ADK Stream Protocol

AI SDK v6 and Google ADK integration demonstrating SSE and WebSocket streaming implementation.

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⚠️ Development Status

This project is under active development and contains experimental features with known issues.

Current Status

✅ Stable Features

• Gemini Direct mode (AI SDK v6 only)
• ADK SSE streaming with tool calling
• ADK BIDI Blocking Mode for tool approval (ADR-0009, ADR-0011)
• ADK Mode History Sharing (chat history preserved across ADK SSE ↔ BIDI transitions)
• Complete E2E test infrastructure (Frontend, Backend, Playwright)

🚧 Experimental Features

• ADK BIDI (WebSocket) native tool confirmation - See known issues below

Known Issues

Critical: ADK BIDI Mode Limitations

BIDI mode (run_live()) has two significant issues:

1. Tool Confirmation Not Working (Native ADK) 🟡

   • ADK's native require_confirmation=True does not trigger approval UI in live mode
   • Root cause: ADK FunctionTool._call_live() TODO - "tool confirmation not yet supported for live mode"
   • Status: Known ADK limitation, awaiting upstream fix
   • Workaround: Use BIDI Blocking Mode (ADR-0009, ADR-0011) or SSE mode for tools requiring confirmation

2. Missing Text Responses After Tool Execution 🟡

   • Tools execute successfully but AI generates no explanatory text
   • Only raw JSON output shown to user
   • Status: Under investigation
   • Workaround: Use SSE mode for full tool support

Recent Fixes

• ✅ ADK Mode History Sharing - chat history preserved across ADK SSE ↔ BIDI transitions (2026-01-18)
• ✅ BIDI Confirmation ID routing bug fixed (2025-12-19)
• ✅ Fixed infinite loop in tool confirmation auto-send logic (2025-12-17)

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🎯 Project Overview

This project demonstrates the integration between:

• Frontend: Next.js 16 with AI SDK v6 beta
• Backend: Google ADK with FastAPI

Three Streaming Modes

1. Gemini Direct - Direct Gemini API via AI SDK (stable)
2. ADK SSE - ADK backend with Server-Sent Events (stable)
3. ADK BIDI ⚡ - ADK backend with WebSocket bidirectional streaming (stable for Blocking Mode, experimental for native confirmation)

Key Insight: All three modes use the same AI SDK v6 Data Stream Protocol format, ensuring consistent frontend behavior regardless of backend implementation.

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✨ Key Features

Streaming Modes

• Gemini Direct: Built-in AI SDK v6 streaming support
• ADK SSE: Token-by-token streaming via Server-Sent Events
• ADK BIDI: Bidirectional WebSocket streaming for voice agents

Multimodal Capabilities

• Text I/O: Token-by-token streaming with AI SDK v6
• Image Input/Output: PNG, JPEG, WebP via data-image custom events
• Audio Input: Microphone recording (16kHz PCM) with CMD key push-to-talk
• Audio Output: PCM streaming (24kHz) with WAV playback
• Audio Transcription: Input and output speech-to-text with native-audio models
• Tool Calling: ADK integration with user approval flow (SSE mode)

Architecture Highlights

• StreamProtocolConverter: Converts ADK events to AI SDK v6 Data Stream Protocol
• SSE format over WebSocket: Backend sends SSE format via WebSocket for BIDI mode
• Frontend Transparency: Same useChat hook works across all three modes
• Custom Transport: WebSocketChatTransport for AI SDK v6 WebSocket support
• Tool Approval Flow: Frontend-delegated execution with AI SDK v6 approval APIs

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🛠️ Tech Stack

Frontend:

• Next.js 16 (App Router)
• React 19
• AI SDK v6 beta (ai, @ai-sdk/react, @ai-sdk/google)
• TypeScript 5.7

Backend:

• Python 3.13
• Google ADK >=1.20.0
• FastAPI >=0.115.0
• Pydantic v2

Development Tools:

• bun (Node.js packages)
• uv (Python packages)
• just (task automation)

