fix(governance): link events to dispatch history

apps/api/src/services/governance_query_service.py

@@ -116,7 +116,11 @@ def _extract_remediation(details: dict) -> str | None:
     return str(remediation)[:160]
 
 
-def _to_governance_event(row: AiGovernanceEvent) -> GovernanceEvent:
+def _to_governance_event(
+    row: AiGovernanceEvent,
+    *,
+    dispatch_ids: list[str] | None = None,
+) -> GovernanceEvent:
     details = row.details if isinstance(row.details, dict) else {}
     return GovernanceEvent(
         id=row.id,
@@ -128,10 +132,60 @@ def _to_governance_event(row: AiGovernanceEvent) -> GovernanceEvent:
         impact=_extract_impact(details),
         details=details,
         remediation=_extract_remediation(details),
-        dispatch_ids=details.get("dispatch_ids", []),
+        dispatch_ids=_merge_dispatch_ids(dispatch_ids or [], details.get("dispatch_ids")),
     )
 
 
+def _merge_dispatch_ids(
+    db_dispatch_ids: list[str],
+    legacy_dispatch_ids: Any,
+) -> list[str]:
+    """合併 DB dispatch trail 與 legacy payload ids，DB truth-first。"""
+    merged: list[str] = []
+    for raw in [*db_dispatch_ids, *(legacy_dispatch_ids if isinstance(legacy_dispatch_ids, list) else [])]:
+        if raw is None:
+            continue
+        value = str(raw)
+        if value and value not in merged:
+            merged.append(value)
+    return merged
+
+
+async def _load_dispatch_ids_for_events(event_ids: list[str]) -> dict[str, list[str]]:
+    """從 governance_remediation_dispatch 讀取事件對應 dispatch ids。
+
+    events endpoint 必須能在 dispatch 表尚未建立的環境 graceful fallback，
+    因此這裡捕捉 ProgrammingError 並回空 dict。
+    """
+    if not event_ids:
+        return {}
+
+    sql = text("""
+        SELECT
+            d.governance_event_id,
+            d.id
+        FROM governance_remediation_dispatch d
+        WHERE d.governance_event_id IN :event_ids
+        ORDER BY d.dispatched_at DESC
+    """).bindparams(bindparam("event_ids", expanding=True))
+
+    try:
+        async with get_db_context() as db:
+            result = await db.execute(sql, {"event_ids": event_ids})
+            rows = result.fetchall()
+    except ProgrammingError as exc:
+        logger.warning(
+            "governance_dispatch_ids_table_not_ready",
+            error=str(exc),
+        )
+        return {}
+
+    dispatch_ids_by_event: dict[str, list[str]] = {}
+    for row in rows:
+        dispatch_ids_by_event.setdefault(str(row.governance_event_id), []).append(str(row.id))
+    return dispatch_ids_by_event
+
+
 # =============================================================================
 # Endpoint 1: events
 # =============================================================================
@@ -175,6 +229,7 @@ async def query_governance_events(
         result = await db.execute(stmt)
         all_rows = result.scalars().all()
 
+    event_rows_by_id = {str(r.id): r for r in all_rows}
     events = [_to_governance_event(r) for r in all_rows]
 
     # severity 過濾（Python 層）
@@ -194,6 +249,15 @@ async def query_governance_events(
     total = len(events)
     offset = (page - 1) * size
     page_items = events[offset: offset + size]
+    dispatch_ids_by_event = await _load_dispatch_ids_for_events([e.id for e in page_items])
+    if dispatch_ids_by_event:
+        page_items = [
+            _to_governance_event(
+                event_rows_by_id[item.id],
+                dispatch_ids=dispatch_ids_by_event.get(item.id, []),
+            )
+            for item in page_items
+        ]
 
     return GovernanceEventsResponse(
         items=page_items,

apps/api/tests/test_ai_governance_endpoints.py

@@ -33,6 +33,7 @@ from src.models.governance import (
 )
 from src.services.governance_query_service import (
     _extract_remediation,
+    _merge_dispatch_ids,
     _query_dispatch_table,
     _to_governance_event,
 )
@@ -221,6 +222,42 @@ class TestEventsReadSideNormalization:
         assert event.remediation == "補齊 SLO emitter"
         assert event.impact == "SLO metrics missing"
 
+    def test_governance_event_uses_db_dispatch_ids_first(self):
+        """events read model 應以 dispatch table ids 補齊 detail/history 鏈路。"""
+        row = type("Row", (), {
+            "id": "evt-001",
+            "event_type": "knowledge_degradation",
+            "triggered_at": NOW,
+            "resolved": False,
+            "resolved_at": None,
+            "details": {
+                "message": "KM stale",
+                "dispatch_ids": ["legacy-dispatch"],
+            },
+        })()
+
+        event = _to_governance_event(row, dispatch_ids=["db-dispatch", "legacy-dispatch"])
+
+        assert event.dispatch_ids == ["db-dispatch", "legacy-dispatch"]
+
+    def test_merge_dispatch_ids_deduplicates_and_preserves_db_priority(self):
+        """DB truth-first，legacy payload 只作 fallback。"""
+        assert _merge_dispatch_ids(
+            ["db-2", "db-1"],
+            ["db-1", "legacy-1", None],
+        ) == ["db-2", "db-1", "legacy-1"]
+
+    def test_events_query_joins_dispatch_table_for_history_buttons(self):
+        """events endpoint 不可只讀 details.dispatch_ids，必須查 dispatch table。"""
+        import inspect
+        from src.services import governance_query_service
+
+        source = inspect.getsource(governance_query_service._load_dispatch_ids_for_events)
+
+        assert "FROM governance_remediation_dispatch d" in source
+        assert "d.governance_event_id IN :event_ids" in source
+        assert "ORDER BY d.dispatched_at DESC" in source
+
 
 # =============================================================================
 # 3. queue endpoint graceful fallback