DiffNo. 003

Thursday, September 10

3 new · 3 still open · ~60 s

shiftagents

Meta Muse: dedicated VM + Sentinel gatekeeper between agent and internet

Meta launched Muse, a personal AI agent where each user gets an isolated VM ("Muse Secure VM") and a separate gatekeeper model ("Sentinel") that must approve every outbound network request before it leaves the environment — nothing reaches the internet without Sentinel's sign-off. The containment is architectural: one model acts, a second model controls egress. This is the first production consumer agent to publish its security architecture at this level of specificity, and the Sentinel pattern is the concrete engineering answer to how you actually sandbox an agent with real-world tool access. Agent safety and sandboxing as an engineering discipline — not a policy statement — is listed as an interest in PROFILE.md; this is the reference design.

via meta (about.fb.com) · axios · techcrunch · cnbc

techniquetooling

Fable 5.1 cache reads dropped 75% — now $0.25/MTok

Cache reads on Claude Fable 5.1 cost $0.25/MTok (0.025× base input price), compared to $1/MTok (0.1×) on Fable 5 and all other models. For a heavily cached agentic loop with a large system prompt or tool spec, this cuts the cache-read cost by three-quarters automatically once you are on Fable 5.1. The cost improvement alone strengthens the Fable 5.1 migration case — though the breaking change on tool_choice: any/tool (those now return 400; switch to auto or the strict tool-use pattern) needs a check before migrating, if Policy Assistant forces tool selection via tool_choice.

via claude platform release notes · claude platform pricing · venturebeat

techniquetooling

`clear_at` lets per-turn reminders render once and cost nothing after

clear_at: "next_user_message" on a mid-conversation system message makes it render once (after a tool result, for example), then silently drop to zero tokens on every subsequent request — while staying in the array byte-for-byte so the prompt cache prefix stays intact. The pattern it solves: per-turn reminders like "verify your previous step" or "request independent reads in one turn" that would otherwise pile up in message history and inflate costs over a long agentic loop. The constraint worth knowing: the cleared message must be re-sent byte-for-byte unchanged on every subsequent call; editing or removing it breaks the cache and any bound thinking blocks. If Policy Assistant has per-turn instruction patterns in its protocol loops, this is the clean fix.

via claude platform docs