feat: transfer resume after page refresh

Transfers now survive page refreshes:
- beforeunload warning prevents accidental refresh during transfer
- Sender's files cached in IndexedDB before sending
- Receiver's chunks persisted in IndexedDB as they arrive
- On reconnect, receiver sends transfer-resume with bytes received
- Sender resumes from offset, skipping already-sent data
- Old transfer data auto-cleaned after 1 hour

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

shared/src/protocol.ts

@@ -141,12 +141,18 @@ export interface TransferResponseMessage {
   accepted: boolean;
 }
 
+export interface TransferResumeMessage {
+  type: "transfer-resume";
+  files: { id: string; bytesReceived: number }[];
+}
+
 export type DataChannelMessage =
   | FileMetaMessage
   | FileEndMessage
   | TextMessage
   | TransferRequestMessage
-  | TransferResponseMessage;
+  | TransferResponseMessage
+  | TransferResumeMessage;
 
 // ── Push notification payload ──
 

web/src/hooks/useSignaling.ts

@@ -1,5 +1,10 @@
 import { useEffect, useRef, useCallback } from "react";
-import type { ServerMessage, TransferRequestMessage, TransferResponseMessage } from "@anydrop/shared";
+import type {
+  ServerMessage,
+  TransferRequestMessage,
+  TransferResponseMessage,
+  TransferResumeMessage,
+} from "@anydrop/shared";
 import { SignalingClient } from "../lib/signaling";
 import { PeerManager } from "../lib/peerManager";
 import {
@@ -10,6 +15,17 @@ import {
 } from "../lib/fileTransfer";
 import { setupPushNotifications, showLocalNotification } from "../lib/notifications";
 import { detectLocalIP } from "../lib/localIP";
+import {
+  saveTransferMeta,
+  updateTransferBytes,
+  cacheSendFile,
+  getCachedSendFile,
+  getAllPendingTransfers,
+  getReceivedData,
+  appendReceivedChunk,
+  cleanupTransfer,
+  cleanupOldTransfers,
+} from "../lib/transferStore";
 import { useStore } from "../stores/useStore";
 import { useProfileStore } from "../stores/useProfileStore";
 
@@ -27,7 +43,7 @@ function downloadBlob(blob: Blob, fileName: string) {
 export function useSignaling(joinCode?: string) {
   const signalingRef = useRef<SignalingClient | null>(null);
   const peerManagerRef = useRef<PeerManager | null>(null);
-  const pendingFilesRef = useRef<Map<string, { files: File[]; text?: string }>>(new Map());
+  const pendingFilesRef = useRef<Map<string, { files: File[] }>>(new Map());
   const fileReceiverRef = useRef<ReturnType<typeof createFileReceiver> | null>(null);
 
   const {
@@ -43,16 +59,42 @@ export function useSignaling(joinCode?: string) {
     setError,
   } = useStore();
 
+  // ── beforeunload: warn during active transfers ──
+  useEffect(() => {
+    const handler = (e: BeforeUnloadEvent) => {
+      const { transfers } = useStore.getState();
+      const active = transfers.some(
+        (t) => t.status === "transferring" || t.status === "pending",
+      );
+      if (active) {
+        e.preventDefault();
+      }
+    };
+    window.addEventListener("beforeunload", handler);
+    return () => window.removeEventListener("beforeunload", handler);
+  }, []);
+
+  // ── Cleanup old transfers on mount ──
+  useEffect(() => {
+    cleanupOldTransfers();
+  }, []);
+
   useEffect(() => {
     fileReceiverRef.current = createFileReceiver({
       onData: () => {},
       onComplete: (fileId, blob, fileName) => {
         updateTransfer(fileId, { progress: 1, status: "done" });
+        cleanupTransfer(fileId);
         downloadBlob(blob, fileName);
       },
       onProgress: (fileId, progress) => {
         updateTransfer(fileId, { progress, status: "transferring" });
       },
+      onChunkReceived: (fileId, chunk, totalReceived) => {
+        // Persist to IndexedDB for resume after refresh (fire-and-forget)
+        appendReceivedChunk(fileId, chunk).catch(() => {});
+        updateTransferBytes(fileId, totalReceived).catch(() => {});
+      },
       onTransferRequest: (msg: TransferRequestMessage) => {
         setIncomingRequest({
           peerId: "",
@@ -69,10 +111,15 @@ export function useSignaling(joinCode?: string) {
           for (const transfer of store.transfers) {
             if (transfer.direction === "send" && transfer.status === "pending") {
               updateTransfer(transfer.id, { status: "error" });
+              cleanupTransfer(transfer.id);
             }
           }
         }
       },
+      onTransferResume: (msg: TransferResumeMessage) => {
+        // Peer is asking us to resume sending from an offset
+        handleResumeRequest(msg);
+      },
       onText: (text) => {
         setIncomingRequest({
           peerId: "",
@@ -84,6 +131,43 @@ export function useSignaling(joinCode?: string) {
     });
   }, []);
 
