amethyst/commons/ARCHITECTURE.md

commons — Shared Module Architecture & Goals

commons is the shared layer between every Amethyst front end:

Consumer	Kind	Uses from commons
amethyst	Android app (touch-first)	everything (models, state, ViewModels) + commonsUI
desktopApp	Desktop JVM app (mouse-first)	everything (models, state, ViewModels) + commonsUI
cli (amy)	Headless JVM CLI (no UI)	everything — commons is headless by construction; it never sees commonsUI
nappletHost	Android WebView sandbox	napplet contract + commonsUI (for the shell/shim Compose resources)
iOS (future)	iOS app	everything + commonsUI; expected to share most UI with Android

commons sits above quartz (the protocol-only Nostr KMP library) and below the apps. The split between the three is:

• quartz/ — Nostr protocol: events, NIPs, crypto, relay framing. No app state, no UI, no caches of "what this user follows."
• commons/ — everything an Amethyst client needs that isn't a platform-native screen, navigation shell, or Compose UI: domain models (Note, User), in-memory state holders, ViewModels, the relay-subscription client, shared business services.
• commonsUI/ — the Compose UI components that more than one front end renders, plus everything only they need (icons, theme, Coil fetchers, markdown, the composeResources strings/fonts and the generated Res). Depends on commons as api. See commonsUI/ARCHITECTURE.md.
• amethyst/ & desktopApp/ — platform-native screens, navigation (bottom-nav vs sidebar), gestures, system integration. They assemble commons pieces; they should not re-implement them.

The goal is "write it once in commons". Before adding a manager, cache, filter, ViewModel, or composable to an app module, check whether it already exists here or belongs here. See the "Where does my code go?" guide below.

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1. The one rule that shapes the package tree: the UI / non-UI boundary

The shared layer is two modules with one package tree:

commons = CLI-safe code. It does not depend on Compose UI. It may use the androidx.compose.runtime annotations @Stable / @Immutable (they are just stability tags) and snapshot state (mutableStateOf, State), but it must not import androidx.compose.ui, androidx.compose.foundation, androidx.compose.material3, Coil, the generated Res, declare @Composable functions, or build ImageVectors. Its build.gradle.kts simply has none of those dependencies, so a violation fails to compile.

commonsUI = UI code. Anything that does the above. It is only usable by the GUI front ends (Android, Desktop, iOS), never by cli.

Both modules share the same com.vitorpamplona.amethyst.commons.* package tree — the split is a module boundary, not a package rename, so a file moves between commons/src/… and commonsUI/src/… without changing its package or any consumer's imports. Kotlin resolves same-package declarations across modules without imports; the only thing that stops working across the boundary is internal visibility (a UI file cannot see an internal declaration in commons — make it public or move it).

This boundary is not a top-level ui/ vs logic/ partition of the package tree (we chose to stay feature-oriented, §3). It is a property of each file: a feature keeps its logic in commons/…/<feature>/ and its composables in commonsUI/…/<feature>/ui/ (or commonsUI/…/<feature>/ for the historical flat packages), and the table in §2 says which module each package lives in.

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2. Package taxonomy

Top-level packages under commonMain/.../commons/, grouped by concern. UI? marks whether the package contains Compose UI (and therefore lives in commonsUI, not here). "mixed" means the feature's logic is in commons and its composables in commonsUI, under the same package.

Domain models & data

Package	UI?	Purpose
model	no¹	Core domain types (Note, User, Channel), thread assembly (ThreadAssembler, ThreadLevelCalculator, ReplyContext, replyingDirectlyTo), and per-NIP event model extensions in model/nipNN… subpackages. model/cache holds the in-memory event-store interfaces + UserMetadataCache. model/account, model/observables. The largest package; keep it organized by NIP.
defaults	no	Static bootstrap data (default relays, channels).

¹ model uses only the @Stable/@Immutable runtime annotations — CLI-safe.

