diff --git a/detect/detect_test.go b/detect/detect_test.go
index 74ab89c..d1848e7 100644
--- a/detect/detect_test.go
+++ b/detect/detect_test.go
@@ -68,6 +68,129 @@ func TestRubyTools(t *testing.T) {
 	assertToolDetected(t, r, "lint", "RuboCop")
 }
 
+func TestRubyAndBEAMRustIntegrations(t *testing.T) {
+	t.Run("projects", func(t *testing.T) {
+		ruby := runOn(t, "../testdata/ruby-rust-project")
+		assertToolDetectedWithConfidence(t, ruby, "native_extension", "rb-sys", brief.ConfidenceHigh)
+		assertToolDetectedWithConfidence(t, ruby, "library", "Magnus", brief.ConfidenceHigh)
+		assertToolDetected(t, ruby, "native_extension", "mkmf")
+
+		elixir := runOn(t, "../testdata/rustler-project")
+		assertToolDetectedWithConfidence(t, elixir, "native_extension", "Rustler", brief.ConfidenceHigh)
+	})
+
+	t.Run("signals", func(t *testing.T) {
+		tests := []struct {
+			name     string
+			files    map[string]string
+			category string
+			tool     string
+		}{
+			{
+				name: "rb-sys Ruby dependency",
+				files: map[string]string{
+					"Gemfile": "source \"https://rubygems.org\"\ngem \"rb_sys\"\n",
+				},
+				category: "native_extension",
+				tool:     "rb-sys",
+			},
+			{
+				name: "rb-sys Cargo dependency",
+				files: map[string]string{
+					"Gemfile":    "source \"https://rubygems.org\"\n",
+					"Cargo.toml": "[package]\nname = \"example\"\nversion = \"0.1.0\"\n[dependencies.rb-sys]\nversion = \"0.9\"\n",
+				},
+				category: "native_extension",
+				tool:     "rb-sys",
+			},
+			{
+				name: "Magnus Cargo dependency",
+				files: map[string]string{
+					"Gemfile":    "source \"https://rubygems.org\"\n",
+					"Cargo.toml": "[package]\nname = \"example\"\nversion = \"0.1.0\"\n[dependencies]\nmagnus = \"0.8\"\n",
+				},
+				category: "library",
+				tool:     "Magnus",
+			},
+			{
+				name: "Rustler Mix dependency",
+				files: map[string]string{
+					"mix.exs": "defmodule Example.MixProject do\n  use Mix.Project\n  def project, do: [deps: [{:rustler, \"~> 0.38\"}]]\nend\n",
+				},
+				category: "native_extension",
+				tool:     "Rustler",
+			},
+			{
+				name: "Rustler Cargo dependency",
+				files: map[string]string{
+					"mix.exs":    "defmodule Example.MixProject do\n  use Mix.Project\n  def project, do: [deps: []]\nend\n",
+					"Cargo.toml": "[package]\nname = \"example\"\nversion = \"0.1.0\"\n[dependencies.rustler]\nversion = \"0.38\"\n",
+				},
+				category: "native_extension",
+				tool:     "Rustler",
+			},
+		}
+
+		for _, tt := range tests {
+			t.Run(tt.name, func(t *testing.T) {
+				dir := t.TempDir()
+				for path, content := range tt.files {
+					writeProjectFile(t, dir, path, content)
+				}
+				assertToolDetectedWithConfidence(t, runOn(t, dir), tt.category, tt.tool, brief.ConfidenceHigh)
+			})
+		}
+	})
+
+	t.Run("plain extconf", func(t *testing.T) {
+		dir := t.TempDir()
+		writeProjectFile(t, dir, "Gemfile", "source \"https://rubygems.org\"\n")
+		writeProjectFile(t, dir, "ext/example/extconf.rb", "require \"mkmf\"\ncreate_makefile(\"example\")\n")
+		writeProjectFile(
+			t,
+			dir,
+			"Cargo.toml",
+			"[package]\nname = \"near-miss\"\nversion = \"0.1.0\"\n[dependencies]\nother-rb-sys = \"1\"\nsuper-magnus = \"1\"\n",
+		)
+
+		r := runOn(t, dir)
+		assertToolDetected(t, r, "native_extension", "mkmf")
