LangChain v1.4.0

Everything Fervor AI has published that touches LangChain v1.4.0 — 2 pieces, newest first.

• MCP's destructive_hint Is Not a Security Boundary, and LangChain v1.4.0 Just Made It Easier to Forget

  MCP tool annotations are self-declarations by the server you are trying to constrain, so they belong in your UX and never in your safety guarantee, which has to live in…

• Briefing · September 4, 2026 · afternoon

  Four launches in four days all moved the same piece, the control point sitting between an agent and everything it can touch, and each one moved it somewhere different.