Jason Warner

Jason Warner is an American software engineer, the co-founder and chief executive officer of poolside, and a former chief technology officer of GitHub who oversaw the launch of GitHub Actions, Codespaces, and the incubation of GitHub Copilot.
Nextomoro
8 min read
Jason Warner

Jason Warner

Jason Warner is an American software engineer and technology executive. He is the co-founder and chief executive officer of poolside, the 2023 San Francisco artificial-intelligence company building foundation models for software engineering with Eiso Kant as chief technology officer. He was previously the chief technology officer of GitHub from 2017 through 2021, vice president of engineering at Heroku from 2014 through 2017, and a managing director at Redpoint Ventures from 2021 through 2023.

At a glance

Origins

Warner is American. He earned a bachelor of science in computer science from Pennsylvania State University and a master of science in computer science from Rensselaer Polytechnic Institute. The Penn State Dare to Disrupt podcast episode of August 2024 frames him as a Penn State College of Engineering alumnus.

The Stack Overflow podcast episode 447 of May 2022 documents the early career, with Warner describing himself as a "very average" programmer who became an effective engineering leader. His residence has historically been split between San Francisco and Victoria, British Columbia.

Career

Warner's first senior software-engineering role of public record was at Canonical, the company behind the Ubuntu Linux distribution, where he led product engineering for Ubuntu Desktop and the short-lived Ubuntu Phone effort. The Canonical period concluded with the May 2014 transition to Heroku, the developer-platform business inside Salesforce, as vice president of engineering. Warner spent three years at Heroku scaling the engineering organization.

In June 2017 Warner joined GitHub as senior vice president of technology under chief executive Chris Wanstrath, with responsibility for product, engineering, support, and security. Microsoft acquired GitHub for $7.5 billion in October 2018; Warner stayed through the transition under Nat Friedman and was elevated to chief technology officer. The Stack Overflow episode characterizes the GitHub period as the most consequential of his career: when he started in May 2017 GitHub had approximately 20 million accounts, 1.5 to 2 million daily active users, and 10,000 new signups per day; by his July 2021 departure, signups had reached approximately 50,000 per day with 7 million daily active users. The product launches he oversaw included GitHub Actions, GitHub Packages, GitHub Codespaces, GitHub Advanced Security, and the internal incubation of GitHub Copilot, launched in technical preview in June 2021 in collaboration with OpenAI and the Codex model.

Warner left GitHub in July 2021 and joined Redpoint Ventures as managing director on the early-growth team. The Redpoint tenure ran approximately two years, focused on developer-infrastructure and infrastructure-software investments.

In May 2023 Warner co-founded poolside with Eiso Kant, the founder of source-code-analysis startup source{d} (2015 to 2021) and subsequently of developer-productivity company Athenian. The pair had developed the company thesis through the Developing Leadership podcast they had co-hosted since 2020. The founding premise was that foundation models optimized for software engineering, trained through what poolside calls Reinforcement Learning from Code Execution Feedback (RLCEF), could surpass general-purpose frontier models on coding work. Redpoint led the May 2023 seed round of $26 million, contributing $20 million.

The fundraising trajectory after the seed has been aggressive. The August 2023 $126 million seed extension, led by Felicis Ventures with Xavier Niel and Bpifrance participation, coincided with the establishment of a French subsidiary in Paris. The $500 million Series B of October 2024 at a $3 billion post-money valuation was led by Bain Capital Ventures with DST Global, NVIDIA, Citi Ventures, eBay Ventures, HSBC Ventures, and others. Cumulative capital reached approximately $626 million.

In October 2025 poolside announced Project Horizon, a planned 2-gigawatt artificial-intelligence campus in Pecos County, Texas, with CoreWeave as anchor tenant for the first 250-megawatt phase. The same month, the company began raising a $2 billion Series C at a $12 billion pre-money valuation that would have been anchored by NVIDIA. The round failed to close in early April 2026, and CoreWeave terminated the 15-year anchor lease shortly afterward. As of May 2026 poolside has not closed a successor financing.

Affiliations

  • Canonical: Product engineering lead, Ubuntu Desktop and Ubuntu Phone, dates of public record approximately 2010 to 2014.
  • Heroku: Vice President of Engineering, May 2014 to May 2017.
  • GitHub: Senior Vice President of Technology and then Chief Technology Officer, June 2017 to July 2021.
  • Redpoint Ventures: Managing Director, July 2021 to May 2023.
  • poolside: Co-founder and Chief Executive Officer, May 2023 to present.
  • Bridgewater Associates: Operating board member, dates of public record from approximately 2022.
  • Atlassian: Board director, October 2025 to present.

Notable contributions

Warner's public work concentrates on developer-platform leadership and the founding of poolside rather than published research.

