refactor: rename shared package to core (#24309)

19 files changed, 1404 insertions, 0 deletions

diff --git a/packages/core/src/filesystem.ts b/packages/core/src/filesystem.ts
new file mode 100644
index 000000000..44346be8f
--- /dev/null
+++ b/packages/core/src/filesystem.ts
@@ -0,0 +1,236 @@
+import { NodeFileSystem } from "@effect/platform-node"
+import { dirname, join, relative, resolve as pathResolve } from "path"
+import { realpathSync } from "fs"
+import * as NFS from "fs/promises"
+import { lookup } from "mime-types"
+import { Effect, FileSystem, Layer, Schema, Context } from "effect"
+import type { PlatformError } from "effect/PlatformError"
+import { Glob } from "./util/glob"
+
+export namespace AppFileSystem {
+  export class FileSystemError extends Schema.TaggedErrorClass<FileSystemError>()("FileSystemError", {
+    method: Schema.String,
+    cause: Schema.optional(Schema.Defect),
+  }) {}
+
+  export type Error = PlatformError | FileSystemError
+
+  export interface DirEntry {
+    readonly name: string
+    readonly type: "file" | "directory" | "symlink" | "other"
+  }
+
+  export interface Interface extends FileSystem.FileSystem {
+    readonly isDir: (path: string) => Effect.Effect<boolean>
+    readonly isFile: (path: string) => Effect.Effect<boolean>
+    readonly existsSafe: (path: string) => Effect.Effect<boolean>
+    readonly readJson: (path: string) => Effect.Effect<unknown, Error>
+    readonly writeJson: (path: string, data: unknown, mode?: number) => Effect.Effect<void, Error>
+    readonly ensureDir: (path: string) => Effect.Effect<void, Error>
+    readonly writeWithDirs: (path: string, content: string | Uint8Array, mode?: number) => Effect.Effect<void, Error>
+    readonly readDirectoryEntries: (path: string) => Effect.Effect<DirEntry[], Error>
+    readonly findUp: (target: string, start: string, stop?: string) => Effect.Effect<string[], Error>
+    readonly up: (options: { targets: string[]; start: string; stop?: string }) => Effect.Effect<string[], Error>
+    readonly globUp: (pattern: string, start: string, stop?: string) => Effect.Effect<string[], Error>
+    readonly glob: (pattern: string, options?: Glob.Options) => Effect.Effect<string[], Error>
+    readonly globMatch: (pattern: string, filepath: string) => boolean
+  }
+
+  export class Service extends Context.Service<Service, Interface>()("@opencode/FileSystem") {}
+
+  export const layer = Layer.effect(
+    Service,
+    Effect.gen(function* () {
+      const fs = yield* FileSystem.FileSystem
+
+      const existsSafe = Effect.fn("FileSystem.existsSafe")(function* (path: string) {
+        return yield* fs.exists(path).pipe(Effect.orElseSucceed(() => false))
+      })
+
+      const isDir = Effect.fn("FileSystem.isDir")(function* (path: string) {
+        const info = yield* fs.stat(path).pipe(Effect.catch(() => Effect.void))
+        return info?.type === "Directory"
+      })
+
+      const isFile = Effect.fn("FileSystem.isFile")(function* (path: string) {
+        const info = yield* fs.stat(path).pipe(Effect.catch(() => Effect.void))
+        return info?.type === "File"
+      })
+
+      const readDirectoryEntries = Effect.fn("FileSystem.readDirectoryEntries")(function* (dirPath: string) {
+        return yield* Effect.tryPromise({
+          try: async () => {
+            const entries = await NFS.readdir(dirPath, { withFileTypes: true })
+            return entries.map(
+              (e): DirEntry => ({
+                name: e.name,
+                type: e.isDirectory() ? "directory" : e.isSymbolicLink() ? "symlink" : e.isFile() ? "file" : "other",
+              }),
+            )
+          },
+          catch: (cause) => new FileSystemError({ method: "readDirectoryEntries", cause }),
+        })
+      })
+
+      const readJson = Effect.fn("FileSystem.readJson")(function* (path: string) {
+        const text = yield* fs.readFileString(path)
+        return JSON.parse(text)
+      })
+
+      const writeJson = Effect.fn("FileSystem.writeJson")(function* (path: string, data: unknown, mode?: number) {
+        const content = JSON.stringify(data, null, 2)
+        yield* fs.writeFileString(path, content)
+        if (mode) yield* fs.chmod(path, mode)
+      })
+
+      const ensureDir = Effect.fn("FileSystem.ensureDir")(function* (path: string) {
+        yield* fs.makeDirectory(path, { recursive: true })
+      })
+
+      const writeWithDirs = Effect.fn("FileSystem.writeWithDirs")(function* (
+        path: string,
+        content: string | Uint8Array,
+        mode?: number,
+      ) {
+        const write = typeof content === "string" ? fs.writeFileString(path, content) : fs.writeFile(path, content)
+
+        yield* write.pipe(
+          Effect.catchIf(
+            (e) => e.reason._tag === "NotFound",
+            () =>
+              Effect.gen(function* () {
+                yield* fs.makeDirectory(dirname(path), { recursive: true })
+                yield* write
+              }),
+          ),
+        )
+        if (mode) yield* fs.chmod(path, mode)
+      })
+
+      const glob = Effect.fn("FileSystem.glob")(function* (pattern: string, options?: Glob.Options) {
+        return yield* Effect.tryPromise({
+          try: () => Glob.scan(pattern, options),
+          catch: (cause) => new FileSystemError({ method: "glob", cause }),
+        })
+      })
+
+      const findUp = Effect.fn("FileSystem.findUp")(function* (target: string, start: string, stop?: string) {
+        const result: string[] = []
+        let current = start
+        while (true) {
+          const search = join(current, target)
+          if (yield* fs.exists(search)) result.push(search)
+          if (stop === current) break
+          const parent = dirname(current)
+          if (parent === current) break
+          current = parent
+        }
+        return result
+      })
+
+      const up = Effect.fn("FileSystem.up")(function* (options: { targets: string[]; start: string; stop?: string }) {
+        const result: string[] = []
+        let current = options.start
+        while (true) {
+          for (const target of options.targets) {
+            const search = join(current, target)
+            if (yield* fs.exists(search)) result.push(search)
+          }
+          if (options.stop === current) break
+          const parent = dirname(current)
