diff --git a/BIBLIOGRAPHY.md b/BIBLIOGRAPHY.md
index 91d7a9a23..6975da8d5 100644
--- a/BIBLIOGRAPHY.md
+++ b/BIBLIOGRAPHY.md
@@ -24,6 +24,7 @@ source code and documentation.
 * URL: https://csrc.nist.gov/projects/cryptographic-module-validation-program/fips-140-3-ig-announcements
 * Referenced from:
   - [examples/basic_deterministic/mldsa_native/custom_no_randomized_config.h](examples/basic_deterministic/mldsa_native/custom_no_randomized_config.h)
+  - [examples/custom_backend/mldsa_native/custom_config.h](examples/custom_backend/mldsa_native/custom_config.h)
   - [examples/monolithic_build/config_44.h](examples/monolithic_build/config_44.h)
   - [examples/monolithic_build/config_65.h](examples/monolithic_build/config_65.h)
   - [examples/monolithic_build/config_87.h](examples/monolithic_build/config_87.h)
@@ -69,6 +70,7 @@ source code and documentation.
 * Referenced from:
   - [README.md](README.md)
   - [examples/basic_deterministic/mldsa_native/custom_no_randomized_config.h](examples/basic_deterministic/mldsa_native/custom_no_randomized_config.h)
+  - [examples/custom_backend/mldsa_native/custom_config.h](examples/custom_backend/mldsa_native/custom_config.h)
   - [examples/monolithic_build/config_44.h](examples/monolithic_build/config_44.h)
   - [examples/monolithic_build/config_65.h](examples/monolithic_build/config_65.h)
   - [examples/monolithic_build/config_87.h](examples/monolithic_build/config_87.h)
@@ -363,6 +365,7 @@ source code and documentation.
   - [examples/bring_your_own_fips202/README.md](examples/bring_your_own_fips202/README.md)
   - [examples/bring_your_own_fips202_static/README.md](examples/bring_your_own_fips202_static/README.md)
   - [examples/bring_your_own_fips202_static/custom_fips202/README.md](examples/bring_your_own_fips202_static/custom_fips202/README.md)
+  - [examples/custom_backend/README.md](examples/custom_backend/README.md)
 
 ### `tweetfips`
 
diff --git a/Makefile b/Makefile
index 55dc7f739..ffa0757cf 100644
--- a/Makefile
+++ b/Makefile
@@ -223,3 +223,4 @@ clean:
 	-make clean -C examples/monolithic_build_multilevel >/dev/null
 	-make clean -C examples/monolithic_build_native >/dev/null
 	-make clean -C examples/monolithic_build_multilevel_native >/dev/null
+	-make clean -C examples/custom_backend >/dev/null
diff --git a/examples/custom_backend/.gitignore b/examples/custom_backend/.gitignore
new file mode 100644
index 000000000..eb98a94f1
--- /dev/null
+++ b/examples/custom_backend/.gitignore
@@ -0,0 +1,3 @@
+# SPDX-License-Identifier: Apache-2.0 OR ISC OR MIT
+
+build
diff --git a/examples/custom_backend/Makefile b/examples/custom_backend/Makefile
new file mode 100644
index 000000000..2bf055cea
--- /dev/null
+++ b/examples/custom_backend/Makefile
@@ -0,0 +1,117 @@
+# Copyright (c) The mldsa-native project authors
+# SPDX-License-Identifier: Apache-2.0 OR ISC OR MIT
+
+.PHONY: build run clean
+.DEFAULT_GOAL := all
+
+CC  ?= gcc
+
+# Adjust CFLAGS if needed
+CFLAGS := \
+	-Wall \
+	-Wextra \
+	-Werror=unused-result \
+	-Wpedantic \
+	-Werror \
+	-Wmissing-prototypes \
+	-Wshadow \
+	-Wpointer-arith \
+	-Wredundant-decls \
+	-Wconversion \
+	-Wsign-conversion \
+	-Wno-long-long \
+	-Wno-unknown-pragmas \
+	-Wno-unused-command-line-argument \
+	-O3 \
+	-fomit-frame-pointer \
+	-std=c99 \
+	-pedantic \
+	-MMD \
+	$(CFLAGS)
+
+# If you want to use the native backends, the compiler needs to know about
+# the target architecture. Here, we import the default host detection from
+# mldsa-native's tests, but you can write your own or specialize accordingly.
+AUTO ?= 1
+include auto.mk
+
+# The following only concerns the cross-compilation tests.
+# You can likely ignore the following for your application.
+#
+# Append cross-prefix for cross compilation
+# When called from the root Makefile, CROSS_PREFIX has already been added here
+ifeq (,$(findstring $(CROSS_PREFIX),$(CC)))
+CC  := $(CROSS_PREFIX)$(CC)
+endif
+
+# Part A:
+#
+# mldsa-native source and header files
+#
+# In this example, we compile the individual mldsa-native source files directly.
+# Alternatively, you can compile the 'monobuild' source file mldsa_native.c.
+# See examples/monolithic_build for that.
+MLD_SOURCE=$(wildcard \
+    mldsa_native/mldsa/src/*.c \
+    mldsa_native/mldsa/src/**/*.c \
+    mldsa_native/mldsa/src/**/**/*.c \
+    mldsa_native/mldsa/src/**/**/**/*.c \
+    mldsa_native/mldsa/src/**/**/**/**/*.c)
+
+INC=-Imldsa_native -Imldsa_native/mldsa
+
+# Part B:
+#
+# Random number generator
+#
+# !!! WARNING !!!
+#
+# The randombytes() implementation used here is for TESTING ONLY.
+# You MUST NOT use this implementation outside of testing.
+#
+# !!! WARNING !!!
+RNG_SOURCE=$(wildcard test_only_rng/*.c)
+
+# Part C:
+#
+# Your application source code
+APP_SOURCE=$(wildcard *.c)
+
+ALL_SOURCE=$(MLD_SOURCE) $(RNG_SOURCE) $(APP_SOURCE)
+
+
+#
+# Configuration adjustments
+#
+
+# Pick custom config file
+CFLAGS+=-DMLD_CONFIG_FILE="\"custom_config.h\""
+
+BUILD_DIR=build
+BIN=test_binary
+
+BINARY_NAME_FULL_44=$(BUILD_DIR)/$(BIN)44
+BINARY_NAME_FULL_65=$(BUILD_DIR)/$(BIN)65
+BINARY_NAME_FULL_87=$(BUILD_DIR)/$(BIN)87
+BINARIES_FULL=$(BINARY_NAME_FULL_44) $(BINARY_NAME_FULL_65) $(BINARY_NAME_FULL_87)
+
+$(BINARY_NAME_FULL_44): CFLAGS += -DMLD_CONFIG_PARAMETER_SET=44
+$(BINARY_NAME_FULL_65): CFLAGS += -DMLD_CONFIG_PARAMETER_SET=65
+$(BINARY_NAME_FULL_87): CFLAGS += -DMLD_CONFIG_PARAMETER_SET=87
+
+$(BINARIES_FULL): $(ALL_SOURCE)
+	echo "$@"
+	mkdir -p $(BUILD_DIR)
+	$(CC) $(CFLAGS) $(INC) $^ -o $@
+
+all: build
+
+build: $(BINARIES_FULL)
+
+run: $(BINARIES_FULL)
+	$(EXEC_WRAPPER) ./$(BINARY_NAME_FULL_44)
+	$(EXEC_WRAPPER) ./$(BINARY_NAME_FULL_65)
+	$(EXEC_WRAPPER) ./$(BINARY_NAME_FULL_87)
+
+clean:
+	rm -rf $(BUILD_DIR)
diff --git a/examples/custom_backend/README.md b/examples/custom_backend/README.md
new file mode 100644
index 000000000..2e7858f5a
--- /dev/null
+++ b/examples/custom_backend/README.md
@@ -0,0 +1,39 @@
+[//]: # (SPDX-License-Identifier: CC-BY-4.0)
+
+# Using a custom configuration and FIPS-202 backend
+
+This directory contains a minimal example for how to use mldsa-native as a code package, with a custom FIPS-202
+backend and a custom configuration. We use [^tiny_sha3] as an example.
+
+## Components
+
+An application using mldsa-native with a custom FIPS-202 backend and custom configuration needs the following:
+
+1. Arithmetic part of the mldsa-native source tree: [`mldsa/src/`](../../mldsa/src). In this example, we disable arithmetic
+   backends, hence it is safe to remove the entire `native` subfolder.
+2. A secure pseudo random number generator, implementing [`randombytes.h`](../../mldsa/src/randombytes.h). **WARNING:** The
+   `randombytes()` implementation used here is for TESTING ONLY. You MUST NOT use this implementation outside of testing.
+3. FIPS-202 part of the mldsa-native source tree, [`fips202/`](../../mldsa/src/fips202). If you only want to use your backend,
+   you can remove all existing backends; that's what this example does.
+4. A custom FIPS-202 backend. In this example, the backend file is
+   [custom.h](mldsa_native/mldsa/src/fips202/native/custom/custom.h), wrapping
+   [sha3.c](mldsa_native/mldsa/src/fips202/native/custom/src/sha3.c) and setting `MLD_USE_FIPS202_X1_NATIVE` to indicate that we
+   replace 1-fold Keccak-F1600.
