use crate::agent::AgentRuntimeConfig;
use crate::agent::{SystemPromptContext, SystemPromptProvider};
use crate::bus::ChatMessage;
use crate::bus::message::ToolMessageState;
use crate::domain::messages::{ContentBlock, ToolCall};
use crate::observability::{
    Observer, ObserverEvent, ToolExecutionOutcome, ToolExecutionState, truncate_args,
};
use crate::providers::{
    ChatCompletionRequest, LLMProvider, Message, StreamCallback, StreamDelta, create_provider,
};
use crate::storage::ConversationRepository;
use crate::text::{char_count, take_prefix_chars, take_suffix_chars};
use crate::tools::{ToolContext, ToolRegistry};
use async_trait::async_trait;
use std::borrow::Cow;
use std::collections::VecDeque;
use std::hash::{Hash, Hasher};
use std::io::Read;
use std::sync::Arc;
use std::sync::atomic::{AtomicBool, Ordering};
use std::time::Instant;
use std::time::Duration;

/// Minimum characters to keep when truncating
const TRUNCATION_SUFFIX_LEN: usize = 200;
const PENDING_USER_ACTION_MARKER: &str = "__PICOBOT_PENDING_USER_ACTION__";
const RECOVERABLE_LLM_ERROR_MESSAGE: &str = "模型服务暂时不可用或响应超时。请稍后重试。";

/// LLM 请求瞬态失败的重试退避延迟（指数退避：1s, 2s, 4s）。
/// 仅对 `is_recoverable_llm_error` 判定为真的错误重试。
/// 索引越界时取最后一个值（避免 attempt > len 时的 panic）。
const LLM_RETRY_DELAYS_MS: &[u64] = &[1000, 2000, 4000];

const SUPPORTED_IMAGE_MIME_TYPES: &[&str] = &["image/jpeg", "image/png", "image/gif", "image/webp"];
const TOKEN_ESTIMATE_CHARS_PER_TOKEN: usize = 4;
const TOKEN_ESTIMATE_SAFETY_MULTIPLIER: f64 = 1.2;
const CONTEXT_INPUT_SAFETY_RATIO: f64 = 0.9;
const DEFAULT_COMPLETION_TOKEN_RESERVE: usize = 2048;
const DATA_URL_OVERHEAD_TOKENS: usize = 16;
const JPEG_QUALITY_STEPS: &[u8] = &[82, 72, 60, 48, 36];
const MIN_COMPRESSED_IMAGE_SIDE: u32 = 64;
const IMAGE_INPUT_NOTICE_PREFIX: &str = "[系统提示] 以下图片未能成功入模：";

/// Build content blocks from text and media paths
fn build_content_blocks(
    text: &str,
    media_paths: &[String],
    budget: &mut ImageInlineBudget,
) -> Vec<ContentBlock> {
    build_content_blocks_with_image_budget(text, media_paths, budget)
}

fn build_content_blocks_with_image_budget(
    text: &str,
    media_paths: &[String],
    budget: &mut ImageInlineBudget,
) -> Vec<ContentBlock> {
    let mut blocks = Vec::new();
    let mut skipped_image_notices = Vec::new();

    // Add text block if there's text
    if !text.is_empty() {
        blocks.push(ContentBlock::text(text));
    }

    // Add image blocks for media paths
    for path in media_paths {
        if supported_image_mime_type(path).is_none() {
            tracing::debug!(media_path = %path, "Skipping non-image media ref for LLM image block");
            continue;
        }

        let Some(target_tokens) = budget.take_next_image_tokens() else {
            tracing::warn!(media_path = %path, "Skipping image media ref because no LLM context budget remains");
            skipped_image_notices.push(format!(
                "- {}：模型上下文预算不足，当前轮无法读取这张图片，请直接告知用户图片未成功入模。",
                display_media_name(path)
            ));
            continue;
        };

        match encode_image_to_base64_with_budget(path, target_tokens) {
            Ok((mime_type, base64_data)) => {
                let url = format!("data:{};base64,{}", mime_type, base64_data);
                blocks.push(ContentBlock::image_url(url));
            }
            Err(err) => {
                tracing::warn!(media_path = %path, target_tokens = target_tokens, error = %err, "Skipping image media ref after compression failed");
                skipped_image_notices.push(format!(
                    "- {}：图片压缩或编码失败，当前轮无法读取这张图片，请直接告知用户图片未成功入模。",
                    display_media_name(path)
                ));
                continue;
            }
        }
    }

    if !skipped_image_notices.is_empty() {
        let mut notice = String::from(IMAGE_INPUT_NOTICE_PREFIX);
        notice.push('\n');
        notice.push_str(&skipped_image_notices.join("\n"));
        blocks.push(ContentBlock::text(notice));
    }

