> ## Documentation Index
> Fetch the complete documentation index at: https://executioncontrolprotocol.io/llms.txt
> Use this file to discover all available pages before exploring further.

# App

> Open a live graph of an ECP (Execution Control Protocol) workflow file with ecp app. Same host as the CLI, on loopback with a pairing token.

# App

`ecp app` opens a live graph of a workflow file on the **same process host** the CLI uses. File edits update the graph. Graph edits rewrite the file. Runs use the same journal as `ecp run`. The App stores no secrets and makes no model calls.

```bash theme={null}
ecp app examples/01-echo/workflow.ecp.ts
```

First use installs `@executioncontrolprotocol/plugin-app` from npm (`oclif.jitPlugins` pins `"^0.50"`). From a source checkout you can still `ecp plugins link plugins/plugin-app`.

There is no hosted browser demo and no `ecp up`. The App is not a chat client and not a secrets host.

## Loopback and token

The server binds **127.0.0.1** on a free port. A pairing token goes in the URL that opens the browser. Every request requires that token (query, `Authorization: Bearer`, or cookie). `--no-open` skips the browser (tests and CI).

```bash theme={null}
ecp app brief.ecp.ts --no-open
ecp app brief.ecp.ts --port 0
```

## Two-way sync

* **File → graph:** the server watches the file (150 ms debounce). Disk edits show up in the graph within a second.
* **Graph → file:** a graph edit patches the manifest, then the file is rewritten with the Fluent encoder.
* **Read-only:** files that cannot round-trip (relative imports, computed `.with()` values) open with a banner explaining why. Losing comments or formatting on save is a warning, not read-only. Encoder-written files stay editable.

## Runs and palette

Runs from the App go through the same host and journal as `ecp run`, so `ecp runs show <id>` works. The palette is the capability catalogue from `ecp describe` on this process.

## Next steps

* [The agent loop](https://executioncontrolprotocol.io/guides/agent-loop.md)
* [MCP](https://executioncontrolprotocol.io/guides/mcp.md)
* [CLI](https://executioncontrolprotocol.io/reference/cli.md)


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