diff --git a/internal/cgen/auxiliary/image.cc b/internal/cgen/auxiliary/image.cc
index 3d48ae7..7fae664 100644
--- a/internal/cgen/auxiliary/image.cc
+++ b/internal/cgen/auxiliary/image.cc
@@ -85,9 +85,11 @@
 }
 
 void  //
-DecodeImageCallbacks::Done(DecodeImageResult& result,
-                           sync_io::Input& input,
-                           IOBuffer& buffer) {}
+DecodeImageCallbacks::Done(
+    DecodeImageResult& result,
+    sync_io::Input& input,
+    IOBuffer& buffer,
+    wuffs_base__image_decoder::unique_ptr image_decoder) {}
 
 const char DecodeImage_BufferIsTooShort[] =  //
     "wuffs_aux::DecodeImage: buffer is too short";
@@ -141,7 +143,8 @@
 }
 
 DecodeImageResult  //
-DecodeImage0(DecodeImageCallbacks& callbacks,
+DecodeImage0(wuffs_base__image_decoder::unique_ptr& image_decoder,
+             DecodeImageCallbacks& callbacks,
              sync_io::Input& input,
              wuffs_base__io_buffer& io_buf,
              uint32_t override_pixel_format_repr,
@@ -167,7 +170,6 @@
   }
 
   wuffs_base__image_config image_config = wuffs_base__null_image_config();
-  wuffs_base__image_decoder::unique_ptr image_decoder(nullptr, &free);
   uint64_t start_pos = io_buf.reader_position();
   bool redirected = false;
   int32_t fourcc = 0;
@@ -358,10 +360,11 @@
     io_buf = &fallback_io_buf;
   }
 
+  wuffs_base__image_decoder::unique_ptr image_decoder(nullptr, &free);
   DecodeImageResult result =
-      DecodeImage0(callbacks, input, *io_buf, override_pixel_format_repr,
-                   pixel_blend, max_incl_dimension);
-  callbacks.Done(result, input, *io_buf);
+      DecodeImage0(image_decoder, callbacks, input, *io_buf,
+                   override_pixel_format_repr, pixel_blend, max_incl_dimension);
+  callbacks.Done(result, input, *io_buf, std::move(image_decoder));
   return result;
 }
 
diff --git a/internal/cgen/auxiliary/image.hh b/internal/cgen/auxiliary/image.hh
index ad3d03d..33de749 100644
--- a/internal/cgen/auxiliary/image.hh
+++ b/internal/cgen/auxiliary/image.hh
@@ -91,12 +91,20 @@
   // not parsing the input encountered an error. Even when successful, trailing
   // data may remain in input and buffer.
   //
+  // The image_decoder is the one returned by OnImageFormat (if OnImageFormat
+  // was successful), or a no-op unique_ptr otherwise. Like any unique_ptr,
+  // ownership moves to the Done implementation.
+  //
   // Do not keep a reference to buffer or buffer.data.ptr after Done returns,
   // as DecodeImage may then de-allocate the backing array.
   //
-  // The default Done implementation is a no-op.
+  // The default Done implementation is a no-op, other than running the
+  // image_decoder unique_ptr destructor.
   virtual void  //
-  Done(DecodeImageResult& result, sync_io::Input& input, IOBuffer& buffer);
+  Done(DecodeImageResult& result,
+       sync_io::Input& input,
+       IOBuffer& buffer,
+       wuffs_base__image_decoder::unique_ptr image_decoder);
 };
 
