feat: resumable transfer UX — surface partial downloads to UI on reconnect

Daemon scans the download directory for .tmp.meta sidecars on network join
and emits resumable_transfers IPC event. Web UI shows them in the Transfers
panel with a dimmed progress bar and "will resume on reconnect" note.

- proto: ResumableFile type, EvtResumableTransfers, resumable_files IpcMessage field
- mesh: ScanResumable() scans download dir and emits the event
- netmgr: call ScanResumable() after join (both Join and JoinByHash paths)
- web: resumableFiles store state, resumable_transfers handler, Transfers UI section

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

internal/mesh/transfer.go

@@ -91,6 +91,47 @@ func writePartialMeta(path string, t *inboundTransfer) {
 	os.WriteFile(path, data, 0o644) //nolint:errcheck
 }
 
+// ScanResumable scans the download directory for .tmp.meta sidecars left by
+// interrupted transfers and emits a resumable_transfers IPC event listing them.
+// Called once after a network is joined so the UI can show pending transfers.
+func (m *Mesh) ScanResumable() {
+	if m.DownloadDir == "" {
+		return
+	}
+	metas, _ := filepath.Glob(filepath.Join(m.DownloadDir, "*.tmp.meta"))
+	var files []proto.ResumableFile
+	for _, mp := range metas {
+		data, err := os.ReadFile(mp)
+		if err != nil {
+			continue
+		}
+		var meta partialMeta
+		if err := json.Unmarshal(data, &meta); err != nil {
+			continue
+		}
+		tp := strings.TrimSuffix(mp, ".meta")
+		info, err := os.Stat(tp)
+		if err != nil {
+			continue
+		}
+		files = append(files, proto.ResumableFile{
+			Name:   meta.Name,
+			SHA256: meta.SHA256,
+			From:   meta.From,
+			Size:   meta.Size,
+			Offset: info.Size(),
+		})
+	}
+	if len(files) == 0 {
+		return
+	}
+	m.emit(proto.IpcMessage{
+		Type:           proto.EvtResumableTransfers,
+		ResumableFiles: files,
+	})
+	log.Printf("transfer: %d resumable transfer(s) found in %s", len(files), m.DownloadDir)
+}
+
 // OfferFile reads filename from ShareDir, computes its SHA-256, and sends a
 // file-offer to peerID over the existing "yaw" DataChannel.
 func (m *Mesh) OfferFile(peerID proto.PeerID, filename string) error {

internal/netmgr/manager.go

@@ -162,6 +162,8 @@ func (mgr *Manager) Join(name, shareDir string) (string, error) {
 		}()
 	}
 
+	go m.ScanResumable()
+
 	mgr.emit(proto.IpcMessage{
 		Type:        proto.EvtNetworkJoined,
 		NetworkID:   netID,
@@ -249,6 +251,8 @@ func (mgr *Manager) JoinByHash(netHash64, shareDir string) (string, error) {
 		}()
 	}
 
+	go m.ScanResumable()
+
 	mgr.emit(proto.IpcMessage{
 		Type:        proto.EvtNetworkJoined,
 		NetworkID:   netID,

internal/proto/proto.go

@@ -99,6 +99,15 @@ type PeerMessage struct {
 	HistoryDone bool           `json:"history_done,omitempty"`
 }
 
+// ResumableFile describes a partially-downloaded file found on daemon startup.
+type ResumableFile struct {
+	Name   string `json:"name"`
+	SHA256 string `json:"sha256"`
+	From   string `json:"from"`    // peer ID hex
+	Size   int64  `json:"size"`
+	Offset int64  `json:"offset"`  // bytes already received
+}
+
 // HistoryEntry is one message in a history_chunk response.
 type HistoryEntry struct {
 	Mid       string `json:"mid"`
@@ -292,6 +301,7 @@ const (
 	EvtSharesList       IpcMsgType = "shares_list"
 	EvtRoomCreated      IpcMsgType = "room_created"    // field: room (name)
 	EvtHistoryLoaded      IpcMsgType = "history_loaded"       // fields: room, messages
+	EvtResumableTransfers IpcMsgType = "resumable_transfers"  // field: resumable_files
 )
 
