[Performance] Optimize Liquid template rendering

[gonzaloriestra]

WHY are these changes introduced?

The renderLiquidTemplate function in @shopify/cli-kit was creating a new Liquid instance on every invocation, which is expensive due to engine initialization. It also parsed and rendered every string regardless of whether it contained actual Liquid templates.

WHAT is this pull request doing?

• Implements a shared, lazy-initialized Liquid engine instance.
• Adds a short-circuit check using includes to skip parsing/rendering for strings without {{ or {%.

Performance Impact (1000 iterations):

• Static strings: 254ms → 0.5ms (~500x improvement)
• Small templates: 252ms → 82ms (~3x improvement)

How to test your changes?

Verify that Liquid rendering still works correctly by running the unit tests:
pnpm --filter @shopify/cli-kit vitest run src/public/node/liquid.test.ts

Checklist

• I've considered possible cross-platform impacts (Mac, Linux, Windows)
• I've considered possible documentation changes
• I've considered analytics changes to measure impact
• The change is user-facing — I've identified the correct bump type (patch) and added a changeset.

---

PR created automatically by Jules for task 9657811168130259180 started by @gonzaloriestra

[google-labs-jules]

👋 Jules, reporting for duty! I'm here to lend a hand with this pull request.

When you start a review, I'll add a 👀 emoji to each comment to let you know I've read it. I'll focus on feedback directed at me and will do my best to stay out of conversations between you and other bots or reviewers to keep the noise down.

I'll push a commit with your requested changes shortly after. Please note there might be a delay between these steps, but rest assured I'm on the job!

For more direct control, you can switch me to Reactive Mode. When this mode is on, I will only act on comments where you specifically mention me with @jules. You can find this option in the Pull Request section of your global Jules UI settings. You can always switch back!

New to Jules? Learn more at jules.google/docs.

---

For security, I will only act on instructions from the user who triggered this task.

[gonzaloriestra]

/snapit

[github-actions]

🫰✨ Thanks @gonzaloriestra! Your snapshot has been published to npm.

Test the snapshot by installing your package globally:

pnpm i -g --@shopify:registry=https://registry.npmjs.org @shopify/cli@0.0.0-snapshot-20260506091709

Caution

After installing, validate the version by running shopify version in your terminal.
If the versions don't match, you might have multiple global instances installed.
Use which shopify to find out which one you are running and uninstall it.

[craigmichaelmartin]

The new includes check is a behavioral change. Lets add tests for this short-circuit path.

[github-actions]

This PR seems inactive. If it's still relevant, please add a comment saying so. Otherwise, take no action.
→ If there's no activity within a week, then a bot will automatically close this.
Thanks for helping to improve Shopify's dev tooling and experience.