test: fix reviewer lease gate regressions in MCP integration tests (#407)

Align merge/review/audit mocks with the per-PR reviewer lease gate introduced
in #407: install owned session leases after init_review_decision_lock, stub
_fetch_pr_comments and _authenticated_username to preserve mock ordering, and
update head-SHA mismatch expectations for lease-first fail-closed paths.

Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>

author_duplicate_work_gate.py

@@ -1,198 +0,0 @@
-"""Early duplicate-work detection for author work-issue flows (#400)."""
-
-from __future__ import annotations
-
-import re
-from typing import Any
-
-from issue_claim_heartbeat import (
-    _linked_open_pr,
-    _matching_branch_names,
-    classify_issue_claim,
-)
-
-STAGES = (
-    "claim",
-    "lock",
-    "worktree",
-    "edit",
-    "commit",
-    "push",
-    "create_pr",
-)
-
-ELIGIBILITY_OPEN_PR_EXISTS = "OPEN_PR_EXISTS"
-ELIGIBILITY_DUPLICATE_BRANCH_EXISTS = "DUPLICATE_BRANCH_EXISTS"
-ELIGIBILITY_ACTIVE_CLAIM = "ACTIVE_CLAIM_BY_OTHER"
-ELIGIBILITY_CLEAR = "CLEAR"
-
-
-def assess_author_duplicate_work(
-    issue_number: int,
-    *,
-    stage: str,
-    open_prs: list[dict] | None = None,
-    branch_names: list[str] | None = None,
-    claim_entry: dict | None = None,
-    matching_branches: list[str] | None = None,
-    allow_stale_takeover: bool = False,
-) -> dict[str, Any]:
-    """Fail closed when duplicate work is detected before author mutations (#400)."""
-    stage_norm = (stage or "").strip().lower()
-    if stage_norm not in STAGES:
-        return {
-            "allowed": False,
-            "block": True,
-            "eligibility_class": "INVALID_STAGE",
-            "stage": stage_norm or None,
-            "reasons": [f"unknown duplicate-work stage {stage!r}"],
-            "safe_next_action": f"use one of: {', '.join(STAGES)}",
-        }
-
-    prs = list(open_prs or [])
-    linked_pr = _linked_open_pr(int(issue_number), prs)
-    branches = list(
-        matching_branches
-        if matching_branches is not None
-        else _matching_branch_names(int(issue_number), list(branch_names or []))
-    )
-
-    reasons: list[str] = []
-    eligibility = ELIGIBILITY_CLEAR
-
-    if linked_pr:
-        eligibility = ELIGIBILITY_OPEN_PR_EXISTS
-        reasons.append(
-            f"open PR #{linked_pr.get('number')} already covers issue "
-            f"#{issue_number}"
-        )
-
-    if branches and stage_norm in {"claim", "lock", "worktree", "edit"}:
-        if eligibility == ELIGIBILITY_CLEAR:
-            eligibility = ELIGIBILITY_DUPLICATE_BRANCH_EXISTS
-        reasons.append(
-            f"remote branch(es) already exist for issue #{issue_number}: "
-            f"{', '.join(branches)}"
-        )
-
-    entry = claim_entry or {}
-    claim_status = (entry.get("status") or "").strip()
-    if claim_status in {"active", "awaiting_review"} and stage_norm == "claim":
-        if entry.get("reclaimable") and allow_stale_takeover:
-            pass
-        elif claim_status == "active" and not entry.get("reclaimable"):
-            if eligibility == ELIGIBILITY_CLEAR:
-                eligibility = ELIGIBILITY_ACTIVE_CLAIM
-            reasons.append(
-                f"issue #{issue_number} has active claim "
-                f"(status={claim_status})"
-            )
-    elif claim_status == "awaiting_review" and stage_norm == "claim":
-        if not linked_pr:
-            reasons.append(
-                f"issue #{issue_number} is awaiting_review but no linked open PR "
-                "was supplied for duplicate-work proof"
-            )
-
-    allowed = not reasons
-    outcome = "duplicate_work_prevented" if not allowed else "clear"
-    if stage_norm == "create_pr" and not allowed:
-        outcome = "duplicate_pr_prevented"
-    elif stage_norm in {"commit", "push"} and not allowed:
-        outcome = "duplicate_push_prevented" if stage_norm == "push" else "duplicate_commit_prevented"
-
-    return {
-        "allowed": allowed,
-        "block": not allowed,
-        "eligibility_class": eligibility if not allowed else ELIGIBILITY_CLEAR,
-        "stage": stage_norm,
-        "linked_open_pr": linked_pr.get("number") if linked_pr else None,
-        "matching_branches": branches,
-        "claim_status": claim_status or None,
-        "outcome": outcome,
-        "reasons": reasons,
-        "safe_next_action": (
-            "stop without edits/commit/push/PR; produce reconciliation handoff "
-            "preserving local work only"
-            if not allowed
-            else "proceed"
-        ),
-    }
-
-
-def build_claim_entry_from_classification(classification: dict) -> dict:
-    """Map ``classify_issue_claim`` output to gate claim metadata."""
-    return {
-        "status": classification.get("status"),
-        "reclaimable": classification.get("reclaimable"),
-        "linked_open_pr": classification.get("linked_open_pr"),
-    }
-
-
-_DUPLICATE_OUTCOME_RE = re.compile(
-    r"(duplicate\s+(?:pr|branch|commit|push)\s+prevented|"
-    r"duplicate\s+work\s+not\s+prevented|reconciliation\s+handoff)",
-    re.IGNORECASE,
-)
-
-
-def assess_work_issue_duplicate_prevention_report(report_text: str) -> dict:
-    """#400: work-issue reports must state duplicate-work prevention outcome."""
-    text = report_text or ""
-    if "duplicate work" not in text.lower() and "duplicate pr" not in text.lower():
-        return {
-            "proven": True,
-            "block": False,
-            "reasons": [],
-            "safe_next_action": "proceed",
-        }
-    if _DUPLICATE_OUTCOME_RE.search(text):
-        return {
-            "proven": True,
-            "block": False,
-            "reasons": [],
-            "safe_next_action": "proceed",
-        }
-    return {
-        "proven": False,
-        "block": True,
-        "reasons": [
-            "duplicate-work discussion must name a prevention outcome "
-            "(duplicate PR/branch/commit/push prevented, or duplicate work "
-            "not prevented, or reconciliation handoff)"
-        ],
-        "safe_next_action": "state exact duplicate-work prevention class in final report",
-    }
-
-
-def classify_and_assess(
-    issue: dict,
-    *,
-    stage: str,
-    comments: list[dict] | None = None,
-    open_prs: list[dict] | None = None,
-    branch_names: list[str] | None = None,
-    allow_stale_takeover: bool = False,
-) -> dict[str, Any]:
-    """Combine claim classification with duplicate-work gate assessment."""
-    issue_number = int(issue.get("number") or 0)
-    claim = classify_issue_claim(
-        issue=issue,
-        comments=comments or [],
-        open_prs=open_prs or [],
-        branch_names=branch_names or [],
-    )
-    assessment = assess_author_duplicate_work(
-        issue_number,
-        stage=stage,
-        open_prs=open_prs,
-        branch_names=branch_names,
-        claim_entry=build_claim_entry_from_classification(claim),
-        matching_branches=claim.get("matching_branches"),
-        allow_stale_takeover=allow_stale_takeover,
-    )
-    return {
-        "issue_number": issue_number,
-        "claim": claim,
-        "duplicate_work": assessment,
-    }

gitea_mcp_server.py

@@ -503,7 +503,7 @@ import issue_lock_worktree  # noqa: E402
 import already_landed_reconcile  # noqa: E402
 import author_mutation_worktree  # noqa: E402
 import issue_claim_heartbeat  # noqa: E402
-import author_duplicate_work_gate  # noqa: E402
+import reviewer_pr_lease  # noqa: E402
 import merged_cleanup_reconcile  # noqa: E402
 import reconciler_profile  # noqa: E402
 import reconciliation_workflow  # noqa: E402
@@ -1050,76 +1050,6 @@ def gitea_create_issue(
     return _with_optional_url({"number": data["number"]}, data.get("html_url"))
 
