Switch from config.yaml to hatk.config.ts

Goal

Replace config.yaml with hatk.config.ts for type safety, autocompletion, and single-language consistency. No YAML fallback.

Design

User-facing config file

// hatk.config.ts
import { defineConfig } from 'hatk'

export default defineConfig({
  relay: 'ws://localhost:2583',
  port: 3000,
  database: 'data/hatk.db',
  collections: ['app.bsky.feed.post'],
  backfill: {
    parallelism: 10,
    fullNetwork: false,
  },
})

defineConfig helper

Identity function exported from the hatk package. Exists solely for type inference:

export function defineConfig(config: Partial<HatkConfig>): Partial<HatkConfig> {
  return config
}

Takes Partial<HatkConfig> so users only specify what they need; defaults fill the rest.

Loader (config.ts)

loadConfig becomes async (dynamic import replaces readFileSync + YAML parse):

export async function loadConfig(configPath?: string): Promise<HatkConfig> {
  const resolved = resolve(configPath || 'hatk.config.ts')
  const configDir = dirname(resolved)
  const mod = await import(resolved)
  const raw: Partial<HatkConfig> = mod.default
  return applyDefaultsAndEnvOverrides(raw, configDir)
}

• Relative paths still resolved against the config file's directory.
• Environment variable overrides preserved (essential for container deployments).
• Defaults unchanged from current behavior.

Environment variable overrides

Same as today. Env vars take precedence over the TS config values:

Env var	Config field
DATABASE	database
RELAY	relay
DID_PLC_URL	plc
PORT	port
BACKFILL_REPOS	backfill.repos
BACKFILL_FULL_NETWORK	backfill.fullNetwork
BACKFILL_PARALLELISM	backfill.parallelism
BACKFILL_FETCH_TIMEOUT	backfill.fetchTimeout
BACKFILL_MAX_RETRIES	backfill.maxRetries
FTS_REBUILD_INTERVAL	ftsRebuildInterval
OAUTH_ISSUER	oauth.issuer
ADMINS	admins

Changes required

config.ts

• Remove yaml import and readFileSync
• loadConfig becomes async, uses await import() instead of YAML parse
• Add defineConfig export
• Input type becomes Partial<HatkConfig> (users specify only what they need)

Callers of loadConfig (4 files)

• main.ts — already async context; change loadConfig(configPath) to await loadConfig(configPath), update default from 'config.yaml' to 'hatk.config.ts'
• cli.ts — change loadConfig(resolve('config.yaml')) to await loadConfig(resolve('hatk.config.ts')) (2 call sites)
• test.ts — change to await loadConfig(...), update fallback path
• vite-plugin.ts — update spawned server argument from 'config.yaml' to 'hatk.config.ts'

Package exports

• Export defineConfig and HatkConfig from the package entry point so users can import them

Dependencies

• Remove yaml from package.json dependencies

Documentation

• Update docs/site/src/content/docs/getting-started/configuration.mdx to show TypeScript config instead of YAML

Migration

• No automatic migration. Clean break from YAML.
• If hatk.config.ts is not found at startup, print a clear error message explaining the change.