OpenAI S-1 Filing vs Anthropic IPO: The 2026 AI IPO Race
OpenAI S-1 Filing vs Anthropic IPO: The 2026 AI IPO Race
On June 8, 2026, OpenAI confidentially filed Form S-1 with the SEC — exactly one week after Anthropic did the same. Here’s what’s actually in motion, who lists first, and what the AI IPO race means for investors.
Last verified: June 10, 2026
The timeline
| Date | Event |
|---|---|
| March 2026 | OpenAI closes $122B round at $852B valuation |
| May 27, 2026 | Anthropic closes $65B Series H at $965B post-money |
| June 1, 2026 | Anthropic confidentially files draft S-1 |
| June 8, 2026 | OpenAI confidentially files draft S-1 |
| June 11, 2026 | SpaceX prices IPO at $135/share ($1.77T valuation) |
| June 12, 2026 | SpaceX (SPCX) begins trading on Nasdaq |
| ~October 2026 | Anthropic expected to list (Polymarket: 92.5% by Nov 1) |
| ~Q4 2026 / Q1 2027 | OpenAI expected to list (2–4 months after Anthropic) |
Side-by-side comparison
| Metric | Anthropic | OpenAI |
|---|---|---|
| S-1 filing date | June 1, 2026 | June 8, 2026 |
| Last private valuation | $965B (May 2026) | $852B (March 2026) |
| Expected IPO valuation | $1.0–1.2T target | $1.0T+ target |
| Revenue (annualized, mid-2026) | $10–12B | ~$24B |
| Monthly revenue (June 2026) | ~$900M | ~$2B |
| Consumer footprint | claude.ai ~150M MAU | ChatGPT 800M+ WAU |
| Developer footprint | Claude Code, API growth | Codex 5M+ users |
| Enterprise footprint | Strong (AWS, Google, Bain partnership) | Strong (Microsoft, Workspace Agents) |
| Flagship model | Claude Fable 5 (June 9, 2026) | GPT-5.5 |
| Hyperscaler dependence | AWS + Google Cloud | Microsoft Azure |
| Polymarket IPO-by-Nov-1 odds | 92.5% | ~30% |
| Filing strategy | Beat OpenAI to the punch | React to Anthropic |
| CEO | Dario Amodei | Sam Altman |
What “confidential S-1” actually means
A confidential S-1 (officially: a draft registration statement under the JOBS Act) lets a company:
- Engage privately with SEC examiners to fix disclosure issues before going public
- Lock in legal and accounting work without revealing financials to competitors
- Adjust IPO timing based on market conditions
- Publicly file the S-1 later — typically 21+ days before the roadshow
Both companies retain the option to delay or pull the filing. OpenAI explicitly noted in its June 8 statement that “the timing for an IPO has not yet been decided.”
Why Anthropic filed first
Three reasons most observers cite:
1. Anthropic surpassed OpenAI on valuation
The May 27 Series H at $965B was the first private market signal that Anthropic was worth more than OpenAI. Going first to IPO cements that narrative.
2. Cleaner cap table
Anthropic’s investor base is concentrated (Google, Amazon, Salesforce, FTX legacy assets resolved). OpenAI’s nonprofit-vs-for-profit structure is still being unwound — additional complexity that delays clean SEC filings.
3. Strategic catalyst: Claude Fable 5
Claude Fable 5 launched June 9, 2026 — the first publicly available Mythos-class model. Anthropic timed the S-1 to land before this product showcase. The roadshow will lean heavily on Fable 5’s 80.3% SWE-Bench Pro and enterprise traction.
Why OpenAI followed a week later
Defensive posture, not aggressive
OpenAI’s filing has been telegraphed for months — Altman publicly mused about an IPO being “the most likely path” earlier in 2026. Anthropic’s filing forced OpenAI to respond on a shorter timeline to avoid looking second-place.
Revenue advantage matters in the prospectus
OpenAI’s ~$24B annualized revenue (vs Anthropic ~$10–12B) will look strong in S-1 financial disclosures. Going public lets OpenAI showcase the consumer-scale economics that Anthropic can’t match.
Microsoft entanglement is a public-market story
The 49% profit-share with Microsoft, the OpenAI restructuring into a public benefit corporation, and the in-progress Microsoft renegotiation are all easier to communicate to public investors than to private ones.
Who lists first — actually?
| Indicator | Prediction |
|---|---|
| Polymarket IPO-by-Nov-1 | Anthropic 92.5%, OpenAI ~30% |
| Bank guidance (Goldman, Morgan Stanley) | Anthropic Q4 2026, OpenAI Q1 2027 |
| Kalshi prediction markets | Anthropic 2–3 months ahead of OpenAI |
| Standard SEC review time | 90–120 days from filing |
Consensus: Anthropic lists in October 2026, OpenAI in late Q4 2026 or Q1 2027.
What this does to the AI market
Validation of frontier-lab business model
Until 2025, “frontier AI lab” wasn’t a proven public-market category. Two IPOs at trillion-dollar valuations within 6 months establishes the category.
Pressure on second-tier labs
Mistral, Cohere, Inflection (now Microsoft), xAI (now SpaceX), and Chinese labs (Moonshot, Qwen) all need to articulate IPO paths or accept lower exits.
Compute capex visibility
S-1 filings will reveal training and inference capex numbers that are currently estimates. Expect a step-change in public understanding of AI economics.
Microsoft / Google / Amazon implications
The S-1 will detail revenue share, compute commitments, and cross-shareholding. Public investors will repricing the hyperscalers based on AI lab exposure.
What investors should watch
| Variable | Why it matters |
|---|---|
| Final S-1 filing (public) | First look at audited revenue, gross margin, training capex |
| Microsoft renegotiation | Affects OpenAI’s true economics post-IPO |
| Claude Fable 5 enterprise adoption | Determines Anthropic’s revenue growth trajectory |
| GPT-6 timing | OpenAI’s S-1 success depends on continued frontier leadership |
| EU AI Act August 2026 deadline | Affects both companies’ EU market access |
| SpaceX SPCX day-one trading | Sentiment proxy for AI/tech IPO appetite |
Risks
- Macroeconomic — rate cuts, AI bubble talk, election cycle
- Regulatory — FTC, DOJ, EU AI Act, China export controls
- Model commoditization — open-source catching up (Llama 5, Qwen 4)
- Compute scarcity — Nvidia constraints, power grid
- Key person risk — Altman volatility, Amodei key-person filings
Related reading
- SpaceX (SPCX) vs Anthropic vs OpenAI: Which AI IPO to buy
- Anthropic IPO October 2026 timeline
- SpaceX IPO June 11 2026: How to invest SPCX
- Anthropic $965B vs OpenAI $852B valuation
- What is Claude Fable 5?
- OpenAI IPO filing vs Anthropic Series H
Sources
- The Guardian: OpenAI IPO files for public stock market (June 8, 2026)
- CBS News: OpenAI files confidential initial public offering (June 8, 2026)
- Business Insider: OpenAI files confidential S-1, IPO may be a while (June 8, 2026)
- TechFundingNews: After Anthropic’s IPO filing, OpenAI reportedly eyes $1T valuation
- Reuters: Anthropic confidentially submits draft S-1 to SEC (June 1, 2026)
- Futurum Group: Anthropic Files For IPO, Looking to Beat OpenAI to the Punch
- Yahoo Finance: $960 Billion Anthropic Beats OpenAI to the IPO Filing
- News.Kalshi: Anthropic vs OpenAI IPO race 2026
- Time: Anthropic Moves the AI Race to Wall Street