An opencode ACP agent got its provider API key only from the hand-placed
backendEnvironmentFile. It now also reads it from the swarm secret store
at swarm/agents/<agent>/acp-provider, field api_key, under its own
certificate, and sets it in the spawned ACP agent's environment only.
Nothing is written to disk.
Precedence: a value already in the process environment (the env file)
wins and the store is not asked. Otherwise the stored key is used when
present. With no store, nothing stored, or a failed read, the agent is
spawned without the key as before, and one line is logged without the
value.
The variable name comes from the existing per-agent option
acp.opencode.provider.apiKeyEnv, exported as HIVE_ACP_API_KEY_ENV on the
harness only for the opencode preset. Other ACP commands are unchanged.
The read lives in hive-runtime, where the ACP child is spawned, so both
hive-agent and hive-subagent-daemon use it. The subagent daemon unit
gets the key name and, when the agent has a store, the agent's store
identity (the same credentials queue-identity.nix gives the harness).
No new option or setting. Closes#4841.
The subagent daemon now reads the parent agent's runtime at startup
(`hive_runtime::RuntimeSpec`, from the harness's `HIVE_RUNTIME` /
`HIVE_ACP_*`, which `mcp.nix` forwards onto its unit). On claude
nothing changes. On ACP, each run drives an `AcpRuntime` whose session
id is kept per name under the harness dir: `start` archives the old one,
`continue` loads it (and fails when none is recorded), `interrupt` sends
`session/cancel`, a role goes in front of the first prompt, and
permission requests get the answers a claude subagent's tool list
gives. The unit loads `backendEnvironmentFile` on ACP only, so the
agent can authenticate.
The end-of-turn handling moves out of the claude loop into `after_turn`
unchanged, so both loops share it.
Refs #4391
