diff --git a/tests/boundary/cli/environmentCompareCli.test.ts b/tests/boundary/cli/environmentCompareCli.test.ts
new file mode 100644
index 0000000000..9d95a210f2
--- /dev/null
+++ b/tests/boundary/cli/environmentCompareCli.test.ts
@@ -0,0 +1,94 @@
+import { writeFile } from "node:fs/promises";
+import { join } from "node:path";
+
+import { describe, expect } from "vitest";
+
+import { timedCaptureEvidence } from "../../fixtures/analysisView.js";
+import { environmentStateServeFixture } from "../../fixtures/environmentServe.js";
+import {
+  BOOK_NOT_FOUND,
+  BOOK_ROWS,
+  book,
+} from "../../fixtures/environmentStateWrites.js";
+import { createTestTempDirectory } from "../../fixtures/temporaryDirectory.js";
+import { cliTest } from "../../support/cli/cliFixture.js";
+
+/** The books environment and a probe of the application re-seeded under other ids, written as Evidence files. */
+const writeCompareFiles = async (root: string) => {
+  const fixture = environmentStateServeFixture(timedCaptureEvidence(BOOK_ROWS));
+  const first = book(101, "First Book", "2026-10-20T09:00:00Z");
+  const second = book(102, "Second Book", "2026-10-20T10:00:00Z");
+  const probe = timedCaptureEvidence([
+    ["GET", "/api/books", [first, second]],
+    ["DELETE", "/api/books/102", "", 204],
+    ["GET", "/api/books/102", BOOK_NOT_FOUND, 404],
+  ]);
+  const paths = {
+    manifest: join(root, "manifest.json"),
+    capture: join(root, "capture.json"),
+    probe: join(root, "probe.json"),
+  };
+  await writeFile(paths.manifest, JSON.stringify(fixture.manifest));
+  await writeFile(paths.capture, JSON.stringify(fixture.capture));
+  await writeFile(paths.probe, JSON.stringify(probe));
+  return paths;
+};
+
+describe("rea environment-compare", () => {
+  cliTest(
+    "compares the served environment with a probe of the re-seeded application and prints the report",
+    async ({ cli }) => {
+      const files = await writeCompareFiles(
+        await createTestTempDirectory("rea-environment-compare-cli-"),
+      );
+      const result = await cli.run({
+        arguments: [
+          "environment-compare",
+          files.manifest,
+          "--evidence",
+          files.capture,
+          "--probe",
+          files.probe,
+          "--json",
+        ],
+        timeoutMs: 30_000,
+      });
+      expect(result.exitCode).toBe(0);
+      expect(result.json).toMatchObject({
+        status: "complete",
+        environment: { state: "served" },
+        summary: { probes: 1, steps: 3, equal: 3, agreement: 1 },
+        probes: [{ label: "probe.json", ids_mapped: 2 }],
+      });
+    },
+  );
+
+  cliTest(
+    "refuses a probe that is not capture Evidence and names it",
+    async ({ cli }) => {
+      const files = await writeCompareFiles(
+        await createTestTempDirectory("rea-environment-compare-refusal-cli-"),
+      );
+      const result = await cli.run({
+        arguments: [
+          "environment-compare",
+          files.manifest,
+          "--evidence",
+          files.capture,
+          "--probe",
+          files.manifest,
+          "--json",
+        ],
+        timeoutMs: 30_000,
+      });
+      expect(result.exitCode).toBe(1);
+      expect(result.json).toMatchObject({
+        code: "invalid_request",
+        details: {
+          operation: "environment-compare",
+          issues: [{ path: ["probe", 0] }],
+        },
+      });
+    },
+  );
+});