshed by a sanctioned
+# merge-based branch synchronization (``gitea_update_pr_branch_by_merge``).
+LOCK_HEAD_REFRESH_PROVENANCE_MERGE_SYNC = "gitea_update_pr_branch_by_merge"
+
+
+def _norm_sha(value: Any) -> str | None:
+    text = str(value or "").strip().lower()
+    return text if _FULL_SHA_RE.match(text) else None
+
+
+def _lock_claimant_view(lock: dict[str, Any] | None) -> dict[str, Any]:
+    if not isinstance(lock, dict):
+        return {}
+    claimant = lock.get("claimant")
+    if not isinstance(claimant, dict):
+        lease = lock.get("work_lease")
+        claimant = lease.get("claimant") if isinstance(lease, dict) else None
+    return dict(claimant) if isinstance(claimant, dict) else {}
+
+
+def assess_durable_lock_head_refresh(
+    existing_lock: dict[str, Any] | None,
+    *,
+    remote: str,
+    org: str,
+    repo: str,
+    issue_number: int,
+    branch_name: str,
+    worktree_path: str,
+    pr_number: int | None,
+    identity: str | None,
+    profile: str | None,
+    current_pid: int | None,
+    expected_old_head: str | None,
+    new_head: str | None,
+    base_head: str | None = None,
+) -> dict[str, Any]:
+    """Fail-closed assessment for refreshing a durable lock's recorded head (#871).
+
+    A successful ``gitea_update_pr_branch_by_merge`` advances the *remote* PR head
+    but must also advance the durable linked-issue lock so a later dead-session
+    recovery can prove ownership. This decides whether that refresh is permitted;
+    it mutates nothing.
+
+    Every element of durable ownership is re-verified against the persisted lock —
+    repository, issue, branch, worktree, claimant identity/profile, and the live
+    owning session — and the recorded head is compare-and-swapped: the lock's
+    currently recorded synced head (if any) must equal ``expected_old_head``, so a
+    lock whose head or provenance changed concurrently is never overwritten.
+    """
+    reasons: list[str] = []
+    old = _norm_sha(expected_old_head)
+    new = _norm_sha(new_head)
+    evidence: dict[str, Any] = {
+        "issue_number": issue_number,
+        "branch_name": branch_name,
+        "worktree_path": worktree_path,
+        "pr_number": pr_number,
+        "expected_old_head": old,
+        "new_head": new,
+        "base_head": _norm_sha(base_head),
+    }
+
+    if not isinstance(existing_lock, dict) or not existing_lock:
+        reasons.append("no durable lock exists for this issue; nothing to refresh")
+        return {"allowed": False, "reasons": reasons, "evidence": evidence,
+                "expected_generation": 0}
+
+    lock = dict(existing_lock)
+    evidence["current_generation"] = lock_generation(lock)
+
+    if lock.get("issue_number") != issue_number:
+        reasons.append(
+            f"durable lock targets issue #{lock.get('issue_number')}, not "
+            f"#{issue_number}; refusing head refresh"
+        )
+
+    for field, expected in (("remote", remote), ("org", org), ("repo", repo)):
+        actual = str(lock.get(field) or "").strip()
+        if actual != str(expected or "").strip():
+            reasons.append(
+                f"lock {field} '{actual}' does not match requested "
+                f"'{str(expected or '').strip()}'"
+            )
+
+    locked_branch = str(lock.get("branch_name") or "").strip()
+    if locked_branch != str(branch_name or "").strip():
+        reasons.append(
+            f"lock branch '{locked_branch}' does not match requested "
+            f"'{str(branch_name or '').strip()}'"
+        )
+
+    locked_worktree = str(lock.get("worktree_path") or "").strip()
+    try:
+        same_wt = bool(locked_worktree) and bool(worktree_path) and (
+            os.path.realpath(locked_worktree) == os.path.realpath(worktree_path)
+        )
+    except OSError:
+        same_wt = locked_worktree == (worktree_path or "")
+    if not same_wt:
+        reasons.append(
+            f"lock worktree '{locked_worktree}' does not match declared "
+            f"'{str(worktree_path or '').strip()}'"
+        )
+
+    claimant = _lock_claimant_view(lock)
+    locked_identity = str(claimant.get("username") or "").strip()
+    locked_profile = str(claimant.get("profile") or "").strip()
+    if not locked_identity or not locked_profile:
+        reasons.append(
+            "durable lock does not record a claimant identity/profile; "
+            "ownership could not be proven for head refresh"
+        )
+    if not str(identity or "").strip() or not str(profile or "").strip():
+        reasons.append(
+            "active session identity/profile is unknown; ownership could not be "
+            "proven for head refresh"
+        )
+    if locked_identity and str(identity or "").strip() and locked_identity != str(identity).strip():
+        reasons.append(
+            f"lock claimant '{locked_identity}' does not match active identity "
+            f"'{str(identity).strip()}'"
+        )
+    if locked_profile and str(profile or "").strip() and locked_profile != str(profile).strip():
+        reasons.append(
+            f"lock profile '{locked_profile}' does not match active profile "
+            f"'{str(profile).strip()}'"
+        )
+
+    # The refresh is written by the LIVE owning author session. A refresh is not
+    # a recovery: the current process must be the recorded owner.
