AI Coding Tools Roundup: Claude Opus 5.5 Launches in Claude Code and GitHub Copilot
AI coding assistants had a busy 48 hours. Between September 21 and 22, 2026, Anthropic, OpenAI, xAI, and the open-source OpenCode project all pushed meaningful model updates into the tools developers use every day — headlined by Claude Opus 5.5 landing in both Claude Code and GitHub Copilot on the same day. Here's what shipped, and what it means for your stack.
Claude Opus 5.5 Ships in Claude Code and GitHub Copilot the Same Day
Anthropic's newest Opus model debuted everywhere at once. Claude Code's v2.1.280 changelog set claude-opus-5-5 as the new default Opus model, with a 1M-token context window and pricing of $4/$20 per million tokens ($0.20/Mtok for cache reads). The same release also added CLAUDE_CODE_MAX_MCP_DESCRIPTION_LENGTH for customizing the 2,048-character cap on MCP tool descriptions, plus fullscreen mouse and dialog fixes.
On the same day, GitHub rolled out Claude Opus 5.5 in GitHub Copilot for Pro+, Max, Business, and Enterprise plans across VS Code, Visual Studio, JetBrains, Xcode, Eclipse, and GitHub.com. In early testing, Opus 5.5 resolved tasks comparably to Opus 5 while using significantly fewer steps and tokens, and recovered from errors in multistep agentic runs faster than its predecessor. The rollout is gradual, so it may take a few days to appear in every account.
GPT-6 Sol and GPT-6 Luna Round Out OpenAI's Lineup in Copilot
OpenAI also expanded its footprint in Copilot on September 22, adding GPT-6 Sol and GPT-6 Luna alongside the existing GPT-6 Astra. Sol is pitched as a balanced, all-round model for interactive and agentic coding that benefits from careful multistep validation, while Luna is the lightweight, cost-efficient option for smaller, faster tasks — the cheapest model in the GPT-6 family, per OpenAI's own announcement. Sol is available on Pro+, Max, Business, and Enterprise; Luna extends down to the Pro tier.
Grok 4.7 Joins Copilot and OpenCode in the Same Week
xAI's Grok 4.7 is rolling out gradually in GitHub Copilot across Pro, Pro+, Max, Business, and Enterprise tiers, building on Grok 4.6 with a focus on agentic coding and complex, multistep workflows. The open-source OpenCode agent picked up the same model days later: version 1.18.32, released September 21, added Grok 4.7 and DeepSeek V4.1 Flash support, alongside fixes for Bedrock image attachments (now scoped to Claude, Nova, and Llama 4 models) and Together AI streaming-usage reporting.
What It Means for Developers
The headline here isn't any single model — it's the pace. Three major coding surfaces, spanning Anthropic, OpenAI, and xAI models, updated their default or available model lineups within a 48-hour window. Opus 5.5 is now the strongest default for long-running Claude Code sessions on cost-per-step efficiency, while Copilot users get the broadest side-by-side choice yet — Opus 5.5, GPT-6 Sol, GPT-6 Luna, and Grok 4.7 in one model picker. It's worth a quick regression pass on any pinned model IDs or CI configs that assume the previous defaults before the gradual rollouts reach your account.
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