+          if (parent === current) break
+          current = parent
+        }
+        return result
+      })
+
+      const globUp = Effect.fn("FileSystem.globUp")(function* (pattern: string, start: string, stop?: string) {
+        const result: string[] = []
+        let current = start
+        while (true) {
+          const matches = yield* glob(pattern, { cwd: current, absolute: true, include: "file", dot: true }).pipe(
+            Effect.catch(() => Effect.succeed([] as string[])),
+          )
+          result.push(...matches)
+          if (stop === current) break
+          const parent = dirname(current)
+          if (parent === current) break
+          current = parent
+        }
+        return result
+      })
+
+      return Service.of({
+        ...fs,
+        existsSafe,
+        isDir,
+        isFile,
+        readDirectoryEntries,
+        readJson,
+        writeJson,
+        ensureDir,
+        writeWithDirs,
+        findUp,
+        up,
+        globUp,
+        glob,
+        globMatch: Glob.match,
+      })
+    }),
+  )
+
+  export const defaultLayer = layer.pipe(Layer.provide(NodeFileSystem.layer))
+
+  // Pure helpers that don't need Effect (path manipulation, sync operations)
+  export function mimeType(p: string): string {
+    return lookup(p) || "application/octet-stream"
+  }
+
+  export function normalizePath(p: string): string {
+    if (process.platform !== "win32") return p
+    const resolved = pathResolve(windowsPath(p))
+    try {
+      return realpathSync.native(resolved)
+    } catch {
+      return resolved
+    }
+  }
+
+  export function normalizePathPattern(p: string): string {
+    if (process.platform !== "win32") return p
+    if (p === "*") return p
+    const match = p.match(/^(.*)[\\/]\*$/)
+    if (!match) return normalizePath(p)
+    const dir = /^[A-Za-z]:$/.test(match[1]) ? match[1] + "\\" : match[1]
+    return join(normalizePath(dir), "*")
+  }
+
+  export function resolve(p: string): string {
+    const resolved = pathResolve(windowsPath(p))
+    try {
+      return normalizePath(realpathSync(resolved))
+    } catch (e: any) {
+      if (e?.code === "ENOENT") return normalizePath(resolved)
+      throw e
+    }
+  }
+
+  export function windowsPath(p: string): string {
+    if (process.platform !== "win32") return p
+    return p
+      .replace(/^\/([a-zA-Z]):(?:[\\/]|$)/, (_, drive) => `${drive.toUpperCase()}:/`)
+      .replace(/^\/([a-zA-Z])(?:\/|$)/, (_, drive) => `${drive.toUpperCase()}:/`)
+      .replace(/^\/cygdrive\/([a-zA-Z])(?:\/|$)/, (_, drive) => `${drive.toUpperCase()}:/`)
+      .replace(/^\/mnt\/([a-zA-Z])(?:\/|$)/, (_, drive) => `${drive.toUpperCase()}:/`)
+  }
+
+  export function overlaps(a: string, b: string) {
+    const relA = relative(a, b)
+    const relB = relative(b, a)
+    return !relA || !relA.startsWith("..") || !relB || !relB.startsWith("..")
+  }
+
+  export function contains(parent: string, child: string) {
+    return !relative(parent, child).startsWith("..")
+  }
+}
diff --git a/packages/core/src/global.ts b/packages/core/src/global.ts
new file mode 100644
index 000000000..538cc091b
--- /dev/null
+++ b/packages/core/src/global.ts
@@ -0,0 +1,42 @@
+import path from "path"
+import { xdgData, xdgCache, xdgConfig, xdgState } from "xdg-basedir"
+import os from "os"
+import { Context, Effect, Layer } from "effect"
+
+export namespace Global {
+  export class Service extends Context.Service<Service, Interface>()("@opencode/Global") {}
+
+  export interface Interface {
+    readonly home: string
+    readonly data: string
+    readonly cache: string
+    readonly config: string
+    readonly state: string
+    readonly bin: string
+    readonly log: string
+  }
+
+  export const layer = Layer.effect(
+    Service,
+    Effect.gen(function* () {
+      const app = "opencode"
+      const home = process.env.OPENCODE_TEST_HOME ?? os.homedir()
+      const data = path.join(xdgData!, app)
+      const cache = path.join(xdgCache!, app)
+      const cfg = path.join(xdgConfig!, app)
+      const state = path.join(xdgState!, app)
+      const bin = path.join(cache, "bin")
+      const log = path.join(data, "log")
+
+      return Service.of({
+        home,
+        data,
+        cache,
+        config: cfg,
+        state,
+        bin,
+        log,
+      })
+    }),
+  )
+}
diff --git a/packages/core/src/types.d.ts b/packages/core/src/types.d.ts
new file mode 100644
index 000000000..60e1639ad
--- /dev/null
+++ b/packages/core/src/types.d.ts
@@ -0,0 +1,46 @@
+declare module "@npmcli/arborist" {
+  export interface ArboristOptions {
+    path: string
+    binLinks?: boolean
+    progress?: boolean
+    savePrefix?: string
+    ignoreScripts?: boolean
+    [key: string]: unknown
+  }
+
+  export interface ArboristNode {
+    name: string
+    path: string
+  }
+
+  export interface ArboristEdge {
+    to?: ArboristNode
+  }
+
+  export interface ArboristTree {
+    edgesOut: Map<string, ArboristEdge>
+  }
+
+  export interface ReifyOptions {
+    add?: string[]
+    save?: boolean
+    saveType?: "prod" | "dev" | "optional" | "peer"
+    [key: string]: unknown
+  }
+
+  export class Arborist {
+    constructor(options: ArboristOptions)
+    loadVirtual(): Promise<ArboristTree | undefined>
+    reify(options?: ReifyOptions): Promise<ArboristTree>
+  }
+}
+
+declare var Bun:
+  | {
+      file(path: string): {
+        text(): Promise<string>
+        json(): Promise<unknown>
+      }
+      write(path: string, content: string | Uint8Array): Promise<void>
+    }
+  | undefined
diff --git a/packages/core/src/util/array.ts b/packages/core/src/util/array.ts
new file mode 100644
index 000000000..1fb8ac69e
--- /dev/null
+++ b/packages/core/src/util/array.ts
@@ -0,0 +1,10 @@
+export function findLast<T>(
+  items: readonly T[],
+  predicate: (item: T, index: number, items: readonly T[]) => boolean,
+): T | undefined {
+  for (let i = items.length - 1; i >= 0; i -= 1) {
+    const item = items[i]
+    if (predicate(item, i, items)) return item
+  }
+  return undefined
+}
diff --git a/packages/core/src/util/binary.ts b/packages/core/src/util/binary.ts
new file mode 100644
index 000000000..3d8f61851
--- /dev/null
+++ b/packages/core/src/util/binary.ts
@@ -0,0 +1,41 @@
+export namespace Binary {
+  export function search<T>(array: T[], id: string, compare: (item: T) => string): { found: boolean; index: number } {