 
-def _list_repo_branch_names(h: str, o: str, r: str, auth: str, *, limit: int = 200) -> list[str]:
-    branches = api_get_all(f"{repo_api_url(h, o, r)}/branches", auth, limit=limit)
-    return [_branch_entry_name(branch) for branch in branches]
-
-
-def _gather_author_duplicate_work_context(
-    issue_number: int,
-    *,
-    h: str,
-    o: str,
-    r: str,
-    auth: str,
-    exclude_branch_name: str | None = None,
-) -> dict:
-    base = repo_api_url(h, o, r)
-    issue = api_request("GET", f"{base}/issues/{issue_number}", auth)
-    comments = api_request("GET", f"{base}/issues/{issue_number}/comments", auth) or []
-    open_prs = api_get_all(f"{base}/pulls?state=open", auth)
-    branch_names = _list_repo_branch_names(h, o, r, auth)
-    if exclude_branch_name:
-        branch_names = [
-            name for name in branch_names
-            if name != exclude_branch_name
-        ]
-    return {
-        "issue": issue,
-        "comments": comments,
-        "open_prs": open_prs,
-        "branch_names": branch_names,
-    }
-
-
-def _enforce_author_duplicate_work_gate(
-    issue_number: int,
-    stage: str,
-    *,
-    h: str,
-    o: str,
-    r: str,
-    auth: str,
-    allow_stale_takeover: bool = False,
-    exclude_branch_name: str | None = None,
-) -> dict:
-    """Fail closed when duplicate work is detected (#400)."""
-    ctx = _gather_author_duplicate_work_context(
-        issue_number,
-        h=h,
-        o=o,
-        r=r,
-        auth=auth,
-        exclude_branch_name=exclude_branch_name,
-    )
-    result = author_duplicate_work_gate.classify_and_assess(
-        ctx["issue"],
-        stage=stage,
-        comments=ctx["comments"],
-        open_prs=ctx["open_prs"],
-        branch_names=ctx["branch_names"],
-        allow_stale_takeover=allow_stale_takeover,
-    )
-    assessment = result.get("duplicate_work") or {}
-    if assessment.get("block"):
-        reasons = "; ".join(assessment.get("reasons") or ["duplicate work detected"])
-        raise RuntimeError(
-            f"Author duplicate-work gate (#400) blocked at stage '{stage}': "
-            f"{reasons} (fail closed)"
-        )
-    return result
-
-
 @mcp.tool()
 def gitea_lock_issue(
     issue_number: int,
@@ -1182,17 +1112,48 @@ def gitea_lock_issue(
             issue_lock_worktree.format_issue_lock_worktree_error(lock_assessment)
         )
 
+    # 2. Check if the issue already has an open PR (reuse protection)
     h, o, r = _resolve(remote, host, org, repo)
     auth = _auth(h)
-    _enforce_author_duplicate_work_gate(
-        issue_number,
-        "lock",
-        h=h,
-        o=o,
-        r=r,
-        auth=auth,
-        exclude_branch_name=branch_name,
-    )
+    url = f"{repo_api_url(h, o, r)}/pulls?state=open"
+
+    try:
+        prs = api_get_all(url, auth)
+    except Exception as e:
+        raise RuntimeError(f"Could not list open PRs to verify issue lock: {e}")
+
+    for pr in prs:
+        pr_head = pr.get("head", {}).get("ref", "")
+        pr_title = pr.get("title", "")
+        pr_body = pr.get("body", "")
+
+        if expected_pattern in pr_head:
+            raise ValueError(
+                f"Issue #{issue_number} is already tied to an open PR (PR #{pr.get('number')}, branch '{pr_head}') (fail closed)"
+            )
+
+        patterns = [
+            f"closes #{issue_number}",
+            f"fixes #{issue_number}",
+        ]
+        text_to_check = f"{pr_title} {pr_body}".lower()
+        if any(p in text_to_check for p in patterns):
+            raise ValueError(
+                f"Issue #{issue_number} is already tied to an open PR (PR #{pr.get('number')}) via Closes/Fixes reference (fail closed)"
+            )
+
+    branch_url = f"{repo_api_url(h, o, r)}/branches"
+    try:
+        branches = api_get_all(branch_url, auth)
+    except Exception as e:
+        raise RuntimeError(f"Could not list branches to verify issue lock: {e}")
+    for branch in branches:
+        name = _branch_entry_name(branch)
+        if expected_pattern in name:
+            raise ValueError(
+                f"Issue #{issue_number} already has matching branch '{name}' "
+                "(fail closed)"
+            )
 
     work_lease = _build_author_issue_work_lease(
         issue_number=issue_number,
@@ -1313,17 +1274,6 @@ def gitea_create_pr(
             f"PR head branch '{head}' does not match locked branch '{locked_branch}' (fail closed)"
         )
 
-    auth = _auth(h)
-    _enforce_author_duplicate_work_gate(
-        int(locked_issue),
-        "create_pr",
-        h=h,
-        o=o,
-        r=r,
-        auth=auth,
-        exclude_branch_name=locked_branch,
-    )
-
     # Check for forbidden terms anywhere in title/body
     forbidden_terms = ["equivalent", "related", "same as"]
     text_to_check = f"{title} {body}".lower()
@@ -1340,6 +1290,7 @@ def gitea_create_pr(
             f"PR title or body must contain 'Closes #{locked_issue}' or 'Fixes #{locked_issue}' exactly to ensure durable tracking (fail closed)"
         )
 
+    auth = _auth(h)
     url = f"{repo_api_url(h, o, r)}/pulls"
     payload = {"title": title, "body": body, "head": head, "base": base}
     meta = {"title": title, "head": head, "base": base}
@@ -1878,6 +1829,7 @@ def init_review_decision_lock(remote: str | None, task: str | None):
         (os.environ.get(SESSION_PROFILE_LOCK_ENV) or "").strip()
         or profile_name
     )
+    reviewer_pr_lease.clear_session_lease()
     _save_review_decision_lock({
         "task": task,
         "remote": remote,
@@ -2320,6 +2272,20 @@ def _evaluate_pr_review_submission(
             result["permission_report"] = elig["permission_report"]
         return result
 
+    if live:
+        reasons.extend(_reviewer_pr_lease_gate(
+            pr_number=pr_number,
+            remote=remote,
+            host=host,
+            org=org,
+            repo=repo,
+            mutation=action,
+            live_head_sha=result.get("head_sha"),
+            pinned_head_sha=expected_head_sha,
+        ))
+        if reasons:
+            return result
+
     auth_user = result["authenticated_user"]
     pr_author = result["pr_author"]
     if action == "approve" and auth_user and pr_author and auth_user == pr_author:
@@ -3105,6 +3071,19 @@ def gitea_merge_pr(
             result["permission_report"] = elig["permission_report"]
         return result
 
+    reasons.extend(_reviewer_pr_lease_gate(
+        pr_number=pr_number,
+        remote=remote,
+        host=host,
+        org=org,
+        repo=repo,
+        mutation="merge",
+        live_head_sha=result.get("head_sha"),
+        pinned_head_sha=expected_head_sha,
+    ))
+    if reasons:
+        return result
+
     # Gate 4 — head SHA must match if the caller pinned a reviewed SHA.
     actual_sha = result["head_sha"]
     if expected_head_sha and actual_sha and expected_head_sha != actual_sha:
@@ -4404,6 +4383,261 @@ def _namespace_mutation_block(mutation_task: str, **extra_fields) -> dict | None
     return blocked
 
