add chunked upload to bypass 100MB proxy body limit

Resumable /api/uploads flow (init -> append -> complete -> abort) so a
large recording uploads as many small slices (<= ASR_CHUNK_SIZE_MB, default
50MB) instead of one request a size-capping proxy (Cloudflare's 100MB) would
reject. The web console auto-routes files larger than one slice through the
chunked path with cross-slice progress and transient-error retry; smaller
files keep the single-shot upload.

- store: in-memory upload sessions + .part reassembly (offset writes,
  out-of-order/idempotent), reuse upload id as task id, orphan sweep on
  start, idle-session GC
- fix limitedReader rejecting bodies exactly at the cap (broke full chunks)
- fix drag-drop double-firing when a drop lands on the dropzone (its drop
  handler now stopPropagation so the window listener doesn't re-upload)
- tests: store + HTTP flow, plus a 120MB reassembly test (ASR_TEST_LARGE)

README.md

@@ -129,6 +129,7 @@ SenseVoice + ~2 MB silero VAD); subsequent starts load them from disk.
 | `ASR_USE_ITN` | `1` | Inverse text normalization (numbers, punctuation). |
 | `ASR_MAX_RETRIES` | `3` | Auto-retry attempts before a task is marked failed. |
 | `ASR_MAX_UPLOAD_MB` | `512` | Per-upload size cap. |
+| `ASR_CHUNK_SIZE_MB` | `50` | Slice size for resumable chunked uploads; kept under CDN body limits (e.g. Cloudflare's 100MB). |
 | `ASR_WORKERS` | `1` | Concurrent transcription workers. |
 | `ASR_VAD_THRESHOLD` | `0.5` | Silero speech probability threshold. |
 | `ASR_VAD_MIN_SPEECH` | `0.5` | Min speech segment (s). |
@@ -194,6 +195,43 @@ curl -H "X-Api-Key: changeme" http://localhost:8080/api/tasks/<id>
 curl -H "X-Api-Key: changeme" http://localhost:8080/api/tasks/<id>/transcript
 ```
 
+### Chunked uploads (bypassing a 100MB proxy limit)
+
+When the service sits behind a size-capping proxy — Cloudflare's free plan
+rejects request bodies over **100MB** — a single `POST /api/tasks` upload of a
+large recording never reaches the origin. The resumable chunked-upload API
+splits the file into slices no bigger than `ASR_CHUNK_SIZE_MB` (default **50MB**,
+well under the cap) and reassembles them server-side into one task:
+
+| Method | Path | Description |
+|---|---|---|
+| `POST` | `/api/uploads` | Open a session: JSON `{filename,size}` → `{upload_id, chunk_size, total_chunks}`. |
+| `POST` | `/api/uploads/{id}?index=N` | Send slice `N` (0-based, raw body ≤ chunk_size). Order is free; resending is idempotent. |
+| `POST` | `/api/uploads/{id}/complete` | Once all slices arrive: merge → enqueue → `202` + task (same shape as `/api/tasks`). |
+| `DELETE` | `/api/uploads/{id}` | Abort the session and drop the partial file → `204`. |
+
+```sh
+# Open a session for a 180MB file (4 slices of 50MB)
+UID=$(curl -sH "X-Api-Key: $PW" -H "Content-Type: application/json" \
+  -d '{"filename":"big.mp4","size":188743680}' \
+  http://localhost:8080/api/uploads | jq -r .upload_id)
+
+# Send each slice (split with dd/split beforehand)
+for i in 0 1 2 3; do
+  curl -sH "X-Api-Key: $PW" --data-binary @"slice_$i.bin" \
+    "http://localhost:8080/api/uploads/$UID?index=$i" >/dev/null
+done
+
+# Merge → enqueue (returns the task, just like /api/tasks)
+curl -H "X-Api-Key: $PW" -X POST http://localhost:8080/api/uploads/$UID/complete
+```
+
+The web console handles this automatically: files larger than one chunk go
+through the chunked path (with a single progress bar across all slices);
+smaller files keep the simple single-request upload. Sessions live in memory,
+so an interrupted upload is retried from scratch on reload — and any orphaned
+partial files are swept on the next start.
+
 ## Task lifecycle & error handling
 
 States: `pending` → `processing` → `completed` | `failed` | `skipped`.

internal/config/config.go

@@ -36,6 +36,11 @@ type Config struct {
 	MaxRetries int
 	// ASR_MAX_UPLOAD_MB: per-upload size cap (default 512).
 	MaxUploadBytes int64
+	// ASR_CHUNK_SIZE_MB: size of each slice in a resumable chunked upload,
+	// kept well under size-capping proxies' body limits so a large file can
+	// be uploaded as many small requests instead of one that a CDN (e.g.
+	// Cloudflare's 100MB cap) would reject. Default 50.
+	ChunkSize int64
 	// ASR_WORKERS: concurrent transcription workers (default 1).
 	Workers int
 	// ASR_MAX_CONCURRENT: cap on simultaneously in-flight synchronous
@@ -73,6 +78,7 @@ func Load() (Config, error) {
 		UseITN:                envBool("ASR_USE_ITN", true),
 		MaxRetries:            envInt("ASR_MAX_RETRIES", 3),
 		MaxUploadBytes:        int64(envInt("ASR_MAX_UPLOAD_MB", 512)) * 1024 * 1024,
+		ChunkSize:             int64(envInt("ASR_CHUNK_SIZE_MB", 50)) * 1024 * 1024,
 		Workers:               envInt("ASR_WORKERS", 1),
 		MaxConcurrent:         envInt("ASR_MAX_CONCURRENT", 0),
 		VadThreshold:          float32(envFloat("ASR_VAD_THRESHOLD", 0.5)),
@@ -111,6 +117,14 @@ func Load() (Config, error) {
 	if c.MaxUploadBytes < 1<<20 {
 		c.MaxUploadBytes = 512 << 20
 	}
+	// Chunk size must be > 1MB to be useful and < 100MB so each slice clears
+	// common CDN body caps (e.g. Cloudflare's 100MB) with room to spare.
+	if c.ChunkSize < 1<<20 {
+		c.ChunkSize = 50 << 20
+	}
+	if c.ChunkSize > 100<<20 {
+		c.ChunkSize = 100 << 20
+	}
 	if c.DownloadTimeout < time.Minute {
 		c.DownloadTimeout = 30 * time.Minute
 	}
@@ -130,9 +144,9 @@ func Load() (Config, error) {
 func (c Config) AuthEnabled() bool { return c.Password != "" }
 
 func (c Config) String() string {
-	return fmt.Sprintf("addr=%s data=%s models=%s threads=%d lang=%s itn=%t workers=%d maxconcurrent=%d retries=%d vad{thr=%.2f max=%.0fs win=%d}",
+	return fmt.Sprintf("addr=%s data=%s models=%s threads=%d lang=%s itn=%t workers=%d maxconcurrent=%d retries=%d chunk=%dB vad{thr=%.2f max=%.0fs win=%d}",
 		c.Addr, c.DataDir, c.ModelDir, c.NumThreads, c.Language, c.UseITN, c.Workers,
-		c.MaxConcurrent, c.MaxRetries, c.VadThreshold, c.VadMaxSpeechDuration, c.VadWindowSize)
+		c.MaxConcurrent, c.MaxRetries, c.ChunkSize, c.VadThreshold, c.VadMaxSpeechDuration, c.VadWindowSize)
 }
 
 func defaultThreads() int {

internal/server/handlers.go

@@ -3,6 +3,7 @@ package server
 import (
 	"encoding/json"
 	"net/http"
+	"strconv"
 	"strings"
 
 	"git.misaka.ren/m1saka/record-asr/internal/audio"
@@ -23,6 +24,7 @@ func (s *Server) handleHealthz(w http.ResponseWriter, r *http.Request) {
 		"models":          s.manager != nil && s.manager.Ready(),
 		"version":         s.modelVersion(),
 		"max_upload_bytes": s.cfg.MaxUploadBytes,
+		"chunk_size":      s.cfg.ChunkSize,
 	})
 }
 
@@ -82,6 +84,109 @@ func (s *Server) handleCreateTask(w http.ResponseWriter, r *http.Request) {
 	writeJSON(w, http.StatusAccepted, t)
 }
 
+// --- resumable chunked uploads ---
+//
+// Files too large to fit a single request through a size-capping proxy (e.g.
+// Cloudflare's 100MB body limit) are uploaded as many small slices instead.
+// handleCreateUpload starts a session, handleUploadChunk appends one slice,
+// handleCompleteUpload finalizes it into a task, and handleAbortUpload drops
+// it. Each slice is <= ASR_CHUNK_SIZE_MB, safely under the proxy cap.
+
+// handleCreateUpload starts a resumable chunked upload session. The request
+// body is a small JSON {filename, size}; the response carries the upload id,
+// the chunk size, and the total chunk count the client should send.
+func (s *Server) handleCreateUpload(w http.ResponseWriter, r *http.Request) {
+	var req struct {
+		Filename string `json:"filename"`
+		Size     int64  `json:"size"`
+	}
+	dec := json.NewDecoder(http.MaxBytesReader(w, r.Body, 1<<20))
+	if err := dec.Decode(&req); err != nil {
+		renderError(w, http.StatusBadRequest, "invalid JSON: "+err.Error())
+		return
+	}
+	if req.Filename == "" {
+		renderError(w, http.StatusBadRequest, "missing 'filename'")
+		return
+	}
+	if req.Size <= 0 {
+		renderError(w, http.StatusBadRequest, "missing or invalid 'size'")
+		return
+	}
+	if !audio.IsSupported(req.Filename) {
+		renderError(w, http.StatusUnsupportedMediaType,
+			"unsupported extension; supported: "+audio.SupportedExtensions())
+		return
+	}
+	sess, err := s.store.CreateUpload(req.Filename, req.Size, s.cfg.ChunkSize, s.cfg.MaxUploadBytes)
+	if err != nil {
+		renderError(w, http.StatusBadRequest, "init upload: "+err.Error())
+		return
+	}
+	writeJSON(w, http.StatusOK, map[string]any{
+		"upload_id":    sess.UploadID,
+		"chunk_size":   sess.ChunkSize,
+		"total_chunks": sess.TotalChunks,
+	})
+}
+
+// handleUploadChunk appends one chunk (#index, the 0-based query param) of a
+// chunked upload session. The request body is the raw chunk bytes
+// (application/octet-stream); each slice is capped at ASR_CHUNK_SIZE_MB.
+func (s *Server) handleUploadChunk(w http.ResponseWriter, r *http.Request) {
+	id := r.PathValue("id")
+	idx, err := strconv.Atoi(r.URL.Query().Get("index"))
+	if err != nil || idx < 0 {
+		renderError(w, http.StatusBadRequest, "missing or invalid 'index' query param")
+		return
+	}
+	r.Body = http.MaxBytesReader(w, r.Body, s.cfg.ChunkSize)
+	if err := s.store.AppendChunk(id, idx, r.Body, s.cfg.ChunkSize); err != nil {
+		if err == store.ErrUploadNotFound {
+			renderError(w, http.StatusNotFound, "upload session not found or expired")
+			return
+		}
+		renderError(w, http.StatusBadRequest, "chunk: "+err.Error())
+		return
+	}
+	received, total, ok := s.store.UploadStatus(id)
+	if !ok {
+		renderError(w, http.StatusNotFound, "upload session not found")
+		return
+	}
+	writeJSON(w, http.StatusOK, map[string]any{
+		"index":    idx,
+		"received": received,
+		"total":    total,
+	})
+}
+
+// handleCompleteUpload finalizes a chunked upload and enqueues the task. The
+// response mirrors POST /api/tasks (202 + the task) so the client treats the
+// finalized upload exactly like a single-shot upload from this point on.
+func (s *Server) handleCompleteUpload(w http.ResponseWriter, r *http.Request) {
+	id := r.PathValue("id")
+	t, err := s.store.CompleteUpload(id, s.cfg.MaxRetries)
+	if err != nil {
+		if err == store.ErrUploadNotFound {
+			renderError(w, http.StatusNotFound, "upload session not found or expired")
+			return
+		}
+		renderError(w, http.StatusBadRequest, "complete: "+err.Error())
+		return
+	}
+	w.Header().Set("Location", "/api/tasks/"+t.ID)
+	writeJSON(w, http.StatusAccepted, t)
+}
+
+// handleAbortUpload cancels a chunked upload session and removes its part
+// file. Idempotent: a missing session still returns 204.
+func (s *Server) handleAbortUpload(w http.ResponseWriter, r *http.Request) {
+	id := r.PathValue("id")
+	_ = s.store.AbortUpload(id)
+	w.WriteHeader(http.StatusNoContent)
+}
+
 // handleListTasks returns all tasks newest-first.
 func (s *Server) handleListTasks(w http.ResponseWriter, r *http.Request) {
 	writeJSON(w, http.StatusOK, map[string]any{"tasks": s.store.List()})

internal/server/server.go

@@ -64,6 +64,14 @@ func (s *Server) Router() http.Handler {
 	mux.HandleFunc("POST /api/tasks/{id}/skip", s.handleSkipTask)
 	mux.HandleFunc("GET /api/tasks/{id}/transcript", s.handleTranscript)
 
+	// Resumable chunked uploads (also authed). Lets a large file slip past
+	// size-capping proxies (e.g. Cloudflare's 100MB body limit) as many
+	// small slices, finalized into a task indistinguishable from /api/tasks.
+	mux.HandleFunc("POST /api/uploads", s.handleCreateUpload)
+	mux.HandleFunc("POST /api/uploads/{id}", s.handleUploadChunk)
+	mux.HandleFunc("POST /api/uploads/{id}/complete", s.handleCompleteUpload)
+	mux.HandleFunc("DELETE /api/uploads/{id}", s.handleAbortUpload)
+
 	// OpenAI-compatible synchronous transcription (also authed).
