From Inner to Outer Loop: Agentic Coding, Stacking PRs, and the Cursor Merger with Greg Foster // CTO @ Graphite
Solving the "Outer Loop" bottleneck: Agentic coding, Stacked PRs, and the future of the CTO role with Graphite's Greg Foster
Greg Foster
Greg Foster, Co-founder and CTO of Graphite (recently acquired by Cursor), joins the podcast to discuss the massive shift occurring in software engineering: the move from maximizing "Inner Loop" speed (writing code) to solving "Outer Loop" bottlenecks (reviewing, testing, merging).
With AI generating code faster than humans can review it, the traditional Pull Request model is under pressure. Greg explains how "Stacked PRs" and agentic review workflows are essential for high-performing teams, and why he believes the role of the software engineer is evolving into an "architect of agents."
We also cover the strategic rationale behind the Graphite/Cursor merger, the controversial "PRs per engineer" metric, and why he predicts that by 2029, manual code writing will be near zero—but demand for engineers will be higher than ever.
Show notes.
The "Inner Loop" of coding (typing syntax) has been solved by AI. The new bottleneck is the "Outer Loop"—reviewing, testing, and merging the flood of code that agents generate.
In this episode, Greg Foster (CTO of Graphite, now part of Cursor) explains why this shift drove their merger and what it means for the future of engineering.
We dive into:
- The Outer Loop Crisis: Why fast code generation breaks traditional review processes (and how to fix it).
- Agentic Engineering: The 2029 vision where engineers become "architects of agents" and writing code trends to zero.
- Stacked PRs: Why smaller, dependent changes are the only way to maintain velocity at scale.
- Metrics that Matter: Why "PRs per engineer" is actually a valid proxy for velocity (velocity = speed + vector).
- The Cursor Merger: Combining the best text editor (Inner Loop) with the best review platform (Outer Loop).
- Provenance in Git: The need for storing "prompts" and AI attribution directly in commit history.
- Advice to Young Engineers: Why understanding the business model is as important as reading O'Reilly books.
Chapters:
- [00:00] Intro: Greg's journey from iOS apps to Airbnb infrastructure
- [01:25] Graphite & The Pivot: Bringing "Phabricator-style" tools to GitHub
- [03:52] Reinventing the Pull Request: Stacked PRs and Merge Queues
- [13:20] The Velocity of Dev Tools: When Copilot/Cursor changed the game
- [20:41] Metrics: Is "PRs per engineer" a vanity metric or a velocity proxy?
- [24:22] Jevons Paradox: Why 2x productivity means more engineers, not fewer
- [26:30] The Merger: Why Graphite joined Cursor (Inner + Outer Loop)
- [33:30] Provenance: Storing AI prompts in Git history
- [52:00] The 2029 Vision: Writing code -> Zero. Reviewing Agents -> 100%.
- [56:17] Future of CI: Auto-generated sandboxes with agentic QA
- [59:26] Advice to his younger self: Understand the business, not just the code