refactor: migrate from Yarn 3.8.7 to pnpm

[misama-ct]

Caution

This PR was created to try out the freshly added AI Agent tooling. Do not merge without thorough review and CI validation.

Summary

• Replace Yarn 3.8.7 with pnpm 10.11.0 as the package manager
• Remove all Yarn artifacts (.yarnrc.yml, .yarn/, yarn.lock, constraints.pro)
• Add pnpm equivalents (pnpm-workspace.yaml, .npmrc, pnpm-lock.yaml)
• Update root package.json (packageManager, engines, pnpm.overrides, pnpm.onlyBuiltDependencies, scripts)
• Migrate all shell scripts, git hooks, CI workflows, config files, and documentation from yarn to pnpm
• Replace manypkg run/exec with native pnpm --filter / pnpm -r exec
• Replace Yarn's Prolog-based constraints.pro with a Node.js validation script
• Fix phantom dependency (yaml in design-system) exposed by pnpm's stricter isolation
• Fix pre-existing incorrect deep import (@commercetools-uikit/constraints/src)
• Regenerate all icon components with updated template comment

Known trade-offs

• shamefully-hoist=true is enabled in .npmrc to match Yarn's flat hoisting behavior — many cross-workspace type references rely on it. Can be tightened later with targeted public-hoist-pattern[] entries.
• pnpm.onlyBuiltDependencies allowlist may need tuning if build script warnings persist in CI.

Test plan

• pnpm install succeeds
• pnpm build succeeds
• pnpm typecheck passes (0 errors)
• pnpm test passes (1402 tests, 125 suites)
• pnpm lint passes (1307 files)
• node scripts/check-workspace-constraints.js passes
• No yarn references in source files
• CI pipeline passes
• Changesets publish flow works
• Percy visual regression tests pass

---

Review Navigator

270 files changed across 7 commits; ~25 are substantive, ~38 are README yarn add → pnpm add replacements, ~17 are regenerated icon comment updates, and ~20 are AI tooling files from the base branch (not part of the migration).

Review in the logical chunks below — start with the core config (commits 1-2), then CI, then spot-check the bulk changes.

File Relationships & Review Order

flowchart TB
    subgraph "1️⃣ Core Configuration"
        A["① package.json<br/><i>packageManager, overrides, scripts</i>"]
        B["② pnpm-workspace.yaml<br/><i>workspace package globs</i>"]
        C["③ .npmrc<br/><i>shamefully-hoist=true</i>"]
        D["④ .gitignore<br/><i>remove .yarn patterns</i>"]
    end

    subgraph "2️⃣ Deleted Yarn Artifacts"
        E["⑤ .yarnrc.yml<br/><i>deleted</i>"]
        F["⑥ constraints.pro<br/><i>deleted, replaced by ⑭</i>"]
        G["⑦ .yarn/*<br/><i>deleted (plugins, releases)</i>"]
    end

    subgraph "3️⃣ Scripts & Hooks"
        H["⑧ scripts/build.sh<br/><i>yarn→pnpm, manypkg→filter</i>"]
        I["⑨ scripts/postinstall.sh<br/><i>yarn→pnpm</i>"]
        J["⑩ .husky/pre-commit<br/><i>yarn→pnpm</i>"]
        K["⑪ .husky/commit-msg<br/><i>yarn→pnpm</i>"]
    end

    subgraph "4️⃣ CI/CD Workflows"
        L["⑫ main.yml<br/><i>pnpm setup, cache, install</i>"]
        M["⑬ publish-release.yml<br/><i>pnpm setup, changeset cmds</i>"]
        N["  preview-release-on-comment.yml<br/><i>pnpm setup, snapshot cmds</i>"]
    end

    subgraph "5️⃣ Constraints Replacement"
        O["⑭ check-workspace-constraints.js<br/><i>new: replaces constraints.pro</i>"]
    end

    subgraph "6️⃣ Config Files & Workspace Packages"
        P["⑮ lint-staged.config.js<br/><i>yarn→pnpm</i>"]
        Q["⑯ jest-puppeteer.config.js<br/><i>yarn→pnpm</i>"]
        R["⑰ svgr.config.js<br/><i>template comment update</i>"]
        S["⑱ design-system/package.json<br/><i>+yaml,rcfile,prettier devDeps</i>"]
        T["⑲ storybook/package.json<br/><i>yarn→pnpm in scripts</i>"]
    end