 extern const char DecodeImage_BufferIsTooShort[];
diff --git a/internal/cgen/data/data.go b/internal/cgen/data/data.go
index 1c91fcc..eb174aa 100644
--- a/internal/cgen/data/data.go
+++ b/internal/cgen/data/data.go
@@ -736,28 +736,29 @@
 const AuxImageCc = "" +
 	"// ---------------- Auxiliary - Image\n\n#if !defined(WUFFS_CONFIG__MODULES) || defined(WUFFS_CONFIG__MODULE__AUX__IMAGE)\n\n#include <utility>\n\nnamespace wuffs_aux {\n\nDecodeImageResult::DecodeImageResult(MemOwner&& pixbuf_mem_owner0,\n                                     wuffs_base__slice_u8 pixbuf_mem_slice0,\n                                     wuffs_base__pixel_buffer pixbuf0,\n                                     std::string&& error_message0)\n    : pixbuf_mem_owner(std::move(pixbuf_mem_owner0)),\n      pixbuf_mem_slice(pixbuf_mem_slice0),\n      pixbuf(pixbuf0),\n      error_message(std::move(error_message0)) {}\n\nDecodeImageResult::DecodeImageResult(std::string&& error_message0)\n    : pixbuf_mem_owner(nullptr, &free),\n      pixbuf_mem_slice(wuffs_base__empty_slice_u8()),\n      pixbuf({0}),\n      error_message(std::move(error_message0)) {}\n\nDecodeImageCallbacks::AllocResult::AllocResult(MemOwner&& mem_owner0,\n                                               wuffs_base__slice_u8 mem_slice0)\n    : mem_owner(std::move(" +
 	"mem_owner0)),\n      mem_slice(mem_slice0),\n      error_message(\"\") {}\n\nDecodeImageCallbacks::AllocResult::AllocResult(std::string&& error_message0)\n    : mem_owner(nullptr, &free),\n      mem_slice(wuffs_base__empty_slice_u8()),\n      error_message(std::move(error_message0)) {}\n\nDecodeImageCallbacks::AllocResult  //\nDecodeImageCallbacks::OnImageConfig(\n    const wuffs_base__image_config& image_config) {\n  uint32_t w = image_config.pixcfg.width();\n  uint32_t h = image_config.pixcfg.height();\n  if ((w == 0) || (h == 0)) {\n    return AllocResult(\"\");\n  }\n  uint64_t len = image_config.pixcfg.pixbuf_len();\n  if ((len == 0) || (SIZE_MAX < len)) {\n    return AllocResult(DecodeImage_UnsupportedPixelConfiguration);\n  }\n  void* ptr = calloc((size_t)len, 1);\n  if (!ptr) {\n    return AllocResult(DecodeImage_OutOfMemory);\n  }\n  return AllocResult(MemOwner(ptr, &free),\n                     wuffs_base__make_slice_u8((uint8_t*)ptr, (size_t)len));\n}\n\nDecodeImageCallbacks::AllocResult  //\nDecodeImageCallbacks::AllocWorkbuf(wuff" +
-	"s_base__range_ii_u64 len) {\n  if (len.max_incl == 0) {\n    return DecodeImageCallbacks::AllocResult(\"\");\n  } else if (SIZE_MAX < len.max_incl) {\n    return DecodeImageCallbacks::AllocResult(DecodeImage_OutOfMemory);\n  }\n  void* p = calloc((size_t)len.max_incl, 1);\n  if (!p) {\n    return DecodeImageCallbacks::AllocResult(DecodeImage_OutOfMemory);\n  }\n  return DecodeImageCallbacks::AllocResult(\n      MemOwner(p, &free),\n      wuffs_base__make_slice_u8((uint8_t*)p, (size_t)len.max_incl));\n}\n\nvoid  //\nDecodeImageCallbacks::Done(DecodeImageResult& result,\n                           sync_io::Input& input,\n                           IOBuffer& buffer) {}\n\nconst char DecodeImage_BufferIsTooShort[] =  //\n    \"wuffs_aux::DecodeImage: buffer is too short\";\nconst char DecodeImage_MaxInclDimensionExceeded[] =  //\n    \"wuffs_aux::DecodeImage: max_incl_dimension exceeded\";\nconst char DecodeImage_OutOfMemory[] =  //\n    \"wuffs_aux::DecodeImage: out of memory\";\nconst char DecodeImage_UnexpectedEndOfFile[] =  //\n    \"wuffs_aux:" +
-	":DecodeImage: unexpected end of file\";\nconst char DecodeImage_UnsupportedImageFormat[] =  //\n    \"wuffs_aux::DecodeImage: unsupported image format\";\nconst char DecodeImage_UnsupportedPixelBlend[] =  //\n    \"wuffs_aux::DecodeImage: unsupported pixel blend\";\nconst char DecodeImage_UnsupportedPixelConfiguration[] =  //\n    \"wuffs_aux::DecodeImage: unsupported pixel configuration\";\nconst char DecodeImage_UnsupportedPixelFormat[] =  //\n    \"wuffs_aux::DecodeImage: unsupported pixel format\";\n\n" +
+	"s_base__range_ii_u64 len) {\n  if (len.max_incl == 0) {\n    return DecodeImageCallbacks::AllocResult(\"\");\n  } else if (SIZE_MAX < len.max_incl) {\n    return DecodeImageCallbacks::AllocResult(DecodeImage_OutOfMemory);\n  }\n  void* p = calloc((size_t)len.max_incl, 1);\n  if (!p) {\n    return DecodeImageCallbacks::AllocResult(DecodeImage_OutOfMemory);\n  }\n  return DecodeImageCallbacks::AllocResult(\n      MemOwner(p, &free),\n      wuffs_base__make_slice_u8((uint8_t*)p, (size_t)len.max_incl));\n}\n\nvoid  //\nDecodeImageCallbacks::Done(\n    DecodeImageResult& result,\n    sync_io::Input& input,\n    IOBuffer& buffer,\n    wuffs_base__image_decoder::unique_ptr image_decoder) {}\n\nconst char DecodeImage_BufferIsTooShort[] =  //\n    \"wuffs_aux::DecodeImage: buffer is too short\";\nconst char DecodeImage_MaxInclDimensionExceeded[] =  //\n    \"wuffs_aux::DecodeImage: max_incl_dimension exceeded\";\nconst char DecodeImage_OutOfMemory[] =  //\n    \"wuffs_aux::DecodeImage: out of memory\";\nconst char DecodeImage_UnexpectedEndOfFile[] =  //" +
+	"\n    \"wuffs_aux::DecodeImage: unexpected end of file\";\nconst char DecodeImage_UnsupportedImageFormat[] =  //\n    \"wuffs_aux::DecodeImage: unsupported image format\";\nconst char DecodeImage_UnsupportedPixelBlend[] =  //\n    \"wuffs_aux::DecodeImage: unsupported pixel blend\";\nconst char DecodeImage_UnsupportedPixelConfiguration[] =  //\n    \"wuffs_aux::DecodeImage: unsupported pixel configuration\";\nconst char DecodeImage_UnsupportedPixelFormat[] =  //\n    \"wuffs_aux::DecodeImage: unsupported pixel format\";\n\n" +
 	"" +
-	"// --------\n\nnamespace {\n\nstd::string  //\nDecodeImageAdvanceIOBuf(sync_io::Input& input,\n                        wuffs_base__io_buffer& io_buf,\n                        bool compactable,\n                        uint64_t min_excl_pos,\n                        uint64_t pos) {\n  if ((pos <= min_excl_pos) || (pos < io_buf.reader_position())) {\n    // Redirects must go forward.\n    return DecodeImage_UnsupportedImageFormat;\n  }\n  while (true) {\n    uint64_t relative_pos = pos - io_buf.reader_position();\n    if (relative_pos <= io_buf.reader_length()) {\n      io_buf.meta.ri += (size_t)relative_pos;\n      break;\n    } else if (io_buf.meta.closed) {\n      return DecodeImage_UnexpectedEndOfFile;\n    }\n    io_buf.meta.ri = io_buf.meta.wi;\n    if (compactable) {\n      io_buf.compact();\n    }\n    std::string error_message = input.CopyIn(&io_buf);\n    if (!error_message.empty()) {\n      return std::move(error_message);\n    }\n  }\n  return \"\";\n}\n\nDecodeImageResult  //\nDecodeImage0(DecodeImageCallbacks& callbacks,\n            " +
