feat: allow operator UI snippets on Cloud instances (#13168)

Adds an optional Cloud-only HTML snippet so operators can load Plain’s
standard chat bubble. **6 files, 16 implementation lines added; 102
additions including tests and docs.**

## Thinking Path

> - Paperclip serves Cloud and self-hosted users.
> - Closed beta users need a way to report problems.
> - Plain provides a ready-made chat widget.
> - Cloud operators can load it through a generic deployment setting.
> - Self-hosted instances ignore that setting.

## Linked Issues or Issue Description

**Subsystem affected**

Server-served UI HTML.

**Problem or motivation**

Enable a chat bubble in Cloud without adding a support feature to the
React app.

**Proposed solution**

Insert trusted `PAPERCLIP_CLOUD_UI_SNIPPET` HTML before `</body>` when
the existing Cloud-managed predicate is true. The setting is off by
default. Related Cloud-gated integration: #12190.

## What Changed

Review the [final
diff](https://github.com/paperclipai/paperclip/pull/13168/files) in this
order:

1. `server/src/cloud-ui-snippet.ts`: the eight-line Cloud gate and HTML
insertion.
2. `server/src/static-index-html.ts` and `server/src/app.ts`: apply it
to static root/index, SPA routes, and Vite HTML.
3. Two test files and `doc/cloud-ui-snippet.md`: boundary checks and
setup instructions.

React UI, customer identity, and database behavior are unchanged. The
existing feedback flag remains. Plain chat is anonymous; no Paperclip
name, email, or organization is supplied.

## Verification

- **Greptile: 5/5**, no actionable findings, reviewed commit
`04bb44515`.
- **[CI
passed](https://github.com/paperclipai/paperclip/actions/runs/34535763243)**,
including build, typecheck, server tests, and end-to-end tests.
- Local: six focused tests, full typecheck, and build passed. The full
local suite has not produced a final result; CI is the completed full
verification.
- Staging deployment and live chat testing remain to be done.

### Staging setup

Set **one server environment variable**, `PAPERCLIP_CLOUD_UI_SNIPPET`,
to:

```html
<script>
(function(d) {
  var script = d.createElement('script');
  script.src = 'https://chat.cdn-plain.com/index.js';
  script.onload = function() {
    Plain.init({ appId: 'liveChatApp_01M26J213F6RR53YRARZVAFCZZ' });
  };
  d.head.appendChild(script);
})(document);
</script>
```

This is the public staging app ID. **No API key or signing secret is
needed.** Deploy to staging and restart the app with this setting. Test
`/`, `/index.html`, and an organization dashboard; send a message and
confirm a support reply returns. Production rollout is separate.

[Plain embed docs](https://www.plain.com/docs/product/channels/chat) ·
[Configuration and
rollback](04bb445151/doc/cloud-ui-snippet.md)

## Risks

Only trusted operators should set this value. The HTML is public and
scripts execute in the app origin; do not include secrets or
user-provided HTML. Plain owns the anonymous browser session, with no
Paperclip account-switch integration. To roll back, unset the variable,
restart, and refresh open tabs.

## Model Used

OpenAI Codex (GPT-6), with repository inspection and code execution.
Exact runtime model identifier and context size are not exposed in this
session.

## Checklist

- [x] I have included a thinking path that traces from project context
to this change
- [x] I have specified the model used (with version and capability
details)
- [x] I have checked ROADMAP.md and confirmed this PR does not duplicate
planned core work
- [x] I have searched GitHub for duplicate or related PRs and linked
them above
- [x] I have either (a) linked existing issues with `Fixes: #` / `Closes
#` / `Refs #` OR (b) described the issue in-PR following the relevant
issue template
- [x] I have not referenced internal/instance-local Paperclip issues or
links (only public GitHub `#NNN` / `github.com/paperclipai/paperclip`
URLs)
- [x] My branch name describes the change and contains no internal
Paperclip ticket id or instance-derived details
- [ ] I have run tests locally and they pass
- [x] I have added or updated tests where applicable
- [x] I have updated relevant documentation to reflect my changes
- [x] I have considered and documented any risks above
- [x] All Paperclip CI gates are green
- [x] Greptile is 5/5 with no open P2s, recommendations, or follow-ups
- [x] I will address all Greptile and reviewer comments before
requesting merge

