01 Article
Tests tell you a block works on the cases you thought of. Replay tells you what it would have done last week.
How replay works
Every trace keeps the inputs of each block. Replay feeds the last seven days of real inputs through your draft workflow, in a sandbox with every write action turned into a dry run.
- Outputs are compared block by block with what production did.
- Differences are grouped, so a hundred identical changes show up once.
- Agent decisions are replayed with the same tools and a separate budget.
Reading the diff
Most diffs are expected. The ones that matter are the runs that would have taken a different path, such as an approval that would now be skipped. Replay puts those at the top.
Teams on the Team plan can replay 30 days. Replays do not count toward your run allowance.
Written by the people who build Tessel. We publish notes on engineering, operations and product every few weeks.
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