diff --git a/.github/workflows/ruby.yml b/.github/workflows/ruby.yml
index 8eda4263..266855f8 100644
--- a/.github/workflows/ruby.yml
+++ b/.github/workflows/ruby.yml
@@ -11,7 +11,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        ruby-version: ['2.6', '2.7']
+        ruby-version: ['3.0', '3.1', '3.2']
 
     steps:
     - uses: actions/checkout@v2
diff --git a/.rubocop.yml b/.rubocop.yml
index ca6fa782..bb3d3428 100644
--- a/.rubocop.yml
+++ b/.rubocop.yml
@@ -1,7 +1,7 @@
 inherit_from: .rubocop_todo.yml
 
 AllCops:
-  TargetRubyVersion: 2.4
+  TargetRubyVersion: 3.0
   Exclude:
     - '*.gemspec'
     - 'Gemfile*'
@@ -10,9 +10,6 @@ AllCops:
     - 'lib/tasks/*'
     - 'vendor/**/*'
 
-Documentation:
-  Enabled: false
-
 Metrics:
   Enabled: false
 
@@ -22,8 +19,5 @@ Style:
 Layout:
   Enabled: false
 
-Performance/Casecmp:
-  Enabled: false
-
 Naming:
   Enabled: false
diff --git a/.rubocop_todo.yml b/.rubocop_todo.yml
index 030b5c77..36f2c2a7 100644
--- a/.rubocop_todo.yml
+++ b/.rubocop_todo.yml
@@ -1,19 +1,7 @@
 # This configuration was generated by
 # `rubocop --auto-gen-config`
-# on 2019-03-22 01:56:17 -0400 using RuboCop version 0.52.1.
+# on 2024-10-14 14:56:48 UTC using RuboCop version 1.23.0.
 # The point is for the user to remove these configuration records
 # one by one as the offenses are removed from the code base.
 # Note that changes in the inspected code, or installation of new
 # versions of RuboCop, may require this file to be generated again.
-
-# Offense count: 4
-# Cop supports --auto-correct.
-Performance/RegexpMatch:
-  Exclude:
-    - 'lib/fhir_client/model/client_reply.rb'
-
-# Offense count: 197
-# Configuration parameters: AllowHeredoc, AllowURI, URISchemes, IgnoreCopDirectives, IgnoredPatterns.
-# URISchemes: http, https
-Metrics/LineLength:
-  Max: 210
diff --git a/Gemfile b/Gemfile
index 7949e731..32bd2f0b 100644
--- a/Gemfile
+++ b/Gemfile
@@ -3,6 +3,6 @@ source 'https://rubygems.org'
 gemspec
 
 group :test do
-  gem 'rubocop', '~> 0.52.1', require: false
+  gem 'rubocop', '~> 1.23.0', require: false
   gem 'awesome_print', require: 'ap'
 end
diff --git a/README.md b/README.md
index e8db0a92..50c7faed 100644
--- a/README.md
+++ b/README.md
@@ -3,7 +3,7 @@
 Ruby FHIR client.
 
 Supports:
-* FHIR R4, STU3 and DSTU2
+* FHIR R5, R4B, R4, STU3 and DSTU2
 * JSON and XML
 * All CRUD, including version read and history
 * Transactions and Batches
@@ -59,7 +59,7 @@ patient.destroy
 ## Advanced Usage
 
 ### Changing FHIR Versions
-The client defaults to `R4` but can be switched to `DSTU2` or `STU3`. It can also attempt to autodetect the FHIR version based on the `metadata` endpoint.
+The client defaults to `R4` but can be switched to other versions. It can also attempt to autodetect the FHIR version based on the `metadata` endpoint.
