fly-io git:20260518.402a41aA

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---
name: fly-io
description: Use when deploying, configuring, troubleshooting, reviewing, or architecting Fly.io apps and infrastructure. Covers flyctl, fly.toml, Fly Launch, Fly Machines, process groups, health checks, deployment strategies, private networking, 6PN, Flycast, egress IPs, volumes, Managed Postgres, Tigris, Redis, LiteFS, extensions, CI/CD, and production readiness.
---

# Fly.io Platform

Use this skill for any Fly.io work, including routine deploy/config changes and
architecture decisions for apps known to run on Fly.

Fly changes quickly. Ground decisions in the local CLI and current official docs
before making version-sensitive claims.

## First Steps

1. Inspect the project shape before prescribing commands.

   ```bash
   rg --files -g 'fly.toml' -g 'Dockerfile*' -g '.dockerignore' -g '.github/workflows/**' -g 'package.json' -g 'pyproject.toml' -g 'go.mod' -g 'Cargo.toml'
   ```

2. Check the current `flyctl` surface for the task.

   ```bash
   fly version
   fly help
   fly <command> --help
   ```

3. Prefer non-mutating validation unless the user explicitly asked to deploy or
   change remote resources.

   ```bash
   fly config show --local
   fly config validate --strict
   fly status
   fly checks list
   ```

4. Use official Fly docs as the source of truth for unstable details. Do not use
   community posts as encoded facts unless the user explicitly asks for forum
   research.

## Reference Routing

- Read `references/deploy-config.md` for `fly.toml`, process groups, health
  checks, deploy strategies, GitHub Actions, secrets, scaling, autostop, and
  config validation.
- Read `references/networking.md` for 6PN, `.internal`, Flycast, public
  services, private services, custom private networks, request routing headers,
  `fly-replay`, and static egress IPs.
- Read `references/data-storage.md` for Managed Postgres, volumes,
  auto-extension, snapshots, backups, Tigris, Upstash Redis, LiteFS, and
  durability decisions.
- Read `references/production.md` for production reviews, security, orgs,
  tokens, public IP audits, backups, monitoring, logging, and extensions.

## Fly-Native Defaults

- For ordinary apps, prefer Fly Launch-managed apps (`fly launch`, `fly deploy`,
  `fly.toml`) over hand-managed Machines.
- Use `fly machine` or the Machines API only when the task needs per-Machine
  control, unmanaged workloads, one-app-per-customer isolation, or runtime code
  execution patterns.
- For production Postgres, prefer Managed Postgres (`fly mpg`) over legacy
  unmanaged Postgres.
- For object storage, prefer Tigris.
- For Redis, use Fly's Upstash integration unless the app has a clear reason to
  run its own Redis.
- For private proxy-routed services, prefer Flycast over raw `.internal` when
  the service needs Fly Proxy behavior such as autostart, load balancing, TLS,
  PROXY protocol, or DNS-hostile clients.
- For fixed outbound allowlisting, prefer app-scoped static egress IPs with
  `fly ips allocate-egress`; do not recommend legacy machine-scoped egress IPs
  for new work.

## Gotchas To Surface Early

- Data locality: Machines, volumes, regions, and data durability are not
  interchangeable. Volumes are local NVMe slices, not replicated network disks.
- Network exposure: a service in `fly.toml` plus public IPs exposes that service
  publicly, even if the intended consumer is private or Flycast.
- CLI surprises: current `fly launch --no-deploy` can also offer GitHub Actions
  setup in GitHub repos; use `--no-github-workflow` when that automation is not
  wanted.
- Process groups: defining `[processes]` makes the list complete. Removing a
  process group from config can destroy Machines in that group on deploy.
- Health checks: service-level checks affect routing, but failing checks do not
  restart or stop Machines by themselves.
- Secrets: `fly secrets set` restarts Machines unless staged; secrets are runtime
  env vars, not build args.
- Release commands: they run in temporary Machines without attached volumes.
- Egress: default outbound IPs are unstable. Allocate app-scoped egress IPs per
  region only when third parties require allowlisting.
- LiteFS: use with caution, keep off-site backups, and do not combine LiteFS
  with Fly Proxy autostop/autostart.
- GPUs: do not recommend Fly GPUs for new work. Fly docs say GPUs are deprecated
  and unavailable after August 1.

## Architecture Triggers

Pause for Fly-specific architecture thinking when the prompt involves state,
databases, volumes, private services, regions, tenants, queues, workers, egress
allowlisting, HA, failover, production, or cost boundaries. In those cases,
answer with:

1. The Fly-native recommendation.
2. The exact commands or `fly.toml` shape.
3. The gotchas checked and any remaining production risks.

Downrank beginner tutorials, dashboard-first workflows, deprecated offerings,
and experimental surfaces unless the user asks directly.