deepseek-harness/examples/coding-agent

coding-agent

The REPL agent demo wiring: DeepSeek V4 + the read/write/edit filesystem tools + the bash tool suite + subagent delegation + todo_write + stdio chat + JSONL persistence, loaded from cordis.yml. The UI is a terminal readline REPL.

Run it

# repo root .env (gitignored) or exported env:
#   DEEPSEEK_API_KEY=sk-…
#   DEEPSEEK_BASE_URL=https://…   # optional; defaults to the public API
pnpm run demo:repl

Type a coding task. The agent works through the read/write/edit filesystem tools for ordinary file operations and bash (+ bash_output / bash_kill for background tasks) for shell commands, searches, and test runs, each in a fresh bash -c (the system prompt tells the model to pass workdir instead of cd). Both the fs tools and bash resolve relative paths against the session workspace. It can also delegate with subagent/subagent_fork and track multi-step work with todo_write (a whole-list task tracker rendered as a checklist). Reasoning streams dimmed; tool calls/results render inline.

> fix the failing test in /path/to/project
[main turn 1] (reasoning…)
  [tool call] bash({"command": "node --test", "workdir": "/path/to/project"})
  [tool result] … [exit code: 1]
  …

Resuming a prior session

Each run starts a fresh session by default (its event log lands under ./.sessions/). To continue a previous conversation, set RESUME_SESSION_ID to that session's id — the main agent then rehydrates the persisted log instead of starting fresh, so the model sees the earlier turns as history:

RESUME_SESSION_ID=<prior-session-id> pnpm run demo:repl

The id is wired through cordis.yml (resumeSessionId: !!js process.env.RESUME_SESSION_ID); unset, the agent starts a new session. A missing/unreadable id is non-fatal — it logs a warning and starts no main agent.

Code Mode

code-mode.cordis.yml overlays the same tree with the worker-thread runtime and tools: { mode: code }. The model receives one run_code transport plus a generated TypeScript SDK for the visible tools; only program output returns to model context. Use mode: both to expose native calls alongside run_code. See the Code Mode RFC for the execution contract.

pnpm run demo:code-mode        # this overlay under the REPL (default UI)
pnpm run demo:code-mode acp    # the acp-agent example's same-shaped overlay

Try a task that spans several tool calls, e.g.:

Count the lines of every *.md file under docs/ and write the three largest to summary.txt.

and watch the transcript: one run_code call, a program looping over tools, and a result the model curated instead of five round-trips of raw tool output.

What each leaf entry demonstrates

This example is a thin leaf cordis.yml: it picks the swappable backends, loads one app package, and adds product tools that are intentionally outside the shared spine. The spine (sessions, system-prompt, tools, agents, invariants, agent-loop) and the front-door cluster (console logger, JSONL persistence, readline UI, the pre-created main agent) live inside the @deepseek-ai/dsh-stdio-agent app and the @deepseek-ai/dsh-agent-core bundle it loads; the leaf wires the backends and model-facing optional tools:

Entry	Demonstrates
hmr (@cordisjs/plugin-hmr)	the dev/demo edit-reload loop — a leaf entry (not baked into the app) because it is Loader-only and needs node --expose-internals, which demo:repl passes
llm-deepseek	real LlmAdapter via config (!!js process.env.… secrets); swap one line to @deepseek-ai/dsh-llm-pi-ai for the library-backed twin
bash (dsh-bash-local)	the executor implementation — the swappable half of the bash seam. The model-facing bash/bash_output/bash_kill tool schemas (tool-bash) come from agent-core, so only the executor is a leaf choice
stdio-agent (@deepseek-ai/dsh-stdio-agent)	the app bundle: the agent-core spine + console logger + JSONL persistence + readline UI + a pre-created main agent. Its config carries the model, system prompt, persistenceRoot (./.sessions), and resumeSessionId — so persistence and the agent are configured here, not wired as separate leaf plugins
subagent, subagent-spawn, subagent-fork	the subagent provider registry plus the two in-process backends: a fresh child and a child seeded with the parent's completed-turn prefix
tool-subagent, tool-subagent-fork	two model-facing dsh-tool-subagent loads, each bound to a different provider and exposed under a distinct tool name (subagent, subagent_fork)
tool-todo	the model-facing todo_write tool; writes the whole task list to the session log and renders as a checklist in stdio
fs-local, fs-policy, tool-fs	the filesystem stack: the local ctx.fs provider, the read-before-write/edit policy gate (on the fs/* event gate), and the model-facing read/write/edit tools. Relative paths resolve against the session workspace

End-to-end tests (pnpm run test:e2e, key-gated)

• tests/full-loop.e2e.ts — the canary: real model runs echo e2e-ok through the real bash tool; asserts tool/call/tool/result session events and the final answer.
• tests/coding-task.e2e.ts — the swebench-style smoke: a temp dir holds add.js (with a - b where a + b belongs) and a failing add.test.js; the agent must fix the bug and verify. The test re-runs node add.test.js ITSELF and inspects the files — agent claims are not trusted.
• tests/resume.e2e.ts — durable continuity across processes: run 1 tells the real model a secret code and persists the turn to a temp JSONL root, then the whole context is disposed; run 2 is a fresh context over the same root that RESUMES the session id and asks the model to recall the code. The recall can only come from the rehydrated log.
• tests/compaction.e2e.ts — the compaction smoke: a real multi-step bash task runs with a deliberately tiny context window so the auto-compaction listener fires MID-SESSION. Verifies the WORLD — a compact/start…end pair landed in the real log, the surface shrank (a replace node shadowed older nodes), and the agent still produced a correct final answer after compaction.
• tests/todo-write.e2e.ts — a real model drives the real todo_write tool and the test verifies the resulting todo/write session event.

These self-skip without DEEPSEEK_API_KEY. tests/code-mode.e2e.ts is the with-key Code Mode proof — a real model, a two-tool task, asserting the wire tool list was exactly [run_code], the tool/code-dispatch events landed under the parent call, and the curated answer came back. The keyless boot smokes run in the default e2e gate: tests/keyless-smoke.e2e.ts (the full real tree, dummy key, no prompt → no model call) and tests/code-mode-keyless-smoke.e2e.ts (the same guard for the Code Mode overlay).