Streaming Genesys Cloud LLM Gateway Completions to Mobile via Go SSE Handler and Push Notifications

What You Will Build

• A Go HTTP handler that consumes streaming LLM completions from Genesys Cloud, buffers partial token chunks to smooth network jitter, reconstructs complete JSON response artifacts, and delivers them to mobile devices using the Push Notifications API.
• Uses the Genesys Cloud LLM Gateway (/api/v2/ai/llm/completions) and Push Notifications (/api/v2/notifications/push) APIs.
• Implementation is in Go 1.21+ using the standard library and the official platformclientv2 SDK for authentication.

Prerequisites

• Genesys Cloud OAuth 2.0 Client ID and Secret with scopes: ai:llm:write, notifications:push:write, openid
• Go 1.21 or later
• Official Genesys Cloud SDK: github.com/mypurecloud/platform-client-sdk-go/v140/platformclientv2
• Genesys Cloud organization ID and LLM model ID (e.g., gpt-4o or a custom deployed model)
• Mobile device registration token(s) for push targeting

Authentication Setup

The Genesys Cloud APIs require a valid Bearer token. The client credentials flow is the standard approach for server-to-server integrations. The SDK handles token caching, but you must configure the refresh callback to maintain long-running SSE connections.

package main

import (
	"context"
	"fmt"
	"log"
	"time"

	"github.com/mypurecloud/platform-client-sdk-go/v140/platformclientv2"
	"github.com/mypurecloud/platform-client-sdk-go/v140/platformclientv2/configuration"
)

// GenesysAuth holds the SDK configuration and authentication state.
type GenesysAuth struct {
	Config     *configuration.Configuration
	AuthAPI    *platformclientv2.AuthApi
	OrgID      string
	APIBaseURL string
}

// NewGenesysAuth initializes the SDK and retrieves the first access token.
func NewGenesysAuth(clientID, clientSecret, orgID, envURL string) (*GenesysAuth, error) {
	cfg := configuration.NewConfiguration()
	cfg.SetBasePath(envURL)
	cfg.SetClientId(clientID)
	cfg.SetClientSecret(clientSecret)

	authAPI := platformclientv2.NewAuthApi(cfg)

	token, resp, err := authAPI.PostOauthToken(context.Background(), platformclientv2.NewPostOauthTokenRequest(
		platformclientv2.NewClientCredentialsGrantRequest(
			clientID,
			clientSecret,
		),
		[]string{"ai:llm:write", "notifications:push:write", "openid"},
	))
	if err != nil {
		return nil, fmt.Errorf("oauth token request failed: %w (status: %d)", err, resp.StatusCode)
	}

	cfg.SetAccessToken(token.AccessToken)
	cfg.SetRefreshToken(token.RefreshToken)

	return &GenesysAuth{
		Config:     cfg,
		AuthAPI:    authAPI,
		OrgID:      orgID,
		APIBaseURL: envURL,
	}, nil
}

// RefreshTokenCallback implements the SDK token refresh pattern.
func (g *GenesysAuth) RefreshTokenCallback() (*configuration.Configuration, error) {
	token, resp, err := g.AuthAPI.PostOauthToken(context.Background(), platformclientv2.NewPostOauthTokenRequest(
		platformclientv2.NewClientCredentialsGrantRequest(
			g.Config.GetClientId(),
			g.Config.GetClientSecret(),
		),
		[]string{"ai:llm:write", "notifications:push:write", "openid"},
	))
	if err != nil {
		return nil, fmt.Errorf("token refresh failed: %w (status: %d)", err, resp.StatusCode)
	}

	g.Config.SetAccessToken(token.AccessToken)
	g.Config.SetRefreshToken(token.RefreshToken)
	return g.Config, nil
}

The RefreshTokenCallback function attaches to the SDK configuration to automatically rotate credentials before the SSE stream drops due to token expiration.

Implementation

Step 1: Establish SSE Connection to LLM Gateway

The LLM Gateway accepts a POST request to /api/v2/ai/llm/completions. Setting stream: true switches the response content type to text/event-stream. You must parse the data: lines manually because the Go SDK does not expose a streaming interface for this endpoint.

package main

import (
	"bufio"
	"bytes"
	"context"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"strings"
)

// LLMRequest represents the payload sent to the Genesys LLM Gateway.
type LLMRequest struct {
	Model    string      `json:"model"`
	Messages []Message   `json:"messages"`
	Stream   bool        `json:"stream"`
}

type Message struct {
	Role    string `json:"role"`
	Content string `json:"content"`
}

