Fix empty search query validation

src/schemas/api.py

@@ -552,11 +552,7 @@ class ConclusionBatchCreate(BaseModel):
 
 
 class MessageSearchOptions(BaseModel):
-    query: Annotated[
-        str,
-        BeforeValidator(strip_nul_bytes),
-        Field(min_length=1, description="Search query"),
-    ]
+    query: Annotated[str, Field(description="Search query")]
     filters: dict[str, Any] | None = Field(
         default=None, description="Filters to scope the search"
     )
@@ -567,15 +563,20 @@ class MessageSearchOptions(BaseModel):
         description="Number of results to return",
     )
 
-    @field_validator("query", mode="after")
+    @field_validator("query", mode="before")
     @classmethod
-    def sanitize_query(cls, v: str) -> str:
-        if not v:
+    def sanitize_query(cls, v: Any) -> Any:
+        if not isinstance(v, str):
+            return v
+
+        sanitized = cast(str, strip_nul_bytes(v))
+        if v != "" and sanitized == "":
             raise PydanticCustomError(
                 "string_too_short",
                 "String should have at least 1 character",
             )
-        return v
+
+        return sanitized
 
 
 # ---------------------------------------------------------------------------

tests/routes/test_peers.py

@@ -689,6 +689,22 @@ def test_search_peer_empty_query(
     assert isinstance(data, list)
 
 
+def test_search_peer_nul_only_query_rejected(
+    client: TestClient, sample_data: tuple[Workspace, Peer]
+):
+    """Test peer search with a query that becomes empty after sanitization."""
+    test_workspace, test_peer = sample_data
+
+    response = client.post(
+        f"/v3/workspaces/{test_workspace.name}/peers/{test_peer.name}/search",
+        json={"query": "\x00", "limit": 10},
+    )
+    assert response.status_code == 422
+    error = response.json()["detail"][0]
+    assert error["loc"] == ["body", "query"]
+    assert error["type"] == "string_too_short"
+
+
 def test_search_peer_nonexistent(
     client: TestClient, sample_data: tuple[Workspace, Peer]
 ):

tests/test_schema_validations.py

@@ -8,6 +8,7 @@ from src.schemas import (
     DialecticOptions,
     DocumentCreate,
     DocumentMetadata,
+    MessageSearchOptions,
     MessageCreate,
     ObservationInput,
     PeerCreate,
@@ -217,6 +218,19 @@ class TestResolvedConfigurationMigration:
 
 
 class TestSanitizedRequiredFields:
+    def test_message_search_query_allows_literal_empty_string(self):
+        search = MessageSearchOptions.model_validate({"query": ""})
+
+        assert search.query == ""
+
+    def test_message_search_query_rejects_nul_only_input(self):
+        with pytest.raises(ValidationError) as exc_info:
+            MessageSearchOptions.model_validate({"query": "\x00"})
+
+        error_dict = exc_info.value.errors()[0]
+        assert error_dict["loc"] == ("query",)
+        assert error_dict["type"] == "string_too_short"
+
     def test_conclusion_content_rejects_nul_only_input(self):
         with pytest.raises(ValidationError) as exc_info:
             ConclusionCreate(