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feat(images): expose rewriter system prompt as admin setting

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CEO feedback: every generated image is anchoring on the cartoon
peptide-with-arms-and-legs character because the hardcoded rewriter
system prompt both lists "anthropomorphized molecules" first in its
primer and ships a few-shot example that literally shows one. The ask
is to give CEO the lever without a code change.

Adds `prautoblogger_image_prompt_instructions` (textarea) in the
Images section. Default value is the existing REWRITER_SYSTEM_PROMPT
constant verbatim, so behaviour is unchanged on upgrade until someone
edits it. `Image_Prompt_Builder::rewrite_via_llm()` reads the option
at call time via a new `resolve_system_prompt()` helper and falls back
to the constant if the option is blank or whitespace-only, so a saved
empty value cannot brick image generation.

Const visibility flipped from `private` to `public` so the settings
field can reference it directly as the field default.

Tests:

- `test_rewrite_uses_setting_when_present` — option set, assert the
  LLM's system message equals the option content.
- `test_rewrite_falls_back_to_default_when_setting_empty` — option
  whitespace, assert the LLM's system message equals the constant.

Uninstall: new option covered by the existing prautoblogger_% LIKE
sweep in uninstall.php.

Cost impact: none by default. Future CEO edits will change prompt
length; current default is ~180 tokens, budget impact linear from
there.

Part of the v0.8.0 image bundle (thread image-mime-bug, message 03).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
This commit is contained in:
peptiderepo
2026-04-21 01:11:15 +07:00
parent fb1451c4dc
commit 0505e50e85
3 changed files with 140 additions and 14 deletions
Download Patch File Download Diff File Expand all files Collapse all files

8
includes/admin/class-settings-fields-extended.php
View File

@@ -256,6 +256,14 @@ class PRAutoBlogger_Settings_Fields_Extended {
'default' => PRAUTOBLOGGER_DEFAULT_IMAGE_STYLE_SUFFIX,
'description' => __( 'Appended to every image prompt. Controls visual look. Changing mid-run causes visible style drift.', 'prautoblogger' ),
],
[
'id' => 'prautoblogger_image_prompt_instructions',
'label' => __( 'Image Prompt Instructions', 'prautoblogger' ),
'type' => 'textarea',
'section' => 'prautoblogger_images',
'default' => PRAutoBlogger_Image_Prompt_Builder::REWRITER_SYSTEM_PROMPT,
'description' => __( 'System prompt given to the rewriter LLM that turns each article into a SCENE + CAPTION for the image generator. Changing this reshapes the look of all future images. Leave blank to use the default.', 'prautoblogger' ),
],
[
'id' => 'prautoblogger_image_nsfw_retry',
'label' => __( 'Retry NSFW-Blocked Images', 'prautoblogger' ),

30
includes/core/class-image-prompt-builder.php
View File

@@ -21,13 +21,12 @@ declare(strict_types=1);
class PRAutoBlogger_Image_Prompt_Builder {
/**
* System prompt that teaches the LLM how to write image-gen prompts.
*
* Why this lives here instead of in wp_options: it's engineering-level
* instruction, not a user-facing setting. Changing it should require a
* code review, not an admin-panel click.
* Default system prompt that teaches the LLM how to write image-gen
* prompts. Exposed as a `public const` so the admin-settings layer can
* use it as the default value for `prautoblogger_image_prompt_instructions`.
* The option, when non-empty, wins at call time (see rewrite_via_llm).
*/
private const REWRITER_SYSTEM_PROMPT = <<<'PROMPT'
public const REWRITER_SYSTEM_PROMPT = <<<'PROMPT'
You are a comedy writer and single-panel cartoon creator, like Gary Larson (The Far Side) meets science humor.
Given an article title and summary about peptides, supplements, or biohacking, create a SINGLE-PANEL COMIC concept. Output TWO parts separated by a blank line:
@@ -141,12 +140,13 @@ PROMPT;
}
try {
$llm = $this->get_llm_provider();
$model = get_option( 'prautoblogger_analysis_model', PRAUTOBLOGGER_DEFAULT_ANALYSIS_MODEL );
$llm = $this->get_llm_provider();
$model = get_option( 'prautoblogger_analysis_model', PRAUTOBLOGGER_DEFAULT_ANALYSIS_MODEL );
$system = $this->resolve_system_prompt();
$result = $llm->send_chat_completion(
[
[ 'role' => 'system', 'content' => self::REWRITER_SYSTEM_PROMPT ],
[ 'role' => 'system', 'content' => $system ],
[ 'role' => 'user', 'content' => $user_message ],
],
$model,
@@ -283,15 +283,17 @@ PROMPT;
];
}
/**
* Lazy-load the OpenRouter provider.
*
* @return PRAutoBlogger_OpenRouter_Provider
*/
/** Lazy-load the OpenRouter provider. */
private function get_llm_provider(): PRAutoBlogger_OpenRouter_Provider {
if ( null === $this->llm ) {
$this->llm = new PRAutoBlogger_OpenRouter_Provider();
}
return $this->llm;
}
/** Admin option wins; blank falls back to REWRITER_SYSTEM_PROMPT. */
private function resolve_system_prompt(): string {
$override = (string) get_option( 'prautoblogger_image_prompt_instructions', '' );
return '' !== trim( $override ) ? $override : self::REWRITER_SYSTEM_PROMPT;
}
}

