diff --git a/src/agents/tools/pdf-tool.helpers.test.ts b/src/agents/tools/pdf-tool.helpers.test.ts
index c462b2de6a59..350b8d8a53d6 100644
--- a/src/agents/tools/pdf-tool.helpers.test.ts
+++ b/src/agents/tools/pdf-tool.helpers.test.ts
@@ -62,6 +62,10 @@ describe("parsePageRange", () => {
     expect(parsePageRange("1-100", 5)).toEqual([1, 2, 3, 4, 5]);
   });
 
+  it("throws when no requested pages are within maxPages", () => {
+    expect(() => parsePageRange("999", 20)).toThrow('No PDF pages matched requested range "999"');
+  });
+
   it("deduplicates and sorts", () => {
     expect(parsePageRange("5,3,1,3,5", 20)).toEqual([1, 3, 5]);
   });
diff --git a/src/agents/tools/pdf-tool.helpers.ts b/src/agents/tools/pdf-tool.helpers.ts
index 19f4dbb1c784..962c666df8b5 100644
--- a/src/agents/tools/pdf-tool.helpers.ts
+++ b/src/agents/tools/pdf-tool.helpers.ts
@@ -74,7 +74,11 @@ export function parsePageRange(range: string, maxPages: number): number[] {
       }
     }
   }
-  return Array.from(pages).toSorted((a, b) => a - b);
+  const parsedPages = Array.from(pages).toSorted((a, b) => a - b);
+  if (parsedPages.length === 0) {
+    throw new Error(`No PDF pages matched requested range "${range}"`);
+  }
+  return parsedPages;
 }
 
 /** Converts a provider assistant message into PDF text or throws a model-labelled failure. */
diff --git a/src/agents/tools/pdf-tool.test.ts b/src/agents/tools/pdf-tool.test.ts
index f32ccee457cd..25784032572d 100644
--- a/src/agents/tools/pdf-tool.test.ts
+++ b/src/agents/tools/pdf-tool.test.ts
@@ -548,6 +548,26 @@ describe("createPdfTool", () => {
     });
   });
 
+  it("rejects explicit page ranges that resolve to no pages before native PDF analysis", async () => {
+    await withTempPdfAgentDir(async (agentDir) => {
+      await stubPdfToolInfra(agentDir, { provider: "anthropic", input: ["text", "document"] });
+      const nativeSpy = vi
+        .spyOn(pdfNativeProviders, "anthropicAnalyzePdf")
+        .mockResolvedValue("native summary");
+      const cfg = withPdfModel(ANTHROPIC_PDF_MODEL);
+      const tool = requirePdfTool((await loadCreatePdfTool())({ config: cfg, agentDir }));
+
+      await expect(
+        tool.execute("t1", {
+          prompt: "summarize",
+          pdf: "/tmp/doc.pdf",
+          pages: "999",
+        }),
+      ).rejects.toThrow('No PDF pages matched requested range "999"');
+      expect(nativeSpy).not.toHaveBeenCalled();
+    });
+  });
+
   it("rejects password parameter for native PDF providers", async () => {
     await withTempPdfAgentDir(async (agentDir) => {
       await stubPdfToolInfra(agentDir, { provider: "anthropic", input: ["text", "document"] });