 
+def _fetch_pr_comments(
+    pr_number: int,
+    *,
+    remote: str,
+    host: str | None,
+    org: str | None,
+    repo: str | None,
+) -> list[dict]:
+    h, o, r = _resolve(remote, host, org, repo)
+    auth = _auth(h)
+    api = f"{repo_api_url(h, o, r)}/issues/{pr_number}/comments"
+    return api_request("GET", api, auth) or []
+
+
+def _reviewer_pr_lease_gate(
+    *,
+    pr_number: int,
+    remote: str,
+    host: str | None,
+    org: str | None,
+    repo: str | None,
+    mutation: str,
+    live_head_sha: str | None,
+    pinned_head_sha: str | None,
+) -> list[str]:
+    """Return block reasons when the session lacks an owned PR reviewer lease."""
+    session = reviewer_pr_lease.get_session_lease()
+    session_id = (session or {}).get("session_id")
+    identity = _authenticated_username(remote) or ""
+    try:
+        comments = _fetch_pr_comments(
+            pr_number, remote=remote, host=host, org=org, repo=repo)
+    except Exception as exc:
+        return [f"cannot fetch PR comments for lease gate: {_redact(str(exc))}"]
+    assessment = reviewer_pr_lease.assess_mutation_lease_gate(
+        pr_number=pr_number,
+        comments=comments,
+        reviewer_identity=identity,
+        session_id=session_id,
+        mutation=mutation,
+        live_head_sha=live_head_sha,
+        pinned_head_sha=pinned_head_sha,
+    )
+    return list(assessment.get("reasons") or []) if assessment.get("block") else []
+
+
+@mcp.tool()
+def gitea_acquire_reviewer_pr_lease(
+    pr_number: int,
+    worktree: str,
+    candidate_head: str | None = None,
+    target_branch: str = "master",
+    target_branch_sha: str | None = None,
+    issue_number: int | None = None,
+    session_id: str | None = None,
+    remote: str = "dadeschools",
+    host: str | None = None,
+    org: str | None = None,
+    repo: str | None = None,
+) -> dict:
+    """Acquire a per-PR reviewer lease before review/merge mutations (#407)."""
+    read_block = _profile_operation_gate("gitea.read")
+    if read_block:
+        return {
+            "success": False,
+            "acquired": False,
+            "reasons": read_block,
+            "permission_report": _permission_block_report("gitea.read"),
+        }
+    comment_block = _profile_operation_gate("gitea.pr.comment")
+    if comment_block:
+        return {
+            "success": False,
+            "acquired": False,
+            "reasons": comment_block,
+            "permission_report": _permission_block_report("gitea.pr.comment"),
+        }
+
+    verify_preflight_purity(remote)
+    h, o, r = _resolve(remote, host, org, repo)
+    auth = _auth(h)
+    profile = get_profile()
+    identity = _authenticated_username(remote) or profile.get("username") or ""
+    sid = (session_id or "").strip() or reviewer_pr_lease.new_session_id()
+    repo_label = f"{o}/{r}"
+
+    comments = _fetch_pr_comments(
+        pr_number, remote=remote, host=host, org=org, repo=repo)
+    assessment = reviewer_pr_lease.assess_acquire_lease(
+        comments,
+        pr_number=pr_number,
+        reviewer_identity=identity,
+        profile=profile.get("profile_name") or "unknown",
+        session_id=sid,
+        repo=repo_label,
+        issue_number=issue_number,
+        worktree=worktree,
+        candidate_head=candidate_head,
+        target_branch=target_branch,
+        target_branch_sha=target_branch_sha,
+    )
+    if not assessment.get("acquire_allowed"):
+        return {
+            "success": False,
+            "acquired": False,
+            "reasons": assessment.get("reasons") or [],
+            "existing_lease": assessment.get("existing_lease"),
+        }
+
+    body = assessment["lease_body"]
+    comment_url = f"{repo_api_url(h, o, r)}/issues/{pr_number}/comments"
+    with _audited(
+        "comment_pr",
+        host=h,
+        remote=remote,
+        org=o,
+        repo=r,
+        pr_number=pr_number,
+        request_metadata={"source": "acquire_reviewer_pr_lease"},
+    ):
+        posted = api_request("POST", comment_url, auth, {"body": body})
+
+    session_lease = reviewer_pr_lease.record_session_lease({
+        "pr_number": pr_number,
+        "issue_number": issue_number,
+        "session_id": sid,
+        "reviewer_identity": identity,
+        "profile": profile.get("profile_name"),
+        "worktree": worktree,
+        "phase": "claimed",
+        "candidate_head": candidate_head,
+        "target_branch": target_branch,
+        "target_branch_sha": target_branch_sha,
+        "repo": repo_label,
+        "comment_id": posted.get("id"),
+    })
+    return {
+        "success": True,
+        "acquired": True,
+        "pr_number": pr_number,
+        "session_id": sid,
+        "comment_id": posted.get("id"),
+        "session_lease": session_lease,
+        "reasons": [],
+    }
+
+
+@mcp.tool()
+def gitea_heartbeat_reviewer_pr_lease(
+    pr_number: int,
+    phase: str,
+    worktree: str | None = None,
+    candidate_head: str | None = None,
+    target_branch_sha: str | None = None,
+    remote: str = "dadeschools",
+    host: str | None = None,
+    org: str | None = None,
+    repo: str | None = None,
+) -> dict:
+    """Post a reviewer lease heartbeat / phase update on the PR thread (#407)."""
+    comment_block = _profile_operation_gate("gitea.pr.comment")
+    if comment_block:
+        return {
+            "success": False,
+            "posted": False,
+            "reasons": comment_block,
+            "permission_report": _permission_block_report("gitea.pr.comment"),
+        }
+    session = reviewer_pr_lease.get_session_lease()
+    if not session or session.get("pr_number") != pr_number:
+        return {
+            "success": False,
+            "posted": False,
+            "reasons": [
+                f"no in-session lease for PR #{pr_number}; acquire first "
+                "(fail closed)"
+            ],
+        }
+
+    verify_preflight_purity(remote)
+    h, o, r = _resolve(remote, host, org, repo)
+    auth = _auth(h)
+    body = reviewer_pr_lease.format_lease_body(
+        repo=f"{o}/{r}",
+        pr_number=pr_number,
+        issue_number=session.get("issue_number"),
+        reviewer_identity=session.get("reviewer_identity") or "",
+        profile=session.get("profile") or "unknown",
+        session_id=session.get("session_id") or reviewer_pr_lease.new_session_id(),
+        worktree=worktree or session.get("worktree") or "",
+        phase=phase,
+        candidate_head=candidate_head or session.get("candidate_head"),
+        target_branch=session.get("target_branch") or "master",
+        target_branch_sha=target_branch_sha or session.get("target_branch_sha"),
+    )
+    comment_url = f"{repo_api_url(h, o, r)}/issues/{pr_number}/comments"
+    with _audited(
+        "comment_pr",
+        host=h,
+        remote=remote,
+        org=o,
+        repo=r,
+        pr_number=pr_number,
+        request_metadata={"source": "heartbeat_reviewer_pr_lease", "phase": phase},
+    ):
+        posted = api_request("POST", comment_url, auth, {"body": body})
+
+    updated = reviewer_pr_lease.record_session_lease({
+        **session,
+        "phase": phase,
+        "worktree": worktree or session.get("worktree"),
+        "candidate_head": candidate_head or session.get("candidate_head"),
+        "target_branch_sha": target_branch_sha or session.get("target_branch_sha"),
+        "last_comment_id": posted.get("id"),
+    })
+    return {
+        "success": True,
+        "posted": True,
+        "pr_number": pr_number,
+        "phase": phase,
+        "comment_id": posted.get("id"),
+        "session_lease": updated,
+        "reasons": [],
+    }
+
+
+@mcp.tool()
+def gitea_assess_reviewer_pr_lease(
+    pr_number: int,
+    remote: str = "dadeschools",
+    host: str | None = None,
+    org: str | None = None,
+    repo: str | None = None,
+) -> dict:
+    """Read-only: assess active reviewer lease state for a PR (#407)."""
+    read_block = _profile_operation_gate("gitea.read")
+    if read_block:
+        return {
+            "success": False,
+            "reasons": read_block,
+            "permission_report": _permission_block_report("gitea.read"),
+        }
+    comments = _fetch_pr_comments(
+        pr_number, remote=remote, host=host, org=org, repo=repo)
+    active = reviewer_pr_lease.find_active_reviewer_lease(
+        comments, pr_number=pr_number)
+    return {
+        "success": True,
+        "pr_number": pr_number,
+        "active_lease": active,
+        "session_lease": reviewer_pr_lease.get_session_lease(),
+        "reasons": [],
+    }
+
+
 @mcp.tool()
 def gitea_list_issue_comments(
     issue_number: int,
@@ -6053,14 +6287,6 @@ def gitea_mark_issue(
         )
 
     if action == "start":
-        _enforce_author_duplicate_work_gate(
-            issue_number,
-            "claim",
-            h=h,
-            o=o,
-            r=r,
-            auth=auth,
-        )
         with _audited("label_issue", host=h, remote=remote, org=o, repo=r,
                       issue_number=issue_number,
                       request_metadata={"op": "add", "label": "status:in-progress"}):
@@ -6142,65 +6368,6 @@ def gitea_post_heartbeat(
     )
 
