diff --git a/packages/backend/src/gateway/transport.ts b/packages/backend/src/gateway/transport.ts
index 477a13b..8d054a1 100644
--- a/packages/backend/src/gateway/transport.ts
+++ b/packages/backend/src/gateway/transport.ts
@@ -8,6 +8,7 @@ import * as broadcast from './broadcast.js'
 import { openTerminal } from './terminal.js'
 
 const HEARTBEAT_INTERVAL_MS = 30_000
+const MAX_PAYLOAD_BYTES = 16 * 1024 * 1024 // 16 MB — enough for base64-encoded 10 MB images
 
 function setupHeartbeat(wss: WebSocketServer) {
   const heartbeat = setInterval(() => {
@@ -31,7 +32,7 @@ function markAlive(ws: WebSocket) {
 // ── Client Gateway (/ws/client) — runs on its own port ────────────────
 
 export function setupClientGateway(server: Server) {
-  const wss = new WebSocketServer({ server })
+  const wss = new WebSocketServer({ server, maxPayload: MAX_PAYLOAD_BYTES })
   const clientRpc = createRpcDispatcher(clientHandlers)
   setupHeartbeat(wss)
 
@@ -73,7 +74,7 @@ export function setupClientGateway(server: Server) {
 // ── Agent Gateway (/ws/agent + terminal) — runs on its own port ───────
 
 export function setupAgentGateway(server: Server) {
-  const wss = new WebSocketServer({ server })
+  const wss = new WebSocketServer({ server, maxPayload: MAX_PAYLOAD_BYTES })
   const agentRpc = createRpcDispatcher(agentHandlers)
   setupHeartbeat(wss)
 
diff --git a/packages/backend/src/slack/slack-connection.ts b/packages/backend/src/slack/slack-connection.ts
index adb6003..267557b 100644
--- a/packages/backend/src/slack/slack-connection.ts
+++ b/packages/backend/src/slack/slack-connection.ts
@@ -626,7 +626,20 @@ export async function sendImageToSlack(
   channelId: string,
 ): Promise<void> {
   if (!webClient) throw new Error('Slack is not connected')
-  await uploadImageToSlack(imageUrl, alt, channelId)
+
+  if (!imageUrl.startsWith('/media/')) {
+    throw new Error(`Only local /media/ URLs are supported, got: ${imageUrl}`)
+  }
+
+  const filename = basename(imageUrl)
+  const filePath = join(MEDIA_DIR, filename)
+  const fileData = readFileSync(filePath)
+  await webClient.filesUploadV2({
+    channel_id: channelId,
+    file: fileData,
+    filename,
+    title: alt,
+  })
 }
 
 // ── Sync / Unsync ──────────────────────────────────────────────────────
diff --git a/packages/frontend/src/components/layout/settings-view.ts b/packages/frontend/src/components/layout/settings-view.ts
index eefa70a..4c3f970 100644
--- a/packages/frontend/src/components/layout/settings-view.ts
+++ b/packages/frontend/src/components/layout/settings-view.ts
@@ -983,7 +983,7 @@ export class SettingsView extends LitElement {
       },
       oauth_config: {
         scopes: {
-          bot: ['channels:history', 'channels:manage', 'channels:read', 'chat:write', 'chat:write.customize', 'users:read', 'app_mentions:read'],
+          bot: ['channels:history', 'channels:manage', 'channels:read', 'chat:write', 'chat:write.customize', 'files:write', 'users:read', 'app_mentions:read'],
         },
       },
       settings: {