diff --git a/include/boost/http/concept/buffer_source.hpp b/include/boost/http/concept/buffer_source.hpp
index ca5d1278..6c400e82 100644
--- a/include/boost/http/concept/buffer_source.hpp
+++ b/include/boost/http/concept/buffer_source.hpp
@@ -90,7 +90,7 @@ namespace http {
         {
             auto [ec, bufs] = co_await source.pull( arr );
             if( ec == cond::eof )
-                co_return {{}, total};
+                co_return {std::error_code(), total};
             if( ec )
                 co_return {ec, total};
             auto [write_ec, n] = co_await stream.write_some( bufs );
diff --git a/include/boost/http/io/any_buffer_sink.hpp b/include/boost/http/io/any_buffer_sink.hpp
index f1fbdfa5..e5c66ee6 100644
--- a/include/boost/http/io/any_buffer_sink.hpp
+++ b/include/boost/http/io/any_buffer_sink.hpp
@@ -1045,7 +1045,7 @@ any_buffer_sink::write_some(CB buffers)
     capy::buffer_param<CB> bp(buffers);
     auto src = bp.data();
     if(src.empty())
-        co_return {{}, 0};
+        co_return {std::error_code(), 0};
 
     // Native WriteSink path
     if(vt_->construct_write_some_awaitable)
@@ -1061,14 +1061,14 @@ any_buffer_sink::write_some(CB buffers)
             co_return {ec, 0};
         dst_bufs = prepare(arr);
         if(dst_bufs.empty())
-            co_return {{}, 0};
+            co_return {std::error_code(), 0};
     }
 
     auto n = capy::buffer_copy(dst_bufs, src);
     auto [ec] = co_await commit(n);
     if(ec)
         co_return {ec, 0};
-    co_return {{}, n};
+    co_return {std::error_code(), n};
 }
 
 template<capy::ConstBufferSequence CB>
@@ -1093,7 +1093,7 @@ any_buffer_sink::write(CB buffers)
                 co_return {ec, total};
             bp.consume(n);
         }
-        co_return {{}, total};
+        co_return {std::error_code(), total};
     }
 
     // Synthesized path: prepare + capy::buffer_copy + commit
@@ -1121,7 +1121,7 @@ any_buffer_sink::write(CB buffers)
         total += n;
     }
 
-    co_return {{}, total};
+    co_return {std::error_code(), total};
 }
 
 inline auto
@@ -1246,7 +1246,7 @@ any_buffer_sink::write_eof(CB buffers)
     if(ec)
         co_return {ec, total};
 
-    co_return {{}, total};
+    co_return {std::error_code(), total};
 }
 
 static_assert(BufferSink<any_buffer_sink>);
diff --git a/include/boost/http/io/any_buffer_source.hpp b/include/boost/http/io/any_buffer_source.hpp
index 83d25a5b..eaaea086 100644
--- a/include/boost/http/io/any_buffer_source.hpp
+++ b/include/boost/http/io/any_buffer_source.hpp
@@ -761,7 +761,7 @@ any_buffer_source::read_some(MB buffers)
     capy::buffer_param<MB> bp(buffers);
     auto dest = bp.data();
     if(dest.empty())
-        co_return {{}, 0};
+        co_return {std::error_code(), 0};
 
     // Native ReadSource path
     if(vt_->construct_read_some_awaitable)
@@ -775,7 +775,7 @@ any_buffer_source::read_some(MB buffers)
 
     auto n = capy::buffer_copy(dest, bufs);
     consume(n);
-    co_return {{}, n};
+    co_return {std::error_code(), n};
 }
 
 template<capy::MutableBufferSequence MB>
@@ -800,7 +800,7 @@ any_buffer_source::read(MB buffers)
                 co_return {ec, total};
             bp.consume(n);
         }
-        co_return {{}, total};
+        co_return {std::error_code(), total};
     }
 
