[BUG] "Tried to unmount a fiber that is already unmounted" in Mastra Studio when running long operations

[DevHusariaSolutions]

Describe the Bug

Once I requested supervisor agent for long task, I jump into error from title. When i refresh site and try to open this chat - the same. Happens when running studio with NODE_ENV=production and without it. Occurs also when Mastra is deployed in debian based container

Steps To Reproduce

1. Create supervisor agent with some subagent
2. Add huge maxSteps (like 100)
3. Run some job which delegates some work to subagent
4. Wait until error is thrown

Link to Minimal Reproducible Example

https://cannot-share.com

Expected Behavior

No matter how long operations are, UI should be able to render them

Environment Information

Node runtime: Bun 1.3
System: Windows 11
Browser: Brave

Package.json:
"dependencies": {
    "@ai-sdk/anthropic": "^3.0.69",
    "@ai-sdk/openai-compatible": "^2.0.41",
    "@mastra/core": "^1.24.1",
    "@mastra/libsql": "^1.8.0",
    "@mastra/loggers": "^1.1.1",
    "@mastra/mcp": "^1.4.2",
    "@mastra/memory": "^1.15.0",
    "@mastra/pg": "^1.9.0",
    "@mastra/qdrant": "^1.0.2",
    "@types/pg": "^8.20.0",
    "pg": "^8.20.0",
    "playwright": "^1.56.0",
    "sharp": "^0.34.4",
    "zod": "^4.3.6"
  },
  "devDependencies": {
    "@playwright/mcp": "^0.0.42",
    "@types/node": "^24.5.2",
    "mastra": "^1.5.0",
    "typescript": "^6.0.2"
  }

Verification

• I have searched the existing issues to make sure this is not a duplicate
• I have included sufficient information for the team to reproduce and understand the issue

[daneatmastra]

Thank you for reporting this issue! We have labeled it for trio-tnt and we will look into it as soon as possible.

If you're experiencing an error, please provide a minimal reproducible example whenever possible to help us resolve it quickly.