release(v4.6.0): broadcast channels — Signal sender-keys for one-to-many fan-out

Lands the broadcast-channel primitive Prism asked for in
Docs/shade-feature-request-sender-keys.md. The crypto in
@shade/core/sender-keys.ts was already in place; this release wires
it up as a first-class app-facing API, adds the persistence schema
across all six storage backends (memory, sqlite, indexeddb +
encrypted variants), introduces wire type 0x21 in @shade/proto,
and ships Prism's three acceptance tests verbatim.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

packages/shade-storage-encrypted/src/crypto/row-codec.ts

@@ -39,6 +39,7 @@ export const COL = {
   trustedIdentity: 'trusted_identity',
   retiredIdentity: 'retired_identity',
   streamSensitive: 'stream_sensitive',
+  broadcastChannelSensitive: 'broadcast_channel_sensitive',
 } as const;
 
 /** Logical table identifiers — used for fieldKey + AAD binding. */
@@ -51,6 +52,7 @@ export const TBL = {
   trustedIdentities: 'trusted_identities',
   retiredIdentities: 'retired_identities',
   streamState: 'stream_state',
+  broadcastChannels: 'broadcast_channels',
 } as const;
 
 /** Encrypt an arbitrary string payload bound to (table, column, pk). */
@@ -226,3 +228,76 @@ export async function openStreamSensitive(
   if (b.overallHashState !== undefined) (out as { overallHashState?: string }).overallHashState = b.overallHashState;
   return out;
 }
+
+/**
+ * Broadcast-channel sensitive bundle (V4.6). Routing fields (channelId,
+ * ownerRole, ownerAddress, label, generation, createdAt, updatedAt) live
+ * in plaintext columns so backends can list/query without unsealing every
+ * row; the chain key, iteration, and signing keys all live in this sealed
+ * blob.
+ */
+interface BroadcastChannelSensitiveBundle {
+  chainKey: string;             // base64(32B)
+  iteration: number;
+  signingPublicKey: string;     // base64(32B)
+  signingPrivateKey?: string;   // base64; only when ownerRole === 'sender'
+}
+
+export async function sealBroadcastChannelSensitive(
+  km: KeyManager,
+  channelId: string,
+  s: {
+    chainKey: Uint8Array;
+    iteration: number;
+    signingPublicKey: Uint8Array;
+    signingPrivateKey?: Uint8Array;
+  },
+): Promise<Uint8Array> {
+  const bundle: BroadcastChannelSensitiveBundle = {
+    chainKey: toBase64(s.chainKey),
+    iteration: s.iteration,
+    signingPublicKey: toBase64(s.signingPublicKey),
+  };
+  if (s.signingPrivateKey !== undefined) {
+    bundle.signingPrivateKey = toBase64(s.signingPrivateKey);
+  }
+  return sealString(
+    km,
+    TBL.broadcastChannels,
+    COL.broadcastChannelSensitive,
+    channelId,
+    JSON.stringify(bundle),
+  );
+}
+
+export async function openBroadcastChannelSensitive(
+  km: KeyManager,
+  channelId: string,
+  blob: Uint8Array,
+): Promise<{
+  chainKey: Uint8Array;
+  iteration: number;
+  signingPublicKey: Uint8Array;
+  signingPrivateKey?: Uint8Array;
+}> {
+  const json = await openString(
+    km,
+    TBL.broadcastChannels,
+    COL.broadcastChannelSensitive,
+    channelId,
+    blob,
+  );
+  const b = JSON.parse(json) as BroadcastChannelSensitiveBundle;
+  const out: {
+    chainKey: Uint8Array;
+    iteration: number;
+    signingPublicKey: Uint8Array;
+    signingPrivateKey?: Uint8Array;
+  } = {
+    chainKey: fromBase64(b.chainKey),
+    iteration: b.iteration,
+    signingPublicKey: fromBase64(b.signingPublicKey),
+  };
+  if (b.signingPrivateKey !== undefined) out.signingPrivateKey = fromBase64(b.signingPrivateKey);
+  return out;
+}

