Sierra Closes $950M at $15B Valuation — Largest Pure-Play Agent Startup Round, Now Deployed by Nearly Half the Fortune 50

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AI customer agent startup Sierra Technologies announced a $950 million funding round at a $15 billion valuation on May 4, led by GV and Tiger Global with Benchmark, Sequoia, and Greenoaks. This comes eight months after a $350M round. Sierra reports $150M ARR with adoption by nearly half the Fortune 50. The round dwarfs every other agentic AI raise in 2026 — the sector has pulled in $2.66B across 44 rounds through April, nearly 2.5x the same period last year.