diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index cbeee39..9367d6a 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -113,6 +113,13 @@ jobs:
             echo "❌ build/crypto.lua missing"
             exit 1
           fi
+          # Check portable build (all dependencies bundled)
+          if [ -f "build/crypto-portable.lua" ]; then
+            echo "✅ build/crypto-portable.lua exists ($(wc -c < "build/crypto-portable.lua") bytes)"
+          else
+            echo "❌ build/crypto-portable.lua missing"
+            exit 1
+          fi
 
       - name: Upload artifacts
         uses: actions/upload-artifact@v4
diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
index d4d3103..f4cf9fd 100644
--- a/.github/workflows/release.yml
+++ b/.github/workflows/release.yml
@@ -45,3 +45,4 @@ jobs:
           generate_release_notes: true
           files: |
             build/crypto.lua
+            build/crypto-portable.lua
diff --git a/CLAUDE.md b/CLAUDE.md
index 7a86adb..ce703e1 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -90,13 +90,19 @@ make test-matrix            # across Lua 5.1–5.4 + LuaJIT
 
 ## Building
 
-`amalg` produces a single-file distribution from `src/crypto/init.lua`:
+`amalg` produces two single-file distributions from `src/crypto/init.lua`:
 
 ```bash
-make build          # Output: build/crypto.lua (bitn bundled in)
+make build          # Output: build/crypto.lua          (core; bitn excluded via `-i bitn`)
+                    #         build/crypto-portable.lua  (all dependencies bundled)
 ```
 
-Version is automatically injected from git tags during release.
+`crypto.lua` is the **canonical core build**: it excludes `bitn` and expects it
+on the Lua path, so it composes with other libraries that share `bitn` without
+duplicating it (e.g. lua-noiseprotocol vendors this as `vendor/crypto.lua`
+alongside its own `vendor/bitn.lua`). `crypto-portable.lua` bundles every
+dependency for a single drop-in file with zero external requires. Version is
+injected from git tags during release.
 
 ## CI/CD
 
diff --git a/Makefile b/Makefile
index e1cc88f..65ef503 100644
--- a/Makefile
+++ b/Makefile
@@ -66,19 +66,23 @@ build/amalg.cache: src/crypto/init.lua
 build: build/amalg.cache
 	@echo "Building single-file distribution..."
 	@if command -v amalg.lua >/dev/null 2>&1; then \
-		LUA_PATH="$(LUA_PATH_LOCAL)" amalg.lua -o build/crypto.lua -C ./build/amalg.cache || exit 1;\
-		echo "Built build/crypto.lua"; \
+		LUA_PATH="$(LUA_PATH_LOCAL)" amalg.lua -o build/crypto.lua -C ./build/amalg.cache -i "bitn" || exit 1;\
+		echo "Built build/crypto.lua (core; bitn excluded, expected on the path)"; \
+		LUA_PATH="$(LUA_PATH_LOCAL)" amalg.lua -o build/crypto-portable.lua -C ./build/amalg.cache || exit 1; \
+		echo "Built build/crypto-portable.lua (portable; all dependencies bundled)"; \
 		VERSION=$$(git describe --exact-match --tags 2>/dev/null || echo "dev"); \
 		if [ "$$VERSION" != "dev" ]; then \
 			echo "Injecting version $$VERSION..."; \
 			sed -i.bak 's/VERSION = "dev"/VERSION = "'$$VERSION'"/' build/crypto.lua && rm build/crypto.lua.bak; \
+			sed -i.bak 's/VERSION = "dev"/VERSION = "'$$VERSION'"/' build/crypto-portable.lua && rm build/crypto-portable.lua.bak; \
 		fi; \
 		echo "Testing version function..."; \
-		LUA_VERSION=$$(lua -e 'local b = require("build.crypto"); print(b.version())' 2>/dev/null || echo "test failed"); \
-		if [ "$$LUA_VERSION" = "$$VERSION" ]; then \
-			echo "Version correctly set to: $$VERSION"; \
+		CORE_VERSION=$$(LUA_PATH="$(LUA_PATH_LOCAL)" lua -e 'local b = require("build.crypto"); print(b.version())' 2>/dev/null || echo "test failed"); \
+		PORTABLE_VERSION=$$(LUA_PATH="$(LUA_PATH_LOCAL)" lua -e 'local b = require("build.crypto-portable"); print(b.version())' 2>/dev/null || echo "test failed"); \
+		if [ "$$CORE_VERSION" = "$$VERSION" ] && [ "$$PORTABLE_VERSION" = "$$VERSION" ]; then \
+			echo "Version correctly set to: $$VERSION (core + portable)"; \
 		else \
-			echo "Version test failed. Expected: $$VERSION, Got: $$LUA_VERSION"; \
+			echo "Version test failed. Expected: $$VERSION, core: $$CORE_VERSION, portable: $$PORTABLE_VERSION"; \
 		fi; \
 	else \
 		echo "Error: amalg not found."; \
diff --git a/README.md b/README.md
index 5167051..e381b68 100644
--- a/README.md
+++ b/README.md
@@ -55,8 +55,12 @@ pure-Lua implementations** regardless of this flag, because the shipped
 Download a pre-built single-file module from the
 [Releases](https://github.com/finitelabs/lua-crypto/releases) page:
 
-- **`crypto.lua`** — complete bundle with all dependencies included (zero
-  external dependencies)
+- **`crypto.lua`** — the canonical **core** build. Requires `bitn`
+  ([lua-bitn](https://github.com/finitelabs/lua-bitn)) on the Lua path. Use this
+  when composing with other libraries that already provide `bitn`, so the shared
+  dependency is vendored only once.
+- **`crypto-portable.lua`** — **portable** build with every dependency bundled
+  in (zero external dependencies). Use this when you want a single drop-in file.
 
 ### Option 2: From Source
 
@@ -87,11 +91,11 @@ local tag = crypto.sha256.hmac_sha256_hex(key, message)
 local sealed = crypto.chacha20_poly1305.encrypt(key, nonce, plaintext, aad)
 local opened = crypto.chacha20_poly1305.decrypt(key, nonce, sealed, aad)
 
--- Diffie-Hellman (X25519)
-local alice = crypto.x25519.generate_keypair()
-local bob = crypto.x25519.generate_keypair()
-local shared_a = crypto.x25519.diffie_hellman(alice.private_key, bob.public_key)
-local shared_b = crypto.x25519.diffie_hellman(bob.private_key, alice.public_key)
+-- Diffie-Hellman (X25519); generate_keypair() returns private, public
+local alice_priv, alice_pub = crypto.x25519.generate_keypair()
+local bob_priv, bob_pub = crypto.x25519.generate_keypair()
+local shared_a = crypto.x25519.diffie_hellman(alice_priv, bob_pub)
+local shared_b = crypto.x25519.diffie_hellman(bob_priv, alice_pub)
 assert(shared_a == shared_b)
 ```