#134 - 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

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:

1. [00:00] Intro: Greg's journey from iOS apps to Airbnb infrastructure
2. [01:25] Graphite & The Pivot: Bringing "Phabricator-style" tools to GitHub
3. [03:52] Reinventing the Pull Request: Stacked PRs and Merge Queues
4. [13:20] The Velocity of Dev Tools: When Copilot/Cursor changed the game
5. [20:41] Metrics: Is "PRs per engineer" a vanity metric or a velocity proxy?
6. [24:22] Jevons Paradox: Why 2x productivity means more engineers, not fewer
7. [26:30] The Merger: Why Graphite joined Cursor (Inner + Outer Loop)
8. [33:30] Provenance: Storing AI prompts in Git history
9. [52:00] The 2029 Vision: Writing code -> Zero. Reviewing Agents -> 100%.
10. [56:17] Future of CI: Auto-generated sandboxes with agentic QA
11. [59:26] Advice to his younger self: Understand the business, not just the code