    subgraph "7️⃣ Generators"
        U["⑳ generators/*/bin/cli.mjs<br/><i>spawnSync yarn→pnpm</i>"]
        V["㉑ generators/readme/src/index.ts<br/><i>template: yarn→pnpm</i>"]
        W["㉒ generators/readme/test/*.spec.ts<br/><i>snapshot updates</i>"]
    end

    subgraph "8️⃣ Documentation"
        X["㉓ CONTRIBUTING.md<br/><i>yarn→pnpm throughout</i>"]
        Y["㉔ test/percy/README.md<br/><i>yarn→pnpm throughout</i>"]
    end

    subgraph Bulk ["9️⃣ Bulk Changes (spot-check only)"]
        Z["~38 component READMEs<br/><i>yarn add → pnpm add</i>"]
        AA["~17 generated icons<br/><i>comment: yarn→pnpm</i>"]
    end

    subgraph "🔧 Bugfix"
        BB["㉕ dropdown-menu.stories.tsx<br/><i>fix: /constraints/src import</i>"]
    end

    A --> H
    A --> L
    A --> I
    F -.->|replaced by| O
    L --> O
    R --> AA
    V --> Z
    V -.->|tested by| W

    style O fill:#e8f5e9
    style BB fill:#fff3e0
    style Bulk fill:#f5f5f5,stroke:#bdbdbd,stroke-dasharray: 5 5

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Suggested Review Order

#	File	What it does	Link
1	package.json	Root config: packageManager, engines, pnpm.overrides, pnpm.onlyBuiltDependencies, scripts (yarn workspace → pnpm --filter)	View
2	pnpm-workspace.yaml	New file defining workspace package globs (mirrors previous workspaces field)	View
3	.npmrc	New file enabling shamefully-hoist for Yarn-compatible hoisting	View
4	.gitignore	Removes .yarn ignore patterns, adds pnpm debug log	View
5	.yarnrc.yml	Deleted: Yarn config with plugins and nodeLinker	View
6	constraints.pro	Deleted: Yarn Prolog-based workspace constraints (replaced by #13)	View
7	scripts/build.sh	Replaces yarn with pnpm, manypkg run with pnpm --filter	View
8	scripts/postinstall.sh	Replaces yarn with pnpm for husky, manypkg, preconstruct, prettier, patch-package	View
9	.husky/pre-commit	yarn → pnpm for generate-package-json and lint-staged	View
10	.github/workflows/main.yml	Adds pnpm/action-setup, pnpm store cache, replaces all yarn commands	View
11	.github/workflows/publish-release.yml	Same CI migration + changeset publish/version commands	View
12	.github/workflows/preview-release-on-comment.yml	Same CI migration + snapshot publish commands	View
13	scripts/check-workspace-constraints.js	New: Node.js replacement for constraints.pro, validates license/repository/publishConfig	View
14	design-system/package.json	Adds yaml, rcfile, prettier as devDeps (phantom deps), updates nodemon exec	View
15	lint-staged.config.js	yarn prettier/lint:js → pnpm	View
16	svgr.config.js	Template comment: yarn generate-icons → pnpm generate-icons	View
17	generators/package-json/bin/cli.mjs	spawnSync('yarn') → spawnSync('pnpm')	View
18	generators/readme/bin/cli.mjs	spawnSync('yarn') → spawnSync('pnpm')	View
19	generators/readme/src/index.ts	Template strings: yarn add/generate-readme → pnpm	View
20	generators/readme/test/generate-readme.spec.ts	Updated inline snapshots for pnpm	View
21	CONTRIBUTING.md	Yarn section → pnpm, all command references updated	View
22	test/percy/README.md	~59 yarn → pnpm replacements	View
23	dropdown-menu.stories.tsx	Bugfix: @commercetools-uikit/constraints/src → @commercetools-uikit/constraints	View
—	~38 component README.md files	Bulk: yarn add → pnpm add install instructions	spot-check a few
—	~17 generated icon .tsx files	Bulk: comment yarn generate-icons → pnpm generate-icons	spot-check a few
—	~20 .agents/, .claude/, AGENTS.md, CLAUDE.md files	AI tooling config from base branch (not part of migration)	skip

🤖 Generated with Claude Code

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Latest commit: 22da04a

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Project	Deployment	Actions	Updated (UTC)
ui-kit	Error		Apr 1, 2026 0:27am

[valoriecarli]

This caught my attention and I read up on it.
When determining what would needed to be done to allow pnpm's default to prevent phantom dependencies, I encountered no errors at all.
Perhaps this file isn't even needed atm?

[valoriecarli]

I can see that the source for this was updated here, but it's not actually generating the changes in any of the README.md files. 🤔

[misama-ct]

Closing for now, we might pick it up at a later time.