packages/shade-storage-encrypted/src/storage/encrypted-indexeddb.ts

@@ -1,5 +1,7 @@
 import { openDB, type IDBPDatabase, type DBSchema } from 'idb';
 import type {
+  BroadcastChannelRecord,
+  BroadcastMemberRecord,
   IdentityKeyPair,
   OneTimePreKey,
   PeerVerification,
@@ -13,10 +15,10 @@ import type {
 import { constantTimeEqual, toBase64 } from '@shade/core';
 import { KeyManager } from '../crypto/key-manager.js';
 import {
-  openConfig, openIdentity, openOneTimePreKey, openRetired, openSession,
-  openSignedPreKey, openStreamSensitive, openTrust, sealConfig, sealIdentity,
-  sealOneTimePreKey, sealRetired, sealSession, sealSignedPreKey,
-  sealStreamSensitive, sealTrust,
+  openBroadcastChannelSensitive, openConfig, openIdentity, openOneTimePreKey,
+  openRetired, openSession, openSignedPreKey, openStreamSensitive, openTrust,
+  sealBroadcastChannelSensitive, sealConfig, sealIdentity, sealOneTimePreKey,
+  sealRetired, sealSession, sealSignedPreKey, sealStreamSensitive, sealTrust,
 } from '../crypto/row-codec.js';
 
 /**
@@ -91,6 +93,13 @@ export class EncryptedIndexedDBStorage implements StorageProvider {
           db.createObjectStore('peer_verifications_enc', { keyPath: 'peerAddress' });
           db.createObjectStore('peer_identity_versions_enc', { keyPath: 'peerAddress' });
         }
+        if (oldVersion < 2) {
+          db.createObjectStore('broadcast_channels_enc', { keyPath: 'channelId' });
+          const members = db.createObjectStore('broadcast_members_enc', {
+            keyPath: ['channelId', 'peerAddress'],
+          });
+          members.createIndex('byChannelId', 'channelId');
+        }
       },
     });
     const store = new EncryptedIndexedDBStorage(db, opts.keyManager);
@@ -341,6 +350,99 @@ export class EncryptedIndexedDBStorage implements StorageProvider {
     return next;
   }
 
+  // ─── Broadcast channels (V4.6) ────────────────────────────
+
+  async saveBroadcastChannel(channel: BroadcastChannelRecord): Promise<void> {
+    const sealed = await sealBroadcastChannelSensitive(this.km, channel.channelId, {
+      chainKey: channel.chainKey,
+      iteration: channel.iteration,
+      signingPublicKey: channel.signingPublicKey,
+      ...(channel.signingPrivateKey !== undefined ? { signingPrivateKey: channel.signingPrivateKey } : {}),
+    });
+    await this.db.put('broadcast_channels_enc', {
+      channelId: channel.channelId,
+      ownerRole: channel.ownerRole,
+      ownerAddress: channel.ownerAddress,
+      label: channel.label ?? null,
+      generation: channel.generation,
+      ciphertext: sealed,
+      createdAt: channel.createdAt,
+      updatedAt: channel.updatedAt,
+    });
+  }
+
+  async getBroadcastChannel(channelId: string): Promise<BroadcastChannelRecord | null> {
+    const row = await this.db.get('broadcast_channels_enc', channelId);
+    if (!row) return null;
+    return this.encRowToChannel(row);
+  }
+
+  async listBroadcastChannels(): Promise<BroadcastChannelRecord[]> {
+    const rows = await this.db.getAll('broadcast_channels_enc');
+    rows.sort((a, b) => a.createdAt - b.createdAt);
+    return Promise.all(rows.map((r) => this.encRowToChannel(r)));
+  }
+
+  async removeBroadcastChannel(channelId: string): Promise<void> {
+    const tx = this.db.transaction(
+      ['broadcast_channels_enc', 'broadcast_members_enc'],
+      'readwrite',
+    );
+    const memIdx = tx.objectStore('broadcast_members_enc').index('byChannelId');
+    let cursor = await memIdx.openCursor(IDBKeyRange.only(channelId));
+    while (cursor) {
+      await cursor.delete();
+      cursor = await cursor.continue();
+    }
+    await tx.objectStore('broadcast_channels_enc').delete(channelId);
+    await tx.done;
+  }
+
+  async saveBroadcastMember(member: BroadcastMemberRecord): Promise<void> {
+    await this.db.put('broadcast_members_enc', { ...member });
+  }
+
+  async getBroadcastMembers(channelId: string): Promise<BroadcastMemberRecord[]> {
+    const rows = await this.db.getAllFromIndex(
+      'broadcast_members_enc',
+      'byChannelId',
+      IDBKeyRange.only(channelId),
+    );
+    rows.sort((a, b) => a.joinedAt - b.joinedAt);
+    return rows.map((r) => ({
+      channelId: r.channelId,
+      peerAddress: r.peerAddress,
+      joinedAt: r.joinedAt,
+      removedAt: r.removedAt,
+    }));
+  }
+
+  async removeBroadcastMember(channelId: string, peerAddress: string): Promise<void> {
+    await this.db.delete('broadcast_members_enc', [channelId, peerAddress]);
+  }
+
+  private async encRowToChannel(row: BroadcastChannelEncRow): Promise<BroadcastChannelRecord> {
+    const sensitive = await openBroadcastChannelSensitive(
+      this.km,
+      row.channelId,
+      row.ciphertext,
+    );
+    const out: BroadcastChannelRecord = {
+      channelId: row.channelId,
+      ownerRole: row.ownerRole,
+      ownerAddress: row.ownerAddress,
+      generation: row.generation,
+      chainKey: sensitive.chainKey,
+      iteration: sensitive.iteration,
+      signingPublicKey: sensitive.signingPublicKey,
+      createdAt: row.createdAt,
+      updatedAt: row.updatedAt,
+    };
+    if (row.label !== null) out.label = row.label;
+    if (sensitive.signingPrivateKey !== undefined) out.signingPrivateKey = sensitive.signingPrivateKey;
+    return out;
+  }
+
   private async rowToStreamState(row: StreamStateEncRow): Promise<PersistedStreamState> {
     const sensitive = await openStreamSensitive(this.km, row.streamId, row.ciphertext);
     const out: PersistedStreamState = {
@@ -364,7 +466,7 @@ export class EncryptedIndexedDBStorage implements StorageProvider {
 
