Symfony defaults Kernel::getCacheDir/getLogDir to <project>/var/cache
and <project>/var/log. In bundled mode those resolve inside the
AppImage's FUSE mount (/tmp/.mount_<hash>/usr/share/<app>/symfony/) —
read-only. Migrations fail at startup with:
Unable to create the "cache" directory
(/tmp/.mount_<hash>/usr/share/<app>/symfony/var/cache/prod).
…and frankenphp's worker can't warm a cache either, so even after the
binary spawns, the app is in a half-working state (which probably also
explains the persistent Reconnecting banner the user reported — once
migrations fail the supervisor sets Offline; even a successful
re-probe of /healthz wouldn't recover from a half-warm state).
Two-part fix, framework-side seam + app-side override:
1. BackendConnection.cpp (runMigrations + spawnChild): mkdir
<m_dataDir>/var/{cache,log} and pass them as APP_CACHE_DIR /
APP_LOG_DIR env vars. <m_dataDir> resolves to
~/.local/share/<app> via QStandardPaths::AppDataLocation, so
it's user-writable.
2. App Kernel.php (skeleton + todo): override getCacheDir /
getLogDir to honour the env vars. Falls back to parent
behaviour when unset (dev mode keeps writing to var/cache like
normal).
Database file already lives at <m_dataDir>/var/data.sqlite, so the DB
side was fine. Caddy autosaves to ~/.config/caddy and TLS storage to
~/.local/share/caddy — both user-writable. Mercure ran in-memory
mode in earlier logs so no extra storage redirect needed there.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>