diff --git a/scripts/lib/lastcode-action-kit.test.ts b/scripts/lib/lastcode-action-kit.test.ts
new file mode 100644
index 000000000000..e1198b319297
--- /dev/null
+++ b/scripts/lib/lastcode-action-kit.test.ts
@@ -0,0 +1,59 @@
+// @effect-diagnostics nodeBuiltinImport:off -- Repository declaration coverage reads local source files.
+import * as NodeFS from "node:fs";
+import * as NodePath from "node:path";
+
+import { describe, expect, it } from "vite-plus/test";
+
+import { createLastCodeActionReporter } from "./lastcode-action-kit.ts";
+
+type ProjectScript = {
+  readonly id?: string;
+  readonly name: string;
+  readonly command: string;
+};
+
+describe("LastCode Action kit", () => {
+  it("allows one terminal result and rejects a second", () => {
+    const output: string[] = [];
+    const action = createLastCodeActionReporter({
+      env: {},
+      write: () => undefined,
+      log: (message) => output.push(message),
+    });
+
+    action.progress({ state: "working", summary: "Running checks" });
+    action.result({ outcome: "success", summary: "Checks passed" });
+
+    expect(output).toHaveLength(2);
+    expect(output[1]).toContain('"summary":"Checks passed"');
+    expect(() =>
+      action.result({ outcome: "attention", summary: "Unexpected second result" }),
+    ).toThrow("only one terminal result");
+    expect(output).toHaveLength(2);
+  });
+
+  it("keeps every repository-owned resumable Action on the shared reporting path", () => {
+    const repoRoot = NodePath.resolve(import.meta.dirname, "../..");
+    const project = JSON.parse(NodeFS.readFileSync(NodePath.join(repoRoot, "t3.json"), "utf8")) as {
+      readonly scripts: ReadonlyArray<ProjectScript>;
+    };
+    const actions = project.scripts.filter(({ id }) => id?.startsWith("lc-"));
+
+    expect(actions.length).toBeGreaterThan(0);
+    for (const action of actions) {
+      const scriptPath = /\bnode (scripts\/[^\s]+\.(?:ts|mjs))\b/u.exec(action.command)?.[1];
+      expect(scriptPath, `${action.name} must run a repository-owned script`).toBeDefined();
+
+      const source = NodeFS.readFileSync(NodePath.join(repoRoot, scriptPath!), "utf8");
+      expect(source, `${action.name} must import the LastCode Action kit`).toContain(
+        'from "./lib/lastcode-action-kit.ts"',
+      );
+      expect(source, `${action.name} must report coarse progress`).toContain(
+        "lastCodeAction.progress",
+      );
+      expect(source, `${action.name} must report a compact terminal result`).toContain(
+        "lastCodeAction.result",
+      );
+    }
+  });
+});
diff --git a/scripts/lib/lastcode-action-kit.ts b/scripts/lib/lastcode-action-kit.ts
index 6604ec28269d..a7b391fd879c 100644
--- a/scripts/lib/lastcode-action-kit.ts
+++ b/scripts/lib/lastcode-action-kit.ts
@@ -1,10 +1,28 @@
 import { createActionReporter } from "@t3tools/shared/actionResumeProtocol";
 
+type ReporterOptions = Parameters<typeof createActionReporter>[0];
+
 /**
  * Structured reporting for LastCode's repository-owned resumable Project Actions.
  * Outside a resumable run, reports remain readable ordinary terminal output.
  */
-export const lastCodeAction = createActionReporter({
+export function createLastCodeActionReporter(options: ReporterOptions) {
+  const reporter = createActionReporter(options);
+  let terminalResultEmitted = false;
+
+  return {
+    progress: reporter.progress,
+    result(report: Parameters<typeof reporter.result>[0]): void {
+      if (terminalResultEmitted) {
+        throw new Error("LastCode Actions may emit only one terminal result.");
+      }
+      terminalResultEmitted = true;
+      reporter.result(report);
+    },
+  };
+}
+
+export const lastCodeAction = createLastCodeActionReporter({
   env: process.env,
   write: (data) => process.stdout.write(data),
   log: (message) => process.stdout.write(`${message}\n`),