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Bump Size Limit

DevOps & Security
bump-size-limit

Bump Size Limit is an Agent Skill for devops & security published in the getsentry/sentry-javascript repository on GitHub: a SKILL.md instruction file an AI agent can load to do this task.

Bump size limits in .size-limit.js when the size-limit CI check is failing. Use when the user mentions size limit failures, bundle size checks failing, CI size check errors, or needs to update size-limit thresholds. Also use when the user says "bumpSizeLimit", "fix size limit", "size check failing", or "update bundle size limits".

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How to use this skill

Bring this guide into your coding agent with a prompt tailored to the tool you use.

  1. Open your project in Codex.
  2. Copy and paste the prompt below.
  3. Review files and risks before approving any action.
Prompt to paste
Inspect the Agent Skill at https://github.com/getsentry/sentry-javascript/blob/HEAD/.agents/skills/bump-size-limit/SKILL.md and all supporting files. Report provenance, permissions, scripts, dependencies, and security risks. Propose an exact installation into .agents/skills/bump-size-limit, but wait for my approval before writing files or running scripts.

Copying this prompt does not install or run the skill. Review third-party files before use.

Bump Size Limit

When the size-limit GitHub Action fails, it means one or more bundle scenarios exceed their configured byte thresholds in .size-limit.js. This skill walks through building, measuring, and bumping only the limits that need it.

Workflow

Step 1: Build all packages (including CDN bundles)

A full build is required because size-limit measures the actual compiled artifacts.

yarn build

This takes a few minutes. CDN bundles in packages/browser/build/bundles/ must be up to date — a dev build is not sufficient.

Step 2: Run the size check in JSON mode

yarn test:size-limit

The JSON output is an array of objects. Each object has:

  • name — the scenario label
  • passed — whether it's within the limit
  • size — actual size in bytes
  • sizeLimit — configured limit in bytes

Step 3: Identify failed scenarios

Filter for entries where "passed": false. These are the only ones that need bumping.

Step 4: Calculate new limits

For each failed scenario, round the actual size up to the next full KB (1 KB = 1000 bytes in this context, matching how size-limit interprets the limits in .size-limit.js).

Example: If actual size is 129,127 bytes, the new limit is 130 KB (i.e. 130,000 bytes).

The heuristic is intentionally conservative — it gives just enough headroom without inflating limits unnecessarily.

Step 5: Update .size-limit.js

Open .size-limit.js at the repository root and update the limit field for each failed scenario. Limits are strings like '130 KB'.

Only change limits for scenarios that actually failed. Do not touch passing scenarios.

Step 6: Verify the fix

Re-run size-limit to confirm everything passes:

yarn test:size-limit

If any scenario still fails (e.g., due to rounding edge cases), bump that specific limit by another 1 KB and re-run.