diff --git a/palantir-java-format/src/main/java/com/palantir/javaformat/java/JavaInput.java b/palantir-java-format/src/main/java/com/palantir/javaformat/java/JavaInput.java
index e13aaa0f3..d78b4c4d1 100644
--- a/palantir-java-format/src/main/java/com/palantir/javaformat/java/JavaInput.java
+++ b/palantir-java-format/src/main/java/com/palantir/javaformat/java/JavaInput.java
@@ -39,10 +39,12 @@
 import com.sun.tools.javac.parser.Tokens.TokenKind;
 import com.sun.tools.javac.tree.JCTree.JCCompilationUnit;
 import com.sun.tools.javac.util.Context;
+import com.sun.tools.javac.util.JCDiagnostic;
 import com.sun.tools.javac.util.Log;
 import com.sun.tools.javac.util.Log.DeferredDiagnosticHandler;
 import com.sun.tools.javac.util.Options;
 import java.io.IOException;
+import java.lang.reflect.Method;
 import java.net.URI;
 import java.util.ArrayList;
 import java.util.Collection;
@@ -366,7 +368,7 @@ public CharSequence getCharContent(boolean ignoreEncodingErrors) throws IOExcept
         });
         DeferredDiagnosticHandler diagnostics = new DeferredDiagnosticHandler(log);
         ImmutableList<RawTok> rawToks = JavacTokens.getTokens(text, context, stopTokens);
-        if (diagnostics.getDiagnostics().stream().anyMatch(d -> d.getKind() == Diagnostic.Kind.ERROR)) {
+        if (getDiagnostics(diagnostics).stream().anyMatch(d -> d.getKind() == Diagnostic.Kind.ERROR)) {
             return ImmutableList.of(new Tok(0, "", "", 0, 0, true, null)); // EOF
         }
         int kN = 0;
@@ -463,6 +465,33 @@ public CharSequence getCharContent(boolean ignoreEncodingErrors) throws IOExcept
         return ImmutableList.copyOf(toks);
     }
 
+    /**
+     * Gets diagnostics from a DeferredDiagnosticHandler using reflection.
+     * This method handles the API change in JDK 25 where getDiagnostics()
+     * changed from returning Queue to List.
+     *
+     * @param handler the diagnostic handler
+     * @return a collection of diagnostics
+     */
+    @SuppressWarnings("unchecked")
+    private static Collection<JCDiagnostic> getDiagnostics(DeferredDiagnosticHandler handler) {
+        try {
+            return (Collection<JCDiagnostic>) GET_DIAGNOSTICS.invoke(handler);
+        } catch (ReflectiveOperationException e) {
+            throw new LinkageError(e.getMessage(), e);
+        }
+    }
+
+    private static final Method GET_DIAGNOSTICS;
+
+    static {
+        try {
+            GET_DIAGNOSTICS = DeferredDiagnosticHandler.class.getMethod("getDiagnostics");
+        } catch (NoSuchMethodException e) {
+            throw new LinkageError(e.getMessage(), e);
+        }
+    }
+
     @SuppressWarnings("for-rollout:NullAway")
     private static int updateColumn(int columnI, String originalTokText) {
         Integer last = Iterators.getLast(Newlines.lineOffsetIterator(originalTokText));