diff --git a/flake.lock b/flake.lock
new file mode 100644
index 00000000..cfb7a8b6
--- /dev/null
+++ b/flake.lock
@@ -0,0 +1,82 @@
+{
+  "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": 1777268161,
+        "narHash": "sha256-bxrdOn8SCOv8tN4JbTF/TXq7kjo9ag4M+C8yzzIRYbE=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "1c3fe55ad329cbcb28471bb30f05c9827f724c76",
+        "type": "github"
+      },
+      "original": {
+        "owner": "NixOS",
+        "ref": "nixos-unstable",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
+    "root": {
+      "inputs": {
+        "flake-utils": "flake-utils",
+        "nixpkgs": "nixpkgs",
+        "rust-overlay": "rust-overlay"
+      }
+    },
+    "rust-overlay": {
+      "inputs": {
+        "nixpkgs": [
+          "nixpkgs"
+        ]
+      },
+      "locked": {
+        "lastModified": 1777605393,
+        "narHash": "sha256-Hjp0VOOHgHcTrX23iVvnfAudPcuCmfkfpQNFwv2v/ks=",
+        "owner": "oxalica",
+        "repo": "rust-overlay",
+        "rev": "ff88db34cfa486fc4964a6991cab1678d82eee8c",
+        "type": "github"
+      },
+      "original": {
+        "owner": "oxalica",
+        "repo": "rust-overlay",
+        "type": "github"
+      }
+    },
+    "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 00000000..e04a1ff8
--- /dev/null
+++ b/flake.nix
@@ -0,0 +1,43 @@
+{
+  description = "WalletKit development shells";
+
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
+    flake-utils.url = "github:numtide/flake-utils";
+    rust-overlay.url = "github:oxalica/rust-overlay";
+    rust-overlay.inputs.nixpkgs.follows = "nixpkgs";
+  };
+
+  outputs = { nixpkgs, flake-utils, rust-overlay, ... }:
+    flake-utils.lib.eachSystem [
+      "x86_64-linux"
+      "aarch64-darwin"
+      "x86_64-darwin"
+    ] (system:
+      let
+        overlays = [ (import rust-overlay) ];
+        pkgs = import nixpkgs {
+          inherit system overlays;
+          config = {
+            allowUnfree = true;
+            android_sdk.accept_license = true;
+          };
+        };
+
+        rustToolchain = pkgs.rust-bin.fromRustupToolchainFile ./rust-toolchain.toml;
+      in
+      {
+        devShells = {
+          default = pkgs.mkShell {
+            packages = [
+              rustToolchain
+              pkgs.curl
+              pkgs.git
+            ];
+          };
+
+          android = import ./nix/android.nix { inherit pkgs; };
+          wasm = import ./nix/wasm.nix { inherit pkgs; };
+        };
+      });
+}
diff --git a/nix/android.nix b/nix/android.nix
new file mode 100644
index 00000000..abd327ad
--- /dev/null
+++ b/nix/android.nix
@@ -0,0 +1,74 @@
+{ pkgs }:
+let
+  androidApiLevel = "23";
+  androidPackages = pkgs.androidenv.composeAndroidPackages {
+    platformVersions = [ androidApiLevel ];
+    includeNDK = true;
+    ndkVersion = "27.2.12479018";
+  };
+  androidNdkPackage = androidPackages.ndk-bundle;
+  androidNdkHome = "${androidNdkPackage}/libexec/android-sdk/ndk-bundle";
+  androidToolchainPlatform = if pkgs.stdenv.isDarwin then "darwin-x86_64" else "linux-x86_64";
+  androidToolchainBin = "${androidNdkHome}/toolchains/llvm/prebuilt/${androidToolchainPlatform}/bin";
+
+  androidClang = "${androidToolchainBin}/aarch64-linux-android${androidApiLevel}-clang";
