diff --git a/dagger/README.md b/dagger/README.md
new file mode 100644
index 0000000..e4d109a
--- /dev/null
+++ b/dagger/README.md
@@ -0,0 +1,24 @@
+# dagger
+
+This directory contains the Nix package for a pinned dev build of `dagger`, the CLI for [Dagger](https://dagger.io).
+
+Source: [`github.com/dagger/dagger`](https://github.com/dagger/dagger)
+
+## Usage
+
+```bash
+dagger version
+dagger --help
+```
+
+## Updating
+
+This package follows Dagger's dev-build endpoint, but pins a concrete commit and hashes for reproducibility.
+
+Fetch the latest dev-build checksums:
+
+```bash
+curl -fsSL https://dl.dagger.io/dagger/main/head/checksums.txt
+```
+
+Then update `commit` and the platform hashes in `default.nix`.
diff --git a/dagger/default.nix b/dagger/default.nix
new file mode 100644
index 0000000..4f48528
--- /dev/null
+++ b/dagger/default.nix
@@ -0,0 +1,75 @@
+{
+  lib,
+  stdenvNoCC,
+  fetchurl,
+  installShellFiles,
+}:
+
+let
+  # Latest Dagger dev build from https://dl.dagger.io/dagger/main/head/checksums.txt
+  # Update this commit and the hashes together when you want a newer unreleased build.
+  commit = "499b5fc3d15f6b9c8a196b81436a805cc6ec7f4e";
+  version = "1.0.0-dev-${lib.substring 0 8 commit}";
+
+  sources = {
+    x86_64-linux = {
+      os = "linux";
+      arch = "amd64";
+      hash = "sha256-nHfqWGeqbOdHG7JR2wlK6mcejLTX0zXF7frMZj7+nyU=";
+    };
+    aarch64-linux = {
+      os = "linux";
+      arch = "arm64";
+      hash = "sha256-ekV6V90Rx4ZgCwcOiwnT6sGeyF8MEvf1Gt3iyhAezzA=";
+    };
+    x86_64-darwin = {
+      os = "darwin";
+      arch = "amd64";
+      hash = "sha256-GuLWq2z82Z3Rw4iEW3koC+edvUwiA+Aba3WzfPJgrts=";
+    };
+    aarch64-darwin = {
+      os = "darwin";
+      arch = "arm64";
+      hash = "sha256-acPG+9uirdZBjzF7RMFhtgQmlp9M+e6MQ7/+S+9JoUU=";
+    };
+  };
+
+  source = sources.${stdenvNoCC.hostPlatform.system} or (throw "Unsupported system: ${stdenvNoCC.hostPlatform.system}");
+in
+stdenvNoCC.mkDerivation {
+  pname = "dagger";
+  inherit version;
+
+  src = fetchurl {
+    url = "https://dl.dagger.io/dagger/main/${commit}/dagger_${commit}_${source.os}_${source.arch}.tar.gz";
+    inherit (source) hash;
+  };
+
+  sourceRoot = ".";
+
+  nativeBuildInputs = [ installShellFiles ];
+
+  installPhase = ''
+    runHook preInstall
+
+    install -Dm755 dagger $out/bin/dagger
+
+    runHook postInstall
+  '';
+
+  postInstall = ''
+    installShellCompletion --cmd dagger \
+      --bash <($out/bin/dagger completion bash) \
+      --zsh <($out/bin/dagger completion zsh) \
+      --fish <($out/bin/dagger completion fish)
+  '';
+
+  meta = {
+    description = "Dagger CLI dev build from main";
+    homepage = "https://github.com/dagger/dagger";
+    license = lib.licenses.asl20;
+    mainProgram = "dagger";
+    sourceProvenance = [ lib.sourceTypes.binaryNativeCode ];
+    platforms = builtins.attrNames sources;
+  };
+}
diff --git a/devenv.nix b/devenv.nix
index 0c44ab4..187082b 100644
--- a/devenv.nix
+++ b/devenv.nix
@@ -4,13 +4,15 @@
 }:
 
 let
-  tang = pkgs.callPackage ./tangled-cli/tang.nix { };
+  dagger = pkgs.callPackage ./dagger { };
+  tang = pkgs.callPackage ./tangled-cli { };
   devenvSummary = pkgs.callPackage ./devenv.custom-code.nix { };
 in
 {
   # https://devenv.sh/packages/
   packages = [
     pkgs.docker-compose # used by application
+    dagger              # dagger CLI dev build (until 1.0)
     pkgs.skills         # used to manage .agents/skills
     tang                # tangled.org cli
   ];
@@ -20,6 +22,7 @@ in
     title = "RSSBase devenv:";
     rows = [
       { pkg = pkgs.docker-compose; }
+      { pkg = dagger; }
       { pkg = pkgs.skills; }
       { pkg = tang; }
     ];
diff --git a/tangled-cli/tang.nix b/tangled-cli/default.nix
similarity index 100%
rename from tangled-cli/tang.nix
rename to tangled-cli/default.nix