feat(projects): three tables, schema 20 -> 21

Phase 2 of docs/project-feature.md. Still nothing that writes a row: this is the
shape, the keys and the queries each screen will want.

A project's contents are real foreign keys into this room's own rows, with
CASCADE, like every reference in this family. That is the one-room scope
decision made load-bearing rather than documented: a membership naming a version
this device does not hold fails at insert, loudly, instead of landing as a row
pointing at nothing that every later read has to be defensive about. Projects
that span rooms take those keys away again -- Phase 9, following
`parentChatRoomId`, which is deliberately not a foreign key because a dangling
value is the normal state there -- and that is a migration rather than something
to carry unused until then. `MantraProjectDaoJvmTest` asserts the refusal, which
is also what says Room has foreign keys switched on at all.

The owners are a comma-joined sorted string with an `ownerPublicKeySet()`
accessor beside it, which is what `DkgSession.participantPublicKeys` already
does with a set of keys, sort included and for the same reason. A fourth table
would buy querying by owner, which no screen does. A set stored as text is a
shape that rots, so the accessor is tested against spacing, empty entries and
the single-entry case rather than the happy path.

`fromProjectEvent` refuses an event with no name, no creator or no owners rather
than filling the gap from local knowledge -- which is exactly the failure the
tags exist to prevent. The empty-owner refusal does double duty: an owner list
that comes back empty is what `ROLE_OWNER` missing from `KNOWN_ROLES` looks like
from here, so the guard against a malformed event is also the alarm for that
bug.

No `toProjectEvent()`. Those eight rebuilds serve rooms whose work predates
`GroupSignedEvent` at v13; projects arrive at v21, so every project this app
will ever hold is on file as a signed event. Adding three more would be adding
to a mechanism with a removal checklist already written for it.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

composeApp/src/commonMain/kotlin/press/mantra/compose/database/MantraDatabase.kt

@@ -29,6 +29,9 @@ import press.mantra.compose.database.dao.MantraChapterDao
 import press.mantra.compose.database.dao.MantraChunkDao
 import press.mantra.compose.database.dao.MantraDao
 import press.mantra.compose.database.dao.MantraDialectDao
+import press.mantra.compose.database.dao.MantraProjectArtifactVersionDao
+import press.mantra.compose.database.dao.MantraProjectDao
+import press.mantra.compose.database.dao.MantraProjectTranslationArtifactVersionDao
 import press.mantra.compose.database.dao.MantraTranslationArtifactVersionDao
 import press.mantra.compose.database.dao.MantraTranslationArtifactVersionContributorDao
 import press.mantra.compose.database.dao.MantraTranslationChapterDao
@@ -81,6 +84,9 @@ import press.mantra.compose.database.model.MantraArtifactVersion
 import press.mantra.compose.database.model.MantraChapter
 import press.mantra.compose.database.model.MantraChunk
 import press.mantra.compose.database.model.MantraDialect
+import press.mantra.compose.database.model.MantraProject
+import press.mantra.compose.database.model.MantraProjectArtifactVersion
+import press.mantra.compose.database.model.MantraProjectTranslationArtifactVersion
 import press.mantra.compose.database.model.MantraTranslation
 import press.mantra.compose.database.model.MantraTranslationArtifactVersion
 import press.mantra.compose.database.model.MantraTranslationArtifactVersionContributor
@@ -146,6 +152,9 @@ val GENESIS_AT = Instant.fromEpochMilliseconds(1231006505000L)
         MantraChapter::class,
         MantraChunk::class,
         MantraDialect::class,
+        MantraProject::class,
+        MantraProjectArtifactVersion::class,
+        MantraProjectTranslationArtifactVersion::class,
         MantraTranslation::class,
         MantraTranslationArtifactVersion::class,
         MantraTranslationArtifactVersionContributor::class,
@@ -177,7 +186,7 @@ val GENESIS_AT = Instant.fromEpochMilliseconds(1231006505000L)
         UnsignedNostrEvent::class,
         Zap::class
     ],
-    version = 20,
+    version = 21,
     autoMigrations = [
         // v2 only adds the DkgSession/DkgParticipantMessage tables, so Room can
         // generate the migration itself — nothing existing changes shape.
@@ -321,6 +330,22 @@ val GENESIS_AT = Instant.fromEpochMilliseconds(1231006505000L)
         // which is what they were, and any identity may drain them. The broadcast
         // queue deliberately gets no owner: a signed event is anyone's to carry.
         AutoMigration(from = 19, to = 20),
+        // v21 adds the three project tables -- a project, and one row per source
+        // version or translation that is part of it. Three new tables and
+        // nothing existing changes shape, so Room generates this itself.
+        //
+        // A project's contents are foreign keys into this room's own rows, with
+        // CASCADE, like every other reference in this family. That is the
+        // one-room scope decision made load-bearing: a membership naming a
+        // version this device does not hold fails at insert rather than landing
+        // as a row pointing at nothing. Projects that span rooms take those keys
+        // away again -- see Phase 9 of docs/project-feature.md -- and that is a
+        // migration rather than something to carry unused until then.
+        //
+        // The owners are a comma-joined sorted string on the project row rather
+        // than a fourth table, which is what DkgSession.participantPublicKeys
+        // already does with a set of keys and for the same reason.
+        AutoMigration(from = 20, to = 21),
     ]
 )
 @ColumnTypeConverters(MantraConverters::class)
@@ -368,6 +393,12 @@ abstract class MantraDatabase: RoomDatabase() {
 
