fix: follow-up nits for AVIF/JXL brotli support

- Fix JXL container ftyp size check (==20 → >=16) to accept
  wider range of valid JXL files
- Add brotli decompression size limit (2 MB) to prevent OOM
- Add trailing newline to requirements.txt
- Add unit tests for new ISOBMFF/brotli extraction paths:
  JXL/AVIF happy paths, missing brob, corrupt payload,
  non-ISOBMFF fallthrough, write-skip on AVIF/JXL,
  JSON dict/list fields, and oversized decompression

tests/utils/test_exif_utils.py

@@ -141,3 +141,150 @@ def test_update_image_metadata_preserves_png_workflow(tmp_path):
             img.info["parameters"]
             == 'prompt text\nRecipe metadata: {"title":"recipe"}'
         )
+
+
+# --- ISOBMFF / brotli extraction tests ---
+
+import struct
+
+import brotli
+
+
+def _build_jxl_with_brob(payload_json: dict) -> bytes:
+    """Build a minimal JXL container with a brob box containing brotli-compressed JSON."""
+    # ISOBMFF box 1: JXL signature box (size=12, type='JXL ', signature)
+    box1 = struct.pack(">I", 12) + b"JXL " + bytes([0x0d, 0x0a, 0x87, 0x0a])
+    # ISOBMFF box 2: ftyp (size=16, type='ftyp', major='jxl ', minor=0)
+    box2 = struct.pack(">I", 16) + b"ftyp" + b"jxl " + struct.pack(">I", 0)
+    # ISOBMFF box 3: brob — payload is b'comf' + brotli(json)
+    compressed = brotli.compress(json.dumps(payload_json).encode("utf-8"))
+    brob_payload = b"comf" + compressed
+    box3 = struct.pack(">I", 8 + len(brob_payload)) + b"brob" + brob_payload
+    return box1 + box2 + box3
+
+
+def _build_avif_with_brob(payload_json: dict) -> bytes:
+    """Build a minimal AVIF container with a brob box containing brotli-compressed JSON."""
+    compressed = brotli.compress(json.dumps(payload_json).encode("utf-8"))
+    brob_payload = b"comf" + compressed
+    ftyp_box = struct.pack(">I", 20) + b"ftyp" + b"avif" + struct.pack(">I", 0) + b"avif"
+    brob_box = struct.pack(">I", 8 + len(brob_payload)) + b"brob" + brob_payload
+    return ftyp_box + brob_box
+
+
+class TestIsobmffBrotliExtraction:
+    """Tests for ISOBMFF brotli metadata extraction in ExifUtils."""
+
+    def test_extract_jxl_brotli_happy_path(self, tmp_path):
+        """JXL container with valid brob box extracts prompt and workflow."""
+        payload = {"prompt": "a cute cat", "workflow": {"nodes": [{"id": 1}]}}
+        data = _build_jxl_with_brob(payload)
+        path = tmp_path / "test.jxl"
+        path.write_bytes(data)
+
+        result = ExifUtils._load_structured_metadata(str(path))
+
+        assert result["prompt"] == "a cute cat"
+        assert result["workflow"] == '{"nodes": [{"id": 1}]}'
+        assert result["parameters"] is None
+        assert result["comment"] is None
+
+    def test_extract_avif_brotli_happy_path(self, tmp_path):
+        """AVIF container with valid brob box extracts prompt and workflow."""
+        payload = {"prompt": "landscape", "workflow": {"nodes": []}}
+        data = _build_avif_with_brob(payload)
+        path = tmp_path / "test.avif"
+        path.write_bytes(data)
+
+        result = ExifUtils._load_structured_metadata(str(path))
+
+        assert result["prompt"] == "landscape"
+        assert result["workflow"] == '{"nodes": []}'
+
+    def test_extract_no_brob_box_returns_none(self, tmp_path):
+        """JXL container without a brob box returns None from _extract_isobmff_brotli."""
+        # Only JXL signature + ftyp, no brob
+        box1 = struct.pack(">I", 12) + b"JXL " + bytes([0x0d, 0x0a, 0x87, 0x0a])
+        box2 = struct.pack(">I", 16) + b"ftyp" + b"jxl " + struct.pack(">I", 0)
+        path = tmp_path / "test.jxl"
+        path.write_bytes(box1 + box2)
+
