[MCP] Update WebMCP registration API by bgrgicak · Pull Request #3844 · WordPress/wordpress-playground

bgrgicak · 2026-06-30T07:04:29Z

Summary

Updates WebMCP tool registration to use the current document.modelContext API and handle asynchronous tool registration without breaking the Playground website.

Motivation for the change, related issues

Chrome's WebMCP API has moved away from navigator.modelContext; the Chrome WebMCP Imperative API documentation notes that navigator.modelContext is deprecated in Chrome 150 and recommends document.modelContext instead.

The registerTool() API is also asynchronous in newer Chrome builds, so registration failures need to be caught from the returned Promise. WebMCP is still a progressive enhancement, so failed or unavailable WebMCP registration should not break the website.

Implementation details

Switches WebMCP registration to document.modelContext only.
Makes registerWebMCPTools() return a Promise and await all registerTool() calls.
Updates website and Personal WP initialization to catch async WebMCP registration failures and log them.
Updates the WebMCP e2e mock and README references to use document.modelContext.

Testing Instructions

Ran git diff --check.
I could not run Nx lint/tests in this worktree because node_modules is missing. The commit hook also attempted nx format --fix --parallel --uncommitted and reported that Nx modules could not be found.

Summary by CodeRabbit

New Features
- Updated WebMCP integration to use the current document.modelContext API.
- WebMCP tools now support asynchronous registration.
- Multiple tools are registered reliably during setup.
Bug Fixes
- Improved registration failure handling and warning reporting.
- Prevented incomplete registrations when setup encounters an error.
Documentation
- Updated WebMCP documentation to reflect the current API usage.

Copilot

Pull request overview

Note

Copilot was unable to run its full agentic suite in this review.

Updates WebMCP tool registration to use Chrome’s current document.modelContext API and to handle asynchronous registerTool() without allowing failures to break the Playground experience.

Changes:

Switched WebMCP registration from navigator.modelContext to document.modelContext.
Made registerWebMCPTools() async and awaited tool registration.
Updated website/personal-wp initialization, e2e mock, and README to align with the new API.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
packages/playground/website/src/lib/state/redux/init-mcp-bridge.ts	Awaits WebMCP registration and logs failures without crashing the site.
packages/playground/personal-wp/src/lib/state/redux/init-mcp-bridge.ts	Same async-safe WebMCP registration pattern for personal-wp.
packages/playground/mcp/tests/e2e/webmcp.spec.ts	Updates e2e mock to provide `document.modelContext` and async `registerTool()`.
packages/playground/mcp/src/webmcp.ts	Migrates registration to `document.modelContext` and supports async registration.
packages/playground/mcp/README.md	Documentation updated to reference `document.modelContext`.

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coderabbitai · 2026-08-26T09:28:10Z

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

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Run ID: 36a1c972-8f59-4215-928f-ca3a90ad0aff

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Reviewing files that changed from the base of the PR and between 24b524e and c9c7c54.

📒 Files selected for processing (1)

packages/playground/mcp/src/webmcp.ts

💤 Files with no reviewable changes (1)

packages/playground/mcp/src/webmcp.ts

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📝 Walkthrough

Walkthrough

WebMCP now uses document.modelContext. Tool registration supports asynchronous completion, cancellation, aggregated failures, and promise rejection handling in Redux bridges.

Changes

WebMCP registration

Layer / File(s)	Summary
Update the WebMCP API contract `packages/playground/mcp/src/webmcp.ts`, `packages/playground/mcp/README.md`, `packages/playground/mcp/tests/e2e/webmcp.spec.ts`	The API, documentation, and end-to-end mock use `document.modelContext`. `registerTool` may complete asynchronously.
Implement asynchronous tool registration `packages/playground/mcp/src/webmcp.ts`	`registerWebMCPTools` validates the document context, tracks an abort controller, registers tools concurrently, waits for completion, and throws an aggregated error for rejected registrations.
Handle asynchronous bridge failures `packages/playground/personal-wp/src/lib/state/redux/init-mcp-bridge.ts`, `packages/playground/website/src/lib/state/redux/init-mcp-bridge.ts`	The Redux bridges handle rejected registration promises with `logger.warn` instead of synchronous `try/catch` blocks.

