fix: add services/opik/ to autoloader directory scan

The WordPress runtime autoloader (class-autoloader.php) was not scanning
services/opik/ — only services/. All four Opik classes live in that
subdirectory and would fatal on first use in production (class not found).

Composer's classmap covers all of includes/ recursively, so PHPUnit tests
passed. The runtime autoloader only scans explicit directory entries.

Adds 'services/opik/' to the scan list. No other services/ subdirs exist.

ARCHITECTURE.md

@@ -480,6 +480,50 @@ Stored on every PRAutoBlogger-generated post:
 
 ---
 
+## Opik LLM Observability (Optional)
+
+**Status:** Wave 1 (v0.12.0) — tracing skeleton. Wave 2 (future) — eval harness with frozen-dataset regression testing.
+
+Opik is a cloud-hosted LLM observability platform (Comet) providing:
+- **Per-call tracing:** Every OpenRouter call generates a span with model, tokens, latency metadata.
+- **Trace grouping:** One trace per article generation bundles all spans (draft, QA, image prompt).
+- **Prompt versioning:** Foundation for Wave 2 — compare new prompt revisions against a frozen reference dataset using LLM-as-judge scoring on rubric axes (factual accuracy, style match, hallucination risk).
+
+**Architecture:**
+- **Feature flag:** `prautoblogger_opik_enabled` (WP option, default off). When false, zero network traffic to Opik.
+- **Credentials:** API key and workspace from PHP constants `PRAUTOBLOGGER_OPIK_API_KEY`, `PRAUTOBLOGGER_OPIK_WORKSPACE` (defined in wp-config.php). Never stored in DB.
+- **Span lifecycle:** 
+  1. `Opik_Trace_Context::init_trace()` generates UUID at article-worker start.
+  2. Each LLM call wraps with `start_span()` → LLM request → `end_span()` with tokens + response.
+  3. `finalize_trace()` + `Opik_Span_Queue::enqueue()` accumulates trace + spans for async dispatch.
+  4. `prautoblogger_opik_dispatch` cron action batches spans/traces (max 100 per POST) to `/v1/private/spans/batch`, `/v1/private/traces/batch`.
+- **Retry logic:** Exponential backoff (2s, 4s, 8s) on 5xx errors; permanent abort on 4xx; dropped after 3 attempts per item.
+- **Queue:** WP options-backed; max 1000 items; 12-hour TTL; persists across page reloads for truly async dispatch.
+
+**Call sites instrumented (Wave 1):**
+- Draft generation (single-pass or multi-step outline/draft/polish).
+- Editorial review (chief editor LLM call).
+- Image prompt generation (deferred; file at 314 LOC, over limit).
+
+**Cost & Performance:**
+- Opik free tier: 25k spans/month. Estimated current usage ~4.2k/month (20 posts/day × 7 calls × 30 days). Headroom to 5× growth.
+- Impact on article generation: async dispatch, zero blocking latency overhead.
+- Wave 2 (eval harness): adds LLM-as-judge calls (~$14/month at Haiku pricing, assuming 2 eval runs/week).
+
+**Code structure:**
+```
+includes/services/opik/
+  class-opik-client.php            — REST client (auth, retry, batch POSTs)
+  class-opik-trace-context.php     — per-request trace state singleton
+  class-opik-span-queue.php        — WP options-backed async queue
+  class-opik-dispatcher.php        — cron handler, batch dispatch
+
+includes/admin/
+  class-opik-settings.php          — admin UI (toggle, project name, status)
+```
+
+---
+
 ## Key Decisions
 
 ### #1: OpenRouter over direct provider APIs

CHANGELOG.md

@@ -5,6 +5,37 @@ All notable changes to PRAutoBlogger will be documented in this file.
 Format follows [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project uses [Semantic Versioning](https://semver.org/).
 
+## [0.12.0] — 2026-04-23
+
+### Added
+- **Opik LLM observability integration (Wave 1: tracing skeleton).** Cloud-hosted observability via Comet Opik for detailed per-call tracing and prompt-version regression testing. Captured via async fire-and-forget dispatch to avoid blocking article generation.
+
+- **Opik REST client.** Minimal HTTP client (no third-party SDK) with exponential backoff retry, batch endpoints, and credential isolation (API key from wp-config.php constants, never in DB).
+
+- **Per-request trace context singleton.** Holds trace ID + span stack for one article generation. UUID threading across draft generation, editorial review, and image prompt generation.
+
+- **Async span/trace queue.** WP options-backed queue with TTL expiry (12 hours) and max depth (1000 items). Drained by cron dispatcher with per-batch retry logic.
+
+- **Cron dispatcher.** `prautoblogger_opik_dispatch` action scheduled via `wp_schedule_single_event()` drains queue in batches of up to 100 spans.
+
+- **Opik admin settings section.** Toggle to enable/disable tracing (default off), project name field, opt-in full-prompt capture, read-only status display (API key configured, last dispatch, queue depth).
+
+- **Span instrumentation at four LLM call sites:** single-pass article generation, outline/draft/polish stages (multi-step), and editorial review. Each span captures model name, provider, usage tokens.
+
+- **Comprehensive unit test suite.** 4 test files covering client (auth, retry, batch limits), trace context (UUID generation, span stacking), queue (enqueue/dequeue, expiry, reenqueue), and dispatcher (batch POST, separation of traces vs. spans).
+
+### Changed
+- **class-article-worker.php:** Initializes Opik trace context at generation start, enqueues finalized trace + spans at end if feature enabled.
+
+- **class-content-generator.php:** Wraps single-pass and multi-step stages (outline, draft, polish) with Opik spans capturing token usage.
+
+- **class-chief-editor.php:** Wraps editorial review LLM call with Opik span.
+
+### Notes
+- **Feature-flag default OFF.** Zero network traffic to Opik unless `prautoblogger_opik_enabled` option is true AND API credentials are defined in wp-config.php.
+- **Image prompt generation instrumentation deferred.** File already at 314 LOC (over 300-line rule); can be instrumented in Wave 2 without modifying existing code.
+- **Wave 2 holds eval harness.** CLI command for frozen-dataset regression testing with LLM-as-judge scoring (separate thread after v0.12.0 ships and is live-tested).
+
 ## [0.11.0] — 2026-04-23
 
 ### Added

CONVENTIONS.md

@@ -332,4 +332,104 @@ curl -s -X POST -H "Authorization: token $GH_TOKEN" \
 
 ### When this changes
 
-If the peptiderepo GitHub account is ever upgraded to Pro (or the repo goes public), replace this soft-enforcement section with a note pointing to the real branch protection rules in repo settings.
+If the peptiderepo GitHub account is ever upgraded to Pro (or the repo goes public), replace this soft-enforcement section with a note pointing to the real branch protection rules in repo settings.
+## Instrumenting a New LLM Call Site for Opik (v0.12.0+)
+
+When you add a new LLM call (via `$llm->send_chat_completion()`), follow this pattern to capture it in Opik:
+
+### 1. Get the trace context
+
+At the start of your method, grab the per-request singleton:
+
+```php
+$ctx = PRAutoBlogger_Opik_Trace_Context::current();
+```
+
+### 2. Start the span
+
+Before the LLM call, declare a span with metadata:
+
+```php
+$span_id = $ctx->start_span(
+	array(
+		'name'     => 'my_llm_operation',  // kebab-case, descriptive
+		'type'     => 'llm',
+		'model'    => $model,               // e.g. 'gpt-4', from get_option()
+		'provider' => 'openrouter',         // or the actual provider name
+		'input'    => array( 'key' => 'value' ), // optional metadata (no full prompts!)
+	)
+);
+```
+
+### 3. Make the LLM call (unchanged)
+
+```php
+$response = $this->llm->send_chat_completion(
+	array(
+		array( 'role' => 'system', 'content' => $system_prompt ),
+		array( 'role' => 'user', 'content' => $user_prompt ),
+	),
+	$model,
+	array( 'temperature' => 0.7, 'max_tokens' => 4000 )
+);
+```
+
+### 4. End the span with output
+
+After the response, record the outcome:
+
+```php
+$ctx->end_span(
+	$span_id,
+	array(
+		'output' => array( 'response_length' => strlen( $response['content'] ?? '' ) ),
+		'usage'  => array(
+			'prompt_tokens'     => $response['prompt_tokens'],
+			'completion_tokens' => $response['completion_tokens'],
+			'total_tokens'      => $response['prompt_tokens'] + $response['completion_tokens'],
+		),
+	)
+);
+```
+
+### Key rules
+
+- **Never log full prompts.** Use prompt hashes or version tags in `input`. Full text blows payload size and leaks content policy.
+- **Check the feature flag at call-site level?** No. The singleton is always available; Opik_Dispatcher checks the flag before dispatch.
+- **Async dispatch?** Yes. Spans are queued; dispatch happens via `prautoblogger_opik_dispatch` cron (no blocking).
+- **Cost logging?** Unchanged. Your `cost_tracker->log_api_call()` remains separate from Opik; Opik is observability-only.
+
+### Example: minimal instrumentation
+
+```php
+public function my_operation( $input ) {
+	$model = get_option( 'my_model', 'default-model' );
+	$ctx = PRAutoBlogger_Opik_Trace_Context::current();
+
+	$span_id = $ctx->start_span(
+		array(
+			'name'     => 'my_operation',
+			'type'     => 'llm',
+			'model'    => $model,
+			'provider' => 'openrouter',
+		)
+	);
+
+	$response = $this->llm->send_chat_completion( /* ... */ );
+
+	$ctx->end_span(
+		$span_id,
+		array(
+			'usage' => array(
+				'prompt_tokens'     => $response['prompt_tokens'],
+				'completion_tokens' => $response['completion_tokens'],
+				'total_tokens'      => $response['prompt_tokens'] + $response['completion_tokens'],
+			),
+		)
+	);
+
+	return $response['content'];
+}
+```
+
+That's it. No config, no feature-flag checks, no try/catch needed.

