`Runtime` gets a fourth operation, `canceller()`: a handle that stops the
turn in flight from outside `run`. The ACP backend returns one; claude
returns `None`, because the harness stops a claude turn by signalling the
`claude` process, and that path is unchanged.
Both stops send the agent `session/cancel`:
- `Canceller::cancel()`, when asked from outside. The turn then ends
normally, reported with stop reason `cancelled` whatever reason the agent
gives. opencode 1.15.10, for one, answers a cancelled prompt with
`end_turn` (`acp/agent.ts` `prompt()` always returns `end_turn`).
- The idle watchdog, once no `session/update` has arrived for
`Config::idle_timeout`, the same field claude's watchdog reads. The turn
fails with `AcpError::IdleTimeout`.
An agent that has not answered the prompt 10s after `session/cancel` is
killed (`IdleKilled` / `CancelIgnored`), and the next turn respawns it.
The watchdog is also what ends a turn stuck on a provider HTTP 429.
opencode 1.15.10 retries a retryable provider error with no attempt limit
(`session/retry.ts` `policy`, `session/processor.ts` `Effect.retry`) and
forwards neither `session.status` nor `session.error` over ACP (its
`handleEvent` only handles `permission.asked` and `message.part.*`). So the
ACP client sees nothing at all until the provider recovers. The
`IdleTimeout` message says a silently retried provider error looks like
this.
Refs #4391
A `Runtime` trait (run / compact / archive) with two backends:
- claude: a pass-through to hive_claude's InfiniteSession and
SessionStore, so a claude turn is the same spawn, session handling
and errors as before.
- acp: a generic Agent Client Protocol client. It spawns the command,
args and env from RuntimeSpec (HIVE_RUNTIME / HIVE_ACP_COMMAND /
HIVE_ACP_ARGS / HIVE_ACP_ENV), refuses an agent whose
mcpCapabilities.http is not true, passes the claude --mcp-config
servers as ACP mcpServers, keeps one session id in a file
(session/load after a restart, session/new otherwise), and maps
session/update into claude stream-json events plus usage_update into
Telemetry. Permission requests are answered by a caller-supplied
policy on the ACP tool kind. compact returns Unsupported for now.
The crate depends on no hyperhive binary crate, so the subagent
daemon can move onto it without pulling in hive-agent.
Refs #4391
