diff --git a/include/ircd/server/tag.h b/include/ircd/server/tag.h
index 41f5cfef5..e4510f94c 100644
--- a/include/ircd/server/tag.h
+++ b/include/ircd/server/tag.h
@@ -30,6 +30,7 @@ struct ircd::server::tag
 	{
 		size_t written {0};
 		size_t head_read {0};          // includes head terminator
+		size_t head_rem {0};           // how much of head buf wasn't used.
 		size_t content_read {0};       // total content read after head
 		size_t content_length {0};     // fixed; or grows monotonic for chunked enc
 		size_t chunk_read {0};         // content read after last chunk head
@@ -50,12 +51,17 @@ struct ircd::server::tag
 
 	size_t content_overflow() const;
 	size_t content_remaining() const;
+
 	mutable_buffer make_read_discard_buffer() const;
+	mutable_buffer make_read_chunk_dynamic_content_buffer() const;
+	mutable_buffer make_read_chunk_dynamic_head_buffer() const;
 	mutable_buffer make_read_chunk_content_buffer() const;
 	mutable_buffer make_read_chunk_head_buffer() const;
 	mutable_buffer make_read_content_buffer() const;
 	mutable_buffer make_read_head_buffer() const;
 
+	const_buffer read_chunk_dynamic_content(const const_buffer &, bool &done);
+	const_buffer read_chunk_dynamic_head(const const_buffer &, bool &done);
 	const_buffer read_chunk_content(const const_buffer &, bool &done);
 	const_buffer read_chunk_head(const const_buffer &, bool &done);
 	const_buffer read_content(const const_buffer &, bool &done);
diff --git a/ircd/server.cc b/ircd/server.cc
index d8f05e13f..8e6259123 100644
--- a/ircd/server.cc
+++ b/ircd/server.cc
@@ -1932,7 +1932,7 @@ noexcept
 	// If the content is chunked encoding and the tag is in the phase of
 	// receiving the chunk head we have to copy what's been received of that
 	// head so far so the grammar can parse a coherent head to continue.
-	if(tag.state.chunk_length == size_t(-1))
+	if(tag.state.chunk_length == size_t(-1) && !null(request.in.content))
 	{
 		const const_buffer src
 		{
@@ -1947,6 +1947,17 @@ noexcept
 
 		copy(dst, src);
 	}
+
+	// Moving the dynamic buffer should have no real effect because the
+	// cancellation buffer already took over for it. We could do it anyway
+	// to prevent regressions but at the cost of maintaining twice the memory
+	// allocated. For now it's commented to let it die with the user's req.
+	//tag.request->in.dynamic = std::move(request.in.dynamic);
+
+	// Moving the chunk vector is important to maintain the state of dynamic
+	// chunk transfers through this cancel. There is no condition here for if
+	// this is not a dynamic chunk transfer because it's trivial.
+	tag.request->in.chunks = std::move(request.in.chunks);
 }
 
 void
@@ -2134,9 +2145,15 @@ ircd::server::tag::read_buffer(const const_buffer &buffer,
 	if(state.status == (http::code)0)
 		return read_head(buffer, done, link);
 
+	if(state.chunk_length == size_t(-1) && null(request->in.content))
+		return read_chunk_dynamic_head(buffer, done);
+
 	if(state.chunk_length == size_t(-1))
 		return read_chunk_head(buffer, done);
 
+	if(state.chunk_length && null(request->in.content))
+		return read_chunk_dynamic_content(buffer, done);
+
 	if(state.chunk_length)
 		return read_chunk_content(buffer, done);
 
@@ -2209,6 +2226,7 @@ ircd::server::tag::read_head(const const_buffer &buffer,
 
 	// Resize the user's head buffer tight to the head; this is how we convey
 	// the size of the dome back to the user.
+	state.head_rem = size(req.in.head) - head_read;
 	req.in.head = mutable_buffer
 	{
 		data(req.in.head), head_read
@@ -2256,29 +2274,19 @@ ircd::server::tag::read_head(const const_buffer &buffer,
 			req.in.chunks.reserve(req.opt->chunks_reserve);
 		}
 
-
-	///TODO: XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
-	if(dynamic)
-	{
-		assert(req.opt);
-		const size_t alloc_size
-		{
-			40_MiB
-		};
-
-		req.in.dynamic = unique_buffer<mutable_buffer>{alloc_size};
-		req.in.content = req.in.dynamic;
-	}
-
 		const const_buffer chunk
 		{
-			data(req.in.content), move(req.in.content, beyond_head)
+			!dynamic?
+				const_buffer{data(req.in.content), move(req.in.content, beyond_head)}:
+				beyond_head
 		};
 
 		state.chunk_length = -1;
 		const const_buffer overrun
 		{
-			read_chunk_head(chunk, done)
+			!dynamic?
+				read_chunk_head(chunk, done):
+				read_chunk_dynamic_head(chunk, done)
 		};
 
 		assert(empty(overrun) || done == true);
@@ -2570,6 +2578,217 @@ ircd::server::tag::read_chunk_content(const const_buffer &buffer,
 	return {};
 }
 