     // Synthesized path: pull + capy::buffer_copy + consume
@@ -822,7 +822,7 @@ any_buffer_source::read(MB buffers)
         bp.consume(n);
     }
 
-    co_return {{}, total};
+    co_return {std::error_code(), total};
 }
 
 static_assert(BufferSource<any_buffer_source>);
diff --git a/include/boost/http/io/any_read_source.hpp b/include/boost/http/io/any_read_source.hpp
index 5c229896..7c775f4a 100644
--- a/include/boost/http/io/any_read_source.hpp
+++ b/include/boost/http/io/any_read_source.hpp
@@ -506,7 +506,7 @@ any_read_source::read_some(MB buffers)
         await_resume()
         {
             if(ba_.to_span().empty())
-                return {{}, 0};
+                return {std::error_code(), 0};
 
             struct guard {
                 any_read_source* self;
@@ -588,7 +588,7 @@ any_read_source::read(MB buffers)
         bp.consume(n);
     }
 
-    co_return {{}, total};
+    co_return {std::error_code(), total};
 }
 
 } // namespace http
diff --git a/include/boost/http/io/any_write_sink.hpp b/include/boost/http/io/any_write_sink.hpp
index 4dbabfa0..44a895a2 100644
--- a/include/boost/http/io/any_write_sink.hpp
+++ b/include/boost/http/io/any_write_sink.hpp
@@ -834,7 +834,7 @@ any_write_sink::write_some(CB buffers)
         await_resume()
         {
             if(ba_.to_span().empty())
-                return {{}, 0};
+                return {std::error_code(), 0};
 
             struct guard {
                 any_write_sink* self;
@@ -870,7 +870,7 @@ any_write_sink::write(CB buffers)
         bp.consume(n);
     }
 
-    co_return {{}, total};
+    co_return {std::error_code(), total};
 }
 
 template<capy::ConstBufferSequence CB>
diff --git a/include/boost/http/io/push_to.hpp b/include/boost/http/io/push_to.hpp
index dc7820a1..d02261d0 100644
--- a/include/boost/http/io/push_to.hpp
+++ b/include/boost/http/io/push_to.hpp
@@ -134,7 +134,7 @@ push_to(Src& source, Stream& stream)
     {
         auto [ec, bufs] = co_await source.pull(arr);
         if(ec == capy::cond::eof)
-            co_return {{}, total};
+            co_return {std::error_code(), total};
         if(ec)
             co_return {ec, total};
 
diff --git a/include/boost/http/metadata.hpp b/include/boost/http/metadata.hpp
index 26fe98c6..376a338f 100644
--- a/include/boost/http/metadata.hpp
+++ b/include/boost/http/metadata.hpp
@@ -21,7 +21,7 @@ namespace http {
 
 /** Identifies the payload type of a message.
 */
-enum class payload
+enum class payload : unsigned char
 {
     /** This message has no payload.
     */
diff --git a/include/boost/http/parser.hpp b/include/boost/http/parser.hpp
index 28b40f24..3dcf351c 100644
--- a/include/boost/http/parser.hpp
+++ b/include/boost/http/parser.hpp
@@ -601,7 +601,7 @@ parser::
 read(Stream& stream, MB buffers)
 {
     if(capy::buffer_empty(buffers))
-        co_return {{}, 0};
+        co_return {std::error_code(), 0};
 
     std::size_t total = 0;
     capy::consuming_buffers dest(buffers);
@@ -622,7 +622,7 @@ read(Stream& stream, MB buffers)
                 dest.consume(copied);
 
                 if(capy::buffer_empty(dest.data()))
-                    co_return {{}, total};
+                    co_return {std::error_code(), total};
             }
 
             if(is_complete())
@@ -681,7 +681,7 @@ pull(std::span<capy::const_buffer> dest)
             std::size_t count = (std::min)(body_data.size(), dest.size());
             for(std::size_t i = 0; i < count; ++i)
                 dest[i] = body_data[i];
-            co_return {{}, dest.first(count)};
+            co_return {std::error_code(), dest.first(count)};
         }
 
         if(pr_->is_complete())
diff --git a/include/boost/http/serializer.hpp b/include/boost/http/serializer.hpp
index 322223cd..a9bce4e0 100644
--- a/include/boost/http/serializer.hpp
+++ b/include/boost/http/serializer.hpp
@@ -825,7 +825,7 @@ class serializer::sink
             }
         }
 
