diff --git a/.github/workflows/Tests.yml b/.github/workflows/Tests.yml
index de08dd726..8fd6d66bb 100644
--- a/.github/workflows/Tests.yml
+++ b/.github/workflows/Tests.yml
@@ -36,7 +36,7 @@ jobs:
           submodules: recursive
       - uses: maxim-lobanov/setup-xcode@v1
         with:
-          xcode-version: 15.3
+          xcode-version: "16.0.0"
       - uses: ruby/setup-ruby@v1
         with:
           ruby-version: 3.2
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 9574fc8af..487f65c7c 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -6,7 +6,8 @@
 
 ##### Enhancements
 
-* None.
+* Support Swift 6.0 / Xcode 16.0  
+  [John Fairhurst](https://github.com/johnfairh)
 
 ##### Bug Fixes
 
diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index 848654197..764d8962f 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -49,7 +49,7 @@ git push
 You'll need push access to the integration specs repo to do this. You can
 request access from one of the maintainers when filing your PR.
 
-You must have Xcode 15.3 installed to build the integration specs.
+You must have Xcode 16.0 installed to build the integration specs.
 
 ## Making changes to SourceKitten
 
diff --git a/lib/jazzy/podspec_documenter.rb b/lib/jazzy/podspec_documenter.rb
index 382d40e33..62956bed8 100644
--- a/lib/jazzy/podspec_documenter.rb
+++ b/lib/jazzy/podspec_documenter.rb
@@ -102,7 +102,7 @@ def self.github_file_prefix(podspec)
     private_class_method :github_file_prefix
 
     # Latest valid value for SWIFT_VERSION.
-    LATEST_SWIFT_VERSION = '5'
+    LATEST_SWIFT_VERSION = '6'
 
     # All valid values for SWIFT_VERSION that are longer
     # than a major version number.  Ordered ascending.
diff --git a/lib/jazzy/sourcekitten.rb b/lib/jazzy/sourcekitten.rb
index 7cafce5ee..608dd6102 100644
--- a/lib/jazzy/sourcekitten.rb
+++ b/lib/jazzy/sourcekitten.rb
@@ -485,10 +485,19 @@ def self.make_swift_declaration(doc, declaration)
       # @available attrs only in compiler 'interface' style
       extract_availability(doc['key.doc.declaration'] || '')
         .concat(extract_documented_attributes(annotated_decl_attrs))
+        .concat(fabricate_spi_attributes(doc, annotated_decl_attrs))
         .push(decl)
         .join("\n")
     end
 
+    # Swift 6 workaround: @_spi attribute & SPI group missing
+    def self.fabricate_spi_attributes(doc, attrs)
+      return [] unless spi_attribute?(doc)
+      return [] if attrs =~ /@_spi/
+
+      ['@_spi(<<unknown>>)']
+    end
+
     # Exclude non-async routines that accept async closures
     def self.swift_async?(fully_annotated_decl)
       document = REXML::Document.new(fully_annotated_decl)
diff --git a/lib/jazzy/symbol_graph/ext_node.rb b/lib/jazzy/symbol_graph/ext_node.rb
index 1ae42c69c..ffc1349fc 100644
--- a/lib/jazzy/symbol_graph/ext_node.rb
+++ b/lib/jazzy/symbol_graph/ext_node.rb
@@ -1,5 +1,7 @@
 # frozen_string_literal: true
 
+require 'set'
+
 module Jazzy
   module SymbolGraph
     # For extensions we need to track constraints of the extended type
@@ -26,7 +28,7 @@ class ExtNode < BaseNode
       attr_accessor :real_usr
       attr_accessor :name
       attr_accessor :all_constraints # ExtConstraints
-      attr_accessor :conformances # array, can be empty
+      attr_accessor :conformances # set, can be empty
 
       # Deduce an extension from a member of an unknown type or
       # of known type with additional constraints
@@ -54,7 +56,7 @@ def initialize(usr, name, constraints)
         self.usr = usr
         self.name = name
         self.all_constraints = constraints
-        self.conformances = []
+        self.conformances = Set.new
         super()
       end
 
@@ -65,13 +67,13 @@ def constraints
       end
 
       def add_conformance(protocol)
-        conformances.append(protocol).sort!
+        conformances.add(protocol)
       end
 
       def full_declaration
         decl = "extension #{name}"
         unless conformances.empty?
-          decl += " : #{conformances.join(', ')}"
+          decl += " : #{conformances.sort.join(', ')}"
         end
         decl + all_constraints.ext.to_where_clause
       end
@@ -90,7 +92,7 @@ def to_sourcekit(module_name, ext_module_name)
         }
 
         unless conformances.empty?
-          hash['key.inheritedtypes'] = conformances.map do |conformance|
+          hash['key.inheritedtypes'] = conformances.sort.map do |conformance|
             { 'key.name' => conformance }
           end
         end
@@ -100,11 +102,13 @@ def to_sourcekit(module_name, ext_module_name)
         hash
       end
 
-      # Sort order - by type name then constraint
+      # Sort order - by type name then constraint then conformances
+      # Conformance check needed for stable order with Swift 5.9
+      # extension symbols that can't merge as well as previously.
       include Comparable
 
       def sort_key
-        name + constraints.map(&:to_swift).join
+        name + constraints.map(&:to_swift).join + conformances.sort.join
       end
 
       def <=>(other)
diff --git a/lib/jazzy/symbol_graph/relationship.rb b/lib/jazzy/symbol_graph/relationship.rb
index 1fb48d917..cf86bd968 100644
--- a/lib/jazzy/symbol_graph/relationship.rb
+++ b/lib/jazzy/symbol_graph/relationship.rb
@@ -34,7 +34,7 @@ def extension_to?
       # Protocol conformances added by compiler to actor decls that
       # users aren't interested in.
       def actor_protocol?
-        %w[Actor Sendable].include?(target_fallback)
+        %w[Actor AnyActor Sendable].include?(target_fallback)
       end
 
       def initialize(hash)
diff --git a/spec/integration_spec.rb b/spec/integration_spec.rb
index c476c0ded..52806869d 100644
--- a/spec/integration_spec.rb
+++ b/spec/integration_spec.rb
@@ -249,7 +249,8 @@ def configure_cocoapods
       behaves_like cli_spec 'misc_jazzy_symgraph_features',
                             '--swift-build-tool symbolgraph ' \
                               '--build-tool-arguments ' \
-                              "-emit-extension-block-symbols,-I,#{module_path}"
+                              '-emit-extension-block-symbols,-I,' \
+                              "#{module_path.chomp}/Modules"
     end
 
     describe 'Creates docs for a multiple-module project' do
diff --git a/spec/integration_specs b/spec/integration_specs
index 73a6ada8a..3c10540eb 160000
--- a/spec/integration_specs
+++ b/spec/integration_specs
@@ -1 +1 @@
-Subproject commit 73a6ada8adcdedb3a9c1f83f910362b91b801109
+Subproject commit 3c10540eb2829f827662d1f0b889c03110fff257