Software engineering student in Morocco. I study what AI agents do when a process dies in the middle of a task, and I build small fixes that can be tested.

An agent sends a payment, then gets killed before it saves that fact. What happens when it restarts?

Often it does the action again. An approval has a similar gap: a person says yes to one call, and a different call can run on that yes. I test these failures by really killing processes and counting what happened.

Call4Agents is a small Python library I maintain. It sits under an existing agent and records each action before and after it runs.

Try it in one command. The demo kills a small agent at every step and shows which action ran twice:

pip install call4agents && call4agents crashtest --demo

• Method: real process kills, then a restart. The test suite also crashes the recovery itself, and old bugs are put back in to check that the tests fail.
• Runs on: Python 3.10 to 3.13 on Linux, macOS and Windows, with no required dependencies.
• Works with: LangGraph, Pydantic AI, the OpenAI Agents SDK, MCP and plain Python.
• Limits: version 0.6 is early, and it has had no independent security audit. If a process dies during an outside call, nobody can tell whether the call went through, so the library stops and asks instead of guessing. An outside tester found real bugs in the approval code, and the changelog records them.

Website · PyPI · Security policy

• A "yes" is not exactly-once (5 November 2026). One approved payment, a crash right after it, a documented resume: 2 payments in LangGraph, Pydantic AI and the OpenAI Agents SDK, in all 30 runs per framework. A record outside the framework brought it to 1. Script and every run's data included.
• hitl approvals spec (v0 draft): the single-use approval rule went into section 3.8 (PR #10, by the spec's maintainer), and my replay-after-restart conformance check was merged (PR #11).
• Agentic AI test checklist v1.3.2 (Dr Srinivas Padmanabhuni): three crash-recovery cases from my dataset were added, with credit (checklist).

• virtual-A2DP-driver: a user-mode Bluetooth audio stack for Windows in C++, written from the AVDTP spec. Work in progress.
• FishoFisho: a real-time Django chat app with an AI assistant and 202 tests. Live demo.

Open an issue or a discussion on Call4Agents, or write to me on LinkedIn. If your agent repeats actions after a crash, I'd like to hear about it and run a crash test on it for free.