 
 ```ruby
 # autodetect the FHIR version
@@ -71,6 +71,10 @@ elsif version == :dstu2
   puts 'FHIR Client using DSTU2'
 elsif version == :r4
   puts 'FHIR Client using R4'
+elsif version == :r4b
+  puts 'FHIR Client using R4B'
+elsif
+  puts 'FHIR Client using R5'
 end
 
 # tell the client to use R4
@@ -79,7 +83,7 @@ client.use_r4
 patient = FHIR::Patient.read('example')
 patient = client.read(FHIR::Patient, 'example').resource
 
-# tell the client to use STU3 (default)
+# tell the client to use STU3
 client.use_stu3
 # now use the client normally
 patient = FHIR::STU3::Patient.read('example')
diff --git a/fhir_client.gemspec b/fhir_client.gemspec
index e36fb211..cdc05d33 100644
--- a/fhir_client.gemspec
+++ b/fhir_client.gemspec
@@ -21,9 +21,10 @@ Gem::Specification.new do |spec|
   spec.executables   = spec.files.grep(%r{^exe/}) { |f| File.basename(f) }
   spec.require_paths = ['lib']
 
+  spec.required_ruby_version = '>= 3.0.0'
   spec.add_dependency 'activesupport', '>= 3'
   spec.add_dependency 'addressable', '>= 2.3'
-  spec.add_dependency 'fhir_models', '>= 4.2.1'
+  spec.add_dependency 'fhir_models', '>= 5.0.0'
   spec.add_dependency 'fhir_stu3_models', '>= 3.1.1'
   spec.add_dependency 'fhir_dstu2_models', '>= 1.1.1'
   spec.add_dependency 'nokogiri', '>= 1.10.4'
diff --git a/lib/fhir_client.rb b/lib/fhir_client.rb
index 338e116b..db59c8c4 100644
--- a/lib/fhir_client.rb
+++ b/lib/fhir_client.rb
@@ -1,4 +1,6 @@
 require 'fhir_models'
+require 'fhir_models/r4b'
+require 'fhir_models/r5'
 require 'fhir_dstu2_models'
 require 'fhir_stu3_models'
 require 'active_support/all'
diff --git a/lib/fhir_client/client.rb b/lib/fhir_client/client.rb
index cb61786e..034c5320 100644
--- a/lib/fhir_client/client.rb
+++ b/lib/fhir_client/client.rb
@@ -77,6 +77,16 @@ def use_r4
       @default_format = versioned_format_class
     end
 
+    def use_r4b
+      @fhir_version = :r4b
+      @default_format = versioned_format_class
+    end
+
+    def use_r5
+      @fhir_version = :r5
+      @default_format = versioned_format_class
+    end
+
     #
     # Instructs the client to specify the minimal Prefer Header where applicable
     def use_minimal_preference
@@ -95,6 +105,10 @@ def detect_version
       cap = capability_statement
       if cap.is_a?(FHIR::CapabilityStatement)
         use_r4
+      elsif cap.is_a?(FHIR::R4B::CapabilityStatement)
+        use_r4b
+      elsif cap.is_a?(FHIR::R5::CapabilityStatement)
+        use_r5
       elsif cap.is_a?(FHIR::STU3::CapabilityStatement)
         use_stu3
       elsif cap.is_a?(FHIR::DSTU2::Conformance)
@@ -275,20 +289,36 @@ def try_conformance_formats(default_format)
         rescue
           @cached_capability_statement = nil
         end
-        if @cached_capability_statement.nil? || !@cached_capability_statement.fhirVersion.starts_with?('4')
-          use_stu3
+        if @cached_capability_statement.nil? || !@cached_capability_statement.fhirVersion.starts_with?('4.0')
+          use_r4b
           begin
-            @cached_capability_statement = parse_reply(FHIR::STU3::CapabilityStatement, frmt, reply)
+            @cached_capability_statement = parse_reply(FHIR::R4B::CapabilityStatement, frmt, reply)
           rescue
             @cached_capability_statement = nil
           end
-          unless @cached_capability_statement
-            use_dstu2
+          if @cached_capability_statement.nil? || !@cached_capability_statement.fhirVersion.starts_with?('4')
+            use_r5
             begin
-              @cached_capability_statement = parse_reply(FHIR::DSTU2::Conformance, frmt, reply)
+              @cached_capability_statement = parse_reply(FHIR::R5::CapabilityStatement, frmt, reply)
             rescue
               @cached_capability_statement = nil
             end
+            if @cached_capability_statement.nil? || !@cached_capability_statement.fhirVersion.starts_with?('5')
+              use_stu3
+              begin
+                @cached_capability_statement = parse_reply(FHIR::STU3::CapabilityStatement, frmt, reply)
+              rescue
+                @cached_capability_statement = nil
+              end
+              unless @cached_capability_statement
+                use_dstu2
+                begin
+                  @cached_capability_statement = parse_reply(FHIR::DSTU2::Conformance, frmt, reply)
+                rescue
+                  @cached_capability_statement = nil
+                end
+              end
+            end
           end
         end
