Anthropic Prepares for Record AI IPO Amid Junk-Rating Forecast and Compute-Cost Risks

Anthropic filed its S-1 registration statement with the SEC on Oct. 26, 2026, outlining a planned IPO that could target a valuation between $1.5 trillion and $2 trillion. The filing shows Blackstone, the anchor investor in a $63 billion financing round for Anthropic’s custom chips, expects the company to receive a “high” junk rating—specifically a double-B range—after the IPO, a shift from an earlier Blackstone statement that anticipated an investment-grade rating before 2027. Both Anthropic and Blackstone declined comment on the rating projection.

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Anthropic’s prospectus reports revenue rising from $1.2 billion in H1 2025 to $16.3 billion in H1 2026, a 1,300 % increase. Growth is attributed to adoption of its Claude models by major technology firms and an expanding focus on life-sciences applications. The “Claude Science” product entered beta in June, and the firm has invested $400 million in biotech startup Coefficient Bio.

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• Revenue (H1 2026): $16.29 billion

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• Cost of revenue (H1 2026): $2.38 billion -> implied gross margin 85 % (up from 12 % in H1 2025)

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• GAAP operating margin (Q2 2026): 8 %

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• Compute-related future minimum payment obligations: ~$417 billion

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• Additional capacity contracts forecast: $125 billion–$150 billion

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• Net loss (first half of 2026): $80 billion

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Blackstone’s internal forecast, cited by the Financial Times, predicts a double-B speculative rating for Anthropic post-IPO. Analysts at Leverage Shares highlighted the steep revenue jump but questioned whether compute costs can stay proportionally lower as demand expands. Morningstar’s chief equity strategist noted uncertainty around a potential sequential growth slowdown, while Futurum Group’s CEO pointed to heightened market headwinds after mixed earnings reports from major hyperscalers.

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• “Everybody's still full steam ahead on AI, but all the things around it took an interesting turn this week,” — Daniel Newman, CEO at Futurum Group

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• “It's a great technology, seems to do things that we never would have imagined, but how does that then translate into a viable business?” — David Hsu, professor, Wharton School

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• “Biology is probably the area where scientific progress has the greatest potential to directly and unambiguously improve the quality of human life,” — Dario Amodei, Anthropic CEO

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• “What the prospectus didn't tell us is management's expectations around the sequential slowdown in the growth rate,” — Michael Field, chief equity strategist, Morningstar

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Rating agencies are expected to assign an official credit rating after Anthropic’s shares begin trading. The prospectus also indicates plans for additional class-share issuances, though the impact on shareholder control remains unclear. Investors will watch final IPO pricing and the company’s ability to secure sufficient compute capacity without eroding margins.

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The Financial Times reports a current Blackstone expectation of a double-B junk rating, while earlier Blackstone communications suggested an investment-grade outlook before 2027. The prospectus does not clarify the timeline or criteria for this rating shift, leaving a gap in understanding how the change may affect Anthropic’s cost of capital post-IPO.

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