Maintenance: Revert pull request #33930 HMR events

[yannbf]

This reverts commit 2b6c4da, reversing changes made to 5a9c6ec.

What I did

This PR reverts the work done in #33930 until we come back to it at a later time

Checklist for Contributors

Testing

The changes in this PR are covered in the following automated tests:

• stories
• unit tests
• integration tests
• end-to-end tests

Manual testing

Caution

This section is mandatory for all contributions. If you believe no manual test is necessary, please state so explicitly. Thanks!

Documentation

• Add or update documentation reflecting your changes
• If you are deprecating/removing a feature, make sure to update
  MIGRATION.MD

Checklist for Maintainers

• When this PR is ready for testing, make sure to add ci:normal, ci:merged or ci:daily GH label to it to run a specific set of sandboxes. The particular set of sandboxes can be found in code/lib/cli-storybook/src/sandbox-templates.ts

• Make sure this PR contains one of the labels below:

  Available labels

  • bug: Internal changes that fixes incorrect behavior.
  • maintenance: User-facing maintenance tasks.
  • dependencies: Upgrading (sometimes downgrading) dependencies.
  • build: Internal-facing build tooling & test updates. Will not show up in release changelog.
  • cleanup: Minor cleanup style change. Will not show up in release changelog.
  • documentation: Documentation only changes. Will not show up in release changelog.
  • feature request: Introducing a new feature.
  • BREAKING CHANGE: Changes that break compatibility in some way with current major version.
  • other: Changes that don't fit in the above categories.

🦋 Canary release

This PR does not have a canary release associated. You can request a canary release of this pull request by mentioning the @storybookjs/core team here.

core team members can create a canary release here or locally with gh workflow run --repo storybookjs/storybook publish.yml --field pr=<PR_NUMBER>

Summary by CodeRabbit

Release Notes

• Refactor
  • Improved hot module replacement handling to enhance the reliability of story updates during development with more consistent update sequencing.
  • Optimized debounce behavior for story index invalidation to better handle rapid file changes.

[nx-cloud]

View your CI Pipeline Execution ↗ for commit 4c77f00

Command	Status	Duration	Result
nx run-many -t compile -c production --parallel=1	✅ Succeeded	5m 44s	View ↗

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☁️ Nx Cloud last updated this comment at 2026-03-18 08:46:41 UTC

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: 8b1ed6de-4eb3-41a8-bd20-30ca3d2b85e0

📥 Commits

Reviewing files that changed from the base of the PR and between e3c5772 and 4c77f00.

📒 Files selected for processing (6)

• code/builders/builder-vite/src/codegen-modern-iframe-script.test.ts
• code/builders/builder-vite/src/codegen-modern-iframe-script.ts
• code/builders/builder-vite/src/codegen-project-annotations.ts
• code/builders/builder-webpack5/templates/virtualModuleModernEntry.js
• code/core/src/core-server/utils/index-json.test.ts
• code/core/src/core-server/utils/index-json.ts

💤 Files with no reviewable changes (1)

• code/builders/builder-vite/src/codegen-project-annotations.ts

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📝 Walkthrough

Walkthrough

The PR restructures HMR event emission across Vite and Webpack5 builders, moving STORY_HOT_UPDATED from module acceptance callbacks to dedicated lifecycle hooks (vite:afterUpdate for Vite, webpack hot.status idle for Webpack), and adjusts the story index debounce strategy from trailing-edge only to both leading and trailing edges.

Changes

Cohort / File(s)	Summary
Vite HMR Flow code/builders/builder-vite/src/codegen-modern-iframe-script.ts, code/builders/builder-vite/src/codegen-modern-iframe-script.test.ts, code/builders/builder-vite/src/codegen-project-annotations.ts	Restructures Vite HMR handling: moves STORY_HOT_UPDATED emission to vite:afterUpdate hook in iframe script, removes it from project annotations callback, and updates corresponding test cases to reflect the new event sequence.
Webpack5 HMR Handler code/builders/builder-webpack5/templates/virtualModuleModernEntry.js	Adds webpack hot status handler that emits STORY_HOT_UPDATED when status becomes idle; removes STORY_HOT_UPDATED emissions from individual module accept callbacks.
Index JSON Debounce Strategy code/core/src/core-server/utils/index-json.ts, code/core/src/core-server/utils/index-json.test.ts	Changes debounce configuration from trailing-edge only to both leading and trailing edges for STORY_INDEX_INVALIDATED emissions; removes a test case validating single-fire behavior and updates debounce documentation comments.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Possibly related PRs

• HMR: Fix race conditions causing stale play functions to fire on re-rendered stories #33930 — Directly related code-level changes to the same HMR flow and STORY_INDEX_INVALIDATED debounce strategy across multiple builders.

✨ Finishing Touches

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• Create stacked PR
• Commit on current branch

📝 Coding Plan

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