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[GPT-OSS] Structure_Tag support for gpt-oss tool-call in cot#25515

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[GPT-OSS] Structure_Tag support for gpt-oss tool-call in cot#25515
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Hanchenli:lhc/oss-try

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@Hanchenli

@Hanchenli Hanchenli commented Sep 23, 2025 •
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Purpose

The model sometimes generates function calls in CoT that have not been provided in tool_server. This PR uses structural tag to force model to 1. do not generate function calls when tool_server is not provided. 2. Only generate function that are present in the tool_server.

example custom structural tags: https://gist.github.com/frank-wei/4929118fe0881ee561ce48f15c1f80ed

Test Plan

Testing with @frank-wei

Test Result

vllm serve run: https://gist.github.com/frank-wei/86d37061685fd45e5b831b6583d865d6

see number of turns reduced:

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@mergify

mergify Bot commented Sep 23, 2025

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This pull request has merge conflicts that must be resolved before it can be
merged. Please rebase the PR, @Hanchenli.

https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/working-with-forks/syncing-a-fork

@mergify mergify Bot added the v1 label Sep 23, 2025
@mergify mergify Bot added the needs-rebase label Sep 23, 2025
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Code Review

This pull request introduces support for structural tags in gpt-oss tool calls, aiming to constrain the model's output to valid function calls. The changes span model configuration, engine arguments, the OpenAI protocol, and a new reasoning parser for gpt-oss. While the overall approach is sound, I've identified a critical bug in gptoss_reasoning_parser.py involving the mutation of a global dictionary, which could lead to incorrect behavior in subsequent requests. Additionally, there's a high-severity bug in a log statement within the same file that could cause runtime errors. I have provided detailed comments and code suggestions to address these issues. The rest of the changes, including new tests and dependency updates, appear to be in good order.

Comment thread vllm/reasoning/gptoss_reasoning_parser.py Outdated
Comment thread vllm/reasoning/gptoss_reasoning_parser.py Outdated
@hmellor

hmellor commented Oct 17, 2025

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Yes this Phi3 test has been unreliable on main for a while. cc @DarkLight1337

@DarkLight1337

DarkLight1337 commented Oct 18, 2025

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I should have fixed it on main already. Let me rebase this PR

@yeqcharlotte yeqcharlotte enabled auto-merge (squash) October 18, 2025 04:16
@vllm-bot vllm-bot merged commit 7c57254 into vllm-project:main Oct 18, 2025
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ci/build frontend gpt-oss Related to GPT-OSS models ready ONLY add when PR is ready to merge/full CI is needed structured-output v1

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