-	" sync_io::Input& input,\n             wuffs_base__io_buffer& io_buf,\n             uint32_t override_pixel_format_repr,\n             wuffs_base__pixel_blend pixel_blend,\n             uint32_t max_incl_dimension) {\n  // Check args.\n  switch (override_pixel_format_repr) {\n    case 0:\n    case WUFFS_BASE__PIXEL_FORMAT__BGR_565:\n    case WUFFS_BASE__PIXEL_FORMAT__BGR:\n    case WUFFS_BASE__PIXEL_FORMAT__BGRA_NONPREMUL:\n    case WUFFS_BASE__PIXEL_FORMAT__BGRA_PREMUL:\n      break;\n    default:\n      return DecodeImageResult(DecodeImage_UnsupportedPixelFormat);\n  }\n  switch (pixel_blend) {\n    case WUFFS_BASE__PIXEL_BLEND__SRC:\n    case WUFFS_BASE__PIXEL_BLEND__SRC_OVER:\n      break;\n    default:\n      return DecodeImageResult(DecodeImage_UnsupportedPixelBlend);\n  }\n\n  wuffs_base__image_config image_config = wuffs_base__null_image_config();\n  wuffs_base__image_decoder::unique_ptr image_decoder(nullptr, &free);\n  uint64_t start_pos = io_buf.reader_position();\n  bool redirected = false;\n  int32_t fourcc = 0;\nredirect:\n  " +
-	"do {\n    // Determine the image format.\n    if (!redirected) {\n      while (true) {\n        fourcc = wuffs_base__magic_number_guess_fourcc(io_buf.reader_slice());\n        if (fourcc > 0) {\n          break;\n        } else if ((fourcc == 0) && (io_buf.reader_length() >= 64)) {\n          break;\n        } else if (io_buf.meta.closed || (io_buf.writer_length() == 0)) {\n          fourcc = 0;\n          break;\n        }\n        std::string error_message = input.CopyIn(&io_buf);\n        if (!error_message.empty()) {\n          return DecodeImageResult(std::move(error_message));\n        }\n      }\n    } else {\n      wuffs_base__io_buffer empty = wuffs_base__empty_io_buffer();\n      wuffs_base__more_information minfo = wuffs_base__empty_more_information();\n      wuffs_base__status tmm_status =\n          image_decoder->tell_me_more(&empty, &minfo, &io_buf);\n      if (minfo.flavor != WUFFS_BASE__MORE_INFORMATION__FLAVOR__IO_REDIRECT) {\n        return DecodeImageResult(DecodeImage_UnsupportedImageFormat);\n      }\n      uint6" +
-	"4_t pos = minfo.io_redirect__range().min_incl;\n      std::string error_message = DecodeImageAdvanceIOBuf(\n          input, io_buf, !input.BringsItsOwnIOBuffer(), start_pos, pos);\n      if (!error_message.empty()) {\n        return DecodeImageResult(std::move(error_message));\n      }\n      fourcc = (int32_t)(minfo.io_redirect__fourcc());\n      if (fourcc == 0) {\n        return DecodeImageResult(DecodeImage_UnsupportedImageFormat);\n      }\n      image_decoder.reset();\n    }\n\n    // Make the image decoder.\n    image_decoder = callbacks.OnImageFormat(\n        (uint32_t)fourcc,\n        fourcc ? wuffs_base__empty_slice_u8() : io_buf.reader_slice());\n    if (!image_decoder) {\n      return DecodeImageResult(DecodeImage_UnsupportedImageFormat);\n    }\n\n    // Decode the image config.\n    while (true) {\n      wuffs_base__status id_dic_status =\n          image_decoder->decode_image_config(&image_config, &io_buf);\n      if (id_dic_status.repr == NULL) {\n        break;\n      } else if (id_dic_status.repr == wuffs_base__note" +
-	"__i_o_redirect) {\n        if (redirected) {\n          return DecodeImageResult(DecodeImage_UnsupportedImageFormat);\n        }\n        redirected = true;\n        goto redirect;\n      } else if (id_dic_status.repr != wuffs_base__suspension__short_read) {\n        return DecodeImageResult(id_dic_status.message());\n      } else if (io_buf.meta.closed) {\n        return DecodeImageResult(DecodeImage_UnexpectedEndOfFile);\n      } else {\n        std::string error_message = input.CopyIn(&io_buf);\n        if (!error_message.empty()) {\n          return DecodeImageResult(std::move(error_message));\n        }\n      }\n    }\n  } while (false);\n\n  // Apply the override pixel format.\n  uint32_t w = image_config.pixcfg.width();\n  uint32_t h = image_config.pixcfg.height();\n  if ((w > max_incl_dimension) || (h > max_incl_dimension)) {\n    return DecodeImageResult(DecodeImage_MaxInclDimensionExceeded);\n  }\n  if (override_pixel_format_repr != 0) {\n    image_config.pixcfg.set(override_pixel_format_repr,\n                            WU" +
-	"FFS_BASE__PIXEL_SUBSAMPLING__NONE, w, h);\n  }\n\n  // Allocate the pixel buffer.\n  size_t pixbuf_len_min_incl = 0;\n  if ((w > 0) && (h > 0)) {\n    pixbuf_len_min_incl = image_config.pixcfg.pixbuf_len();\n    if (pixbuf_len_min_incl == 0) {\n      return DecodeImageResult(DecodeImage_UnsupportedPixelFormat);\n    }\n  }\n  DecodeImageCallbacks::AllocResult oic_result =\n      callbacks.OnImageConfig(image_config);\n  if (!oic_result.error_message.empty()) {\n    return DecodeImageResult(std::move(oic_result.error_message));\n  } else if (oic_result.mem_slice.len < pixbuf_len_min_incl) {\n    return DecodeImageResult(DecodeImage_BufferIsTooShort);\n  }\n  wuffs_base__pixel_buffer pixel_buffer;\n  wuffs_base__status pb_sfs_status =\n      pixel_buffer.set_from_slice(&image_config.pixcfg, oic_result.mem_slice);\n  if (!pb_sfs_status.is_ok()) {\n    return DecodeImageResult(pb_sfs_status.message());\n  }\n\n  // Allocate the work buffer.\n  wuffs_base__range_ii_u64 workbuf_len = image_decoder->workbuf_len();\n  DecodeImageCallbacks::All" +
-	"ocResult alloc_workbuf_result =\n      callbacks.AllocWorkbuf(workbuf_len);\n  if (!alloc_workbuf_result.error_message.empty()) {\n    return DecodeImageResult(std::move(alloc_workbuf_result.error_message));\n  } else if (alloc_workbuf_result.mem_slice.len < workbuf_len.min_incl) {\n    return DecodeImageResult(DecodeImage_BufferIsTooShort);\n  }\n\n  // Decode the frame config.\n  wuffs_base__frame_config frame_config = wuffs_base__null_frame_config();\n  while (true) {\n    wuffs_base__status id_dfc_status =\n        image_decoder->decode_frame_config(&frame_config, &io_buf);\n    if (id_dfc_status.repr == NULL) {\n      break;\n    } else if (id_dfc_status.repr != wuffs_base__suspension__short_read) {\n      return DecodeImageResult(id_dfc_status.message());\n    } else if (io_buf.meta.closed) {\n      return DecodeImageResult(DecodeImage_UnexpectedEndOfFile);\n    } else {\n      std::string error_message = input.CopyIn(&io_buf);\n      if (!error_message.empty()) {\n        return DecodeImageResult(std::move(error_message));\n" +
