diff --git a/apps/api/src/routes/tools/image-to-pdf.ts b/apps/api/src/routes/tools/image-to-pdf.ts
index bc2e8420..001a1eb9 100644
--- a/apps/api/src/routes/tools/image-to-pdf.ts
+++ b/apps/api/src/routes/tools/image-to-pdf.ts
@@ -7,8 +7,10 @@ import sharp from "sharp";
 import { z } from "zod";
 import { autoOrient } from "../../lib/auto-orient.js";
 import { formatZodErrors } from "../../lib/errors.js";
+import { validateImageBuffer } from "../../lib/file-validation.js";
 import { sanitizeFilename } from "../../lib/filename.js";
-import { ensureSharpCompat } from "../../lib/heic-converter.js";
+import { decodeToSharpCompat, needsCliDecode } from "../../lib/format-decoders.js";
+import { decodeHeic } from "../../lib/heic-converter.js";
 import { createWorkspace } from "../../lib/workspace.js";
 
 const targetSizeSchema = z.object({
@@ -179,8 +181,21 @@ export function registerImageToPdf(app: FastifyInstance) {
 
       const preparedBuffers: Buffer[] = [];
       for (const file of files) {
-        const compatBuffer = await autoOrient(await ensureSharpCompat(file.buffer));
-        preparedBuffers.push(compatBuffer);
+        let buf = file.buffer;
+
+        const validation = await validateImageBuffer(buf, file.filename);
+        if (!validation.valid) {
+          return reply.status(400).send({ error: `Invalid image: ${validation.reason}` });
+        }
+
+        if (validation.format === "heif") {
+          buf = await decodeHeic(buf);
+        } else if (needsCliDecode(validation.format)) {
+          const fileExt = file.filename.split(".").pop()?.toLowerCase();
+          buf = await decodeToSharpCompat(buf, validation.format, fileExt);
+        }
+
+        preparedBuffers.push(await autoOrient(buf));
       }
 
       let imageBuffers: Buffer[];
diff --git a/tests/integration/image-to-pdf.test.ts b/tests/integration/image-to-pdf.test.ts
index 5cec2f38..2bb055ef 100644
--- a/tests/integration/image-to-pdf.test.ts
+++ b/tests/integration/image-to-pdf.test.ts
@@ -216,7 +216,7 @@ describe("image-to-pdf", () => {
 
   // ── Branch coverage: lines 143-147 (processing failure) ───────────
 
-  it("returns 422 when processing fails on corrupted image data", async () => {
+  it("returns 400 when image format is unrecognized", async () => {
     const corruptedBuffer = Buffer.alloc(100, 0xff);
     const { body, contentType } = createMultipartPayload([
       { name: "file", filename: "bad.png", contentType: "image/png", content: corruptedBuffer },
@@ -230,9 +230,9 @@ describe("image-to-pdf", () => {
       body,
     });
 
-    expect(res.statusCode).toBe(422);
+    expect(res.statusCode).toBe(400);
     const json = JSON.parse(res.body);
-    expect(json.error).toContain("PDF creation failed");
+    expect(json.error).toContain("Invalid image");
   });
 
   // ── HEIC input handling ───────────────────────────────────────────