nerva dev & nerva test

nerva dev and nerva test are local development helpers. They do not start a server — Nerva is a library, and your HTTP layer belongs to your framework.

Note

Nerva never owns your HTTP layer. nerva dev is a local REPL and trace viewer for development. In production, your agents run inside your FastAPI / Express / NestJS app.

nerva dev

Start an interactive REPL that loads your nerva.yaml, discovers agents, tools, and middleware, and lets you send messages to your orchestrator from the terminal.

nerva dev

What it does:

• Loads nerva.yaml and registers all components
• Watches agents/, tools/, and middleware/ for file changes and auto-reloads
• Opens an interactive prompt where you type messages and see agent responses
• Records traces for every request and displays them inline

Tip

nerva dev watches component directories, not nerva.yaml itself. If you edit nerva.yaml, restart the session to pick up changes.

Trace output

Every request produces a trace tree printed below the response:

[req_abc] handle "What's the weather in Berlin?"  (52ms)
  +-- [req_abc.1] router.classify                   (1ms)
  +-- [req_abc.2] runtime.invoke weather_agent       (48ms)
  |   +-- [req_abc.2.1] tools.call get_weather       (45ms)
  +-- [req_abc.3] responder.format                   (1ms)

Color coding: agents (purple), tools (blue), middleware (gold), router (orange), system (cyan).

nerva test

Run your project’s test suite with automatic language detection.

nerva test [--coverage]

The test command reads nerva.yaml to detect the project language and runs the appropriate runner:

Language	Runner	Command
Python	pytest	python -m pytest
TypeScript	vitest	npx vitest run

Add --coverage to enable coverage reporting.

Tip

The --coverage flag requires the appropriate coverage tool: pytest-cov for Python or @vitest/coverage-v8 for TypeScript.

Examples

# Interactive development REPL
nerva dev

# Run tests
nerva test

# Run tests with coverage
nerva test --coverage