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🚀 Quick Start

Prerequisites

• Python 3.13+
• Node.js 18+
• bun, uv, just

Installation

# Install all dependencies
just install

# Or manually:
uv sync
bun install

Environment Setup

Copy the example file:

cp .env.example .env.local

Edit .env.local:

For Gemini Direct:

GOOGLE_GENERATIVE_AI_API_KEY=your_api_key_here
BACKEND_MODE=gemini
NEXT_PUBLIC_BACKEND_MODE=gemini

For ADK SSE/BIDI:

GOOGLE_API_KEY=your_api_key_here
BACKEND_MODE=adk-sse
NEXT_PUBLIC_BACKEND_MODE=adk-sse
ADK_BACKEND_URL=http://localhost:8000
NEXT_PUBLIC_ADK_BACKEND_URL=http://localhost:8000

Running

Gemini Direct (frontend only):

bun dev

ADK SSE/BIDI (backend + frontend):

# Run both concurrently:
just dev

# Or separately:
just server  # Backend on :8000
bun dev     # Frontend on :3000

For all available commands:

just --list

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🧪 Testing

Python Backend Tests:

just test-python
# Expected: ~200 passed (unit + integration + e2e)

TypeScript Frontend Tests:

bun test:lib
# Expected: ~565 passed (unit + integration + e2e)

Playwright E2E Tests:

just test-e2e-clean  # Recommended: clean server restart
just test-e2e-ui     # Interactive UI mode

Code Quality:

just format  # Format code
just lint    # Run linters
just check   # Run type checks

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📚 Documentation

Complete documentation is available in the docs/ directory:

Quick Start

• Getting Started Guide - Detailed setup, usage, troubleshooting, AI SDK v6 migration
• Glossary - Key terms, concepts, and patterns

Architecture & Specs

• Architecture Overview - Complete system architecture

  • AudioWorklet PCM Streaming
  • Tool Approval Flow (Frontend Delegation Pattern)
  • Per-Connection State Management
  • Multimodal Support Architecture

• Protocol Implementation - ADK ↔ AI SDK v6 protocol

  • Event/Part field mapping
  • Implementation status
  • Custom extensions (data-pcm, data-image, etc.)

Backend (Python)

• Result Type Pattern - Ok(value) / Error(value) error handling

Frontend (TypeScript)

• Library Structure - lib/ organization and module dependencies
• React Optimization - Memoization and performance patterns
• Vitest Tests - lib/tests/ structure (unit, integration, e2e)

Testing

• Testing Strategy - Overall test architecture (pytest, Vitest, Playwright)
• E2E Testing Guide - Complete E2E testing documentation
  • Backend E2E (pytest golden files)
  • Frontend E2E (Vitest browser tests)
  • Fixtures management
  • Chunk Logger debugging
• Coverage Audit - Test coverage verification

Architecture Decision Records

• ADR-0001 - Per-Connection State Management
• ADR-0002 - Tool Approval Architecture
• ADR-0003 - SSE vs BIDI Confirmation Protocol
• ADR-0004 - Multi-Tool Response Timing
• ADR-0005 - Frontend Execute Pattern and [DONE] Timing
• ADR-0006 - sendAutomaticallyWhen Decision Logic Order
• ADR-0007 - Approval Value Independence
• ADR-0008 - SSE Mode Pattern A Only
• ADR-0009 - BIDI Blocking Mode
• ADR-0010 - BIDI Confirmation Chunk Generation
• ADR-0011 - BIDI Approval Deadlock Fix (finish-step Injection)

Additional Resources

• Experiments - Research notes, protocol investigations, multimodal experiments

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🔬 Experiments & Research

All experiment notes and architectural investigations are documented in experiments/:

• Bidirectional protocol investigations
• Multimodal support (images, audio, video)
• Tool approval flow implementations
• Test coverage investigations
• ADK field mapping completeness

See experiments/README.md for the complete experiment index and results.

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📄 License

MIT License. See LICENSE file for details.

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🔗 References

• AI SDK Documentation
• Google ADK Documentation
• BGM

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Last Updated: 2026-01-18