feat(billing): add billing_mode to providers (postpaid support) & UI/migration

migrations/001-add-billing-mode.sql

@@ -0,0 +1,13 @@
+-- Migration: add billing_mode to provider_configs
+-- Adds a billing_mode TEXT column with default 'prepaid'
+-- After applying, set Gemini to postpaid with:
+--   UPDATE provider_configs SET billing_mode = 'postpaid' WHERE id = 'gemini';
+
+BEGIN TRANSACTION;
+
+ALTER TABLE provider_configs ADD COLUMN billing_mode TEXT DEFAULT 'prepaid';
+
+COMMIT;
+
+-- NOTE: If you use a production SQLite file, run the following to set Gemini to postpaid:
+-- sqlite3 /path/to/db.sqlite "UPDATE provider_configs SET billing_mode='postpaid' WHERE id='gemini';"

src/dashboard/providers.rs

@@ -17,6 +17,7 @@ pub(super) struct UpdateProviderRequest {
     pub(super) api_key: Option<String>,
     pub(super) credit_balance: Option<f64>,
     pub(super) low_credit_threshold: Option<f64>,
+    pub(super) billing_mode: Option<String>,
 }
 
 pub(super) async fn handle_get_providers(State(state): State<DashboardState>) -> Json<ApiResponse<serde_json::Value>> {
@@ -24,9 +25,10 @@ pub(super) async fn handle_get_providers(State(state): State<DashboardState>) ->
     let config = &state.app_state.config;
     let pool = &state.app_state.db_pool;
 
-    // Load all overrides from database
-    let db_configs_result =
-        sqlx::query("SELECT id, enabled, base_url, credit_balance, low_credit_threshold FROM provider_configs")
+    // Load all overrides from database (including billing_mode)
+    let db_configs_result = sqlx::query(
+        "SELECT id, enabled, base_url, credit_balance, low_credit_threshold, billing_mode FROM provider_configs",
+    )
     .fetch_all(pool)
     .await;
 
@@ -38,7 +40,8 @@ pub(super) async fn handle_get_providers(State(state): State<DashboardState>) ->
             let base_url: Option<String> = row.get("base_url");
             let balance: f64 = row.get("credit_balance");
             let threshold: f64 = row.get("low_credit_threshold");
-            db_configs.insert(id, (enabled, base_url, balance, threshold));
+            let billing_mode: Option<String> = row.get("billing_mode");
+            db_configs.insert(id, (enabled, base_url, balance, threshold, billing_mode));
         }
     }
 
@@ -80,15 +83,17 @@ pub(super) async fn handle_get_providers(State(state): State<DashboardState>) ->
 
         let mut balance = 0.0;
         let mut threshold = 5.0;
+        let mut billing_mode: Option<String> = None;
 
         // Apply database overrides
-        if let Some((db_enabled, db_url, db_balance, db_threshold)) = db_configs.get(id) {
+        if let Some((db_enabled, db_url, db_balance, db_threshold, db_billing)) = db_configs.get(id) {
             enabled = *db_enabled;
             if let Some(url) = db_url {
                 base_url = url.clone();
             }
             balance = *db_balance;
             threshold = *db_threshold;
+            billing_mode = db_billing.clone();
         }
 
         // Find models for this provider in registry
@@ -138,6 +143,7 @@ pub(super) async fn handle_get_providers(State(state): State<DashboardState>) ->
             "base_url": base_url,
             "credit_balance": balance,
             "low_credit_threshold": threshold,
+            "billing_mode": billing_mode,
             "last_used": None::<String>,
         }));
     }
@@ -185,10 +191,11 @@ pub(super) async fn handle_get_provider(
 
     let mut balance = 0.0;
     let mut threshold = 5.0;
+    let mut billing_mode: Option<String> = None;
 
     // Apply database overrides
     let db_config = sqlx::query(
-        "SELECT enabled, base_url, credit_balance, low_credit_threshold FROM provider_configs WHERE id = ?",
+        "SELECT enabled, base_url, credit_balance, low_credit_threshold, billing_mode FROM provider_configs WHERE id = ?",
     )
     .bind(&name)
     .fetch_optional(pool)
@@ -201,6 +208,7 @@ pub(super) async fn handle_get_provider(
         }
         balance = row.get::<f64, _>("credit_balance");
         threshold = row.get::<f64, _>("low_credit_threshold");
+        billing_mode = row.get::<Option<String>, _>("billing_mode");
     }
 
     // Find models for this provider
@@ -246,6 +254,7 @@ pub(super) async fn handle_get_provider(
         "base_url": base_url,
         "credit_balance": balance,
         "low_credit_threshold": threshold,
+        "billing_mode": billing_mode,
         "last_used": None::<String>,
     })))
 }
@@ -262,19 +271,20 @@ pub(super) async fn handle_update_provider(
 
     let pool = &state.app_state.db_pool;
 
