fastly/fastly-agent-toolkit

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 Component Model, or troubleshooting local Compute testing issues (connection refused, missing backends, stor…

First seen Mar 13, 2026

Installation

$ npx skills add fastly/fastly-agent-toolkit --skill viceroy

Summary

  • 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 Component Model, or troubleshooting local Compute testing issues (connection refused, missing backends, store config).
  • For non-Rust Compute work or understanding the Compute API, prefer the fastlike skill instead — its source code is easier to understand as a Fastly Compute API reference.

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More details

Agent compatibility

Declared targets from SKILL.md / docs. Unmarked agents are not listed — the skill may still install via the CLI.

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Repository health

Stars 32
License LICENSE
Default branch main
Open issues 0
Status Active

Package contents

Files included with this skill beyond the listing page.

  • skill md SKILL.md 2,992 B
  • docs SUMMARY.md 697 B

History

  1. First seen on skills.sh
  2. First recorded snapshot · 78 installs

SKILL.md

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 [localserver.dictionaries] as inline key-value maps or JSON files. ConfigStores go under [localserver.config_stores].
  • fastly.toml must have a [localserver] section. Without it, Viceroy won't know about your backends, stores, or other local overrides. Every backend your app calls must be listed under [localserver.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

# 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