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

# Environments

> Bind ECP (Execution Control Protocol) environments: runtime, extensions, policies, harnesses, and init() to an Ecp instance.

# Environments

An **environment** is the governed execution container for ECP (Execution Control Protocol) workflows. Workflows stay portable; environments hold host bindings.

## Create and bind

Node host (CLI and server apps):

```ts theme={null}
import { environment, extension, policy } from "@executioncontrolprotocol/node"
import "@executioncontrolprotocol/core/testing"
import "@executioncontrolprotocol/format-toon"

export default (await environment("echo-dev", "Echo development"))
  .withExtensions([
    extension("@executioncontrolprotocol/test").with({}),
    extension("@executioncontrolprotocol/format-toon").with({}),
  ])
```

Common builder methods:

| Method                   | Role                                    |
| ------------------------ | --------------------------------------- |
| `.withRuntime(…)`        | Override or set runtime                 |
| `.withExtensions([...])` | Bind cataloged extensions               |
| `.withPolicies([...])`   | Bind policies                           |
| `.withHarnesses([...])`  | Bind harnesses (common in browser apps) |
| `.init()`                | Return operational **Ecp**              |

Import extension packages for side-effect catalog registration before binding by string id.

## Init and operational APIs

```ts theme={null}
const env = await environment("dev")
  .withExtensions([extension("@executioncontrolprotocol/test").with({})])

const ecp = await env.init()

await ecp.describe()
await ecp.search("echo")
await ecp.validate(manifest)
await ecp.run(manifest)
await ecp.encode(source).uses("@executioncontrolprotocol/format-toon").to("@executioncontrolprotocol.workflow").process()
await ecp.terminate()
```

Do not call run/encode on the environment builder — use the `Ecp` returned by `init()`.

## Browser hosts

`@executioncontrolprotocol/browser` provides a slim host (executor, registry, session). **Apps** bind providers and harnesses. The [browser demo](/getting-started/browser-demo) is one such app; see [Demo providers and configuration](/getting-started/browser-demo-providers).

## CLI

Point commands at an environment module:

```bash theme={null}
ecp run workflow.ts --env environment.ts
ecp describe --env environment.ts
ecp search "echo" --env environment.ts
```

## Next steps

* [Extensions](/guides/extensions)
* [Security](/learn/security)
* [Concepts](/learn/concepts)