+    let left = 0
+    let right = array.length - 1
+
+    while (left <= right) {
+      const mid = Math.floor((left + right) / 2)
+      const midId = compare(array[mid])
+
+      if (midId === id) {
+        return { found: true, index: mid }
+      } else if (midId < id) {
+        left = mid + 1
+      } else {
+        right = mid - 1
+      }
+    }
+
+    return { found: false, index: left }
+  }
+
+  export function insert<T>(array: T[], item: T, compare: (item: T) => string): T[] {
+    const id = compare(item)
+    let left = 0
+    let right = array.length
+
+    while (left < right) {
+      const mid = Math.floor((left + right) / 2)
+      const midId = compare(array[mid])
+
+      if (midId < id) {
+        left = mid + 1
+      } else {
+        right = mid
+      }
+    }
+
+    array.splice(left, 0, item)
+    return array
+  }
+}
diff --git a/packages/core/src/util/effect-flock.ts b/packages/core/src/util/effect-flock.ts
new file mode 100644
index 000000000..16bcf091b
--- /dev/null
+++ b/packages/core/src/util/effect-flock.ts
@@ -0,0 +1,283 @@
+import path from "path"
+import os from "os"
+import { randomUUID } from "crypto"
+import { Context, Effect, Function, Layer, Option, Schedule, Schema } from "effect"
+import type { FileSystem, Scope } from "effect"
+import type { PlatformError } from "effect/PlatformError"
+import { AppFileSystem } from "../filesystem"
+import { Global } from "../global"
+import { Hash } from "./hash"
+
+export namespace EffectFlock {
+  // ---------------------------------------------------------------------------
+  // Errors
+  // ---------------------------------------------------------------------------
+
+  export class LockTimeoutError extends Schema.TaggedErrorClass<LockTimeoutError>()("LockTimeoutError", {
+    key: Schema.String,
+  }) {}
+
+  export class LockCompromisedError extends Schema.TaggedErrorClass<LockCompromisedError>()("LockCompromisedError", {
+    detail: Schema.String,
+  }) {}
+
+  class ReleaseError extends Schema.TaggedErrorClass<ReleaseError>()("ReleaseError", {
+    detail: Schema.String,
+    cause: Schema.optional(Schema.Defect),
+  }) {
+    override get message() {
+      return this.detail
+    }
+  }
+
+  /** Internal: signals "lock is held, retry later". Never leaks to callers. */
+  class NotAcquired extends Schema.TaggedErrorClass<NotAcquired>()("NotAcquired", {}) {}
+
+  export type LockError = LockTimeoutError | LockCompromisedError
+
+  // ---------------------------------------------------------------------------
+  // Timing (baked in — no caller ever overrides these)
+  // ---------------------------------------------------------------------------
+
+  const STALE_MS = 60_000
+  const TIMEOUT_MS = 5 * 60_000
+  const BASE_DELAY_MS = 100
+  const MAX_DELAY_MS = 2_000
+  const HEARTBEAT_MS = Math.max(100, Math.floor(STALE_MS / 3))
+
+  const retrySchedule = Schedule.exponential(BASE_DELAY_MS, 1.7).pipe(
+    Schedule.either(Schedule.spaced(MAX_DELAY_MS)),
+    Schedule.jittered,
+    Schedule.while((meta) => meta.elapsed < TIMEOUT_MS),
+  )
+
+  // ---------------------------------------------------------------------------
+  // Lock metadata schema
+  // ---------------------------------------------------------------------------
+
+  const LockMetaJson = Schema.fromJsonString(
+    Schema.Struct({
+      token: Schema.String,
+      pid: Schema.Number,
+      hostname: Schema.String,
+      createdAt: Schema.String,
+    }),
+  )
+
+  const decodeMeta = Schema.decodeUnknownSync(LockMetaJson)
+  const encodeMeta = Schema.encodeSync(LockMetaJson)
+
+  // ---------------------------------------------------------------------------
+  // Service
+  // ---------------------------------------------------------------------------
+
+  export interface Interface {
+    readonly acquire: (key: string, dir?: string) => Effect.Effect<void, LockError, Scope.Scope>
+    readonly withLock: {
+      (key: string, dir?: string): <A, E, R>(body: Effect.Effect<A, E, R>) => Effect.Effect<A, E | LockError, R>
+      <A, E, R>(body: Effect.Effect<A, E, R>, key: string, dir?: string): Effect.Effect<A, E | LockError, R>
+    }
+  }
+
+  export class Service extends Context.Service<Service, Interface>()("EffectFlock") {}
+
+  // ---------------------------------------------------------------------------
+  // Layer
+  // ---------------------------------------------------------------------------
+
+  function wall() {
+    return performance.timeOrigin + performance.now()
+  }
+
+  const mtimeMs = (info: FileSystem.File.Info) => Option.getOrElse(info.mtime, () => new Date(0)).getTime()
+
+  const isPathGone = (e: PlatformError) => e.reason._tag === "NotFound" || e.reason._tag === "Unknown"
+
+  export const layer: Layer.Layer<Service, never, Global.Service | AppFileSystem.Service> = Layer.effect(
+    Service,
+    Effect.gen(function* () {
+      const global = yield* Global.Service
+      const fs = yield* AppFileSystem.Service
+      const lockRoot = path.join(global.state, "locks")
+      const hostname = os.hostname()
+      const ensuredDirs = new Set<string>()
+
+      // -- helpers (close over fs) --
+
+      const safeStat = (file: string) =>
+        fs.stat(file).pipe(
+          Effect.catchIf(isPathGone, () => Effect.void),
+          Effect.orDie,
+        )
+
+      const forceRemove = (target: string) => fs.remove(target, { recursive: true }).pipe(Effect.ignore)
+
+      /** Atomic mkdir — returns true if created, false if already exists, dies on other errors. */
+      const atomicMkdir = (dir: string) =>
+        fs.makeDirectory(dir, { mode: 0o700 }).pipe(
+          Effect.as(true),
+          Effect.catchIf(
+            (e) => e.reason._tag === "AlreadyExists",
+            () => Effect.succeed(false),
+          ),
+          Effect.orDie,
+        )
+
+      /** Write with exclusive create — compromised error if file already exists. */
+      const exclusiveWrite = (filePath: string, content: string, lockDir: string, detail: string) =>
+        fs.writeFileString(filePath, content, { flag: "wx" }).pipe(
+          Effect.catch(() =>
+            Effect.gen(function* () {
+              yield* forceRemove(lockDir)
+              return yield* new LockCompromisedError({ detail })
+            }),
+          ),
+        )
+
+      const cleanStaleBreaker = Effect.fnUntraced(function* (breakerPath: string) {
