diff --git a/authbridge/sparc-service/sparc_service/__main__.py b/authbridge/sparc-service/sparc_service/__main__.py
index a0f387a4..65d7ba23 100644
--- a/authbridge/sparc-service/sparc_service/__main__.py
+++ b/authbridge/sparc-service/sparc_service/__main__.py
@@ -8,6 +8,8 @@
 
 
 def main() -> None:
+    import logging
+    logging.basicConfig(level=logging.INFO)
     settings = Settings.from_env()
     uvicorn.run("sparc_service.api:app", host=settings.host, port=settings.port, log_level="info")
 
diff --git a/authbridge/sparc-service/sparc_service/api.py b/authbridge/sparc-service/sparc_service/api.py
index 67df2c24..c120b1a1 100644
--- a/authbridge/sparc-service/sparc_service/api.py
+++ b/authbridge/sparc-service/sparc_service/api.py
@@ -8,7 +8,9 @@
 
 from __future__ import annotations
 
+import json
 import logging
+import os
 
 from fastapi import FastAPI, HTTPException
 from fastapi.concurrency import run_in_threadpool
@@ -19,6 +21,37 @@
 
 log = logging.getLogger(__name__)
 
+# When SPARC_LOG_REQUESTS=true, log the full incoming ReflectRequest JSON so
+# you can inspect exactly what the caller sends (useful for diagnosing
+# unexpected tool argument keys). Disabled by default — payloads can be large.
+_LOG_REQUESTS = os.getenv("SPARC_LOG_REQUESTS", "").strip().lower() in {"1", "true", "yes"}
+
+# When SPARC_STRIP_TOOL_ARG_KEYS is set (comma-separated key names), those keys
+# are removed from every tool_calls[].function.arguments JSON object before the
+# request reaches SPARC. Use to drop agent-injected keys that are not in the
+# tool spec and would cause SPARC to reject the call.
+# Example: SPARC_STRIP_TOOL_ARG_KEYS=session_id,request_id
+_STRIP_KEYS: frozenset[str] = frozenset(
+    k.strip() for k in os.getenv("SPARC_STRIP_TOOL_ARG_KEYS", "").split(",") if k.strip()
+)
+
+
+def _strip_tool_arg_keys(tool_calls: list[dict], keys: frozenset[str]) -> list[dict]:
+    """Return a copy of tool_calls with the named argument keys removed."""
+    result = []
+    for tc in tool_calls:
+        fn = tc.get("function", {})
+        raw_args = fn.get("arguments", "")
+        try:
+            args = json.loads(raw_args) if isinstance(raw_args, str) else raw_args
+            if isinstance(args, dict):
+                args = {k: v for k, v in args.items() if k not in keys}
+            new_args = json.dumps(args) if isinstance(args, dict) else raw_args
+        except (json.JSONDecodeError, TypeError):
+            new_args = raw_args
+        result.append({**tc, "function": {**fn, "arguments": new_args}})
+    return result
+
 
 def create_app(engine: ReflectionEngine | None = None) -> FastAPI:
     """Build the FastAPI app. Inject ``engine`` in tests; defaults to env config."""
@@ -51,6 +84,16 @@ def readyz() -> dict[str, object]:
 
     @app.post("/reflect", response_model=ReflectResponse)
     async def reflect(request: ReflectRequest) -> ReflectResponse:
+        if _LOG_REQUESTS:
+            log.info("incoming reflect request: %s", request.model_dump_json())
+
+        if _STRIP_KEYS and request.tool_calls:
+            request = request.model_copy(
+                update={"tool_calls": _strip_tool_arg_keys(request.tool_calls, _STRIP_KEYS)}
+            )
+            if _LOG_REQUESTS:
+                log.info("after strip (%s): tool_calls=%s", sorted(_STRIP_KEYS), request.tool_calls)
+
         # SPARCReflectionComponent.process is synchronous (and CPU/IO bound on the
         # LLM call); run it off the event loop so the service stays responsive.
         try: