Hermes never set clientInfo, so servers saw the SDK's placeholder name

Kind: gap · Status: stale · Last verified: 2026-11-09 · Clients: hermes-agent · Revisions: 2025-11-25

Update, 2026-11-09

At 9dcf7714, _session_kwargs passes client_info=Implementation(name="hermes-agent", version=get_version_info().base_version) on every configurable session, with the comment "Servers key logs/behaviour on clientInfo; the SDK default is "mcp"/"0.1.0"". The probe run against build 0.23.0+689.ga9ff979 recorded "clientInfo":{"name":"hermes-agent","version":"0.23.0"}. The note below describes a24c12d1 and is kept for older builds, which still send mcp.

Hermes now puts three names on the wire. hermes-agent is the real session. hermes-probe is the non-MCP-endpoint preflight frame described below, unchanged. hermes with version probe is a new hand-written initialize at 2025-06-18 that checks whether a declared desktop app's loopback MCP endpoint is answering. The internal cua-driver computer-use session is still constructed bare and sends mcp, but it talks only to a binary Hermes ships.

At a24c12d1

ClientSession.__init__ takes an optional client_info and falls back to DEFAULT_CLIENT_INFO, which mcp 2.0.0 defines as Implementation(name="mcp", version="0.1.0"). Hermes builds its session kwargs from the sampling handler, the elicitation handler, a message handler and a logging callback. client_info is not among them at any of the four construction sites, so the fallback applies on every connection, on both transports.

The name is not merely generic — it is the SDK's own placeholder, shared with every Python client that also declines to set it. A server writing per-client compatibility shims, or rate-limiting by caller, has nothing to key on. 2026-07-28's per-request _meta envelope carries the same value, so the modern path does not fix it either.

This has a direct consequence for the observed tier. The Hugging Face client telemetry feed identifies callers by the name in clientInfo, so Hermes traffic either never appears or appears aggregated under mcp alongside unrelated clients. Any observed-tier row attributed to mcp cannot be attributed to a client at all.

There is one place Hermes does name itself. When a configured URL answers with a content type that is not an MCP media type, it POSTs a hand-written minimal initialize frame at 2025-03-26 with clientInfo.name of hermes-probe to decide whether the endpoint speaks MCP before reporting a NonMcpEndpointError. That frame is a diagnostic and never carries a real session, so hermes-probe is the only recognisable name Hermes puts on the wire and it appears only on endpoints that failed a content-type check.

Recorded as a gap rather than an idiosyncrasy: the SDK provides the field, Hermes has a name, and nothing in the code suggests the omission was decided.

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