+5. Either modify the existing [config.h](mldsa_native/mldsa/src/config.h), or register a new config. In this example, we add
+   a new config [custom_config.h](mldsa_native/custom_config.h) and register it from the command line for
+   `-DMLD_CONFIG_FILE="custom_config.h"` -- no further changes to the build are needed. For the sake of
+   demonstration, we set a custom namespace. We set `MLD_CONFIG_FIPS202_BACKEND_FILE` to point to our custom FIPS-202
+   backend, but leave `MLD_CONFIG_USE_NATIVE_BACKEND_ARITH` undefined to indicate that we wish to use the C backend.
+
+## Note
+
+The tiny_sha3 code uses a byte-reversed presentation of the Keccakf1600 state for big-endian targets. Since
+mldsa-native's FIPS202 frontend assumes a standard presentation, the corresponding byte-reversal in
+[sha3.c](mldsa_native/mldsa/src/fips202/native/custom/src/sha3.c) is removed.
+
+## Usage
+
+Build this example with `make build`, run with `make run`.
+
+<!--- bibliography --->
+[^tiny_sha3]: Markku-Juhani O. Saarinen: tiny_sha3, [https://github.com/mjosaarinen/tiny_sha3](https://github.com/mjosaarinen/tiny_sha3)
diff --git a/examples/custom_backend/auto.mk b/examples/custom_backend/auto.mk
new file mode 120000
index 000000000..ce5c161cb
--- /dev/null
+++ b/examples/custom_backend/auto.mk
@@ -0,0 +1 @@
+../../test/mk/auto.mk
\ No newline at end of file
diff --git a/examples/custom_backend/expected_signatures.h b/examples/custom_backend/expected_signatures.h
new file mode 120000
index 000000000..694d65628
--- /dev/null
+++ b/examples/custom_backend/expected_signatures.h
@@ -0,0 +1 @@
+../basic/expected_signatures.h
\ No newline at end of file
diff --git a/examples/custom_backend/main.c b/examples/custom_backend/main.c
new file mode 100644
index 000000000..46a7269f8
--- /dev/null
+++ b/examples/custom_backend/main.c
@@ -0,0 +1,137 @@
+/*
+ * Copyright (c) The mldsa-native project authors
+ * SPDX-License-Identifier: Apache-2.0 OR ISC OR MIT
+ */
+
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+/* Import public mldsa-native API
+ *
+ * This requires specifying the parameter set and namespace prefix
+ * used for the build.
+ */
+#define MLD_CONFIG_API_PARAMETER_SET MLD_CONFIG_PARAMETER_SET
+#define MLD_CONFIG_API_NAMESPACE_PREFIX CUSTOM_TINY_SHA3
+#include <mldsa_native.h>
+#include "expected_signatures.h"
+#include "test_only_rng/notrandombytes.h"
+
+#define CHECK(x)                                              \
+  do                                                          \
+  {                                                           \
+    int rc;                                                   \
+    rc = (x);                                                 \
+    if (!rc)                                                  \
+    {                                                         \
+      fprintf(stderr, "ERROR (%s,%d)\n", __FILE__, __LINE__); \
+      return 1;                                               \
+    }                                                         \
+  } while (0)
+
+#define TEST_MSG \
+  "This is a test message for ML-DSA digital signature algorithm!"
+#define TEST_MSG_LEN (sizeof(TEST_MSG) - 1)
+
+#define TEST_CTX "test_context_123"
+#define TEST_CTX_LEN (sizeof(TEST_CTX) - 1)
+
+int main(void)
+{
+  const char test_msg[] = TEST_MSG;
+  const char test_ctx[] = TEST_CTX;
+
+  uint8_t pk[CRYPTO_PUBLICKEYBYTES];
+  uint8_t sk[CRYPTO_SECRETKEYBYTES];
+  uint8_t sig[CRYPTO_BYTES];
+  uint8_t sm[TEST_MSG_LEN + CRYPTO_BYTES]; /* signed message buffer */
+  uint8_t m2[TEST_MSG_LEN + CRYPTO_BYTES]; /* recovered message buffer */
+  size_t siglen;
+  size_t smlen;
+  size_t mlen;
+
+  /* WARNING: Test-only
+   * Normally, you would want to seed a PRNG with trustworthy entropy here. */
+  randombytes_reset();
+
+  printf("ML-DSA-%d Custom Backend Example\n", MLD_CONFIG_PARAMETER_SET);
+  printf("======================\n\n");
+
+  printf("Message: %s\n", test_msg);
+  printf("Context: %s\n\n", test_ctx);
+
+  printf("Generating keypair ... ");
+
+  /* Alice generates a public/private key pair */
+  CHECK(crypto_sign_keypair(pk, sk) == 0);
+
+  printf("DONE\n");
+  printf("Signing message... ");
+
+  /* Alice signs the message */
+  CHECK(crypto_sign_signature(sig, &siglen, (const uint8_t *)test_msg,
+                              TEST_MSG_LEN, (const uint8_t *)test_ctx,
+                              TEST_CTX_LEN, sk) == 0);
+
+  printf("DONE\n");
+  printf("Verifying signature... ");
+
+  /* Bob verifies Alice's signature */
+  CHECK(crypto_sign_verify(sig, siglen, (const uint8_t *)test_msg, TEST_MSG_LEN,
+                           (const uint8_t *)test_ctx, TEST_CTX_LEN, pk) == 0);
+
+  printf("DONE\n");
+  printf("Creating signed message... ");
+
+  /* Alternative API: Create a signed message (signature + message combined) */
+  CHECK(crypto_sign(sm, &smlen, (const uint8_t *)test_msg, TEST_MSG_LEN,
+                    (const uint8_t *)test_ctx, TEST_CTX_LEN, sk) == 0);
+
+  printf("DONE\n");
+  printf("Opening signed message... ");
+
+  /* Bob opens the signed message to recover the original message */
+  CHECK(crypto_sign_open(m2, &mlen, sm, smlen, (const uint8_t *)test_ctx,
+                         TEST_CTX_LEN, pk) == 0);
+
+  printf("DONE\n");
+  printf("Compare messages... ");
+
+  /* Verify the recovered message matches the original */
+  CHECK(mlen == TEST_MSG_LEN);
+  CHECK(memcmp(test_msg, m2, TEST_MSG_LEN) == 0);
+
+  printf("DONE\n\n");
+
+  printf("Results:\n");
+  printf("--------\n");
+  printf("Public key size:  %d bytes\n", CRYPTO_PUBLICKEYBYTES);
+  printf("Secret key size:  %d bytes\n", CRYPTO_SECRETKEYBYTES);
+  printf("Signature size:   %d bytes\n", CRYPTO_BYTES);
+  printf("Message length:   %lu bytes\n", (unsigned long)TEST_MSG_LEN);
+  printf("Signature length: %lu bytes\n", (unsigned long)siglen);
+  printf("Signed msg length: %lu bytes\n", (unsigned long)smlen);
+
+#if !defined(MLD_CONFIG_KEYGEN_PCT)
+  /* Check against expected signature to make sure that
+   * we integrated the library correctly */
+  printf("Checking deterministic signature... ");
+  {
+    /* Compare the generated signature directly against the expected signature
+     */
+    CHECK(siglen == sizeof(expected_signature));
+    CHECK(memcmp(sig, expected_signature, siglen) == 0);
+  }
+  printf("DONE\n");
+#else  /* !MLD_CONFIG_KEYGEN_PCT */
+  printf(
+      "[WARNING] Skipping KAT test since PCT is enabled and modifies PRNG\n");
+#endif /* MLD_CONFIG_KEYGEN_PCT */
+
+  printf("Signature verification completed successfully!\n");
+
+  printf("\nAll tests passed! ML-DSA signature verification successful.\n");
+  return 0;
+}
diff --git a/examples/custom_backend/mldsa_native/custom_config.h b/examples/custom_backend/mldsa_native/custom_config.h
new file mode 100644
index 000000000..bb28b363e
--- /dev/null
+++ b/examples/custom_backend/mldsa_native/custom_config.h
@@ -0,0 +1,568 @@
+/*
+ * Copyright (c) The mldsa-native project authors
+ * SPDX-License-Identifier: Apache-2.0 OR ISC OR MIT
+ */
+
+/* References
+ * ==========
+ *
+ * - [FIPS140_3_IG]
+ *   Implementation Guidance for FIPS 140-3 and the Cryptographic Module
+ *   Validation Program
+ *   National Institute of Standards and Technology
+ *   https://csrc.nist.gov/projects/cryptographic-module-validation-program/fips-140-3-ig-announcements
+ *
+ * - [FIPS204]
+ *   FIPS 204 Module-Lattice-Based Digital Signature Standard
+ *   National Institute of Standards and Technology
+ *   https://csrc.nist.gov/pubs/fips/204/final
+ */
+
+/*
+ * WARNING: This file is auto-generated from scripts/autogen
+ *          in the mldsa-native repository.
+ *          Do not modify it directly.
+ */
+
+/*
+ * Test configuration: Custom backend config with tiny SHA3
+ *
+ * This configuration differs from the default mldsa/src/config.h in the
+ * following places:
+ *   - MLD_CONFIG_USE_NATIVE_BACKEND_ARITH
+ *   - MLD_CONFIG_NAMESPACE_PREFIX
+ *   - MLD_CONFIG_USE_NATIVE_BACKEND_FIPS202
+ *   - MLD_CONFIG_FIPS202_BACKEND_FILE
+ */
+
+
+#ifndef MLD_CONFIG_H
+#define MLD_CONFIG_H
+
+/******************************************************************************
+ * Name:        MLD_CONFIG_PARAMETER_SET
+ *
+ * Description: Specifies the parameter set for ML-DSA
+ *              - MLD_CONFIG_PARAMETER_SET=44 corresponds to ML-DSA-44
+ *              - MLD_CONFIG_PARAMETER_SET=65 corresponds to ML-DSA-65
+ *              - MLD_CONFIG_PARAMETER_SET=87 corresponds to ML-DSA-87
+ *
+ *              This can also be set using CFLAGS.