     abstract fun mantraDialectDao(): MantraDialectDao
 
+    abstract fun mantraProjectDao(): MantraProjectDao
+
+    abstract fun mantraProjectArtifactVersionDao(): MantraProjectArtifactVersionDao
+
+    abstract fun mantraProjectTranslationArtifactVersionDao(): MantraProjectTranslationArtifactVersionDao
+
     abstract fun mantraTranslationArtifactVersionDao(): MantraTranslationArtifactVersionDao
 
     abstract fun mantraTranslationArtifactVersionContributorDao(): MantraTranslationArtifactVersionContributorDao

composeApp/src/commonMain/kotlin/press/mantra/compose/database/dao/MantraProjectArtifactVersionDao.kt

@@ -0,0 +1,47 @@
+package press.mantra.compose.database.dao
+
+import androidx.room3.Dao
+import androidx.room3.Query
+import androidx.room3.Upsert
+import press.mantra.compose.database.model.MantraArtifactVersion
+import press.mantra.compose.database.model.MantraProject
+import press.mantra.compose.database.model.MantraProjectArtifactVersion
+
+@Dao
+interface MantraProjectArtifactVersionDao {
+    @Upsert
+    suspend fun upsert(mantraProjectArtifactVersion: MantraProjectArtifactVersion)
+
+    @Query("SELECT * FROM MantraProjectArtifactVersion WHERE projectId = :projectId")
+    suspend fun getByProjectId(projectId: String): List<MantraProjectArtifactVersion>
+
+    @Query("SELECT * FROM MantraProjectArtifactVersion WHERE id = :id")
+    suspend fun getById(id: String): MantraProjectArtifactVersion?
+
+    /**
+     * The versions themselves, resolved here rather than by the caller.
+     *
+     * No screen wants a join row, and resolving it in one indexed query beats an
+     * N+1 in a view model.
+     */
+    @Query(
+        """
+        SELECT v.* FROM MantraArtifactVersion v
+        INNER JOIN MantraProjectArtifactVersion m ON m.artifactVersionId = v.id
+        WHERE m.projectId = :projectId
+        ORDER BY v.versionLabel
+        """
+    )
+    suspend fun getArtifactVersionsByProjectId(projectId: String): List<MantraArtifactVersion>
+
+    /** The inverse: which projects a version is part of. */
+    @Query(
+        """
+        SELECT p.* FROM MantraProject p
+        INNER JOIN MantraProjectArtifactVersion m ON m.projectId = p.id
+        WHERE m.artifactVersionId = :artifactVersionId
+        ORDER BY p.name
+        """
+    )
+    suspend fun getProjectsByArtifactVersionId(artifactVersionId: String): List<MantraProject>
+}

composeApp/src/commonMain/kotlin/press/mantra/compose/database/dao/MantraProjectDao.kt

