[BUG] Claude Code corrupted FlutterFlow project via deprecated proto field in MCP integration — server-level damage, project completely frozen

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

Environment

• Claude Code Version: 2.1.145
• Platform: FlutterFlow MCP integration (FlutterFlow AI DSL CLI)
• Integration: FlutterFlow-Anthropic official MCP partnership (announced May 5, 2026)
• FlutterFlow Project ID: keekot-836qfa

Summary
Claude Code used a deprecated proto field (customWidgetName, field 16) instead of the modern
customWidgetIdentifier (field 28) when attempting to insert a custom widget (ViewportVideoCell)
into my FlutterFlow project. This corrupted my CapsulePage at the server database level.

This diagnosis came from Claude Code itself — during debugging sessions, Claude Code
identified that it had used an unsupported raw proto mutation that bypassed FlutterFlow's
dimension validator, causing server-level corruption that cannot be repaired from the DSL side.

Timeline

• May 5, 2026: Received official FlutterFlow email announcing FlutterFlow-Anthropic MCP partnership
• May 12–24, 2026: Claude Code made 17+ pushes via FlutterFlow AI DSL CLI
• During ViewportVideoCell widget insertion: deprecated proto field used, project corrupted
• 18+ subsequent repair attempts by Claude Code made situation progressively worse

Current state of project

• CapsulePage: // Error generating code, please contact support@flutterflow.io
• Browser test mode: "Build Failed — Error loading project for test mode"
• Download Code: "Code Download Failed — Unknown error"
• iPhone testing: impossible
• Project completely frozen for 12+ days

Specific nodes affected

• Card: Card_enpv49au
• Stack: Stack_0yc6jiy3
• GridView: GridView_vgu2u9sd

What I have done

• Reported to FlutterFlow support (support@flutterflow.io) with full timeline — they confirmed

the FlutterFlow MCP workflow is officially supported and are investigating

• Reported to Anthropic support (support@anthropic.com) — received automated AI bot response only
• Manually deleted/recreated ON_TAP action in FlutterFlow editor — error persists at server level

Impact
Solo non-technical founder. Startup completely on hold. 12+ days of lost development.
I used this integration because it was officially promoted by both FlutterFlow and Anthropic.

Request

1. Engineering review of how Claude Code handles FlutterFlow DSL proto fields
2. Coordination with FlutterFlow to assist with server-level recovery
3. Safety guardrails to prevent raw proto mutations on external platform integrations

Contact: keren@keekot.com
Support ticket reference: [add your Anthropic ticket number if you have one]

What Should Happen?

Claude Code should never use deprecated or unsupported proto fields when
pushing changes to external platforms via MCP integrations. When using the
FlutterFlow AI DSL CLI, Claude Code should only use supported, current API
fields (e.g., customWidgetIdentifier, field 28) and should never attempt to
bypass platform validators using deprecated fields (e.g., customWidgetName,
field 16). If an operation cannot be completed safely within supported API
boundaries, Claude Code should stop and inform the user rather than
attempting raw proto mutations that can corrupt the target platform's
server-side database.

Error Messages/Logs

CapsulePage: // Error generating code, please contact support@flutterflow.io
FlutterFlow browser test mode: Build Failed — Error loading project for test mode
Download Code: Code Download Failed — Unknown error

Affected node keys:
- Card: Card_enpv49au
- Stack: Stack_0yc6jiy3  
- GridView: GridView_vgu2u9sd

Root cause identified by Claude Code itself during debugging:
Deprecated proto field customWidgetName (field 16) was used instead of 
customWidgetIdentifier (field 28) when inserting ViewportVideoCell custom 
widget, bypassing FlutterFlow's dimension validator and causing server-level 
corruption that cannot be repaired from the DSL side.

Steps to Reproduce

1. Receive official FlutterFlow email announcing FlutterFlow-Anthropic MCP

partnership (May 5, 2026)

1. Connect Claude Code to FlutterFlow project via FlutterFlow AI DSL CLI

(FlutterFlow Project ID: keekot-836qfa)

1. Ask Claude Code to add a custom widget (ViewportVideoCell) for

viewport-aware video playback to CapsulePage

1. Claude Code attempts to insert the widget node using deprecated proto

field customWidgetName (field 16) instead of the supported
customWidgetIdentifier (field 28)

1. The push bypasses FlutterFlow's dimension validator
2. CapsulePage becomes permanently broken at server database level
3. All subsequent repair attempts (18+ DSL pushes by Claude Code) fail —

corruption cannot be fixed from the DSL side

Claude Model

None

Is this a regression?

No, this never worked

Last Working Version

_No response_

Claude Code Version

2.1.145

Platform

Other

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

Context for Anthropic engineering team:

I am a solo non-technical founder. I used this integration because it was
officially promoted to me via a FlutterFlow email announcing the
FlutterFlow-Anthropic MCP partnership (May 5, 2026).

FlutterFlow has confirmed:

• The FlutterFlow MCP workflow is officially supported
• They are investigating the server-level corruption
• The damage cannot be repaired from the DSL side

Anthropic support status:

• Email sent to support@anthropic.com — received automated AI bot response only
• No human contact from Anthropic to date

This issue represents a safety gap: Claude Code is able to make destructive,
irreversible changes to external platforms via MCP integrations without any
guardrails, particularly dangerous for non-technical users who cannot
evaluate whether a proposed DSL push is safe.

My startup (Keekot) has been completely frozen for 7+ days.
Contact: keren@keekot.com