Agent replay infrastructure.
Capture call stacks from any point in your code and replay them dynamically.
- Test specific code changes by freezing any parts of the call stack
- Seamlessly replay normal code and agent frameworks in a single call
- Accelerate agent development velocity by fanning out many code change experiments
Capture, emulate, verify.
The loop lets you regression test and experiment on your agents rapidly, and drive them toward the outcomes you care about.
Bitfab · Experimentsrefund-emails · 20 scenariosCapture scenarios from production.
A scenario is everything needed to relive one real customer interaction, captured automatically: the code execution, the database it read, and every external API response.
Every call recorded in execution order with inputs, outputs, and timestamps, two-way serializable down to datetimes, at zero added latency to your production code.
Emulate any scenario during development.
Replay any scenario locally against the database as it was at capture time, with every external call mocked. Or change one detail, a different user, a different order, and test the what-if. Every result is judged against the scenario's outcome, so a pass means what your team says it means.
Handles side effects
- Detects and instruments dangerous calls
- Replays original outputs for safe emulation
- Configurable on the fly by you or your coding agent
Managed scenario data
- Search across billions of scenarios and connect to your monitoring tools
- Adapts scenarios to survive code changes automatically
- Groups similar traces into scenarios that define behavior
Verify every change against the outcomes you care about.
With Bitfab, you can build coding agent loops that weren't possible for AI features without emulation or adding your team's judgement. Bitfab provides interfaces connected to your coding agent so your team can define outcomes, review changes, and visualize results.
Fix issues
Start from a failing scenario, replay it until it passes, and keep it as a regression test.
Run regression tests
Replay the whole scenario set and catch what broke before you deploy.
Run experiments
Compare before and after across every scenario to see if a change actually helped.
Optimize costs
Profile token spend and iterate to reduce it without losing output quality.
One-line install. 15-minute setup.
Works with TypeScript, Python, Ruby, and Go, driven from Claude Code, Cursor, or Codex. Start building methodically now.