Two-person and three-person founding teams considering formalising shareholding, plus solo founders evaluating prospective cofounders. Useful before signing any cofounder agreement, share certificate, or investor-facing document. Also reusable mid-relationship to surface drift before it becomes a blow-up.
What does it measure?
Thirty questions across five dimensions: values alignment (6 q), complementary skills (6 q), work compatibility (6 q), financial alignment (6 q), life circumstance (6 q). Score 0-90 with tiered output: Red flags / Misaligned / Workable fit / Strong fit. Per-dimension breakdown surfaces the lowest two for the gap-action plan.
When to take it?
At three points: (1) before formalising the cofounder agreement; (2) at year 1 of operating, as a relationship-health check; (3) when something feels wrong but the source is unclear. Most useful at point 1 — most cofounder breakups trace back to dimensions that were observable at formation but not surfaced.
Where does the result apply?
To any 2-3 person team in the first 36 months of operating. The five dimensions are formation-stage agnostic — the same alignment matters at pre-seed, seed, and Series A. After Series A, structural dynamics (board, investors, hire pyramid) dominate; at that stage rerun more sparingly.
Why this diagnostic?
Because the postmortem literature on cofounder breakup converges on these five. Values alignment is the slowest-moving and most structural; complementary skills is the most observable; work compatibility is the most under-tested at formation; financial alignment is the most often-avoided; life circumstance is the most ignored. Together they cover ~85% of the failure modes.
Which questions matter most?
Empirically, values_alignment dominates long-run partnership outcome. A team with values misalignment but strong skills can produce a viable company that breaks up at exit. A team with skills misalignment but strong values can grow through hires. Skills are fixable; values are structural.
Whose framework underwrites it?
Composed against the cofounder-breakup literature — Noam Wasserman (Founder's Dilemmas), Y Combinator essays on cofounder selection, plus practitioner reports from accelerator selection committees, late-stage VC partner interviews on founding-team risk-flagging, and AJG editorial review of MSME and family-business succession dynamics for the principal-context lens.
How does the scoring work?
Each question is 0-3 weight (3 = strong alignment, 0 = strong red flag). Sum across all 30 = total raw score (max 90). Per-dimension percentage normalises across the six questions. Tier thresholds: 71-90 strong fit, 56-70 workable, 41-55 misaligned, 0-40 red flags. The lowest two dimensions automatically generate the gap-action plan.
Totality lens · 32 points to ponder · 16 user POV + 16 developer POV · this tool
User POV — for the practitioner using this tool
Eight dimensions
1 · Possibility
Two prospective cofounders can in principle assess fit across the 18 dimensions the diagnostic surfaces — operating-philosophy alignment, work-rhythm compatibility, conflict-resolution style, financial-risk tolerance, equity-philosophy, exit-horizon expectations, family-context constraints, communication cadence preferences, and 10 more. Few do; most assess on 2-3 dimensions (chemistry + complementary-skills + shared-vision) and discover the missing dimensions during the first crisis.
2 · Plausibility
A pair completing the diagnostic honestly typically reveals 3-6 dimensions of meaningful divergence, of which 1-2 are critical-path (would surface as conflict during a crisis). Resolving the divergences pre-commitment takes 4-12 weeks of structured conversation; resolving post-commitment usually requires equity restructuring or co-founder split, both expensive. The 4-12 weeks of pre-commitment work is the trade.
3 · Probability
Of pairs who run the diagnostic pre-commitment and address the surfaced divergences, perhaps 75-85 percent build durable cofounder relationships through the first 5 years. Of pairs who skip the diagnostic, perhaps 50-60 percent reach year 5 intact. The diagnostic does not predict success; it filters out the avoidable failure modes that show up in the relationship rather than in the market.
4 · What works
What works: completing the diagnostic separately first, then comparing answers, then having structured conversation on the divergent dimensions; setting explicit decision-making protocols for the disagreement-likely dimensions; documenting equity vesting + reverse-vesting + buy-back triggers in writing pre-commitment; agreeing to revisit the diagnostic annually for the first 3 years.
