diff --git a/docs/packages/cli.mdx b/docs/packages/cli.mdx
index 8546c740f66..e4be6efe574 100644
--- a/docs/packages/cli.mdx
+++ b/docs/packages/cli.mdx
@@ -150,6 +150,10 @@ The positional name is a registry item, or a tag — a tag installs every block
 carrying it. `--dir` picks the project directory, `--json` prints the written
 files and paste snippet, and `--no-clipboard` skips the clipboard copy for CI.
 
+If any block in a tag fails to install, `add` keeps the successful installs and
+exits with code 1. With `--json`, `ok` is `false` and `errors` lists each failed
+block's `name` and `error`; `installed` lists the blocks that succeeded.
+
 Every install produces files plus a **paste snippet**: the `<iframe>` tag for a
 block, or the fragment path for a component. It goes to your clipboard by
 default. Naming an example instead of a registry item (`add warm-grain`) gets
diff --git a/packages/cli/src/commands/add.test.ts b/packages/cli/src/commands/add.test.ts
index 4bbd5a49cfe..4df3966279b 100644
--- a/packages/cli/src/commands/add.test.ts
+++ b/packages/cli/src/commands/add.test.ts
@@ -618,6 +618,89 @@ describe("tagAddJson", () => {
       tag: "lower-thirds",
       installed: ["a", "b"],
       warnings: ["b: no id"],
+      errors: [],
     });
   });
 });
+
+describe("tag installation failures", () => {
+  let dir: string;
+
+  beforeEach(() => {
+    dir = tmp();
+    writeRegistryConfig(dir);
+  });
+
+  afterEach(() => {
+    vi.restoreAllMocks();
+    vi.unstubAllGlobals();
+    rmSync(dir, { recursive: true, force: true });
+  });
+
+  it.each([
+    { names: ["my-block"], failed: ["my-block"], installed: [], json: true },
+    {
+      names: ["my-block", "deprecated-block"],
+      failed: ["my-block"],
+      installed: ["deprecated-block"],
+      json: true,
+    },
+    { names: ["my-block"], failed: [], installed: ["my-block"], json: true },
+    { names: ["my-block"], failed: ["my-block"], installed: [], json: false },
+    { names: ["my-block"], failed: [], installed: ["my-block"], json: false },
+  ])("reports failed downloads and keeps successful installs: %j", async (scenario) => {
+    vi.stubGlobal(
+      "fetch",
+      vi.fn(async (input: string | URL) => {
+        const url = new URL(input);
+        if (url.pathname.endsWith("/registry.json")) {
+          return Response.json({
+            ...MANIFEST,
+            items: MANIFEST.items.filter((item) => scenario.names.includes(item.name)),
+          });
+        }
+        const name = scenario.names.find((item) => url.pathname.includes(`/blocks/${item}/`));
+        if (!name) return new Response("not found", { status: 404 });
+        if (url.pathname.endsWith("/registry-item.json")) {
+          return Response.json({ ...ITEM_BY_NAME[name], tags: ["test-tag"] });
+        }
+        if (scenario.failed.includes(name)) return new Response("not found", { status: 404 });
+        return new Response(FILE_BODIES[`${name}.html`]);
+      }),
+    );
+    const log = vi.spyOn(console, "log").mockImplementation(() => {});
+    const run = runCittyCommand(addCommand, {
+      rawArgs: ["test-tag", "--dir", dir, "--no-clipboard", ...(scenario.json ? ["--json"] : [])],
+    });
+    if (scenario.failed.length > 0) {
+      await expect(run).rejects.toMatchObject({ result: { exitCode: 1, presented: true } });
+    } else {
+      await expect(run).resolves.toBeDefined();
+    }
+
+    if (scenario.json) {
+      expect(log).toHaveBeenCalledTimes(1);
+      expect(JSON.parse(String(log.mock.calls[0]?.[0]))).toMatchObject({
+        ok: scenario.failed.length === 0,
+        tag: "test-tag",
+        installed: scenario.installed,
+        errors: scenario.failed.map((name) => ({
+          name,
+          error: expect.stringContaining("HTTP 404"),
+        })),
+      });
+    } else {
+      expect(log).toHaveBeenLastCalledWith(
+        `${scenario.failed.length > 0 ? "✗" : "✓"} Installed ${scenario.installed.length}/${scenario.names.length} blocks`,
+      );
+      if (scenario.failed.length > 0) {
+        expect(log.mock.calls.flat().join(" ")).toContain("HTTP 404");
+      }
+    }
+    for (const name of scenario.names) {
+      expect(existsSync(join(dir, "compositions", `${name}.html`))).toBe(
+        scenario.installed.includes(name),
+      );
+    }
+  });
+});
diff --git a/packages/cli/src/commands/add.ts b/packages/cli/src/commands/add.ts
index 43b077d97fa..1b1cd54a845 100644
--- a/packages/cli/src/commands/add.ts
+++ b/packages/cli/src/commands/add.ts
@@ -146,13 +146,18 @@ export function buildSnippet(
   return "";
 }
 
-/** `add <tag> --json` output: each item's warnings, prefixed with its name. */
-export function tagAddJson(tag: string, results: RunAddResult[]) {
+/** `add <tag> --json` output: successful installs and each item's warnings or failure. */
+export function tagAddJson(
+  tag: string,
+  results: RunAddResult[],
+  errors: Array<{ name: string; error: string }> = [],
+) {
   return {
-    ok: true,
+    ok: errors.length === 0,
     tag,
     installed: results.map((r) => r.name),
     warnings: results.flatMap((r) => r.warnings.map((w) => `${r.name}: ${w}`)),
+    errors,
   };
 }
 
@@ -584,6 +589,7 @@ export default defineCommand({
       }
 
       const results: RunAddResult[] = [];
+      const errors: Array<{ name: string; error: string }> = [];
       for (const item of items) {
         try {
           const result = await runAdd({
@@ -600,16 +606,19 @@ export default defineCommand({
           if (!json) console.log(`  ${c.success("✓")} ${result.name}`);
         } catch (err) {
           const reason = err instanceof Error ? err.message : String(err);
+          errors.push({ name: item.name, error: reason });
           if (!json) console.log(`  ${c.error("✗")} ${item.name} (skipped: ${reason})`);
         }
       }
 
       if (json) {
-        console.log(JSON.stringify(tagAddJson(args.name, results)));
+        console.log(JSON.stringify(tagAddJson(args.name, results, errors)));
       } else {
         console.log("");
-        console.log(`${c.success("✓")} Installed ${results.length}/${items.length} blocks`);
+        const summary = `Installed ${results.length}/${items.length} blocks`;
+        console.log(`${errors.length > 0 ? c.error("✗") : c.success("✓")} ${summary}`);
       }
+      if (errors.length > 0) failCommand();
     }
   },
 });