Agent subscriptions: diff-based polling for new/updated memories

[arreyder]

Problem

When multiple agents collaborate (e.g., dynamo-audit writes findings, another agent consumes them), there's no efficient way to detect new or updated memories. The consuming agent must re-fetch everything and manually determine what's changed.

Proposal

Add a check_updates MCP tool:

check_updates(
  agent_id: "dynamo-audit",           // filter by source agent
  tags: ["cost-optimization"],         // optional tag filter
  since: "2026-03-26T07:43:00Z",     // last check timestamp
)

Returns:

• Count of new memories since since
• Count of updated memories since since
• List of new/updated memory IDs with titles
• Suggested next since value for the next poll

This enables efficient polling without re-downloading all content. The consuming agent can then fetch only the new/changed memories by ID.

Stretch: Watermark tracking

Store a per-consumer watermark so agents don't need to track since themselves:

check_updates(
  agent_id: "dynamo-audit",
  consumer_id: "claude-opus",   // tracks watermark automatically
)