docs: add incremental session recovery design and implementation plan

docs/plans/2026-05-10-incremental-session-recovery-design.md

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+# 启动增量恢复设计
+
+## 问题
+
+PicoBot 重启后，`Session::from_storage()` 全量加载 `messages` 表，恢复的 history 可能直接超出上下文窗口，首次 LLM 调用即触发压缩，浪费 token。
+
+## 设计
+
+### 核心思路
+
+用 `last_compressed_message_at` 标记最后压缩时刻。恢复时：
+- 加载该标记之后的原始消息
+- 用该 session 的 Timeline 条目替代已压缩部分
+- `seq_counter` 统一从 SQLite 查 `MAX(seq) + 1`
+
+```
+messages 表                          memories(timeline)
+┌──────────────────────────┐         ┌───────────────────────────┐
+│ created_at = T1..T5      │ ← 跳过  │ session = feishu:oc:dialog │
+│ (压缩已覆盖，用Timeline替代)│       │ created_at 降序             │
+├──────────────────────────┤         ├───────────────────────────┤
+│ created_at > T6          │ ← 加载  │ 只取最近 3 条               │
+└──────────────────────────┘         └───────────────────────────┘
+```
+
+### 数据变更
+
+**`sessions` 表加列：**
+```sql
+last_compressed_message_at INTEGER
+```
+
+**`SessionMeta` / `Session` 加字段：** `last_compressed_message_at: Option<i64>`
+
+### Storage 层新增方法
+
+| 方法 | SQL |
+|------|-----|
+| `get_max_message_seq(session_id)` | `SELECT MAX(seq) FROM messages WHERE session_id = ?` |
+| `load_messages_after_timestamp(session_id, after_ts)` | `WHERE created_at > ?` |
+| `load_session_timelines(session_id, limit)` | `WHERE session_id = ? AND category = 'timeline' ORDER BY created_at DESC LIMIT ?` |
+
+### 压缩跟踪
+
+`compress_if_needed()` 返回值改为 `CompressionResult { history, created_timelines: bool }`。
+`compress_once()` 中 LLM 摘要路径才置 `true`（Tier 2），Tier 1/3 不产生 Timeline。
+
+**记录时机**（`handle_message` 正常流、溢出重试流、`/compact` 统一）：
+```rust
+if result.created_timelines {
+    session.last_compressed_message_at = Some(now());
+    session.persist_session_meta().await;
+}
+```
+
+### Session::from_storage() 恢复逻辑
+
+有压缩标记时：
+1. `load_session_timelines(limit=4)` → 取 3 条给 LLM，第 4 条判"有更多"
+2. 有更多 → 插入提示 user 消息
+3. 逐条插入 Timeline 为 `[Previous Context]` user 消息
+4. `load_messages_after_timestamp(after_ts)` → 原始尾消息
+5. `repair_tool_call_chains`
+
+无压缩标记 → 全量加载（现有行为）。
+
+统一：`seq_counter = MAX(seq) + 1`
+
+### 系统提示词
+
+`Session.last_compressed_message_at` 非空时追加：
+```
+## 历史会话
+之前的对话摘要已归档。如需回顾历史上下文，使用 `timeline_recall` 工具搜索。
+```
+
+## 改动清单
+
+| # | 文件 | 改动 |
+|---|------|------|
+| 1 | `storage/session.rs` | `SessionMeta` 加 `last_compressed_message_at` |
+| 2 | `storage/mod.rs` | DDL migration + upsert/get_session 加列 |
+| 3 | `storage/mod.rs` | 新增 `get_max_message_seq`, `load_messages_after_timestamp` |
+| 4 | `storage/memory.rs` | 新增 `load_session_timelines` |
+| 5 | `agent/context_compressor.rs` | 返回值改为 `CompressionResult` 含 `created_timelines` |
+| 6 | `session/session.rs` | `Session` 加字段，`persist_session_meta` 加字段 |
+| 7 | `session/session.rs` | `from_storage()` 重写恢复逻辑 |
+| 8 | `session/session.rs` | `handle_message()` 压缩后记录标记 |
+| 9 | `session/session.rs` | `/compact` 命令压缩后记录标记 |
+| 10 | `session/session.rs` | `build_system_prompt()` 注入 `last_compressed_message_at` |

docs/plans/2026-05-10-incremental-session-recovery.md

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+# 启动增量恢复 Implementation Plan
+
+> **For Claude:** REQUIRED SUB-SKILL: Use superpowers:executing-plans to implement this plan task-by-task.