    // If nothing, add empty text block
    if blocks.is_empty() {
        blocks.push(ContentBlock::text(""));
    }

    blocks
}

fn supported_image_mime_type(path: &str) -> Option<String> {
    let mime = mime_guess::from_path(path).first_or_octet_stream();
    let essence = mime.essence_str();

    if SUPPORTED_IMAGE_MIME_TYPES.contains(&essence) {
        Some(essence.to_string())
    } else {
        None
    }
}

fn display_media_name(path: &str) -> String {
    std::path::Path::new(path)
        .file_name()
        .and_then(|name| name.to_str())
        .map(ToOwned::to_owned)
        .unwrap_or_else(|| path.to_string())
}

#[derive(Debug, Clone)]
struct ImageInlineBudget {
    remaining_tokens: usize,
    remaining_images: usize,
}

impl ImageInlineBudget {
    fn new(total_tokens: usize, image_count: usize) -> Self {
        Self {
            remaining_tokens: total_tokens,
            remaining_images: image_count,
        }
    }

    fn take_next_image_tokens(&mut self) -> Option<usize> {
        if self.remaining_tokens == 0 || self.remaining_images == 0 {
            self.remaining_images = self.remaining_images.saturating_sub(1);
            return None;
        }

        let target = self.remaining_tokens.div_ceil(self.remaining_images);
        self.remaining_tokens = self.remaining_tokens.saturating_sub(target);
        self.remaining_images = self.remaining_images.saturating_sub(1);
        Some(target)
    }
}

fn estimate_tokens_from_serialized_json<T: serde::Serialize>(value: &T) -> usize {
    let raw_len = serde_json::to_string(value)
        .map(|serialized| serialized.len())
        .unwrap_or_default();
    ((raw_len.div_ceil(TOKEN_ESTIMATE_CHARS_PER_TOKEN) as f64) * TOKEN_ESTIMATE_SAFETY_MULTIPLIER)
        as usize
}

/// 轻量 token 估算：直接从 ChatMessage 累加文本字段长度，
/// 避免对完整 Vec<Message> 做 serde_json::to_string（O(N) 序列化）。
/// 精度略低于完整 JSON 序列化（忽略 role/tool_call_id 等 overhead），
/// 但作为图片预算估算已足够——上下文窗口有 CONTEXT_INPUT_SAFETY_RATIO 兜底。
/// 与原 text_only_messages 路径等价覆盖：content + reasoning_content + tool_calls。
fn estimate_text_tokens_from_chat_messages(
    messages: &[ChatMessage],
    system_prompt: Option<&str>,
) -> usize {
    let mut total_chars: usize = system_prompt.map(|s| s.len()).unwrap_or(0);
    for m in messages {
        total_chars += m.content.len();
        if let Some(rc) = m.reasoning_content.as_ref() {
            total_chars += rc.len();
        }
        if let Some(tcs) = m.tool_calls.as_ref() {
            for tc in tcs {
                total_chars += tc.name.len();
                total_chars += serde_json::to_string(&tc.arguments)
                    .map(|s| s.len())
                    .unwrap_or(0);
            }
        }
    }
    ((total_chars.div_ceil(TOKEN_ESTIMATE_CHARS_PER_TOKEN) as f64)
        * TOKEN_ESTIMATE_SAFETY_MULTIPLIER) as usize
}

fn image_token_budget_for_request(
    runtime_config: &AgentRuntimeConfig,
    text_tokens: usize,
    tools_tokens: usize,
) -> usize {
    let completion_reserve = runtime_config
        .provider
        .max_tokens
        .map(|tokens| tokens as usize)
        .unwrap_or(DEFAULT_COMPLETION_TOKEN_RESERVE);
    let input_window = runtime_config
        .context_window_tokens
        .saturating_sub(completion_reserve);
    let safe_input_window = (input_window as f64 * CONTEXT_INPUT_SAFETY_RATIO) as usize;

    safe_input_window.saturating_sub(text_tokens + tools_tokens)
}

fn count_supported_image_media_refs(messages: &[ChatMessage]) -> usize {
    messages
        .iter()
        .flat_map(|message| message.media_refs.iter())
        .filter(|path| supported_image_mime_type(path).is_some())
        .count()
}

