deepseek-harness/examples/plan-acp-agent

plan-acp-agent

The coding agent as an ACP server with session modes composed — the live composition of the plan-mode RFC.

What it demonstrates

session/new advertises the mode picker (default / plan) plus the sandbox-mode and approval config options; the editor's session/set_mode switches the session, applied at the next turn boundary. Plan mode adds the plan guidance section and the exit_plan_mode tool, and enforces its read-only stance where an enforcer exists: plan's access: read-only cap clamps every bash call's sandbox resolution (a bash/resolve-mode waterfall listener), so exploration commands run for real while a write is denied by the sandbox itself — and the session's own sandbox-mode knob is never written, so it re-emerges intact on exit. Sandbox escalation (sandbox_permissions) is denied inside plan — the widened step belongs in the plan; in the default mode it raises a real session/request_permission prompt through the approval seam. There is deliberately no per-mode tool list: the write/edit tools stay present in plan and the section's guidance is what defers changes to after the review (the effects-based generalization is the RFC's deferred item). A blocking decision goes to the user through ask_user_question. The model leaves by presenting its plan through exit_plan_mode: the plan markdown renders as the tool's call card, the review question arrives as an elicitation form (approve / keep planning, free text welcome), and a keep-planning answer returns the feedback to the model verbatim.

Run

pnpm run demo:plan-acp   # needs DEEPSEEK_API_KEY (repo-root .env works)

Drive it from Zed or any ACP client; the mode picker appears on the session. Switching back to default (or an approved exit_plan_mode) lifts the plan constraints — the sandbox clamp included — on the next step.

Tests

pnpm run test:snapshot replays three scenarios keyless (the recorded bash re-executes for real under the host's sandbox runner — Seatbelt on macOS, bwrap on Linux CI). modes-advertise (authored): the modes advertisement and both config options on session/new, both session/set_mode round-trips with their optimistic current_mode_update, and the loud rejection of an unknown mode id, as committed wire bytes. plan-mode (recorded, the header pin): the full arc — setMode(plan), the plan-shaped initial header (full toolset + exit tool + section), a real cat run inside plan under the clamped read-only sandbox, the plan presented via exit_plan_mode, a scripted elicitation approve, the boundary-flushed mode/set back with its pure-removal request/header-delta, then a real edit mid-turn. plan-mode-reject (recorded): the keep-planning branch, whose corrective isError carries the reviewer's free-text feedback verbatim and leaves the session in plan mode. The cap-guard deny texts and the sandbox-denial marker stay pinned at the unit tier (packages/mode/mode/tests, packages/bash/tool-bash/tests — a recorded denial's stderr would be the backend's dialect and replay only where it was recorded).