Web Shell Custom Slash Command Actions

Problem

Web Shell handles built-in slash commands locally and forwards other slash commands to the daemon. Embedders cannot observe a command before that default behavior or replace it with an application-specific action.

Design

Add an optional onSlashCommand prop. It runs before hidden-command, built-in-command, daemon-connection, and daemon-forwarding behavior in both the main composer and split-view composers. It receives:

• command: the slash command name, normalized to lower case;
• args: the trimmed text after the command name;
• input: the original submitted text.

Returning true marks the command as handled and skips Web Shell's default behavior. Returning false or nothing lets the existing command pipeline continue unchanged. The callback is synchronous so composer acceptance keeps the existing synchronous submit contract; embedders may start asynchronous work inside the callback. Callback errors are reported through Web Shell's existing error path before default handling continues.

Only a leading slash followed by a word-or-hyphen command name and then whitespace or the end of the input is recognized. This keeps absolute paths such as /usr/local/bin/tool out of the host callback.

Compatibility

The prop is optional, so existing embedders and all current command behavior remain unchanged. The callback also observes unknown commands, allowing an embedder to implement a command without daemon support.

Test Plan

• Verify an unknown slash command invokes the callback with parsed fields and still reaches the daemon when the callback does not handle it.
• Verify returning true prevents the command from reaching the daemon.
• Verify returning true prevents a built-in command's local behavior.
• Verify main and split-view callbacks can handle commands while disconnected.
• Verify callback errors are reported before default handling continues.
• Verify absolute paths do not invoke the callback.