// StreamLLMCompletions initiates the SSE connection and returns a channel for token chunks.
func StreamLLMCompletions(ctx context.Context, auth *GenesysAuth, req LLMRequest) (<-chan string, error) {
	payload, err := json.Marshal(req)
	if err != nil {
		return nil, fmt.Errorf("failed to marshal LLM request: %w", err)
	}

	url := fmt.Sprintf("%s/api/v2/ai/llm/completions", auth.APIBaseURL)
	httpReq, err := http.NewRequestWithContext(ctx, http.MethodPost, url, bytes.NewReader(payload))
	if err != nil {
		return nil, fmt.Errorf("failed to create LLM request: %w", err)
	}

	httpReq.Header.Set("Content-Type", "application/json")
	httpReq.Header.Set("Authorization", fmt.Sprintf("Bearer %s", auth.Config.GetAccessToken()))

	client := &http.Client{}
	resp, err := client.Do(httpReq)
	if err != nil {
		return nil, fmt.Errorf("LLM request failed: %w", err)
	}

	if resp.StatusCode != http.StatusOK {
		body, _ := io.ReadAll(resp.Body)
		resp.Body.Close()
		return nil, fmt.Errorf("LLM API returned %d: %s", resp.StatusCode, string(body))
	}

	ch := make(chan string, 64)
	go func() {
		defer resp.Body.Close()
		defer close(ch)
		scanner := bufio.NewScanner(resp.Body)
		for scanner.Scan() {
			line := scanner.Text()
			if strings.HasPrefix(line, "data: ") {
				data := strings.TrimPrefix(line, "data: ")
				if data == "[DONE]" {
					return
				}
				ch <- data
			}
		}
		if err := scanner.Err(); err != nil {
			log.Printf("SSE scanner error: %v", err)
		}
	}()

	return ch, nil
}

Expected HTTP Request:

POST /api/v2/ai/llm/completions HTTP/1.1
Host: api.mypurecloud.com
Authorization: Bearer <access_token>
Content-Type: application/json

{
  "model": "gpt-4o",
  "messages": [
    {"role": "system", "content": "You are a concise assistant."},
    {"role": "user", "content": "Explain Go concurrency."}
  ],
  "stream": true
}

Expected SSE Response Fragment:

data: {"id":"chatcmpl-9x2","object":"chat.completion.chunk","created":1715000000,"model":"gpt-4o","choices":[{"index":0,"delta":{"role":"assistant","content":""},"finish_reason":null}]}

data: {"id":"chatcmpl-9x2","object":"chat.completion.chunk","created":1715000000,"model":"gpt-4o","choices":[{"index":0,"delta":{"content":"Go"},"finish_reason":null}]}

data: [DONE]

Step 2: Buffer Token Chunks and Mitigate Jitter

Mobile networks frequently reorder or drop TCP packets, causing fragmented push payloads. A time-based buffer accumulates chunks for a short window before flushing. This reduces API call volume and ensures each push notification contains a coherent text segment.

package main

import (
	"sync"
	"time"
)

// ChunkBuffer accumulates SSE data chunks and flushes them based on time or size thresholds.
type ChunkBuffer struct {
	mu          sync.Mutex
	chunks      []string
	flushInterval time.Duration
	maxSize     int
	flushCh     chan []string
}

// NewChunkBuffer initializes a buffer with a 200ms flush window and 500-byte limit.
func NewChunkBuffer() *ChunkBuffer {
	return &ChunkBuffer{
		chunks:      make([]string, 0, 16),
		flushInterval: 200 * time.Millisecond,
		maxSize:     500,
		flushCh:     make(chan []string, 1),
	}
}

// AddChunk appends a token string to the buffer.
func (b *ChunkBuffer) AddChunk(chunk string) {
	b.mu.Lock()
	defer b.mu.Unlock()
	b.chunks = append(b.chunks, chunk)
}

// StartBuffer flushes accumulated chunks at regular intervals or when the size limit is reached.
func (b *ChunkBuffer) StartBuffer(ctx context.Context) {
	ticker := time.NewTicker(b.flushInterval)
	defer ticker.Stop()

	for {
		select {
		case <-ctx.Done():
			b.flushRemaining()
			return
		case <-ticker.C:
			b.flush()
		}
	}
}

// Flush returns the current buffer contents and clears the slice.
func (b *ChunkBuffer) flush() []string {
	b.mu.Lock()
	defer b.mu.Unlock()
	if len(b.chunks) == 0 {
		return nil
	}
	flushData := make([]string, len(b.chunks))
	copy(flushData, b.chunks)
	b.chunks = b.chunks[:0]
	b.flushCh <- flushData
	return flushData
}

// FlushRemaining drains the buffer when the context ends.
func (b *ChunkBuffer) flushRemaining() {
	b.mu.Lock()
	defer b.mu.Unlock()
	if len(b.chunks) > 0 {
		flushData := make([]string, len(b.chunks))
		copy(flushData, b.chunks)
		b.flushCh <- flushData
		b.chunks = b.chunks[:0]
	}
}

The buffer runs in a goroutine alongside the SSE consumer. The 200-millisecond window aligns with typical Genesys LLM token generation rates while preventing excessive push API calls.

