announcement aidev SIG 4/5

Cursor SDK: custom tools, auto-review, JSONL stores, and nested subagents

The Cursor TypeScript and Python SDKs gain function-based custom tools exposed via a built-in MCP server, an auto-review classifier for local tool calls steered by natural-language rules, JSONL-backed agent stores as an alternative to SQLite, and unlimited subagent nesting. The release also includes reliability fixes for run correlation, checkpoint safety, and HTTP/1.1 streaming, plus lighter imports and bundled ripgrep.

PUBLISHED2026-06-04
OBSERVED2026-08-11
AGE2mo
SOURCES1
  • Custom tools: pass function definitions through local.customTools on Agent.create() or send(); exposed via a built-in custom-user-tools MCP server; visible to all subagents
  • Auto-review: set local.autoReview to route local tool calls through a classifier; steered via autoRun.allow_instructions and autoRun.block_instructions in permissions.json
  • Custom stores: JsonlLocalAgentStore writes append-only JSONL; implement the public LocalAgentStore interface for custom backends (in-memory, Postgres, etc.); Python SDK exposes host, JSONL, and composed stores
  • Nested subagents: subagents can spawn subagents to any depth; no opt-in required
  • Reliability: every send() carries a platform-generated requestId; wait() on local runs no longer resolves before terminal state; safe checkpoint disposal; HTTP/1.1 cloud streaming
  • Performance: lazy import of the local agent stack; self-contained .d.ts files; bundled ripgrep without global PATH modification
  • Models: retired composer-2 slugs routed to Composer 2.5 automatically
  • Python SDK: list_runs accepts optional cwd; clearer not-found errors; 0.1.6 release with Buildkite path and analytics labels
featurecapabilityapi-change

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