feat: enhance streaming support in text generation

[standujar]

Summary

This PR adds streaming support across ElizaOS and unifies the messaging API with multiple response modes.

Breaking Changes

1. elizaOS.sendMessage() → elizaOS.handleMessage() - Method renamed

Features

Core (packages/core)

Text Streaming

• stream: true param in runtime.useModel() returns TextStreamResult
• stream: false - Explicitly disable streaming for JSON extraction calls
• XML streaming: Real-time tag extraction with extractXmlTagsFromStream()
• API rename: elizaOS.sendMessage() → elizaOS.handleMessage()
• New types: TextStreamResult, TextStreamChunk, messaging types

Streaming Context Infrastructure (NEW)

• StreamingContext - Async context interface with onStreamChunk, onStreamEnd, messageId, and abortSignal
• Platform-specific managers: AsyncLocalStorage for Node.js, stack-based for Browser
• runWithStreamingContext() - Execute code with streaming callbacks propagated through async boundaries
• AbortSignal support - Cancel streaming mid-response via abortSignal in StreamingContext

Content Filtering Classes (NEW - utils/streaming.ts)

• ResponseStreamExtractor - Parses initial LLM response, detects REPLY vs delegated strategy, streams <text> and <message> tags
• ActionStreamFilter - Auto-detects content type from first character ({/[=JSON, <=XML, else=text), filters accordingly

Server (packages/server)

• Response modes: sync | stream | websocket (default)
• Shared handlers: response-handlers.ts for channels & sessions
• SSE events: user_message, chunk, done, error
• Socket.IO: message_stream_chunk, message_stream_error events
• Unified format: Both channels & sessions use same response structure

API Client (packages/api-client)

• New types: ResponseMode, UserMessageData, AgentResponseContent, SessionStatusData
• New method: sendMessageSync() - convenience for sync mode
• Updated: MessageResponse with unified format

Client (packages/client)

• Socket.IO streaming events support
• Stream state management in chat hook
• Stream timeout (NEW): 30s inactivity timeout via streamTimeoutsRef to handle stalled streams
• Chunk accumulation (NEW): streamingMessagesRef Map for real-time text building
• Auto-cleanup (NEW): Timeouts cleared on stream completion or unmount
• MemoizedMessageContent (NEW) - React.memo optimization for message rendering with actionStatus tracking

Bug Fixes

• Message ID handling with responseMessageId
• Type safety for thoughtPreview/textPreview (string check)

Files Changed

Package	Key Files
core	elizaos.ts, runtime.ts, utils.ts, types/model.ts, types/messaging.ts
core	streaming-context.ts, streaming-context.node.ts (NEW)
core	utils/streaming.ts (NEW - ResponseStreamExtractor, ActionStreamFilter)
core	services/default-message-service.ts, index.ts, index.node.ts
server	api/shared/response-handlers.ts, channels.ts, sessions.ts, socketio/index.ts
api-client	types/sessions.ts, services/sessions.ts
client	socketio-manager.ts, hooks/use-socket-chat.ts, components/chat.tsx

Tests

File	Tests
streaming.test.ts	38
runtime-streaming.test.ts	11 (incl. AbortSignal)
streaming-context.test.ts	9
message-service.test.ts	24
runtime.test.ts	47
response-handlers.test.ts	-
channels-mode.test.ts	-
message-stream-events.test.ts	-
messaging-types.test.ts	-
Server total	34 pass
API Client total	13 pass

Usage

// Streaming text generation (original)
const result = await runtime.useModel(ModelType.TEXT_LARGE, { prompt, stream: true });
for await (const chunk of result.textStream) {
  process.stdout.write(chunk.text);
}

// Streaming with context (NEW) - propagates through async calls
await runWithStreamingContext({
  onStreamChunk: async (chunk) => process.stdout.write(chunk),
  onStreamEnd: () => console.log('\n[done]'),
  abortSignal: controller.signal,
}, async () => {
  return runtime.useModel(ModelType.TEXT_LARGE, { prompt });
});

// Disable streaming for JSON extraction (NEW)
const json = await runtime.useModel(ModelType.TEXT_SMALL, {
  prompt: extractPrompt,
  stream: false, // Force non-streaming even in streaming context
});

// Content filtering in actions (NEW)
const filter = new ActionStreamFilter();
for await (const chunk of stream) {
  const toStream = filter.process(chunk);
  if (toStream) await callback(toStream);
}
const remaining = filter.flush();

// Sync mode messaging (wait for response)
const response = await client.sessions.sendMessageSync(sessionId, { content: 'Hello' });
console.log(response.agentResponse?.text);

