perf(usage): coalesce session-sync notifications and serialize sync execution

Replace per-insert usage notifications with a single notification per
sync pass, guard all sync entry points (startup backfill, 60s loop,
manual sync) behind a process-wide single-flight tokio mutex, and move
blocking file/DB work onto spawn_blocking with MissedTickBehavior::Skip.

Extend SessionSyncResult with deferredFiles/suspectedDuplicates
observability fields (saturating aggregation) and add a test seam that
counts notifications even without an injected AppHandle.

src-tauri/src/services/session_usage.rs

@@ -22,18 +22,80 @@ use std::collections::HashMap;
 use std::fs;
 use std::io::{BufRead, BufReader};
 use std::path::{Path, PathBuf};
+use std::sync::OnceLock;
 use std::time::SystemTime;
 
 /// 同步结果
-#[derive(Debug, Clone, Serialize, Deserialize)]
+#[derive(Debug, Clone, Default, Serialize, Deserialize)]
 #[serde(rename_all = "camelCase")]
 pub struct SessionSyncResult {
     pub imported: u32,
     pub skipped: u32,
     pub files_scanned: u32,
+    pub suspected_duplicates: u32,
+    pub deferred_files: u32,
     pub errors: Vec<String>,
 }
 
+impl SessionSyncResult {
+    pub fn merge(&mut self, other: SessionSyncResult) {
+        self.imported = self.imported.saturating_add(other.imported);
+        self.skipped = self.skipped.saturating_add(other.skipped);
+        self.files_scanned = self.files_scanned.saturating_add(other.files_scanned);
+        self.suspected_duplicates = self
+            .suspected_duplicates
+            .saturating_add(other.suspected_duplicates);
+        self.deferred_files = self.deferred_files.saturating_add(other.deferred_files);
+        self.errors.extend(other.errors);
+    }
+}
+
+pub fn session_sync_mutex() -> &'static tokio::sync::Mutex<()> {
+    static LOCK: OnceLock<tokio::sync::Mutex<()>> = OnceLock::new();
+    LOCK.get_or_init(|| tokio::sync::Mutex::new(()))
+}
+
+fn merge_sync_step(
+    aggregate: &mut SessionSyncResult,
+    name: &str,
+    step: Result<SessionSyncResult, AppError>,
+) {
+    match step {
+        Ok(result) => aggregate.merge(result),
+        Err(error) => aggregate.errors.push(format!("{name} 同步失败: {error}")),
+    }
+}
+
+/// 调用方必须持有 [`session_sync_mutex`]。此函数是同步内核，供后台任务、
+/// 手动同步和 Codex 重建共享，避免 tokio Mutex 重入。
+pub fn sync_all_unlocked(db: &Database) -> SessionSyncResult {
+    let mut result = SessionSyncResult::default();
+    merge_sync_step(&mut result, "Claude", sync_claude_session_logs(db));
+    merge_sync_step(
+        &mut result,
+        "Codex",
+        crate::services::session_usage_codex::sync_codex_usage(db),
+    );
+    merge_sync_step(
+        &mut result,
+        "Gemini",
+        crate::services::session_usage_gemini::sync_gemini_usage(db),
+    );
+    merge_sync_step(
+        &mut result,
+        "OpenCode",
+        crate::services::session_usage_opencode::sync_opencode_usage(db),
+    );
+    notify_sync_result(&result);
+    result
+}
+
+pub(crate) fn notify_sync_result(result: &SessionSyncResult) {
+    if result.imported > 0 {
+        crate::usage_events::notify_log_recorded();
+    }
+}
+
 /// 数据来源分布
 #[derive(Debug, Clone, Serialize, Deserialize)]
 #[serde(rename_all = "camelCase")]
@@ -65,6 +127,8 @@ pub fn sync_claude_session_logs(db: &Database) -> Result<SessionSyncResult, AppE
             imported: 0,
             skipped: 0,
             files_scanned: 0,
+            suspected_duplicates: 0,
+            deferred_files: 0,
             errors: vec![],
         });
     }
@@ -73,6 +137,8 @@ pub fn sync_claude_session_logs(db: &Database) -> Result<SessionSyncResult, AppE
         imported: 0,
         skipped: 0,
         files_scanned: 0,
+        suspected_duplicates: 0,
+        deferred_files: 0,
         errors: vec![],
     };
 