+  const handleResumeRequest = useCallback(
+    async (msg: TransferResumeMessage) => {
+      const pm = peerManagerRef.current;
+      if (!pm) return;
+
+      for (const { id, bytesReceived } of msg.files) {
+        const cachedFile = await getCachedSendFile(id);
+        if (!cachedFile) continue;
+
+        // Find which peer to send to from the stored metadata
+        const meta = await import("../lib/transferStore").then((m) =>
+          m.getTransferMeta(id),
+        );
+        if (!meta) continue;
+
+        const peer = pm.getPeer(meta.peerId);
+        if (!peer) continue;
+
+        updateTransfer(id, {
+          progress: bytesReceived / meta.fileSize,
+          status: "transferring",
+        });
+
+        sendFile(peer, cachedFile, id, (progress) => {
+          updateTransfer(id, {
+            progress,
+            status: progress >= 1 ? "done" : "transferring",
+          });
+          if (progress >= 1) {
+            cleanupTransfer(id);
+          }
+        }, bytesReceived);
+      }
+    },
+    [updateTransfer],
+  );
+
   const startSending = useCallback(() => {
     const store = useStore.getState();
     for (const [peerId, { files }] of pendingFilesRef.current) {
@@ -94,7 +178,10 @@ export function useSignaling(joinCode?: string) {
 
       for (const file of files) {
         const transfer = store.transfers.find(
-          (t) => t.direction === "send" && t.fileName === file.name && t.status === "pending",
+          (t) =>
+            t.direction === "send" &&
+            t.fileName === file.name &&
+            t.status === "pending",
         );
         if (transfer) {
           sendFile(peer, file, transfer.id, (progress) => {
@@ -102,6 +189,9 @@ export function useSignaling(joinCode?: string) {
               progress,
               status: progress >= 1 ? "done" : "transferring",
             });
+            if (progress >= 1) {
+              cleanupTransfer(transfer.id);
+            }
           });
         }
       }
@@ -119,10 +209,16 @@ export function useSignaling(joinCode?: string) {
           setConnection(msg.peerId, msg.roomId);
           setPeers(msg.peers);
 
-          // Subscribe to push notifications if server provides VAPID key
           if (msg.vapidPublicKey && signalingRef.current) {
-            setupPushNotifications(msg.vapidPublicKey, profile.deviceId, signalingRef.current);
+            setupPushNotifications(
+              msg.vapidPublicKey,
+              profile.deviceId,
+              signalingRef.current,
+            );
           }
+
+          // Check for pending transfers to resume
+          checkPendingResumes();
           break;
         case "peer-joined":
           addPeer({
@@ -131,8 +227,10 @@ export function useSignaling(joinCode?: string) {
             deviceType: msg.deviceType,
             avatar: msg.avatar,
           });
-          // Notify if tab is in background
-          showLocalNotification("AnyDrop", `${msg.displayName} est à proximité`);
+          showLocalNotification(
+            "AnyDrop",
+            `${msg.displayName} est à proximité`,
+          );
           break;
         case "peer-left":
           removePeer(msg.peerId);
@@ -150,6 +248,62 @@ export function useSignaling(joinCode?: string) {
       }
     };
 
