---
title: "Run the whole test suite under a leak sanitizer with a curated suppression list"
description: "A sanitizer lane runs every test in CI, and each leak it reports is fixed or listed with a reason."
url: https://starsling.dev/ci-playbooks/techniques/suite-under-leak-sanitizer
canonicalUrl: https://starsling.dev/ci-playbooks/techniques/suite-under-leak-sanitizer
---

# Run the whole test suite under a leak sanitizer with a curated suppression list

A sanitizer lane runs every test in CI, and each leak it reports is fixed or listed with a reason.

## How to choose an approach

This technique currently has one documented company example. Validate its prerequisites, tradeoffs and original CI environment against your repository before adapting it.

- **[Anthropic](https://starsling.dev/ci-playbooks/anthropic#suite-under-leak-sanitizer)**: Use it when A repository with native code (C, C++, Rust or Zig) or another language with a leak or memory checker runs its tests only in regular builds. Check before adopting: The sanitizer lane runs beside the regular lanes with its own machine size and per-test timeout, and each suppression carries a written reason.

## Apply this technique

````text
Evaluate and apply this CI technique to my repository: Run the whole test suite under a leak sanitizer with a curated suppression list.

A sanitizer lane runs every test in CI, and each leak it reports is fixed or listed with a reason.

Read the technique and its source-backed company examples: https://starsling.dev/ci-playbooks/techniques/suite-under-leak-sanitizer.md

Inspect this repository’s CI workflows, build and test commands, dependencies, and recent run timings. Identify where this technique applies and explain the expected benefit using this repository’s evidence.
Measure a baseline from recent comparable runs: elapsed time, queue time, runner minutes and failures where available. If data is unavailable, say what cannot be measured.
Compare relevant company approaches, checking prerequisites, platform differences and tradeoffs. Rank applicable options by evidence, fit and measurable opportunity; do not present company results as predictions for this repo.
Recommend the smallest safe change, show what checks and fallback paths remain, and ASK ME WHICH CHANGE TO APPROVE BEFORE EDITING ANY FILES.
Only after approval, work on a new feature branch, make one reversible change, and open a reviewable pull request. Never merge or push to a default or protected branch.
Keep required checks, test coverage, deployment and release behavior intact. Validate the change and compare equivalent runs where possible; report limitations and what should be monitored after merge.
````

## How Anthropic used this technique

Read what Anthropic changed and follow the original sources.

### Anthropic: Run the whole test suite under a leak sanitizer with a curated suppression list

Bun's CI runs the entire test suite under LeakSanitizer with a curated suppression list. After an allocator change let the sanitizer see every heap allocation, every leak it reported was fixed. The sanitizer test agents moved to machines with more memory, and each test gets a wider timeout in the sanitizer lane.

Evidence: Source PR/commit evidence

Use it when: A repository with native code (C, C++, Rust or Zig) or another language with a leak or memory checker runs its tests only in regular builds.

Before applying it: The sanitizer lane runs beside the regular lanes with its own machine size and per-test timeout, and each suppression carries a written reason.

[Read more in the Anthropic playbook](https://starsling.dev/ci-playbooks/anthropic#suite-under-leak-sanitizer)

[Primary source](https://github.com/oven-sh/bun/pull/30875)

## CI optimization is continuous work.

Apply this technique yourself, or use StarSling Runners for faster GitHub Actions and optional agent-driven optimization PRs, which teams on eligible paid plans can turn on.

[Get self-improving CI](https://starsling.dev/products/runners)

## Company Playbooks

### [Anthropic](https://starsling.dev/ci-playbooks/anthropic)

Run only affected tests

### [DoorDash](https://starsling.dev/ci-playbooks/doordash)

Run build and test in parallel, sharded across CI agents

### [Linear](https://starsling.dev/ci-playbooks/linear)

Benchmark the same job on faster hardware

### [Mastra](https://starsling.dev/ci-playbooks/mastra)

StarSling runners for the slowest test workflow

### [OpenAI](https://starsling.dev/ci-playbooks/openai)

Rank CI fixes by the minutes they save

### [Ramp](https://starsling.dev/ci-playbooks/ramp)

Move a CPU-bound test suite to a faster CPU

### [Shopify](https://starsling.dev/ci-playbooks/shopify)

Let an agent iterate against one CI metric

### [Spotify](https://starsling.dev/ci-playbooks/spotify)

Build arm64 on native arm64 runners

### [Stripe](https://starsling.dev/ci-playbooks/stripe)

Run only the tests a change can reach

### [Uber](https://starsling.dev/ci-playbooks/uber)

Build the merge-queue speculations most likely to be needed