+ *
+ *****************************************************************************/
+/* This is set on the command line */
+#ifndef MLD_CONFIG_PARAMETER_SET
+#define MLD_CONFIG_PARAMETER_SET \
+  44 /* Change this for different security strengths */
+#endif
+
+/******************************************************************************
+ * Name:        MLD_CONFIG_NAMESPACE_PREFIX
+ *
+ * Description: The prefix to use to namespace global symbols from mldsa/.
+ *
+ *              In a multi-level build (that is, if either
+ *              - MLD_CONFIG_MULTILEVEL_WITH_SHARED, or
+ *              - MLD_CONFIG_MULTILEVEL_NO_SHARED,
+ *              are set, level-dependent symbols will additionally be prefixed
+ *              with the parameter set (44/65/87).
+ *
+ *              This can also be set using CFLAGS.
+ *
+ *****************************************************************************/
+#define MLD_CONFIG_NAMESPACE_PREFIX CUSTOM_TINY_SHA3
+
+/******************************************************************************
+ * Name:        MLD_CONFIG_MULTILEVEL_WITH_SHARED
+ *
+ * Description: This is for multi-level builds of mldsa-native only. If you
+ *              need only a single parameter set, keep this unset.
+ *
+ *              If this is set, all MLD_CONFIG_PARAMETER_SET-independent
+ *              code will be included in the build, including code needed only
+ *              for other parameter sets.
+ *
+ *              Example: TODO: add example
+ *
+ *              To build mldsa-native with support for all parameter sets,
+ *              build it three times -- once per parameter set -- and set the
+ *              option MLD_CONFIG_MULTILEVEL_WITH_SHARED for exactly one of
+ *              them, and MLD_CONFIG_MULTILEVEL_NO_SHARED for the others.
+ *
+ *              See examples/multilevel_build_mldsa for an example.
+ *
+ *              This can also be set using CFLAGS.
+ *
+ *****************************************************************************/
+/* #define MLD_CONFIG_MULTILEVEL_WITH_SHARED */
+
+/******************************************************************************
+ * Name:        MLD_CONFIG_MULTILEVEL_NO_SHARED
+ *
+ * Description: This is for multi-level builds of mldsa-native only. If you
+ *              need only a single parameter set, keep this unset.
+ *
+ *              If this is set, no MLD_CONFIG_PARAMETER_SET-independent code
+ *              will be included in the build.
+ *
+ *              To build mldsa-native with support for all parameter sets,
+ *              build it three times -- once per parameter set -- and set the
+ *              option MLD_CONFIG_MULTILEVEL_WITH_SHARED for exactly one of
+ *              them, and MLD_CONFIG_MULTILEVEL_NO_SHARED for the others.
+ *
+ *              See examples/multilevel_build_mldsa for an example.
+ *
+ *              This can also be set using CFLAGS.
+ *
+ *****************************************************************************/
+/* #define MLD_CONFIG_MULTILEVEL_NO_SHARED */
+
+/******************************************************************************
+ * Name:        MLD_CONFIG_FILE
+ *
+ * Description: If defined, this is a header that will be included instead
+ *              of the default configuration file mldsa/src/config.h.
+ *
+ *              When you need to build mldsa-native in multiple configurations,
+ *              using varying MLD_CONFIG_FILE can be more convenient
+ *              then configuring everything through CFLAGS.
+ *
+ *              To use, MLD_CONFIG_FILE _must_ be defined prior
+ *              to the inclusion of any mldsa-native headers. For example,
+ *              it can be set by passing `-DMLD_CONFIG_FILE="..."`
+ *              on the command line.
+ *
+ *****************************************************************************/
+/* No need to set this -- we _are_ already in a custom config */
+/* #define MLD_CONFIG_FILE "config.h" */
+
+/******************************************************************************
+ * Name:        MLD_CONFIG_USE_NATIVE_BACKEND_ARITH
+ *
+ * Description: Determines whether an native arithmetic backend should be used.
+ *
+ *              The arithmetic backend covers performance critical functions
+ *              such as the number-theoretic transform (NTT).
+ *
+ *              If this option is unset, the C backend will be used.
+ *
+ *              If this option is set, the arithmetic backend to be use is
+ *              determined by MLD_CONFIG_ARITH_BACKEND_FILE: If the latter is
+ *              unset, the default backend for your the target architecture
+ *              will be used. If set, it must be the name of a backend metadata
+ *              file.
+ *
+ *              This can also be set using CFLAGS.
+ *
+ *****************************************************************************/
+/* No native arithmetic backend */
+/* #define MLD_CONFIG_USE_NATIVE_BACKEND_ARITH */
+
+/******************************************************************************
+ * Name:        MLD_CONFIG_ARITH_BACKEND_FILE
+ *
+ * Description: The arithmetic backend to use.
+ *
+ *              If MLD_CONFIG_USE_NATIVE_BACKEND_ARITH is unset, this option
+ *              is ignored.
+ *
+ *              If MLD_CONFIG_USE_NATIVE_BACKEND_ARITH is set, this option must
+ *              either be undefined or the filename of an arithmetic backend.
+ *              If unset, the default backend will be used.
+ *
+ *              This can be set using CFLAGS.
+ *
+ *****************************************************************************/
+#if defined(MLD_CONFIG_USE_NATIVE_BACKEND_ARITH) && \
+    !defined(MLD_CONFIG_ARITH_BACKEND_FILE)
+#define MLD_CONFIG_ARITH_BACKEND_FILE "native/meta.h"
+#endif
+
+/******************************************************************************
+ * Name:        MLD_CONFIG_USE_NATIVE_BACKEND_FIPS202
+ *
+ * Description: Determines whether an native FIPS202 backend should be used.
+ *
+ *              The FIPS202 backend covers 1x/2x/4x-fold Keccak-f1600, which is
+ *              the performance bottleneck of SHA3 and SHAKE.
+ *
+ *              If this option is unset, the C backend will be used.
+ *
+ *              If this option is set, the FIPS202 backend to be use is
+ *              determined by MLD_CONFIG_FIPS202_BACKEND_FILE: If the latter is
+ *              unset, the default backend for your the target architecture
+ *              will be used. If set, it must be the name of a backend metadata
+ *              file.
+ *
+ *              This can also be set using CFLAGS.
+ *
+ *****************************************************************************/
+#define MLD_CONFIG_USE_NATIVE_BACKEND_FIPS202
+
+/******************************************************************************
+ * Name:        MLD_CONFIG_FIPS202_BACKEND_FILE
+ *
+ * Description: The FIPS-202 backend to use.
+ *
+ *              If MLD_CONFIG_USE_NATIVE_BACKEND_FIPS202 is set, this option
+ *              must either be undefined or the filename of a FIPS202 backend.
+ *              If unset, the default backend will be used.
+ *
+ *              This can be set using CFLAGS.
+ *
+ *****************************************************************************/
+#define MLD_CONFIG_FIPS202_BACKEND_FILE "fips202/native/custom/custom.h"
+/******************************************************************************
+ * Name:        MLD_CONFIG_FIPS202_CUSTOM_HEADER
+ *
+ * Description: Custom header to use for FIPS-202
+ *
+ *              This should only be set if you intend to use a custom
+ *              FIPS-202 implementation, different from the one shipped
+ *              with mldsa-native.
+ *
+ *              If set, it must be the name of a file serving as the
+ *              replacement for mldsa/src/fips202/fips202.h, and exposing
+ *              the same API (see FIPS202.md).
+ *
+ *****************************************************************************/
+/* #define MLD_CONFIG_FIPS202_CUSTOM_HEADER "SOME_FILE.h" */
+
+/******************************************************************************
+ * Name:        MLD_CONFIG_FIPS202X4_CUSTOM_HEADER
+ *
+ * Description: Custom header to use for FIPS-202-X4
+ *
+ *              This should only be set if you intend to use a custom
+ *              FIPS-202 implementation, different from the one shipped
+ *              with mldsa-native.
+ *
+ *              If set, it must be the name of a file serving as the
+ *              replacement for mldsa/src/fips202/fips202x4.h, and exposing
+ *              the same API (see FIPS202.md).
+ *
+ *****************************************************************************/
+/* #define MLD_CONFIG_FIPS202X4_CUSTOM_HEADER "SOME_FILE.h" */
+
+/******************************************************************************
+ * Name:        MLD_CONFIG_CUSTOM_ZEROIZE
+ *
+ * Description: In compliance with @[FIPS204, Section 3.6.3], mldsa-native,
+ *              zeroizes intermediate stack buffers before returning from
+ *              function calls.
+ *
+ *              Set this option and define `mld_zeroize_native` if you want to
+ *              use a custom method to zeroize intermediate stack buffers.
+ *              The default implementation uses SecureZeroMemory on Windows
+ *              and a memset + compiler barrier otherwise. If neither of those
+ *              is available on the target platform, compilation will fail,
+ *              and you will need to use MLD_CONFIG_CUSTOM_ZEROIZE to provide
+ *              a custom implementation of `mld_zeroize_native()`.
+ *
+ *              WARNING:
+ *              The explicit stack zeroization conducted by mldsa-native
+ *              reduces the likelihood of data leaking on the stack, but
+ *              does not eliminate it! The C standard makes no guarantee about
+ *              where a compiler allocates structures and whether/where it makes
+ *              copies of them. Also, in addition to entire structures, there
+ *              may also be potentially exploitable leakage of individual values
+ *              on the stack.
