Background
Fern is a 240-engineer platform company shipping a developer tools product. Their engineers' IDE preferences spanned an AI-native editor, a hosted long-horizon agent, the established JetBrains and VS Code surfaces, and a stubborn population using a terminal-first agent. Standardising on one was politically impossible and culturally undesirable.
The challenge
Existing coding-agent rollouts inside Fern had failed twice — once on standardisation, once on poor handling of architecture-level work. The platform team wanted an agent that would meet engineers in their existing IDE, share memory across surfaces, and handle whole-repo work the way senior engineers do.
What we did
- Aether for software deployed behind Fern's existing SSO. The fifteen vendor adapters meant every engineer kept their IDE; the agent's memory and review history were shared across surfaces.
- Whole-repo edits scoped to a blast radius; performance profiling for the hot-path services; CVE-aware review on every PR.
- On-call drafting wired into Fern's incident workflow.
- Capability policy restricted production access to a small set of senior engineers, with the agent gated through the same policy layer.
In their words
“The senior engineers stopped pushing back the day it started reviewing diffs the way they would.”
The outcome
- Senior engineers' resistance dropped within two weeks once the agent started reviewing diffs the way they would.
- PR merge velocity up 18%; review-cycle time down 42%.
- No IDE migration forced; the agent met each engineer where they were.
- Three on-call rotations now use Aether for first-draft postmortems.