Flow Observe on Flow Messaging: no code

If your agent already talks to people through Flow Messaging, you write no code for Observe. The Flow team connects Observe to your app, and from then on Observe reads your app’s message.received and message.sent events, stores each conversation, and grades every reply your agent sends.

Early access: the Flow team connects Observe to your app by hand. Observe reads your app with a key of the same mode, so a test key shows test conversations (sandbox and simulated contacts). Live conversations need your account enabled for production.

What you do

Make a test key just for Observe in the Flow Messaging dashboard’s Keys page, so you can revoke it alone.
Sign in to Observe and add your agent: choose Flow Messaging and paste that key. Paste it only into the Observe page, never into a chat with an AI assistant. If Observe isn’t on for you yet, write to the Flow team at samyak@flow.engineer or prabal@flow.engineer.
Talk to your agent (the sandbox from your phone, or simulated contacts from a script). Each conversation appears in the Observe dashboard within seconds, and each reply gets its verdict shortly after.

Observe reads your app’s whole event log from the start, so conversations from before you connected it appear too.

Optional: see the inside of each turn

Conversations and grades need nothing more. To also see what your agent did between the person’s message and its reply (model calls, tools, errors, retries, timings), send your agent’s OpenTelemetry traces to Observe and tag each turn with the Flow ids of the message it answers:

Attribute	Value
`flow.conversation_id`	`event.conversation.id` (`conv_...`) of the `message.received` event you are answering
`flow.message_id`	`event.data.message.id` (`msg_...`). For a turn that answers several messages at once, the last one
`flow.agent_version`	Optional: your agent’s version (prompt, model, tools), such as `2026-10-12.1`

Set them on any span of the turn’s trace. Observe then links the trace to the conversation and shows its steps under the reply. Do not set flow.user_message or flow.agent_reply here: Observe already has the messages from Flow Messaging. Set up the exporter as on Send traces from any agent, with your trace key (otk_test_... for a test app), then wrap each turn in a span:

import { trace } from "@opentelemetry/api";
import { FlowMessaging, contentText } from "@flow-engineer/messaging";
import { runAgent } from "./agent"; // your agent: returns a string or an LLM stream

const flow = new FlowMessaging();
const tracer = trace.getTracer("my-agent");

for await (const event of flow.events.stream({ types: ["message.received"] })) {
  await tracer.startActiveSpan("agent.turn", async (span) => {
    span.setAttribute("flow.conversation_id", event.conversation.id);
    span.setAttribute("flow.message_id", event.data.message.id);
    try {
      const input = contentText(event.data.message.content);
      await event.conversation.reply(await runAgent(input), { idempotencyKey: event.id });
    } finally {
      span.end();
    }
  });
}

from opentelemetry import trace

tracer = trace.get_tracer("my-agent")

async def answer(event: dict):
    message = event["data"]["message"]
    with tracer.start_as_current_span("agent.turn") as span:
        span.set_attribute("flow.conversation_id", event["conversation"]["id"])
        span.set_attribute("flow.message_id", message["id"])
        reply = await run_agent(message["content"].get("text", ""))  # your agent
        send_reply(event, reply)  # POST /v1/conversations/{conversation_id}/messages

Spans your framework makes inside agent.turn (model and tool calls) join the same trace. If your framework starts its own traces instead, see Traces from agent frameworks.

Only Flow’s ids are accepted here: a value that is not a conv_... or msg_... id is ignored, and the trace is kept but not linked to a conversation.
A trace often arrives before Observe has read the message from your event log. It is linked a few seconds later, when the message arrives.
You do not need reply_to for Observe: it pairs each reply with the message before it. (reply_to shows your reply as an inline quote of the person’s message on channels that support quotes; use it only if you want that look.)

What Flow Messaging adds

Because Flow Messaging carries the messages, Observe sees exactly what was delivered and sent, after bubble splitting and fallbacks, with no reporting code that can drift from what your agent really did. And you can test with simulated contacts on Telegram, WhatsApp, iMessage or SMS: their conversations are graded like any other test conversation.

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Flow Observe on Flow Messaging: no code

What you do

Optional: see the inside of each turn

What Flow Messaging adds

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Optional: see the inside of each turn

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