---
license: mit
language:
  - en
pretty_name: Serving-Stack Confounds in Local Tool-Use Evaluation
size_categories:
  - n<1K
task_categories:
  - text-generation
tags:
  - tool-calling
  - function-calling
  - llm-evaluation
  - llm-agents
  - ollama
  - vllm
  - sglang
  - llama-cpp
configs:
  - config_name: serving_modes
    default: true
    data_files: serving_modes.csv
  - config_name: chain_compare
    data_files: chain_compare.csv
  - config_name: crossstack
    data_files: crossstack.csv
  - config_name: humaneval_probe
    data_files: humaneval_probe.csv
---

# Serving-Stack Confounds in Local Tool-Use Evaluation

Result tables for **Measuring the Serving Stack Instead of the Model: Hidden Confounds in
Local Tool-Use Evaluation** (Lijuan Tang, Yuemeng Zheng; REALM Workshop @ EMNLP 2026).

- Paper: [ACL Anthology](https://aclanthology.org/2026.realm-1.7/) · [arXiv:2609.26693](https://arxiv.org/abs/2609.26693)
- Code, configs, and reproduction steps: [github.com/LijuanTang94/serving-confound-repo](https://github.com/LijuanTang94/serving-confound-repo)

![Per-seed protocol fidelity under three serving conditions](serving_modes.png)

## What this measures

**Protocol fidelity** = the rate of valid, in-schema tool calls over the turns the model
actually produced. Requests the server refused (for example Ollama's HTTP 400
`does not support tools` for Phi-3 and Gemma-3) are counted separately as rejected and
excluded from the denominator. A naive analysis that counts them as model non-calls
reports a capable model at 0% even though it never ran.

Serving conditions:

| condition | `tools=` sent | text tool list in prompt |
|---|---|---|
| `native` (default) | yes | no |
| `native_hint` | yes | yes |
| `text_tools` / `tt` | no | yes |

All local models run on Ollama 0.30.8 with default (Q4_K_M) quantization;
`deepseek-v4-flash` is a cloud anchor. A "seed" indexes a task instance; decoding is
sampled at T=1.0.

## Configs

### `serving_modes` (default): aggregation task, 8 seeds, three conditions

For each condition prefix (`native`, `native_hint`, `text_tools`):

| column | meaning |
|---|---|
| `<cond>_seed` | per-seed mean fidelity |
| `<cond>_lo`, `<cond>_hi` | seed-level bootstrap 95% CI |
| `<cond>_pooled` | turn-pooled fidelity |
| `<cond>_n` | model-produced turns in the pool |
| `<cond>_rej` | rejected requests (excluded from the denominator) |
| `<cond>_n_seeds` | seeds with at least one produced turn |

Empty cells mean the condition was not run or the rate is undefined (every request was
rejected).

### `chain_compare`: dependency-chain task, 4 seeds

`native_*` and `tt_*` (text-tools) with `_seed` (per-seed mean), `_pool` (turn-pooled),
`_n` (turns), `_rej` (rejected requests).

### `crossstack`: same `tools=` request on four serving stacks

One row per model; each cell is the outcome on that stack: `200_native` (native
`tool_calls`), `200_text` / `200_text_json_block` (call returned as text),
`200_runs_text` (request accepted, model runs), `200_prose_nocall` / `200_text_prose`
(prose, no call), `HTTP400_rejected` (Ollama per-model gating), `HTTP400_no_parser`
(vLLM without `--enable-auto-tool-choice --tool-call-parser`), `not_probed`, `n/a`.
`vllm_configured` is vLLM with tool parsing enabled. The vLLM and SGLang probes cover
only the models shown.

### `humaneval_probe`: single-turn replication on 6 HumanEval problems

`native_gating` is the Ollama response to `tools=` (`-` = not probed), then
`text_tools_valid` of `n` problems produced a valid call under the text-tools protocol.

## Citation

```bibtex
@inproceedings{tang-zheng-2026-measuring,
    title = "Measuring the Serving Stack Instead of the Model: Hidden Confounds in Local Tool-Use Evaluation",
    author = "Tang, Lijuan  and
      Zheng, Yuemeng",
    booktitle = "Proceedings of the Second Workshop for {RE}search on Agent Language Models ({REALM} 2026)",
    month = oct,
    year = "2026",
    address = "Budapest, Hungary",
    publisher = "Association for Computational Linguistics",
    url = "https://aclanthology.org/2026.realm-1.7/",
    doi = "10.18653/2026.realm-1.7",
    pages = "86--94"
}
```