+    const checkPendingResumes = async () => {
+      const pending = await getAllPendingTransfers();
+      if (pending.length === 0) return;
+
+      for (const meta of pending) {
+        // Restore transfer in UI
+        addTransfer({
+          id: meta.id,
+          peerId: meta.peerId,
+          fileName: meta.fileName,
+          fileSize: meta.fileSize,
+          mime: meta.mime,
+          direction: meta.direction,
+          progress: meta.bytesTransferred / meta.fileSize,
+          status: "pending",
+        });
+
+        if (meta.direction === "receive") {
+          // We were receiving — need to tell the sender to resume
+          const existingBlob = await getReceivedData(meta.id);
+          const bytesReceived = existingBlob?.size ?? 0;
+
+          if (bytesReceived > 0) {
+            // Restore partial data in file receiver
+            fileReceiverRef.current?.restoreReceiving(
+              meta.id,
+              meta.fileName,
+              meta.fileSize,
+              meta.mime,
+              bytesReceived,
+              existingBlob!,
+            );
+          }
+
+          // When we reconnect with this peer, send a resume request
+          const pm = peerManagerRef.current;
+          if (pm) {
+            const sendResumeWhenReady = () => {
+              const peer = pm.getPeer(meta.peerId);
+              if (peer && (peer as any).connected) {
+                const resumeMsg: TransferResumeMessage = {
+                  type: "transfer-resume",
+                  files: [{ id: meta.id, bytesReceived }],
+                };
+                peer.send(JSON.stringify(resumeMsg));
+              } else {
+                setTimeout(sendResumeWhenReady, 500);
+              }
+            };
+            // Delay to let peer connection establish
+            setTimeout(sendResumeWhenReady, 2000);
+          }
+        }
+      }
+    };
+
     const init = async () => {
       const localIP = await detectLocalIP().catch(() => undefined);
       if (cancelled) return;
@@ -190,7 +344,10 @@ export function useSignaling(joinCode?: string) {
                   text: msg.text,
                 });
                 const fileCount = msg.files?.length || 0;
-                const label = fileCount > 1 ? `${fileCount} fichiers` : msg.files?.[0]?.name || "un fichier";
+                const label =
+                  fileCount > 1
+                    ? `${fileCount} fichiers`
+                    : msg.files?.[0]?.name || "un fichier";
                 showLocalNotification(
                   "Transfert entrant",
                   `${peerInfo?.displayName || "Quelqu'un"} veut vous envoyer ${label}`,
@@ -203,6 +360,10 @@ export function useSignaling(joinCode?: string) {
                 }
                 return;
               }
+              if (msg.type === "transfer-resume") {
+                handleResumeRequest(msg);
+                return;
+              }
               if (msg.type === "text") {
                 setIncomingRequest({
                   peerId,
@@ -242,48 +403,68 @@ export function useSignaling(joinCode?: string) {
     };
   }, [joinCode]);
 
-  const sendFiles = useCallback((peerId: string, files: File[]) => {
-    const pm = peerManagerRef.current;
-    const signaling = signalingRef.current;
-    if (!pm || !signaling) return;
+  const sendFiles = useCallback(
+    async (peerId: string, files: File[]) => {
+      const pm = peerManagerRef.current;
+      const signaling = signalingRef.current;
+      if (!pm || !signaling) return;
 
-    let peer = pm.getPeer(peerId);
-    if (!peer) {
-      peer = pm.createPeer(peerId, true);
-    }
-
-    const request = createTransferRequest(files);
-
-    for (const fileMeta of request.files) {
-      addTransfer({
-        id: fileMeta.id,
-        peerId,
-        fileName: fileMeta.name,
-        fileSize: fileMeta.size,
-        mime: fileMeta.mime,
-        direction: "send",
-        progress: 0,
-        status: "pending",
-      });
-    }
-
-    pendingFilesRef.current.set(peerId, { files });
-
-    const sendRequest = () => {
-      const p = pm.getPeer(peerId);
-      if (p && (p as any)._channel?.readyState === "open") {
-        p.send(JSON.stringify(request));
-      } else {
-        setTimeout(sendRequest, 100);
+      let peer = pm.getPeer(peerId);
+      if (!peer) {
+        peer = pm.createPeer(peerId, true);
       }
-    };
 