+ *
+ *              If you need bullet-proof zeroization of the stack, you need to
+ *              consider additional measures instead of what this feature
+ *              provides. In this case, you can set mld_zeroize_native to a
+ *              no-op.
+ *
+ *****************************************************************************/
+/* #define MLD_CONFIG_CUSTOM_ZEROIZE
+   #if !defined(__ASSEMBLER__)
+   #include <stdint.h>
+   #include "sys.h"
+   static MLD_INLINE void mld_zeroize_native(void *ptr, size_t len)
+   {
+       ... your implementation ...
+   }
+   #endif
+*/
+
+/******************************************************************************
+ * Name:        MLD_CONFIG_CUSTOM_MEMCPY
+ *
+ * Description: Set this option and define `mld_memcpy` if you want to
+ *              use a custom method to copy memory instead of the standard
+ *              library memcpy function.
+ *
+ *              The custom implementation must have the same signature and
+ *              behavior as the standard memcpy function:
+ *              void *mld_memcpy(void *dest, const void *src, size_t n)
+ *
+ *****************************************************************************/
+/* #define MLD_CONFIG_CUSTOM_MEMCPY
+   #if !defined(__ASSEMBLER__)
+   #include <stdint.h>
+   #include "sys.h"
+   static MLD_INLINE void *mld_memcpy(void *dest, const void *src, size_t n)
+   {
+       ... your implementation ...
+   }
+   #endif
+*/
+
+/******************************************************************************
+ * Name:        MLD_CONFIG_CUSTOM_MEMSET
+ *
+ * Description: Set this option and define `mld_memset` if you want to
+ *              use a custom method to set memory instead of the standard
+ *              library memset function.
+ *
+ *              The custom implementation must have the same signature and
+ *              behavior as the standard memset function:
+ *              void *mld_memset(void *s, int c, size_t n)
+ *
+ *****************************************************************************/
+/* #define MLD_CONFIG_CUSTOM_MEMSET
+   #if !defined(__ASSEMBLER__)
+   #include <stdint.h>
+   #include "sys.h"
+   static MLD_INLINE void *mld_memset(void *s, int c, size_t n)
+   {
+       ... your implementation ...
+   }
+   #endif
+*/
+
+/******************************************************************************
+ * Name:        MLD_CONFIG_CUSTOM_RANDOMBYTES
+ *
+ * Description: mldsa-native does not provide a secure randombytes
+ *              implementation. Such an implementation has to provided by the
+ *              consumer.
+ *
+ *              If this option is not set, mldsa-native expects a function
+ *              void randombytes(uint8_t *out, size_t outlen).
+ *
+ *              Set this option and define `mld_randombytes` if you want to
+ *              use a custom method to sample randombytes with a different name
+ *              or signature.
+ *
+ *****************************************************************************/
+/* #define MLD_CONFIG_CUSTOM_RANDOMBYTES
+   #if !defined(__ASSEMBLER__)
+   #include <stdint.h>
+   #include "sys.h"
+   static MLD_INLINE void mld_randombytes(uint8_t *ptr, size_t len)
+   {
+       ... your implementation ...
+   }
+   #endif
+*/
+
+
+/******************************************************************************
+ * Name:        MLD_CONFIG_CUSTOM_CAPABILITY_FUNC
+ *
+ * Description: mldsa-native backends may rely on specific hardware features.
+ *              Those backends will only be included in an mldsa-native build
+ *              if support for the respective features is enabled at
+ *              compile-time. However, when building for a heteroneous set
+ *              of CPUs to run the resulting binary/library on, feature
+ *              detection at _runtime_ is needed to decided whether a backend
+ *              can be used or not.
+ *
+ *              Set this option and define `mld_sys_check_capability` if you
+ *              want to use a custom method to dispatch between implementations.
+ *
+ *              If this option is not set, mldsa-native uses compile-time
+ *              feature detection only to decide which backend to use.
+ *
+ *              If you compile mldsa-native on a system with different
+ *              capabilities than the system that the resulting binary/library
+ *              will be run on, you must use this option.
+ *
+ *****************************************************************************/
+/* #define MLD_CONFIG_CUSTOM_CAPABILITY_FUNC
+   static MLD_INLINE int mld_sys_check_capability(mld_sys_cap cap)
+   {
+       ... your implementation ...
+   }
+*/
+
+/******************************************************************************
+ * Name:        MLD_CONFIG_NO_RANDOMIZED_API
+ *
+ * Description: If this option is set, mldsa-native will be built without the
+ *              randomized API functions (crypto_sign_keypair,
+ *              crypto_sign, crypto_sign_signature, and
+ *              crypto_sign_signature_extmu).
+ *              This allows users to build mldsa-native without providing a
+ *              randombytes() implementation if they only need the
+ *              internal deterministic API
+ *              (crypto_sign_keypair_internal, crypto_sign_signature_internal).
+ *
+ *              NOTE: This option is incompatible with MLD_CONFIG_KEYGEN_PCT
+ *              as the current PCT implementation requires
+ *              crypto_sign_signature().
+ *
+ *****************************************************************************/
+/* #define MLD_CONFIG_NO_RANDOMIZED_API */
+
+/******************************************************************************
+ * Name:        MLD_CONFIG_KEYGEN_PCT
+ *
+ * Description: Compliance with @[FIPS140_3_IG, p.87] requires a
+ *              Pairwise Consistency Test (PCT) to be carried out on a freshly
+ *              generated keypair before it can be exported.
+ *
+ *              Set this option if such a check should be implemented.
+ *              In this case, crypto_sign_keypair_internal and
+ *              crypto_sign_keypair will return a non-zero error code if the
+ *              PCT failed.
+ *
+ *              NOTE: This feature will drastically lower the performance of
+ *              key generation.
+ *
+ *****************************************************************************/
+/* #define MLD_CONFIG_KEYGEN_PCT */
+
+/******************************************************************************
+ * Name:        MLD_CONFIG_KEYGEN_PCT_BREAKAGE_TEST
+ *
+ * Description: If this option is set, the user must provide a runtime
+ *              function `static inline int mld_break_pct() { ... }` to
+ *              indicate whether the PCT should be made fail.
+ *
+ *              This option only has an effect if MLD_CONFIG_KEYGEN_PCT is set.
+ *
+ *****************************************************************************/
+/* #define MLD_CONFIG_KEYGEN_PCT_BREAKAGE_TEST
+   #if !defined(__ASSEMBLER__)
+   #include "sys.h"
+   static MLD_INLINE int mld_break_pct(void)
+   {
+       ... return 0/1 depending on whether PCT should be broken ...
+   }
+   #endif
+*/
+
+/******************************************************************************
+ * Name:        MLD_CONFIG_INTERNAL_API_QUALIFIER
+ *
+ * Description: If set, this option provides an additional function
+ *              qualifier to be added to declarations of internal API.
+ *
+ *              The primary use case for this option are single-CU builds,
+ *              in which case this option can be set to `static`.
+ *
+ *****************************************************************************/
+/* #define MLD_CONFIG_INTERNAL_API_QUALIFIER */
+
+/******************************************************************************
+ * Name:        MLD_CONFIG_EXTERNAL_API_QUALIFIER
+ *
+ * Description: If set, this option provides an additional function
+ *              qualifier to be added to declarations of mldsa-native's
+ *              public API.
+ *
+ *              The primary use case for this option are single-CU builds
+ *              where the public API exposed by mldsa-native is wrapped by
+ *              another API in the consuming application. In this case,
+ *              even mldsa-native's public API can be marked `static`.
+ *
+ *****************************************************************************/
+/* #define MLD_CONFIG_EXTERNAL_API_QUALIFIER */
+
+/******************************************************************************
+ * Name:        MLD_CONFIG_CT_TESTING_ENABLED
+ *
+ * Description: If set, mldsa-native annotates data as secret / public using
+ *              valgrind's annotations VALGRIND_MAKE_MEM_UNDEFINED and
+ *              VALGRIND_MAKE_MEM_DEFINED, enabling various checks for secret-
+ *              dependent control flow of variable time execution (depending
+ *              on the exact version of valgrind installed).
+ *
+ *****************************************************************************/
+/* #define MLD_CONFIG_CT_TESTING_ENABLED */
+
+/******************************************************************************
+ * Name:        MLD_CONFIG_NO_ASM
+ *
+ * Description: If this option is set, mldsa-native will be built without
+ *              use of native code or inline assembly.
+ *
+ *              By default, inline assembly is used to implement value barriers.
+ *              Without inline assembly, mldsa-native will use a global volatile
+ *              'opt blocker' instead; see ct.h.
+ *
+ *              Inline assembly is also used to implement a secure zeroization
+ *              function on non-Windows platforms. If this option is set and
+ *              the target platform is not Windows, you MUST set
+ *              MLD_CONFIG_CUSTOM_ZEROIZE and provide a custom zeroization
+ *              function.
+ *
+ *              If this option is set, MLD_CONFIG_USE_NATIVE_BACKEND_FIPS202 and
+ *              and MLD_CONFIG_USE_NATIVE_BACKEND_ARITH will be ignored, and no
+ *              native backends will be used.
+ *
+ *****************************************************************************/
+/* #define MLD_CONFIG_NO_ASM */
+
+/******************************************************************************
+ * Name:        MLD_CONFIG_NO_ASM_VALUE_BARRIER
+ *
+ * Description: If this option is set, mldsa-native will be built without
+ *              use of native code or inline assembly for value barriers.