 	mux.HandleFunc("POST /v1/audio/transcriptions", s.handleOpenAITranscription)
 

internal/server/ui/index.html

@@ -311,6 +311,26 @@
       </table>
     </div>
 
+    <div class="api-section">
+      <h3>分片上传 <span class="tag">绕过代理体积上限（如 Cloudflare 100MB）</span></h3>
+      <table class="api-tbl">
+        <tr><th>方法</th><th>路径</th><th>说明</th></tr>
+        <tr><td class="m post">POST</td><td><code>/api/uploads</code></td><td>开启上传会话（JSON：<code>{filename,size}</code>）→ <code>{upload_id, chunk_size, total_chunks}</code></td></tr>
+        <tr><td class="m post">POST</td><td><code>/api/uploads/{id}?index=N</code></td><td>上传第 N 片（0 起，原始字节，≤ chunk_size）。乱序/重发幂等</td></tr>
+        <tr><td class="m post">POST</td><td><code>/api/uploads/{id}/complete</code></td><td>收齐后合并并入队 → 202 + 任务（等同 <code>/api/tasks</code>）</td></tr>
+        <tr><td class="m del">DELETE</td><td><code>/api/uploads/{id}</code></td><td>放弃会话并删除分片 → 204</td></tr>
+      </table>
+      <pre class="code"><span class="c"># 大文件分片上传（每片 50MB，默认）</span>
+curl -H "X-Api-Key: $PW" -H "Content-Type: application/json" \
+  -d '{"filename":"big.mp4","size":123456789}' http://localhost:8080/api/uploads
+# → {"upload_id":"ab12cd34","chunk_size":52428800,"total_chunks":3}
+for i in 0 1 2; do
+  curl -H "X-Api-Key: $PW" --data-binary @"part_$i.bin" \
+    "http://localhost:8080/api/uploads/ab12cd34?index=$i"
+done
+curl -H "X-Api-Key: $PW" -X POST http://localhost:8080/api/uploads/ab12cd34/complete</pre>
+    </div>
+
     <div class="api-section">
       <h3>OpenAI 兼容 <span class="tag">同步</span></h3>
       <table class="api-tbl">
@@ -368,7 +388,7 @@ const fmtTime = iso=>{ if(!iso) return "—"; const d=new Date(iso); return isNa
 const fmtDur = s=> s==null?"—": (s<60?s.toFixed(1)+"s" : Math.floor(s/60)+"m"+String(Math.round(s%60)).padStart(2,"0")+"s");
 const escapeHtml = s=>(s||"").replace(/[&<>]/g,c=>({"&":"&amp;","<":"&lt;",">":"&gt;"}[c]));
 
-const state = { pw: localStorage.getItem("asr_pw")||"", tasks:[], sel:null, busy:false, authing:false, uploading:false, maxUpload:0 };
+const state = { pw: localStorage.getItem("asr_pw")||"", tasks:[], sel:null, busy:false, authing:false, uploading:false, maxUpload:0, chunkSize:0 };
 
 // --- password modal (shown only when verification is needed) ---
 const authModal=$("#authModal"), authPw=$("#authPw"), authMsg=$("#authMsg"), authOk=$("#authOk"), authCancel=$("#authCancel");
@@ -480,6 +500,7 @@ async function loadHealth(){
   try{
     const h = await api("/healthz");
     state.maxUpload = h.max_upload_bytes || 0;
+    state.chunkSize = h.chunk_size || 0;
     $("#htext").textContent = h.models?"模型就绪":"模型加载中";
     $("#hdot").className = "dot "+(h.models?"ok":"down");
   }catch(e){ $("#htext").textContent="服务不可达"; $("#hdot").className="dot down"; }
@@ -606,9 +627,12 @@ function renderDropzone(c){
   const dz=el("div",{class:"dropzone"});
   dz.innerHTML=`<svg viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="1.5"><path d="M12 16V4M5 11l7-7 7 7M4 20h16"/></svg><h3>拖拽音频或视频到这里，或点击上传</h3><p>音频直接转写；视频会自动提取音轨。约 1~3 秒出结果。</p><div class="ext">音频 .wav/.mp3/.flac/.ogg/.m4a/.aac/.opus · 视频 .mp4/.mkv/.mov/.avi/.ts…</div>`;
   dz.onclick=()=>$("#file").click();
-  dz.addEventListener("dragover",e=>{e.preventDefault();dz.classList.add("drag")});
+  dz.addEventListener("dragover",e=>{e.preventDefault();e.stopPropagation();dz.classList.add("drag")});
   dz.addEventListener("dragleave",()=>dz.classList.remove("drag"));
-  dz.addEventListener("drop",e=>{e.preventDefault();dz.classList.remove("drag"); if(e.dataTransfer.files.length) uploadFiles(e.dataTransfer.files);});
+  // stopPropagation: the global window 'drop' listener also uploads, so
+  // without this a drop landing on the dropzone would bubble up and upload
+  // the same file twice. The dropzone owns drops on itself.
+  dz.addEventListener("drop",e=>{e.preventDefault();e.stopPropagation();dz.classList.remove("drag"); if(e.dataTransfer.files.length) uploadFiles(e.dataTransfer.files);});
   w.appendChild(dz); c.appendChild(w);
 }
 
@@ -627,9 +651,27 @@ async function uploadFiles(files){
     item.querySelector(".upload-name").textContent=f.name;
     list.appendChild(item);
     const bar=item.querySelector(".upload-bar>div"), pct=item.querySelector(".upload-pct"), st=item.querySelector(".upload-status");
-    const fd=new FormData(); fd.append("file",f);
+    // Large files go through the chunked path so each request stays under
+    // size-capping proxies' body limits (e.g. Cloudflare's 100MB). Files no
+    // bigger than one chunk use the simple single-shot multipart upload.
+    const useChunked = state.chunkSize && f.size>state.chunkSize;
     try{
-      const t=await new Promise((res,rej)=>{
+      const t = useChunked ? await uploadChunked(f,bar,pct,st) : await uploadSingle(f,bar,pct,st);
+      bar.style.width="100%"; pct.textContent="100%";
+      st.textContent="已入队，转写排队中…"; item.classList.add("done");
+      toast("已加入队列: "+(t.original_name||t.id),"ok");
+      state.sel=t.id;
+    }catch(e){ st.textContent="失败: "+e.message; item.classList.add("err"); toast(e.message,"err"); }
+  }
+  // Let the user see the finished state briefly, then refresh the queue.
+  setTimeout(()=>{ state.uploading=false; loadTasks(); }, 600);
+}
+
+// uploadSingle sends a whole file as one multipart request (POST /api/tasks)
+// with XHR so the progress bar reflects bytes sent.
+function uploadSingle(f,bar,pct,st){
+  return new Promise((res,rej)=>{
+    const fd=new FormData(); fd.append("file",f);
     const x=new XMLHttpRequest();
     x.open("POST","/api/tasks");
     x.setRequestHeader("X-Api-Key",state.pw);
@@ -642,14 +684,69 @@ async function uploadFiles(files){
     x.onerror=()=>rej(new Error("网络错误，上传失败"));
     x.send(fd);
   });
-      bar.style.width="100%"; pct.textContent="100%";
-      st.textContent="已入队，转写排队中…"; item.classList.add("done");
-      toast("已加入队列: "+(t.original_name||t.id),"ok");
-      state.sel=t.id;
-    }catch(e){ st.textContent="失败: "+e.message; item.classList.add("err"); toast(e.message,"err"); }
 }
-  // Let the user see the finished state briefly, then refresh the queue.
-  setTimeout(()=>{ state.uploading=false; loadTasks(); }, 600);
+
+// uploadChunked sends a file as ceil(size/chunkSize) slices to the resumable
+// upload API (POST /api/uploads -> /api/uploads/{id}?index=N -> /complete),
+// tracking overall progress across slices. A failing slice is retried a few
+// times on transient errors; on give-up the partial session is aborted.
+async function uploadChunked(f,bar,pct,st){
+  let uid=null; // declared outside try so the catch can reference it safely
+  try{
+    const init = await api("/api/uploads", {
+      method:"POST",
+      headers:{"Content-Type":"application/json"},
+      body: JSON.stringify({filename:f.name, size:f.size})
+    });
+    uid=init.upload_id;
+    const cs=+init.chunk_size, total=+init.total_chunks;
+    const setPct=bytes=>{ const p=Math.min(100,Math.round(bytes/f.size*100)); bar.style.width=p+"%"; pct.textContent=p+"%"; };
+    let uploaded=0;
+    for(let i=0;i<total;i++){
+      const start=i*cs, end=Math.min(start+cs,f.size);
+      const blob=f.slice(start,end);
+      let done=false, lastErr;
+      for(let attempt=0; attempt<3 && !done; attempt++){
+        try{
+          await new Promise((res,rej)=>{
+            const x=new XMLHttpRequest();
+            x.open("POST", `/api/uploads/${uid}?index=${i}`);
+            x.setRequestHeader("X-Api-Key",state.pw);
+            x.upload.onprogress=e=>{ if(e.lengthComputable) setPct(uploaded+e.loaded); };
+            x.onload=()=>{
+              if(x.status>=200&&x.status<300){ try{res(JSON.parse(x.responseText));}catch(e){res(null);} return; }
+              const m=(()=>{ let s="HTTP "+x.status; try{s=(JSON.parse(x.responseText).error)||s;}catch(e){} return s; })();
+              const e=new Error(m); e.status=x.status; rej(e);
+            };
+            x.onerror=()=>{ const e=new Error("网络错误"); e.status=0; rej(e); };
+            x.send(blob);
+          });
+          done=true;
+        }catch(e){
+          lastErr=e;
+          // Auth failure: surface immediately (the modal reopens); don't retry.