Protocol-adjacent business logic (CLI-safe)

Package	UI?	Purpose
actions	no	Event builders for user actions (follow, zap…). The canonical entry point for non-UI callers.
account	no	New-account bootstrap events.
onchain	no	On-chain zap splitting/broadcasting.
marmot	no	MLS group-chat event processing.
nip53LiveActivities	mixed	Live-activity zapper aggregation (logic) + the stream card in nip53LiveActivities/ui.
search	no	Event search filtering/ranking, kind registry.
preview	no	OpenGraph / meta-tag link-preview parsing.
emojicoder	no	Variation-selector emoji encode/decode.
richtext	no	URL/media/pattern parsing for rich text.
blurhash	no	BlurHash encode/decode (pure math; platform image bridge in platform sets).
thumbhash	no	ThumbHash encode/decode.
nipACWebRtcCalls	no	NIP-AC WebRTC call state machine + peer-session abstraction. See nipACWebRtcCalls/ARCHITECTURE.md. (Mirrors quartz/.../nipACWebRtcCalls.)

State holders & ViewModels

Package	UI?	Purpose
state	no²	Small feature StateFlow machines (FollowState, UserMetadataState, LoadingState).
viewmodels	no²	Larger list/feed-backed ViewModels (androidx.lifecycle.ViewModel). Shared by all GUI front ends; cli usually drives the layers below instead. The few that hold Compose UI state (ChatNewMessageState — TextFieldValue; thread/LevelFeedViewModel — LazyListState) live in commonsUI under the same package.
feeds	no	The feed data-access layer at the root (FeedFilter, AdditiveFeedFilter, AdditiveComplexFeedFilter, ChangesFlowFilter, FeedContentState, FeedState, InvalidatableContent, DefaultFeedOrder, RepostRenderability…) plus feeds/custom (FeedDefinitionRepository — custom-feed definitions & ordering) and feeds/related. See the feed-patterns skill.
profile	mixed	ProfileBroadcastStatus (state) + EditProfileFields at the root; the ProfileBroadcastBanner composable lives in commonsUI profile/ui.
privacylock	mixed	Lock state machine + settings here; LocalPrivacyLockState/lockStateFor (CompositionLocal accessor) in commonsUI.

² may touch compose.runtime state types (snapshot state, @Stable); they are shared across the GUI apps. A state holder that needs a foundation/ui type (LazyListState, TextFieldValue, TextFieldState) goes to commonsUI.

Relay client

Package	UI?	Purpose
relayClient	mixed	Compose-scoped subscription managers, filter assemblers, EOSE managers, preloaders. (Despite a composeSubscriptionManagers subpackage name, this is subscription-lifecycle logic, not UI.) The @Composable entry points — relayClient/user/ (observeUser* — kind-0 metadata), relayClient/event/ (EventFinderFilterAssemblerSubscription/observeNote*), the other *FilterAssemblerSubscriptions, KeyDataSourceSubscription, auth/AuthApprovalBanner — are in commonsUI under the same packages. See the relay-client skill.
relays	no	Low-level EOSE/relay-timing bookkeeping (EOSECache, EOSERelayList).

Platform abstractions (expect/actual)

Package	UI?	Purpose
util	no	KMP primitives: KmpLock, WeakReference, number/URL/codepoint helpers, list/debug helpers. This is the only general-utility package — there is no utils.
keystorage	no	Secure key storage interface (Keystore / keychain / keyring actuals).
tor	no	Tor manager interface + settings.
service	no	Cross-cutting services: BundledUpdate batching (common); service/upload (JVM), service/nwc, service/lnurl (jvmAndroid). Singular service — there is no services.

