If you’re using OpenRouter , you can send traces to Fallom automatically using OpenRouter’s Broadcast feature. No SDK installation required.
Broadcast provides observability only . For Model A/B Testing and Prompt
Management, use the Fallom SDK . What You Get Feature Broadcast SDK Trace logging ✅ ✅ Token tracking ✅ ✅ Cost tracking ✅ ✅ Session grouping ✅ ✅ Customer tracking ✅ ✅ Model A/B Testing ❌ ✅ Prompt Management ❌ ✅ Prompt A/B Testing ❌ ✅
Setup (5 minutes) 1. Get Your Fallom API Key Go to app.fallom.com/settings and copy your API key.
Go to OpenRouter Broadcast Settings
Click Add destination
Select OTel Collector
Enter:
Endpoint: https://broadcast.fallom.com/v1/traces
Headers: { "Authorization" : "Bearer YOUR_FALLOM_API_KEY" }
Click Save
That’s it! All your OpenRouter requests will now appear in Fallom.
You can also set broadcast headers on each request instead of configuring in OpenRouter’s dashboard:
import OpenAI from "openai" ; const openrouter = new OpenAI ({ apiKey: process . env . OPENROUTER_API_KEY , baseURL: "https://openrouter.ai/api/v1" , defaultHeaders: { "X-Broadcast-URL" : "https://broadcast.fallom.com/v1/traces" , "X-Broadcast-Auth" : "Bearer YOUR_FALLOM_API_KEY" , }, }); const response = await openrouter . chat . completions . create ({ model: "openai/gpt-4o-mini" , messages: [{ role: "user" , content: "Hello!" }], // @ts-ignore - OpenRouter-specific fields session_id: "conversation-123" , user: "customer-456" , });
This approach is useful for testing or when you want different API keys per environment.
Adding Session & User Tracking Include session_id and user in your OpenRouter request body :
Fetch
OpenAI SDK
Vercel AI SDK
Python
const response = await fetch ( "https://openrouter.ai/api/v1/chat/completions" , { method: "POST" , headers: { Authorization: `Bearer ${ OPENROUTER_API_KEY } ` , "Content-Type" : "application/json" , }, body: JSON . stringify ({ model: "openai/gpt-4o-mini" , messages: [{ role: "user" , content: "Hello!" }], // These get included in your Fallom traces session_id: "conversation-123" , // Groups related requests user: "customer-456" , // Identifies end users }), });
import OpenAI from "openai" ; const client = new OpenAI ({ baseURL: "https://openrouter.ai/api/v1" , apiKey: process . env . OPENROUTER_API_KEY , }); const response = await client . chat . completions . create ({ model: "openai/gpt-4o-mini" , messages: [{ role: "user" , content: "Hello!" }], // @ts-ignore - OpenRouter-specific fields session_id: "conversation-123" , user: "customer-456" , });
Vercel AI SDK doesn’t pass custom body fields to OpenRouter. For session tracking
with Vercel AI SDK + Broadcast, use the Fallom SDK wrapper
or the OpenAI SDK tab below. // Recommended: Use Fallom SDK session wrapper for Vercel AI SDK import fallom from "@fallom/trace" ; import * as ai from "ai" ; import { createOpenAI } from "@ai-sdk/openai" ; await fallom . init ({ apiKey: "your-fallom-api-key" }); const session = fallom . session ({ configKey: "my-app" , sessionId: "conversation-123" , customerId: "customer-456" , }); const { generateText } = session . wrapAISDK ( ai ); const openrouter = createOpenAI ({ baseURL: "https://openrouter.ai/api/v1" , apiKey: process . env . OPENROUTER_API_KEY , }); const { text } = await generateText ({ model: openrouter ( "openai/gpt-4o-mini" ), prompt: "Hello!" , });
from openai import OpenAI client = OpenAI( base_url = "https://openrouter.ai/api/v1" , api_key = "your-openrouter-key" ) response = client.chat.completions.create( model = "openai/gpt-4o-mini" , messages = [{ "role" : "user" , "content" : "Hello!" }], extra_body = { "session_id" : "conversation-123" , "user" : "customer-456" } )
Available Fields Field Description Fallom Mapping session_idGroups related requests (conversations, agent runs) session_iduserIdentifies end users (up to 128 chars) customer_id
These fields must be in the request body , not headers. OpenRouter only
broadcasts body fields to OTEL destinations.
Structured Output (JSON Mode) with Broadcast For structured output with broadcast, use the OpenAI SDK with response_format:
import OpenAI from "openai" ; const openrouter = new OpenAI ({ apiKey: process . env . OPENROUTER_API_KEY , baseURL: "https://openrouter.ai/api/v1" , defaultHeaders: { "X-Broadcast-URL" : "https://broadcast.fallom.com/v1/traces" , "X-Broadcast-Auth" : "Bearer YOUR_FALLOM_API_KEY" , }, }); const response = await openrouter . chat . completions . create ({ model: "openai/gpt-4o-mini" , messages: [ { role: "system" , content: "Output JSON only. Format: {name: string, price: number, description: string}" , }, { role: "user" , content: "Generate a tech gadget." }, ], response_format: { type: "json_object" }, // @ts-ignore - OpenRouter extensions session_id: "conversation-123" , user: "customer-456" , }); const product = JSON . parse ( response . choices [ 0 ]. message . content ! ); console . log ( product ); // { name: "...", price: 99.99, description: "..." }
For Vercel AI SDK’s generateObject/streamObject with session tracking, use
the Fallom SDK wrapper instead of
broadcast. The SDK wrapper provides full tracing with fallom.session(). What Gets Traced Every OpenRouter request automatically includes:
Field Description Model Full model path (e.g., openai/gpt-4o) Provider Which provider served the request Duration Request latency Tokens Input, output, cached tokens Cost OpenRouter’s cost calculation Prompts Input messages Completions Model response Session Your session_id (if provided) Customer Your user ID (if provided)
Troubleshooting Traces not appearing
Verify Broadcast is enabled in OpenRouter settings
Check the endpoint is exactly https://broadcast.fallom.com/v1/traces
Confirm your API key starts with flm_
Check the Authorization header format: Bearer YOUR_API_KEY (with a space)
401 Unauthorized Your API key is invalid or the header format is wrong:
{ "Authorization" : "Bearer flm_xxxxx" }
Missing session or customer data Include session_id and user in the request body , not as headers.
Next Steps
OpenRouter SDK Use SDK for A/B testing and prompts.
View Dashboard See your traces.
