Hermes Agent OpenCode Attribution Headers in the Hermes Agent v0.21.1 OpenCode Update

Hermes Agent now sends Referer, X-Title, and a User-Agent identifying it as HermesAgent when calling OpenCode’s Zen and Go services. Nous Research’s implementing commit says OpenCode identifies clients through request headers, making Hermes-originated traffic distinguishable at those endpoints. Nous Research’s attribution-header commit

The change is part of Hermes Agent v0.21.1, tagged v2026.9.7. Nous Research says the September 7, 2026 release includes 5,139 non-merge commits and 632 merged pull requests, spanning provider and model updates, MCP authorization improvements, session controls, scheduling fixes, and delegation reliability work. Hermes Agent v0.21.1 release

Attribution, not a documented behavioral change

The concrete implementation is limited to client identification on the relevant OpenCode calls. The commit establishes that Hermes Agent is adding headers because OpenCode uses them to identify clients; it does not say that Hermes traffic was previously misidentified, blocked, fraudulent, or otherwise problematic. Nous Research’s attribution-header commit

Nor does the published change explain how OpenCode uses the headers after receiving them. There is no attached traffic analysis, service policy, benchmark, billing documentation, or availability data showing an effect on reliability, support, routing, or enforcement.

For developers operating through shared model gateways, the update provides explicit client labeling rather than a new model capability. It makes Hermes Agent’s requests recognizable to the receiving service, but the available material does not demonstrate a user-visible outcome.

Broad maintenance release

The release notes describe changes across several production-facing areas. Provider and model updates can alter supported backends; session controls affect how agent work is retained; scheduling fixes concern automated execution; and delegation reliability work concerns task handoffs. The release record confirms work in those areas, but does not quantify results or enumerate every affected case. Hermes Agent v0.21.1 release

Nous Research also lists MCP authorization improvements. The notes do not describe a vulnerability, provide a threat model, or state that a specific security flaw was fixed, so the item should not be read as a disclosed security incident. Hermes Agent v0.21.1 release

The next evidence to watch is whether Nous Research or OpenCode documents how these attribution headers are used in practice. For now, the verified change is straightforward: Hermes Agent labels its OpenCode Zen and Go traffic as Hermes Agent traffic.