fix(runtime): fix identity derivation disarming in canonical root guard (Closes #973)

canonical_repository_root.py

@@ -132,6 +132,7 @@ def assess_canonical_repository_root(
     process_project_root: str,
     remote: str | None = None,
     require_binding: bool = False,
+    mode: str = "validation",
 ) -> dict:
     """Validate the canonical repository root binding, failing closed on forgery.
 
@@ -140,14 +141,13 @@ def assess_canonical_repository_root(
     ``configured`` (whether a cross-repo binding was declared),
     ``resolved_slug`` and ``source``.
 
-    Without a configured binding the single-repo default is preserved: the
-    canonical root is derived from *process_project_root* and never blocks
-    (unless *require_binding* explicitly demands one).
-
-    With a configured binding the path must exist, be a git repository, and —
-    when *expected_slug* is known — carry a matching repository identity. A
-    mismatched or (when *require_binding*) unprovable identity is a forged or
-    conflicting binding and fails closed.
+    *mode*:
+    - ``"validation"`` (default): an independently trusted expected repository
+      slug is known (or required). Candidate root's observed identity must match.
+      Unprovable or missing expected identity fails closed when *require_binding* is True.
+    - ``"derivation"``: caller is deriving the canonical repository identity.
+      No expected slug exists yet by design. Derivation succeeds if the configured
+      root exists, is a git repository, and carries a resolvable git remote identity.
     """
     process_root = os.path.realpath(process_project_root)
     declared = (configured_value or "").strip()
@@ -168,12 +168,28 @@ def assess_canonical_repository_root(
             )
         # Single-repo default: canonical root follows the install checkout.
         derived = resolve_repo_toplevel(process_root) or process_root
+        resolved_slug = repository_identity_slug(derived, remote=remote)
+        reasons: list[str] = []
+        if mode == "validation" and expected_slug:
+            expected = expected_slug.strip()
+            if resolved_slug and resolved_slug.lower() != expected.lower():
+                reasons.append(
+                    f"canonical repository root identity mismatch: '{derived}' resolves "
+                    f"to repository '{resolved_slug}' but expected repository identity "
+                    f"is '{expected}' (forged or conflicting binding, fail closed)"
+                )
+            elif not resolved_slug and require_binding:
+                reasons.append(
+                    f"canonical repository root '{derived}' has no resolvable git "
+                    f"remote identity to confirm authorization for '{expected}' "
+                    "(fail closed)"
+                )
         return _assessment(
-            proven=True,
-            reasons=[],
+            proven=not reasons,
+            reasons=reasons,
             configured=False,
             canonical_repo_root=derived,
-            resolved_slug=None,
+            resolved_slug=resolved_slug,
             source=None,
         )
 
@@ -207,26 +223,34 @@ def assess_canonical_repository_root(
 
     resolved_slug = repository_identity_slug(toplevel, remote=remote)
     reasons: list[str] = []
-    expected = (expected_slug or "").strip() or None
-    if expected:
-        if resolved_slug and resolved_slug.lower() != expected.lower():
+
+    if mode == "derivation":
+        if not resolved_slug:
             reasons.append(
-                f"canonical repository root identity mismatch: '{toplevel}' resolves "
-                f"to repository '{resolved_slug}' but the session is authorized for "
-                f"'{expected}' (forged or conflicting binding, fail closed)"
+                f"configured canonical repository root '{toplevel}' has no resolvable "
+                "git remote identity (fail closed)"
             )
-        elif not resolved_slug and require_binding:
+    else:
+        expected = (expected_slug or "").strip() or None
+        if expected:
+            if resolved_slug and resolved_slug.lower() != expected.lower():
+                reasons.append(
+                    f"canonical repository root identity mismatch: '{toplevel}' resolves "
+                    f"to repository '{resolved_slug}' but the session is authorized for "
+                    f"'{expected}' (forged or conflicting binding, fail closed)"
+                )
+            elif not resolved_slug and require_binding:
+                reasons.append(
+                    f"canonical repository root '{toplevel}' has no resolvable git "
+                    f"remote identity to confirm authorization for '{expected}' "
+                    "(fail closed)"
+                )
+        elif require_binding:
             reasons.append(
-                f"canonical repository root '{toplevel}' has no resolvable git "
-                f"remote identity to confirm authorization for '{expected}' "
-                "(fail closed)"
+                f"canonical repository root '{toplevel}' has configured value "
+                f"'{configured_value}' but authoritative expected repository identity "
+                "is unprovable or missing (fail closed)"
             )
-    elif require_binding:
-        reasons.append(
-            f"canonical repository root '{toplevel}' has configured value "
-            f"'{configured_value}' but authoritative expected repository identity "
-            "is unprovable or missing (fail closed)"
-        )
 
     return _assessment(
         proven=not reasons,

gitea_mcp_server.py

@@ -526,18 +526,21 @@ def _resolve_expected_repository_slug(
     org: str | None = None,
     repo: str | None = None,
 ) -> str | None:
-    """Resolve expected repository slug from parameters, session context, or process root.
+    """Resolve expected repository slug from session context, parameters, or process root.
 