UI (Compose — lives in commonsUI)

Package	UI?	Purpose
ui	yes	Cross-cutting shared composables only, organized by area: ui/components, ui/theme, ui/signing, ui/thread, ui/note, ui/richtext, ui/search, ui/notifications, ui/screens, ui/layouts, ui/markdown, ui/privacylock, plus Compose helpers in ui/state (cached-state) and ui/text (TextField extensions). Feature-specific UI lives in <feature>/ui, not here. Nothing under ui.* lives in this module any more: the feed DAL that used to sit in ui/feeds is now feeds/, and the reply-context logic that sat in ui/note (replyingDirectlyTo, ReplyContext) is now in model/ next to ThreadAssembler.
nip23LongContent	yes	Long-form (NIP-23) article UI: nip23LongContent/ui/article (reader) + …/ui/editor (authoring). The model lives in model/nip23LongContent (here).
icons	yes	ImageVector icon definitions + builders, Material Symbols codepoints, the icon-font glyph tables.
hashtags	yes	Custom hashtag ImageVectors.
robohash	yes	Procedural robohash avatar ImageVector assembly.
audio	mixed	Spectrum/visualizer data (AudioSpectrum, SpectrumAnalyzer…) here; the VisualizerRenderers, VisualizerRegistry and the canvas composables in commonsUI.
service/image	mixed	CoilImageBridge + the BlurHash/ThumbHash/Base64/Blossom Coil fetchers are commonsUI (they are Coil); the headless image helpers stay here.
napplet	mixed	Protocol/permission logic here; NappletWebContract (serves the shell/shim from composeResources) in commonsUI.
favorites, nip30CustomEmojis, nip34Git, nip85TrustedAssertions, nip53LiveActivities	mixed	Logic here; each feature's ui/ (or the flat FavoriteAppIcon, EmojiSuggestionState) in commonsUI.

Mixed (documented debt — see §4)

Package	UI?	Purpose
nip64Chess	mixed	Live-chess feature: game/lobby/subscription logic here; board/lobby composables in commonsUI under nip64Chess/ui. (Mirrors quartz/.../nip64Chess.)
domain	no	Currently only domain/nip46 (Nostr Connect signer flows). Sparse; candidate to fold into a clearer home.

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3. Conventions

Feature-oriented, not layer-partitioned

We keep a feature's model, state, and UI together under one feature package rather than splitting the whole module into top-level ui/ / viewmodels/ / model/ layers. Within a feature, separate UI from logic with a ui subpackage (e.g. profile/ProfileBroadcastStatus vs profile/ui/ProfileBroadcastBanner) so the CLI-safe boundary (§1) stays visible.

The big shared cross-feature packages (model, ui, relayClient, util, icons) are the exception — they are organized by layer because many features share them.

Naming

• Singular, no synonyms. util (not utils), service (not services). One concept → one package name.
• Feature UI vs cross-cutting UI — the deciding test. A composable goes in <feature>/ui if it renders/edits one feature's content (it would make no sense outside that feature) — e.g. profile/ui, nip53LiveActivities/ui, nip23LongContent/ui. It goes in ui/<area> only if it is reusable across features (theme, avatars, buttons, layouts, markdown rendering, shimmer…). When in doubt, ask "could a second, unrelated feature reuse this as-is?" — yes → ui/<area>, no → <feature>/ui. The top-level ui/ package holds no feature-specific composables.

NIP as the second axis (mirror quartz)

quartz is ~94% organized by NIP (nipNN<slug> per spec), and that is correct there — the protocol layer is naturally NIP-partitioned. commons is not organized by NIP at the top level, and should not be: most of it is cross-cutting infrastructure (ui, relayClient, viewmodels, feeds, util…) that serves many NIPs at once, and the load-bearing UI/non-UI boundary (§1) cuts across NIPs, so a NIP-first top level would just nest the same problem one level down.

Instead, layer is the primary axis, NIP is the secondary axis:

• The big shared layers stay layer-organized (model, relayClient, the cross-cutting ui, …).
• Inside a layer, NIP-specific code goes in a nipNN<slug> subpackage whose name matches quartz exactly — e.g. model/nip57Zaps. This gives a clean trace: quartz/nip57Zaps → commons/model/nip57Zaps.
• A top-level package that is a single self-contained NIP feature takes the same name as its quartz counterpart, and owns its own UI under <feature>/ui: nip64Chess, nipACWebRtcCalls, nip53LiveActivities, nip23LongContent, marmot. (marmot is un-numbered in quartz too.) Generic/multi-NIP packages keep their concern name (search, preview, actions, richtext…).
• Feature UI is never under ui/. A single-NIP feature's composables live in <feature>/ui (e.g. nip53LiveActivities/ui), not ui/nip53LiveActivities. ui/ is exclusively cross-cutting (§2, Naming).

