Plugin slash commands fail in Desktop app with "Failed to send command" — work fine in TUI

[rkkautsar]

Description

Slash commands registered by plugins via the command.execute.before hook fail in opencode Desktop with the error:

Failed to send command — request failed

The same commands work correctly in the TUI.

Reproduction

1. Install the opencode-pty plugin
2. Open opencode Desktop
3. Run /pty-open-background-spy or /pty-show-server-url
4. Result: Toast error "Failed to send command — request failed"
5. Run the same commands in TUI → works correctly

Analysis

The plugin registers commands via command.execute.before hook in the plugin SDK. In TUI mode, commands are dispatched via direct HTTP to the server, and the hook fires successfully. In Desktop mode, commands go through the Tauri IPC bridge → sidecar process → HTTP, and appear to fail before the server-side hook is ever reached.

Evidence that the hook never fires:

• /pty-show-server-url calls client.session.prompt() before throwing — if the hook executed, the URL would appear in chat. It doesn't.
• Both commands fail with the same generic error, suggesting the failure is in the command dispatch layer, not the plugin handler.

The error originates from the catch block in packages/app/src/components/prompt-input/submit.ts (prompt.toast.commandSendFailed.title).

Expected Behavior

Plugin-registered slash commands should work identically in Desktop and TUI modes.

Environment

• opencode Desktop (latest)
• Plugin: opencode-pty
• OS: macOS

[github-actions]

This issue might be a duplicate of existing issues. Please check:

• Desktop shows plugin sentinel errors, TUI does not #13922: Desktop shows plugin sentinel errors, TUI does not — both issues describe plugin slash commands via command.execute.before failing in Desktop but working in TUI, with the same Desktop vs TUI behavioral disparity.