Add WP AI Client

[JasonTheAdams]

Trac ticket: https://core.trac.wordpress.org/ticket/64591
Merge Proposal: https://make.wordpress.org/core/2026/02/03/proposal-for-merging-wp-ai-client-into-wordpress-7-0

Summary

Adds a provider-agnostic AI Client, enabling developers to interact with generative AI services through a single, fluent API — without needing to know which provider is configured.

This PR includes three layers:

• PHP AI Client SDK (php-ai-client): The upstream SDK from WordPress/php-ai-client, bundled into wp-includes/php-ai-client/ with all third-party dependencies (PSR interfaces, HTTPlug) scoped to WordPress\AiClientDependencies\* to avoid conflicts with plugins shipping their own versions.

• Import tooling (tools/php-ai-client/): An installer script and PHP-Scoper configuration that fetches, scopes, and reorganizes the SDK for bundling. Running bash tools/php-ai-client/installer.sh reproduces the bundled output deterministically.

• WP AI Client (ai-client-utils/, ai-client.php): The WordPress integration layer. This provides minimal PSR-7/PSR-17 implementations backed by string buffers and wp_parse_url(), an HTTP client adapter that routes requests through wp_remote_request(), a discovery strategy so the SDK automatically finds these implementations, and an event dispatcher that bridges PSR-14 events to WordPress hooks.

The public API is a single function:

$summary = wp_ai_client_prompt( 'Summarize this post' )
    ->with_text( $post->post_content )
    ->generate_text();

WP_AI_Client_Prompt_Builder wraps the SDK's fluent builder with WordPress conventions — snake_case methods, WP_Error returns instead of exceptions, and using_abilities() for connecting the Abilities API to AI function calling.

The wp_ai_client_prevent_prompt filter gives site owners and plugins centralized control over AI availability. When a prompt is prevented, generating methods return WP_Error while is_supported_* methods return false — giving plugin developers a graceful way to hide AI features entirely when AI is not available.

This gives plugin and theme developers a stable, provider-neutral way to add AI features without bundling their own HTTP clients or managing provider-specific SDKs.

Follow up PRs

There will be a couple more PRs. I broke up the WP AI Client, introducing only the main core files in this one. Following PRs will be:

• The REST API
• The provider credentials settings screen

Use of AI Tools

This is a compilation of work from the PHP AI Client and WP AI Client repositories, with some changes made in porting to core. Claude Code was used in both the original development of those packages as well as the porting over and creation of the tooling. All code was generated by Claude Code and reviewed by myself and @felixarntz.

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This Pull Request is for code review only. Please keep all other discussion in the Trac ticket. Do not merge this Pull Request. See GitHub Pull Requests for Code Review in the Core Handbook for more details.

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[desrosj]

I just wanted to confirm. Is this entire directory "external library" code?

[felixarntz]

Yes, correct.

[desrosj]

Are there no tests for the src/wp-includes/ai-client-utils directory? At a quick glance, it seems like tests/phpunit/tests/ai-client/wpAiClientAbilityFunctionResolver.php may test the class within the wp-includes/ai-client-utils/class-wp-ai-client-ability-function-resolver.php file.

[felixarntz]

Good catch, I agree. This should not be excluded, it needs test because this will be Core code.