 // NetworkInfo summarises one joined network for state_snapshot and network_joined events.
@@ -347,6 +357,7 @@ type IpcMessage struct {
 	InviteGenerated string      `json:"invite,omitempty"`
 	Files          []FileEntry    `json:"files,omitempty"`
 	Messages        []ChatMessage   `json:"messages,omitempty"`          // history_loaded
+	ResumableFiles  []ResumableFile `json:"resumable_files,omitempty"`   // resumable_transfers
 	Shares         []ShareEntry `json:"shares,omitempty"`
 	ShareNetworks  []string     `json:"network_ids,omitempty"` // for add_share command: scope to specific network IDs, or ["*"] for global
 	// export_identity / import_identity

web/src/components/Transfers.tsx

@@ -7,12 +7,13 @@ function fmt(bytes: number): string {
 }
 
 export function Transfers() {
-  const { pendingOffers, fileProgress, acceptOffer, rejectOffer, cancelTransfer, connectedPeers } = useWaste()
+  const { pendingOffers, fileProgress, resumableFiles, acceptOffer, rejectOffer, cancelTransfer, connectedPeers } = useWaste()
 
   const hasPending = Object.keys(pendingOffers).length > 0
   const hasActive = Object.keys(fileProgress).length > 0
+  const hasResumable = Object.keys(resumableFiles).length > 0
 
-  if (!hasPending && !hasActive) return null
+  if (!hasPending && !hasActive && !hasResumable) return null
 
   function alias(peerId: string) {
     return connectedPeers.find(p => p.id === peerId)?.alias ?? peerId.slice(0, 8)
@@ -22,6 +23,24 @@ export function Transfers() {
     <div className="sidebar-section">
       <span className="sidebar-label">Transfers</span>
 
+      {hasResumable && (
+        <>
+          <span className="sidebar-label" style={{ fontSize: 10, opacity: 0.6 }}>resumable</span>
+          {Object.entries(resumableFiles).map(([sha256, f]) => {
+            const pct = f.size > 0 ? Math.round((f.offset / f.size) * 100) : 0
+            return (
+              <div key={sha256} className="transfer-row">
+                <span className="transfer-name" title={f.name}>{f.name}</span>
+                <span className="transfer-meta">{fmt(f.offset)} / {fmt(f.size)} · {alias(f.from)} · will resume on reconnect</span>
+                <div className="transfer-progress">
+                  <div className="transfer-progress-bar" style={{ width: `${pct}%`, opacity: 0.5 }} />
+                </div>
+              </div>
+            )
+          })}
+        </>
+      )}
+
       {Object.entries(pendingOffers).map(([xid, offer]) => (
         <div key={xid} className="transfer-row">
           <span className="transfer-name" title={offer.name}>{offer.name}</span>

web/src/store/index.ts

@@ -55,6 +55,8 @@ interface WasteState {
   pendingOffers: Record<string, { peerId: string; name: string; size: number }>
   // active in-progress transfers: xid → progress
   fileProgress: Record<string, { peerId: string; name: string; received: number; total: number }>
+  // partial downloads found on daemon startup: sha256 → info
+  resumableFiles: Record<string, { name: string; from: string; size: number; offset: number }>
 
   // actions
   connect: (url: string) => void
@@ -96,6 +98,7 @@ export const useWaste = create<WasteState>((set, get) => ({
   sharedFilesByNetwork: {},
   pendingOffers: {},
   fileProgress: {},
+  resumableFiles: {},
 
   connect(url: string) {
     const adapter = new DaemonAdapter(url)
@@ -355,6 +358,14 @@ export const useWaste = create<WasteState>((set, get) => ({
         }
         break
       }
+      case 'resumable_transfers': {
+        const files = (msg.resumable_files ?? []) as Array<{ name: string; sha256: string; from: string; size: number; offset: number }>
+        if (files.length === 0) break
+        const byHash: Record<string, { name: string; from: string; size: number; offset: number }> = {}
+        for (const f of files) byHash[f.sha256] = { name: f.name, from: f.from, size: f.size, offset: f.offset }
+        set(s => ({ resumableFiles: { ...s.resumableFiles, ...byHash } }))
+        break
+      }
       case 'history_loaded': {
         const room = msg.room
         const incoming = (msg.messages ?? []) as ChatMessage[]

web/src/types.ts

@@ -85,6 +85,7 @@ export type IpcMsgType =
   | 'history_loaded'
   | 'room_created'
   | 'create_room'
+  | 'resumable_transfers'
 
 export interface IpcMessage {
   type: IpcMsgType
@@ -129,4 +130,6 @@ export interface IpcMessage {
   remote_address?: string
   // history_loaded
   messages?: ChatMessage[]
+  // resumable_transfers
+  resumable_files?: Array<{ name: string; sha256: string; from: string; size: number; offset: number }>
 }