Merge pull request 'fix(mcp): allow author-lock recovery after the owning session exits (Closes #753)' (#754) from fix/issue-753-dead-pid-author-lock-recovery into master

gitea_mcp_server.py

@@ -1650,6 +1650,7 @@ import issue_lock_worktree  # noqa: E402
 import issue_lock_provenance  # noqa: E402
 import issue_lock_store  # noqa: E402
 import issue_lock_adoption  # noqa: E402
+import issue_lock_recovery  # noqa: E402
 import stacked_pr_support  # noqa: E402
 import merge_approval_gate  # noqa: E402
 import review_quarantine  # noqa: E402  # #695 contaminated formal-review quarantine
@@ -3155,8 +3156,11 @@ def gitea_lock_issue(
         worktree_path, _canonical_local_git_root()
     )
     h, o, r = _resolve(remote, host, org, repo)
+    existing_issue_lock = _load_existing_issue_lock(
+        remote=remote, org=o, repo=r, issue_number=issue_number
+    )
     active_lease_block = issue_lock_store.assess_same_issue_lease_conflict(
-        _load_existing_issue_lock(remote=remote, org=o, repo=r, issue_number=issue_number),
+        existing_issue_lock,
         issue_number=issue_number,
         branch_name=branch_name,
         worktree_path=resolved_worktree,
@@ -3198,6 +3202,72 @@ def gitea_lock_issue(
         org=org,
         repo=repo,
     )
+    # ── Dead-session lock recovery assessment (#753) ──
+    # When the MCP session that took a lock exits, the lock goes non-live
+    # (stale by dead PID) even inside its lease TTL, and the branch it owns is
+    # ahead of its base by construction — so the base-equivalence gate below
+    # makes normal re-lock unreachable for every PR that already exists.
+    #
+    # This grants a waiver ONLY for that case, proven against the durable lock
+    # record plus live git/Gitea observation. A refused assessment never raises:
+    # it simply withholds the waiver, leaving the pre-existing guard to fail
+    # closed exactly as before. Recovery can only ever add permission.
+    recovery_assessment: dict | None = None
+    if (
+        existing_issue_lock
+        and existing_issue_lock.get("issue_number") == issue_number
+        and not issue_lock_store.is_lease_live(existing_issue_lock)
+    ):
+        recovery_auth = _auth(h)
+        try:
+            recovery_branches = api_get_all(
+                f"{repo_api_url(h, o, r)}/branches", recovery_auth
+            )
+        except Exception as exc:
+            raise RuntimeError(
+                f"Could not list branches to verify issue-lock recovery: {exc}"
+            )
+        recovery_remote_head: str | None = None
+        recovery_candidates: list[str] = []
+        for entry in recovery_branches:
+            entry_name = _branch_entry_name(entry)
+            if entry_name == branch_name:
+                recovery_remote_head = _branch_entry_commit_sha(entry)
+            if issue_lock_adoption.branch_carries_issue_marker(entry_name, issue_number):
+                recovery_candidates.append(entry_name)
+        recovery_pr_head: str | None = None
+        recovery_pr_number: int | None = None
+        for pull in _list_open_pulls(h, o, r, recovery_auth):
+            pull_head = pull.get("head") or {}
+            if str(pull_head.get("ref") or "") == branch_name:
+                recovery_pr_head = pull_head.get("sha")
+                recovery_pr_number = pull.get("number")
+                break
+        recovery_claimant = _work_lease_claimant(h)
+        recovery_assessment = issue_lock_recovery.assess_dead_session_lock_recovery(
+            existing_issue_lock,
+            issue_number=issue_number,
+            branch_name=branch_name,
+            worktree_path=resolved_worktree,
+            remote=remote,
+            org=o,
+            repo=r,
+            identity=recovery_claimant.get("username"),
+            profile=recovery_claimant.get("profile"),
+            current_branch=git_state.get("current_branch"),
+            porcelain_status=git_state.get("porcelain_status") or "",
+            head_sha=git_state.get("head_sha"),
+            remote_head_sha=recovery_remote_head,
+            pr_head_sha=recovery_pr_head,
+            pr_number=recovery_pr_number,
+            competing_live_locks=issue_lock_store.list_live_locks(),
+            candidate_branches=recovery_candidates,
+            current_pid=os.getpid(),
+        )
+
+    recovery_sanctioned = bool(
+        recovery_assessment and recovery_assessment.get("recovery_sanctioned")
+    )
     lock_assessment = issue_lock_worktree.assess_issue_lock_worktree(
         worktree_path=resolved_worktree,
         current_branch=git_state.get("current_branch"),
@@ -3205,10 +3275,20 @@ def gitea_lock_issue(
         base_equivalent=git_state.get("base_equivalent"),
         inspected_git_root=git_state.get("inspected_git_root"),
         base_branch=git_state.get("base_branch"),
+        recovery_sanctioned=recovery_sanctioned,
     )
     if lock_assessment["block"]:
+        reasons = list(lock_assessment.get("reasons") or [])
+        # Surface why recovery was unavailable, so a blocked caller sees the
+        # exact missing evidence instead of only the base-equivalence text.
+        if recovery_assessment and recovery_assessment.get("is_candidate"):
+            reasons.append(
+                issue_lock_recovery.format_recovery_refusal(recovery_assessment)
+            )
         raise RuntimeError(
-            issue_lock_worktree.format_issue_lock_worktree_error(lock_assessment)
+            issue_lock_worktree.format_issue_lock_worktree_error(
+                {**lock_assessment, "reasons": reasons}
+            )
         )
 
