> This page is for version v1.2.0.
> For other versions, use one of these documentation indexes:
> - Latest (v1.5.1) (default): https://docs.nvidia.com/dynamo/latest/llms.txt
> - dev: https://docs.nvidia.com/dynamo/dev/llms.txt
> - v1.5.1: https://docs.nvidia.com/dynamo/v1.5.1/llms.txt
> - v1.5.0: https://docs.nvidia.com/dynamo/v1.5.0/llms.txt
> - v1.4.2: https://docs.nvidia.com/dynamo/v1.4.2/llms.txt
> - v1.4.1: https://docs.nvidia.com/dynamo/v1.4.1/llms.txt
> - v1.4.0: https://docs.nvidia.com/dynamo/v1.4.0/llms.txt
> - v1.3.0: https://docs.nvidia.com/dynamo/v1.3.0/llms.txt
> - v1.2.1: https://docs.nvidia.com/dynamo/v1.2.1/llms.txt
> - v1.2.0: https://docs.nvidia.com/dynamo/v1.2.0/llms.txt
> - v1.1.1: https://docs.nvidia.com/dynamo/v1.1.1/llms.txt
> - v1.1.0: https://docs.nvidia.com/dynamo/v1.1.0/llms.txt
> - v1.0.2: https://docs.nvidia.com/dynamo/v1.0.2/llms.txt
> - v1.0.1: https://docs.nvidia.com/dynamo/v1.0.1/llms.txt
> - v1.0.0: https://docs.nvidia.com/dynamo/v1.0.0/llms.txt
> - v0.9.1: https://docs.nvidia.com/dynamo/v-0-9-1/llms.txt
> - v0.9.0: https://docs.nvidia.com/dynamo/v-0-9-0/llms.txt
> - v0.8.1: https://docs.nvidia.com/dynamo/v-0-8-1/llms.txt
> - v0.8.0: https://docs.nvidia.com/dynamo/v-0-8-0/llms.txt
> - v0.7.1: https://docs.nvidia.com/dynamo/v-0-7-1/llms.txt
> - v0.7.0: https://docs.nvidia.com/dynamo/v-0-7-0/llms.txt

> For clean Markdown content of this page, append .md to this URL. For the complete documentation index, see https://docs.nvidia.com/dynamo/llms.txt. For full content including API reference and SDK examples, see https://docs.nvidia.com/dynamo/llms-full.txt.

# Agent Hints

Agent hints are optional per-request metadata that a harness sends under
`nvext.agent_hints`. Dynamo parses these hints in the frontend and passes them
to the router and, where supported, backend runtimes.

Use hints only for serving-relevant intent. Use
[`nvext.agent_context`](/dynamo/v1.2.0/user-guides/agents/agent-tracing#request-schema) for passive trace
identity.

## Request Schema

```json
{
    "model": "my-model",
    "messages": [
        { "role": "user", "content": "Continue the report." }
    ],
    "nvext": {
        "agent_hints": {
            "priority": 5,
            "osl": 1024,
            "speculative_prefill": true
        }
    }
}
```

| Hint | Description |
|------|-------------|
| `priority` | Unified request priority. Higher values move the request earlier in the router queue and are forwarded to backends that support priority scheduling or eviction. |
| `osl` | Expected output sequence length in tokens. Used by the router for output block tracking and load-balancing accuracy when `--router-track-output-blocks` is enabled. |
| `speculative_prefill` | When true, Dynamo can prefill the predicted next-turn prefix after the current turn completes to warm the KV cache for the next request. |

## Request Flow

```mermaid
flowchart LR
    Harness[Agent harness] -->|nvext.agent_hints| Frontend[Dynamo frontend]
    Frontend --> Router[Router]
    Router --> Worker[Backend worker]
```

The frontend parses `nvext.agent_hints`, the router uses hints for queueing and
worker selection, and supported backends use forwarded hints for engine-level
scheduling and cache policy.

## Backend Support

Backend support is runtime-specific. For SGLang flags and behavior, see
[SGLang for Agentic Workloads](/dynamo/v1.2.0/backends/sg-lang/agentic-workloads).

| Feature | vLLM | SGLang | TensorRT-LLM |
|---------|:----:|:------:|:-------------:|
| Priority-aware routing | Yes | Yes | Yes |
| Priority-based cache eviction | Planned | Yes | Planned |
| Speculative prefill | Yes | Yes | Yes |
| Subagent KV isolation with session control | No | Experimental | No |

## Related Request Extensions

`agent_hints` is separate from `agent_context`:

- `agent_context` is passive identity for traces and joins.
- `agent_hints` is active serving intent for routing, scheduling, and cache
  behavior.

Session-control metadata for SGLang subagent KV isolation lives under
`nvext.session_control`; see [NVIDIA Request Extensions](/dynamo/v1.2.0/additional-resources/nvidia-request-extensions-nvext#session-control).