-	"      }\n    }\n  }\n\n  // Decode the frame (the pixels).\n  //\n  // From here on, always returns the pixel_buffer. If we get this far, we can\n  // still display a partial image, even if we encounter an error.\n  std::string message(\"\");\n  if ((pixel_blend == WUFFS_BASE__PIXEL_BLEND__SRC_OVER) &&\n      frame_config.overwrite_instead_of_blend()) {\n    pixel_blend = WUFFS_BASE__PIXEL_BLEND__SRC;\n  }\n  while (true) {\n    wuffs_base__status id_df_status =\n        image_decoder->decode_frame(&pixel_buffer, &io_buf, pixel_blend,\n                                    alloc_workbuf_result.mem_slice, NULL);\n    if (id_df_status.repr == NULL) {\n      break;\n    } else if (id_df_status.repr != wuffs_base__suspension__short_read) {\n      message = id_df_status.message();\n      break;\n    } else if (io_buf.meta.closed) {\n      message = DecodeImage_UnexpectedEndOfFile;\n      break;\n    } else {\n      std::string error_message = input.CopyIn(&io_buf);\n      if (!error_message.empty()) {\n        message = std::move(error_message);" +
-	"\n        break;\n      }\n    }\n  }\n  return DecodeImageResult(std::move(oic_result.mem_owner),\n                           oic_result.mem_slice, pixel_buffer,\n                           std::move(message));\n}\n\n}  // namespace\n\nDecodeImageResult  //\nDecodeImage(DecodeImageCallbacks& callbacks,\n            sync_io::Input& input,\n            uint32_t override_pixel_format_repr,\n            wuffs_base__pixel_blend pixel_blend,\n            uint32_t max_incl_dimension) {\n  wuffs_base__io_buffer* io_buf = input.BringsItsOwnIOBuffer();\n  wuffs_base__io_buffer fallback_io_buf = wuffs_base__empty_io_buffer();\n  std::unique_ptr<uint8_t[]> fallback_io_array(nullptr);\n  if (!io_buf) {\n    fallback_io_array = std::unique_ptr<uint8_t[]>(new uint8_t[32768]);\n    fallback_io_buf =\n        wuffs_base__ptr_u8__writer(fallback_io_array.get(), 32768);\n    io_buf = &fallback_io_buf;\n  }\n\n  DecodeImageResult result =\n      DecodeImage0(callbacks, input, *io_buf, override_pixel_format_repr,\n                   pixel_blend, max_incl_dim" +
-	"ension);\n  callbacks.Done(result, input, *io_buf);\n  return result;\n}\n\n}  // namespace wuffs_aux\n\n#endif  // !defined(WUFFS_CONFIG__MODULES) ||\n        // defined(WUFFS_CONFIG__MODULE__AUX__IMAGE)\n" +
+	"// --------\n\nnamespace {\n\nstd::string  //\nDecodeImageAdvanceIOBuf(sync_io::Input& input,\n                        wuffs_base__io_buffer& io_buf,\n                        bool compactable,\n                        uint64_t min_excl_pos,\n                        uint64_t pos) {\n  if ((pos <= min_excl_pos) || (pos < io_buf.reader_position())) {\n    // Redirects must go forward.\n    return DecodeImage_UnsupportedImageFormat;\n  }\n  while (true) {\n    uint64_t relative_pos = pos - io_buf.reader_position();\n    if (relative_pos <= io_buf.reader_length()) {\n      io_buf.meta.ri += (size_t)relative_pos;\n      break;\n    } else if (io_buf.meta.closed) {\n      return DecodeImage_UnexpectedEndOfFile;\n    }\n    io_buf.meta.ri = io_buf.meta.wi;\n    if (compactable) {\n      io_buf.compact();\n    }\n    std::string error_message = input.CopyIn(&io_buf);\n    if (!error_message.empty()) {\n      return std::move(error_message);\n    }\n  }\n  return \"\";\n}\n\nDecodeImageResult  //\nDecodeImage0(wuffs_base__image_decoder::unique_ptr& image_" +
+	"decoder,\n             DecodeImageCallbacks& callbacks,\n             sync_io::Input& input,\n             wuffs_base__io_buffer& io_buf,\n             uint32_t override_pixel_format_repr,\n             wuffs_base__pixel_blend pixel_blend,\n             uint32_t max_incl_dimension) {\n  // Check args.\n  switch (override_pixel_format_repr) {\n    case 0:\n    case WUFFS_BASE__PIXEL_FORMAT__BGR_565:\n    case WUFFS_BASE__PIXEL_FORMAT__BGR:\n    case WUFFS_BASE__PIXEL_FORMAT__BGRA_NONPREMUL:\n    case WUFFS_BASE__PIXEL_FORMAT__BGRA_PREMUL:\n      break;\n    default:\n      return DecodeImageResult(DecodeImage_UnsupportedPixelFormat);\n  }\n  switch (pixel_blend) {\n    case WUFFS_BASE__PIXEL_BLEND__SRC:\n    case WUFFS_BASE__PIXEL_BLEND__SRC_OVER:\n      break;\n    default:\n      return DecodeImageResult(DecodeImage_UnsupportedPixelBlend);\n  }\n\n  wuffs_base__image_config image_config = wuffs_base__null_image_config();\n  uint64_t start_pos = io_buf.reader_position();\n  bool redirected = false;\n  int32_t fourcc = 0;\nredirect:\n  do {" +
+	"\n    // Determine the image format.\n    if (!redirected) {\n      while (true) {\n        fourcc = wuffs_base__magic_number_guess_fourcc(io_buf.reader_slice());\n        if (fourcc > 0) {\n          break;\n        } else if ((fourcc == 0) && (io_buf.reader_length() >= 64)) {\n          break;\n        } else if (io_buf.meta.closed || (io_buf.writer_length() == 0)) {\n          fourcc = 0;\n          break;\n        }\n        std::string error_message = input.CopyIn(&io_buf);\n        if (!error_message.empty()) {\n          return DecodeImageResult(std::move(error_message));\n        }\n      }\n    } else {\n      wuffs_base__io_buffer empty = wuffs_base__empty_io_buffer();\n      wuffs_base__more_information minfo = wuffs_base__empty_more_information();\n      wuffs_base__status tmm_status =\n          image_decoder->tell_me_more(&empty, &minfo, &io_buf);\n      if (minfo.flavor != WUFFS_BASE__MORE_INFORMATION__FLAVOR__IO_REDIRECT) {\n        return DecodeImageResult(DecodeImage_UnsupportedImageFormat);\n      }\n      uint64_t " +
