docs: refresh cycle 16 research queue

Author: SysAdminDoc

.ai/research/2026-06-04/CYCLE_16_FINDINGS.md

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+# Cycle 16 Findings - 2026-06-04
+
+## Scope
+
+- Repository: `SwiftFloris`
+- Baseline: clean worktree at pushed `master` `caf6bea`
+  (`docs: refresh cycle 15 research queue`), described as
+  `v1.8.246-4-gcaf6bea`.
+- Sync: `git pull --rebase` fast-forwarded the local checkout to the pushed
+  Cycle 15 docs state before this cycle.
+- Constraint: research/docs only. No feature source, tests, build files,
+  manifests, assets, or generated outputs were edited.
+
+## Anti-Duplicate Checks
+
+- Did not duplicate R12-1, R13-1, or R14-1. Those rows already cover personal
+  n-gram durability, stats/reset serialization, and TSV token safety.
+- Did not duplicate R15-1. The Honeycomb parser diagnostic row remains the
+  focused parser/degradation handoff.
+- Did not reopen `switchToNextSubtype` / `switchToPrevSubtype`. The 2026-06-02
+  audit records those fallback paths as fixed; this cycle isolates the still-open
+  `switchToSubtypeById` double-read path.
+- Did not add new platform/API rows for Android 17 subtype limits, Play target
+  SDK policy, or 16 KB page-size enforcement. Existing roadmap/dependency rows
+  already track API 37, native dependency, release, and device-gated work.
+- Did not propose networked, closed-source, or incompatible-licensed keyboard
+  features. Those remain outside `:app` invariants or existing addon/sibling-repo
+  decision rows.
+
+## Local Evidence
+
+- `SubtypeManager.kt:276-278` snapshots `subtypes` inside `getSubtypeById(id)`.
+- `SubtypeManager.kt:402-404` first checks `subtypes.any { it.id == id }`, then
+  calls `getSubtypeById(id)!!`, which reads the subtype list again and asserts
+  non-null.
+- `SelectSubtypePanel.kt:83` calls `subtypeManager.switchToSubtypeById(it.id)`
+  from the subtype chooser UI.
+- `docs/AUDIT_2026-05-28.md:61-63` records the deferred TOCTOU/NPE finding and
+  recommends reading the subtype once.
+- `docs/AUDIT_2026-06-02.md:37` records the closed next/previous subtype fallback
+  fix, not a closure for `switchToSubtypeById`.
+- `app/src/test/.../ime/core` has focused subtype preset/classifier/per-app
+  memory tests, but no visible switch-by-id regression test.
+
+## External Landscape Sources Reviewed
+
+1. Android `InputMethodSubtype` API: https://developer.android.com/reference/android/view/inputmethod/InputMethodSubtype
+2. Android `InputMethodManager` API: https://developer.android.com/reference/android/view/inputmethod/InputMethodManager
+3. Android `InputMethod` API: https://developer.android.com/reference/android/view/inputmethod/InputMethod
+4. Android `InputConnection` API: https://developer.android.com/reference/android/view/inputmethod/InputConnection
+5. Android `EditorInfo.IME_FLAG_NO_PERSONALIZED_LEARNING`: https://developer.android.com/reference/android/view/inputmethod/EditorInfo#IME_FLAG_NO_PERSONALIZED_LEARNING
+6. Android 17 behavior changes for all apps: https://developer.android.com/about/versions/17/behavior-changes-all
+7. Google Play target API policy: https://developer.android.com/google/play/requirements/target-sdk
+8. Android 16 KB page-size support: https://developer.android.com/guide/practices/page-sizes
+9. Android security bulletin overview: https://source.android.com/docs/security/bulletin/asb-overview
+10. Kotlin null safety and `!!`: https://kotlinlang.org/docs/null-safety.html
+11. Kotlin `StateFlow`: https://kotlinlang.org/api/kotlinx.coroutines/kotlinx-coroutines-core/kotlinx.coroutines.flow/-state-flow/
+12. Kotlin `MutableStateFlow`: https://kotlinlang.org/api/kotlinx.coroutines/kotlinx-coroutines-core/kotlinx.coroutines.flow/-mutable-state-flow/