+    recorded_pid = lock.get("session_pid")
+    if recorded_pid is None:
+        recorded_pid = lock.get("pid")
+    evidence["recorded_pid"] = recorded_pid
+    evidence["current_pid"] = current_pid
+    if current_pid is None:
+        reasons.append("current session pid is unknown; cannot prove live ownership")
+    else:
+        try:
+            if recorded_pid is None or int(recorded_pid) != int(current_pid):
+                reasons.append(
+                    f"durable lock is owned by pid {recorded_pid}, not the current "
+                    f"session pid {current_pid}; head refresh requires the live owner"
+                )
+        except (TypeError, ValueError):
+            reasons.append(
+                "durable lock owner pid is malformed; cannot prove live ownership"
+            )
+
+    if not old:
+        reasons.append("expected_old_head is not a full 40-char hex SHA (fail closed)")
+    if not new:
+        reasons.append("new_head is not a full 40-char hex SHA (fail closed)")
+    if old and new and old == new:
+        reasons.append(
+            "new head equals the expected old head; a sync must advance the head"
+        )
+
+    # Compare-and-swap on the recorded head: if the lock already records a synced
+    # head it must be exactly the expected old head, else another sync moved it.
+    recorded_synced = _norm_sha(lock.get("synced_pr_head"))
+    evidence["recorded_synced_pr_head"] = recorded_synced
+    if recorded_synced is not None and old is not None and recorded_synced != old:
+        reasons.append(
+            f"durable lock already records synced head {recorded_synced}, not the "
+            f"expected old head {old}; a concurrent sync changed it (CAS fail closed)"
+        )
+
+    if reasons:
+        return {"allowed": False, "reasons": reasons, "evidence": evidence,
+                "expected_generation": lock_generation(lock)}
+
+    return {
+        "allowed": True,
+        "reasons": [
+            f"durable lock for issue #{issue_number} branch '{locked_branch}' is "
+            f"owned by the live session; refresh recorded head {old} -> {new}"
+        ],
+        "evidence": evidence,
+        "expected_generation": lock_generation(lock),
+    }
+
+
+def apply_durable_lock_head_refresh(
+    *,
+    remote: str,
+    org: str,
+    repo: str,
+    issue_number: int,
+    branch_name: str,
+    worktree_path: str,
+    pr_number: int | None,
+    identity: str | None,
+    profile: str | None,
+    current_pid: int | None,
+    expected_old_head: str | None,
+    new_head: str | None,
+    synced_at: str,
+    base_head: str | None = None,
+    provenance: str = LOCK_HEAD_REFRESH_PROVENANCE_MERGE_SYNC,
+    lock_dir: str | None = None,
+) -> dict[str, Any]:
+    """CAS-refresh the durable lock's recorded head after a branch sync (#871).
+
+    Reads the durable lock from disk, re-asserts ownership via
+    ``assess_durable_lock_head_refresh``, and — only when permitted — writes the
+    new synced head through ``bind_session_lock`` with a generation compare-and-
+    swap. Then re-reads the lock and proves it records the complete new head
+    (read-after-write). Any failure at any step returns ``refreshed=False`` with
+    reasons; the caller must treat that as a partial lifecycle failure and never
+    report a fully successful synchronization.
+    """
+    existing = load_issue_lock(
+        remote=remote, org=org, repo=repo, issue_number=issue_number, lock_dir=lock_dir
+    )
+    assessment = assess_durable_lock_head_refresh(
+        existing,
+        remote=remote,
+        org=org,
+        repo=repo,
+        issue_number=issue_number,
+        branch_name=branch_name,
+        worktree_path=worktree_path,
+        pr_number=pr_number,
+        identity=identity,
+        profile=profile,
+        current_pid=current_pid,
+        expected_old_head=expected_old_head,
+        new_head=new_head,
+        base_head=base_head,
+    )
+    result: dict[str, Any] = {
+        "refreshed": False,
+        "read_after_write_ok": False,
+        "prior_head": _norm_sha(expected_old_head),
+        "new_head": _norm_sha(new_head),
+        "reasons": list(assessment.get("reasons") or []),
+        "evidence": assessment.get("evidence"),
+    }
+    if not assessment.get("allowed"):
+        return result
+
+    new = _norm_sha(new_head)
+    old = _norm_sha(expected_old_head)
+    record = dict(existing or {})
+    sync_block = {
+        "last_synced_pr_head": new,
+        "prior_pr_head": old,
+        "base_head": _norm_sha(base_head),
+        "pr_number": pr_number,
+        "provenance": provenance,
+        "synced_at": synced_at,
+        "synced_by_pid": current_pid,
+        "synced_by": {
+            "username": str(identity or "").strip() or None,
+            "profile": str(profile or "").strip() or None,
+        },
+    }
+    record["synced_pr_head"] = new
+    record["branch_sync"] = sync_block
+    history = record.get("branch_sync_history")
+    if not isinstance(history, list):
+        history = []
+    history = list(history)
+    history.append(sync_block)
+    record["branch_sync_history"] = history
+
+    try:
+        bind_session_lock(
+            record,
+            lock_dir=lock_dir,
+            expected_generation=assessment.get("expected_generation"),
+            renewal_sanctioned=True,
+        )
+    except Exception as exc:  # CAS miss or write failure — partial lifecycle failure
+        result["reasons"].append(
+            f"durable lock head refresh write failed (fail closed): {exc}"
+        )
+        return result
+
+    after = load_issue_lock(
+        remote=remote, org=org, repo=repo, issue_number=issue_number, lock_dir=lock_dir
+    )
+    after_head = _norm_sha((after or {}).get("synced_pr_head"))
+    result["lock_generation_after"] = lock_generation(after)
+    if after_head == new and new is not None:
+        result["refreshed"] = True
+        result["read_after_write_ok"] = True
+        result["reasons"].append(
+            f"durable lock recorded head refreshed to {new} and verified by "
+            "read-after-write"
+        )
+    else:
+        result["reasons"].append(
+            "read-after-write verification failed: durable lock does not record "
+            f"the new head {new} (found {after_head}); partial lifecycle failure"
+        )
+    return result

issue_lock_worktree.py

@@ -145,6 +145,175 @@ def read_head_ancestry(
     return result
 
 
+def read_merge_sync_provenance(
+    worktree_path: str,
+    *,
+    prior_head_sha: str | None,
+    synced_head_sha: str | None,
+) -> dict:
+    """Observe whether ``synced_head_sha`` is a sanctioned merge-based branch sync
+    that advanced the PR branch past ``prior_head_sha`` (#871).