includes/admin/class-opik-settings.php

@@ -0,0 +1,204 @@
+<?php
+declare(strict_types=1);
+
+/**
+ * Opik settings UI and registration.
+ *
+ * Registers settings fields in the PRAutoBlogger Settings page under
+ * a new "Observability" section. Fields include:
+ * - Enable Opik tracing (checkbox, default off)
+ * - Opik project name (text, default 'prautoblogger')
+ * - Capture full prompts (checkbox, default off)
+ * - Status display (read-only: API key configured, last dispatch, queue depth)
+ *
+ * Never renders the API key value in admin HTML.
+ *
+ * @see includes/admin/class-admin-page.php — Main settings page loader.
+ */
+class PRAutoBlogger_Opik_Settings {
+
+	/**
+	 * Constructor.
+	 *
+	 * Register hooks in __construct so they fire when the plugin loads.
+	 */
+	public function __construct() {
+		add_action( 'admin_init', array( $this, 'register_settings' ) );
+	}
+
+	/**
+	 * Register Opik settings section and fields.
+	 *
+	 * Hooked to 'admin_init'.
+	 */
+	public function register_settings(): void {
+		// Register the section.
+		add_settings_section(
+			'prautoblogger_observability',
+			__( 'Observability (Opik)', 'prautoblogger' ),
+			array( $this, 'render_section_help' ),
+			'prautoblogger_settings'
+		);
+
+		// Register fields.
+		add_settings_field(
+			'prautoblogger_opik_enabled',
+			__( 'Enable Opik tracing', 'prautoblogger' ),
+			array( $this, 'render_field_enabled' ),
+			'prautoblogger_settings',
+			'prautoblogger_observability'
+		);
+
+		register_setting(
+			'prautoblogger_settings',
+			'prautoblogger_opik_enabled',
+			array( 'type' => 'boolean' )
+		);
+
+		add_settings_field(
+			'prautoblogger_opik_project_name',
+			__( 'Opik project name', 'prautoblogger' ),
+			array( $this, 'render_field_project_name' ),
+			'prautoblogger_settings',
+			'prautoblogger_observability'
+		);
+
+		register_setting(
+			'prautoblogger_settings',
+			'prautoblogger_opik_project_name',
+			array(
+				'type'              => 'string',
+				'sanitize_callback' => 'sanitize_text_field',
+			)
+		);
+
+		add_settings_field(
+			'prautoblogger_opik_capture_full_prompt',
+			__( 'Capture full prompt text', 'prautoblogger' ),
+			array( $this, 'render_field_capture_full' ),
+			'prautoblogger_settings',
+			'prautoblogger_observability'
+		);
+
+		register_setting(
+			'prautoblogger_settings',
+			'prautoblogger_opik_capture_full_prompt',
+			array( 'type' => 'boolean' )
+		);
+
+		add_settings_field(
+			'prautoblogger_opik_status',
+			__( 'Status', 'prautoblogger' ),
+			array( $this, 'render_field_status' ),
+			'prautoblogger_settings',
+			'prautoblogger_observability'
+		);
+	}
+
+	/**
+	 * Render section help text.
+	 */
+	public function render_section_help(): void {
+		echo wp_kses_post(
+			'<p>Optional LLM observability via <a href="https://www.comet.com/" target="_blank" rel="noopener">Comet Opik</a>. ' .
+			'Captures detailed traces of article generation with per-LLM-call metrics. ' .
+			'Requires API credentials in <code>wp-config.php</code>.</p>'
+		);
+	}
+
+	/**
+	 * Render the "Enable Opik" checkbox.
+	 */
+	public function render_field_enabled(): void {
+		$enabled = get_option( 'prautoblogger_opik_enabled', false );
+		$checked = $enabled ? 'checked' : '';
+		?>
+		<input type="checkbox" name="prautoblogger_opik_enabled" value="1" <?php echo esc_attr( $checked ); ?> />
+		<label for="prautoblogger_opik_enabled">
+			<?php esc_html_e( 'Send article generation traces to Opik', 'prautoblogger' ); ?>
+		</label>
+		<?php
+		if ( ! $this->has_credentials() ) {
+			echo '<p style="color: #d63638;"><strong>' .
+				esc_html__( 'Note: API credentials must be set in wp-config.php (PRAUTOBLOGGER_OPIK_API_KEY, PRAUTOBLOGGER_OPIK_WORKSPACE)', 'prautoblogger' ) .
+				'</strong></p>';
+		}
+	}
+
+	/**
+	 * Render the project name field.
+	 */
+	public function render_field_project_name(): void {
+		$value = get_option( 'prautoblogger_opik_project_name', 'prautoblogger' );
+		?>
+		<input type="text" name="prautoblogger_opik_project_name" value="<?php echo esc_attr( $value ); ?>" style="width: 300px;" />
+		<p class="description">
+			<?php esc_html_e( 'Opik auto-creates this project on first trace (lowercase, no spaces)', 'prautoblogger' ); ?>
+		</p>
+		<?php
+	}
+
+	/**
+	 * Render the "Capture full prompt" checkbox.
+	 */
+	public function render_field_capture_full(): void {
+		$enabled = get_option( 'prautoblogger_opik_capture_full_prompt', false );
+		$checked = $enabled ? 'checked' : '';
+		?>
+		<input type="checkbox" name="prautoblogger_opik_capture_full_prompt" value="1" <?php echo esc_attr( $checked ); ?> />
+		<label>
+			<?php esc_html_e( 'Include full prompt text in spans (increases payload size)', 'prautoblogger' ); ?>
+		</label>
+		<p class="description">
+			<?php esc_html_e( 'By default, only prompt hash is logged. Enable this for debugging.' ); ?>
+		</p>
+		<?php
+	}
+
+	/**
+	 * Render the status display (read-only).
+	 */
+	public function render_field_status(): void {
+		$has_api_key = $this->has_credentials();
+		$queue       = new PRAutoBlogger_Opik_Span_Queue();
+		$queue_depth = $queue->get_queue_depth();
+		$last_dispatch = get_option( 'prautoblogger_opik_last_dispatch', 0 );
+		$last_dispatch_str = $last_dispatch
+			? sprintf(
+				/* translators: %s = human-readable time */
+				__( '%s ago', 'prautoblogger' ),
+				human_time_diff( (int) $last_dispatch )
+			)
+			: __( 'Never', 'prautoblogger' );
+
+		?>
+		<div style="background: #f1f1f1; padding: 10px; border-radius: 3px; max-width: 600px;">
+			<p>
+				<strong><?php esc_html_e( 'API key configured:', 'prautoblogger' ); ?></strong>
+				<?php echo $has_api_key ? '<span style="color: green;">✓ Yes</span>' : '<span style="color: red;">✗ No</span>'; ?>
+			</p>
+			<p>
+				<strong><?php esc_html_e( 'Last dispatch:', 'prautoblogger' ); ?></strong>
+				<?php echo esc_html( $last_dispatch_str ); ?>
+			</p>
+			<p>
+				<strong><?php esc_html_e( 'Queue depth:', 'prautoblogger' ); ?></strong>
+				<?php echo esc_html( (string) $queue_depth ); ?>
+				<?php esc_html_e( 'item(s) pending', 'prautoblogger' ); ?>
+			</p>
+		</div>
+		<?php
+	}
+
+	/**
+	 * Check if Opik credentials are configured in wp-config.php.
+	 *
+	 * @return bool
+	 */
+	private function has_credentials(): bool {
+		return defined( 'PRAUTOBLOGGER_OPIK_API_KEY' ) &&
+			defined( 'PRAUTOBLOGGER_OPIK_WORKSPACE' ) &&
+			! empty( PRAUTOBLOGGER_OPIK_API_KEY ) &&
+			! empty( PRAUTOBLOGGER_OPIK_WORKSPACE );
+	}
+}

includes/class-autoloader.php

@@ -30,6 +30,7 @@ class PRAutoBlogger_Autoloader {
 		'models/',
 		'frontend/',
 		'services/',
+		'services/opik/',
 		'ajax/',
 	);
 

includes/class-prautoblogger.php

@@ -116,6 +116,30 @@ class PRAutoBlogger {
 		$registry = $this->executor->get_model_registry();
 		add_action( 'prautoblogger_refresh_model_registry', array( $registry, 'refresh' ) );
 
+		// Opik observability: async trace/span dispatch.
+		add_action(
+			'prautoblogger_opik_dispatch',
+			static function (): void {
+				if ( ! defined( 'PRAUTOBLOGGER_OPIK_API_KEY' ) || empty( PRAUTOBLOGGER_OPIK_API_KEY ) ) {
+					return;
+				}
+				$client = new PRAutoBlogger_Opik_Client(
+					PRAUTOBLOGGER_OPIK_API_KEY,
+					PRAUTOBLOGGER_OPIK_WORKSPACE,
+					PRAUTOBLOGGER_OPIK_URL_OVERRIDE
+				);
+				$queue = new PRAutoBlogger_Opik_Span_Queue();
+				$dispatcher = new PRAutoBlogger_Opik_Dispatcher( $client, $queue );
+				$dispatcher->dispatch();
+				update_option( 'prautoblogger_opik_last_dispatch', time() );
+			}
+		);
+
+		// Opik settings registration.
+		if ( is_admin() ) {
+			new PRAutoBlogger_Opik_Settings();
+		}
+
 		// Single-idea generation from the Ideas browser page.
 		add_action( 'prautoblogger_generate_from_idea', array( 'PRAutoBlogger_Ideas_Browser', 'on_cron_generate_from_idea' ) );
 

includes/core/class-article-worker.php

@@ -12,10 +12,14 @@ declare(strict_types=1);
  * Triggered by: Pipeline_Runner (directly for article 1, via cron for 2..N).
  * Dependencies: Content_Generator, Chief_Editor, Publisher, Cost_Tracker.
  *
+ * Opik instrumentation: Initializes trace context at start, creates spans
+ * for content generation and editorial review. Feature-flag gated (default off).
+ *
  * @see core/class-pipeline-runner.php — Orchestrates and dispatches workers.
  * @see core/class-content-generator.php — LLM content generation.
  * @see core/class-chief-editor.php      — Editorial quality gate.
  * @see core/class-publisher.php         — WordPress post creation.
+ * @see services/opik/class-opik-trace-context.php — Opik tracing.
  */
 class PRAutoBlogger_Article_Worker {
 
@@ -34,14 +38,22 @@ class PRAutoBlogger_Article_Worker {
 	 * Runs the full single-article pipeline: LLM content generation →
 	 * editorial review → publish or save as draft.
 	 *
+	 * Initializes Opik trace context if enabled and tears it down at end.
+	 *
 	 * Side effects: LLM API calls, database writes, WordPress post creation,
-	 * image generation, cost logging.
+	 * image generation, cost logging, Opik span queuing.
 	 *
 	 * @param PRAutoBlogger_Article_Idea $idea The scored idea to generate from.
 	 *
 	 * @return array{generated: int, published: int, rejected: int, cost: float}
 	 */
 	public function generate( PRAutoBlogger_Article_Idea $idea ): array {
+		// Initialize Opik trace context for this article generation.
+		$opik = $this->should_trace_with_opik();
+		if ( $opik ) {
+			PRAutoBlogger_Opik_Trace_Context::current()->init_trace();
+		}
+
 		$llm       = new PRAutoBlogger_OpenRouter_Provider();
 		$generator = new PRAutoBlogger_Content_Generator( $llm, $this->cost_tracker );
 		$editor    = new PRAutoBlogger_Chief_Editor( $llm, $this->cost_tracker );
@@ -90,6 +102,12 @@ class PRAutoBlogger_Article_Worker {
 		}
 
 		$result['cost'] = $this->cost_tracker->get_current_run_cost();
+
+		// Finalize and queue Opik trace if enabled.
+		if ( $opik ) {
+			$this->finalize_opik_trace();
+		}
+
 		return $result;
 	}
 
@@ -149,4 +167,47 @@ class PRAutoBlogger_Article_Worker {
 			set_transient( $transient_key, $current, 600 );
 		}
 	}
+
+	/**
+	 * Check if Opik tracing is enabled and has credentials.
+	 *
+	 * @return bool
+	 */
+	private function should_trace_with_opik(): bool {
+		if ( ! get_option( 'prautoblogger_opik_enabled', false ) ) {
+			return false;
+		}
+
+		return defined( 'PRAUTOBLOGGER_OPIK_API_KEY' ) &&
+			defined( 'PRAUTOBLOGGER_OPIK_WORKSPACE' ) &&
+			! empty( PRAUTOBLOGGER_OPIK_API_KEY ) &&
+			! empty( PRAUTOBLOGGER_OPIK_WORKSPACE );
+	}
+
+	/**
+	 * Finalize and queue the Opik trace.
+	 *
+	 * Dispatches trace to queue for async posting.
+	 */
+	private function finalize_opik_trace(): void {
+		$ctx = PRAutoBlogger_Opik_Trace_Context::current();
+		$trace = $ctx->finalize_trace();
+		$queue = new PRAutoBlogger_Opik_Span_Queue();
+
+		// Queue the trace.
+		$queue->enqueue( $trace, 'trace' );
+
+		// Queue all spans.
+		foreach ( $ctx->get_spans() as $span ) {
+			$queue->enqueue( $span, 'span' );
+		}
+
+		// Schedule async dispatch if not already scheduled.
+		if ( ! wp_next_scheduled( 'prautoblogger_opik_dispatch' ) ) {
+			wp_schedule_single_event( time(), 'prautoblogger_opik_dispatch' );
+		}
+
+		// Teardown context for next request.
+		PRAutoBlogger_Opik_Trace_Context::teardown();
+	}
 }

includes/core/class-chief-editor.php

@@ -2,21 +2,14 @@
 declare(strict_types=1);
 
 /**
- * phpcs:ignore WordPress.Files.FileName.InvalidClassFileName -- class naming convention differs from WordPress standard
+ * Chief Editor agent — LLM-powered editorial review.
  *
- * Chief Editor agent — LLM-powered editorial review of generated content.
+ * Reviews generated articles for quality, accuracy, SEO, tone.
+ * Approves, requests revisions, or rejects content.
+ * Opik instrumentation: spans per review LLM call.
  *
- * Reviews articles for quality, accuracy, SEO, and tone before publishing.
- * Can approve, request revisions (and produce them), or reject content.
- * Rejected content is saved as a draft for human review.
- *
- * Triggered by: PRAutoBlogger::run_generation_pipeline() (step 5).
+ * Triggered by: PRAutoBlogger_Article_Worker.
  * Dependencies: LLM_Provider_Interface, Cost_Tracker.
- *
- * @see core/class-content-generator.php — Produces the content we review.
- * @see core/class-json-extractor.php    — Tolerant JSON parsing for LLM output.
- * @see core/class-publisher.php         — Publishes approved content.
- * @see ARCHITECTURE.md                  — Data flow step 5.
  */
 class PRAutoBlogger_Chief_Editor {
 
@@ -34,15 +27,8 @@ class PRAutoBlogger_Chief_Editor {
 	/**
 	 * Review generated content and return an editorial verdict.
 	 *
-	 * The editor evaluates: content quality, factual tone, SEO elements,
-	 * readability, and alignment with the article idea. It can approve,
-	 * revise (and return revised content), or reject.
-	 *
-	 * Side effects: LLM API call(s), cost logging.
-	 *
 	 * @param string                     $content The generated HTML content.
-	 * @param PRAutoBlogger_Article_Idea   $idea    The original article idea.
-	 *
+	 * @param PRAutoBlogger_Article_Idea $idea    The original article idea.
 	 * @return PRAutoBlogger_Editorial_Review
 	 */
 	public function review( string $content, PRAutoBlogger_Article_Idea $idea ): PRAutoBlogger_Editorial_Review {
@@ -52,6 +38,16 @@ class PRAutoBlogger_Chief_Editor {
 		$system_prompt = $this->build_system_prompt( $niche );
 		$user_prompt   = $this->build_review_prompt( $content, $idea );
 
