diff --git a/build_ts/index.ts b/build_ts/index.ts
index 311bef4..8a72839 100644
--- a/build_ts/index.ts
+++ b/build_ts/index.ts
@@ -2,13 +2,13 @@ export interface Workflow {
   slug: WorkflowSlug;
   name: string;
   command: string;
-  tags?: [string];
+  tags?: string[];
   description?: string;
-  arguments?: [Argument];
+  arguments?: Argument[];
   source_url?: string;
   author?: string;
   author_url?: string;
-  shells?: [Shell];
+  shells?: Shell[];
   relative_git_url: string;
 }
 
diff --git a/build_ts/package.json b/build_ts/package.json
index c6e5790..6cf11c5 100644
--- a/build_ts/package.json
+++ b/build_ts/package.json
@@ -6,6 +6,7 @@
   "types": "dist/index.d.ts",
   "scripts": {
     "build": "tsc && webpack",
+    "check-types": "tsc -p tsconfig.typetest.json",
     "prepare": "npm run build"
   },
   "author": "Warp Team (eng@warp.dev)",
diff --git a/build_ts/tsconfig.json b/build_ts/tsconfig.json
index 4682020..b50d848 100644
--- a/build_ts/tsconfig.json
+++ b/build_ts/tsconfig.json
@@ -9,5 +9,6 @@
     "strict": true,
     "esModuleInterop": true,
     "moduleResolution": "node"
-  }
+  },
+  "exclude": ["node_modules", "dist", "type-tests"]
 }
diff --git a/build_ts/tsconfig.typetest.json b/build_ts/tsconfig.typetest.json
new file mode 100644
index 0000000..8270b93
--- /dev/null
+++ b/build_ts/tsconfig.typetest.json
@@ -0,0 +1,9 @@
+{
+  "extends": "./tsconfig.json",
+  "compilerOptions": {
+    "noEmit": true,
+    "declaration": false,
+    "sourceMap": false
+  },
+  "include": ["index.ts", "type-tests/**/*.ts"]
+}
diff --git a/build_ts/type-tests/workflow-types.test-d.ts b/build_ts/type-tests/workflow-types.test-d.ts
new file mode 100644
index 0000000..12aa056
--- /dev/null
+++ b/build_ts/type-tests/workflow-types.test-d.ts
@@ -0,0 +1,48 @@
+// Type-level regression test for the exported `Workflow` interface.
+//
+// These declarations do not run; they exist so that `tsc` fails to compile if
+// the multi-value fields (`tags`, `arguments`, `shells`) are ever narrowed back
+// to single-element tuple types. Every literal below mirrors an example that is
+// already documented in FORMAT.md / README.md or shipped under specs/.
+//
+// Compile with: npm run check-types
+
+import { Argument, Shell, Workflow } from "../index";
+
+// Mirrors FORMAT.md's own for-loop example, which documents a command with the
+// three arguments `variable`, `sequence`, and `command`, alongside a two-tag
+// list and two valid shells. Under the old `[string]` / `[Argument]` / `[Shell]`
+// tuple types this fails to type-check even though it is the documented format.
+const multiValued: Workflow = {
+  slug: "for-loop",
+  name: "For loop",
+  command: "for {{variable}} in {{sequence}}; do\n  {{command}}\ndone",
+  tags: ["shell", "loops"],
+  description: "Iterate over a sequence",
+  arguments: [
+    { name: "variable" },
+    { name: "sequence" },
+    { name: "command" },
+  ],
+  shells: [Shell.Bash, Shell.Zsh],
+  relative_git_url: "/specs/shell/for_loop.yaml",
+};
+
+// Mirrors the README's example workflow, which uses a single tag/argument and
+// an empty `shells: []` (valid in all shells). A single-element tuple type would
+// reject `shells: []` because it requires exactly one element.
+const singleValued: Workflow = {
+  slug: "brew-rmtree",
+  name: "Uninstall a Homebrew package and all of its dependencies",
+  command: "brew tap beeftornado/rmtree\nbrew rmtree {{package_name}}",
+  tags: ["homebrew"],
+  arguments: [{ name: "package_name" }],
+  shells: [],
+  relative_git_url: "/specs/homebrew/brew_rmtree.yaml",
+};
+
+// Reference the declarations so `noUnusedLocals`-style checks stay quiet and the
+// `Argument` import is exercised.
+const _arg: Argument = multiValued.arguments![0];
+void _arg;
+void singleValued;