+
+    ``gitea_update_pr_branch_by_merge`` advances a PR branch by merging the base
+    branch *into* the branch (``POST /pulls/{n}/update?style=merge``). The result
+    is a merge commit ``M`` on the branch whose **first** parent is the prior
+    branch head and whose second parent is the base tip. When the owning session
+    then dies without the durable lock's recorded head being refreshed, the local
+    worktree still sits at ``prior_head_sha`` while the live PR head is ``M``.
+
+    Recovering that drift safely requires proving the remote head is *exactly*
+    such a merge-sync — not a rewrite, rebase, force-push, or an unrelated
+    commit. This is that server-side observation. It reports facts only; the
+    disposition lives in ``issue_lock_recovery``. Every field is read from git in
+    the declared worktree — nothing is supplied by, or reachable from, an MCP
+    caller (#871).
+
+    Provenance is proven only when ALL hold:
+
+    * both commits are present (a rewritten/force-moved prior head leaves the
+      object graph and fails closed);
+    * ``prior_head_sha`` is a strict ancestor of ``synced_head_sha`` (the branch
+      history is preserved, never replaced);
+    * ``synced_head_sha`` is a merge commit (two or more parents), i.e. a base
+      merged in — a plain fast-forward of new direct commits is not a sync;
+    * ``prior_head_sha`` is an ancestor of the merge's **first** parent, so the
+      branch mainline (first-parent lineage) still reaches the prior head — a
+      rebase/force-push that re-authored the branch side fails this.
+    """
+    path = (worktree_path or "").strip()
+    prior = (prior_head_sha or "").strip()
+    synced = (synced_head_sha or "").strip()
+    result: dict = {
+        "prior_head_sha": prior or None,
+        "synced_head_sha": synced or None,
+        "probe_ok": False,
+        "prior_present": False,
+        "synced_present": False,
+        "prior_is_ancestor": False,
+        "synced_is_merge": False,
+        "first_parent_reaches_prior": False,
+        "is_merge_sync": False,
+        "first_parent_sha": None,
+        "parent_count": None,
+        "proof": None,
+        "reasons": [],
+    }
+    if not path or not prior or not synced:
+        result["reasons"].append(
+            "merge-sync provenance probe requires a worktree path and both "
+            "commit SHAs"
+        )
+        return result
+    if prior == synced:
+        result["reasons"].append(
+            "prior and synced heads are identical; no branch sync occurred"
+        )
+        return result
+
+    def _present(sha: str) -> bool:
+        res = subprocess.run(
+            ["git", "-C", path, "rev-parse", "--verify", "--quiet", f"{sha}^{{commit}}"],
+            capture_output=True,
+            text=True,
+            check=False,
+        )
+        return res.returncode == 0
+
+    def _is_ancestor(ancestor: str, descendant: str) -> bool | None:
+        res = subprocess.run(
+            ["git", "-C", path, "merge-base", "--is-ancestor", ancestor, descendant],
+            capture_output=True,
+            text=True,
+            check=False,
+        )
+        if res.returncode == 0:
+            return True
+        if res.returncode == 1:
+            return False
+        return None  # failed probe — never a silent "no"
+
+    try:
+        result["prior_present"] = _present(prior)
+        result["synced_present"] = _present(synced)
+    except OSError as exc:  # git unavailable — fail closed, never assume
+        result["reasons"].append(f"merge-sync provenance probe could not run: {exc}")
+        return result
+
+    if not result["prior_present"]:
+        result["reasons"].append(
+            f"prior head {prior} is not reachable in '{path}'; history may have "
+            "been rewritten or force-moved"
+        )
+    if not result["synced_present"]:
+        result["reasons"].append(
+            f"synced head {synced} is not reachable in '{path}'"
+        )
+    if not (result["prior_present"] and result["synced_present"]):
+        return result
+
+    ancestor = _is_ancestor(prior, synced)
+    if ancestor is None:
+        result["reasons"].append(
+            "ancestry probe failed; merge-sync provenance unproven"
+        )
+        return result
+    result["prior_is_ancestor"] = bool(ancestor)
+    if not ancestor:
+        result["reasons"].append(
+            f"prior head {prior} is not an ancestor of synced head {synced}; "
+            "the branch history was not preserved (not a merge-based sync)"
+        )
+        return result
+
+    parents_res = subprocess.run(
+        ["git", "-C", path, "rev-list", "--parents", "-n", "1", synced],
+        capture_output=True,
+        text=True,
+        check=False,
+    )
+    if parents_res.returncode != 0:
+        result["reasons"].append(
+            f"could not read parents of {synced}; merge-sync provenance unproven"
+        )
+        return result
+    tokens = (parents_res.stdout or "").split()
+    # tokens[0] is the commit itself; the rest are its parents.
