fix: ensure permission/stats persist until explicit disconnect (#110)

Also includes cached tokens in cost calculations to provide more accurate billing estimates.

Reviewed-on: #110
Co-authored-by: Naomi Carrigan <commits@nhcarrigan.com>
Co-committed-by: Naomi Carrigan <commits@nhcarrigan.com>

src-tauri/src/stats.rs

@@ -154,6 +154,16 @@ pub struct UsageStats {
     // Achievement tracking
     #[serde(skip)]
     pub achievements: AchievementProgress,
+
+    // Track current in-flight request for cost estimation on interrupt
+    #[serde(skip)]
+    pub current_request_input: Option<String>,
+    #[serde(skip)]
+    pub current_request_output_chars: u64,
+    #[serde(skip)]
+    pub current_request_thinking_chars: u64,
+    #[serde(skip)]
+    pub current_request_tools: Vec<String>,
 }
 
 impl UsageStats {
@@ -163,13 +173,26 @@ impl UsageStats {
         stats
     }
 
-    pub fn add_usage(&mut self, input_tokens: u64, output_tokens: u64, model: &str) {
+    pub fn add_usage(
+        &mut self,
+        input_tokens: u64,
+        output_tokens: u64,
+        model: &str,
+        cache_creation_tokens: Option<u64>,
+        cache_read_tokens: Option<u64>,
+    ) {
         self.total_input_tokens += input_tokens;
         self.total_output_tokens += output_tokens;
         self.session_input_tokens += input_tokens;
         self.session_output_tokens += output_tokens;
 
-        let cost = calculate_cost(input_tokens, output_tokens, model);
+        let cost = calculate_cost(
+            input_tokens,
+            output_tokens,
+            model,
+            cache_creation_tokens,
+            cache_read_tokens,
+        );
         self.total_cost_usd += cost;
         self.session_cost_usd += cost;
 
@@ -439,6 +462,10 @@ impl UsageStats {
             potential_cache_hits: self.potential_cache_hits,
             potential_cache_savings_tokens: self.potential_cache_savings_tokens,
             achievements: AchievementProgress::new(), // Dummy for copy
+            current_request_input: None, // Don't copy tracking fields
+            current_request_output_chars: 0,
+            current_request_thinking_chars: 0,
+            current_request_tools: Vec::new(),
         };
         check_achievements(&stats_copy, &mut self.achievements)
     }
@@ -462,7 +489,14 @@ fn is_consecutive_day(prev_date: &str, current_date: &str) -> bool {
 
 // Pricing as of February 2026
 // https://platform.claude.com/docs/en/about-claude/models/overview
-pub fn calculate_cost(input_tokens: u64, output_tokens: u64, model: &str) -> f64 {
+// Cache pricing: https://platform.claude.com/docs/en/build-with-claude/prompt-caching
+pub fn calculate_cost(
+    input_tokens: u64,
+    output_tokens: u64,
+    model: &str,
+    cache_creation_tokens: Option<u64>,
+    cache_read_tokens: Option<u64>,
+) -> f64 {
     let (input_price_per_million, output_price_per_million) = match model {
         // Current generation (Claude 4.5)
         "claude-opus-4-5-20251101" => (5.0, 25.0),
@@ -487,10 +521,25 @@ pub fn calculate_cost(input_tokens: u64, output_tokens: u64, model: &str) -> f64
         _ => (3.0, 15.0),
     };
 
+    // Regular input/output tokens
     let input_cost = (input_tokens as f64 / 1_000_000.0) * input_price_per_million;
     let output_cost = (output_tokens as f64 / 1_000_000.0) * output_price_per_million;
 
-    input_cost + output_cost
+    // Cache write tokens (cache creation) cost 1.25x the base input price
+    let cache_write_cost = if let Some(cache_creation) = cache_creation_tokens {
+        (cache_creation as f64 / 1_000_000.0) * input_price_per_million * 1.25
+    } else {
+        0.0
+    };
+
+    // Cache read tokens cost 0.1x (10%) the base input price
+    let cache_read_cost = if let Some(cache_read) = cache_read_tokens {
+        (cache_read as f64 / 1_000_000.0) * input_price_per_million * 0.1
+    } else {
+        0.0
+    };
+
+    input_cost + output_cost + cache_write_cost + cache_read_cost
 }
 
 #[derive(Debug, Clone, Serialize, Deserialize)]
@@ -609,7 +658,7 @@ mod tests {
 
     #[test]
     fn test_cost_calculation_sonnet() {
-        let cost = calculate_cost(1000, 2000, "claude-sonnet-4-20250514");
+        let cost = calculate_cost(1000, 2000, "claude-sonnet-4-20250514", None, None);
         // 1000 input * $3/M = $0.003
         // 2000 output * $15/M = $0.030
         // Total = $0.033
@@ -618,7 +667,7 @@ mod tests {
 
     #[test]
     fn test_cost_calculation_opus() {
-        let cost = calculate_cost(1000, 2000, "claude-opus-4-20250514");
+        let cost = calculate_cost(1000, 2000, "claude-opus-4-20250514", None, None);
         // 1000 input * $15/M = $0.015
         // 2000 output * $75/M = $0.150
         // Total = $0.165
@@ -627,7 +676,7 @@ mod tests {
 
     #[test]
     fn test_cost_calculation_opus_45() {
-        let cost = calculate_cost(1000, 2000, "claude-opus-4-5-20251101");
+        let cost = calculate_cost(1000, 2000, "claude-opus-4-5-20251101", None, None);
         // Opus 4.5 pricing: $5/MTok input, $25/MTok output
         // 1000 input tokens = $0.005, 2000 output tokens = $0.05
         // Total = $0.055
@@ -636,7 +685,7 @@ mod tests {
 
