# Build brief — a focused alternative to SubSignal

> **Verdict:** Not faithfully · **Buildability:** 18/100 · **Category:** Sales Outreach
> **Source:** https://www.canitbevibecoded.com/subsignal
> Independent editorial assessment from Can It Be Vibe Coded? Not affiliated with, endorsed by, or derived from SubSignal. Verify current pricing and capabilities before acting.

## Context

**SubSignal** — Watches Reddit for people describing the problem you solve, and surfaces them as leads.

Do not mistake the loop for the product. Polling subreddits and asking a model "is this a buying signal?" is an evening, and it is also the part that does not matter. What makes this useful is the accumulated archive behind it: years of threads at a scale you cannot backfill, which is what lets it tell a recurring complaint from a one-off and rank a lead against everything already seen. Your build starts empty on day one and stays empty, because Reddit will not sell you the past. That is a data problem, not a code problem.

This brief describes a focused, single-operator replacement for the part of SubSignal that is genuinely reproducible. It is deliberately narrower than the product it replaces, and it says so in writing. Build the useful core; do not pretend to have rebuilt the rest.

## What you are building

Poll a list of subreddits on a schedule, filter new posts by keyword, ask one model whether each is a buying signal for your product, and send the hits to Slack or email.

- Track contacts, sequence outreach, and log replies for a pipeline you own.
- A responsive interface with real empty, loading, success, and error states.

## Requirements

### Functional

- Node.js 22 and a scheduler such as cron.
- SQLite to remember what you have already seen.

### Data and integrations

- Reddit API credentials, within Reddit's terms of use.
- OpenAI or Anthropic API key in .env.

Each of these needs a real account, credential, or quota. Set them up before writing feature code.

### Non-functional

- Accessibility: semantic markup, labelled controls, visible focus, and reduced-motion support.
- Security: server-side secrets, validated input, and no credentials in the client bundle.
- Reliability: retries with backoff on external calls, and a clear failure state when a provider is down.
- Portability: the operator can export their data and leave without losing it.

## Implementation brief

Build a Reddit buying-signal monitor inspired by SubSignal.
Use exactly this stack: Node.js 22 + TypeScript + SQLite.
Primary job: on a schedule, fetch new posts and comments from a configured list of subreddits, ask one language model whether each one describes a problem the user's product solves, and deliver the matches to Slack or email with a link and a one-line reason.
Start from an empty folder and create the complete working project.
Use the official Reddit API with credentials from .env and respect its rate limits and terms of use; never scrape around them.
Store every item you have seen in SQLite so the same thread is never delivered twice, including across restarts.
Let the user describe their product in plain language in a config file, and build the classification prompt from that rather than from a hardcoded keyword list.
Score each match and let the user set a threshold, so the digest can be tightened without code changes.
Send a digest rather than one alert per hit, and make the schedule configurable.
Alert the user when a run fails or returns nothing for several consecutive runs - a silent crawler is the main failure mode of this kind of tool.
Put every secret in .env and provide .env.example.
Deliberately exclude these paid-product advantages: a curated subreddit and keyword set, accumulated cross-customer history, managed uptime.
Do not fake integrations, deliverability or data you do not have.
Write unit tests for deduplication and scoring, and one end-to-end smoke test against recorded fixtures rather than the live API.
Create a README with setup, Reddit API terms, cost estimate, architecture and limitations.
Run the tests and build before finishing, then fix what fails.

## Delivery standard

- Inspect the repository first, then write a short implementation plan before writing code.
- Deliver the smallest complete end-to-end workflow first; every primary control must work against persisted data.
- Use real validation and storage; never substitute fake dashboards, decorative controls, hard-coded success states, or mock integrations.
- Include responsive layouts plus genuine empty, loading, success, validation, and failure states.
- Keep secrets server-side in environment variables, provide .env.example, and never commit credentials or user data.
- Add structured logs around every external call and return actionable errors without leaking sensitive details.
- Write unit tests for the core logic and one automated test of the main user journey.
- Finish with a README covering setup, architecture, data location, backups, tests, deployment, and known limitations.

## Acceptance criteria

- [ ] A clean install starts the app using only the README and .env.example.
- [ ] The primary journey works from first visit through saved result, reload, edit, export, and deletion where applicable.
- [ ] Invalid input, missing configuration, provider failure, and an empty database each have a usable state.
- [ ] The interface works at 390px and 1440px, is keyboard navigable, and shows visible focus on every control.
- [ ] Tests, type checking, linting, and a production build all pass with no ignored failures.
- [ ] No part of the interface implies a live integration, security guarantee, or scale capability that was not actually built and verified.

## Non-goals

Do not build these, and do not claim to have replaced them:

- A historical archive you cannot backfill from the live API.
- Ranking a lead against everything seen before, instead of judging it alone.
- A curated subreddit and keyword set you did not have to discover.
- Deduplication and history across runs.
- Someone tracking Reddit API terms and rate-limit changes for you.

## What you still own after launch

- Secure credentials, rotate secrets, and handle provider rate limits.
- Run migrations, backups, restores, and dependency updates.
- Test the critical journey after every model, API, or hosting change.
- Monitor failures and fix the edge cases a first prompt will miss.

## Risk

**Operational risk.** The code is achievable; dependable data, integrations, and ongoing operations are the real cost.

Editorial confidence in this assessment: medium. No reviewed project implementation is linked yet.

## Existing alternatives

Before building, compare these checked options:

- [F5Bot](https://f5bot.com/) — Reddit keyword alerts by email; no dashboard, no scoring, no theatre

## Prior art

Working open-source software you can read, fork, or borrow from before starting:

- [PRAW](https://github.com/praw-dev/praw) — Python Reddit API wrapper; the standard way to poll subreddits
- [Huginn](https://github.com/huginn/huginn) — Self-hosted agents that watch feeds and act on events
- [changedetection.io](https://github.com/dgtlmoon/changedetection.io) — Self-hosted change monitoring with notifications

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