Insiders Feedback: Carl Laliberté #3435

Version: Insiders

Feature: MCP Apps write deferral (issue_write, create_pull_request, update_pull_request)

Feedback:
mcp_apps_disable_form_deferral is a mask, not the fix. It stops handing write calls to forms while keeping result views. The default path still drops parameters and blocks writes when a host advertises io.modelcontextprotocol/ui.

Observed:

• Claude (claude.ai / Desktop), issue Insiders Feedback: MCP Apps: issue_write form widget collapses immediately in Claude clients — parameters never hydrate, submit impossible #2823, still open: issue_write with owner/repo/title/body or issue_number flashes a blank create form, collapses, parameters never hydrate, submit unreachable. The deferral text is shown as an error. 4/4, payload-independent. get_me still renders.
• Same class as Skip MCP Apps UI form when issue_write update includes a state change #2163: the form cannot represent state, so the update was swallowed until a special-case bypass.
• Add explicit show_ui parameter to UI-enabled write tools #2601 show_ui defaults true and is stripped for non-UI clients. An opt-out does not hydrate the form.
• Grok iOS renders get_me. Footer is plain text, not an action.

Required behavior, one tool, two transports:

1. Call parameters are the form's initial state. Dropping them is a bug.
2. No UI capability, automated host, or show_ui=false: execute directly with the same parameters.
3. UI host: hydrate, then submit. If hydration fails, return an explicit error. Never a success with no write, never a silent wait.
4. Result views stay available after the write. Do not require mcp_apps_disable_form_deferral for that.
5. Read-only must not register write-form resources (MCP App UI resources for write tools are registered in --read-only mode #2519).

Hosts that must pass the same case: VS Code, Claude, Grok, headless. Parameters in = parameters written, or a hard error.