Open sourcing demo of llamaindex by CoderOMaster · Pull Request #125 · usemoss/moss

CoderOMaster · 2026-04-07T05:01:58Z

Pull Request Checklist

Please ensure that your PR meets the following requirements:

I have read the CONTRIBUTING guide.
I have updated the documentation (if applicable).
My code follows the style guidelines of this project.
I have performed a self-review of my own code.
I have added tests that prove my fix is effective or that my feature works.
New and existing unit tests pass locally with my changes.

Description

Open sourcing code of llama index demo

Type of Change

Bug fix (non-breaking change which fixes an issue)
New feature (non-breaking change which adds functionality)
Breaking change (fix or feature that would cause existing functionality to not work as expected)
This change requires a documentation update

Copilot

Pull request overview

This PR adds an open-source “LiteParse + Moss + LlamaIndex” demo app, consisting of a Next.js frontend for uploading/querying PDFs and a FastAPI backend that parses PDFs, chunks them, builds a Moss index, and streams retrieval results via SSE.

Changes:

Added a Next.js (App Router) frontend with Tailwind styling and demo UX (upload, indexing progress, retrieval display).
Added a FastAPI backend with upload → parse → chunk → index flow and SSE-based retrieval endpoint, plus a seeding script and Docker image.
Added static assets (icons/logos) and basic project configuration (.gitignore, PostCSS, TS config, lockfiles).

Reviewed changes

Copilot reviewed 21 out of 28 changed files in this pull request and generated 11 comments.

Show a summary per file

File	Description
apps/moss-llamaindex/frontend/tsconfig.json	TypeScript configuration for the demo frontend.
apps/moss-llamaindex/frontend/public/X.svg	Added X icon asset.
apps/moss-llamaindex/frontend/public/liteparse.png	Added LiteParse image asset.
apps/moss-llamaindex/frontend/public/Icon.png	Added app icon asset.
apps/moss-llamaindex/frontend/public/Favicon.svg	Added favicon asset.
apps/moss-llamaindex/frontend/postcss.config.mjs	Tailwind PostCSS configuration.
apps/moss-llamaindex/frontend/package.json	Frontend dependencies/scripts (Next/React/Tailwind/UI libs).
apps/moss-llamaindex/frontend/package-lock.json	Frontend dependency lockfile.
apps/moss-llamaindex/frontend/next.config.mjs	Next.js config (headers/images settings).
apps/moss-llamaindex/frontend/next-env.d.ts	Next.js TypeScript env declarations.
apps/moss-llamaindex/frontend/lib/utils.ts	Utility for className merging (`cn`).
apps/moss-llamaindex/frontend/components/ui/button.tsx	Reusable Button component/variants.
apps/moss-llamaindex/frontend/components/demo/upload-section.tsx	Upload UI with drag/drop and file list.
apps/moss-llamaindex/frontend/components/demo/indexing-progress.tsx	Indexing progress UI/animation.
apps/moss-llamaindex/frontend/components/demo/chat-section.tsx	Retrieval “chat” UI consuming SSE stream.
apps/moss-llamaindex/frontend/components/common/navbar.tsx	Demo site navbar with mobile drawer.
apps/moss-llamaindex/frontend/components/common/footer.tsx	Demo site footer with external links/social icons.
apps/moss-llamaindex/frontend/app/page.tsx	Main demo page flow (upload → indexing → ready).
apps/moss-llamaindex/frontend/app/layout.tsx	App layout, metadata, fonts, navbar/footer, toaster.
apps/moss-llamaindex/frontend/app/globals.css	Tailwind import + global styles and tokens.
apps/moss-llamaindex/backend/seed_index.py	Script to pre-index a PDF into Moss for reuse.
apps/moss-llamaindex/backend/requirements.txt	Backend Python dependencies.
apps/moss-llamaindex/backend/package.json	Backend dev dependency for LiteParse CLI.
apps/moss-llamaindex/backend/main.py	FastAPI backend implementing upload/index/query endpoints.
apps/moss-llamaindex/backend/Dockerfile	Docker image for the backend with Node + LiteParse CLI.
apps/moss-llamaindex/backend/.dockerignore	Docker ignore rules for backend build context.
apps/moss-llamaindex/.gitignore	Repo ignore rules for the moss-llamaindex app.

Files not reviewed (1)

apps/moss-llamaindex/frontend/package-lock.json: Language not supported

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

Copilot · 2026-04-07T05:07:27Z

+const nextConfig = {
+  poweredByHeader: false,
+  reactStrictMode: true,
+  images: {
+    remotePatterns: [{ protocol: 'https', hostname: '**' }],


images.remotePatterns is configured to allow https://** (any hostname), which means the Next.js image optimizer can be abused to fetch arbitrary remote URLs. Consider restricting this to the specific hostnames you need (or removing remotePatterns entirely if not required).

