fix: resolve conflicts for PR #490

Merge prgs/master into feat/issue-470-preflight-contract, keeping stacked-PR
lock base support (#484) and explicit task binding on lock_issue preflight (#470).

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

gitea_mcp_server.py

@@ -464,8 +464,13 @@ def record_preflight_check(
 
 
 def _enforce_branches_only_author_mutation(worktree_path: str | None = None) -> None:
-    """#274: author mutations must run from a branches/ session worktree."""
-    if _preflight_resolved_role == "reviewer":
+    """#274: author file/branch mutations must run from a branches/ worktree.
+
+    Reviewer and reconciler roles are exempt: reconciler ``close_pr`` is a
+    Gitea metadata mutation and must not require ``GITEA_AUTHOR_WORKTREE``
+    (#468).
+    """
+    if _preflight_resolved_role in ("reviewer", "reconciler"):
         return
     ctx = _resolve_author_mutation_context(worktree_path)
     workspace = ctx["workspace_path"]
@@ -597,6 +602,7 @@ 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 stacked_pr_support  # noqa: E402
 import merge_approval_gate  # noqa: E402
 import already_landed_reconcile  # noqa: E402
 import author_mutation_worktree  # noqa: E402
@@ -1325,6 +1331,16 @@ def gitea_create_issue(
 
 
 @mcp.tool()
+def _list_open_pulls(h: str, o: str, r: str, auth: str) -> list[dict]:
+    """Fetch all OPEN pull requests for a repo (used for stacked-base proof, #484)."""
+    try:
+        return api_get_all(f"{repo_api_url(h, o, r)}/pulls?state=open", auth) or []
+    except Exception as exc:  # fail closed: no proof of an open dependency PR
+        raise RuntimeError(
+            f"Could not list open pull requests to verify stacked base: {exc}"
+        )
+
+
 def gitea_lock_issue(
     issue_number: int,
     branch_name: str,
@@ -1333,6 +1349,8 @@ def gitea_lock_issue(
     org: str | None = None,
     repo: str | None = None,
     worktree_path: str | None = None,
+    stacked_base_branch: str | None = None,
+    stacked_base_pr: int | None = None,
 ) -> dict:
     """Lock exactly one Gitea issue and its branch name to ensure durable tracking.
 
@@ -1345,6 +1363,15 @@ def gitea_lock_issue(
         repo: Override Repo.
         worktree_path: Author scratch-clone path to validate (defaults to
             GITEA_AUTHOR_WORKTREE or the MCP server project root).
+        stacked_base_branch: Opt-in. Declare a non-master base branch for a
+            *stacked* PR (a PR based on another unmerged PR's branch). Normal work
+            leaves this ``None`` and stays master-equivalent. When set, the
+            worktree may be base-equivalent to this branch instead of
+            master/main/dev, and the approved base is recorded on the lock (#484).
+        stacked_base_pr: Required when ``stacked_base_branch`` is set. The number
+            of the OPEN pull request that owns the stacked base branch. The lock
+            fails closed unless this open PR exists and owns that branch, so
+            arbitrary or stale branches cannot be used as stacked bases.
     """
     # 1. Enforce branch name includes issue number
     expected_pattern = f"issue-{issue_number}"
@@ -1372,7 +1399,31 @@ def gitea_lock_issue(
     if active_lease_block:
         raise RuntimeError(active_lease_block)
 
-    git_state = issue_lock_worktree.read_worktree_git_state(resolved_worktree)
+    # ── Stacked-PR base declaration (opt-in, #484) ──
+    # Normal work leaves stacked_base_branch None → master-equivalent path.
+    # A declared stacked base must be proven to own an OPEN PR before it can
+    # anchor base-equivalence; this never bypasses the lock.
+    stacked_extra_bases: tuple[str, ...] = ()
+    stacked_approved: dict | None = None
+    if stacked_base_branch:
+        stacked_assessment = stacked_pr_support.assess_stacked_base_declaration(
+            stacked_base_branch=stacked_base_branch,
+            stacked_base_pr=stacked_base_pr,
+            open_prs=_list_open_pulls(h, o, r, _auth(h)),
+        )
+        if stacked_assessment["block"]:
+            raise RuntimeError(
+                "; ".join(stacked_assessment["reasons"]) + " (fail closed)"
+            )
+        stacked_approved = stacked_assessment["approved"]
+        stacked_extra_bases = (stacked_approved["branch"],)
+
+    if stacked_extra_bases:
+        git_state = issue_lock_worktree.read_worktree_git_state(
+            resolved_worktree, extra_bases=stacked_extra_bases
+        )
+    else:
+        git_state = issue_lock_worktree.read_worktree_git_state(resolved_worktree)
     verify_preflight_purity(remote, worktree_path=resolved_worktree, task="lock_issue")
     lock_assessment = issue_lock_worktree.assess_issue_lock_worktree(
         worktree_path=resolved_worktree,
@@ -1445,6 +1496,8 @@ def gitea_lock_issue(
             claimant=work_lease.get("claimant"),
         ),
     }
+    if stacked_approved:
+        data["approved_stacked_base"] = stacked_approved
 
