Slash command arguments are stripped before submission in Cowork desktop client

Summary

In the Cowork desktop client, typing a slash command with a positional argument (e.g. /product-dev:create-spec <ticketId>) submits only the command name — the argument after the space is silently dropped before the message reaches the agent.

Reproduction

1. Open the Cowork desktop client (v1.9659.4 in my case).
2. In the prompt input, type a custom slash command with an argument:

/product-dev:create-spec abc123XYZ

1. Press Enter to submit.

Expected

The agent receives /product-dev:create-spec abc123XYZ and can read abc123XYZ as the skill's argument.

Actual

The agent receives only /product-dev:create-spec — the argument is gone. The skill then has to ask the user for the missing argument, and pasting it as plain text in a follow-up message works fine, confirming the issue is in the slash-command submission path, not the skill.

This reproduces in a fresh session and is reliable — not a one-off.

Impact

For any custom slash command that takes an argument (ticket IDs, file paths, issue numbers, etc.), there is no working in-client invocation. The only workaround is to submit the slash command, wait for the agent to ask, then paste the argument as a plain follow-up message — which defeats the point of arg-taking slash commands.

Environment

• Cowork desktop client v1.9659.4
• macOS (Darwin 23.6.0)