         if @cached_capability_statement
@@ -317,23 +347,35 @@ def parse_reply(klass, format, response)
       return nil unless [200, 201].include? response.code
       res =
         begin
-          if(@fhir_version == :dstu2 || klass&.ancestors&.include?(FHIR::DSTU2::Model))
+          if(@fhir_version == :dstu2 || klass < FHIR::DSTU2::Model)
             if(format.include?('xml'))
               FHIR::DSTU2::Xml.from_xml(response.body)
             else
               FHIR::DSTU2::Json.from_json(response.body)
             end
-          elsif(@fhir_version == :r4 || klass&.ancestors&.include?(FHIR::Model))
+          elsif(@fhir_version == :stu3 || klass < FHIR::STU3::Model)
             if(format.include?('xml'))
-              FHIR::Xml.from_xml(response.body)
+              FHIR::STU3::Xml.from_xml(response.body)
             else
-              FHIR::Json.from_json(response.body)
+              FHIR::STU3::Json.from_json(response.body)
+            end
+          elsif(@fhir_version == :r4b || klass < FHIR::R4B::Model)
+            if(format.include?('xml'))
+              FHIR::R4B::Xml.from_xml(response.body)
+            else
+              FHIR::R4B::Json.from_json(response.body)
+            end
+          elsif(@fhir_version == :r5 || klass < FHIR::R5::Model)
+            if(format.include?('xml'))
+              FHIR::R5::Xml.from_xml(response.body)
+            else
+              FHIR::R5::Json.from_json(response.body)
             end
           else
             if(format.include?('xml'))
-              FHIR::STU3::Xml.from_xml(response.body)
+              FHIR::Xml.from_xml(response.body)
             else
-              FHIR::STU3::Json.from_json(response.body)
+              FHIR::Json.from_json(response.body)
             end
           end
         rescue => e
@@ -349,7 +391,7 @@ def set_client_on_resource(resource)
 
       resource.client = self
       resource.each_element do |element, _, _|
-        if element.is_a?(Reference) || element.is_a?(STU3::Reference) || element.is_a?(DSTU2::Reference) || element.respond_to?(:resourceType)
+        if element.is_a?(Reference) || element.is_a?(FHIR::R4B::Reference) || element.is_a?(FHIR::R5::Reference) || element.is_a?(STU3::Reference) || element.is_a?(DSTU2::Reference) || element.respond_to?(:resourceType)
           element.client = self
         end
       end
diff --git a/lib/fhir_client/ext/bundle.rb b/lib/fhir_client/ext/bundle.rb
index cacd7f8b..0c43e212 100644
--- a/lib/fhir_client/ext/bundle.rb
+++ b/lib/fhir_client/ext/bundle.rb
@@ -67,4 +67,20 @@ class Bundle
       include FHIR::BundleExtras
     end
   end
+end
+
+module FHIR
+  module R4B
+    class Bundle < FHIR::R4B::Model
+      include FHIR::BundleExtras
+    end
+  end
+end
+
+module FHIR
+  module R5
+    class Bundle < FHIR::R5::Model
+      include FHIR::BundleExtras
+    end
+  end
 end
\ No newline at end of file
diff --git a/lib/fhir_client/ext/model.rb b/lib/fhir_client/ext/model.rb
index 009b18dd..7d61fc8a 100644
--- a/lib/fhir_client/ext/model.rb
+++ b/lib/fhir_client/ext/model.rb
@@ -144,3 +144,19 @@ class Model
     end
   end
 end
+
+module FHIR
+  module R4B
+    class Model < FHIR::Model
+      include FHIR::ModelExtras
+    end
+  end
+end
+
+module FHIR
+  module R5
+    class Model < FHIR::Model
+      include FHIR::ModelExtras
+    end
+  end
+end
diff --git a/lib/fhir_client/ext/reference.rb b/lib/fhir_client/ext/reference.rb
index 47878abf..344ea736 100644
--- a/lib/fhir_client/ext/reference.rb
+++ b/lib/fhir_client/ext/reference.rb
@@ -82,7 +82,7 @@ class Reference
     include FHIR::ReferenceExtras
 
     def resource_class
-      "FHIR::#{resource_type}".constantize unless contained?
+      FHIR.const_get(resource_type) unless contained?
     end
   end
 end
@@ -93,7 +93,7 @@ class Reference
       include FHIR::ReferenceExtras
 
       def resource_class
-        "FHIR::DSTU2::#{resource_type}".constantize unless contained?
+        FHIR::DSTU2.const_get(resource_type) unless contained?
       end
     end
   end
@@ -101,12 +101,36 @@ def resource_class
 
 module FHIR
   module STU3
-    class Reference
+    class Reference 
+      include FHIR::ReferenceExtras
+
+      def resource_class
+        FHIR::STU3.const_get(resource_type) unless contained?
+      end
+    end
+  end
+end
+
+module FHIR
+  module R4B
+    class Reference < FHIR::R4B::Model
       include FHIR::ReferenceExtras
 
       def resource_class
-        "FHIR::STU3::#{resource_type}".constantize unless contained?