5 · What doesn't work
What does not work: skipping the diagnostic because "we already know each other"; running the diagnostic together rather than separately first (suppresses honest divergence); discussing only the dimensions where you align (false reassurance); committing equity before the divergent-dimension conversations have produced explicit decisions; treating cofounder-fit as a one-time check rather than annual review.
6 · Common pitfall
The most common pitfall is over-weighting "we are great friends" as predictive of cofounder fit. Friendship and cofounder partnership are correlated but not identical: friendships tolerate divergent operating-philosophies because the stakes are low, partnerships do not. Many pairs assume their friendship will buffer cofounder disagreements; instead, the disagreements typically destroy the friendship in addition to the partnership.
7 · Counter-intuitive insight
Counter-intuitively, complementary skills matter less than aligned operating philosophy. Two pairs with identical complementary-skills (e.g., a technical cofounder + a business cofounder) can have radically different outcomes based on whether their operating-philosophies (move-fast-and-iterate vs measure-twice-and-cut-once; high-risk-tolerance vs medium-risk-tolerance; aggressive-equity-dilution vs conservative) align. Skills can be hired; philosophy cannot be hired.
8 · Highest-leverage move
The single highest-leverage move at the cofounder-fit stage is to complete the diagnostic separately, then meet for 4-6 hours of structured conversation specifically on the divergent dimensions. Most pairs spend 100+ hours discussing the company idea and 4 hours discussing themselves; the inverse allocation produces better outcomes. The 4-6 hours of structured self-discussion is the highest-leverage time investment in the entire cofounder-formation process.
Eight user intents
9 · Who gains most
Pre-commitment cofounder pairs (highest impact), early-stage cofounder pairs in months 1-12 of operating together (still cheap to course-correct), advisors counselling cofounder formation, accelerator-cohort cofounder-matching mentors, executive-team-formation in larger contexts. The 25-50 age band dominates first-time cofounders.
10 · Irreducible essence
The irreducible essence: complete the 18-dimension diagnostic separately, compare honestly, schedule 4-6 hours of structured conversation on the divergent dimensions, document explicit decisions in writing, revisit annually.
11 · Optimal timing
Best applied pre-commitment (before equity is allocated, before incorporation, before any external commitments are made). Acceptable in months 1-12 of operating together (still cheap to course-correct). Less useful after year 2 — by then the patterns are entrenched and the diagnostic surfaces problems without offering cheap remedies. Run as annual review for the first 3-5 years.
12 · Where it matters most
Geographically agnostic. Specific dimensions weight differently across cultures: equity-philosophy tilts more egalitarian in Northern Europe + more hierarchical in some Asian contexts; family-context constraints weight heavier in some emerging-market contexts than others; communication-cadence varies with country defaults. The diagnostic surfaces the dimensions; the pair interprets within their cultural context.
13 · Why misunderstood
Cofounder-fit is misunderstood because the early-stage ecosystem rewards cofounder-pair-formation visibility (announcement, demo days, pitch competitions) more than honest pre-commitment self-assessment. The visibility creates psychological cost-of-exit before the assessment has happened. The diagnostic forces honest pre-commitment self-assessment which the visibility-incentives discourage.
14 · Highest-leverage sub-paths
Highest-leverage dimensions vary by pair-type. For technical+business pairs: operating-philosophy + financial-risk tolerance + equity-philosophy. For peer-technical pairs: decision-making protocol + conflict-resolution style + role-clarity. For pairs with significant age gap: work-rhythm compatibility + exit-horizon + family-context constraints. For pairs from same prior-employer: team-formation cadence + delegation philosophy.
15 · Whose advice to trust
Trust: Founder Institute + Y Combinator cofounder-formation guidance, longitudinal-study data on cofounder split-rates (e.g., Wasserman "The Founder Dilemmas"), peer-cofounder honest conversations 2-3 years into their partnership, your accountant + lawyer for the equity-mechanics specifically. Ignore: pitch-competition cofounder-matchmaking sessions (selection-biased optimism), accelerator-marketing about cofounder-fit tools (often shallow), well-meaning but inexperienced advisors.
16 · How to proceed differently
Proceed by completing the diagnostic individually, scoring divergences, scheduling 4-6 hours of dedicated conversation focused on the top 3 divergent dimensions, documenting explicit decisions (in writing, signed) on equity vesting + decision-making protocols + buy-back triggers + exit-horizon expectations. Re-run annually with the same 18 dimensions. Adjust documents if patterns shift.
