Worker mode (Phase 84.4)

Complement to coordinator mode. Bindings with role: worker get a worker-specific system prompt block prepended to the agent's existing system_prompt. Workers run self-contained tasks dispatched by a coordinator; the persona steers them away from user-facing dialogue and toward terse, verified, on-spec output.

What 84.4 ships

When a binding's resolved BindingRole is Worker, the runtime prepends the worker persona block. Coordinator bindings get the coordinator block instead; Proactive and absent role are byte-identical to today.

# WORKER ROLE
{persona block — sections below}

{agent.system_prompt}

# CHANNEL ADDENDUM
{binding.system_prompt_extra — when set}

Persona block sections

1. Role declaration — frames the agent as an executor: do the work, report results, do not initiate user-facing dialogue. Scope questions go back to the coordinator via the final answer ("blocked: need X").
2. Output discipline — the final answer is read by another agent, not a human. Optimize for parseability:
   • Code work: file path + line range + actual diff (or commit hash).
   • Research: bullet list with file_path:line references.
   • Failures: actual error output verbatim, not paraphrased.
3. Self-verification — typecheck + test + read the diff before reporting done. False "done" reports poison the synthesis above.
4. Tools available to you — the binding's allowed_tools list verbatim (workers see exactly the surface the operator granted, no curated subset). Followed by an explicit reminder that TeamCreate, SendToPeer, SendMessageToWorker, and TaskStop are not worker tools — wanting one means the task scope is too large.
5. Scratchpad (optional) — appears when TodoWrite is in allowed_tools. Worker scratchpad is for the worker's own multi-step state, not for cross-worker coordination.

Configuring a worker binding

agents:
  ana-worker:
    inbound_bindings:
      - plugin: whatsapp
        instance: ana_worker
        role: worker
        allowed_tools:
          - BashTool
          - FileEdit
          - WebFetch
          - TodoWrite

Composition with other phases

Inspecting the rendered prompt

The full path is exercised in cargo test -p nexo-core agent::effective::tests::worker_role_loaded_from_yaml_renders_persona_block, which deserializes a YAML binding fixture and asserts the # WORKER ROLE prefix lands ahead of the agent's own prompt with the expected sections.