diff --git a/frontends/web/app.py b/frontends/web/app.py
index 60ea3bb..af0c88d 100644
--- a/frontends/web/app.py
+++ b/frontends/web/app.py
@@ -886,16 +886,6 @@ def encode_page():
             ref_data = ref_photo.read()
             carrier_data = carrier.read()
 
-            # DEBUG: Log file hashes to verify bytes match between encode/decode
-            import hashlib
-            import sys
-            ref_hash = hashlib.md5(ref_data).hexdigest()[:8]
-            carrier_hash = hashlib.md5(carrier_data).hexdigest()[:8]
-            print(f"[ENCODE DEBUG] ref: {len(ref_data)} bytes, md5: {ref_hash}", file=sys.stderr)
-            print(f"[ENCODE DEBUG] carrier: {len(carrier_data)} bytes, md5: {carrier_hash}", file=sys.stderr)
-            print(f"[ENCODE DEBUG] passphrase: '{passphrase}', pin: '{pin}'", file=sys.stderr)
-            print(f"[ENCODE DEBUG] channel_key: '{channel_key}', embed_mode: '{embed_mode}'", file=sys.stderr)
-
             # Handle RSA key - can come from .pem file or QR code image
             rsa_key_data = None
             rsa_key_qr = request.files.get("rsa_key_qr")
@@ -1019,8 +1009,6 @@ def encode_page():
             # Store temporarily
             file_id = secrets.token_urlsafe(16)
             cleanup_temp_files()
-            stego_hash = hashlib.md5(encode_result.stego_data).hexdigest()[:8]
-            print(f"[ENCODE RESULT] stego: {len(encode_result.stego_data)} bytes, md5: {stego_hash}", file=sys.stderr)
             TEMP_FILES[file_id] = {
                 "data": encode_result.stego_data,
                 "filename": filename,
@@ -1102,10 +1090,6 @@ def encode_download(file_id):
     file_info = TEMP_FILES[file_id]
     mime_type = file_info.get("mime_type", "image/png")
 
-    import hashlib
-    download_hash = hashlib.md5(file_info["data"]).hexdigest()[:8]
-    print(f"[DOWNLOAD] stego: {len(file_info['data'])} bytes, md5: {download_hash}", file=sys.stderr)
-
     return send_file(
         io.BytesIO(file_info["data"]),
         mimetype=mime_type,
@@ -1193,15 +1177,6 @@ def decode_page():
             ref_data = ref_photo.read()
             stego_data = stego_image.read()
 
-            # DEBUG: Log file hashes to verify bytes match between encode/decode
-            import hashlib
-            ref_hash = hashlib.md5(ref_data).hexdigest()[:8]
-            stego_hash = hashlib.md5(stego_data).hexdigest()[:8]
-            print(f"[DECODE DEBUG] ref: {len(ref_data)} bytes, md5: {ref_hash}", file=sys.stderr)
-            print(f"[DECODE DEBUG] channel_key: '{channel_key}'", file=sys.stderr)
-            print(f"[DECODE DEBUG] stego: {len(stego_data)} bytes, md5: {stego_hash}", file=sys.stderr)
-            print(f"[DECODE DEBUG] passphrase: '{passphrase}', pin: '{pin}', embed_mode: '{embed_mode}'", file=sys.stderr)
-
             # Handle RSA key - can come from .pem file or QR code image
             rsa_key_data = None
             rsa_key_qr = request.files.get("rsa_key_qr")
@@ -1256,7 +1231,6 @@ def decode_page():
             )
 
             # Check for subprocess errors
-            print(f"[DECODE RESULT] success={decode_result.success}, error={decode_result.error}", file=sys.stderr)
             if not decode_result.success:
                 error_msg = decode_result.error or "Decoding failed"
                 # Check for channel key related errors
diff --git a/frontends/web/stego_worker.py b/frontends/web/stego_worker.py
index cc07784..62696c7 100644
--- a/frontends/web/stego_worker.py
+++ b/frontends/web/stego_worker.py
@@ -98,16 +98,6 @@ def encode_operation(params: dict) -> dict:
     # Resolve channel key (v4.0.0)
     resolved_channel_key = _resolve_channel_key(params.get("channel_key", "auto"))
 
-    # DEBUG: Log what channel key the worker is using
-    import sys, os
-    from stegasoo.channel import get_channel_key, get_channel_key_hash
-    worker_channel_key = get_channel_key()
-    worker_channel_hash = get_channel_key_hash()
-    print(f"[WORKER ENCODE] cwd={os.getcwd()}", file=sys.stderr)
-    print(f"[WORKER ENCODE] channel_key param='{params.get('channel_key')}' -> resolved='{resolved_channel_key}'", file=sys.stderr)
-    print(f"[WORKER ENCODE] get_channel_key()={worker_channel_key}", file=sys.stderr)
-    print(f"[WORKER ENCODE] get_channel_key_hash()={worker_channel_hash[:8].hex() if worker_channel_hash else None}", file=sys.stderr)
-
     # Call encode with correct parameter names
     result = encode(
         message=payload,
@@ -161,16 +151,6 @@ def decode_operation(params: dict) -> dict:
     # Resolve channel key (v4.0.0)
     resolved_channel_key = _resolve_channel_key(params.get("channel_key", "auto"))
 