Developer POV — for the architect, maintainer, AI tool, future contributor
Eight dev dimensions
17 · Data architecture
Cofounder-fit composes from data/atlas-cofounder-fit.php (18-dimension schema with question-set, scoring-bands, divergence-thresholds, conversation-prompts), the diagnostic engine in includes/atlas-cofounder-fit-engine.php (computes divergence scores + identifies critical-path dimensions), and the conversation-prompt composer at includes/atlas-cofounder-fit-prompts.php. Single-file render; deterministic; pure PHP.
18 · Schema markup
SoftwareApplication on the toolkit page; ItemList of the 18 dimensions; HowTo schema for the diagnostic-running flow with paired-completion + conversation steps. Quiz schema with paired-question structure (rare; most Quiz schema is single-respondent). Result-display emits Recommendation schema per divergent-dimension.
19 · Internal linking
Forward to /toolkit/founder-burnout/, /toolkit/async-office-hours/. Outward to /capital-raises/{stage}/, /accelerators/{program}/, /library/cofounder-formation/. Cross-content injector tokens: "cofounder", "partnership", "early-stage", "team-formation". Link weaver hyperlinks the 18 dimension names automatically.
20 · Page-speed posture
Payload ~20 KB total. The 18-dimension question-set is rendered as paired-input form (each cofounder fills separately, paired result computes on submission). JS ~7 KB minified vanilla. Render ~250-400 ms. The paired-input flow uses sessionStorage to hold first-cofounders answers temporarily before second-cofounders submission (no server-side state).
21 · Mobile UX
Question-set renders one-dimension-at-a-time on mobile, full-grid on desktop. Tap-targets ≥48px on each answer-option. Sticky progress-bar showing dimension N of 18. Result-display collapses divergence-table to card-grid at narrow viewports.
22 · Accessibility
Native <fieldset> + <legend> per dimension. <input type="radio"> + <label> for answer-options. Keyboard-accessible. Focus-visible outline. Result-display divergence-table uses <thead> + <th scope="col">. Color-blind-safe palette for divergence-bands.
23 · SEO saturation
URL: /toolkit/cofounder-fit/. Canonical. OG. Twitter. Sitemap. IndexNow on edit. SoftwareApplication schema. The 18-dimension breakout pages at /toolkit/cofounder-fit/{dimension}/ provide indexable surface for dimension-specific queries (ramping in v149.x+).
24 · Extensibility
To add a 19th dimension: append to data/atlas-cofounder-fit.php $dimensions array with required fields (id, name, question-set, divergence-threshold, conversation-prompt). Diagnostic engine auto-picks up. Total ship: ~30 min including handwritten conversation-prompt prose.
Eight dev intents
25 · Who maintains
Joint maintenance. Dimension-set edits are bilateral. Conversation-prompt prose is handwritten per-dimension (currently 18 unique paragraphs, ~2,200 words). Refresh annually as cofounder-formation patterns evolve.
26 · What tech stack
Tech: PHP 8.3 + vanilla JS. Helpers: ajg_atlas_cofounder_fit_dimensions(), ajg_atlas_cofounder_fit_compute(), ajg_atlas_cofounder_fit_prompts(). sessionStorage for paired-input flow (no server-side state per SO #14 zero APIs at runtime).
27 · When to refresh
Annual dimension-set review. Conversation-prompt prose refreshed as new patterns emerge from peer-founder feedback. IndexNow on edit.
Same ownership. Dimension-set verified against published cofounder-formation literature (Wasserman, Founders At Work, YC Startup School lectures, Founder Institute curriculum) plus direct interviews with cofounder pairs. Conversation-prompt prose composed from observed-pattern synthesis.
32 · How to extend
To add a new dimension cluster (e.g., "remote-work-dynamics" cluster of 3-4 dimensions): (1) define cluster theme; (2) draft individual dimensions; (3) define divergence-thresholds; (4) write conversation-prompt prose per dimension; (5) add cluster-grouping to engine. Total ship: ~3-4 hours.