diff --git a/design.md b/design.md
index 06e555c..ed06296 100644
--- a/design.md
+++ b/design.md
@@ -140,7 +140,7 @@ module Protocol
 			
 			# Parse service and method from gRPC path
 			# @parameter path [String] e.g., "/my_service.Greeter/SayHello"
-			# @returns [Array(String, String)] [service, method]
+			# @returns [Tuple(String, String)] of service and method.
 			def self.parse_path(path)
 				parts = path.split("/")
 				[parts[1], parts[2]]
@@ -287,7 +287,7 @@ module Protocol
 			
 			# Extract gRPC status message from headers
 			# @parameter headers [Protocol::HTTP::Headers]
-			# @returns [String, nil] Status message
+			# @returns [String | Nil] Status message
 			def self.extract_message(headers)
 				message = headers["grpc-message"]
 				message ? URI.decode_www_form_component(message) : nil
@@ -329,7 +329,7 @@ module Protocol
 				# @parameter body [Protocol::HTTP::Body::Readable] The underlying HTTP body
 				# @parameter message_class [Class, nil] Protobuf message class with .decode method
 				#   If nil, returns raw binary data (useful for channel adapters)
-				# @parameter encoding [String, nil] Compression encoding (from grpc-encoding header)
+				# @parameter encoding [String | Nil] Compression encoding (from grpc-encoding header)
 				def initialize(body, message_class: nil, encoding: nil)
 					super(body)
 					@message_class = message_class
@@ -408,7 +408,7 @@ module Protocol
 			# Writes length-prefixed gRPC messages
 			# This is the standard writable body for gRPC - all gRPC requests use message framing
 			class Writable < Protocol::HTTP::Body::Writable
-				# @parameter encoding [String, nil] Compression encoding (gzip, deflate, identity)
+				# @parameter encoding [String | Nil] Compression encoding (gzip, deflate, identity)
 				# @parameter level [Integer] Compression level if encoding is used
 				def initialize(encoding: nil, level: Zlib::DEFAULT_COMPRESSION, **options)
 					super(**options)
@@ -574,7 +574,7 @@ module Protocol
 			end
 			
 			# Get peer information (client address)
-			# @returns [String, nil]
+			# @returns [String | Nil]
 			def peer
 				@request.peer&.to_s
 			end
diff --git a/lib/protocol/grpc/header.rb b/lib/protocol/grpc/header.rb
index 71fcdb4..9e74308 100644
--- a/lib/protocol/grpc/header.rb
+++ b/lib/protocol/grpc/header.rb
@@ -4,120 +4,16 @@
 # Copyright, 2025, by Samuel Williams.
 
 require "protocol/http"
-require "uri"
 
 require_relative "status"
+require_relative "header/status"
+require_relative "header/message"
+require_relative "header/metadata"
 
