Startupsby GlyphWhy it ranks
How the rank works- went through YCProgram · this site+4
- team of 2Team size · YC's directory+2.5
- hiringHiring · Titles (titles.fru.dev), YC+2
A sum of public facts, not a judgement and not investment advice.
Competitors
| Company | Category | Status | Program |
|---|---|---|---|
| AI | Active | YCW22 | |
| AI | Not stated | Plug and Play |
Adjacent
| Company | Category | Status | Program |
|---|---|---|---|
| Other | Not stated | Antler2024 | |
| AI | Inactive | YCW22 | |
| AI | Active | YCW19 | |
| AI | Active | YCS15 | |
| AI | Active | YCW24 |
Also from S26 in AI
All of S26Founders
- Merlin KafkaFounder/CEO
- Lewis BlackwoodFounder/CTO
About Rex
Rex is a managed AI service for AR and order-to-cash. AI agents and finance experts run the work that delays payment, from collections, portals, disputes and remittances to the shared AR inbox, so cash keeps moving. Order to cash is a $60B outsourced function because the work is too messy for traditional automation. Every customer has different context, exceptions do not follow clean rules, and the next step is often buried in emails, portals, handoffs, or someone’s memory. Rex agents run continuously in the background and resolve work to SLA standards so cash keeps moving. We're live with pre-IPO tech companies, managing >$500m in receivables from F100 companies, cutting manual follow-up cycles from weeks to hours. We founded Rex after spending four years building Sequence, an a16z-backed finance ops platform, from zero to Series A, where we saw firsthand that at-scale, O2C still runs on manual labour. Rex is the #1 winner of the Vercel AI Accelerator out of 2,500 teams, selected by Guillermo Rauch and leaders from OpenAI, Anthropic, Browserbase and more.
- YC batch
- S26 · Summer 2026
- Status, per YC
- Active
- Category
- AI
- Team size
- 2
- Location
- San Francisco, CA, USA
- Founded
- 2026
- Checked
- 6h ago
YC tags: B2B, Enterprise, Enterprise Software, AI
Changes seen
Rex: questions
Which YC batch was Rex in?
Rex was in Y Combinator's Summer 2026 batch (S26).
Is Rex still active?
Y Combinator lists Rex as active.
Who founded Rex?
Rex's founders, as listed on its YC page: Merlin Kafka (Founder/CEO), Lewis Blackwood (Founder/CTO).
Where is Rex based?
Rex lists San Francisco, CA, USA as its location on YC's directory.