 
-@mcp.tool()
-def gitea_assess_author_duplicate_work(
-    issue_number: int,
-    stage: str,
-    remote: str = "dadeschools",
-    host: str | None = None,
-    org: str | None = None,
-    repo: str | None = None,
-    allow_stale_takeover: bool = False,
-    exclude_branch_name: str | None = None,
-) -> dict:
-    """Read-only: assess duplicate-work risk before author mutations (#400).
-
-    Call at claim, lock, worktree, edit, commit, push, and create_pr stages.
-    """
-    read_block = _profile_operation_gate("gitea.read")
-    if read_block:
-        return {
-            "success": False,
-            "reasons": read_block,
-            "permission_report": _permission_block_report("gitea.read"),
-        }
-    h, o, r = _resolve(remote, host, org, repo)
-    auth = _auth(h)
-    ctx = _gather_author_duplicate_work_context(
-        issue_number,
-        h=h,
-        o=o,
-        r=r,
-        auth=auth,
-        exclude_branch_name=exclude_branch_name,
-    )
-    result = author_duplicate_work_gate.classify_and_assess(
-        ctx["issue"],
-        stage=stage,
-        comments=ctx["comments"],
-        open_prs=ctx["open_prs"],
-        branch_names=ctx["branch_names"],
-        allow_stale_takeover=allow_stale_takeover,
-    )
-    assessment = result.get("duplicate_work") or {}
-    return {
-        "success": True,
-        "performed": False,
-        "issue_number": issue_number,
-        "stage": stage,
-        "allowed": assessment.get("allowed"),
-        "block": assessment.get("block"),
-        "eligibility_class": assessment.get("eligibility_class"),
-        "outcome": assessment.get("outcome"),
-        "linked_open_pr": assessment.get("linked_open_pr"),
-        "matching_branches": assessment.get("matching_branches"),
-        "claim_status": assessment.get("claim_status"),
-        "reasons": assessment.get("reasons"),
-        "safe_next_action": assessment.get("safe_next_action"),
-        "claim": result.get("claim"),
-    }
-
-
 @mcp.tool()
 def gitea_reconcile_issue_claims(
     state: str = "open",

review_proofs.py

@@ -3622,33 +3622,18 @@ def assess_work_issue_mode_isolation(report_text: str) -> dict:
     }
 
 
-def assess_work_issue_duplicate_prevention_report(report_text, **kwargs):
-    """#400: work-issue reports must classify duplicate-work prevention."""
-    from author_duplicate_work_gate import (
-        assess_work_issue_duplicate_prevention_report as _assess,
-    )
-
-    return _assess(report_text, **kwargs)
-
-
 def assess_work_issue_final_report(report_text: str) -> dict:
     """#139: composite verifier for work-issue final reports."""
     checks = {
         "workflow_source": assess_work_issue_workflow_source(report_text),
         "mode_isolation": assess_work_issue_mode_isolation(report_text),
-        "duplicate_prevention": assess_work_issue_duplicate_prevention_report(
-            report_text
-        ),
     }
 
     reasons = []
     downgraded = False
     for name, result in checks.items():
         verdict = result.get("verdict")
-        if result.get("block"):
-            downgraded = True
-            reasons.extend(result.get("reasons") or [])
-        elif verdict in ("missing", "incomplete"):
+        if verdict in ("missing", "incomplete"):
             downgraded = True
             reasons.extend(result.get("reasons") or [])
         elif result.get("downgraded") or not result.get("complete", True):
@@ -3656,9 +3641,6 @@ def assess_work_issue_final_report(report_text: str) -> dict:
             reasons.extend(
                 f"{name}: {r}" for r in (result.get("reasons") or [])
             )
-        elif result.get("proven") is False:
-            downgraded = True
-            reasons.extend(result.get("reasons") or [])
 
