October 21, 2026

Mastra releases published October 21, 2026. This automated release-watch entry was generated from the project's official GitHub release feed and is kept separate from human-reviewed editorial analysis. Release notes: Highlights MCP Events (poll/stream/webhooks + Studio inspection) Experimental MCP Events (SEP-3415 draft) let MCP servers publish event streams that clients can poll, keep a stream open for, or receive via signed webhooks. Core/server/client add inspection APIs so Studio can list event types, stream occurrences, and test-emit events under mastra dev . Observability Upgrades: Span Aggregation + “Time to First Chunk” + Richer Trace/Span Querying New aggregateSpans() storage contract enables per-span analytics (e.g., p95 latency per tool, token/cost per agent) via the span-aggregate feature. Observability queries gain timeToFirstChunkMs fields, filtering, and sorting, plus expanded trace-scope fields (root entityId , root name , root spanType ) and richer querySpans() context/parent/root-entity filters (with updated store capabilities to detect support). Agent Controller Sessions Move to…

• Review the official Mastra releases release notes before upgrading.
• Check compatibility, migration, and security notes against your current agent stack.
• Run focused regression tests before production rollout.