-    // Update or insert into database
+    // Update or insert into database (include billing_mode)
     let result = sqlx::query(
         r#"
-        INSERT INTO provider_configs (id, display_name, enabled, base_url, api_key, credit_balance, low_credit_threshold)
-        VALUES (?, ?, ?, ?, ?, ?, ?)
+        INSERT INTO provider_configs (id, display_name, enabled, base_url, api_key, credit_balance, low_credit_threshold, billing_mode)
+        VALUES (?, ?, ?, ?, ?, ?, ?, ?)
         ON CONFLICT(id) DO UPDATE SET
             enabled = excluded.enabled,
             base_url = excluded.base_url,
             api_key = COALESCE(excluded.api_key, provider_configs.api_key),
             credit_balance = COALESCE(excluded.credit_balance, provider_configs.credit_balance),
             low_credit_threshold = COALESCE(excluded.low_credit_threshold, provider_configs.low_credit_threshold),
+            billing_mode = COALESCE(excluded.billing_mode, provider_configs.billing_mode),
             updated_at = CURRENT_TIMESTAMP
-        "#
+        "#,
     )
     .bind(&name)
     .bind(name.to_uppercase())
@@ -283,6 +293,7 @@ pub(super) async fn handle_update_provider(
     .bind(&payload.api_key)
     .bind(payload.credit_balance)
     .bind(payload.low_credit_threshold)
+    .bind(payload.billing_mode)
     .execute(pool)
     .await;
 

src/logging/mod.rs

@@ -100,9 +100,14 @@ impl RequestLogger {
         .execute(&mut *tx)
         .await?;
 
-        // Deduct from provider balance if successful (skip postpaid like Gemini)
-        if log.cost > 0.0 && log.provider != "gemini" {
-            sqlx::query("UPDATE provider_configs SET credit_balance = credit_balance - ? WHERE id = ?")
+        // Deduct from provider balance if successful.
+        // Providers configured with billing_mode = 'postpaid' will not have their
+        // credit_balance decremented. Use a conditional UPDATE so we don't need
+        // a prior SELECT and avoid extra round-trips.
+        if log.cost > 0.0 {
+            sqlx::query(
+                "UPDATE provider_configs SET credit_balance = credit_balance - ? WHERE id = ? AND (billing_mode IS NULL OR billing_mode != 'postpaid')",
+            )
             .bind(log.cost)
             .bind(&log.provider)
             .execute(&mut *tx)

static/js/pages/providers.js

@@ -70,6 +70,10 @@ class ProvidersPage {
                             <span>Balance: ${provider.id === 'ollama' ? 'FREE' : window.api.formatCurrency(provider.credit_balance)}</span>
                             ${isLowBalance ? '<i class="fas fa-exclamation-triangle" title="Low Balance"></i>' : ''}
                         </div>
+                        <div class="meta-item">
+                            <i class="fas fa-exchange-alt"></i>
+                            <span>Billing: ${provider.billing_mode ? provider.billing_mode.toUpperCase() : 'PREPAID'}</span>
+                        </div>
                         <div class="meta-item">
                             <i class="fas fa-clock"></i>
                             <span>Last used: ${provider.last_used ? window.api.formatTimeAgo(provider.last_used) : 'Never'}</span>
@@ -173,6 +177,13 @@ class ProvidersPage {
                                 <input type="number" id="provider-threshold" value="${provider.low_credit_threshold}" step="0.50">
                             </div>
                         </div>
+                        <div class="form-control">
+                            <label for="provider-billing-mode">Billing Mode</label>
+                            <select id="provider-billing-mode">
+                                <option value="prepaid" ${!provider.billing_mode || provider.billing_mode === 'prepaid' ? 'selected' : ''}>Prepaid</option>
+                                <option value="postpaid" ${provider.billing_mode === 'postpaid' ? 'selected' : ''}>Postpaid</option>
+                            </select>
+                        </div>
                 </div>
                 <div class="modal-footer">
                     <button class="btn btn-secondary" onclick="this.closest('.modal').remove()">Cancel</button>
@@ -189,6 +200,7 @@ class ProvidersPage {
             const apiKey = modal.querySelector('#provider-api-key').value;
                     const balance = parseFloat(modal.querySelector('#provider-balance').value);
                     const threshold = parseFloat(modal.querySelector('#provider-threshold').value);
+                    const billingMode = modal.querySelector('#provider-billing-mode').value;
             
             try {
                     await window.api.put(`/providers/${id}`, {
@@ -196,7 +208,8 @@ class ProvidersPage {
                         base_url: baseUrl || null,
                         api_key: apiKey || null,
                         credit_balance: isNaN(balance) ? null : balance,
-                    low_credit_threshold: isNaN(threshold) ? null : threshold
+                        low_credit_threshold: isNaN(threshold) ? null : threshold,
+                        billing_mode: billingMode || null,
                     });
                 
                 window.authManager.showToast(`${provider.name} configuration saved`, 'success');