[BUG] `/context` is silently sent as a chat message (not executed) in Claude Code on the web — `/usage` works fine

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

Summary

In Claude Code on the web, typing /context in the chat box no longer runs the command — it is sent to the model as a plain user message and no context-usage panel is rendered. Other slash commands in the same web session (/usage, /model) still work correctly. This started ~2026-06-12 ~15:24 UTC; earlier in the same session /context worked.

Environment

• Client: Claude Code on the web (cloud / remote execution environment)
• CLI version: 2.1.177 (/opt/claude-code/bin/claude)
• Model: Opus 4.8

Steps to reproduce

1. Open a Claude Code web session.
2. Type /context in the chat box and send.
3. Observe: no panel renders; the model receives the literal text /context.
4. In the same session, type /usage → panel renders correctly.

Expected

/context is intercepted by the client and renders the context-usage panel locally (as it does in the terminal, and as it did at the start of this same web session).

Actual

/context is not intercepted. It is delivered to the model as a normal chat message and the assistant just replies in text. No panel, no command output.

Evidence

• /usage works in the same session (panel below), proving the web client does execute some slash commands — so this is specific to /context (and possibly other terminal-only commands), not a general "web can't run commands" issue.

<img width="2000" height="1110" alt="Image" src="https://github.com/user-attachments/assets/3c9f4419-0200-4768-9173-f34638e2c037" />

• Session-transcript evidence (same session):
• Before ~2026-06-12 15:24 UTC: /context messages are wrapped as a command and immediately followed by command stdout (the rendered panel). No Message sent at … prefix.
• After that point: every /context arrives as a plain user message prefixed with ``, with no command wrapper and no command output — i.e. it was never intercepted as a command.
• /model and /usage sent after that point still execute normally (no Message sent at prefix; proper command output).

Notes

This looks like a per-client missing/unrouted slash-command problem, similar to #8569 (VS Code extension missing /help, /doctor, etc.) — here the affected client is the web UI and the affected command is /context.

What Should Happen?

/context should be intercepted by the web client and render the context-usage panel locally — exactly like /usage does, and like /context itself did earlier in the same session. It should NOT be forwarded to the model as a plain chat message.

Error Messages/Logs

Steps to Reproduce

1. Open a Claude Code web session (claude.ai/code).
2. Type /context in the chat box and send.
3. Observe: no context panel renders; the model receives the literal text /context and just replies in prose.
4. In the same session, type /usage → its panel renders correctly (proving the web client does execute some slash commands).

Claude Model

Opus

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

2.1.177 (Claude Code)

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Other

Additional Information

_No response_