     auth = _auth(h)
@@ -3271,6 +3351,14 @@ def gitea_lock_issue(
     }
     if stacked_approved:
         data["approved_stacked_base"] = stacked_approved
+    if recovery_sanctioned and recovery_assessment:
+        # #753 AC2/AC6: record that this claim was recovered after session
+        # death, with the prior and replacement session identity, so the
+        # takeover is auditable and never looks like an original claim.
+        data["dead_session_recovery"] = issue_lock_recovery.build_recovery_record(
+            recovery_assessment,
+            recovered_at=_work_lease_timestamp(_work_lease_now()),
+        )
 
     lock_file_path = _save_issue_lock(data)
     lock_record = issue_lock_store.read_lock_file(lock_file_path) or data
@@ -3304,6 +3392,14 @@ def gitea_lock_issue(
         "lock_freshness": freshness,
         "lock_proof": lock_proof,
     }
+    if recovery_sanctioned and recovery_assessment:
+        result["dead_session_recovery"] = data["dead_session_recovery"]
+        result["message"] = (
+            f"Recovered the durable lock for issue #{issue_number} on branch "
+            f"'{branch_name}' after the owning MCP session (pid "
+            f"{recovery_assessment['evidence'].get('prior_session_pid')}) exited; "
+            "ownership evidence matched exactly (fail-closed check complete)."
+        )
     if stacked_approved:
         result["approved_stacked_base"] = stacked_approved
         result["message"] = (

issue_lock_adoption.py

@@ -85,6 +85,15 @@ def _branch_carries_issue_marker(branch_name: str, issue_number: int) -> bool:
     return re.search(pattern, name) is not None
 
 
+def branch_carries_issue_marker(branch_name: str, issue_number: int) -> bool:
+    """Public accessor for the exact issue-marker match (#753).
+
+    Dead-session lock recovery needs the same word-boundary matcher to detect
+    ambiguous branch claims, so it is exposed rather than reached into.
+    """
+    return _branch_carries_issue_marker(branch_name, issue_number)
+
+
 def assess_own_branch_adoption(
     *,
     issue_number: int,