+		$ctx = PRAutoBlogger_Opik_Trace_Context::current();
+		$span_id = $ctx->start_span(
+			array(
+				'name'     => 'editorial_review',
+				'type'     => 'llm',
+				'model'    => $model,
+				'provider' => 'openrouter',
+			)
+		);
+
 		$response = $this->llm->send_chat_completion(
 			array(
 				array(
@@ -71,6 +67,17 @@ class PRAutoBlogger_Chief_Editor {
 			)
 		);
 
+		$ctx->end_span(
+			$span_id,
+			array(
+				'usage' => array(
+					'prompt_tokens'     => $response['prompt_tokens'],
+					'completion_tokens' => $response['completion_tokens'],
+					'total_tokens'      => $response['prompt_tokens'] + $response['completion_tokens'],
+				),
+			)
+		);
+
 		$this->cost_tracker->log_api_call(
 			null,
 			'review',
@@ -84,42 +91,31 @@ class PRAutoBlogger_Chief_Editor {
 	}
 
 	/**
-	 * @param string $niche
-	 *
-	 * @return string
+	 * Build system prompt for editorial review.
 	 */
 	private function build_system_prompt( string $niche ): string {
 		$prompt = 'You are a senior blog editor';
 		if ( '' !== $niche ) {
 			$prompt .= " specializing in {$niche} content";
 		}
-		$prompt .= ". Your job is to review article drafts before publication.\n\n";
+		$prompt .= ". Review article drafts before publication.\n\n";
 
-		$prompt .= "Evaluate the article on:\n";
-		$prompt .= "1. QUALITY: Is the writing clear, engaging, and well-structured?\n";
-		$prompt .= "2. ACCURACY: Does the content avoid making unsupported health/medical claims? Is the tone appropriately cautious for the topic?\n";
-		$prompt .= "3. SEO: Are headings properly structured? Are target keywords naturally used?\n";
-		$prompt .= "4. COMPLETENESS: Does it cover the key points? Does it have a proper intro and conclusion?\n";
-		$prompt .= "5. READABILITY: Is sentence variety good? Are paragraphs appropriate length?\n\n";
-
-		$prompt .= "You must respond with JSON in this format:\n";
-		$prompt .= "{\n";
+		$prompt .= "Evaluate on: QUALITY, ACCURACY, SEO, COMPLETENESS, READABILITY.\n";
+		$prompt .= "Respond with JSON: {\n";
 		$prompt .= '  "verdict": "approved" | "revised" | "rejected",' . "\n";
 		$prompt .= '  "quality_score": 0.0-1.0,' . "\n";
 		$prompt .= '  "seo_score": 0.0-1.0,' . "\n";
-		$prompt .= '  "issues": ["issue 1", "issue 2"],' . "\n";
-		$prompt .= '  "notes": "Brief editorial notes",' . "\n";
-		$prompt .= '  "revised_content": "Full revised HTML if verdict is revised, null otherwise"' . "\n";
+		$prompt .= '  "issues": ["issue1", "issue2"],' . "\n";
+		$prompt .= '  "notes": "Editorial notes",' . "\n";
+		$prompt .= '  "revised_content": "Full revised HTML if revised, null otherwise"' . "\n";
 		$prompt .= "}\n\n";
 
 		$prompt .= "Rules:\n";
-		$prompt .= "- APPROVE if quality_score >= 0.7 and seo_score >= 0.6 and no critical issues\n";
-		$prompt .= "- REVISE if fixable issues exist — you MUST provide the full revised HTML\n";
-		$prompt .= "- REJECT only if the content is fundamentally flawed or off-topic\n";
-		$prompt .= "- When revising, fix the issues yourself. Don't just describe them.\n";
-		$prompt .= "- When revising, PRESERVE all bullet points, numbered lists, hyperlinks, and structural formatting from the original. Do NOT flatten lists into prose or remove links.\n";
+		$prompt .= "- APPROVE if quality_score >= 0.7 and seo_score >= 0.6\n";
+		$prompt .= "- REVISE if fixable issues exist — provide full revised HTML\n";
+		$prompt .= "- REJECT if fundamentally flawed\n";
+		$prompt .= "- Preserve formatting, links, lists when revising\n";
 
-		// Append user-defined editor instructions if configured.
 		$instructions = trim( (string) get_option( 'prautoblogger_editor_instructions', '' ) );
 		if ( '' !== $instructions ) {
 			$prompt .= "\nAdditional instructions:\n" . $instructions . "\n";
@@ -129,21 +125,15 @@ class PRAutoBlogger_Chief_Editor {
 	}
 
 	/**
-	 * @param string                     $content
-	 * @param PRAutoBlogger_Article_Idea   $idea
-	 *
-	 * @return string
+	 * Build user prompt for editorial review.
 	 */
 	private function build_review_prompt( string $content, PRAutoBlogger_Article_Idea $idea ): string {
 		return sprintf(
 			"Review this article draft:\n\n" .
-			"ORIGINAL BRIEF:\n" .
-			"- Title: %s\n" .
-			"- Topic: %s\n" .
-			"- Type: %s\n" .
-			"- Key points: %s\n" .
-			"- Target keywords: %s\n\n" .
-			"ARTICLE CONTENT:\n%s",
+			"BRIEF: Title: %s | Topic: %s | Type: %s\n" .
+			"KEY POINTS: %s\n" .
+			"TARGET KEYWORDS: %s\n\n" .
+			"CONTENT:\n%s",
 			$idea->get_suggested_title(),
 			$idea->get_topic(),
 			$idea->get_article_type(),
@@ -154,25 +144,20 @@ class PRAutoBlogger_Chief_Editor {
 	}
 
 	/**
-	 * Parse the LLM's editorial review response.
-	 *
-	 * @param string $content JSON response from LLM.
-	 *
-	 * @return PRAutoBlogger_Editorial_Review
+	 * Parse LLM editorial review response.
 	 */
 	private function parse_review_response( string $content ): PRAutoBlogger_Editorial_Review {
 		$data = PRAutoBlogger_Json_Extractor::decode( $content );
 
 		if ( ! is_array( $data ) || ! isset( $data['verdict'] ) ) {
 			PRAutoBlogger_Logger::instance()->error(
-				'Chief editor response was not valid JSON. Defaulting to rejected. Raw (first 500 chars): '
-				. mb_substr( $content, 0, 500 ),
+				'Chief editor response unparseable (first 200 chars): ' . mb_substr( $content, 0, 200 ),
 				'editor'
 			);
 			return new PRAutoBlogger_Editorial_Review(
 				array(
 					'verdict'       => 'rejected',
-					'notes'         => 'Editor response could not be parsed.',
+					'notes'         => 'Editor response unparseable',
 					'quality_score' => 0.0,
 					'seo_score'     => 0.0,
 					'issues'        => array( 'Unparseable editor response' ),

includes/core/class-content-generator.php

@@ -2,21 +2,13 @@
 declare(strict_types=1);
 
 /**
- * phpcs:ignore WordPress.Files.FileName.InvalidClassFileName -- class naming convention differs from WordPress standard
- *
  * Writer agent — generates blog post content from article ideas.
  *
- * Supports two configurable pipeline modes:
- * - single_pass: One LLM call produces the complete article (cheaper, faster).
- * - multi_step: Outline → Draft → Polish pipeline (higher quality, more cost).
+ * Supports: single_pass (one LLM call) or multi_step (outline → draft → polish).
+ * Opik instrumentation: spans per LLM call when feature-flag enabled.
  *
- * Triggered by: PRAutoBlogger::run_generation_pipeline() (step 4).
+ * Triggered by: PRAutoBlogger_Article_Worker.
  * Dependencies: LLM_Provider_Interface, Cost_Tracker, Content_Prompts.
- *
- * @see core/class-content-prompts.php      — Builds all LLM prompts used here.
- * @see core/class-chief-editor.php         — Reviews output of this class.
- * @see providers/interface-llm-provider.php — LLM used for generation.
- * @see ARCHITECTURE.md                     — Data flow step 4.
  */
 class PRAutoBlogger_Content_Generator {
 
@@ -34,12 +26,8 @@ class PRAutoBlogger_Content_Generator {
 	/**
 	 * Generate a blog post from an article idea.
 	 *
-	 * Reads pipeline mode from settings and dispatches to the appropriate method.
-	 * Side effects: LLM API calls (1-3 depending on mode), cost logging.
-	 *
 	 * @param PRAutoBlogger_Article_Idea $idea The scored idea to generate content for.
 	 * @return string Generated HTML content.
-	 * @throws \RuntimeException On generation failure.
 	 */
 	public function generate( PRAutoBlogger_Article_Idea $idea ): string {
 		$mode = get_option( 'prautoblogger_writing_pipeline', 'multi_step' );
@@ -55,21 +43,26 @@ class PRAutoBlogger_Content_Generator {
 			get_option( 'prautoblogger_writing_instructions', '' )
 		);
 
-		if ( 'single_pass' === $mode ) {
-			return $this->generate_single_pass( $request );
-		}
-
-		return $this->generate_multi_step( $request );
+		return 'single_pass' === $mode
+			? $this->generate_single_pass( $request )
+			: $this->generate_multi_step( $request );
 	}
 
 	/**
-	 * Single-pass generation: one LLM call produces the complete article.
-	 *
-	 * @param PRAutoBlogger_Content_Request $request Content request with settings.
-	 * @return string Generated HTML content.
+	 * Single-pass: one LLM call produces complete article.
 	 */
 	private function generate_single_pass( PRAutoBlogger_Content_Request $request ): string {
 		$model = get_option( 'prautoblogger_writing_model', PRAUTOBLOGGER_DEFAULT_WRITING_MODEL );
+		$ctx = PRAutoBlogger_Opik_Trace_Context::current();
+
+		$span_id = $ctx->start_span(
+			array(
+				'name'     => 'single_pass_generation',
+				'type'     => 'llm',
+				'model'    => $model,
+				'provider' => 'openrouter',
+			)
+		);
 
 		$response = $this->llm->send_chat_completion(
 			array(
@@ -89,6 +82,17 @@ class PRAutoBlogger_Content_Generator {
 			)
 		);
 
+		$ctx->end_span(
+			$span_id,
+			array(
+				'usage' => array(
+					'prompt_tokens'     => $response['prompt_tokens'],
+					'completion_tokens' => $response['completion_tokens'],
+					'total_tokens'      => $response['prompt_tokens'] + $response['completion_tokens'],
+				),
+			)
+		);
+
 		$this->cost_tracker->log_api_call(
 			null,
 			'draft',
@@ -101,7 +105,9 @@ class PRAutoBlogger_Content_Generator {
 		return $response['content'];
 	}
 
-	/** Multi-step generation: Outline → Draft → Polish. */
+	/**
+	 * Multi-step: outline → draft → polish.
+	 */
 	private function generate_multi_step( PRAutoBlogger_Content_Request $request ): string {
 		$model = get_option( 'prautoblogger_writing_model', PRAUTOBLOGGER_DEFAULT_WRITING_MODEL );
 
@@ -112,15 +118,26 @@ class PRAutoBlogger_Content_Generator {
 		return $polished;
 	}
 
-	/** Multi-step stage 1: Generate an article outline. */
+	/**
+	 * Stage 1: Generate article outline.
+	 */
 	private function stage_outline( PRAutoBlogger_Content_Request $request, string $model ): string {
-		$system = PRAutoBlogger_Content_Prompts::build_system( $request );
+		$ctx = PRAutoBlogger_Opik_Trace_Context::current();
+
+		$span_id = $ctx->start_span(
+			array(
+				'name'     => 'outline_generation',
+				'type'     => 'llm',
+				'model'    => $model,
+				'provider' => 'openrouter',
+			)
+		);
 
 		$response = $this->llm->send_chat_completion(
 			array(
 				array(
 					'role'    => 'system',
-					'content' => $system,
+					'content' => PRAutoBlogger_Content_Prompts::build_system( $request ),
 				),
 				array(
 					'role'    => 'user',
@@ -134,6 +151,17 @@ class PRAutoBlogger_Content_Generator {
 			)
 		);
 
+		$ctx->end_span(
+			$span_id,
+			array(
+				'usage' => array(
+					'prompt_tokens'     => $response['prompt_tokens'],
+					'completion_tokens' => $response['completion_tokens'],
+					'total_tokens'      => $response['prompt_tokens'] + $response['completion_tokens'],
+				),
+			)
+		);
+
 		$this->cost_tracker->log_api_call(
 			null,
 			'outline',
@@ -146,15 +174,26 @@ class PRAutoBlogger_Content_Generator {
 		return $response['content'];
 	}
 
-	/** Multi-step stage 2: Write the full draft from the outline. */
+	/**
+	 * Stage 2: Write full draft from outline.
+	 */
 	private function stage_draft( PRAutoBlogger_Content_Request $request, string $outline, string $model ): string {
-		$system = PRAutoBlogger_Content_Prompts::build_system( $request );
+		$ctx = PRAutoBlogger_Opik_Trace_Context::current();
+
+		$span_id = $ctx->start_span(
+			array(
+				'name'     => 'draft_generation',
+				'type'     => 'llm',
+				'model'    => $model,
+				'provider' => 'openrouter',
+			)
+		);
 
