Haystack (YC S24) — Replay real customer journeys against every change before you ship
Haystack automatically learns real customer journeys from production traffic, figures out which ones a code change could affect, and replays them in isolated copies of production to catch regressions before they ship. When something breaks, Haystack shows exactly what changed across the UI, network calls, and events, then gives the failure back to your coding agent to fix and rerun.
Haystack is a Y Combinator company in the Summer 2024 batch. Its directory entry describes it as: Replay real customer journeys against every change before you ship. The founders listed are Akshay Subramaniam (Founder/CEO), Jake Yatvitskiy (Founder/CTO) (Y Combinator directory entry, July 30, 2024).
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Example from a real report (our sample on Target): “The Q2 2026 earnings report, published August 19, 2026, showed adjusted EPS of $2.46 against an expected $2.33” Source: CNBC
Haystack automatically learns real customer journeys from production traffic, figures out which ones a code change could affect, and replays them in isolated copies of production to catch regressions before they ship.
When something breaks, Haystack shows exactly what changed across the UI, network calls, and events, then gives the failure back to your coding agent to fix and rerun. Teams get high-fidelity QA without having to write or maintain test cases.
Akshay Subramaniam
Founder/CEO
Jake Yatvitskiy
Founder/CTO
Founders, titles and bios as the company published them. Photographs are our own copies of the ones on that record, so they do not break when the original link expires.
One of 641 companies held here in B2B › Engineering, Product and Design.
No investor is drawn from a Form D — the form states how many invested and never who. The one investor on this graph is named because a batch has exactly one.
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Example from a real report (our sample on Target): “The Q2 2026 earnings report, published August 19, 2026, showed adjusted EPS of $2.46 against an expected $2.33” Source: CNBC
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What the Full Report on Haystack covers
The Short Answer
Which Company This Is
What They Do, And How The Money Works
Who Runs It, And How To Reach Them
The Money: Funding, Valuation, Runway
Who Pays Them, And Who They Are Up Against
Warning Bells
Sources
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Haystack (YC S24) — Replay real customer journeys against every change before you ship. MentionFox, 2026-10-29. https://mentionfox.com/funding/yc-haystackeditor