Suggested change

const nextConfig = {

poweredByHeader: false,

reactStrictMode: true,

images: {

remotePatterns: [{ protocol: 'https', hostname: '**' }],

const allowedImageHostnames = (process.env.NEXT_IMAGE_REMOTE_HOSTNAMES ?? '')

.split(',')

.map((hostname) => hostname.trim())

.filter(Boolean);

const nextConfig = {

poweredByHeader: false,

reactStrictMode: true,

images: {

remotePatterns: allowedImageHostnames.map((hostname) => ({

protocol: 'https',

hostname,

})),

Copilot · 2026-04-07T05:07:29Z

+@app.middleware("http")
+async def add_hsts_header(request, call_next):
+    response = await call_next(request)
+    response.headers["Strict-Transport-Security"] = "max-age=30"
+    return response
+
+
+app.add_middleware(CORSMiddleware, allow_origins=["*"], allow_methods=["*"], allow_headers=["*"])
+


allow_origins=["*"] effectively disables CORS protection for this API. If this is intended for local demos only, consider making allowed origins configurable via env var and defaulting to a safer value in production deployments.

Copilot · 2026-04-07T05:07:29Z

+@app.middleware("http")
+async def add_hsts_header(request, call_next):
+    response = await call_next(request)
+    response.headers["Strict-Transport-Security"] = "max-age=30"
+    return response


Strict-Transport-Security is being set for all requests with max-age=30. HSTS should generally only be sent over HTTPS and usually with a much longer max-age; consider making this conditional (e.g., only when behind TLS / in production) or removing it for local dev to avoid confusing client behavior.

vercel · 2026-04-07T05:08:57Z

The latest updates on your projects. Learn more about Vercel for GitHub.

Project	Deployment	Actions	Updated (UTC)
next-js	Ready	Preview, Comment	Apr 7, 2026 5:09am

devin-ai-integration

Devin Review found 2 new potential issues.

View 10 additional findings in Devin Review.

devin-ai-integration · 2026-04-08T07:40:23Z

+		const apiPromise = fetch(`${API_URL}/api/sample`).then((r) => {
+			if (!r.ok) throw new Error('Failed to load sample');
+			return r.json();
+		});


🟡 Unhandled promise rejection in loadSample when API call fails during animation

The apiPromise is created outside the try block at line 92, but isn't awaited until line 104, after a ~4-second animation loop. If the fetch rejects quickly (e.g., network error, backend is down), the promise is rejected with no .catch() handler attached for up to 4 seconds. This triggers the browser's unhandledrejection event, which logs console errors and fires global error handlers (e.g., Sentry). The error IS eventually caught when await apiPromise runs inside the try, but the unhandledrejection event has already fired.

Fix approach

Either move the fetch call inside the try block, or attach a no-op .catch() to suppress the intermediate rejection: const apiPromise = fetch(...).then(...).catch(() => { throw ... }) — or simply store a caught version and re-throw on await.

Prompt for agents

In the loadSample callback in apps/moss-llamaindex/frontend/app/page.tsx, the fetch promise (apiPromise) is created at line 92 outside the try block but not awaited until line 104, after a 4-second animation loop. If the fetch rejects quickly (e.g. backend is down), the browser fires an unhandledrejection event during the animation window because no .catch() is attached. The simplest fix is to move the fetch call inside the try block, or store the rejection for later re-throw: Option A: Move inside try: try { const apiPromise = fetch(...)... for (animation loop)... const data = await apiPromise; } Option B: Swallow-and-rethrow pattern: let apiError; const apiPromise = fetch(...)...catch(e => { apiError = e; }); try { for (animation loop)... if (apiError) throw apiError; const data = await apiPromise; } Option A is simpler and preferred.

Was this helpful? React with 👍 or 👎 to provide feedback.

yatharthk2 · 2026-04-08T23:20:09Z

is this ready for review ?

feat: open sourcing demo of llamaindex

928cae0

CoderOMaster requested review from HarshaNalluru, r4ghu and yatharthk2 as code owners April 7, 2026 05:01

Copilot AI review requested due to automatic review settings April 7, 2026 05:02

Copilot started reviewing on behalf of CoderOMaster April 7, 2026 05:02 View session

This comment was marked as resolved.

Sign in to view

Copilot AI reviewed Apr 7, 2026

View reviewed changes

devin suggestions

ac4a7aa

copliot fixes

bf0b055

This comment was marked as resolved.

Sign in to view

minor bugs

afe48cf

devin-ai-integration bot reviewed Apr 8, 2026

View reviewed changes

Conversation

CoderOMaster commented Apr 7, 2026 • edited by devin-ai-integration bot Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Pull Request Checklist

Description

Type of Change

Uh oh!

This comment was marked as resolved.

Uh oh!

Copilot AI left a comment

Choose a reason for hiding this comment

Pull request overview

Reviewed changes

Uh oh!

Copilot AI Apr 7, 2026

Choose a reason for hiding this comment

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Copilot AI Apr 7, 2026

Choose a reason for hiding this comment

Uh oh!

Copilot AI Apr 7, 2026

Choose a reason for hiding this comment

Uh oh!

Uh oh!

Uh oh!

vercel bot commented Apr 7, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

This comment was marked as resolved.

Uh oh!

devin-ai-integration bot left a comment

Choose a reason for hiding this comment

Uh oh!

devin-ai-integration bot Apr 8, 2026

Choose a reason for hiding this comment

Uh oh!

Uh oh!

yatharthk2 commented Apr 8, 2026

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

3 participants

CoderOMaster commented Apr 7, 2026 •

edited by devin-ai-integration bot

Loading

vercel bot commented Apr 7, 2026 •

edited

Loading