-    if (peer && (peer as any).connected) {
-      sendRequest();
-    } else {
-      peer.on("connect", sendRequest);
-    }
-  }, [addTransfer]);
+      const request = createTransferRequest(files);
+      const store = useStore.getState();
+      const peerInfo = store.peers.find((p) => p.peerId === peerId);
+
+      for (let i = 0; i < request.files.length; i++) {
+        const fileMeta = request.files[i];
+        addTransfer({
+          id: fileMeta.id,
+          peerId,
+          fileName: fileMeta.name,
+          fileSize: fileMeta.size,
+          mime: fileMeta.mime,
+          direction: "send",
+          progress: 0,
+          status: "pending",
+        });
+
+        // Persist file and metadata for resume
+        await cacheSendFile(fileMeta.id, files[i]);
+        await saveTransferMeta({
+          id: fileMeta.id,
+          peerId,
+          peerDisplayName: peerInfo?.displayName || peerId,
+          fileName: fileMeta.name,
+          fileSize: fileMeta.size,
+          mime: fileMeta.mime,
+          direction: "send",
+          bytesTransferred: 0,
+          createdAt: Date.now(),
+        });
+      }
+
+      pendingFilesRef.current.set(peerId, { files });
+
+      const sendRequest = () => {
+        const p = pm.getPeer(peerId);
+        if (p && (p as any)._channel?.readyState === "open") {
+          p.send(JSON.stringify(request));
+        } else {
+          setTimeout(sendRequest, 100);
+        }
+      };
+
+      if (peer && (peer as any).connected) {
+        sendRequest();
+      } else {
+        peer.on("connect", sendRequest);
+      }
+    },
+    [addTransfer],
+  );
 
   const sendText = useCallback((peerId: string, text: string) => {
     const pm = peerManagerRef.current;
@@ -297,7 +478,9 @@ export function useSignaling(joinCode?: string) {
     const sendMsg = () => {
       const p = pm.getPeer(peerId);
       if (p) {
-        p.send(JSON.stringify({ type: "text", id: `t-${Date.now()}`, content: text }));
+        p.send(
+          JSON.stringify({ type: "text", id: `t-${Date.now()}`, content: text }),
+        );
       }
     };
 
@@ -308,44 +491,64 @@ export function useSignaling(joinCode?: string) {
     }
   }, []);
 
-  const acceptTransfer = useCallback((peerId: string) => {
-    const pm = peerManagerRef.current;
-    if (!pm) return;
+  const acceptTransfer = useCallback(
+    async (peerId: string) => {
+      const pm = peerManagerRef.current;
+      if (!pm) return;
 
-    const peer = pm.getPeer(peerId);
-    if (!peer) return;
+      const peer = pm.getPeer(peerId);
+      if (!peer) return;
 
-    const store = useStore.getState();
-    const request = store.incomingRequest;
-    if (request) {
-      for (const file of request.files) {
-        addTransfer({
-          id: file.id,
-          peerId,
-          fileName: file.name,
-          fileSize: file.size,
-          mime: file.mime,
-          direction: "receive",
-          progress: 0,
-          status: "pending",
-        });
+      const store = useStore.getState();
+      const request = store.incomingRequest;
+      if (request) {
+        const peerInfo = store.peers.find((p) => p.peerId === peerId);
+        for (const file of request.files) {
+          addTransfer({
+            id: file.id,
+            peerId,
+            fileName: file.name,
+            fileSize: file.size,
+            mime: file.mime,
+            direction: "receive",
+            progress: 0,
+            status: "pending",
+          });
+
+          // Persist receive metadata for resume
+          await saveTransferMeta({
+            id: file.id,
+            peerId,
+            peerDisplayName: peerInfo?.displayName || peerId,
+            fileName: file.name,
+            fileSize: file.size,
+            mime: file.mime,
+            direction: "receive",
+            bytesTransferred: 0,
+            createdAt: Date.now(),
+          });
+        }
       }
-    }
 