+        FHIR::R4B.const_get(resource_type) unless contained?
       end
     end
   end
 end
+
+module FHIR
+  module R5
+    class Reference < FHIR::R5::Model
+      include FHIR::ReferenceExtras
+
+      def resource_class
+        FHIR::R5.const_get(resource_type) unless contained?
+      end
+    end
+  end
+end
\ No newline at end of file
diff --git a/lib/fhir_client/version_management.rb b/lib/fhir_client/version_management.rb
index bb584083..7a8c22ea 100644
--- a/lib/fhir_client/version_management.rb
+++ b/lib/fhir_client/version_management.rb
@@ -7,6 +7,10 @@ def versioned_resource_class(klass = nil)
               FHIR::STU3
             when :dstu2
               FHIR::DSTU2
+            when :r4b
+              FHIR::R4B
+            when :r5
+              FHIR::R5
             else
               FHIR
             end
diff --git a/test/fixtures/r4b_capabilitystatement.json b/test/fixtures/r4b_capabilitystatement.json
new file mode 100644
index 00000000..408bf3d9
--- /dev/null
+++ b/test/fixtures/r4b_capabilitystatement.json
@@ -0,0 +1,148 @@
+{
+  "resourceType" : "CapabilityStatement",
+  "id" : "example",
+  "text" : {
+    "status" : "generated",
+    "div" : "<div xmlns=\"http://www.w3.org/1999/xhtml\">\n\t\t\t<p>The EHR Server supports the following transactions for the resource Person: read, vread, \n        update, history, search(name,gender), create and updates.</p>\n\t\t\t<p>The EHR System supports the following message: admin-notify::Person.</p>\n\t\t\t<p>The EHR Application has a \n        <a href=\"http://fhir.hl7.org/base/Profilebc054d23-75e1-4dc6-aca5-838b6b1ac81d/_history/b5fdd9fc-b021-4ea1-911a-721a60663796\">general document profile</a>.\n      </p>\n\t\t</div>"
+  },
+  "url" : "urn:uuid:68d043b5-9ecf-4559-a57a-396e0d452311",
+  "version" : "20130510",
+  "name" : "ACME-EHR",
+  "title" : "ACME EHR capability statement",
+  "status" : "draft",
+  "experimental" : true,
+  "date" : "2012-01-04",
+  "publisher" : "ACME Corporation",
+  "contact" : [{
+    "name" : "System Administrator",
+    "telecom" : [{
+      "system" : "email",
+      "value" : "wile@acme.org"
+    }]
+  }],
+  "description" : "This is the FHIR capability statement for the main EHR at ACME for the private interface - it does not describe the public interface",
+  "useContext" : [{
+    "code" : {
+      "system" : "http://terminology.hl7.org/CodeSystem/usage-context-type",
+      "code" : "focus"
+    },
+    "valueCodeableConcept" : {
+      "coding" : [{
+        "system" : "http://terminology.hl7.org/CodeSystem/variant-state",
+        "code" : "positive"
+      }]
+    }
+  }],
+  "jurisdiction" : [{
+    "coding" : [{
+      "system" : "urn:iso:std:iso:3166",
+      "code" : "US",
+      "display" : "United States of America (the)"
+    }]
+  }],
+  "purpose" : "Main EHR capability statement, published for contracting and operational support",
+  "copyright" : "Copyright © Acme Healthcare and GoodCorp EHR Systems",
+  "kind" : "instance",
+  "instantiates" : ["http://ihe.org/fhir/CapabilityStatement/pixm-client"],
+  "software" : {
+    "name" : "EHR",
+    "version" : "0.00.020.2134",
+    "releaseDate" : "2012-01-04"
+  },
+  "implementation" : {
+    "description" : "main EHR at ACME",
+    "url" : "http://10.2.3.4/fhir"
+  },
+  "fhirVersion" : "4.3.0",
+  "format" : ["xml",
+  "json"],
+  "patchFormat" : ["application/xml-patch+xml",
+  "application/json-patch+json"],
+  "implementationGuide" : ["http://hl7.org/fhir/us/lab"],
+  "rest" : [{
+    "mode" : "server",
+    "documentation" : "Main FHIR endpoint for acem health",
+    "security" : {
+      "cors" : true,
+      "service" : [{
+        "coding" : [{
+          "system" : "http://terminology.hl7.org/CodeSystem/restful-security-service",
+          "code" : "SMART-on-FHIR"
+        }]
+      }],
+      "description" : "See Smart on FHIR documentation"
+    },
+    "resource" : [{
+      "type" : "Patient",
