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Module extensions_actions

rpi_cli

Module extensions_actions 

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B5a — the RuntimeActionHost impl over the harness, lived in rpi-cli (NOT rpi-harness) so rpi-extensions stays a leaf in the crate DAG. The trait is defined in rpi-extensions (JSON + primitives only); this is the host side that bridges the 16 [RuntimeActionId] actions to the harness.

10 ops delegate to harness.lane("main") (the AgentLane surface backs prompt_message/prompt_text/get_active_tools/set_active_tools/ set_model/get_thinking_level/set_thinking_level/compact/ navigate_tree). Run-ops serialize via acquire_run’s active_run guard — a concurrent plugin invocation surfaces lane_busy as the harness error string, the right behavior (a plugin can’t re-enter an active run).

6 non-lane ops:

  • append_entry → the harness’s boundary-aware message writer, or raw extension data on the session; set_session_name → set_name.
  • get_system_prompt → AgentHarness::get_system_prompt (B5a accessor).
  • new_session/fork/switch_session → reuse crate::session’s create/fork/open helpers + harness.set_session.
  • reload → handled by ActionBridge.reload (B5d); the host impl is the “not configured” fallback for bridges without a callback.

§Construction ordering (the load-bearing wrinkle)

Extensions load before the harness is created (extensions provide the tools the harness is built with), but the plugin stores the ActionBridge’s user_data pointer during register and that pointer must remain valid for the whole session. So the host cannot hold the AgentHarness directly — it holds an Arc<OnceLock<WeakAgentHarness>> that is empty at register time and filled once by HarnessActionHost::set_harness immediately after AgentHarness::create succeeds. Each action upgrades that weak binding for its duration; the host must not keep tools/providers alive via adapter -> keepalive -> bridge -> host. Before construction or after final harness release, actions fail explicitly. The bridge’s opaque handle stays stable without retaining the harness.

The impl needs the model catalog for set_model(id) (the lane wants a Model, not an id) and the cwd for session create/fork/switch. Both are held by rpi-cli at build time and moved into the host.

Structs§

HarnessActionHost
The RuntimeActionHost impl over an AgentHarness. Built once per session in crate::session::build — constructed empty before extension load (the harness doesn’t exist yet), then filled via set_harness once AgentHarness::create succeeds. Carried inside the [ActionBridge] as Arc<dyn RuntimeActionHost>.