Eleven months into the company, my co-founder told me he was done. Not angry, not dramatic — just done. He'd taken a job offer from a company that could pay him a real salary, and he was moving on. My first thought wasn't about the product roadmap or the fundraising deck we'd just started. It was: does he still own half my company?
The answer turned out to be the single most important legal decision we'd made and almost skipped.
The clause neither of us wanted to talk about
When we incorporated, our lawyer put standard four-year vesting with a one-year cliff into both of our founder stock purchase agreements. I remember pushing back. We'd known each other for six years. We'd already built two side projects together. Vesting felt like a prenup for people who didn't trust each other, and we did.
Our lawyer didn't argue the trust point. She just said this isn't about whether you trust him today, it's about what happens if the company is a different company in two years, with different people in it. I signed anyway, mostly to move the closing along. That clause is the only reason I still run this company.
The mechanics that actually mattered
Here's what a standard vesting schedule does, stripped of the legal language: nothing vests for the first twelve months. If someone leaves before that first anniversary, the company can repurchase 100% of their founder shares at the original nominal price, effectively as if they'd never been granted. At the twelve-month mark, 25% vests all at once. From month thirteen through month forty-eight, the rest vests monthly in equal increments.
My co-founder left at month eleven. Twenty-nine days before the cliff.
Under our agreement, that meant every single share he'd been issued reverted to the company's option pool. Not 90%. Not most of it, minus what feels fair. All of it. He walked away with zero equity in a company he'd co-founded, built the first version of our product for, and pitched to our first five customers.
I want to be direct about the part founders don't like admitting: this felt brutal to watch happen to someone I liked. It also felt necessary in a way I didn't expect until I was living it. If he'd left at month thirteen instead of month eleven, he would have walked away with roughly 27% of his total grant, 25% from the cliff plus one month of monthly vesting, and I'd have been staring at a cap table with a meaningful, permanent stakeholder who wasn't doing any of the work anymore.
Why this almost never gets talked about until it's too late
Most founder content about equity covers the split itself, the 50/50 versus 60/40 conversation you have on day one. Almost none of it prepares you for the conversation you have eighteen months later, when one person's life circumstances have changed and the other person is left holding a company that still has to answer to that original agreement.
Talk to any startup attorney who's handled a handful of seed-stage cap tables and you'll hear a version of the same story: a two-person company skips vesting because we trust each other, one co-founder leaves within the first year for a reason that has nothing to do with the relationship, health, family, a spouse's job relocation, sheer burnout, and the remaining founder is now negotiating a buyout with someone who legally owns half the company and has zero obligation to make that buyout easy or cheap. By the time an investor is doing diligence for a priced round, that unresolved cap table entry is a red flag serious enough to delay or kill the deal. I've seen the number quoted at three to six months of delay when a founder buyout has to get negotiated mid-raise. I believe it. Watching my own situation resolve cleanly because the paperwork already answered the question, I can't imagine what those six months of renegotiation actually cost in legal fees, investor patience, and founder sanity.
What I'd tell a founder setting this up today
If you're pre-incorporation or just past it, here's what I'd actually do differently, having lived through the other side of this clause instead of just reading about it.
First, put standard vesting in place even if it feels insulting to suggest to someone you trust. Frame it to your co-founder exactly the way our lawyer framed it to me: this protects both of you from a version of the company neither of you can predict yet, not just you from them.
Second, know your numbers cold before you need them. I didn't do the math on what a month-eleven departure meant until I was living through it. I should have known, from day one, exactly what percentage would be locked in at month twelve, month twenty-four, month thirty-six.
Third, if a co-founder is going to leave and there's any ambiguity about timing, get real legal advice immediately, not because you're trying to be adversarial, but because the difference between month eleven and month thirteen turned out to be the difference between a clean cap table and a messy one that could have haunted every fundraising conversation for the next two years.
The vesting cliff isn't a trust problem. It's a timing problem waiting to happen to a relationship you can't fully predict on day one. Put it in place before you need it, because you'll only find out how much it matters on the day you do.