+    parents = tokens[1:]
+    result["parent_count"] = len(parents)
+    result["synced_is_merge"] = len(parents) >= 2
+    if not result["synced_is_merge"]:
+        result["probe_ok"] = True
+        result["reasons"].append(
+            f"synced head {synced} has {len(parents)} parent(s); a merge-based "
+            "branch sync produces a merge commit (two or more parents)"
+        )
+        return result
+    first_parent = parents[0]
+    result["first_parent_sha"] = first_parent
+
+    fp_reaches = _is_ancestor(prior, first_parent) if prior != first_parent else True
+    if fp_reaches is None:
+        result["reasons"].append(
+            "first-parent ancestry probe failed; merge-sync provenance unproven"
+        )
+        return result
+    result["first_parent_reaches_prior"] = bool(fp_reaches)
+    result["probe_ok"] = True
+    if not fp_reaches:
+        result["reasons"].append(
+            f"merge first parent {first_parent} does not reach prior head "
+            f"{prior}; the branch mainline was re-authored (not a sanctioned sync)"
+        )
+        return result
+
+    result["is_merge_sync"] = True
+    result["proof"] = (
+        f"synced head {synced} is a merge commit (parents={len(parents)}) whose "
+        f"first-parent lineage reaches prior head {prior}; base merged into branch"
+    )
+    return result
+
+
 def read_recorded_base(
     worktree_path: str,
     *,

tests/test_issue_871_durable_lock_head_refresh.py

@@ -0,0 +1,630 @@
+"""Durable linked-issue lock head refresh + merge-sync dead-session recovery (#871).
+
+``gitea_update_pr_branch_by_merge`` advances a PR's *remote* head but historically
+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).
+
+Two halves are covered:
+
+* the write-side refresh (``issue_lock_store.assess/apply_durable_lock_head_refresh``)
+  that records the new synced head under compare-and-swap with read-after-write; and
+* the read-side recovery relation (``issue_lock_recovery`` +
+  ``issue_lock_worktree.read_merge_sync_provenance``) that lets a dead-session lock
+  whose recorded head is a merge-sync *ancestor* of the live PR head be recovered —
+  and nothing else.
+"""
+
+from __future__ import annotations
+
+import os
+import subprocess
+import sys
+import tempfile
+import unittest
+from datetime import datetime, timedelta, timezone
+from pathlib import Path
+
+sys.path.insert(0, str(Path(__file__).resolve().parent.parent))
+
+import issue_lock_recovery  # noqa: E402
+import issue_lock_store  # noqa: E402
+import issue_lock_worktree  # noqa: E402
+
+ISSUE = 8710
+PR_NUMBER = 8711
+BRANCH = f"fix/issue-{ISSUE}-durable-lock-head-refresh"
+IDENTITY = "example-user"
+PROFILE = "example-author"
+OLD = "a" * 40
+NEW1 = "b" * 40
+NEW2 = "c" * 40
+BASE = "d" * 40
+REMOTE = "prgs"
+ORG = "ExampleOrg"
+REPO = "ExampleRepo"
+
+
+def dead_pid() -> int:
+    proc = subprocess.Popen([sys.executable, "-c", "pass"])
+    proc.wait()
+    return proc.pid
+
+
+def future_ts(hours: int = 4) -> str:
+    return (
+        (datetime.now(timezone.utc) + timedelta(hours=hours))
+        .isoformat()
+        .replace("+00:00", "Z")
+    )
+
+
+def _git(cwd, *args):
+    return subprocess.run(
+        ["git", "-C", cwd, *args],
+        capture_output=True,
+        text=True,
+        check=True,
+    )
+
+
+def _rev(cwd, ref="HEAD") -> str:
+    return _git(cwd, "rev-parse", ref).stdout.strip()
+
+
+def build_merge_sync_repo(tmp: str) -> dict:
+    """Build a repo where a feature branch was synced by merging master in.
+
+    Returns a dict with the prior (branch) head, the synced merge-commit head,
+    the master tip, plus a rebase-style linear descendant and an unrelated head.
+    """
+    _git(tmp, "init", "-q", "-b", "master")
+    _git(tmp, "config", "user.email", "[email protected]")
+    _git(tmp, "config", "user.name", "T")
+    Path(tmp, "base.txt").write_text("base\n")
+    _git(tmp, "add", "-A")
+    _git(tmp, "commit", "-q", "-m", "root")
+
+    # Feature branch cut from root, one commit — this is the PRIOR/recorded head.
+    _git(tmp, "checkout", "-q", "-b", BRANCH)
+    Path(tmp, "feature.txt").write_text("feature\n")
+    _git(tmp, "add", "-A")
+    _git(tmp, "commit", "-q", "-m", "feature work")
+    prior = _rev(tmp)
+
+    # Master advances (the base the sync will merge in).
+    _git(tmp, "checkout", "-q", "master")
+    Path(tmp, "base.txt").write_text("base\nmore\n")
+    _git(tmp, "add", "-A")
+    _git(tmp, "commit", "-q", "-m", "master advance")
+    master_tip = _rev(tmp)
+
+    # Sync: merge master INTO the feature branch → merge commit, first parent = prior.
+    _git(tmp, "checkout", "-q", BRANCH)
+    _git(tmp, "merge", "-q", "--no-ff", "-m", "Merge master into feature", "master")
+    synced = _rev(tmp)
+
+    # A plain linear descendant of prior (NOT a merge) — a rebase/extra-commit shape.
+    _git(tmp, "checkout", "-q", "-b", "linear-branch", prior)
+    Path(tmp, "extra.txt").write_text("extra\n")
+    _git(tmp, "add", "-A")
+    _git(tmp, "commit", "-q", "-m", "extra linear commit")
+    linear = _rev(tmp)
+
+    # An unrelated root (force-push / rewritten history shape).
+    unrelated_dir = tempfile.mkdtemp()
+    _git(unrelated_dir, "init", "-q", "-b", "x")
+    _git(unrelated_dir, "config", "user.email", "[email protected]")
+    _git(unrelated_dir, "config", "user.name", "T")
+    Path(unrelated_dir, "z.txt").write_text("z\n")
+    _git(unrelated_dir, "add", "-A")
+    _git(unrelated_dir, "commit", "-q", "-m", "unrelated")
+    unrelated = _rev(unrelated_dir)
+
+    # Leave the worktree checked out on the feature branch at the PRIOR head, as
+    # a dead author session that never advanced would have left it.
