Persistent can only transition from true to false.

lib/protocol/http1/connection.rb

@@ -148,7 +148,7 @@ def persistent?(version, method, headers)
 					else
 						return false
 					end
-				else
+				else # HTTP/1.1+
 					if connection = headers[CONNECTION]
 						return !connection.close?
 					else
@@ -320,7 +320,11 @@ def read_request
 
 				headers = read_headers
 
-				@persistent = persistent?(version, method, headers)
+				# If we are not persistent, we can't become persistent even if the request might allow it:
+				if @persistent
+					# In other words, `@persistent` can only transition from true to false.
+					@persistent = persistent?(version, method, headers)
+				end
 
 				body = read_request_body(method, headers)
 
@@ -358,7 +362,9 @@ def read_response(method)
 
 				headers = read_headers
 
-				@persistent = persistent?(version, method, headers)
+				if @persistent
+					@persistent = persistent?(version, method, headers)
+				end
 
 				unless interim_status?(status)
 					body = read_response_body(method, status, headers)

test/protocol/http1/connection.rb

@@ -30,6 +30,8 @@
 			expect(version).to be == "HTTP/1.1"
 			expect(headers).to be == {}
 			expect(body).to be_nil
+
+			expect(server).to be(:persistent)
 		end
 
 		it "reads request without body after closing connection" do
@@ -44,6 +46,8 @@
 			expect(version).to be == "HTTP/1.1"
 			expect(headers).to be == {"accept" => ["*/*"], "header-0" => ["value 1"]}
 			expect(body).to be_nil
+
+			expect(server).to be(:persistent)
 		end
 
 		it "reads request with fixed body" do
@@ -58,6 +62,8 @@
 			expect(version).to be == "HTTP/1.1"
 			expect(headers).to be == {}
 			expect(body.join).to be == "Hello World"
+
+			expect(server).to be(:persistent)
 		end
 
 		it "reads request with chunked body" do
@@ -72,7 +78,9 @@
 			expect(version).to be == "HTTP/1.1"
 			expect(headers).to be == {}
 			expect(body.join).to be == "Hello World"
+
 			expect(server).to be(:persistent?, version, method, headers)
+			expect(server).to be(:persistent)
 		end
 
 		it "reads request with CONNECT method" do

test/protocol/http1/connection/persistent.rb

@@ -0,0 +1,133 @@
+# frozen_string_literal: true
+
+# Released under the MIT License.
+# Copyright, 2025, by Samuel Williams.
+
+require "protocol/http1/connection"
+require "protocol/http/body/buffered"
+require "protocol/http/body/writable"
+
+require "connection_context"
+
+describe Protocol::HTTP1::Connection do
+	include_context ConnectionContext
+
+	with "multiple requests in a single connection" do
+		it "handles two back-to-back GET requests (HTTP/1.1 keep-alive)" do
+			client.write_request("localhost", "GET", "/first", "HTTP/1.1", {"Header-A" => "Value-A"})
+			client.write_body("HTTP/1.1", nil)
+			expect(client).to be(:half_closed_local?)
+
+			# Server reads it:
+			authority, method, path, version, headers, body = server.read_request
+			expect(authority).to be == "localhost"
+			expect(method).to be == "GET"
+			expect(path).to be == "/first"
+			expect(version).to be == "HTTP/1.1"
+			expect(headers["header-a"]).to be == ["Value-A"]
+			expect(body).to be_nil
+
+			# Server writes a response:
+			expect(server).to be(:half_closed_remote?)
+			server.write_response("HTTP/1.1", 200, {"Res-A" => "ValA"}, "OK")
+			server.write_body("HTTP/1.1", nil)
+			expect(server).to be(:idle?)
+
+			# Client reads first response:
+			version, status, reason, headers, body = client.read_response("GET")
+			expect(version).to be == "HTTP/1.1"
+			expect(status).to be == 200
+			expect(reason).to be == "OK"
+			expect(headers["res-a"]).to be == ["ValA"]
+			expect(body).to be_nil
+
+			# Now both sides should be back to :idle (persistent re-use):
+			expect(client).to be(:idle?)
+			expect(server).to be(:idle?)
+
+			# Second request:
+			client.write_request("localhost", "GET", "/second", "HTTP/1.1", {"Header-B" => "Value-B"})
+			client.write_body("HTTP/1.1", nil)
+			expect(client).to be(:half_closed_local?)
+
+			# Server reads it:
+			authority, method, path, version, headers, body = server.read_request
+			expect(authority).to be == "localhost"
+			expect(method).to be == "GET"
+			expect(path).to be == "/second"
+			expect(version).to be == "HTTP/1.1"
+			expect(headers["header-b"]).to be == ["Value-B"]
+			expect(body).to be_nil
+
+			# Server writes a response:
+			expect(server).to be(:half_closed_remote?)
+			server.write_response("HTTP/1.1", 200, {"Res-B" => "ValB"}, "OK")
+			server.write_body("HTTP/1.1", nil)
+
+			# Client reads second response:
+			version, status, reason, headers, body = client.read_response("GET")
+			expect(version).to be == "HTTP/1.1"
+			expect(status).to be == 200
+			expect(reason).to be == "OK"
+			expect(headers["res-b"]).to be == ["ValB"]
+			expect(body).to be_nil
+
+			# Confirm final states:
+			expect(client).to be(:idle?)
+			expect(server).to be(:idle?)
+		end
+	end
+
+	with "partial body read" do
+		it "closes correctly if server does not consume entire fixed-length body" do
+			# Indicate Content-Length = 11 but only read part of it on server side:
+			client.stream.write "POST / HTTP/1.1\r\nHost: localhost\r\nContent-Length: 11\r\n\r\nHello"
+			client.stream.close
+
+			# Server reads request line/headers:
+			authority, method, path, version, headers, body = server.read_request
+			expect(method).to be == "POST"
+			expect(body).to be_a(Protocol::HTTP1::Body::Fixed)
+
+			# Partially read 5 bytes only:
+			partial = body.read
+			expect(partial).to be == "Hello"
+
+			expect do
+				body.read
+			end.to raise_exception(EOFError)
+
+			# Then server forcibly closes read (simulating a deliberate stop):
+			server.close_read
+
+			# Because of partial consumption, that should move the state to half-closed remote or closed, etc.
+			expect(server).to be(:half_closed_remote?)
+			expect(server).not.to be(:persistent)
+		end
+	end
+
+	with "no persistence" do
+		it "closes connection after request" do
+			server.persistent = false
+
+			client.write_request("localhost", "GET", "/first", "HTTP/1.1", {"Header-A" => "Value-A"})
+			client.write_body("HTTP/1.1", nil)
+			expect(client).to be(:half_closed_local?)
+
+			# Server reads it:
+			authority, method, path, version, headers, body = server.read_request
+			expect(authority).to be == "localhost"
+			expect(method).to be == "GET"
+			expect(path).to be == "/first"
+			expect(version).to be == "HTTP/1.1"
+			expect(headers["header-a"]).to be == ["Value-A"]
+			expect(body).to be_nil
+
+			# Server writes a response:
+			expect(server).to be(:half_closed_remote?)
+			server.write_response("HTTP/1.1", 200, {"Res-A" => "ValA"}, "OK")
+			server.write_body("HTTP/1.1", nil)
+			expect(server).to be(:closed?)
+		end
+	end
+end