Reasoning models
How reasoning effort flows through Syntax — three distinct mechanisms behind one consistent control.
Modern frontier models support reasoning — explicit thinking before answering. Different model families implement reasoning differently, and Syntax normalizes those differences behind one consistent control so your harness doesn't have to know.
The three reasoning mechanisms
| Mechanism | Used by | What "reasoning effort" maps to |
|---|---|---|
| Native API reasoning | Provider-native APIs that already expose a reasoning field (e.g., the Anthropic and Google reasoning fields, OpenAI's reasoning.effort, DeepSeek's native think modes). | Directly forwarded to the provider in the format they expect. |
| Mechanism A | Open-weight models that expose an explicit "thinking" toggle and budget through their chat template. | Translated into the model's native thinking control plus a budget appropriate to the model's context length. |
| Mechanism B | Models without a native thinking control. | An orchestrator runs a planning → execution → critique → repair → verify loop on top of the model. |
What you see in the harness
Across all three mechanisms, your harness sets a reasoning effort (low / medium / high). Syntax translates that into whatever the specific model's family expects and the response comes back with the reasoning fields intact. The harness doesn't have to know which mechanism is in use.
Reasoning enabled by default
When a model is deployed and the catalog declares it as a reasoning model, Syntax enables reasoning by default at sensible levels:
- Mechanism A models get their native thinking toggle on, with a budget appropriate to the model's context length (long-context variants get a larger budget).
- Mechanism B models get the orchestrator at "high" effort.
- Native-API reasoning models get the provider's "high" or equivalent setting.
You can override at any level — per session, per request, or per deployment.
Reasoning + tool calls
Reasoning and tool calls compose. Reasoning models can plan, call tools, and incorporate tool results back into their reasoning before answering. The Bridge preserves both the reasoning and the tool-call fields end-to-end.
Where to go next
- Models → Tool use
- Concepts → Plan Mode — a different flavor of structured reasoning, applied to the whole task.
- Differentiators → First-class inter-compatibility — how the Bridge surfaces the reasoning channel through Chat Completions and Messages.