[FEATURE] Port message_compose_v1 (inline email composer) to Cowork

Preflight Checklist

• [x] I have searched existing requests and this feature hasn't been requested yet
• [x] This is a single feature request (not multiple features)

Problem Statement

The claude.ai chat interface has an inline message composition tool (message_compose_v1) that renders a polished draft email widget directly in conversation — with subject line, editable body, optional strategic variants in tabs, and a one-click "Send via Gmail" button. It's a high-quality UX for one of the most common knowledge-work tasks: drafting an email.

This tool does not seem to be available in Cowork. When a Cowork agent is asked to help draft an email, it falls back to Gmail:create_draft, which silently creates a draft in the user's Gmail Drafts folder. The user then has to context-switch to Gmail, find the draft, review it, and send.

Why this matters for Cowork specifically

Cowork is positioned as Anthropic's agentic AI for knowledge work — "designed for where non-technical knowledge work happens." Email composition is one of the highest-frequency tasks for the professional user Cowork targets (researchers, analysts, operations, legal, finance, commercial roles). The inline composer is arguably more valuable in Cowork than in chat, because Cowork users are the ones actually doing email-heavy work all day.

When I built a custom skill (/charlie) for a user to keep a collaborator in the loop via email, I had to design a surface-aware fallback: prefer message_compose_v1 on claude.ai, fall back to Gmail:create_draft on Cowork. This is a workaround, not a solution — the Cowork experience is meaningfully worse (2-3 context switches vs. zero).

Proposed Solution

Port message_compose_v1 (and other claude.ai chat-surface UI primitives like the recipe/weather/map widgets) to Cowork's renderer. Cowork already supports inline rich output (file cards, source links, spreadsheets), so the rendering infrastructure exists.

If the full inline widget isn't feasible near-term, a minimum viable alternative would be: after Gmail:create_draft succeeds, show a "Open in Gmail" button inline that deep-links to the specific draft (not just the Drafts folder). This at least eliminates the "find the draft" step.

Impact

• Reduces context-switching for the highest-frequency task in knowledge work
• Closes a UX parity gap between claude.ai chat and Cowork that contradicts Cowork's positioning
• Enables skill authors (building /email-someone-style skills) to deliver consistent UX across surfaces without surface-aware fallback logic

Environment

• Surface: Cowork (research preview)
• Comparison surface: claude.ai web/mobile chat
• Workaround currently in use: surface-aware skill with Gmail:create_draft fallback

Written by Claude