 // ─── Schema ────────────────────────────────────────────────
 
-const SCHEMA_VERSION = 1;
+const SCHEMA_VERSION = 2;
 
 interface MetaRow { key: string; value: string }
 interface IdentityRow { id: 1; ciphertext: Uint8Array }
@@ -395,6 +497,24 @@ interface PeerVerificationRow {
 
 interface PeerIdentityVersionRow { peerAddress: string; version: number }
 
+interface BroadcastChannelEncRow {
+  channelId: string;
+  ownerRole: 'sender' | 'receiver';
+  ownerAddress: string;
+  label: string | null;
+  generation: number;
+  ciphertext: Uint8Array;
+  createdAt: number;
+  updatedAt: number;
+}
+
+interface BroadcastMemberEncRow {
+  channelId: string;
+  peerAddress: string;
+  joinedAt: number;
+  removedAt: number | null;
+}
+
 interface EncryptedShadeSchema extends DBSchema {
   meta_enc: { key: string; value: MetaRow };
   identity_enc: { key: number; value: IdentityRow };
@@ -419,4 +539,10 @@ interface EncryptedShadeSchema extends DBSchema {
   };
   peer_verifications_enc: { key: string; value: PeerVerificationRow };
   peer_identity_versions_enc: { key: string; value: PeerIdentityVersionRow };
+  broadcast_channels_enc: { key: string; value: BroadcastChannelEncRow };
+  broadcast_members_enc: {
+    key: [string, string];
+    value: BroadcastMemberEncRow;
+    indexes: { byChannelId: string };
+  };
 }

packages/shade-storage-encrypted/src/storage/encrypted-postgres.ts

@@ -1,6 +1,8 @@
 import type { Sql } from 'postgres';
 import postgres from 'postgres';
 import type {
+  BroadcastChannelRecord,
+  BroadcastMemberRecord,
   IdentityKeyPair,
   OneTimePreKey,
   PeerVerification,
@@ -14,10 +16,10 @@ import type {
 import { constantTimeEqual, toBase64 } from '@shade/core';
 import { KeyManager } from '../crypto/key-manager.js';
 import {
-  openConfig, openIdentity, openOneTimePreKey, openRetired, openSession,
-  openSignedPreKey, openStreamSensitive, openTrust, sealConfig, sealIdentity,
-  sealOneTimePreKey, sealRetired, sealSession, sealSignedPreKey,
-  sealStreamSensitive, sealTrust,
+  openBroadcastChannelSensitive, openConfig, openIdentity, openOneTimePreKey,
+  openRetired, openSession, openSignedPreKey, openStreamSensitive, openTrust,
+  sealBroadcastChannelSensitive, sealConfig, sealIdentity, sealOneTimePreKey,
+  sealRetired, sealSession, sealSignedPreKey, sealStreamSensitive, sealTrust,
 } from '../crypto/row-codec.js';
 