-        co_return {{}, total};
+        co_return {std::error_code(), total};
     }
 
     /** Write final body data and signal end-of-stream.
@@ -877,7 +877,7 @@ class serializer::sink
                 co_return {ec2, n};
         }
 
-        co_return {{}, n};
+        co_return {std::error_code(), n};
     }
 
     /** Signal end-of-stream with no additional data.
diff --git a/include/boost/http/test/buffer_source.hpp b/include/boost/http/test/buffer_source.hpp
index 5fb6fe4c..cd3d93ee 100644
--- a/include/boost/http/test/buffer_source.hpp
+++ b/include/boost/http/test/buffer_source.hpp
@@ -192,14 +192,14 @@ class buffer_source
                 std::size_t to_return = (std::min)(avail, self_->max_pull_size_);
 
                 if(dest_.empty())
-                    return {{}, {}};
+                    return {std::error_code(), {}};
 
                 // Fill a single buffer descriptor
                 dest_[0] = capy::make_buffer(
                     self_->data_.data() + self_->pos_,
                     to_return);
 
-                return {{}, dest_.first(1)};
+                return {std::error_code(), dest_.first(1)};
             }
         };
         return awaitable{this, dest};
diff --git a/include/boost/http/test/read_source.hpp b/include/boost/http/test/read_source.hpp
index aea5c840..94385b16 100644
--- a/include/boost/http/test/read_source.hpp
+++ b/include/boost/http/test/read_source.hpp
@@ -163,7 +163,7 @@ class read_source
             await_resume()
             {
                 if(capy::buffer_empty(buffers_))
-                    return {{}, 0};
+                    return {std::error_code(), 0};
 
                 if(canceled_)
                     return {capy::error::canceled, 0};
@@ -181,7 +181,7 @@ class read_source
                 auto src = capy::make_buffer(self_->data_.data() + self_->pos_, avail);
                 std::size_t const n = capy::buffer_copy(buffers_, src);
                 self_->pos_ += n;
-                return {{}, n};
+                return {std::error_code(), n};
             }
         };
         return awaitable{this, buffers};
@@ -238,7 +238,7 @@ class read_source
             await_resume()
             {
                 if(capy::buffer_empty(buffers_))
-                    return {{}, 0};
+                    return {std::error_code(), 0};
 
                 if(canceled_)
                     return {capy::error::canceled, 0};
@@ -257,7 +257,7 @@ class read_source
 
                 if(n < capy::buffer_size(buffers_))
                     return {capy::error::eof, n};
-                return {{}, n};
+                return {std::error_code(), n};
             }
         };
         return awaitable{this, buffers};
diff --git a/include/boost/http/test/write_sink.hpp b/include/boost/http/test/write_sink.hpp
index 68f2d96d..00cc2c0f 100644
--- a/include/boost/http/test/write_sink.hpp
+++ b/include/boost/http/test/write_sink.hpp
@@ -196,7 +196,7 @@ class write_sink
             await_resume()
             {
                 if(capy::buffer_empty(buffers_))
-                    return {{}, 0};
+                    return {std::error_code(), 0};
 
                 if(canceled_)
                     return {capy::error::canceled, 0};
@@ -220,7 +220,7 @@ class write_sink
                     return {ec, 0};
                 }
 
