diff --git a/packages/cli-workflow/src/__tests__/cas-exit-code.test.ts b/packages/cli-workflow/src/__tests__/cas-exit-code.test.ts
new file mode 100644
index 0000000..dc53769
--- /dev/null
+++ b/packages/cli-workflow/src/__tests__/cas-exit-code.test.ts
@@ -0,0 +1,152 @@
+import { execSync } from "node:child_process";
+import { mkdir, rm } from "node:fs/promises";
+import { tmpdir } from "node:os";
+import { join } from "node:path";
+import { afterEach, beforeEach, describe, expect, test } from "vitest";
+import { cmdCasPutText } from "../commands/cas.js";
+
+let storageRoot: string;
+let uwfPath: string;
+
+beforeEach(async () => {
+  storageRoot = join(
+    tmpdir(),
+    `uwf-cas-exit-test-${Date.now()}-${Math.random().toString(36).slice(2)}`,
+  );
+  await mkdir(storageRoot, { recursive: true });
+
+  // Find the uwf CLI path
+  uwfPath = join(__dirname, "../../src/cli.ts");
+});
+
+afterEach(async () => {
+  await rm(storageRoot, { recursive: true, force: true });
+});
+
+type ExecResult = {
+  stdout: string;
+  stderr: string;
+  exitCode: number;
+};
+
+function execUwf(args: string[]): ExecResult {
+  try {
+    const stdout = execSync(`bun ${uwfPath} ${args.join(" ")}`, {
+      env: { ...process.env, WORKFLOW_STORAGE_ROOT: storageRoot },
+      encoding: "utf-8",
+      stdio: ["pipe", "pipe", "pipe"],
+    });
+    return { stdout, stderr: "", exitCode: 0 };
+  } catch (error: unknown) {
+    if (
+      error &&
+      typeof error === "object" &&
+      "stdout" in error &&
+      "stderr" in error &&
+      "status" in error
+    ) {
+      return {
+        stdout: (error.stdout as Buffer | string).toString(),
+        stderr: (error.stderr as Buffer | string).toString(),
+        exitCode: error.status as number,
+      };
+    }
+    throw error;
+  }
+}
+
+describe("uwf cas has CLI exit codes", () => {
+  test("exits 0 when hash exists", async () => {
+    // Setup: Create a temp storage root, put a text node, capture hash
+    const putResult = await cmdCasPutText(storageRoot, "test content");
+    const hash = putResult.hash;
+
+    // Execute: uwf cas has <hash>
+    const result = execUwf(["cas", "has", hash]);
+
+    // Assert: stdout contains {"exists":true}, exit code === 0
+    expect(result.stdout).toContain('"exists":true');
+    expect(result.exitCode).toBe(0);
+  });
+
+  test("exits 1 when hash does not exist", () => {
+    // Setup: Create a temp storage root (empty CAS store)
+    // Execute: uwf cas has NOSUCHHASH123
+    const result = execUwf(["cas", "has", "NOSUCHHASH123"]);
+
+    // Assert: stdout contains {"exists":false}, exit code === 1
+    expect(result.stdout).toContain('"exists":false');
+    expect(result.exitCode).toBe(1);
+  });
+
+  test("JSON output format unchanged for exists=true", async () => {
+    // Setup: Create store, put node
+    const putResult = await cmdCasPutText(storageRoot, "test");
+    const hash = putResult.hash;
+
+    // Execute: uwf cas has <hash>
+    const result = execUwf(["cas", "has", hash]);
+
+    // Assert: stdout JSON parses correctly to {exists: true}
+    const parsed = JSON.parse(result.stdout.trim());
+    expect(parsed).toEqual({ exists: true });
+  });
+
+  test("JSON output format unchanged for exists=false", () => {
+    // Setup: Create empty store
+    // Execute: uwf cas has INVALID
+    const result = execUwf(["cas", "has", "INVALID"]);
+
+    // Assert: stdout JSON parses correctly to {exists: false}
+    const parsed = JSON.parse(result.stdout.trim());
+    expect(parsed).toEqual({ exists: false });
+  });
+
+  test("YAML output format preserves exit code behavior for exists=true", async () => {
+    // Setup: Create store with node
+    const putResult = await cmdCasPutText(storageRoot, "test");
+    const hash = putResult.hash;
+
+    // Execute: uwf --format yaml cas has <hash>
+    const result = execUwf(["--format", "yaml", "cas", "has", hash]);
+
+    // Assert: exit code === 0, output is YAML format
+    expect(result.exitCode).toBe(0);
+    expect(result.stdout).toContain("exists:");
+    expect(result.stdout).toContain("true");
+  });
+
+  test("YAML output format preserves exit code behavior for exists=false", () => {
+    // Setup: Create empty store
+    // Execute: uwf --format yaml cas has INVALID
+    const result = execUwf(["--format", "yaml", "cas", "has", "INVALID"]);
+
+    // Assert: exit code === 1, output is YAML format
