# How to Vibe Code Your Own SubSignal (and Stop Paying for It)

> AI-powered Reddit monitoring, brand tracking, and sales lead generation

- Site: https://subsignal.ai
- Category: Marketing & Sales SaaS
- Platforms: Web app
- Verdict: **Solid side project** (68/100 vibecodeable)
- Estimated effort: 2-3 weeks part-time

## Verdict

Build a personal clone if you want an automated Reddit lead finder for your own projects, but keep paying if you expect commercial-grade uptime and advanced shill heuristics.

The core loop—pulling recent Reddit posts via RSS or the Reddit API, passing them through an LLM to check buying intent against your product profile, and displaying them in a dashboard—is a classic solid side project. The engineering trap here is not the frontend UI, but building a resilient ingestion worker queue that does not get rate-limited by Reddit, combined with managing LLM API costs when scanning thousands of conversational posts daily.

### What you can't replicate

- SubSignal's accumulated brand-matching heuristics and refined alert tuning
- Their exact production customer base and organic community footprint

## What it does

SubSignal scans Reddit for high-intent buying signals, competitor mentions, and sentiment insights, providing an intelligence layer tailored to founders and SaaS companies.

### Core features

- Continuous Reddit ingestion engine
- Semantic intent scoring via LLMs
- Brand monitoring and competitor tracking
- Real-time mention alerting (Email/In-app)
- Shill detection and user forensics
- Contextual AI reply generation

## The business

### Pricing

- Free: $0/mo
- Pro: $129/mo

Founded 2025.
Team size: Solo / micro-team.

## The hard parts

- Handling Reddit API rate limits, schema changes, and scraping/feed queuing without getting blocked
- Running reliable background background jobs for continuous thread ingestion across thousands of subreddits
- Designing semantic vector classification matching product descriptions accurately against casual colloquial phrasing
- Building behavioral heuristics and forensics for shill and bot ring detection

## How to vibe code SubSignal

### Prerequisites

- Node.js (free): Runtime environment for the Next.js web application and background workers.
- GitHub (free): Version control and CI/CD triggers for deployment.
- Anthropic API key (pay-as-you-go): Powers semantic intent classification and draft reply generation.

### Recommended AI tools

- Claude Code: Best-in-class terminal agent for bootstrapping full-stack Next.js applications and writing robust background scraping/queuing logic.
- Cursor: Ideal for iterative UI work, fine-tuning dashboard components, and inspecting database query diffs.

### Stack

- Frontend: Next.js
- Backend: Next.js API routes & Inngest background workers
- Database: Turso
- Auth: better-auth
- Payments: none (personal use clone)
- Other: Vercel AI SDK, Resend, Tailwind CSS

### Hosting

- Vercel (Hosting the Next.js frontend and serverless API endpoints.): $0/mo (Hobby tier)
- Railway (Running persistent background worker processes for scheduled Reddit ingestion cron jobs.): $5/mo

### Build guide

1. **Scaffold Project & Database Schema** — Initialize the Next.js project with Tailwind CSS, configure Turso SQLite via Drizzle ORM, and set up better-auth for single-user or multi-user access.

```
Create a new Next.js 16 project using TypeScript and Tailwind CSS v4. Set up Drizzle ORM configured for Turso SQLite. Define database schemas for users, monitored_keywords (id, userId, keyword, subreddits, active), posts (id, redditId, title, url, subreddit, author, content, score, intentScore, matchedKeywordId, createdAt), and alerts. Integrate better-auth for local credential authentication. Verify the schema compiles cleanly and migration scripts run without errors.
```

2. **Reddit Ingestion Engine** — Build a robust ingestion module that polls Reddit JSON feeds or API endpoints with exponential backoff and request rate limiting.

```
Create a backend worker service using Node.js and TypeScript that periodically queries Reddit search JSON endpoints and target subreddit RSS/JSON feeds. Implement strict rate-limiting, request deduplication by redditId, and error handling with exponential backoff to prevent blocks. Save newly discovered posts into the Turso database, ensuring old duplicates are ignored.
```

3. **Semantic AI Intent Scorer** — Integrate the Vercel AI SDK and Anthropic API to analyze incoming Reddit posts against user-defined product descriptions and keywords.

```
Implement an intent scoring service using the Vercel AI SDK and Anthropic API (Claude Sonnet). For every newly ingested Reddit post, send the post title, body, and the user's product description to the LLM to output a JSON object containing: isMatch (boolean), buyingIntentScore (1-10), urgency (low/medium/high), and a brief rationale. Store these results back in the posts table.
```

4. **Dashboard Lead Finder & Filtering UI** — Build the main SaaS dashboard views to display, filter, and sort high-intent Reddit leads by urgency, score, and subreddit.

```
Build a responsive SaaS dashboard UI using Tailwind CSS and Lucide icons in Next.js. Create a 'Lead Finder' view that lists ingested Reddit posts matching the user's criteria. Include filter controls for minimum intent score, subreddit selection, and date range. Add card components showing post metadata, AI rationale badges, and direct links to the Reddit threads.
```

5. **AI Reply Generator & Notifications** — Add contextual draft reply generation for individual leads and email notification dispatches via Resend for urgent matches.

```
Add an AI Reply Generator modal to the lead detail view that calls Claude to draft 3 authentic, non-spammy engagement response options tailored to the specific subreddit's culture. Implement an alert dispatcher using Resend that triggers instant email notifications when a post with an intent score above 8 is indexed. Verify end-to-end flow from ingestion to email delivery.
```

### Cost vs paying

**Starting costs (one-time):**

- Domain name registration: $12 one-time
- Total: ~$12 one-time

**Ongoing costs (monthly):**

- Railway background worker hosting: $5/mo
- Anthropic API usage for intent scanning & replies: ~$10/mo
- Total: ~$15/mo

- Paying for the SaaS instead: $129/mo
- Build time: 35-50 hours
- AI tool credits: $20 (Claude Pro)
- Break-even: 1 month

## Sources

- [SubSignal Official Website & Features](https://subsignal.ai)
- [GitHub - Redsignal Open Source Alternative Blueprint](https://github.com)