diff --git a/.gitignore b/.gitignore
index 65d8d32..df15b77 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,5 +1,13 @@
 syntax: glob
 
+# Misc
+/.direnv
+/.envrc
+
+# Bazel
+bazel-*
+MODULE.bazel.lock
+
 # Temporary, cache, swap files
 \#\#* 
 *.swp
diff --git a/BUILD.bazel b/BUILD.bazel
index a6cd021..a66fae7 100644
--- a/BUILD.bazel
+++ b/BUILD.bazel
@@ -6,11 +6,3 @@ cc_library(
     strip_include_prefix = "include",
     visibility = ["//visibility:public"],
 )
-
-load("@rules_fuzzing//fuzzing:cc_defs.bzl", "cc_fuzz_test")
-
-cc_fuzz_test(
-    name = "cxxopts_fuzz_test",
-    srcs = ["test/fuzz.cpp"],
-    deps = [":cxxopts"],
-)
\ No newline at end of file
diff --git a/MODULE.bazel b/MODULE.bazel
new file mode 100644
index 0000000..482681e
--- /dev/null
+++ b/MODULE.bazel
@@ -0,0 +1,7 @@
+module(
+    name = "cxxopts",
+    version = "3.2.0",
+    compatibility_level = 0,
+)
+
+bazel_dep(name = "rules_cc", version = "0.1.1")
diff --git a/WORKSPACE b/WORKSPACE
deleted file mode 100644
index 6a0fa27..0000000
--- a/WORKSPACE
+++ /dev/null
@@ -1,16 +0,0 @@
-load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")
-
-http_archive(
-    name = "rules_fuzzing",
-    sha256 = "d9002dd3cd6437017f08593124fdd1b13b3473c7b929ceb0e60d317cb9346118",
-    strip_prefix = "rules_fuzzing-0.3.2",
-    urls = ["https://github.com/bazelbuild/rules_fuzzing/archive/v0.3.2.zip"],
-)
-
-load("@rules_fuzzing//fuzzing:repositories.bzl", "rules_fuzzing_dependencies")
-
-rules_fuzzing_dependencies()
-
-load("@rules_fuzzing//fuzzing:init.bzl", "rules_fuzzing_init")
-
-rules_fuzzing_init()
diff --git a/flake.lock b/flake.lock
new file mode 100644
index 0000000..376925f
--- /dev/null
+++ b/flake.lock
@@ -0,0 +1,61 @@
+{
+  "nodes": {
+    "flake-utils": {
+      "inputs": {
+        "systems": "systems"
+      },
+      "locked": {
+        "lastModified": 1731533236,
+        "narHash": "sha256-l0KFg5HjrsfsO/JpG+r7fRrqm12kzFHyUHqHCVpMMbI=",
+        "owner": "numtide",
+        "repo": "flake-utils",
+        "rev": "11707dc2f618dd54ca8739b309ec4fc024de578b",
+        "type": "github"
+      },
+      "original": {
+        "owner": "numtide",
+        "repo": "flake-utils",
+        "type": "github"
+      }
+    },
+    "nixpkgs": {
+      "locked": {
+        "lastModified": 1743583204,
+        "narHash": "sha256-F7n4+KOIfWrwoQjXrL2wD9RhFYLs2/GGe/MQY1sSdlE=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "2c8d3f48d33929642c1c12cd243df4cc7d2ce434",
+        "type": "github"
+      },
+      "original": {
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "2c8d3f48d33929642c1c12cd243df4cc7d2ce434",
+        "type": "github"
+      }
+    },
+    "root": {
+      "inputs": {
+        "flake-utils": "flake-utils",
+        "nixpkgs": "nixpkgs"
+      }
+    },
+    "systems": {
+      "locked": {
+        "lastModified": 1681028828,
+        "narHash": "sha256-Vy1rq5AaRuLzOxct8nz4T6wlgyUR7zLU309k9mBC768=",
+        "owner": "nix-systems",
+        "repo": "default",
+        "rev": "da67096a3b9bf56a91d16901293e51ba5b49a27e",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nix-systems",
+        "repo": "default",
+        "type": "github"
+      }
+    }
+  },
+  "root": "root",
+  "version": 7
+}
diff --git a/flake.nix b/flake.nix
new file mode 100644
index 0000000..879c5ea
--- /dev/null
+++ b/flake.nix
@@ -0,0 +1,164 @@
+{
+  description = "fpga-assembler";
+
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs/2c8d3f48d33929642c1c12cd243df4cc7d2ce434";
+    flake-utils.url = "github:numtide/flake-utils";
+  };
+
+  outputs =
+    {
+      self,
+      nixpkgs,
+      flake-utils,
+    }@inputs:
+    flake-utils.lib.eachDefaultSystem (
+      system:
+      let
+        pkgs = import nixpkgs {
+          inherit system;
+        };
+        common = with pkgs; {
+          bazel = bazel_7;
+          jdk = jdk;
+        };
+      in
+      {
+        devShells.default =
+          let
+            # There is too much volatility between even micro-versions of
+            # newer clang-format. Use slightly older version for now.