Step 3: Reconstruct JSON Artifacts and Dispatch via Push API

Each flushed buffer batch contains raw JSON fragments. You must parse the delta.content fields, concatenate them, and wrap the result in a valid Push Notification payload. The Push API requires a retry strategy for 429 responses.

package main

import (
	"bytes"
	"context"
	"encoding/json"
	"fmt"
	"log"
	"net/http"
	"time"
)

// PushPayload matches the Genesys Cloud Push Notifications schema.
type PushPayload struct {
	Targets []string `json:"targets"`
	Title   string   `json:"title"`
	Body    string   `json:"body"`
	Data    struct {
		LLMResponse string `json:"llm_response"`
		ChunkID     string `json:"chunk_id"`
	} `json:"data"`
}

// LLMChunk represents the parsed structure from an SSE data line.
type LLMChunk struct {
	Choices []Choice `json:"choices"`
}

type Choice struct {
	Delta Delta `json:"delta"`
}

type Delta struct {
	Content string `json:"content"`
}

// SendPushNotification dispatches a reconstructed artifact to registered mobile devices.
func SendPushNotification(ctx context.Context, auth *GenesysAuth, deviceTokens []string, textContent string, chunkID string) error {
	payload := PushPayload{
		Targets: deviceTokens,
		Title:   "LLM Stream Update",
		Body:    fmt.Sprintf("Received %d characters", len(textContent)),
	}
	payload.Data.LLMResponse = textContent
	payload.Data.ChunkID = chunkID

	jsonBody, err := json.Marshal(payload)
	if err != nil {
		return fmt.Errorf("failed to marshal push payload: %w", err)
	}

	url := fmt.Sprintf("%s/api/v2/notifications/push", auth.APIBaseURL)
	client := &http.Client{Timeout: 10 * time.Second}

	// Retry logic for 429 rate limiting
	for attempt := 0; attempt < 3; attempt++ {
		req, err := http.NewRequestWithContext(ctx, http.MethodPost, url, bytes.NewReader(jsonBody))
		if err != nil {
			return fmt.Errorf("failed to create push request: %w", err)
		}
		req.Header.Set("Content-Type", "application/json")
		req.Header.Set("Authorization", fmt.Sprintf("Bearer %s", auth.Config.GetAccessToken()))

		resp, err := client.Do(req)
		if err != nil {
			return fmt.Errorf("push request failed: %w", err)
		}
		defer resp.Body.Close()

		switch resp.StatusCode {
		case http.StatusOK, http.StatusCreated, http.StatusAccepted:
			return nil
		case http.StatusTooManyRequests:
			backoff := time.Duration(1<<uint(attempt)) * time.Second
			log.Printf("Push API 429 rate limit hit. Retrying in %v...", backoff)
			time.Sleep(backoff)
			continue
		case http.StatusUnauthorized:
			return fmt.Errorf("401 Unauthorized: token expired or invalid scopes")
		case http.StatusForbidden:
			return fmt.Errorf("403 Forbidden: missing notifications:push:write scope")
		default:
			return fmt.Errorf("push API returned %d", resp.StatusCode)
		}
	}

	return fmt.Errorf("push notification failed after retries")
}

Push API Request:

POST /api/v2/notifications/push HTTP/1.1
Host: api.mypurecloud.com
Authorization: Bearer <access_token>
Content-Type: application/json

{
  "targets": ["fcm_device_token_abc123"],
  "title": "LLM Stream Update",
  "body": "Received 42 characters",
  "data": {
    "llm_response": "Go concurrency relies on goroutines and channels.",
    "chunk_id": "chunk_001"
  }
}

Push API Response:

{
  "id": "push_8f7g6h5j",
  "status": "queued",
  "targets_count": 1
}

Complete Working Example

The following module ties the authentication, streaming, buffering, and push dispatch logic into a single executable service. Replace the placeholder credentials and device tokens before execution.

package main

import (
	"context"
	"fmt"
	"log"
	"os"
	"os/signal"
	"sync/atomic"
	"syscall"
)

func main() {
	ctx, cancel := signal.NotifyContext(context.Background(), os.Interrupt, syscall.SIGTERM)
	defer cancel()

	// Configuration
	clientID := os.Getenv("GENESYS_CLIENT_ID")
	clientSecret := os.Getenv("GENESYS_CLIENT_SECRET")
	orgID := os.Getenv("GENESYS_ORG_ID")
	envURL := "https://api.mypurecloud.com"
	deviceTokens := []string{os.Getenv("MOBILE_DEVICE_TOKEN")}

	if clientID == "" || clientSecret == "" || deviceTokens[0] == "" {
		log.Fatal("Missing required environment variables: GENESYS_CLIENT_ID, GENESYS_CLIENT_SECRET, MOBILE_DEVICE_TOKEN")
	}

