Brief 2 — Largest 2026 rounds by YC / YC-like alumni

Scope: Rounds announced 1 Jan 2026 – 4 Sep 2026 (UTC+4 window end = today). Universe: Companies with clear evidence of Y Combinator or a named YC-like program (Techstars, a16z Speedrun, Antler, EF, SPC, Sequoia Arc, PearX, Neo, 500 Global). Rank: By disclosed round size (USD), descending. One row = one announced round (companies may appear twice). Research only — not posted to inbox/threadbus.

Ranked top 10

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Per-company detail

1. Kalshi — $1B Series F

• What it does: Federally regulated prediction-market exchange for trading event contracts.
• Program / batch: Y Combinator Winter 2019 (YC directory).
• Round size & stage: $1 billion Series F at $22B valuation.
• Date announced: 7 May 2026.
• Lead investors: Coatue; participants include Sequoia, a16z, IVP, Paradigm, Morgan Stanley, ARK Invest.
• Revenue / ARR: Annualized revenue >$1.5B (company told Bloomberg / reported by TechCrunch).
• Sources:
  • Announcement: https://news.kalshi.com/p/kalshi-raises-1-billion-22-billion-valuation-institutional-demand-surges
  • Independent: https://techcrunch.com/2026/05/07/kalshi-doubles-valuation-in-5-months-hitting-22-billion/
  • Program: https://www.ycombinator.com/companies/kalshi
• Verification: Announcement → TechCrunch → YC directory (3 hops). Round size multi-source.

2. Whatnot — $545M Series G

• What it does: Livestream shopping / live-commerce marketplace (collectibles → fashion, food, etc.).
• Program / batch: Y Combinator Winter 2020 (YC directory).
• Round size & stage: $545 million Series G at $20B valuation.
• Date announced: 7 Aug 2026.
• Lead investors: ICONIQ, Lightspeed, Avra; new/returning include Kleiner Perkins, Wellington, Robinhood Ventures, S32, Standard Capital, CapitalG, YC, Durable, Alkeon, a16z, Greycroft, BOND, DST.
• Revenue / ARR: On track to surpass $1B annual revenue in 2026 (company to Inc.); H1’26 GMV already > full-year 2025 (~$8B+ GMV).
• Sources:
  • Announcement: https://blog.teamwhatnot.com/unitedstates/seriesg
  • Independent: https://www.inc.com/jennifer-conrad/whatnot-just-clinched-a-20-billion-valuation/91386777
  • Also: https://www.tubefilter.com/2026/08/07/whatnot-series-g-funding-round-545-million-live-shopping/
  • Program: https://www.ycombinator.com/companies/whatnot
• Verification: Company blog → Inc. / Tubefilter → YC directory. Round size multi-source.

3. Supabase — $500M Series F

• What it does: Open-source Postgres developer platform (auth, APIs, realtime, backend for apps / AI agents).
• Program / batch: Y Combinator Summer 2020 (YC directory).
• Round size & stage: $500 million Series F; company blog: $10B pre-money; PR/CNBC: $10.5B post-money.
• Date announced: 4 Jun 2026.
• Lead investors: GIC; existing Accel, YC, Craft, Felicis, Peak XV, Coatue; Stripe (2nd investment); new Georgian, Salesforce Ventures.
• Revenue / ARR: not public in company Series F post; third-party estimate ~$170M ARR (Sacra) — mark as estimate only.
• Sources:
  • Announcement: https://supabase.com/blog/series-f
  • Independent: https://www.cnbc.com/2026/06/04/database-startup-supabase-raises-500-million-10point5-billion-valuation.html
  • Also: https://www.prnewswire.com/news-releases/supabase-raises-500m-at-10-5b-to-accelerate-lead-in-agentic-infrastructure-302791787.html
  • Program: https://www.ycombinator.com/companies/supabase
• Verification: Company blog → CNBC / PR Newswire → YC directory. Size multi-source; valuation pre vs post wording differs by outlet.

4. Helion Energy — $465M Series G

• What it does: Commercial fusion power plant company (Polaris prototype; Orion plant under construction).
• Program / batch: Y Combinator Summer 2014 (YC directory).
• Round size & stage: $465 million Series G at $15.5B post-money.
• Date announced: 4 Jun 2026.
• Lead investors: Thrive Capital; new Alta Park, Anti Fund, BoxGroup, Lux, Peak XV, Bill Ford; existing Capricorn, Lightspeed, Mithril, Good Ventures / Moskovitz, SoftBank Vision Fund 2, university endowment.
• Revenue / ARR: not public (pre-revenue deep tech / plant under construction).
• Sources:
  • Announcement: https://www.helionenergy.com/newsroom/helion-raises-465-million-series-g-funding-round-to-meet-surging-global-demand-for-power
  • Independent: https://techcrunch.com/2026/06/04/helion-the-sam-altman-backed-fusion-startup-raises-465m-to-build-a-power-plant-for-microsoft/
  • Also: https://www.geekwire.com/2026/helion-hits-15-5b-valuation-with-465m-in-new-cash-to-commercialize-fusion-this-decade/
  • Program: https://www.ycombinator.com/companies/helion-energy
• Verification: Company newsroom → TechCrunch / GeekWire → YC directory.