@@ -0,0 +1,18 @@
+package press.mantra.compose.database.dao
+
+import androidx.room3.Dao
+import androidx.room3.Query
+import androidx.room3.Upsert
+import press.mantra.compose.database.model.MantraProject
+
+@Dao
+interface MantraProjectDao {
+    @Upsert
+    suspend fun upsert(mantraProject: MantraProject)
+
+    @Query("SELECT * FROM MantraProject WHERE chatRoomId = :chatRoomId ORDER BY name")
+    suspend fun getProjectsByChatRoomId(chatRoomId: String): List<MantraProject>
+
+    @Query("SELECT * FROM MantraProject WHERE id = :id")
+    suspend fun getProjectById(id: String): MantraProject?
+}

composeApp/src/commonMain/kotlin/press/mantra/compose/database/dao/MantraProjectTranslationArtifactVersionDao.kt

@@ -0,0 +1,49 @@
+package press.mantra.compose.database.dao
+
+import androidx.room3.Dao
+import androidx.room3.Query
+import androidx.room3.Upsert
+import press.mantra.compose.database.model.MantraProject
+import press.mantra.compose.database.model.MantraProjectTranslationArtifactVersion
+import press.mantra.compose.database.model.MantraTranslationArtifactVersion
+
+@Dao
+interface MantraProjectTranslationArtifactVersionDao {
+    @Upsert
+    suspend fun upsert(
+        mantraProjectTranslationArtifactVersion: MantraProjectTranslationArtifactVersion
+    )
+
+    @Query("SELECT * FROM MantraProjectTranslationArtifactVersion WHERE projectId = :projectId")
+    suspend fun getByProjectId(projectId: String): List<MantraProjectTranslationArtifactVersion>
+
+    @Query("SELECT * FROM MantraProjectTranslationArtifactVersion WHERE id = :id")
+    suspend fun getById(id: String): MantraProjectTranslationArtifactVersion?
+
+    /** The translations themselves. See the sibling DAO's note. */
+    @Query(
+        """
+        SELECT t.* FROM MantraTranslationArtifactVersion t
+        INNER JOIN MantraProjectTranslationArtifactVersion m
+            ON m.translationArtifactVersionId = t.id
+        WHERE m.projectId = :projectId
+        ORDER BY t.name
+        """
+    )
+    suspend fun getTranslationArtifactVersionsByProjectId(
+        projectId: String
+    ): List<MantraTranslationArtifactVersion>
+
+    /** The inverse: which projects a translation is part of. */
+    @Query(
+        """
+        SELECT p.* FROM MantraProject p
+        INNER JOIN MantraProjectTranslationArtifactVersion m ON m.projectId = p.id
+        WHERE m.translationArtifactVersionId = :translationArtifactVersionId
+        ORDER BY p.name
+        """
+    )
+    suspend fun getProjectsByTranslationArtifactVersionId(
+        translationArtifactVersionId: String
+    ): List<MantraProject>
+}

composeApp/src/commonMain/kotlin/press/mantra/compose/database/model/MantraProject.kt

