Decides the stack (NEXT item 3): TypeScript/Node core on first-party @atproto/* packages, SvelteKit for SSR public sites + admin, hand-rolled direct PDS reads for v1 (quickslice/HappyView declined; Tap named the v2 liveness candidate), provisional SQLite pending the hosted-infra decision, and Elixir/Gleam explicitly benched for v2 auxiliary services. Checkpoints three new research files (language ecosystems, AppView infra, comparable stacks) and updates FEASIBILITY, AGENTS, NEXT accordingly. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_014mXNfP5m9NhhjVgM5VVJ5E