+    _git(tmp, "checkout", "-q", BRANCH)
+    _git(tmp, "reset", "-q", "--hard", prior)
+
+    return {
+        "prior": prior,
+        "master_tip": master_tip,
+        "synced": synced,
+        "linear": linear,
+        "unrelated": unrelated,
+    }
+
+
+# ─────────────────────────── write-side refresh ───────────────────────────
+
+
+class TestDurableLockHeadRefresh(unittest.TestCase):
+    def setUp(self):
+        self.lock_dir = tempfile.mkdtemp()
+        self.wt = tempfile.mkdtemp()
+        lock_data = {
+            "issue_number": ISSUE,
+            "branch_name": BRANCH,
+            "worktree_path": self.wt,
+            "remote": REMOTE,
+            "org": ORG,
+            "repo": REPO,
+            "claimant": {"username": IDENTITY, "profile": PROFILE},
+            "work_lease": {
+                "operation_type": issue_lock_store.AUTHOR_ISSUE_WORK_LEASE,
+                "issue_number": ISSUE,
+                "branch": BRANCH,
+                "worktree_path": self.wt,
+                "claimant": {"username": IDENTITY, "profile": PROFILE},
+                "expires_at": future_ts(),
+            },
+        }
+        issue_lock_store.bind_session_lock(lock_data, lock_dir=self.lock_dir)
+
+    def _apply(self, **over):
+        kw = dict(
+            remote=REMOTE, org=ORG, repo=REPO, issue_number=ISSUE,
+            branch_name=BRANCH, worktree_path=self.wt, pr_number=PR_NUMBER,
+            identity=IDENTITY, profile=PROFILE, current_pid=os.getpid(),
+            expected_old_head=OLD, new_head=NEW1, synced_at=future_ts(0),
+            base_head=BASE, lock_dir=self.lock_dir,
+        )
+        kw.update(over)
+        return issue_lock_store.apply_durable_lock_head_refresh(**kw)
+
+    def _load(self):
+        return issue_lock_store.load_issue_lock(
+            remote=REMOTE, org=ORG, repo=REPO, issue_number=ISSUE,
+            lock_dir=self.lock_dir,
+        )
+
+    def test_first_sync_updates_recorded_head(self):
+        """AC1: first base sync writes the resulting head to the durable lock."""
+        res = self._apply()
+        self.assertTrue(res["refreshed"], res["reasons"])
+        self.assertTrue(res["read_after_write_ok"])
+        self.assertEqual(self._load().get("synced_pr_head"), NEW1)
+
+    def test_second_sync_after_master_advance(self):
+        """AC2: a later master advance permits a second sanctioned sync."""
+        self.assertTrue(self._apply()["refreshed"])
+        res2 = self._apply(expected_old_head=NEW1, new_head=NEW2)
+        self.assertTrue(res2["refreshed"], res2["reasons"])
+        self.assertEqual(self._load().get("synced_pr_head"), NEW2)
+        history = self._load().get("branch_sync_history")
+        self.assertEqual(len(history), 2)
+        self.assertEqual(history[0]["last_synced_pr_head"], NEW1)
+        self.assertEqual(history[1]["prior_pr_head"], NEW1)
+
+    def test_cas_detects_concurrent_head_change(self):
+        """AC6: CAS refuses when the recorded synced head is not the old head."""
+        self.assertTrue(self._apply()["refreshed"])  # recorded head now NEW1
+        # A second sync claiming the old head is still OLD must fail closed.
+        res = self._apply(expected_old_head=OLD, new_head=NEW2)
+        self.assertFalse(res["refreshed"])
+        self.assertTrue(any("CAS" in r or "concurrent" in r for r in res["reasons"]))
+        self.assertEqual(self._load().get("synced_pr_head"), NEW1)
+
+    def test_wrong_issue_fails_closed(self):
+        res = self._apply(issue_number=999999)
+        self.assertFalse(res["refreshed"])
+
+    def test_wrong_branch_fails_closed(self):
+        res = self._apply(branch_name="fix/issue-8710-wrong")
+        self.assertFalse(res["refreshed"])
+
+    def test_wrong_repo_fails_closed(self):
+        res = self._apply(repo="OtherRepo")
+        self.assertFalse(res["refreshed"])
+
+    def test_wrong_identity_fails_closed(self):
+        res = self._apply(identity="intruder")
+        self.assertFalse(res["refreshed"])
+
+    def test_wrong_profile_fails_closed(self):
+        res = self._apply(profile="prgs-reviewer")
+        self.assertFalse(res["refreshed"])
+
+    def test_foreign_session_fails_closed(self):
+        """A refresh is not a recovery: the current process must own the lock."""
