# llama.cpp update adds id_slot handling for Anthropic API

> The Oct 20 2026 release lets servers pin sessions to specific KV cache slots, avoiding full re‑prefill on Anthropic /v1/messages calls.

Oossa · 2026-10-20 · https://oossa.com/en/llama-cpp-update-adds-id-slot-handling-for-anthropic-api

On 2026‑10‑20 the open‑source project llama.cpp released version b11756. The change makes the server copy the id_slot field from Anthropic /v1/messages requests into its internal OAI‑style body. This lets a proxy keep a session bound to a particular KV cache slot, preventing the model from having to refill its context each time. A new test confirms that requests with id_slot are served by the correct slot.

## The facts

- Release date: 2026‑10‑20 ("Tue Oct 20 2026 15:48:11 GMT+0200")
- Feature: id_slot passed through Anthropic /v1/messages conversion

## Why it matters

Developers using llama.cpp with Anthropic‑compatible APIs can keep chat sessions faster by avoiding costly cache reloads.

## Sources & references

1. [ggml-org/llama.cpp b11756](https://github.com/ggml-org/llama.cpp/releases/tag/b11756) – llama.cpp, 2026-10-20

Last updated: 2026-10-20