HarnessRouter gives agent backends a shared protocol, with Qoder support

Epsilla wants software teams to use an existing coding agent as their product’s backend. Its HarnessRouter project has introduced the Unified Harness Protocol, an open specification for handing work to complete agent runtimes, and says Alibaba’s Qoder now supports it.

The proposal tackles an awkward integration problem. An agent that can edit files or run commands still needs a way to receive a task from an application, report progress, return its output and explain a failure. Different agents handle those interactions differently. Connecting several of them can leave a product team maintaining several separate integrations.

UHP defines a common HTTP contract for that conversation. An application submits a job rather than simply asking a model to complete some text. It can then follow the job, continue it, cancel it or retrieve the files it produced. The agent runtime remains responsible for doing the work.

That distinction matters for products whose users expect an artifact or a finished action. A model response is only one part of such a workflow. The surrounding runtime may also need to inspect files, select tools, execute commands and keep track of what has happened.

According to Epsilla’s launch announcement, the same interface can connect a product to Qoder, Codex, Claude Code, Hermes and more than 20 agent harnesses. The Qoder adoption claim comes from the company; the announcement does not provide an independent interoperability benchmark across that entire group.

The project separates the standard from the service that runs it. UHP is Apache 2.0 licensed, while HarnessRouter is an open-source server implementing the protocol. Teams can run a conforming server locally with their own model keys, or use HarnessRouter Cloud to manage execution.

Epsilla says the protocol is shaped like the OpenAI Responses API so developers can reuse familiar streaming parsers and interface code. It also provides a versioned specification, an OpenAPI schema and a conformance suite with 95 runnable checks. Those checks give implementers a concrete compatibility target, although passing a protocol test is different from proving that an agent will reliably complete every user task.

In the hosted setup, the company describes isolated sandboxes for individual jobs, orchestration across harnesses and execution tracing. Product builders can configure tools, plugins and skills while retaining a common way to start and observe work. The practical appeal is being able to change the underlying agent without rebuilding the application around a new control interface.

Epsilla is part of Y Combinator’s Summer 2023 batch. Its founders, Richard Song, Ricki Qin and Eric Yang, previously worked on TigerGraph’s cloud products, according to their public YC profiles. Epsilla’s own website identifies HarnessRouter as the runtime beneath its agent platform.

For another harness developer, the next step is specific: implement the contract and run the conformance suite. The standard’s usefulness will depend on whether that shared contract continues to cover the lifecycle details that applications otherwise have to handle separately.