viceroy

Files (5)

• SKILL.md
• fastly-compute-adapt.md · references/
• fastly-compute-config.md · references/
• fastly-compute-serve.md · references/
• fastly-compute-test.md · references/

SKILL.md (first lines)

# Viceroy — Local Fastly Compute Runtime

Viceroy is Fastly's official local testing environment for Compute applications. It emulates the Fastly Compute platform, allowing you to develop and test WASM services locally.

**Viceroy documentation**: https://github.com/fastly/Viceroy

## Common Gotchas

- **Dictionaries and ConfigStores are both supported** but configured differently in `fastly.toml`. Dictionaries go under `[local_server.dictionaries]` as inline key-value maps or JSON files. ConfigStores go under `[local_server.config_stores]`.
- **`fastly.toml` must have a `[local_server]` section.** Without it, Viceroy won't know about your backends, stores, or other local overrides. Every backend your app calls must be listed under `[local_server.backends]`.
- **Default port is 7676**, not 5000 (which is Fastlike's default). Access your app at `http://127.0.0.1:7676`.
- **Backends should point to local servers** when developing locally. Avoid proxying to remote production origins to prevent accidentally leaking request data.

## Quick Start

```bash
# Install Viceroy
cargo install --locked viceroy

# Build your Compute app
fastly compute build

# Start local server (default: 127.0.0.1:7676)
viceroy -C fastly.toml bin/main.wasm

# Or use the Fastly CLI wrapper
fastly compute serve
```

## References

| Topic  | File                                                            | Use when...                                                                    |
| ------ | --------------------------------------------------------------- | ------------------------------------------------------------------------------ |
| Serve  | [fastly-compute-serve.md](references/fastly-compute-serve.md)   | Starting local dev server, profiling, advanced server options                  |
| Config | [fastly-compute-config.md](references/fastly-compute-config.md) | Configuring fastly.toml backends, stores, geolocation, device detection, ACLs  |
| Test   | [fastly-compute-test.md](references/fastly-compute-test.md)     | Running Rust unit tests with cargo-nextest, writing tests for Compute services |
| Adapt  | [fastly-compute-adapt.md](references/fastly-compute-adapt.md)   | Converting core WASM modules to Component Model, custom build pipelines        |

From fastly/fastly-agent-toolkit, MIT.

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