PowerShell · KirtiRamchandani · May 25, 2026
@@ -580,10 +580,7 @@ protected override void ProcessRecord()
 
                             // Check if the Resume range was not satisfiable because the file already completed downloading.
                             // This happens when the local file is the same size as the remote file.
-                            if (Resume.IsPresent
-                                && response.StatusCode == HttpStatusCode.RequestedRangeNotSatisfiable
-                                && response.Content.Headers.ContentRange.HasLength
-                                && response.Content.Headers.ContentRange.Length == _resumeFileSize)
+                            if (IsResumeRangeAlreadyComplete(response))
                             {
                                 _isSuccess = true;
                                 WriteVerbose(string.Format(
@@ -1354,10 +1351,7 @@ internal virtual HttpResponseMessage GetResponse(HttpClient client, HttpRequestM
                 // Request again without the Range header because the server indicated the range was not satisfiable.
                 // This happens when the local file is larger than the remote file.
                 // If the size of the remote file is the same as the local file, there is nothing to resume.
-                if (Resume.IsPresent
-                    && response.StatusCode == HttpStatusCode.RequestedRangeNotSatisfiable
-                    && (response.Content.Headers.ContentRange.HasLength
-                    && response.Content.Headers.ContentRange.Length != _resumeFileSize))
+                if (ShouldRetryWithoutResumeRange(response))
                 {
                     _cancelToken.Cancel();
 
@@ -1736,6 +1730,31 @@ private void ProcessAuthentication()
 
         private bool IsPersistentSession() => MyInvocation.BoundParameters.ContainsKey(nameof(WebSession)) || MyInvocation.BoundParameters.ContainsKey(nameof(SessionVariable));
 
+        private bool IsResumeRangeAlreadyComplete(HttpResponseMessage response)
+        {
+            if (!Resume.IsPresent || response.StatusCode != HttpStatusCode.RequestedRangeNotSatisfiable)
+            {
+                return false;
+            }
+
+            ContentRangeHeaderValue contentRange = response.Content.Headers.ContentRange;
+
+            // RFC 9110 only says 416 responses SHOULD include Content-Range. Treat a missing
+            // header as an already-complete resume instead of failing with a null reference.
+            return contentRange is null || (contentRange.HasLength && contentRange.Length == _resumeFileSize);
+        }
+
+        private bool ShouldRetryWithoutResumeRange(HttpResponseMessage response)
+        {
+            if (!Resume.IsPresent || response.StatusCode != HttpStatusCode.RequestedRangeNotSatisfiable)
+            {
+                return false;
+            }
+
+            ContentRangeHeaderValue contentRange = response.Content.Headers.ContentRange;
+            return contentRange is not null && contentRange.HasLength && contentRange.Length != _resumeFileSize;
+        }
+
         /// <summary>
         /// Sets the ContentLength property of the request and writes the specified content to the request's RequestStream.
         /// </summary>

@@ -2213,6 +2213,23 @@ Describe "Invoke-WebRequest tests" -Tags "Feature", "RequireAdminOnWindows" {
             $response.StatusCode | Should -Be 416
             $response.Headers.'Content-Range'[0] | Should -BeExactly "bytes */$referenceFileSize"
         }
+
+        It "Invoke-WebRequest -Resume treats 416 without Content-Range as a completed download" {
+            # Download the entire file
+            $uri = Get-WebListenerUrl -Test 'Resume' -TestValue 'MissingContentRange'
+            $null = Invoke-WebRequest -Uri $uri -OutFile $outFile
+            $fileSize = Get-Item $outFile | Select-Object -ExpandProperty Length
+
+            $response = Invoke-WebRequest -Uri $uri -OutFile $outFile -Resume -PassThru
+
+            $outFileHash = Get-FileHash -Algorithm SHA256 -Path $outFile
+            $outFileHash.Hash | Should -BeExactly $referenceFileHash.Hash
+            Get-Item $outFile | Select-Object -ExpandProperty Length | Should -Be $referenceFileSize
+            $response.Headers.'X-WebListener-Has-Range'[0] | Should -BeExactly 'true'
+            $response.Headers.'X-WebListener-Request-Range'[0] | Should -BeExactly "bytes=$fileSize-"
+            $response.StatusCode | Should -Be 416
+            $response.Headers.ContainsKey('Content-Range') | Should -BeFalse
+        }
     }
 
     Context "Invoke-WebRequest retry tests" {
@@ -4244,6 +4261,22 @@ Describe "Invoke-RestMethod tests" -Tags "Feature", "RequireAdminOnWindows" {
             $Headers.'X-WebListener-Request-Range'[0] | Should -BeExactly "bytes=$fileSize-"
             $Headers.'Content-Range'[0] | Should -BeExactly "bytes */$referenceFileSize"
         }
+
+        It "Invoke-RestMethod -Resume treats 416 without Content-Range as a completed download" {
+            # Download the entire file
+            $uri = Get-WebListenerUrl -Test 'Resume' -TestValue 'MissingContentRange'
+            $null = Invoke-RestMethod -Uri $uri -OutFile $outFile
+            $fileSize = Get-Item $outFile | Select-Object -ExpandProperty Length
+
+            Invoke-RestMethod -Uri $uri -OutFile $outFile -ResponseHeadersVariable 'Headers' -Resume
+
+            $outFileHash = Get-FileHash -Algorithm SHA256 -Path $outFile
+            $outFileHash.Hash | Should -BeExactly $referenceFileHash.Hash
+            Get-Item $outFile | Select-Object -ExpandProperty Length | Should -Be $referenceFileSize
+            $Headers.'X-WebListener-Has-Range'[0] | Should -BeExactly 'true'
+            $Headers.'X-WebListener-Request-Range'[0] | Should -BeExactly "bytes=$fileSize-"
+            $Headers.ContainsKey('Content-Range') | Should -BeFalse
+        }
     }
 
     Context "Invoke-RestMethod retry tests" {

@@ -74,6 +74,22 @@ public async void NoResume()
             await Response.Body.WriteAsync(FileBytes, 0, FileBytes.Length);
         }
 
+        public async void MissingContentRange()
+        {
+            SetResumeResponseHeaders();
+            string rangeHeader;
+            if (TryGetRangeHeader(out rangeHeader))
+            {
+                Response.StatusCode = StatusCodes.Status416RequestedRangeNotSatisfiable;
+                return;
+            }
+
+            Response.ContentType = MediaTypeNames.Application.Octet;
+            Response.ContentLength = FileBytes.Length;
+            Response.StatusCode = StatusCodes.Status200OK;
+            await Response.Body.WriteAsync(FileBytes, 0, FileBytes.Length);
+        }
+
         public async void Bytes(int NumberBytes)
         {
             if (NumberBytes > FileBytes.Length || NumberBytes < 0)