Beta testers of macOS 27 Golden Gate have discovered a hidden “lightweight UI” for Siri AI that automatically surfaces AI Writing Tools and contextual actions when text is highlighted. The feature is disabled by default in developer beta 3 and public beta 1, but it can be activated using a specific command-line feature flag found by a member of the r/MacOSBeta Reddit community.
Functionality of the Siri AI Popover
The hidden interface manifests as a floating icon at the top-left of selected text, which expands into a compact popover when the pointer hovers over it. This system replaces the standard method of using Writing Tools, which typically requires selecting text, right-clicking, and navigating a context menu. According to Mashable SEA, the pop-up menu provides an array of AI tools, including:
- Rewrite and Proofread
- “How does this sound?”
- “Edit with Siri”
- Summarization and the creation of key points or bullet points
Beyond general writing assistance, the popover offers contextual actions based on the specific content selected. For example, highlighting a phone number allows the user to add the contact, while selecting an address provides an “Open in Maps” option. Other available contextual tools include tracking flights or packages, creating calendar events, and composing emails or messages.
How to Enable and Disable the Feature
The feature can be toggled via the Terminal application (located in Applications > Utilities > Terminal). To enable the popover, users must paste the following command and then restart their Mac: sudo mkdir -p /Library/Preferences/FeatureFlags/Domain && sudo defaults write /Library/Preferences/FeatureFlags/Domain/WritingTools LightweightUI_macOS -dict Enabled -bool true
To disable the interface and return to default settings, users can input this command and restart the device: sudo defaults write /Library/Preferences/FeatureFlags/Domain/WritingTools LightweightUI_macOS -dict Enabled -bool false
Current Limitations and System Requirements
The interface is described as an unfinished product. MacRumors reports that some actions within the popover do not respond, and the overall behavior of the UI remains inconsistent. Current limitations include a lack of integration with third-party apps—such as Slack, Notion, or Google Docs in Safari—and the absence of tone controls for the Rewrite tool, which currently only provides one generic rewrite. Additionally, there is no way to ask Siri follow-up questions directly from the popover or generate new text from scratch.
Regarding hardware and connectivity, the Writing Tools’ proofreading and rewriting functions can run locally on any Apple Silicon Mac. However, more complex queries are routed to the cloud via Apple’s Private Cloud Compute. The feature is not compatible with Intel Macs. This popover is distinct from a previous Terminal workaround used in developer beta 2 to skip the Siri AI waitlist, which Apple patched in late June.
Broader AI Integration in macOS 27
The popover is part of a wider trend of embedded AI in macOS 27. Memeburn notes that a developer recently found a hidden command-line LLM tool located at /usr/bin/fm. This tool, powered by Apple Foundation Models, runs entirely on-device without requiring an internet connection. These developments align with the WWDC 2026 keynote, which emphasized Siri AI functioning across the entire operating system.
Worth a look