Design concept by Krishna Bhupathi. Aftercast is not a real product, and this incident is invented.
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Report
AC-0417
Occurred
2 Sep 2026, 02:14 UTC
Agent
Refund agent, v3
Operator
Online retailer, name withheld
Run length
41 min 02 s
Status
Final report
This report replays the run from its Aftercast recording. Drag the playhead to see what the agent saw, what it did, and the moment it went wrong.
Drag the track, or focus it and use the arrow keys. Page Down jumps to the next finding.
02:14 UTC
One engineer on call. The dashboard showed every refund as a success.
Summary
For 41 minutes the agent did what it was asked: refund customers whose orders arrived damaged. When the payments service slowed down, one refund looked like it had failed. The agent tried again. It had already worked.
Every log line said 200 OK. The agent's own checkpoint said “all successful”. It took a finance alert, not an engineering one, to stop it.
1
Sequence of events
Time
Event
00:00
The run starts with 1,140 refund requests in the queue.
06:14
The payments service slows to 9.8 s per call. The agent's tool gives up after 8 s.
06:24
A refund times out. It has in fact gone through.
06:31
The agent retries and refunds the same order a second time.
14:50
The agent's checkpoint: 412 refunds processed, all successful.
38:40
Finance flags refunds at 3.1× a normal day.
41:02
The on-call engineer stops the run. 312 orders were refunded twice.
2
Findings
F1
The timeout hid a success
The payment went through. The tool stopped waiting at 8 s and told the agent the call had failed.
F2
Retries had no idempotency key
Each retry was a brand-new refund, so the payments service had no way to know it was a repeat.
F3
Success was counted, not checked
The agent counted calls that returned 200. Nothing compared refunds paid with refunds owed.
3
What the agent believed
Why a recorder
Air accident investigators replay the flight recorder before they change a rule. Agents that spend money deserve the same.
4
Recommendations
This is what Aftercast does. It sits between your agent and its tools, so nothing in your prompts or code changes.
R2
Replay
Scrub any run like the one above. See what the agent knew at each moment, not just what it logged.
run
AC-0417 at 06:31
paid twice
1
confidence
0.94
R3
Guard
A finding becomes a rule that stops the next run before it repeats the mistake.
guard
one-refund-per-order
when
payments.refund
block
repeat within 24h
5
From the interviews
On-call engineer, name withheld
Other reports
AC-0417
The refund agent paid 312 orders twice, and reported success
2 Sep 2026
Reading
AC-0388
The outreach agent sent one draft to 1,780 leads
19 Aug 2026
Final
AC-0362
The coding agent deleted the migration it had just written
4 Aug 2026
Final
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Aftercast is a design concept by Krishna Bhupathi. The product, the incident and the people are fictional. Photos from Unsplash.
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