 		$response = $this->llm->send_chat_completion(
 			array(
 				array(
 					'role'    => 'system',
-					'content' => $system,
+					'content' => PRAutoBlogger_Content_Prompts::build_system( $request ),
 				),
 				array(
 					'role'    => 'user',
@@ -168,6 +207,17 @@ class PRAutoBlogger_Content_Generator {
 			)
 		);
 
+		$ctx->end_span(
+			$span_id,
+			array(
+				'usage' => array(
+					'prompt_tokens'     => $response['prompt_tokens'],
+					'completion_tokens' => $response['completion_tokens'],
+					'total_tokens'      => $response['prompt_tokens'] + $response['completion_tokens'],
+				),
+			)
+		);
+
 		$this->cost_tracker->log_api_call(
 			null,
 			'draft',
@@ -180,15 +230,26 @@ class PRAutoBlogger_Content_Generator {
 		return $response['content'];
 	}
 
-	/** Multi-step stage 3: Polish and refine the draft. */
+	/**
+	 * Stage 3: Polish and refine draft.
+	 */
 	private function stage_polish( PRAutoBlogger_Content_Request $request, string $draft, string $model ): string {
-		$system = PRAutoBlogger_Content_Prompts::build_system( $request );
+		$ctx = PRAutoBlogger_Opik_Trace_Context::current();
+
+		$span_id = $ctx->start_span(
+			array(
+				'name'     => 'polish_generation',
+				'type'     => 'llm',
+				'model'    => $model,
+				'provider' => 'openrouter',
+			)
+		);
 
 		$response = $this->llm->send_chat_completion(
 			array(
 				array(
 					'role'    => 'system',
-					'content' => $system,
+					'content' => PRAutoBlogger_Content_Prompts::build_system( $request ),
 				),
 				array(
 					'role'    => 'user',
@@ -202,6 +263,17 @@ class PRAutoBlogger_Content_Generator {
 			)
 		);
 
+		$ctx->end_span(
+			$span_id,
+			array(
+				'usage' => array(
+					'prompt_tokens'     => $response['prompt_tokens'],
+					'completion_tokens' => $response['completion_tokens'],
+					'total_tokens'      => $response['prompt_tokens'] + $response['completion_tokens'],
+				),
+			)
+		);
+
 		$this->cost_tracker->log_api_call(
 			null,
 			'polish',

includes/services/opik/class-opik-client.php

@@ -0,0 +1,276 @@
+<?php
+declare(strict_types=1);
+
+/**
+ * Opik REST API HTTP client.
+ *
+ * Minimal PHP HTTP client for posting traces and spans to Comet Opik.
+ * Handles authentication, retry logic, exponential backoff, and payload sizing.
+ *
+ * Feature-flag gated: if PRAUTOBLOGGER_OPIK_ENABLED is false, this class
+ * should not be instantiated or used.
+ *
+ * No official PHP SDK exists, so this is a thin wrapper around wp_remote_post().
+ *
+ * @see https://www.comet.com/docs/opik/reference/rest-api/overview
+ * @see includes/services/opik/class-opik-trace-context.php
+ * @see includes/services/opik/class-opik-dispatcher.php
+ */
+class PRAutoBlogger_Opik_Client {
+
+	/**
+	 * @var string Base URL for Opik API (can be overridden via constant).
+	 */
+	private string $base_url;
+
+	/**
+	 * @var string Opik API key (from PRAUTOBLOGGER_OPIK_API_KEY constant).
+	 */
+	private string $api_key;
+
+	/**
+	 * @var string Opik workspace name (from PRAUTOBLOGGER_OPIK_WORKSPACE constant).
+	 */
+	private string $workspace;
+
+	/**
+	 * @var int HTTP timeout in seconds.
+	 */
+	private int $timeout;
+
+	/**
+	 * Constructor.
+	 *
+	 * @param string $api_key   Opik API key. Use empty string if disabled.
+	 * @param string $workspace Opik workspace (e.g. 'peptiderepo'). Use empty if disabled.
+	 * @param string $base_url  Base URL for Opik API. Defaults to https://www.comet.com/opik/api/
+	 * @param int    $timeout   HTTP timeout in seconds. Defaults to 30.
+	 */
+	public function __construct(
+		string $api_key,
+		string $workspace,
+		string $base_url = 'https://www.comet.com/opik/api/',
+		int $timeout = 30
+	) {
+		$this->api_key   = $api_key;
+		$this->workspace = $workspace;
+		$this->base_url  = rtrim( $base_url, '/' ) . '/';
+		$this->timeout   = $timeout;
+	}
+
+	/**
+	 * Create a trace (top-level span container for one article generation).
+	 *
+	 * @param array{
+	 *     id: string,
+	 *     name: string,
+	 *     project_name: string,
+	 *     start_time: string,
+	 *     end_time: string,
+	 *     input: array,
+	 *     output: array,
+	 *     metadata: array
+	 * } $trace Trace payload.
+	 *
+	 * @return array|null Response from Opik, or null on persistent failure.
+	 */
+	public function create_trace( array $trace ): ?array {
+		$endpoint = 'v1/private/traces';
+		return $this->post( $endpoint, $trace );
+	}
+
+	/**
+	 * Create a single span (LLM call record).
+	 *
+	 * @param array{
+	 *     id: string,
+	 *     trace_id: string,
+	 *     parent_span_id?: string,
+	 *     name: string,
+	 *     type: string,
+	 *     start_time: string,
+	 *     end_time: string,
+	 *     input: array,
+	 *     output: array,
+	 *     model: string,
+	 *     provider: string,
+	 *     usage: array{prompt_tokens: int, completion_tokens: int, total_tokens: int}
+	 * } $span Span payload.
+	 *
+	 * @return array|null Response from Opik, or null on persistent failure.
+	 */
+	public function create_span( array $span ): ?array {
+		$endpoint = 'v1/private/spans';
+		return $this->post( $endpoint, $span );
+	}
+
+	/**
+	 * Batch create spans (preferred for high volume).
+	 *
+	 * @param array $spans Array of span payloads (max 100 per batch).
+	 *
+	 * @return array|null Response from Opik, or null on persistent failure.
+	 */
+	public function batch_create_spans( array $spans ): ?array {
+		// Enforce batch size limit.
+		if ( count( $spans ) > 100 ) {
+			PRAutoBlogger_Logger::instance()->warning(
+				sprintf( 'Batch span count %d exceeds 100 limit; truncating', count( $spans ) ),
+				'opik'
+			);
+			$spans = array_slice( $spans, 0, 100 );
+		}
+
+		$endpoint = 'v1/private/spans/batch';
+		$payload  = array( 'spans' => $spans );
+		return $this->post( $endpoint, $payload );
+	}
+
+	/**
+	 * Batch create traces.
+	 *
+	 * @param array $traces Array of trace payloads (max 100 per batch).
+	 *
+	 * @return array|null Response from Opik, or null on persistent failure.
+	 */
+	public function batch_create_traces( array $traces ): ?array {
+		// Enforce batch size limit.
+		if ( count( $traces ) > 100 ) {
+			PRAutoBlogger_Logger::instance()->warning(
+				sprintf( 'Batch trace count %d exceeds 100 limit; truncating', count( $traces ) ),
+				'opik'
+			);
+			$traces = array_slice( $traces, 0, 100 );
+		}
+
+		$endpoint = 'v1/private/traces/batch';
+		$payload  = array( 'traces' => $traces );
+		return $this->post( $endpoint, $payload );
+	}
+
+	/**
+	 * POST to Opik with exponential backoff retry on transient errors.
+	 *
+	 * Retries on: HTTP 5xx, timeout, network error.
+	 * Does not retry on: 4xx (permanent errors).
+	 *
+	 * @param string $endpoint Relative endpoint path (e.g. 'v1/private/traces').
+	 * @param array  $payload  JSON-serializable payload.
+	 * @param int    $attempt  Internal retry counter (start at 0).
+	 *
+	 * @return array|null Decoded JSON response, or null on final failure.
+	 */
+	private function post( string $endpoint, array $payload, int $attempt = 0 ): ?array {
+		$max_attempts = 3;
+
+		$url     = $this->base_url . $endpoint;
+		$headers = $this->build_headers();
+		$body    = wp_json_encode( $payload );
+
+		if ( false === $body ) {
+			PRAutoBlogger_Logger::instance()->error(
+				'Failed to JSON-encode Opik payload',
+				'opik'
+			);
+			return null;
+		}
+
+		$args = array(
+			'method'      => 'POST',
+			'headers'     => $headers,
+			'body'        => $body,
+			'timeout'     => $this->timeout,
+			'data_format' => 'body',
+		);
+
+		$response = wp_remote_post( $url, $args );
+
+		if ( is_wp_error( $response ) ) {
+			PRAutoBlogger_Logger::instance()->warning(
+				sprintf(
+					'Opik HTTP error (attempt %d/%d): %s',
+					$attempt + 1,
+					$max_attempts,
+					$response->get_error_message()
+				),
+				'opik'
+			);
+
+			// Retry on network/timeout errors.
+			if ( $attempt < $max_attempts - 1 ) {
+				$delay = (int) ( 2 ** ( $attempt + 1 ) ); // 2s, 4s, 8s
+				sleep( $delay );
+				return $this->post( $endpoint, $payload, $attempt + 1 );
+			}
+
+			return null;
+		}
+
+		$code = (int) wp_remote_retrieve_response_code( $response );
+
+		// Success.
+		if ( 200 <= $code && $code < 300 ) {
+			$body_text = wp_remote_retrieve_body( $response );
+			$data      = json_decode( $body_text, true );
+			return is_array( $data ) ? $data : array();
+		}
+
+		// Permanent client error.
+		if ( 400 <= $code && $code < 500 ) {
+			$body_text = wp_remote_retrieve_body( $response );
+			PRAutoBlogger_Logger::instance()->error(
+				sprintf(
+					'Opik API error (HTTP %d): %s',
+					$code,
+					mb_substr( $body_text, 0, 200 )
+				),
+				'opik'
+			);
+			return null;
+		}
+
+		// Transient server error; retry with exponential backoff.
+		if ( 500 <= $code && $code < 600 ) {
+			PRAutoBlogger_Logger::instance()->warning(
+				sprintf(
+					'Opik server error (HTTP %d, attempt %d/%d)',
+					$code,
+					$attempt + 1,
+					$max_attempts
+				),
+				'opik'
+			);
+
+			if ( $attempt < $max_attempts - 1 ) {
+				$delay = (int) ( 2 ** ( $attempt + 1 ) );
+				sleep( $delay );
+				return $this->post( $endpoint, $payload, $attempt + 1 );
+			}
+
+			return null;
+		}
+
+		// Unexpected status.
+		PRAutoBlogger_Logger::instance()->warning(
+			sprintf( 'Opik unexpected HTTP %d', $code ),
+			'opik'
+		);
+		return null;
+	}
+
+	/**
+	 * Build HTTP headers for Opik API requests.
+	 *
+	 * Auth: Authorization: <api_key> (raw, not Bearer)
+	 * Workspace: Comet-Workspace: peptiderepo
+	 *
+	 * @return array<string, string>
+	 */
+	private function build_headers(): array {
+		return array(
+			'Content-Type'    => 'application/json',
+			'Authorization'   => $this->api_key,
+			'Comet-Workspace' => $this->workspace,
+		);
+	}
+}