+ *
+ *              By default, inline assembly (if available) is used to implement
+ *              value barriers.
+ *              Without inline assembly, mldsa-native will use a global volatile
+ *              'opt blocker' instead; see ct.h.
+ *
+ *****************************************************************************/
+/* #define MLD_CONFIG_NO_ASM_VALUE_BARRIER */
+
+/******************************************************************************
+ * Name:        MLD_CONFIG_SERIAL_FIPS202_ONLY
+ *
+ * Description: Set this to use a FIPS202 implementation with global state
+ *              that supports only one active Keccak computation at a time
+ *              (e.g. some hardware accelerators).
+ *
+ *              If this option is set, ML-DSA will use FIPS202 operations
+ *              serially, ensuring that only one SHAKE context is active
+ *              at any given time.
+ *
+ *              This allows offloading Keccak computations to a hardware
+ *              accelerator that holds only a single Keccak state locally,
+ *              rather than requiring support for multiple concurrent
+ *              Keccak states.
+ *
+ *              NOTE: Depending on the target CPU, this may reduce
+ *              performance when using software FIPS202 implementations.
+ *              Only enable this when you have to.
+ *
+ *****************************************************************************/
+/* #define MLD_CONFIG_SERIAL_FIPS202_ONLY */
+
+/*************************  Config internals  ********************************/
+
+/* Default namespace
+ *
+ * Don't change this. If you need a different namespace, re-define
+ * MLD_CONFIG_NAMESPACE_PREFIX above instead, and remove the following.
+ *
+ * The default MLDSA namespace is
+ *
+ *   PQCP_MLDSA_NATIVE_MLDSA<LEVEL>_
+ *
+ * e.g., PQCP_MLDSA_NATIVE_MLDSA44_
+ */
+
+#if MLD_CONFIG_PARAMETER_SET == 44
+#define MLD_DEFAULT_NAMESPACE_PREFIX PQCP_MLDSA_NATIVE_MLDSA44
+#elif MLD_CONFIG_PARAMETER_SET == 65
+#define MLD_DEFAULT_NAMESPACE_PREFIX PQCP_MLDSA_NATIVE_MLDSA65
+#elif MLD_CONFIG_PARAMETER_SET == 87
+#define MLD_DEFAULT_NAMESPACE_PREFIX PQCP_MLDSA_NATIVE_MLDSA87
+#endif
+
+#endif /* !MLD_CONFIG_H */
diff --git a/examples/custom_backend/mldsa_native/mldsa/mldsa_native.h b/examples/custom_backend/mldsa_native/mldsa/mldsa_native.h
new file mode 120000
index 000000000..771223a87
--- /dev/null
+++ b/examples/custom_backend/mldsa_native/mldsa/mldsa_native.h
@@ -0,0 +1 @@
+../../../../mldsa/mldsa_native.h
\ No newline at end of file
diff --git a/examples/custom_backend/mldsa_native/mldsa/src/cbmc.h b/examples/custom_backend/mldsa_native/mldsa/src/cbmc.h
new file mode 120000
index 000000000..3bb0397f4
--- /dev/null
+++ b/examples/custom_backend/mldsa_native/mldsa/src/cbmc.h
@@ -0,0 +1 @@
+../../../../../mldsa/src/cbmc.h
\ No newline at end of file
diff --git a/examples/custom_backend/mldsa_native/mldsa/src/common.h b/examples/custom_backend/mldsa_native/mldsa/src/common.h
new file mode 120000
index 000000000..13ce091e1
--- /dev/null
+++ b/examples/custom_backend/mldsa_native/mldsa/src/common.h
@@ -0,0 +1 @@
+../../../../../mldsa/src/common.h
\ No newline at end of file
diff --git a/examples/custom_backend/mldsa_native/mldsa/src/config.h b/examples/custom_backend/mldsa_native/mldsa/src/config.h
new file mode 120000
index 000000000..0082048af
--- /dev/null
+++ b/examples/custom_backend/mldsa_native/mldsa/src/config.h
@@ -0,0 +1 @@
+../../../../../mldsa/src/config.h
\ No newline at end of file
diff --git a/examples/custom_backend/mldsa_native/mldsa/src/ct.c b/examples/custom_backend/mldsa_native/mldsa/src/ct.c
new file mode 120000
index 000000000..de3a51984
--- /dev/null
+++ b/examples/custom_backend/mldsa_native/mldsa/src/ct.c
@@ -0,0 +1 @@
+../../../../../mldsa/src/ct.c
\ No newline at end of file
diff --git a/examples/custom_backend/mldsa_native/mldsa/src/ct.h b/examples/custom_backend/mldsa_native/mldsa/src/ct.h
new file mode 120000
index 000000000..a0baf328e
--- /dev/null
+++ b/examples/custom_backend/mldsa_native/mldsa/src/ct.h
@@ -0,0 +1 @@
+../../../../../mldsa/src/ct.h
\ No newline at end of file
diff --git a/examples/custom_backend/mldsa_native/mldsa/src/debug.c b/examples/custom_backend/mldsa_native/mldsa/src/debug.c
new file mode 120000
index 000000000..ff35fcf68
--- /dev/null
+++ b/examples/custom_backend/mldsa_native/mldsa/src/debug.c
@@ -0,0 +1 @@
+../../../../../mldsa/src/debug.c
\ No newline at end of file
diff --git a/examples/custom_backend/mldsa_native/mldsa/src/debug.h b/examples/custom_backend/mldsa_native/mldsa/src/debug.h
new file mode 120000
index 000000000..cf59a6ce1
--- /dev/null
+++ b/examples/custom_backend/mldsa_native/mldsa/src/debug.h
@@ -0,0 +1 @@
+../../../../../mldsa/src/debug.h
\ No newline at end of file
diff --git a/examples/custom_backend/mldsa_native/mldsa/src/fips202/fips202.c b/examples/custom_backend/mldsa_native/mldsa/src/fips202/fips202.c
new file mode 120000
index 000000000..06d7b07be
--- /dev/null
+++ b/examples/custom_backend/mldsa_native/mldsa/src/fips202/fips202.c
@@ -0,0 +1 @@
+../../../../../../mldsa/src/fips202/fips202.c
\ No newline at end of file
diff --git a/examples/custom_backend/mldsa_native/mldsa/src/fips202/fips202.h b/examples/custom_backend/mldsa_native/mldsa/src/fips202/fips202.h
new file mode 120000
index 000000000..b564c1828
--- /dev/null
+++ b/examples/custom_backend/mldsa_native/mldsa/src/fips202/fips202.h
@@ -0,0 +1 @@
+../../../../../../mldsa/src/fips202/fips202.h
\ No newline at end of file
diff --git a/examples/custom_backend/mldsa_native/mldsa/src/fips202/fips202x4.c b/examples/custom_backend/mldsa_native/mldsa/src/fips202/fips202x4.c
new file mode 120000
index 000000000..21e6e6a49
--- /dev/null
+++ b/examples/custom_backend/mldsa_native/mldsa/src/fips202/fips202x4.c
@@ -0,0 +1 @@
+../../../../../../mldsa/src/fips202/fips202x4.c
\ No newline at end of file
diff --git a/examples/custom_backend/mldsa_native/mldsa/src/fips202/fips202x4.h b/examples/custom_backend/mldsa_native/mldsa/src/fips202/fips202x4.h
new file mode 120000
index 000000000..60f666a21
--- /dev/null
+++ b/examples/custom_backend/mldsa_native/mldsa/src/fips202/fips202x4.h
@@ -0,0 +1 @@
+../../../../../../mldsa/src/fips202/fips202x4.h
\ No newline at end of file
diff --git a/examples/custom_backend/mldsa_native/mldsa/src/fips202/keccakf1600.c b/examples/custom_backend/mldsa_native/mldsa/src/fips202/keccakf1600.c
new file mode 120000
index 000000000..493a4b368
--- /dev/null
+++ b/examples/custom_backend/mldsa_native/mldsa/src/fips202/keccakf1600.c
@@ -0,0 +1 @@
+../../../../../../mldsa/src/fips202/keccakf1600.c
\ No newline at end of file
diff --git a/examples/custom_backend/mldsa_native/mldsa/src/fips202/keccakf1600.h b/examples/custom_backend/mldsa_native/mldsa/src/fips202/keccakf1600.h
new file mode 120000
index 000000000..9fe1baac4
--- /dev/null
+++ b/examples/custom_backend/mldsa_native/mldsa/src/fips202/keccakf1600.h
@@ -0,0 +1 @@
+../../../../../../mldsa/src/fips202/keccakf1600.h
\ No newline at end of file
diff --git a/examples/custom_backend/mldsa_native/mldsa/src/fips202/native/api.h b/examples/custom_backend/mldsa_native/mldsa/src/fips202/native/api.h
new file mode 120000
index 000000000..4aa982866
--- /dev/null
+++ b/examples/custom_backend/mldsa_native/mldsa/src/fips202/native/api.h
@@ -0,0 +1 @@
+../../../../../../../mldsa/src/fips202/native/api.h
\ No newline at end of file
diff --git a/examples/custom_backend/mldsa_native/mldsa/src/fips202/native/custom/custom.h b/examples/custom_backend/mldsa_native/mldsa/src/fips202/native/custom/custom.h
new file mode 100644
index 000000000..afd8a3fd3
--- /dev/null
+++ b/examples/custom_backend/mldsa_native/mldsa/src/fips202/native/custom/custom.h
@@ -0,0 +1,22 @@
+/*
+ * Copyright (c) The mldsa-native project authors
+ * SPDX-License-Identifier: Apache-2.0 OR ISC OR MIT
+ */
+
+#if !defined(MLD_FIPS202_CUSTOM_TINY_SHA3_H)
+#define MLD_FIPS202_CUSTOM_TINY_SHA3_H
+
+#if !defined(__ASSEMBLER__)
+#include "../api.h"
+#include "src/sha3.h"
+/* Replace (single) Keccak-F1600 by tiny-SHA3's */
+#define MLD_USE_FIPS202_X1_NATIVE
+static MLD_INLINE int mld_keccak_f1600_x1_native(uint64_t *state)
+{
+  tiny_sha3_keccakf(state);
+
+  return MLD_NATIVE_FUNC_SUCCESS;
+}
+#endif /* !__ASSEMBLER__ */
+
+#endif /* !MLD_FIPS202_CUSTOM_TINY_SHA3_H */
diff --git a/examples/custom_backend/mldsa_native/mldsa/src/fips202/native/custom/src/LICENSE b/examples/custom_backend/mldsa_native/mldsa/src/fips202/native/custom/src/LICENSE
new file mode 100644
index 000000000..35741e52a
--- /dev/null
+++ b/examples/custom_backend/mldsa_native/mldsa/src/fips202/native/custom/src/LICENSE
@@ -0,0 +1,23 @@
+[//]: # (SPDX-License-Identifier: CC-BY-4.0)
+
+The MIT License (MIT)
+
+Copyright (c) 2015 Markku-Juhani O. Saarinen
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
diff --git a/examples/custom_backend/mldsa_native/mldsa/src/fips202/native/custom/src/README.md b/examples/custom_backend/mldsa_native/mldsa/src/fips202/native/custom/src/README.md
new file mode 100644
index 000000000..38785e462
--- /dev/null
+++ b/examples/custom_backend/mldsa_native/mldsa/src/fips202/native/custom/src/README.md
@@ -0,0 +1,63 @@
+[//]: # (SPDX-License-Identifier: MIT)
+
+# tiny_sha3
+Very small, readable implementation of the FIPS 202 and SHA3 hash function.