+13. Android Compose accessibility semantics: https://developer.android.com/develop/ui/compose/accessibility/semantics
+14. Android package visibility: https://developer.android.com/training/package-visibility
+15. Android custom permission element: https://developer.android.com/guide/topics/manifest/permission-element
+16. Android `SigningInfo`: https://developer.android.com/reference/android/content/pm/SigningInfo
+17. Android `Locale`: https://developer.android.com/reference/java/util/Locale
+18. IANA Language Subtag Registry: https://www.iana.org/assignments/language-subtag-registry/language-subtag-registry
+19. Unicode Emoji technical report: https://unicode.org/reports/tr51/
+20. Unicode latest version page: https://www.unicode.org/versions/latest/
+21. CLDR downloads: https://cldr.unicode.org/index/downloads
+22. Unicode LDML keyboards: https://www.unicode.org/reports/tr35/tr35-keyboards.html
+23. Keyman Android engine: https://help.keyman.com/developer/engine/android/
+24. Keyman source repository: https://github.com/keymanapp/keyman
+25. FlorisBoard v0.6.0-alpha02 release: https://github.com/florisboard/florisboard/releases/tag/v0.6.0-alpha02
+26. HeliBoard releases: https://github.com/HeliBorg/HeliBoard/releases
+27. AnySoftKeyboard releases: https://github.com/AnySoftKeyboard/AnySoftKeyboard/releases
+28. FUTO Keyboard v0.1.29 release: https://github.com/futo-org/android-keyboard/releases/tag/0.1.29
+29. FUTO Swipe dataset: https://huggingface.co/datasets/futo-org/swipe.futo.org
+30. OpenBoard repository: https://github.com/openboard-team/openboard
+31. AOSP LatinIME source: https://android.googlesource.com/platform/packages/inputmethods/LatinIME/
+32. Rime input method engine: https://github.com/rime/librime
+33. Mozc source repository: https://github.com/google/mozc
+34. Mozc for Android F-Droid package: https://f-droid.org/en/packages/org.mozc.android.inputmethod.japanese/
+35. F-Droid reproducible builds: https://f-droid.org/docs/Reproducible_Builds/
+36. SQLCipher 4.16.0 release: https://www.zetetic.net/blog/2026/05/12/sqlcipher-4.16.0-release/
+37. SQLCipher Android repository: https://github.com/sqlcipher/sqlcipher-android
+38. AndroidX `MimeTypeFilter`: https://developer.android.com/reference/androidx/core/content/MimeTypeFilter
+
+## Roadmap Changes Fed
+
+- R16-1: Collapse subtype switch-by-id to a single nullable lookup. The
+  implementation should avoid proving existence against one subtype-list
+  snapshot and then force-unwrapping a second lookup from a later snapshot.
+  Missing or concurrently removed subtype ids should no-op, while valid ids keep
+  the current manual activation path.
+
+## Rejected / Deferred Ideas
+
+- Android 17 subtype-count validation: relevant, but no current live code path
+  showed SwiftFloris approaching the 1500-subtype platform cap. Keep this under
+  the existing API 37/Android 17 compatibility follow-up instead of adding a
+  duplicate.
+- HeliBoard/FUTO glide and gesture ideas: already represented by F9/F21 and
+  device/ML-gated rows; no new in-tree feature should bypass the Apache-2.0,
+  no-network, and no-closed-blob constraints.
+- Keyman/Rime/Mozc engine integration: useful landscape context, but adding
+  engines would introduce native/runtime scope or license/product decisions
+  larger than a focused SwiftFloris build-machine item. Keep such work in
+  external addon/sibling-repo decision lanes if it ever becomes active.
+
+## Non-Adds
+
+- No source fix was made in this cycle.
+- No new permission, network, telemetry, export/import, or storage behavior was
+  proposed.
+- No product decision is required for R16-1; it is a local crash-hardening and
+  test-coverage item.