-                return {{}, n};
+                return {std::error_code(), n};
             }
         };
         return awaitable{this, buffers};
@@ -288,7 +288,7 @@ class write_sink
 
                 std::size_t n = capy::buffer_size(buffers_);
                 if(n == 0)
-                    return {{}, 0};
+                    return {std::error_code(), 0};
 
                 std::size_t const old_size = self_->data_.size();
                 self_->data_.resize(old_size + n);
@@ -299,7 +299,7 @@ class write_sink
                 if(ec)
                     return {ec, n};
 
-                return {{}, n};
+                return {std::error_code(), n};
             }
         };
         return awaitable{this, buffers};
@@ -386,7 +386,7 @@ class write_sink
 
                 self_->eof_called_ = true;
 
-                return {{}, n};
+                return {std::error_code(), n};
             }
         };
         return awaitable{this, buffers};
diff --git a/test/unit/io/any_buffer_sink.cpp b/test/unit/io/any_buffer_sink.cpp
index bd61f847..ec4f4fe9 100644
--- a/test/unit/io/any_buffer_sink.cpp
+++ b/test/unit/io/any_buffer_sink.cpp
@@ -169,7 +169,7 @@ class buffer_write_sink
             {
                 self_->write_api_used_ = true;
                 if(buffer_empty(buffers_))
-                    return {{}, 0};
+                    return {std::error_code(), 0};
                 auto ec = self_->f_.maybe_fail();
                 if(ec) return {ec, 0};
 
@@ -178,7 +178,7 @@ class buffer_write_sink
                 self_->data_.resize(old_size + n);
                 buffer_copy(make_buffer(
                     self_->data_.data() + old_size, n), buffers_, n);
-                return {{}, n};
+                return {std::error_code(), n};
             }
         };
         return awaitable{this, buffers};
@@ -204,12 +204,12 @@ class buffer_write_sink
                 if(ec) return {ec, 0};
 
                 std::size_t n = buffer_size(buffers_);
-                if(n == 0) return {{}, 0};
+                if(n == 0) return {std::error_code(), 0};
                 std::size_t const old_size = self_->data_.size();
                 self_->data_.resize(old_size + n);
                 buffer_copy(make_buffer(
                     self_->data_.data() + old_size, n), buffers_);
-                return {{}, n};
+                return {std::error_code(), n};
             }
         };
         return awaitable{this, buffers};
@@ -243,7 +243,7 @@ class buffer_write_sink
                         self_->data_.data() + old_size, n), buffers_);
                 }
                 self_->eof_called_ = true;
-                return {{}, n};
+                return {std::error_code(), n};
             }
         };
         return awaitable{this, buffers};
@@ -299,7 +299,7 @@ struct resuming_size_awaitable
     std::coroutine_handle<>
     await_suspend(std::coroutine_handle<> h, io_env const*) noexcept
         { return h; }
-    io_result<std::size_t> await_resume() { return {{}, 1}; }
+    io_result<std::size_t> await_resume() { return {std::error_code(), 1}; }
 };
 
 // Satisfies BufferSink + WriteSink with suspending operations.
diff --git a/test/unit/io/any_buffer_source.cpp b/test/unit/io/any_buffer_source.cpp
index 56f41654..ca37f7c0 100644
--- a/test/unit/io/any_buffer_source.cpp
+++ b/test/unit/io/any_buffer_source.cpp
@@ -115,12 +115,12 @@ class buffer_read_source
                 std::size_t to_return = (std::min)(avail, self_->max_pull_size_);
 
                 if(dest_.empty())
-                    return {{}, {}};
+                    return {std::error_code(), {}};
 
