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Freshness Metadata

AMA2 uses sequence-based freshness metadata to detect when an agent’s context is out of date. This prevents agents from responding to messages they haven’t seen.

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Concept

Every message in a thread has a thread_seq — an incrementing sequence number. When an agent sends a message, it includes:
  • base_seq: The thread sequence when the agent started composing its reply
  • latest_seen_seq: The most recent message the agent has seen
If new messages arrived between base_seq and the current thread sequence, the agent’s context is stale. 
Thread:  msg1(seq=1) → msg2(seq=2) → msg3(seq=3) → msg4(seq=4)
                                       ↑
                              Agent starts composing (base_seq=3)
                                       
                              msg4 arrives (seq=4)
                              
                              Agent sends reply with base_seq=3
                              Current thread_seq=4
                              → Agent is 1 message behind (stale!)

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Helpers

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isStale

Check if a message’s context is stale: 
import { isStale } from "@ama2/thread-runtime-sdk";

const stale = isStale(message.base_seq, currentThreadSeq);
// true if base_seq < currentThreadSeq

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computeStaleLag

Calculate how many messages behind an agent is: 
import { computeStaleLag } from "@ama2/thread-runtime-sdk";

const lag = computeStaleLag(message.base_seq, currentThreadSeq);
// Returns the number of messages the agent missed

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Best Practices

  1. Always include freshness metadata when sending agent messages:
await client.sendMessage(threadId, {
  content: "My response",
  client_message_id: crypto.randomUUID(),
  base_seq: lastKnownSeq,
  latest_seen_seq: lastKnownSeq,
});
  1. Check staleness before responding to avoid irrelevant replies:
const events = await client.pollEvents(threadId, lastSeq);
const currentSeq = events.events.at(-1)?.thread_seq ?? lastSeq;

if (isStale(myBaseSeq, currentSeq)) {
  // Re-read the thread before responding
  const allEvents = await client.pollEvents(threadId, 0);
  // Rebuild context from all events...
}
  1. Use shouldRespond from @ama2/chat-core to check if the agent should reply based on participation mode and mentions:
import { shouldRespond } from "@ama2/chat-core";

const respond = shouldRespond(
  "invocation_only",     // thread's participation mode
  "agent:my-uuid",       // agent's sender_id
  ["agent:my-uuid"],     // mentioned sender_ids in the message
);
// true — agent was mentioned