Visible context window usage indicator in Cowork[FEATURE]

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

Cowork (the desktop agent mode built on Claude Code) gives no visibility into context window usage during a session. There is no token count, no percentage-full indicator, and no /context-equivalent command. When the window fills, the conversation is silently compacted — older messages are replaced with a summary — with no warning beforehand. In long-running, multi-day projects (I maintain a persistent CLAUDE.md file in a working folder and return to it across many sessions), this makes it impossible to judge when to wrap up a session, checkpoint progress, or start a fresh chat before compaction happens on its own. Claude Code's CLI already solves this with /context and a visible token count — Cowork has no equivalent, even though it's built on the same underlying engine.

Proposed Solution

Add a small, persistent usage indicator in the Cowork chat UI — for example a percentage or a simple bar under the chat input ("~70% of context used") — so users can see how full the window is in real time. Ideally also expose a slash command or menu action equivalent to Claude Code's /context that shows a fuller breakdown (system prompt, tool definitions, conversation history, etc.). When compaction is about to trigger, a brief in-UI notice ("approaching context limit, summarizing older messages") would also help, since right now it happens invisibly.

Alternative Solutions

Currently I work around this by maintaining a CLAUDE.md file in my project folder as a manual checkpoint system (status block updated at the end of each session: what's done, what's next, open decisions), and starting new chats periodically to avoid hitting the limit unexpectedly. This works but requires guessing when compaction is close, since there's no signal. Using Claude Code CLI directly instead of Cowork is the other workaround, since it does show token/context usage — but that means giving up Cowork's file-tools/skills/task-list features.

Priority

Medium - Would be very helpful

Feature Category

CLI commands and flags

Use Case Example

1. I run a long-term family curriculum project inside a Cowork session, working from a folder of Word/Excel files with a CLAUDE.md project-context file.
2. Sessions run long — many tool calls, file reads/writes, back-and-forth on content.
3. With a visible usage indicator, I could see "80% full" and proactively update my checkpoint file and start a new chat on my own terms.
4. Without it, compaction happens with no warning, and I only learn it happened after the fact when a new session opens with "continuing from a previous conversation" and a summary — by which point I've lost the ability to decide what to preserve.

Additional Context

This request specifically concerns Cowork mode (the desktop agent/file-tools experience), not just the Claude Code CLI — Cowork doesn't currently expose a category for itself in this template, hence "Other." A related closed issue (#38605) requested the same thing for Cowork/claude.ai specifically; reopening the concept here since compaction/visibility still isn't solved there even though Claude Code CLI already has /context.