fix: use exact issue-number boundary in own-branch adoption (#442)

Replace substring issue-marker matching with a numeric word-boundary
regex so issue-42 adoption is not false-blocked by unrelated issue-420
branches. Add regression tests for the #42 vs #420 collision.

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

issue_lock_adoption.py

@@ -14,6 +14,8 @@ this module additionally records whether they passed for proof purposes.
 
 from __future__ import annotations
 
+import re
+
 ADOPT = "adopt_existing_branch"
 BLOCK_COMPETING = "block_competing_branch"
 NO_MATCH = "no_matching_branch"
@@ -33,6 +35,19 @@ def _branch_sha(entry) -> str | None:
     return None
 
 
+def _branch_carries_issue_marker(branch_name: str, issue_number: int) -> bool:
+    """Return True when *branch_name* references issue *issue_number* exactly.
+
+    Uses a numeric word-boundary so ``issue-42`` does not match inside
+    ``issue-420`` (AC6 / #440).
+    """
+    name = (branch_name or "").strip()
+    if not name:
+        return False
+    pattern = rf"(?:^|/)issue-{int(issue_number)}(?![0-9])"
+    return re.search(pattern, name) is not None
+
+
 def assess_own_branch_adoption(
     *,
     issue_number: int,
@@ -59,13 +74,12 @@ def assess_own_branch_adoption(
     BLOCK_COMPETING: at least one same-issue branch is not the requested branch.
     NO_MATCH: no branch carries the issue marker — normal lock path applies.
     """
-    marker = f"issue-{issue_number}"
     requested = (requested_branch or "").strip()
 
     matches: list[tuple[str, str | None]] = []
     for entry in existing_branches or []:
         name = _branch_name(entry).strip()
-        if marker in name:
+        if _branch_carries_issue_marker(name, issue_number):
             matches.append((name, _branch_sha(entry)))
 
     competing = sorted({name for name, _ in matches if name != requested})

tests/test_agent_temp_artifacts.py

@@ -84,6 +84,7 @@ class TestIssueLockArtifactWarning(unittest.TestCase):
         "mcp_server.issue_duplicate_context_fetcher",
         return_value=([], [], {"status": "not_claimed"}),
     )
+    @patch("mcp_server.api_get_all", return_value=[])
     @patch("mcp_server._auth", return_value="token x")
     @patch("mcp_server._resolve", return_value=("h", "o", "r"))
     @patch("mcp_server.ISSUE_LOCK_FILE", new_callable=lambda: tempfile.mktemp())

tests/test_issue_lock_adoption.py

@@ -75,17 +75,31 @@ class TestAssessOwnBranchAdoption(unittest.TestCase):
         )
         self.assertEqual(result["outcome"], NO_MATCH)
 
-    def test_substring_issue_number_not_falsely_matched_as_exact(self):
-        # A different issue's branch must not be adopted as ours.
+    def test_higher_issue_number_branch_does_not_block_lower_issue_adoption(self):
+        # issue-420 must not be treated as competing work for issue #42.
+        own_branch = "feat/issue-42-widget"
+        result = assess_own_branch_adoption(
+            issue_number=42,
+            requested_branch=own_branch,
+            existing_branches=[
+                {"name": own_branch, "commit_sha": "abc1234"},
+                {"name": "feat/issue-420-server-code-parity"},
+            ],
+        )
+        self.assertEqual(result["outcome"], ADOPT)
+        self.assertTrue(result["adopt"])
+        self.assertFalse(result["block"])
+        self.assertEqual(result["matched_branch"], own_branch)
+
+    def test_unrelated_higher_number_branch_is_ignored_without_own_branch(self):
         result = assess_own_branch_adoption(
             issue_number=42,
             requested_branch="feat/issue-42-thing",
             existing_branches=[{"name": "feat/issue-420-server-code-parity"}],
         )
-        # 'issue-42' is a substring of 'issue-420', so marker matches but the
-        # name differs -> competing block, never adoption of the wrong branch.
-        self.assertEqual(result["outcome"], BLOCK_COMPETING)
-        self.assertNotEqual(result["matched_branch"], "feat/issue-420-server-code-parity")
+        self.assertEqual(result["outcome"], NO_MATCH)
+        self.assertFalse(result["block"])
+        self.assertFalse(result["adopt"])
 
 
 class TestBuildAdoptionProof(unittest.TestCase):

tests/test_issue_work_duplicate_gate.py

@@ -123,8 +123,9 @@ class TestDuplicateReportOutcome(unittest.TestCase):
 
 
 class TestInjectableDuplicateFetcher(unittest.TestCase):
+    @patch("mcp_server.api_get_all", return_value=[])
     @patch("mcp_server.get_auth_header", return_value="token x")
-    def test_lock_issue_uses_injected_fetcher(self, _auth):
+    def test_lock_issue_uses_injected_fetcher(self, _auth, _api):
         seen = {}
 
         def fetcher(h, o, r, auth, issue_number):