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Anthropic Launches Claude Opus 5.5, Cutting Coding-Agent Costs 40% While Arriving Same-Day in GitHub Copilot

Claude Opus 5.5 becomes Claude Code's default model and lands in GitHub Copilot the same day, at roughly 40% lower cost than Opus 5.

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Overview

Anthropic released Claude Opus 5.5 on September 22, 2026, describing it as “the first model in our new Claude 5.5 family” that “performs at the level of Claude Fable 5.1 on most work and costs 40% less to run than Opus 5,” according to Anthropic. The model became the new default Opus model inside Claude Code the same day, and GitHub Copilot added it to its model picker within hours, according to GitHub.

What We Know

  • Opus 5.5 is priced at $4 per million input tokens and $20 per million output tokens, which Anthropic says is “20% less than Opus 5,” while cache reads fell 60% to $0.20 per million tokens, according to Anthropic. The company said the combined effect on typical workloads is “a 40% drop in costs,” and that Opus 5.5 “generates output more than 30% faster than Opus 5.”
  • On the agentic-coding benchmarks Anthropic highlighted, Opus 5.5 posted the top score among the models it tested: 66.4% on Terminal-Bench 4.0, 54.4% on FrontierCode v1.1, and 57.8% on CursorBench 4.0, according to Anthropic. Run at its default effort setting rather than maximum effort, Opus 5.5 still scored 52.5% on CursorBench — 11 points ahead of GPT-5.6 Sol’s top score — “for about a third of the cost per task.”
  • Claude Code’s own changelog lists version 2.1.280 as having “Added Claude Opus 5.5 (claude-opus-5-5), now the default Opus model — 1M context, $4/$20 per Mtok with $0.20/Mtok cache reads,” according to Claude Code’s changelog. Registry records on npm show that version was published on September 22, 2026.
  • GitHub said that “in early testing, Opus 5.5 resolved tasks comparably to Claude Opus 5 while using significantly fewer steps and tokens” and that it “quickly recovered from errors in multistep tasks,” according to GitHub. Access is limited to Copilot Pro+, Max, Business, and Enterprise users, with GitHub noting the rollout “will be gradual” across Visual Studio Code, Visual Studio, Copilot CLI, GitHub Copilot coding agent, the Copilot app, github.com, GitHub Mobile, JetBrains IDEs, Xcode, and Eclipse.
  • Mario Rodriguez, GitHub’s Chief Product Officer, said: “In our testing across GitHub Copilot CLI and VS Code, Claude Opus 5.5 used among the fewest tokens and steps we measured. In VS Code, it solved more terminal tasks than Opus 5 in less than half the steps,” according to Anthropic.
  • Stripe staff software engineer Cristian Rivera described running Opus 5.5 on “a multi-day rebase of 40 stacked pull requests,” during which “one Claude Opus 5.5 session directed a dozen more sessions and laid out every conflict plainly.” He added: “All 40 passed CI the next afternoon,” according to Anthropic.
  • Anthropic said Opus 5.5 carries heavier safeguards than Opus 5: most cybersecurity tasks are rerouted to Claude Opus 4.8, and organizations must apply to Anthropic’s Life Sciences Verification Program to use the model for biology research, according to Anthropic. The company also said that on a benchmark run by security firm Gray Swan, Opus 5.5 “ties Fable 5.1 for the lowest prompt injection success rate of any model tested.”
  • Claude Sonnet 5.5 and Claude Haiku 5.5 are due “in the coming weeks,” Anthropic said.

What We Don’t Know

  • Anthropic’s own announcement does not state Opus 5.5’s context window size; the 1-million-token figure comes only from Claude Code’s changelog, not from Anthropic’s product page.
  • GitHub has not said how long its “gradual” Copilot rollout will take before all eligible users see Opus 5.5 in their model picker.
  • The benchmark figures above come from Anthropic’s own testing; neither Anthropic nor GitHub has published an independently reproduced set of scores.

Analysis

The near-simultaneous rollout — a new Anthropic flagship becoming Claude Code’s default Opus model and reaching GitHub Copilot’s picker within hours of its announcement — illustrates how closely coding-agent products now track upstream model releases from their underlying labs. Anthropic built much of its pitch around cost and speed rather than a pure capability jump, framing Opus 5.5 as cheaper and faster to run per task even where its benchmark scores are close to its predecessor’s. That framing is aimed at the kind of long, unattended agent sessions GitHub, Stripe, and other Anthropic customers described testing the model on, where token and step efficiency compounds over hours or days of autonomous work rather than a single prompt.