Root cause: OcamlBridge._send() used write() without drain().
asyncio.StreamWriter buffers writes — without drain(), multiple
commands accumulate and flush as a batch. The kernel processes
them sequentially, sending responses, but Python only reads one
response per command → pipe desync → "unexpected response" errors.
Fix: _send() is now async, calls drain() after every write.
All 14 callers updated to await.
Playwright tests rewritten:
- test_home_has_header: verifies #logo-opacity visible (was only
checking for "sx" text — never caught missing header)
- test_home_has_nav_children: Geography link must be visible
- test_home_has_main_panel: #main-panel must have child elements
- TestDirectPageLoad: fresh browser.new_context() per test to
avoid stale component hash in localStorage
- _setup_error_capture + _check_no_fatal_errors helpers
_render_to_sx uses aser_slot (not aser) — layout wrappers contain
re-parsed content that needs full expansion capability.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
giles
d3b3b4b720