diff --git a/src/pull_module/curl_downloader.cpp b/src/pull_module/curl_downloader.cpp
index 5c0243550b..ad6f53e18d 100644
--- a/src/pull_module/curl_downloader.cpp
+++ b/src/pull_module/curl_downloader.cpp
@@ -46,13 +46,45 @@ static void print_download_speed_info(size_t received_size, size_t elapsed_time)
     printf(" [%.2f %s/s] ", rate, sizeUnits[rate_unit_idx]);
 }
 
+int computeProgressBarCells(size_t count, size_t max, int barWidth) {
+    if (max == 0 || barWidth <= 0) {
+        return 0;
+    }
+    const double ratio = static_cast<double>(count) / static_cast<double>(max);
+    // Written as a positive test so a NaN ratio also lands here rather than falling through.
+    if (!(ratio > 0.0)) {
+        return 0;
+    }
+    if (ratio >= 1.0) {
+        return barWidth;
+    }
+    return static_cast<int>(ratio * barWidth);
+}
+
 static void print_progress(size_t count, size_t max, bool first_run, size_t elapsed_time) {
+    // A response with no Content-Length reports dltotal == 0, so there is no ratio to show;
+    // report the running byte count instead. Dividing by max here yielded an infinite ratio
+    // whose conversion to int is undefined - in practice INT_MIN, which drove the padding
+    // loop below through roughly 2.1 billion putchar calls on every progress tick.
+    if (max == 0) {
+        double received = (double)count;
+        size_t receivedUnitId = 0;
+        while (received > 1000 && sizeUnits[receivedUnitId + 1]) {
+            received /= 1000.0;
+            receivedUnitId++;
+        }
+        printf("\rProgress: %.2f %s downloaded, total size unknown", received, sizeUnits[receivedUnitId]);
+        print_download_speed_info(count, elapsed_time);
+        fflush(stdout);
+        return;
+    }
+
     float progress = (float)count / max;
     if (!first_run && progress < 0.01 && count > 0)
         return;
 
     const int bar_width = 50;
-    int bar_length = progress * bar_width;
+    const int bar_length = computeProgressBarCells(count, max, bar_width);
 
     printf("\rProgress: [");
     int i;
diff --git a/src/pull_module/curl_downloader.hpp b/src/pull_module/curl_downloader.hpp
index 12a9ab39c5..386757a20d 100644
--- a/src/pull_module/curl_downloader.hpp
+++ b/src/pull_module/curl_downloader.hpp
@@ -14,6 +14,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 //*****************************************************************************
+#include <cstddef>
 #include <string>
 
 namespace ovms {
@@ -23,4 +24,9 @@ Status downloadFileWithCurl(const std::string& url, const std::string& filePath)
 Status downloadFileWithCurl(const std::string& url, const std::string& filePath, const std::string& authTokenHF);
 Status fetchUrlToString(const std::string& url, const std::string& authToken, std::string& responseBody);
 
+// Number of filled cells in a barWidth-wide progress bar for count out of max bytes,
+// clamped to [0, barWidth]. max == 0 means the server sent no Content-Length, so there is
+// no ratio to render and the result is 0. Declared here so the arithmetic can be unit tested.
+int computeProgressBarCells(size_t count, size_t max, int barWidth);
+
 }  // namespace ovms
diff --git a/src/test/pull_hf_model_test.cpp b/src/test/pull_hf_model_test.cpp
index 5995159f78..9ba9170b61 100644
--- a/src/test/pull_hf_model_test.cpp
+++ b/src/test/pull_hf_model_test.cpp
@@ -18,6 +18,7 @@
 #include <cstdlib>
 #include <fstream>
 #include <iomanip>
+#include <limits>
 #include <memory>
 #include <openssl/sha.h>
 #include <mutex>
@@ -47,6 +48,7 @@
 #include "src/test/test_file_utils.hpp"
 #include "src/test/test_with_temp_dir.hpp"
 #include "src/filesystem/filesystem.hpp"
+#include "src/pull_module/curl_downloader.hpp"
 #include "src/pull_module/hf_pull_model_module.hpp"
 #include "src/pull_module/libgit2.hpp"
 #include "src/pull_module/optimum_export.hpp"
@@ -378,6 +380,29 @@ ::testing::AssertionResult interruptPosixWorkerAndExpectGracefulExit(pid_t child
 
 }  // namespace
 
+// A response without Content-Length makes libcurl report dltotal == 0. The progress bar must
+// not divide by it: the ratio becomes infinite and converting that to int is undefined, which
+// in practice produced INT_MIN and a ~2.1 billion iteration padding loop.
+TEST(CurlDownloaderProgressTest, UnknownTotalYieldsNoFilledCells) {
+    EXPECT_EQ(ovms::computeProgressBarCells(0, 0, 50), 0);
+    EXPECT_EQ(ovms::computeProgressBarCells(1024, 0, 50), 0);
+    EXPECT_EQ(ovms::computeProgressBarCells(std::numeric_limits<size_t>::max(), 0, 50), 0);
+}
+
+TEST(CurlDownloaderProgressTest, FilledCellsTrackRatio) {
+    EXPECT_EQ(ovms::computeProgressBarCells(0, 100, 50), 0);
+    EXPECT_EQ(ovms::computeProgressBarCells(50, 100, 50), 25);
+    EXPECT_EQ(ovms::computeProgressBarCells(100, 100, 50), 50);
+}
+
+// Some servers report more bytes transferred than announced; the bar must stay within its width
+// so the padding loop below it always runs a sane number of times.
+TEST(CurlDownloaderProgressTest, FilledCellsClampToBarWidth) {
+    EXPECT_EQ(ovms::computeProgressBarCells(200, 100, 50), 50);
+    EXPECT_EQ(ovms::computeProgressBarCells(100, 100, 0), 0);
+    EXPECT_EQ(ovms::computeProgressBarCells(100, 100, -1), 0);
+}
+
 // RAII helper class for managing log file lifecycle.
 // Creates a log file path and automatically removes it on destruction.
 class LogFileGuard {