fix(downloader): retry checksum mismatches (#11536)

A remote can serve stale or corrupted bytes for one request. Mark the
integrity failure as transient so the bounded download planner retries it.

Assisted-by: Codex:gpt-5.6

Co-authored-by: localai-org-maint-bot <306269227+localai-org-maint-bot@users.noreply.github.com>

pkg/downloader/retry_test.go

@@ -179,6 +179,37 @@ var _ = Describe("DownloadFilesWithContext retries", func() {
 		}
 	})
 
+	It("retries a checksum mismatch", func() {
+		wrongPayload := []byte("stale model bytes")
+		requests := 0
+		server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			requests++
+			body := payload
+			if requests == 1 {
+				body = wrongPayload
+			}
+			w.Header().Set("Content-Length", strconv.Itoa(len(body)))
+			w.WriteHeader(http.StatusOK)
+			_, _ = w.Write(body)
+		}))
+		DeferCleanup(server.Close)
+
+		err := downloader.DownloadFilesWithContext(context.Background(), []downloader.FileTask{{
+			URI:         downloader.URI(server.URL),
+			Destination: destPath,
+			SHA256:      payloadSHA,
+			FileIndex:   1,
+			TotalFiles:  1,
+		}}, nil)
+		Expect(requests).To(Equal(2), "the checksum failure must trigger one retry")
+		Expect(err).ToNot(HaveOccurred())
+
+		got, err := os.ReadFile(destPath)
+		Expect(err).ToNot(HaveOccurred())
+		Expect(got).To(Equal(payload))
+		Expect(destPath + downloader.PartialFileSuffix).ToNot(BeAnExistingFile())
+	})
+
 	It("does not retry a permanent failure", func() {
 		attempts := 0
 		server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {

pkg/downloader/uri.go

@@ -850,7 +850,7 @@ func (uri URI) DownloadFileWithContext(ctx context.Context, filePath, sha string
 		if calculatedSHA != sha {
 			xlog.Debug("SHA mismatch for file", "file", filePath, "calculated", calculatedSHA, "metadata", sha)
 			_ = removePartialFile(tmpFilePath)
-			return fmt.Errorf("SHA mismatch for file %q ( calculated: %s != metadata: %s )", filePath, calculatedSHA, sha)
+			return asTransient(fmt.Errorf("SHA mismatch for file %q ( calculated: %s != metadata: %s )", filePath, calculatedSHA, sha))
 		}
 	} else {
 		// Visible at the default log level so missing-digest configs are