5. Starcloud — $250M Series A extension

• What it does: Orbital / space-based data centers and on-orbit GPU compute.
• Program / batch: Y Combinator Summer 2024 (YC directory).
• Round size & stage: $250 million Series A extension at $2.3B post-money (total raised ~$450M).
• Date announced: 21 Aug 2026.
• Lead investors: Manhattan West; Nvidia, Cisco Investments; existing Benchmark, EQT, Soma, NFX, 776, others.
• Revenue / ARR: not public.
• Sources:
  • Announcement (Business Wire syndication): https://www.financialcontent.com/article/bizwire-2026-8-21-starcloud-raises-250-million-at-23-billion-valuation-to-scale-ai-with-orbital-data-centers
  • Independent: https://techcrunch.com/2026/08/21/starcloud-raises-200-million-for-orbital-data-centers-as-launch-options-dry-up/
  • Also: https://www.geekwire.com/2026/starcloud-250m-data-center-satellite-network-nvidia/
  • Program: https://www.ycombinator.com/companies/starcloud
• Verification: Business Wire → TechCrunch / GeekWire → YC directory. (TC URL slug says “200-million” but body states $250M — size confirmed elsewhere.)

6. REGENT Craft — $240M Series B

• What it does: Electric Seagliders (wing-in-ground-effect craft) for coastal / maritime mobility + defense (Squire).
• Program / batch: Y Combinator Winter 2021 (YC LinkedIn post: REGENT YC W21).
• Round size & stage: $240 million Series B — equal mix equity + debt ($120M equity co-led Mare Liberum & AE Ventures; $120M debt from Erebor Bank). Total capital raised >$340M.
• Date announced: 27 Aug 2026.
• Lead investors: Mare Liberum & AE Ventures (equity); Erebor Bank (debt); DCVC new; Founders Fund, Caffeinated Capital, Lockheed Martin Ventures, Japan Airlines, Giant Step Capital returning.
• Revenue / ARR: not public (order book / manufacturing scale-up; not disclosed ARR).
• Sources:
  • Announcement: https://www.regentcraft.com/news/regent-secures-240-million-series-b-funding-to-scale-seaglider-manufacturing-and-transform-maritime-mobility
  • Independent: https://www.undiluted.com/news/erebor-bank-provides-regent-craft-with-120m-debt-in-240m-series-b
  • Also: https://www.tectonicdefense.com/regent-craft-raises-240m-series-b/
  • Program: https://www.linkedin.com/posts/y-combinator_regent-yc-w21-has-raised-240-million-in-activity-7498813426060644352-ARTv
• Caveat: Headline $240M includes debt; equity sleeve alone is $120M. Ranked by announced round total per company framing.

7. Starcloud — $170M Series A

• What it does: (same as #5) orbital data centers / space GPU compute.
• Program / batch: YC S24.
• Round size & stage: $170 million Series A at $1.1B valuation (~$200M cumulative at time).
• Date announced: 30 Mar 2026.
• Lead investors: Benchmark and EQT Ventures.
• Revenue / ARR: not public.
• Sources:
  • Announcement / press: Business Wire correction on Starcloud $170M Series A (Benchmark / EQT)
  • Independent: https://techcrunch.com/2026/03/30/starcloud-raises-170-million-series-ato-build-data-centers-in-space/
  • Program: https://www.ycombinator.com/companies/starcloud
• Verification: TechCrunch + Business Wire + YC directory. Multi-source on size.

8. Corgi — $160M Series B

• What it does: AI-native full-stack insurance carrier for startups / tech (GL, cyber, tech E&O, etc.).
• Program / batch: Y Combinator Summer 2024 (YC directory). (TechCrunch once wrote “Spring 2024”; YC directory = S24 — use directory.)
• Round size & stage: $160 million Series B at $1.3B valuation.
• Date announced: 6 May 2026.
• Lead investors: TCV; Kindred Ventures, Leblon Capital, First Order Fund and others.
• Revenue / ARR: Company/Forbes-circle reporting: run-rate surpassed ~$40M after carrier license; projected ~$450M ARR by YE2026 — not a company-audited public ARR; treat as single-source / reported. Later TFN: profitable as of ~May 2026.
• Sources:
  • Independent primary write-up: https://techcrunch.com/2026/05/06/insurance-startup-corgi-hits-1-3b-valuation-4-months-after-its-series-a/
  • Also: https://techfundingnews.com/y-combinators-latest-unicorn-corgi-raises-160m-led-by-tcv-at-1-3b-valuation-just-four-months-after-its-series-a/
  • Program: https://www.ycombinator.com/companies/corgi-insurance
• Verification: TechCrunch + TFN + YC directory. Founder LinkedIn cited by TC as announcement channel.