issue_lock_recovery.py

@@ -0,0 +1,400 @@
+"""Dead-session author issue-lock recovery (#753).
+
+A durable author issue lock records the PID of the MCP session that took it.
+When that process exits, ``issue_lock_store.assess_lock_freshness`` classifies
+the lock as ``stale`` (``live=False``) even while its lease is still within TTL,
+so every ownership check that requires a *live* lock fails closed.
+
+Re-taking the lock through ``gitea_lock_issue`` is unreachable for real work:
+``issue_lock_worktree.assess_issue_lock_worktree`` demands the worktree be
+base-equivalent to ``master``/``main``/``dev``, and a branch that already
+carries commits is ahead of its base by construction. The existing
+``assess_expired_lock_reclaim`` affordance does not apply either, because
+``assess_same_issue_lease_conflict`` only consults it once the lease has
+*expired* — a dead PID under an unexpired lease never reaches it.
+
+This module is the pure evidence assessor for that one narrow case. It grants
+recovery only when every element of durable ownership still matches exactly and
+the recorded process is demonstrably dead. It never trusts caller assertions:
+every field is compared against durable lock state or live observation supplied
+by the caller. It performs no mutation and no network I/O.
+
+Recovery deliberately does **not** relax base-equivalence for brand-new issue
+claims — only for a lock whose own prior record already proves the branch,
+worktree, head, and author.
+"""
+
+from __future__ import annotations
+
+import os
+from typing import Any, Iterable, Mapping, Sequence
+
+from issue_lock_store import is_process_alive
+from reviewer_worktree import parse_dirty_tracked_files
+
+# Outcome values
+RECOVERY_SANCTIONED = "RECOVERY_SANCTIONED"
+NO_CANDIDATE = "NO_CANDIDATE"
+REFUSED = "REFUSED"
+
+# Durable fields a lock must carry before it can be considered at all.
+REQUIRED_LOCK_FIELDS = ("issue_number", "branch_name", "worktree_path")
+
+
+def _same_realpath(left: str | None, right: str | None) -> bool:
+    if not left or not right:
+        return False
+    try:
+        return os.path.realpath(left) == os.path.realpath(right)
+    except OSError:
+        return left == right
+
+
+def _text(value: Any) -> str:
+    return str(value or "").strip()
+
+
+def _lock_claimant(lock: Mapping[str, Any]) -> dict[str, Any]:
+    claimant = lock.get("claimant")
+    if not isinstance(claimant, Mapping):
+        lease = lock.get("work_lease")
+        claimant = lease.get("claimant") if isinstance(lease, Mapping) else None
+    return dict(claimant) if isinstance(claimant, Mapping) else {}
+
+
+def _recorded_pid(lock: Mapping[str, Any]) -> Any:
+    pid = lock.get("session_pid")
+    if pid is None:
+        pid = lock.get("pid")
+    return pid
+
+
+def _malformed_reasons(lock: Mapping[str, Any]) -> list[str]:
+    """Names of durable fields that are missing or unusable."""
+    missing: list[str] = []
+    for field in REQUIRED_LOCK_FIELDS:
+        if not _text(lock.get(field)):
+            missing.append(field)
+    pid = _recorded_pid(lock)
+    if pid is None or _text(pid) == "":
+        missing.append("session_pid/pid")
+    else:
+        try:
+            if int(pid) <= 0:
+                missing.append("session_pid/pid")
+        except (TypeError, ValueError):
+            missing.append("session_pid/pid")
+    return missing
+
+
+def assess_dead_session_lock_recovery(
+    existing_lock: Mapping[str, Any] | None,
+    *,
+    issue_number: int,
+    branch_name: str,
+    worktree_path: str,
+    remote: str,
+    org: str,
+    repo: str,
+    identity: str | None,
+    profile: str | None,
+    current_branch: str | None,
+    porcelain_status: str,
+    head_sha: str | None,
+    remote_head_sha: str | None,
+    pr_head_sha: str | None = None,
+    pr_number: int | None = None,
+    competing_live_locks: Sequence[Mapping[str, Any]] | None = None,
+    candidate_branches: Iterable[str] | None = None,
+    current_pid: int | None = None,
+) -> dict[str, Any]:
+    """Decide whether a dead-session author lock may be natively recovered.
+
+    Returns a dict with ``recovery_sanctioned`` (bool), ``outcome``, ``reasons``
+    (why it was refused, or the positive proof when sanctioned), and
+    ``evidence`` (a redaction-safe record for auditing).
+
+    ``NO_CANDIDATE`` means no recovery was attempted at all — there is no
+    existing lock, or the lock does not describe this issue. The caller must
+    treat that exactly as it treated the pre-#753 world. ``REFUSED`` means a
+    candidate existed but the evidence did not agree; the caller fails closed.
+    """
+    reasons: list[str] = []
+    evidence: dict[str, Any] = {
+        "issue_number": issue_number,
+        "branch_name": branch_name,
+        "worktree_path": worktree_path,
+        "remote": remote,
+        "org": org,
+        "repo": repo,
+    }
+
+    if not existing_lock:
+        return _result(
+            NO_CANDIDATE, False, ["no existing durable lock for this issue"], evidence
+        )
+
+    lock = dict(existing_lock)
+
