HookChaos: Stress Testing Webhook Reliability with Local-First Chaos Simulation

HookChaos: Webhook Stress Tester CLI/Open-Sourced Project

Umut Keskin developed HookChaos after a non-idempotent handler caused duplicate order fulfillment in production. The tool functions as a local-first CLI that injects failure scenarios like timestamp skew and signature failures into webhook endpoints.

Why This Matters

Most webhook testing only verifies successful happy-path requests, failing to account for production realities where providers retry on timeouts or deliver events out of sequence. Without simulating these edge cases, developers risk state corruption and duplicate processing when handlers lack idempotency or robust signature validation.

Key Insights

• Fact: A 2026 production bug caused by non-idempotent handlers and provider retries led to double fulfillment (Source: Umut Keskin).
• Concept: Chaos testing for signature validation failures using specific scenarios like trailing newlines.
• Tool: HookChaos CLI used for local-first failure simulation with Git-backed scenario packs.

Working Examples

Running a duplicate event simulation pack.

hookchaos run --pack duplicates --target http://localhost:3000/webhooks

Installation commands for HookChaos.

cd /path/to/hookchaos && make install && export PATH="$HOME/.local/bin:$PATH"

Practical Applications

• Use Case: E-commerce order systems testing for idempotency. Pitfall: Happy-path testing only, resulting in double fulfillment.
• Use Case: Webhook consumers validating signatures. Pitfall: Missing edge cases like trailing newlines, causing production failures.

References:

• https://dev.to/umutkeskin1001/hookchaos-webhook-stress-tester-cliopen-sourced-project-21ne