Stale generated files in app/.well-known/workflow break streaming after code changes

[snarktank]

Bug Description

Generated route files in app/.well-known/workflow/ become stale after workflow code changes, causing streams to never reach the client even though workflows complete successfully.

Reproduction Steps

1. Create a workflow using DurableAgent with getWritable<UIMessageChunk>()
2. Run the workflow successfully (streaming works)
3. Make any code change to the workflow file
4. Hot reload triggers, workflow bundles rebuild
5. Send a new message - workflow completes but stream never delivers to client

Observed Behavior

• Workflow step completes in ~1-2 seconds (verified via npx workflow inspect step)
• API POST hangs for 30+ seconds until timeout
• ResponseAborted errors in console
• No stream data reaches the client

Expected Behavior

Stream should deliver to client after code changes without manual intervention.

Workaround

Delete generated files before each dev server start:

"dev": "rm -rf app/.well-known && next dev --turbopack"

Environment

• workflow: 4.0.1-beta.19
• @workflow/ai: 4.0.1-beta.19
• ai: 5.0.104
• Next.js 15 with Turbopack
• macOS