@@ -0,0 +1,165 @@
+package press.mantra.compose.database.model
+
+import androidx.room3.Entity
+import androidx.room3.ForeignKey
+import androidx.room3.Index
+import androidx.room3.PrimaryKey
+import com.vitorpamplona.quartz.nip01Core.core.HexKey
+import com.vitorpamplona.quartz.nip01Core.crypto.EventHasher
+import com.vitorpamplona.quartz.nip01Core.signers.EventTemplate
+import press.mantra.compose.database.model.traits.OptionalNostrEventEntity
+import press.mantra.compose.database.model.traits.TimestampedEntity
+import press.mantra.compose.nostr.nip30303.ProjectEvent
+import kotlin.time.Clock
+import kotlin.time.Instant
+
+/**
+ * 30330
+ *
+ * No `toProjectEvent()`, deliberately. The eight `toXEvent()` methods exist to
+ * rebuild events for a chronicle in rooms whose work predates `GroupSignedEvent`
+ * (schema v13); they are deprecated and there is a removal checklist in
+ * docs/member-chronicle.md. Projects arrive at v21, so every project this app
+ * will ever hold is on file as a signed event and `signedEventsOf` finds it. A
+ * rebuild here would be adding to a mechanism being retired, to serve rows that
+ * cannot exist.
+ */
+@Entity(
+    foreignKeys = [
+        ForeignKey(
+            entity = ChatRoom::class,
+            parentColumns = ["id"],
+            childColumns = ["chatRoomId"],
+            onDelete = ForeignKey.CASCADE,
+        ),
+    ],
+    indices = [
+        Index("chatRoomId"),
+    ],
+)
+data class MantraProject(
+    @PrimaryKey
+    val id: HexKey,
+
+    /** The room's own key on a group-signed row, which is every project. */
+    val publicKey: HexKey,
+
+    val name: String,
+    val description: String,
+
+    /**
+     * Who started it, off the event's `creator` tag.
+     *
+     * Never the submitter, and never filled in from what this device happens to
+     * know: the point of the tag is that it is inside the id the quorum signed,
+     * and a column that could disagree with it would be worth less than no
+     * column. It is the group's claim about whose work this is rather than proof
+     * -- the creator signs nothing, the room does -- and the fact about who
+     * actually acted is on the `FrostSigningSession`.
+     */
+    val creatorPublicKey: HexKey,
+
+    /**
+     * Who it belongs to: the owner contributor tags, comma-joined and sorted.
+     * Read it through [ownerPublicKeySet].
+     *
+     * One column rather than a join table, following
+     * `DkgSession.participantPublicKeys` -- including the sort, which is there so
+     * two devices that assembled the set in different orders store the same
+     * string. A table would buy querying by owner, which no screen does.
+     *
+     * Never empty: `ProjectEvent.build` refuses an empty set and
+     * [fromProjectEvent] refuses an event with no owners.
+     */
+    val ownerPublicKeys: String,
+
+    val chatRoomId: String,
+
+    /** Signature will be an empty string if this is a rumor */
+    val signature: String,
+
+    val relayHint: String? = null,
+    val marmotGroupEventId: HexKey? = null,
+
+    /** The [GroupSignedEvent] this row was made from, when the group signed it. */
+    val groupSignedEventId: HexKey? = null,
+
+    /** Related nostrEventId if this is not a rumor... */
+    override val nostrEventId: HexKey? = null,
+
+    override val createdAt: Instant = Clock.System.now(),
