diff --git a/mateclaw-server/src/main/java/vip/mate/wiki/service/WikiDirectoryScanService.java b/mateclaw-server/src/main/java/vip/mate/wiki/service/WikiDirectoryScanService.java
index d381591d..a7e985ad 100644
--- a/mateclaw-server/src/main/java/vip/mate/wiki/service/WikiDirectoryScanService.java
+++ b/mateclaw-server/src/main/java/vip/mate/wiki/service/WikiDirectoryScanService.java
@@ -165,14 +165,9 @@ public class WikiDirectoryScanService {
                     continue;
                 }
 
-                // Binary files: dedup by source path. Re-ingest on content change
-                // is not detected here (hashing large binaries each scan is
-                // expensive) — modified binaries should be re-uploaded explicitly.
-                WikiRawMaterialEntity existing = rawService.findBySourcePath(kbId, absolutePath);
-                if (existing != null) {
-                    skipped++;
-                    continue;
-                }
+                // Binary files: dedup by content hash too, so a modified file is
+                // re-ingested. The unchanged case reads the file once to hash it;
+                // only a new/changed file is read again to import.
                 String sourceType = switch (ext) {
                     case "pdf" -> "pdf";
                     case "docx", "doc" -> "docx";
@@ -181,8 +176,13 @@ public class WikiDirectoryScanService {
                     case "html", "htm" -> "html";
                     default -> "text";
                 };
-                rawService.addFile(kbId, fileName, sourceType, absolutePath, Files.size(file));
-                added++;
+                boolean freshBinary = rawService.ingestBinaryFileFromScan(
+                        kbId, fileName, sourceType, absolutePath, Files.size(file));
+                if (freshBinary) {
+                    added++;
+                } else {
+                    skipped++;
+                }
 
             } catch (Exception e) {
                 errors.add("Failed to import: " + file.getFileName() + " (" + e.getMessage() + ")");
diff --git a/mateclaw-server/src/main/java/vip/mate/wiki/service/WikiRawMaterialService.java b/mateclaw-server/src/main/java/vip/mate/wiki/service/WikiRawMaterialService.java
index 087ff385..6f3b8d4a 100644
--- a/mateclaw-server/src/main/java/vip/mate/wiki/service/WikiRawMaterialService.java
+++ b/mateclaw-server/src/main/java/vip/mate/wiki/service/WikiRawMaterialService.java
@@ -115,6 +115,37 @@ public class WikiRawMaterialService {
         return sameContent == null;
     }
 
+    /**
+     * Import a binary file discovered by a directory scan, detecting content
+     * changes by hashing the bytes: unchanged content (a raw with the same hash
+     * exists) is skipped, while changed content is re-ingested via
+     * {@link #addFile}. The unchanged case reads the file once; only a
+     * new/changed file is read again by addFile.
+     *
+     * @return {@code true} when newly ingested, {@code false} when unchanged
+     */
+    public boolean ingestBinaryFileFromScan(Long kbId, String title, String sourceType,
+                                            String absolutePath, long fileSize) {
+        String hash = null;
+        try {
+            hash = computeHashOfBytes(java.nio.file.Files.readAllBytes(java.nio.file.Paths.get(absolutePath)));
+        } catch (Exception e) {
+            log.warn("[Wiki] Could not hash file for change detection: {}", e.getMessage());
+        }
+        if (hash != null) {
+            WikiRawMaterialEntity sameContent = rawMapper.selectOne(
+                    new LambdaQueryWrapper<WikiRawMaterialEntity>()
+                            .eq(WikiRawMaterialEntity::getKbId, kbId)
+                            .eq(WikiRawMaterialEntity::getContentHash, hash)
+                            .last("LIMIT 1"));
+            if (sameContent != null) {
+                return false; // unchanged — addFile not called, avoids a second read
+            }
+        }
+        addFile(kbId, title, sourceType, absolutePath, fileSize);
+        return true;
+    }
+
     /**
      * Record the originating file path on a raw material via a partial update,
      * so a later directory re-scan can dedup it by source path. Used for
diff --git a/mateclaw-server/src/test/java/vip/mate/wiki/service/WikiSourceWatcherServiceE2ETest.java b/mateclaw-server/src/test/java/vip/mate/wiki/service/WikiSourceWatcherServiceE2ETest.java
index 86173ee0..d669117b 100644
--- a/mateclaw-server/src/test/java/vip/mate/wiki/service/WikiSourceWatcherServiceE2ETest.java
+++ b/mateclaw-server/src/test/java/vip/mate/wiki/service/WikiSourceWatcherServiceE2ETest.java
@@ -87,6 +87,21 @@ class WikiSourceWatcherServiceE2ETest {
                 "the escaping symlink should be reported as skipped");
     }
 
+    @Test
+    void modifiedBinaryFile_isReingested(@TempDir Path sourceDir) throws java.io.IOException {
+        Path pdf = sourceDir.resolve("doc.pdf");
+        Files.write(pdf, "PDF-VERSION-ONE-bytes".getBytes());
+        long kb = SEQ.incrementAndGet();
+
+        assertEquals(1, scanService.scanDirectory(kb, sourceDir.toString()).added());
+        // Unchanged binary re-scan ingests nothing.
+        assertEquals(0, scanService.scanDirectory(kb, sourceDir.toString()).added());
+        // Changed bytes -> different content hash -> re-ingested.
+        Files.write(pdf, "PDF-VERSION-TWO-different-bytes".getBytes());
+        assertEquals(1, scanService.scanDirectory(kb, sourceDir.toString()).added(),
+                "a modified binary file must be re-ingested");
+    }
+
     @Test
     void kbsWithoutSourceDirectory_areSkipped() {
         // A KB with no source directory must not cause errors in the cycle.