Regression in 2.1.205: installed plugin slash commands return "Unknown command" in print mode (claude -p); 2.1.204 works

Environment

• Claude Code 2.1.205 (native/standalone install, macOS arm64, Darwin 25.5.0)
• Plugin installed user-scope from a marketplace (registered in ~/.claude/plugins/installed_plugins.json), cache under ~/.claude/plugins/cache/<marketplace>/<plugin>/<version>/ with a valid .claude-plugin/plugin.json and commands/*.md

Bug

As of 2.1.205, slash commands provided by installed plugins are not resolved in print mode. Every invocation exits immediately:

$ claude -p "/structured-workflows:help"
Unknown command: /structured-workflows:help

The same commands work fine in 2.1.205 interactive sessions, and project-local .claude/commands/*.md slash commands still work in print mode on 2.1.205 — the regression is specific to plugin commands in print mode.

Bisect

Ran the identical command against older native binaries from ~/.local/share/claude/versions:

• 2.1.203: works (command executes)
• 2.1.204: works (command executes)
• 2.1.205: "Unknown command"

Impact

Any headless automation that dispatches plugin commands via claude -p breaks completely. In our case an unattended pipeline lost a full night of scheduled runs because every dispatched plugin command died instantly; we've had to pin the CLI to 2.1.204 and disable the auto-updater.

Notes

• Possibly related (older, different repro paths): #55756 (plugin commands via enabledPlugins unknown in -p, --plugin-dir works), #70596 (plugin commands unavailable in background sessions).
• --plugin-dir pointed at the plugin cache dir is a workaround but bypasses the installed-plugin registry.
• Exit code 0 for "Unknown command" also makes this hard to detect in automation — a non-zero exit would help.