+    override val updatedAt: Instant = createdAt
+): OptionalNostrEventEntity, TimestampedEntity {
+
+    /** The owners as the set they are. Empty only on a row written around this. */
+    fun ownerPublicKeySet(): Set<HexKey> = ownerPublicKeys
+        .split(",")
+        .mapNotNull { key -> key.trim().takeIf { it.isNotEmpty() } }
+        .toSet()
+
+    /** Whether [publicKey] owns this, for a screen deciding what to say. */
+    fun isOwnedBy(publicKey: HexKey) = publicKey in ownerPublicKeySet()
+
+    companion object {
+        fun fromProjectEventTemplate(
+            projectEventTemplate: EventTemplate<ProjectEvent>,
+            chatRoomId: HexKey,
+            userPublicKey: HexKey,
+        ): MantraProject? {
+            return fromProjectEvent(
+                ProjectEvent(
+                    id = EventHasher.hashId(
+                        pubKey = userPublicKey,
+                        tags = projectEventTemplate.tags,
+                        content = projectEventTemplate.content,
+                        createdAt = projectEventTemplate.createdAt,
+                        kind = projectEventTemplate.kind,
+                    ),
+                    content = projectEventTemplate.content,
+                    tags = projectEventTemplate.tags,
+                    createdAt = projectEventTemplate.createdAt,
+                    pubKey = userPublicKey,
+                    sig = "", // Unsigned rumor
+                ),
+                chatRoomId = chatRoomId,
+            )
+        }
+
+        /**
+         * Null for an event missing anything it was built to carry.
+         *
+         * The name, the creator and at least one owner are all required, and an
+         * event without one of them has either been truncated or is not what it
+         * claims. Filling the gap from local knowledge is exactly the failure the
+         * tags exist to prevent, so this refuses instead.
+         *
+         * An empty owner list is also what `ContributorTag.ROLE_OWNER` missing
+         * from that tag's known roles looks like from here -- the role parses as
+         * null and every owner disappears -- so refusing is the alarm for that
+         * bug as well as the guard against a malformed event.
+         */
+        fun fromProjectEvent(
+            projectEvent: ProjectEvent,
+            chatRoomId: HexKey,
+        ): MantraProject? {
+            val name = projectEvent.name() ?: return null
+            val creatorPublicKey = projectEvent.creator() ?: return null
+            val owners = projectEvent.owners().takeIf { it.isNotEmpty() } ?: return null
+
+            return MantraProject(
+                id = projectEvent.id,
+                publicKey = projectEvent.pubKey,
+                name = name,
+                description = projectEvent.content,
+                creatorPublicKey = creatorPublicKey,
+                // Sorted here as well as in the event. The event's order is what
+                // the signature covers; this is so two rows built from the same
+                // owners compare equal whatever order they arrived in.
+                ownerPublicKeys = owners.toSortedSet().joinToString(","),
+                chatRoomId = chatRoomId,
+                signature = projectEvent.sig,
+                createdAt = Instant.fromEpochSeconds(projectEvent.createdAt),
+            )
+        }
+    }
+}