+        const bs = yield* safeStat(breakerPath)
+        if (bs && wall() - mtimeMs(bs) > STALE_MS) yield* forceRemove(breakerPath)
+        return false
+      })
+
+      const ensureDir = Effect.fnUntraced(function* (dir: string) {
+        if (ensuredDirs.has(dir)) return
+        yield* fs.makeDirectory(dir, { recursive: true }).pipe(Effect.orDie)
+        ensuredDirs.add(dir)
+      })
+
+      const isStale = Effect.fnUntraced(function* (lockDir: string, heartbeatPath: string, metaPath: string) {
+        const now = wall()
+
+        const hb = yield* safeStat(heartbeatPath)
+        if (hb) return now - mtimeMs(hb) > STALE_MS
+
+        const meta = yield* safeStat(metaPath)
+        if (meta) return now - mtimeMs(meta) > STALE_MS
+
+        const dir = yield* safeStat(lockDir)
+        if (!dir) return false
+
+        return now - mtimeMs(dir) > STALE_MS
+      })
+
+      // -- single lock attempt --
+
+      type Handle = { token: string; metaPath: string; heartbeatPath: string; lockDir: string }
+
+      const tryAcquireLockDir = (lockDir: string, key: string) =>
+        Effect.gen(function* () {
+          const token = randomUUID()
+          const metaPath = path.join(lockDir, "meta.json")
+          const heartbeatPath = path.join(lockDir, "heartbeat")
+
+          // Atomic mkdir — the POSIX lock primitive
+          const created = yield* atomicMkdir(lockDir)
+
+          if (!created) {
+            if (!(yield* isStale(lockDir, heartbeatPath, metaPath))) return yield* new NotAcquired()
+
+            // Stale — race for breaker ownership
+            const breakerPath = lockDir + ".breaker"
+
+            const claimed = yield* fs.makeDirectory(breakerPath, { mode: 0o700 }).pipe(
+              Effect.as(true),
+              Effect.catchIf(
+                (e) => e.reason._tag === "AlreadyExists",
+                () => cleanStaleBreaker(breakerPath),
+              ),
+              Effect.catchIf(isPathGone, () => Effect.succeed(false)),
+              Effect.orDie,
+            )
+
+            if (!claimed) return yield* new NotAcquired()
+
+            // We own the breaker — double-check staleness, nuke, recreate
+            const recreated = yield* Effect.gen(function* () {
+              if (!(yield* isStale(lockDir, heartbeatPath, metaPath))) return false
+              yield* forceRemove(lockDir)
+              return yield* atomicMkdir(lockDir)
+            }).pipe(Effect.ensuring(forceRemove(breakerPath)))
+
+            if (!recreated) return yield* new NotAcquired()
+          }
+
+          // We own the lock dir — write heartbeat + meta with exclusive create
+          yield* exclusiveWrite(heartbeatPath, "", lockDir, "heartbeat already existed")
+
+          const metaJson = encodeMeta({ token, pid: process.pid, hostname, createdAt: new Date().toISOString() })
+          yield* exclusiveWrite(metaPath, metaJson, lockDir, "meta.json already existed")
+
+          return { token, metaPath, heartbeatPath, lockDir } satisfies Handle
+        }).pipe(
+          Effect.withSpan("EffectFlock.tryAcquire", {
+            attributes: { key },
+          }),
+        )
+
+      // -- retry wrapper (preserves Handle type) --
+
+      const acquireHandle = (lockfile: string, key: string): Effect.Effect<Handle, LockError> =>
+        tryAcquireLockDir(lockfile, key).pipe(
+          Effect.retry({
+            while: (err) => err._tag === "NotAcquired",
+            schedule: retrySchedule,
+          }),
+          Effect.catchTag("NotAcquired", () => Effect.fail(new LockTimeoutError({ key }))),
+        )
+
+      // -- release --
+
+      const release = (handle: Handle) =>
+        Effect.gen(function* () {
+          const raw = yield* fs.readFileString(handle.metaPath).pipe(
+            Effect.catch((err) => {
+              if (isPathGone(err)) return Effect.die(new ReleaseError({ detail: "metadata missing" }))
+              return Effect.die(err)
+            }),
+          )
+
+          const parsed = yield* Effect.try({
+            try: () => decodeMeta(raw),
+            catch: (cause) => new ReleaseError({ detail: "metadata invalid", cause }),
+          }).pipe(Effect.orDie)
+
+          if (parsed.token !== handle.token) return yield* Effect.die(new ReleaseError({ detail: "token mismatch" }))
+
+          yield* forceRemove(handle.lockDir)
+        })
+
+      // -- build service --
+
+      const acquire = Effect.fn("EffectFlock.acquire")(function* (key: string, dir?: string) {
+        const lockDir = dir ?? lockRoot
+        yield* ensureDir(lockDir)
+
+        const lockfile = path.join(lockDir, Hash.fast(key) + ".lock")
+
+        // acquireRelease: acquire is uninterruptible, release is guaranteed
+        const handle = yield* Effect.acquireRelease(acquireHandle(lockfile, key), (handle) => release(handle))
+
+        // Heartbeat fiber — scoped, so it's interrupted before release runs
+        yield* fs
+          .utimes(handle.heartbeatPath, new Date(), new Date())
+          .pipe(Effect.ignore, Effect.repeat(Schedule.spaced(HEARTBEAT_MS)), Effect.forkScoped)
+      })
+
+      const withLock: Interface["withLock"] = Function.dual(
+        (args) => Effect.isEffect(args[0]),
+        <A, E, R>(body: Effect.Effect<A, E, R>, key: string, dir?: string): Effect.Effect<A, E | LockError, R> =>
+          Effect.scoped(
+            Effect.gen(function* () {
+              yield* acquire(key, dir)
+              return yield* body
+            }),
+          ),
+      )
+
+      return Service.of({ acquire, withLock })
+    }),
+  )
+
+  export const defaultLayer = layer.pipe(Layer.provide(AppFileSystem.defaultLayer), Layer.provide(Global.layer))
+}
diff --git a/packages/core/src/util/encode.ts b/packages/core/src/util/encode.ts
new file mode 100644
index 000000000..e4c6e70ac
--- /dev/null
+++ b/packages/core/src/util/encode.ts
@@ -0,0 +1,51 @@
+export function base64Encode(value: string) {
+  const bytes = new TextEncoder().encode(value)
+  const binary = Array.from(bytes, (b) => String.fromCharCode(b)).join("")
+  return btoa(binary).replace(/\+/g, "-").replace(/\//g, "_").replace(/=/g, "")
+}
+
+export function base64Decode(value: string) {
+  const binary = atob(value.replace(/-/g, "+").replace(/_/g, "/"))
+  const bytes = Uint8Array.from(binary, (c) => c.charCodeAt(0))
