Anthropic S-1: Top Customers and Concentration Disclosures

Anthropic’s public S-1, filed October 26, 2026, shows a business that still sells a large share of Claude through hyperscaler marketplaces and still depends on rapid expansion inside a relatively small set of heavy users—but the concentration picture in the public document is milder than the draft leaks that dominated coverage in September and October. The filing does not name its largest revenue customers. Metrics such as 900% net revenue retention and customer counts are defined inside the prospectus; press “run rate” figures are mostly company or investor updates, not the same thing as recognized revenue in the S-1.

What the filing actually says about concentration

The public prospectus, as read on filing day, does not show a single customer above 10% of revenue. Share of revenue outside the top five rose from 64% in Q1 2026 to about 79% in Q3 2026, even as every top-five account set a spending record in Q3. That is a different snapshot from the confidential drafts the press reviewed weeks earlier.

Earlier draft language, reported by Reuters from a prospectus covering 2025, said two unnamed customers each accounted for 12% of 2025 revenue—nearly a quarter combined. A later draft reviewed by The Wall Street Journal said about one-fifth of first-half 2026 revenue came from two unnamed customers, and that a “significant portion” of revenue was expected to keep coming from a “limited number of customers for the foreseeable future.” Those customers were not named in either draft. Many of the largest accounts are usage-based and not locked into long-term spend commitments, so revenue can fall without a formal cancellation.

• Public filing (readers of the October 26 S-1): no single customer above 10%; non-top-five share ~64% (Q1 2026) to ~79% (Q3 2026).
• Reuters on the confidential draft: two unnamed customers at 12% each of 2025 revenue.
• WSJ on a later draft: ~20% of H1 2026 revenue ($16.3 billion) from two unnamed customers.
• Press identification of those two as SpaceX/Cursor and Microsoft/GitHub Copilot is speculation, not a filing disclosure.

The practical implication is that headline concentration improved as the base scaled, but the economic risk did not disappear. A usage account that is “under 10%” can still move a quarter if it reroutes traffic, and the company’s compute commitments do not flex down with that traffic.

How revenue actually reaches customers: API, marketplaces, subscriptions

Nearly half of recognized revenue is sold through cloud marketplaces rather than Anthropic’s own checkout. A reader of the public S-1 put marketplace share at 48% of first-half 2026 revenue—about $7.8 billion in six months—sold through Amazon Bedrock, Google Cloud’s Vertex AI (now often called Agent Platform in Google’s own docs), and Azure Marketplace, up from 11% of revenue in 2023. Reuters’ review of the earlier draft had the same channel at 47% of 2025 revenue, or about $2.16 billion, after 11% in 2023 and 32% in 2024. The prospectus treats Amazon, Google, and Microsoft as distribution partners whose sales networks Anthropic says it could not replicate on its own.

The accounting choice matters as much as the percentage. Anthropic recognizes the full contract value as revenue because it sets price and delivers the model (it is the principal), and books the platform’s cut inside “sales, marketing, and partnerships,” not in cost of revenue. Reuters calculated roughly $351 million of distribution fees on the 2025 marketplace book, about 16 cents per marketplace dollar. A reader of today’s filing said channel-partner fees rose about $2.7 billion year over year in the first half of 2026 and still sit in that operating-expense line, so they do not reduce the gross margin figure the market has been quoting. OpenAI has told investors this gross presentation inflates Anthropic’s top line relative to a net-of-fee method; Anthropic has said the treatment follows principal accounting. Cash collection is also intermediated: at the end of 2025, Amazon and Google collected 60% of $909 million in outstanding customer bills, up from 42% a year earlier, even though Anthropic contracts directly with the end customer.

Revenue mix in the 2025 draft was already consumption-heavy: about $3.8 billion from usage of Claude versus $789 million of subscription revenue, with the company saying consumption-based revenue should remain “the substantial majority.” The United States was nearly two-thirds of 2025 sales. That mix is why marketplace share and customer concentration move together: a coding product or enterprise deployment that burns tokens at scale often buys through the cloud contract the customer already has, so Bedrock or Vertex shows up both as channel and, in some periods, as a large “customer” on a gross basis.

Named customers versus named examples

The S-1 does not name the accounts that drive the concentration percentages. Press outlets filled that gap. The Motley Fool and others pointed to SpaceX (via Cursor) and Microsoft (via GitHub Copilot) as the likely pair behind the draft’s two large customers. That is an inference from product relationships, not a line in the prospectus. Older reporting had also floated Cursor and GitHub Copilot as a large share of an earlier run rate. Those identifications should be treated as press characterization.

