diff --git a/scripts/consistency_check.py b/scripts/consistency_check.py
index 35826e6..01f2143 100644
--- a/scripts/consistency_check.py
+++ b/scripts/consistency_check.py
@@ -2547,10 +2547,10 @@ def _write_custodian_brief(api_base: str, repo_slug: str, repo_path: str) -> boo
         return False
 
     repo_id: str = repo.get("id", "")
-    domain_slug: str = ""
+    domain_slug = str(repo.get("domain_slug") or "")
 
-    # Resolve domain slug: prefer active workstreams, fall back to any workstream
-    # so that a fully-finished repo doesn't degrade to "(unknown)".
+    # The repository projection owns domain identity. Retain the workplan/topic
+    # lookup only for compatibility with older API responses that omitted it.
     workstreams: list[dict] = []
     for status in OPEN_WORKSTREAM_STATUSES:
         rows = _api_get(api_base, "/workplans", {"repo_id": repo_id, "status": status}) or []
@@ -2560,7 +2560,7 @@ def _write_custodian_brief(api_base: str, repo_slug: str, repo_path: str) -> boo
     if not _ws_for_domain:
         all_ws = _api_get(api_base, "/workplans", {"repo_id": repo_id}) or []
         _ws_for_domain = all_ws if isinstance(all_ws, list) else []
-    if _ws_for_domain:
+    if not domain_slug and _ws_for_domain:
         topic = _api_get(api_base, f"/topics/{_ws_for_domain[0].get('topic_id', '')}")
         if topic:
             domain_slug = topic.get("domain_slug", "")
diff --git a/tests/test_consistency_check.py b/tests/test_consistency_check.py
index d7c752e..a58f6f0 100644
--- a/tests/test_consistency_check.py
+++ b/tests/test_consistency_check.py
@@ -41,6 +41,7 @@ from consistency_check import (
     _patch_frontmatter_field,
     _patch_task_status_in_file,
     _report_needs_action,
+    _write_custodian_brief,
     archive_closed_workplans,
     canonical_workplan_filename,
     check_repo,
@@ -72,6 +73,63 @@ class TestResolveTopicDomainSlug:
         assert resolve_topic_domain_slug("custodian", repo_market_domain="infotech") == "infotech"
 
 
+class TestCustodianBriefDomain:
+    @staticmethod
+    def _install_common_mocks(monkeypatch, calls, repo_payload, topic_payload=None):
+        def fake_get(_api_base, path, params=None):
+            calls.append((path, params))
+            if path == "/repos/demo":
+                return repo_payload
+            if path == "/workplans":
+                return [{"id": "wp-1", "title": "Open", "topic_id": None}]
+            if path == "/tasks":
+                return []
+            if path == "/repo-goals":
+                return []
+            if path.startswith("/topics/"):
+                return topic_payload
+            if path == "/messages":
+                return []
+            return None
+
+        monkeypatch.setattr("consistency_check._api_get", fake_get)
+        monkeypatch.setattr(
+            "consistency_check._git_commit_writeback", lambda *args, **kwargs: True
+        )
+
+    def test_brief_prefers_repository_domain_when_workplan_topic_is_null(
+        self, tmp_path, monkeypatch
+    ):
+        calls = []
+        self._install_common_mocks(
+            monkeypatch,
+            calls,
+            {"id": "repo-1", "domain_slug": "infotech"},
+        )
+
+        assert _write_custodian_brief("http://unused", "demo", str(tmp_path)) is True
+        brief = (tmp_path / ".custodian-brief.md").read_text(encoding="utf-8")
+        assert "**Domain:** infotech" in brief
+        assert '`get_domain_summary("infotech")`' in brief
+        assert not any(path.startswith("/topics/") for path, _params in calls)
+
+    def test_brief_retains_topic_fallback_for_legacy_repo_response(
+        self, tmp_path, monkeypatch
+    ):
+        calls = []
+        self._install_common_mocks(
+            monkeypatch,
+            calls,
+            {"id": "repo-1"},
+            {"domain_slug": "financials"},
+        )
+
+        assert _write_custodian_brief("http://unused", "demo", str(tmp_path)) is True
+        brief = (tmp_path / ".custodian-brief.md").read_text(encoding="utf-8")
+        assert "**Domain:** financials" in brief
+        assert any(path.startswith("/topics/") for path, _params in calls)
+
+
 class TestRepoManagerConformanceAdapter:
     def test_surfaces_repo_manager_findings_without_reimplementing_rules(self, tmp_path, monkeypatch):
         rmgr = tmp_path / "rmgr"
diff --git a/workplans/STATE-WP-0079-retirement-strangler.md b/workplans/STATE-WP-0079-retirement-strangler.md
index 16dc194..760de4b 100644
--- a/workplans/STATE-WP-0079-retirement-strangler.md
+++ b/workplans/STATE-WP-0079-retirement-strangler.md
@@ -346,6 +346,16 @@ project repos are already routed to `rmgr scaffold`. Gate the deletion on
 `RMGR-WP-0004-T06` proving byte-identical durable output and idempotent
 re-scaffolding.
 
+**Brief compatibility repair (2026-08-23):** the surviving consistency
+generator degraded `the-custodian` to `Domain: (unknown)` and emitted
+`get_domain_summary("")` even though `GET /repos/the-custodian` correctly
+projected `domain_slug: infotech`. Active workplans can legitimately have no
+topic, so topic inference is not authoritative. The generator now prefers the
+repository projection and retains topic lookup only for legacy API responses
+that omit `domain_slug`. Two regression tests cover both paths; all 131
+consistency-check tests pass. This is a compatibility fix until the generator
+moves or retires, not new permanent State Hub authority.
+
 ## Retire legacy surfaces
 
 ```task