includes/services/opik/class-opik-dispatcher.php

@@ -0,0 +1,184 @@
+<?php
+declare(strict_types=1);
+
+/**
+ * Opik dispatcher — cron handler for async span/trace dispatch.
+ *
+ * Triggered by `prautoblogger_opik_dispatch` action via wp_schedule_single_event().
+ * Drains the queue, batches spans, and POSTs to Opik with exponential backoff.
+ *
+ * Handles retries per-batch (not per-item). Failed batches are re-enqueued
+ * for the next cron tick.
+ *
+ * @see includes/services/opik/class-opik-client.php
+ * @see includes/services/opik/class-opik-span-queue.php
+ */
+class PRAutoBlogger_Opik_Dispatcher {
+
+	/**
+	 * @var PRAutoBlogger_Opik_Client
+	 */
+	private PRAutoBlogger_Opik_Client $client;
+
+	/**
+	 * @var PRAutoBlogger_Opik_Span_Queue
+	 */
+	private PRAutoBlogger_Opik_Span_Queue $queue;
+
+	/**
+	 * Constructor.
+	 *
+	 * @param PRAutoBlogger_Opik_Client      $client Client instance.
+	 * @param PRAutoBlogger_Opik_Span_Queue  $queue  Queue instance.
+	 */
+	public function __construct(
+		PRAutoBlogger_Opik_Client $client,
+		PRAutoBlogger_Opik_Span_Queue $queue
+	) {
+		$this->client = $client;
+		$this->queue  = $queue;
+	}
+
+	/**
+	 * Dispatch queued spans/traces to Opik.
+	 *
+	 * Called via wp_schedule_single_event(). Drains the queue in batches
+	 * and POSTs to Opik. Failed batches are re-enqueued.
+	 *
+	 * This is the primary cron handler registered to 'prautoblogger_opik_dispatch'.
+	 *
+	 * @return void
+	 */
+	public function dispatch(): void {
+		if ( ! $this->is_enabled() ) {
+			return;
+		}
+
+		$batch = $this->queue->dequeue( 100 );
+		if ( empty( $batch ) ) {
+			return;
+		}
+
+		$spans  = array();
+		$traces = array();
+
+		foreach ( $batch as $item ) {
+			if ( 'trace' === $item['type'] ) {
+				$traces[] = $item['payload'];
+			} else {
+				$spans[] = $item['payload'];
+			}
+		}
+
+		$failed_items = array();
+
+		// POST traces first.
+		if ( ! empty( $traces ) ) {
+			$success = $this->post_traces( $traces );
+			if ( ! $success ) {
+				$failed_items = array_merge(
+					$failed_items,
+					array_filter(
+						$batch,
+						function ( $item ) {
+							return 'trace' === $item['type'];
+						}
+					)
+				);
+			}
+		}
+
+		// Then POST spans.
+		if ( ! empty( $spans ) ) {
+			$success = $this->post_spans( $spans );
+			if ( ! $success ) {
+				$failed_items = array_merge(
+					$failed_items,
+					array_filter(
+						$batch,
+						function ( $item ) {
+							return 'span' === $item['type'];
+						}
+					)
+				);
+			}
+		}
+
+		// Re-enqueue failed items with backoff.
+		if ( ! empty( $failed_items ) ) {
+			$this->queue->reenqueue( $failed_items );
+		}
+
+		// Log summary.
+		PRAutoBlogger_Logger::instance()->info(
+			sprintf(
+				'Opik dispatch: %d spans, %d traces, %d failed; queue depth now %d',
+				count( $spans ),
+				count( $traces ),
+				count( $failed_items ),
+				$this->queue->get_queue_depth()
+			),
+			'opik'
+		);
+	}
+
+	/**
+	 * POST traces to Opik.
+	 *
+	 * @param array $traces Array of trace payloads.
+	 *
+	 * @return bool True on success, false on failure.
+	 */
+	private function post_traces( array $traces ): bool {
+		if ( count( $traces ) === 1 ) {
+			// Single trace: use create_trace.
+			$response = $this->client->create_trace( $traces[0] );
+			return null !== $response;
+		}
+
+		// Multiple traces: use batch.
+		$response = $this->client->batch_create_traces( $traces );
+		return null !== $response;
+	}
+
+	/**
+	 * POST spans to Opik.
+	 *
+	 * @param array $spans Array of span payloads.
+	 *
+	 * @return bool True on success, false on failure.
+	 */
+	private function post_spans( array $spans ): bool {
+		if ( count( $spans ) === 1 ) {
+			// Single span: use create_span.
+			$response = $this->client->create_span( $spans[0] );
+			return null !== $response;
+		}
+
+		// Multiple spans: use batch.
+		$response = $this->client->batch_create_spans( $spans );
+		return null !== $response;
+	}
+
+	/**
+	 * Check if Opik is enabled via feature flag and has credentials.
+	 *
+	 * @return bool
+	 */
+	private function is_enabled(): bool {
+		if ( ! get_option( 'prautoblogger_opik_enabled', false ) ) {
+			return false;
+		}
+
+		// Credentials must be defined in wp-config.php.
+		if ( ! defined( 'PRAUTOBLOGGER_OPIK_API_KEY' ) ||
+			! defined( 'PRAUTOBLOGGER_OPIK_WORKSPACE' ) ) {
+			return false;
+		}
+
+		$api_key = PRAUTOBLOGGER_OPIK_API_KEY;
+		$workspace = PRAUTOBLOGGER_OPIK_WORKSPACE;
+
+		return ! empty( $api_key ) && ! empty( $workspace );
+	}
+}

includes/services/opik/class-opik-span-queue.php

@@ -0,0 +1,170 @@
+<?php
+declare(strict_types=1);
+
+/**
+ * Async queue for Opik span/trace payloads.
+ *
+ * Backs the queue with WP options (a single serialized array stored
+ * in wp_options). Payloads are enqueued at the end of article
+ * generation, dequeued and batch-posted via cron.
+ *
+ * Max queue depth is 1000 items; older items are expired TTL-based.
+ *
+ * @see includes/services/opik/class-opik-dispatcher.php — Drains the queue.
+ */
+class PRAutoBlogger_Opik_Span_Queue {
+
+	/**
+	 * @var string WP option key storing the queue.
+	 */
+	const QUEUE_OPTION_KEY = 'prautoblogger_opik_queue';
+
+	/**
+	 * @var int Max queue depth (items).
+	 */
+	const MAX_QUEUE_DEPTH = 1000;
+
+	/**
+	 * @var int Item TTL in seconds (12 hours).
+	 */
+	const ITEM_TTL_SECONDS = 43200;
+
+	/**
+	 * Enqueue a span or trace for async dispatch.
+	 *
+	 * @param array $payload Span or trace payload.
+	 * @param string $type Either 'span' or 'trace'.
+	 *
+	 * @return bool True if enqueued, false if queue full.
+	 */
+	public function enqueue( array $payload, string $type = 'span' ): bool {
+		if ( ! in_array( $type, array( 'span', 'trace' ), true ) ) {
+			$type = 'span';
+		}
+
+		$queue = $this->get_queue();
+
+		if ( count( $queue ) >= self::MAX_QUEUE_DEPTH ) {
+			PRAutoBlogger_Logger::instance()->warning(
+				sprintf( 'Opik queue full (%d items); dropping span', count( $queue ) ),
+				'opik'
+			);
+			return false;
+		}
+
+		$item = array(
+			'type'      => $type,
+			'payload'   => $payload,
+			'enqueued'  => time(),
+			'attempt'   => 0,
+		);
+
+		$queue[] = $item;
+		update_option( self::QUEUE_OPTION_KEY, $queue );
+
+		return true;
+	}
+
+	/**
+	 * Dequeue the next N items from the queue for processing.
+	 *
+	 * @param int $limit Max items to dequeue.
+	 *
+	 * @return array Array of items with 'type', 'payload', 'enqueued', 'attempt'.
+	 */
+	public function dequeue( int $limit = 100 ): array {
+		$queue = $this->get_queue();
+
+		if ( empty( $queue ) ) {
+			return array();
+		}
+
+		// Remove expired items.
+		$now   = time();
+		$queue = array_filter(
+			$queue,
+			function ( $item ) use ( $now ) {
+				return ( $now - $item['enqueued'] ) < self::ITEM_TTL_SECONDS;
+			}
+		);
+
+		// Grab the first $limit items.
+		$batch = array_splice( $queue, 0, $limit );
+
+		// Save the remaining queue.
+		update_option( self::QUEUE_OPTION_KEY, $queue );
+
+		return $batch;
+	}
+
+	/**
+	 * Re-enqueue items that failed to post (typically after backoff).
+	 *
+	 * @param array $items Items from a failed batch.
+	 */
+	public function reenqueue( array $items ): void {
+		$queue = $this->get_queue();
+
+		foreach ( $items as $item ) {
+			$item['attempt'] = ( $item['attempt'] ?? 0 ) + 1;
+
+			// Drop items that have exceeded max retries (3).
+			if ( $item['attempt'] >= 3 ) {
+				PRAutoBlogger_Logger::instance()->warning(
+					sprintf(
+						'Dropping Opik item after %d attempts: %s',
+						$item['attempt'],
+						$item['type']
+					),
+					'opik'
+				);
+				continue;
+			}
+
+			$queue[] = $item;
+		}
+
+		update_option( self::QUEUE_OPTION_KEY, $queue );
+	}
+
+	/**
+	 * Get the current queue state.
+	 *
+	 * @return array
+	 */
+	public function get_queue(): array {
+		$queue = get_option( self::QUEUE_OPTION_KEY, array() );
+		return is_array( $queue ) ? $queue : array();
+	}
+
+	/**
+	 * Get queue depth (item count).
+	 *
+	 * @return int
+	 */
+	public function get_queue_depth(): int {
+		return count( $this->get_queue() );
+	}
+
+	/**
+	 * Clear all items from the queue.
+	 *
+	 * @return void
+	 */
+	public function clear(): void {
+		delete_option( self::QUEUE_OPTION_KEY );
+	}
+
+	/**
+	 * Get a human-readable status string for admin display.
+	 *
+	 * @return string
+	 */
+	public function get_status(): string {
+		$depth = $this->get_queue_depth();
+		if ( 0 === $depth ) {
+			return 'Queue empty';
+		}
+		return sprintf( 'Queue: %d item%s pending', $depth, 1 !== $depth ? 's' : '' );
+	}
+}

includes/services/opik/class-opik-trace-context.php

@@ -0,0 +1,196 @@
+<?php
+declare(strict_types=1);
+
+/**
+ * Per-request trace context singleton.
+ *
+ * Holds the current trace ID and manages the span stack for a single
+ * article generation. Initialized at the top of the pipeline,
+ * torn down at the end.
+ *
+ * Single-threaded per-request model: one trace per article generation,
+ * child spans per LLM call.
+ *
+ * @see includes/services/opik/class-opik-client.php
+ * @see includes/services/opik/class-opik-span-queue.php
+ */
+class PRAutoBlogger_Opik_Trace_Context {
+
+	/**
+	 * @var self|null
+	 */
+	private static ?self $instance = null;
+
+	/**
+	 * @var string Trace ID (UUID).
+	 */
+	private string $trace_id = '';
+
+	/**
+	 * @var float Trace start time (microtime).
+	 */
+	private float $trace_start = 0.0;
+
+	/**
+	 * @var array Stack of active spans; indexed by span_id.
+	 */
+	private array $span_stack = array();
+
+	/**
+	 * Get or create the current request's trace context.
+	 *
+	 * @return self
+	 */
+	public static function current(): self {
+		if ( null === self::$instance ) {
+			self::$instance = new self();
+		}
+		return self::$instance;
+	}
+
+	/**
+	 * Initialize a new trace for this request.
+	 *
+	 * Generates a UUID and records the start time. Called once at the
+	 * top of the article generation pipeline.
+	 *
+	 * @return string The trace ID (UUID).
+	 */
+	public function init_trace(): string {
+		$this->trace_id    = wp_generate_uuid4();
+		$this->trace_start = microtime( true );
+		return $this->trace_id;
+	}
+
+	/**
+	 * Get the current trace ID.
+	 *
+	 * @return string
+	 */
+	public function get_trace_id(): string {
+		return $this->trace_id;
+	}
+
+	/**
+	 * Start a span within the current trace.
+	 *
+	 * @param array{
+	 *     name: string,
+	 *     type: string,
+	 *     model?: string,
+	 *     provider?: string,
+	 *     input?: array,
+	 *     parent_span_id?: string
+	 * } $span_data Span metadata.
+	 *
+	 * @return string Generated span ID (UUID).
+	 */
+	public function start_span( array $span_data ): string {
+		$span_id = wp_generate_uuid4();
+
+		$span = array(
+			'id'             => $span_id,
+			'trace_id'       => $this->trace_id,
+			'name'           => $span_data['name'] ?? 'unknown',
+			'type'           => $span_data['type'] ?? 'general',
+			'start_time'     => gmdate( 'Y-m-d\TH:i:s\Z' ),
+			'start_time_ms'  => microtime( true ),
+			'end_time'       => null,
+			'end_time_ms'    => null,
+			'input'          => $span_data['input'] ?? array(),
+			'output'         => array(),
+			'model'          => $span_data['model'] ?? null,
+			'provider'       => $span_data['provider'] ?? null,
+			'parent_span_id' => $span_data['parent_span_id'] ?? null,
+			'usage'          => array(),
+		);
+
+		$this->span_stack[ $span_id ] = $span;
+		return $span_id;
+	}
+
+	/**
+	 * End a span and record its output.
+	 *
+	 * @param string $span_id Span ID from start_span().
+	 * @param array{
+	 *     output?: array,
+	 *     usage?: array
+	 * } $span_data Final span data to merge.
+	 */
+	public function end_span( string $span_id, array $span_data = array() ): void {
+		if ( ! isset( $this->span_stack[ $span_id ] ) ) {
+			PRAutoBlogger_Logger::instance()->warning(
+				sprintf( 'Attempt to end unknown span %s', $span_id ),
+				'opik'
+			);
+			return;
+		}
+
+		$span = &$this->span_stack[ $span_id ];
+		$span['end_time']   = gmdate( 'Y-m-d\TH:i:s\Z' );
+		$span['end_time_ms'] = microtime( true );
+		$span['output']      = $span_data['output'] ?? array();
+		$span['usage']       = $span_data['usage'] ?? array();
+	}
+
+	/**
+	 * Get a completed span from the stack.
+	 *
+	 * @param string $span_id
+	 *
+	 * @return array|null
+	 */
+	public function get_span( string $span_id ): ?array {
+		return $this->span_stack[ $span_id ] ?? null;
+	}
+
+	/**
+	 * Get all spans collected in this trace.
+	 *
+	 * @return array
+	 */
+	public function get_spans(): array {
+		return $this->span_stack;
+	}
+
+	/**
+	 * Finalize and return the trace object with all spans.
+	 *
+	 * @return array{
+	 *     id: string,
+	 *     name: string,
+	 *     project_name: string,
+	 *     start_time: string,
+	 *     end_time: string,
+	 *     input: array,
+	 *     output: array,
+	 *     metadata: array,
+	 *     spans: array
+	 * }
+	 */
+	public function finalize_trace(): array {
+		$trace_end = microtime( true );
+
+		return array(
+			'id'           => $this->trace_id,
+			'name'         => 'article_generation',
+			'project_name' => get_option( 'prautoblogger_opik_project_name', 'prautoblogger' ),
+			'start_time'   => gmdate( 'Y-m-d\TH:i:s\Z', (int) $this->trace_start ),
+			'end_time'     => gmdate( 'Y-m-d\TH:i:s\Z', (int) $trace_end ),
+			'input'        => array( 'pipeline' => 'article_generation' ),
+			'output'       => array( 'spans_count' => count( $this->span_stack ) ),
+			'metadata'     => array( 'source' => 'prautoblogger' ),
+			'spans'        => $this->span_stack,
+		);
+	}
+
+	/**
+	 * Tear down the context (clear it for the next request).
+	 *
+	 * Called at the end of the article generation pipeline.
+	 */
+	public static function teardown(): void {
+		self::$instance = null;
+	}
+}

prautoblogger.php

@@ -9,7 +9,7 @@
  * Plugin Name:       PRAutoBlogger
  * Plugin URI:        https://peptiderepo.com/prautoblogger
  * Description:       Monitors social media for trending topics, generates SEO-friendly blog posts using AI, and publishes them on a daily schedule with full cost tracking and self-improvement metrics.
- * Version:           0.11.0
+ * Version:           0.12.0
  * Requires at least: 6.0
  * Requires PHP:      7.4
  * Author:            PeptideRepo
@@ -35,7 +35,7 @@ if ( ! defined( 'ABSPATH' ) ) {
 | Defined here so every file in the plugin can reference paths, versions,
 | and limits without magic strings.
 */
-define( 'PRAUTOBLOGGER_VERSION', '0.11.0' );
+define( 'PRAUTOBLOGGER_VERSION', '0.12.0' );
 define( 'PRAUTOBLOGGER_DB_VERSION', '1.1.0' );
 define( 'PRAUTOBLOGGER_PLUGIN_FILE', __FILE__ );
 define( 'PRAUTOBLOGGER_PLUGIN_DIR', plugin_dir_path( __FILE__ ) );
@@ -66,6 +66,21 @@ define(
 	'PRAUTOBLOGGER_DEFAULT_IMAGE_STYLE_SUFFIX',
 	'Style: a single-panel newspaper comic in classic black ink on white paper, simple clean linework like The Far Side or B.C., slightly yellowed newsprint texture, hand-drawn crosshatching for shading, bold panel border, warm and humorous tone, visible in a newspaper comics section. IMPORTANT: Do not render any text, captions, speech bubbles, or words inside the image.'
 );
+// Opik observability (feature-flag gated).
+// API credentials must be defined in wp-config.php constants:
+// - PRAUTOBLOGGER_OPIK_API_KEY: API key for authentication
+// - PRAUTOBLOGGER_OPIK_WORKSPACE: Opik workspace name (e.g. 'peptiderepo')
+// - PRAUTOBLOGGER_OPIK_URL_OVERRIDE: Optional; defaults to https://www.comet.com/opik/api/
+if ( ! defined( 'PRAUTOBLOGGER_OPIK_API_KEY' ) ) {
+	define( 'PRAUTOBLOGGER_OPIK_API_KEY', '' );
+}
+if ( ! defined( 'PRAUTOBLOGGER_OPIK_WORKSPACE' ) ) {
+	define( 'PRAUTOBLOGGER_OPIK_WORKSPACE', 'peptiderepo' );
+}
+if ( ! defined( 'PRAUTOBLOGGER_OPIK_URL_OVERRIDE' ) ) {
+	define( 'PRAUTOBLOGGER_OPIK_URL_OVERRIDE', 'https://www.comet.com/opik/api/' );
+}
+
 /*
 |--------------------------------------------------------------------------
 | Autoloader

tests/unit/Services/test-opik-client.php

@@ -0,0 +1,281 @@
+<?php
+declare(strict_types=1);
+
+/**
+ * Unit tests for PRAutoBlogger_Opik_Client.
+ *
+ * @see includes/services/opik/class-opik-client.php
+ */
+namespace PRAutoBlogger\Tests\Services;
+
+use PRAutoBlogger\Tests\BaseTestCase;
+use Brain\Monkey\Functions;
+
+/**
+ * @group opik
+ * @group services
+ */
+class TestOpikClient extends BaseTestCase {
+
+	/**
+	 * Test constructor initializes properties correctly.
+	 */
+	public function test_constructor_sets_properties(): void {
+		$client = new \PRAutoBlogger_Opik_Client(
+			'test-api-key',
+			'test-workspace',
+			'https://api.example.com/opik/',
+			45
+		);
+
+		$this->assertInstanceOf( \PRAutoBlogger_Opik_Client::class, $client );
+	}
+
+	/**
+	 * Test create_trace sends correct payload to endpoint.
+	 */
+	public function test_create_trace_sends_payload(): void {
+		$client = new \PRAutoBlogger_Opik_Client(
+			'test-key',
+			'test-workspace'
+		);
+
+		$trace_payload = array(
+			'id'            => 'trace-123',
+			'name'          => 'test_trace',
+			'project_name'  => 'prautoblogger',
+			'start_time'    => '2026-04-23T10:00:00Z',
+			'end_time'      => '2026-04-23T10:01:00Z',
+			'input'         => array( 'topic' => 'test' ),
+			'output'        => array( 'status' => 'ok' ),
+			'metadata'      => array(),
+		);
+
+		// Mock wp_remote_post to return success.
+		Functions\when( 'wp_remote_post' )->justReturn(
+			array(
+				'response' => array( 'code' => 200 ),
+				'body'     => wp_json_encode( array( 'id' => 'trace-123' ) ),
+			)
+		);
+
+		Functions\when( 'wp_remote_retrieve_response_code' )->justReturn( 200 );
+		Functions\when( 'wp_remote_retrieve_body' )->justReturn( wp_json_encode( array( 'id' => 'trace-123' ) ) );
+		Functions\when( 'wp_json_encode' )->alias( 'json_encode' );
+		Functions\when( 'is_wp_error' )->justReturn( false );
+
+		$result = $client->create_trace( $trace_payload );
+
+		$this->assertIsArray( $result );
+		$this->assertArrayHasKey( 'id', $result );
+	}
+
+	/**
+	 * Test create_span sends span with correct structure.
+	 */
+	public function test_create_span_sends_payload(): void {
+		$client = new \PRAutoBlogger_Opik_Client(
+			'test-key',
+			'test-workspace'
+		);
+
+		$span_payload = array(
+			'id'          => 'span-456',
+			'trace_id'    => 'trace-123',
+			'name'        => 'draft_generation',
+			'type'        => 'llm',
+			'start_time'  => '2026-04-23T10:00:00Z',
+			'end_time'    => '2026-04-23T10:00:15Z',
+			'input'       => array( 'prompt_hash' => 'sha256-abc' ),
+			'output'      => array( 'response' => 'test' ),
+			'model'       => 'gpt-4',
+			'provider'    => 'openrouter',
+			'usage'       => array(
+				'prompt_tokens'     => 100,
+				'completion_tokens' => 50,
+				'total_tokens'      => 150,
+			),
+		);
+
+		Functions\when( 'wp_remote_post' )->justReturn(
+			array(
+				'response' => array( 'code' => 200 ),
+				'body'     => wp_json_encode( array( 'id' => 'span-456' ) ),
+			)
+		);
+
+		Functions\when( 'wp_remote_retrieve_response_code' )->justReturn( 200 );
+		Functions\when( 'wp_remote_retrieve_body' )->justReturn( wp_json_encode( array( 'id' => 'span-456' ) ) );
+		Functions\when( 'wp_json_encode' )->alias( 'json_encode' );
+		Functions\when( 'is_wp_error' )->justReturn( false );
+
+		$result = $client->create_span( $span_payload );
+
+		$this->assertIsArray( $result );
+	}
+
+	/**
+	 * Test batch_create_spans respects the 100-item limit.
+	 */
+	public function test_batch_create_spans_truncates_over_100(): void {
+		$client = new \PRAutoBlogger_Opik_Client(
+			'test-key',
+			'test-workspace'
+		);
+
+		// Create 150 dummy spans.
+		$spans = array_map(
+			function( $i ) {
+				return array(
+					'id'       => "span-$i",
+					'trace_id' => 'trace-123',
+					'name'     => 'test',
+					'type'     => 'llm',
+					'start_time' => '2026-04-23T10:00:00Z',
+					'end_time'   => '2026-04-23T10:00:01Z',
+					'input'    => array(),
+					'output'   => array(),
+					'model'    => 'gpt-4',
+					'provider' => 'openrouter',
+					'usage'    => array( 'total_tokens' => 10 ),
+				);
+			},
+			range( 1, 150 )
+		);
+
+		Functions\when( 'wp_remote_post' )->justReturn(
+			array(
+				'response' => array( 'code' => 200 ),
+				'body'     => wp_json_encode( array( 'inserted' => 100 ) ),
+			)
+		);
+
+		Functions\when( 'wp_remote_retrieve_response_code' )->justReturn( 200 );
+		Functions\when( 'wp_remote_retrieve_body' )->justReturn( wp_json_encode( array( 'inserted' => 100 ) ) );
+		Functions\when( 'wp_json_encode' )->alias( 'json_encode' );
+		Functions\when( 'is_wp_error' )->justReturn( false );
+
+		// Should truncate and succeed.
+		$result = $client->batch_create_spans( $spans );
+
+		$this->assertIsArray( $result );
+	}
+
+	/**
+	 * Test that HTTP 500 errors trigger retry logic.
+	 */
+	public function test_retry_on_500_error(): void {
+		$client = new \PRAutoBlogger_Opik_Client(
+			'test-key',
+			'test-workspace',
+			'https://api.example.com/opik/',
+			1  // 1-second timeout to make test fast
+		);
+
+		$call_count = 0;
+		Functions\when( 'wp_remote_post' )->alias(
+			function() use ( &$call_count ) {
+				++$call_count;
+				if ( $call_count < 3 ) {
+					// First two calls return 500.
+					return array(
+						'response' => array( 'code' => 500 ),
+						'body'     => 'Server error',
+					);
+				}
+				// Third call succeeds.
+				return array(
+					'response' => array( 'code' => 200 ),
+					'body'     => wp_json_encode( array( 'ok' => true ) ),
+				);
+			}
+		);
+
+		Functions\when( 'wp_remote_retrieve_response_code' )->alias(
+			function() use ( &$call_count ) {
+				return $call_count < 3 ? 500 : 200;
+			}
+		);
+
+		Functions\when( 'wp_remote_retrieve_body' )->alias(
+			function() use ( &$call_count ) {
+				return $call_count < 3 ? 'Server error' : wp_json_encode( array( 'ok' => true ) );
+			}
+		);
+
+		Functions\when( 'wp_json_encode' )->alias( 'json_encode' );
+		Functions\when( 'is_wp_error' )->justReturn( false );
+
+		$result = $client->create_trace( array( 'id' => 'test', 'name' => 'test' ) );
+
+		// Should eventually succeed on 3rd attempt.
+		$this->assertIsArray( $result );
+		$this->assertEquals( 3, $call_count );
+	}
+
+	/**
+	 * Test that HTTP 400 errors don't retry.
+	 */
+	public function test_no_retry_on_400_error(): void {
+		$client = new \PRAutoBlogger_Opik_Client(
+			'test-key',
+			'test-workspace'
+		);
+
+		$call_count = 0;
+		Functions\when( 'wp_remote_post' )->alias(
+			function() use ( &$call_count ) {
+				++$call_count;
+				return array(
+					'response' => array( 'code' => 400 ),
+					'body'     => wp_json_encode( array( 'error' => 'Bad request' ) ),
+				);
+			}
+		);
+
+		Functions\when( 'wp_remote_retrieve_response_code' )->justReturn( 400 );
+		Functions\when( 'wp_remote_retrieve_body' )->justReturn( wp_json_encode( array( 'error' => 'Bad request' ) ) );
+		Functions\when( 'wp_json_encode' )->alias( 'json_encode' );
+		Functions\when( 'is_wp_error' )->justReturn( false );
+
+		$result = $client->create_trace( array( 'id' => 'test', 'name' => 'test' ) );
+
+		// Should fail on first attempt, not retry.
+		$this->assertNull( $result );
+		$this->assertEquals( 1, $call_count );
+	}
+
+	/**
+	 * Test that API key and workspace are included in headers.
+	 */
+	public function test_headers_include_credentials(): void {
+		$client = new \PRAutoBlogger_Opik_Client(
+			'secret-key-12345',
+			'my-workspace'
+		);
+
+		$captured_headers = null;
+		Functions\when( 'wp_remote_post' )->alias(
+			function( $url, $args ) use ( &$captured_headers ) {
+				$captured_headers = $args['headers'] ?? array();
+				return array(
+					'response' => array( 'code' => 200 ),
+					'body'     => wp_json_encode( array() ),
+				);
+			}
+		);
+
+		Functions\when( 'wp_remote_retrieve_response_code' )->justReturn( 200 );
+		Functions\when( 'wp_remote_retrieve_body' )->justReturn( wp_json_encode( array() ) );
+		Functions\when( 'wp_json_encode' )->alias( 'json_encode' );
+		Functions\when( 'is_wp_error' )->justReturn( false );
+
+		$client->create_trace( array( 'id' => 'test', 'name' => 'test' ) );
+
+		$this->assertIsArray( $captured_headers );
+		$this->assertArrayHasKey( 'Authorization', $captured_headers );
+		$this->assertEquals( 'secret-key-12345', $captured_headers['Authorization'] );
+		$this->assertArrayHasKey( 'Comet-Workspace', $captured_headers );
+		$this->assertEquals( 'my-workspace', $captured_headers['Comet-Workspace'] );
+	}
+}

tests/unit/Services/test-opik-dispatcher.php

@@ -0,0 +1,241 @@
+<?php
+declare(strict_types=1);
+
+/**
+ * Unit tests for PRAutoBlogger_Opik_Dispatcher.
+ *
+ * @see includes/services/opik/class-opik-dispatcher.php
+ */
+namespace PRAutoBlogger\Tests\Services;
+
+use PRAutoBlogger\Tests\BaseTestCase;
+use Brain\Monkey\Functions;
+
+/**
+ * @group opik
+ * @group services
+ */
+class TestOpikDispatcher extends BaseTestCase {
+
+	private array $option_store = array();
+
+	protected function setUp(): void {
+		parent::setUp();
+
+		// Mock WP options.
+		Functions\when( 'get_option' )->alias(
+			function( $option, $default = false ) {
+				return $this->option_store[ $option ] ?? $default;
+			}
+		);
+
+		Functions\when( 'update_option' )->alias(
+			function( $option, $value ) {
+				$this->option_store[ $option ] = $value;
+				return true;
+			}
+		);
+
+		Functions\when( 'delete_option' )->alias(
+			function( $option ) {
+				unset( $this->option_store[ $option ] );
+				return true;
+			}
+		);
+	}
+
+	/**
+	 * Test dispatcher skips if Opik is not enabled.
+	 */
+	public function test_dispatch_skips_if_disabled(): void {
+		$client = $this->create_mock_client();
+		$queue  = $this->create_mock_queue();
+
+		// Queue has items but feature is disabled.
+		$this->option_store['prautoblogger_opik_enabled'] = false;
+
+		$dispatcher = new \PRAutoBlogger_Opik_Dispatcher( $client, $queue );
+		$dispatcher->dispatch();
+
+		// Client should not have been called.
+		$this->assertTrue( true );
+	}
+
+	/**
+	 * Test dispatch() batches and posts spans.
+	 */
+	public function test_dispatch_posts_spans(): void {
+		// Enable Opik and set credentials.
+		$this->option_store['prautoblogger_opik_enabled'] = true;
+
+		// Mock constants.
+		if ( ! defined( 'PRAUTOBLOGGER_OPIK_API_KEY' ) ) {
+			define( 'PRAUTOBLOGGER_OPIK_API_KEY', 'test-key' );
+		}
+		if ( ! defined( 'PRAUTOBLOGGER_OPIK_WORKSPACE' ) ) {
+			define( 'PRAUTOBLOGGER_OPIK_WORKSPACE', 'test-workspace' );
+		}
+
+		$posted_spans = null;
+
+		$client = $this->getMockBuilder( \PRAutoBlogger_Opik_Client::class )
+			->disableOriginalConstructor()
+			->onlyMethods( array( 'batch_create_spans', 'batch_create_traces' ) )
+			->getMock();
+
+		$client->expects( $this->once() )
+			->method( 'batch_create_spans' )
+			->willReturnCallback( function( $spans ) use ( &$posted_spans ) {
+				$posted_spans = $spans;
+				return array( 'inserted' => count( $spans ) );
+			} );
+
+		$queue = $this->getMockBuilder( \PRAutoBlogger_Opik_Span_Queue::class )
+			->disableOriginalConstructor()
+			->onlyMethods( array( 'dequeue', 'get_queue_depth' ) )
+			->getMock();
+
+		$queue->expects( $this->once() )
+			->method( 'dequeue' )
+			->with( 100 )
+			->willReturn(
+				array(
+					array(
+						'type'     => 'span',
+						'payload'  => array( 'id' => 'span-1', 'name' => 'test' ),
+						'attempt'  => 0,
+						'enqueued' => time(),
+					),
+				)
+			);
+
+		$queue->method( 'get_queue_depth' )->willReturn( 0 );
+
+		$dispatcher = new \PRAutoBlogger_Opik_Dispatcher( $client, $queue );
+		$dispatcher->dispatch();
+
+		$this->assertNotNull( $posted_spans );
+		$this->assertCount( 1, $posted_spans );
+	}
+
+	/**
+	 * Test dispatcher handles empty queue gracefully.
+	 */
+	public function test_dispatch_handles_empty_queue(): void {
+		$this->option_store['prautoblogger_opik_enabled'] = true;
+
+		if ( ! defined( 'PRAUTOBLOGGER_OPIK_API_KEY' ) ) {
+			define( 'PRAUTOBLOGGER_OPIK_API_KEY', 'test-key' );
+		}
+		if ( ! defined( 'PRAUTOBLOGGER_OPIK_WORKSPACE' ) ) {
+			define( 'PRAUTOBLOGGER_OPIK_WORKSPACE', 'test-workspace' );
+		}
+
+		$client = $this->create_mock_client();
+		$queue  = $this->create_mock_queue( array() );
+
+		$dispatcher = new \PRAutoBlogger_Opik_Dispatcher( $client, $queue );
+		$dispatcher->dispatch();
+
+		// Should not error.
+		$this->assertTrue( true );
+	}
+
+	/**
+	 * Test dispatcher separates spans and traces.
+	 */
+	public function test_dispatch_separates_types(): void {
+		$this->option_store['prautoblogger_opik_enabled'] = true;
+
+		if ( ! defined( 'PRAUTOBLOGGER_OPIK_API_KEY' ) ) {
+			define( 'PRAUTOBLOGGER_OPIK_API_KEY', 'test-key' );
+		}
+		if ( ! defined( 'PRAUTOBLOGGER_OPIK_WORKSPACE' ) ) {
+			define( 'PRAUTOBLOGGER_OPIK_WORKSPACE', 'test-workspace' );
+		}
+
+		$posted_traces = null;
+		$posted_spans  = null;
+
+		$client = $this->getMockBuilder( \PRAutoBlogger_Opik_Client::class )
+			->disableOriginalConstructor()
+			->onlyMethods( array( 'batch_create_traces', 'batch_create_spans' ) )
+			->getMock();
+
+		$client->method( 'batch_create_traces' )->willReturnCallback(
+			function( $traces ) use ( &$posted_traces ) {
+				$posted_traces = $traces;
+				return array( 'inserted' => count( $traces ) );
+			}
+		);
+
+		$client->method( 'batch_create_spans' )->willReturnCallback(
+			function( $spans ) use ( &$posted_spans ) {
+				$posted_spans = $spans;
+				return array( 'inserted' => count( $spans ) );
+			}
+		);
+
+		$queue = $this->getMockBuilder( \PRAutoBlogger_Opik_Span_Queue::class )
+			->disableOriginalConstructor()
+			->onlyMethods( array( 'dequeue', 'get_queue_depth' ) )
+			->getMock();
+
+		$queue->method( 'dequeue' )->willReturn(
+			array(
+				array(
+					'type'     => 'trace',
+					'payload'  => array( 'id' => 'trace-1' ),
+					'attempt'  => 0,
+					'enqueued' => time(),
+				),
+				array(
+					'type'     => 'span',
+					'payload'  => array( 'id' => 'span-1' ),
+					'attempt'  => 0,
+					'enqueued' => time(),
+				),
+			)
+		);
+
+		$queue->method( 'get_queue_depth' )->willReturn( 0 );
+
+		$dispatcher = new \PRAutoBlogger_Opik_Dispatcher( $client, $queue );
+		$dispatcher->dispatch();
+
+		$this->assertNotNull( $posted_traces );
+		$this->assertCount( 1, $posted_traces );
+		$this->assertNotNull( $posted_spans );
+		$this->assertCount( 1, $posted_spans );
+	}
+
+	/**
+	 * Helper to create a mock client.
+	 */
+	private function create_mock_client() {
+		$client = $this->getMockBuilder( \PRAutoBlogger_Opik_Client::class )
+			->disableOriginalConstructor()
+			->onlyMethods( array( 'batch_create_spans', 'batch_create_traces' ) )
+			->getMock();
+
+		$client->method( 'batch_create_spans' )->willReturn( array() );
+		$client->method( 'batch_create_traces' )->willReturn( array() );
+
+		return $client;
+	}
+
+	/**
+	 * Helper to create a mock queue.
+	 */
+	private function create_mock_queue( array $items = array() ) {
+		$queue = $this->getMockBuilder( \PRAutoBlogger_Opik_Span_Queue::class )
+			->disableOriginalConstructor()
+			->onlyMethods( array( 'dequeue', 'get_queue_depth' ) )
+			->getMock();
+
+		$queue->method( 'dequeue' )->willReturn( $items );
+		$queue->method( 'get_queue_depth' )->willReturn( count( $items ) );
+
+		return $queue;
+	}
+}

tests/unit/Services/test-opik-span-queue.php

@@ -0,0 +1,248 @@
+<?php
+declare(strict_types=1);
+
+/**
+ * Unit tests for PRAutoBlogger_Opik_Span_Queue.
+ *
+ * @see includes/services/opik/class-opik-span-queue.php
+ */
+namespace PRAutoBlogger\Tests\Services;
+
+use PRAutoBlogger\Tests\BaseTestCase;
+use Brain\Monkey\Functions;
+
+/**
+ * @group opik
+ * @group services
+ */
+class TestOpikSpanQueue extends BaseTestCase {
+
+	private array $option_store = array();
+
+	protected function setUp(): void {
+		parent::setUp();
+
+		// Mock WP options functions.
+		Functions\when( 'get_option' )->alias(
+			function( $option, $default = false ) {
+				return $this->option_store[ $option ] ?? $default;
+			}
+		);
+
+		Functions\when( 'update_option' )->alias(
+			function( $option, $value ) {
+				$this->option_store[ $option ] = $value;
+				return true;
+			}
+		);
+
+		Functions\when( 'delete_option' )->alias(
+			function( $option ) {
+				unset( $this->option_store[ $option ] );
+				return true;
+			}
+		);
+	}
+
+	/**
+	 * Test enqueue() adds item to queue.
+	 */
+	public function test_enqueue_adds_item(): void {
+		$queue = new \PRAutoBlogger_Opik_Span_Queue();
+
+		$payload = array(
+			'id'       => 'span-1',
+			'name'     => 'test',
+			'trace_id' => 'trace-1',
+		);
+
+		$success = $queue->enqueue( $payload, 'span' );
+
+		$this->assertTrue( $success );
+		$this->assertEquals( 1, $queue->get_queue_depth() );
+	}
+
+	/**
+	 * Test enqueue() respects max depth limit.
+	 */
+	public function test_enqueue_respects_max_depth(): void {
+		$queue = new \PRAutoBlogger_Opik_Span_Queue();
+
+		// Fill queue to max.
+		for ( $i = 0; $i < 1000; ++$i ) {
+			$success = $queue->enqueue(
+				array( 'id' => "span-$i", 'name' => 'test' ),
+				'span'
+			);
+			if ( ! $success ) {
+				// Queue full.
+				$this->assertEquals( 1000, $queue->get_queue_depth() );
+				return;
+			}
+		}
+
+		// If we got here, queue filled successfully.
+		$this->assertEquals( 1000, $queue->get_queue_depth() );
+
+		// Try to add one more — should fail.
+		$success = $queue->enqueue(
+			array( 'id' => 'overflow', 'name' => 'test' ),
+			'span'
+		);
+		$this->assertFalse( $success );
+	}
+
+	/**
+	 * Test dequeue() returns items in order.
+	 */
+	public function test_dequeue_returns_items(): void {
+		$queue = new \PRAutoBlogger_Opik_Span_Queue();
+
+		$queue->enqueue( array( 'id' => 'span-1' ), 'span' );
+		$queue->enqueue( array( 'id' => 'span-2' ), 'span' );
+		$queue->enqueue( array( 'id' => 'span-3' ), 'span' );
+
+		$batch = $queue->dequeue( 10 );
+
+		$this->assertCount( 3, $batch );
+		$this->assertEquals( 'span-1', $batch[0]['payload']['id'] );
+		$this->assertEquals( 'span-2', $batch[1]['payload']['id'] );
+		$this->assertEquals( 'span-3', $batch[2]['payload']['id'] );
+	}
+
+	/**
+	 * Test dequeue() respects limit parameter.
+	 */
+	public function test_dequeue_respects_limit(): void {
+		$queue = new \PRAutoBlogger_Opik_Span_Queue();
+
+		for ( $i = 1; $i <= 50; ++$i ) {
+			$queue->enqueue( array( 'id' => "span-$i" ), 'span' );
+		}
+
+		$batch = $queue->dequeue( 10 );
+
+		$this->assertCount( 10, $batch );
+		$this->assertEquals( 40, $queue->get_queue_depth() );
+	}
+
+	/**
+	 * Test reenqueue() increments attempt counter.
+	 */
+	public function test_reenqueue_increments_attempt(): void {
+		$queue = new \PRAutoBlogger_Opik_Span_Queue();
+
+		$items = array(
+			array(
+				'type'     => 'span',
+				'payload'  => array( 'id' => 'span-1' ),
+				'attempt'  => 0,
+				'enqueued' => time(),
+			),
+		);
+
+		$queue->reenqueue( $items );
+
+		$batch = $queue->dequeue( 10 );
+		$this->assertEquals( 1, $batch[0]['attempt'] );
+	}
+
+	/**
+	 * Test reenqueue() drops items after max retries.
+	 */
+	public function test_reenqueue_drops_after_max_attempts(): void {
+		$queue = new \PRAutoBlogger_Opik_Span_Queue();
+
+		$items = array(
+			array(
+				'type'     => 'span',
+				'payload'  => array( 'id' => 'span-1' ),
+				'attempt'  => 3,  // Already at max.
+				'enqueued' => time(),
+			),
+		);
+
+		$queue->reenqueue( $items );
+
+		// Item should be dropped, queue should be empty.
+		$this->assertEquals( 0, $queue->get_queue_depth() );
+	}
+
+	/**
+	 * Test dequeue() removes expired items (TTL > 12 hours).
+	 */
+	public function test_dequeue_removes_expired_items(): void {
+		$queue = new \PRAutoBlogger_Opik_Span_Queue();
+
+		$now = time();
+
+		// Add a fresh item.
+		$fresh = array(
+			'type'     => 'span',
+			'payload'  => array( 'id' => 'fresh' ),
+			'enqueued' => $now,
+		);
+
+		// Add an expired item (13 hours old).
+		$expired = array(
+			'type'     => 'span',
+			'payload'  => array( 'id' => 'expired' ),
+			'enqueued' => $now - 46800,  // 13 hours in seconds.
+		);
+
+		$this->option_store['prautoblogger_opik_queue'] = array( $fresh, $expired );
+
+		$batch = $queue->dequeue( 10 );
+
+		// Only fresh item should be returned.
+		$this->assertCount( 1, $batch );
+		$this->assertEquals( 'fresh', $batch[0]['payload']['id'] );
+	}
+
+	/**
+	 * Test get_queue_depth() returns item count.
+	 */
+	public function test_get_queue_depth(): void {
+		$queue = new \PRAutoBlogger_Opik_Span_Queue();
+
+		$this->assertEquals( 0, $queue->get_queue_depth() );
+
+		$queue->enqueue( array( 'id' => 'span-1' ), 'span' );
+		$this->assertEquals( 1, $queue->get_queue_depth() );
+
+		$queue->enqueue( array( 'id' => 'span-2' ), 'span' );
+		$this->assertEquals( 2, $queue->get_queue_depth() );
+	}
+
+	/**
+	 * Test clear() empties the queue.
+	 */
+	public function test_clear_empties_queue(): void {
+		$queue = new \PRAutoBlogger_Opik_Span_Queue();
+
+		$queue->enqueue( array( 'id' => 'span-1' ), 'span' );
+		$queue->enqueue( array( 'id' => 'span-2' ), 'span' );
+
+		$this->assertEquals( 2, $queue->get_queue_depth() );
+
+		$queue->clear();
+
+		$this->assertEquals( 0, $queue->get_queue_depth() );
+	}
+
+	/**
+	 * Test enqueue() with both span and trace types.
+	 */
+	public function test_enqueue_handles_trace_type(): void {
+		$queue = new \PRAutoBlogger_Opik_Span_Queue();
+
+		$queue->enqueue( array( 'id' => 'trace-1' ), 'trace' );
+		$queue->enqueue( array( 'id' => 'span-1' ), 'span' );
+
+		$batch = $queue->dequeue( 10 );
+
+		$this->assertCount( 2, $batch );
+		$this->assertEquals( 'trace', $batch[0]['type'] );
+		$this->assertEquals( 'span', $batch[1]['type'] );
+	}
+}

tests/unit/Services/test-opik-trace-context.php

@@ -0,0 +1,222 @@
+<?php
+declare(strict_types=1);
+
+/**
+ * Unit tests for PRAutoBlogger_Opik_Trace_Context.
+ *
+ * @see includes/services/opik/class-opik-trace-context.php
+ */
+namespace PRAutoBlogger\Tests\Services;
+
+use PRAutoBlogger\Tests\BaseTestCase;
+use Brain\Monkey\Functions;
+
+/**
+ * @group opik
+ * @group services
+ */
+class TestOpikTraceContext extends BaseTestCase {
+
+	protected function setUp(): void {
+		parent::setUp();
+
+		// Stub UUID generation.
+		Functions\when( 'wp_generate_uuid4' )->alias( function() {
+			static $counter = 0;
+			return 'uuid-' . ++$counter;
+		} );
+	}
+
+	protected function tearDown(): void {
+		// Clean up singleton.
+		\PRAutoBlogger_Opik_Trace_Context::teardown();
+		parent::tearDown();
+	}
+
+	/**
+	 * Test current() returns singleton instance.
+	 */
+	public function test_current_returns_singleton(): void {
+		$ctx1 = \PRAutoBlogger_Opik_Trace_Context::current();
+		$ctx2 = \PRAutoBlogger_Opik_Trace_Context::current();
+
+		$this->assertSame( $ctx1, $ctx2 );
+	}
+
+	/**
+	 * Test init_trace() generates a UUID.
+	 */
+	public function test_init_trace_generates_uuid(): void {
+		$ctx = \PRAutoBlogger_Opik_Trace_Context::current();
+		$trace_id = $ctx->init_trace();
+
+		$this->assertNotEmpty( $trace_id );
+		$this->assertStringStartsWith( 'uuid-', $trace_id );
+		$this->assertEquals( $trace_id, $ctx->get_trace_id() );
+	}
+
+	/**
+	 * Test start_span() creates span and returns ID.
+	 */
+	public function test_start_span_creates_span(): void {
+		$ctx = \PRAutoBlogger_Opik_Trace_Context::current();
+		$ctx->init_trace();
+
+		$span_id = $ctx->start_span(
+			array(
+				'name'     => 'draft_generation',
+				'type'     => 'llm',
+				'model'    => 'gpt-4',
+				'provider' => 'openrouter',
+				'input'    => array( 'prompt_hash' => 'sha256-abc' ),
+			)
+		);
+
+		$this->assertNotEmpty( $span_id );
+		$this->assertStringStartsWith( 'uuid-', $span_id );
+
+		$span = $ctx->get_span( $span_id );
+		$this->assertIsArray( $span );
+		$this->assertEquals( 'draft_generation', $span['name'] );
+		$this->assertEquals( 'llm', $span['type'] );
+		$this->assertEquals( 'gpt-4', $span['model'] );
+	}
+
+	/**
+	 * Test end_span() records output and usage.
+	 */
+	public function test_end_span_records_data(): void {
+		$ctx = \PRAutoBlogger_Opik_Trace_Context::current();
+		$ctx->init_trace();
+
+		$span_id = $ctx->start_span(
+			array(
+				'name' => 'test_span',
+				'type' => 'llm',
+			)
+		);
+
+		$ctx->end_span(
+			$span_id,
+			array(
+				'output' => array( 'response' => 'Hello world' ),
+				'usage'  => array(
+					'prompt_tokens'     => 50,
+					'completion_tokens' => 25,
+					'total_tokens'      => 75,
+				),
+			)
+		);
+
+		$span = $ctx->get_span( $span_id );
+		$this->assertIsArray( $span['output'] );
+		$this->assertEquals( 'Hello world', $span['output']['response'] );
+		$this->assertEquals( 75, $span['usage']['total_tokens'] );
+	}
+
+	/**
+	 * Test get_spans() returns all active spans.
+	 */
+	public function test_get_spans_returns_all(): void {
+		$ctx = \PRAutoBlogger_Opik_Trace_Context::current();
+		$ctx->init_trace();
+
+		$span1 = $ctx->start_span( array( 'name' => 'span1', 'type' => 'llm' ) );
+		$span2 = $ctx->start_span( array( 'name' => 'span2', 'type' => 'llm' ) );
+		$span3 = $ctx->start_span( array( 'name' => 'span3', 'type' => 'llm' ) );
+
+		$all_spans = $ctx->get_spans();
+
+		$this->assertCount( 3, $all_spans );
+		$this->assertArrayHasKey( $span1, $all_spans );
+		$this->assertArrayHasKey( $span2, $all_spans );
+		$this->assertArrayHasKey( $span3, $all_spans );
+	}
+
+	/**
+	 * Test finalize_trace() returns complete trace object.
+	 */
+	public function test_finalize_trace_includes_all_data(): void {
+		Functions\when( 'get_option' )->alias(
+			function( $option, $default = false ) {
+				if ( 'prautoblogger_opik_project_name' === $option ) {
+					return 'prautoblogger';
+				}
+				return $default;
+			}
+		);
+
+		$ctx = \PRAutoBlogger_Opik_Trace_Context::current();
+		$trace_id = $ctx->init_trace();
+
+		$span1 = $ctx->start_span( array( 'name' => 'step1', 'type' => 'llm' ) );
+		$ctx->end_span( $span1, array( 'output' => array( 'ok' => true ) ) );
+
+		$span2 = $ctx->start_span( array( 'name' => 'step2', 'type' => 'llm' ) );
+		$ctx->end_span( $span2, array( 'output' => array( 'ok' => true ) ) );
+
+		$trace = $ctx->finalize_trace();
+
+		$this->assertEquals( $trace_id, $trace['id'] );
+		$this->assertEquals( 'article_generation', $trace['name'] );
+		$this->assertEquals( 'prautoblogger', $trace['project_name'] );
+		$this->assertArrayHasKey( 'start_time', $trace );
+		$this->assertArrayHasKey( 'end_time', $trace );
+		$this->assertCount( 2, $trace['spans'] );
+	}
+
+	/**
+	 * Test teardown() clears the singleton.
+	 */
+	public function test_teardown_clears_singleton(): void {
+		$ctx1 = \PRAutoBlogger_Opik_Trace_Context::current();
+		$ctx1->init_trace();
+
+		\PRAutoBlogger_Opik_Trace_Context::teardown();
+
+		$ctx2 = \PRAutoBlogger_Opik_Trace_Context::current();
+
+		// Should be a new instance.
+		$this->assertNotSame( $ctx1, $ctx2 );
+		$this->assertEmpty( $ctx2->get_trace_id() );
+	}
+
+	/**
+	 * Test warning logged for ending unknown span.
+	 */
+	public function test_warning_for_unknown_span(): void {
+		$ctx = \PRAutoBlogger_Opik_Trace_Context::current();
+		$ctx->init_trace();
+
+		// Try to end a span that doesn't exist.
+		$ctx->end_span( 'unknown-uuid-12345' );
+
+		// If we got here without an exception, the warning was logged.
+		$this->assertTrue( true );
+	}
+
+	/**
+	 * Test span input is stored as-is (caller responsible for redaction).
+	 */
+	public function test_span_input_stored_as_is(): void {
+		$ctx = \PRAutoBlogger_Opik_Trace_Context::current();
+		$ctx->init_trace();
+
+		$input_data = array(
+			'prompt_hash' => 'sha256-abc123',
+			'model'       => 'gpt-4',
+			'version'     => '1.0',
+		);
+
+		$span_id = $ctx->start_span(
+			array(
+				'name'  => 'test',
+				'type'  => 'llm',
+				'input' => $input_data,
+			)
+		);
+
+		$span = $ctx->get_span( $span_id );
+		$this->assertEquals( $input_data, $span['input'] );
+	}
+}