+	"pos = minfo.io_redirect__range().min_incl;\n      std::string error_message = DecodeImageAdvanceIOBuf(\n          input, io_buf, !input.BringsItsOwnIOBuffer(), start_pos, pos);\n      if (!error_message.empty()) {\n        return DecodeImageResult(std::move(error_message));\n      }\n      fourcc = (int32_t)(minfo.io_redirect__fourcc());\n      if (fourcc == 0) {\n        return DecodeImageResult(DecodeImage_UnsupportedImageFormat);\n      }\n      image_decoder.reset();\n    }\n\n    // Make the image decoder.\n    image_decoder = callbacks.OnImageFormat(\n        (uint32_t)fourcc,\n        fourcc ? wuffs_base__empty_slice_u8() : io_buf.reader_slice());\n    if (!image_decoder) {\n      return DecodeImageResult(DecodeImage_UnsupportedImageFormat);\n    }\n\n    // Decode the image config.\n    while (true) {\n      wuffs_base__status id_dic_status =\n          image_decoder->decode_image_config(&image_config, &io_buf);\n      if (id_dic_status.repr == NULL) {\n        break;\n      } else if (id_dic_status.repr == wuffs_base__note__i_" +
+	"o_redirect) {\n        if (redirected) {\n          return DecodeImageResult(DecodeImage_UnsupportedImageFormat);\n        }\n        redirected = true;\n        goto redirect;\n      } else if (id_dic_status.repr != wuffs_base__suspension__short_read) {\n        return DecodeImageResult(id_dic_status.message());\n      } else if (io_buf.meta.closed) {\n        return DecodeImageResult(DecodeImage_UnexpectedEndOfFile);\n      } else {\n        std::string error_message = input.CopyIn(&io_buf);\n        if (!error_message.empty()) {\n          return DecodeImageResult(std::move(error_message));\n        }\n      }\n    }\n  } while (false);\n\n  // Apply the override pixel format.\n  uint32_t w = image_config.pixcfg.width();\n  uint32_t h = image_config.pixcfg.height();\n  if ((w > max_incl_dimension) || (h > max_incl_dimension)) {\n    return DecodeImageResult(DecodeImage_MaxInclDimensionExceeded);\n  }\n  if (override_pixel_format_repr != 0) {\n    image_config.pixcfg.set(override_pixel_format_repr,\n                            WUFFS_" +
+	"BASE__PIXEL_SUBSAMPLING__NONE, w, h);\n  }\n\n  // Allocate the pixel buffer.\n  size_t pixbuf_len_min_incl = 0;\n  if ((w > 0) && (h > 0)) {\n    pixbuf_len_min_incl = image_config.pixcfg.pixbuf_len();\n    if (pixbuf_len_min_incl == 0) {\n      return DecodeImageResult(DecodeImage_UnsupportedPixelFormat);\n    }\n  }\n  DecodeImageCallbacks::AllocResult oic_result =\n      callbacks.OnImageConfig(image_config);\n  if (!oic_result.error_message.empty()) {\n    return DecodeImageResult(std::move(oic_result.error_message));\n  } else if (oic_result.mem_slice.len < pixbuf_len_min_incl) {\n    return DecodeImageResult(DecodeImage_BufferIsTooShort);\n  }\n  wuffs_base__pixel_buffer pixel_buffer;\n  wuffs_base__status pb_sfs_status =\n      pixel_buffer.set_from_slice(&image_config.pixcfg, oic_result.mem_slice);\n  if (!pb_sfs_status.is_ok()) {\n    return DecodeImageResult(pb_sfs_status.message());\n  }\n\n  // Allocate the work buffer.\n  wuffs_base__range_ii_u64 workbuf_len = image_decoder->workbuf_len();\n  DecodeImageCallbacks::AllocRe" +
+	"sult alloc_workbuf_result =\n      callbacks.AllocWorkbuf(workbuf_len);\n  if (!alloc_workbuf_result.error_message.empty()) {\n    return DecodeImageResult(std::move(alloc_workbuf_result.error_message));\n  } else if (alloc_workbuf_result.mem_slice.len < workbuf_len.min_incl) {\n    return DecodeImageResult(DecodeImage_BufferIsTooShort);\n  }\n\n  // Decode the frame config.\n  wuffs_base__frame_config frame_config = wuffs_base__null_frame_config();\n  while (true) {\n    wuffs_base__status id_dfc_status =\n        image_decoder->decode_frame_config(&frame_config, &io_buf);\n    if (id_dfc_status.repr == NULL) {\n      break;\n    } else if (id_dfc_status.repr != wuffs_base__suspension__short_read) {\n      return DecodeImageResult(id_dfc_status.message());\n    } else if (io_buf.meta.closed) {\n      return DecodeImageResult(DecodeImage_UnexpectedEndOfFile);\n    } else {\n      std::string error_message = input.CopyIn(&io_buf);\n      if (!error_message.empty()) {\n        return DecodeImageResult(std::move(error_message));\n    " +
+	"  }\n    }\n  }\n\n  // Decode the frame (the pixels).\n  //\n  // From here on, always returns the pixel_buffer. If we get this far, we can\n  // still display a partial image, even if we encounter an error.\n  std::string message(\"\");\n  if ((pixel_blend == WUFFS_BASE__PIXEL_BLEND__SRC_OVER) &&\n      frame_config.overwrite_instead_of_blend()) {\n    pixel_blend = WUFFS_BASE__PIXEL_BLEND__SRC;\n  }\n  while (true) {\n    wuffs_base__status id_df_status =\n        image_decoder->decode_frame(&pixel_buffer, &io_buf, pixel_blend,\n                                    alloc_workbuf_result.mem_slice, NULL);\n    if (id_df_status.repr == NULL) {\n      break;\n    } else if (id_df_status.repr != wuffs_base__suspension__short_read) {\n      message = id_df_status.message();\n      break;\n    } else if (io_buf.meta.closed) {\n      message = DecodeImage_UnexpectedEndOfFile;\n      break;\n    } else {\n      std::string error_message = input.CopyIn(&io_buf);\n      if (!error_message.empty()) {\n        message = std::move(error_message);\n   " +
+	"     break;\n      }\n    }\n  }\n  return DecodeImageResult(std::move(oic_result.mem_owner),\n                           oic_result.mem_slice, pixel_buffer,\n                           std::move(message));\n}\n\n}  // namespace\n\nDecodeImageResult  //\nDecodeImage(DecodeImageCallbacks& callbacks,\n            sync_io::Input& input,\n            uint32_t override_pixel_format_repr,\n            wuffs_base__pixel_blend pixel_blend,\n            uint32_t max_incl_dimension) {\n  wuffs_base__io_buffer* io_buf = input.BringsItsOwnIOBuffer();\n  wuffs_base__io_buffer fallback_io_buf = wuffs_base__empty_io_buffer();\n  std::unique_ptr<uint8_t[]> fallback_io_array(nullptr);\n  if (!io_buf) {\n    fallback_io_array = std::unique_ptr<uint8_t[]>(new uint8_t[32768]);\n    fallback_io_buf =\n        wuffs_base__ptr_u8__writer(fallback_io_array.get(), 32768);\n    io_buf = &fallback_io_buf;\n  }\n\n  wuffs_base__image_decoder::unique_ptr image_decoder(nullptr, &free);\n  DecodeImageResult result =\n      DecodeImage0(image_decoder, callbacks, input," +
+	" *io_buf,\n                   override_pixel_format_repr, pixel_blend, max_incl_dimension);\n  callbacks.Done(result, input, *io_buf, std::move(image_decoder));\n  return result;\n}\n\n}  // namespace wuffs_aux\n\n#endif  // !defined(WUFFS_CONFIG__MODULES) ||\n        // defined(WUFFS_CONFIG__MODULE__AUX__IMAGE)\n" +
 	""
 