+          if(e.status===401){ state.pw=""; localStorage.removeItem("asr_pw"); openAuthModal("密码不正确或服务已重启，请重新输入。",true); throw e; }
+          // 4xx (bad request / session gone): retrying won't help; give up.
+          if(e.status>=400 && e.status<500 && e.status!==0) throw e;
+          // Transient (network/5xx): back off and retry unless last attempt.
+          if(attempt<2){ await new Promise(r=>setTimeout(r, 800*(attempt+1))); }
+        }
+      }
+      if(!done) throw lastErr || new Error("上传分片失败");
+      uploaded += (end-start);
+      setPct(uploaded);
+    }
+    const task = await api(`/api/uploads/${uid}/complete`, {method:"POST"});
+    return task;
+  }catch(e){
+    // Best-effort cleanup of the partial session — but only if one was
+    // actually created (init may have failed) and not on an auth failure
+    // (the password is already cleared and a retry would just 401 again).
+    if(uid && e.status!==401 && state.pw){
+      try{ await fetch(`/api/uploads/${uid}`,{method:"DELETE",headers:{"X-Api-Key":state.pw}}); }catch(_){}
+    }
+    throw e;
+  }
 }
 $("#file").addEventListener("change",e=>{ if(e.target.files.length) uploadFiles(e.target.files); e.target.value=""; });
 $("#uploadBtn").addEventListener("click",()=>$("#file").click());

internal/server/upload_large_test.go

@@ -0,0 +1,153 @@
+package server
+
+import (
+	"bytes"
+	"crypto/sha256"
+	"encoding/hex"
+	"encoding/json"
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"os"
+	"path/filepath"
+	"strconv"
+	"testing"
+
+	"git.misaka.ren/m1saka/record-asr/internal/config"
+	"git.misaka.ren/m1saka/record-asr/internal/store"
+)
+
+// posReader emits a deterministic, position-dependent byte stream so that no
+// two slices of the generated file are identical — a reorder would then
+// change the reassembled hash and be caught.
+type posReader struct{ pos int64 }
+
+func (r *posReader) Read(p []byte) (int, error) {
+	for i := range p {
+		x := r.pos + int64(i)
+		p[i] = byte((x*127 ^ (x >> 7)) & 0xff)
+	}
+	r.pos += int64(len(p))
+	return len(p), nil
+}
+
+// sha256sum returns the hex SHA-256 of a file, streaming so 120MB never sits
+// in memory at once.
+func sha256sum(t *testing.T, path string) string {
+	t.Helper()
+	f, err := os.Open(path)
+	if err != nil {
+		t.Fatalf("open %s: %v", path, err)
+	}
+	defer f.Close()
+	h := sha256.New()
+	if _, err := io.Copy(h, f); err != nil {
+		t.Fatalf("hash %s: %v", path, err)
+	}
+	return hex.EncodeToString(h.Sum(nil))
+}
+
+// TestChunkedUploadLargeFile uploads a 120MB file — larger than the 100MB CDN
+// body cap the feature exists to bypass — as 25MB slices and checks that the
+// reassembled file is byte-identical to the original. Guarded so the default
+// test suite stays fast; run with:
+//
+//	ASR_TEST_LARGE=1 go test -run Large ./internal/server/...
+func TestChunkedUploadLargeFile(t *testing.T) {
+	if os.Getenv("ASR_TEST_LARGE") == "" {
+		t.Skip("set ASR_TEST_LARGE=1 to run the large-file chunked upload test (~120MB on disk)")
+	}
+	const total = 120 << 20 // 120 MiB — over the 100MB cap, no per-request limit here
+	const chunk = 25 << 20  // 25 MiB slices → 5 chunks (last is 20 MiB, partial)
+
+	dir := t.TempDir()
+	st, err := store.Open(dir)
+	if err != nil {
+		t.Fatalf("store.Open: %v", err)
+	}
+	cfg := config.Config{DataDir: dir, ChunkSize: chunk, MaxUploadBytes: 512 << 20, MaxRetries: 3}
+	srv := New(cfg, st, nil, nil) // upload path never touches the transcribe/model stack
+	ts := httptest.NewServer(srv.Router())
+	t.Cleanup(ts.Close)
+
+	// 1. Generate the 120MB original on disk, hashing as we go.
+	origPath := filepath.Join(dir, "original.wav")
+	of, err := os.Create(origPath)
+	if err != nil {
+		t.Fatalf("create orig: %v", err)
+	}
+	if _, err := io.Copy(of, io.LimitReader(&posReader{}, total)); err != nil {
+		t.Fatalf("write orig: %v", err)
+	}
+	of.Close()
+	wantHash := sha256sum(t, origPath)
+
+	// 2. Open a chunked-upload session.
+	body, _ := json.Marshal(map[string]any{"filename": "large.wav", "size": total})
+	resp, err := http.Post(ts.URL+"/api/uploads", "application/json", bytes.NewReader(body))
+	if err != nil {
+		t.Fatalf("init: %v", err)
+	}
+	var init struct {
+		UploadID    string `json:"upload_id"`
+		ChunkSize   int64  `json:"chunk_size"`
+		TotalChunks int    `json:"total_chunks"`
+	}
+	json.NewDecoder(resp.Body).Decode(&init)
+	resp.Body.Close()
+	if init.UploadID == "" || init.ChunkSize != chunk || init.TotalChunks != 5 {
+		t.Fatalf("init = %+v", init)
+	}
+
+	// 3. Stream each slice straight from the original file (no full copy in RAM).
+	src, err := os.Open(origPath)
+	if err != nil {
+		t.Fatalf("open src: %v", err)
+	}
+	defer src.Close()
+	for i := 0; i < init.TotalChunks; i++ {
+		offset := int64(i) * chunk
+		size := int64(chunk)
+		if offset+size > total {
+			size = total - offset
+		}
+		req, _ := http.NewRequest("POST",
+			ts.URL+"/api/uploads/"+init.UploadID+"?index="+strconv.Itoa(i),
+			io.NewSectionReader(src, offset, size))
+		req.Header.Set("Content-Type", "application/octet-stream")
+		cresp, cerr := http.DefaultClient.Do(req)
+		if cerr != nil {
+			t.Fatalf("chunk %d: %v", i, cerr)
+		}
+		if cresp.StatusCode != http.StatusOK {
+			t.Fatalf("chunk %d status = %d", i, cresp.StatusCode)
+		}
+		cresp.Body.Close()
+	}
+
+	// 4. Complete → 202 + pending task.
+	req, _ := http.NewRequest("POST", ts.URL+"/api/uploads/"+init.UploadID+"/complete", nil)
+	resp, err = http.DefaultClient.Do(req)
+	if err != nil {
+		t.Fatalf("complete: %v", err)
+	}
+	defer resp.Body.Close()
+	if resp.StatusCode != http.StatusAccepted {
+		t.Fatalf("complete status = %d", resp.StatusCode)
+	}
+	var task store.Task
+	json.NewDecoder(resp.Body).Decode(&task)
+	if task.Status != store.StatusPending {
+		t.Fatalf("task status = %q, want %q", task.Status, store.StatusPending)
+	}
+
+	// 5. The reassembled file must be byte-identical (same SHA-256) and exact size.
+	gotHash := sha256sum(t, st.AudioPath(&task))
+	if gotHash != wantHash {
+		t.Fatalf("reassembled file hash mismatch:\n want %s\n got  %s", wantHash, gotHash)
+	}
+	fi, err := os.Stat(st.AudioPath(&task))
+	if err != nil || fi.Size() != total {
+		t.Fatalf("final size = %d (%v), want %d", fi.Size(), err, total)
+	}
+}

internal/server/upload_test.go

@@ -0,0 +1,200 @@
+package server
+
+import (
+	"bytes"
+	"encoding/json"
+	"net/http"
+	"net/http/httptest"
+	"os"
+	"strconv"
+	"testing"
+
+	"git.misaka.ren/m1saka/record-asr/internal/config"
+	"git.misaka.ren/m1saka/record-asr/internal/store"
+)
+
+// newUploadTestServer wires a Server backed by a real store + a minimal config
+// (auth disabled, tiny 100B chunks) with nil pipeline/manager — the upload
+// handlers never touch the transcribe/model stack, so this is safe.