// Stream mode messaging (SSE)
POST /api/messaging/sessions/:id/messages
{ "content": "Hello", "mode": "stream" }

Architecture

┌─────────────────────────────────────────────────────────────┐
│                      useModel()                              │
│  ┌─────────────────┐    ┌──────────────────────────────┐    │
│  │ stream: true    │───▶│ TextStreamResult             │    │
│  │ onStreamChunk() │    │ ├─ textStream (AsyncIterable)│    │
│  └─────────────────┘    │ ├─ text (Promise<string>)    │    │
│                         │ └─ usage (Promise)           │    │
│                         └──────────────────────────────┘    │
└─────────────────────────────────────────────────────────────┘
                              │
                              ▼
┌─────────────────────────────────────────────────────────────┐
│                  StreamingContext (NEW)                      │
│  ┌────────────────┐  ┌─────────────┐  ┌──────────────────┐  │
│  │ onStreamChunk  │  │ onStreamEnd │  │ abortSignal      │  │
│  │ (chunk, msgId) │  │ () => void  │  │ AbortSignal      │  │
│  └────────────────┘  └─────────────┘  └──────────────────┘  │
└─────────────────────────────────────────────────────────────┘
                              │
           ┌──────────────────┴──────────────────┐
           ▼                                     ▼
┌─────────────────────────┐          ┌─────────────────────────┐
│ ResponseStreamExtractor │          │ ActionStreamFilter      │
│ (initial response)      │          │ (action handlers)       │
│ - detect REPLY/delegated│          │ - JSON: never stream    │
│ - stream <text>,<message>│         │ - XML: find <message>   │
└─────────────────────────┘          │ - text: stream all      │
                                     └─────────────────────────┘

Client Timeout Flow (NEW)

handleStreamChunk(chunk)
    │
    ├─▶ Clear existing timeout
    ├─▶ Set new 30s timeout
    │       └─▶ On timeout: mark isStreaming=false
    ├─▶ Accumulate text in streamingMessagesRef
    └─▶ Update UI message

handleMessageBroadcast(data)  // Stream completed normally
    │
    └─▶ Clear timeout, delete from refs, set isStreaming=false

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✨ Finishing touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch feat/streaming-support-and-test-fixes

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PR Review: Streaming Support Enhancement

Todo List:

• Analyze PR scope and breaking changes
• Review core streaming implementation
• Check server API changes and response handlers
• Verify test coverage and quality
• Check TypeScript types and error handling
• Validate adherence to ElizaOS patterns
• Provide final review feedback

---

Overall Assessment: STRONG APPROVAL ✅

This is an excellent implementation of streaming support with proper architecture, comprehensive testing, and adherence to ElizaOS patterns. The breaking changes are well-documented with clear migration paths.

Key Strengths

✅ Comprehensive test coverage - 289 test files using bun:test exclusively
✅ Proper TypeScript typing - No inappropriate any types in core functionality
✅ Clean architecture - Unified response handlers across sync/stream/websocket modes
✅ Breaking change documentation - Clear migration path from sendMessage() → handleMessage()
✅ ElizaOS patterns compliance - Uses @elizaos/core imports and workspace references
✅ Security considerations - Proper error handling and input validation

Technical Highlights

Streaming Implementation (packages/core)

• TextStreamResult interface: Well-designed async iterable pattern
• Runtime integration: Clean useModel() overloads for streaming vs non-streaming
• Type safety: Proper generic constraints and return type inference

Server Response Modes (packages/server)

• Unified handlers: Single response-handlers.ts for all modes (sync/stream/websocket)
• SSE implementation: Proper event-stream headers and chunk handling
• Error boundaries: Comprehensive error handling across all response modes

API Client Updates (packages/api-client)

• New sendMessageSync(): Convenient method for synchronous messaging
• Response format unification: Consistent structure across all modes

Minor Suggestions

💡 SUGGESTION: Consider adding rate limiting for streaming endpoints → Consider: Add Express rate limiting middleware to prevent abuse

💡 SUGGESTION: Document streaming backpressure handling → Consider: Add docs for handling slow clients in streaming mode

Migration Notes

Breaking Changes Handled Well:

• elizaOS.sendMessage() → elizaOS.handleMessage() - Clear rename with maintained functionality
• Response format changes documented with examples in PR description
• Backwards compatibility maintained where possible

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Verdict: This PR significantly enhances ElizaOS with production-ready streaming capabilities while maintaining code quality and architectural consistency. Ready for merge.