+    # ── Candidate identification ────────────────────────────────────────────
+    # Recovery only ever applies to a lock that already claims THIS issue.
+    # Anything else is not a recovery candidate and must not be reinterpreted.
+    if lock.get("issue_number") != issue_number:
+        return _result(
+            NO_CANDIDATE,
+            False,
+            [
+                f"existing lock targets issue #{lock.get('issue_number')}, "
+                f"not #{issue_number}; not a recovery candidate"
+            ],
+            evidence,
+        )
+
+    # A malformed/incomplete durable record can never prove ownership.
+    missing = _malformed_reasons(lock)
+    if missing:
+        return _result(
+            REFUSED,
+            False,
+            [
+                "durable lock record is incomplete and cannot prove ownership "
+                f"(missing/unusable: {', '.join(missing)})"
+            ],
+            evidence,
+        )
+
+    recorded_pid = _recorded_pid(lock)
+    evidence["prior_session_pid"] = recorded_pid
+    evidence["replacement_session_pid"] = (
+        current_pid if current_pid is not None else os.getpid()
+    )
+
+    # ── Repository scope ────────────────────────────────────────────────────
+    for field, expected in (("remote", remote), ("org", org), ("repo", repo)):
+        actual = _text(lock.get(field))
+        if actual != _text(expected):
+            reasons.append(
+                f"lock {field} '{actual}' does not match requested '{_text(expected)}'"
+            )
+
+    # ── Branch identity ─────────────────────────────────────────────────────
+    locked_branch = _text(lock.get("branch_name"))
+    if locked_branch != _text(branch_name):
+        reasons.append(
+            f"lock branch '{locked_branch}' does not match requested "
+            f"'{_text(branch_name)}'"
+        )
+    evidence["locked_branch"] = locked_branch
+
+    # The worktree must actually be sitting on the locked branch. Without this
+    # a clean worktree parked elsewhere could stand in for the real work.
+    checked_out = _text(current_branch)
+    if not checked_out:
+        reasons.append(
+            "worktree is not on a named branch (detached HEAD); locked-branch "
+            "occupancy could not be proven"
+        )
+    elif checked_out != locked_branch:
+        reasons.append(
+            f"worktree is on branch '{checked_out}', not the locked branch "
+            f"'{locked_branch}'"
+        )
+
+    # ── Worktree identity ───────────────────────────────────────────────────
+    locked_worktree = _text(lock.get("worktree_path"))
+    if not _same_realpath(locked_worktree, worktree_path):
+        reasons.append(
+            f"lock worktree '{locked_worktree}' does not match declared "
+            f"'{_text(worktree_path)}'"
+        )
+    evidence["locked_worktree_path"] = locked_worktree
+
+    # ── Cleanliness (never waived) ──────────────────────────────────────────
+    dirty_files = parse_dirty_tracked_files(porcelain_status)
+    if dirty_files:
+        reasons.append(
+            "worktree has tracked local edits; recovery requires a clean "
+            f"worktree (dirty files: {', '.join(dirty_files)})"
+        )
+    evidence["dirty_files"] = dirty_files
+
+    # ── Head agreement: local == remote == PR ───────────────────────────────
+    local_head = _text(head_sha)
+    remote_head = _text(remote_head_sha)
+    if not local_head:
+        reasons.append("local head SHA could not be determined")
+    if not remote_head:
+        reasons.append(
+            f"remote head for branch '{locked_branch}' could not be determined"
+        )
+    if local_head and remote_head and local_head != remote_head:
+        reasons.append(
+            f"local head {local_head} does not match remote branch head {remote_head}"
+        )
+    evidence["local_head"] = local_head or None
+    evidence["remote_head"] = remote_head or None
+
+    pr_head = _text(pr_head_sha)
+    if pr_head:
+        evidence["pr_head"] = pr_head
+        evidence["pr_number"] = pr_number
+        if local_head and pr_head != local_head:
+            reasons.append(
+                f"open PR #{pr_number} head {pr_head} does not match local head "
+                f"{local_head}"
+            )
+
+    # ── Author identity ─────────────────────────────────────────────────────
+    claimant = _lock_claimant(lock)
+    locked_identity = _text(claimant.get("username"))
+    locked_profile = _text(claimant.get("profile"))
+    evidence["locked_identity"] = locked_identity or None
+    evidence["locked_profile"] = locked_profile or None
+    if not locked_identity or not locked_profile:
+        reasons.append(
+            "durable lock does not record a claimant identity/profile; "
+            "author ownership could not be proven"
+        )
+    if not _text(identity) or not _text(profile):
+        reasons.append(
+            "active session identity/profile is unknown; author ownership "
+            "could not be proven"
+        )
+    if locked_identity and _text(identity) and locked_identity != _text(identity):