@@ -513,12 +579,7 @@ fn insert_session_log_entry(
         )
         .map_err(|e| AppError::Database(format!("插入会话日志失败: {e}")))?;
 
-    // 仅在确实写入新行时通知前端，避免 INSERT OR IGNORE 跳过时产生空刷新
-    if inserted_rows > 0 {
-        crate::usage_events::notify_log_recorded();
-    }
-
-    Ok(true)
+    Ok(inserted_rows > 0)
 }
 
 /// 从 model_pricing 表查找模型定价（支持模糊匹配）
@@ -565,6 +626,26 @@ pub fn get_data_source_breakdown(db: &Database) -> Result<Vec<DataSourceSummary>
 mod tests {
     use super::*;
 
+    #[test]
+    fn sync_result_notification_is_coalesced_to_one_call() {
+        crate::usage_events::take_test_notify_count();
+        notify_sync_result(&SessionSyncResult::default());
+        let result = SessionSyncResult {
+            imported: 25,
+            ..SessionSyncResult::default()
+        };
+        notify_sync_result(&result);
+        assert_eq!(crate::usage_events::take_test_notify_count(), 1);
+    }
+
+    #[tokio::test]
+    async fn session_sync_mutex_serializes_callers() {
+        let first = session_sync_mutex().lock().await;
+        assert!(session_sync_mutex().try_lock().is_err());
+        drop(first);
+        assert!(session_sync_mutex().try_lock().is_ok());
+    }
+
     #[test]
     fn test_parse_usage_from_jsonl_line() {
         let line = r#"{"type":"assistant","message":{"id":"msg_test123","model":"claude-opus-4-6","usage":{"input_tokens":3,"output_tokens":150,"cache_read_input_tokens":5000,"cache_creation_input_tokens":10000},"stop_reason":"end_turn"},"timestamp":"2026-04-05T12:00:00Z","sessionId":"session-abc"}"#;

src-tauri/src/services/session_usage_codex.rs

@@ -307,6 +307,8 @@ pub fn sync_codex_usage(db: &Database) -> Result<SessionSyncResult, AppError> {
         skipped: 0,
         files_scanned: files.len() as u32,
         errors: vec![],
+        suspected_duplicates: 0,
+        deferred_files: 0,
     };
 
     if files.is_empty() {

src-tauri/src/services/session_usage_gemini.rs

@@ -46,6 +46,8 @@ pub fn sync_gemini_usage(db: &Database) -> Result<SessionSyncResult, AppError> {
         imported: 0,
         skipped: 0,
         files_scanned: files.len() as u32,
+        suspected_duplicates: 0,
+        deferred_files: 0,
         errors: vec![],
     };
 
@@ -351,9 +353,6 @@ fn insert_gemini_session_entry(
 
     // changes() > 0 表示新插入或已更新，== 0 表示值完全相同（无实际变更）
     let changed = conn.changes() > 0;
-    if changed {
-        crate::usage_events::notify_log_recorded();
-    }
     Ok(changed)
 }
 

src-tauri/src/services/session_usage_opencode.rs

@@ -50,6 +50,8 @@ pub fn sync_opencode_usage(db: &Database) -> Result<SessionSyncResult, AppError>
             imported: 0,
             skipped: 0,
             files_scanned: 0,
+            suspected_duplicates: 0,
+            deferred_files: 0,
             errors: vec![],
         });
     }
@@ -77,6 +79,8 @@ pub fn sync_opencode_usage(db: &Database) -> Result<SessionSyncResult, AppError>
             imported: 0,
             skipped: 0,
             files_scanned: 1,
+            suspected_duplicates: 0,
+            deferred_files: 0,
             errors: vec![],
         });
     }
@@ -90,6 +94,8 @@ pub fn sync_opencode_usage(db: &Database) -> Result<SessionSyncResult, AppError>
         imported: 0,
         skipped: 0,
         files_scanned: 1,
+        suspected_duplicates: 0,
+        deferred_files: 0,
         errors: vec![],
     };
     let mut has_sync_errors = false;