/// 过滤超出轮次限制的图片，并限制总图片数量
///
/// # 参数
/// - `messages`: 原始消息列表
/// - `max_age_rounds`: 图片超过多少消息轮次后不再发送（从最新消息向前数，包括所有 role）
/// - `max_images`: 最多发送多少张图片（优先保留最近的图片）
///
/// # 返回
/// 过滤后的消息列表，图片被转换为文本提示 "[图片已过期]"。
/// 无图片或无需过滤时返回 `Cow::Borrowed`（零拷贝），有图片需过滤时返回 `Cow::Owned`。
fn filter_images_by_age_and_count(
    messages: &[ChatMessage],
    max_age_rounds: usize,
    max_images: usize,
) -> Cow<'_, [ChatMessage]> {
    if messages.is_empty() || (max_age_rounds == 0 && max_images == 0) {
        return Cow::Borrowed(messages);
    }

    let total_images = count_supported_image_media_refs(messages);
    if total_images == 0 {
        return Cow::Borrowed(messages);
    }

    // 从最新消息向前遍历，优先保留最新的图片
    // 消息列表顺序：[old, ..., new]，所以末尾是最新的
    let msg_count = messages.len();

    // 先从后向前遍历，计算每条消息应该保留多少张图片
    // 使用 Vec<usize> 存储每条消息应该保留的图片数量
    let mut images_to_keep_per_msg: Vec<usize> = vec![0; msg_count];
    let mut images_kept = 0usize;

    // 从后向前遍历（从最新到最旧）
    for (idx, message) in messages.iter().enumerate().rev() {
        // 计算距离最新消息的消息数（末尾消息的 age = 0）
        let age_from_end = msg_count.saturating_sub(idx).saturating_sub(1);

        // 检查是否超出轮次限制
        let exceeds_age_limit = max_age_rounds > 0 && age_from_end >= max_age_rounds;

        if exceeds_age_limit {
            continue; // 超出轮次限制的图片不保留
        }

        // 计算这条消息中的图片数量
        let image_count_in_msg = message
            .media_refs
            .iter()
            .filter(|p| supported_image_mime_type(p).is_some())
            .count();

        if image_count_in_msg == 0 {
            continue;
        }

        // 计算可以保留多少张
        let can_keep = std::cmp::min(image_count_in_msg, max_images.saturating_sub(images_kept));
        if can_keep > 0 {
            images_to_keep_per_msg[idx] = can_keep;
            images_kept += can_keep;
        }
    }

    // 然后从前向后遍历，构建过滤后的消息列表
    let mut filtered = Vec::with_capacity(msg_count);

    for (idx, message) in messages.iter().enumerate() {
        // 计算距离最新消息的消息数（末尾消息的 age = 0）
        let age_from_end = msg_count.saturating_sub(idx).saturating_sub(1);

        // 检查是否超出轮次限制
        let exceeds_age_limit = max_age_rounds > 0 && age_from_end >= max_age_rounds;

        let keep_count = images_to_keep_per_msg[idx];

        // 过滤图片：保留非图片媒体和指定数量的图片
        let mut images_kept_in_msg = 0usize;
        let filtered_media_refs: Vec<String> = message
            .media_refs
            .iter()
            .filter_map(|path| {
                if supported_image_mime_type(path).is_some() {
                    if images_kept_in_msg < keep_count {
                        images_kept_in_msg += 1;
                        Some(path.clone())
                    } else {
                        None
                    }
                } else {
                    Some(path.clone()) // 保留非图片媒体
                }
            })
            .collect();