-    peer.send(JSON.stringify(createTransferResponse(true)));
-    setIncomingRequest(null);
-  }, [addTransfer, setIncomingRequest]);
+      peer.send(JSON.stringify(createTransferResponse(true)));
+      setIncomingRequest(null);
+    },
+    [addTransfer, setIncomingRequest],
+  );
 
-  const rejectTransfer = useCallback((peerId: string) => {
-    const pm = peerManagerRef.current;
-    if (!pm) return;
+  const rejectTransfer = useCallback(
+    (peerId: string) => {
+      const pm = peerManagerRef.current;
+      if (!pm) return;
 
-    const peer = pm.getPeer(peerId);
-    if (peer) {
-      peer.send(JSON.stringify(createTransferResponse(false)));
-    }
-    setIncomingRequest(null);
-  }, [setIncomingRequest]);
+      const peer = pm.getPeer(peerId);
+      if (peer) {
+        peer.send(JSON.stringify(createTransferResponse(false)));
+      }
+      setIncomingRequest(null);
+    },
+    [setIncomingRequest],
+  );
 
   const createPublicRoom = useCallback(() => {
     signalingRef.current?.send({ type: "create-public-room" });

web/src/lib/fileTransfer.ts

@@ -6,6 +6,7 @@ import {
   type FileEndMessage,
   type TransferRequestMessage,
   type TransferResponseMessage,
+  type TransferResumeMessage,
   type DataChannelMessage,
 } from "@anydrop/shared";
 
@@ -34,6 +35,7 @@ export async function sendFile(
   file: File,
   fileId: string,
   onProgress: (progress: number) => void,
+  resumeOffset = 0,
 ): Promise<void> {
   // Send file metadata
   const meta: FileMetaMessage = {
@@ -45,9 +47,10 @@ export async function sendFile(
   };
   peer.send(JSON.stringify(meta));
 
-  // Stream file in chunks
-  let offset = 0;
-  const reader = file.stream().getReader();
+  // If resuming, slice the file to skip already-sent data
+  const blob = resumeOffset > 0 ? file.slice(resumeOffset) : file;
+  let offset = resumeOffset;
+  const reader = blob.stream().getReader();
 
   let buffer = new Uint8Array(0);
 
@@ -55,18 +58,15 @@ export async function sendFile(
     const { done, value } = await reader.read();
     if (done) break;
 
-    // Append to buffer
     const newBuffer = new Uint8Array(buffer.length + value.length);
     newBuffer.set(buffer);
     newBuffer.set(value, buffer.length);
     buffer = newBuffer;
 
-    // Send complete chunks from buffer
     while (buffer.length >= CHUNK_SIZE) {
       const chunk = buffer.slice(0, CHUNK_SIZE);
       buffer = buffer.slice(CHUNK_SIZE);
 
-      // Backpressure: wait if buffer is full
       await waitForDrain(peer);
 
       peer.send(chunk);
@@ -75,7 +75,6 @@ export async function sendFile(
     }
   }
 
-  // Send remaining bytes
   if (buffer.length > 0) {
     await waitForDrain(peer);
     peer.send(buffer);
@@ -83,7 +82,6 @@ export async function sendFile(
     onProgress(offset / file.size);
   }
 
-  // Send end-of-file marker
   const eof: FileEndMessage = { type: "file-end", id: fileId };
   peer.send(JSON.stringify(eof));
   onProgress(1);
@@ -107,8 +105,10 @@ export interface FileReceiver {
   onData: (data: Uint8Array | string) => void;
   onComplete: (fileId: string, blob: Blob, fileName: string) => void;
   onProgress: (fileId: string, progress: number) => void;
+  onChunkReceived?: (fileId: string, chunk: Uint8Array, totalReceived: number) => void;
   onTransferRequest: (msg: TransferRequestMessage) => void;
   onTransferResponse: (msg: TransferResponseMessage) => void;
+  onTransferResume: (msg: TransferResumeMessage) => void;
   onText: (text: string) => void;
 }
 
