diff --git a/lib/protocol/http/request.rb b/lib/protocol/http/request.rb
index 648fff0..60d4794 100644
--- a/lib/protocol/http/request.rb
+++ b/lib/protocol/http/request.rb
@@ -36,7 +36,8 @@ class Request
 			# @parameter body [Body::Readable] The request body.
 			# @parameter protocol [String | Array(String) | Nil] The request protocol, usually empty, but occasionally `"websocket"` or `"webtransport"`.
 			# @parameter interim_response [Proc] A callback which is called when an interim response is received.
-			def initialize(scheme = nil, authority = nil, method = nil, path = nil, version = nil, headers = Headers.new, body = nil, protocol = nil, interim_response = nil)
+			# @parameter idempotent [Boolean | Nil] An override for {#idempotent?}, or `nil` to use the default method-based heuristic.
+			def initialize(scheme = nil, authority = nil, method = nil, path = nil, version = nil, headers = Headers.new, body = nil, protocol = nil, interim_response = nil, idempotent: nil)
 				@scheme = scheme
 				@authority = authority
 				@method = method
@@ -46,6 +47,7 @@ def initialize(scheme = nil, authority = nil, method = nil, path = nil, version
 				@body = body
 				@protocol = protocol
 				@interim_response = interim_response
+				@idempotent = idempotent
 			end
 			
 			# @attribute [String] the request scheme, usually `"http"` or `"https"`.
@@ -75,6 +77,9 @@ def initialize(scheme = nil, authority = nil, method = nil, path = nil, version
 			# @attribute [Proc] a callback which is called when an interim response is received.
 			attr_accessor :interim_response
 			
+			# @attribute [Boolean | Nil] an override for {#idempotent?}, or `nil` to use the default method-based heuristic.
+			attr_accessor :idempotent
+			
 			# A request that is generated by a server, may choose to include the peer (address) associated with the request. It should be implemented by a sub-class.
 			#
 			# @returns [Peer | Nil] The peer (address) associated with the request.
@@ -124,16 +129,21 @@ def connect?
 			# @parameter path [String] The path, e.g. `"/index.html"`, `"/search?q=hello"`, etc.
 			# @parameter headers [Hash] The headers, e.g. `{"accept" => "text/html"}`, etc.
 			# @parameter body [String | Array(String) | Body::Readable] The body, e.g. `"Hello, World!"`, etc. See {Body::Buffered.wrap} for more information about .
-			def self.[](method, path = nil, _headers = nil, _body = nil, scheme: nil, authority: nil, headers: _headers, body: _body, protocol: nil, interim_response: nil)
+			# @parameter idempotent [Boolean | Nil] Override the default idempotency heuristic.
+			def self.[](method, path = nil, _headers = nil, _body = nil, scheme: nil, authority: nil, headers: _headers, body: _body, protocol: nil, interim_response: nil, idempotent: nil)
 				path = path&.to_s
 				body = Body::Buffered.wrap(body)
 				headers = Headers[headers]
 				
-				self.new(scheme, authority, method, path, nil, headers, body, protocol, interim_response)
+				self.new(scheme, authority, method, path, nil, headers, body, protocol, interim_response, idempotent: idempotent)
 			end
 			
 			# Whether the request can be replayed without side-effects.
 			def idempotent?
+				unless @idempotent.nil?
+					return @idempotent
+				end
+				
 				@method != Methods::POST && (@body.nil? || @body.empty?)
 			end
 			
diff --git a/test/protocol/http/request.rb b/test/protocol/http/request.rb
index a4e8e40..fb1e872 100644
--- a/test/protocol/http/request.rb
+++ b/test/protocol/http/request.rb
@@ -128,6 +128,10 @@
 			expect(request).to be(:idempotent?)
 		end
 		
+		it "defaults idempotent to nil" do
+			expect(request.idempotent).to be_nil
+		end
+		
 		it "should have a string representation" do
 			expect(request.to_s).to be == "http://localhost: GET /index.html HTTP/1.0"
 		end
@@ -141,6 +145,42 @@
 		end
 	end
 	
+	with "simple POST request" do
+		let(:request) {subject.new("http", "localhost", "POST", "/submit", "HTTP/1.1", headers, nil)}
+		
+		it "should not be idempotent" do
+			expect(request).not.to be(:idempotent?)
+		end
+		
+		with "idempotent: true" do
+			let(:request) {subject.new("http", "localhost", "POST", "/submit", "HTTP/1.1", headers, nil, nil, nil, idempotent: true)}
+			
+			it "should be idempotent" do
+				expect(request).to be(:idempotent?)
+			end
+		end
+	end
+	
+	with "idempotent: false" do
+		let(:request) {subject.new("http", "localhost", "GET", "/index.html", "HTTP/1.0", headers, body, nil, nil, idempotent: false)}
+		
+		it "should not be idempotent" do
+			expect(request).not.to be(:idempotent?)
+		end
+	end
+	
+	with ".[] with idempotent: true" do
+		let(:request) {subject["POST", "/submit", idempotent: true]}
+		
+		it "should be idempotent" do
+			expect(request).to be(:idempotent?)
+		end
+		
+		it "should expose the idempotent attribute" do
+			expect(request.idempotent).to be == true
+		end
+	end
+	
 	with "interim response" do
 		let(:request) {subject.new("http", "localhost", "GET", "/index.html", "HTTP/1.0", headers, body)}