Problem

StatusManager::write_atomic bridged to the async fbuild_core::fs::write_atomic via tokio::task::block_in_place + Handle::block_on. block_in_place panics inside a current-thread tokio runtime — the default flavor of #[tokio::test] — so every unit test that constructed a DaemonContext (which constructs a StatusManager, whose new calls flush(), which calls write_atomic) panicked on macOS + Windows CI. Three named tests were affected:

• handlers::health::tests::shutdown_refuses_non_force_when_operation_in_progress
• handlers::locks::tests::lock_status_reports_held_project_locks_without_stale_entries
• handlers::locks::tests::clear_locks_removes_only_unheld_project_lock_entries

Fix

Add fbuild_core::fs::write_atomic_sync — same write-tempfile / fsync / rename semantics as the async helper, but std::fs end-to-end so it has no runtime-flavor requirement. Switch StatusManager::write_atomic to call it. The status file's atomicity contract is preserved verbatim; the only behavior change is that the call is no longer runtime-aware.

Why sync instead of runtime-flavor sniffing

The fix sketch in the issue proposed Handle::current().runtime_flavor() matching to route current-thread runtimes to a spawned tokio::runtime::Runtime for the block_on. That nests runtimes (also disallowed) and adds a per-write Runtime::new() allocation. A sync std::fs helper sidesteps both issues — and the status writer was already inside synchronous code paths inside a sync-locked Mutex<DaemonStatus>, so there's no async-blocking concern.

Tests

Two regression tests in fs::tests:

• write_atomic_sync_runs_inside_current_thread_runtime — exact panic scenario, asserts no panic + correct content
• write_atomic_sync_works_without_runtime — cold-bootstrap path

Verification

• soldr cargo check -p fbuild-core -p fbuild-daemon clean
• soldr cargo clippy -p fbuild-core -p fbuild-daemon --all-targets -- -D warnings clean
• soldr cargo test -p fbuild-core --lib fs::tests::write_atomic_sync_ clean

Closes #865

🤖 Generated with Claude Code

Summary by CodeRabbit

• New Features

  • Added a more reliable atomic file-writing path for synchronous operations.

• Bug Fixes

  • Improved file writes in daemon status handling to avoid runtime-related panics in certain environments.
  • Added safeguards so atomic writes fail cleanly when the target folder does not exist.
  • Expanded test coverage for atomic writes across common runtime and non-runtime scenarios.