# Viceroy

> Runs Fastly Compute WASM applications locally with Viceroy, specifically for Rust and Component Model projects. Use when starting a local Fastly Compute dev server with Viceroy, configuring fastly.toml for local backend overrides and store definitions, running Rust unit tests with cargo-nextest against the Compute runtime, debugging Compute apps locally, adapting core WASM modules to the Componen…

- **Type:** Skill
- **Install:** `agentstack add skill-fastly-fastly-agent-toolkit-viceroy`
- **Verified:** Yes — security-reviewed for prompt injection and unsafe behavior
- **Seller:** [fastly](https://agentstack.voostack.com/s/fastly)
- **Installs:** 0
- **Category:** [Agent Skills](https://agentstack.voostack.com/c/agent-skills)
- **Latest version:** 0.1.0
- **License:** MIT
- **Upstream author:** [fastly](https://github.com/fastly)
- **Source:** https://github.com/fastly/fastly-agent-toolkit/tree/main/skills/viceroy

## Install

```sh
agentstack add skill-fastly-fastly-agent-toolkit-viceroy
```

Requires the [AgentStack CLI](https://agentstack.voostack.com/docs/cli). Works with Claude Code, Cursor, and any MCP-compatible agent.

## About

# 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        |

## Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

- **Author:** [fastly](https://github.com/fastly)
- **Source:** [fastly/fastly-agent-toolkit](https://github.com/fastly/fastly-agent-toolkit)
- **License:** MIT

Install and usage instructions live in the source repository linked above.

## Pricing

- **Free** — Free

## Security capabilities

Automated source analysis of v0.1.0 — what this tool can access:

- **Network access:** no
- **Filesystem access:** no
- **Shell / process execution:** no
- **Environment & secrets:** no
- **Dynamic code execution:** no

*"Yes" means the capability is present in the source — more access means more to trust, not that it is unsafe.*


## Versions

- **0.1.0** — security scan: passed — Imported from the upstream source.

## Links

- Listing page: https://agentstack.voostack.com/l/skill-fastly-fastly-agent-toolkit-viceroy
- Seller: https://agentstack.voostack.com/s/fastly
- Browse the marketplace: https://agentstack.voostack.com/browse

---
Listed on AgentStack — the marketplace for AI agent skills and MCP servers. Every listing is security-reviewed. Creators keep 70%.