Mastra won't build due to "ZodOptional" is not exported by ".mastra/.build/zod.mjs"

λ bun run build
$ mastra build
INFO [2025-11-19 22:44:14.986 +0800] (Mastra CLI): Analyzing dependencies...
INFO [2025-11-19 22:44:17.741 +0800] (Mastra CLI): Optimizing dependencies...
INFO [2025-11-19 22:44:43.171 +0800] (Mastra CLI): Bundling Mastra application
ERROR [2025-11-19 22:44:47.216 +0800] (Mastra CLI): Failed during bundler bundle stage: node_modules/@mastra/schema-compat/dist/index.js (2:12): "ZodOptional" is not exported by ".mastra/.build/zod.mjs", imported by "node_modules/@mastra/schema-compat/dist/index.js".
    domain: "DEPLOYER"
    category: "SYSTEM"
    details: {}
error: script "build" exited with code 1

{
  "name": "redacted",
  "private": true,
  "type": "module",
  "scripts": {
    "build": "mastra build",
    "check": "biome check",
    "dev": "mastra dev",
    "start": "mastra start"
  },
  "dependencies": {
    "@ai-sdk/openai": "^2.0.68",
    "@aws-sdk/client-s3": "^3.934.0",
    "@aws-sdk/s3-request-presigner": "^3.934.0",
    "@mastra/ai-sdk": "^0.2.7",
    "@mastra/core": "^0.24.1",
    "@mastra/libsql": "^0.16.2",
    "@mastra/loggers": "^0.10.19",
    "@mastra/memory": "^0.15.11",
    "@mastra/pg": "^0.17.8",
    "@mastra/pinecone": "^0.11.16",
    "@mastra/rag": "^1.3.4",
    "@t3-oss/env-core": "^0.13.8",
    "dedent": "^1.7.0",
    "docx": "^9.5.1",
    "exceljs": "^4.4.0",
    "pdf-lib": "^1.17.1",
    "pptxgenjs": "^4.0.1",
    "zod": "^4.1.12"
  },
  "devDependencies": {
    "@biomejs/biome": "^2.3.6",
    "@types/bun": "^1.3.2",
    "mastra": "^0.18.1",
    "typescript": "^5.9.3"
  },
  "packageManager": "[email protected]"
}