9. HappyRobot — $150M Series C

• What it does: Agentic / voice AI workers for enterprise operations (logistics-first; expanding to insurance, energy, telecom, airlines).
• Program / batch: Y Combinator Summer 2023 (YC directory).
• Round size & stage: $150 million Series C at ~$1.2B post-money (some secondary write-ups split C-1/C-2 tranches).
• Date announced: 4 Aug 2026.
• Lead investors: Prysm Capital (lead), Eurazeo (co-lead); a16z, Base10, YC returning; strategics KDT, KFund, Orange, T.Capital, Bankinter, Endeavor Catalyst, Wave-X.
• Revenue / ARR: Absolute ARR not public; company/press: 5× growth since Series B, 150+ enterprise customers (DHL, Kuehne+Nagel, Uber, etc.).
• Sources:
  • Independent: https://tech.eu/2026/08/04/happyrobot-lands-150m-series-c-to-scale-agentic-ai-for-enterprise-operations/
  • Also: https://siliconvalleyinvestclub.com/2026/08/06/happyrobot-raises-150-million-and-hits-unicorn-status-at-a-1-2-billion-valuation/
  • Program: https://www.ycombinator.com/companies/happyrobot
• Verification: Tech.eu → SV InvestClub / valueadd write-ups → YC directory. Size multi-source.

10. Emergent — $130M Series C

• What it does: AI app builder — natural-language → full-stack production web/mobile apps (“vibe coding” for non-technical founders/SMBs).
• Program / batch: Y Combinator Summer 2024 (YC directory).
• Round size & stage: $130 million Series C at $1.5B valuation (total funding $230M).
• Date announced: 16 Jul 2026 (company post; PR Newswire ~17 Jul).
• Lead investors: Creaegis; co-leads MNI Ventures – Claypond Capital, Sentinel Global; Khosla, SoftBank Vision Fund 2, Lightspeed, YC.
• Revenue / ARR: Company: $50M ARR in 7 months from launch (stated at Jan 2026 Series B); Series C post does not restate a new ARR figure — use $50M ARR (as of Jan 2026 company claim) unless updated.
• Sources:
  • Announcement: https://emergent.sh/news/emergent-now-a-unicorn-at-1-5-billion-valuation
  • Independent: https://www.prnewswire.com/apac/news-releases/emergent-raises-series-c-at-1-5-billion-valuation-becomes-unicorn-in-a-year-of-launch-302828611.html
  • Also: https://www.ycombinator.com/companies/emergent (links TC Jul 15 coverage)
  • Series B ARR context: https://www.businesswire.com/news/home/20260120852493/en/Emergent-Raises-%2470M-from-Khosla-Ventures-and-SoftBank-Vision-Fund-2-to-Enable-Anyone-to-Turn-Ideas-into-Monetizable-Software
• Verification: Company post → PR Newswire → YC directory. Size multi-source.

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Just outside top 10 (disclosed sizes; eligible programs)

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Excluded notable large rounds (checked; not eligible or incomplete)

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COUNTS

Missing / caveats

1. REGENT $240M includes $120M debt — apples-to-apples equity ranking would place equity sleeve below Starcloud $170M; kept at announced total with explicit note.
2. AfterQuery would likely crack top ranks if size were public; excluded for missing disclosed amount.
3. Corgi batch string conflict (TC “Spring 2024” vs YC directory S24) — directory wins.
4. Supabase ARR not in company announcement; Sacra ~$170M is third-party.
5. HappyRobot ARR absolute figure not public.
6. Starcloud / Helion / REGENT revenue largely not public.
7. Non-YC accelerators under-represented in top 10: only Railway (Techstars) approached the cutoff; no Antler / EF / Speedrun / Arc / PearX / Neo / 500 Global / SPC alumni rounds ≥$130M found in this pass with solid confirmation.
8. Coverage bias toward English-language US/EU press; some Asia-heavy YC alumni (e.g. Groww) had smaller disclosed 2026 checks in this sweep.
9. Ranking by announced round size, not valuation or equity-only proceeds.

Method notes (for recurring routines)

Queries used (examples):

• largest funding rounds 2026 Y Combinator
• YC OR "Y Combinator" OR "YC-backed" raises "$100M" OR "$150M" … 2026
• Whatnot OR Kalshi OR Supabase OR Helion OR Starcloud OR REGENT OR Corgi OR HappyRobot OR Emergent funding 2026
• Per-company: {Company} Y Combinator batch site:ycombinator.com
• Negative filters: exclude non-program companies (Ramp, Modal, Cognition, OpenAI…)
• Accelerator alumni: Techstars OR Antler OR "Entrepreneurs First" OR PearX OR "a16z Speedrun" OR "Sequoia Arc" OR Neo OR "500 Global" OR SPC raises 2026 Sources prioritized:

1. Company blog / newsroom / Business Wire / PR Newswire
2. TechCrunch, CNBC, GeekWire, Inc., Tech.eu, Tubefilter
3. YC company directory for program/batch
4. Cross-check: second press outlet or YC LinkedIn Hop rule applied: announcement → independent press → YC directory / LinkedIn (where available). Do-not-invent rule: Only ranked rounds with a disclosed dollar amount in ≥1 credible outlet; valuations-only / rumored rounds parked in caveats. Next-pass suggestions: PitchBook/Crunchbase export filtered by accelerator affiliation; Dealroom YC batch indexes; Techstars portfolio funding RSS; Antler/EF portfolio pages for H2 2026.