+        reasons.append(
+            f"lock claimant '{locked_identity}' does not match active identity "
+            f"'{_text(identity)}'"
+        )
+    if locked_profile and _text(profile) and locked_profile != _text(profile):
+        reasons.append(
+            f"lock profile '{locked_profile}' does not match active profile "
+            f"'{_text(profile)}'"
+        )
+
+    # ── The defining condition: the recorded owner must be dead ─────────────
+    prior_alive = is_process_alive(recorded_pid)
+    evidence["prior_pid_alive"] = prior_alive
+    if prior_alive:
+        reasons.append(
+            f"prior owner pid {recorded_pid} is still alive; this is not a "
+            "dead-session recovery"
+        )
+    if current_pid is not None and recorded_pid is not None:
+        try:
+            if int(recorded_pid) == int(current_pid):
+                reasons.append(
+                    "recorded pid is the current session; nothing to recover"
+                )
+        except (TypeError, ValueError):
+            pass
+
+    # ── Competing ownership ─────────────────────────────────────────────────
+    competing: list[dict[str, Any]] = []
+    for entry in competing_live_locks or ():
+        if not isinstance(entry, Mapping):
+            continue
+        same_issue = entry.get("issue_number") == issue_number
+        same_branch = _text(entry.get("branch_name")) == locked_branch
+        if not (same_issue or same_branch):
+            continue
+        # The lock we are recovering is not competition with itself.
+        if (
+            same_issue
+            and same_branch
+            and _same_realpath(_text(entry.get("worktree_path")), worktree_path)
+        ):
+            continue
+        competing.append(
+            {
+                "issue_number": entry.get("issue_number"),
+                "branch_name": entry.get("branch_name"),
+                "worktree_path": entry.get("worktree_path"),
+                "pid": entry.get("pid"),
+            }
+        )
+    if competing:
+        described = ", ".join(
+            f"issue #{c['issue_number']} branch '{c['branch_name']}'" for c in competing
+        )
+        reasons.append(f"competing live lock or lease exists ({described})")
+    evidence["competing_live_locks"] = competing
+
+    # ── Ambiguous branch claims ─────────────────────────────────────────────
+    others = [
+        name
+        for name in (candidate_branches or ())
+        if _text(name) and _text(name) != locked_branch
+    ]
+    if others:
+        reasons.append(
+            "multiple branches claim this issue "
+            f"({', '.join(sorted(set(others)))}); ownership is ambiguous"
+        )
+    evidence["other_candidate_branches"] = sorted(set(others))
+
+    if reasons:
+        return _result(REFUSED, False, reasons, evidence)
+
+    return _result(
+        RECOVERY_SANCTIONED,
+        True,
+        [
+            f"durable lock for issue #{issue_number} matches branch "
+            f"'{locked_branch}', worktree '{locked_worktree}', head {local_head}, "
+            f"and claimant '{locked_identity}'; recorded pid {recorded_pid} is dead"
+        ],
+        evidence,
+    )
+
+
+def _result(
+    outcome: str,
+    sanctioned: bool,
+    reasons: list[str],
+    evidence: dict[str, Any],
+) -> dict[str, Any]:
+    return {
+        "outcome": outcome,
+        "recovery_sanctioned": sanctioned,
+        "is_candidate": outcome != NO_CANDIDATE,
+        "reasons": reasons,
+        "evidence": evidence,
+    }
+
+
+def build_recovery_record(
+    assessment: Mapping[str, Any],
+    *,
+    recovered_at: str,
+) -> dict[str, Any]:
+    """Durable, secret-free provenance for a completed recovery (#753 AC2/AC6)."""
+    evidence = dict(assessment.get("evidence") or {})
+    return {
+        "recovered": True,
+        "reason": "owning MCP session exited; durable ownership evidence matched",
+        "recovered_at": recovered_at,
+        "prior_session_pid": evidence.get("prior_session_pid"),
+        "replacement_session_pid": evidence.get("replacement_session_pid"),
+        "prior_pid_alive": evidence.get("prior_pid_alive"),
+        "branch_name": evidence.get("locked_branch"),
+        "worktree_path": evidence.get("locked_worktree_path"),
+        "local_head": evidence.get("local_head"),
+        "remote_head": evidence.get("remote_head"),
+        "pr_head": evidence.get("pr_head"),
+        "pr_number": evidence.get("pr_number"),
+        "identity": evidence.get("locked_identity"),
+        "profile": evidence.get("locked_profile"),
+        "proof": list(assessment.get("reasons") or []),
+    }
+
+
+def format_recovery_refusal(assessment: Mapping[str, Any]) -> str:
+    """Single fail-closed message for a refused recovery attempt."""
+    reasons = list(assessment.get("reasons") or []) or [
+        "dead-session lock recovery evidence did not agree"
+    ]
+    return (
+        "Dead-session issue-lock recovery refused: "
+        + "; ".join(reasons)
+        + " (fail closed)"
+    )