 module Protocol
 	module GRPC
 		# @namespace
 		module Header
-			# The `grpc-status` header represents the gRPC status code.
-			#
-			# The `grpc-status` header contains a numeric status code (0-16) indicating the result of the RPC call.
-			# Status code 0 indicates success (OK), while other codes indicate various error conditions.
-			# This header can appear both as an initial header (for trailers-only responses) and as a trailer.
-			class Status
-				# Initialize the status header with the given value.
-				#
-				# @parameter value [String, Integer, Array] The status code as a string, integer, or array (takes first element).
-				def initialize(value)
-					@value = normalize_value(value)
-				end
-				
-				# Get the status code as an integer.
-				#
-				# @returns [Integer] The status code.
-				def to_i
-					@value
-				end
-				
-				# Serialize the status code to a string.
-				#
-				# @returns [String] The status code as a string.
-				def to_s
-					@value.to_s
-				end
-				
-				# Merge another status value (takes the new value, as status should only appear once)
-				# @parameter value [String, Integer, Array] The new status code
-				def <<(value)
-					@value = normalize_value(value)
-					self
-				end
-				
-			private
-				
-				# Normalize a value to an integer status code.
-				# Handles arrays (from external clients), strings, and integers.
-				# @parameter value [String, Integer, Array] The raw value
-				# @returns [Integer] The normalized status code
-				def normalize_value(value)
-					# Handle Array case (may occur with external clients)
-					actual_value = value.is_a?(Array) ? value.flatten.compact.first : value
-					actual_value.to_i
-				end
-				
-				# Whether this header is acceptable in HTTP trailers.
-				# The `grpc-status` header can appear in trailers as per the gRPC specification.
-				# @returns [Boolean] `true`, as grpc-status can appear in trailers.
-				def self.trailer?
-					true
-				end
-			end
-			
-			# The `grpc-message` header represents the gRPC status message.
-			#
-			# The `grpc-message` header contains a human-readable error message, URL-encoded according to RFC 3986.
-			# This header is optional and typically only present when there's an error (non-zero status code).
-			# This header can appear both as an initial header (for trailers-only responses) and as a trailer.
-			class Message < String
-				# Initialize the message header with the given value.
-				#
-				# @parameter value [String] The message value (will be URL-encoded if not already encoded).
-				def initialize(value)
-					super(value.to_s)
-				end
-				
-				# Decode the URL-encoded message.
-				#
-				# @returns [String] The decoded message.
-				def decode
-					URI.decode_www_form_component(self)
-				end
-				
-				# Encode the message for use in headers.
-				#
-				# @parameter message [String] The message to encode.
-				# @returns [String] The URL-encoded message.
-				def self.encode(message)
-					URI.encode_www_form_component(message).gsub("+", "%20")
-				end
-				
-				# Merge another message value (takes the new value, as message should only appear once)
-				# @parameter value [String] The new message value
-				def <<(value)
-					replace(value.to_s)
-					self
-				end
-				
-				# Whether this header is acceptable in HTTP trailers.
-				# The `grpc-message` header can appear in trailers as per the gRPC specification.
-				# @returns [Boolean] `true`, as grpc-message can appear in trailers.
-				def self.trailer?
-					true
-				end
-			end
-			
-			# Base class for custom gRPC metadata (allowed in trailers).
-			class Metadata < Protocol::HTTP::Header::Split
-				# Whether this header is acceptable in HTTP trailers.
-				# The `grpc-metadata` header can appear in trailers as per the gRPC specification.
-				# @returns [Boolean] `true`, as grpc-metadata can appear in trailers.
-				def self.trailer?
-					true
-				end
-			end
 		end
 		