@@ -120,7 +120,6 @@ export function createFileReceiver(callbacks: FileReceiver) {
 
   return {
     handleData(data: Uint8Array | string) {
-      // Try to parse as JSON control message
       if (typeof data === "string") {
         try {
           const msg: DataChannelMessage = JSON.parse(data);
@@ -152,6 +151,9 @@ export function createFileReceiver(callbacks: FileReceiver) {
             case "transfer-response":
               callbacks.onTransferResponse(msg);
               break;
+            case "transfer-resume":
+              callbacks.onTransferResume(msg);
+              break;
           }
         } catch {
           // Not JSON, ignore
@@ -159,15 +161,40 @@ export function createFileReceiver(callbacks: FileReceiver) {
         return;
       }
 
-      // Binary data = file chunk
-      // Find which file we're receiving (first active one)
+      // Binary data = file chunk — route to first active receiving file
       for (const [id, file] of receiving) {
         const chunk = data instanceof Uint8Array ? data : new Uint8Array(data as ArrayBuffer);
         file.chunks.push(chunk);
         file.received += chunk.length;
         callbacks.onProgress(id, file.received / file.size);
+        // Persist chunk for resume (fire-and-forget)
+        callbacks.onChunkReceived?.(id, chunk, file.received);
         break;
       }
     },
+
+    /** Restore a partially received file (from IndexedDB after refresh) */
+    restoreReceiving(
+      id: string,
+      name: string,
+      size: number,
+      mime: string,
+      receivedBytes: number,
+      existingBlob: Blob,
+    ) {
+      receiving.set(id, {
+        name,
+        size,
+        mime,
+        chunks: [new Uint8Array(0)], // placeholder, actual data is in existingBlob
+        received: receivedBytes,
+      });
+      // Replace chunks array with the existing blob as first entry
+      const entry = receiving.get(id)!;
+      entry.chunks = [];
+      existingBlob.arrayBuffer().then((buf) => {
+        entry.chunks.push(new Uint8Array(buf));
+      });
+    },
   };
 }