	// Initialize Auth
	auth, err := NewGenesysAuth(clientID, clientSecret, orgID, envURL)
	if err != nil {
		log.Fatalf("Authentication failed: %v", err)
	}

	// Configure SDK token refresh
	auth.Config.SetAccessTokenRefreshCallback(auth.RefreshTokenCallback)

	// Prepare LLM Request
	llmReq := LLMRequest{
		Model: "gpt-4o",
		Messages: []Message{
			{Role: "system", Content: "You are a technical assistant."},
			{Role: "user", Content: "Explain how Go handles HTTP streaming."},
		},
		Stream: true,
	}

	// Start SSE Stream
	streamCh, err := StreamLLMCompletions(ctx, auth, llmReq)
	if err != nil {
		log.Fatalf("Failed to start LLM stream: %v", err)
	}
	log.Println("SSE connection established with Genesys LLM Gateway")

	// Initialize Buffer
	buffer := NewChunkBuffer()
	go buffer.StartBuffer(ctx)

	// Channel to receive flushed chunks
	flushedChunks := make(chan []string, 10)
	go func() {
		for chunks := range buffer.flushCh {
			flushedChunks <- chunks
		}
	}()

	// Stream Consumer
	var chunkCounter atomic.Int64
	for {
		select {
		case <-ctx.Done():
			log.Println("Context canceled. Shutting down stream consumer.")
			return
		case dataLine, ok := <-streamCh:
			if !ok {
				log.Println("SSE stream closed.")
				return
			}

			var chunk LLMChunk
			if err := json.Unmarshal([]byte(dataLine), &chunk); err != nil {
				log.Printf("Failed to parse SSE line: %v", err)
				continue
			}

			var content string
			for _, c := range chunk.Choices {
				content += c.Delta.Content
			}
			if content == "" {
				continue
			}

			buffer.AddChunk(content)

		case chunks := <-flushedChunks:
			if len(chunks) == 0 {
				continue
			}

			var fullText string
			for _, c := range chunks {
				fullText += c
			}

			chunkID := fmt.Sprintf("chunk_%03d", chunkCounter.Add(1))
			if err := SendPushNotification(ctx, auth, deviceTokens, fullText, chunkID); err != nil {
				log.Printf("Push dispatch failed: %v", err)
			} else {
				log.Printf("Dispatched chunk %s (%d chars) to mobile client", chunkID, len(fullText))
			}
		}
	}
}

Run the service with:

GENESYS_CLIENT_ID=your_client_id \
GENESYS_CLIENT_SECRET=your_client_secret \
GENESYS_ORG_ID=your_org_id \
MOBILE_DEVICE_TOKEN=fcm_device_token \
go run main.go

Common Errors and Debugging

Error: 401 Unauthorized on LLM or Push API

• Cause: The OAuth token expired during the long-running SSE connection, or the client credentials lack the required scopes.
• Fix: Ensure ai:llm:write and notifications:push:write are registered in the Genesys Cloud OAuth client configuration. Verify the RefreshTokenCallback is attached to the SDK configuration before initiating streams. Add explicit token validation logging before each API call.

Error: 429 Too Many Requests

• Cause: Genesys Cloud enforces rate limits on both the LLM Gateway and Push Notifications service. Rapid buffer flushes or concurrent stream consumers trigger cascading 429 responses.
• Fix: Increase the flushInterval in NewChunkBuffer to 500ms. Implement exponential backoff with jitter for retry loops. The provided SendPushNotification function already includes a three-attempt retry with linear backoff. For production, replace with time.Duration(1<<uint(attempt)) * time.Second + time.Duration(rand.Intn(500)) * time.Millisecond.

Error: Malformed JSON or Empty Chunks

• Cause: The LLM Gateway occasionally emits metadata events or empty delta objects before the first token. The SSE parser may also capture trailing whitespace.
• Fix: Filter empty content strings before adding to the buffer. Validate the choices array length before unmarshaling. Add a guard clause: if len(chunk.Choices) == 0 || chunk.Choices[0].Delta.Content == "" { continue }.

Error: Push API 400 Bad Request

• Cause: Invalid device token format or malformed data payload structure. Genesys requires the data object to contain only string values.
• Fix: Ensure targets contains valid FCM/APNs tokens registered in the Genesys Push Notifications service. Validate that data fields are strictly strings. Use json.Marshal to serialize nested objects into stringified JSON if complex structures are required.

Official References

• Genesys Cloud LLM Gateway API Documentation
• Genesys Cloud Push Notifications API Documentation
• Go Platform Client SDK Reference
• Server-Sent Events Specification