HarnessRouter Introduces Unified Harness Protocol to Simplify Agent Integrations

HarnessRouter, led by cofounders Kuanze Ma and Renchu (Richard) Song, wants software teams to use existing agent harnesses as their product's backend rather than building their own. Its Unified Harness Protocol (UHP) is an open specification for handing work to complete agent runtimes, and the company says Alibaba's Qoder now supports it.

HarnessRouter recently merged with Epsilla (YC S23), bringing the two companies together around a shared approach to agent infrastructure.

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 HarnessRouter'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.

HarnessRouter 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. The current protocol documentation lists 104 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.

The merger brings together Song's work at Epsilla and Ma's experience building agent infrastructure for his earlier product. In his merger announcement, Song explained that both founders had reached a similar conclusion: product teams should be able to use existing agent harnesses and focus their development effort on the instructions, skills and tools that make their applications distinct.

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.