+        # The low-level extraction should return None (no brob box)
+        result = ExifUtils._extract_isobmff_brotli(str(path))
+        assert result is None
+
+    def test_extract_corrupt_brob_returns_none(self, tmp_path):
+        """Broken brob box payload gracefully returns None."""
+        box1 = struct.pack(">I", 12) + b"JXL " + bytes([0x0d, 0x0a, 0x87, 0x0a])
+        box2 = struct.pack(">I", 16) + b"ftyp" + b"jxl " + struct.pack(">I", 0)
+        # brob with garbage payload that doesn't start with b'comf'
+        garbage = b"\xff\xff\xff\xff" * 32
+        box3 = struct.pack(">I", 8 + len(garbage)) + b"brob" + garbage
+        path = tmp_path / "test.jxl"
+        path.write_bytes(box1 + box2 + box3)
+
+        result = ExifUtils._extract_isobmff_brotli(str(path))
+        assert result is None
+
+    def test_extract_non_isobmff_file_falls_through(self, tmp_path):
+        """A regular PNG file is not processed as ISOBMFF and returns PIL metadata."""
+        png_info = PngImagePlugin.PngInfo()
+        png_info.add_text("prompt", "from png")
+        path = tmp_path / "test.png"
+        Image.new("RGB", (4, 4), color="red").save(path, pnginfo=png_info)
+
+        result = ExifUtils._load_structured_metadata(str(path))
+        assert result["prompt"] == "from png"
+
+    def test_extract_skip_on_update_and_optimize(self, tmp_path):
+        """AVIF/JXL files are skipped for write operations (update/append/optimize)."""
+        path = tmp_path / "test.avif"
+        path.write_bytes(b"fake avif data")
+
+        # update_image_metadata should return the path unchanged
+        result = ExifUtils.update_image_metadata(str(path), "some metadata")
+        assert result == str(path)
+
+        # append_recipe_metadata should also skip
+        result = ExifUtils.append_recipe_metadata(str(path), {"title": "test"})
+        assert result == str(path)
+
+        # optimize_image should passthrough for AVIF/JXL paths
+        result_data, ext = ExifUtils.optimize_image(str(path))
+        assert ext == ".avif"
+        assert result_data == b"fake avif data"
+
+    def test_extract_prompt_as_dict(self, tmp_path):
+        """prompt field as dict is JSON-serialized."""
+        payload = {"prompt": {"text": "hello", "negative": "bad"}}
+        data = _build_jxl_with_brob(payload)
+        path = tmp_path / "test.jxl"
+        path.write_bytes(data)
+
+        result = ExifUtils._load_structured_metadata(str(path))
+        assert json.loads(result["prompt"]) == {"text": "hello", "negative": "bad"}
+
+    def test_extract_workflow_as_list(self, tmp_path):
+        """workflow field as list is JSON-serialized."""
+        payload = {"workflow": [{"id": 1}, {"id": 2}]}
+        data = _build_avif_with_brob(payload)
+        path = tmp_path / "test.avif"
+        path.write_bytes(data)
+
+        result = ExifUtils._load_structured_metadata(str(path))
+        assert json.loads(result["workflow"]) == [{"id": 1}, {"id": 2}]
+
+    def test_over_decompressed_size_limit(self, tmp_path, monkeypatch):
+        """Decompressed data exceeding _BROTLI_MAX_DECOMPRESSED is rejected."""
+        # Monkey-patch the limit to a small value to avoid large test data
+        monkeypatch.setattr(ExifUtils, "_BROTLI_MAX_DECOMPRESSED", 100)
+
+        large_content = "x" * 200
+        payload = {"prompt": large_content}
+        data = _build_jxl_with_brob(payload)
+        path = tmp_path / "test.jxl"
+        path.write_bytes(data)
+
+        # Direct extraction should return None because decompressed size exceeds limit
+        result = ExifUtils._extract_isobmff_brotli(str(path))
+        assert result is None