+    expect(result.exitCode).toBe(1);
+    expect(result.stdout).toContain("exists:");
+    expect(result.stdout).toContain("false");
+  });
+});
+
+describe("regression: other cas commands unaffected", () => {
+  test("uwf cas get still exits 1 on not-found with error message", () => {
+    // Execute: uwf cas get NOSUCHHASH
+    const result = execUwf(["cas", "get", "NOSUCHHASH"]);
+
+    // Assert: exit code === 1, stderr contains "Node not found"
+    expect(result.exitCode).toBe(1);
+    expect(result.stderr).toContain("Node not found");
+  });
+
+  test("uwf cas put-text behavior unchanged", () => {
+    // Execute: uwf cas put-text "hello"
+    const result = execUwf(["cas", "put-text", "hello"]);
+
+    // Assert: exit code === 0, returns hash
+    expect(result.exitCode).toBe(0);
+    const parsed = JSON.parse(result.stdout.trim());
+    expect(parsed).toHaveProperty("hash");
+    expect(typeof parsed.hash).toBe("string");
+    expect(parsed.hash.length).toBe(13); // Crockford Base32 XXH64 hash length
+  });
+});
diff --git a/packages/cli-workflow/src/__tests__/cas.test.ts b/packages/cli-workflow/src/__tests__/cas.test.ts
new file mode 100644
index 0000000..a56e3ec
--- /dev/null
+++ b/packages/cli-workflow/src/__tests__/cas.test.ts
@@ -0,0 +1,74 @@
+import { mkdir, rm } from "node:fs/promises";
+import { tmpdir } from "node:os";
+import { join } from "node:path";
+import { afterEach, beforeEach, describe, expect, test } from "vitest";
+import { cmdCasHas, cmdCasPutText } from "../commands/cas.js";
+
+let storageRoot: string;
+
+beforeEach(async () => {
+  storageRoot = join(tmpdir(), `uwf-cas-test-${Date.now()}-${Math.random().toString(36).slice(2)}`);
+  await mkdir(storageRoot, { recursive: true });
+});
+
+afterEach(async () => {
+  await rm(storageRoot, { recursive: true, force: true });
+});
+
+describe("cmdCasHas", () => {
+  test("returns {exists: true} for existing hash", async () => {
+    // Setup: Create a test store, put a node, get its hash
+    const putResult = await cmdCasPutText(storageRoot, "test content");
+    const hash = putResult.hash;
+
+    // Execute: Call cmdCasHas with the valid hash
+    const result = await cmdCasHas(storageRoot, hash);
+
+    // Assert: Result equals {exists: true}
+    expect(result).toEqual({ exists: true });
+  });
+
+  test("returns {exists: false} for non-existent hash", async () => {
+    // Setup: Create an empty test store
+    // (storageRoot already created in beforeEach)
+
+    // Execute: Call cmdCasHas with an invalid hash
+    const result = await cmdCasHas(storageRoot, "INVALIDHASH12");
+
+    // Assert: Result equals {exists: false}
+    expect(result).toEqual({ exists: false });
+  });
+
+  test("does not throw for non-existent hash", async () => {
+    // Setup: Create an empty test store
+    // Execute & Assert: Does not throw, returns {exists: false}
+    await expect(cmdCasHas(storageRoot, "NOSUCHHASH123")).resolves.toEqual({
+      exists: false,
+    });
+  });
+
+  test("handles malformed hash gracefully", async () => {
+    // Setup: Create a test store
+    // Execute: Call cmdCasHas with a too-short hash
+    const result = await cmdCasHas(storageRoot, "xyz");
+
+    // Assert: Returns {exists: false} (store.has() returns false)
+    expect(result).toEqual({ exists: false });
+  });
+
+  test("handles empty hash string", async () => {
+    // Execute: Call cmdCasHas with an empty string
+    const result = await cmdCasHas(storageRoot, "");
+
+    // Assert: Returns {exists: false}
+    expect(result).toEqual({ exists: false });
+  });
+
+  test("handles hash with special characters", async () => {
+    // Execute: Call cmdCasHas with special characters
+    const result = await cmdCasHas(storageRoot, "HASH!@#");
+
+    // Assert: Returns {exists: false}
+    expect(result).toEqual({ exists: false });
+  });
+});
diff --git a/packages/cli-workflow/src/cli.ts b/packages/cli-workflow/src/cli.ts
index 1ed04d6..ef1559c 100755
--- a/packages/cli-workflow/src/cli.ts
+++ b/packages/cli-workflow/src/cli.ts
@@ -549,7 +549,11 @@ cas
   .action((hash: string) => {
     const storageRoot = resolveStorageRoot();
     runAction(async () => {
-      writeOutput(await cmdCasHas(storageRoot, hash));
+      const result = await cmdCasHas(storageRoot, hash);
+      writeOutput(result);
+      if (!result.exists) {
+        process.exit(1);
+      }
     });
   });