Add full Hermes Agent ACP harness support - #12
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Adds Hermes Agent (NousResearch/hermes-agent) as a first-class harness, driven through `hermes acp` — the Agent Client Protocol stdio server Hermes also serves to Zed/VS Code/JetBrains. Because ACP runs the same agent core as the CLI and the Electron desktop app, Comet sessions inherit the device's ~/.hermes config, skills, memory, and session history. Every wire shape here was captured from a live `hermes acp` 0.19.1 session rather than inferred, including the fixtures the tests replay. - crates/harness/src/hermes/: initialize handshake (no client-side fs/terminal capability — Hermes owns its tools), session/new + session/load, prompt, cancel, and the session/update stream. session/load replays the whole prior transcript before responding, so replays are drained concurrently and dropped: Comet's doc already holds those parts, and a long history would otherwise fill the incoming channel and deadlock the response. - Live model catalog: Hermes's models are whatever providers are authenticated on the device, so they come from session/new (cached 5min) instead of a curated snapshot. No per-turn effort knob exists over ACP, so the reasoning ladder is deliberately empty. - Steering: a mid-turn session/prompt is redirected into the running turn by Hermes's core (verified live). Its ack resolves immediately and is NOT a turn end — in-flight state tells them apart — and the "Redirected the active turn…" text Hermes streams as assistant output is swallowed so it can't land in the transcript. - Tool normalization: Hermes omits rawInput for its "polished" tools, so operands come from its deterministic title prefixes, locations[], and content blocks (the `$ cmd` block wins over the title, which truncates at 80 chars). - Permissions bridge session/request_permission to RunControls::request_input; sandbox level + auto_approve map onto Hermes's edit-approval session modes. - codex/rpc.rs → jsonrpc.rs: the stdio JSON-RPC client is now shared by both the Codex app-server and Hermes ACP adapters. - Registry slot, harness picker mark, COMET_HARNESS=hermes, docs. Tests: 12 integration tests against a fake ACP server (tests/fixtures/ fake-hermes.sh) plus unit tests, and an #[ignore]d end-to-end test against a real installed hermes. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
juanmiret
marked this pull request as ready for review
August 3, 2026 17:48
Author
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@wingleeio let me know if this is something you'd like to have, and what would be required for this PR to get merged. Cheers! |
Contributor
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hermes support in comet is definitely something i'd like to have right now i'm considering how i want to handle acp, ideally acp would be introduced to comet in a way that it's easy to add other acp compatible harnesses afterwards |
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Summary
Adds full Hermes Agent support over ACP/JSON-RPC, including model and mode discovery, streaming events, tool calls, approvals, steering, interruption, resume behavior, and coverage with a fake Hermes fixture.
Why
Allows Comet to use Hermes Agent as a first-class harness alongside Claude and Codex.
Validation
cargo fmt --all -- --checkcargo test -p comet-harnessThe branch is rebased onto
zeronsh/comet:main; the follow-up compatibility fix updates Hermes to the current shared child-PATH helper.Need help on this PR? Tag
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