What the public filing does name, according to readers, are adoption examples and franchise stats, which are not the same as the 10% customers: every Fortune 10 company is a customer; more than half of the Fortune 500 and more than 30% of the Global 2000; within the Fortune 500, all 10 of the largest banks, 9 of the top 10 pharma companies, and 9 of the top 10 chipmakers. Specific rollout stories cited from the filing include Eli Lilly (about 10,000 users to more than 50,000 in nine months), Mercado Libre (about 31,000 employees on Cowork), and Verizon (about 33,000 Claude Code users). Those names illustrate breadth. They do not identify who accounted for 12% in 2025.

Metrics the filing defines, and how press has used different ones

Recognized revenue, not run rate. The S-1’s audited (or prospectus) revenue is period revenue: $16.3 billion in the first half of 2026, versus about $1.1 billion (WSJ’s draft figure) or $1.2 billion (a filing-day summary) in the year-earlier half, and about $4.6 billion for all of 2025. “Run rate” figures that circulated for months—$14 billion in February 2026, $30 billion in April, $47 billion in May, $65 billion by late July—are annualizations of a recent month or company updates to investors. They are not the S-1’s revenue line. Q3 revenue of $16.8 billion, up about 45% from Q2, was told to investors at an October 14 meeting; it is not a substitute for the half-year GAAP number in the prospectus. Using run rate as if it were filing revenue overstates current booked scale and understates how much of the growth is still inside the last few months.

Net revenue retention is a filing metric, and it is 900%. Readers of the public S-1 describe it as the same customers spending about 9 times as much in Q3 2026 as in Q3 2025, with churned customers still left in the base. That is expansion-heavy cohort math, not a logo-retention rate and not a net-of-marketplace-fee retention rate. Jason Lemkin’s reading of the same filing put it as usage customers spending 9 times what they spent a year earlier. Pre-filing analyst notes (for example PitchBook’s 140–170% estimate) were guesses made before the prospectus defined the metric; they are not the company’s number. A 900% figure on gross marketplace revenue can also overstate economic retention if a growing share of each dollar is paid out as a channel fee—the fee never hits gross margin, but it does reduce what Anthropic keeps.

Customer counts are threshold counts, not logos. As of September 30, 2026, the filing shows more than 11,900 customers spending over $100,000 a year, up from 20 at the end of 2023, and about 250 customers spending over $10 million a year. There are also more than 40 million accounts spending under $100,000. Older press and company statements—more than 1,000 customers above $1 million annualized, or “eight of the Fortune 10”—were earlier cuts and should not be stacked on top of the S-1 thresholds as if they were the same cohort. Enterprise seats without Claude Code average under $75 a month; the top 5% of Claude Code users spend about 20 times that, which is why a modest seat count can still produce the 900% NRR.

Contracted versus recognized. One filing-day summary also cited about $10.8 billion of contracted revenue. That is backlog-style commitment, not the $16.3 billion of H1 recognized revenue, and not the hundreds of billions of take-or-pay compute obligations on the cost side.

What this means if you are underwriting the IPO or competing with Claude

The concentration risk the drafts flagged is real but time-stamped. By the public filing, no single customer clears 10%, and the non-top-five share is rising, while the absolute dollars inside the top five are still growing. The structural exposure is the channel, not a named logo: 48% of H1 revenue is gross marketplace revenue on which Amazon, Google, or Microsoft take a fee, collect a large share of receivables, supply the compute, invest in the company, and sell competing models. Losing a Bedrock or Vertex route is not the same event as losing a direct API logo, and the gross-versus-net presentation means headline revenue, gross margin, and NRR all look stronger than a net-of-fee view of the same tokens.

Anyone modeling Anthropic against a software comp should separate three numbers the press has blurred: recognized revenue in the S-1 ($16.3 billion in H1 2026), investor-day run rate and Q3 updates (which annualize a much larger recent month), and NRR (900% on a gross, churn-in-the-base definition). The first is what the prospectus stands behind. The second is why the multiple on 2025 revenue looks absurd and the multiple on a July run rate does not. The third explains how a company can add 11,900 six-figure customers and still have its growth rate depend on a few hundred accounts spending ten times more than they did a year ago—with no long-term contract forcing them to keep doing it.

