runtimeuse-client 0.4.0

Client library for AI agent runtime communication over WebSocket

runtimeuse (Python)

Python client library for communicating with a runtimeuse agent runtime over WebSocket.

Handles the WebSocket connection lifecycle, message dispatch, artifact upload handshake, cancellation, and structured result parsing -- so you can focus on what to do with agent results rather than wire protocol details.

Installation

pip install runtimeuse

Quick Start

Start the runtime inside any sandbox, then connect from outside:

import asyncio
from runtimeuse import RuntimeUseClient, InvocationMessage, ResultMessageInterface

async def main():
    # Start the runtime in a sandbox (provider-specific)
    sandbox = Sandbox.create()
    sandbox.run("npx -y runtimeuse")
    ws_url = sandbox.get_url(8080)

    # Connect and invoke
    client = RuntimeUseClient(ws_url=ws_url)

    invocation = InvocationMessage(
        message_type="invocation_message",
        source_id="my-run-001",
        system_prompt="You are a helpful assistant.",
        user_prompt="Do the thing and return the result.",
        output_format_json_schema_str='{"type":"json_schema","schema":{"type":"object"}}',
        secrets_to_redact=["sk-secret-key"],
        agent_env={"API_KEY": "sk-secret-key"},
    )

    async def on_result(result: ResultMessageInterface):
        print(f"Success: {result.structured_output.get('success')}")
        print(f"Output: {result.structured_output}")

    await client.invoke(
        invocation=invocation,
        on_result_message=on_result,
        result_message_cls=ResultMessageInterface,
    )

asyncio.run(main())

For local development without a sandbox, connect directly:

client = RuntimeUseClient(ws_url="ws://localhost:8080")

Usage

RuntimeUseClient

Manages the WebSocket connection to the agent runtime and runs the message loop: sends an invocation, iterates the response stream, and dispatches typed messages to your callbacks.

client = RuntimeUseClient(ws_url="ws://localhost:8080")

await client.invoke(
    invocation=invocation,
    on_result_message=on_result,
    result_message_cls=ResultMessageInterface,
    on_assistant_message=on_assistant,       # optional
    on_artifact_upload_request=on_artifact,  # optional -- return (presigned_url, content_type)
    on_error_message=on_error,               # optional
    is_cancelled=check_cancelled,            # optional -- async () -> bool
    timeout=300,                             # optional -- seconds
)

Artifact Upload Handshake

When the agent runtime requests an artifact upload, provide a callback that returns a presigned URL and content type. The client sends the response back automatically.

async def on_artifact(request: ArtifactUploadRequestMessageInterface) -> tuple[str, str]:
    presigned_url = await my_storage.create_presigned_url(request.filename)
    content_type = guess_content_type(request.filename)
    return presigned_url, content_type

Cancellation

Pass an is_cancelled callback to cancel a running invocation. When it returns True, the client sends a cancel message to the runtime and raises CancelledException.

from runtimeuse import CancelledException

async def check_cancelled() -> bool:
    return await db.is_run_cancelled(run_id)

try:
    await client.invoke(
        invocation=invocation,
        on_result_message=on_result,
        result_message_cls=ResultMessageInterface,
        is_cancelled=check_cancelled,
    )
except CancelledException:
    print("Run was cancelled")

Custom Result Types

Subclass ResultMessageInterface to add domain-specific fields:

from runtimeuse import ResultMessageInterface

class MyResultMessage(ResultMessageInterface):
    custom_score: float | None = None

await client.invoke(
    invocation=invocation,
    on_result_message=handle_my_result,
    result_message_cls=MyResultMessage,
)

API Reference

Message Types

Class	Description
InvocationMessage	Sent to the runtime to start an agent invocation
ResultMessageInterface	Structured result from the agent
AssistantMessageInterface	Intermediate assistant text messages
ArtifactUploadRequestMessageInterface	Runtime requesting a presigned URL for artifact upload
ArtifactUploadResponseMessageInterface	Response with presigned URL sent back to runtime
ErrorMessageInterface	Error from the agent runtime
CancelMessage	Sent to cancel a running invocation
CommandInterface	Pre/post invocation shell command
RuntimeEnvironmentDownloadableInterface	File to download into the runtime before invocation

Exceptions

Class	Description
CancelledException	Raised when is_cancelled() returns True