 		# Custom header policy for gRPC.
diff --git a/lib/protocol/grpc/header/message.rb b/lib/protocol/grpc/header/message.rb
new file mode 100644
index 0000000..acf5ac5
--- /dev/null
+++ b/lib/protocol/grpc/header/message.rb
@@ -0,0 +1,64 @@
+# frozen_string_literal: true
+
+# Released under the MIT License.
+# Copyright, 2025, by Samuel Williams.
+
+require "uri"
+
+module Protocol
+	module GRPC
+		module Header
+			# The `grpc-message` header represents the gRPC status message.
+			#
+			# The `grpc-message` header contains a human-readable error message, URL-encoded according to RFC 3986.
+			# This header is optional and typically only present when there's an error (non-zero status code).
+			# This header can appear both as an initial header (for trailers-only responses) and as a trailer.
+			class Message < String
+				# Parse a message from a header value.
+				#
+				# @parameter value [String] The header value to parse.
+				# @returns [Message] A new Message instance.
+				def self.parse(value)
+					new(value)
+				end
+				
+				# Initialize the message header with the given value.
+				#
+				# @parameter value [String] The message value (will be URL-encoded if not already encoded).
+				def initialize(value)
+					super(value)
+				end
+				
+				# Decode the URL-encoded message.
+				#
+				# @returns [String] The decoded message.
+				def decode
+					::URI.decode_www_form_component(self)
+				end
+				
+				# Encode the message for use in headers.
+				#
+				# @parameter message [String] The message to encode.
+				# @returns [String] The URL-encoded message.
+				def self.encode(message)
+					URI.encode_www_form_component(message).gsub("+", "%20")
+				end
+				
+				# Merge another message value (takes the new value, as message should only appear once)
+				# @parameter value [String] The new message value
+				def <<(value)
+					replace(value.to_s)
+					
+					return self
+				end
+				
+				# Whether this header is acceptable in HTTP trailers.
+				# The `grpc-message` header can appear in trailers as per the gRPC specification.
+				# @returns [Boolean] `true`, as grpc-message can appear in trailers.
+				def self.trailer?
+					true
+				end
+			end
+		end
+	end
+end
diff --git a/lib/protocol/grpc/header/metadata.rb b/lib/protocol/grpc/header/metadata.rb
new file mode 100644
index 0000000..0ba2856
--- /dev/null
+++ b/lib/protocol/grpc/header/metadata.rb
@@ -0,0 +1,22 @@
+# frozen_string_literal: true
+
+# Released under the MIT License.
+# Copyright, 2025, by Samuel Williams.
+
+require "protocol/http"
+
+module Protocol
+	module GRPC
+		module Header
+			# Base class for custom gRPC metadata (allowed in trailers).
+			class Metadata < Protocol::HTTP::Header::Split
+				# Whether this header is acceptable in HTTP trailers.
+				# The `grpc-metadata` header can appear in trailers as per the gRPC specification.
+				# @returns [Boolean] `true`, as grpc-metadata can appear in trailers.
+				def self.trailer?
+					true
+				end
+			end
+		end
+	end
+end
diff --git a/lib/protocol/grpc/header/status.rb b/lib/protocol/grpc/header/status.rb
new file mode 100644
index 0000000..69cfd66
--- /dev/null
+++ b/lib/protocol/grpc/header/status.rb
@@ -0,0 +1,85 @@
+# frozen_string_literal: true
+
+# Released under the MIT License.
+# Copyright, 2025, by Samuel Williams.
+
+module Protocol
+	module GRPC
+		module Header
+			# The `grpc-status` header represents the gRPC status code.
+			#
+			# The `grpc-status` header contains a numeric status code (0-16) indicating the result of the RPC call.
+			# Status code 0 indicates success (OK), while other codes indicate various error conditions.
+			# This header can appear both as an initial header (for trailers-only responses) and as a trailer.
+			class Status
+				# Parse a status code from a header value.
+				#
+				# @parameter value [String] The header value to parse.
+				# @returns [Status] A new Status instance.
+				def self.parse(value)
+					new(value.to_i)
+				end
+				
+				# Initialize the status header with the given value.
+				#
+				# @parameter value [String | Integer] The status code as a string or integer.
+				def initialize(value)
+					@value = value.to_i
+				end
+				
+				# Get the status code as an integer.
+				#
+				# @returns [Integer] The status code.
+				def to_i
+					@value
+				end
+				
+				# Serialize the status code to a string.
+				#
+				# @returns [String] The status code as a string.
+				def to_s
+					@value.to_s
+				end
+				
+				# Check equality with another status or integer value.
+				#
+				# @parameter other [Status | Integer] The value to compare with.
+				# @returns [Boolean] if the status codes are equal.
+				def ==(other)
+					@value == other.to_i
+				end
+				
+				alias eql? ==
+				
+				# Generate hash for use in Hash/Set collections.
+				#
+				# @returns [Integer] The hash value based on the status code.
+				def hash
+					@value.hash
+				end
+				
+				# Check if this status represents success (status code 0).
+				#
+				# @returns [Boolean] `true` if the status code is 0 (OK).
+				def ok?
+					@value == 0
+				end
+				
+				# Merge another status value (takes the new value, as status should only appear once)
+				# @parameter value [String | Integer] The new status code
+				def <<(value)
+					@value = value.to_i
+					
+					return self
+				end
+				
+				# Whether this header is acceptable in HTTP trailers.
+				# The `grpc-status` header can appear in trailers as per the gRPC specification.
+				# @returns [Boolean] `true`, as grpc-status can appear in trailers.
+				def self.trailer?
+					true
+				end
+			end
+		end
+	end
+end
diff --git a/lib/protocol/grpc/interface.rb b/lib/protocol/grpc/interface.rb
index 9c847f3..bf5e238 100644
--- a/lib/protocol/grpc/interface.rb
+++ b/lib/protocol/grpc/interface.rb
@@ -10,6 +10,8 @@ module GRPC
 		# Wrapper class to mark a message type as streamed.
 		# Used with the stream() helper method in RPC definitions.
 		class Streaming
+			# Initialize a new Streaming wrapper.
+			# @parameter message_class [Class] The message class being wrapped
 			def initialize(message_class)
 				@message_class = message_class
 			end
@@ -148,7 +150,7 @@ def initialize(name)
 			attr :name
 			