     #[test]
     fn test_cost_calculation_haiku() {
-        let cost = calculate_cost(1000, 2000, "claude-3-5-haiku-20241022");
+        let cost = calculate_cost(1000, 2000, "claude-3-5-haiku-20241022", None, None);
         // 1000 input * $1/M = $0.001
         // 2000 output * $5/M = $0.010
         // Total = $0.011
@@ -645,14 +694,14 @@ mod tests {
 
     #[test]
     fn test_cost_calculation_unknown_defaults_to_sonnet() {
-        let cost = calculate_cost(1000, 2000, "some-unknown-model");
+        let cost = calculate_cost(1000, 2000, "some-unknown-model", None, None);
         // Should default to Sonnet pricing
         assert!((cost - 0.033).abs() < 0.0001);
     }
 
     #[test]
     fn test_cost_calculation_legacy_sonnet() {
-        let cost = calculate_cost(1000, 2000, "claude-3-5-sonnet-20241022");
+        let cost = calculate_cost(1000, 2000, "claude-3-5-sonnet-20241022", None, None);
         // Same as Sonnet 4 pricing
         assert!((cost - 0.033).abs() < 0.0001);
     }
@@ -660,7 +709,7 @@ mod tests {
     #[test]
     fn test_usage_stats_accumulation() {
         let mut stats = UsageStats::new();
-        stats.add_usage(1000, 2000, "claude-sonnet-4-20250514");
+        stats.add_usage(1000, 2000, "claude-sonnet-4-20250514", None, None);
 
         assert_eq!(stats.total_input_tokens, 1000);
         assert_eq!(stats.total_output_tokens, 2000);
@@ -672,8 +721,8 @@ mod tests {
     #[test]
     fn test_usage_stats_multiple_accumulations() {
         let mut stats = UsageStats::new();
-        stats.add_usage(1000, 1000, "claude-sonnet-4-20250514");
-        stats.add_usage(500, 500, "claude-sonnet-4-20250514");
+        stats.add_usage(1000, 1000, "claude-sonnet-4-20250514", None, None);
+        stats.add_usage(500, 500, "claude-sonnet-4-20250514", None, None);
 
         assert_eq!(stats.total_input_tokens, 1500);
         assert_eq!(stats.total_output_tokens, 1500);
@@ -684,17 +733,17 @@ mod tests {
     #[test]
     fn test_usage_stats_model_updated() {
         let mut stats = UsageStats::new();
-        stats.add_usage(1000, 1000, "claude-sonnet-4-20250514");
+        stats.add_usage(1000, 1000, "claude-sonnet-4-20250514", None, None);
         assert_eq!(stats.model, Some("claude-sonnet-4-20250514".to_string()));
 
-        stats.add_usage(500, 500, "claude-opus-4-20250514");
+        stats.add_usage(500, 500, "claude-opus-4-20250514", None, None);
         assert_eq!(stats.model, Some("claude-opus-4-20250514".to_string()));
     }
 
     #[test]
     fn test_session_reset() {
         let mut stats = UsageStats::new();
-        stats.add_usage(1000, 2000, "claude-sonnet-4-20250514");
+        stats.add_usage(1000, 2000, "claude-sonnet-4-20250514", None, None);
         stats.reset_session();
 
         assert_eq!(stats.total_input_tokens, 1000);
@@ -921,7 +970,7 @@ mod tests {
     #[test]
     fn test_usage_stats_serialization() {
         let mut stats = UsageStats::new();
-        stats.add_usage(1000, 2000, "claude-sonnet-4-20250514");
+        stats.add_usage(1000, 2000, "claude-sonnet-4-20250514", None, None);
         stats.increment_messages();
 
         // UsageStats should be serializable (for events)
@@ -950,7 +999,7 @@ mod tests {
     #[test]
     fn test_stats_update_event_serialization() {
         let mut stats = UsageStats::new();
-        stats.add_usage(100, 200, "claude-sonnet-4-20250514");
+        stats.add_usage(100, 200, "claude-sonnet-4-20250514", None, None);
 
         let event = StatsUpdateEvent { stats };
         let json = serde_json::to_string(&event).expect("Failed to serialize");
@@ -1004,7 +1053,7 @@ mod tests {
     #[test]
     fn test_context_tracking_update() {
         let mut stats = UsageStats::new();
-        stats.add_usage(50_000, 10_000, "claude-sonnet-4-20250514");
+        stats.add_usage(50_000, 10_000, "claude-sonnet-4-20250514", None, None);
 
         assert_eq!(stats.context_tokens_used, 50_000);
         assert_eq!(stats.context_window_limit, 200_000);
@@ -1014,8 +1063,8 @@ mod tests {
     #[test]
     fn test_context_tracking_accumulates() {
         let mut stats = UsageStats::new();
-        stats.add_usage(50_000, 10_000, "claude-sonnet-4-20250514");
-        stats.add_usage(50_000, 10_000, "claude-sonnet-4-20250514");
+        stats.add_usage(50_000, 10_000, "claude-sonnet-4-20250514", None, None);
+        stats.add_usage(50_000, 10_000, "claude-sonnet-4-20250514", None, None);
 
         assert_eq!(stats.context_tokens_used, 100_000);
         assert!((stats.context_utilisation_percent - 50.0).abs() < 0.1);
@@ -1079,7 +1128,7 @@ mod tests {
     #[test]
     fn test_context_reset_on_session_reset() {
         let mut stats = UsageStats::new();
-        stats.add_usage(100_000, 20_000, "claude-sonnet-4-20250514");
+        stats.add_usage(100_000, 20_000, "claude-sonnet-4-20250514", None, None);
 
         assert!(stats.context_tokens_used > 0);
         assert!(stats.context_utilisation_percent > 0.0);