+		if slices.ContainsFunc(r.Tools["native_extension"], func(d brief.Detection) bool {
+			return d.Name == "rb-sys"
+		}) {
+			t.Error("plain extconf.rb should not detect rb-sys")
+		}
+		if slices.ContainsFunc(r.Tools["library"], func(d brief.Detection) bool {
+			return d.Name == "Magnus"
+		}) {
+			t.Error("plain extconf.rb should not detect Magnus")
+		}
+	})
+
+	t.Run("plain Mix project", func(t *testing.T) {
+		dir := t.TempDir()
+		writeProjectFile(
+			t,
+			dir,
+			"mix.exs",
+			"defmodule Example.MixProject do\n  use Mix.Project\n  def project, do: [deps: []]\nend\n",
+		)
+		writeProjectFile(
+			t,
+			dir,
+			"README.md",
+			"Rustler can be added later if this project needs a native extension.\n",
+		)
+
+		r := runOn(t, dir)
+		if slices.ContainsFunc(r.Tools["native_extension"], func(d brief.Detection) bool {
+			return d.Name == "Rustler"
+		}) {
+			t.Error("plain Mix project should not detect Rustler")
+		}
+	})
+}
+
 func TestRubyTaxonomyPassesThrough(t *testing.T) {
 	r := rubyReport(t)
 
diff --git a/knowledge/elixir/rustler.toml b/knowledge/elixir/rustler.toml
new file mode 100644
index 0000000..43b6571
--- /dev/null
+++ b/knowledge/elixir/rustler.toml
@@ -0,0 +1,26 @@
+[tool]
+name = "Rustler"
+category = "native_extension"
+homepage = "https://github.com/rusterlium/rustler"
+docs = "https://hexdocs.pm/rustler/"
+repo = "https://github.com/rusterlium/rustler"
+description = "Builds safe Erlang NIFs written in Rust"
+
+# Match the Mix package in mix.exs and the Cargo crate in Cargo.toml rather than
+# relying on the global dependency cache shared by all manifest ecosystems.
+[detect]
+ecosystems = ["elixir"]
+
+[detect.file_contains]
+"mix.exs" = ["{:rustler,"]
+"Cargo.toml" = ["\nrustler =", "\nrustler=", "[dependencies.rustler]"]
+
+[commands]
+run = "mix compile"
+alternatives = ["mix compile --force"]
+
+[config]
+files = ["mix.exs", "Cargo.toml", "native/**/Cargo.toml"]
+
+[taxonomy]
+role = ["native-extension"]
diff --git a/knowledge/ruby/magnus.toml b/knowledge/ruby/magnus.toml
new file mode 100644
index 0000000..3e17c11
--- /dev/null
+++ b/knowledge/ruby/magnus.toml
@@ -0,0 +1,21 @@
+[tool]
+name = "Magnus"
+category = "library"
+homepage = "https://github.com/matsadler/magnus"
+docs = "https://docs.rs/magnus/"
+repo = "https://github.com/matsadler/magnus"
+description = "Rust bindings for the Ruby API"
+
+# Match the Cargo crate in Cargo.toml rather than through the global dependency
+# cache so a same-named dependency from another ecosystem does not trigger it.
+[detect]
+ecosystems = ["ruby"]
+
+[detect.file_contains]
+"Cargo.toml" = ["\nmagnus =", "\nmagnus=", "[dependencies.magnus]"]
+
+[config]
+files = ["Cargo.toml"]
+
+[taxonomy]
+role = ["library"]
diff --git a/knowledge/ruby/rb-sys.toml b/knowledge/ruby/rb-sys.toml
new file mode 100644
index 0000000..9ff6488
--- /dev/null
+++ b/knowledge/ruby/rb-sys.toml
@@ -0,0 +1,26 @@
+[tool]
+name = "rb-sys"
+category = "native_extension"
+homepage = "https://oxidize-rb.github.io/rb-sys/"
+docs = "https://oxidize-rb.github.io/rb-sys/"
+repo = "https://github.com/oxidize-rb/rb-sys"
+description = "Builds Ruby native extensions written in Rust"
+
+# Match the Cargo crate in Cargo.toml rather than through the global dependency
+# cache so a same-named dependency from another ecosystem does not trigger it.