 			# Build gRPC path for a method.
-			# @parameter method_name [String, Symbol] Method name in PascalCase (e.g., :SayHello)
+			# @parameter method_name [String | Symbol] Method name in PascalCase (e.g., :SayHello)
 			# @returns [String] gRPC path with PascalCase method name
 			def path(method_name)
 				Methods.build_path(@name, method_name.to_s)
diff --git a/lib/protocol/grpc/methods.rb b/lib/protocol/grpc/methods.rb
index b0b2473..a2dd171 100644
--- a/lib/protocol/grpc/methods.rb
+++ b/lib/protocol/grpc/methods.rb
@@ -20,7 +20,7 @@ def self.build_path(service, method)
 			
 			# Parse service and method from gRPC path.
 			# @parameter path [String] e.g., "/my_service.Greeter/SayHello"
-			# @returns [Array(String, String)] [service, method]
+			# @returns [Array(String | String)] [service, method]
 			def self.parse_path(path)
 				parts = path.split("/")
 				[parts[1], parts[2]]
diff --git a/test/protocol/grpc/header.rb b/test/protocol/grpc/header.rb
new file mode 100644
index 0000000..90aac6c
--- /dev/null
+++ b/test/protocol/grpc/header.rb
@@ -0,0 +1,20 @@
+# frozen_string_literal: true
+
+# Released under the MIT License.
+# Copyright, 2025, by Samuel Williams.
+
+require "protocol/grpc/header"
+
+describe Protocol::GRPC::HEADER_POLICY do
+	it "includes grpc-status mapping" do
+		expect(subject["grpc-status"]).to be == Protocol::GRPC::Header::Status
+	end
+	
+	it "includes grpc-message mapping" do
+		expect(subject["grpc-message"]).to be == Protocol::GRPC::Header::Message
+	end
+	
+	it "is frozen" do
+		expect(subject).to be(:frozen?)
+	end
+end
diff --git a/test/protocol/grpc/header/message.rb b/test/protocol/grpc/header/message.rb
new file mode 100644
index 0000000..6443947
--- /dev/null
+++ b/test/protocol/grpc/header/message.rb
@@ -0,0 +1,83 @@
+# frozen_string_literal: true
+
+# Released under the MIT License.
+# Copyright, 2025, by Samuel Williams.
+
+require "protocol/grpc/header/message"
+
+describe Protocol::GRPC::Header::Message do
+	with ".parse" do
+		it "parses string value" do
+			message = subject.parse("Error%20occurred")
+			expect(message).to be == "Error%20occurred"
+		end
+	end
+	
+	with "#initialize" do
+		it "accepts string value" do
+			message = subject.new("Test message")
+			expect(message).to be == "Test message"
+		end
+	end
+	
+	with "#decode" do
+		it "decodes URL-encoded message" do
+			message = subject.new("Error%20occurred")
+			expect(message.decode).to be == "Error occurred"
+		end
+		
+		it "decodes special characters" do
+			message = subject.new("Error%3A%20not%20found")
+			expect(message.decode).to be == "Error: not found"
+		end
+		
+		it "handles unencoded message" do
+			message = subject.new("Simple error")
+			expect(message.decode).to be == "Simple error"
+		end
+	end
+	
+	with ".encode" do
+		it "encodes message for headers" do
+			encoded = subject.encode("Error occurred")
+			expect(encoded).to be == "Error%20occurred"
+		end
+		
+		it "encodes special characters" do
+			encoded = subject.encode("Error: not found")
+			expect(encoded).to be == "Error%3A%20not%20found"
+		end
+		
+		it "does not use plus for spaces" do
+			encoded = subject.encode("Test message")
+			expect(encoded).not.to be =~ /\+/
+			expect(encoded).to be =~ /%20/
+		end
+	end
+	
+	with "#<<" do
+		it "merges new string value" do
+			message = subject.new("Old message")
+			message << "New message"
+			expect(message).to be == "New message"
+		end
+		
+		it "converts non-string to string" do
+			message = subject.new("Old")
+			message << 123
+			expect(message).to be == "123"
+		end
+		
+		it "returns self for chaining" do
+			message = subject.new("Old")
+			result = message << "New"
+			expect(result).to be_equal(message)
+		end
+	end
+	
+	with ".trailer?" do
+		it "returns true as grpc-message can appear in trailers" do
+			expect(subject).to be(:trailer?)
+		end
+	end
+end
diff --git a/test/protocol/grpc/header/metadata.rb b/test/protocol/grpc/header/metadata.rb
new file mode 100644
index 0000000..fa1c034
--- /dev/null
+++ b/test/protocol/grpc/header/metadata.rb
@@ -0,0 +1,14 @@
+# frozen_string_literal: true
+
+# Released under the MIT License.
+# Copyright, 2025, by Samuel Williams.
+
+require "protocol/grpc/header/metadata"
+
+describe Protocol::GRPC::Header::Metadata do
+	with ".trailer?" do
+		it "returns true as grpc-metadata can appear in trailers" do
+			expect(subject).to be(:trailer?)
+		end
+	end
+end
diff --git a/test/protocol/grpc/header/status.rb b/test/protocol/grpc/header/status.rb
new file mode 100644
index 0000000..3f0b73e
--- /dev/null
+++ b/test/protocol/grpc/header/status.rb
@@ -0,0 +1,140 @@
+# frozen_string_literal: true
+
+# Released under the MIT License.
+# Copyright, 2025, by Samuel Williams.
+
+require "protocol/grpc/header/status"
+
+describe Protocol::GRPC::Header::Status do
+	with ".parse" do
+		it "parses string value to integer" do
+			status = subject.parse("0")
+			expect(status.to_i).to be == 0
+		end
+		
+		it "parses numeric string" do
+			status = subject.parse("14")
+			expect(status.to_i).to be == 14
+		end
+	end
+	
+	with "#initialize" do
+		it "accepts integer value" do
+			status = subject.new(0)
+			expect(status.to_i).to be == 0
+		end
+		
+		it "accepts string value" do
+			status = subject.new("5")
+			expect(status.to_i).to be == 5
+		end
+	end
+	
+	with "#to_i" do
+		it "returns integer status code" do
+			status = subject.new(13)
+			expect(status.to_i).to be == 13
+		end
+	end
+	
+	with "#to_s" do
+		it "returns string representation of status code" do
+			status = subject.new(0)
+			expect(status.to_s).to be == "0"
+		end
+		
+		it "converts integer to string" do
+			status = subject.new(14)
+			expect(status.to_s).to be == "14"
+		end
+	end
+	
+	with "#==" do
+		it "compares equal status instances" do
+			status1 = subject.new(0)
+			status2 = subject.new(0)
+			expect(status1).to be == status2
+		end
+		
+		it "compares unequal status instances" do
+			status1 = subject.new(0)
+			status2 = subject.new(1)
+			expect(status1).not.to be == status2
+		end
+		
+		it "compares status with integer" do
+			status = subject.new(5)
+			expect(status).to be == 5
+		end
+		
+		it "compares status with different integer" do
+			status = subject.new(5)
+			expect(status).not.to be == 3
+		end
+	end
+	
+	with "#eql?" do
+		it "works same as ==" do
+			status1 = subject.new(0)
+			status2 = subject.new(0)
+			expect(status1.eql?(status2)).to be == true
+		end
+	end
+	
+	with "#hash" do
+		it "returns consistent hash for same status code" do
+			status1 = subject.new(0)
+			status2 = subject.new(0)
+			expect(status1.hash).to be == status2.hash
+		end
+		
+		it "can be used as hash key" do
+			status = subject.new(0)
+			hash = {status => "success"}
+			expect(hash[subject.new(0)]).to be == "success"
+		end
+	end
+	
+	with "#ok?" do
+		it "returns true for status code 0" do
+			status = subject.new(0)
+			expect(status).to be(:ok?)
+		end
+		
+		it "returns false for non-zero status code" do
+			status = subject.new(1)
+			expect(status.ok?).to be == false
+		end
+		
+		it "returns false for error status" do
+			status = subject.new(14)
+			expect(status.ok?).to be == false
+		end
+	end
+	
+	with "#<<" do
+		it "merges new integer value" do
+			status = subject.new(0)
+			status << 1
+			expect(status.to_i).to be == 1
+		end
+		
+		it "merges new string value" do
+			status = subject.new(0)
+			status << "5"
+			expect(status.to_i).to be == 5
+		end
+		
+		it "returns self for chaining" do
+			status = subject.new(0)
+			result = status << 1
+			expect(result).to be_equal(status)
+		end
+	end
+	
+	with ".trailer?" do
+		it "returns true as grpc-status can appear in trailers" do
+			expect(subject).to be(:trailer?)
+		end
+	end
+end