 /**
@@ -332,6 +334,108 @@ export class EncryptedPostgresStorage implements StorageProvider {
     return next;
   }
 
+  // ─── Broadcast channels (V4.6) ────────────────────────────
+
+  async saveBroadcastChannel(channel: BroadcastChannelRecord): Promise<void> {
+    const sealed = await sealBroadcastChannelSensitive(this.km, channel.channelId, {
+      chainKey: channel.chainKey,
+      iteration: channel.iteration,
+      signingPublicKey: channel.signingPublicKey,
+      ...(channel.signingPrivateKey !== undefined ? { signingPrivateKey: channel.signingPrivateKey } : {}),
+    });
+    await this.sql`
+      INSERT INTO shade_broadcast_channels_enc
+        (channel_id, owner_role, owner_address, label, generation, ciphertext, created_at, updated_at)
+      VALUES
+        (${channel.channelId}, ${channel.ownerRole}, ${channel.ownerAddress},
+         ${channel.label ?? null}, ${channel.generation}, ${sealed},
+         ${channel.createdAt}, ${channel.updatedAt})
+      ON CONFLICT (channel_id) DO UPDATE SET
+        owner_role    = EXCLUDED.owner_role,
+        owner_address = EXCLUDED.owner_address,
+        label         = EXCLUDED.label,
+        generation    = EXCLUDED.generation,
+        ciphertext    = EXCLUDED.ciphertext,
+        updated_at    = EXCLUDED.updated_at
+    `;
+  }
+
+  async getBroadcastChannel(channelId: string): Promise<BroadcastChannelRecord | null> {
+    const rows = await this.sql<Array<BroadcastChannelEncRow>>`
+      SELECT * FROM shade_broadcast_channels_enc WHERE channel_id = ${channelId}
+    `;
+    if (rows.length === 0) return null;
+    return this.encRowToChannel(rows[0]!);
+  }
+
+  async listBroadcastChannels(): Promise<BroadcastChannelRecord[]> {
+    const rows = await this.sql<Array<BroadcastChannelEncRow>>`
+      SELECT * FROM shade_broadcast_channels_enc ORDER BY created_at ASC
+    `;
+    return Promise.all(rows.map((r) => this.encRowToChannel(r)));
+  }
+
+  async removeBroadcastChannel(channelId: string): Promise<void> {
+    await this.sql`DELETE FROM shade_broadcast_members_enc WHERE channel_id = ${channelId}`;
+    await this.sql`DELETE FROM shade_broadcast_channels_enc WHERE channel_id = ${channelId}`;
+  }
+
+  async saveBroadcastMember(member: BroadcastMemberRecord): Promise<void> {
+    await this.sql`
+      INSERT INTO shade_broadcast_members_enc
+        (channel_id, peer_address, joined_at, removed_at)
+      VALUES
+        (${member.channelId}, ${member.peerAddress}, ${member.joinedAt}, ${member.removedAt})
+      ON CONFLICT (channel_id, peer_address) DO UPDATE SET
+        joined_at  = EXCLUDED.joined_at,
+        removed_at = EXCLUDED.removed_at
+    `;
+  }
+
+  async getBroadcastMembers(channelId: string): Promise<BroadcastMemberRecord[]> {
+    const rows = await this.sql<Array<{ channel_id: string; peer_address: string; joined_at: string | number; removed_at: string | number | null }>>`
+      SELECT channel_id, peer_address, joined_at, removed_at
+      FROM shade_broadcast_members_enc
+      WHERE channel_id = ${channelId}
+      ORDER BY joined_at ASC
+    `;
+    return rows.map((r) => ({
+      channelId: r.channel_id,
+      peerAddress: r.peer_address,
+      joinedAt: Number(r.joined_at),
+      removedAt: r.removed_at === null ? null : Number(r.removed_at),
+    }));
+  }
+
+  async removeBroadcastMember(channelId: string, peerAddress: string): Promise<void> {
+    await this.sql`
+      DELETE FROM shade_broadcast_members_enc
+      WHERE channel_id = ${channelId} AND peer_address = ${peerAddress}
+    `;
+  }
+
+  private async encRowToChannel(row: BroadcastChannelEncRow): Promise<BroadcastChannelRecord> {
+    const sensitive = await openBroadcastChannelSensitive(
+      this.km,
+      String(row.channel_id),
+      row.ciphertext,
+    );
+    const out: BroadcastChannelRecord = {
+      channelId: String(row.channel_id),
+      ownerRole: row.owner_role,
+      ownerAddress: String(row.owner_address),
+      generation: Number(row.generation),
+      chainKey: sensitive.chainKey,
+      iteration: sensitive.iteration,
+      signingPublicKey: sensitive.signingPublicKey,
+      createdAt: Number(row.created_at),
+      updatedAt: Number(row.updated_at),
+    };
+    if (row.label !== null && row.label !== undefined) out.label = row.label;
+    if (sensitive.signingPrivateKey !== undefined) out.signingPrivateKey = sensitive.signingPrivateKey;
+    return out;
+  }
+
   private async rowToStreamState(row: StreamRow): Promise<PersistedStreamState> {
     const sensitive = await openStreamSensitive(this.km, String(row.stream_id), row.ciphertext);
     const out: PersistedStreamState = {
@@ -363,6 +467,17 @@ interface StreamRow {
   updated_at: string | number;
 }
 