+  return new TextDecoder().decode(bytes)
+}
+
+export async function hash(content: string, algorithm = "SHA-256"): Promise<string> {
+  const encoder = new TextEncoder()
+  const data = encoder.encode(content)
+  const hashBuffer = await crypto.subtle.digest(algorithm, data)
+  const hashArray = Array.from(new Uint8Array(hashBuffer))
+  const hashHex = hashArray.map((b) => b.toString(16).padStart(2, "0")).join("")
+  return hashHex
+}
+
+export function checksum(content: string): string | undefined {
+  if (!content) return undefined
+  let hash = 0x811c9dc5
+  for (let i = 0; i < content.length; i++) {
+    hash ^= content.charCodeAt(i)
+    hash = Math.imul(hash, 0x01000193)
+  }
+  return (hash >>> 0).toString(36)
+}
+
+export function sampledChecksum(content: string, limit = 500_000): string | undefined {
+  if (!content) return undefined
+  if (content.length <= limit) return checksum(content)
+
+  const size = 4096
+  const points = [
+    0,
+    Math.floor(content.length * 0.25),
+    Math.floor(content.length * 0.5),
+    Math.floor(content.length * 0.75),
+    content.length - size,
+  ]
+  const hashes = points
+    .map((point) => {
+      const start = Math.max(0, Math.min(content.length - size, point - Math.floor(size / 2)))
+      return checksum(content.slice(start, start + size)) ?? ""
+    })
+    .join(":")
+  return `${content.length}:${hashes}`
+}
diff --git a/packages/core/src/util/error.ts b/packages/core/src/util/error.ts
new file mode 100644
index 000000000..9d3b7c661
--- /dev/null
+++ b/packages/core/src/util/error.ts
@@ -0,0 +1,60 @@
+import z from "zod"
+
+export abstract class NamedError extends Error {
+  abstract schema(): z.core.$ZodType
+  abstract toObject(): { name: string; data: any }
+
+  static hasName(error: unknown, name: string): boolean {
+    return (
+      typeof error === "object" && error !== null && "name" in error && (error as Record<string, unknown>).name === name
+    )
+  }
+
+  static create<Name extends string, Data extends z.core.$ZodType>(name: Name, data: Data) {
+    const schema = z
+      .object({
+        name: z.literal(name),
+        data,
+      })
+      .meta({
+        ref: name,
+      })
+    const result = class extends NamedError {
+      public static readonly Schema = schema
+
+      public override readonly name = name as Name
+
+      constructor(
+        public readonly data: z.input<Data>,
+        options?: ErrorOptions,
+      ) {
+        super(name, options)
+        this.name = name
+      }
+
+      static isInstance(input: any): input is InstanceType<typeof result> {
+        return typeof input === "object" && "name" in input && input.name === name
+      }
+
+      schema() {
+        return schema
+      }
+
+      toObject() {
+        return {
+          name: name,
+          data: this.data,
+        }
+      }
+    }
+    Object.defineProperty(result, "name", { value: name })
+    return result
+  }
+
+  public static readonly Unknown = NamedError.create(
+    "UnknownError",
+    z.object({
+      message: z.string(),
+    }),
+  )
+}
diff --git a/packages/core/src/util/flock.ts b/packages/core/src/util/flock.ts
new file mode 100644
index 000000000..958bd9fd1
--- /dev/null
+++ b/packages/core/src/util/flock.ts
@@ -0,0 +1,358 @@
+import path from "path"
+import os from "os"
+import { randomBytes, randomUUID } from "crypto"
+import { mkdir, readFile, rm, stat, utimes, writeFile } from "fs/promises"
+import { Hash } from "./hash"
+import { Effect } from "effect"
+
+export type FlockGlobal = {
+  state: string
+}
+
+export namespace Flock {
+  let global: FlockGlobal | undefined
+
+  export function setGlobal(g: FlockGlobal) {
+    global = g
+  }
+
+  const root = () => {
+    if (!global) throw new Error("Flock global not set")
+    return path.join(global.state, "locks")
+  }
+
+  // Defaults for callers that do not provide timing options.
+  const defaultOpts = {
+    staleMs: 60_000,
+    timeoutMs: 5 * 60_000,
+    baseDelayMs: 100,
+    maxDelayMs: 2_000,
+  }
+
+  export interface WaitEvent {
+    key: string
+    attempt: number
+    delay: number
+    waited: number
+  }
+
+  export type Wait = (input: WaitEvent) => void | Promise<void>
+
+  export interface Options {
+    dir?: string
+    signal?: AbortSignal
+    staleMs?: number
+    timeoutMs?: number
+    baseDelayMs?: number
+    maxDelayMs?: number
+    onWait?: Wait
+  }
+
+  type Opts = {
+    staleMs: number
+    timeoutMs: number
+    baseDelayMs: number
+    maxDelayMs: number
+  }
+
+  type Owned = {
+    acquired: true
+    startHeartbeat: (intervalMs?: number) => void
+    release: () => Promise<void>
+  }
+
+  export interface Lease {
+    release: () => Promise<void>
+    [Symbol.asyncDispose]: () => Promise<void>
+  }
+
+  function code(err: unknown) {
+    if (typeof err !== "object" || err === null || !("code" in err)) return
+    const value = err.code
+    if (typeof value !== "string") return
+    return value
+  }
+
+  function sleep(ms: number, signal?: AbortSignal) {
+    return new Promise<void>((resolve, reject) => {
+      if (signal?.aborted) {
+        reject(signal.reason ?? new Error("Aborted"))
+        return
+      }
+
+      let timer: NodeJS.Timeout | undefined
+
+      const done = () => {
+        signal?.removeEventListener("abort", abort)
+        resolve()
+      }
+
+      const abort = () => {
+        if (timer) {
+          clearTimeout(timer)
+        }
+        signal?.removeEventListener("abort", abort)
+        reject(signal?.reason ?? new Error("Aborted"))
+      }
+
+      signal?.addEventListener("abort", abort, { once: true })
+      timer = setTimeout(done, ms)
+    })
+  }
+
+  function jitter(ms: number) {
+    const j = Math.floor(ms * 0.3)
+    const d = Math.floor(Math.random() * (2 * j + 1)) - j
+    return Math.max(0, ms + d)
+  }
+
+  function mono() {
+    return performance.now()
+  }
+
+  function wall() {
+    return performance.timeOrigin + mono()
+  }
+
+  async function stats(file: string) {
+    try {
+      return await stat(file)
+    } catch (err) {
+      const errCode = code(err)
+      if (errCode === "ENOENT" || errCode === "ENOTDIR") return
+      throw err
+    }
+  }
+
+  async function stale(lockDir: string, heartbeatPath: string, metaPath: string, staleMs: number) {
+    // Stale detection allows automatic recovery after crashed owners.