+
+**Goal:** PicoBot 重启后不再全量加载 messages 表，而是基于 `last_compressed_message_at` 标记增量恢复，用 Timeline 替代已压缩部分。
+
+**Architecture:** 在 `sessions` 表加 `last_compressed_message_at` 列，`compress_if_needed` 返回值增加 `created_timelines` 标志，恢复时按时间戳增量加载消息并用近 3 条 Timeline 前置，`seq_counter` 统一从 SQLite 查 MAX(seq)。
+
+**Tech Stack:** Rust, sqlx (SQLite), tokio
+
+---
+
+### Task 1: SessionMeta 和数据库 DDL 加列
+
+**Files:**
+- Modify: `src/storage/session.rs:15`
+- Modify: `src/storage/mod.rs:44-45` (DDL), `:172-180` (migration)
+- Modify: `src/storage/mod.rs:317-326` (upsert_session SQL + ON CONFLICT)
+- Modify: `src/storage/mod.rs:345-369` (get_session SELECT + struct)
+- Modify: `src/storage/mod.rs:380-406`, `:454-479`, `:564-588`, `:728`, `:754` (list_sessions 及测试 mock)
+
+**Step 1: 在 `src/storage/session.rs` SessionMeta 加字段**
+
+在 `last_consolidated_at: Option<i64>` 后加一行：
+```rust
+pub last_compressed_message_at: Option<i64>,
+```
+
+**Step 2: DDL schema 加列**
+
+在 `src/storage/mod.rs` 的 CREATE TABLE sessions 中 (line 44)，`last_consolidated_at INTEGER` 后加逗号和：
+```sql
+last_compressed_message_at INTEGER
+```
+
+**Step 3: migration 加列**
+
+在 `src/storage/mod.rs` line 182 之后（现有 migration 的 `); .ok();` 之后），添加新 migration：
+```rust
+// Migration: add last_compressed_message_at column if not exists
+sqlx::query(
+    r#"ALTER TABLE sessions ADD COLUMN last_compressed_message_at INTEGER"#,
+)
+.execute(&self.pool)
+.await
+.ok();
+```
+
+**Step 4: upsert_session SQL 加列**
+
+`src/storage/mod.rs` line 317: INSERT 列列表加 `last_compressed_message_at`，VALUES 加 `?`，ON CONFLICT DO UPDATE SET 加 `last_compressed_message_at = excluded.last_compressed_message_at`。line 338 后加 `.bind(meta.last_compressed_message_at)`。
+
+**Step 5: get_session SELECT 加列**
+
+`src/storage/mod.rs` line 348: SELECT 列加 `last_compressed_message_at`。line 368 后加：
+```rust
+last_compressed_message_at: row.get("last_compressed_message_at"),
+```
+
+**Step 6: 其他 SELECT sessions 的地方（list_sessions 多个变体）**
+
+同样补 `last_compressed_message_at` 到 SELECT 列和 struct 构造。以及测试中的 mock SessionMeta 构造（line 728, 754 等）。
+
+**Step 7: 编译检查**
+
+```bash
+cargo check 2>&1
+```
+
+**Step 8: Commit**
+
+```bash
+git add src/storage/session.rs src/storage/mod.rs
+git commit -m "feat(storage): add last_compressed_message_at column to sessions"
+```
+
+---
+
+### Task 2: Storage 新增加载方法
+
+**Files:**
+- Modify: `src/storage/mod.rs` (在 load_messages 之后)
+- Modify: `src/storage/memory.rs` (在 cleanup_old_timelines 之后)
+
+**Step 1: `get_max_message_seq`**
+
+在 `src/storage/mod.rs` 中 `load_messages` 函数后面添加：
+```rust
+pub async fn get_max_message_seq(&self, session_id: &str) -> Result<i64, StorageError> {
+    let row = sqlx::query(
+        "SELECT COALESCE(MAX(seq), 0) as max_seq FROM messages WHERE session_id = ?",
+    )
+    .bind(session_id)
+    .fetch_one(self.pool())
+    .await?;
+    Ok(row.get::<i64, _>("max_seq"))
+}
+```
+
+**Step 2: `load_messages_after_timestamp`**
+
+```rust
+pub async fn load_messages_after_timestamp(
+    &self,
+    session_id: &str,
+    after_ts: i64,
+) -> Result<Vec<crate::storage::message::MessageMeta>, StorageError> {
+    let rows = sqlx::query(
+        r#"
+        SELECT id, session_id, seq, role, content, media_refs, tool_call_id, tool_name, tool_calls, source, created_at
+        FROM messages
+        WHERE session_id = ? AND created_at > ?