+Public domain.
+
+### Updated 27-Dec-15:
+
+Added SHAKE128 and SHAKE256 code and test vectors. The code can actually do
+a XOF of arbitrary size (like "SHAKE512").
+
+
+### Updated 03-Sep-15:
+
+Made the implementation portable. The API is now pretty much the
+same that OpenSSL uses.
+
+
+### Updated 07-Aug-15:
+
+Now that SHA3 spec is out, I've updated the package to match with the
+new padding rules. There is literally one line difference between
+Keccak 3.0 and SHA-3 implementations:
+
+```
+    temp[inlen++] = 0x06;           // XXX Padding Changed from Keccak 3.0
+```
+
+The 0x06 constant there used to be 0x01. But this of course totally
+breaks compatibility and test vectors had to be revised.
+
+SHA-3 Spec: http://nvlpubs.nist.gov/nistpubs/FIPS/NIST.FIPS.202.pdf
+
+Cheers,
+- markku
+
+
+### Original README.TXT from 19-Nov-11:
+
+Hi.
+
+The SHA-3 competition is nearing it's end and I would personally like
+to support Keccak as the winner. I have a PhD in hash function cryptanalysis
+so don't take my word for it, go ahead and look into the code !
+
+Since I couldn't find a *compact* and/or *readable* implementation of Keccak
+anywhere, here's one I cooked up as a service to the curious.
+
+This implementation is intended for study of the algorithm, not for
+production use.
+
+The code works correctly on 64-bit little-endian platforms with gcc.
+Like your Linux box. The main.c module contains self-tests for all
+officially supported hash sizes.
+
+If you're looking for production code, the official multi-megabyte package
+covers everything you could possibly need and too much much more:
+http://keccak.noekeon.org/
+
+Cheers,
+- Markku  19-Nov-11
+
+Dr. Markku-Juhani O. Saarinen <mjos@iki.fi>
diff --git a/examples/custom_backend/mldsa_native/mldsa/src/fips202/native/custom/src/sha3.c b/examples/custom_backend/mldsa_native/mldsa/src/fips202/native/custom/src/sha3.c
new file mode 100644
index 000000000..c7e0910f0
--- /dev/null
+++ b/examples/custom_backend/mldsa_native/mldsa/src/fips202/native/custom/src/sha3.c
@@ -0,0 +1,218 @@
+/* SPDX-License-Identifier: MIT
+ *
+ * sha3.c
+ * 19-Nov-11  Markku-Juhani O. Saarinen <mjos@iki.fi> */
+
+/* Revised 07-Aug-15 to match with official release of FIPS PUB 202 "SHA3" */
+/* Revised 03-Sep-15 for portability + OpenSSL - style API */
+
+#include "sha3.h"
+
+/* update the state with given number of rounds */
+
+void tiny_sha3_keccakf(uint64_t st[25])
+{
+  /* constants */
+  const uint64_t keccakf_rndc[24] = {
+      0x0000000000000001, 0x0000000000008082, 0x800000000000808a,
+      0x8000000080008000, 0x000000000000808b, 0x0000000080000001,
+      0x8000000080008081, 0x8000000000008009, 0x000000000000008a,
+      0x0000000000000088, 0x0000000080008009, 0x000000008000000a,
+      0x000000008000808b, 0x800000000000008b, 0x8000000000008089,
+      0x8000000000008003, 0x8000000000008002, 0x8000000000000080,
+      0x000000000000800a, 0x800000008000000a, 0x8000000080008081,
+      0x8000000000008080, 0x0000000080000001, 0x8000000080008008};
+  const int keccakf_rotc[24] = {1,  3,  6,  10, 15, 21, 28, 36, 45, 55, 2,  14,
+                                27, 41, 56, 8,  25, 43, 62, 18, 39, 61, 20, 44};
+  const int keccakf_piln[24] = {10, 7,  11, 17, 18, 3, 5,  16, 8,  21, 24, 4,
+                                15, 23, 19, 13, 12, 2, 20, 14, 22, 9,  6,  1};
+
+  /* variables */
+  int i, j, r;
+  uint64_t t, bc[5];
+
+  /* NOTE:
+   * This is present in the tiny_sha3 implementation because it uses
+   * a byte-reversed presentation of the Keccakf1600 state for big endian
+   * targets. mldsa-native uses the standard presentation, hence we don't
+   * the reversal here. */
+  /* #if __BYTE_ORDER__ != __ORDER_LITTLE_ENDIAN__ */
+  /*   uint8_t *v; */
+
+  /*   /\* endianness conversion. this is redundant on little-endian targets *\/
+   */
+  /*   for (i = 0; i < 25; i++) */
+  /*   { */
+  /*     v = (uint8_t *)&st[i]; */
+  /*     st[i] = ((uint64_t)v[0]) | (((uint64_t)v[1]) << 8) | */
+  /*             (((uint64_t)v[2]) << 16) | (((uint64_t)v[3]) << 24) | */
+  /*             (((uint64_t)v[4]) << 32) | (((uint64_t)v[5]) << 40) | */
+  /*             (((uint64_t)v[6]) << 48) | (((uint64_t)v[7]) << 56); */
+  /*   } */
+  /* #endif */
+
+  /* actual iteration */
+  for (r = 0; r < KECCAKF_ROUNDS; r++)
+  {
+    /* Theta */
+    for (i = 0; i < 5; i++)
+    {
+      bc[i] = st[i] ^ st[i + 5] ^ st[i + 10] ^ st[i + 15] ^ st[i + 20];
+    }
+
+    for (i = 0; i < 5; i++)
+    {
+      t = bc[(i + 4) % 5] ^ ROTL64(bc[(i + 1) % 5], 1);
+      for (j = 0; j < 25; j += 5)
+      {
+        st[j + i] ^= t;
+      }
+    }
+
+    /* Rho Pi */
+    t = st[1];
+    for (i = 0; i < 24; i++)
+    {
+      j = keccakf_piln[i];
+      bc[0] = st[j];
+      st[j] = ROTL64(t, keccakf_rotc[i]);
+      t = bc[0];
+    }
+
+    /*  Chi */
+    for (j = 0; j < 25; j += 5)
+    {
+      for (i = 0; i < 5; i++)
+      {
+        bc[i] = st[j + i];
+      }
+      for (i = 0; i < 5; i++)
+      {
+        st[j + i] ^= (~bc[(i + 1) % 5]) & bc[(i + 2) % 5];
+      }
+    }
+
+    /*  Iota */
+    st[0] ^= keccakf_rndc[r];
+  }
+  /* NOTE:
+   * This is present in the tiny_sha3 implementation because it uses
+   * a byte-reversed presentation of the Keccakf1600 state for big endian
+   * targets. mldsa-native uses the standard presentation, hence we don't
+   * the reversal here. */
+  /* #if __BYTE_ORDER__ != __ORDER_LITTLE_ENDIAN__ */
+  /*   /\* endianness conversion. this is redundant on little-endian targets *\/
+   */
+  /*   for (i = 0; i < 25; i++) */
+  /*   { */
+  /*     v = (uint8_t *)&st[i]; */
+  /*     t = st[i]; */
+  /*     v[0] = t & 0xFF; */
+  /*     v[1] = (t >> 8) & 0xFF; */
+  /*     v[2] = (t >> 16) & 0xFF; */
+  /*     v[3] = (t >> 24) & 0xFF; */
+  /*     v[4] = (t >> 32) & 0xFF; */
+  /*     v[5] = (t >> 40) & 0xFF; */
+  /*     v[6] = (t >> 48) & 0xFF; */
+  /*     v[7] = (t >> 56) & 0xFF; */
+  /*   } */
+  /* #endif */
+}
+
+/* Initialize the context for SHA3 */
+
+int tiny_sha3_init(sha3_ctx_t *c, int mdlen)
+{
+  int i;
+
+  for (i = 0; i < 25; i++)
+  {
+    c->st.q[i] = 0;
+  }
+  c->mdlen = mdlen;
+  c->rsiz = 200 - 2 * mdlen;
+  c->pt = 0;
+
+  return 1;
+}
+
+/* update state with more data */
+
+int tiny_sha3_update(sha3_ctx_t *c, const void *data, size_t len)
+{
+  size_t i;
+  int j;
+
+  j = c->pt;
+  for (i = 0; i < len; i++)
+  {
+    c->st.b[j++] ^= ((const uint8_t *)data)[i];
+    if (j >= c->rsiz)
+    {
+      tiny_sha3_keccakf(c->st.q);
+      j = 0;
+    }
+  }
+  c->pt = j;
+
+  return 1;
+}
+
+/* finalize and output a hash */
+
+int tiny_sha3_final(void *md, sha3_ctx_t *c)
+{
+  int i;
+
+  c->st.b[c->pt] ^= 0x06;
+  c->st.b[c->rsiz - 1] ^= 0x80;
+  tiny_sha3_keccakf(c->st.q);
+
+  for (i = 0; i < c->mdlen; i++)
