496f85c8c6
TurnStop is the enum over hive-claude's Cancel and the ACP Canceller, with stop() -> bool (false when no turn was in flight). It signals SIGINT only and never waits. The subagent daemon tracks a TurnStop per turn, so interrupt has one stop path; whether the name stays claimed afterwards (claude) or is freed (ACP) still follows the runtime.
75 lines
3.8 KiB
Markdown
75 lines
3.8 KiB
Markdown
# hive-runtime
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The layer an agent's turns are driven through: one `Runtime` interface
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(`run`, `compact`, `archive`, `canceller`, `choices`) with a backend per runtime.
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- **claude** — `claude --print` through the `hive-claude` crate's
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`InfiniteSession`. A pass-through: same spawn, same session handling, same
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errors.
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- **acp** — any [Agent Client Protocol](https://agentclientprotocol.com)
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agent, spawned from a command, args and env handed to it (`RuntimeSpec`,
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read from `HIVE_RUNTIME` / `HIVE_ACP_COMMAND` / `HIVE_ACP_ARGS` /
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`HIVE_ACP_ENV`). It knows no agent by name; which agent runs, and how it is
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configured, is decided in nix (`services.hyperhive.agent.runtime`,
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`services.hyperhive.agent.acp.*`).
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Both backends report a turn through `hive_claude::Sink` in claude's
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`stream-json` shape. The ACP backend translates `session/update`
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notifications into it (text and thought chunks as whole blocks, tool calls as
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`tool_use` + `tool_result`, MCP tools named `mcp__<server>__<tool>`), so the
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harness's stream consumers read either backend unchanged. Context usage comes
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from ACP `usage_update`.
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The crate depends on no hyperhive binary crate, so `hive-agent` and
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`hive-subagent-mcp` can both drive turns through it.
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## ACP backend: what it needs from the agent
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- `mcpCapabilities.http` in its `initialize` response. The hyperhive tools
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are only served over HTTP, so an agent without it is refused at startup.
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- `loadSession`, to pick its session back up after a harness restart.
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Without it every restart starts a new session.
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## ACP backend: stopping a turn
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A turn is stopped with `session/cancel`: by the `Canceller` handle (`TurnStop`
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wraps it, and claude's cancel handle, for callers that run either), or by the
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idle watchdog once no `session/update` has arrived for
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`Config::idle_timeout`. An agent that has not answered the prompt 10s later
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is sent SIGINT, and the next turn respawns it. A watchdog stop fails the turn
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with `AcpError::IdleTimeout` (`IdleKilled` if the agent was sent SIGINT). This is
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the only way a provider error the agent retries without reporting it, such as
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an HTTP 429, ends the turn.
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The agent leads its own process group. Stopping it, and dropping the runtime,
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sends that group SIGINT, so the commands the agent started get it too.
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Nothing escalates to SIGKILL: an agent that ignores SIGINT keeps running,
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and the next turn starts a new one beside it.
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## ACP backend: compaction
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The same `CompactionPolicy` as the claude backend decides when: after a turn
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past the watermark, or on `compact` (the operator's `/compact`, the agent's
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`compact` tool).
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- If the agent advertises a `compact` command (`available_commands_update`),
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it is sent as the prompt `/compact` on the same session, as the ACP spec
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runs any advertised command. A proactive compaction runs the policy's
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checkpoint turn first, as on claude.
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- Otherwise the policy's checkpoint turn runs, then the session is archived,
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and the next turn starts a new one, carrying the system prompt again.
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- A `compact` command that fails, or sends nothing for 180s (the turn's idle
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window if that is shorter), is cancelled and handled as the case above; the
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checkpoint turn is not run a second time. So a compaction always leaves a
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smaller session behind, and a failed one is not retried on the next turn.
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## ACP backend: model and effort
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Before each prompt, `Config::model` and then `Config::effort` are set on the
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session with `session/set_config_option`, as the value of its first `model`
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and `thought_level` config option. A value the session does not offer, or
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already holds, is not sent, so a claude alias such as `haiku` does nothing
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on an ACP agent. Model goes first because the effort levels on offer depend
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on it. The `Choices` handle (`Runtime::choices`) reads what the session
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offers now, including after a `config_option_update`. It is empty until a
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session is attached.
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