     Must derive expected repository identity ONLY from trusted sources independent
     of the candidate configured canonical root (#973 B8).
+
+    Bound session context takes precedence over request parameters so request-supplied
+    coordinates cannot replace a bound canonical root (#741 / #973 B9).
     """
-    if org and repo:
-        return session_ctx.format_repository_slug(org, repo)
     bound = session_ctx.get_session_context() or {}
     b_org = bound.get("org")
     b_repo = bound.get("repository")
     if b_org and b_repo:
         return session_ctx.format_repository_slug(b_org, b_repo)
+    if org and repo:
+        return session_ctx.format_repository_slug(org, repo)
     eff_remote = remote or bound.get("remote") or _effective_remote()
     parsed = remote_repo_guard.parse_org_repo_from_remote_url(
         _process_root_git_remote_url(eff_remote)
@@ -2250,6 +2253,7 @@ def _canonical_repository_slug(
         process_project_root=PROJECT_ROOT,
         remote=remote,
         require_binding=True,
+        mode="derivation",
     )
     slug = assessment.get("resolved_slug")
     if assessment.get("block") or not slug:

tests/test_cross_repo_canonical_consumption.py

@@ -313,6 +313,7 @@ class TestCanonicalRootGuardBinding(_ServerHarness):
             process_project_root=self.install_root,
             remote="prgs",
             require_binding=True,
+            mode="derivation",
         )
         self.assertFalse(got.get("block"), got.get("reasons"))
         self.assertEqual(got["resolved_slug"], TARGET_SLUG)

tests/test_issue_973_cross_repo_canonical_roots.py

@@ -479,6 +479,68 @@ class TestIssue973CrossRepoCanonicalRoots(unittest.TestCase):
             self.assertTrue(rel_res.get("success"), rel_res)
             mock_clear.assert_called_once()
 
+    def test_unbound_session_derives_and_retains_configured_target_repository(self):
+        """B9: Unbound session with a legitimate configured target root derives and retains target repository."""
+        prof = {
+            "profile_name": "prgs-author",
+            "allowed_repositories": ["Scaled-Tech-Consulting/mcp-control-plane"],
+            "canonical_repository_root": self.target_root,
+        }
+        with patch.object(mcp_server, "PROJECT_ROOT", self.install_root), \
+             patch.object(mcp_server.session_ctx, "get_session_context", return_value=None):
+            slug, reasons = mcp_server._canonical_repository_slug(prof, "prgs")
+            self.assertEqual(slug, "Scaled-Tech-Consulting/mcp-control-plane", f"reasons: {reasons}")
+            self.assertEqual(reasons, [])
+            res = mcp_server._trusted_session_repository(prof, "prgs")
+            self.assertEqual(res["org"], "Scaled-Tech-Consulting")
+            self.assertEqual(res["repository"], "mcp-control-plane")
+
+    def test_process_root_a_configured_target_b_retains_b(self):
+        """B9: Process root A (Gitea-Tools) and configured target B (mcp-control-plane) keep B as expected identity when bound."""
+        bound_ctx = {"org": "Scaled-Tech-Consulting", "repository": "mcp-control-plane", "remote": "prgs"}
+        with patch.object(mcp_server, "PROJECT_ROOT", self.install_root), \
+             patch.object(mcp_server.session_ctx, "get_session_context", return_value=bound_ctx):
+            expected = mcp_server._resolve_expected_repository_slug("prgs")
+            self.assertEqual(expected, "Scaled-Tech-Consulting/mcp-control-plane")
+
+    def test_request_supplied_repository_c_cannot_replace_derived_or_bound_repository_b(self):
+        """B9: Request-supplied repository C (Timesheet) cannot replace bound repository B (mcp-control-plane)."""
+        bound_ctx = {"org": "Scaled-Tech-Consulting", "repository": "mcp-control-plane", "remote": "prgs"}
+        with patch.object(mcp_server, "PROJECT_ROOT", self.install_root), \
+             patch.object(mcp_server.session_ctx, "get_session_context", return_value=bound_ctx):
+            expected = mcp_server._resolve_expected_repository_slug("prgs", org="Scaled-Tech-Consulting", repo="Timesheet")
+            self.assertEqual(expected, "Scaled-Tech-Consulting/mcp-control-plane")
+
+    def test_known_expected_repo_a_plus_candidate_root_b_fails_closed(self):
+        """B9: Known expected repository A plus candidate root B fails closed in validation mode."""
+        assessment = crr.assess_canonical_repository_root(
+            configured_value=self.target_root,
+            source="env",
+            expected_slug="Scaled-Tech-Consulting/Gitea-Tools",
+            process_project_root=self.install_root,
+            remote="prgs",
+            require_binding=True,
+            mode="validation",
+        )
+        self.assertFalse(assessment["proven"])
+        self.assertTrue(assessment["block"])
+        self.assertTrue(any("identity mismatch" in r for r in assessment["reasons"]))
+
+    def test_validation_mode_with_unprovable_expected_identity_fails_closed(self):
+        """B9: Validation mode with expected_slug=None and require_binding=True fails closed."""
+        assessment = crr.assess_canonical_repository_root(
+            configured_value=self.target_root,
+            source="env",
+            expected_slug=None,
+            process_project_root=self.install_root,
+            remote="prgs",
+            require_binding=True,
+            mode="validation",
+        )
+        self.assertFalse(assessment["proven"])
+        self.assertTrue(assessment["block"])
+        self.assertTrue(any("unprovable or missing" in r for r in assessment["reasons"]))
+
 
 if __name__ == "__main__":
     unittest.main()