     lock_file_path = _save_issue_lock(data)
     lock_record = issue_lock_store.read_lock_file(lock_file_path) or data
@@ -1478,6 +1531,13 @@ def gitea_lock_issue(
         "lock_freshness": freshness,
         "lock_proof": lock_proof,
     }
+    if stacked_approved:
+        result["approved_stacked_base"] = stacked_approved
+        result["message"] = (
+            f"Successfully locked issue #{issue_number} to branch '{branch_name}' "
+            f"as a STACKED PR on base '{stacked_approved['branch']}' "
+            f"(open PR #{stacked_approved['pr_number']}); fail-closed check complete."
+        )
     if adoption["adopt"]:
         result["adoption"] = issue_lock_adoption.build_adoption_proof(
             issue_number=issue_number,
@@ -1492,6 +1552,14 @@ def gitea_lock_issue(
             f"Adopted existing branch '{branch_name}' and locked issue "
             f"#{issue_number} for recovery (fail-closed check complete)."
         )
+    else:
+        # #477 AC2: normal (no-adoption) lock responses carry explicit,
+        # adoption-free proof metadata so they stay clear and cannot be
+        # misread as claiming a branch was adopted.
+        result["adoption_check"] = issue_lock_adoption.build_non_adoption_lock_proof(
+            issue_number=issue_number,
+            branch_name=branch_name,
+        )
     if agent_artifacts:
         result["warnings"] = [
             "Agent temp artifacts at repo root (delete before implementation): "
@@ -1634,6 +1702,24 @@ 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)"
         )
 
+    # ── Stacked-PR base validation (#484) ──
+    # Normal base branches (master/main/dev) pass unchanged. A non-base target is
+    # allowed only when it matches the lock's approved stacked base, that base still
+    # has an open PR, and the body documents the stack. This never bypasses the lock.
+    base_open_prs = (
+        []
+        if stacked_pr_support.is_base_branch(base)
+        else _list_open_pulls(h, o, r, _auth(h))
+    )
+    base_check = stacked_pr_support.assess_create_pr_base(
+        base=base,
+        approved_stacked_base=lock_data.get("approved_stacked_base"),
+        body=body,
+        open_prs=base_open_prs,
+    )
+    if base_check["block"]:
+        raise ValueError("; ".join(base_check["reasons"]) + " (fail closed)")
+
     duplicate_block = _enforce_locked_issue_duplicate_recheck(
         remote,
         issue_work_duplicate_gate.PHASE_CREATE_PR,
@@ -2578,7 +2664,12 @@ def _list_pr_lease_comments(
     h, o, r = _resolve(remote, host, org, repo)
     auth = _auth(h)
     api = f"{repo_api_url(h, o, r)}/issues/{pr_number}/comments"
-    comments = api_request("GET", api, auth) or []
+    comments = api_request("GET", api, auth)
+    # Fail safe to no lease comments when the API returns a non-list payload
+    # (e.g. an error object such as an HTTP 401 body): lease state can only be
+    # proven from real comment entries, never inferred from an error shape (#485).
+    if not isinstance(comments, list):
+        return []
     return list(comments[:limit])
 
 
@@ -5182,7 +5273,12 @@ def gitea_list_issue_comments(
     h, o, r = _resolve(remote, host, org, repo)
     auth = _auth(h)
     api = f"{repo_api_url(h, o, r)}/issues/{issue_number}/comments"
-    comments = api_request("GET", api, auth) or []
+    comments = api_request("GET", api, auth)
+    # Fail safe to no comments when the API returns a non-list payload (e.g. an
+    # error object such as an HTTP 401 body) so listing never crashes on a
+    # malformed response (#485).
+    if not isinstance(comments, list):
+        comments = []
     reveal = _reveal_endpoints()
     out = []
     for c in comments[:limit]: