Toolchain bumps are an operational risk, not just a compiler upgrade — mismatched CI and local toolchains can introduce flaky PRs, signing issues, and stalled releases.

• Regenerate Package.resolved in CI using the same xcodebuild invocation your pipeline uses and publish CI-built artifacts; sign CI-produced binaries for traceability.
• Include an identifier for the Xcode/toolchain in CI cache keys and run multiple clean builds to validate cache hygiene before merging.
• Rebuild and verify XCFramework slices (device + simulator) after a toolchain change; add a CI job to assert slice contents and signing metadata.
• Instrument critical paths with signposts (e.g., os_signpost) and collect MetricKit payloads from device runs to surface regressions; gate verbose diagnostics behind runtime flags and sampling.

Prefer aggressive caching when iteration speed matters; prefer conservative invalidation when artifact correctness or signing is at risk.

Which migration step caused the most friction for your team — cache invalidation, XCFramework regeneration, or diagnostic noise — and how did you resolve it? Share a concrete tactic that worked.