+        ORDER BY seq ASC
+        "#,
+    )
+    .bind(session_id)
+    .bind(after_ts)
+    .fetch_all(self.pool())
+    .await?;
+
+    Ok(rows.into_iter().map(|row| crate::storage::message::MessageMeta {
+        id: row.get("id"),
+        session_id: row.get("session_id"),
+        seq: row.get("seq"),
+        role: row.get("role"),
+        content: row.get("content"),
+        media_refs: row.get("media_refs"),
+        tool_call_id: row.get("tool_call_id"),
+        tool_name: row.get("tool_name"),
+        tool_calls: row.get("tool_calls"),
+        source: row.get("source"),
+        created_at: row.get("created_at"),
+    }).collect())
+}
+```
+
+**Step 3: `load_session_timelines`**
+
+在 `src/storage/memory.rs` 的 `cleanup_old_timelines` 之后（line 252 的 `}` 之前）添加：
+```rust
+pub async fn load_session_timelines(
+    &self,
+    session_id: &str,
+    limit: usize,
+) -> Result<Vec<MemoryEntry>, StorageError> {
+    let rows = sqlx::query(
+        r#"
+        SELECT id, key, content, category, importance,
+               session_id, created_at, updated_at
+        FROM memories
+        WHERE session_id = ? AND category = 'timeline'
+        ORDER BY created_at DESC
+        LIMIT ?
+        "#,
+    )
+    .bind(session_id)
+    .bind(limit as i64)
+    .fetch_all(self.pool())
+    .await?;
+
+    parse_memory_rows(&rows)
+}
+```
+
+**Step 4: 编译检查**
+
+```bash
+cargo check 2>&1
+```
+
+**Step 5: Commit**
+
+```bash
+git add src/storage/mod.rs src/storage/memory.rs
+git commit -m "feat(storage): add load_messages_after_timestamp, load_session_timelines, get_max_message_seq"
+```
+
+---
+
+### Task 3: ContextCompressor 引入 CompressionResult
+
+**Files:**
+- Modify: `src/agent/context_compressor.rs:172-274` (compress_if_needed)
+- Modify: `src/agent/context_compressor.rs:320-402` (compress_once)
+
+**Step 1: 定义 CompressionResult**
+
+在 context_compressor.rs 中 `ContextCompressor` struct 定义之后添加：
+```rust
+pub struct CompressionResult {
+    pub history: Vec<ChatMessage>,
+    pub created_timelines: bool,
+}
+```
+
+**Step 2: 修改 compress_if_needed 签名和返回**
+
+将 `pub async fn compress_if_needed(&self, mut history: Vec<ChatMessage>) -> Result<Vec<ChatMessage>, AgentError>` 改为：
+```rust
+pub async fn compress_if_needed(
+    &self,
+    mut history: Vec<ChatMessage>,
+) -> Result<CompressionResult, AgentError> {
+```
+
+内部的 `return Ok(history)` 改为 `return Ok(CompressionResult { history, created_timelines: false })`（Tier 1 fast trim 和不需要压缩时）。
+
+**Step 3: 修改 LLM summarization pass 部分**
+
+在压缩循环中维护一个 `created_timelines` 标志：
+```rust
+let mut created_timelines = false;
+for pass in 0..self.config.max_passes {
+    // ...
+    match self.compress_once(...).await {
+        Ok(Some(compressed)) => {
+            current_history = compressed;
+            created_timelines = true;
+        }
+        // ...
