> ## 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/*`. Run every CLI command as `npx @reticlehq/server <command>`, for example `npx @reticlehq/server init`. `reticle` is a bin name that `@reticlehq/server` installs once it is on your PATH, NOT a package on npm: `npx reticle` fetches an unrelated package published by somebody else, so never run that. The complete tool surface is on the `/usage` page; `/agent-cheatsheet` is the one-screen version.

# @reticlehq/engine

> The rules that decide a verdict, with no browser, daemon or CLI attached. Evidence in, verdict out.

`@reticlehq/engine` is the part of Reticle that DECIDES. It reads what happened in a running app and says whether the declared consequence held. It has no browser, no daemon and no command line: evidence goes in, a verdict comes out.

**Apache 2.0. Depends on [`@reticlehq/core`](/packages/core) and `zod`.**

## Why it is a separate package

It was nine thousand lines in the middle of the server, which meant the rules that decide a verdict could only be read, tested or trusted by running the whole daemon. Carving it out has three consequences that matter more than tidiness:

* **It can be audited.** The verdict is the product, so the code that produces one is the code a sceptical reader most wants to see. It is Apache 2.0 for that reason, carved out of an otherwise source-available server.
* **It can be reused.** Anything that has evidence in the protocol's shape can reach a verdict without Reticle in the loop.
* **It cannot quietly depend on the daemon.** A rule that needs a browser to decide something is not a rule, it is a measurement, and the package boundary is what makes that confusion a compile error.

## What is in it

| Subpath            | What it decides                                                                                                                                             |
| ------------------ | ----------------------------------------------------------------------------------------------------------------------------------------------------------- |
| `./question/*`     | Predicates: what a claim means and whether the evidence satisfies it.                                                                                       |
| `./evidence/*`     | What a run proved, how strongly, and what it failed to observe. Includes the honesty grades a verdict is qualified by, and the learned guards a flow earns. |
| `./disagreement/*` | Contradictions: two of the app's own channels saying different things.                                                                                      |
| `./window/*`       | What counts as "during" an action, and what is ambient noise.                                                                                               |

Absence is treated as evidence with care, and that is most of the difficulty: a thing that did not happen is only meaningful if something was watching, so the engine distinguishes "it did not happen" from "nothing was looking".

## Do you install it?

Only if you are building your own verification tool on top of the protocol. It arrives as a dependency of `@reticlehq/server`.

```bash theme={"dark"}
npm install @reticlehq/engine
```

## Relationship to the protocol

[`open-verification`](/packages/open-verification) states the rules; this package implements them for a real runtime and adds the machinery a real app needs, such as windowing and contradiction detection. `pnpm gate:conformance` is what keeps the two honest: it scores this implementation using the specification's own adjudicator rather than its own.