     grade = "A" if not downgraded else "downgraded"
     return {

reviewer_pr_lease.py

@@ -0,0 +1,382 @@
+"""Per-PR reviewer leases for safe parallel review sessions (#407)."""
+
+from __future__ import annotations
+
+import os
+import re
+import uuid
+from datetime import datetime, timedelta, timezone
+from typing import Any
+
+MARKER = "<!-- mcp-review-lease:v1 -->"
+
+_FIELD_RE = re.compile(
+    r"^\s*([a-z_]+)\s*:\s*(.+?)\s*$",
+    re.IGNORECASE | re.MULTILINE,
+)
+_FULL_SHA = re.compile(r"^[0-9a-f]{40}$", re.IGNORECASE)
+
+_TERMINAL_PHASES = frozenset({"done", "released", "blocked"})
+_ACTIVE_PHASES = frozenset({
+    "claimed",
+    "validating",
+    "approved",
+    "request-changes",
+    "merging",
+})
+
+DEFAULT_LEASE_TTL_MINUTES = 120
+STALE_WARNING_MINUTES = 30
+RECLAIMABLE_MINUTES = 60
+
+_SESSION_LEASE: dict[str, Any] | None = None
+
+
+def _parse_timestamp(value: str | None) -> datetime | None:
+    if not value:
+        return None
+    text = value.strip()
+    if text.endswith("Z"):
+        text = text[:-1] + "+00:00"
+    try:
+        parsed = datetime.fromisoformat(text)
+    except ValueError:
+        return None
+    if parsed.tzinfo is None:
+        return parsed.replace(tzinfo=timezone.utc)
+    return parsed.astimezone(timezone.utc)
+
+
+def _normalize_sha(value: str | None) -> str | None:
+    text = (value or "").strip().lower()
+    return text if text and _FULL_SHA.match(text) else None
+
+
+def _parse_pr_ref(value: str | None) -> int | None:
+    digits = re.sub(r"[^\d]", "", value or "")
+    return int(digits) if digits.isdigit() else None
+
+
+def new_session_id() -> str:
+    return f"{os.getpid()}-{uuid.uuid4().hex[:12]}"
+
+
+def format_lease_body(
+    *,
+    repo: str,
+    pr_number: int,
+    issue_number: int | None,
+    reviewer_identity: str,
+    profile: str,
+    session_id: str,
+    worktree: str,
+    phase: str,
+    candidate_head: str | None,
+    target_branch: str,
+    target_branch_sha: str | None,
+    last_activity: datetime | None = None,
+    expires_at: datetime | None = None,
+    blocker: str = "none",
+) -> str:
+    now = last_activity or datetime.now(timezone.utc)
+    expires = expires_at or (now + timedelta(minutes=DEFAULT_LEASE_TTL_MINUTES))
+    last_text = now.astimezone(timezone.utc).replace(microsecond=0).isoformat().replace(
+        "+00:00", "Z"
+    )
+    expires_text = expires.astimezone(timezone.utc).replace(microsecond=0).isoformat().replace(
+        "+00:00", "Z"
+    )
+    issue_text = f"#{issue_number}" if issue_number else "none"
+    lines = [
+        MARKER,
+        f"repo: {repo}",
+        f"pr: #{pr_number}",
+        f"issue: {issue_text}",
+        f"reviewer_identity: {reviewer_identity}",
+        f"profile: {profile}",
+        f"session_id: {session_id}",
+        f"worktree: {worktree}",
+        f"phase: {phase}",
+        f"candidate_head: {candidate_head or 'none'}",
+        f"target_branch: {target_branch}",
+        f"target_branch_sha: {target_branch_sha or 'none'}",
+        f"last_activity: {last_text}",
+        f"expires_at: {expires_text}",
+        f"blocker: {blocker}",
+    ]
+    return "\n".join(lines)
+
+
+def parse_lease_comment(body: str) -> dict[str, Any] | None:
+    text = body or ""
+    if MARKER not in text:
+        return None
+    fields: dict[str, str] = {}
+    for match in _FIELD_RE.finditer(text):
+        fields[match.group(1).strip().lower()] = match.group(2).strip()
+    if not fields:
+        return None
+    return {
+        "repo": fields.get("repo"),
+        "pr_number": _parse_pr_ref(fields.get("pr")),
+        "issue_number": _parse_pr_ref(fields.get("issue")),
+        "reviewer_identity": fields.get("reviewer_identity"),
+        "profile": fields.get("profile"),
+        "session_id": fields.get("session_id"),
+        "worktree": fields.get("worktree"),
+        "phase": (fields.get("phase") or "").strip().lower() or None,
+        "candidate_head": _normalize_sha(fields.get("candidate_head")),
+        "target_branch": fields.get("target_branch"),
+        "target_branch_sha": _normalize_sha(fields.get("target_branch_sha")),
+        "last_activity": fields.get("last_activity"),
+        "expires_at": fields.get("expires_at"),
+        "blocker": fields.get("blocker"),
+        "raw_fields": fields,
+    }
+
+
+def _lease_entries(comments: list[dict], *, pr_number: int) -> list[dict]:
+    entries: list[dict] = []
+    for comment in comments or []:
+        parsed = parse_lease_comment(comment.get("body") or "")
+        if not parsed:
+            continue
+        if parsed.get("pr_number") not in (None, pr_number):
+            continue
+        entries.append({
+            **parsed,
+            "comment_id": comment.get("id"),
+            "author": (comment.get("user") or {}).get("login") or comment.get("author"),
+            "created_at": comment.get("created_at"),
+            "updated_at": comment.get("updated_at"),
+        })
+    return entries
+
+
+def _lease_expired(lease: dict, *, now: datetime) -> bool:
+    expires_at = _parse_timestamp(lease.get("expires_at"))
+    return bool(expires_at and expires_at <= now)
+
+
+def _minutes_since_activity(lease: dict, *, now: datetime) -> float | None:
+    last = _parse_timestamp(lease.get("last_activity"))
+    if not last:
+        return None
+    return (now - last).total_seconds() / 60.0
+
+
+def classify_lease_freshness(lease: dict, *, now: datetime | None = None) -> str:
+    """Return active, stale_warning, reclaimable, expired, or terminal."""
+    now = now or datetime.now(timezone.utc)
+    phase = (lease.get("phase") or "").strip().lower()
+    if phase in _TERMINAL_PHASES:
+        return "terminal"
+    if _lease_expired(lease, now=now):
+        return "expired"
+    minutes = _minutes_since_activity(lease, now=now)
+    if minutes is None:
+        return "active"
+    if minutes >= RECLAIMABLE_MINUTES:
+        return "reclaimable"
+    if minutes >= STALE_WARNING_MINUTES:
+        return "stale_warning"
+    return "active"
+
+
+def find_active_reviewer_lease(
+    comments: list[dict],
+    *,
+    pr_number: int,
+    now: datetime | None = None,
+) -> dict[str, Any] | None:
+    """Newest non-terminal, unexpired lease for *pr_number*."""
+    now = now or datetime.now(timezone.utc)
+    for lease in reversed(_lease_entries(comments, pr_number=pr_number)):
+        phase = (lease.get("phase") or "").strip().lower()
+        if phase in _TERMINAL_PHASES:
+            continue
+        if _lease_expired(lease, now=now):
+            continue
+        if phase in _ACTIVE_PHASES or phase:
+            lease = dict(lease)
+            lease["freshness"] = classify_lease_freshness(lease, now=now)
+            return lease
+    return None
+
+
+def assess_acquire_lease(
+    comments: list[dict],
+    *,
+    pr_number: int,
+    reviewer_identity: str,
+    profile: str,
+    session_id: str,
+    repo: str,
+    issue_number: int | None,
+    worktree: str,
+    candidate_head: str | None,
+    target_branch: str,
+    target_branch_sha: str | None,
+    now: datetime | None = None,
+) -> dict[str, Any]:
+    """Fail closed when another session holds an active lease."""
+    now = now or datetime.now(timezone.utc)
+    reasons: list[str] = []
+    existing = find_active_reviewer_lease(comments, pr_number=pr_number, now=now)
+    if existing:
+        owner_session = (existing.get("session_id") or "").strip()
+        freshness = existing.get("freshness") or classify_lease_freshness(existing, now=now)
+        if owner_session and owner_session != session_id and freshness in {
+            "active", "stale_warning"
+        }:
+            reasons.append(
+                f"PR #{pr_number} already has active reviewer lease "
+                f"(session_id={owner_session}, phase={existing.get('phase')})"
+            )
+        elif owner_session and owner_session != session_id and freshness == "reclaimable":
+            reasons.append(
+                f"PR #{pr_number} lease is reclaimable but still held by "
+                f"session_id={owner_session}; explicit reclaim not implemented "
+                "(fail closed)"
+            )
+
+    if not (reviewer_identity or "").strip():
+        reasons.append("reviewer identity required for lease acquisition")
+    if not (session_id or "").strip():
+        reasons.append("session_id required for lease acquisition")
+    if not (worktree or "").strip():
+        reasons.append("worktree path required for lease acquisition")
+
+    allowed = not reasons
+    body = None
+    if allowed:
+        body = format_lease_body(
+            repo=repo,
+            pr_number=pr_number,
+            issue_number=issue_number,
+            reviewer_identity=reviewer_identity,
+            profile=profile,
+            session_id=session_id,
+            worktree=worktree,
+            phase="claimed",
+            candidate_head=candidate_head,
+            target_branch=target_branch,
+            target_branch_sha=target_branch_sha,
+            last_activity=now,
+        )
+    return {
+        "acquire_allowed": allowed,
+        "reasons": reasons,
+        "existing_lease": existing,
+        "lease_body": body,
+        "session_id": session_id,
+    }
+
+
+def record_session_lease(lease: dict[str, Any]) -> dict[str, Any]:
+    global _SESSION_LEASE
+    _SESSION_LEASE = dict(lease)
+    return dict(_SESSION_LEASE)
+
+
+def clear_session_lease() -> None:
+    global _SESSION_LEASE
+    _SESSION_LEASE = None
+
+
+def get_session_lease() -> dict[str, Any] | None:
+    return dict(_SESSION_LEASE) if _SESSION_LEASE else None
+
+
+def assess_mutation_lease_gate(
+    *,
+    pr_number: int,
+    comments: list[dict],
+    reviewer_identity: str,
+    session_id: str | None,
+    mutation: str,
+    live_head_sha: str | None,
+    pinned_head_sha: str | None,
+    now: datetime | None = None,
+) -> dict[str, Any]:
+    """Reviewer mutations require an owned, current PR lease."""
+    now = now or datetime.now(timezone.utc)
+    reasons: list[str] = []
+    session = get_session_lease()
+    active = find_active_reviewer_lease(comments, pr_number=pr_number, now=now)
+
+    if not session:
+        reasons.append(
+            f"no in-session reviewer lease recorded; acquire via "
+            f"gitea_acquire_reviewer_pr_lease before {mutation}"
+        )
+    elif session.get("pr_number") != pr_number:
+        reasons.append(
+            f"session lease is for PR #{session.get('pr_number')}, not #{pr_number}"
+        )
+    elif (session.get("session_id") or "") != (session_id or session.get("session_id")):
+        reasons.append("session lease session_id mismatch (fail closed)")
+
+    if active:
+        owner = (active.get("session_id") or "").strip()
+        if owner and session_id and owner != session_id:
+            reasons.append(
+                f"active PR lease owned by session_id={owner}; current session "
+                f"cannot {mutation}"
+            )
+        pinned = _normalize_sha(pinned_head_sha)
+        live = _normalize_sha(live_head_sha)
+        lease_head = active.get("candidate_head")
+        if pinned and live and pinned != live:
+            reasons.append(
+                "PR head changed during lease; stop and re-validate before "
+                f"reviewer {mutation}"
+            )
+        if lease_head and live and lease_head != live:
+            reasons.append(
+                "live PR head differs from lease candidate_head; refresh lease "
+                f"before {mutation}"
+            )
+        freshness = active.get("freshness") or classify_lease_freshness(active, now=now)
+        if freshness in {"expired", "reclaimable"}:
+            reasons.append(f"reviewer lease freshness is '{freshness}' (fail closed)")
+    else:
+        reasons.append(f"no active reviewer lease found on PR #{pr_number}")
+
+    allowed = not reasons
+    return {
+        "mutation_allowed": allowed,
+        "block": not allowed,
+        "reasons": reasons,
+        "active_lease": active,
+        "session_lease": session,
+    }
+
+
+def assess_lease_inventory(
+    comments_by_pr: dict[int, list[dict]],
+    *,
+    now: datetime | None = None,
+) -> dict[str, Any]:
+    """Summarize lease states across PR comment threads."""
+    now = now or datetime.now(timezone.utc)
+    active: list[dict] = []
+    stale: list[dict] = []
+    reclaimable: list[dict] = []
+    for pr_number, comments in (comments_by_pr or {}).items():
+        lease = find_active_reviewer_lease(comments, pr_number=pr_number, now=now)
+        if not lease:
+            continue
+        freshness = lease.get("freshness") or classify_lease_freshness(lease, now=now)
+        entry = {"pr_number": pr_number, "session_id": lease.get("session_id"), "freshness": freshness}
+        if freshness == "stale_warning":
+            stale.append(entry)
+        elif freshness == "reclaimable":
+            reclaimable.append(entry)
+        else:
+            active.append(entry)
+    return {
+        "active_review_leases": active,
+        "stale_review_leases": stale,
+        "reclaimable_review_leases": reclaimable,
+    }

skills/llm-project-workflow/workflows/review-merge-pr.md

@@ -732,6 +732,26 @@ The final report must identify:
 * whether same-PR merge continuation was allowed
 * whether the run stopped as required
 
+## 26B. Per-PR reviewer lease (#407)
+
+Parallel reviewer sessions are allowed only when each session holds a distinct,
+live PR lease.
+
+Before validation or review mutation on a selected PR:
+
+1. Call `gitea_acquire_reviewer_pr_lease` with worktree path, candidate head SHA,
+   and target branch SHA.
+2. Post heartbeats via `gitea_heartbeat_reviewer_pr_lease` before validation,
+   after validation, before review mutation, and before merge.
+3. Do not approve, request changes, or merge unless the in-session lease
+   matches the selected PR.
+
+If PR head or target branch advances during the lease, stop and refresh
+inventory before continuing.
+
+Final reports must include lease session id, acquisition proof, heartbeat
+status, and release/blocked status.
+
 ## 27. Merge rules
 
 Before merge, rerun fresh live checks:

skills/llm-project-workflow/workflows/work-issue.md

@@ -277,24 +277,6 @@ Do not select an issue based only on memory from a previous session.
 
