What is UHP?
Understand the problem UHP addresses, what an agent harness is, and what the protocol standardizes.
Current state: 21 August 2026
The protocol itself has not changed since launch: the current published UHP version remains 2026-08-11 and is still described by the project as a draft standard. HarnessRouter Community Edition, however, has continued shipping quickly and the newest official tag observed is v0.8.3, dated 23 August 2026 (session-isolation and share-link fixes; the backend expansion through v0.8.0 preceded it).
The reference implementation currently supports Codex, Claude Code, Hermes, Pi and DeepSeek Harness (dsh) as harness backends. That support is an implementation fact about HarnessRouter; it is not evidence that OpenAI, Anthropic, the Hermes project, Pi or DeepSeek have adopted UHP natively.
New since the original site launch: HarnessRouter moved from the early
0.3.x line through media-routing and video-workflow changes in 0.5.0–0.5.4, tagged v0.5.5 with a harness-page UX update, then expanded its backend set with v0.6.0 (LLMTR provider), v0.7.0 (Pi) and v0.8.0 (DeepSeek Harness), each publishing a Full 52/52 UHP conformance run. See the release tracker for the dated ledger.Explore the guide
| Topic | Best page | Question answered |
|---|---|---|
| Basics | What is UHP? | What does the protocol actually standardize? |
| System model | Architecture | How do client, UHP server and harness relate? |
| Normative rules | Specification guide | What is in version 2026-08-11? |
| Implementation | Getting started | Minimum path to implement or evaluate UHP. |
| API reference | HTTP API map | Normative endpoint surface for UHP 2026-08-11. |
| Governance | Governance and versioning | How UHP changes, date-based versions, and what must stay synchronized. |
| Security | Security and trust boundaries | Normative UHP 2026-08-11 requirements: credentials, scoping, artifacts, tool risk. |
| Lifecycle | Lifecycle | Version negotiation, states, sessions, streaming, cancellation, retries. |
| Release state | Release tracker | What changed, and was it protocol or implementation? |
| Verification | Conformance | What does “UHP conformant” mean? |
| Tool interoperability | UHP vs MCP | How do harness execution and tool/context access differ? |
| Agent interoperability | UHP vs A2A | How does harness execution differ from agent-to-agent communication? |
| Client interoperability | UHP vs ACP | How does harness execution differ from editor/agent integration? |
| Clients | UHP clients | Which independent UHP client implementations exist, verified how? |
| Reference implementation | HarnessRouter CE | Which capabilities belong to HarnessRouter rather than UHP itself? |
| Harness backends | Codex, Claude Code, Hermes, Pi, DeepSeek Harness | What is verified about each backend? |
| Market signal | Adoption tracker | Who has actually implemented or endorsed UHP? |
How this site stays current
The update cycle checks protocol versions, HarnessRouter tags, conformance evidence, backend support and independent adoption. A new date is not treated as content. When no material UHP news exists, the site expands evergreen technical coverage instead.