        // 如果图片被过滤，添加文本提示
        let original_image_count = message
            .media_refs
            .iter()
            .filter(|p| supported_image_mime_type(p).is_some())
            .count();
        let filtered_image_count = filtered_media_refs
            .iter()
            .filter(|p| supported_image_mime_type(p).is_some())
            .count();

        let content = if original_image_count > filtered_image_count {
            let notice = if exceeds_age_limit {
                format!(
                    "{} [图片已过期：超出 {} 条消息范围]",
                    message.content, max_age_rounds
                )
            } else {
                format!("{} [图片已过期：超出最大图片数量限制]", message.content)
            };
            notice
        } else {
            message.content.clone()
        };

        filtered.push(ChatMessage {
            id: message.id.clone(),
            role: message.role.clone(),
            content,
            media_refs: filtered_media_refs,
            timestamp: message.timestamp,
            system_context: message.system_context.clone(),
            reasoning_content: message.reasoning_content.clone(),
            tool_call_id: message.tool_call_id.clone(),
            tool_name: message.tool_name.clone(),
            tool_state: message.tool_state.clone(),
            tool_duration_ms: message.tool_duration_ms,
            tool_calls: message.tool_calls.clone(),
            usage: message.usage.clone(),
        });
    }

    Cow::Owned(filtered)
}

fn target_image_bytes_for_tokens(target_tokens: usize) -> usize {
    target_tokens
        .saturating_sub(DATA_URL_OVERHEAD_TOKENS)
        .saturating_mul(TOKEN_ESTIMATE_CHARS_PER_TOKEN)
        .saturating_mul(3)
        / 4
}

/// Encode an image file to base64 data URL
fn encode_image_to_base64(path: &str) -> Result<(String, String), std::io::Error> {
    use base64::{Engine as _, engine::general_purpose::STANDARD};

    let mime = supported_image_mime_type(path).ok_or_else(|| {
        std::io::Error::new(
            std::io::ErrorKind::InvalidInput,
            format!("unsupported image media type for path: {}", path),
        )
    })?;

    let mut file = std::fs::File::open(path)?;
    let mut buffer = Vec::new();
    file.read_to_end(&mut buffer)?;

    let encoded = STANDARD.encode(&buffer);
    Ok((mime, encoded))
}

fn encode_image_to_base64_with_budget(
    path: &str,
    target_tokens: usize,
) -> Result<(String, String), std::io::Error> {
    use base64::{Engine as _, engine::general_purpose::STANDARD};

    let (mime, encoded) = encode_image_to_base64(path)?;
    let target_base64_chars = target_tokens
        .saturating_sub(DATA_URL_OVERHEAD_TOKENS)
        .saturating_mul(TOKEN_ESTIMATE_CHARS_PER_TOKEN);
    if encoded.len() <= target_base64_chars {
        return Ok((mime, encoded));
    }

    let target_bytes = target_image_bytes_for_tokens(target_tokens);
    let image_bytes = std::fs::read(path)?;
    let image = image::load_from_memory(&image_bytes)
        .map_err(|err| std::io::Error::new(std::io::ErrorKind::InvalidData, err))?;
    let compressed = compress_image_to_jpeg_budget(&image, target_bytes)?;

    Ok(("image/jpeg".to_string(), STANDARD.encode(compressed)))
}

fn compress_image_to_jpeg_budget(
    image: &image::DynamicImage,
    target_bytes: usize,
) -> Result<Vec<u8>, std::io::Error> {
    use image::codecs::jpeg::JpegEncoder;
    use image::imageops::FilterType;

    let mut best: Option<Vec<u8>> = None;
    let mut max_side = image
        .width()
        .max(image.height())
        .max(MIN_COMPRESSED_IMAGE_SIDE);

    loop {
        let candidate = if image.width().max(image.height()) > max_side {
            image.resize(max_side, max_side, FilterType::Triangle)
        } else {
            image.clone()
        };

        for quality in JPEG_QUALITY_STEPS {
            let mut encoded = Vec::new();
            let mut encoder = JpegEncoder::new_with_quality(&mut encoded, *quality);
            encoder
                .encode_image(&candidate)
                .map_err(|err| std::io::Error::new(std::io::ErrorKind::InvalidData, err))?;

            if encoded.len() <= target_bytes {
                return Ok(encoded);
            }

            if best
                .as_ref()
                .map(|current| encoded.len() < current.len())
                .unwrap_or(true)
            {
                best = Some(encoded);
            }
        }

        if max_side <= MIN_COMPRESSED_IMAGE_SIDE {
            break;
        }
        max_side = (max_side * 3 / 4).max(MIN_COMPRESSED_IMAGE_SIDE);
    }

    best.ok_or_else(|| {
        std::io::Error::new(std::io::ErrorKind::InvalidData, "image compression failed")
    })
}