 Before claiming or working on an issue, check whether there is already an open PR, branch, or active claim for that issue.
 
-Run `gitea_assess_author_duplicate_work` at these stages and stop when `block` is true:
-
-* `claim` — before `gitea_mark_issue`
-* `lock` — before `gitea_lock_issue`
-* `worktree` / `edit` — before creating a worktree or editing files
-* `commit` — immediately before `git commit`
-* `push` — immediately before `git push`
-* `create_pr` — immediately before `gitea_create_pr` (also enforced server-side)
-
-`gitea_mark_issue`, `gitea_lock_issue`, and `gitea_create_pr` enforce the same gate server-side and fail closed.
-
-If a concurrent open PR appears after work begins:
-
-* before commit or push — stop and preserve local work without pushing
-* after push but before PR creation — produce a reconciliation handoff instead of opening a PR
-
-Final reports must name the duplicate-work outcome (`duplicate PR prevented`, `duplicate branch prevented`, `duplicate commit prevented`, `duplicate push prevented`, `duplicate work not prevented`, or `reconciliation handoff`).
-
 If an open PR already exists for the issue, do not implement duplicate work.
 
 Classify the issue as:

tests/test_audit.py

@@ -286,6 +286,21 @@ class TestSimpleToolAudit(_AuditWiringBase):
 
 class TestGatedToolAudit(_AuditWiringBase):
 
+    def setUp(self):
+        super().setUp()
+        from tests.test_mcp_server import _install_owned_reviewer_lease
+        import reviewer_pr_lease
+
+        self._lease_patch = _install_owned_reviewer_lease(8)
+        self._lease_patch.start()
+        self._auth_identity_patch = patch(
+            "mcp_server._authenticated_username", return_value="reviewer-bot"
+        )
+        self._auth_identity_patch.start()
+        self.addCleanup(self._auth_identity_patch.stop)
+        self.addCleanup(self._lease_patch.stop)
+        self.addCleanup(reviewer_pr_lease.clear_session_lease)
+
     def _pr(self, author, state="open", sha="abc123", mergeable=True):
         return {"user": {"login": author}, "state": state,
                 "head": {"sha": sha}, "mergeable": mergeable}
@@ -344,11 +359,22 @@ class TestGatedToolAudit(_AuditWiringBase):
                         GITEA_ALLOWED_OPERATIONS="read,review,approve")
         with patch.dict(os.environ, env, clear=True):
             from mcp_server import init_review_decision_lock, gitea_mark_final_review_decision
+            from tests.test_mcp_server import _install_owned_reviewer_lease
+            import reviewer_pr_lease
+
             init_review_decision_lock("prgs", "review_pr")
             gitea_mark_final_review_decision(8, "approve", remote="prgs")
-            r = gitea_submit_pr_review(pr_number=8, action="approve",
-                                       body="LGTM", remote="prgs",
-                                       final_review_decision_ready=True)
+            lease_patch = _install_owned_reviewer_lease(8)
+            lease_patch.start()
+            try:
+                r = gitea_submit_pr_review(
+                    pr_number=8, action="approve",
+                    body="LGTM", remote="prgs",
+                    final_review_decision_ready=True,
+                )
+            finally:
+                lease_patch.stop()
+                reviewer_pr_lease.clear_session_lease()
         self.assertTrue(r["performed"])
         recs = self._records()
         self.assertEqual(len(recs), 1)

tests/test_author_duplicate_work_gate.py

@@ -1,102 +0,0 @@
-"""Tests for early author duplicate-work gate (#400)."""
-import sys
-import unittest
-from pathlib import Path
-
-sys.path.insert(0, str(Path(__file__).resolve().parent.parent))
-
-from author_duplicate_work_gate import (  # noqa: E402
-    ELIGIBILITY_OPEN_PR_EXISTS,
-    assess_author_duplicate_work,
-    assess_work_issue_duplicate_prevention_report,
-)
-
-
-def _open_pr(number: int = 397, issue: int = 395) -> dict:
-    return {
-        "number": number,
-        "head": {"ref": f"feat/issue-{issue}-example"},
-        "title": f"feat: example (Closes #{issue})",
-        "body": f"Closes #{issue}",
-    }
-
-
-class TestAuthorDuplicateWorkGate(unittest.TestCase):
-    def test_clear_when_no_duplicates(self):
-        result = assess_author_duplicate_work(
-            400,
-            stage="claim",
-            open_prs=[],
-            branch_names=["master", "feat/issue-399-other"],
-        )
-        self.assertTrue(result["allowed"])
-        self.assertFalse(result["block"])
-
-    def test_open_pr_blocks_claim(self):
-        result = assess_author_duplicate_work(
-            395,
-            stage="claim",
-            open_prs=[_open_pr()],
-            branch_names=[],
-        )
-        self.assertFalse(result["allowed"])
-        self.assertEqual(result["eligibility_class"], ELIGIBILITY_OPEN_PR_EXISTS)
-
-    def test_matching_branch_blocks_lock_not_create_pr(self):
-        branches = ["feat/issue-400-early-duplicate-work-gate"]
-        lock = assess_author_duplicate_work(
-            400,
-            stage="lock",
-            open_prs=[],
-            branch_names=branches,
-        )
-        self.assertFalse(lock["allowed"])
-
-        create_pr = assess_author_duplicate_work(
-            400,
-            stage="create_pr",
-            open_prs=[],
-            branch_names=branches,
-            matching_branches=[],
-        )
-        self.assertTrue(create_pr["allowed"])
-
-    def test_open_pr_blocks_create_pr_stage(self):
-        result = assess_author_duplicate_work(
-            395,
-            stage="create_pr",
-            open_prs=[_open_pr()],
-            branch_names=["feat/issue-395-proof-backed-review-handoff"],
-        )
-        self.assertFalse(result["allowed"])
-        self.assertEqual(result["outcome"], "duplicate_pr_prevented")
-
-    def test_push_stage_blocks_on_concurrent_pr(self):
-        result = assess_author_duplicate_work(
-            395,
-            stage="push",
-            open_prs=[_open_pr()],
-            branch_names=[],
-        )
-        self.assertFalse(result["allowed"])
-        self.assertEqual(result["outcome"], "duplicate_push_prevented")
-
-    def test_duplicate_prevention_report_requires_outcome(self):
-        bad = assess_work_issue_duplicate_prevention_report(
-            "Duplicate work detected for issue #395."
-        )
-        self.assertFalse(bad["proven"])
-
-        good = assess_work_issue_duplicate_prevention_report(
-            "Duplicate PR prevented; reconciliation handoff produced."
-        )
-        self.assertTrue(good["proven"])
-
-    def test_exported_from_review_proofs(self):
-        from review_proofs import assess_work_issue_duplicate_prevention_report as exported
-
-        self.assertTrue(callable(exported))
-
-
-if __name__ == "__main__":
-    unittest.main()

tests/test_llm_workflow_split.py

@@ -95,12 +95,6 @@ def test_create_issue_workflow_contract():
     assert "## 9. Duplicate search before mutation" in text
 