composeApp/src/commonMain/kotlin/press/mantra/compose/database/model/MantraProjectArtifactVersion.kt

@@ -0,0 +1,125 @@
+package press.mantra.compose.database.model
+
+import androidx.room3.Entity
+import androidx.room3.ForeignKey
+import androidx.room3.Index
+import androidx.room3.PrimaryKey
+import com.vitorpamplona.quartz.nip01Core.core.HexKey
+import com.vitorpamplona.quartz.nip01Core.crypto.EventHasher
+import com.vitorpamplona.quartz.nip01Core.signers.EventTemplate
+import press.mantra.compose.database.model.traits.OptionalNostrEventEntity
+import press.mantra.compose.database.model.traits.TimestampedEntity
+import press.mantra.compose.nostr.nip30303.ProjectArtifactVersionEvent
+import kotlin.time.Clock
+import kotlin.time.Instant
+
+/**
+ * 30331 -- one source version is part of one project.
+ *
+ * Both references are real foreign keys, which is the whole of the
+ * one-room scope decision: a proposal naming a version this room does not hold
+ * fails loudly at apply time rather than landing as a row pointing at nothing.
+ * Cross-room projects are Phase 9 of docs/project-feature.md and start by taking
+ * these away, following `parentChatRoomId`'s precedent -- a plain column, never a
+ * foreign key, because a dangling value is the normal state there.
+ */
+@Entity(
+    foreignKeys = [
+        ForeignKey(
+            entity = MantraProject::class,
+            parentColumns = ["id"],
+            childColumns = ["projectId"],
+            onDelete = ForeignKey.CASCADE,
+        ),
+        ForeignKey(
+            entity = MantraArtifactVersion::class,
+            parentColumns = ["id"],
+            childColumns = ["artifactVersionId"],
+            onDelete = ForeignKey.CASCADE,
+        ),
+        ForeignKey(
+            entity = ChatRoom::class,
+            parentColumns = ["id"],
+            childColumns = ["chatRoomId"],
+            onDelete = ForeignKey.CASCADE,
+        ),
+    ],
+    indices = [
+        // Every read of this table is "this project's contents".
+        Index("projectId"),
+        // And the inverse, for an artifact version saying which projects it is in.
+        Index("artifactVersionId"),
+        Index("chatRoomId"),
+    ],
+)
+data class MantraProjectArtifactVersion(
+    @PrimaryKey
+    val id: HexKey,
+    val publicKey: HexKey,
+
+    val projectId: HexKey,
+    val artifactVersionId: HexKey,
+
+    val chatRoomId: String,
+
+    /** Signature will be an empty string if this is a rumor */
+    val signature: String,
+
+    val relayHint: String? = null,
+    val marmotGroupEventId: HexKey? = null,
+
+    /** The [GroupSignedEvent] this row was made from, when the group signed it. */
+    val groupSignedEventId: HexKey? = null,
+
+    /** Related nostrEventId if this is not a rumor... */
+    override val nostrEventId: HexKey? = null,
+
+    override val createdAt: Instant = Clock.System.now(),
+    override val updatedAt: Instant = createdAt
+): OptionalNostrEventEntity, TimestampedEntity {
+
+    companion object {
+        fun fromProjectArtifactVersionEventTemplate(
+            projectArtifactVersionEventTemplate: EventTemplate<ProjectArtifactVersionEvent>,
+            chatRoomId: HexKey,
+            userPublicKey: HexKey,
+        ): MantraProjectArtifactVersion? {
+            return fromProjectArtifactVersionEvent(
+                ProjectArtifactVersionEvent(
+                    id = EventHasher.hashId(
+                        pubKey = userPublicKey,
+                        tags = projectArtifactVersionEventTemplate.tags,
+                        content = projectArtifactVersionEventTemplate.content,
+                        createdAt = projectArtifactVersionEventTemplate.createdAt,
+                        kind = projectArtifactVersionEventTemplate.kind,
+                    ),
+                    content = projectArtifactVersionEventTemplate.content,
+                    tags = projectArtifactVersionEventTemplate.tags,
+                    createdAt = projectArtifactVersionEventTemplate.createdAt,
+                    pubKey = userPublicKey,
+                    sig = "", // Unsigned rumor
+                ),
+                chatRoomId = chatRoomId,
+            )
+        }
+
+        fun fromProjectArtifactVersionEvent(
+            projectArtifactVersionEvent: ProjectArtifactVersionEvent,
+            chatRoomId: HexKey,
+        ): MantraProjectArtifactVersion? {
+            val projectId = projectArtifactVersionEvent.projectId() ?: return null
+            val artifactVersionId =
+                projectArtifactVersionEvent.artifactVersionId() ?: return null
+
+            return MantraProjectArtifactVersion(
+                id = projectArtifactVersionEvent.id,
+                publicKey = projectArtifactVersionEvent.pubKey,
+                projectId = projectId,
+                artifactVersionId = artifactVersionId,
+                chatRoomId = chatRoomId,
+                signature = projectArtifactVersionEvent.sig,
+                createdAt = Instant.fromEpochSeconds(projectArtifactVersionEvent.createdAt),
+            )
+        }
+    }
+}

composeApp/src/commonMain/kotlin/press/mantra/compose/database/model/MantraProjectTranslationArtifactVersion.kt