116
tests/unit/Core/ImagePromptBuilderTest.php
View File

@@ -29,6 +29,21 @@ class ImagePromptBuilderTest extends BaseTestCase {
} );
}
/**
* Inject a mock OpenRouter provider into the Prompt_Builder via
* reflection so the rewrite path can be exercised without a real HTTP
* call. Used by the system-prompt override tests below.
*/
private function inject_llm(
\PRAutoBlogger_Image_Prompt_Builder $builder,
$mock_llm
): void {
$ref = new \ReflectionClass( \PRAutoBlogger_Image_Prompt_Builder::class );
$prop = $ref->getProperty( 'llm' );
$prop->setAccessible( true );
$prop->setValue( $builder, $mock_llm );
}
/**
* Test build_article_prompt() generates a prompt from article title and content.
*/
@@ -119,4 +134,105 @@ class ImagePromptBuilderTest extends BaseTestCase {
// Prompt should be under 500 chars (concept + style suffix).
$this->assertLessThan( 500, strlen( $prompt ) );
}
/**
* When `prautoblogger_image_prompt_instructions` is non-empty, the
* rewriter LLM must receive that content as its system message —
* NOT the hardcoded REWRITER_SYSTEM_PROMPT constant.
*/
public function test_rewrite_uses_setting_when_present(): void {
$custom_system = 'CUSTOM-OVERRIDE: tell the LLM a very different thing.';
Functions\when( 'get_option' )->alias( function ( $key, $default = false ) use ( $custom_system ) {
if ( 'prautoblogger_image_prompt_instructions' === $key ) {
return $custom_system;
}
if ( 'prautoblogger_image_style_suffix' === $key ) {
return 'Style: x';
}
return $default;
} );
$captured_messages = [];
$mock_llm = $this->createMock( \PRAutoBlogger_OpenRouter_Provider::class );
$mock_llm->method( 'send_chat_completion' )->willReturnCallback(
function ( $messages ) use ( &$captured_messages ) {
$captured_messages = $messages;
return [
'content' => "A scene.\n\n\"A caption.\"",
'prompt_tokens' => 10,
'completion_tokens' => 10,
];
}
);
$mock_llm->method( 'estimate_cost' )->willReturn( 0.0 );
// Stub $wpdb so Cost_Tracker::log_api_call inside rewrite_via_llm
// can insert without blowing up.
$mock_wpdb = $this->create_mock_wpdb();
$mock_wpdb->insert_id = 1;
$mock_wpdb->method( 'insert' )->willReturn( 1 );
$GLOBALS['wpdb'] = $mock_wpdb;
$builder = new \PRAutoBlogger_Image_Prompt_Builder();
$this->inject_llm( $builder, $mock_llm );
$builder->build_article_prompt( [ 'post_title' => 'Test', 'post_content' => '<p>Body.</p>' ] );
unset( $GLOBALS['wpdb'] );
$this->assertNotEmpty( $captured_messages, 'Rewriter LLM was not called.' );
$this->assertSame( 'system', $captured_messages[0]['role'] ?? '' );
$this->assertSame( $custom_system, $captured_messages[0]['content'] ?? '' );
}
/**
* When the option is empty (or whitespace-only), the rewriter must
* fall back to REWRITER_SYSTEM_PROMPT — belt-and-braces so a blank
* save from the admin UI cannot brick image generation.
*/
public function test_rewrite_falls_back_to_default_when_setting_empty(): void {
Functions\when( 'get_option' )->alias( function ( $key, $default = false ) {
if ( 'prautoblogger_image_prompt_instructions' === $key ) {
return ' '; // whitespace — should trigger fallback.
}
if ( 'prautoblogger_image_style_suffix' === $key ) {
return 'Style: x';
}
return $default;
} );
$captured_messages = [];
$mock_llm = $this->createMock( \PRAutoBlogger_OpenRouter_Provider::class );
$mock_llm->method( 'send_chat_completion' )->willReturnCallback(
function ( $messages ) use ( &$captured_messages ) {
$captured_messages = $messages;
return [
'content' => "A scene.\n\n\"A caption.\"",
'prompt_tokens' => 10,
'completion_tokens' => 10,
];
}
);
$mock_llm->method( 'estimate_cost' )->willReturn( 0.0 );
// Stub $wpdb so Cost_Tracker::log_api_call inside rewrite_via_llm
// can insert without blowing up.
$mock_wpdb = $this->create_mock_wpdb();
$mock_wpdb->insert_id = 1;
$mock_wpdb->method( 'insert' )->willReturn( 1 );
$GLOBALS['wpdb'] = $mock_wpdb;
$builder = new \PRAutoBlogger_Image_Prompt_Builder();
$this->inject_llm( $builder, $mock_llm );
$builder->build_article_prompt( [ 'post_title' => 'Test', 'post_content' => '<p>Body.</p>' ] );
unset( $GLOBALS['wpdb'] );
$this->assertSame(
\PRAutoBlogger_Image_Prompt_Builder::REWRITER_SYSTEM_PROMPT,
$captured_messages[0]['content'] ?? ''
);
}
}