Estimated code review effort: 3 (Moderate) | ~20 minutes

Merge Risk: ⚪ Minimal · up to c9c7c

The change updates WebMCP registration and preserves website behavior when registration is unavailable or fails; no actionable merge-blocking risk remains after normal checks and review.

Sequence Diagram(s)

sequenceDiagram
  participant ReduxMCPBridge
  participant registerWebMCPTools
  participant documentModelContext
  participant WebMCPTools
  ReduxMCPBridge->>registerWebMCPTools: start registration
  registerWebMCPTools->>documentModelContext: read document.modelContext
  registerWebMCPTools->>WebMCPTools: register tools concurrently
  WebMCPTools-->>registerWebMCPTools: resolve or reject registrations
  registerWebMCPTools-->>ReduxMCPBridge: resolve or reject with aggregated error
  ReduxMCPBridge->>ReduxMCPBridge: log rejected registration with logger.warn

Suggested reviewers: akirk

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 5 functions across 4 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly describes the main change: updating the WebMCP registration API, including the move to the current registration approach and asynchronous behavior.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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fellyph

@bgrgicak, It all good. I have tested locally.

I just used codex to suggest a few items.

Co-authored-by: Fellyph Cintra <fellyph.cintra@gmail.com>

bgrgicak requested review from a team, Copilot and mho22 June 30, 2026 07:04

github-actions Bot added [Package][@wp-playground] Website [Type] Documentation Improvements or additions to documentation [Aspect] Browser [Aspect] Website labels Jun 30, 2026

Copilot AI reviewed Jun 30, 2026

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bgrgicak marked this pull request as draft June 30, 2026 07:12

bgrgicak self-assigned this Jul 24, 2026

bgrgicak marked this pull request as ready for review July 24, 2026 17:49

bgrgicak assigned fellyph Jul 24, 2026

bgrgicak added 2 commits August 26, 2026 11:26

[MCP] Update WebMCP registration API

b8a3190

[MCP] Harden async WebMCP registration

47ab963

akirk force-pushed the bgrgicak/async-modelcontext-registertool branch from 7e71cee to 47ab963 Compare August 26, 2026 09:26

mho22 removed their request for review August 26, 2026 09:53

bgrgicak requested a review from akirk August 27, 2026 19:25

fellyph approved these changes Aug 28, 2026

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Comment thread packages/playground/mcp/src/webmcp.ts

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Comment thread packages/playground/mcp/src/webmcp.ts Outdated

fellyph added 3 commits August 28, 2026 11:02

Update packages/playground/mcp/src/webmcp.ts

f679198

Apply suggestion from @fellyph

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24b524e

Co-authored-by: Fellyph Cintra <fellyph.cintra@gmail.com>

fellyph reviewed Aug 28, 2026

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Comment thread packages/playground/mcp/src/webmcp.ts

Update packages/playground/mcp/src/webmcp.ts

c9c7c54

fellyph merged commit f29eca6 into WordPress:trunk Aug 28, 2026
58 checks passed

fellyph mentioned this pull request Oct 8, 2026

[Enhancement]: Improve AI discovery, crawler indexing, and browser-agent integration (WebMCP, ChatGPT, Claude, Gemini) #4408

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[MCP] Update WebMCP registration API - #3844

[MCP] Update WebMCP registration API#3844
fellyph merged 6 commits into
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bgrgicak:bgrgicak/async-modelcontext-registertool

bgrgicak commented Jun 30, 2026 •

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coderabbitai Bot commented Aug 26, 2026 •

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Summary

Motivation for the change, related issues

Implementation details

Testing Instructions

Summary by CodeRabbit

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