+ircd::const_buffer
+ircd::server::tag::read_chunk_dynamic_head(const const_buffer &buffer,
+                                           bool &done)
+{
+	assert(request);
+	auto &req{*request};
+
+	// informal search for head terminator
+	static const string_view terminator{"\r\n"};
+	const auto pos
+	{
+		string_view{buffer}.find(terminator)
+	};
+
+	if(pos == string_view::npos)
+	{
+		state.chunk_read += size(buffer);
+		state.content_read += size(buffer);
+		return {};
+	}
+
+	// This indicates how much head was just received from this buffer only.
+	const size_t addl_head_bytes
+	{
+		pos + size(terminator)
+	};
+
+	// The received buffer may go past the end of the head.
+	assert(addl_head_bytes <= size(buffer));
+	const size_t beyond_head_length
+	{
+		size(buffer) - addl_head_bytes
+	};
+
+	state.chunk_read += addl_head_bytes;
+	const auto head_length{state.chunk_read};
+	state.chunk_read = 0;
+
+	// Window on any data in the buffer after the head.
+	const const_buffer beyond_head
+	{
+		data(buffer) + addl_head_bytes, beyond_head_length
+	};
+
+	// Setup the capstan and mark the end of the tape
+	parse::buffer pb
+	{
+		mutable_buffer
+		{
+			data(req.in.head) + state.head_read, head_length
+		}
+	};
+	parse::capstan pc{pb};
+	pc.read += head_length;
+
+	// Play the tape through the formal grammar.
+	const http::response::chunk chunk{pc};
+	assert(state.chunk_length == size_t(-1));
+	state.chunk_length = chunk.size + size(terminator);
+
+	// Increment the content_length to now include this chunk
+	state.content_length += state.chunk_length;
+
+	// Allocate the chunk content on the vector.
+	//TODO: maxalloc
+	req.in.chunks.emplace_back(state.chunk_length);
+
+	// Now we check how much chunk was received beyond the head
+	// state.chunk_head is still 0 here because that's only incremented
+	// in the content read function.
+	const auto &chunk_read
+	{
+		std::min(state.chunk_length, beyond_head_length)
+	};
+
+	// Now we know how much bleed into the next message was also received
+	assert(beyond_head_length >= chunk_read);
+	const size_t beyond_chunk_length
+	{
+		beyond_head_length - chunk_read
+	};
+
+	const const_buffer partial_chunk
+	{
+		data(beyond_head), chunk_read
+	};
+
+	const size_t copied
+	{
+		copy(req.in.chunks.back(), partial_chunk)
+	};
+
+	const const_buffer overrun
+	{
+		data(beyond_head) + chunk_read, beyond_chunk_length
+	};
+
+	assert(state.chunk_length >= 2);
+	read_chunk_dynamic_content(partial_chunk, done);
+
+	if(done)
+		return overrun;
+
+	return read_chunk_dynamic_head(overrun, done);        // gobble gobbles
+}
+
+ircd::const_buffer
+ircd::server::tag::read_chunk_dynamic_content(const const_buffer &buffer,
+                                              bool &done)
+{
+	assert(request);
+	auto &req{*request};
+
+	assert(state.chunk_length != size_t(-1));
+	assert(null(req.in.content));
+	assert(!req.in.chunks.empty());
+	const auto &chunk
+	{
+		req.in.chunks.back()
+	};
+
+	// The amount of remaining content for the response sequence
+	assert(state.chunk_read <= size(chunk));
+	const size_t remaining
+	{
+		size(chunk) - state.chunk_read
+	};
+
+	// The amount of content read in this buffer only.
+	const size_t addl_content_read
+	{
+		std::min(size(buffer), remaining)
+	};
+
+	// Increment the read counters for this chunk and all chunks.
+	state.chunk_read += addl_content_read;
+	state.content_read += addl_content_read;
+	assert(state.chunk_read <= state.content_read);
+
+	if(state.chunk_read == state.chunk_length)
+	{
+		static const string_view terminator{"\r\n"};
+		state.content_length -= size(terminator);
+		state.content_read -= size(terminator);
+
+		assert(state.chunk_length >= 2);
+		assert(state.chunk_read == state.chunk_length);
+		state.chunk_length -= size(terminator);
+		state.chunk_read -= size(terminator);
+
+		auto &chunk{req.in.chunks.back()};
+		std::get<1>(chunk) -= size(terminator);
+		assert(size(chunk) == state.chunk_length);
+		assert(std::get<0>(chunk) <= std::get<1>(chunk));
+
+		if(state.chunk_length == 0)
+		{
+			assert(state.chunk_read == 0);
+			assert(!done);
+			done = true;
+
+			assert(req.opt);
+			if(req.opt->contiguous_content)
+			{
+				assert(state.content_length == size_chunks(req.in));
+				assert(req.in.chunks.size() >= 1);
+				assert(empty(req.in.chunks.back()));
+				req.in.chunks.pop_back();
+
+				if(req.in.chunks.size() > 1)
+				{
+					req.in.dynamic = size_chunks(req.in);
+					req.in.content = req.in.dynamic;
+
+					size_t copied{0};
+					for(const auto &buffer : req.in.chunks)
+						copied += copy(req.in.content + copied, buffer);
+
+					assert(copied == size(req.in.content));
+					assert(copied == state.content_length);
+				}
+				else if(req.in.chunks.size() == 1)
+				{
+					req.in.dynamic = std::move(req.in.chunks.front());
+					req.in.content = req.in.dynamic;
+					assert(size(req.in.content) == state.content_length);
+				}
+
+				req.in.chunks.clear();
+			}
+
+			set_value(state.status);
+		}
+	}
+
+	// Invoke the user's optional progress callback; this function
+	// should be marked noexcept for the time being.
+	if(req.in.progress && !done)
+		req.in.progress(buffer, const_buffer{data(chunk), state.chunk_read});
+
+	if(state.chunk_read == state.chunk_length)
+	{
+		assert(state.chunk_read == state.chunk_length);
+		assert(state.chunk_read <= state.content_read);
+		state.chunk_length = size_t(-1);
+		state.chunk_read = 0;
+	}
+
+	return {};
+}
+
 /// An idempotent operation that provides the location of where the socket
 /// should place the next received data. The tag figures this out based on
 /// whether it receiving HTTP head data or whether it is in content mode.
@@ -2585,15 +2804,21 @@ const
 	if(state.status == (http::code)0)
 		return make_read_head_buffer();
 