+func newUploadTestServer(t *testing.T) (*store.Store, *httptest.Server) {
+	t.Helper()
+	dir := t.TempDir()
+	st, err := store.Open(dir)
+	if err != nil {
+		t.Fatalf("store.Open: %v", err)
+	}
+	cfg := config.Config{
+		DataDir:        dir,
+		ChunkSize:      100,
+		MaxUploadBytes: 1 << 20,
+		MaxRetries:     3,
+	}
+	srv := New(cfg, st, nil, nil)
+	ts := httptest.NewServer(srv.Router())
+	t.Cleanup(ts.Close)
+	return st, ts
+}
+
+// initSession opens a chunked-upload session and returns the upload id.
+func initSession(t *testing.T, ts *httptest.Server, name string, size int64) string {
+	t.Helper()
+	body, _ := json.Marshal(map[string]any{"filename": name, "size": size})
+	resp, err := http.Post(ts.URL+"/api/uploads", "application/json", bytes.NewReader(body))
+	if err != nil {
+		t.Fatalf("init: %v", err)
+	}
+	defer resp.Body.Close()
+	if resp.StatusCode != http.StatusOK {
+		t.Fatalf("init status = %d", resp.StatusCode)
+	}
+	var r struct {
+		UploadID    string `json:"upload_id"`
+		ChunkSize   int64  `json:"chunk_size"`
+		TotalChunks int    `json:"total_chunks"`
+	}
+	if err := json.NewDecoder(resp.Body).Decode(&r); err != nil {
+		t.Fatalf("init decode: %v", err)
+	}
+	if r.UploadID == "" || r.ChunkSize != 100 {
+		t.Fatalf("init resp = %+v", r)
+	}
+	return r.UploadID
+}
+
+func sendChunk(t *testing.T, ts, id string, idx int, data []byte) int {
+	t.Helper()
+	req, _ := http.NewRequest("POST", ts+"/api/uploads/"+id+"?index="+strconv.Itoa(idx), bytes.NewReader(data))
+	req.Header.Set("Content-Type", "application/octet-stream")
+	resp, err := http.DefaultClient.Do(req)
+	if err != nil {
+		t.Fatalf("chunk %d: %v", idx, err)
+	}
+	defer resp.Body.Close()
+	if resp.StatusCode != http.StatusOK {
+		t.Fatalf("chunk %d status = %d", idx, resp.StatusCode)
+	}
+	var r struct {
+		Received int `json:"received"`
+		Total    int `json:"total"`
+	}
+	json.NewDecoder(resp.Body).Decode(&r)
+	return r.Received
+}
+
+// TestChunkedUploadHTTP exercises the full endpoint flow end-to-end.
+func TestChunkedUploadHTTP(t *testing.T) {
+	st, ts := newUploadTestServer(t)
+
+	// /healthz advertises the chunk size the client uses as its threshold.
+	hresp, _ := http.Get(ts.URL + "/healthz")
+	var hz struct {
+		ChunkSize      int64 `json:"chunk_size"`
+		MaxUploadBytes int64 `json:"max_upload_bytes"`
+	}
+	json.NewDecoder(hresp.Body).Decode(&hz)
+	hresp.Body.Close()
+	if hz.ChunkSize != 100 || hz.MaxUploadBytes != 1<<20 {
+		t.Fatalf("healthz = %+v", hz)
+	}
+
+	// 250B file -> 3 chunks (100, 100, 50). Send out of order.
+	uid := initSession(t, ts, "clip.wav", 250)
+	c0 := bytes.Repeat([]byte{0xAA}, 100)
+	c1 := bytes.Repeat([]byte{0xBB}, 100)
+	c2 := bytes.Repeat([]byte{0xCC}, 50)
+	want := append(append([]byte{}, c0...), c1...)
+	want = append(want, c2...)
+	if got := sendChunk(t, ts.URL, uid, 1, c1); got != 1 {
+		t.Fatalf("after chunk 1 received=%d want 1", got)
+	}
+	if got := sendChunk(t, ts.URL, uid, 0, c0); got != 2 {
+		t.Fatalf("after chunk 0 received=%d want 2", got)
+	}
+	if got := sendChunk(t, ts.URL, uid, 2, c2); got != 3 {
+		t.Fatalf("after chunk 2 received=%d want 3", got)
+	}
+
+	// Complete -> 202 + task (same shape as /api/tasks).
+	req, _ := http.NewRequest("POST", ts.URL+"/api/uploads/"+uid+"/complete", nil)
+	resp, err := http.DefaultClient.Do(req)
+	if err != nil {
+		t.Fatalf("complete: %v", err)
+	}
+	defer resp.Body.Close()
+	if resp.StatusCode != http.StatusAccepted {
+		t.Fatalf("complete status = %d", resp.StatusCode)
+	}
+	var task store.Task
+	json.NewDecoder(resp.Body).Decode(&task)
+	if task.Status != store.StatusPending || task.OriginalName != "clip.wav" {
+		t.Fatalf("task = %+v", task)
+	}
+
+	// The reassembled file matches the original bytes exactly.
+	got, err := os.ReadFile(st.AudioPath(&task))
+	if err != nil {
+		t.Fatalf("read final file: %v", err)
+	}
+	if !bytes.Equal(got, want) {
+		t.Fatalf("reassembled bytes mismatch:\n got %x\n want %x", got, want)
+	}
+}
+
+// TestChunkedUploadHTTPErrors checks the error paths: missing index, unknown
+// session, oversized chunk, and idempotent abort.
+func TestChunkedUploadHTTPErrors(t *testing.T) {
+	_, ts := newUploadTestServer(t)
+
+	// Missing ?index -> 400.
+	resp, _ := http.Post(ts.URL+"/api/uploads/someid", "application/octet-stream", bytes.NewReader([]byte("x")))
+	resp.Body.Close()
+	if resp.StatusCode != http.StatusBadRequest {
+		t.Fatalf("missing-index status = %d, want 400", resp.StatusCode)
+	}
+
+	// Complete on an unknown session -> 404.
+	req, _ := http.NewRequest("POST", ts.URL+"/api/uploads/doesnotexist/complete", nil)
+	resp, err := http.DefaultClient.Do(req)
+	if err != nil {
+		t.Fatalf("unknown complete: %v", err)
+	}
+	resp.Body.Close()
+	if resp.StatusCode != http.StatusNotFound {
+		t.Fatalf("unknown complete status = %d, want 404", resp.StatusCode)
+	}
+
+	// Oversized chunk (101B > 100B cap) -> 400.
+	uid := initSession(t, ts, "big.wav", 250)
+	req, _ = http.NewRequest("POST", ts.URL+"/api/uploads/"+uid+"?index=0", bytes.NewReader(bytes.Repeat([]byte{0x9}, 101)))
+	req.Header.Set("Content-Type", "application/octet-stream")
+	resp, err = http.DefaultClient.Do(req)
+	if err != nil {
+		t.Fatalf("oversized chunk: %v", err)
+	}
+	resp.Body.Close()
+	if resp.StatusCode != http.StatusBadRequest {
+		t.Fatalf("oversized chunk status = %d, want 400", resp.StatusCode)
+	}
+
+	// Abort a fresh session -> 204, and the id is gone afterwards.
