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.ts
const shouldPreserveForApi = 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.

• Bug Fixes

  • Ensured model configuration remains unchanged when the option is disabled.

[coderabbitai]

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📥 Commits

Reviewing files that changed from the base of the PR and between 7918f6b and beef72e.

📒 Files selected for processing (2)

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

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📝 Walkthrough

Walkthrough

OpenAiHandler.getModel now adds preserveReasoning: true when openAiR1FormatEnabled is enabled. Tests verify the enabled state and confirm that the property remains undefined by default.

Changes

OpenAI reasoning configuration

Layer / File(s)	Summary
Conditional model configuration src/api/providers/openai.ts, src/api/providers/__tests__/openai.spec.ts	getModel adds preserveReasoning: true when the R1 format setting is enabled. Tests cover 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 — Updates openai.ts to enable preserveReasoning through openAiR1FormatEnabled.
• [BUG] Reasoning is never sent back to the API for the OpenAI Compatible provider — preserveReasoning cannot be enabled from the UI #1096 — Modifies OpenAiHandler.getModel() to control preserveReasoning.

Possibly related PRs

• Zoo-Code-Org/Zoo-Code#892 — Consumes preserveReasoning for R1-format message conversion in another provider.
• Zoo-Code-Org/Zoo-Code#899 — Applies the same model-metadata pattern for LiteLLM models.
• Zoo-Code-Org/Zoo-Code#945 — Relates to preserveReasoning behavior used by the Kimi Code provider.

Suggested labels: awaiting-review

Suggested reviewers: edelauna, taltas

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly identifies the OpenAI fix and the R1 toggle behavior.
Description check	✅ Passed	The description explains the root cause, implementation, tests, and linked issue, but does not follow every template heading.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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

ESLint skipped: missing config or dependency (missing-dependency). The ESLint configuration references a package that is not available in the sandbox.

src/api/providers/openai.ts

ESLint skipped: the ESLint configuration for this file references a package that is not available in the sandbox.

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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).

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✅ 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.