diff --git a/gitea_mcp_server.py b/gitea_mcp_server.py
index 6fb55cd..7097ac0 100644
--- a/gitea_mcp_server.py
+++ b/gitea_mcp_server.py
@@ -4096,9 +4096,6 @@ def _evaluate_pr_review_submission(
     worktree_path: str | None = None,
 ) -> dict:
     """Shared gate chain for live submit and dry-run review tools."""
-    _verify_role_mutation_workspace(
-        remote, worktree_path=worktree_path, task="review_pr"
-    )
     action = (action or "").strip().lower()
     workflow_blockers = _review_workflow_load_gate_reasons() if live else []
     result = {
@@ -4115,6 +4112,13 @@ def _evaluate_pr_review_submission(
         "remote": remote if remote in REMOTES else None,
         "reasons": [],
     }
+    try:
+        _verify_role_mutation_workspace(
+            remote, worktree_path=worktree_path, task="review_pr"
+        )
+    except RuntimeError as e:
+        result["reasons"].append(str(e))
+        return result
     reasons = result["reasons"]
     if workflow_blockers:
         reasons.extend(workflow_blockers)
@@ -10018,9 +10022,20 @@ def gitea_adopt_merger_pr_lease(
             "permission_report": _permission_block_report("gitea.pr.merge"),
         }
 
-    _verify_role_mutation_workspace(
-        remote, worktree=worktree, task="adopt_merger_pr_lease"
-    )
+    try:
+        _verify_role_mutation_workspace(
+            remote, worktree=worktree, task="adopt_merger_pr_lease"
+        )
+    except RuntimeError as e:
+        return {
+            "success": False,
+            "adopted": False,
+            "pr_number": pr_number,
+            "reasons": [str(e)],
+            "active_lease": None,
+            "expected_head_sha": expected_head_sha,
+            "live_head_sha": None,
+        }
     h, o, r = _resolve(remote, host, org, repo)
     auth = _auth(h)
     profile = get_profile()
@@ -13921,8 +13936,6 @@ def gitea_resolve_task_capability(
                         "exact_safe_next_action": next_safe_action,
                     }
 
-    record_preflight_check("capability", required_role, resolved_task=task)
-
     # Try automatic dispatch switching
     _ensure_matching_profile(required_permission, required_role, remote, host)
 
@@ -13956,6 +13969,9 @@ def gitea_resolve_task_capability(
         permission_allowed_in_current_session and role_matches_current_session
     )
 
+    if allowed_in_current_session:
+        record_preflight_check("capability", required_role, resolved_task=task)
+
     switching = gitea_config.is_runtime_switching_enabled()
     available_in_session = allowed_in_current_session
     configured = False
diff --git a/tests/test_resolve_task_capability.py b/tests/test_resolve_task_capability.py
index 23f05bc..9a0b0aa 100644
--- a/tests/test_resolve_task_capability.py
+++ b/tests/test_resolve_task_capability.py
@@ -442,5 +442,23 @@ class TestResolveTaskCapability(unittest.TestCase):
                 with self.assertRaises(ValueError):
                     mcp_server.gitea_resolve_task_capability(task=unknown, remote="prgs")
 
+    @patch("mcp_server.api_request", return_value={"login": "author-user"})
+    @patch("mcp_server.get_auth_header", return_value="token author-pass")
+    def test_resolve_task_capability_does_not_poison_role_stamp_on_denial(self, _auth, _api):
+        # Issue #723: attempting to acquire a reviewer lease from a merger profile
+        # should fail without poisoning the session role stamp as 'reviewer'.
+        with patch.dict(os.environ, self._env("merger-profile")):
+            # Initially no preflight check is recorded
+            self.assertEqual(mcp_server._preflight_resolved_role, None)
+            
+            # Request reviewer lease task which should be denied for merger
+            res = mcp_server.gitea_resolve_task_capability(task="review_pr", remote="prgs")
+            
+            # The task is denied
+            self.assertFalse(res["allowed_in_current_session"])
+            
+            # The session role stamp should NOT be poisoned
+            self.assertNotEqual(mcp_server._preflight_resolved_role, "reviewer")
+
 if __name__ == "__main__":
     unittest.main()