doc: ADR for lazy quote preview resolution in message-list query

docs/adr/0012-lazy-quote-preview-resolution.md

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+# 12. Lazy Quote Preview Resolution
+
+Date: 2026-06-09
+
+## Status
+
+Proposed
+
+## Context
+
+The main Kalium message-list query uses `MessageDetailsView` as a hot path for conversation rendering. Quote previews were hydrated directly in this view through extra `LEFT JOIN`s to the quoted message, quoted sender, and quoted content tables.
+
+This made every message-list query pay the cost of quote hydration, even when most visible messages do not render a quote preview. The cost is more noticeable because the local database uses SQLCipher, where larger views and extra joins can be more expensive.
+
+We still need to preserve current quote behavior:
+
+- quoted message previews should update when the quoted message is edited
+- deleted or unavailable quoted messages should render as deleted/unavailable
+- invalid quote references must not expose quoted content
+- cross-conversation quote previews should be able to show the source conversation name
+- private reply drafts and quoted assets must keep using the quoted message conversation id
+- we need to extewnd it to include conv name for the reply in private feature
+
+## Decision
+
+Remove quoted-message hydration from Kalium's `MessageDetailsView` and keep only quote reference data in the main message-list query:
+
+- quoted message id
+- quoted message conversation id
+- quote verification state
+
+Kalium message mappers will continue exposing quote references on text and multipart messages, but the main message-list query will no longer populate quoted message details.
+
+The app will resolve quote previews lazily only when a rendered message needs one:
+
+1. Map unresolved quote references to an app UI quote reference model.
+2. Resolve that reference through an observer of the quoted message row.
+3. Keep the resolver scoped to the current conversation screen lifetime.
+4. Cache quote preview state by quoted conversation id, quoted message id, and verification state.
+5. Render already resolved quote data directly, unavailable data with the current unavailable UI, and unresolved references through the lazy preview state holder.
+
+For invalid quote references, the resolver returns invalid quoted content without exposing the quoted message body.
+
+For cross-conversation quotes, the resolver may also observe conversation details to derive a source conversation display name:
+
+- group/channel: conversation name
+- one-to-one: other user display name
+- failure or null: omit the source conversation name
+
+The source conversation name is rendered in the quote header only when present.
+
+## Consequences
+
+### Positive
+
+- The hot message-list query becomes smaller and avoids quote hydration joins.
+- SQLCipher has less work to do for ordinary message-list rendering.
+- Quote previews remain live with respect to quoted message edits and deletes.
+- Cross-conversation quote previews can show source conversation context without adding more joins to the main view.
+- Quote asset loading can use the quoted message conversation id instead of assuming the current conversation.
+
+### Trade-offs
+
+- Quote rendering now has a second-stage lazy resolution path in the app.
+- Visible quoted messages may trigger additional per-quote observers.
+- The app owns a conversation-scoped quote preview cache and must keep its lifecycle aligned with the conversation screen.
+- Initial quote preview rendering may briefly show loading-style fallback until the quoted message observer emits.
+
+### Maintenance rules
+
+When changing quote preview behavior:
+
+1. Keep `MessageDetailsView` limited to quote reference fields; do not reintroduce quoted-message hydration joins without revisiting this ADR.
+2. Preserve live quote updates by observing the quoted message row, not by one-shot loading keyed only by message id.
+3. Keep invalid quote references from exposing quoted content.
+4. Include quoted conversation id in quote preview cache keys and asset loading paths.
+5. Resolve source conversation names only for cross-conversation quotes.
+6. Cover text and multipart quote references in mapper tests, and cover edited, deleted/unavailable, invalid, same-conversation, and cross-conversation cases in resolver tests.