diff --git a/Library/Homebrew/api/formula/formula_struct_generator.rb b/Library/Homebrew/api/formula/formula_struct_generator.rb
index 0c0219c301..16c9b6b4d5 100644
--- a/Library/Homebrew/api/formula/formula_struct_generator.rb
+++ b/Library/Homebrew/api/formula/formula_struct_generator.rb
@@ -247,18 +247,18 @@ module Homebrew
         sig { params(deps_hash: DependencyHash).returns(T::Array[FormulaStruct::DependsOnArgs]) }
         def process_dependencies(deps_hash)
           no_linkage_names = deps_hash.fetch("no_linkage_dependencies", [])
-          dependencies = deps_hash.fetch("dependencies", []).map do |dep|
+          dependencies = deps_hash.fetch("dependencies", []).uniq.map do |dep|
             next dep unless no_linkage_names.include?(dep)
 
             { dep => :no_linkage }
           end
-          dependencies + [:build, :test, :recommended, :optional].filter_map do |type|
-            deps_hash["#{type}_dependencies"]&.map do |dep|
-              next { dep => type } unless no_linkage_names.include?(dep)
+          types = [:build, :test, :recommended, :optional]
+          dependencies + types.flat_map { |type| deps_hash.fetch("#{type}_dependencies", []) }.uniq.map do |dep|
+            tags = types.select { |type| deps_hash.fetch("#{type}_dependencies", []).include?(dep) }
+            tags << :no_linkage if no_linkage_names.include?(dep)
 
-              { dep => [type, :no_linkage] }
-            end
-          end.flatten(1)
+            { dep => (tags.one? ? tags.fetch(0) : tags) }
+          end
         end
 
         sig { params(requirements_array: RequirementsArray, spec: Symbol).returns(T::Array[FormulaStruct::DependsOnArgs]) }
diff --git a/Library/Homebrew/test/api/formula/formula_struct_generator_spec.rb b/Library/Homebrew/test/api/formula/formula_struct_generator_spec.rb
index 6dd06fc441..17fffcf397 100644
--- a/Library/Homebrew/test/api/formula/formula_struct_generator_spec.rb
+++ b/Library/Homebrew/test/api/formula/formula_struct_generator_spec.rb
@@ -236,6 +236,57 @@ RSpec.describe Homebrew::API::Formula::FormulaStructGenerator do
     expect(output).to eq dependency_args
   end
 
+  describe "::process_dependencies" do
+    it "combines build and test tags into one dependency" do
+      expect(described_class.process_dependencies({
+        "build_dependencies" => ["foo"],
+        "test_dependencies"  => ["foo"],
+      })).to eq [{ "foo" => [:build, :test] }]
+    end
+
+    it "appends no_linkage to combined dependency tags" do
+      expect(described_class.process_dependencies({
+        "build_dependencies"      => ["foo"],
+        "test_dependencies"       => ["foo"],
+        "no_linkage_dependencies" => ["foo"],
+      })).to eq [{ "foo" => [:build, :test, :no_linkage] }]
+    end
+
+    it "preserves runtime dependencies alongside combined build and test tags" do
+      expect(described_class.process_dependencies({
+        "dependencies"       => ["foo"],
+        "build_dependencies" => ["foo"],
+        "test_dependencies"  => ["foo"],
+      })).to eq ["foo", { "foo" => [:build, :test] }]
+    end
+
+    it "preserves no_linkage on runtime and tagged dependencies" do
+      expect(described_class.process_dependencies({
+        "dependencies"            => ["foo"],
+        "test_dependencies"       => ["foo"],
+        "no_linkage_dependencies" => ["foo"],
+      })).to eq [{ "foo" => :no_linkage }, { "foo" => [:test, :no_linkage] }]
+    end
+
+    it "preserves recommended and no_linkage tags" do
+      expect(described_class.process_dependencies({
+        "recommended_dependencies" => ["foo"],
+        "no_linkage_dependencies"  => ["foo"],
+      })).to eq [{ "foo" => [:recommended, :no_linkage] }]
+    end
+
+    it "preserves first appearance and uses a fixed tag order" do
+      expect(described_class.process_dependencies({
+        "optional_dependencies"    => ["multi", "optional"],
+        "recommended_dependencies" => ["multi", "recommended"],
+        "test_dependencies"        => ["multi", "test"],
+        "build_dependencies"       => ["build", "multi"],
+        "dependencies"             => ["runtime"],
+      })).to eq ["runtime", { "build" => :build }, { "multi" => [:build, :test, :recommended, :optional] },
+                 { "test" => :test }, { "recommended" => :recommended }, { "optional" => :optional }]
+    end
+  end
+
   specify "::process_uses_from_macos" do
     output = described_class.process_uses_from_macos(symbolized_dependency_hash)
     expect(output).to eq uses_from_macos_args
diff --git a/Library/Homebrew/test/formulary_spec.rb b/Library/Homebrew/test/formulary_spec.rb
index 18e366152c..f283ab22ec 100644
--- a/Library/Homebrew/test/formulary_spec.rb
+++ b/Library/Homebrew/test/formulary_spec.rb
@@ -185,6 +185,7 @@ RSpec.describe Formulary do
           license "MIT"
           url "https://example.com/no-linkage-round-trip-1.0.tar.gz"
           depends_on "shared" => :no_linkage
+          depends_on "runtime"
 
           on_macos do
             depends_on "platform" => :no_linkage
@@ -192,6 +193,8 @@ RSpec.describe Formulary do
           on_linux do
             depends_on "platform"
           end
+          depends_on "multi" => [:build, :test]
+          depends_on "runtime" => [:build, :test]
 
           head do
             url "https://example.com/no-linkage-round-trip.git", branch: "main"
@@ -210,7 +213,10 @@ RSpec.describe Formulary do
 
     before do
       stub_const("OnSystem::VALID_OS_ARCH_TAGS", [mac_tag, linux_tag])
-      allow(CoreTap.instance).to receive(:git_head).and_return("0" * 40)
+      allow(Homebrew::API).to receive_messages(formula_names: [formula_name], formula_aliases: {},
+                                               formula_renames: {})
+      allow(CoreTap.instance).to receive_messages(git_head: "0" * 40, tap_migrations: {})
+      allow(CoreCaskTap.instance).to receive(:tap_migrations).and_return({})
       allow(DevelopmentTools).to receive_messages(needs_libc_formula?: false, needs_compiler_formula?: false)
       formula_path.dirname.mkpath
       formula_path.write formula_content
@@ -218,7 +224,7 @@ RSpec.describe Formulary do
 
     test_each([:arm64_sequoia, :x86_64_linux].product([:stable, :head],
                                                       [:public, :internal])) do |(tag_symbol, spec, format)|
-      it "preserves #{spec} declarations through the #{format} API on #{tag_symbol}" do
+      it "preserves #{spec} declarations through the #{format} API on #{tag_symbol}", :aggregate_failures do
         payload = json
         tag = (tag_symbol == :arm64_sequoia) ? mac_tag : linux_tag
         Homebrew::SimulateSystem.with_tag(tag) do
@@ -238,6 +244,7 @@ RSpec.describe Formulary do
 
           expect(restored.declared_deps.map { |dep| [dep.name, dep.tags] })
             .to eq(source.declared_deps.map { |dep| [dep.name, dep.tags] })
+          expect(restored.to_hash.slice(*source.dependencies_hash.keys)).to eq(source.dependencies_hash)
         end
       end
     end