## Motivation
The socket-based internet connectivity probes (connecting to
1.1.1.1/8.8.8.8/1.0.0.1 every 10 seconds) are flaky — they produce false
negatives on some networks/ISPs, causing downloads to silently fail or
get stuck. Instead of dynamically detecting connectivity, this replaces
it with an explicit offline mode that the user opts into.
## Changes
- **Removed internet check infrastructure**: Deleted
`_test_internet_connection()` (socket probes) and
`_check_internet_connection()` (10s polling loop) from
`DownloadCoordinator`
- **Renamed `internet_connection` → `offline`** on `ShardDownloader`
base class and all subclasses (`SingletonShardDownloader`,
`CachedShardDownloader`, `ResumableShardDownloader`)
- **Removed `on_connection_lost` callbacks** from download calls — no
longer needed without dynamic connectivity detection
- **Added `EXO_OFFLINE` env var support** in `constants.py` and `Args`
default in `main.py`
- **Added Offline Mode toggle** to macOS app Settings → General tab,
which sets `EXO_OFFLINE=true` in the process environment and restarts
## Why It Works
The download behavior (`skip_internet` conditionals in
`download_utils.py`) is unchanged — we just changed what drives it.
Instead of a flaky socket probe setting
`internet_connection=True/False`, the user explicitly sets offline mode
via:
1. `--offline` CLI flag
2. `EXO_OFFLINE=true` environment variable
3. macOS app Settings → General → Offline Mode toggle
This is more reliable and predictable. Users on flaky networks no longer
get intermittent download failures.
## Test Plan
### Manual Testing
- `uv run exo --offline` starts without internet checks, rejects
downloads for unavailable models
- `EXO_OFFLINE=true uv run exo` behaves identically
- macOS app Settings toggle persists across restarts and passes env var
to the exo process
### Automated Testing
- All existing tests pass (222 passed), including 8 offline-mode
specific tests
- `uv run basedpyright` — 0 errors
- `uv run ruff check` — all checks passed
- `nix fmt` — 0 files changed
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>
Alex Cheema
7660893538