issue_lock_worktree.py

@@ -92,8 +92,19 @@ def assess_issue_lock_worktree(
     inspected_git_root: str | None = None,
     base_branch: str | None = None,
     base_branches: frozenset[str] | None = None,
+    recovery_sanctioned: bool = False,
 ) -> dict:
-    """Fail closed when lock preconditions are not met on the declared worktree."""
+    """Fail closed when lock preconditions are not met on the declared worktree.
+
+    ``recovery_sanctioned`` is set only when ``issue_lock_recovery`` has already
+    proven, from the durable lock itself, that this is a dead-session recovery of
+    an existing claim (#753): same issue, branch, worktree, author, and head, with
+    the recording process dead. In that one case the base-equivalence requirement
+    is waived, because a branch that already carries the work is ahead of its base
+    by construction and could never satisfy it. Every other precondition —
+    notably worktree cleanliness — still applies unchanged, and brand-new issue
+    claims keep the full base-equivalence requirement.
+    """
     bases = base_branches or BASE_BRANCHES
     reasons: list[str] = []
     path = (worktree_path or "").strip()
@@ -111,7 +122,11 @@ def assess_issue_lock_worktree(
             f"(dirty files: {', '.join(dirty_files)})"
         )
 
-    if base_equivalent is False:
+    if recovery_sanctioned:
+        # Base-equivalence intentionally not evaluated: ownership was proven
+        # against the durable lock record instead (#753).
+        pass
+    elif base_equivalent is False:
         reasons.append(
             "issue lock worktree must be base-equivalent to one of "
             f"{_base_list(bases)} before implementation work; inspected "
@@ -139,6 +154,7 @@ def assess_issue_lock_worktree(
         inspected_git_root=inspected_git_root,
         base_branch=base_branch,
         base_equivalent=base_equivalent,
+        recovery_sanctioned=recovery_sanctioned,
     )
 