/// Truncate tool result if it exceeds the configured limit.
/// Preserves the end of the output as it often contains the conclusion/useful result.
fn truncate_tool_result(output: &str, max_tool_result_chars: usize) -> String {
    let total_chars = char_count(output);
    if total_chars <= max_tool_result_chars {
        return output.to_string();
    }

    let truncated_start_len = total_chars.saturating_sub(TRUNCATION_SUFFIX_LEN);
    if truncated_start_len > max_tool_result_chars {
        // Even after removing suffix, still too long - take from beginning
        let head_len = max_tool_result_chars.saturating_sub(100);
        let head = take_prefix_chars(output, head_len);
        format!(
            "{}...\n\n[Output truncated - {} characters removed]",
            head,
            total_chars - max_tool_result_chars + 100
        )
    } else {
        // Keep most of the end which usually contains the useful result
        let tail = take_suffix_chars(output, total_chars.saturating_sub(truncated_start_len));
        format!(
            "...\n\n[Output truncated - {} characters removed]\n\n{}",
            truncated_start_len, tail
        )
    }
}

fn parse_pending_tool_output(output: &str) -> Option<String> {
    output
        .strip_prefix(PENDING_USER_ACTION_MARKER)
        .map(|rest| rest.trim().to_string())
}

fn normalize_tool_arguments(arguments: &serde_json::Value) -> serde_json::Value {
    match arguments {
        serde_json::Value::String(raw) => {
            serde_json::from_str(raw).unwrap_or_else(|_| arguments.clone())
        }
        _ => arguments.clone(),
    }
}

fn format_error_chain(error: &(dyn std::error::Error + 'static)) -> String {
    let mut details = vec![error.to_string()];
    let mut current = error.source();

    while let Some(source) = current {
        details.push(source.to_string());
        current = source.source();
    }

    details.join("\ncaused by: ")
}

fn is_recoverable_llm_error(error: &str) -> bool {
    let normalized = error.to_ascii_lowercase();
    // 瞬态可恢复错误：服务端过载/限流/网关错误/超时/连接重置。
    // 注意：401/403/400/404 等不可恢复错误不含这些子串，不会被误判。
    normalized.contains("429")
        || normalized.contains("502")
        || normalized.contains("503")
        || normalized.contains("504")
        || normalized.contains("gateway timeout")
        || normalized.contains("stream timeout")
        || normalized.contains("timed out")
        || normalized.contains("timeout")
        || normalized.contains("connection reset")
        || normalized.contains("connection refused")
}

fn recoverable_llm_message(error: &str) -> String {
    if is_recoverable_llm_error(error) {
        RECOVERABLE_LLM_ERROR_MESSAGE.to_string()
    } else {
        format!("模型请求失败：{}", error)
    }
}

/// Loop detection result.
#[derive(Debug, Clone, PartialEq, Eq)]
enum LoopDetectionResult {
    /// No warning needed.
    Ok,
    /// Warning: same tool + args repeated N times.
    Warning(String),
}

/// Configuration for loop detector.
#[derive(Debug, Clone)]
struct LoopDetectorConfig {
    /// Master switch.
    enabled: bool,
    /// Warn every N consecutive identical calls.
    warn_every: usize,
}

impl Default for LoopDetectorConfig {
    fn default() -> Self {
        Self {
            enabled: true,
            warn_every: 5,
        }
    }
}

/// A single recorded tool invocation in the sliding window.
#[derive(Debug, Clone)]
struct ToolCallRecord {
    name: String,
    args_hash: u64,
}

/// Stateful loop detector that monitors for repetitive patterns.
struct LoopDetector {
    config: LoopDetectorConfig,
    window: VecDeque<ToolCallRecord>,
}

impl LoopDetector {
    fn new(config: LoopDetectorConfig) -> Self {
        Self {
            window: VecDeque::with_capacity(config.warn_every * 2),
            config,
        }
    }

    /// Record a completed tool call and check for loop patterns.
    /// Returns Warning every `warn_every` consecutive identical calls.
    fn record(&mut self, name: &str, args: &serde_json::Value) -> LoopDetectionResult {
        if !self.config.enabled {
            return LoopDetectionResult::Ok;
        }

        let record = ToolCallRecord {
            name: name.to_string(),
            args_hash: hash_json_value(args),
        };

        // Maintain sliding window
        if self.window.len() >= self.config.warn_every * 2 {
            self.window.pop_front();
        }
        self.window.push_back(record);