 const AuxImageHh = "" +
 	"// ---------------- Auxiliary - Image\n\nnamespace wuffs_aux {\n\nstruct DecodeImageResult {\n  DecodeImageResult(MemOwner&& pixbuf_mem_owner0,\n                    wuffs_base__slice_u8 pixbuf_mem_slice0,\n                    wuffs_base__pixel_buffer pixbuf0,\n                    std::string&& error_message0);\n  DecodeImageResult(std::string&& error_message0);\n\n  MemOwner pixbuf_mem_owner;\n  wuffs_base__slice_u8 pixbuf_mem_slice;\n  wuffs_base__pixel_buffer pixbuf;\n  std::string error_message;\n};\n\n// DecodeImageCallbacks are the callbacks given to DecodeImage. They are always\n// called in this order:\n//  1. OnImageFormat\n//  2. OnImageConfig\n//  3. AllocWorkbuf\n//  4. Done\n//\n// It may return early - the third callback might not be invoked if the second\n// one fails (returns a non-empty error message) - but the final callback\n// (Done) is always invoked.\nclass DecodeImageCallbacks {\n public:\n  // AllocResult holds a memory allocation (the result of malloc or new, a\n  // statically allocated pointer, etc), or an error " +
 	"message. The memory is\n  // de-allocated when mem_owner goes out of scope and is destroyed.\n  struct AllocResult {\n    AllocResult(MemOwner&& mem_owner0, wuffs_base__slice_u8 mem_slice0);\n    AllocResult(std::string&& error_message0);\n\n    MemOwner mem_owner;\n    wuffs_base__slice_u8 mem_slice;\n    std::string error_message;\n  };\n\n  // OnImageFormat returns the image decoder for the input data's file format.\n  // Returning a nullptr means failure (DecodeImage_UnsupportedImageFormat).\n  //\n  // Common formats will have a non-zero FourCC value, such as\n  // WUFFS_BASE__FOURCC__JPEG. A zero FourCC code means that the caller is\n  // responsible for examining the opening bytes (a prefix) of the input data.\n  // OnImageFormat implementations should not modify those bytes.\n  //\n  // OnImageFormat might be called more than once, since some image file\n  // formats can wrap others. For example, a nominal BMP file can actually\n  // contain a JPEG or a PNG.\n  //\n  // There is no default implementation, as modular Wuffs b" +
 	"uilds (those that\n  // define WUFFS_CONFIG__MODULES) may enable or disable particular codecs.\n  virtual wuffs_base__image_decoder::unique_ptr  //\n  OnImageFormat(uint32_t fourcc, wuffs_base__slice_u8 prefix) = 0;\n\n  // OnImageConfig allocates the pixel buffer.\n  //\n  // The default OnImageConfig implementation allocates zeroed memory.\n  virtual AllocResult  //\n  OnImageConfig(const wuffs_base__image_config& image_config);\n\n  // AllocWorkbuf allocates the work buffer. The allocated buffer's length\n  // should be at least len.min_incl, but larger allocations (up to\n  // len.max_incl) may have better performance (by using more memory).\n  //\n  // The default AllocWorkbuf implementation allocates len.max_incl bytes of\n  // zeroed memory.\n  virtual AllocResult  //\n  AllocWorkbuf(wuffs_base__range_ii_u64 len);\n\n  // Done is always the last Callback method called by DecodeImage, whether or\n  // not parsing the input encountered an error. Even when successful, trailing\n  // data may remain in input and buffer.\n  //\n  " +
-	"// Do not keep a reference to buffer or buffer.data.ptr after Done returns,\n  // as DecodeImage may then de-allocate the backing array.\n  //\n  // The default Done implementation is a no-op.\n  virtual void  //\n  Done(DecodeImageResult& result, sync_io::Input& input, IOBuffer& buffer);\n};\n\nextern const char DecodeImage_BufferIsTooShort[];\nextern const char DecodeImage_MaxInclDimensionExceeded[];\nextern const char DecodeImage_OutOfMemory[];\nextern const char DecodeImage_UnexpectedEndOfFile[];\nextern const char DecodeImage_UnsupportedImageFormat[];\nextern const char DecodeImage_UnsupportedPixelBlend[];\nextern const char DecodeImage_UnsupportedPixelConfiguration[];\nextern const char DecodeImage_UnsupportedPixelFormat[];\n\n// DecodeImage decodes the image data in input. A variety of image file formats\n// can be decoded, depending on what callbacks.OnImageFormat returns. For\n// animated formats, only the first frame is returned.\n//\n//  - On total success, the returned error_message is empty.\n//  - On partial success " +
-	"(e.g. the input file was truncated but we are still\n//    able to decode some pixels), error_message is non-empty but the returned\n//    pixbuf.pixcfg.is_valid() is true.\n//  - On failure, the error_message is non_empty and pixbuf.pixcfg.is_valid()\n//    is false.\n//\n// The callbacks allocate the pixel buffer memory and work buffer memory. On\n// success, pixel buffer memory ownership is passed to the DecodeImage caller\n// as the returned pixbuf_mem_owner. Regardless of success or failure, the work\n// buffer memory is deleted.\n//\n// If override_pixel_format_repr is zero then the pixel buffer will have the\n// image file's natural pixel format. For example, GIF images' natural pixel\n// format is an indexed one.\n//\n// If override_pixel_format_repr is non-zero (and one of the constants listed\n// below) then the image will be decoded to that particular pixel format:\n//  - WUFFS_BASE__PIXEL_FORMAT__BGR_565\n//  - WUFFS_BASE__PIXEL_FORMAT__BGR\n//  - WUFFS_BASE__PIXEL_FORMAT__BGRA_NONPREMUL\n//  - WUFFS_BASE__PIXEL_FORM" +
-	"AT__BGRA_PREMUL\n//\n// The pixel_blend (one of the constants listed below) determines how to\n// composite the decoded image over the pixel buffer's original pixels (as\n// returned by callbacks.OnImageConfig):\n//  - WUFFS_BASE__PIXEL_BLEND__SRC\n//  - WUFFS_BASE__PIXEL_BLEND__SRC_OVER\n//\n// Decoding fails (with DecodeImage_MaxInclDimensionExceeded) if the image's\n// width or height is greater than max_incl_dimension.\nDecodeImageResult  //\nDecodeImage(DecodeImageCallbacks& callbacks,\n            sync_io::Input& input,\n            uint32_t override_pixel_format_repr,\n            wuffs_base__pixel_blend pixel_blend = WUFFS_BASE__PIXEL_BLEND__SRC,\n            uint32_t max_incl_dimension = 1048575);  // 0x000F_FFFF\n\n}  // namespace wuffs_aux\n" +
+	"// The image_decoder is the one returned by OnImageFormat (if OnImageFormat\n  // was successful), or a no-op unique_ptr otherwise. Like any unique_ptr,\n  // ownership moves to the Done implementation.\n  //\n  // Do not keep a reference to buffer or buffer.data.ptr after Done returns,\n  // as DecodeImage may then de-allocate the backing array.\n  //\n  // The default Done implementation is a no-op, other than running the\n  // image_decoder unique_ptr destructor.\n  virtual void  //\n  Done(DecodeImageResult& result,\n       sync_io::Input& input,\n       IOBuffer& buffer,\n       wuffs_base__image_decoder::unique_ptr image_decoder);\n};\n\nextern const char DecodeImage_BufferIsTooShort[];\nextern const char DecodeImage_MaxInclDimensionExceeded[];\nextern const char DecodeImage_OutOfMemory[];\nextern const char DecodeImage_UnexpectedEndOfFile[];\nextern const char DecodeImage_UnsupportedImageFormat[];\nextern const char DecodeImage_UnsupportedPixelBlend[];\nextern const char DecodeImage_UnsupportedPixelConfiguration[];\nextern c" +
+	"onst char DecodeImage_UnsupportedPixelFormat[];\n\n// DecodeImage decodes the image data in input. A variety of image file formats\n// can be decoded, depending on what callbacks.OnImageFormat returns. For\n// animated formats, only the first frame is returned.\n//\n//  - On total success, the returned error_message is empty.\n//  - On partial success (e.g. the input file was truncated but we are still\n//    able to decode some pixels), error_message is non-empty but the returned\n//    pixbuf.pixcfg.is_valid() is true.\n//  - On failure, the error_message is non_empty and pixbuf.pixcfg.is_valid()\n//    is false.\n//\n// The callbacks allocate the pixel buffer memory and work buffer memory. On\n// success, pixel buffer memory ownership is passed to the DecodeImage caller\n// as the returned pixbuf_mem_owner. Regardless of success or failure, the work\n// buffer memory is deleted.\n//\n// If override_pixel_format_repr is zero then the pixel buffer will have the\n// image file's natural pixel format. For example, GIF images' na" +
+	"tural pixel\n// format is an indexed one.\n//\n// If override_pixel_format_repr is non-zero (and one of the constants listed\n// below) then the image will be decoded to that particular pixel format:\n//  - WUFFS_BASE__PIXEL_FORMAT__BGR_565\n//  - WUFFS_BASE__PIXEL_FORMAT__BGR\n//  - WUFFS_BASE__PIXEL_FORMAT__BGRA_NONPREMUL\n//  - WUFFS_BASE__PIXEL_FORMAT__BGRA_PREMUL\n//\n// The pixel_blend (one of the constants listed below) determines how to\n// composite the decoded image over the pixel buffer's original pixels (as\n// returned by callbacks.OnImageConfig):\n//  - WUFFS_BASE__PIXEL_BLEND__SRC\n//  - WUFFS_BASE__PIXEL_BLEND__SRC_OVER\n//\n// Decoding fails (with DecodeImage_MaxInclDimensionExceeded) if the image's\n// width or height is greater than max_incl_dimension.\nDecodeImageResult  //\nDecodeImage(DecodeImageCallbacks& callbacks,\n            sync_io::Input& input,\n            uint32_t override_pixel_format_repr,\n            wuffs_base__pixel_blend pixel_blend = WUFFS_BASE__PIXEL_BLEND__SRC,\n            uint32_t max_inc" +
+	"l_dimension = 1048575);  // 0x000F_FFFF\n\n}  // namespace wuffs_aux\n" +
 	""
 