+  {
+    ((uint8_t *)md)[i] = c->st.b[i];
+  }
+
+  return 1;
+}
+
+/* compute a SHA-3 hash (md) of given byte length from "in" */
+
+void *tiny_sha3(const void *in, size_t inlen, void *md, int mdlen)
+{
+  sha3_ctx_t sha3;
+
+  tiny_sha3_init(&sha3, mdlen);
+  tiny_sha3_update(&sha3, in, inlen);
+  tiny_sha3_final(md, &sha3);
+
+  return md;
+}
+
+/* SHAKE128 and SHAKE256 extensible-output functionality */
+
+void tiny_shake_xof(sha3_ctx_t *c)
+{
+  c->st.b[c->pt] ^= 0x1F;
+  c->st.b[c->rsiz - 1] ^= 0x80;
+  tiny_sha3_keccakf(c->st.q);
+  c->pt = 0;
+}
+
+void tiny_shake_out(sha3_ctx_t *c, void *out, size_t len)
+{
+  size_t i;
+  int j;
+
+  j = c->pt;
+  for (i = 0; i < len; i++)
+  {
+    if (j >= c->rsiz)
+    {
+      tiny_sha3_keccakf(c->st.q);
+      j = 0;
+    }
+    ((uint8_t *)out)[i] = c->st.b[j++];
+  }
+  c->pt = j;
+}
diff --git a/examples/custom_backend/mldsa_native/mldsa/src/fips202/native/custom/src/sha3.h b/examples/custom_backend/mldsa_native/mldsa/src/fips202/native/custom/src/sha3.h
new file mode 100644
index 000000000..a70c3d352
--- /dev/null
+++ b/examples/custom_backend/mldsa_native/mldsa/src/fips202/native/custom/src/sha3.h
@@ -0,0 +1,50 @@
+/* SPDX-License-Identifier: MIT
+ *
+ * sha3.h
+ * 19-Nov-11  Markku-Juhani O. Saarinen <mjos@iki.fi> */
+
+#ifndef SHA3_H
+#define SHA3_H
+
+#include <stddef.h>
+#include <stdint.h>
+
+#ifndef KECCAKF_ROUNDS
+#define KECCAKF_ROUNDS 24
+#endif
+
+#ifndef ROTL64
+#define ROTL64(x, y) (((x) << (y)) | ((x) >> (64 - (y))))
+#endif
+
+/* state context */
+typedef struct
+{
+  union
+  {                 /* state: */
+    uint8_t b[200]; /* 8-bit bytes */
+    uint64_t q[25]; /* 64-bit words */
+  } st;
+  int pt, rsiz, mdlen; /* these don't overflow */
+} sha3_ctx_t;
+
+/* Compression function. */
+void tiny_sha3_keccakf(uint64_t st[25]);
+
+/* OpenSSL - like interfece */
+int tiny_sha3_init(sha3_ctx_t *c, int mdlen); /* mdlen = hash output in bytes */
+int tiny_sha3_update(sha3_ctx_t *c, const void *data, size_t len);
+int tiny_sha3_final(void *md, sha3_ctx_t *c); /* digest goes to md */
+
+/* compute a sha3 hash (md) of given byte length from "in" */
+void *tiny_sha3(const void *in, size_t inlen, void *md, int mdlen);
+
+/* SHAKE128 and SHAKE256 extensible-output functions */
+#define tiny_shake128_init(c) tiny_sha3_init(c, 16)
+#define tiny_shake256_init(c) tiny_sha3_init(c, 32)
+#define tiny_shake_update tiny_sha3_update
+
+void tiny_shake_xof(sha3_ctx_t *c);
+void tiny_shake_out(sha3_ctx_t *c, void *out, size_t len);
+
+#endif /* !SHA3_H */
diff --git a/examples/custom_backend/mldsa_native/mldsa/src/ntt.c b/examples/custom_backend/mldsa_native/mldsa/src/ntt.c
new file mode 120000
index 000000000..591aae8f1
--- /dev/null
+++ b/examples/custom_backend/mldsa_native/mldsa/src/ntt.c
@@ -0,0 +1 @@
+../../../../../mldsa/src/ntt.c
\ No newline at end of file
diff --git a/examples/custom_backend/mldsa_native/mldsa/src/ntt.h b/examples/custom_backend/mldsa_native/mldsa/src/ntt.h
new file mode 120000
index 000000000..130ce95e9
--- /dev/null
+++ b/examples/custom_backend/mldsa_native/mldsa/src/ntt.h
@@ -0,0 +1 @@
+../../../../../mldsa/src/ntt.h
\ No newline at end of file
diff --git a/examples/custom_backend/mldsa_native/mldsa/src/packing.c b/examples/custom_backend/mldsa_native/mldsa/src/packing.c
new file mode 120000
index 000000000..f9858bbf7
--- /dev/null
+++ b/examples/custom_backend/mldsa_native/mldsa/src/packing.c
@@ -0,0 +1 @@
+../../../../../mldsa/src/packing.c
\ No newline at end of file
diff --git a/examples/custom_backend/mldsa_native/mldsa/src/packing.h b/examples/custom_backend/mldsa_native/mldsa/src/packing.h
new file mode 120000
index 000000000..c2c549970
--- /dev/null
+++ b/examples/custom_backend/mldsa_native/mldsa/src/packing.h
@@ -0,0 +1 @@
+../../../../../mldsa/src/packing.h
\ No newline at end of file
diff --git a/examples/custom_backend/mldsa_native/mldsa/src/params.h b/examples/custom_backend/mldsa_native/mldsa/src/params.h
new file mode 120000
index 000000000..f937b182b
--- /dev/null
+++ b/examples/custom_backend/mldsa_native/mldsa/src/params.h
@@ -0,0 +1 @@
+../../../../../mldsa/src/params.h
\ No newline at end of file
diff --git a/examples/custom_backend/mldsa_native/mldsa/src/poly.c b/examples/custom_backend/mldsa_native/mldsa/src/poly.c
new file mode 120000
index 000000000..80d9cddfb
--- /dev/null
+++ b/examples/custom_backend/mldsa_native/mldsa/src/poly.c
@@ -0,0 +1 @@
+../../../../../mldsa/src/poly.c
\ No newline at end of file
diff --git a/examples/custom_backend/mldsa_native/mldsa/src/poly.h b/examples/custom_backend/mldsa_native/mldsa/src/poly.h
new file mode 120000
index 000000000..d35a25290
--- /dev/null
+++ b/examples/custom_backend/mldsa_native/mldsa/src/poly.h
@@ -0,0 +1 @@
+../../../../../mldsa/src/poly.h
\ No newline at end of file
diff --git a/examples/custom_backend/mldsa_native/mldsa/src/poly_kl.c b/examples/custom_backend/mldsa_native/mldsa/src/poly_kl.c
new file mode 120000
index 000000000..3e06c6042
--- /dev/null
+++ b/examples/custom_backend/mldsa_native/mldsa/src/poly_kl.c
@@ -0,0 +1 @@
+../../../../../mldsa/src/poly_kl.c
\ No newline at end of file
diff --git a/examples/custom_backend/mldsa_native/mldsa/src/poly_kl.h b/examples/custom_backend/mldsa_native/mldsa/src/poly_kl.h
new file mode 120000
index 000000000..58915edbd
--- /dev/null
+++ b/examples/custom_backend/mldsa_native/mldsa/src/poly_kl.h
@@ -0,0 +1 @@
+../../../../../mldsa/src/poly_kl.h
\ No newline at end of file
diff --git a/examples/custom_backend/mldsa_native/mldsa/src/polyvec.c b/examples/custom_backend/mldsa_native/mldsa/src/polyvec.c
new file mode 120000
index 000000000..811e00ff7
--- /dev/null
+++ b/examples/custom_backend/mldsa_native/mldsa/src/polyvec.c
@@ -0,0 +1 @@
+../../../../../mldsa/src/polyvec.c
\ No newline at end of file
diff --git a/examples/custom_backend/mldsa_native/mldsa/src/polyvec.h b/examples/custom_backend/mldsa_native/mldsa/src/polyvec.h
new file mode 120000
index 000000000..21c07b544
--- /dev/null
+++ b/examples/custom_backend/mldsa_native/mldsa/src/polyvec.h
@@ -0,0 +1 @@
+../../../../../mldsa/src/polyvec.h
\ No newline at end of file
diff --git a/examples/custom_backend/mldsa_native/mldsa/src/randombytes.h b/examples/custom_backend/mldsa_native/mldsa/src/randombytes.h
new file mode 120000
index 000000000..62f18cd46
--- /dev/null
+++ b/examples/custom_backend/mldsa_native/mldsa/src/randombytes.h
@@ -0,0 +1 @@
+../../../../../mldsa/src/randombytes.h
\ No newline at end of file
diff --git a/examples/custom_backend/mldsa_native/mldsa/src/reduce.h b/examples/custom_backend/mldsa_native/mldsa/src/reduce.h
new file mode 120000
index 000000000..eff62136f
--- /dev/null
+++ b/examples/custom_backend/mldsa_native/mldsa/src/reduce.h
@@ -0,0 +1 @@
+../../../../../mldsa/src/reduce.h
