feat: add source_diversity_window setting (migration + model + DB + validation tests)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

CLAUDE.md

@@ -117,7 +117,7 @@ cd frontend && npx tsc --noEmit
 - `GET /api/v1/admin/users` — user list
 - `PUT /api/v1/admin/users/:id/role` — role management
 
-## Database (12 migrations)
+## Database (13 migrations)
 Tables: `users`, `sessions`, `magic_link_tokens`, `user_settings`, `sources`, `syntheses`, `admin_providers`, `admin_rate_limits`, `user_api_keys`, `audit_log`
 
 ## Environment Variables

backend/migrations/20260323000013_add_source_diversity_window.sql

@@ -0,0 +1 @@
+ALTER TABLE settings ADD COLUMN source_diversity_window INTEGER NOT NULL DEFAULT 3;

backend/src/db/settings.rs

@@ -18,6 +18,7 @@ struct SettingsRow {
     categories: serde_json::Value,
     max_items_per_category: i32,
     max_articles_per_source: i32,
+    source_diversity_window: i32,
     search_agent_behavior: String,
     ai_provider: String,
     ai_model: String,
@@ -42,6 +43,7 @@ impl TryFrom<SettingsRow> for UserSettings {
             categories,
             max_items_per_category: row.max_items_per_category,
             max_articles_per_source: row.max_articles_per_source,
+            source_diversity_window: row.source_diversity_window,
             search_agent_behavior: row.search_agent_behavior,
             ai_provider: row.ai_provider,
             ai_model: row.ai_model,
@@ -68,10 +70,10 @@ pub async fn get_or_create_default(
 
     let row = sqlx::query_as::<_, SettingsRow>(
         r#"
-        INSERT INTO settings (user_id, theme, max_age_days, categories, max_items_per_category, search_agent_behavior, ai_provider, ai_model, ai_model_writing, rate_limit_max_requests, rate_limit_time_window_seconds, max_articles_per_source)
-        VALUES ($1, $2, $3, $4, $5, $6, $7, $8, $9, $10, $11, $12)
+        INSERT INTO settings (user_id, theme, max_age_days, categories, max_items_per_category, search_agent_behavior, ai_provider, ai_model, ai_model_writing, rate_limit_max_requests, rate_limit_time_window_seconds, max_articles_per_source, source_diversity_window)
+        VALUES ($1, $2, $3, $4, $5, $6, $7, $8, $9, $10, $11, $12, $13)
         ON CONFLICT (user_id) DO UPDATE SET user_id = settings.user_id
-        RETURNING user_id, theme, max_age_days, categories, max_items_per_category, search_agent_behavior, ai_provider, ai_model, ai_model_writing, rate_limit_max_requests, rate_limit_time_window_seconds, max_articles_per_source, updated_at
+        RETURNING user_id, theme, max_age_days, categories, max_items_per_category, search_agent_behavior, ai_provider, ai_model, ai_model_writing, rate_limit_max_requests, rate_limit_time_window_seconds, max_articles_per_source, source_diversity_window, updated_at
         "#,
     )
     .bind(user_id)
@@ -86,6 +88,7 @@ pub async fn get_or_create_default(
     .bind(defaults.rate_limit_max_requests)
     .bind(defaults.rate_limit_time_window_seconds)
     .bind(defaults.max_articles_per_source)
+    .bind(defaults.source_diversity_window)
     .fetch_one(pool)
     .await?;
 
@@ -104,8 +107,8 @@ pub async fn upsert(
 
     let row = sqlx::query_as::<_, SettingsRow>(
         r#"
-        INSERT INTO settings (user_id, theme, max_age_days, categories, max_items_per_category, search_agent_behavior, ai_provider, ai_model, ai_model_writing, rate_limit_max_requests, rate_limit_time_window_seconds, max_articles_per_source)
-        VALUES ($1, $2, $3, $4, $5, $6, $7, $8, $9, $10, $11, $12)
+        INSERT INTO settings (user_id, theme, max_age_days, categories, max_items_per_category, search_agent_behavior, ai_provider, ai_model, ai_model_writing, rate_limit_max_requests, rate_limit_time_window_seconds, max_articles_per_source, source_diversity_window)
+        VALUES ($1, $2, $3, $4, $5, $6, $7, $8, $9, $10, $11, $12, $13)
         ON CONFLICT (user_id) DO UPDATE SET
             theme = EXCLUDED.theme,
             max_age_days = EXCLUDED.max_age_days,
@@ -118,8 +121,9 @@ pub async fn upsert(
             rate_limit_max_requests = EXCLUDED.rate_limit_max_requests,
             rate_limit_time_window_seconds = EXCLUDED.rate_limit_time_window_seconds,
             max_articles_per_source = EXCLUDED.max_articles_per_source,
+            source_diversity_window = EXCLUDED.source_diversity_window,
             updated_at = now()
-        RETURNING user_id, theme, max_age_days, categories, max_items_per_category, search_agent_behavior, ai_provider, ai_model, ai_model_writing, rate_limit_max_requests, rate_limit_time_window_seconds, max_articles_per_source, updated_at
+        RETURNING user_id, theme, max_age_days, categories, max_items_per_category, search_agent_behavior, ai_provider, ai_model, ai_model_writing, rate_limit_max_requests, rate_limit_time_window_seconds, max_articles_per_source, source_diversity_window, updated_at
         "#,
     )
     .bind(user_id)
@@ -134,6 +138,7 @@ pub async fn upsert(
     .bind(req.rate_limit_max_requests)
     .bind(req.rate_limit_time_window_seconds)
     .bind(req.max_articles_per_source)
+    .bind(req.source_diversity_window)
     .fetch_one(pool)
     .await?;
 