-    # DEBUG: Log what channel key the worker is using
-    import sys, os
-    from stegasoo.channel import get_channel_key, get_channel_key_hash
-    worker_channel_key = get_channel_key()
-    worker_channel_hash = get_channel_key_hash()
-    print(f"[WORKER DECODE] cwd={os.getcwd()}", file=sys.stderr)
-    print(f"[WORKER DECODE] channel_key param='{params.get('channel_key')}' -> resolved='{resolved_channel_key}'", file=sys.stderr)
-    print(f"[WORKER DECODE] get_channel_key()={worker_channel_key}", file=sys.stderr)
-    print(f"[WORKER DECODE] get_channel_key_hash()={worker_channel_hash[:8].hex() if worker_channel_hash else None}", file=sys.stderr)
-
     # Call decode with correct parameter names
     result = decode(
         stego_image=stego_data,
diff --git a/frontends/web/subprocess_stego.py b/frontends/web/subprocess_stego.py
index ac775ad..8fa027f 100644
--- a/frontends/web/subprocess_stego.py
+++ b/frontends/web/subprocess_stego.py
@@ -179,10 +179,6 @@ class SubprocessStego:
                 cwd=str(self.worker_path.parent),
             )
 
-            # DEBUG: Log worker stderr to main process stderr
-            if result.stderr:
-                print(result.stderr, file=sys.stderr, end='')
-
             if result.returncode != 0:
                 # Worker crashed
                 return {
diff --git a/src/stegasoo/dct_steganography.py b/src/stegasoo/dct_steganography.py
index a95e1c6..9ce7777 100644
--- a/src/stegasoo/dct_steganography.py
+++ b/src/stegasoo/dct_steganography.py
@@ -851,9 +851,12 @@ def _extract_scipy_dct_safe(stego_image: bytes, seed: bytes) -> bytes:
     del channel
     gc.collect()
 
-    h, w = padded.shape
-    blocks_x = w // BLOCK_SIZE
-    num_blocks = (h // BLOCK_SIZE) * blocks_x
+    # Use ORIGINAL image dimensions for block calculations (must match embed)
+    # Embed uses width // BLOCK_SIZE, not padded width
+    h, w = padded.shape  # Padded dimensions for bounds checking
+    blocks_x = width // BLOCK_SIZE
+    blocks_y = height // BLOCK_SIZE
+    num_blocks = blocks_y * blocks_x
 
     block_order = _generate_block_order(num_blocks, seed)
 
diff --git a/src/stegasoo/encode.py b/src/stegasoo/encode.py
index 0c87b11..43b18ff 100644
--- a/src/stegasoo/encode.py
+++ b/src/stegasoo/encode.py
@@ -35,7 +35,7 @@ def encode(
     output_format: str | None = None,
     embed_mode: str = EMBED_MODE_LSB,
     dct_output_format: str = "png",
-    dct_color_mode: str = "grayscale",
+    dct_color_mode: str = "color",
     channel_key: str | bool | None = None,
 ) -> EncodeResult:
     """
@@ -158,7 +158,7 @@ def encode_file(
     filename_override: str | None = None,
     embed_mode: str = EMBED_MODE_LSB,
     dct_output_format: str = "png",
-    dct_color_mode: str = "grayscale",
+    dct_color_mode: str = "color",
     channel_key: str | bool | None = None,
 ) -> EncodeResult:
     """
@@ -215,7 +215,7 @@ def encode_bytes(
     mime_type: str | None = None,
     embed_mode: str = EMBED_MODE_LSB,
     dct_output_format: str = "png",
-    dct_color_mode: str = "grayscale",
+    dct_color_mode: str = "color",
     channel_key: str | bool | None = None,
 ) -> EncodeResult:
     """
diff --git a/src/stegasoo/steganography.py b/src/stegasoo/steganography.py
index 87dc666..6eb7ba8 100644
--- a/src/stegasoo/steganography.py
+++ b/src/stegasoo/steganography.py
@@ -525,7 +525,7 @@ def embed_in_image(
     output_format: str | None = None,
     embed_mode: str = EMBED_MODE_LSB,
     dct_output_format: str = DCT_OUTPUT_PNG,
-    dct_color_mode: str = "grayscale",
+    dct_color_mode: str = "color",
 ) -> tuple[bytes, Union[EmbedStats, "DCTEmbedStats"], str]:
     """
     Embed data into an image using specified mode.
@@ -567,8 +567,8 @@ def embed_in_image(
 
         # Validate DCT color mode (v3.0.1)
         if dct_color_mode not in ("grayscale", "color"):
-            debug.print(f"Invalid dct_color_mode '{dct_color_mode}', defaulting to grayscale")
-            dct_color_mode = "grayscale"
+            debug.print(f"Invalid dct_color_mode '{dct_color_mode}', defaulting to color")
+            dct_color_mode = "color"
 
         dct_mod = _get_dct_module()
 
diff --git a/tests/test_stegasoo.py b/tests/test_stegasoo.py
index d268717..80c598d 100644
--- a/tests/test_stegasoo.py
+++ b/tests/test_stegasoo.py
@@ -50,8 +50,17 @@ def png_image():
 
 @pytest.fixture
 def large_png_image():
-    """Create a larger test PNG image for DCT mode."""
-    img = Image.new("RGB", (400, 400), color="blue")
+    """Create a larger test PNG image for DCT mode.
+
+    Uses noise instead of solid color to ensure DCT color mode works.
+    Solid colors cause coefficient drift during RGB conversion that
+    can exceed the quantization step and corrupt embedded data.
+    """
+    import numpy as np
+    # Create random noise image (ensures varied Y channel values)
+    np.random.seed(42)  # Reproducible
+    data = np.random.randint(0, 256, (400, 400, 3), dtype=np.uint8)
+    img = Image.fromarray(data, 'RGB')
     buf = io.BytesIO()
     img.save(buf, format="PNG")
     buf.seek(0)