Now in beta · 7-day free trial

Your side hustle's second brain.

SideBrain ships publishable X threads, replies, and newsletter drafts in your voice. Generate a week of content in 5 minutes — and actually grow.

Start your 7-day trial See how it works →

No credit card required · Cancel anytime · Solo from $9/mo

How it works

Five minutes a day. Five publishable assets.

Take a 10-question diagnostic. Pick a vertical. Paste 3 of your past posts so we lock in your voice. Then ship.

Step 1

Diagnose

10-question diagnostic. We map your goals, niche, voice, and constraints into a structured profile.

Step 2

Calibrate

Paste 3 past posts. Memory locks your voice so outputs sound hand-typed.

Step 3

Ship

Generate your daily X thread or weekly newsletter draft. Review, edit, publish. Friday digest.

Features

Built like the tool you wish your side hustle had.

Two verticals out of the box

X / Twitter Growth and Newsletter (Substack · Beehiiv · Ghost). 16 production-grade Skills shipping every kind of content you need each week.

Voice memory

Sounds like you, not GPT-4

Voice-aware memory remembers your past posts, audience, and what works. Outputs feel hand-typed, not auto-generated.

Solo-priced

Costs less than coffee

Solo $9 · Pro $19 · Studio $49. 7-day free trial. 90-day money-back if your audience didn't grow.

Human-in-loop

You drive, AI rides shotgun

No auto-posting. We draft, you review, you ship. Trust > automation.

Sundays calmer

Weekly performance reports

Friday email digest of what worked and what didn't — with 3 specific moves for next week.

Engineering matters

Built for solo founders

Vercel + Neon + TypeScript. Open monorepo. Eval-gated CI. Latency under 30s for full threads.

Skills

16 P0 Skills, eval-gated in CI.

Every Skill ships with golden fixtures. PromptFoo blocks the merge if quality drops. So the bar only goes up.

X-02

Thread Writer (5 styles)

Hook · Insight · Story · Listicle · Spicy

X-03

Reply Generator

3 tones for high-leverage replies

X-06

Lead-Magnet Hook

Convert thread readers to subscribers

NL-02

Long-Form Draft

1500-3000 words in your voice

NL-03

Subject Line + Predictor

5 candidates with open-rate

NL-05

Welcome Sequence

7-email onboarding for new subs

Pricing

Less than your weekly coffee.

7-day trial. No credit card. Annual saves 20%.

Activation tier

Solo

$9/mo

$86 billed annually

✓1 vertical (X or Newsletter)
✓500 agent steps / month
✓All core Skills
✓Email support

Start free trial

Stop drafting at midnight.

Your side hustle is one diagnostic away from running on autopilot.

Start your 7-day trial