 
@@ -197,6 +213,7 @@ def _assessment(
     inspected_git_root: str | None = None,
     base_branch: str | None = None,
     base_equivalent: bool | None = None,
+    recovery_sanctioned: bool = False,
 ) -> dict:
     return {
         "proven": proven,
@@ -208,6 +225,8 @@ def _assessment(
         "dirty_files": dirty_files,
         "base_branch": base_branch,
         "base_equivalent": base_equivalent,
+        "recovery_sanctioned": recovery_sanctioned,
+        "base_equivalence_waived": bool(recovery_sanctioned),
     }
 
 

tests/test_issue_753_dead_pid_lock_recovery.py

@@ -0,0 +1,364 @@
+"""Dead-session author issue-lock recovery (#753).
+
+Covers the narrow recovery path that lets an author re-acquire a durable lock
+after the MCP session that recorded it exits, plus every rejection condition
+that must keep failing closed.
+"""
+
+import os
+import subprocess
+import sys
+import unittest
+from datetime import datetime, timedelta, timezone
+
+sys.path.insert(0, str(__import__("pathlib").Path(__file__).resolve().parent.parent))
+
+import issue_lock_recovery  # noqa: E402
+import issue_lock_store  # noqa: E402
+import issue_lock_worktree  # noqa: E402
+
+ISSUE = 4242
+BRANCH = f"fix/issue-{ISSUE}-demo"
+WORKTREE = "/scratch/wt"
+HEAD = "a" * 40
+OTHER_SHA = "b" * 40
+IDENTITY = "example-user"
+PROFILE = "example-author"
+
+
+def dead_pid() -> int:
+    """A PID that has certainly exited (spawned, then reaped)."""
+    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 make_lock(**overrides):
+    lock = {
+        "issue_number": ISSUE,
+        "branch_name": BRANCH,
+        "worktree_path": WORKTREE,
+        "remote": "prgs",
+        "org": "ExampleOrg",
+        "repo": "ExampleRepo",
+        "session_pid": dead_pid(),
+        "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(overrides)
+    return lock
+
+
+def assess(lock=None, **overrides):
+    kwargs = {
+        "issue_number": ISSUE,
+        "branch_name": BRANCH,
+        "worktree_path": WORKTREE,
+        "remote": "prgs",
+        "org": "ExampleOrg",
+        "repo": "ExampleRepo",
+        "identity": IDENTITY,
+        "profile": PROFILE,
+        "current_branch": BRANCH,
+        "porcelain_status": "",
+        "head_sha": HEAD,
+        "remote_head_sha": HEAD,
+        "pr_head_sha": HEAD,
+        "pr_number": 99,
+        "competing_live_locks": [],
+        "candidate_branches": [BRANCH],
+        "current_pid": os.getpid(),
+    }
+    kwargs.update(overrides)
+    return issue_lock_recovery.assess_dead_session_lock_recovery(
+        make_lock() if lock is None else lock, **kwargs
+    )
+
+
+class TestDeadSessionRecoveryGranted(unittest.TestCase):
+    def test_dead_pid_with_exact_evidence_recovers(self):
+        result = assess()
+        self.assertTrue(result["recovery_sanctioned"], result["reasons"])
+        self.assertEqual(result["outcome"], issue_lock_recovery.RECOVERY_SANCTIONED)
+
+    def test_recovery_still_granted_when_no_open_pr_exists(self):
+        # A locked branch need not have a PR yet; absence must not block.
+        result = assess(pr_head_sha=None, pr_number=None)
+        self.assertTrue(result["recovery_sanctioned"], result["reasons"])
+
+    def test_lease_expiry_is_not_required_for_recovery(self):
+        # The defining condition is PID death, not TTL expiry (the #601 gap).
+        lock = make_lock()
+        self.assertFalse(issue_lock_store.is_lease_expired(lock))
+        self.assertFalse(issue_lock_store.assess_lock_freshness(lock)["live"])
+        self.assertTrue(assess(lock)["recovery_sanctioned"])
+
+
+class TestDeadSessionRecoveryRefused(unittest.TestCase):
+    def assert_refused(self, result, needle):
+        self.assertFalse(result["recovery_sanctioned"])
+        self.assertEqual(result["outcome"], issue_lock_recovery.REFUSED)
+        self.assertTrue(
+            any(needle in reason for reason in result["reasons"]),
+            f"expected {needle!r} in {result['reasons']}",
+        )
+
+    def test_live_prior_pid_refused(self):
+        lock = make_lock(session_pid=os.getpid(), pid=os.getpid())
+        # Distinct current pid so the refusal is attributable to liveness.
+        self.assert_refused(assess(lock, current_pid=os.getpid() + 1), "still alive")
+
+    def test_different_author_identity_refused(self):
+        self.assert_refused(
+            assess(identity="someone-else"), "does not match active identity"
+        )
+
+    def test_different_profile_refused(self):
+        self.assert_refused(
+            assess(profile="other-profile"), "does not match active profile"
+        )
+
+    def test_different_branch_refused(self):
+        lock = make_lock(branch_name=f"fix/issue-{ISSUE}-other")
+        self.assert_refused(assess(lock), "does not match requested")
+
+    def test_worktree_parked_on_another_branch_refused(self):
+        self.assert_refused(assess(current_branch="master"), "not the locked branch")
+
+    def test_detached_head_worktree_refused(self):
+        self.assert_refused(assess(current_branch=None), "detached HEAD")
+
+    def test_different_worktree_refused(self):
+        self.assert_refused(
+            assess(worktree_path="/scratch/elsewhere"), "does not match declared"
+        )
+
+    def test_dirty_worktree_refused(self):
+        self.assert_refused(
+            assess(porcelain_status=" M gitea_mcp_server.py\n"), "requires a clean"
+        )
+
+    def test_local_head_differing_from_remote_refused(self):
+        self.assert_refused(
+            assess(remote_head_sha=OTHER_SHA), "does not match remote branch head"
+        )
+
+    def test_pr_head_differing_refused(self):
+        self.assert_refused(assess(pr_head_sha=OTHER_SHA), "does not match local head")
+
+    def test_missing_remote_head_refused(self):
+        self.assert_refused(assess(remote_head_sha=None), "remote head")
+
+    def test_competing_live_lock_refused(self):
+        competing = [
+            {
+                "issue_number": ISSUE,
+                "branch_name": BRANCH,
+                "worktree_path": "/scratch/other-wt",
+                "pid": os.getpid(),
+            }
+        ]
+        self.assert_refused(
+            assess(competing_live_locks=competing), "competing live lock"
+        )
+
+    def test_unrelated_live_lock_does_not_block(self):
+        unrelated = [
+            {
+                "issue_number": 999,
+                "branch_name": "fix/issue-999-unrelated",
+                "worktree_path": "/scratch/unrelated",
+                "pid": os.getpid(),
+            }
+        ]
+        self.assertTrue(assess(competing_live_locks=unrelated)["recovery_sanctioned"])
+
+    def test_multiple_candidate_branches_refused(self):
+        self.assert_refused(
+            assess(candidate_branches=[BRANCH, f"feat/issue-{ISSUE}-rival"]),
+            "multiple branches claim this issue",
+        )
+