backend/src/models/settings.rs

@@ -13,6 +13,7 @@ pub struct UserSettings {
     pub categories: Vec<String>,
     pub max_items_per_category: i32,
     pub max_articles_per_source: i32,
+    pub source_diversity_window: i32,
     pub search_agent_behavior: String,
     pub ai_provider: String,
     pub ai_model: String,
@@ -30,6 +31,7 @@ pub struct SettingsResponse {
     pub categories: Vec<String>,
     pub max_items_per_category: i32,
     pub max_articles_per_source: i32,
+    pub source_diversity_window: i32,
     pub search_agent_behavior: String,
     pub ai_provider: String,
     pub ai_model: String,
@@ -46,6 +48,7 @@ impl From<UserSettings> for SettingsResponse {
             categories: s.categories,
             max_items_per_category: s.max_items_per_category,
             max_articles_per_source: s.max_articles_per_source,
+            source_diversity_window: s.source_diversity_window,
             search_agent_behavior: s.search_agent_behavior,
             ai_provider: s.ai_provider,
             ai_model: s.ai_model,
@@ -64,6 +67,7 @@ pub struct UpdateSettingsRequest {
     pub categories: Vec<String>,
     pub max_items_per_category: i32,
     pub max_articles_per_source: i32,
+    pub source_diversity_window: i32,
     pub search_agent_behavior: String,
     pub ai_provider: String,
     pub ai_model: String,
@@ -110,6 +114,9 @@ impl UpdateSettingsRequest {
         if !(1..=10).contains(&self.max_articles_per_source) {
             return Err("max_articles_per_source must be between 1 and 10".into());
         }
+        if !(0..=10).contains(&self.source_diversity_window) {
+            return Err("source_diversity_window must be between 0 and 10".into());
+        }
         if self.search_agent_behavior.len() > 2000 {
             return Err("search_agent_behavior must be at most 2000 characters".into());
         }
@@ -152,6 +159,7 @@ impl Default for UserSettings {
             ],
             max_items_per_category: 4,
             max_articles_per_source: 3,
+            source_diversity_window: 3,
             search_agent_behavior: String::new(),
             ai_provider: String::new(),
             ai_model: String::new(),
@@ -175,6 +183,7 @@ mod tests {
             categories: vec!["Category 1".into(), "Category 2".into()],
             max_items_per_category: 4,
             max_articles_per_source: 3,
+            source_diversity_window: 3,
             search_agent_behavior: String::new(),
             ai_provider: String::new(),
             ai_model: String::new(),
@@ -379,4 +388,32 @@ mod tests {
         let err = req.validate().unwrap_err();
         assert!(err.contains("ai_model_writing"));
     }
+
+    #[test]
+    fn test_source_diversity_window_zero_is_valid() {
+        let mut req = valid_request();
+        req.source_diversity_window = 0;
+        assert!(req.validate().is_ok());
+    }
+
+    #[test]
+    fn test_source_diversity_window_ten_is_valid() {
+        let mut req = valid_request();
+        req.source_diversity_window = 10;
+        assert!(req.validate().is_ok());
+    }
+
+    #[test]
+    fn test_source_diversity_window_below_range() {
+        let mut req = valid_request();
+        req.source_diversity_window = -1;
+        assert!(req.validate().is_err());
+    }
+
+    #[test]
+    fn test_source_diversity_window_above_range() {
+        let mut req = valid_request();
+        req.source_diversity_window = 11;
+        assert!(req.validate().is_err());
+    }
 }

backend/src/services/prompts.rs

@@ -145,6 +145,7 @@ mod tests {
             ],
             max_items_per_category: 4,
             max_articles_per_source: 3,
+            source_diversity_window: 3,
             search_agent_behavior: String::new(),
             ai_provider: String::new(),
             ai_model: String::new(),