fix(api-server): validate previous_response_id type and length (salvage of #2961 by @aydnOktay)

contributors/emails/seraphine@Seraphines-Mac-Studio.local

@@ -0,0 +1,2 @@
+Bartok9
+# Seraphine Mac Studio local email on Bartok9 PR tips (per-PR attribution; Teknium/Daniel 2026-08-01)

gateway/platforms/api_server.py

@@ -123,6 +123,7 @@ def _hermes_version() -> str:
 DEFAULT_HOST = "127.0.0.1"
 DEFAULT_PORT = 8642
 MAX_STORED_RESPONSES = 100
+MAX_PREVIOUS_RESPONSE_ID_LENGTH = 128
 MAX_REQUEST_BYTES = 10_000_000  # 10 MB — accommodates long agent conversations with tool calls
 CHAT_COMPLETIONS_SSE_KEEPALIVE_SECONDS = 30.0
 MAX_NORMALIZED_TEXT_LENGTH = 65_536  # 64 KB cap for normalized content parts
@@ -4891,6 +4892,27 @@ async def _handle_responses(self, request: "web.Request") -> "web.Response":
 
         instructions = body.get("instructions")
         previous_response_id = body.get("previous_response_id")
+
+        # Basic hardening: ensure previous_response_id is a reasonable string.
+        if previous_response_id is not None:
+            if not isinstance(previous_response_id, str):
+                return web.json_response(
+                    _openai_error("Invalid 'previous_response_id' type"),
+                    status=400,
+                )
+            if not previous_response_id:
+                return web.json_response(
+                    _openai_error("Invalid 'previous_response_id' value"),
+                    status=400,
+                )
+            if len(previous_response_id) > MAX_PREVIOUS_RESPONSE_ID_LENGTH:
+                return web.json_response(
+                    _openai_error(
+                        "previous_response_id is too long.",
+                        code="previous_response_id_too_long",
+                    ),
+                    status=400,
+                )
         conversation = body.get("conversation")
         store = _coerce_request_bool(body.get("store"), default=True)
 
@@ -6110,6 +6132,27 @@ async def _handle_runs(self, request: "web.Request") -> "web.Response":
         instructions = body.get("instructions")
         previous_response_id = body.get("previous_response_id")
 
+        # Basic hardening: ensure previous_response_id is a reasonable string.
+        if previous_response_id is not None:
+            if not isinstance(previous_response_id, str):
+                return web.json_response(
+                    _openai_error("Invalid 'previous_response_id' type"),
+                    status=400,
+                )
+            if not previous_response_id:
+                return web.json_response(
+                    _openai_error("Invalid 'previous_response_id' value"),
+                    status=400,
+                )
+            if len(previous_response_id) > MAX_PREVIOUS_RESPONSE_ID_LENGTH:
+                return web.json_response(
+                    _openai_error(
+                        "previous_response_id is too long.",
+                        code="previous_response_id_too_long",
+                    ),
+                    status=400,
+                )
+
         # Accept explicit conversation_history from the request body.
         # Precedence: explicit conversation_history > previous_response_id.
         conversation_history: List[Dict[str, str]] = []

tests/gateway/test_api_server.py

@@ -29,6 +29,7 @@
 from gateway.config import GatewayConfig, Platform, PlatformConfig
 from gateway.platforms.api_server import (
     APIServerAdapter,
+    MAX_PREVIOUS_RESPONSE_ID_LENGTH,
     ResponseStore,
     _IdempotencyCache,
     _derive_chat_session_id,
@@ -318,6 +319,7 @@ def _create_app(adapter: APIServerAdapter) -> web.Application:
     app.router.add_post("/v1/responses", adapter._handle_responses)
     app.router.add_get("/v1/responses/{response_id}", adapter._handle_get_response)
     app.router.add_delete("/v1/responses/{response_id}", adapter._handle_delete_response)
+    app.router.add_post("/v1/runs", adapter._handle_runs)
     app.router.add_post(
         "/api/platforms/{platform}/events",
         adapter._handle_platform_event_callback,