+        path = issue_lock_store.lock_file_path(
+            remote=REMOTE, org=ORG, repo=REPO, issue_number=ISSUE,
+            lock_dir=self.lock_dir,
+        )
+        rec = issue_lock_store.read_lock_file(path)
+        rec["session_pid"] = dead_pid()
+        rec["pid"] = rec["session_pid"]
+        issue_lock_store.save_lock_file(path, rec)
+        res = self._apply()
+        self.assertFalse(res["refreshed"])
+        self.assertTrue(any("current session" in r or "live owner" in r for r in res["reasons"]))
+
+    def test_new_equals_old_fails_closed(self):
+        res = self._apply(expected_old_head=OLD, new_head=OLD)
+        self.assertFalse(res["refreshed"])
+
+    def test_non_full_sha_fails_closed(self):
+        self.assertFalse(self._apply(new_head="deadbeef")["refreshed"])
+        self.assertFalse(self._apply(expected_old_head="xyz")["refreshed"])
+
+    def test_no_lock_fails_closed(self):
+        assessment = issue_lock_store.assess_durable_lock_head_refresh(
+            None, remote=REMOTE, org=ORG, repo=REPO, issue_number=ISSUE,
+            branch_name=BRANCH, worktree_path=self.wt, pr_number=PR_NUMBER,
+            identity=IDENTITY, profile=PROFILE, current_pid=os.getpid(),
+            expected_old_head=OLD, new_head=NEW1,
+        )
+        self.assertFalse(assessment["allowed"])
+
+
+# ─────────────────────── merge-sync provenance (real git) ───────────────────
+
+
+class TestMergeSyncProvenanceObservation(unittest.TestCase):
+    def setUp(self):
+        self.tmp = tempfile.mkdtemp()
+        self.shas = build_merge_sync_repo(self.tmp)
+
+    def test_merge_sync_is_recognized(self):
+        obs = issue_lock_worktree.read_merge_sync_provenance(
+            self.tmp, prior_head_sha=self.shas["prior"],
+            synced_head_sha=self.shas["synced"],
+        )
+        self.assertTrue(obs["is_merge_sync"], obs["reasons"])
+        self.assertTrue(obs["prior_is_ancestor"])
+        self.assertTrue(obs["synced_is_merge"])
+        self.assertTrue(obs["first_parent_reaches_prior"])
+
+    def test_linear_descendant_is_not_a_merge_sync(self):
+        """A plain non-merge descendant (rebase/extra commit) is not a sync."""
+        obs = issue_lock_worktree.read_merge_sync_provenance(
+            self.tmp, prior_head_sha=self.shas["prior"],
+            synced_head_sha=self.shas["linear"],
+        )
+        self.assertTrue(obs["probe_ok"])
+        self.assertFalse(obs["is_merge_sync"])
+        self.assertFalse(obs["synced_is_merge"])
+
+    def test_unrelated_history_fails_closed(self):
+        """A rewritten/force-pushed head where prior is unreachable fails closed."""
+        obs = issue_lock_worktree.read_merge_sync_provenance(
+            self.tmp, prior_head_sha=self.shas["prior"],
+            synced_head_sha=self.shas["unrelated"],
+        )
+        self.assertFalse(obs["is_merge_sync"])
+
+    def test_missing_args_fail_closed(self):
+        obs = issue_lock_worktree.read_merge_sync_provenance(
+            self.tmp, prior_head_sha=None, synced_head_sha=self.shas["synced"],
+        )
+        self.assertFalse(obs["is_merge_sync"])
+
+
+# ──────────────────── merge-sync dead-session recovery ──────────────────────
+
+
+def make_dead_lock(worktree, **over):
+    pid = dead_pid()
+    lock = {
+        "issue_number": ISSUE,
+        "branch_name": BRANCH,
+        "worktree_path": worktree,
+        "remote": REMOTE,
+        "org": ORG,
+        "repo": REPO,
+        "session_pid": pid,
+        "pid": pid,
+        "claimant": {"username": IDENTITY, "profile": PROFILE},
+        "work_lease": {
+            "operation_type": issue_lock_store.AUTHOR_ISSUE_WORK_LEASE,
+            "issue_number": ISSUE,
+            "branch": BRANCH,
+            "worktree_path": worktree,
+            "claimant": {"username": IDENTITY, "profile": PROFILE},
+            "expires_at": future_ts(),
+        },
+    }
+    lock.update(over)
+    return lock
+
+
+def sync_prov(prior, synced, **over):
+    d = {
+        "prior_head_sha": prior,
+        "synced_head_sha": synced,
+        "probe_ok": True,
+        "prior_present": True,
+        "synced_present": True,
+        "prior_is_ancestor": True,
+        "synced_is_merge": True,
+        "first_parent_reaches_prior": True,
+        "is_merge_sync": True,
+        "first_parent_sha": prior,
+        "parent_count": 2,
+        "proof": f"{synced} merged base into branch above {prior}",
+        "reasons": [],
+    }
+    d.update(over)
+    return d
+
+
+class TestMergeSyncRecovery(unittest.TestCase):
+    def setUp(self):
+        self.tmp = tempfile.mkdtemp()
+        self.shas = build_merge_sync_repo(self.tmp)
+        self.prior = self.shas["prior"]
+        self.synced = self.shas["synced"]
+
+    def _assess(self, **over):
+        lock = over.pop("_lock", None) or make_dead_lock(self.tmp)
+        kw = dict(
+            issue_number=ISSUE, branch_name=BRANCH, worktree_path=self.tmp,
+            remote=REMOTE, org=ORG, repo=REPO, identity=IDENTITY, profile=PROFILE,
+            current_branch=BRANCH, porcelain_status="",
+            head_sha=self.prior, remote_head_sha=self.synced,
+            pr_head_sha=self.synced, pr_number=PR_NUMBER,
+            competing_live_locks=[], candidate_branches=[BRANCH],
+            current_pid=os.getpid(),
+            remote_branch_exists=True,
+            sync_provenance=sync_prov(self.prior, self.synced),
+        )
+        kw.update(over)
+        return issue_lock_recovery.assess_dead_session_lock_recovery(lock, **kw)
+
+    def test_merge_sync_drift_is_recoverable(self):
+        """AC3/AC4: dead session, recorded head is a merge-sync ancestor of PR head."""
+        res = self._assess()
+        self.assertEqual(res["outcome"], issue_lock_recovery.RECOVERY_SANCTIONED, res["reasons"])
+        self.assertEqual(
+            res["evidence"]["head_relation"],
+            issue_lock_recovery.HEAD_RELATION_REMOTE_MERGE_SYNCED,
+        )
+        self.assertEqual(res["evidence"]["accepted_head"], self.synced)
+
+    def test_missing_provenance_fails_closed(self):
+        """No server-derived provenance → cannot accept a remote ahead of local."""