-	if(state.content_read >= size(request->in.content))
-		return make_read_discard_buffer();
+	if(state.chunk_length == size_t(-1) && null(request->in.content))
+		return make_read_chunk_dynamic_head_buffer();
 
 	if(state.chunk_length == size_t(-1))
 		return make_read_chunk_head_buffer();
 
+	if(state.chunk_length && null(request->in.content))
+		return make_read_chunk_dynamic_content_buffer();
+
 	if(state.chunk_length)
 		return make_read_chunk_content_buffer();
 
+	if(state.content_read >= size(request->in.content))
+		return make_read_discard_buffer();
+
 	return make_read_content_buffer();
 }
 
@@ -2669,6 +2894,7 @@ const
 
 	const auto &req{*request};
 	const auto &content{req.in.content};
+
 	if(unlikely(size(content) <= state.content_read))
 		throw buffer_overrun
 		{
@@ -2736,6 +2962,87 @@ const
 	return buffer;
 }
 
+/// The dynamic chunk head buffer starts after the main head and has a size
+/// of the remaining main head buffer. This area is overwritten for each
+/// chunk head.
+///
+ircd::mutable_buffer
+ircd::server::tag::make_read_chunk_dynamic_head_buffer()
+const
+{
+	assert(request);
+	const auto &req{*request};
+
+	assert(state.chunk_length == size_t(-1));
+	assert(null(req.in.content));
+	assert(size(req.in.head) >= state.head_read);
+
+	const size_t head_max
+	{
+		size(req.in.head) + state.head_rem
+	};
+
+	// The total offset in the head buffer is the message head plus the
+	// amount of chunk head received so far, which is kept in chunk_read.
+	const size_t head_offset
+	{
+		state.head_read + state.chunk_read
+	};
+
+	assert(head_max >= head_offset);
+	if(unlikely(head_max - head_offset <= 16))
+		throw buffer_overrun
+		{
+			"Remaining head buffer of %zu bytes too small to read next chunk header",
+			head_max - state.head_read
+		};
+
+	const size_t remaining
+	{
+		head_max - head_offset
+	};
+
+	const mutable_buffer buffer
+	{
+		data(req.in.head) + state.head_read + state.chunk_read, remaining
+	};
+
+	assert(size(buffer) > 0);
+	return buffer;
+}
+
+ircd::mutable_buffer
+ircd::server::tag::make_read_chunk_dynamic_content_buffer()
+const
+{
+	assert(request);
+	const auto &req{*request};
+
+	assert(state.chunk_length > 0);
+	assert(state.content_read <= state.content_length);
+	assert(null(req.in.content));
+	assert(!req.in.chunks.empty());
+	const auto &buffer
+	{
+		req.in.chunks.back()
+	};
+
+	assert(size(buffer) == state.chunk_length);
+	assert(state.chunk_read <= size(buffer));
+	const size_t buffer_remaining
+	{
+		size(buffer) - state.chunk_read
+	};
+
+	const mutable_buffer ret
+	{
+		data(buffer) + state.chunk_read, buffer_remaining
+	};
+
+	assert(size(ret) > 0);
+	return ret;
+}
+
 ircd::mutable_buffer
 ircd::server::tag::make_read_discard_buffer()
 const