+    const now = wall()
+    const heartbeat = await stats(heartbeatPath)
+    if (heartbeat) {
+      return now - heartbeat.mtimeMs > staleMs
+    }
+
+    const meta = await stats(metaPath)
+    if (meta) {
+      return now - meta.mtimeMs > staleMs
+    }
+
+    const dir = await stats(lockDir)
+    if (!dir) {
+      return false
+    }
+
+    return now - dir.mtimeMs > staleMs
+  }
+
+  async function tryAcquireLockDir(lockDir: string, opts: Opts): Promise<Owned | { acquired: false }> {
+    const token = randomUUID?.() ?? randomBytes(16).toString("hex")
+    const metaPath = path.join(lockDir, "meta.json")
+    const heartbeatPath = path.join(lockDir, "heartbeat")
+
+    try {
+      await mkdir(lockDir, { mode: 0o700 })
+    } catch (err) {
+      if (code(err) !== "EEXIST") {
+        throw err
+      }
+
+      if (!(await stale(lockDir, heartbeatPath, metaPath, opts.staleMs))) {
+        return { acquired: false }
+      }
+
+      const breakerPath = lockDir + ".breaker"
+      try {
+        await mkdir(breakerPath, { mode: 0o700 })
+      } catch (claimErr) {
+        const errCode = code(claimErr)
+        if (errCode === "EEXIST") {
+          const breaker = await stats(breakerPath)
+          if (breaker && wall() - breaker.mtimeMs > opts.staleMs) {
+            await rm(breakerPath, { recursive: true, force: true }).catch(() => undefined)
+          }
+          return { acquired: false }
+        }
+
+        if (errCode === "ENOENT" || errCode === "ENOTDIR") {
+          return { acquired: false }
+        }
+
+        throw claimErr
+      }
+
+      try {
+        // Breaker ownership ensures only one contender performs stale cleanup.
+        if (!(await stale(lockDir, heartbeatPath, metaPath, opts.staleMs))) {
+          return { acquired: false }
+        }
+
+        await rm(lockDir, { recursive: true, force: true })
+
+        try {
+          await mkdir(lockDir, { mode: 0o700 })
+        } catch (retryErr) {
+          const errCode = code(retryErr)
+          if (errCode === "EEXIST" || errCode === "ENOTEMPTY") {
+            return { acquired: false }
+          }
+          throw retryErr
+        }
+      } finally {
+        await rm(breakerPath, { recursive: true, force: true }).catch(() => undefined)
+      }
+    }
+
+    const meta = {
+      token,
+      pid: process.pid,
+      hostname: os.hostname(),
+      createdAt: new Date().toISOString(),
+    }
+
+    await writeFile(heartbeatPath, "", { flag: "wx" }).catch(async () => {
+      await rm(lockDir, { recursive: true, force: true })
+      throw new Error("Lock acquired but heartbeat already existed (possible compromise).")
+    })
+
+    await writeFile(metaPath, JSON.stringify(meta, null, 2), { flag: "wx" }).catch(async () => {
+      await rm(lockDir, { recursive: true, force: true })
+      throw new Error("Lock acquired but meta.json already existed (possible compromise).")
+    })
+
+    let timer: NodeJS.Timeout | undefined
+
+    const startHeartbeat = (intervalMs = Math.max(100, Math.floor(opts.staleMs / 3))) => {
+      if (timer) return
+      // Heartbeat prevents long critical sections from being evicted as stale.
+      timer = setInterval(() => {
+        const t = new Date()
+        void utimes(heartbeatPath, t, t).catch(() => undefined)
+      }, intervalMs)
+      timer.unref?.()
+    }
+
+    const release = async () => {
+      if (timer) {
+        clearInterval(timer)
+        timer = undefined
+      }
+
+      const current = await readFile(metaPath, "utf8")
+        .then((raw) => {
+          const parsed = JSON.parse(raw)
+          if (!parsed || typeof parsed !== "object") return {}
+          return {
+            token: "token" in parsed && typeof parsed.token === "string" ? parsed.token : undefined,
+          }
+        })
+        .catch((err) => {
+          const errCode = code(err)
+          if (errCode === "ENOENT" || errCode === "ENOTDIR") {
+            throw new Error("Refusing to release: lock is compromised (metadata missing).")
+          }
+          if (err instanceof SyntaxError) {
+            throw new Error("Refusing to release: lock is compromised (metadata invalid).")
+          }
+          throw err
+        })
+      // Token check prevents deleting a lock that was re-acquired by another process.
+      if (current.token !== token) {
+        throw new Error("Refusing to release: lock token mismatch (not the owner).")