+    }
+}
+```
+
+最后返回：
+```rust
+Ok(CompressionResult { history: current_history, created_timelines })
+```
+
+**Step 4: 更新所有 compress_if_needed 调用方**
+
+所有 `compress_if_needed(history)` 改为 `compress_if_needed(history).await?.history`。在 `handle_message` 和 `/compact` 中还需要用到 `created_timelines`。
+
+**Step 5: 编译检查**
+
+```bash
+cargo check 2>&1
+```
+
+**Step 6: Commit**
+
+```bash
+git add src/agent/context_compressor.rs src/session/session.rs
+git commit -m "feat(compressor): return CompressionResult with created_timelines flag"
+```
+
+---
+
+### Task 4: Session 结构体和持久化
+
+**Files:**
+- Modify: `src/session/session.rs:52-74` (Session struct)
+- Modify: `src/session/session.rs:76-121` (Session::new)
+- Modify: `src/session/session.rs:298-320` (persist_session_meta)
+
+**Step 1: Session struct 加字段**
+
+在 `pub last_consolidated_at: Option<i64>` 后加：
+```rust
+pub last_compressed_message_at: Option<i64>,
+```
+
+**Step 2: Session::new 初始化**
+
+在 `last_consolidated_at: None` 后加：
+```rust
+last_compressed_message_at: None,
+```
+
+**Step 3: persist_session_meta 加字段**
+
+在 `last_consolidated_at: self.last_consolidated_at` 后加：
+```rust
+last_compressed_message_at: self.last_compressed_message_at,
+```
+
+**Step 4: 编译检查**
+
+```bash
+cargo check 2>&1
+```
+
+**Step 5: Commit**
+
+```bash
+git add src/session/session.rs
+git commit -m "feat(session): add last_compressed_message_at field to Session and persist"
+```
+
+---
+
+### Task 5: Session::from_storage() 增量恢复
+
+**Files:**
+- Modify: `src/session/session.rs:124-189` (from_storage)
+
+**Step 1: 重写 from_storage**
+
+替换现有实现为：
+
+```rust
+pub async fn from_storage(
+    id: UnifiedSessionId,
+    provider_config: LLMProviderConfig,
+    tools: Arc<ToolRegistry>,
+    storage: StdArc<Storage>,
+    memory_manager: Arc<crate::memory::MemoryManager>,
+) -> Result<Self, AgentError> {
+    let session_meta = storage.get_session(&id.to_string()).await
+        .map_err(|e| AgentError::Other(format!("failed to load session from storage: {}", e)))?;
+
+    let mut provider_box = create_provider(provider_config.clone())
+        .map_err(|e| AgentError::Other(format!("provider creation error: {}", e)))?;
+    provider_box.set_storage(storage.clone());
+    let provider: Arc<dyn LLMProvider> = Arc::from(provider_box);
+
+    let compressor_config = ContextCompressionConfig {
+        protect_first_n: 2,
+        ..Default::default()
+    };
+
+    let mut compressor = ContextCompressor::with_config(provider.clone(), provider_config.token_limit, compressor_config, memory_manager.clone());
+    compressor.set_session_id(Some(id.to_string()));
+
+    // Determine recovery strategy
+    let mut chat_messages: Vec<ChatMessage> = Vec::new();
+
+    if let Some(after_ts) = session_meta.last_compressed_message_at {
+        // Load last 4 timelines to determine if there are > 3
+        let timelines = storage
+            .load_session_timelines(&id.to_string(), 4)
+            .await
+            .unwrap_or_default();
+
+        let has_more_timelines = timelines.len() > 3;
+
+        // Insert hint if more timelines exist
+        if has_more_timelines {
+            chat_messages.push(ChatMessage::user(
+                "[Earlier conversation summaries exist. \
+                 Use `timeline_recall` to search if needed.]"
+            ));
+        }
+
+        // Insert latest 3 timelines as context (reversed: oldest first)
+        for tl in timelines.iter().take(3).rev() {
+            chat_messages.push(ChatMessage::user(format!(
+                "[Previous Context]\n{}", tl.content
+            )));
+        }
+
+        // Load raw messages after compressed timestamp
+        let tail = storage
+            .load_messages_after_timestamp(&id.to_string(), after_ts)
+            .await
+            .unwrap_or_default();
+
+        let mut tail_msgs: Vec<ChatMessage> = tail.into_iter().map(|m| {
+            ChatMessage {
+                id: m.id,
+                role: m.role,
+                content: m.content,
+                media_refs: m.media_refs.map(|refs| serde_json::from_str(&refs).unwrap_or_default()).unwrap_or_default(),
+                timestamp: m.created_at,
