diff --git a/agentscope-core/src/main/java/io/agentscope/core/formatter/gemini/GeminiMediaConverter.java b/agentscope-core/src/main/java/io/agentscope/core/formatter/gemini/GeminiMediaConverter.java
index cdaca84256..8b23d46cd9 100644
--- a/agentscope-core/src/main/java/io/agentscope/core/formatter/gemini/GeminiMediaConverter.java
+++ b/agentscope-core/src/main/java/io/agentscope/core/formatter/gemini/GeminiMediaConverter.java
@@ -128,7 +128,9 @@ private Part convertMediaBlockToInlineDataPart(Source source, String mediaType)
     /**
      * Read a file from URL/path as byte array.
      *
-     * <p>Supports both remote URLs (http://, https://) and local file paths.
+     * <p>Supports both remote URLs (http://, https://) and local file paths. Query string
+     * and fragment are stripped from local file paths so that paths like {@code
+     * /tmp/cat.png?token=abc} resolve to the actual file on disk.
      *
      * @param url File URL or path
      * @return File content as byte array
@@ -146,8 +148,9 @@ private byte[] readFileAsBytes(String url) throws IOException {
                 throw new IOException("Failed to download remote file: " + url, e);
             }
         } else {
-            // Local file path
-            Path path = Paths.get(url);
+            // Local file path — strip query string / fragment before resolving
+            String localPath = stripQueryAndFragment(url);
+            Path path = Paths.get(localPath);
             if (!Files.exists(path)) {
                 throw new IOException("File not found: " + url);
             }
@@ -155,6 +158,22 @@ private byte[] readFileAsBytes(String url) throws IOException {
         }
     }
 
+    /**
+     * Strips query string ({@code ?...}) and fragment ({@code #...}) from a URL/path string.
+     */
+    private static String stripQueryAndFragment(String url) {
+        String path = url;
+        int fragmentIndex = path.indexOf('#');
+        if (fragmentIndex >= 0) {
+            path = path.substring(0, fragmentIndex);
+        }
+        int queryIndex = path.indexOf('?');
+        if (queryIndex >= 0) {
+            path = path.substring(0, queryIndex);
+        }
+        return path;
+    }
+
     /**
      * Determine MIME type from file extension.
      *
@@ -186,14 +205,19 @@ private String getMimeType(String url, String mediaType) {
     /**
      * Extract file extension from URL or path.
      *
+     * <p>Strips query string ({@code ?...}) and fragment ({@code #...}) before extracting
+     * the extension so that URLs like {@code http://example.com/cat.png?token=abc} produce
+     * {@code png} rather than {@code png?token=abc}.
+     *
      * @param url File URL or path
      * @return File extension in lowercase (without dot)
      */
     private String extractExtension(String url) {
-        int lastDotIndex = url.lastIndexOf('.');
-        if (lastDotIndex == -1 || lastDotIndex == url.length() - 1) {
+        String path = stripQueryAndFragment(url);
+        int lastDotIndex = path.lastIndexOf('.');
+        if (lastDotIndex == -1 || lastDotIndex == path.length() - 1) {
             throw new IllegalArgumentException("Cannot extract file extension from: " + url);
         }
-        return url.substring(lastDotIndex + 1).toLowerCase();
+        return path.substring(lastDotIndex + 1).toLowerCase();
     }
 }
diff --git a/agentscope-core/src/test/java/io/agentscope/core/formatter/gemini/GeminiMediaConverterTest.java b/agentscope-core/src/test/java/io/agentscope/core/formatter/gemini/GeminiMediaConverterTest.java
index 90c520dd6c..81daa27085 100644
--- a/agentscope-core/src/test/java/io/agentscope/core/formatter/gemini/GeminiMediaConverterTest.java
+++ b/agentscope-core/src/test/java/io/agentscope/core/formatter/gemini/GeminiMediaConverterTest.java
@@ -142,6 +142,45 @@ void testUnsupportedExtension() {
         assertThrows(RuntimeException.class, () -> converter.convertToInlineDataPart(block));
     }
 
+    @Test
+    void testUrlWithQueryString() {
+        // Issue #1645: URL with query string should strip ?... before extracting extension
+        URLSource source =
+                URLSource.builder().url(tempImageFile.toString() + "?token=abc123").build();
+        ImageBlock block = ImageBlock.builder().source(source).build();
+
+        // Should resolve to image/png and read the file successfully
+        Part result = converter.convertToInlineDataPart(block);
+        assertNotNull(result);
+        assertTrue(result.inlineData().isPresent());
+        assertEquals("image/png", result.inlineData().get().mimeType().get());
+    }
+
+    @Test
+    void testUrlWithFragment() {
+        // Issue #1645: URL with fragment should strip #... before extracting extension
+        URLSource source = URLSource.builder().url(tempAudioFile.toString() + "#preview").build();
+        AudioBlock block = AudioBlock.builder().source(source).build();
+
+        Part result = converter.convertToInlineDataPart(block);
+        assertNotNull(result);
+        assertTrue(result.inlineData().isPresent());
+        assertEquals("audio/mp3", result.inlineData().get().mimeType().get());
+    }
+
+    @Test
+    void testUrlWithQueryStringAndFragment() {
+        // Issue #1645: URL with both query string and fragment
+        URLSource source =
+                URLSource.builder().url(tempImageFile.toString() + "?download=1#preview").build();
+        ImageBlock block = ImageBlock.builder().source(source).build();
+
+        Part result = converter.convertToInlineDataPart(block);
+        assertNotNull(result);
+        assertTrue(result.inlineData().isPresent());
+        assertEquals("image/png", result.inlineData().get().mimeType().get());
+    }
+
     @Test
     void testFileNotFound() {
         URLSource source = URLSource.builder().url("/nonexistent/file.png").build();