feat(memory): structured reflection + correction detection in MemoryMiddleware (#1620) (#1668)

* feat(memory): add structured reflection and correction detection

* fix(memory): align sourceError schema and prompt guidance

---------

Co-authored-by: Willem Jiang <willem.jiang@gmail.com>

backend/app/gateway/routers/memory.py

@@ -49,6 +49,7 @@ class Fact(BaseModel):
     confidence: float = Field(default=0.5, description="Confidence score (0-1)")
     createdAt: str = Field(default="", description="Creation timestamp")
     source: str = Field(default="unknown", description="Source thread ID")
+    sourceError: str | None = Field(default=None, description="Optional description of the prior mistake or wrong approach")
 
 
 class MemoryResponse(BaseModel):
@@ -108,6 +109,7 @@ class MemoryStatusResponse(BaseModel):
 @router.get(
     "/memory",
     response_model=MemoryResponse,
+    response_model_exclude_none=True,
     summary="Get Memory Data",
     description="Retrieve the current global memory data including user context, history, and facts.",
 )
@@ -152,6 +154,7 @@ async def get_memory() -> MemoryResponse:
 @router.post(
     "/memory/reload",
     response_model=MemoryResponse,
+    response_model_exclude_none=True,
     summary="Reload Memory Data",
     description="Reload memory data from the storage file, refreshing the in-memory cache.",
 )
@@ -171,6 +174,7 @@ async def reload_memory() -> MemoryResponse:
 @router.delete(
     "/memory",
     response_model=MemoryResponse,
+    response_model_exclude_none=True,
     summary="Clear All Memory Data",
     description="Delete all saved memory data and reset the memory structure to an empty state.",
 )
@@ -187,6 +191,7 @@ async def clear_memory() -> MemoryResponse:
 @router.post(
     "/memory/facts",
     response_model=MemoryResponse,
+    response_model_exclude_none=True,
     summary="Create Memory Fact",
     description="Create a single saved memory fact manually.",
 )
@@ -209,6 +214,7 @@ async def create_memory_fact_endpoint(request: FactCreateRequest) -> MemoryRespo
 @router.delete(
     "/memory/facts/{fact_id}",
     response_model=MemoryResponse,
+    response_model_exclude_none=True,
     summary="Delete Memory Fact",
     description="Delete a single saved memory fact by its fact id.",
 )
@@ -227,6 +233,7 @@ async def delete_memory_fact_endpoint(fact_id: str) -> MemoryResponse:
 @router.patch(
     "/memory/facts/{fact_id}",
     response_model=MemoryResponse,
+    response_model_exclude_none=True,
     summary="Patch Memory Fact",
     description="Partially update a single saved memory fact by its fact id while preserving omitted fields.",
 )
@@ -252,6 +259,7 @@ async def update_memory_fact_endpoint(fact_id: str, request: FactPatchRequest) -
 @router.get(
     "/memory/export",
     response_model=MemoryResponse,
+    response_model_exclude_none=True,
     summary="Export Memory Data",
     description="Export the current global memory data as JSON for backup or transfer.",
 )
@@ -264,6 +272,7 @@ async def export_memory() -> MemoryResponse:
 @router.post(
     "/memory/import",
     response_model=MemoryResponse,
+    response_model_exclude_none=True,
     summary="Import Memory Data",
     description="Import and overwrite the current global memory data from a JSON payload.",
 )
@@ -317,6 +326,7 @@ async def get_memory_config_endpoint() -> MemoryConfigResponse:
 @router.get(
     "/memory/status",
     response_model=MemoryStatusResponse,
+    response_model_exclude_none=True,
     summary="Get Memory Status",
     description="Retrieve both memory configuration and current data in a single request.",
 )