diff --git a/.gitignore b/.gitignore
index c6d90c5..e85e355 100644
--- a/.gitignore
+++ b/.gitignore
@@ -11,3 +11,9 @@
 # the .iss script and .ico are the tracked sources.
 /packaging/windows/peerspeak.exe
 /packaging/windows/output/
+
+# Nix: the symlink `nix build` drops, and direnv's local cache. flake.nix and
+# flake.lock ARE tracked — the lock is what pins the toolchain.
+/result
+/result-*
+/.direnv/
diff --git a/flake.lock b/flake.lock
new file mode 100644
index 0000000..d339b4d
--- /dev/null
+++ b/flake.lock
@@ -0,0 +1,27 @@
+{
+  "nodes": {
+    "nixpkgs": {
+      "locked": {
+        "lastModified": 1785989512,
+        "narHash": "sha256-HFQhkQcl5D1hUNoen3SGHCSFCt2Bg6uP+HgbrnA3InQ=",
+        "owner": "nixos",
+        "repo": "nixpkgs",
+        "rev": "445d861c6d31b4af0c79d8d4be2331f762a361d7",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nixos",
+        "ref": "nixos-26.05",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
+    "root": {
+      "inputs": {
+        "nixpkgs": "nixpkgs"
+      }
+    }
+  },
+  "root": "root",
+  "version": 7
+}
diff --git a/flake.nix b/flake.nix
new file mode 100644
index 0000000..87ab119
--- /dev/null
+++ b/flake.nix
@@ -0,0 +1,134 @@
+{
+  description = "PeerSpeak — decentralized P2P voice chat (Rust/iroh/PipeWire/Opus/iced)";
+
+  # Pinned to the same channel the hosts run (nixos-config tracks nixos-26.05),
+  # so the libraries this shell links and dlopens are built against the same
+  # release as the PipeWire daemon and Vulkan ICD actually running on the
+  # machine. Floating to unstable here would reintroduce precisely the
+  # client/server version skew the pin exists to prevent.
+  inputs.nixpkgs.url = "github:nixos/nixpkgs/nixos-26.05";
+
+  outputs =
+    { nixpkgs, ... }:
+    let
+      system = "x86_64-linux";
+      pkgs = nixpkgs.legacyPackages.${system};
+
+      # Libraries that iced/winit/wgpu open with dlopen at RUNTIME rather than
+      # linking at build time. Because nothing links them, they never land in
+      # the binary's rpath — under `cargo run` the loader finds them only
+      # through LD_LIBRARY_PATH. Leaving them out builds fine and then panics
+      # at window creation, which is a genuinely confusing failure, so they are
+      # listed explicitly instead of discovered the hard way.
+      runtimeLibs = with pkgs; [
+        vulkan-loader # wgpu's Vulkan backend (iced's renderer)
+        libxkbcommon # winit keyboard handling
+        wayland # wayland-sys, dlopen'd on a Wayland session
+        libx11 # x11-dl, dlopen'd on the X11 fallback path
+        libxcursor
+        libxrandr
+        libxi
+      ];
+
+      # Screen sharing spawns pixelpass as a CHILD PROCESS, and pixelpass in
+      # turn drives GStreamer as a subprocess. That makes these tools a
+      # dependency of peerspeak's own test suite, not just of pixelpass:
+      # `tests/screenshare_host_fault.rs` starts a real pixelpass host, which
+      # aborts at its preflight if gst-launch-1.0 is missing.
+      #
+      # Deliberately duplicated from pixelpass's flake rather than importing it
+      # as an input. The two projects are mutually optional by design — neither
+      # is a dependency of the other, and the coupling is a runtime subprocess
+      # contract. Making one flake consume the other would quietly reintroduce
+      # exactly the build-level dependency that rule exists to prevent.
+      screenshareTools = with pkgs; [
+        gst_all_1.gstreamer
+        gst_all_1.gst-plugins-base
+        gst_all_1.gst-plugins-good
+        gst_all_1.gst-plugins-bad
+        gst_all_1.gst-plugins-ugly
+        gst_all_1.gst-libav
+        pipewire # pipewiresrc (Wayland capture; ships in this pkg)
+      ];
+    in
+    {
+      devShells.${system}.default = pkgs.mkShell {
+        nativeBuildInputs = with pkgs; [
+          rustc
+          cargo
+          rustfmt
+          clippy
+
+          # The supply-chain gates .gitea/workflows/ci.yml runs, so the same
+          # checks are reproducible locally before a push. These were `cargo
+          # install`ed on the CachyOS side, which does not carry over — those
+          # binaries link that distro's glibc and will not run here.
+          # cargo-deny reads deny.toml; cargo-audit reads .cargo/audit.toml.
+          cargo-audit
+          cargo-deny
+          # Debian packaging (`cargo deb --no-build`). Note the .deb itself
+          # should still be built inside a Debian/Ubuntu distrobox so the
+          # binary links that distro's glibc — see the packaging notes in
+          # Cargo.toml.
+          cargo-deb
+
+          pkg-config
+
+          # pipewire-sys and libspa-sys generate their bindings with bindgen,
+          # which needs a real libclang present at build time.
+          clang
+
+          # audiopus_sys prefers the system libopus via pkg-config but falls
+          # back to a vendored CMake build; cmake keeps that fallback working
+          # rather than failing obscurely inside a build script.
+          cmake
+
+          # build.rs shells out to `git rev-parse --short=8 HEAD` to stamp
+          # PEERSPEAK_GIT_SHORT into the binary (surfaced in Settings).
+          git
+        ]
+        ++ screenshareTools
+        ++ [
+          pkgs.pulseaudio # `pactl`, used by pixelpass's audio routing
+          pkgs.mpv # the screen-share viewer
+        ];
+
+        buildInputs =
+          with pkgs;
+          [
+            alsa-lib # alsa-sys, pulled in by rodio/cpal
+            libopus # audiopus_sys, linked dynamically
+            pipewire # pipewire-sys + libspa-sys: the Linux audio backend
+          ]
+          ++ runtimeLibs;
+
+        # bindgen finds libclang through this variable specifically — having
+        # clang on PATH is not sufficient.
+        LIBCLANG_PATH = "${pkgs.llvmPackages.libclang.lib}/lib";
+
+        LD_LIBRARY_PATH = pkgs.lib.makeLibraryPath runtimeLibs;
+
+        # NixOS keeps every GStreamer plugin in its own store path, so the
+        # gst-launch-1.0 that pixelpass spawns discovers them ONLY through this
+        # search path. Same reasoning as hosts/darp5 and hosts/cazen in
+        # nixos-config.
+        GST_PLUGIN_SYSTEM_PATH_1_0 =
+          pkgs.lib.makeSearchPathOutput "lib" "lib/gstreamer-1.0" screenshareTools;
+
+        # Only greet an interactive shell. shellHook also runs under
+        # `nix develop --command …`, where printing this would interleave the
+        # banner with the command's own output.
+        shellHook = ''
+          if [ -t 1 ]; then
+            echo "peerspeak — rustc $(rustc --version | cut -d' ' -f2) / cargo $(cargo --version | cut -d' ' -f2)"
+            echo "  cargo build --release                       build"
+            echo "  cargo test                                  lib tests"
+            echo "  cargo clippy --all-targets -- -D warnings    lint"
+            echo
+            echo "Screen sharing spawns pixelpass as a child process — it must be"
+            echo "on PATH. Build it from ../pixelpass and add its target/release."
+          fi
+        '';
+      };
+    };
+}