+        res = self._assess(sync_provenance=None)
+        self.assertEqual(res["outcome"], issue_lock_recovery.REFUSED)
+
+    def test_non_ancestor_recorded_head_fails_closed(self):
+        """AC7: provenance that does not prove ancestry is rejected."""
+        res = self._assess(
+            sync_provenance=sync_prov(
+                self.prior, self.synced, prior_is_ancestor=False, is_merge_sync=False,
+                reasons=["prior head is not an ancestor"],
+            )
+        )
+        self.assertEqual(res["outcome"], issue_lock_recovery.REFUSED)
+
+    def test_force_pushed_history_fails_closed(self):
+        """AC8: a rewritten head (not a merge sync) stays protected."""
+        res = self._assess(
+            sync_provenance=sync_prov(
+                self.prior, self.synced, is_merge_sync=False, synced_is_merge=False,
+                reasons=["not a merge-based sync"],
+            )
+        )
+        self.assertEqual(res["outcome"], issue_lock_recovery.REFUSED)
+
+    def test_provenance_for_other_commits_fails_closed(self):
+        """Provenance whose endpoints differ from the heads under assessment is rejected."""
+        res = self._assess(
+            sync_provenance=sync_prov("f" * 40, self.synced),
+        )
+        self.assertEqual(res["outcome"], issue_lock_recovery.REFUSED)
+
+    def test_dirty_worktree_fails_closed(self):
+        """AC11: dirty worktrees remain protected."""
+        res = self._assess(porcelain_status=" M feature.txt\n")
+        self.assertEqual(res["outcome"], issue_lock_recovery.REFUSED)
+
+    def test_live_owner_fails_closed(self):
+        """AC10: a live recorded owner is not a dead-session recovery."""
+        lock = make_dead_lock(self.tmp, session_pid=os.getpid(), pid=os.getpid())
+        res = self._assess(_lock=lock)
+        self.assertEqual(res["outcome"], issue_lock_recovery.REFUSED)
+
+    def test_competing_claimant_fails_closed(self):
+        """AC13: a competing live lock blocks recovery."""
+        res = self._assess(
+            competing_live_locks=[{
+                "issue_number": ISSUE, "branch_name": BRANCH,
+                "worktree_path": "/some/other/wt", "pid": os.getpid(),
+            }]
+        )
+        self.assertEqual(res["outcome"], issue_lock_recovery.REFUSED)
+
+    def test_wrong_branch_fails_closed(self):
+        """AC9: worktree on a different branch fails closed."""
+        res = self._assess(current_branch="fix/issue-8710-other")
+        self.assertEqual(res["outcome"], issue_lock_recovery.REFUSED)
+
+    def test_wrong_identity_fails_closed(self):
+        res = self._assess(identity="intruder")
+        self.assertEqual(res["outcome"], issue_lock_recovery.REFUSED)
+
+    def test_pr_head_mismatch_fails_closed(self):
+        """The open PR must sit at the synced remote head."""
+        res = self._assess(pr_head_sha="e" * 40)
+        self.assertEqual(res["outcome"], issue_lock_recovery.REFUSED)
+
+    def test_owning_pr_evidence_for_merge_sync(self):
+        res = self._assess()
+        ev = issue_lock_recovery.owning_pr_recovery_evidence(res)
+        self.assertIsNotNone(ev)
+        self.assertEqual(ev["pr_number"], PR_NUMBER)
+        self.assertEqual(ev["head_sha"], self.synced)
+        self.assertEqual(
+            ev["head_relation"],
+            issue_lock_recovery.HEAD_RELATION_REMOTE_MERGE_SYNCED,
+        )
+
+    def test_recovered_owning_pr_from_persisted_record(self):
+        res = self._assess()
+        record = issue_lock_recovery.build_recovery_record(res, recovered_at=future_ts(0))
+        lock = {"issue_number": ISSUE, "branch_name": BRANCH,
+                "dead_session_recovery": record}
+        rebuilt = issue_lock_recovery.recovered_owning_pr_from_lock(lock)
+        self.assertIsNotNone(rebuilt)
+        self.assertEqual(rebuilt["head_sha"], self.synced)
+        self.assertEqual(
+            rebuilt["head_relation"],
+            issue_lock_recovery.HEAD_RELATION_REMOTE_MERGE_SYNCED,
+        )
+
+
+class TestExistingRelationsUnchanged(unittest.TestCase):
+    """AC14/AC15: equal-head recovery still works; merge-sync did not weaken it."""
+
+    def setUp(self):
+        self.tmp = tempfile.mkdtemp()
+        self.shas = build_merge_sync_repo(self.tmp)
+
+    def test_equal_head_recovery_still_sanctioned(self):
+        # Worktree at prior head; remote also at prior head → the #753 equal case.
+        prior = self.shas["prior"]
+        lock = make_dead_lock(self.tmp)
+        res = issue_lock_recovery.assess_dead_session_lock_recovery(
+            lock, issue_number=ISSUE, branch_name=BRANCH, worktree_path=self.tmp,
+            remote=REMOTE, org=ORG, repo=REPO, identity=IDENTITY, profile=PROFILE,
+            current_branch=BRANCH, porcelain_status="",
+            head_sha=prior, remote_head_sha=prior,
+            pr_head_sha=prior, pr_number=PR_NUMBER,
+            competing_live_locks=[], candidate_branches=[BRANCH],
+            current_pid=os.getpid(), remote_branch_exists=True,
+        )
+        self.assertEqual(res["outcome"], issue_lock_recovery.RECOVERY_SANCTIONED, res["reasons"])
+        self.assertEqual(
+            res["evidence"]["head_relation"], issue_lock_recovery.HEAD_RELATION_EQUAL,
+        )
+
+
+class TestUpdatePrWrapperPartialFailure(unittest.TestCase):
+    """AC5/AC16: the tool advances the remote head then refreshes the durable lock.
