VS Code Extension: 'invalid beta flag' ValidationException in API calls

Issue

The Claude Code VS Code extension fails with a ValidationException when making API requests, while the CLI works fine.

Error

ValidationException: An error occurred (ValidationException) when calling the ConverseStream operation: The model returned the following errors: invalid beta flag

Details

• Affected component: VS Code extension
• Working component: Claude CLI (no issues)
• Error occurs on: Both streaming (ConverseStream) and non-streaming (Converse) API requests
• Authentication: Succeeds (OAuth token check complete)
• Root cause: Extension is sending a beta flag parameter that AWS Bedrock rejects as invalid

Environment

• Claude CLI version: 2.1.45
• VS Code version: 1.109.4 (c3a26841a84f20dfe0850d0a5a9bd01da4f003ea, x64)
• Claude Code Extension version: 2.1.45
• Platform: Windows (WSL2)
• OS: Linux 6.6.87.2-microsoft-standard-WSL2
• Issue Date: 2026-02-18

Troubleshooting Attempted

• Tried updating /C:/Users/pplenkov/AppData/Roaming/Code/User/settings.json (Windows Code settings)
• Tried updating /home/pplenkov/.vscode-server/data/Machine/settings.json (WSL Code settings)
• Tried updating ~/.claude/settings.json (Claude CLI settings)
• Extension appears to ignore all settings files

Logs

The extension logs show:

ERROR Error streaming, falling back to non-streaming mode: ... invalid beta flag
ERROR API error (attempt 1/11): 400 ... invalid beta flag

The error originates from the extension code making the API call with an unsupported/outdated beta flag parameter.

Notes

• Claude CLI works without this error
• Suggests extension code/config is outdated or misconfigured
• Settings appear to have no effect on extension behavior