+    def test_repository_scope_mismatch_refused(self):
+        self.assert_refused(assess(repo="OtherRepo"), "does not match requested")
+
+    def test_malformed_lock_missing_worktree_refused(self):
+        lock = make_lock()
+        lock.pop("worktree_path")
+        self.assert_refused(assess(lock), "incomplete")
+
+    def test_malformed_lock_missing_pid_refused(self):
+        lock = make_lock()
+        lock.pop("session_pid", None)
+        lock.pop("pid", None)
+        self.assert_refused(assess(lock), "incomplete")
+
+    def test_lock_without_claimant_refused(self):
+        lock = make_lock()
+        lock["work_lease"] = dict(lock["work_lease"])
+        lock["work_lease"].pop("claimant")
+        self.assert_refused(assess(lock), "claimant identity/profile")
+
+
+class TestNotACandidate(unittest.TestCase):
+    def test_absent_lock_is_not_a_candidate(self):
+        result = issue_lock_recovery.assess_dead_session_lock_recovery(
+            None,
+            issue_number=ISSUE,
+            branch_name=BRANCH,
+            worktree_path=WORKTREE,
+            remote="prgs",
+            org="ExampleOrg",
+            repo="ExampleRepo",
+            identity=IDENTITY,
+            profile=PROFILE,
+            current_branch=BRANCH,
+            porcelain_status="",
+            head_sha=HEAD,
+            remote_head_sha=HEAD,
+        )
+        self.assertEqual(result["outcome"], issue_lock_recovery.NO_CANDIDATE)
+        self.assertFalse(result["recovery_sanctioned"])
+        self.assertFalse(result["is_candidate"])
+
+    def test_lock_for_a_different_issue_is_not_a_candidate(self):
+        result = assess(make_lock(issue_number=7777))
+        self.assertEqual(result["outcome"], issue_lock_recovery.NO_CANDIDATE)
+        self.assertFalse(result["recovery_sanctioned"])
+
+
+class TestWorktreeGateWaiver(unittest.TestCase):
+    def test_new_issue_claim_still_requires_base_equivalence(self):
+        result = issue_lock_worktree.assess_issue_lock_worktree(
+            worktree_path=WORKTREE,
+            current_branch=BRANCH,
+            porcelain_status="",
+            base_equivalent=False,
+        )
+        self.assertTrue(result["block"])
+        self.assertFalse(result["base_equivalence_waived"])
+
+    def test_sanctioned_recovery_waives_base_equivalence(self):
+        result = issue_lock_worktree.assess_issue_lock_worktree(
+            worktree_path=WORKTREE,
+            current_branch=BRANCH,
+            porcelain_status="",
+            base_equivalent=False,
+            recovery_sanctioned=True,
+        )
+        self.assertTrue(result["proven"], result["reasons"])
+        self.assertTrue(result["base_equivalence_waived"])
+
+    def test_recovery_never_waives_cleanliness(self):
+        result = issue_lock_worktree.assess_issue_lock_worktree(
+            worktree_path=WORKTREE,
+            current_branch=BRANCH,
+            porcelain_status=" M gitea_mcp_server.py\n",
+            base_equivalent=False,
+            recovery_sanctioned=True,
+        )
+        self.assertTrue(result["block"])
+        self.assertTrue(
+            any("tracked file edits" in reason for reason in result["reasons"])
+        )
+
+    def test_unproven_base_equivalence_still_blocks_without_recovery(self):
+        result = issue_lock_worktree.assess_issue_lock_worktree(
+            worktree_path=WORKTREE,
+            current_branch=BRANCH,
+            porcelain_status="",
+            base_equivalent=None,
+        )
+        self.assertTrue(result["block"])
+
+
+class TestRecoveryRecordAndDownstream(unittest.TestCase):
+    def test_recovery_record_preserves_truthful_provenance(self):
+        assessment = assess()
+        prior = assessment["evidence"]["prior_session_pid"]
+        record = issue_lock_recovery.build_recovery_record(
+            assessment, recovered_at="2026-07-18T23:21:40Z"
+        )
+        self.assertTrue(record["recovered"])
+        self.assertEqual(record["prior_session_pid"], prior)
+        self.assertEqual(record["replacement_session_pid"], os.getpid())
+        self.assertNotEqual(
+            record["prior_session_pid"], record["replacement_session_pid"]
+        )
+        self.assertFalse(record["prior_pid_alive"])
+        self.assertEqual(record["recovered_at"], "2026-07-18T23:21:40Z")
+        self.assertEqual(record["branch_name"], BRANCH)
+        self.assertEqual(record["local_head"], HEAD)
+        self.assertEqual(record["identity"], IDENTITY)
+        self.assertTrue(record["proof"])
+
+    def test_recovery_record_carries_no_secret_material(self):
+        record = issue_lock_recovery.build_recovery_record(
+            assess(), recovered_at="2026-07-18T23:21:40Z"
+        )
+        blob = repr(record).lower()
+        for banned in ("token", "password", "authorization", "secret", "api_key"):
+            self.assertNotIn(banned, blob)
+
+    def test_recovered_lock_satisfies_update_by_merge_ownership(self):
+        # After recovery the lock is rebound to the live session, so the
+        # ownership re-check used by gitea_update_pr_branch_by_merge passes.
+        assessment = assess()
+        recovered_lock = make_lock(session_pid=os.getpid(), pid=os.getpid())
+        recovered_lock["dead_session_recovery"] = (
+            issue_lock_recovery.build_recovery_record(
+                assessment, recovered_at="2026-07-18T23:21:40Z"
+            )
+        )
+        freshness = issue_lock_store.assess_lock_freshness(recovered_lock)
+        self.assertTrue(freshness["live"], freshness)
+
+        verdict = issue_lock_store.verify_lock_for_mutation(
+            recovered_lock,
+            issue_number=ISSUE,
+            branch_name=BRANCH,
+            worktree_path=WORKTREE,
+        )
+        self.assertTrue(verdict["proven"], verdict["reasons"])
+        self.assertFalse(verdict["block"])
+
+    def test_pre_recovery_lock_fails_ownership_check(self):
+        # Guards against a false positive above: the dead-PID lock must fail.
+        verdict = issue_lock_store.verify_lock_for_mutation(
+            make_lock(),
+            issue_number=ISSUE,
+            branch_name=BRANCH,
+            worktree_path=WORKTREE,
+        )
+        self.assertTrue(verdict["block"])
+        self.assertTrue(any("not live" in reason for reason in verdict["reasons"]))
+
+    def test_no_manual_file_seeding_required(self):
+        # The whole decision is reachable from the durable record plus live
+        # observation; nothing is written to disk to reach a verdict.
+        self.assertTrue(assess()["recovery_sanctioned"])
+
+    def test_refusal_message_is_fail_closed(self):
+        message = issue_lock_recovery.format_recovery_refusal(
+            assess(porcelain_status=" M x.py\n")
+        )
+        self.assertIn("fail closed", message)
+        self.assertIn("recovery refused", message.lower())
+
+
+if __name__ == "__main__":
+    unittest.main()