+  androidClangxx = "${androidToolchainBin}/aarch64-linux-android${androidApiLevel}-clang++";
+  androidI686Clang = "${androidToolchainBin}/i686-linux-android${androidApiLevel}-clang";
+  androidI686Clangxx = "${androidToolchainBin}/i686-linux-android${androidApiLevel}-clang++";
+  androidArmv7Clang = "${androidToolchainBin}/armv7a-linux-androideabi${androidApiLevel}-clang";
+  androidArmv7Clangxx = "${androidToolchainBin}/armv7a-linux-androideabi${androidApiLevel}-clang++";
+  androidX8664Clang = "${androidToolchainBin}/x86_64-linux-android${androidApiLevel}-clang";
+  androidX8664Clangxx = "${androidToolchainBin}/x86_64-linux-android${androidApiLevel}-clang++";
+  androidRustflags = "-Clink-arg=-z -Clink-arg=max-page-size=16384 -Clink-arg=-z -Clink-arg=common-page-size=4096";
+
+  rustToolchain = pkgs.rust-bin.fromRustupToolchainFile ../rust-toolchain.toml;
+in
+pkgs.mkShell {
+  packages = [
+    rustToolchain
+    androidNdkPackage
+    pkgs.curl
+    pkgs.git
+  ];
+
+  ANDROID_API_LEVEL = androidApiLevel;
+  ANDROID_NDK_HOME = androidNdkHome;
+  ANDROID_NDK_ROOT = androidNdkHome;
+  NDK_HOME = androidNdkHome;
+
+  CC_aarch64_linux_android = androidClang;
+  CXX_aarch64_linux_android = androidClangxx;
+  AR_aarch64_linux_android = "${androidToolchainBin}/llvm-ar";
+  RANLIB_aarch64_linux_android = "${androidToolchainBin}/llvm-ranlib";
+  CARGO_TARGET_AARCH64_LINUX_ANDROID_LINKER = androidClang;
+  CARGO_TARGET_AARCH64_LINUX_ANDROID_RUSTFLAGS = androidRustflags;
+
+  CC_i686_linux_android = androidI686Clang;
+  CXX_i686_linux_android = androidI686Clangxx;
+  AR_i686_linux_android = "${androidToolchainBin}/llvm-ar";
+  RANLIB_i686_linux_android = "${androidToolchainBin}/llvm-ranlib";
+  CARGO_TARGET_I686_LINUX_ANDROID_LINKER = androidI686Clang;
+  CARGO_TARGET_I686_LINUX_ANDROID_RUSTFLAGS = androidRustflags;
+
+  CC_armv7_linux_androideabi = androidArmv7Clang;
+  CXX_armv7_linux_androideabi = androidArmv7Clangxx;
+  AR_armv7_linux_androideabi = "${androidToolchainBin}/llvm-ar";
+  RANLIB_armv7_linux_androideabi = "${androidToolchainBin}/llvm-ranlib";
+  CARGO_TARGET_ARMV7_LINUX_ANDROIDEABI_LINKER = androidArmv7Clang;
+  CARGO_TARGET_ARMV7_LINUX_ANDROIDEABI_RUSTFLAGS = androidRustflags;
+
+  CC_x86_64_linux_android = androidX8664Clang;
+  CXX_x86_64_linux_android = androidX8664Clangxx;
+  AR_x86_64_linux_android = "${androidToolchainBin}/llvm-ar";
+  RANLIB_x86_64_linux_android = "${androidToolchainBin}/llvm-ranlib";
+  CARGO_TARGET_X86_64_LINUX_ANDROID_LINKER = androidX8664Clang;
+  CARGO_TARGET_X86_64_LINUX_ANDROID_RUSTFLAGS = androidRustflags;
+
+  shellHook = ''
+    echo "WalletKit Android dev shell"
+    echo "  targets: aarch64-linux-android, armv7-linux-androideabi, i686-linux-android, x86_64-linux-android (API $ANDROID_API_LEVEL)"
+    echo "  ndk:    $ANDROID_NDK_HOME"
+    echo ""
+    echo "Build with: cargo build -p walletkit --release --target aarch64-linux-android --features compress-zkeys,v3"
+  '';
+}
diff --git a/nix/build-android.sh b/nix/build-android.sh
new file mode 100755
index 00000000..4f34f909
--- /dev/null
+++ b/nix/build-android.sh
@@ -0,0 +1,72 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+cd "$(dirname "${BASH_SOURCE[0]}")/.."