+      "profile" : "http://registry.fhir.org/r4/StructureDefinition/7896271d-57f6-4231-89dc-dcc91eab2416",
+      "supportedProfile" : ["http://registry.fhir.org/r4/StructureDefinition/00ab9e7a-06c7-4f77-9234-4154ca1e3347"],
+      "documentation" : "This server does not let the clients create identities.",
+      "interaction" : [{
+        "code" : "read"
+      },
+      {
+        "code" : "vread",
+        "documentation" : "Only supported for patient records since 12-Dec 2012"
+      },
+      {
+        "code" : "update"
+      },
+      {
+        "code" : "history-instance"
+      },
+      {
+        "code" : "create"
+      },
+      {
+        "code" : "history-type"
+      }],
+      "versioning" : "versioned-update",
+      "readHistory" : true,
+      "updateCreate" : false,
+      "conditionalCreate" : true,
+      "conditionalRead" : "full-support",
+      "conditionalUpdate" : false,
+      "conditionalDelete" : "not-supported",
+      "searchInclude" : ["Organization"],
+      "searchRevInclude" : ["Person"],
+      "searchParam" : [{
+        "name" : "identifier",
+        "definition" : "http://hl7.org/fhir/SearchParameter/Patient-identifier",
+        "type" : "token",
+        "documentation" : "Only supports search by institution MRN"
+      },
+      {
+        "name" : "general-practitioner",
+        "definition" : "http://hl7.org/fhir/SearchParameter/Patient-general-practitioner",
+        "type" : "reference"
+      }]
+    }],
+    "interaction" : [{
+      "code" : "transaction"
+    },
+    {
+      "code" : "history-system"
+    }],
+    "compartment" : ["http://hl7.org/fhir/CompartmentDefinition/patient"]
+  }],
+  "messaging" : [{
+    "endpoint" : [{
+      "protocol" : {
+        "system" : "http://terminology.hl7.org/CodeSystem/message-transport",
+        "code" : "mllp"
+      },
+      "address" : "mllp:10.1.1.10:9234"
+    }],
+    "reliableCache" : 30,
+    "documentation" : "ADT A08 equivalent for external system notifications",
+    "supportedMessage" : [{
+      "mode" : "receiver",
+      "definition" : "http://hl7.org/fhir/MessageDefinition/example"
+    }]
+  }],
+  "document" : [{
+    "mode" : "consumer",
+    "documentation" : "Basic rules for all documents in the EHR system",
+    "profile" : "http://fhir.hl7.org/base/Profilebc054d23-75e1-4dc6-aca5-838b6b1ac81d/_history/b5fdd9fc-b021-4ea1-911a-721a60663796"
+  }]
+}
\ No newline at end of file
diff --git a/test/fixtures/r5_capabilitystatement.json b/test/fixtures/r5_capabilitystatement.json
new file mode 100644
index 00000000..79a207cb
--- /dev/null
+++ b/test/fixtures/r5_capabilitystatement.json
@@ -0,0 +1,151 @@
+{
+  "resourceType" : "CapabilityStatement",
+  "id" : "example",
+  "text" : {
+    "status" : "generated",
+    "div" : "<div xmlns=\"http://www.w3.org/1999/xhtml\">\n\t\t\t\n      <p>The EHR Server supports the following transactions for the resource Person: read, vread, \n        update, history, search(name,gender), create and updates.</p>\n\t\t\t\n      <p>The EHR System supports the following message: admin-notify::Person.</p>\n\t\t\t\n      <p>The EHR Application has a \n        \n        <a href=\"http://fhir.hl7.org/base/Profilebc054d23-75e1-4dc6-aca5-838b6b1ac81d/_history/b5fdd9fc-b021-4ea1-911a-721a60663796\">general document profile</a>.\n      \n      </p>\n\t\t\n    </div>"
+  },
+  "url" : "urn:uuid:68d043b5-9ecf-4559-a57a-396e0d452311",
+  "version" : "20130510",
+  "name" : "ACMEEHR",
+  "title" : "ACME EHR capability statement",
+  "status" : "draft",
+  "experimental" : true,
+  "date" : "2012-01-04",
+  "publisher" : "ACME Corporation",
+  "contact" : [{
+    "name" : "System Administrator",
+    "telecom" : [{
+      "system" : "email",
+      "value" : "wile@acme.org"
+    }]
+  }],
+  "description" : "This is the FHIR capability statement for the main EHR at ACME for the private interface - it does not describe the public interface",
+  "useContext" : [{
+    "code" : {
+      "system" : "http://terminology.hl7.org/CodeSystem/usage-context-type",
+      "code" : "focus"
+    },
+    "valueCodeableConcept" : {
+      "coding" : [{
+        "system" : "http://terminology.hl7.org/CodeSystem/variant-state",
+        "code" : "positive"
+      }]
+    }
+  }],
+  "jurisdiction" : [{
+    "coding" : [{
+      "system" : "urn:iso:std:iso:3166",
+      "code" : "US",
+      "display" : "United States of America (the)"
+    }]
+  }],
+  "purpose" : "Main EHR capability statement, published for contracting and operational support",
+  "copyright" : "Copyright © Acme Healthcare and GoodCorp EHR Systems",
+  "kind" : "instance",
+  "instantiates" : ["http://ihe.org/fhir/CapabilityStatement/pixm-client"],
+  "software" : {
+    "name" : "EHR",
+    "version" : "0.00.020.2134",
+    "releaseDate" : "2012-01-04"
+  },
+  "implementation" : {
+    "description" : "main EHR at ACME",
+    "url" : "http://10.2.3.4/fhir"
+  },
+  "fhirVersion" : "5.0.0",
+  "format" : ["xml",
+  "json"],
+  "patchFormat" : ["application/xml-patch+xml",
+  "application/json-patch+json"],
+  "acceptLanguage" : ["en",
+  "es"],
+  "implementationGuide" : ["http://example.org/fhir/us/lab"],
+  "rest" : [{
+    "mode" : "server",
+    "documentation" : "Main FHIR endpoint for acem health",
+    "security" : {
+      "cors" : true,
+      "service" : [{
+        "coding" : [{
+          "system" : "http://hl7.org/fhir/restful-security-service",
+          "code" : "SMART-on-FHIR"
+        }]
+      }],
+      "description" : "See Smart on FHIR documentation"
+    },
+    "resource" : [{
+      "type" : "Patient",
+      "profile" : "http://registry.fhir.org/r5/StructureDefinition/7896271d-57f6-4231-89dc-dcc91eab2416",
+      "supportedProfile" : ["http://registry.fhir.org/r5/StructureDefinition/00ab9e7a-06c7-4f77-9234-4154ca1e3347"],
+      "documentation" : "This server does not let the clients create identities.",
+      "interaction" : [{
+        "code" : "read"
+      },
+      {
+        "code" : "vread",
+        "documentation" : "Only supported for patient records since 12-Dec 2012"
+      },
+      {
+        "code" : "update"
+      },
+      {
+        "code" : "history-instance"
+      },
+      {
+        "code" : "create"
+      },
+      {
+        "code" : "history-type"
+      }],
+      "versioning" : "versioned-update",
+      "readHistory" : true,
+      "updateCreate" : false,
+      "conditionalCreate" : true,
+      "conditionalRead" : "full-support",
+      "conditionalUpdate" : false,
+      "conditionalPatch" : false,
+      "conditionalDelete" : "not-supported",
+      "searchInclude" : ["Patient:organization"],
+      "searchRevInclude" : ["Person:patient"],
+      "searchParam" : [{
+        "name" : "identifier",
+        "definition" : "http://hl7.org/fhir/SearchParameter/Patient-identifier",
+        "type" : "token",
+        "documentation" : "Only supports search by institution MRN"
+      },
+      {
+        "name" : "general-practitioner",
+        "definition" : "http://hl7.org/fhir/SearchParameter/Patient-general-practitioner",
+        "type" : "reference"
+      }]
+    }],
+    "interaction" : [{
+      "code" : "transaction"
+    },
+    {
+      "code" : "history-system"
+    }],
+    "compartment" : ["http://hl7.org/fhir/CompartmentDefinition/patient"]
+  }],
+  "messaging" : [{
+    "endpoint" : [{
+      "protocol" : {
+        "system" : "http://hl7.org/fhir/message-transport",
+        "code" : "mllp"
+      },
+      "address" : "mllp:10.1.1.10:9234"
+    }],
+    "reliableCache" : 30,
+    "documentation" : "ADT A08 equivalent for external system notifications",
+    "supportedMessage" : [{
+      "mode" : "receiver",
+      "definition" : "http://hl7.org/fhir/MessageDefinition/example"
+    }]
+  }],
+  "document" : [{
+    "mode" : "consumer",
+    "documentation" : "Basic rules for all documents in the EHR system",
+    "profile" : "http://fhir.hl7.org/base/Profilebc054d23-75e1-4dc6-aca5-838b6b1ac81d/_history/b5fdd9fc-b021-4ea1-911a-721a60663796"
+  }]
+}
\ No newline at end of file
diff --git a/test/unit/client_interface_sections/read_test.rb b/test/unit/client_interface_sections/read_test.rb
index 14219503..87d8ea1f 100644
--- a/test/unit/client_interface_sections/read_test.rb
+++ b/test/unit/client_interface_sections/read_test.rb
@@ -15,7 +15,7 @@ def test_read
     patient = FHIR::Patient.new({'gender'=>'female', 'active'=>true, 'deceasedBoolean'=>false})
     stub_request(:get, /read-test/).to_return(status: 200, body: patient.to_json, headers: {'Content-Type'=>'application/fhir+json', 'ETag'=>'W/"foo"', 'Last-Modified'=>Time.now.strftime("%a, %e %b %Y %T %Z")})
     temp = client
-    temp.use_stu3
+    temp.use_r4
     temp.default_json
     reply = temp.read(FHIR::Patient,'foo')
     assert reply.resource.is_a?(FHIR::Patient)
@@ -29,7 +29,7 @@ def test_vread
     patient = FHIR::Patient.new({'gender'=>'female', 'active'=>true, 'deceasedBoolean'=>false})
     stub_request(:get, /read-test\/.*_history\/2/).to_return(status: 200, body: patient.to_json, headers: {'Content-Type'=>'application/fhir+json', 'ETag'=>'W/"foo"', 'Last-Modified'=>Time.now.strftime("%a, %e %b %Y %T %Z")})
     temp = client
-    temp.use_stu3
+    temp.use_r4
     temp.default_json
     reply = temp.vread(FHIR::Patient,'foo', 2)
     assert reply.resource.is_a?(FHIR::Patient)
@@ -46,7 +46,7 @@ def test_conditional_read_since
     patient = FHIR::Patient.new({'gender'=>'female', 'active'=>true, 'deceasedBoolean'=>false})
     stub_request(:get, /read-test/).with(headers: {'If-Modified-Since' => 'Wed, 21 Oct 2015 07:28:00 GMT'}).to_return(status: 200, body: patient.to_json, headers: {'Content-Type'=>'application/fhir+json', 'ETag'=>'W/"foo"', 'Last-Modified'=>Time.now.strftime("%a, %e %b %Y %T %Z")})
     temp = client
-    temp.use_stu3
+    temp.use_r4
     temp.default_json
     reply = temp.conditional_read_since(FHIR::Patient,'foo', 'Wed, 21 Oct 2015 07:28:00 GMT')
     assert reply.resource.is_a?(FHIR::Patient)
@@ -59,7 +59,7 @@ def test_conditional_read_version
     patient = FHIR::Patient.new({'gender'=>'female', 'active'=>true, 'deceasedBoolean'=>false})
     stub_request(:get, /read-test/).with(headers: {'If-None-Match' => 'W/ABC'}).to_return(status: 200, body: patient.to_json, headers: {'Content-Type'=>'application/fhir+json', 'ETag'=>'W/"foo"', 'Last-Modified'=>Time.now.strftime("%a, %e %b %Y %T %Z")})
     temp = client
-    temp.use_stu3
+    temp.use_r4
     temp.default_json
     reply = temp.conditional_read_version(FHIR::Patient,'foo','ABC')
     assert reply.resource.is_a?(FHIR::Patient)
@@ -77,7 +77,7 @@ def test_raw_read
                              'ETag'=>'W/"foo"',
                              'Last-Modified'=>Time.now.strftime("%a, %e %b %Y %T %Z")})
     temp = client
-    temp.use_stu3
+    temp.use_r4
     temp.default_json
     options = {resource: FHIR::Patient, id: 'foo'}
     reply = temp.raw_read(options)
diff --git a/test/unit/multiversion_test.rb b/test/unit/multiversion_test.rb
index b96d02d9..bba165c6 100644
--- a/test/unit/multiversion_test.rb
+++ b/test/unit/multiversion_test.rb
@@ -1,5 +1,4 @@
 require_relative '../test_helper'
-
 class MultiversionTest < Test::Unit::TestCase
 
   def test_autodetect_stu3
@@ -47,6 +46,36 @@ def test_autodetect_r4
     assert client.default_format.include? 'json'
   end
 
+  def test_autodetect_r4b
+    root = File.expand_path '..', File.dirname(File.absolute_path(__FILE__))
+    capabilitystatement = File.read(File.join(root, 'fixtures', 'r4b_capabilitystatement.json'))
+    stub_request(:get, /autodetect/).to_return(body: capabilitystatement)
+    client = FHIR::Client.new('autodetect')
+    # Intentionally set the client incorrectly
+    client.default_xml
+    client.use_r4
+    assert client.cached_capability_statement.nil?
+    assert client.detect_version == :r4b, "Expected Version to be r4b, but found #{client.detect_version.to_s}"
+    assert !client.cached_capability_statement.nil?, 'Expected Capability Statement to be cached'
+    assert client.cached_capability_statement.is_a?(FHIR::R4B::CapabilityStatement)
+    assert client.default_format.include? 'json'
+  end
+
+  def test_autodetect_r5
+    root = File.expand_path '..', File.dirname(File.absolute_path(__FILE__))
+    capabilitystatement = File.read(File.join(root, 'fixtures', 'r5_capabilitystatement.json'))
+    stub_request(:get, /autodetect/).to_return(body: capabilitystatement)
+    client = FHIR::Client.new('autodetect')
+    # Intentionally set the client incorrectly
+    client.default_xml
+    client.use_r4
+    assert client.cached_capability_statement.nil?
+    assert client.detect_version == :r5, "Expected Version to be r5, but found #{client.detect_version.to_s}"
+    assert !client.cached_capability_statement.nil?, 'Expected Capability Statement to be cached'
+    assert client.cached_capability_statement.is_a?(FHIR::R5::CapabilityStatement)
+    assert client.default_format.include? 'json'
+  end
+
   def test_stu3_patient_manual
     stub_request(:get, /stu3/).to_return(body: FHIR::STU3::Patient.new.to_json)
     client = FHIR::Client.new('stu3')
@@ -65,6 +94,23 @@ def test_dstu2_patient_manual
     assert client.read(FHIR::DSTU2::Patient, 'foo').resource.is_a?(FHIR::DSTU2::Patient)
   end
 
+  def test_r4b_patient_manual
+    stub_request(:get, /r4b/).to_return(body: FHIR::R4B::Patient.new({ 'id': 'foo' }).to_json)
+    client = FHIR::Client.new('r4b')
+    client.default_json
+    client.use_r4b
+    assert_equal :r4b, client.fhir_version
+    assert client.read(FHIR::R4B::Patient, 'foo').resource.is_a?(FHIR::R4B::Patient)
+  end
+
+  def test_r5_patient_manual
+    stub_request(:get, /r5/).to_return(body: FHIR::R5::Patient.new({ 'id': 'foo' }).to_json)
+    client = FHIR::Client.new('r5')
+    client.default_json
+    client.use_r5
+    assert_equal :r5, client.fhir_version
+    assert client.read(FHIR::R5::Patient, 'foo').resource.is_a?(FHIR::R5::Patient)
+  end
 
   def test_r4_patient_manual
     stub_request(:get, /r4/).to_return(body: FHIR::Patient.new({ 'id': 'foo' }).to_json)
@@ -132,6 +178,26 @@ def test_r4_reply_fhir_version
     assert_equal :r4, client.reply.fhir_version
   end
 
+  def test_r4b_reply_fhir_version
+    stub_request(:get, /r4b/).to_return(body: FHIR::R4B::Patient.new({ 'id': 'foo' }).to_json)
+    client = FHIR::Client.new('r4b')
+    client.default_json
+    client.use_r4b
+    FHIR::R4B::Model.client = client
+    patient = FHIR::R4B::Patient.read('foo')
+    assert_equal :r4b, client.reply.fhir_version
+  end
+
+  def test_r5_reply_fhir_version
+    stub_request(:get, /r5/).to_return(body: FHIR::R5::Patient.new({ 'id': 'foo' }).to_json)
+    client = FHIR::Client.new('r5')
+    client.default_json
+    client.use_r5
+    FHIR::R5::Model.client = client
+    patient = FHIR::R5::Patient.read('foo')
+    assert_equal :r5, client.reply.fhir_version
+  end
+
   def test_stu3_accept_mime_type_json
     stub_request(:get, /stu3/).to_return(body: FHIR::STU3::Patient.new({'id': 'foo'}).to_json)
     client = FHIR::Client.new('stu3')
diff --git a/test/unit/set_client_on_resource_test.rb b/test/unit/set_client_on_resource_test.rb
index cd55aee5..8371bda5 100644
--- a/test/unit/set_client_on_resource_test.rb
+++ b/test/unit/set_client_on_resource_test.rb
@@ -18,6 +18,32 @@ def test_r4
     assert_equal(client, condition.subject.client)
   end
 
+  def test_r4b
+    condition = FHIR::R4B::Condition.new(
+      resourceType: 'Condition',
+      subject: {
+        reference: 'Patient/123'
+      }
+    )
+    client.set_client_on_resource(condition)
+
+    assert_equal(client, condition.client)
+    assert_equal(client, condition.subject.client)
+  end
+
+  def test_r5
+    condition = FHIR::R5::Condition.new(
+      resourceType: 'Condition',
+      subject: {
+        reference: 'Patient/123'
+      }
+    )
+    client.set_client_on_resource(condition)
+
+    assert_equal(client, condition.client)
+    assert_equal(client, condition.subject.client)
+  end
+
   def test_stu3
     condition = FHIR::STU3::Condition.new(
       resourceType: 'Condition',