+interface BroadcastChannelEncRow {
+  channel_id: string;
+  owner_role: 'sender' | 'receiver';
+  owner_address: string;
+  label: string | null;
+  generation: string | number;
+  ciphertext: Uint8Array;
+  created_at: string | number;
+  updated_at: string | number;
+}
+
 export async function ensureEncryptedClientTables(sql: Sql): Promise<void> {
   await sql`
     CREATE TABLE IF NOT EXISTS shade_meta_enc (
@@ -454,4 +569,29 @@ export async function ensureEncryptedClientTables(sql: Sql): Promise<void> {
       version      BIGINT NOT NULL
     )
   `;
+  await sql`
+    CREATE TABLE IF NOT EXISTS shade_broadcast_channels_enc (
+      channel_id    TEXT PRIMARY KEY,
+      owner_role    TEXT NOT NULL CHECK (owner_role IN ('sender','receiver')),
+      owner_address TEXT NOT NULL,
+      label         TEXT,
+      generation    BIGINT NOT NULL,
+      ciphertext    BYTEA NOT NULL,
+      created_at    BIGINT NOT NULL,
+      updated_at    BIGINT NOT NULL
+    )
+  `;
+  await sql`
+    CREATE TABLE IF NOT EXISTS shade_broadcast_members_enc (
+      channel_id   TEXT NOT NULL,
+      peer_address TEXT NOT NULL,
+      joined_at    BIGINT NOT NULL,
+      removed_at   BIGINT,
+      PRIMARY KEY (channel_id, peer_address)
+    )
+  `;
+  await sql`
+    CREATE INDEX IF NOT EXISTS shade_broadcast_members_enc_channel_idx
+    ON shade_broadcast_members_enc(channel_id)
+  `;
 }

packages/shade-storage-encrypted/src/storage/encrypted-sqlite.ts

@@ -1,5 +1,7 @@
 import { Database } from 'bun:sqlite';
 import type {
+  BroadcastChannelRecord,
+  BroadcastMemberRecord,
   IdentityKeyPair,
   OneTimePreKey,
   PeerVerification,
@@ -13,10 +15,10 @@ import type {
 import { constantTimeEqual, toBase64 } from '@shade/core';
 import { KeyManager } from '../crypto/key-manager.js';
 import {
-  openConfig, openIdentity, openOneTimePreKey, openRetired, openSession,
-  openSignedPreKey, openStreamSensitive, openTrust, sealConfig, sealIdentity,
-  sealOneTimePreKey, sealRetired, sealSession, sealSignedPreKey,
-  sealStreamSensitive, sealTrust,
+  openBroadcastChannelSensitive, openConfig, openIdentity, openOneTimePreKey, openRetired,
+  openSession, openSignedPreKey, openStreamSensitive, openTrust,
+  sealBroadcastChannelSensitive, sealConfig, sealIdentity, sealOneTimePreKey,
+  sealRetired, sealSession, sealSignedPreKey, sealStreamSensitive, sealTrust,
 } from '../crypto/row-codec.js';
 