        // Count consecutive identical calls
        let last = self.window.back().unwrap();
        let consecutive: usize = self
            .window
            .iter()
            .rev()
            .take_while(|r| r.name == last.name && r.args_hash == last.args_hash)
            .count();

        // Warn every warn_every times
        if consecutive > 0 && consecutive % self.config.warn_every == 0 {
            LoopDetectionResult::Warning(format!(
                "注意: 工具 '{}' 已连续执行 {} 次，参数相同。如果任务没有进展，请尝试其他方法。",
                last.name, consecutive
            ))
        } else {
            LoopDetectionResult::Ok
        }
    }
}

/// Hash a JSON value deterministically (key-order independent).
fn hash_json_value(value: &serde_json::Value) -> u64 {
    let mut hasher = std::collections::hash_map::DefaultHasher::new();
    let canonical = canonicalise_json(value);
    canonical.hash(&mut hasher);
    hasher.finish()
}

/// Return a clone of value with all object keys sorted recursively.
fn canonicalise_json(value: &serde_json::Value) -> serde_json::Value {
    match value {
        serde_json::Value::Object(map) => {
            let mut sorted: Vec<(&String, &serde_json::Value)> = map.iter().collect();
            sorted.sort_by_key(|(k, _)| *k);
            let new_map: serde_json::Map<String, serde_json::Value> = sorted
                .into_iter()
                .map(|(k, v)| (k.clone(), canonicalise_json(v)))
                .collect();
            serde_json::Value::Object(new_map)
        }
        serde_json::Value::Array(arr) => {
            serde_json::Value::Array(arr.iter().map(canonicalise_json).collect())
        }
        other => other.clone(),
    }
}

/// Convert ChatMessage to LLM Message format
fn chat_message_to_llm_message(m: &ChatMessage, image_budget: &mut ImageInlineBudget) -> Message {
    let content = if m.media_refs.is_empty() {
        vec![ContentBlock::text(&m.content)]
    } else {
        build_content_blocks(&m.content, &m.media_refs, image_budget)
    };

    Message {
        role: m.role.clone(),
        content,
        reasoning_content: m.reasoning_content.clone(),
        tool_call_id: m.tool_call_id.clone(),
        name: m.tool_name.clone(),
        tool_calls: m.tool_calls.clone(),
    }
}

/// AgentLoop - Stateless agent that processes messages with tool calling support.
/// History is managed externally by SessionManager.
pub struct AgentLoop {
    runtime_config: AgentRuntimeConfig,
    provider: Box<dyn LLMProvider>,
    tools: Arc<ToolRegistry>,
    /// 系统提示词提供者（统一注入 Agent 和 Skill 提示词）
    system_prompt_provider: Option<Arc<dyn SystemPromptProvider>>,
    /// Skill 提供者（用于匹配错误提示）
    skills: Option<Arc<dyn SkillProvider>>,
    tool_context: ToolContext,
    observer: Option<Arc<dyn Observer>>,
    emitted_message_handler: Option<Arc<dyn EmittedMessageHandler>>,
    max_iterations: usize,
    /// 取消信号接收端：Agent 在每次迭代开始时检查是否被取消。
    /// 包装在 Mutex 中以支持 interior mutability ——
    /// watch::Receiver::changed() 需要 &mut self，但 process() 持有 &self。
    cancel_token: Option<tokio::sync::Mutex<tokio::sync::watch::Receiver<()>>>,
}

#[derive(Debug, Clone)]
pub struct AgentProcessResult {
    pub final_response: ChatMessage,
    pub emitted_messages: Vec<ChatMessage>,
}

#[async_trait]
pub trait EmittedMessageHandler: Send + Sync + 'static {
    async fn handle(&self, message: ChatMessage);

    /// Handle a tool result message with optional execution timing.
    /// Default implementation delegates to `handle()`, ignoring timing.
    async fn handle_tool_result(&self, message: ChatMessage, _duration_ms: Option<u64>) {
        self.handle(message).await;
    }

    /// Handle a streaming delta. Default is no-op.
    async fn handle_stream_delta(&self, _delta: &StreamDelta) {
        // Non-streaming channels ignore this
    }

    /// Set the message ID to use for stream deltas (so the final assistant message
    /// can share the same ID, enabling front-end replacement).
    async fn set_stream_message_id(&self, _id: &str) {
        // Default: no-op for handlers that don't stream
    }
}

/// 装饰器：在内部 emitter 广播前，先将消息持久化到 DB
pub struct PersistingEmittedMessageHandler<H: EmittedMessageHandler> {
    inner: H,
    conversation_repository: Arc<dyn ConversationRepository>,
    session_id: String,
    topic_id: Option<String>,
}

impl<H: EmittedMessageHandler> PersistingEmittedMessageHandler<H> {
    pub fn new(
        inner: H,
        conversation_repository: Arc<dyn ConversationRepository>,
        session_id: impl Into<String>,
        topic_id: Option<String>,
    ) -> Self {
        Self {
            inner,
            conversation_repository,
            session_id: session_id.into(),
            topic_id,
        }
    }
}

#[async_trait]
impl<H: EmittedMessageHandler> EmittedMessageHandler for PersistingEmittedMessageHandler<H> {
    async fn handle(&self, message: ChatMessage) {
        // SQLite 是同步 I/O，直接调用会阻塞 tokio worker 线程。
        // 用 spawn_blocking 把写操作挪到 blocking 线程池，不改变语义：
        // 失败仅记日志不阻断主流程（与原 if let Err 一致）。
        let repo = self.conversation_repository.clone();
        let session_id = self.session_id.clone();
        let topic_id = self.topic_id.clone();
        let msg_for_persist = message.clone();
        tokio::task::spawn_blocking(move || {
            if let Err(e) =
                repo.append_message_with_topic(&session_id, topic_id.as_deref(), &msg_for_persist)
            {
                tracing::error!(error = %e, session_id = %session_id,
                    "Failed to persist emitted message");
            }
        })
        .await
        .ok(); // JoinError 不影响主流程
        self.inner.handle(message).await;
    }

    async fn handle_tool_result(&self, message: ChatMessage, duration_ms: Option<u64>) {
        // Persist the ChatMessage first (no duration field, same as before)
        let repo = self.conversation_repository.clone();
        let session_id = self.session_id.clone();
        let topic_id = self.topic_id.clone();
        let msg_for_persist = message.clone();
        tokio::task::spawn_blocking(move || {
            if let Err(e) =
                repo.append_message_with_topic(&session_id, topic_id.as_deref(), &msg_for_persist)
            {
                tracing::error!(error = %e, session_id = %session_id,
                    "Failed to persist emitted message");
            }
        })
        .await
        .ok();
        self.inner.handle_tool_result(message, duration_ms).await;
    }

    async fn set_stream_message_id(&self, id: &str) {
        self.inner.set_stream_message_id(id).await;
    }

    async fn handle_stream_delta(&self, delta: &StreamDelta) {
        // Deltas are transient — do NOT persist, just forward to inner handler
        self.inner.handle_stream_delta(delta).await;
    }
}

pub trait SkillProvider: Send + Sync + 'static {
    fn system_index_prompt(&self) -> Option<String>;

    fn matching_skill_summary(&self, _name: &str) -> Option<String> {
        None
    }
}

impl AgentLoop {
    pub fn new(config: impl Into<AgentRuntimeConfig>) -> Result<Self, AgentError> {
        let runtime_config = config.into();
        let max_iterations = runtime_config.max_tool_iterations;
        let provider = create_provider(runtime_config.provider.clone())
            .map_err(|e| AgentError::ProviderCreation(e.to_string()))?;

        Ok(Self {
            runtime_config,
            provider,
            tools: Arc::new(ToolRegistry::new()),
            system_prompt_provider: None,
            skills: None,
            tool_context: ToolContext::default(),
            observer: None,
            emitted_message_handler: None,
            cancel_token: None,
            max_iterations,
        })
    }

    pub fn with_tools(
        config: impl Into<AgentRuntimeConfig>,
        tools: Arc<ToolRegistry>,
    ) -> Result<Self, AgentError> {
        let runtime_config = config.into();
        let max_iterations = runtime_config.max_tool_iterations;
        let provider = create_provider(runtime_config.provider.clone())
            .map_err(|e| AgentError::ProviderCreation(e.to_string()))?;