+	uid2 := initSession(t, ts, "abort.wav", 100)
+	req, _ = http.NewRequest("DELETE", ts.URL+"/api/uploads/"+uid2, nil)
+	resp, err = http.DefaultClient.Do(req)
+	if err != nil {
+		t.Fatalf("abort: %v", err)
+	}
+	resp.Body.Close()
+	if resp.StatusCode != http.StatusNoContent {
+		t.Fatalf("abort status = %d, want 204", resp.StatusCode)
+	}
+	// Completing an aborted session -> 404.
+	req, _ = http.NewRequest("POST", ts.URL+"/api/uploads/"+uid2+"/complete", nil)
+	resp, err = http.DefaultClient.Do(req)
+	if err != nil {
+		t.Fatalf("post-abort complete: %v", err)
+	}
+	resp.Body.Close()
+	if resp.StatusCode != http.StatusNotFound {
+		t.Fatalf("post-abort complete status = %d, want 404", resp.StatusCode)
+	}
+}

internal/store/errors.go

@@ -4,3 +4,7 @@ import "errors"
 
 // ErrNotFound is returned when a task id does not exist.
 var ErrNotFound = errors.New("task not found")
+
+// ErrUploadNotFound is returned when a chunked-upload session id does not exist
+// (never created, already completed, or swept after being idle too long).
+var ErrUploadNotFound = errors.New("upload session not found")

internal/store/store.go

@@ -57,6 +57,7 @@ type Store struct {
 
 	mu       sync.Mutex
 	tasks    map[string]*Task
+	sessions map[string]*UploadSession // in-progress chunked uploads
 }
 
 // Open initializes the store at dir, creating directories and loading any
@@ -75,10 +76,14 @@ func Open(dir string) (*Store, error) {
 		tasksFile:  filepath.Join(dir, "tasks.json"),
 		uploadsDir: uploads,
 		tasks:      map[string]*Task{},
+		sessions:   map[string]*UploadSession{},
 	}
 	if err := s.load(); err != nil {
 		return nil, err
 	}
+	// In-memory upload sessions do not survive a restart; sweep any .part
+	// files left behind by an interrupted chunked upload so they don't leak.
+	s.sweepParts()
 	return s, nil
 }
 
@@ -130,7 +135,9 @@ func (s *Store) Create(originalName string, r io.Reader, maxBytes int64, maxRetr
 	rel := filepath.Join("uploads", id+ext)
 	dst := filepath.Join(s.dir, rel)
 
-	// Copy with a size cap so a malicious upload can't exhaust disk.
+	// Copy with a size cap so a malicious upload can't exhaust disk. The cap
+	// is inclusive: a body of exactly maxBytes is accepted, and anything past
+	// it is rejected.
 	tmp := dst + ".tmp"
 	f, err := os.Create(tmp)
 	if err != nil {
@@ -142,10 +149,7 @@ func (s *Store) Create(originalName string, r io.Reader, maxBytes int64, maxRetr
 		os.Remove(tmp)
 		return nil, fmt.Errorf("read upload: %w", err)
 	}
-	if n >= maxBytes {
-		// Could be exactly at the limit; treat hitting the cap as too large
-		// unless the reader is now exhausted. We err on the side of caution.
-	}
+	_ = n // bytes copied (<= maxBytes); the cap above is the real guard
 	if err := os.Rename(tmp, dst); err != nil {
 		os.Remove(tmp)
 		return nil, fmt.Errorf("save upload: %w", err)
@@ -364,8 +368,9 @@ func newID() string {
 	return hex.EncodeToString(b)
 }
 
-// limitedReader wraps io.Reader with a hard byte cap; exceeding it returns an
-// error so the upload is rejected before it fills the disk.
+// limitedReader wraps io.Reader with an inclusive byte cap: a body that ends
+// at exactly max is accepted (max is the allowed maximum), while any bytes
+// past it are rejected so an oversized body can't fill the disk.
 type limitedReader struct {
 	r   io.Reader
 	max int64
@@ -373,9 +378,7 @@ type limitedReader struct {
 }
 
 func (l *limitedReader) Read(p []byte) (int, error) {
-	if l.n >= l.max {
-		return 0, fmt.Errorf("upload exceeds %d bytes", l.max)
-	}
+	if l.n < l.max {
 		remain := l.max - l.n
 		if int64(len(p)) > remain {
 			p = p[:remain]
@@ -384,3 +387,13 @@ func (l *limitedReader) Read(p []byte) (int, error) {
 		l.n += int64(n)
 		return n, err
 	}
+	// Already at the cap. Tell an exactly-at-cap body (reader now exhausted)
+	// from one that still has bytes (over the cap): read once — any non-zero
+	// return means the body exceeded the cap.
+	n, err := l.r.Read(p)
+	l.n += int64(n)
+	if n > 0 {
+		return n, fmt.Errorf("upload exceeds %d bytes", l.max)
+	}
+	return 0, err
+}

internal/store/upload.go

@@ -0,0 +1,274 @@
+// upload.go extends the store with resumable chunked uploads: a way to receive
+// a large file as many small requests (each under a size-capping proxy's body
+// limit, e.g. Cloudflare's 100MB) and reassemble it into one task.
+//
+// Lifecycle:
+//  1. CreateUpload  — allocate an id + an empty "<id>.part" file, record the
+//     expected total size and chunk layout.
+//  2. AppendChunk    — write chunk #index at offset index*chunkSize into the
+//     .part file. Chunks may arrive in any order and re-sending one is
+//     idempotent (it overwrites the same offset).
+//  3. CompleteUpload — once every chunk has arrived, truncate the .part file
+//     to the exact size, rename it to "<id><ext>", and enqueue a pending task
+//     (reusing the upload id as the task id).
+//  4. AbortUpload    — drop the session and delete the .part file.
+//
+// Sessions live in memory (the .part file is the on-disk durability). A
+// restart therefore loses in-flight sessions; sweepParts cleans up orphaned
+// .part files on Open, and gcUploads lazily reaps sessions idle too long.
+//
+// Locking: Store.mu guards the sessions map; each UploadSession has its own
+// mutex guarding its received[] slice and the part file it owns. The rule that
+// prevents deadlock is: never acquire Store.mu while holding a session mutex.
+// Append/Complete/GC all phase the two locks separately to honour this.
+
+package store
+
+import (
+	"fmt"
+	"io"
+	"os"
+	"path/filepath"
+	"strings"
+	"sync"
+	"time"
+)
+
+// sessionTTL is how long an upload session may stay idle before it (and its
+// .part file) is garbage-collected.
+const sessionTTL = 2 * time.Hour
+
+// UploadSession tracks a resumable chunked upload whose slices are written
+// into a single .part file and finalized into a task on completion.
+type UploadSession struct {
+	UploadID    string
+	Filename    string
+	Size        int64
+	ChunkSize   int64
+	TotalChunks int
+
+	// Unexported state — callers reach these only through Store methods.
+	received  []bool
+	partPath  string
+	ext       string
+	createdAt time.Time
+	lastSeen  time.Time
+	mu        sync.Mutex
+}
+
+// CreateUpload starts a resumable chunked upload session. It allocates an
+// upload id, creates an empty .part file, and records the expected chunk
+// layout. maxBytes caps the total file size; chunkSize is the per-chunk size
+// (must be > 0). The returned session's id is later reused as the task id.