 /**
@@ -68,6 +70,14 @@ export class EncryptedSQLiteStorage implements StorageProvider {
     removePeerVerification:     ReturnType<Database['prepare']>;
     getPeerIdentityVersion:     ReturnType<Database['prepare']>;
     upsertPeerIdentityVersion:  ReturnType<Database['prepare']>;
+    saveBroadcastChannel:       ReturnType<Database['prepare']>;
+    getBroadcastChannel:        ReturnType<Database['prepare']>;
+    listBroadcastChannels:      ReturnType<Database['prepare']>;
+    removeBroadcastChannel:     ReturnType<Database['prepare']>;
+    removeBroadcastChannelMembers: ReturnType<Database['prepare']>;
+    saveBroadcastMember:        ReturnType<Database['prepare']>;
+    getBroadcastMembers:        ReturnType<Database['prepare']>;
+    removeBroadcastMember:      ReturnType<Database['prepare']>;
   };
 
   private constructor(db: Database, km: KeyManager, ownsDb: boolean) {
@@ -156,6 +166,24 @@ export class EncryptedSQLiteStorage implements StorageProvider {
         peer_address TEXT PRIMARY KEY,
         version      INTEGER NOT NULL
       );
+      CREATE TABLE IF NOT EXISTS broadcast_channels_enc (
+        channel_id    TEXT PRIMARY KEY,
+        owner_role    TEXT NOT NULL,
+        owner_address TEXT NOT NULL,
+        label         TEXT,
+        generation    INTEGER NOT NULL,
+        ciphertext    BLOB NOT NULL,
+        created_at    INTEGER NOT NULL,
+        updated_at    INTEGER NOT NULL
+      );
+      CREATE TABLE IF NOT EXISTS broadcast_members_enc (
+        channel_id   TEXT NOT NULL,
+        peer_address TEXT NOT NULL,
+        joined_at    INTEGER NOT NULL,
+        removed_at   INTEGER,
+        PRIMARY KEY (channel_id, peer_address)
+      );
+      CREATE INDEX IF NOT EXISTS idx_broadcast_members_enc_channel ON broadcast_members_enc(channel_id);
     `);
   }
 
@@ -212,6 +240,35 @@ export class EncryptedSQLiteStorage implements StorageProvider {
         `INSERT INTO peer_identity_versions_enc (peer_address, version) VALUES (?, ?)
          ON CONFLICT(peer_address) DO UPDATE SET version = excluded.version`,
       ),
+      saveBroadcastChannel: this.db.prepare(
+        `INSERT OR REPLACE INTO broadcast_channels_enc
+           (channel_id, owner_role, owner_address, label, generation,
+            ciphertext, created_at, updated_at)
+         VALUES (?, ?, ?, ?, ?, ?, ?, ?)`,
+      ),
+      getBroadcastChannel: this.db.prepare(
+        'SELECT * FROM broadcast_channels_enc WHERE channel_id = ?',
+      ),
+      listBroadcastChannels: this.db.prepare(
+        'SELECT * FROM broadcast_channels_enc ORDER BY created_at ASC',
+      ),
+      removeBroadcastChannel: this.db.prepare(
+        'DELETE FROM broadcast_channels_enc WHERE channel_id = ?',
+      ),
+      removeBroadcastChannelMembers: this.db.prepare(
+        'DELETE FROM broadcast_members_enc WHERE channel_id = ?',
+      ),
+      saveBroadcastMember: this.db.prepare(
+        `INSERT OR REPLACE INTO broadcast_members_enc
+           (channel_id, peer_address, joined_at, removed_at)
+         VALUES (?, ?, ?, ?)`,
+      ),
+      getBroadcastMembers: this.db.prepare(
+        'SELECT channel_id, peer_address, joined_at, removed_at FROM broadcast_members_enc WHERE channel_id = ? ORDER BY joined_at ASC',
+      ),
+      removeBroadcastMember: this.db.prepare(
+        'DELETE FROM broadcast_members_enc WHERE channel_id = ? AND peer_address = ?',
+      ),
     };
   }
 
@@ -432,6 +489,88 @@ export class EncryptedSQLiteStorage implements StorageProvider {
     return next;
   }
 
