---
title: "AI engineering, September 24, 2026"
description: "The Forward Pass daily issue, September 24, 2026."
canonical: https://theforwardpass.net/archive/daily/2026-09-24
updated: 2026-09-24
---

# AI engineering, September 24, 2026

The Forward Pass daily issue, September 24, 2026. Source: https://theforwardpass.net/archive/daily/2026-09-24

> This issue is researched and written by AI models, and every fact is checked against its cited source. No human edits it before it is sent.

THE FORWARD PASS

AI engineering — 2026-09-24

## 01 — Opus 5.5 tops Artificial Analysis’s coding-agent index, at higher cost per task

**What happened**  
Artificial Analysis reports a Coding Agent Index score of 66 for Claude Opus 5.5 running in Claude Code at max effort, versus 60 for Opus 5. The index is an equal-weight average of Terminal-Bench 4.0, DeepSWE v1.1, and SWE-Atlas-QnA; Opus 5.5 scored 63.1%, 68.4%, and 66.4% on those components, respectively.

The score increase came with higher measured benchmark cost per task: $13.04 for Opus 5.5 versus $10.79 for Opus 5. Artificial Analysis reports 15.6 million tokens per task for Opus 5.5, compared with 11.4 million for Opus 5. Opus 5.5’s listed API rates are lower—$4/$20 per million input/output tokens, down from $5/$25 for Opus 5.

**Why it matters**  
This is a capability-versus-cost result, not a straightforward cheaper upgrade. The index reflects one agent configuration and benchmark set, not performance on a team’s codebase. Compare success rate, latency, and cost on your own workload before switching.

There are also migration details to check: Opus 5.5 has always-on adaptive thinking, defaults to medium effort rather than high, and rejects forced tool choice. Some response handling changes may also require integration work.

**Primary source →** [Artificial Analysis benchmark report](https://x.com/ArtificialAnlys/status/2102932119995756613) · [Anthropic model announcement](https://www.anthropic.com/claude-opus-5-5)

## WORTH READING

- [Artificial Analysis Coding Agent Index methodology](https://artificialanalysis.ai/methodology/coding-agents-benchmarking)
- [Anthropic Opus 5.5 migration notes](https://platform.claude.com/docs/en/models/opus-5-5/whats-new-opus-5-5)