---
title: "Prefill phase mathematical notation"
description: "Prefill phase is a recurring research-paper notation family. Processes all prompt tokens in parallel to build hidden states and initialize each layer's…"
canonical_url: "https://fanout.sh/labs/math-decoder/symbol/prefill-phase"
md_url: "https://fanout.sh/labs/math-decoder/symbol/prefill-phase.md"
last_updated: "2026-08-09"
access: "public"
---

# Prefill phase mathematical notation

Prefill phase is a recurring research-paper notation family. Processes all prompt tokens in parallel to build hidden states and initialize each layer's…

## Public overview

Prefill phase is a recurring research-paper notation family. Processes all prompt tokens in parallel to build hidden states and initialize each layer's key-value cache before decoding.

Prefill phase: Processes all prompt tokens in parallel to build hidden states and initialize each layer's key-value cache before decoding. Example: Most first-token delay comes before iterative decoding begins.

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