+            clang_for_formatting = pkgs.llvmPackages_17.clang-tools;
+
+            # clang tidy: use latest.
+            clang_for_tidy = pkgs.llvmPackages_18.clang-tools;
+          in
+          with pkgs;
+          pkgs.mkShell {
+            packages = with pkgs; [
+              git
+              common.bazel
+              common.jdk
+              bash
+              gdb
+
+              # For clang-tidy and clang-format.
+              clang_for_formatting
+              clang_for_tidy
+
+              # For buildifier, buildozer.
+              bazel-buildtools
+              bant
+
+              # Profiling and sanitizers.
+              linuxPackages_latest.perf
+              pprof
+              perf_data_converter
+              valgrind
+
+              # FPGA utils.
+              openfpgaloader
+            ];
+
+            CLANG_TIDY = "${clang_for_tidy}/bin/clang-tidy";
+            CLANG_FORMAT = "${clang_for_formatting}/bin/clang-format";
+
+            shellHook = ''
+              exec bash
+            '';
+          };
+
+        # Package fpga-assembler.
+        packages.default =
+          (pkgs.callPackage (
+            {
+              buildBazelPackage,
+              stdenv,
+              fetchFromGitHub,
+              lib,
+              nix-gitignore,
+            }:
+            let
+              system = stdenv.hostPlatform.system;
+              registry = fetchFromGitHub {
+                owner = "bazelbuild";
+                repo = "bazel-central-registry";
+                rev = "63f3af762b2fdd7acaa7987856cd3ac314eaea09";
+                hash = "sha256-ugNzoP0gdrhl9vH1TRdwoevuTsSqjitXnAoMSSTlCgI=";
+              };
+            in
+            buildBazelPackage {
+              pname = "fpga-as";
+
+              version = "0.0.1";
+
+              src = nix-gitignore.gitignoreSourcePure [ ] ./.;
+
+              bazelFlags = [
+                "--registry"
+                "file://${registry}"
+              ];
+
+              postPatch = ''
+                patchShebangs scripts/create-workspace-status.sh
+              '';
+
+              fetchAttrs = {
+                hash =
+                  {
+                    aarch64-linux = "sha256-E4VHjDa0qkHmKUNpTBfJi7dhMLcd1z5he+p31/XvUl8=";
+                    x86_64-linux = "sha256-hVBJB0Hsd9sXuEoNcjhTkbPl89vlZT1w39JppCD+n8Y=";
+                  }
+                  .${system} or (throw "No hash for system: ${system}");
+              };
+
+              removeRulesCC = false;
+              removeLocalConfigCc = false;
+              removeLocalConfigSh = false;
+
+              nativeBuildInputs = [
+                common.jdk
+                pkgs.git
+                pkgs.bash
+                # Convenient tool to enter into the sandbox and start debugging.
+                pkgs.breakpointHook
+              ];
+
+              bazel = common.bazel;
+
+              bazelBuildFlags = [ "-c opt" ];
+              bazelTestTargets = [ "//..." ];
+              bazelTargets = [ "//fpga:fpga-as" ];
+
+              buildAttrs = {
+                installPhase = ''
+                  install -D --strip bazel-bin/fpga/fpga-as "$out/bin/fpga-as"
+                '';
+              };
+
+              meta = {
+                description = "Tool to convert FASM to FPGA bitstream.";
+                homepage = "https://github.com/lromor/fpga-assembler";
+                license = lib.licenses.asl20;
+                platforms = lib.platforms.linux;
+              };
+            }
+          ) { }).overrideAttrs
+            (
+              final: prev: {
+                # Fixup the deps so they always contain correrct
+                # shebangs paths pointing to the store.
+                deps = prev.deps.overrideAttrs (
+                  final: prev: {
+                    installPhase =
+                      ''
+                        patchShebangs $bazelOut/external
+                      ''
+                      + prev.installPhase;
+                  }
+                );
+              }
+            );
+      }
+    );
+}