Source sets

Source set	For
commonMain	KMP code for all targets (Android, JVM, iOS). Gated by verifyKmpPurity — no Jackson/OkHttp/System.currentTimeMillis/java.util.UUID/JVM @Synchronized/@Volatile. Use the KMP replacements.
jvmAndroid	Shared by Android + Desktop, not iOS. Where JVM-bound deps live (nestsClient, OkHttp, NWC/LNURL).
jvmMain	Desktop-only (keyring, EXIF, service/upload, OS notifications). dependsOn(jvmAndroid).
androidMain	Android-only (Keystore, DataStore, the Android R string resources used by the napplet host). dependsOn(jvmAndroid).
iosMain	iOS actuals. Compile-only spike today.

commonsUI mirrors the same source-set layout (plus skikoMain, shared by desktop JVM + iOS for org.jetbrains.skia pixel helpers); Coil-OkHttp, markdown and the viewModel() helper live in its jvmAndroid.

When adding platform code, prefer the most common source set that still compiles: commonMain → jvmAndroid → platform-specific. See /kotlin-multiplatform.

Where does my code go? (quick guide)

1. Pure Nostr protocol (events/NIPs/crypto)? → not here, it's quartz.
2. A composable rendered by ≥2 front ends, or that you want iOS to share? → commonsUI, in ui/<area> or <feature>/ui (same package tree as here). Also anything that imports Coil, Res, or a foundation/ui state type.
3. A ViewModel / StateFlow state holder? → viewmodels or state (or <feature> if feature-scoped). Keep it CLI-safe where practical.
4. Relay subscription / filter assembly? → relayClient.
5. A domain model or per-NIP event wrapper? → model (model/nipNN…).
6. A platform capability behind expect/actual (storage, crypto)? → the matching abstraction package + actuals in platform sets.
7. A generic helper? → util. (Resist creating a new top-level package for one file.)

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4. Known debt / follow-ups

These are intentionally documented, not silently tolerated. Fix opportunistically.

• commons applies the Compose compiler plugin without declaring any composable. Deliberate, not debt: the plugin's @StabilityInferred stamps are what keep unannotated commons classes stable from the apps' point of view. Measured on full recompiles (2026-09-12): without it, unstable composable params go 20→28 in commonsUI, 33→65 in desktopApp, 90→149 in amethyst. Don't remove it; if a class must be stable for a hot path, annotate it explicitly as well.
• Same package tree in two modules. Intentional (zero-import-churn split), but it means a package's module is not visible from its name. Rule of thumb: if it imports Compose UI it is in commonsUI; check §2 when unsure.
• domain is sparse (only nip46). Either grow it as the home for use-case/flow types or rename it to the matching nip46RemoteSigner per the NIP-second-axis rule.
• relays vs relayClient are coherent but close in name; relays is low-level EOSE bookkeeping, relayClient is the subscription client. Keep the distinction in mind when adding files.
• Several single-file feature packages (account, marmot, nip53LiveActivities, keystorage) are kept as feature/abstraction namespaces expected to grow; do not fold them into util just for size.
• onchain (on-chain zap splitting) is quartz-adjacent but un-numbered; leave readable unless a clear NIP number lands.

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5. See also

• nipACWebRtcCalls/ARCHITECTURE.md — WebRTC call state machine deep-dive.
• Root .claude/CLAUDE.md — module overview, sharing philosophy, build commands.
• /kotlin-multiplatform, /compose-expert, /feed-patterns, /relay-client, /account-state skills for the patterns referenced above.