Reasoning

Reasoning is model-dependent. Check supported_features and model_info in GET /v1/models before sending reasoning controls.

One total completion budget¶

max_completion_tokens in Chat Completions and max_output_tokens in Responses limit all completion tokens. Reasoning tokens and visible answer tokens share that limit. reasoning.max_tokens is a sub-budget; it never expands the total.

If reasoning consumes the remaining budget, the response can end with finish_reason:"length" and little visible text. Increase the total completion budget or reduce the reasoning effort.

Chat Completions controls¶

{
  "model": "qwen/qwen3.8-27b",
  "messages": [{"role": "user", "content": "Compare two retry strategies."}],
  "max_completion_tokens": 1200,
  "reasoning": {"effort": "medium", "max_tokens": 700}
}

Compatible controls include reasoning.enabled, reasoning.effort, reasoning.max_tokens, reasoning.exclude, and the top-level reasoning_effort alias. Exact efforts are published per model. Do not assume that a value accepted by one model is accepted by every reasoning model.

Binary reasoning models¶

Some models expose reasoning as an on/off policy rather than a continuous token budget. For these models, none disables reasoning and supported non-zero efforts enable the same mode. reasoning.max_tokens may be unsupported. The model catalog is authoritative.

Visibility and usage¶

KosCompute does not expose private chain-of-thought or reasoning summaries. Usage can report completion_tokens_details.reasoning_tokens in Chat Completions or output_tokens_details.reasoning_tokens in Responses. These counters are suitable for accounting and budget diagnostics, not for reconstructing private reasoning.

Structured output and some vision routes can disable thinking to preserve schema reliability or modality constraints. Treat this as model/route behavior, not a universal rule.