+func (s *Store) CreateUpload(filename string, size, chunkSize, maxBytes int64) (*UploadSession, error) {
+	if chunkSize <= 0 {
+		return nil, fmt.Errorf("chunk size must be > 0")
+	}
+	if size <= 0 {
+		return nil, fmt.Errorf("size must be > 0")
+	}
+	if size > maxBytes {
+		return nil, fmt.Errorf("upload size %d exceeds cap %d", size, maxBytes)
+	}
+	ext := filepath.Ext(filename)
+	id := newID()
+	partPath := filepath.Join(s.uploadsDir, id+".part")
+	f, err := os.OpenFile(partPath, os.O_CREATE|os.O_WRONLY|os.O_TRUNC, 0o644)
+	if err != nil {
+		return nil, fmt.Errorf("create part file: %w", err)
+	}
+	f.Close()
+	total := int((size + chunkSize - 1) / chunkSize)
+	now := time.Now().UTC()
+	sess := &UploadSession{
+		UploadID:    id,
+		Filename:    filename,
+		Size:        size,
+		ChunkSize:   chunkSize,
+		TotalChunks: total,
+		received:    make([]bool, total),
+		partPath:    partPath,
+		ext:         ext,
+		createdAt:   now,
+		lastSeen:    now,
+	}
+	s.gcUploads() // reap idle sessions opportunistically before adding a new one
+	s.mu.Lock()
+	s.sessions[id] = sess
+	s.mu.Unlock()
+	return sess, nil
+}
+
+// AppendChunk writes chunk #index (0-based) of the session's file at offset
+// index*chunkSize and marks it received. Chunks may arrive in any order and
+// are idempotent (re-sending a chunk overwrites the same offset). The reader
+// is capped at maxChunkBytes so a malicious or corrupt body can't overrun the
+// slot; the written length must match the expected chunk length.
+func (s *Store) AppendChunk(uploadID string, index int, r io.Reader, maxChunkBytes int64) error {
+	s.mu.Lock()
+	sess, ok := s.sessions[uploadID]
+	s.mu.Unlock()
+	if !ok {
+		return ErrUploadNotFound
+	}
+	sess.mu.Lock()
+	defer sess.mu.Unlock()
+	sess.lastSeen = time.Now().UTC()
+	if index < 0 || index >= sess.TotalChunks {
+		return fmt.Errorf("chunk index %d out of range [0,%d)", index, sess.TotalChunks)
+	}
+	offset := int64(index) * sess.ChunkSize
+	f, err := os.OpenFile(sess.partPath, os.O_WRONLY, 0o644)
+	if err != nil {
+		return fmt.Errorf("open part: %w", err)
+	}
+	defer f.Close()
+	if _, err := f.Seek(offset, io.SeekStart); err != nil {
+		return fmt.Errorf("seek: %w", err)
+	}
+	n, err := io.Copy(f, &limitedReader{r: r, max: maxChunkBytes})
+	if err != nil {
+		return fmt.Errorf("write chunk: %w", err)
+	}
+	// Validate length: every full chunk == chunkSize; the last chunk is the
+	// remainder. A short or oversized body is rejected (not marked received).
+	expected := sess.ChunkSize
+	if index == sess.TotalChunks-1 {
+		expected = sess.Size - offset
+	}
+	if n != expected {
+		return fmt.Errorf("chunk %d length mismatch: got %d want %d", index, n, expected)
+	}
+	sess.received[index] = true
+	return nil
+}
+
+// CompleteUpload finalizes a chunked upload: verifies every chunk arrived,
+// truncates the part file to the exact size (repairing any overwrite from a
+// rejected chunk), renames it to the task's audio file, and enqueues a
+// pending transcription task. The upload id becomes the task id.
+func (s *Store) CompleteUpload(uploadID string, maxRetries int) (*Task, error) {
+	s.mu.Lock()
+	sess, ok := s.sessions[uploadID]
+	s.mu.Unlock()
+	if !ok {
+		return nil, ErrUploadNotFound
+	}
+	// Session-scoped work (file ops) under the session lock only.
+	sess.mu.Lock()
+	for i, got := range sess.received {
+		if !got {
+			sess.mu.Unlock()
+			return nil, fmt.Errorf("missing chunk %d of %d", i, sess.TotalChunks)
+		}
+	}
+	if err := os.Truncate(sess.partPath, sess.Size); err != nil {
+		sess.mu.Unlock()
+		return nil, fmt.Errorf("truncate part: %w", err)
+	}
+	rel := filepath.Join("uploads", sess.UploadID+sess.ext)
+	dst := filepath.Join(s.dir, rel)
+	if err := os.Rename(sess.partPath, dst); err != nil {
+		sess.mu.Unlock()
+		return nil, fmt.Errorf("finalize upload: %w", err)
+	}
+	sess.mu.Unlock()
+
+	// Register the task under the store lock (no session lock held).
+	now := time.Now().UTC()
+	t := &Task{
+		ID:           sess.UploadID,
+		Filename:     rel,
+		OriginalName: sess.Filename,
+		Status:       StatusPending,
+		CreatedAt:    now,
+		UpdatedAt:    now,
+		MaxRetries:   maxRetries,
+	}
+	s.mu.Lock()
+	delete(s.sessions, uploadID)
+	s.tasks[uploadID] = t
+	serr := s.save()
+	s.mu.Unlock()
+	if serr != nil {
+		return nil, fmt.Errorf("persist task: %w", serr)
+	}
+	return t, nil
+}
+
+// AbortUpload abandons a chunked upload session and removes its part file.
+// It is idempotent (a missing session is not an error).
+func (s *Store) AbortUpload(uploadID string) error {
+	s.mu.Lock()
+	sess, ok := s.sessions[uploadID]
+	if ok {
+		delete(s.sessions, uploadID)
+	}
+	s.mu.Unlock()
+	if !ok {
+		return nil
+	}
+	_ = os.Remove(sess.partPath)
+	return nil
+}
+
+// UploadStatus reports how many chunks of a session have arrived so far. It
+// lets a client show progress and decide whether a complete is safe.
+func (s *Store) UploadStatus(uploadID string) (received, total int, ok bool) {
+	s.mu.Lock()
+	sess, ok2 := s.sessions[uploadID]
+	s.mu.Unlock()
+	if !ok2 {
+		return 0, 0, false
+	}
+	sess.mu.Lock()
+	defer sess.mu.Unlock()
+	n := 0
+	for _, b := range sess.received {
+		if b {
+			n++
+		}
+	}
+	return n, sess.TotalChunks, true
+}
+
+// gcUploads reaps sessions idle for longer than sessionTTL and deletes their
+// .part files. It is called lazily from CreateUpload so no extra goroutine is
+// needed. The two locks are phased (map under Store.mu, idle-check under the
+// session mutex; file removal after Store.mu is released) to honour the
+// "never hold Store.mu while taking a session lock for long" rule.
+func (s *Store) gcUploads() {
+	cutoff := time.Now().Add(-sessionTTL)
+	var dead []*UploadSession
+	s.mu.Lock()
+	for id, sess := range s.sessions {
+		sess.mu.Lock()
+		idle := sess.lastSeen.Before(cutoff)
+		sess.mu.Unlock()
+		if idle {
+			dead = append(dead, sess)
+			delete(s.sessions, id)
+		}
+	}
+	s.mu.Unlock()
+	for _, sess := range dead {
+		_ = os.Remove(sess.partPath)
+	}
+}
+
+// sweepParts removes leftover .part files from interrupted chunked uploads
+// after a restart (in-memory sessions don't survive). Called once from Open.
+func (s *Store) sweepParts() {
+	entries, err := os.ReadDir(s.uploadsDir)
+	if err != nil {
+		return
+	}
+	for _, e := range entries {
+		if !e.Type().IsRegular() {
+			continue
+		}
+		if strings.HasSuffix(e.Name(), ".part") {
+			_ = os.Remove(filepath.Join(s.uploadsDir, e.Name()))
+		}
+	}
+}

internal/store/upload_test.go

@@ -0,0 +1,203 @@
+package store
+
+import (
+	"bytes"
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+// chunkBytes returns a deterministic slice of n bytes whose value is b.
+func chunkBytes(n int, b byte) []byte {
+	out := make([]byte, n)
+	for i := range out {
+		out[i] = b
+	}
+	return out
+}
+
+// newTestStore opens a store in a fresh temp dir.
+func newTestStore(t *testing.T) *Store {
+	t.Helper()
+	s, err := Open(t.TempDir())
+	if err != nil {
+		t.Fatalf("Open: %v", err)
+	}
+	return s
+}
+
+// TestChunkedUploadReassemble verifies that out-of-order, idempotent chunks
+// reassemble into the exact original bytes and enqueue a pending task.
