CapStack GP

The problem is real and precisely named. Anyone who has built or reviewed a waterfall in Excel knows that liquidation preference stacks, participation caps, anti-dilution ratchets, and option pool timing get encoded in cell references that nobody audits before a partner meeting. The founder's framing — 'silent defaults are fine in the base case and wrong in edge cases' — is the correct diagnosis. Edge cases are precisely where the modeling matters, because that's where common holders, management, and later-round preferred all diverge. That said, the pain is chronic, not acute. GPs have lived with spreadsheets for 40 years. The consequence of a bad waterfall model is usually a mildly wrong IC memo, not a blown deal — the LP capital gets deployed either way, and the actual exit reconciliation happens years later with lawyers involved. So the problem is real but the willingness-to-pay curve is unclear. This is a 'quietly costly' problem, not a 'CFO is calling you at 11pm' problem. The buyer is also narrow: investment professionals at venture funds and, adjacent to them, corporate development, secondaries buyers, and startup CFOs preparing for financings. That's a defined but small TAM, and most of these buyers already have a workflow — Carta for cap tables, Excel for waterfalls, and a junior associate to redo it when partners ask.

The product philosophy — 47 named assumptions across six domains, each defaulted to institutional standard but individually overridable, with a warning that unreviewed defaults produce wrong edge-case outputs — is genuinely differentiated. It reframes the tool from 'a calculator' to 'a checklist that also calculates.' That is a real product insight and it maps to how careful GPs actually want to work. The glossary and prompt library suggest the founder understands that half the value is education and audit trail, not raw computation. The risks in the solution are two. First, 'assumption transparency' is a feature, not a moat — Carta, Pulley, LTSE Equity, and any determined competitor can add an 'assumptions panel' in a quarter. Second, the browser-based, no-account-required posture is founder-friendly and demo-friendly but works against the enterprise procurement motion venture funds actually use. GPs want SOC 2, SSO, an audit log, and a signed MSA before they put a portfolio cap table into a SaaS tool. The stronger wedge, if the founder wants one, is probably not 'better than a spreadsheet' — it's 'the shareable, auditable model that the whole IC and the LPs can inspect,' i.e. selling collaboration and defensibility rather than calculation. Nothing in the current description leans into that.

Bottom-up: there are roughly 2,000-3,000 active venture funds in the US and perhaps 1,500-2,500 more globally that matter. Each has 3-15 investment professionals who might use this tool. Call it ~30,000-50,000 potential seats globally. At a plausible $50-150/seat/month for a specialized modeling tool, that's a $20M-$90M ARR ceiling for the pure-GP wedge — small for a VC-scale outcome, potentially excellent for an angel-scale outcome. Expanding into startup CFOs, secondaries, search funds, PE growth, and corp dev could 5-10x that. For an angel, this sizing is fine. A $3-8M ARR business selling to venture professionals is a very plausible acquisition target for Carta, AngelList, Pulley, or a fund-admin player like Juniper Square or Carta itself. That's a credible 5-10x angel outcome if entry is at a sensible pre-seed valuation.

Carta — the incumbent. Owns cap tables for startups and increasingly for funds via Carta LP. Has waterfall modeling but it's widely regarded as clunky and opinionated. CapStack GP is complementary (works on models Carta users export) and eventually competitive; the realistic exit path here is 'acquired by Carta or a Carta competitor.' Pulley and LTSE Equity — Carta alternatives focused on startups. Less relevant on the GP side today but expanding. Could add GP-side waterfall modeling as a feature. AngelList Stack / AngelList for Funds — services the fund-formation and admin side. Not a direct modeling tool but sits close to the workflow and has GP relationships CapStack lacks. Chronograph and Tactyc — portfolio monitoring and fund construction/forecasting tools for VCs. Tactyc in particular does fund-level modeling (recently acquired by Carta, based on what I know through my training cutoff). This is the closest analogue in terms of buyer and workflow, and its acquisition is the clearest signal that this category has strategic value to incumbents. Foundersuite / Visible.vc — adjacent GP tools, not competitive on modeling but share the same buyer. As of my training data, the fund-tech category has seen meaningful consolidation activity (Carta acquiring Tactyc being the most visible example), which is a positive tailwind for a well-built point tool with a defensible niche.

1. Buyer inertia and Excel gravity. GPs have modeled waterfalls in spreadsheets for decades and IC memos circulate as .xlsx attachments. Switching requires not just a better tool but a change in how a fund's investment memo pipeline works. Mitigation: sell to individual associates first as a 'shadow tool' before selling to the fund; make Excel import/export bulletproof. 2. Feature, not company. 'Explicit assumptions' can be copied by Carta or Tactyc in one release cycle. There is no data moat, no network effect, and no obvious lock-in in what's described. Mitigation: build workflow lock-in via shared IC-ready model artifacts, audit trails, and integration with fund admin — none currently in evidence. 3. Distribution from Richmond, VA. The venture GP buyer clusters in SF, NYC, and Boston. Selling into this audience without a warm network is brutal; cold outbound to GPs has abysmal conversion. Mitigation: unknown from the input — the founder's network and background aren't described. This is the single biggest thing an angel should probe on the call. 4. Compliance and data sensitivity. Cap tables and fund economics are among the most confidential documents a fund handles. A browser-based tool with 'no apparent account requirement' is great for demos and disqualifying for production use. Mitigation: SOC 2, SSO, and an on-prem or private-tenant option — none mentioned. 5. Small buyer universe. Even at 100% share of active US venture GPs, the ARR ceiling is modest without adjacent expansion. Mitigation: an explicit second-market plan (startup CFOs, secondaries, search funds) that the founder should be able to articulate.

1. At least a handful of GPs will pay for this over using Excel. Validation in the next 60 days: 5 paid pilots or LOIs from named funds (not just associates using the free tool), with a stated price point above $50/seat/month. 2. The founder can reach venture GPs despite being outside the SF/NYC network. Validation: 20 discovery calls with GPs at named funds within 60 days, sourced from the founder's own outreach, with call notes on what those GPs actually said about their current workflow. 3. The product's 'explicit assumptions' philosophy is a durable wedge, not a copyable feature. Validation is qualitative: does the founder have a credible roadmap toward workflow lock-in (shared IC artifacts, audit trails, fund admin integration) rather than more calculator features?