web/src/lib/transferStore.ts

@@ -0,0 +1,193 @@
+/**
+ * IndexedDB persistence for transfer state + data.
+ * Allows transfers to resume after page refresh.
+ */
+
+const DB_NAME = "anydrop-transfers";
+const DB_VERSION = 1;
+const STORE_META = "meta";
+const STORE_CHUNKS = "chunks";
+const STORE_FILES = "files";
+
+let dbPromise: Promise<IDBDatabase> | null = null;
+
+function getDB(): Promise<IDBDatabase> {
+  if (!dbPromise) {
+    dbPromise = new Promise((resolve, reject) => {
+      const req = indexedDB.open(DB_NAME, DB_VERSION);
+      req.onupgradeneeded = () => {
+        const db = req.result;
+        if (!db.objectStoreNames.contains(STORE_META)) {
+          db.createObjectStore(STORE_META, { keyPath: "id" });
+        }
+        if (!db.objectStoreNames.contains(STORE_CHUNKS)) {
+          // chunks keyed by transferId, stored as one growing blob per transfer
+          db.createObjectStore(STORE_CHUNKS, { keyPath: "transferId" });
+        }
+        if (!db.objectStoreNames.contains(STORE_FILES)) {
+          // sender's files cached for resume
+          db.createObjectStore(STORE_FILES, { keyPath: "transferId" });
+        }
+      };
+      req.onsuccess = () => resolve(req.result);
+      req.onerror = () => reject(req.error);
+    });
+  }
+  return dbPromise;
+}
+
+function tx(
+  storeName: string,
+  mode: IDBTransactionMode,
+): Promise<IDBObjectStore> {
+  return getDB().then(
+    (db) => db.transaction(storeName, mode).objectStore(storeName),
+  );
+}
+
+function reqToPromise<T>(req: IDBRequest<T>): Promise<T> {
+  return new Promise((resolve, reject) => {
+    req.onsuccess = () => resolve(req.result);
+    req.onerror = () => reject(req.error);
+  });
+}
+
+// ── Transfer metadata ──
+
+export interface TransferMeta {
+  id: string;
+  peerId: string;
+  peerDisplayName: string;
+  fileName: string;
+  fileSize: number;
+  mime: string;
+  direction: "send" | "receive";
+  bytesTransferred: number;
+  createdAt: number;
+}
+
+export async function saveTransferMeta(meta: TransferMeta): Promise<void> {
+  const store = await tx(STORE_META, "readwrite");
+  await reqToPromise(store.put(meta));
+}
+
+export async function getTransferMeta(
+  id: string,
+): Promise<TransferMeta | null> {
+  const store = await tx(STORE_META, "readonly");
+  return (await reqToPromise(store.get(id))) ?? null;
+}
+
+export async function getAllPendingTransfers(): Promise<TransferMeta[]> {
+  const store = await tx(STORE_META, "readonly");
+  const all: TransferMeta[] = await reqToPromise(store.getAll());
+  return all.filter(
+    (m) => m.bytesTransferred < m.fileSize,
+  );
+}
+
+export async function updateTransferBytes(
+  id: string,
+  bytesTransferred: number,
+): Promise<void> {
+  const store = await tx(STORE_META, "readwrite");
+  const meta: TransferMeta | undefined = await reqToPromise(store.get(id));
+  if (meta) {
+    meta.bytesTransferred = bytesTransferred;
+    await reqToPromise(store.put(meta));
+  }
+}
+
+export async function deleteTransferMeta(id: string): Promise<void> {
+  const store = await tx(STORE_META, "readwrite");
+  await reqToPromise(store.delete(id));
+}
+
+// ── Received chunks (receiver side) ──
+
+export async function saveReceivedData(
+  transferId: string,
+  blob: Blob,
+): Promise<void> {
+  const store = await tx(STORE_CHUNKS, "readwrite");
+  await reqToPromise(store.put({ transferId, blob }));
+}
+
+export async function getReceivedData(
+  transferId: string,
+): Promise<Blob | null> {
+  const store = await tx(STORE_CHUNKS, "readonly");
+  const result = await reqToPromise(store.get(transferId));
+  return result?.blob ?? null;
+}
+
+export async function appendReceivedChunk(
+  transferId: string,
+  chunk: Uint8Array,
+): Promise<number> {
+  const store = await tx(STORE_CHUNKS, "readwrite");
+  const existing = await reqToPromise(store.get(transferId));
+  const oldBlob: Blob = existing?.blob ?? new Blob();
+  const newBlob = new Blob([oldBlob, chunk]);
+  await reqToPromise(store.put({ transferId, blob: newBlob }));
+  return newBlob.size;
+}
+
+export async function deleteReceivedData(transferId: string): Promise<void> {
+  const store = await tx(STORE_CHUNKS, "readwrite");
+  await reqToPromise(store.delete(transferId));
+}
+
+// ── Sender file cache ──
+
+export async function cacheSendFile(
+  transferId: string,
+  file: File,
+): Promise<void> {
+  const store = await tx(STORE_FILES, "readwrite");
+  // Store as blob with metadata
+  await reqToPromise(
+    store.put({
+      transferId,
+      blob: file,
+      name: file.name,
+      mime: file.type,
+      size: file.size,
+    }),
+  );
+}
+
+export async function getCachedSendFile(
+  transferId: string,
+): Promise<File | null> {
+  const store = await tx(STORE_FILES, "readonly");
+  const result = await reqToPromise(store.get(transferId));
+  if (!result) return null;
+  return new File([result.blob], result.name, { type: result.mime });
+}
+
+export async function deleteCachedSendFile(transferId: string): Promise<void> {
+  const store = await tx(STORE_FILES, "readwrite");
+  await reqToPromise(store.delete(transferId));
+}
+
+// ── Cleanup ──
+
+export async function cleanupTransfer(transferId: string): Promise<void> {
+  await Promise.all([
+    deleteTransferMeta(transferId),
+    deleteReceivedData(transferId),
+    deleteCachedSendFile(transferId),
+  ]);
+}
+
+export async function cleanupOldTransfers(maxAgeMs = 3600_000): Promise<void> {
+  const store = await tx(STORE_META, "readonly");
+  const all: TransferMeta[] = await reqToPromise(store.getAll());
+  const cutoff = Date.now() - maxAgeMs;
+  for (const meta of all) {
+    if (meta.createdAt < cutoff) {
+      await cleanupTransfer(meta.id);
+    }
+  }
+}