> ## Documentation Index
> Fetch the complete documentation index at: https://docs.usesynth.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# Models and Harnesses

> Public Managed Research harnesses, model IDs, and reasoning-effort support.

Managed Research supports two public harnesses:

* `codex`
* `opencode_sdk`

Model compatibility is harness-specific. Public model IDs are not the same thing
as launch entitlement. Backend preflight remains authoritative for the caller's
plan, Beta Access state, provider readiness, and budget limits.

## Launch availability

| Access                 | What it allows                                                                     |
| ---------------------- | ---------------------------------------------------------------------------------- |
| Free                   | `lite`, `directed_effort`, standard models, and one-time Managed Research credits. |
| Pro / Team             | Paid GA model bundle and higher included usage.                                    |
| Any plan + Beta Access | `open_ended_discovery`, `heavy`, and all-model access.                             |

`lite` and `heavy` describe run depth and coordination limits. They do not mean
"smaller model" and "bigger model." Choose the model explicitly when a harness
supports model selection.

## Codex harness

| Model ID              | Reasoning effort support | Launch access                           | Default  |
| --------------------- | ------------------------ | --------------------------------------- | -------- |
| `gpt-5.3-codex`       | `medium`                 | Beta Access; worker/engineer roles only | `medium` |
| `gpt-5.3-codex-spark` | `medium`                 | Standard                                | `medium` |
| `gpt-5.4`             | `medium`, `high`         | Beta Access                             | `medium` |
| `gpt-5.4-mini`        | `low`, `medium`, `high`  | Standard                                | `medium` |
| `gpt-5.4-nano`        | `low`                    | Standard                                | `low`    |
| `gpt-oss-120b`        | `high`                   | Standard                                | `high`   |

Example:

```python theme={null}
run = client.runs.start(
    "Review the repo and leave evidence for the smallest safe fix.",
    host_kind="daytona",
    work_mode="directed_effort",
    providers=[{"provider": "openrouter"}],
    agent_harness="codex",
    agent_model="gpt-5.4-mini",
    agent_model_params={"reasoning_effort": "medium"},
)
```

## OpenCode SDK harness

| Model ID                              | Reasoning effort support | Launch access |
| ------------------------------------- | ------------------------ | ------------- |
| `anthropic/claude-sonnet-4-6`         | None in the catalog      | Beta Access   |
| `anthropic/claude-haiku-4-5-20251001` | None in the catalog      | Standard      |
| `x-ai/grok-4.1-fast`                  | None in the catalog      | Standard      |
| `moonshotai/kimi-k2.6`                | None in the catalog      | Standard      |

Example:

```python theme={null}
run = client.runs.start(
    "Review the repo and propose the smallest high-impact fix.",
    host_kind="daytona",
    work_mode="directed_effort",
    providers=[{"provider": "openrouter"}],
    agent_harness="opencode_sdk",
    agent_model="anthropic/claude-haiku-4-5-20251001",
)
```

## Source of truth

The backend-owned Managed Research model catalog is the source of truth. The `synth-ai` SDK mirrors public model IDs, but backend preflight is the final authority for launch availability.