A complete Cordis app loaded from cordis.yml — the standard "stack of plugins" pattern
mock-llm.ts — a mock LlmAdapter that streams scripted responses and calls the echo tool when the user types "echo "
echo-tool.ts — a tool registered via ctx.tools.register() that echoes text back uppercased
@deepseek-ai/dsh-session-persistence-jsonl — the durable JSONL persistence backend (loaded from cordis.yml, root: ./.sessions): append-only event log per session with crash-safe atomic writes, replacing the old write-only example plugin
stdio-chat.ts — a minimal UI plugin: reads stdin lines and send/steers the agent, renders stream deltas, tool calls, and tool results

Plugin files

File	Role	Key patterns demonstrated
`mock-llm.ts`	`LlmAdapter` registration	`ctx.llm.registerAdapter(['mock-echo'], …)`, streaming chunks with proper `block-start`/`block-end` protocol
`echo-tool.ts`	Tool registration	`ctx.tools.register(defineTool(…))` with typed `execute` args, tool execution returning `ContentBlock[]`
`stdio-chat.ts`	UI	`agent/stream-chunk`, `session/event` (tool/*), stdin→send/steer
`start.ts`	Bootstrap	`Context` + `Loader` + `plugin-include` wired to `cordis.yml`

Persistence is the shared @deepseek-ai/dsh-session-persistence-jsonl plugin (not a per-example file).

Run

pnpm run demo:echo
# or:
node --expose-internals --import tsx examples/echo-agent/start.ts

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/ (a session with no cwd goes in the _no-cwd/ bucket, one .jsonl log per session). Clean up with: rm -rf .sessions