 const AuxJsonCc = "" +
diff --git a/release/c/wuffs-unsupported-snapshot.c b/release/c/wuffs-unsupported-snapshot.c
index d7e2bda..36e6d164 100644
--- a/release/c/wuffs-unsupported-snapshot.c
+++ b/release/c/wuffs-unsupported-snapshot.c
@@ -9444,12 +9444,20 @@
   // not parsing the input encountered an error. Even when successful, trailing
   // data may remain in input and buffer.
   //
+  // The image_decoder is the one returned by OnImageFormat (if OnImageFormat
+  // was successful), or a no-op unique_ptr otherwise. Like any unique_ptr,
+  // ownership moves to the Done implementation.
+  //
   // Do not keep a reference to buffer or buffer.data.ptr after Done returns,
   // as DecodeImage may then de-allocate the backing array.
   //
-  // The default Done implementation is a no-op.
+  // The default Done implementation is a no-op, other than running the
+  // image_decoder unique_ptr destructor.
   virtual void  //
-  Done(DecodeImageResult& result, sync_io::Input& input, IOBuffer& buffer);
+  Done(DecodeImageResult& result,
+       sync_io::Input& input,
+       IOBuffer& buffer,
+       wuffs_base__image_decoder::unique_ptr image_decoder);
 };
 