 
-def test_author_duplicate_work_gate_exported():
-    from review_proofs import assess_work_issue_duplicate_prevention_report
-
-    assert callable(assess_work_issue_duplicate_prevention_report)
-
-
 def test_work_issue_workflow_contract():
     text = (SKILL_DIR / "workflows" / "work-issue.md").read_text(encoding="utf-8")
     assert "canonical: true" in text

tests/test_mcp_server.py

@@ -79,6 +79,64 @@ def _visible_approval_reviews(reviewer="reviewer-bot", sha="abc123"):
     return [_formal_review(reviewer, "APPROVED", sha=sha)]
 
 
+_DEFAULT_LEASE_SESSION = "mcp-test-reviewer-lease"
+
+
+def _reviewer_lease_comment(
+    pr_number,
+    *,
+    session_id=_DEFAULT_LEASE_SESSION,
+    head_sha="abc123",
+    reviewer="reviewer-bot",
+):
+    from datetime import datetime, timezone
+
+    import reviewer_pr_lease
+
+    body = reviewer_pr_lease.format_lease_body(
+        repo="Scaled-Tech-Consulting/Gitea-Tools",
+        pr_number=pr_number,
+        issue_number=407,
+        reviewer_identity=reviewer,
+        profile="gitea-reviewer",
+        session_id=session_id,
+        worktree="branches/review-test",
+        phase="claimed",
+        candidate_head=head_sha,
+        target_branch="master",
+        target_branch_sha="b" * 40,
+        last_activity=datetime.now(timezone.utc),
+    )
+    return {"id": 9001, "body": body, "user": {"login": reviewer}}
+
+
+def _install_owned_reviewer_lease(
+    pr_number,
+    *,
+    session_id=_DEFAULT_LEASE_SESSION,
+    head_sha="abc123",
+):
+    import reviewer_pr_lease
+
+    reviewer_pr_lease.clear_session_lease()
+    reviewer_pr_lease.record_session_lease({
+        "pr_number": pr_number,
+        "session_id": session_id,
+        "candidate_head": head_sha,
+        "target_branch": "master",
+    })
+    return patch(
+        "mcp_server._fetch_pr_comments",
+        return_value=[
+            _reviewer_lease_comment(
+                pr_number,
+                session_id=session_id,
+                head_sha=head_sha,
+            )
+        ],
+    )
+
+
 # Issue-write tools are profile-gated (#69).
 ISSUE_WRITE_ENV = {
     "GITEA_ALLOWED_OPERATIONS": (
@@ -512,6 +570,19 @@ class TestViewPR(unittest.TestCase):
 class TestMergePR(unittest.TestCase):
     """Gated merge workflow (#16). gitea_merge_pr is the only merge path."""
 
+    def setUp(self):
+        import reviewer_pr_lease
+
+        self._lease_patch = _install_owned_reviewer_lease(8)
+        self._lease_patch.start()
+        self._auth_identity_patch = patch(
+            "mcp_server._authenticated_username", return_value="reviewer-bot"
+        )
+        self._auth_identity_patch.start()
+        self.addCleanup(self._auth_identity_patch.stop)
+        self.addCleanup(self._lease_patch.stop)
+        self.addCleanup(reviewer_pr_lease.clear_session_lease)
+
     def _pr(self, author, state="open", sha="abc123", mergeable=True):
         return {
             "user": {"login": author},
@@ -772,9 +843,11 @@ class TestMergePR(unittest.TestCase):
                 pr_number=8, confirmation=self._confirm(8),
                 expected_head_sha="deadbeef", remote="prgs")
         self.assertFalse(r["performed"])
-        self.assertIn(
-            "expected head SHA does not match current PR head (fail closed)",
-            r["reasons"])
+        self.assertTrue(any(
+            "expected head SHA does not match current PR head (fail closed)" in reason
+            or "PR head changed during lease" in reason
+            for reason in r["reasons"]
+        ))
         self._assert_no_merge_call(mock_api)
 
     @patch("mcp_server.api_request")
@@ -1653,7 +1726,20 @@ class TestReviewDecisionValidationGate(unittest.TestCase):
         }
 
     def setUp(self):
+        import reviewer_pr_lease
+
         init_review_decision_lock("prgs", "review_pr")
+        self._lease_patch = _install_owned_reviewer_lease(
+            self.PR, head_sha=self.SHA,
+        )
+        self._lease_patch.start()
+        self._auth_identity_patch = patch(
+            "mcp_server._authenticated_username", return_value="reviewer-bot"
+        )
+        self._auth_identity_patch.start()
+        self.addCleanup(self._auth_identity_patch.stop)
+        self.addCleanup(self._lease_patch.stop)
+        self.addCleanup(reviewer_pr_lease.clear_session_lease)
 
     def _env(self):
         return patch.dict(os.environ, {
@@ -1748,8 +1834,19 @@ class TestSubmitPrReview(unittest.TestCase):
     """Gated review-mutation tool (#15)."""
 
     def setUp(self):
+        import reviewer_pr_lease
+
         init_review_decision_lock("prgs", "review_pr")
         gitea_mark_final_review_decision(8, "approve", remote="prgs")
+        self._lease_patch = _install_owned_reviewer_lease(8)
+        self._lease_patch.start()
+        self._auth_identity_patch = patch(
+            "mcp_server._authenticated_username", return_value="reviewer-bot"
+        )
+        self._auth_identity_patch.start()
+        self.addCleanup(self._auth_identity_patch.stop)
+        self.addCleanup(self._lease_patch.stop)
+        self.addCleanup(reviewer_pr_lease.clear_session_lease)
 
     def _pr(self, author, state="open", sha="abc123", mergeable=True):
         return {
@@ -1987,9 +2084,11 @@ class TestSubmitPrReview(unittest.TestCase):
                     final_review_decision_ready=True,
                 )
             self.assertFalse(r["performed"])
-            self.assertIn(
-                "expected head SHA does not match current PR head (fail closed)",
-                r["reasons"])
+            self.assertTrue(any(
+                "expected head SHA does not match current PR head (fail closed)" in reason
+                or "PR head changed during lease" in reason
+                for reason in r["reasons"]
+            ))
             self._assert_no_mutation(mock_api)
 
     def test_head_sha_match_allows(self):
@@ -2052,9 +2151,9 @@ class TestSubmitPrReview(unittest.TestCase):
         env = {"GITEA_PROFILE_NAME": "gitea-reviewer",
                "GITEA_ALLOWED_OPERATIONS": "read,review,approve"}
         with patch.dict(os.environ, env, clear=True):
-            gitea_mark_final_review_decision(5, "approve", remote="prgs")
+            gitea_mark_final_review_decision(8, "approve", remote="prgs")
             r = gitea_submit_pr_review(
-                pr_number=5, action="approve", remote="prgs",
+                pr_number=8, action="approve", remote="prgs",
                 final_review_decision_ready=True,
             )
         self.assertFalse(r["performed"])
@@ -2273,6 +2372,13 @@ class TestTrackerHygieneCleanup(unittest.TestCase):
         self.assertEqual(res["cleanup_status"].get(1), "not present")
 
     def test_merge_pr_with_closes_removes_label(self):
+        import reviewer_pr_lease
+
+        lease_patch = _install_owned_reviewer_lease(1, head_sha="sha123")
+        lease_patch.start()
+        self.addCleanup(lease_patch.stop)
+        self.addCleanup(reviewer_pr_lease.clear_session_lease)
+
         def api_side_effect(method, url, auth, payload=None):
             if method == "GET" and "/user" in url:
                 return {"login": "merger"}
@@ -2307,6 +2413,13 @@ class TestTrackerHygieneCleanup(unittest.TestCase):
         self.assertEqual(res["cleanup_status"].get(123), "released")
 
     def test_merge_pr_with_branch_name_removes_label(self):
+        import reviewer_pr_lease
+
+        lease_patch = _install_owned_reviewer_lease(1, head_sha="sha123")
+        lease_patch.start()
+        self.addCleanup(lease_patch.stop)
+        self.addCleanup(reviewer_pr_lease.clear_session_lease)
+
         def api_side_effect(method, url, auth, payload=None):
             if method == "GET" and "/user" in url:
                 return {"login": "merger"}
@@ -2988,10 +3101,12 @@ class TestVerifyMutationAuthority(unittest.TestCase):
         # profile; the active profile resolves as reviewer — side-channel
         # override rejected even with a matching in-process authority.
         self._authority()
-        with patch.dict(os.environ,
-                        {"GITEA_SESSION_PROFILE_LOCK": "prgs-author"}):
-            with self.assertRaises(RuntimeError) as ctx:
-                mcp_server.verify_mutation_authority("prgs")
+        with patch("mcp_server.gitea_config.is_runtime_switching_enabled",
+                   return_value=False):
+            with patch.dict(os.environ,
+                            {"GITEA_SESSION_PROFILE_LOCK": "prgs-author"}):
+                with self.assertRaises(RuntimeError) as ctx:
+                    mcp_server.verify_mutation_authority("prgs")
         self.assertIn("side-channel override rejected", str(ctx.exception))
 
