400 errors when using MCPs

[max-mapper]

If I set an mcp config

{
  "mcpServers": {
    "github": {
      "command": "github-mcp-server",
      "args": ["stdio"],
      "envFile": "${workspaceFolder}/.env"
    },
    "context7": {
      "command": "npx",
      "args": [
        "-y",
        "@upstash/context7-mcp",
        "--api-key",
        "${env:CONTEXT7_API_KEY}"
      ],
      "envFile": "${workspaceFolder}/.env"
    }
  }
}

Then when late sends a prompt it will include tools from those MCPs like

"name": "context7:query-docs"
"name": "github:add_comment_to_pending_review"
"name": "github:create_branch"

But that causes a generic stream error: 400 with no error message printed. Removing the MCP config fixes the error. This is from opencode's endpoint https://opencode.ai/zen/v1.

[mlhher]

Thank you for the report. We really do need a better logging system I will tackle this, I will also look into the issue itself. Note that 400 usually implies the API rejected our call due to invalid content (e.g. the model producing malformed JSON for tool calls).

Please also check the respective session file in ~/.local/share/late/session/*.json if there is e.g. any malformed JSON inside.