[BUG] Thinking level is not supported for this model

[proidit]

Problem (one or two sentences)

I didn't enable reasoning!
I registered Gemini in root code with my api gemini key.

Date/time: 2026-01-13T21:59:05.733Z
Extension version: 3.39.3
Provider: gemini
Model: gemini-2.5-flash

Errore del flusso di contesto di generazione Gemini: {"error":{"message":"{\n "error": {\n "code": 400,\n "message": "Thinking level is not supported for this model.",\n "status": "INVALID_ARGUMENT"\n }\n}\n","code":400,"status":"Bad Request"}}

Context (who is affected and when)

when I ask a question with the gemini model

Reproduction steps

1. create gemini profile with api key
2. write a question

Expected result

I'm waiting for the answer

Actual result

error

Variations tried (optional)

No response

App Version

vscode extension Version: 3.39.3 (85d253c)

API Provider (optional)

None

Model Used (optional)

No response

Roo Code Task Links (optional)

No response

Relevant logs or errors (optional)

[roomote]

I have analyzed this issue and identified the root cause.

Problem:
The gemini-2.5-flash model is defined with supportsReasoningBudget: true but does NOT have supportsReasoningEffort. When reasoning is not explicitly enabled, the getGeminiReasoning function in src/api/transform/reasoning.ts falls through to effort-based logic and incorrectly sends thinkingLevel if any reasoningEffort setting is persisted from a previous model session.

The error "Thinking level is not supported for this model" confirms that thinkingLevel was sent instead of nothing (since you did not enable reasoning).

Proposed Implementation Plan:

1. Modify src/api/transform/reasoning.ts in the getGeminiReasoning function to add a guard that prevents sending thinkingLevel to models that do not explicitly support effort-based reasoning:

// After the budget-based check, add:
// Models that only support budget-based reasoning should not receive thinkingLevel
// Early exit if model does not explicitly support effort-based reasoning
if (!model.supportsReasoningEffort) {
    return undefined
}

2. Add a test case to verify this behavior in the reasoning tests.

This approach ensures that:

• Models with supportsReasoningBudget only receive thinkingBudget (when enabled)
• Models without supportsReasoningEffort never receive thinkingLevel
• Only models explicitly marked with supportsReasoningEffort can receive thinkingLevel

Please mention @roomote in a comment saying that you approve this plan, and I will proceed with the implementation.