Use the Fly.io flyctl CLI for deploying and operating apps on Fly.io. Default to read-only diagnostics (status/logs/config/releases). Only perform state-changing operations (deploys, SSH exec, secrets, scaling, machines, volumes, Postgres changes) with explicit user approval. Use when asked to deploy to Fly.io, debug fly deploy/build/runtime failures, set up GitHub Actions deploys/previews, or safely manage Fly apps and Postgres.