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

> ## Agent Instructions
> Reticle is a dev-only, localhost-only verification layer for AI coding agents. It reads program truth (network, state, console, routing, animations, framework state) from inside a running web app and returns a deterministic verdict with evidence. It is not a screenshot tool and not a browser automation library.
> Only `reticle_act_and_wait` and `reticle_assert` produce a verdict. Every other tool moves or reads the app and proves nothing. A drive that ends without one of those two has no result, however many tools it used.
> A verdict of `verified: "unknown"` is not a pass. It means Reticle drove the app and could not tell what happened. Report it as unknown; never weaken a check to make it pass.
> Package names are scoped `@reticlehq/*` and the CLI is `reticle`. Install with `npx reticle init`. The complete tool surface is on the `/usage` page; `/agent-cheatsheet` is the one-screen version.

# reticle open

> Show the app in a browser, reusing the already-connected tab when there is one.

`reticle open` is the one-command "show me the app". It resolves the port, makes sure a daemon is up, and then either reuses the tab that is already connected or opens a new one.

```bash theme={"dark"}
npx reticle open [url] [--port N]
```

## Arguments and flags

| Argument   | Type                         | Default                                                    | What it does                                                                                    |
| ---------- | ---------------------------- | ---------------------------------------------------------- | ----------------------------------------------------------------------------------------------- |
| `url`      | string, positional, optional | unset                                                      | The URL to open. Omit it to reuse a connected tab                                               |
| `--port N` | number                       | `4400` (or `RETICLE_PORT`, or the port in `.reticle.json`) | Bridge port. If nothing is on it, `open` discovers a running daemon rather than making you hunt |

It is idempotent. Re-running never piles up duplicate tabs.

## What it prints

One `reticle_open` line, whose fields say which of four things happened.

| Fields                                 | Meaning                                                                                                                                                            |
| -------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------ |
| `reusing`                              | A connected tab was already on the right page. Nothing was opened                                                                                                  |
| `reusing` + `requested` + `note`       | A tab is connected on that origin but sitting on a different page. It was **left there**, not navigated. Drive it with `reticle_navigate` or open the URL yourself |
| `opened` + `connected: true`           | A browser was launched and a Reticle session appeared                                                                                                              |
| `opened` + `connected: false` + `note` | The URL went to the system default browser and no session showed up within 8 seconds. Almost always means the app carries no SDK, or dials a different port        |
| `error`                                | No app connected and no URL given, or the browser could not be launched                                                                                            |

<Note>
  `connected` is measured, not assumed. This command polls for a **new** session rather than printing
  `{"opened": url}` unconditionally, so a run where nothing opened no longer looks like one where it did.
  When the launcher itself cannot run, there is no `opened` field at all. Real capture:

  ```
  {"event":"reticle_open","port":4499,"error":"could not launch a browser: spawn open ENOENT","recovery":"Nothing was opened. This command asks the OS to open a url in your default browser (`open` on this platform) and that failed, so the fix is on the OS side: open the url yourself, or set a default browser."}
  ```
</Note>

<Warning>
  This command does **not** use Reticle's own Chromium. It hands the URL to your system default
  browser, so a `chromium` warning from `reticle doctor` has nothing to do with an `open` that came
  back `connected: false`. That misread cost a reporter an afternoon in their bridge config.
</Warning>

<Warning>
  For an Electron or Tauri app there is no URL to open. Start the app the way you normally would; it
  dials the bridge itself.
</Warning>

## Exit codes

| Code | Meaning                                                             |
| ---- | ------------------------------------------------------------------- |
| `0`  | Reused, opened, or reported that no app is connected                |
| `1`  | A browser could not be launched, or the daemon could not be reached |

## Worked example

```bash theme={"dark"}
npx reticle open http://localhost:5173
npx reticle status    # confirm the session is really there
```