@@ -0,0 +1,123 @@
+package press.mantra.compose.database.model
+
+import androidx.room3.Entity
+import androidx.room3.ForeignKey
+import androidx.room3.Index
+import androidx.room3.PrimaryKey
+import com.vitorpamplona.quartz.nip01Core.core.HexKey
+import com.vitorpamplona.quartz.nip01Core.crypto.EventHasher
+import com.vitorpamplona.quartz.nip01Core.signers.EventTemplate
+import press.mantra.compose.database.model.traits.OptionalNostrEventEntity
+import press.mantra.compose.database.model.traits.TimestampedEntity
+import press.mantra.compose.nostr.nip30303.ProjectTranslationArtifactVersionEvent
+import kotlin.time.Clock
+import kotlin.time.Instant
+
+/**
+ * 30332 -- one translation is part of one project.
+ *
+ * The other half of [MantraProjectArtifactVersion]; see there for why both
+ * references are real foreign keys.
+ */
+@Entity(
+    foreignKeys = [
+        ForeignKey(
+            entity = MantraProject::class,
+            parentColumns = ["id"],
+            childColumns = ["projectId"],
+            onDelete = ForeignKey.CASCADE,
+        ),
+        ForeignKey(
+            entity = MantraTranslationArtifactVersion::class,
+            parentColumns = ["id"],
+            childColumns = ["translationArtifactVersionId"],
+            onDelete = ForeignKey.CASCADE,
+        ),
+        ForeignKey(
+            entity = ChatRoom::class,
+            parentColumns = ["id"],
+            childColumns = ["chatRoomId"],
+            onDelete = ForeignKey.CASCADE,
+        ),
+    ],
+    indices = [
+        Index("projectId"),
+        Index("translationArtifactVersionId"),
+        Index("chatRoomId"),
+    ],
+)
+data class MantraProjectTranslationArtifactVersion(
+    @PrimaryKey
+    val id: HexKey,
+    val publicKey: HexKey,
+
+    val projectId: HexKey,
+    val translationArtifactVersionId: HexKey,
+
+    val chatRoomId: String,
+
+    /** Signature will be an empty string if this is a rumor */
+    val signature: String,
+
+    val relayHint: String? = null,
+    val marmotGroupEventId: HexKey? = null,
+
+    /** The [GroupSignedEvent] this row was made from, when the group signed it. */
+    val groupSignedEventId: HexKey? = null,
+
+    /** Related nostrEventId if this is not a rumor... */
+    override val nostrEventId: HexKey? = null,
+
+    override val createdAt: Instant = Clock.System.now(),
+    override val updatedAt: Instant = createdAt
+): OptionalNostrEventEntity, TimestampedEntity {
+
+    companion object {
+        fun fromProjectTranslationArtifactVersionEventTemplate(
+            template: EventTemplate<ProjectTranslationArtifactVersionEvent>,
+            chatRoomId: HexKey,
+            userPublicKey: HexKey,
+        ): MantraProjectTranslationArtifactVersion? {
+            return fromProjectTranslationArtifactVersionEvent(
+                ProjectTranslationArtifactVersionEvent(
+                    id = EventHasher.hashId(
+                        pubKey = userPublicKey,
+                        tags = template.tags,
+                        content = template.content,
+                        createdAt = template.createdAt,
+                        kind = template.kind,
+                    ),
+                    content = template.content,
+                    tags = template.tags,
+                    createdAt = template.createdAt,
+                    pubKey = userPublicKey,
+                    sig = "", // Unsigned rumor
+                ),
+                chatRoomId = chatRoomId,
+            )
+        }
+
+        fun fromProjectTranslationArtifactVersionEvent(
+            projectTranslationArtifactVersionEvent: ProjectTranslationArtifactVersionEvent,
+            chatRoomId: HexKey,
+        ): MantraProjectTranslationArtifactVersion? {
+            val projectId =
+                projectTranslationArtifactVersionEvent.projectId() ?: return null
+            val translationArtifactVersionId =
+                projectTranslationArtifactVersionEvent.translationArtifactVersionId()
+                    ?: return null
+
+            return MantraProjectTranslationArtifactVersion(
+                id = projectTranslationArtifactVersionEvent.id,
+                publicKey = projectTranslationArtifactVersionEvent.pubKey,
+                projectId = projectId,
+                translationArtifactVersionId = translationArtifactVersionId,
+                chatRoomId = chatRoomId,
+                signature = projectTranslationArtifactVersionEvent.sig,
+                createdAt = Instant.fromEpochSeconds(
+                    projectTranslationArtifactVersionEvent.createdAt
+                ),
+            )
+        }
+    }
+}