+      }
+
+      await rm(lockDir, { recursive: true, force: true })
+    }
+
+    return {
+      acquired: true,
+      startHeartbeat,
+      release,
+    }
+  }
+
+  async function acquireLockDir(
+    lockDir: string,
+    input: { key: string; onWait?: Wait; signal?: AbortSignal },
+    opts: Opts,
+  ) {
+    const stop = mono() + opts.timeoutMs
+    let attempt = 0
+    let waited = 0
+    let delay = opts.baseDelayMs
+
+    while (true) {
+      input.signal?.throwIfAborted()
+
+      const res = await tryAcquireLockDir(lockDir, opts)
+      if (res.acquired) {
+        return res
+      }
+
+      if (mono() > stop) {
+        throw new Error(`Timed out waiting for lock: ${input.key}`)
+      }
+
+      attempt += 1
+      const ms = jitter(delay)
+      await input.onWait?.({
+        key: input.key,
+        attempt,
+        delay: ms,
+        waited,
+      })
+      await sleep(ms, input.signal)
+      waited += ms
+      delay = Math.min(opts.maxDelayMs, Math.floor(delay * 1.7))
+    }
+  }
+
+  export async function acquire(key: string, input: Options = {}): Promise<Lease> {
+    input.signal?.throwIfAborted()
+    const cfg: Opts = {
+      staleMs: input.staleMs ?? defaultOpts.staleMs,
+      timeoutMs: input.timeoutMs ?? defaultOpts.timeoutMs,
+      baseDelayMs: input.baseDelayMs ?? defaultOpts.baseDelayMs,
+      maxDelayMs: input.maxDelayMs ?? defaultOpts.maxDelayMs,
+    }
+    const dir = input.dir ?? root()
+
+    await mkdir(dir, { recursive: true })
+    const lockfile = path.join(dir, Hash.fast(key) + ".lock")
+    const lock = await acquireLockDir(
+      lockfile,
+      {
+        key,
+        onWait: input.onWait,
+        signal: input.signal,
+      },
+      cfg,
+    )
+    lock.startHeartbeat()
+
+    const release = () => lock.release()
+    return {
+      release,
+      [Symbol.asyncDispose]() {
+        return release()
+      },
+    }
+  }
+
+  export async function withLock<T>(key: string, fn: () => Promise<T>, input: Options = {}) {
+    await using _ = await acquire(key, input)
+    input.signal?.throwIfAborted()
+    return await fn()
+  }
+
+  export const effect = Effect.fn("Flock.effect")(function* (key: string, input: Options = {}) {
+    return yield* Effect.acquireRelease(
+      Effect.promise((signal) => Flock.acquire(key, { ...input, signal })).pipe(
+        Effect.withSpan("Flock.acquire", {
+          attributes: { key },
+        }),
+      ),
+      (lock) => Effect.promise(() => lock.release()).pipe(Effect.withSpan("Flock.release")),
+    ).pipe(Effect.asVoid)
+  })
+}
diff --git a/packages/core/src/util/fn.ts b/packages/core/src/util/fn.ts
new file mode 100644
index 000000000..9efe4622f
--- /dev/null
+++ b/packages/core/src/util/fn.ts
@@ -0,0 +1,11 @@
+import { z } from "zod"
+
+export function fn<T extends z.ZodType, Result>(schema: T, cb: (input: z.infer<T>) => Result) {
+  const result = (input: z.infer<T>) => {
+    const parsed = schema.parse(input)
+    return cb(parsed)
+  }
+  result.force = (input: z.infer<T>) => cb(input)
+  result.schema = schema
+  return result
+}
diff --git a/packages/core/src/util/glob.ts b/packages/core/src/util/glob.ts
new file mode 100644
index 000000000..febf062da
--- /dev/null
+++ b/packages/core/src/util/glob.ts
@@ -0,0 +1,34 @@
+import { glob, globSync, type GlobOptions } from "glob"
+import { minimatch } from "minimatch"
+
+export namespace Glob {
+  export interface Options {
+    cwd?: string
+    absolute?: boolean
+    include?: "file" | "all"
+    dot?: boolean
+    symlink?: boolean
+  }
+
+  function toGlobOptions(options: Options): GlobOptions {
+    return {
+      cwd: options.cwd,
+      absolute: options.absolute,
+      dot: options.dot,
+      follow: options.symlink ?? false,
+      nodir: options.include !== "all",
+    }
+  }
+
+  export async function scan(pattern: string, options: Options = {}): Promise<string[]> {
+    return glob(pattern, toGlobOptions(options)) as Promise<string[]>
+  }
+
+  export function scanSync(pattern: string, options: Options = {}): string[] {
+    return globSync(pattern, toGlobOptions(options)) as string[]
+  }
+
+  export function match(pattern: string, filepath: string): boolean {
+    return minimatch(filepath, pattern, { dot: true })
+  }
+}
diff --git a/packages/core/src/util/hash.ts b/packages/core/src/util/hash.ts
new file mode 100644
index 000000000..680e0f40b
--- /dev/null
+++ b/packages/core/src/util/hash.ts
@@ -0,0 +1,7 @@
+import { createHash } from "crypto"
+
+export namespace Hash {
+  export function fast(input: string | Buffer): string {
+    return createHash("sha1").update(input).digest("hex")
+  }
+}
diff --git a/packages/core/src/util/identifier.ts b/packages/core/src/util/identifier.ts
new file mode 100644
index 000000000..ba28a351b
--- /dev/null
+++ b/packages/core/src/util/identifier.ts
@@ -0,0 +1,48 @@
+import { randomBytes } from "crypto"
+
+export namespace Identifier {
+  const LENGTH = 26
+
+  // State for monotonic ID generation
+  let lastTimestamp = 0
+  let counter = 0
+
+  export function ascending() {
+    return create(false)
+  }
+
+  export function descending() {
+    return create(true)
+  }
+
+  function randomBase62(length: number): string {
+    const chars = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"
+    let result = ""
+    const bytes = randomBytes(length)
+    for (let i = 0; i < length; i++) {
+      result += chars[bytes[i] % 62]
+    }
+    return result
+  }
+
+  export function create(descending: boolean, timestamp?: number): string {
+    const currentTimestamp = timestamp ?? Date.now()
+
+    if (currentTimestamp !== lastTimestamp) {
+      lastTimestamp = currentTimestamp
+      counter = 0
+    }
+    counter++
+
+    let now = BigInt(currentTimestamp) * BigInt(0x1000) + BigInt(counter)
+
+    now = descending ? ~now : now