                 dest_[0] = make_buffer(
                     self_->data_.data() + self_->pos_,
                     to_return);
-                return {{}, dest_.first(1)};
+                return {std::error_code(), dest_.first(1)};
             }
         };
         return awaitable{this, dest};
@@ -146,7 +146,7 @@ class buffer_read_source
             {
                 self_->read_api_used_ = true;
                 if(buffer_empty(buffers_))
-                    return {{}, 0};
+                    return {std::error_code(), 0};
                 auto ec = self_->f_.maybe_fail();
                 if(ec)
                     return {ec, 0};
@@ -161,7 +161,7 @@ class buffer_read_source
                     self_->data_.data() + self_->pos_, avail);
                 std::size_t const n = buffer_copy(buffers_, src);
                 self_->pos_ += n;
-                return {{}, n};
+                return {std::error_code(), n};
             }
         };
         return awaitable{this, buffers};
@@ -184,7 +184,7 @@ class buffer_read_source
             {
                 self_->read_api_used_ = true;
                 if(buffer_empty(buffers_))
-                    return {{}, 0};
+                    return {std::error_code(), 0};
                 auto ec = self_->f_.maybe_fail();
                 if(ec)
                     return {ec, 0};
@@ -200,7 +200,7 @@ class buffer_read_source
 
                 if(n < buffer_size(buffers_))
                     return {capy::error::eof, n};
-                return {{}, n};
+                return {std::error_code(), n};
             }
         };
         return awaitable{this, buffers};
@@ -221,9 +221,9 @@ struct resuming_pull_awaitable
     await_resume()
     {
         if(dest_.empty())
-            return {{}, {}};
+            return {std::error_code(), {}};
         dest_[0] = make_buffer(data_, 3);
-        return {{}, dest_.first(1)};
+        return {std::error_code(), dest_.first(1)};
     }
 };
 
@@ -233,7 +233,7 @@ struct resuming_io_awaitable
     std::coroutine_handle<>
     await_suspend(std::coroutine_handle<> h, io_env const*) noexcept
         { return h; }
-    io_result<std::size_t> await_resume() { return {{}, 3}; }
+    io_result<std::size_t> await_resume() { return {std::error_code(), 3}; }
 };
 
 // Satisfies BufferSource + ReadSource with suspending operations.
diff --git a/test/unit/io/any_read_source.cpp b/test/unit/io/any_read_source.cpp
index 0e3c412b..82d15e7a 100644
--- a/test/unit/io/any_read_source.cpp
+++ b/test/unit/io/any_read_source.cpp
@@ -48,7 +48,7 @@ struct pending_source_awaitable
     std::coroutine_handle<> await_suspend(std::coroutine_handle<>, io_env const*)
         { return std::noop_coroutine(); }
     io_result<std::size_t> await_resume()
-        { return {{}, 0}; }
+        { return {std::error_code(), 0}; }
 };
 
 struct pending_read_source
@@ -70,7 +70,7 @@ struct resuming_source_awaitable
     std::coroutine_handle<>
     await_suspend(std::coroutine_handle<> h, io_env const*) noexcept
         { return h; }
-    io_result<std::size_t> await_resume() { return {{}, 5}; }
+    io_result<std::size_t> await_resume() { return {std::error_code(), 5}; }
 };
 
 struct resuming_read_source
diff --git a/test/unit/io/any_write_sink.cpp b/test/unit/io/any_write_sink.cpp
index 94533dab..2aebc914 100644
--- a/test/unit/io/any_write_sink.cpp
+++ b/test/unit/io/any_write_sink.cpp
@@ -48,7 +48,7 @@ struct pending_sink_awaitable
     std::coroutine_handle<> await_suspend(std::coroutine_handle<>, io_env const*)
         { return std::noop_coroutine(); }
     io_result<std::size_t> await_resume()
-        { return {{}, 0}; }
+        { return {std::error_code(), 0}; }
 };
 
 struct pending_sink_eof_awaitable
@@ -89,7 +89,7 @@ struct resuming_sink_awaitable
     std::coroutine_handle<>
     await_suspend(std::coroutine_handle<> h, io_env const*) noexcept
         { return h; }
-    io_result<std::size_t> await_resume() { return {{}, 1}; }
+    io_result<std::size_t> await_resume() { return {std::error_code(), 1}; }
 };
 
 struct resuming_sink_eof_awaitable