[Misc] Rename think_start_str/think_end_str to reasoning_start_str/reasoning_end_str by chaunceyjiang · Pull Request #38242 · vllm-project/vllm

chaunceyjiang · 2026-03-26T14:25:54Z

Purpose

follow up #20859
Rename think_start_str/think_end_str to reasoning_start_str/reasoning_end_str.

Avoid being too tightly coupled to <think>. Some models experiment with fields like <seed:think>, or patterns such as </think>\n<answer>\n.

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…reasoning_end_str Signed-off-by: chaunceyjiang <chaunceyjiang@gmail.com>

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mergify · 2026-03-26T14:27:01Z

Documentation preview: https://vllm--38242.org.readthedocs.build/en/38242/

gemini-code-assist

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This pull request renames think_start_str and think_end_str to reasoning_start_str and reasoning_end_str across the codebase, including documentation, tests, and core configuration files, to improve naming consistency. However, an offline inference example in docs/features/reasoning_outputs.md was not updated and still uses the old parameter names, which will cause a TypeError. Additionally, it is suggested to consider renaming other related terms like thinking_token_budget and ThinkingTokenBudgetLogitsProcessor for further consistency.

…reasoning_end_str Signed-off-by: chaunceyjiang <chaunceyjiang@gmail.com>

sfeng33 · 2026-03-26T18:59:05Z

I noticed a couple of things:

1. Missing rename in tests/v1/logits_processors/test_correctness.py

This file still references the old property names and would break after this PR merges:

tests/v1/logits_processors/test_correctness.py:106:    think_start_token_ids = [THINK_START_TOKEN_ID]
tests/v1/logits_processors/test_correctness.py:107:    think_end_token_ids = [THINK_END_TOKEN_ID]
tests/v1/logits_processors/test_correctness.py:494:        start_tokens = tb_processor.think_start_token_ids
tests/v1/logits_processors/test_correctness.py:521:        end_tokens = tb_processor.think_end_token_ids

2. Breaking change for --reasoning-config JSON input

Since the @config decorator uses extra="forbid", existing deployments passing {"think_start_str": "<think>", "think_end_str": "</think>"} via --reasoning-config will get a validation error after upgrading.

…reasoning_end_str Signed-off-by: chaunceyjiang <chaunceyjiang@gmail.com>

chaunceyjiang · 2026-03-27T02:35:59Z

@sfeng33 Thanks for the review. Regarding the second issue, since the preceding PR was merged not long ago and hasn’t been included in any released version yet, I’d like to merge this PR as soon as possible.

njhill

Thanks @chaunceyjiang

…asoning_end_str (#38242) Signed-off-by: chaunceyjiang <chaunceyjiang@gmail.com> (cherry picked from commit cbe7d18)

…asoning_end_str (vllm-project#38242) Signed-off-by: chaunceyjiang <chaunceyjiang@gmail.com> Signed-off-by: Rishi Puri <riship@nvidia.com>

…asoning_end_str (vllm-project#38242) Signed-off-by: chaunceyjiang <chaunceyjiang@gmail.com>

…asoning_end_str (vllm-project#38242) Signed-off-by: chaunceyjiang <chaunceyjiang@gmail.com> (cherry picked from commit f81920a)

…asoning_end_str (vllm-project#38242) Signed-off-by: chaunceyjiang <chaunceyjiang@gmail.com>

…asoning_end_str (vllm-project#38242) Signed-off-by: chaunceyjiang <chaunceyjiang@gmail.com> (cherry picked from commit e361770)

…asoning_end_str (vllm-project#38242) Signed-off-by: chaunceyjiang <chaunceyjiang@gmail.com>

…asoning_end_str (vllm-project#38242) Signed-off-by: chaunceyjiang <chaunceyjiang@gmail.com> Signed-off-by: Matt Van Horn <455140+mvanhorn@users.noreply.github.com>

chaunceyjiang added 3 commits March 26, 2026 22:16

[Rename] Rename think_start_str/think_end_str to reasoning_start_str/…

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…reasoning_end_str Signed-off-by: chaunceyjiang <chaunceyjiang@gmail.com>

[Rename] Rename think_start_str/think_end_str to reasoning_start_str/…

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…reasoning_end_str Signed-off-by: chaunceyjiang <chaunceyjiang@gmail.com>

[Rename] Rename think_start_str/think_end_str to reasoning_start_str/…

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…reasoning_end_str Signed-off-by: chaunceyjiang <chaunceyjiang@gmail.com>

chaunceyjiang requested review from 22quinn, ProExpertProg, WoosukKwon, hmellor, houseroad, mgoin, njhill, robertgshaw2-redhat, tlrmchlsmth, yewentao256 and youkaichao as code owners March 26, 2026 14:25

claude Bot reviewed Mar 26, 2026

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mergify Bot added documentation Improvements or additions to documentation v1 labels Mar 26, 2026

gemini-code-assist Bot reviewed Mar 26, 2026

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Comment thread docs/features/reasoning_outputs.md

[Rename] Rename think_start_str/think_end_str to reasoning_start_str/…

307f8d6

…reasoning_end_str Signed-off-by: chaunceyjiang <chaunceyjiang@gmail.com>

chaunceyjiang changed the title ~~[Rename] Rename think_start_str/think_end_str to reasoning_start_str/reasoning_end_str~~ [Misc] Rename think_start_str/think_end_str to reasoning_start_str/reasoning_end_str Mar 26, 2026

[Rename] Rename think_start_str/think_end_str to reasoning_start_str/…

00552bd

…reasoning_end_str Signed-off-by: chaunceyjiang <chaunceyjiang@gmail.com>

chaunceyjiang added the ready ONLY add when PR is ready to merge/full CI is needed label Mar 31, 2026

chaunceyjiang added this to the v0.19.0 cherry picks milestone Mar 31, 2026

Merge branch 'main' into rename_think_start_end_str

b46d9db

njhill approved these changes Apr 1, 2026

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njhill merged commit cbe7d18 into vllm-project:main Apr 1, 2026
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khluu pushed a commit that referenced this pull request Apr 1, 2026

[Misc] Rename think_start_str/think_end_str to reasoning_start_str/re…

3a30a1a

…asoning_end_str (#38242) Signed-off-by: chaunceyjiang <chaunceyjiang@gmail.com> (cherry picked from commit cbe7d18)

mtparet pushed a commit to blackfuel-ai/vllm that referenced this pull request Apr 9, 2026

[Misc] Rename think_start_str/think_end_str to reasoning_start_str/re…

aab8477

…asoning_end_str (vllm-project#38242) Signed-off-by: chaunceyjiang <chaunceyjiang@gmail.com>

llsj14 mentioned this pull request Apr 17, 2026

[Feature] limit thinking tokens (hard limit) #20859

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mystous pushed a commit to mystous/vllm_hybrid that referenced this pull request May 10, 2026

[Misc] Rename think_start_str/think_end_str to reasoning_start_str/re…

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…asoning_end_str (vllm-project#38242) Signed-off-by: chaunceyjiang <chaunceyjiang@gmail.com>

jhu960213 pushed a commit to jhu960213/vllm that referenced this pull request May 20, 2026

[Misc] Rename think_start_str/think_end_str to reasoning_start_str/re…

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…asoning_end_str (vllm-project#38242) Signed-off-by: chaunceyjiang <chaunceyjiang@gmail.com>

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[Misc] Rename think_start_str/think_end_str to reasoning_start_str/reasoning_end_str#38242

[Misc] Rename think_start_str/think_end_str to reasoning_start_str/reasoning_end_str#38242
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chaunceyjiang commented Mar 26, 2026 •

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