Axiom v27.3.0

Released October 5, 2026

New

• Build and test capture – Build errors and failed tests now reach the assistant even when a long build’s output is truncated: the new axbuild tool runs the xcodebuild, swift build, or swift test command you’d normally run, saves the full log and report, and returns a short summary with each error’s location and each failed test’s message and Swift Testing’s evaluated values. It ships in the Claude Code and Codex plugins (in Pi, put it on your PATH; Cursor and MCP setups save build output to a file instead), and build-fixer, test-runner, and /axiom:fix-build read its saved log before rebuilding.

Updated

• Derived Data and simulator cleanup – Deletes only the current project’s Derived Data folder, shuts down or erases only the affected simulator, and inspects a running build before stopping it. The change covers build-debugging, xcode-debugging, swiftui-debugging, swiftui-debugging-diag, swiftui-previews-ref, app-store-diag, app-launch, and simulator-tester.
• Also updated – A new temporary folder for each build and test run, so concurrent runs keep their own results, and an app-launch clean-boot sequence that erases a simulator whether or not it was already shut down.

Changed

• Build cleanup approval – build-fixer and /axiom:fix-build now stop before killing a build, deleting Derived Data, or resetting a simulator, and return the cause, the evidence, and the exact command to approve.

Full Changelog: v27.2.1...v27.3.0