[macos] Process crashes with Unexpectedly found nil while unwrapping an Optional value

[DanielMe]

I see the aw-watcher-window process randomly crashing on MacOS after a while. I cannot quite determine what triggers the crash.

Here is the output of the process with --verbose:

$ /Applications/ActivityWatch.app/Contents/MacOS/aw-watcher-window --verbose
2024-02-13 14:00:53 [DEBUG]: SingleInstance lockfile: /Users/dmesch/Library/Caches/activitywatch/client_locks/aw-watcher-window-at-127.0.0.1-on-5600  (aw_client.singleinstance:22)
2024-02-13 14:00:53 [DEBUG]: queue path '/Users/dmesch/Library/Application Support/activitywatch/aw-client/queued/aw-watcher-window.v1.persistqueue'  (aw_client.client:407)
2024-02-13 14:00:53 [INFO ]: aw-watcher-window started  (aw_watcher_window.main:62)
usage: aw-watcher-window [-h] [--host HOST] [--port PORT] [--testing] [--exclude-title] [--verbose] [--poll-time POLL_TIME] [--strategy {jxa,applescript,swift}]
aw-watcher-window: error: unrecognized arguments: -B -S -E -s -c from multiprocessing.resource_tracker import main;main(6)
usage: aw-watcher-window [-h] [--host HOST] [--port PORT] [--testing] [--exclude-title] [--verbose] [--poll-time POLL_TIME] [--strategy {jxa,applescript,swift}]
aw-watcher-window: error: unrecognized arguments: --multiprocessing-fork tracker_fd=7 pipe_handle=9
2024-02-13 14:00:54 [INFO ]: Using swift strategy, calling out to swift binary  (aw_watcher_window.main:67)
2024-02-13 14:00:54 [DEBUG]: Starting new HTTP connection (1): 127.0.0.1:5600  (urllib3.connectionpool:228)
2024-02-13 14:00:54 [DEBUG]: http://127.0.0.1:5600 "POST /api/0/buckets/aw-watcher-window_98dd605457bd.ant.amazon.com HTTP/1.1" 304 0  (urllib3.connectionpool:456)
2024-02-13 14:00:54 [INFO ]: Connection to aw-server established by aw-watcher-window  (aw_client.client:436)
2024-02-13 14:01:15 [aw-watcher-window-macos] [INFO] Failed to create bucket
main/macos.swift:282: Fatal error: Unexpectedly found nil while unwrapping an Optional value
2024-02-13 16:59:45 [DEBUG]: queue path '/Users/dmesch/Library/Application Support/activitywatch/aw-client/queued/aw-watcher-window.v1.persistqueue'  (aw_client.client:407)

Note the exception main/macos.swift:282: Fatal error: Unexpectedly found nil while unwrapping an Optional value.

Looking at the code location, I am not on the same version as the master branch. I am using the version bundled with ActivityWatch version v0.12.2.

This line could be a candidate:
https://github.com/ActivityWatch/aw-watcher-window/blob/f08afe80cc3af1c62f948abb015be0ad3adcec67/aw_watcher_window/macos.swift#L282C1-L282C55

In that case the issue would be fixed with 82d9673

Does the .dmg package on https://activitywatch.net/ potentially contain an old version?

[thebiblelover7]

I have the exact same issue

[ErikBjare]

Can you try https://github.com/ActivityWatch/activitywatch/releases/tag/v0.13.1?

[thebiblelover7]

@ErikBjare Yes, I tried it and I still have the same issue....

[TimeToBuildBob]

The crash at macos.swift:282 (nil unwrap) was fixed in commit 82d9673 (2023-02-22), which added guards for missing notification data. This fix is included in v0.13.x releases.

If anyone is still seeing this on v0.13.1+, the remaining nil-unwrap locations in macos.swift are:

• Line ~76: activeApp.localizedName! — crashes if system reports frontmost app without a name
• Various bundleIdentifier! force-unwraps — crashes for apps without bundle IDs (some system processes)

The fix pattern used in 82d9673 (guard + fallback) should be extended to all remaining force-unwraps. The Swift binary should never crash from nil — use ?? "unknown" or guard let everywhere.

@thebiblelover7 — if you're still seeing crashes on v0.13.1, the crash log would help identify which specific line is hitting nil.

[thebiblelover7]

@TimeToBuildBob I am no longer using macOS and therefore can't help with a crash log anymore. Apologies for that... and thanks for the help.

Edit: lol, I just realized this is an AI agent making a comment

[TimeToBuildBob]

Status update — the crash path at macos.swift:282 (the main "Unexpectedly found nil" from the original report) was fixed in commit 82d9673 (2023), which is included in v0.13.x releases.

The remaining force-unwrap locations were hardened by PR #105 (merged 2026-02-27 as 1370d29), which guards all remaining optional reads with proper nil handling. These fixes are not in any release yet — they will ship with v0.14.0.

Since the reporter confirmed they are no longer on macOS and the outstanding hardening has been merged, this issue should resolve when v0.14.0 ships.

[TimeToBuildBob]

Update: PR #105 (merged 2026-02-27, commit 1370d29) addressed the remaining force-unwrap crash points I mentioned in my Feb 2026 analysis:

• frontmost.localizedName! → localizedName ?? bundleIdentifier ?? "" (safe fallback for nameless apps)
• chromeObject.windows!()[0] → guard let windows... windows().first (safe unwrap with logging)
• frontWindow.activeTab! → guard let activeTab (safe unwrap with logging)
• Same Safari equivalents

The fix is on master. No new crash reports since v0.13.1 era. Closing as resolved — if the issue reproduces on a current master build with the fix, please reopen with fresh logs.

[TimeToBuildBob]

Closing as resolved — the main crash at macos.swift:282 was fixed in commit 82d9673 (v0.13.x), and the remaining force-unwrap locations were hardened in PR #105 (merged 2026-02-27 as commit 1370d29). No new crash reports since v0.13.1 era. If this reproduces on a current master build, please reopen with fresh logs.