@ai-sdk/workflow breaks workflow bundling on Nitro/Nuxt: Dynamic require of "ajv/dist/core.js" is not supported

Description

Importing @ai-sdk/workflow anywhere in a project that uses workflow/nitro (via workflow/nuxt) breaks the workflow steps bundle for every workflow in the project — including workflows that have nothing to do with @ai-sdk/workflow.

The root cause is a transitive dependency: @ai-sdk/workflow depends on ajv (confirmed via pnpm why ajv). ajv is CommonJS and uses a non-statically-analyzable require() internally to load ajv/dist/core.js. When workflow/nitro's esbuild step bundles the workflow steps as ESM, it can't resolve this dynamic require(), and generates a shim that throws at runtime instead of failing at build time.

Because the steps bundle (.nuxt/workflow/steps.mjs) is built from every file in the project containing a 'use workflow'/'use step' directive — not scoped to files that are actually reachable/used — a single unrelated file importing @ai-sdk/workflow (even an unused prototype file sitting outside server/) poisons the shared bundle for all workflows.

Environment

• @ai-sdk/workflow: 1.0.31
• workflow / @workflow/core: 4.6.0
• Nuxt: 4.5.0
• Nitro: 2.13.4
• Vite: 8.1.5
• Node: v24.18.0
• Package manager: pnpm
• ajv: 8.20.0 (pulled in transitively by @ai-sdk/workflow)

Steps to Reproduce

1. Create a Nuxt project with workflow/nuxt configured (modules: ["workflow/nuxt"]).

2. Create a minimal workflow that does not use @ai-sdk/workflow at all:

   // server/workflows/echo-test.ts
   export async function echoTest(items: string[]) {
     'use workflow'
     return { received: items, count: items.length }
   }
   

   // server/api/echo-test.post.ts
   import { start } from 'workflow/api'
   import { echoTest } from '../workflow/echo-test'
   
   export default defineEventHandler(async (event) => {
     const body = await readBody(event)
     const run = await start(echoTest, [body.items ?? ['a', 'b', 'c']])
     return await run.returnValue
   })
   

3. Confirm this works fine on its own — curl -X POST http://localhost:3000/api/echo-test -d '{"items":["x","y","z"]}' returns {"received":["x","y","z"],"count":3}.

4. Anywhere else in the project (any file, any directory — doesn't need to be imported/used by anything), add a file with 'use workflow' that imports @ai-sdk/workflow:

   import { WorkflowAgent } from '@ai-sdk/workflow'
   
   export async function chat(messages: any[]) {
     'use workflow'
     // ...
   }
   

5. Restart the dev server (rm -rf .nuxt .output && pnpm dev to rule out cache).

6. Repeat the curl from step 3 against echo-test again.

Expected Behavior

The echoTest workflow should keep working exactly as before — it has no relationship to @ai-sdk/workflow or ajv.

Actual Behavior

The request to echo-test fails with:

ERROR [request error] [unhandled] [POST] http://localhost:3000/.well-known/workflow/v1/flow
Error: Dynamic require of "../../node_modules/.pnpm/ajv@8.20.0/node_modules/ajv/dist/core.js" is not supported
  at (.nuxt/workflow/steps.mjs:15:9)
  at node_modules/.pnpm/ajv@8.20.0/node_modules/ajv/dist/ajv.js (.nuxt/workflow/steps.mjs:49:18)
  at __require2 (.nuxt/workflow/steps.mjs:19:52)
  ...
ERROR [world-local] Queue message failed (attempt 1, HTTP 500) { queueName: '__wkf_workflow_workflow//./server/workflows/echo-test//echoTest', ... }

Removing the @ai-sdk/workflow import (and the package itself, confirmed via pnpm remove @ai-sdk/workflow + full node_modules reinstall) makes the error disappear completely and echo-test returns clean output again. Workflow count in the build log also drops (e.g. from 3 workflows to 2 workflows), confirming the unrelated file was being scanned and bundled in.

Additional Notes

• This reproduced consistently across multiple dev server restarts with .nuxt/.output cleared, so it is not a hot-reload/timing issue.
• This may be related to the broader class of CJS/ESM interop bugs already tracked in this repo:
  • #140 — bundler fails to resolve Node.js built-ins (stream, http, etc.), treating them as browser externals
  • #258 — ERR_REQUIRE_ESM with @workflow/world-postgres on Next.js App Router
• Two separate concerns worth splitting if useful:
  1. ajv's dynamic require() isn't handled correctly by the esbuild step-bundling pass (likely needs ajv marked external, or the step bundler needs a CJS-compatible require shim for cases like this).
  2. The step/workflow bundler appears to scan the whole project (or at least beyond the configured serverDir) for 'use workflow'/'use step' directives, rather than only files actually reachable from used entry points — meaning dead/unused files can silently poison the shared bundle for unrelated workflows.

Minimal Reproduction

Happy to share a minimal repo if useful — the repro above is ~15 lines of code across 3 files.

Start by reproducing with workflow/nuxt using server/workflows/echo-test.ts and server/api/echo-test.post.ts, then inspect the generated .nuxt/workflow/steps.mjs and the workflow/nitro bundling path. Compare builds with and without the @ai-sdk/workflow import and determine whether the fix belongs in handling ajv's dynamic require or in scanning unrelated workflow files. Done means echo-test works despite the unrelated import.