+[detect]
+dependencies = ["rb_sys"]
+ecosystems = ["ruby"]
+
+[detect.file_contains]
+"Cargo.toml" = ["\nrb-sys =", "\nrb-sys=", "[dependencies.rb-sys]"]
+
+[commands]
+run = "bundle exec rake compile"
+alternatives = ["rake compile"]
+
+[config]
+files = ["Gemfile", "Cargo.toml", "extconf.rb", "ext/**/extconf.rb"]
+
+[taxonomy]
+role = ["native-extension"]
diff --git a/testdata/ruby-rust-project/Cargo.toml b/testdata/ruby-rust-project/Cargo.toml
new file mode 100644
index 0000000..a1954f3
--- /dev/null
+++ b/testdata/ruby-rust-project/Cargo.toml
@@ -0,0 +1,11 @@
+[package]
+name = "ruby-rust-project"
+version = "0.1.0"
+edition = "2024"
+
+[lib]
+crate-type = ["cdylib"]
+
+[dependencies]
+magnus = "0.8"
+rb-sys = "0.9"
diff --git a/testdata/ruby-rust-project/Gemfile b/testdata/ruby-rust-project/Gemfile
new file mode 100644
index 0000000..5b17fe8
--- /dev/null
+++ b/testdata/ruby-rust-project/Gemfile
@@ -0,0 +1,3 @@
+source "https://rubygems.org"
+
+gem "rb_sys"
diff --git a/testdata/ruby-rust-project/ext/ruby_rust_project/extconf.rb b/testdata/ruby-rust-project/ext/ruby_rust_project/extconf.rb
new file mode 100644
index 0000000..d0438b5
--- /dev/null
+++ b/testdata/ruby-rust-project/ext/ruby_rust_project/extconf.rb
@@ -0,0 +1,4 @@
+require "mkmf"
+require "rb_sys/mkmf"
+
+create_rust_makefile("ruby_rust_project/ruby_rust_project")
diff --git a/testdata/ruby-rust-project/src/lib.rs b/testdata/ruby-rust-project/src/lib.rs
new file mode 100644
index 0000000..ace84d3
--- /dev/null
+++ b/testdata/ruby-rust-project/src/lib.rs
@@ -0,0 +1 @@
+pub fn fixture() {}
diff --git a/testdata/rustler-project/mix.exs b/testdata/rustler-project/mix.exs
new file mode 100644
index 0000000..dbbc0f6
--- /dev/null
+++ b/testdata/rustler-project/mix.exs
@@ -0,0 +1,21 @@
+defmodule RustlerProject.MixProject do
+  use Mix.Project
+
+  def project do
+    [
+      app: :rustler_project,
+      version: "0.1.0",
+      deps: deps()
+    ]
+  end
+
+  def application do
+    [extra_applications: [:logger]]
+  end
+
+  defp deps do
+    [
+      {:rustler, "~> 0.38"}
+    ]
+  end
+end
diff --git a/testdata/rustler-project/native/rustler_project/Cargo.toml b/testdata/rustler-project/native/rustler_project/Cargo.toml
new file mode 100644
index 0000000..53b3bd7
--- /dev/null
+++ b/testdata/rustler-project/native/rustler_project/Cargo.toml
@@ -0,0 +1,10 @@
+[package]
+name = "rustler_project"
+version = "0.1.0"
+edition = "2024"
+
+[lib]
+crate-type = ["cdylib"]
+
+[dependencies]
+rustler = "0.38"
diff --git a/testdata/rustler-project/native/rustler_project/src/lib.rs b/testdata/rustler-project/native/rustler_project/src/lib.rs
new file mode 100644
index 0000000..ace84d3
--- /dev/null
+++ b/testdata/rustler-project/native/rustler_project/src/lib.rs
@@ -0,0 +1 @@
+pub fn fixture() {}