diff --git a/.editorconfig b/.editorconfig
new file mode 100644
index 0000000..6e4c9e5
--- /dev/null
+++ b/.editorconfig
@@ -0,0 +1,13 @@
+# EditorConfig helps maintain consistent coding styles
+root = true
+
+[*]
+charset = utf-8
+end_of_line = lf
+insert_final_newline = true
+trim_trailing_whitespace = true
+indent_style = space
+indent_size = 2
+
+[*.md]
+trim_trailing_whitespace = false
diff --git a/.eslintrc.cjs b/.eslintrc.cjs
new file mode 100644
index 0000000..1c5c0fb
--- /dev/null
+++ b/.eslintrc.cjs
@@ -0,0 +1,12 @@
+// Root ESLint config for monorepo
+/** @type {import('eslint').Linter.Config} */
+module.exports = {
+  root: true,
+  env: { es2022: true, node: true, browser: true },
+  extends: ['eslint:recommended', 'prettier'],
+  parserOptions: { ecmaVersion: 'latest', sourceType: 'module' },
+  ignorePatterns: ['node_modules/', 'dist/', 'build/', '.svelte-kit/', 'coverage/'],
+  overrides: [
+    { files: ['**/*.cjs'], parserOptions: { sourceType: 'script' } },
+  ],
+};
diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..5737097
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,45 @@
+# Node & package managers
+node_modules/
+.npm/
+.pnpm-store/
+.npmrc.local
+
+# Logs & caches
+*.log
+pnpm-debug.log*
+.npm-debug.log*
+.yarn-debug.log*
+.yarn-error.log*
+.eslintcache
+.cache/
+
+# Build & dist
+build/
+dist/
+coverage/
+
+# SvelteKit / Vite
+.svelte-kit/
+.vite/
+
+# Test artifacts (Vitest/Playwright)
+playwright-report/
+blob-report/
+test-results/
+coverage/
+
+# Nix & direnv
+result
+.direnv/
+.devenv/
+
+# OS/editor
+.DS_Store
+Thumbs.db
+.vscode/
+.idea/
+
+# Misc
+*.local
+*.swp
+*.swo
diff --git a/.npmrc b/.npmrc
new file mode 100644
index 0000000..0fca347
--- /dev/null
+++ b/.npmrc
@@ -0,0 +1,5 @@
+shamefully-hoist=false
+prefer-workspace-packages=true
+workspace-concurrency=3
+auto-install-peers=true
+fund=false
diff --git a/.prettierignore b/.prettierignore
new file mode 100644
index 0000000..67d2b32
--- /dev/null
+++ b/.prettierignore
@@ -0,0 +1,6 @@
+node_modules
+pnpm-lock.yaml
+coverage
+build
+dist
+.svelte-kit
diff --git a/.prettierrc b/.prettierrc
new file mode 100644
index 0000000..fe25ad3
--- /dev/null
+++ b/.prettierrc
@@ -0,0 +1,9 @@
+{
+  "printWidth": 100,
+  "singleQuote": true,
+  "semi": true,
+  "trailingComma": "es5",
+  "arrowParens": "avoid",
+  "tabWidth": 2,
+  "useTabs": false
+}
diff --git a/package.json b/package.json
index aacc258..89743a7 100644
--- a/package.json
+++ b/package.json
@@ -9,5 +9,13 @@
     "lint": "pnpm -r --if-present lint",
     "typecheck": "pnpm -r --if-present typecheck || pnpm -r --if-present check",
     "format": "pnpm -r --if-present format"
-  }
+  },
+  "devDependencies": {
+    "eslint": "^8.57.0",
+    "eslint-config-prettier": "^9.1.0",
+    "prettier": "^3.3.3",
+    "typescript": "^5.5.4",
+    "svelte-check": "^3.8.5"
+  },
+  "packageManager": "pnpm@9.0.0"
 }
diff --git a/specs/001-glowtrack-a-mood/tasks.md b/specs/001-glowtrack-a-mood/tasks.md
index 5df497f..24a63e2 100644
--- a/specs/001-glowtrack-a-mood/tasks.md
+++ b/specs/001-glowtrack-a-mood/tasks.md
@@ -37,7 +37,7 @@ Paths below are absolute to this repo.
   - Create /home/jawz/Development/Projects/GlowTrack/pnpm-workspace.yaml listing apps/* and packages/*
   - Dependencies: T001
 
-- [ ] T004 Configure linting, formatting, types
+- [X] T004 Configure linting, formatting, types
   - Root: .editorconfig, .eslintrc.cjs, .prettierrc, .prettierignore, .npmrc (pnpm settings)
   - Add dev deps: eslint, eslint-config-prettier, prettier, typescript, svelte-check
   - Dependencies: T003