+                tool_call_id: m.tool_call_id,
+                tool_name: m.tool_name,
+                tool_calls: m.tool_calls
+                    .and_then(|tc| serde_json::from_str::<Vec<crate::providers::ToolCall>>(&tc).ok())
+                    .filter(|v| !v.is_empty()),
+                source: m.source.and_then(|s| serde_json::from_str(&s).ok()),
+            }
+        }).collect();
+
+        repair_tool_call_chains(&mut tail_msgs);
+        chat_messages.extend(tail_msgs);
+    } else {
+        // No prior compression — load all messages (existing behavior)
+        let messages = storage.load_messages(&id.to_string(), 0).await
+            .map_err(|e| AgentError::Other(format!("failed to load messages from storage: {}", e)))?;
+
+        chat_messages = messages.into_iter().map(|m| {
+            ChatMessage {
+                id: m.id,
+                role: m.role,
+                content: m.content,
+                media_refs: m.media_refs.map(|refs| serde_json::from_str(&refs).unwrap_or_default()).unwrap_or_default(),
+                timestamp: m.created_at,
+                tool_call_id: m.tool_call_id,
+                tool_name: m.tool_name,
+                tool_calls: m.tool_calls
+                    .and_then(|tc| serde_json::from_str::<Vec<crate::providers::ToolCall>>(&tc).ok())
+                    .filter(|v| !v.is_empty()),
+                source: m.source.and_then(|s| serde_json::from_str(&s).ok()),
+            }
+        }).collect();
+
+        repair_tool_call_chains(&mut chat_messages);
+    }
+
+    // seq_counter from actual DB max
+    let max_seq = storage
+        .get_max_message_seq(&id.to_string())
+        .await
+        .unwrap_or(0);
+    let seq_counter = max_seq + 1;
+    let total_message_count = session_meta.message_count;
+
+    Ok(Self {
+        id: id.clone(),
+        title: session_meta.title,
+        created_at: session_meta.created_at,
+        last_active_at: session_meta.last_active_at,
+        message_count: session_meta.message_count,
+        total_message_count,
+        messages: chat_messages,
+        seq_counter,
+        provider_config: provider_config.clone(),
+        provider: provider.clone(),
+        tools,
+        compressor,
+        storage: Some(storage),
+        routing_info: session_meta.routing_info.unwrap_or_default(),
+        last_consolidated_at: session_meta.last_consolidated_at,
+        last_compressed_message_at: session_meta.last_compressed_message_at,
+        memory_manager,
+    })
+}
+```
+
+**Step 2: 编译检查**
+
+```bash
+cargo check 2>&1
+```
+
+**Step 3: Commit**
+
+```bash
+git add src/session/session.rs
+git commit -m "feat(session): incremental recovery from storage using compressed timeline"
+```
+
+---
+
+### Task 6: 系统提示词加历史会话提示
+
+**Files:**
+- Modify: `src/agent/system_prompt.rs:289-304` (MemorySection)
+- Modify: `src/agent/system_prompt.rs:16-23` (PromptContext)
+- Modify: `src/agent/system_prompt.rs:343-358` (build_system_prompt free function)
+- Modify: `src/session/session.rs:411-426` (build_system_prompt)
+
+**Step 1: PromptContext 加 has_compressed_history 字段**
+
+```rust
+pub struct PromptContext<'a> {
+    pub workspace_dir: &'a Path,
+    pub model_name: &'a str,
+    pub tools: &'a ToolRegistry,
+    pub session_id: Option<&'a str>,
+    pub memory_context: Option<&'a str>,
+    pub has_compressed_history: bool,
+}
+```
+
+**Step 2: 加 HistorySection**
+
+在 MemorySection 后面添加：
+```rust
+pub struct HistorySection;
+
+impl PromptSection for HistorySection {
+    fn name(&self) -> &str {
+        "history"
+    }
+
+    fn build(&self, ctx: &PromptContext<'_>) -> String {
+        if ctx.has_compressed_history {
+            "## 历史会话\n之前的对话摘要已归档。如需回顾历史上下文，使用 `timeline_recall` 工具搜索。".to_string()
+        } else {
+            String::new()
+        }
+    }
+}
+```
+
+**Step 3: 注册到 SystemPromptBuilder::with_defaults**
+
+在 `with_defaults()` 的 sections vec 中 `Box::new(MemorySection)` 后加 `Box::new(HistorySection)`。
+
+**Step 4: 更新 build_system_prompt 签名和调用**
+
+```rust
+pub fn build_system_prompt(
+    workspace_dir: &Path,
+    model_name: &str,
+    tools: &ToolRegistry,
+    session_id: Option<&str>,
