Gemini Model Layer

Last updated: May 2026

This directory contains the core business logic, data models, tab helpers, browser agents, and backend service bridges for the Gemini (BWG) feature integration on Chrome for iOS.

Due to the comprehensive integration of Gemini, the components are categorized into distinct logical subsystems:

---

Subsystems & Core Components

1. Core State & Scope Management

• gemini_browser_agent.h & gemini_browser_agent.mm: A browser-scoped agent (BrowserUserData) managing the presentation of the Gemini UI overlay ("floaty"). It monitors scroll and keyboard events to temporarily hide/show the overlay, handles user preferences, and constructs the active session configuration.
• gemini_tab_helper.h & gemini_tab_helper.mm: A tab-scoped agent (web::WebStateObserver & web::WebStateUserData) that governs the Gemini context for a single tab. It monitors navigation, page loading, title settings, and favicon changes, coordinates with PageContextWrapper to package page data, and implements the zero-state suggestion chips pipeline.
• gemini_page_context.h & gemini_page_context.mm: An Objective-C data container wrapping C++ move-only optimization_guide::proto::PageContext objects. Implements custom getters with "consume-on-read" semantics, moving ownership of the proto context exactly once to the consumer.
• gemini_configuration.h & gemini_configuration.mm: A configuration class encapsulating settings (client ID, server ID, animations, suggestions, image attachments) required to initialize or resume a Gemini overlay session.
• gemini_startup_configuration.h & gemini_startup_configuration.mm: Data model representing entry-point configurations used during startup flows.

2. Session Management

• gemini_session_handler.h & gemini_session_handler.mm: Bridges callbacks from the Gemini UI SDK (GeminiSessionDelegate) into actual Chrome systems, mapping unique client IDs back to active WebStates, updating background session storage, and logging telemetry.
• gemini_session_delegate.h: Declares callback hooks for session creations, prompts, responses, feedback, cancel reasons, and settings taps.
• gemini_view_state_delegate.h: Internal delegate protocol transmitting view state updates.

3. Task Actuation (AI-Agent Automation)

• gemini_actuation_handler.h & gemini_actuation_handler.mm: Implements the GeminiActuationDelegate protocol, bridging between the Gemini UI and the C++ actor::ActorService.
• Capabilities:
  • Creates automated browser automation tasks.
  • Executes serialized action Protos (e.g., clicking, typing, navigating).
  • Captures page inner-text and screenshot context across multiple controlled tabs asynchronously via base::BarrierCallback.

4. Smart Suggestions & zero-state Chips

• gemini_suggestion_handler.h & gemini_suggestion_handler.mm: Implements the GeminiSuggestionDelegate protocol to fetch Zero-State suggestion chips (e.g. "Summarize", "Ask about page") via the active GeminiTabHelper pipeline.

5. Camera & Link Management

• gemini_camera_handler.h & gemini_camera_handler.mm: Implements the GeminiCameraDelegate protocol. Coordinates system camera permissions and presents UIImagePickerController to take pictures for attachment within Gemini.
• gemini_link_opening_handler.h & gemini_link_opening_handler.mm: Implements BWGLinkOpeningDelegate, using the UrlLoadingBrowserAgent to load hyperlinks clicked inside the Gemini UI in new, same, or background tabs.

6. Page & View State Handlers

• gemini_page_state_change_handler.h & gemini_page_state_change_handler.mm: Monitors page changes and coordinates user preferences/consents (such as page content sharing) with the active profile. Presents prompt alerts if consent needs to be granted.
• gemini_view_state_change_handler.h & gemini_view_state_change_handler.mm: Target handler listening to overlay view state transitions (e.g., expanded, collapsed).

7. Services & Factories

• gemini_service.h & gemini_service_impl.h / gemini_service_impl.mm: Profile-scoped service managing profile-level Gemini eligibility checks (workspace policies, capabilities).
• gemini_service_factory.h & gemini_service_factory.mm: Standard profile service factory defining lifecycle and dependency injection rules for the service.
• fake_gemini_service.h & fake_gemini_service.mm: A test double service providing mock capabilities for unit and integration testing.

8. Observers & Utilities

• bwg_snapshot_utils.h & bwg_snapshot_utils.mm: Utility capturing cropped screenshots (omitting status bars and omniboxes) of active tabs to pass as image attachments to Gemini.
• gemini_scroll_observer.h & gemini_scroll_observer.mm: Scroll observer forwarding scroll coordinates and events.
• gemini_tab_helper_observer.h: Observation protocol notifying of tab-specific context changes.

---

Test Suites

All components in this folder are covered by specialized unit test suites in the main ios_chrome_unittests target:

• gemini_browser_agent_unittest.mm
• gemini_tab_helper_unittest.mm
• gemini_page_context_unittest.mm
• gemini_session_handler_unittest.mm
• gemini_actuation_handler_unittest.mm
• gemini_camera_handler_unittest.mm
• gemini_link_opening_handler_unittest.mm
• gemini_page_state_change_handler_unittest.mm
• gemini_suggestion_handler_unittest.mm
• gemini_view_state_change_handler_unittest.mm
• gemini_configuration_unittest.mm
• gemini_service_factory_unittest.mm
• gemini_service_impl_unittest.mm
• bwg_snapshot_utils_unittest.mm