---------

Co-authored-by: Paperclip <noreply@paperclip.ing>
Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

doc/cloud-ui-snippet.md

@@ -0,0 +1,42 @@
+# Cloud UI snippet
+
+Cloud operators can set `PAPERCLIP_CLOUD_UI_SNIPPET` to an HTML snippet.
+The server inserts it before `</body>` in static and Vite-served UI pages.
+It requires the existing Cloud-managed instance signal. Self-hosted instances
+ignore this setting. No snippet is enabled by default.
+
+This is trusted deployment configuration, not user input. It executes in the
+application origin and is visible to every browser that receives the UI shell.
+Do not include secrets or customer data. Restart the app after changing it.
+Operators must review scripts and any required CSP changes before deployment.
+
+## Plain closed beta
+
+Set the value to this standard embed, replacing `YOUR_CHAT_APP_ID` with the
+public chat app ID for the target environment:
+
+```html
+<script>
+(function(d) {
+  var script = d.createElement('script');
+  script.src = 'https://chat.cdn-plain.com/index.js';
+  script.onload = function() { Plain.init({ appId: 'YOUR_CHAT_APP_ID' }); };
+  d.head.appendChild(script);
+})(document);
+</script>
+```
+
+No signing secret or Plain API key is required. No Paperclip customer identity
+or organization data is passed. Plain manages the anonymous browser session;
+there is no Paperclip account-switch integration. Ask users for identifying
+information when needed. The existing feedback flag remains unchanged.
+
+Docs: [Plain chat](https://www.plain.com/docs/product/channels/chat).
+
+## Verification and rollback
+
+On staging, open `/`, `/index.html`, and an organization dashboard directly.
+Confirm the bubble appears and a test message reaches Plain. Verify the support
+reply returns. On a self-hosted instance, confirm no snippet or widget is loaded.
+Unset the snippet and restart to remove it on the next page load. Existing open
+tabs retain the widget until refreshed. No production deployment is implied.

server/src/__tests__/cloud-ui-snippet.test.ts

@@ -0,0 +1,30 @@
+import { describe, expect, it } from "vitest";
+import { injectCloudUiSnippet } from "../cloud-ui-snippet.js";
+
+const html = '<html><body><div id="root"></div></body></html>';
+const snippet = '<script src="https://example.com/widget.js"></script>';
+
+describe("Cloud UI snippet", () => {
+  it("leaves self-hosted HTML unchanged even when a snippet is configured", () => {
+    expect(injectCloudUiSnippet(html, { PAPERCLIP_CLOUD_UI_SNIPPET: snippet })).toBe(html);
+  });
+
+  it.each([
+    { PAPERCLIP_CLOUD_TENANT_SERVER_TOKEN: "test-token" },
+    { PAPERCLIP_MANAGED_CONFIG: "{}" },
+  ])("injects only on a configured Cloud instance: %j", (cloud) => {
+    expect(injectCloudUiSnippet(html, { ...cloud, PAPERCLIP_CLOUD_UI_SNIPPET: snippet }))
+      .toBe(html.replace("</body>", `${snippet}\n</body>`));
+    expect(injectCloudUiSnippet(html, cloud)).toBe(html);
+    expect(injectCloudUiSnippet(html, { ...cloud, PAPERCLIP_CLOUD_UI_SNIPPET: "  " })).toBe(html);
+  });
+
+  it("preserves literal replacement tokens in operator JavaScript", () => {
+    const script = '<script>console.log("$&", "$`", "$\'");</script>';
+    const result = injectCloudUiSnippet(html, {
+      PAPERCLIP_MANAGED_CONFIG: "{}", PAPERCLIP_CLOUD_UI_SNIPPET: script,
+    });
+    expect(result).toContain(script);
+    expect(result).not.toContain("test-token");
+  });
+});

server/src/__tests__/static-index-html.test.ts

@@ -3,18 +3,31 @@ import os from "node:os";
 import path from "node:path";
 import express from "express";
 import request from "supertest";
-import { afterEach, describe, expect, it } from "vitest";
+import { afterEach, describe, expect, it, vi } from "vitest";
 import { readBrandedStaticIndexHtml } from "../static-index-html.js";
 
 describe("static SPA fallback HTML", () => {
   const tempDirs: string[] = [];
 
   afterEach(() => {
+    vi.unstubAllEnvs();
     for (const dir of tempDirs.splice(0)) {
       fs.rmSync(dir, { recursive: true, force: true });
     }
   });
 
