fix(openai): preserve reasoning for local OpenAI-compatible models via R1 toggle

[ch405canova-sudo]

Summary

Local OpenAI-compatible reasoning models (llama.cpp llama-server, LM Studio, Ollama's OpenAI endpoint, vLLM, etc.) stream a reasoning_content field, but Zoo Code strips it from the follow-up context for these providers — so the model can never see its own reasoning chain on the next turn.

Root cause

openAiR1FormatEnabled (exposed as a UI checkbox via R1FormatSetting and declared in provider-settings.ts) only forces the R1 request format in openai.ts. It never propagates to info.preserveReasoning, which is what gates reasoning retention in Task.ts:

// src/core/task/Task.tsconstshouldPreserveForApi=this.api.getModel().info.preserveReasoning===true

OpenAiHandler.getModel() builds its ModelInfo from openAiCustomModelInfo ?? openAiModelInfoSaneDefaults — neither sets preserveReasoning. For the built-in OpenAI-compatible provider the value is therefore always undefined, and reasoning is stripped from messages sent back to the API.

Fix

When the user enables the R1 format toggle, getModel() now sets preserveReasoning: true on the returned model info:

return{
id,info: this.options.openAiR1FormatEnabled ? { ...info,preserveReasoning: true} : info,
...params,}

This preserves reasoning_content in the assistant history sent to the model on follow-up turns. Default behaviour (toggle off) is unchanged.

Tests

Added two getModel cases to src/api/providers/__tests__/openai.spec.ts:

• preserveReasoning is true when openAiR1FormatEnabled is on
• preserveReasoning stays undefined by default

Related

• Issue: [BUG] Reasoning from local OpenAI-compatible models (llama.cpp/Ollama/LM Studio) is discarded — no official toggle #1118 (bug report for the same root cause)

Fixes#1118

Summary by CodeRabbit

• New Features

  • Added support for preserving reasoning information when the OpenAI R1 format option is enabled, allowing compatible responses to retain their reasoning details.

• Bug Fixes

  • Ensured model configuration remains unchanged when the option is disabled, preserving existing behavior by default.

[coderabbitai]

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📥 Commits

Reviewing files that changed from the base of the PR and between beef72e and f4a69cc.

📒 Files selected for processing (1)

• src/api/providers/__tests__/openai.spec.ts

🚧 Files skipped from review as they are similar to previous changes (1)

• src/api/providers/tests/openai.spec.ts

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📝 Walkthrough

Walkthrough

OpenAiHandler.getModel now adds preserveReasoning: true when openAiR1FormatEnabled is enabled. Tests cover enabled and default behavior.

Changes

OpenAI reasoning configuration

Layer / File(s)	Summary
Conditional model configuration src/api/providers/openai.ts, src/api/providers/__tests__/openai.spec.ts	getModel copies model information and adds preserveReasoning: true when the R1 format setting is enabled. Tests verify enabled and default behavior.

Estimated code review effort: 2 (Simple) | ~10 minutes

Possibly related issues

• [BUG] Reasoning from local OpenAI-compatible models (llama.cpp/Ollama/LM Studio) is discarded — no official toggle #1118 — Tracks missing reasoning preservation for local OpenAI-compatible models.
• [BUG] Reasoning is never sent back to the API for the OpenAI Compatible provider — preserveReasoning cannot be enabled from the UI #1096 — Requests exposing reasoning preservation for OpenAI-compatible models.

Possibly related PRs

• Zoo-Code-Org/Zoo-Code#775 — Uses preserveReasoning to round-trip reasoning_content.
• Zoo-Code-Org/Zoo-Code#892 — Implements related OpenAI R1 reasoning preservation behavior.
• Zoo-Code-Org/Zoo-Code#933 — Modifies OpenAI provider reasoning behavior.

Suggested reviewers:taltas, navedmerchant

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly identifies the OpenAI-compatible provider fix and the R1 toggle behavior.
Description check	✅ Passed	The description explains the root cause, implementation, linked issue, and tests, despite omitting the repository checklist sections.
Linked Issues check	✅ Passed	The changes connect the R1 toggle to reasoning preservation and address issue #1118 without changing default behavior.
Out of Scope Changes check	✅ Passed	The code and test changes are limited to the OpenAI-compatible provider behavior required by issue #1118.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

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src/api/providers/__tests__/openai.spec.ts

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[ch405canova-sudo]

This work is a joint effort by chaos (@ch405canova-sudo) and opencode — the bug was found and the fix developed together on a local llama.cpp stack (August 2026).

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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[ch405canova-sudo]

This PR addresses the same root cause as #1096 (local OpenAI-compatible reasoning is discarded because preserveReasoning is never enabled for the built-in OpenAI-compatible provider).

Note on approach: #1096 proposes a separate preserveReasoning checkbox, while this PR couples it to the existing R1-format toggle. Both solve the underlying issue — happy to align with whichever approach the maintainers prefer.

[edelauna]

Thank you for your contribution, but could we align with #1096 and include this a a checkbox in the ui, I don't feel great about reusing an unrelated flag.

[edelauna]

createMessage() treats a model as R1-format via modelId.includes("deepseek-reasoner") || enabledR1Format (line 90), but this gate only checks the toggle. If someone points openAiModelId at a custom endpoint whose id contains deepseek-reasoner without flipping the toggle, wouldn't createMessage still use R1 conversion while preserveReasoning never gets set here — leaving the original bug open for that case?

[edelauna]

This forces preserveReasoning: true whenever the toggle is on, even if openAiCustomModelInfo.preserveReasoning was explicitly set to false. Should an explicit value win here, e.g. info.preserveReasoning ?? true?

[github-actions]

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