The co-founder breakdown investors see before you do

What if the single biggest risk to your next funding round is not your traction, your valuation, your cap table, or even your technology - but the person sitting next to you on the call?

Most DeepTech founders, asked what could derail their Series A, would point almost anywhere else. They would talk about milestone slippage, about whether the science is ready, about the difficulty of finding investors who understand the technology. Almost none would name their co-founder. They would be looking in the wrong direction.

The relationship between founders is doing more underwriting work than most founders realise - quietly, in the background of every investor conversation, and increasingly explicitly inside the deal team's internal discussion. And the failure mode is rarely a dramatic blow-up. It is the slow, mostly invisible drift that surfaces, fully formed, in the room with an investor - by which point the deal is usually already lost.

This week's piece is uncomfortable on purpose. The DeepTech founders most exposed to this risk are the ones who would tell you, with complete sincerity, that they don't have it.


The data founders never quote

The most comprehensive study of how venture capitalists actually decide is the survey of more than 1,000 VCs at over 900 firms conducted by Gompers, Gornall, Kaplan and Strebulaev, the findings of which were published in the Harvard Business Review. The headline finding cuts straight at the question of what gets companies funded.

When asked what contributed most to their failures, 92% of VCs named the team. When asked what contributed most to their successes, 96% named the team. Every other factor - market, business model, technology, timing, luck - sat between 45% and 67%. The Gompers finding reinforces Noam Wasserman's earlier and methodologically independent HBS research on 10,000 founders, which reached the same essential answer a decade ago through a separate research programme.

The headline isn't that founders fight; everyone knows that founders fight. The headline is that most failures look like business problems on the surface and turn out to be relationship problems at the root. The pivot that came too late, the hire that didn't work out, the round that stalled - trace each one back through a few rounds of honest questioning and the fault line is usually inside the founding team. The silence is itself the diagnostic. If you cannot recall a substantive disagreement with your co-founder in the last quarter, the problem is not that you don't have any. It is that you have found a way not to surface them.


Why DeepTech makes this structurally worse

In SaaS, co-founders are often functionally interchangeable. Everyone codes, everyone sells, the gradient between roles is shallow, and a misalignment can usually be papered over by the speed of the underlying business. In DeepTech, the geometry is different. The CEO–CTO split is structural rather than situational, and the gap is wider in every dimension that matters: training, vocabulary, time horizons, definitions of progress, tolerance for ambiguity, and the cultural reflex on whether to over- or under-promise.

The Scenarionist's analysis of DeepTech team-building describes the CEO–CTO dynamic as the operating system of the company - and observes that when it is misaligned, brilliant science dies in tension. That is a stronger claim than it first reads. A scientifically world-class CTO paired with a CEO who overhypes timelines, or a commercially fluent CEO who shuts down legitimate engineering trade-offs, produces a company that looks fine externally but is structurally unstable internally. The DeepTech founder who insists this is just a personality dynamic to be managed has misread the geometry of their own company.


How investors actually probe the relationship

The investor's read of the relationship does not begin in formal due diligence. It begins on the first call. Allied Venture Partners' due diligence guidance lists imbalanced roles, equity disputes, misaligned strategy and poor leadership dynamics as the warning signs that surface in standard meetings - not in a deep DD process, but in the ordinary back-and-forth of a normal pitch. The founder thinks the meeting is about the deck. The investor is also watching the room.

The Scenarionist piece is more direct: if a CEO interrupts a CTO's answer in diligence, that is a red flag - and the investor is not just judging the answer, they are judging the trust. The mechanics are simple, and once you know what to look for they become almost embarrassingly obvious. Investors track who answers which questions, who defers to whom, where sentences finish and where they get cut off, what happens when one founder disagrees with the other in real time.

Founders rehearse the pitch and ignore the choreography. Sophisticated investors do the opposite. By the time the deal team writes the IC memo, the relationship has already been graded - and the founders almost never know that the grading happened.


