Real Agent Cases

Migrate 180 microservices to a new framework version with Cursor agents

Posted
by Sofhia de Souza Gonçalves (Brex)
Last checked
Method:
How we verify

Evidence: Company case studyA write-up published by the company that makes the agent or uses it.

Outcome

Brex reports that its self-correcting, self-hosted Cursor agents let one engineer migrate 180 microservices from Micronaut 3 to 4 in a month, which it calls a 32x per-capita speedup.

According to Brex:180 microservices migrated in one month

This is the source's own number. We haven't measured it.

Agent

Cursor (self-hosted agents)

Prompt Recreated prompt

The source didn't share its exact prompt, so we wrote this from what it describes.

Migrate this service from Micronaut 3 to Micronaut 4: update the build targets and imports, build it, fix every compilation and test failure, and repeat until CI passes.

Try this in:

ChatGPT Gemini Grok

Sends the Recreated prompt shown above. ChatGPT and Grok open with it filled in, and ChatGPT may send it straight away. Gemini opens empty, so we copy the prompt for you to paste. Every button also copies it.

The source used Cursor (self-hosted agents), which can take actions in a browser or app. These are general chat tools, so results may differ, and a normal chat may only give you a plan.

Opens in a new tab. We don't see what you send.

These links are only a shortcut. We're not affiliated with OpenAI, Google or xAI, and your results may not match the source.

Optional stronger version

Our rewrite with extra checks. The poster didn't test it.

Goal: Migrate this service from Micronaut 3 to 4 and iterate until CI is green.

Inputs (fill in or confirm):
- Service repo and branch
- Migration guide link
- CI command
- Services or modules that must not change behaviour

Rules:
- Update build targets, dependencies and imports per the official guide.
- Fix compilation errors first, then test failures, in small commits.
- Don't change behaviour or public APIs; note any unavoidable change.
- Record each error and fix in a migration log for reuse on other services.
- Prefer the framework's documented replacements over custom workarounds.
- Check deprecation warnings after the build and fix the ones the guide marks as removed in v4.
- Migrate one service end to end first as a pilot, and review it with me.
- Keep a per-service checklist: compiled, tests green, behaviour diff checked.
- Open one pull request per service so each can be reviewed and rolled back.

Checkpoint: Open a PR; don't merge or deploy.

If you get stuck: If a failure isn't covered after three attempts, stop and summarize it. If a login, CAPTCHA or two-step code appears, stop and ask me to handle it; never guess or store passwords.

Verify before you finish: Run the full test suite and CI; list any skipped tests.

Output: PR link, migration log and CI result.

Done when: CI passes with no behaviour changes.

Source

https://www.brex.com/journal/agent-automations-for-big-migrations

Related cases

  • Upgrade a plugin to a new framework alpha with Codex CLIEvidence: Screenshots or logs

    A one-line `codex exec` loop read the Datasette 1.0a20 upgrade docs, fixed the failing tests, and got the datasette-checkbox plugin passing again.

    OpenAI Codex CLI · Coding · Source date:

  • Migrate two websites from WordPress to Wagtail with Claude CodeRecreated promptEvidence: Described by poster

    Over a weekend Claude Code migrated two sites from WordPress to Wagtail (PHP to Python), including server setup, data transfer, testing and fixes, and redesigned a homepage; the poster reports nothing broke and traffic and tools stayed in place.

    Claude Code · Coding · Source date:

  • Port a backend to Convex in four hours with Factory's DroidRecreated promptEvidence: Described by poster

    The poster reports that Factory's Droid ported their tRPC/Drizzle custom backend to Convex in about 4 hours, with some bugs left to fix.

    Factory Droid · Coding · Source date: