KN005: Translating Notifications Before a Two-Second Deadline
How Karui translates notifications without holding them up, how long Apple’s two translation models took, and why nearly half still missed the deadline.
Overview
Karui can translate notifications in languages you don’t read before it passes them on. Translation runs on your iPhone, inside the action your Karui shortcut runs for each notification. Karui never holds up a notification to wait for translation. Translation gets 2 seconds, and if it takes longer, Karui sends the original and saves the translation to History once it finishes.
This note covers the two models Apple’s Translation framework offers, how long each took over one morning of notifications, mostly in Japanese, and why 13 of 28 still missed the deadline.
Two models
A TranslationSession can prefer one of two strategies:
- Low latency uses Apple’s traditional translation models. It’s fast, but needs a language pack downloaded to the iPhone. Karui calls this Fast.
- High fidelity uses Apple Intelligence. It reads more naturally and needs no separate pack, but takes longer. Karui calls this High Quality.
To service the shortcut and rebroadcast the notification if it’s important, Karui tries Fast first and High Quality only if Fast isn’t available. After the notification is sent, it translates again with High Quality for History, so History always ends up with the better translation.
How long translation took
Karui logs how long each translation takes. These are from an iPhone 17 Pro, 7:00 to 10:35 one morning, mostly Japanese to English:
| Model | Translations | Median | Slowest |
|---|---|---|---|
| Fast | 21 | 0.7 seconds | 17.7 seconds |
| High Quality | 35 | 2.7 seconds | 128 seconds |
Times cover the translation itself, not the check for which model is available. One more High Quality translation failed after 10 minutes.
Fast usually finishes within the 2 seconds. High Quality usually takes longer.
Why 13 of 28 missed the deadline
iOS said the language pack wasn’t installed
Seven times, LanguageAvailability reported Japanese to English as supported rather than installed, so Karui skipped Fast and used High Quality, which took 2 to 6 seconds. Fast translations had worked minutes before and worked again minutes after. I haven’t found why the status changes.
Fast translation was slow
Six times, Fast itself took 1.7 to 2.3 seconds, and once 17.7. Checking which model is available also comes out of the 2 seconds, so a Fast translation slower than about 1.7 seconds misses.
Translations compete with each other
The slowest ones came together. From 8:41 to 8:46, while High Quality translations for History were still running for earlier notifications, they slowed from about 2 seconds to between 7 and 128, and the 17.7-second Fast translation in the shortcut happened during that time too.
Coping
- Karui doesn’t extend the deadline. A notification whose translation is late arrives untranslated and on time, and its translation is saved to History a few seconds later.
- Settings shows whether each language’s Fast pack is downloaded, and offers to download it.
- Each regional variant of the language is tried, your region first, because a generic language like English can pass Apple’s check and still fail to translate. The same flickering status shows up here. Twice that morning iOS reported only the Japanese to Canadian English pack as installed, so those two notifications came out in Canadian English.
Revision History
- 2026-09-30 First published.