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Recent Findings Supplement (October 2026)

Anthropic’s draft S-1 (IPO prospectus) disclosures, reported in October 2026 from a confidential or draft filing reviewed by outlets like the Wall Street Journal and Reuters, reveal extreme customer and channel concentration alongside explosive revenue growth.[1][2]

The company routes a large and growing share of sales through Amazon Bedrock and Google Cloud Vertex AI (its primary distribution and billing partners), while a small number of unnamed enterprise customers drive a disproportionate share of revenue. These details come from a draft registration statement (confidentially submitted around June 2026, with public versions anticipated later), distinct from press summaries that frame the numbers as acute “risks” or “dependence” on competitors who also supply compute and invest in Anthropic.[3]

H1 2026 revenue reached $16.3 billion (vs. $1.1 billion in H1 2025), with full-year 2025 revenue at approximately $4.6 billion (roughly 12x growth from 2024). Q3 2026 revenue hit $16.8 billion (45% QoQ). These figures represent the core disclosed run-rate proxy in the filing.[4]

• Press outlets (WSJ, Reuters) consistently cite these exact numbers from the draft prospectus without material variance across reports.
• No explicit “annual recurring revenue” (ARR) or “run-rate revenue” definition appears in summaries; the filing uses period revenue, with emphasis on forward-looking concentration risks rather than standardized SaaS-style metrics.
• Net loss for H1 2026 was $80.7 billion (largely a ~$72 billion non-cash accounting charge tied to rising valuation of convertible notes/financing); compute and infrastructure spend was ~$9 billion in the half (exceeding full-year 2025 levels in some reports).[5]

Customer concentration is explicitly flagged: two unnamed customers accounted for ~20% of H1 2026 revenue (or “about one-fifth”), while in 2025 the same two each represented 12% (~24% combined). The filing states it “expects a significant portion” of revenue to continue coming from a “limited number of customers for the foreseeable future,” with many large customers lacking long-term contracts.[1]

• No named customers are disclosed in any reports.
• This is presented in risk-factor sections as a core vulnerability (loss or reduction in spend from top accounts would materially impact results).
• Press characterizations amplify this as “two mystery customers,” “revenue base built on two customers,” or “durability question,” while the filing ties it directly to contract terms and forward expectations without naming parties.[1]

Reliance on platform channels (primarily Amazon Bedrock and Google Vertex AI) is substantial and increasing: 47% of 2025 revenue (~$2.16 billion) was routed through these cloud partners’ marketplaces, up from 32% in 2024 and 11% in 2023. Anthropic paid ~$351 million in distribution fees (~16% of channel revenue). These partners also handled collection of 60% of outstanding customer receivables at year-end 2025 (up from 42% in 2024).[2]

• Anthropic contracts directly with end customers but uses the platforms for distribution, billing, and access (API-like consumption via Bedrock/Vertex).
• The filing notes the dual role of these partners as distributors, compute suppliers, investors, and potential competitors, with risks around rationing of capacity.
• No specific breakdowns for “consumer vs. enterprise subscriptions” or pure direct API revenue appear in summaries; emphasis is on the channel split and associated fees/collections.
• Press highlights this as “deep dependence on Big Tech partners,” “reseller reliance,” or supply-chain concentration (same entities sell the model and control underlying compute).[1]

No disclosures on net revenue retention (NRR), gross revenue retention, exact customer counts, or precise definitions of “run-rate” metrics are detailed in the October 2026 reporting. The filing prioritizes concentration percentages, channel routing, and forward risks over retention or cohort metrics common in SaaS S-1s.[6]

• Earlier or unrelated filings (e.g., non-Anthropic companies) sometimes include NRR/ARR per customer or customer counts, but these are absent from Anthropic coverage.
• Press does not introduce or reinterpret such metrics; focus remains on the concentration and channel data provided.

For competitors or entrants in the AI model/platform space, these disclosures underscore the structural challenges of scaling via hyperscaler channels while managing top-account concentration and massive non-cancelable compute commitments (hundreds of billions over 7–10+ years, including ~$111B Google, ~$110B AWS, ~$31B Microsoft in one reporting). Broadening the customer base beyond a handful of large accounts and reducing platform fees/dependencies will be critical for sustainable margins and valuation multiples. The data is from draft materials and subject to change before any final public filing.[7]

All figures and characterizations derive from October 2026 reporting on the draft S-1; no earlier post-April 2026 updates on these specific metrics were identified in searches.