+  // ─── Broadcast channels (V4.6) ────────────────────────────
+
+  async saveBroadcastChannel(channel: BroadcastChannelRecord): Promise<void> {
+    const sealed = await sealBroadcastChannelSensitive(this.km, channel.channelId, {
+      chainKey: channel.chainKey,
+      iteration: channel.iteration,
+      signingPublicKey: channel.signingPublicKey,
+      ...(channel.signingPrivateKey !== undefined ? { signingPrivateKey: channel.signingPrivateKey } : {}),
+    });
+    this.stmts.saveBroadcastChannel.run(
+      channel.channelId,
+      channel.ownerRole,
+      channel.ownerAddress,
+      channel.label ?? null,
+      channel.generation,
+      sealed,
+      channel.createdAt,
+      channel.updatedAt,
+    );
+  }
+
+  async getBroadcastChannel(channelId: string): Promise<BroadcastChannelRecord | null> {
+    const row = this.stmts.getBroadcastChannel.get(channelId) as BroadcastChannelEncRow | undefined;
+    if (!row) return null;
+    return this.encRowToChannel(row);
+  }
+
+  async listBroadcastChannels(): Promise<BroadcastChannelRecord[]> {
+    const rows = this.stmts.listBroadcastChannels.all() as BroadcastChannelEncRow[];
+    return Promise.all(rows.map((r) => this.encRowToChannel(r)));
+  }
+
+  async removeBroadcastChannel(channelId: string): Promise<void> {
+    this.stmts.removeBroadcastChannelMembers.run(channelId);
+    this.stmts.removeBroadcastChannel.run(channelId);
+  }
+
+  async saveBroadcastMember(member: BroadcastMemberRecord): Promise<void> {
+    this.stmts.saveBroadcastMember.run(
+      member.channelId,
+      member.peerAddress,
+      member.joinedAt,
+      member.removedAt,
+    );
+  }
+
+  async getBroadcastMembers(channelId: string): Promise<BroadcastMemberRecord[]> {
+    const rows = this.stmts.getBroadcastMembers.all(channelId) as BroadcastMemberEncRow[];
+    return rows.map((r) => ({
+      channelId: r.channel_id,
+      peerAddress: r.peer_address,
+      joinedAt: Number(r.joined_at),
+      removedAt: r.removed_at === null || r.removed_at === undefined ? null : Number(r.removed_at),
+    }));
+  }
+
+  async removeBroadcastMember(channelId: string, peerAddress: string): Promise<void> {
+    this.stmts.removeBroadcastMember.run(channelId, peerAddress);
+  }
+
+  private async encRowToChannel(row: BroadcastChannelEncRow): Promise<BroadcastChannelRecord> {
+    const sensitive = await openBroadcastChannelSensitive(
+      this.km,
+      row.channel_id,
+      toBytes(row.ciphertext),
+    );
+    const out: BroadcastChannelRecord = {
+      channelId: row.channel_id,
+      ownerRole: row.owner_role,
+      ownerAddress: row.owner_address,
+      generation: Number(row.generation),
+      chainKey: sensitive.chainKey,
+      iteration: sensitive.iteration,
+      signingPublicKey: sensitive.signingPublicKey,
+      createdAt: Number(row.created_at),
+      updatedAt: Number(row.updated_at),
+    };
+    if (row.label !== null && row.label !== undefined) out.label = row.label;
+    if (sensitive.signingPrivateKey !== undefined) out.signingPrivateKey = sensitive.signingPrivateKey;
+    return out;
+  }
+
   private async rowToStreamState(row: StreamRow): Promise<PersistedStreamState> {
     const sensitive = await openStreamSensitive(this.km, row.stream_id, toBytes(row.ciphertext));
     const out: PersistedStreamState = {
@@ -463,6 +602,24 @@ interface StreamRow {
   updated_at: number | bigint;
 }
 
+interface BroadcastChannelEncRow {
+  channel_id: string;
+  owner_role: 'sender' | 'receiver';
+  owner_address: string;
+  label: string | null;
+  generation: number | bigint;
+  ciphertext: Uint8Array | ArrayBuffer;
+  created_at: number | bigint;
+  updated_at: number | bigint;
+}
+
+interface BroadcastMemberEncRow {
+  channel_id: string;
+  peer_address: string;
+  joined_at: number | bigint;
+  removed_at: number | bigint | null;
+}
+
 function toBytes(value: Uint8Array | ArrayBuffer | unknown): Uint8Array {
   if (value instanceof Uint8Array) return value;
   if (value instanceof ArrayBuffer) return new Uint8Array(value);