The signals you didn't know you were giving

The signals are linguistic and behavioural, and they pre-date the formal process by months. Vocabulary mismatch is the first one - co-founders using different words for the same concept, or worse, the same word for different concepts. Then contradictory answers to the same question across separate calls, which investors track meticulously. Then body language asymmetries when one co-founder is asked about the other's domain. None of these is conscious. All of them are visible.

The instinct in most founders, particularly first-time founders, is to over-coordinate before investor calls in the hope of presenting a unified front. Y Combinator's Michael Seibel and executive coach Amy Buechler argue that the urge to over-coordinate is itself the warning sign. The need to rehearse a unified position usually points to underlying conversations the co-founders have been avoiding - and those avoided conversations always surface eventually.

The investor meeting is the worst possible place for that to happen. The founders who handle these moments well haven't rehearsed answers - they have had the underlying conversation. The difference between rehearsal and resolution is detectable inside thirty seconds, by anyone who has seen it before. And every experienced investor has seen it before.


The structures that hold

The relational work described above is necessary, but it is not sufficient. Even the most self-aware co-founder pair, with every difficult conversation surfaced and every pattern named, cannot prevent a co-founder from deciding to leave, falling ill, losing interest, or simply turning out to want a different life than the one the company demands. For those scenarios, the company needs structural protection - and that protection arrives with institutional capital, in two forms.

The first form of protection is founder vesting, which institutional investors typically require at Seed and sometimes again at Series A. Vesting over four years with a one-year cliff is the convention. Founders sometimes resist the reset on grounds of fatigue, but those who push back hardest tend to be read as the weakest on commitment. The reset is a normal cost of institutional capital.

The second form is the shareholders' agreement, and it is the document that actually carries the weight when a co-founder departs at year four, five, or six - long after the vesting schedule has fully matured. This is where good-leaver and bad-leaver provisions live: the mechanism by which fully-vested shares can be repurchased by the company at fair value or at a discount, depending on the circumstances of departure. Successful founders treat the shareholders' agreement as the load-bearing document for downstream co-founder risk. The founders who absorb a co-founder departure cleanly years later are almost always the ones whose shareholders' agreement was negotiated with the possibility of departure already in mind.

This is unromantic advice, and most co-founders resist it because the technical-commercial pairing usually originates in friendship, lab partnership or shared academic supervision - relationships that pre-date the company and feel somehow violated by the introduction of formal mechanics. That resistance is itself the warning sign. The structures do not manufacture conflict. They make conflict survivable when it arrives. And over the long arc of DeepTech development, with rounds that stretch the relationship across more time and more pressure than any SaaS journey, it always arrives.


The Colonna question, applied to the relationship

The most useful tool for surfacing the underlying dynamic is Jerry Colonna's foundational coaching question - how have I been complicit in creating the conditions I say I don't want? As we discussed last week, it is the question that exposes the founder's own contribution to outcomes they would prefer to attribute to others. Applied to the co-founder relationship, it cuts in directions most founders will not voluntarily go.

The CEO who complains the CTO is uncommercial rarely asks how their own habit of overcommitting to customers has trained the CTO into defensive silence. The CTO who feels the CEO doesn't respect the science rarely asks how their own gatekeeping of technical detail has made the CEO's job impossible.

Colonna told Lenny Rachitsky's audience the question only works if it is asked sincerely - as a tool for self-examination, not as ammunition in an argument. Co-founder pairs that have been through this process do not present as conflict-free in front of investors. They present as something more valuable: two people who have surfaced their friction, named their patterns, and built the capacity to repair when the inevitable next breach happens. That muscle is what investors are actually buying.


The takeaway

The most fundable DeepTech teams are not the ones without conflict. They are the ones who have made the conflict visible - to themselves, to each other, and on the page. The founder who walks into a Series A meeting presenting a frictionless, we just get each other facade is presenting a fragility an experienced investor reads inside the first ten minutes. Genuine harmony in a co-founder pair is the product of conflict worked through, not conflict avoided. The two look different, and experienced investors can tell which one they are seeing.

The technology might be the reason an investor takes the meeting. The relationship is the reason they sign.

 
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