diff --git a/node/opendataloader-pdf/src/index.ts b/node/opendataloader-pdf/src/index.ts
index 7f68ae36b..db61fb606 100644
--- a/node/opendataloader-pdf/src/index.ts
+++ b/node/opendataloader-pdf/src/index.ts
@@ -37,13 +37,21 @@ function executeJar(args: string[], executionOptions: JarExecutionOptions = {}):
 
     let stdout = '';
     let stderr = '';
+    let streamedStdoutTail = '';
+    const MAX_STDOUT_TAIL = 64 * 1024;
 
     javaProcess.stdout.on('data', (data) => {
       const chunk = data.toString();
       if (streamOutput) {
         process.stdout.write(chunk);
+        streamedStdoutTail += chunk;
+        if (streamedStdoutTail.length > MAX_STDOUT_TAIL) {
+          streamedStdoutTail = streamedStdoutTail.slice(-MAX_STDOUT_TAIL);
+        }
+      } else {
+        // Only accumulate when not streaming to avoid double-write by the caller
+        stdout += chunk;
       }
-      stdout += chunk;
     });
 
     javaProcess.stderr.on('data', (data) => {
@@ -56,9 +64,11 @@ function executeJar(args: string[], executionOptions: JarExecutionOptions = {}):
 
     javaProcess.on('close', (code) => {
       if (code === 0) {
-        resolve(stdout);
+        // When streamOutput=true, content was already written to process.stdout in real-time.
+        // Return empty string to prevent callers from double-writing the same output.
+        resolve(streamOutput ? '' : stdout);
       } else {
-        const errorOutput = stderr || stdout;
+        const errorOutput = stderr || (streamOutput ? streamedStdoutTail : stdout);
         const error = new Error(
           `The opendataloader-pdf CLI exited with code ${code}.\n\n${errorOutput}`,
         );