  • GitHub Actions (2018 to 2019). Cloud-hosted continuous-integration product, announced October 2018 in beta and generally available November 2019.
  • GitHub Codespaces (2020 to 2021). Cloud-hosted development environments, announced May 2020 in beta and generally available August 2021.
  • GitHub Advanced Security (2019 to 2020). Code-scanning, secret-detection, and software-supply-chain-security analytics.
  • GitHub Copilot (2021). AI pair-programming product launched in technical preview June 2021. Incubated under Warner's leadership in collaboration with OpenAI and the Codex effort.
  • poolside co-founding (May 2023). Coding-foundation-model lab co-founded with Eiso Kant. As of May 2026, poolside has raised approximately $626 million in cumulative capital, shipped its first proprietary foundation-model family, signed a U.S. Department of Defense partnership, and navigated the failed Series C round of 2025 to 2026.
  • Public-talk record. SDS 754: A Code-Specialized LLM Will Realize AGI on the SuperDataScience podcast with Jon Krohn (August 2024); Future of Code with Poolside CEO Jason Warner on Five Year Frontier with Daniel Darling (released January 2025); Developing the Future of AI on the Penn State Dare to Disrupt podcast (August 2024); How a very average programmer became GitHub's CTO on the Stack Overflow podcast (May 2022).
  • Written record. Medium writing on engineering leadership plus GitHub blog posts from his GitHub period.

Investments and boards

Entries below are limited to AI, semiconductors, datacenters, software, and energy.

  • Redpoint Ventures (Software / AI): Managing Director, July 2021 to May 2023. Early-growth investor at the San Francisco venture-capital firm.
  • poolside (AI): Co-founder and Chief Executive Officer, May 2023 to present. Cumulative funding through May 2026 approximately $626 million across the seed, seed extension, and Series B rounds.
  • Bridgewater Associates (Software): Operating board member, from approximately 2022 to present.
  • Atlassian (Software): Board director, since October 1, 2025, announced September 17, 2025.

No other public investor activity on record as of May 2026.

Network

Warner's longest-running professional partnership is with Eiso Kant, his poolside co-founder. The pair developed the poolside thesis through the Developing Leadership podcast they have co-hosted since 2020. Kant's prior ventures include source{d} and Athenian, providing a complementary technical anchor to Warner's developer-platform operating record.

The GitHub period from 2017 to 2021 produced several lasting relationships. Chris Wanstrath recruited him into the senior vice president of technology role; Nat Friedman, GitHub chief executive after the Microsoft acquisition, worked alongside Warner on the GitHub Copilot incubation; Thomas Dohmke, the current GitHub chief executive, was on the leadership team during Warner's CTO tenure. The GitHub Copilot collaboration connected Warner to the OpenAI Codex research effort and to senior OpenAI staff including Sam Altman. Erica Brescia, his former GitHub COO colleague, later led the Redpoint Series A participation in poolside.

Among coding-AI peer founders, his poolside position runs in parallel with Eric Ho at Goodfire, Misha Laskin at Reflection AI, and Aidan Gomez at Cohere, with closer commercial overlap to Cursor (Anysphere) and Cognition AI.

Position in the field

As of May 2026, Warner occupies a distinctive position among coding-AI chief executives through the combination of the GitHub CTO operating credential, the venture-capital partnership at Redpoint, and the foundation-model bet at poolside. The career arc through Canonical, Heroku, GitHub, and Redpoint maps onto the developer-platform stack that poolside foundation models target.

Industry coverage has consistently characterized poolside under Warner's leadership as a principal commercial coding-foundation-model lab globally, alongside Cursor (Anysphere), Cognition AI, Codeium / Windsurf, and the in-house coding-AI products at Anthropic, OpenAI, and Google DeepMind. The competitive frame is unusual: Warner formerly oversaw GitHub Copilot, one of the products poolside now positions itself against.

The Series C failure of 2026 and the CoreWeave Project Horizon collapse have shifted the public framing of poolside's near-term trajectory. DataCenterDynamics coverage of April 2026 has characterized the company as facing a more constrained capital environment than the October 2024 Series B and October 2025 Series C announcement implied.

Outlook

Open questions over the next 6 to 18 months:

  • Series C successor. Whether poolside closes a successor financing in 2026, at what valuation relative to the $3 billion Series B and the $12 billion attempted level, and the lead-investor profile.
  • Project Horizon recovery. Whether the Pecos County campus finds a replacement anchor tenant after the CoreWeave departure, and whether the project proceeds at the 2-gigawatt scale.
  • Foundation-model release cadence. Capability profile of poolside's next foundation-model release relative to peer commercial coding-AI products, and published benchmark positions.
  • Department of Defense partnership. Whether the partnership produces additional disclosed contracts or extends to allied-government customers.
  • Atlassian board work. Whether the directorship produces a commercial collaboration between poolside and Atlassian's developer-platform products.
  • Senior-team stability. Whether the Warner and Kant founding partnership remains intact through the post-Series-C-failure phase.

Sources

Person poolside
About the author
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