+func TestChunkedUploadReassemble(t *testing.T) {
+	s := newTestStore(t)
+	const chunk = 10
+	const total = 25 // 3 chunks: 10 + 10 + 5
+
+	sess, err := s.CreateUpload("note.wav", total, chunk, 512)
+	if err != nil {
+		t.Fatalf("CreateUpload: %v", err)
+	}
+	if sess.TotalChunks != 3 {
+		t.Fatalf("TotalChunks = %d, want 3", sess.TotalChunks)
+	}
+
+	// Expected file content: three slices with distinct byte values.
+	c0 := chunkBytes(10, 0xAA)
+	c1 := chunkBytes(10, 0xBB)
+	c2 := chunkBytes(5, 0xCC)
+	want := append(append([]byte{}, c0...), c1...)
+	want = append(want, c2...)
+
+	// Send out of order: 1, 0, 2.
+	for _, step := range []struct {
+		idx  int
+		data []byte
+	}{
+		{1, c1}, {0, c0}, {2, c2},
+	} {
+		if err := s.AppendChunk(sess.UploadID, step.idx, bytes.NewReader(step.data), chunk); err != nil {
+			t.Fatalf("AppendChunk(%d): %v", step.idx, err)
+		}
+		got, total, ok := s.UploadStatus(sess.UploadID)
+		if !ok {
+			t.Fatalf("UploadStatus: session gone")
+		}
+		_ = total
+		// After the last append all 3 should be received.
+		if step.idx == 2 && got != 3 {
+			t.Fatalf("after last chunk received=%d want 3", got)
+		}
+	}
+
+	// Re-send chunk 0 (idempotent): content must be unchanged.
+	if err := s.AppendChunk(sess.UploadID, 0, bytes.NewReader(c0), chunk); err != nil {
+		t.Fatalf("AppendChunk(0) re-send: %v", err)
+	}
+
+	task, err := s.CompleteUpload(sess.UploadID, 3)
+	if err != nil {
+		t.Fatalf("CompleteUpload: %v", err)
+	}
+	if task.Status != StatusPending {
+		t.Fatalf("task status = %q, want %q", task.Status, StatusPending)
+	}
+	if task.OriginalName != "note.wav" {
+		t.Fatalf("original_name = %q", task.OriginalName)
+	}
+
+	// The part file is gone; the final audio file holds the exact bytes.
+	if _, err := os.Stat(filepath.Join(s.uploadsDir, sess.UploadID+".part")); !os.IsNotExist(err) {
+		t.Fatalf("part file still present: %v", err)
+	}
+	got, err := os.ReadFile(filepath.Join(s.dir, task.Filename))
+	if err != nil {
+		t.Fatalf("read final file: %v", err)
+	}
+	if !bytes.Equal(got, want) {
+		t.Fatalf("final bytes mismatch:\n got %x\n want %x", got, want)
+	}
+	if int64(len(got)) != total {
+		t.Fatalf("final size = %d, want %d", len(got), total)
+	}
+
+	// The session became a task the store knows about.
+	if s.Get(task.ID) == nil {
+		t.Fatalf("Get(task) returned nil after complete")
+	}
+	// ...and is no longer an upload session.
+	if _, _, ok := s.UploadStatus(sess.UploadID); ok {
+		t.Fatalf("session still present after complete")
+	}
+}
+
+// TestChunkedUploadMissingChunk ensures complete fails when a chunk is absent.
+func TestChunkedUploadMissingChunk(t *testing.T) {
+	s := newTestStore(t)
+	sess, _ := s.CreateUpload("x.wav", 20, 10, 512) // 2 chunks
+	_ = s.AppendChunk(sess.UploadID, 0, bytes.NewReader(chunkBytes(10, 1)), 10)
+	if _, err := s.CompleteUpload(sess.UploadID, 3); err == nil {
+		t.Fatalf("CompleteUpload succeeded with a missing chunk")
+	}
+	// The session survives a failed complete so the client can send the rest.
+	if _, _, ok := s.UploadStatus(sess.UploadID); !ok {
+		t.Fatalf("session dropped after failed complete")
+	}
+}
+
+// TestChunkedUploadLengthMismatch rejects a chunk whose size is wrong.
+func TestChunkedUploadLengthMismatch(t *testing.T) {
+	s := newTestStore(t)
+	sess, _ := s.CreateUpload("x.wav", 20, 10, 512) // 2 chunks of 10
+	// Send only 7 bytes for a chunk that should be 10.
+	if err := s.AppendChunk(sess.UploadID, 0, bytes.NewReader(chunkBytes(7, 1)), 10); err == nil {
+		t.Fatalf("AppendChunk accepted a short chunk")
+	}
+}
+
+// TestChunkedUploadAbort removes the part file and drops the session.
+func TestChunkedUploadAbort(t *testing.T) {
+	s := newTestStore(t)
+	sess, _ := s.CreateUpload("x.wav", 10, 10, 512)
+	_ = s.AppendChunk(sess.UploadID, 0, bytes.NewReader(chunkBytes(10, 1)), 10)
+	part := filepath.Join(s.uploadsDir, sess.UploadID+".part")
+	if _, err := os.Stat(part); err != nil {
+		t.Fatalf("part file missing before abort: %v", err)
+	}
+	if err := s.AbortUpload(sess.UploadID); err != nil {
+		t.Fatalf("AbortUpload: %v", err)
+	}
+	if _, err := os.Stat(part); !os.IsNotExist(err) {
+		t.Fatalf("part file present after abort: %v", err)
+	}
+	if _, _, ok := s.UploadStatus(sess.UploadID); ok {
+		t.Fatalf("session still present after abort")
+	}
+	// Abort of an unknown session is idempotent, not an error.
+	if err := s.AbortUpload("nope"); err != nil {
+		t.Fatalf("AbortUpload(unknown) = %v, want nil", err)
+	}
+}
+
+// TestSweepPartsOnOpen confirms a leftover .part file from a previous run is
+// removed when the store reopens (in-memory sessions don't survive restarts).
+func TestSweepPartsOnOpen(t *testing.T) {
+	dir := t.TempDir()
+	s1, err := Open(dir)
+	if err != nil {
+		t.Fatalf("Open: %v", err)
+	}
+	sess, _ := s1.CreateUpload("x.wav", 10, 10, 512)
+	part := filepath.Join(s1.uploadsDir, sess.UploadID+".part")
+	if _, err := os.Stat(part); err != nil {
+		t.Fatalf("part missing: %v", err)
+	}
+	s1.gcUploads() // no-op: session not idle yet; part must survive
+	if _, err := os.Stat(part); err != nil {
+		t.Fatalf("part swept too early: %v", err)
+	}
+
+	// Reopen the same dir: the orphan .part file must be swept.
+	s2, err := Open(dir)
+	if err != nil {
+		t.Fatalf("Open(2): %v", err)
+	}
+	if _, err := os.Stat(filepath.Join(s2.uploadsDir, sess.UploadID+".part")); !os.IsNotExist(err) {
+		t.Fatalf("orphan .part file survived reopen: %v", err)
+	}
+}
+
+// TestSweepPartsPreservesTaskAudio ensures the startup sweep only touches
+// .part files, never finalized task audio (uploads/<id>.<ext>).
+func TestSweepPartsPreservesTaskAudio(t *testing.T) {
+	dir := t.TempDir()
+	s1, _ := Open(dir)
+	task, err := s1.Create("kept.wav", bytes.NewReader(chunkBytes(10, 7)), 512, 1)
+	if err != nil {
+		t.Fatalf("Create: %v", err)
+	}
+	audioPath := filepath.Join(s1.dir, task.Filename)
+	s1.sweepParts() // must not delete the task's audio
+	if _, err := os.Stat(audioPath); err != nil {
+		t.Fatalf("task audio swept by sweepParts: %v", err)
+	}
+}