Hydrogen Development Workflow

Hydrogen Recipes

Recipes are documented cookbook entries for adding features to a Hydrogen storefront. They exist as markdown files in the dev docs. The "apply" command and related tooling are purely for internal use to test or update the recipes -- merchants cannot programmatically apply recipes to their storefronts.

Cookbook Architecture: Ingredients and Generated Docs

Each recipe has two layers that need to stay in sync:

Ingredient files (cookbook/recipes/{name}/ingredients/templates/skeleton/app/routes/*.tsx): These are real, standalone .tsx route implementations — not patches or diffs. They are applied when a merchant follows the recipe. When the skeleton has a bug (e.g., a missing await), the corresponding cookbook ingredient files may have the same bug independently and need to be fixed separately.

Generated documentation (cookbook/recipes/{name}/README.md and cookbook/llms/{name}.prompt.md): These files are auto-generated from the ingredient source files. They inline the full route source code, so if you fix the ingredient .tsx files, you MUST also regenerate the docs:

pnpm run cookbook -- render --recipe {name}
pnpm run cookbook -- validate --recipe {name}

Both the README.md and llms/{name}.prompt.md must be committed as part of the same fix. Failing to regenerate means the docs teach the wrong pattern even after the ingredient files are correct.

Example: The markets recipe has ($locale).account.$.tsx, ($locale).account.addresses.tsx, and ($locale).account.profile.tsx as ingredient files. These are independent of the skeleton and don't automatically inherit skeleton fixes.

Fixing Broken Recipes (Patch Files)

Recipe patch files can break when the skeleton template changes. Two approaches:

For trivial 1-line changes: Edit the patch files directly.

For nontrivial changes:

1. Create a new branch locally
2. Hard reset to the latest commit where the recipes DID apply cleanly
3. For each recipe: a. Apply the recipe b. Use Claude/LLM to apply all changes from that commit to latest main on the skeleton template with recipe applied c. Generate new patch files d. Un-apply the recipe and repeat for the next one

Upgrading Hydrogen

The best way to upgrade a Hydrogen storefront is the upgrade CLI command:

pnpm exec shopify hydrogen upgrade

This command:

• Automatically bumps and installs all necessary dependencies
• For manual changes, generates a markdown file containing all required changes
• The markdown file is excellent for feeding to Claude or other LLMs to apply changes

Best practice: When upgrading across multiple major versions, upgrade one major version at a time and verify everything works between each bump. This is smoother than attempting multiple major version bumps at once.

Skeleton Template

The skeleton template serves two purposes:

1. Internal testing: It is the single Hydrogen storefront we use to test and validate changes to Hydrogen. Located at templates/skeleton in the Hydrogen repo.
2. New project scaffolding: When a user scaffolds a new Hydrogen project (via shopify hydrogen init or npm create @shopify/hydrogen), they get a copy of the skeleton template.

Key facts:

• Lives in the Hydrogen monorepo at templates/skeleton
• Uses built versions of Hydrogen packages from the monorepo (not from npm)
• Bundled and released with the Hydrogen CLI
• Should always be up to date before a Hydrogen CLI release
• Can be updated before a release even if the Hydrogen CLI version isn't being bumped

Any change to the skeleton template requires a changeset — see the Changeset Rules in CLAUDE.md for details.

PR Conventions

Link Issues to PRs

Always include a link to the GitHub issue in your PR. Use Closes <issue> or Fixes <issue> so the issue automatically closes when the PR merges.

Hydrogen Analytics Architecture

The analytics system in packages/hydrogen/src/analytics-manager/ has several non-obvious design constraints worth knowing before debugging.

Module-scoped singletons

subscribers, registers, and waitForReadyQueue are module-scoped (not instance-scoped). This means:

• They persist across React renders and React tree unmounts/remounts
• In tests, they accumulate state across test cases — a test that calls register() without ready() will block all subsequent tests
• There is exactly one analytics bus per JS context; multiple <Analytics.Provider> instances share state

Consent enforcement is in the subscriber, not the publisher

publish() always enqueues events regardless of consent state. Consent is enforced at three downstream layers:

1. ShopifyAnalytics only calls shopifyAnalyticsReady() after privacyReady is true (privacy SDK loaded)
2. prepareBasePageViewPayload evaluates customerPrivacy.analyticsProcessingAllowed() at handler invocation time
3. sendShopifyAnalytics (in hydrogen-react) drops the event if payload.hasUserConsent is false

Do NOT add consent gating to publish() — it causes events to be dropped (not queued) before consent resolves, creating a race condition where events fired during initialization are permanently lost.

Hydrogen CLI

The Hydrogen CLI source code lives at packages/cli-hydrogen in the Hydrogen repo. It is released to npm as its own package.

Bundling in Shopify CLI: Merchants typically do not use the Hydrogen CLI directly. Instead, it is bundled inside the Shopify CLI (in the Shopify/cli repo). After releasing a new version of the Hydrogen CLI to npm, you must also bump its version in the Shopify CLI.

Timing: The Shopify CLI releases a new minor version on a regular cadence. Hydrogen CLI bumps should NOT wait for the next Shopify CLI minor — release the bump as a patch of the current Shopify CLI minor version to get it out sooner.

How to update: A shopify-cli-update command exists in the Hydrogen repo at .claude/commands/shopify-cli-update.md. This is a Claude Code command — invoke it with /shopify-cli-update when working in the Hydrogen repo. It documents the full, nuanced, multi-step process. Always reference this command when performing the update — do not try to wing it from memory.

Project Scaffolding

There are two ways to scaffold a new Hydrogen project:

1. shopify hydrogen init — via the Shopify CLI (which bundles the Hydrogen CLI)
2. npm create @shopify/hydrogen — via the create-hydrogen package

Both ultimately use the skeleton template. The create-hydrogen package uses the Hydrogen CLI's init function under the hood.

Version Tags

• @latest: The most recent official release
• @next: Contains all Hydrogen changes that have been merged to main (with changesets), even before they have been officially released. A new next version is auto-published every time code is pushed to main.

The next tag is useful for merchant bug-fix validation: after merging a fix to main, the merchant can test with npm create @shopify/hydrogen@next to confirm the fix resolves their issue — before waiting for an official release.

Scaffolding a Specific Version

create-hydrogen uses SemVer while Hydrogen uses CalVer — see the hydrogen-versioning skill for details on the relationship. Scaffolding a specific historical Hydrogen version requires a lookup step to find which create-hydrogen SemVer version includes the desired Hydrogen CalVer skeleton.

Related Skills

• hydrogen-release-process — Release process, back-fixes, changelog.json, release failure recovery
• hydrogen-versioning — CalVer formats, version support policies, release cadence
• CLAUDE.md — Changeset rules (apply to every PR), skeleton/CLI bundling chain