+  it("includes the operator snippet only in Cloud-served static HTML", () => {
+    const dir = fs.mkdtempSync(path.join(os.tmpdir(), "paperclip-cloud-html-"));
+    tempDirs.push(dir);
+    fs.writeFileSync(path.join(dir, "index.html"), "<html><body>App</body></html>");
+    vi.stubEnv("PAPERCLIP_CLOUD_UI_SNIPPET", '<script src="https://example.com/chat.js"></script>');
+    vi.stubEnv("PAPERCLIP_CLOUD_TENANT_SERVER_TOKEN", undefined);
+    vi.stubEnv("PAPERCLIP_MANAGED_CONFIG", undefined);
+    expect(readBrandedStaticIndexHtml(dir)).not.toContain("chat.js");
+    vi.stubEnv("PAPERCLIP_MANAGED_CONFIG", "{}");
+    expect(readBrandedStaticIndexHtml(dir)).toContain('chat.js"></script>\n</body>');
+  });
+
   it("serves the current index.html instead of reusing stale asset hashes", async () => {
     const tempDir = fs.mkdtempSync(path.join(os.tmpdir(), "paperclip-static-index-"));
     tempDirs.push(tempDir);

server/src/app.ts

@@ -113,6 +113,7 @@ import { adapterRoutes } from "./routes/adapters.js";
 import { managedAgentProfileRoutes } from "./routes/managed-agent-profiles.js";
 import { remoteAgentProfileRoutes } from "./routes/remote-agent-profiles.js";
 import { pluginUiStaticRoutes } from "./routes/plugin-ui-static.js";
+import { injectCloudUiSnippet } from "./cloud-ui-snippet.js";
 import { readBrandedStaticIndexHtml } from "./static-index-html.js";
 import { staticUiCacheControl } from "./static-ui-cache.js";
 import { applyUiBranding } from "./ui-branding.js";
@@ -950,6 +951,10 @@ export async function createApp(
           immutable: true,
         }),
       );
+      // Serve root/index through the same runtime HTML transform as SPA routes.
+      app.get(["/", "/index.html"], (_req, res) => {
+        res.type("html").set("Cache-Control", "no-cache").send(readBrandedStaticIndexHtml(uiDist));
+      });
       // Non-hashed static files (favicon.ico, manifest, robots.txt, etc.):
       // short cache so operators who swap them out see the new version
       // reasonably fast, with must-revalidate overrides for index.html and
@@ -1058,7 +1063,7 @@ export async function createApp(
     viteHtmlRenderer = createCachedViteHtmlRenderer({
       vite,
       uiRoot,
-      brandHtml: applyUiBranding,
+      brandHtml: (html) => injectCloudUiSnippet(applyUiBranding(html)),
     });
     const renderViteHtml = viteHtmlRenderer;
 

server/src/cloud-ui-snippet.ts

@@ -0,0 +1,8 @@
+import { isCloudManagedInstance, type CloudInstanceEnv } from "./services/cloud-instance.js";
+
+/** Trusted operator HTML only. This content is public and runs in the app origin. */
+export function injectCloudUiSnippet(html: string, env: CloudInstanceEnv = process.env): string {
+  const snippet = env.PAPERCLIP_CLOUD_UI_SNIPPET;
+  if (!isCloudManagedInstance(env) || !snippet?.trim()) return html;
+  return html.replace(/<\/body>/i, () => `${snippet}\n</body>`);
+}

server/src/static-index-html.ts

@@ -1,7 +1,8 @@
 import fs from "node:fs";
 import path from "node:path";
+import { injectCloudUiSnippet } from "./cloud-ui-snippet.js";
 import { applyUiBranding } from "./ui-branding.js";
 
 export function readBrandedStaticIndexHtml(uiDist: string): string {
-  return applyUiBranding(fs.readFileSync(path.join(uiDist, "index.html"), "utf-8"));
+  return injectCloudUiSnippet(applyUiBranding(fs.readFileSync(path.join(uiDist, "index.html"), "utf-8")));
 }