+
+    When the durable refresh fails after the remote advance, the tool must report a
+    partial lifecycle failure and NOT a fully successful synchronization. Exact PR-
+    head / base-head pinning is preserved (delegated to the real preflight, stubbed
+    here only to isolate the post-update lifecycle branch).
+    """
+
+    def setUp(self):
+        import gitea_mcp_server as gms  # noqa: E402
+        self.gms = gms
+        self._orig = {}
+
+        def _patch(name, value):
+            self._orig[name] = getattr(gms, name)
+            setattr(gms, name, value)
+
+        _patch("get_profile", lambda *a, **k: {
+            "allowed_operations": ["gitea.branch.push"],
+            "forbidden_operations": [],
+            "profile_name": "prgs-author",
+        })
+        _patch("_role_kind", lambda *a, **k: "author")
+        _patch("_profile_operation_gate", lambda *a, **k: None)
+        _patch("_permission_block_report", lambda *a, **k: {})
+        _patch("_resolve", lambda *a, **k: ("gitea.prgs.cc", ORG, REPO))
+        _patch("_verify_role_mutation_workspace", lambda *a, **k: None)
+        _patch("_get_workspace_porcelain", lambda *a, **k: "")
+        _patch("_canonical_local_git_root", lambda *a, **k: "/x")
+        _patch("_master_parity_block", lambda *a, **k: None)
+        _patch("_auth", lambda *a, **k: {"token": "x"})
+        _patch("repo_api_url", lambda *a, **k: "http://api")
+        _patch("_redact", lambda s: s)
+        _patch("_work_lease_claimant", lambda *a, **k: {
+            "username": IDENTITY, "profile": PROFILE,
+        })
+        _patch("_prove_author_ownership_for_pr", lambda *a, **k: {
+            "has_author_lock": True, "matched_issue": ISSUE,
+            "matched_via": "branch", "linked_issues": [ISSUE],
+            "recovered_owning_pr": None, "reasons": [],
+        })
+
+        # Real preflight is unit-tested elsewhere; stub it to isolate the
+        # post-update durable-lock lifecycle branch under test.
+        orig_pf = gms.pr_sync_status.assess_update_pr_branch_preflight
+        self._orig_pf = orig_pf
+        gms.pr_sync_status.assess_update_pr_branch_preflight = (
+            lambda *a, **k: {"mutation_allowed": True, "reasons": [], "performed": False}
+        )
+
+        # Sequence the two GET /pulls calls: OLD before update, NEW after.
+        self._pull_calls = {"n": 0}
+
+        def fake_api_request(method, url, auth, *a, **k):
+            m = method.upper()
+            if m == "GET" and url.endswith(f"/pulls/{PR_NUMBER}"):
+                self._pull_calls["n"] += 1
+                head = OLD if self._pull_calls["n"] == 1 else NEW1
+                return {
+                    "state": "open",
+                    "head": {"sha": head, "ref": BRANCH},
+                    "base": {"sha": BASE, "ref": "master"},
+                    "mergeable": True, "title": "t", "body": "b",
+                }
+            if m == "GET" and "/branches/" in url:
+                return {"commit": {"id": BASE}}
+            if m == "POST" and "/update" in url:
+                return {}
+            return {}
+
+        _patch("api_request", fake_api_request)
+
+    def tearDown(self):
+        for name, value in self._orig.items():
+            setattr(self.gms, name, value)
+        self.gms.pr_sync_status.assess_update_pr_branch_preflight = self._orig_pf
+
+    def _run(self):
+        return self.gms.gitea_update_pr_branch_by_merge(
+            pr_number=PR_NUMBER,
+            expected_pr_head_sha=OLD,
+            expected_base_head_sha=BASE,
+            remote=REMOTE,
+            worktree_path="/tmp/branches/wt-871",
+        )
+
+    def test_partial_failure_when_refresh_fails(self):
+        self._orig["apply_durable_lock_head_refresh"] = (
+            self.gms.issue_lock_store.apply_durable_lock_head_refresh
+        )
+        self.gms.issue_lock_store.apply_durable_lock_head_refresh = (
+            lambda **k: {"refreshed": False, "reasons": ["forced refresh failure"]}
+        )
+        try:
+            res = self._run()
+        finally:
+            self.gms.issue_lock_store.apply_durable_lock_head_refresh = (
+                self._orig["apply_durable_lock_head_refresh"]
+            )
+        self.assertTrue(res["performed"])
+        self.assertEqual(res["new_pr_head_sha"], NEW1)
+        self.assertFalse(res["success"])
+        self.assertTrue(res["partial_lifecycle_failure"])
+        self.assertFalse(res["durable_lock_refreshed"])
+
+    def test_full_success_when_refresh_succeeds(self):
+        self._orig["apply_durable_lock_head_refresh"] = (
+            self.gms.issue_lock_store.apply_durable_lock_head_refresh
+        )
+        self.gms.issue_lock_store.apply_durable_lock_head_refresh = (
+            lambda **k: {"refreshed": True, "read_after_write_ok": True,
+                         "new_head": NEW1, "reasons": ["ok"]}
+        )
+        try:
+            res = self._run()
+        finally:
+            self.gms.issue_lock_store.apply_durable_lock_head_refresh = (
+                self._orig["apply_durable_lock_head_refresh"]
+            )
+        self.assertTrue(res["success"])
+        self.assertTrue(res["performed"])
+        self.assertTrue(res["durable_lock_refreshed"])
+        self.assertTrue(res["fully_synchronized"])
+        self.assertEqual(res["new_pr_head_sha"], NEW1)
+
+
+if __name__ == "__main__":
+    unittest.main()