+
+    const timeBytes = Buffer.alloc(6)
+    for (let i = 0; i < 6; i++) {
+      timeBytes[i] = Number((now >> BigInt(40 - 8 * i)) & BigInt(0xff))
+    }
+
+    return timeBytes.toString("hex") + randomBase62(LENGTH - 12)
+  }
+}
diff --git a/packages/core/src/util/iife.ts b/packages/core/src/util/iife.ts
new file mode 100644
index 000000000..ca9ae6c10
--- /dev/null
+++ b/packages/core/src/util/iife.ts
@@ -0,0 +1,3 @@
+export function iife<T>(fn: () => T) {
+  return fn()
+}
diff --git a/packages/core/src/util/lazy.ts b/packages/core/src/util/lazy.ts
new file mode 100644
index 000000000..935ebe0f9
--- /dev/null
+++ b/packages/core/src/util/lazy.ts
@@ -0,0 +1,11 @@
+export function lazy<T>(fn: () => T) {
+  let value: T | undefined
+  let loaded = false
+
+  return (): T => {
+    if (loaded) return value as T
+    loaded = true
+    value = fn()
+    return value as T
+  }
+}
diff --git a/packages/core/src/util/module.ts b/packages/core/src/util/module.ts
new file mode 100644
index 000000000..6ed3b23d7
--- /dev/null
+++ b/packages/core/src/util/module.ts
@@ -0,0 +1,10 @@
+import { createRequire } from "node:module"
+import path from "node:path"
+
+export namespace Module {
+  export function resolve(id: string, dir: string) {
+    try {
+      return createRequire(path.join(dir, "package.json")).resolve(id)
+    } catch {}
+  }
+}
diff --git a/packages/core/src/util/path.ts b/packages/core/src/util/path.ts
new file mode 100644
index 000000000..b87316358
--- /dev/null
+++ b/packages/core/src/util/path.ts
@@ -0,0 +1,37 @@
+export function getFilename(path: string | undefined) {
+  if (!path) return ""
+  const trimmed = path.replace(/[/\\]+$/, "")
+  const parts = trimmed.split(/[/\\]/)
+  return parts[parts.length - 1] ?? ""
+}
+
+export function getDirectory(path: string | undefined) {
+  if (!path) return ""
+  const trimmed = path.replace(/[/\\]+$/, "")
+  const parts = trimmed.split(/[/\\]/)
+  return parts.slice(0, parts.length - 1).join("/") + "/"
+}
+
+export function getFileExtension(path: string | undefined) {
+  if (!path) return ""
+  const parts = path.split(".")
+  return parts[parts.length - 1]
+}
+
+export function getFilenameTruncated(path: string | undefined, maxLength: number = 20) {
+  const filename = getFilename(path)
+  if (filename.length <= maxLength) return filename
+  const lastDot = filename.lastIndexOf(".")
+  const ext = lastDot <= 0 ? "" : filename.slice(lastDot)
+  const available = maxLength - ext.length - 1 // -1 for ellipsis
+  if (available <= 0) return filename.slice(0, maxLength - 1) + "…"
+  return filename.slice(0, available) + "…" + ext
+}
+
+export function truncateMiddle(text: string, maxLength: number = 20) {
+  if (text.length <= maxLength) return text
+  const available = maxLength - 1 // -1 for ellipsis
+  const start = Math.ceil(available / 2)
+  const end = Math.floor(available / 2)
+  return text.slice(0, start) + "…" + text.slice(-end)
+}
diff --git a/packages/core/src/util/retry.ts b/packages/core/src/util/retry.ts
new file mode 100644
index 000000000..831d23800
--- /dev/null
+++ b/packages/core/src/util/retry.ts
@@ -0,0 +1,42 @@
+export interface RetryOptions {
+  attempts?: number
+  delay?: number
+  factor?: number
+  maxDelay?: number
+  retryIf?: (error: unknown) => boolean
+}
+
+const TRANSIENT_MESSAGES = [
+  "load failed",
+  "network connection was lost",
+  "network request failed",
+  "failed to fetch",
+  "econnreset",
+  "econnrefused",
+  "etimedout",
+  "socket hang up",
+]
+
+function isTransientError(error: unknown): boolean {
+  if (!error) return false
+  // oxlint-disable-next-line no-base-to-string -- error is unknown, intentional coercion for message matching
+  const message = String(error instanceof Error ? error.message : error).toLowerCase()
+  return TRANSIENT_MESSAGES.some((m) => message.includes(m))
+}
+
+export async function retry<T>(fn: () => Promise<T>, options: RetryOptions = {}): Promise<T> {
+  const { attempts = 3, delay = 500, factor = 2, maxDelay = 10000, retryIf = isTransientError } = options
+
+  let lastError: unknown
+  for (let attempt = 0; attempt < attempts; attempt++) {
+    try {
+      return await fn()
+    } catch (error) {
+      lastError = error
+      if (attempt === attempts - 1 || !retryIf(error)) throw error
+      const wait = Math.min(delay * Math.pow(factor, attempt), maxDelay)
+      await new Promise((resolve) => setTimeout(resolve, wait))
+    }
+  }
+  throw lastError
+}
diff --git a/packages/core/src/util/slug.ts b/packages/core/src/util/slug.ts
new file mode 100644
index 000000000..62cf0e57b
--- /dev/null
+++ b/packages/core/src/util/slug.ts
@@ -0,0 +1,74 @@
+export namespace Slug {
+  const ADJECTIVES = [
+    "brave",
+    "calm",
+    "clever",
+    "cosmic",
+    "crisp",
+    "curious",
+    "eager",
+    "gentle",
+    "glowing",
+    "happy",
+    "hidden",
+    "jolly",
+    "kind",
+    "lucky",
+    "mighty",
+    "misty",
+    "neon",
+    "nimble",
+    "playful",
+    "proud",
+    "quick",
+    "quiet",
+    "shiny",
+    "silent",
+    "stellar",
+    "sunny",
+    "swift",
+    "tidy",
+    "witty",
+  ] as const
+
+  const NOUNS = [
+    "cabin",
+    "cactus",
+    "canyon",
+    "circuit",
+    "comet",
+    "eagle",
+    "engine",
+    "falcon",
+    "forest",
+    "garden",
+    "harbor",
+    "island",
+    "knight",
+    "lagoon",
+    "meadow",
+    "moon",
+    "mountain",
+    "nebula",
+    "orchid",
+    "otter",
+    "panda",
+    "pixel",
+    "planet",
+    "river",
+    "rocket",
+    "sailor",
+    "squid",
+    "star",
+    "tiger",
+    "wizard",
+    "wolf",
+  ] as const
+
+  export function create() {
+    return [
+      ADJECTIVES[Math.floor(Math.random() * ADJECTIVES.length)],
+      NOUNS[Math.floor(Math.random() * NOUNS.length)],
+    ].join("-")
+  }
+}