Reasoning Effort

reasoning_effort caps how much a model thinks before it answers. On models that reason without a bound by default it is the single largest cost lever — and what it does depends entirely on which upstream your model runs on.

Values

Send one of these on the request body. Higher effort means more reasoning tokens billed and slower replies:

minimal · low · medium · high

Example request

curl https://synthorai.io/v1/chat/completions \
  -H "Authorization: Bearer $SYNTHORAI_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "glm-5.2",
    "messages": [{"role": "user", "content": "Refactor this function."}],
    "reasoning_effort": "low"
  }'

What happens per upstream

The gateway speaks one protocol to you and another to each provider. This table states what the parameter becomes on the way out — including the case where it is dropped.

You call	Upstream	Behaviour	說明
`/v1/chat/completions`	OpenAI-compatible (GPT, GLM, DeepSeek, Qwen, Kimi…)	透傳	Forwarded to the provider as sent — the gateway neither validates the value nor guarantees the provider honours it. Commonly minimal, low, medium and high, but the accepted set is the provider's: OpenAI also takes none, GLM takes up to max.
`/v1/chat/completions`	Google Vertex — Gemini 3.x	對應	Becomes Gemini's `thinkingLevel`: none and minimal both map to minimal, low/medium/high map straight across. An explicit `google.thinking_config` in the request wins over this mapping.
`/v1/chat/completions`	Google Vertex — Gemini 2.5	丟棄	Gemini 2.5 only understands `thinkingBudget` and rejects `thinkingLevel` outright, so the gateway sends neither and leaves the model at its default thinking behaviour. Use `google.thinking_config` with `thinking_budget` to control 2.5.
`/v1/chat/completions`	Anthropic (Claude)	丟棄	Not forwarded. Anthropic does have an equivalent (`thinking.budget_tokens`) and the gateway maps it in the other direction, but this direction was never implemented — set `thinking.budget_tokens` with the Anthropic-native request shape instead.
`/v1/messages`	OpenAI-compatible (GPT, GLM, DeepSeek, Qwen, Kimi…)	對應	Derived from `thinking.budget_tokens` by bucket, when extended thinking is enabled and the budget is above zero: up to 2,048 tokens becomes low, up to 8,192 becomes medium, above that becomes high. A zero or absent budget sends nothing.
`/v1/responses`	OpenAI-compatible (GPT, GLM, DeepSeek, Qwen, Kimi…)	對應	Read out of the Responses-API `reasoning.effort` object and sent as the flat `reasoning_effort` field.

Each row is transcribed from the converter that implements it and pinned by a Go test, so this table cannot drift from the running gateway without a build failing.

Cost impact

Reasoning tokens are billed as output tokens. On a model that reasons unbounded by default, setting an explicit effort is usually the difference between a few cents and a few dollars for the same answer — measure it on your own prompts before choosing a default.

Models that reason

These models document a reasoning mode. Check the model page for how its upstream handles the parameter:

ByteDance-Seed-1.8 · Dola-Seed-2.0-lite · Dola-Seed-2.0-mini · Dola-Seed-2.0-pro · claude-fable-5 · claude-haiku-4-5 · claude-opus-4-5 · claude-opus-4-6 · claude-opus-4-7 · claude-opus-4-8 · claude-opus-5 · claude-sonnet-4-5 · claude-sonnet-4-6 · claude-sonnet-5 · deepseek-v4-flash · deepseek-v4-pro · gemini-2.5-flash · gemini-2.5-flash-lite · gemini-2.5-flash-native-audio · gemini-2.5-pro · gemini-3-flash-preview · gemini-3-pro-image-preview · gemini-3.1-flash-image-preview · gemini-3.1-flash-lite-image · gemini-3.1-flash-lite-preview · gemini-3.1-flash-live · gemini-3.1-pro-preview · gemini-3.5-flash · gemini-3.5-flash-lite · gemini-3.6-flash · glm-5 · glm-5-turbo · glm-5.1 · glm-5.2 · gpt-5.2 · gpt-5.2-codex · gpt-5.3-codex · gpt-5.4 · gpt-5.4-mini · gpt-5.4-nano · gpt-5.4-pro · gpt-5.5 · gpt-5.5-pro · gpt-5.6 · gpt-5.6-luna · gpt-5.6-sol · gpt-5.6-terra · kimi-k2.5 · kimi-k2.7-code · kimi-k3 · minimax-m3 · qwen3-max · qwen3-vl-flash · qwen3-vl-plus · qwen3.5-flash · qwen3.5-plus · qwen3.6-flash · qwen3.7-max · qwen3.7-plus

Full request body reference: Chat Completions