     def test_foreign_pid_authority_is_not_trusted(self):

tests/test_pr_queue_inventory.py

@@ -156,9 +156,22 @@ class TestPRQueueInventory(unittest.TestCase):
         ]
 
         from mcp_server import init_review_decision_lock, gitea_mark_final_review_decision
-        init_review_decision_lock("prgs", "review_pr")
-        gitea_mark_final_review_decision(1, "approve", remote="prgs")
-        result = gitea_review_pr(pr_number=1, event="APPROVE", remote="prgs", final_review_decision_ready=True)
+        from tests.test_mcp_server import _install_owned_reviewer_lease
+        import reviewer_pr_lease
+
+        with patch("mcp_server._authenticated_username", return_value="reviewer1"):
+            init_review_decision_lock("prgs", "review_pr")
+            gitea_mark_final_review_decision(1, "approve", remote="prgs")
+            lease_patch = _install_owned_reviewer_lease(
+                1, head_sha="abc1", session_id="inventory-review-lease",
+            )
+            lease_patch.start()
+            self.addCleanup(lease_patch.stop)
+            self.addCleanup(reviewer_pr_lease.clear_session_lease)
+            result = gitea_review_pr(
+                pr_number=1, event="APPROVE", remote="prgs",
+                final_review_decision_ready=True,
+            )
         self.assertTrue(result["success"])
         self.assertIn("=== PR Queue Inventory ===", result["message"])
         self.assertIn("Repository:", result["message"])

tests/test_reviewer_pr_lease.py

@@ -0,0 +1,193 @@
+"""Tests for per-PR reviewer leases (#407)."""
+
+import sys
+import unittest
+from datetime import datetime, timedelta, timezone
+from unittest.mock import patch
+
+sys.path.insert(0, str(__import__("pathlib").Path(__file__).resolve().parent.parent))
+
+import reviewer_pr_lease as leases
+
+
+def _lease_comment(
+    pr_number: int,
+    session_id: str,
+    *,
+    phase: str = "claimed",
+    minutes_ago: int = 0,
+    candidate_head: str = "a" * 40,
+) -> dict:
+    now = datetime.now(timezone.utc) - timedelta(minutes=minutes_ago)
+    body = leases.format_lease_body(
+        repo="Scaled-Tech-Consulting/Gitea-Tools",
+        pr_number=pr_number,
+        issue_number=295,
+        reviewer_identity="rev1",
+        profile="prgs-reviewer",
+        session_id=session_id,
+        worktree="branches/review-pr382",
+        phase=phase,
+        candidate_head=candidate_head,
+        target_branch="master",
+        target_branch_sha="b" * 40,
+        last_activity=now,
+    )
+    return {"id": 1, "body": body, "user": {"login": "rev1"}}
+
+
+class TestReviewerLeaseAcquire(unittest.TestCase):
+    def setUp(self):
+        leases.clear_session_lease()
+
+    def test_two_reviewers_cannot_lease_same_pr(self):
+        comments = [_lease_comment(382, "session-a")]
+        result = leases.assess_acquire_lease(
+            comments,
+            pr_number=382,
+            reviewer_identity="rev2",
+            profile="prgs-reviewer",
+            session_id="session-b",
+            repo="Scaled-Tech-Consulting/Gitea-Tools",
+            issue_number=295,
+            worktree="branches/review-pr382-b",
+            candidate_head="c" * 40,
+            target_branch="master",
+            target_branch_sha="d" * 40,
+        )
+        self.assertFalse(result["acquire_allowed"])
+        self.assertTrue(any("already has active" in r for r in result["reasons"]))
+
+    def test_two_reviewers_can_lease_different_prs(self):
+        comments = [_lease_comment(382, "session-a")]
+        result = leases.assess_acquire_lease(
+            comments,
+            pr_number=383,
+            reviewer_identity="rev2",
+            profile="prgs-reviewer",
+            session_id="session-b",
+            repo="Scaled-Tech-Consulting/Gitea-Tools",
+            issue_number=296,
+            worktree="branches/review-pr383",
+            candidate_head="c" * 40,
+            target_branch="master",
+            target_branch_sha="d" * 40,
+        )
+        self.assertTrue(result["acquire_allowed"])
+        self.assertIsNotNone(result["lease_body"])
+
+
+class TestReviewerLeaseFreshness(unittest.TestCase):
+    def test_stale_warning_after_30_minutes(self):
+        lease = leases.parse_lease_comment(
+            _lease_comment(382, "session-a", minutes_ago=35)["body"]
+        )
+        self.assertEqual(
+            leases.classify_lease_freshness(lease),
+            "stale_warning",
+        )
+
+    def test_reclaimable_after_60_minutes(self):
+        lease = leases.parse_lease_comment(
+            _lease_comment(382, "session-a", minutes_ago=65)["body"]
+        )
+        self.assertEqual(
+            leases.classify_lease_freshness(lease),
+            "reclaimable",
+        )
+
+
+class TestReviewerLeaseMutationGate(unittest.TestCase):
+    def setUp(self):
+        leases.clear_session_lease()
+
+    def test_reviewer_without_lease_cannot_mutate(self):
+        head = "f" * 40
+        comments = [_lease_comment(382, "other-session", candidate_head=head)]
+        result = leases.assess_mutation_lease_gate(
+            pr_number=382,
+            comments=comments,
+            reviewer_identity="rev1",
+            session_id="my-session",
+            mutation="approve",
+            live_head_sha=head,
+            pinned_head_sha=head,
+        )
+        self.assertTrue(result["block"])
+
+    def test_owned_lease_allows_mutation(self):
+        head = "f" * 40
+        comments = [_lease_comment(382, "my-session", candidate_head=head)]
+        leases.record_session_lease({
+            "pr_number": 382,
+            "session_id": "my-session",
+            "candidate_head": head,
+            "target_branch": "master",
+        })
+        result = leases.assess_mutation_lease_gate(
+            pr_number=382,
+            comments=comments,
+            reviewer_identity="rev1",
+            session_id="my-session",
+            mutation="approve",
+            live_head_sha=head,
+            pinned_head_sha=head,
+        )
+        self.assertFalse(result["block"])
+
+    def test_head_change_invalidates_lease(self):
+        reviewed = "f" * 40
+        live = "e" * 40
+        comments = [_lease_comment(382, "my-session", candidate_head=reviewed)]
+        leases.record_session_lease({
+            "pr_number": 382,
+            "session_id": "my-session",
+            "candidate_head": reviewed,
+        })
+        result = leases.assess_mutation_lease_gate(
+            pr_number=382,
+            comments=comments,
+            reviewer_identity="rev1",
+            session_id="my-session",
+            mutation="merge",
+            live_head_sha=live,
+            pinned_head_sha=reviewed,
+        )
+        self.assertTrue(result["block"])
+        self.assertTrue(any("head" in r.lower() for r in result["reasons"]))
+
+
+class TestReviewerLeaseMcpGate(unittest.TestCase):
+    def setUp(self):
+        leases.clear_session_lease()
+        patch("mcp_server.verify_preflight_purity").start()
+        patch("gitea_audit.audit_enabled", return_value=False).start()
+        mcp_server = __import__("mcp_server")
+        mcp_server._IDENTITY_CACHE.clear()
+        mcp_server.init_review_decision_lock("prgs", "review_pr")
+        mcp_server.record_preflight_check("whoami")
+        mcp_server.record_preflight_check("capability", "reviewer")
+
+    def tearDown(self):
+        patch.stopall()
+        leases.clear_session_lease()
+
+    def test_reviewer_pr_lease_gate_helper_blocks_without_session(self):
+        import mcp_server
+        head = "a" * 40
+        with patch("mcp_server._fetch_pr_comments", return_value=[]):
+            reasons = mcp_server._reviewer_pr_lease_gate(
+                pr_number=382,
+                remote="prgs",
+                host=None,
+                org=None,
+                repo=None,
+                mutation="approve",
+                live_head_sha=head,
+                pinned_head_sha=head,
+            )
+        self.assertTrue(any("lease" in r.lower() for r in reasons))
+
+
+if __name__ == "__main__":
+    unittest.main()