deepseek-harness/examples/echo-agent

echo-agent

Runnable demo: stdin chat with a scripted mock model and an echo tool. The all-mock skeleton — "swap the backend, keep the app".

What it shows

This example is just a leaf cordis.yml: it loads the @deepseek-ai/dsh-stdio-demo app (which bundles the whole @deepseek-ai/dsh-agent-spine-demo spine, JSONL persistence, the TTY-selected dsh-tui/dsh-stdio front doors, and a pre-created main agent), and swaps in two example-local backends plus hmr:

• mock-llm.ts — a mock LlmAdapter that streams scripted responses and calls the echo tool when the user types "echo ". Registered with ctx.llm.registerAdapter(['mock-echo'], …).
• echo-tool.ts — a tool registered via ctx.tools.register(defineTool(…)) with typed execute args; echoes text back uppercased.

Swapping mock-llm for the real llm-deepseek adapter is all that separates this from repl-agent — the same app, a different backend.

Plugin files

File	Role	Key patterns demonstrated
src/mock-llm.ts	LlmAdapter registration	ctx.llm.registerAdapter(['mock-echo'], …), streaming chunks with the proper block-start/block-end protocol
src/echo-tool.ts	Tool registration	ctx.tools.register(defineTool(…)) with typed execute args, returning ContentBlock[]
cordis.yml	Leaf wiring	the two backends + hmr + one @deepseek-ai/dsh-stdio-demo entry carrying the app config

The spine, UI, persistence, and boot glue all live in @deepseek-ai/dsh-stdio-demo and the bundle it loads — this folder holds only the demo-specific mocks and the leaf wiring.

Run

pnpm run demo:echo
# or:
node --expose-internals --import tsx packages/examples/stdio-demo/src/bin.ts examples/echo-agent/cordis.yml

Type a message and press Enter. "echo " triggers a tool call round-trip (the mock model requests the echo tool, which echoes the text uppercased, and the next model step acknowledges it).

The session is persisted under .sessions/ relative to the directory you launch the demo from. pnpm run demo:echo runs from the repo root, so the logs land in <repo-root>/.sessions/cwd-<hash>/ (one .jsonl log per session). Clean up with: rm -rf .sessions