\ No newline at end of file
diff --git a/examples/custom_backend/mldsa_native/mldsa/src/rounding.h b/examples/custom_backend/mldsa_native/mldsa/src/rounding.h
new file mode 120000
index 000000000..245ec8a8b
--- /dev/null
+++ b/examples/custom_backend/mldsa_native/mldsa/src/rounding.h
@@ -0,0 +1 @@
+../../../../../mldsa/src/rounding.h
\ No newline at end of file
diff --git a/examples/custom_backend/mldsa_native/mldsa/src/sign.c b/examples/custom_backend/mldsa_native/mldsa/src/sign.c
new file mode 120000
index 000000000..1363c3296
--- /dev/null
+++ b/examples/custom_backend/mldsa_native/mldsa/src/sign.c
@@ -0,0 +1 @@
+../../../../../mldsa/src/sign.c
\ No newline at end of file
diff --git a/examples/custom_backend/mldsa_native/mldsa/src/sign.h b/examples/custom_backend/mldsa_native/mldsa/src/sign.h
new file mode 120000
index 000000000..1a2f09b39
--- /dev/null
+++ b/examples/custom_backend/mldsa_native/mldsa/src/sign.h
@@ -0,0 +1 @@
+../../../../../mldsa/src/sign.h
\ No newline at end of file
diff --git a/examples/custom_backend/mldsa_native/mldsa/src/symmetric.h b/examples/custom_backend/mldsa_native/mldsa/src/symmetric.h
new file mode 120000
index 000000000..5ac08bdb5
--- /dev/null
+++ b/examples/custom_backend/mldsa_native/mldsa/src/symmetric.h
@@ -0,0 +1 @@
+../../../../../mldsa/src/symmetric.h
\ No newline at end of file
diff --git a/examples/custom_backend/mldsa_native/mldsa/src/sys.h b/examples/custom_backend/mldsa_native/mldsa/src/sys.h
new file mode 120000
index 000000000..9aeae3de5
--- /dev/null
+++ b/examples/custom_backend/mldsa_native/mldsa/src/sys.h
@@ -0,0 +1 @@
+../../../../../mldsa/src/sys.h
\ No newline at end of file
diff --git a/examples/custom_backend/mldsa_native/mldsa/src/zetas.inc b/examples/custom_backend/mldsa_native/mldsa/src/zetas.inc
new file mode 120000
index 000000000..d1703f74e
--- /dev/null
+++ b/examples/custom_backend/mldsa_native/mldsa/src/zetas.inc
@@ -0,0 +1 @@
+../../../../../mldsa/src/zetas.inc
\ No newline at end of file
diff --git a/examples/custom_backend/test_only_rng/notrandombytes.c b/examples/custom_backend/test_only_rng/notrandombytes.c
new file mode 120000
index 000000000..65b7801b8
--- /dev/null
+++ b/examples/custom_backend/test_only_rng/notrandombytes.c
@@ -0,0 +1 @@
+../../../test/notrandombytes/notrandombytes.c
\ No newline at end of file
diff --git a/examples/custom_backend/test_only_rng/notrandombytes.h b/examples/custom_backend/test_only_rng/notrandombytes.h
new file mode 120000
index 000000000..e72c12b9c
--- /dev/null
+++ b/examples/custom_backend/test_only_rng/notrandombytes.h
@@ -0,0 +1 @@
+../../../test/notrandombytes/notrandombytes.h
\ No newline at end of file
diff --git a/scripts/lint b/scripts/lint
index 175fcfac5..4b749386f 100755
--- a/scripts/lint
+++ b/scripts/lint
@@ -157,7 +157,7 @@ check-spdx()
       success=false
     fi
   done
-  for file in $(git ls-files -- "*.[chsS]" "*.py" "*.mk" "*.yml" "**/Makefile*" ":/!proofs/cbmc/*.py" ":/!examples/bring_your_own_fips202/custom_fips202/tiny_sha3/*"); do
+  for file in $(git ls-files -- "*.[chsS]" "*.py" "*.mk" "*.yml" "**/Makefile*" ":/!proofs/cbmc/*.py" ":/!examples/bring_your_own_fips202/custom_fips202/tiny_sha3/*" ":/!examples/custom_backend/mldsa_native/mldsa/src/fips202/native/custom/src/*"); do
     # Ignore symlinks
     if [[ ! -L $file && $(grep "Copyright (c) The mldsa-native project authors" $file | wc -l) == 0 ]]; then
       gh_error "$file" "${line:-1}" "Missing copyright header error" "$file is missing copyright header"
diff --git a/scripts/tests b/scripts/tests
index 1be4894a7..221fa6b7b 100755
--- a/scripts/tests
+++ b/scripts/tests
@@ -208,6 +208,7 @@ class TEST_TYPES(Enum):
     BRING_YOUR_OWN_FIPS202_STATIC = 13
     MONOLITHIC_BUILD_NATIVE = 14
     MONOLITHIC_BUILD_MULTILEVEL_NATIVE = 15
+    CUSTOM_BACKEND = 16
 
     def is_benchmark(self):
         return self in [TEST_TYPES.BENCH, TEST_TYPES.BENCH_COMPONENTS]
@@ -226,6 +227,7 @@ class TEST_TYPES(Enum):
             TEST_TYPES.BRING_YOUR_OWN_FIPS202_STATIC,
             TEST_TYPES.MONOLITHIC_BUILD_NATIVE,
             TEST_TYPES.MONOLITHIC_BUILD_MULTILEVEL_NATIVE,
+            TEST_TYPES.CUSTOM_BACKEND,
         ]
 
     @staticmethod
@@ -271,6 +273,8 @@ class TEST_TYPES(Enum):
             return "Example (monobuild with native)"
         if self == TEST_TYPES.MONOLITHIC_BUILD_MULTILEVEL_NATIVE:
             return "Example (monobuild, multilevel with native)"
+        if self == TEST_TYPES.CUSTOM_BACKEND:
+            return "Example (Custom Backend)"
 
     def make_dir(self):
         if self == TEST_TYPES.BASIC:
@@ -289,6 +293,8 @@ class TEST_TYPES(Enum):
             return "examples/monolithic_build_native"
         if self == TEST_TYPES.MONOLITHIC_BUILD_MULTILEVEL_NATIVE:
             return "examples/monolithic_build_multilevel_native"
+        if self == TEST_TYPES.CUSTOM_BACKEND:
+            return "examples/custom_backend"
         return ""
 
     def make_target(self):
@@ -322,6 +328,8 @@ class TEST_TYPES(Enum):
             return ""
         if self == TEST_TYPES.MONOLITHIC_BUILD_MULTILEVEL_NATIVE:
             return ""
+        if self == TEST_TYPES.CUSTOM_BACKEND:
+            return ""
 
     def make_run_target(self, scheme):
         t = self.make_target()
@@ -1100,7 +1108,7 @@ def cli():
         choices=[
             "bring_your_own_fips202",
             "bring_your_own_fips202_static",
-            # "custom_backend",
+            "custom_backend",
             "basic",
             "basic_deterministic",
             "monolithic_build",
@@ -1156,6 +1164,7 @@ def cli():
             "bring_your_own_fips202_static",
             "monolithic_build_native",
             "monolithic_build_multilevel_native",
+            "custom_backend",
         ],
         action="append",
     )
diff --git a/test/configs.yml b/test/configs.yml
index 45b5660e9..fd0b7f7b6 100644
--- a/test/configs.yml
+++ b/test/configs.yml
@@ -379,6 +379,20 @@ configs:
           }
           #endif /* !__ASSEMBLER__ */
 
+  - path: examples/custom_backend/mldsa_native/custom_config.h
+    description: "Custom backend config with tiny SHA3"
+    defines:
+      MLD_CONFIG_PARAMETER_SET:
+        comment: "/* This is set on the command line */"
+      MLD_CONFIG_USE_NATIVE_BACKEND_ARITH:
+        comment: "/* No native arithmetic backend */"
+        value: false
+      MLD_CONFIG_NAMESPACE_PREFIX: CUSTOM_TINY_SHA3
+      MLD_CONFIG_USE_NATIVE_BACKEND_FIPS202: true
+      MLD_CONFIG_FIPS202_BACKEND_FILE: '"fips202/native/custom/custom.h"'
+      MLD_CONFIG_FILE:
+        comment: "/* No need to set this -- we _are_ already in a custom config */"
+
   - path: examples/basic_deterministic/mldsa_native/custom_no_randomized_config.h
     description: "Config without randomized API"
     defines: