diff --git a/backend/src/models/synthesis.rs b/backend/src/models/synthesis.rs
index 42f005a..2f09243 100644
--- a/backend/src/models/synthesis.rs
+++ b/backend/src/models/synthesis.rs
@@ -153,6 +153,8 @@ pub struct ScrapedNewsItem {
     pub original_title: String,
     #[serde(rename = "scrapedContent")]
     pub scraped_content: String,
+    #[serde(default)]
+    pub source_url: Option<String>,
 }
 
 #[cfg(test)]
diff --git a/backend/src/services/prompts.rs b/backend/src/services/prompts.rs
index e06ce72..a008347 100644
--- a/backend/src/services/prompts.rs
+++ b/backend/src/services/prompts.rs
@@ -402,6 +402,7 @@ mod tests {
                 summary: "A summary".into(),
                 original_title: "Original Test Article".into(),
                 scraped_content: "Full article text here...".into(),
+                source_url: None,
             }],
         );
 
@@ -453,6 +454,7 @@ mod tests {
                 summary: "s".into(),
                 original_title: "t".into(),
                 scraped_content: "OpenAI released GPT-5 today with major improvements".into(),
+                source_url: None,
             },
         ];
         let categories = vec!["AI News".to_string(), "Autre".to_string()];
@@ -470,7 +472,7 @@ mod tests {
             ScrapedNewsItem {
                 title: "T".into(), url: "https://a.com/1".into(),
                 summary: "s".into(), original_title: "t".into(),
-                scraped_content: "Content".into(),
+                scraped_content: "Content".into(), source_url: None,
             },
         ];
         let categories = vec!["AI News".to_string(), "Autre".to_string()];
diff --git a/backend/src/services/synthesis.rs b/backend/src/services/synthesis.rs
index bb64afa..cd7824c 100644
--- a/backend/src/services/synthesis.rs
+++ b/backend/src/services/synthesis.rs
@@ -386,6 +386,16 @@ async fn run_generation_inner(
             .await;
 
             // 1c. Filter empty content
+            // Trace articles with empty content
+            if settings.article_history_days > 0 {
+                for article in &scraped_articles {
+                    if article.scraped_content.trim().is_empty() {
+                        trace_article(&state.pool, user_id, job_id, &article.url, &article.title,
+                            "personalized_source", article.source_url.as_deref(), None, None,
+                            "filtered_empty", false).await;
+                    }
+                }
+            }
             let valid_articles: Vec<ScrapedNewsItem> = scraped_articles
                 .into_iter()
                 .filter(|a| !a.scraped_content.trim().is_empty())
@@ -393,6 +403,7 @@ async fn run_generation_inner(
 
             // 1d. Filter against article history (cross-synthesis dedup)
             let mut valid_articles = if settings.article_history_days > 0 {
+                let pre_history_articles = valid_articles.clone();
                 let hashes: Vec<String> = valid_articles.iter().map(|a| hash_article_url(&a.url)).collect();
                 let existing = db::article_history::check_urls_exist(&state.pool, user_id, &hashes)
                     .await
@@ -400,6 +411,16 @@ async fn run_generation_inner(
                 if !existing.is_empty() {
                     tracing::info!(filtered = existing.len(), "Phase 1: filtered articles already in history");
                 }
+                // Trace history-filtered articles
+                if !existing.is_empty() {
+                    for article in &pre_history_articles {
+                        if existing.contains(&hash_article_url(&article.url)) {
+                            trace_article(&state.pool, user_id, job_id, &article.url, &article.title,
+                                "personalized_source", article.source_url.as_deref(), None, None,
+                                "filtered_history", true).await;
+                        }
+                    }
+                }
                 valid_articles
                     .into_iter()
                     .filter(|a| !existing.contains(&hash_article_url(&a.url)))
@@ -515,6 +536,12 @@ async fn run_generation_inner(
                 // (reuse domain counting logic)
                 let max_per_source = settings.max_articles_per_source as usize;
                 let mut domain_counts: HashMap<String, usize> = HashMap::new();
+                // Collect items before diversity pruning for tracing
+                let pre_diversity_snapshot: Vec<ScrapedNewsItem> = if settings.article_history_days > 0 {
+                    all_scraped.values().flat_map(|items| items.iter().cloned()).collect()
+                } else {
+                    Vec::new()
+                };
                 for (_, items) in &mut all_scraped {
                     items.retain(|item| {
                         if let Some(domain) = extract_domain(&item.url) {
@@ -530,6 +557,19 @@ async fn run_generation_inner(
                         }
                     });
                 }
+                // Trace diversity-filtered articles
+                if settings.article_history_days > 0 {
+                    let post_urls: std::collections::HashSet<String> = all_scraped.values()
+                        .flat_map(|items| items.iter().map(|i| i.url.clone()))
+                        .collect();
+                    for article in &pre_diversity_snapshot {
+                        if !post_urls.contains(&article.url) {
+                            trace_article(&state.pool, user_id, job_id, &article.url, &article.title,
+                                "personalized_source", article.source_url.as_deref(), None, None,
+                                "filtered_diversity", true).await;
+                        }
+                    }
+                }
 
                 // Recount filled_counts after trimming
                 filled_counts.clear();
@@ -626,7 +666,28 @@ async fn run_generation_inner(
         // Parse + filter
         emit_progress(tx, "parsing", "Analyse des resultats...", 55);
         let parsed = parse_llm_output(&raw_results, &settings.categories)?;
+
+        // Trace homepage-filtered articles
+        let pre_homepage_parsed = if settings.article_history_days > 0 {
+            Some(parsed.clone())
+        } else {
+            None
+        };
         let parsed = filter_homepage_urls(parsed);
+        if let Some(ref pre) = pre_homepage_parsed {
+            let post_urls: std::collections::HashSet<String> = parsed.iter()
+                .flat_map(|(_, items)| items.iter().map(|i| i.url.clone()))
+                .collect();
+            for (_, items) in pre {
+                for item in items {
+                    if !post_urls.contains(&item.url) {
+                        trace_article(&state.pool, user_id, job_id, &item.url, &item.title,
+                            "web_search", None, None, None,
+                            "filtered_homepage", false).await;
+                    }
+                }
+            }
+        }
 
         // Cross-phase dedup: remove URLs already found in Phase 1
         let parsed: Vec<(String, Vec<NewsItem>)> = parsed
@@ -634,11 +695,36 @@ async fn run_generation_inner(
             .map(|(cat_key, items)| {
                 let deduped: Vec<NewsItem> = items
                     .into_iter()
-                    .filter(|item| !seen_urls.contains(&item.url.to_lowercase()))
+                    .filter(|item| {
+                        if seen_urls.contains(&item.url.to_lowercase()) {
+                            // Tracing is handled below for async context
+                            false
+                        } else {
+                            true
+                        }
+                    })
                     .collect();
                 (cat_key, deduped)
             })
             .collect();
+        // Trace cross-phase dedup drops (we need to check pre vs post since filter is sync)
+        if settings.article_history_days > 0 {
+            if let Some(ref pre) = pre_homepage_parsed {
+                let post_urls: std::collections::HashSet<String> = parsed.iter()
+                    .flat_map(|(_, items)| items.iter().map(|i| i.url.to_lowercase()))
+                    .collect();
+                for (_, items) in pre {
+                    for item in items {
+                        let lower = item.url.to_lowercase();
+                        if seen_urls.contains(&lower) && !post_urls.contains(&lower) {
+                            trace_article(&state.pool, user_id, job_id, &item.url, &item.title,
+                                "web_search", None, None, None,
+                                "filtered_cross_phase_dedup", false).await;
+                        }
+                    }
+                }
+            }
+        }
 
         let parsed = dedup_by_url(parsed);
         let parsed = limit_articles_per_source(parsed, settings.max_articles_per_source);
@@ -654,6 +740,16 @@ async fn run_generation_inner(
                 .unwrap_or_default();
             if !existing.is_empty() {
                 tracing::info!(filtered = existing.len(), "Phase 2: filtered articles already in history");
+                // Trace history-filtered articles
+                for (_, items) in &parsed {
+                    for item in items {
+                        if existing.contains(&hash_article_url(&item.url)) {
+                            trace_article(&state.pool, user_id, job_id, &item.url, &item.title,
+                                "web_search", None, None, None,
+                                "filtered_history", false).await;
+                        }
+                    }
+                }
             }
             parsed
                 .into_iter()
@@ -672,6 +768,18 @@ async fn run_generation_inner(
         // Scrape web search results
         emit_progress(tx, "scraping", "Verification des sources web...", 60);
         let scraped = scrape_articles(state, &parsed, settings.max_age_days as i64, tx, llm_for_scraping.clone()).await;
+        // Trace empty content drops from Phase 2 scraping
+        if settings.article_history_days > 0 {
+            for (_, items) in &scraped {
+                for item in items {
+                    if item.scraped_content.trim().is_empty() {
+                        trace_article(&state.pool, user_id, job_id, &item.url, &item.title,
+                            "web_search", None, None, None,
+                            "filtered_empty", false).await;
+                    }
+                }
+            }
+        }
         let scraped = filter_empty_scraped_articles(scraped);
 
         // Flatten scraped articles for classification
@@ -810,16 +918,15 @@ async fn run_generation_inner(
     let synthesis =
         db::syntheses::create(&state.pool, user_id, &week, &sections_json, job_id).await?;
 
-    // Record article URLs in history for cross-synthesis dedup
+    // Record used articles in history with full tracing metadata
     if settings.article_history_days > 0 {
-        let article_urls: Vec<(String, String)> = final_sections
-            .iter()
-            .flat_map(|section| section.items.iter())
-            .map(|item| (item.url.clone(), hash_article_url(&item.url)))
-            .collect();
-        db::article_history::insert_urls(&state.pool, user_id, &article_urls)
-            .await
-            .ok(); // Don't fail synthesis if history insert fails
+        for section in &final_sections {
+            for item in &section.items {
+                trace_article(&state.pool, user_id, job_id, &item.url, &item.title,
+                    "used", None, Some(&section.title), Some(synthesis.id),
+                    "used", true).await;
+            }
+        }
     }
 
     Ok(synthesis.id)
@@ -862,6 +969,36 @@ fn emit_progress(tx: &watch::Sender<ProgressEvent>, step: &str, message: &str, p
     .ok();
 }
 
+/// Insert a trace entry into article_history for debugging pipeline behavior.
+async fn trace_article(
+    pool: &sqlx::PgPool,
+    user_id: Uuid,
+    job_id: Uuid,
+    url: &str,
+    title: &str,
+    source_type: &str,
+    source_url: Option<&str>,
+    category: Option<&str>,
+    synthesis_id: Option<Uuid>,
+    status: &str,
+    scraped_ok: bool,
+) {
+    let entry = db::article_history::ArticleHistoryEntry {
+        user_id,
+        url: url.to_string(),
+        url_hash: hash_article_url(url),
+        title: title.to_string(),
+        source_type: source_type.to_string(),
+        source_url: source_url.map(|s| s.to_string()),
+        category: category.map(|s| s.to_string()),
+        synthesis_id,
+        status: status.to_string(),
+        scraped_ok,
+        job_id,
+    };
+    db::article_history::insert_entry(pool, &entry).await.ok();
+}
+
 /// Look up or create a per-user rate limiter stored in AppState.
 ///
 /// Returns `None` if the user has no rate limit overrides, in which case the
@@ -1393,6 +1530,7 @@ async fn scrape_articles(
                 summary: item.summary,
                 original_title: page_title,
                 scraped_content,
+                source_url: None,
             };
 
             result
@@ -1494,6 +1632,7 @@ async fn scrape_flat_urls(
                 summary: String::new(), // No LLM summary yet
                 original_title: page_title,
                 scraped_content,
+                source_url: None,
             });
         }
 
@@ -2266,17 +2405,17 @@ mod tests {
             ScrapedNewsItem {
                 title: "Good".into(), url: "https://a.com/1".into(),
                 summary: "s".into(), original_title: "t".into(),
-                scraped_content: "Real content here".into(),
+                scraped_content: "Real content here".into(), source_url: None,
             },
             ScrapedNewsItem {
                 title: "Empty".into(), url: "https://b.com/2".into(),
                 summary: "s".into(), original_title: "t".into(),
-                scraped_content: "".into(),
+                scraped_content: "".into(), source_url: None,
             },
             ScrapedNewsItem {
                 title: "Whitespace".into(), url: "https://c.com/3".into(),
                 summary: "s".into(), original_title: "t".into(),
-                scraped_content: "   ".into(),
+                scraped_content: "   ".into(), source_url: None,
             },
         ]);
 
@@ -2293,7 +2432,7 @@ mod tests {
             ScrapedNewsItem {
                 title: "A".into(), url: "https://a.com/1".into(),
                 summary: "s".into(), original_title: "t".into(),
-                scraped_content: "Content".into(),
+                scraped_content: "Content".into(), source_url: None,
             },
         ]);
 
@@ -2312,7 +2451,7 @@ mod tests {
             ScrapedNewsItem {
                 title: "T".into(), url: "https://real-source.com/article".into(),
                 summary: "s".into(), original_title: "t".into(),
-                scraped_content: "c".into(),
+                scraped_content: "c".into(), source_url: None,
             },
         ]);
 
@@ -2342,7 +2481,7 @@ mod tests {
             ScrapedNewsItem {
                 title: "T".into(), url: "https://correct.com/article".into(),
                 summary: "s".into(), original_title: "t".into(),
-                scraped_content: "c".into(),
+                scraped_content: "c".into(), source_url: None,
             },
         ]);
 
@@ -2473,8 +2612,8 @@ mod tests {
     fn classification_assigns_articles_to_categories() {
         use crate::models::synthesis::ScrapedNewsItem;
         let articles = vec![
-            ScrapedNewsItem { title: "A".into(), url: "https://a.com/1".into(), summary: "s".into(), original_title: "t".into(), scraped_content: "c".into() },
-            ScrapedNewsItem { title: "B".into(), url: "https://b.com/2".into(), summary: "s".into(), original_title: "t".into(), scraped_content: "c".into() },
+            ScrapedNewsItem { title: "A".into(), url: "https://a.com/1".into(), summary: "s".into(), original_title: "t".into(), scraped_content: "c".into(), source_url: None },
+            ScrapedNewsItem { title: "B".into(), url: "https://b.com/2".into(), summary: "s".into(), original_title: "t".into(), scraped_content: "c".into(), source_url: None },
         ];
         let categories = vec!["AI News".to_string(), "Autre".to_string()];
         let response = serde_json::json!({
@@ -2493,7 +2632,7 @@ mod tests {
     fn classification_unknown_category_goes_to_autre() {
         use crate::models::synthesis::ScrapedNewsItem;
         let articles = vec![
-            ScrapedNewsItem { title: "A".into(), url: "https://a.com/1".into(), summary: "s".into(), original_title: "t".into(), scraped_content: "c".into() },
+            ScrapedNewsItem { title: "A".into(), url: "https://a.com/1".into(), summary: "s".into(), original_title: "t".into(), scraped_content: "c".into(), source_url: None },
         ];
         let categories = vec!["AI News".to_string(), "Autre".to_string()];
         let response = serde_json::json!({
@@ -2509,7 +2648,7 @@ mod tests {
         use crate::models::synthesis::ScrapedNewsItem;
         let articles: Vec<ScrapedNewsItem> = (0..5).map(|i| ScrapedNewsItem {
             title: format!("Art{}", i), url: format!("https://a.com/{}", i),
-            summary: "s".into(), original_title: "t".into(), scraped_content: "c".into(),
+            summary: "s".into(), original_title: "t".into(), scraped_content: "c".into(), source_url: None,
         }).collect();
         let categories = vec!["AI News".to_string(), "Autre".to_string()];
         let response = serde_json::json!({
@@ -2528,7 +2667,7 @@ mod tests {
     fn classification_invalid_index_ignored() {
         use crate::models::synthesis::ScrapedNewsItem;
         let articles = vec![
-            ScrapedNewsItem { title: "A".into(), url: "https://a.com/1".into(), summary: "s".into(), original_title: "t".into(), scraped_content: "c".into() },
+            ScrapedNewsItem { title: "A".into(), url: "https://a.com/1".into(), summary: "s".into(), original_title: "t".into(), scraped_content: "c".into(), source_url: None },
         ];
         let categories = vec!["AI News".to_string(), "Autre".to_string()];
         let response = serde_json::json!({
@@ -2544,7 +2683,7 @@ mod tests {
     fn classification_case_insensitive() {
         use crate::models::synthesis::ScrapedNewsItem;
         let articles = vec![
-            ScrapedNewsItem { title: "A".into(), url: "https://a.com/1".into(), summary: "s".into(), original_title: "t".into(), scraped_content: "c".into() },
+            ScrapedNewsItem { title: "A".into(), url: "https://a.com/1".into(), summary: "s".into(), original_title: "t".into(), scraped_content: "c".into(), source_url: None },
         ];
         let categories = vec!["AI News".to_string(), "Autre".to_string()];
         let response = serde_json::json!({
@@ -2654,7 +2793,7 @@ mod tests {
         use crate::models::synthesis::ScrapedNewsItem;
         let articles: Vec<ScrapedNewsItem> = (0..6).map(|i| ScrapedNewsItem {
             title: format!("Art{}", i), url: format!("https://a.com/{}", i),
-            summary: "s".into(), original_title: "t".into(), scraped_content: "c".into(),
+            summary: "s".into(), original_title: "t".into(), scraped_content: "c".into(), source_url: None,
         }).collect();
         let categories = vec!["AI News".to_string(), "Autre".to_string()];
         let response = serde_json::json!({