On May 1, 2026, Google briefly published a 1.13 GB app to the Play Store under the package name com.google.research.air.cosmo. It was pulled within hours — but not before the AI community had downloaded it, dissected it, and shared what they found. The result is one of the most detailed accidental previews of a major AI product we’ve seen.
This is COSMO: Google’s next-generation on-device AI assistant. Here’s how its architecture actually works.
What COSMO Is
COSMO is not a simple chatbot widget. It’s a full agent runtime built around Gemini Nano, capable of operating both entirely on-device and in hybrid modes that reach out to Google’s servers. The name stands for nothing publicly stated, but the leaked app reveals a system designed to be persistently running, proactively useful, and deeply integrated into the Android OS.
The browser automation component, Mariner, comes directly from Google DeepMind — the same Mariner browser agent that was previously announced as a research project. Its appearance inside COSMO confirms that DeepMind’s agentic browser capabilities are being productized for consumer devices.
The Three Operational Modes
This is the core architectural insight from the COSMO leak. The app exposes three distinct modes of operation:
Mode 1: On-Device (Local Only)
In this mode, all inference runs on-device using Gemini Nano. No network request is made to Google’s servers for model computation. The device’s NPU handles the full stack.
What it enables:
- Fully private processing — nothing leaves your phone
- Works without an internet connection
- Faster response times for simple tasks
- Battery-efficient for light workloads
What it can’t do:
- Complex multi-step reasoning that exceeds Nano’s context window
- Mariner browser automation (requires server-side support)
- Real-time information retrieval
Best for: Screen reading, quick lookups, photo recall, short document drafting
Mode 2: PI Server (Cloud-Backed)
In this mode, COSMO routes inference to what the app calls the “PI server” — Google’s cloud infrastructure running full Gemini models. The device acts as a thin client.
What it enables:
- Access to full Gemini model capabilities
- Complex reasoning and long-context tasks
- Mariner browser agent execution at scale
- Real-time web data integration
Tradeoff: Requires connectivity; data leaves the device
Best for: Deep research, complex document generation, multi-site web browsing tasks
Mode 3: Hybrid
This is where COSMO gets genuinely interesting. In hybrid mode, COSMO dynamically routes between on-device and server processing depending on the task, available connectivity, and privacy settings.
The architecture appears to use the on-device Gemini Nano as an orchestration layer — it decides which subtasks can be handled locally and which require server-side resources. Think of Nano as a local task router that knows when to call home.
What it enables:
- Best-of-both-worlds capability: privacy for simple tasks, power for complex ones
- Graceful degradation when offline
- Adaptive behavior based on network quality
Best for: Everyday use where you want optimal performance without sacrificing privacy on everything
The 14 Proactive Skills
The leaked app manifests 14 agent skills that COSMO can invoke autonomously:
- Deep Research — multi-step web queries via Mariner
- Document Drafting — generates documents from context
- Calendar Automation — reads and modifies calendar entries
- Photo Recall — retrieves photos based on conversational context
- Email Summarization — processes inbox with AccessibilityService
- Contact Lookup — surfaces contacts from conversation context
- Package Tracking — monitors shipping updates
- Meeting Prep — aggregates context for upcoming calendar events
- Travel Planning — multi-source itinerary building
- News Briefing — curates news based on user interests
- Shopping Assist — price comparison via browser automation
- App Control — executes in-app actions via AccessibilityService
- Reminder Creation — context-aware reminder setting
- Screen Summary — describes and summarizes current on-screen content
Note: These names are inferred from the decompiled app. Google has not officially confirmed skill names.
AccessibilityService: The Permission That Makes It Work
COSMO uses Android’s AccessibilityService API to read screen content and control apps. This is the same mechanism used by accessibility software for the visually impaired — and the same one that powerful automation apps use.
This matters because AccessibilityService is a high-privilege API. For COSMO to do what it promises — draft emails, control apps, read your screen mid-conversation — it needs this permission. Users will be explicitly prompted to grant it.
Why This Matters for Mobile Agentic AI
COSMO represents a design philosophy that’s different from “AI in an app.” Rather than waiting to be invoked, COSMO is designed to be an ambient agent — always running, observing context, ready to act. The three-mode architecture solves one of the hardest problems in mobile AI: how do you give users powerful cloud AI capabilities while preserving privacy and not burning battery?
The answer Google is proposing: make the on-device model smart enough to be the orchestration layer. Let Nano decide what Nano can handle. Escalate to the cloud only when necessary.
With Google I/O 2026 coming up in a few weeks, this leak gives us our clearest picture yet of what Google’s agentic roadmap looks like. COSMO may be announced officially there — and now you know how it works before it does.
Sources
- Nokia Power User — Google Just Accidentally Leaked Its Most Powerful On-Device AI Yet: Meet COSMO
- 9to5Google — Independent confirmation of COSMO leak
- Android Police — App package name
com.google.research.air.cosmoconfirmed - Android Authority — COSMO feature breakdown
- Google DeepMind — Prior Mariner browser agent announcement
Researched by Searcher → Analyzed by Analyst → Written by Writer Agent (Sonnet 4.6). Full pipeline log: subagentic-20260502-2000
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