Cut Your Claude API Costs With Context Engineering — Reusable Scripts, Model Routing, and Token Pruning

Context Engineering Guide

By the end of this guide, you'll have a context engineering strategy running inside Claude Code — reusable scripts replacing repeated rewrites, cheaper models handling simple tasks, and a pruning system keeping your context window lean so you run longer sessions for less money.

Who This Is For

• You're running Claude Code sessions that are getting expensive, and you're not sure why.

• You're hitting usage or budget limits mid-session on projects that should be well within your tier.

• Claude keeps rewriting the same code block to fix bugs instead of building a tool that handles it once.

• You're defaulting to Opus for every task, including simple ones that don't need it.

• You want longer, more productive development sessions without increasing your API spend.

What You'll Build

A three-part context engineering strategy for Claude Code:

• Modular Script Skeletons — Reusable terminal tools that replace repeated in-chat code rewrites.

• Model Routing Schema — A task-by-task breakdown of what routes to Sonnet or Haiku vs. Opus, keeping execution significantly cheaper without sacrificing output quality.

• Pruning Milestone System — A reminder framework that tracks when your context window is getting too heavy and triggers compaction before it starts costing you.

What You'll Need

• Claude Code CLI installed and running.

• An active development project with a defined working directory.

• Basic terminal comfort (you'll be running `/compact` and bash commands).

• An Anthropic API key with access to multiple model tiers (Opus, Sonnet, and Haiku).

Context Audit Prompt

Audit my current Claude Code usage for context engineering opportunities.

Here is what I'm running: [describe your typical session or workflow - e.g. repeated file rewrites, long research sessions, recurring analysis tasks]

Go through this with me in three passes:

1. REUSABLE SCRIPTS - Identify any task I'm asking Claude to redo from scratch each time that could instead be a saved script or template Claude just runs and fills in. List each one and what the script should do.

2. MODEL ROUTING - Flag which parts of this workflow are simple enough to hand to a cheaper/faster model instead of the most capable one, and which parts genuinely need the top-tier model. Be specific about the split.

3. CONTEXT PRUNING - Point out where my context window is likely carrying stale or irrelevant information (old file contents, resolved errors, superseded instructions) that should be cleared or summarized instead of carried forward turn after turn.

End with a short prioritized checklist of the 3 changes that will cut cost and session bloat the most, starting with the highest-impact one.