Set up Advent of Code 2025 with Bun, Effect-TS, DevContainer, and Biome

[Copilot]

Bootstrap a Bun-based TypeScript project using Effect-TS for Advent of Code 2025, with full DevContainer/Codespaces support and modern tooling.

Project Structure

• Days organized under src/days/dayXX/index.ts
• Day 1 implements Hello World using Effect-TS

Tooling

• Runtime: Bun with bleeding-edge TypeScript 5.9.3
• Linting/Formatting: Biome 2.3.8 (replaces ESLint/Prettier)
• Framework: Effect-TS 3.19.8 with platform packages

VS Code / Codespaces

• DevContainer with Bun feature for local and Codespaces use
• Required extensions: Effect language server, Biome, Bun
• Launch configs, tasks, and MCP configuration included
• Watch mode support for iterative development:
  • VS Code launch config: "Watch Current File" with automatic re-run on file changes
  • Package.json script: bun run day01:watch
  • VS Code tasks: "Watch Day 01" and "Watch Current Day"

CI

• GitHub Actions workflow for lint, format check, and typecheck
• Minimal permissions (contents: read)

// src/days/day01/index.ts
import { Effect, Console } from "effect";

const program = Effect.gen(function* () {
  yield* Console.log("Hello World from Day 1!");
});

Effect.runPromise(program).catch(console.error);

Original prompt

A Bun-based codebase in typescript using Effect-TS. It's for advent of code 2025, so organise by day. Also create a minimal devcontainer setup that I can run in vscode with remote containers. Start off with day 1 only, which for now only does Hello World

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[Nvveen]

@copilot Add a watch launch script to iteratively develop per day solution

[Copilot]

@copilot Add a watch launch script to iteratively develop per day solution

Added watch mode support in cbad051:

• VS Code launch config: "Watch Current File" with watchMode: true
• Package.json script: bun run day01:watch
• VS Code tasks: "Watch Day 01" and "Watch Current Day"

You can use any of these to re-run your solution automatically on file changes.