ci: build on macos-26 (Xcode 26) so the Python module map resolves

[torlando-tech]

main's test workflow has been red since the dual-backend merge — every open PR inherits it (this is why #84's CI failed; it's not the CallKit change).

Root cause

The Build (Python backend — default) step fails precompiling ColumbaApp's bridging header:

error: module 'Python' in AST file … clang importer creation failed
SwiftGeneratePch … Compiling bridging header (ColumbaApp) Failed → exit code 65

The embedded-Python (Columba) scheme's Python.framework clang module map only resolves under Xcode 26.x, but the runner was pinned to macos-15 / Xcode 16. The fix was made on the combined #82 branch (feat/dual-backend-arch), which was closed, not merged — so it was stranded (same pattern as the interop-harness fixes in #83).

Fix (recovered verbatim from #82)

• runs-on: macos-15 → macos-26 (carries Xcode 26.x)
• Select Xcode: pick the newest Xcode_* instead of Xcode_16*
• Add an explicit Resolve Swift packages step (fresh-runner resolution race for the test target)

No app/source changes. Merging this fixes main's CI; #83 and #84 should go green on re-run once this lands (their pull_request checks build the merge with main's fixed workflow).

[greptile-apps]

Greptile Summary

This CI-only fix recovers the macos-26 / Xcode 26 runner change that was stranded on the closed #82 branch. It restores a green main by supplying the Xcode version that the embedded-Python scheme requires for its clang module map, and adds an upfront package-resolve step to eliminate a fresh-runner resolution race for the test target.

• Runner & Xcode – runs-on is bumped from macos-15 to macos-26; the Select Xcode step now globs Xcode_*.app (instead of Xcode_16*.app) and version-sorts so Xcode 26.x wins even if an older installation is also present.
• Package resolution – A new Resolve Swift packages step calls xcodebuild -resolvePackageDependencies for both Columba and Columba-Swift schemes before any build or test step, warming the shared project-level package cache for all downstream steps.

Confidence Score: 5/5

Safe to merge — this is a targeted CI infrastructure fix with no app source changes.

All three changes (runner label, Xcode glob, package-resolve step) are straightforward and well-commented. The Xcode sort -V | tail -1 pattern correctly handles version ordering, the two-scheme resolve step addresses the previous reviewer concern about the Swift-native scheme not being explicitly warmed, and there are no app or test source changes that could introduce regressions.

No files require special attention.

Important Files Changed

Filename	Overview
.github/workflows/tests.yml	Runner bumped to macos-26, Xcode selection broadened to pick the newest installed version, and an explicit two-scheme package-resolve step added before any build; no logic regressions found.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    A[checkout] --> B[Clone sibling packages]
    B --> C[Fetch Python framework + wheels]
    C --> D[Select Xcode
macos-26 → pick newest Xcode_*.app]
    D --> E[Resolve Swift packages
-scheme Columba
-scheme Columba-Swift]
    E --> F[Find simulator]
    F --> G[Build — Python backend
-scheme Columba]
    F --> H[Build — Swift-native backend
-scheme Columba-Swift]
    G --> I[Build and run tests
-scheme Columba]
    H --> I
    I --> J[Export coverage report
lcov via xccov + python3]
    J --> K[Upload to Codecov]

Loading

_{Reviews (3): Last reviewed commit: "address greptile review feedback (greplo..." | Re-trigger Greptile}

[torlando-tech]

@greptile review

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

📢 Thoughts on this report? Let us know!