 extern const char DecodeImage_BufferIsTooShort[];
@@ -36734,9 +36742,11 @@
 }
 
 void  //
-DecodeImageCallbacks::Done(DecodeImageResult& result,
-                           sync_io::Input& input,
-                           IOBuffer& buffer) {}
+DecodeImageCallbacks::Done(
+    DecodeImageResult& result,
+    sync_io::Input& input,
+    IOBuffer& buffer,
+    wuffs_base__image_decoder::unique_ptr image_decoder) {}
 
 const char DecodeImage_BufferIsTooShort[] =  //
     "wuffs_aux::DecodeImage: buffer is too short";
@@ -36790,7 +36800,8 @@
 }
 
 DecodeImageResult  //
-DecodeImage0(DecodeImageCallbacks& callbacks,
+DecodeImage0(wuffs_base__image_decoder::unique_ptr& image_decoder,
+             DecodeImageCallbacks& callbacks,
              sync_io::Input& input,
              wuffs_base__io_buffer& io_buf,
              uint32_t override_pixel_format_repr,
@@ -36816,7 +36827,6 @@
   }
 
   wuffs_base__image_config image_config = wuffs_base__null_image_config();
-  wuffs_base__image_decoder::unique_ptr image_decoder(nullptr, &free);
   uint64_t start_pos = io_buf.reader_position();
   bool redirected = false;
   int32_t fourcc = 0;
@@ -37007,10 +37017,11 @@
     io_buf = &fallback_io_buf;
   }
 
+  wuffs_base__image_decoder::unique_ptr image_decoder(nullptr, &free);
   DecodeImageResult result =
-      DecodeImage0(callbacks, input, *io_buf, override_pixel_format_repr,
-                   pixel_blend, max_incl_dimension);
-  callbacks.Done(result, input, *io_buf);
+      DecodeImage0(image_decoder, callbacks, input, *io_buf,
+                   override_pixel_format_repr, pixel_blend, max_incl_dimension);
+  callbacks.Done(result, input, *io_buf, std::move(image_decoder));
   return result;
 }