+
+readonly TARGETS=(
+  "aarch64-linux-android"
+  "armv7-linux-androideabi"
+  "x86_64-linux-android"
+  "i686-linux-android"
+)
+
+usage() {
+  cat <<EOF
+Usage: $0 --target <target>
+
+Targets:
+$(printf '  %s\n' "${TARGETS[@]}")
+
+EOF
+}
+
+TARGET=""
+
+while [[ $# -gt 0 ]]; do
+  case "$1" in
+  --target | -t)
+    if [[ $# -lt 2 ]]; then
+      echo "error: --target requires a value" >&2
+      usage >&2
+      exit 1
+    fi
+    TARGET="$2"
+    shift 2
+    ;;
+  --help | -h)
+    usage
+    exit 0
+    ;;
+  *)
+    echo "error: unknown argument: $1" >&2
+    usage >&2
+    exit 1
+    ;;
+  esac
+done
+
+if [[ -z "${TARGET}" ]]; then
+  echo "error: --target is required" >&2
+  usage >&2
+  exit 1
+fi
+
+valid_target=false
+for candidate in "${TARGETS[@]}"; do
+  if [[ "${TARGET}" == "${candidate}" ]]; then
+    valid_target=true
+    break
+  fi
+done
+
+if [[ "${valid_target}" != true ]]; then
+  echo "error: unsupported target: ${TARGET}" >&2
+  usage >&2
+  exit 1
+fi
+
+exec nix develop .#android --command cargo build \
+  -p walletkit \
+  --release \
+  --target "${TARGET}" \
+  --features compress-zkeys,v3
diff --git a/nix/build-wasm.sh b/nix/build-wasm.sh
new file mode 100755
index 00000000..f53b7542
--- /dev/null
+++ b/nix/build-wasm.sh
@@ -0,0 +1,10 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+cd "$(dirname "${BASH_SOURCE[0]}")/.."
+
+exec nix develop .#wasm --command cargo build \
+  -p walletkit \
+  --release \
+  --target wasm32-unknown-unknown \
+  "$@"
diff --git a/nix/wasm.nix b/nix/wasm.nix
new file mode 100644
index 00000000..5c88d893
--- /dev/null
+++ b/nix/wasm.nix
@@ -0,0 +1,26 @@
+{ pkgs }:
+let
+  rustToolchain = pkgs.rust-bin.fromRustupToolchainFile ../rust-toolchain.toml;
+  llvm = pkgs.llvmPackages;
+in
+pkgs.mkShell {
+  packages = [
+    rustToolchain
+    llvm.clang-unwrapped
+    llvm.bintools-unwrapped
+    pkgs.curl
+    pkgs.git
+  ];
+
+  # Use unwrapped clang: cc-wrapper injects host hardening flags that are invalid for wasm.
+  CC_wasm32_unknown_unknown = "${llvm.clang-unwrapped}/bin/clang";
+  AR_wasm32_unknown_unknown = "${llvm.bintools-unwrapped}/bin/llvm-ar";
+
+  shellHook = ''
+    echo "WalletKit wasm dev shell"
+    echo "  target: wasm32-unknown-unknown"
+    echo "  clang: $CC_wasm32_unknown_unknown"
+    echo ""
+    echo "Build with: cargo build -p walletkit --target wasm32-unknown-unknown"
+  '';
+}