GitHub launches Copilot Fusion as agents start 40% of pull requests

GitHub launched Copilot Fusion at GitHub Universe, its developer conference, on Wednesday. The system decides which AI model, or mix of models, should handle each step of a coding task. It weighs what the task needs across reasoning, code generation, debugging and tool use. Jay Parikh, executive vice president of CoreAI at Microsoft, described it in a GitHub blog post.

Parikh wrote that Fusion Max scored within two points of Anthropic’s Claude Opus 5.5 Max on the Artificial Analysis Coding Agent Index. It did so at half the cost and with 40% less time per task. In a LinkedIn post, Microsoft chief executive Satya Nadella said Fusion delivers frontier-level quality 40% faster and at up to 77% lower cost.

SDLC is the software development life cycle, the path from planning through coding, testing and release. Nadella also said the unified system that runs Copilot’s agents is now in Foundry. Foundry is Microsoft’s managed service for building long-running agents. In September, a group of coders lost their DMCA case against Copilot at the Ninth Circuit.

Copilot without a separate subscription

From Wednesday, GitHub Enterprise customers can use every Copilot feature without buying a separate subscription. They pay for the AI credits they use. The offer runs through GitHub’s sales team for now, with self-serve coming soon. Existing Copilot Business and Copilot Enterprise customers can keep their plans or switch when they choose.

GitHub also showed the GitHub Copilot app, which connects agents and tools across projects. Inside it, Copilot projects run agent work across several repositories in parallel managed sessions. Session continuity lets one cloud agent session move between the app, VS Code, the command line and the web.

Copilot automations can now learn from their results and propose changes for developers to approve. Microsoft added coding to its own Copilot app, a separate product, in September.

For review, GitHub added Copilot code review Max. The company says it posted the highest F1 score on ReviewBench for high-severity issues. Startups sell AI code review too. CodeRabbit raised $143m in August to check code written by AI.

More capacity for agents

This year GitHub has added 4 million CPU cores and 160 PB of high-speed storage, Parikh wrote. It has added 50 Tb/s of network capacity too. GitHub is moving to a multi-region deployment on Microsoft’s Azure and expects to finish early next year. Nadella said the work will make GitHub more resilient.

“I think all the software we’ve written to date will amount to less than 1% of the software we’ll write in the next five years,” Parikh wrote.

What the Octoverse numbers show

GitHub published its annual Octoverse report on the same day. Developers pushed code 17.9 billion times in the 12 months to 30 September. That is more than in 2024 and 2025 combined. Commits reached 34.3 billion and merged pull requests 1.3 billion.

By September, more than 40% of pull requests started with a draft from an agent, up from 17% in March. That was 110 million in September alone. Activity rose sharply around June, when agents began working across days and running in the cloud, according to the report. GitHub says its agent count is a floor, because it cannot detect every agent.

The platform now has more than 225 million developers. The United States has 38.3 million and India 32 million. In September, 61% of Copilot users who picked their own model used more than one. TypeScript remained the most used language, and Rust grew fastest among the top languages, doubling in a year.