+    memory_context: Option<&str>,
+    has_compressed_history: bool,
+) -> String {
+    let ctx = PromptContext {
+        workspace_dir,
+        model_name,
+        tools,
+        session_id,
+        memory_context,
+        has_compressed_history,
+    };
+    SystemPromptBuilder::with_defaults().build(&ctx)
+}
+```
+
+**Step 5: 更新 Session::build_system_prompt**
+
+```rust
+pub fn build_system_prompt(&self, skills_prompt: &str, memory_context: Option<&str>) -> String {
+    let base_prompt = build_system_prompt(
+        &self.provider_config.workspace_dir,
+        &self.provider_config.model_id,
+        &self.tools,
+        Some(&self.id.to_string()),
+        memory_context,
+        self.last_compressed_message_at.is_some(),
+    );
+
+    if skills_prompt.trim().is_empty() {
+        base_prompt
+    } else {
+        format!("{}\n\n## Skills\n\n{}\n\nUse the `get_skill` tool to load a skill's full content when needed.", base_prompt, skills_prompt)
+    }
+}
+```
+
+**Step 6: 更新所有其他 build_system_prompt 调用方**
+
+搜索 `build_system_prompt(` 的所有调用位置，每个都要加 `false` 参数。主要有 `agent/agent_loop.rs` 中的两个调用。
+
+**Step 7: 编译检查**
+
+```bash
+cargo check 2>&1
+```
+
+**Step 8: Commit**
+
+```bash
+git add src/agent/system_prompt.rs src/session/session.rs src/agent/agent_loop.rs
+git commit -m "feat(system-prompt): add history section for archived conversation context"
+```
+
+---
+
+### Task 7: handle_message 和 /compact 记录压缩标记
+
+**Files:**
+- Modify: `src/session/session.rs:1339-1355` (handle_message 压缩后)
+- Modify: `src/session/session.rs:1372-1376` (handle_message 溢出重试)
+- Modify: `src/session/session.rs:851-872` (/compact 命令)
+
+**Step 1: handle_message 正常流**
+
+在 `compress_if_needed(history).await?` 之后（line 1346），改为：
+```rust
+let result = session_guard.compressor
+    .compress_if_needed(history)
+    .await?;
+if result.created_timelines {
+    session_guard.last_compressed_message_at = Some(chrono::Utc::now().timestamp_millis());
+    if let Err(e) = session_guard.persist_session_meta().await {
+        tracing::warn!(error = %e, "Failed to persist compressed message marker");
+    }
+}
+let mut history = result.history;
+```
+
+同时删除后面（line 1350-1355）单独的 `persist_session_meta` 调用（现在已合入上面的逻辑）。
+
+**Step 2: handle_message 溢出重试流**
+
+```rust
+let raw = session_guard.get_history().to_vec();
+let result = session_guard.compressor.compress_if_needed(raw).await?;
+if result.created_timelines {
+    session_guard.last_compressed_message_at = Some(chrono::Utc::now().timestamp_millis());
+    let _ = session_guard.persist_session_meta().await;
+}
+let mut retry = result.history;
+retry.insert(0, ChatMessage::system(system_prompt));
+agent.process(retry).await?
+```
+
+**Step 3: /compact 命令**
+
+```rust
+let result = session_guard.compressor
+    .compress_if_needed(history)
+    .await?;
+let compressed_count = result.history.len();
+if result.created_timelines {
+    session_guard.last_compressed_message_at = Some(chrono::Utc::now().timestamp_millis());
+    let _ = session_guard.persist_session_meta().await;
+}
+session_guard.clear_history();
+for msg in result.history {
+    session_guard.add_message(msg, false).await
+        .map_err(|e| AgentError::Other(format!("persist error: {}", e)))?;
+}
+```
+
+同时确认 `compress_if_needed` 的 import 正常（已在 scope 中）。
+
+**Step 4: 编译检查**
+
+```bash
+cargo check 2>&1
+```
+
+**Step 5: Commit**
+
+```bash
+git add src/session/session.rs
+git commit -m "feat(session): record last_compressed_message_at after compression"
+```
+
+---
+
+### Task 8: 全局编译和测试
+
+**Step 1: 全局编译**
+
+```bash
+cargo check 2>&1
+```
+
+修复所有编译错误，确保全部文件一致。
+
+**Step 2: 运行单元测试**
+
+```bash
+cargo test --lib 2>&1
+```
+
+**Step 3: 测试通过后 commit**
+
+```bash
+git add -A
+git commit -m "chore: fix remaining compilation and test issues for incremental recovery"
+```
+
+**Step 4: 运行 lint**
+
+```bash
+cargo clippy --lib 2>&1 | head -50
+```
+
+修复任何 warning。
+
+---
+
+### Task 9: 验证 & 提交设计文档
+
+**Step 1: 最终验证**
+
+```bash
+cargo test --lib 2>&1
+```
+
+**Step 2: Commit 设计文档**
+
+```bash
+git add docs/plans/2026-05-10-incremental-session-recovery-design.md
+git commit -m "docs: add incremental session recovery design doc"
+```