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Installation

Each LangStage stage is its own PyPI package, so install only the surfaces you want. They all share langstage-core, which is pulled in automatically.

pip install langstage
pip install "langstage[deepagents]"   # optional: the built-in default agent

pip install langstage-cli

pip install langstage-jupyter

pip install langstage-vscode          # the Python sidecar
code --install-extension dkedar7.langstage-vscode

Or search LangStage in the Extensions view. VS Code installs it from the VS Code Marketplace; Cursor, VSCodium and Windsurf install it from Open VSX. The .vsix on the latest extension release is the fallback (Extensions: Install from VSIX…). Its LangStage panel works in VS Code without Copilot, Cursor, VSCodium, Windsurf and code-server; see VS Code.

pip install langstage-hermes

pip install "langstage-core[agui]"    # the langstage-agui command

Requirements

  • Python 3.11 or newer, for every package including the core.
  • Your agent's own dependencies. Every surface already depends on langgraph, so a plain LangGraph graph (and every --demo) works on a bare install. If your agent uses deepagents or a provider package such as langchain-anthropic, install those yourself.
  • An API key for whatever model your agent calls (for example ANTHROPIC_API_KEY). Not needed for the demos or the keyless preflights.

langstage run with no agent

With no --agent and no configured spec, langstage run falls back to a built-in default agent. That agent needs pip install "langstage[deepagents]" and ANTHROPIC_API_KEY. Use --demo for a zero-setup first run instead.

Check it works, no key needed

langstage run --demo            # web UI at http://localhost:8050
langstage-cli --demo "hello"    # one-shot terminal reply

Both run the built-in echo agent (langstage_core.demo.stub:graph), so a fresh install is provably working before you wire up a real agent. Every surface has a keyless demo:

Surface Keyless demo
Web langstage run --demo
Terminal langstage-cli --demo "hello", or langstage-cli -a langstage_core.demo.tools:graph "use a tool" for tool calls, reasoning and an approval prompt
JupyterLab langstage-jupyter --demo
VS Code sidecar langstage-vscode-sidecar --demo --message "hello", or --demo=tools
Reference agent langstage-hermes demo (a subcommand, not a flag)
AG-UI server langstage-agui --demo, or --demo=tools

Preflight your own agent

Once you point a stage at your agent, each surface has a preflight that loads it and runs one real turn, so a typo'd spec, a missing key or a broken tool shows up before the first chat:

Surface Preflight
Web langstage check --live (drop --live for the fast, keyless static checks)
Terminal langstage-cli --verify
JupyterLab langstage-jupyter --verify (the agent) or --serve-check (the HTTP endpoint)
VS Code sidecar langstage-vscode-sidecar --selfcheck
Reference agent langstage-hermes verify (and doctor for the environment)
AG-UI server langstage-agui --verify

They all exit 0 when the agent is healthy and non-zero when it isn't. See Exit codes.

Next: Quickstart →