        Ok(Self {
            runtime_config,
            provider,
            tools,
            system_prompt_provider: None,
            skills: None,
            tool_context: ToolContext::default(),
            observer: None,
            emitted_message_handler: None,
            cancel_token: None,
            max_iterations,
        })
    }

    pub fn with_tools_and_skill_provider(
        config: impl Into<AgentRuntimeConfig>,
        tools: Arc<ToolRegistry>,
        skills: Arc<dyn SkillProvider>,
    ) -> Result<Self, AgentError> {
        let runtime_config = config.into();
        let max_iterations = runtime_config.max_tool_iterations;
        let provider = create_provider(runtime_config.provider.clone())
            .map_err(|e| AgentError::ProviderCreation(e.to_string()))?;

        Ok(Self {
            runtime_config,
            provider,
            tools,
            system_prompt_provider: None,
            skills: Some(skills),
            tool_context: ToolContext::default(),
            observer: None,
            emitted_message_handler: None,
            cancel_token: None,
            max_iterations,
        })
    }

    /// 使用系统提示词提供者创建 AgentLoop
    ///
    /// 这是新的推荐方式，支持统一注入 Agent 和 Skill 提示词。
    pub fn with_tools_and_system_prompt_provider(
        config: impl Into<AgentRuntimeConfig>,
        tools: Arc<ToolRegistry>,
        system_prompt_provider: Arc<dyn SystemPromptProvider>,
        skills: Option<Arc<dyn SkillProvider>>,
    ) -> Result<Self, AgentError> {
        let runtime_config = config.into();
        let max_iterations = runtime_config.max_tool_iterations;
        let provider = create_provider(runtime_config.provider.clone())
            .map_err(|e| AgentError::ProviderCreation(e.to_string()))?;

        Ok(Self {
            runtime_config,
            provider,
            tools,
            system_prompt_provider: Some(system_prompt_provider),
            skills,
            tool_context: ToolContext::default(),
            observer: None,
            emitted_message_handler: None,
            cancel_token: None,
            max_iterations,
        })
    }

    pub fn with_tool_context(mut self, context: ToolContext) -> Self {
        self.tool_context = context;
        self
    }

    /// Set an observer for tracking events.
    pub fn with_observer(mut self, observer: Arc<dyn Observer>) -> Self {
        self.observer = Some(observer);
        self
    }

    pub fn with_emitted_message_handler(mut self, handler: Arc<dyn EmittedMessageHandler>) -> Self {
        self.emitted_message_handler = Some(handler);
        self
    }

    /// 设置取消信号接收端。
    ///
    /// Agent 在每次迭代开始时检查 `cancel_token.has_changed()`，
    /// 如果已收到取消信号则提前返回。
    /// 同时，LLM 调用和工具执行期间通过 tokio::select! 与 cancel_signal() 竞速。
    pub fn with_cancel_token(mut self, token: tokio::sync::watch::Receiver<()>) -> Self {
        self.cancel_token = Some(tokio::sync::Mutex::new(token));
        self
    }

    pub fn tools(&self) -> &Arc<ToolRegistry> {
        &self.tools
    }

    /// Process a message using the provided conversation history.
    /// History management is handled externally by SessionManager.
    ///
    /// This method supports multi-round tool calling: after executing tools,
    /// it loops back to the LLM with the tool results until either:
    /// - The LLM returns no more tool calls (final response)
    /// - Maximum iterations are reached
    ///
    /// # 参数
    /// - `messages`: 会话历史消息
    /// - `system_prompt_context`: 系统提示词上下文（用于动态注入，可选）
    pub async fn process(
        &self,
        mut messages: Vec<ChatMessage>,
        system_prompt_context: Option<&SystemPromptContext>,
    ) -> Result<AgentProcessResult, AgentError> {
        #[cfg(debug_assertions)]
        tracing::debug!(
            history_len = messages.len(),
            max_iterations = self.max_iterations,
            "Starting agent process"
        );

        // Sanitize: remove any trailing incomplete tool call sequences
        // that may have been persisted before a process interruption.
        {
            let tool_call_ids: Vec<_> = messages
                .iter()
                .filter(|m| m.role == "assistant")
                .filter_map(|m| m.tool_calls.as_ref())
                .flatten()
                .map(|tc| tc.id.clone())
                .collect();
            let tool_result_ids: Vec<_> = messages
                .iter()
                .filter(|m| m.role == "tool")
                .filter_map(|m| m.tool_call_id.clone())
                .collect();
            tracing::debug!(
                total_messages = messages.len(),
                tool_call_ids = ?tool_call_ids,
                tool_result_ids = ?tool_result_ids,
                "Pre-process message state before sanitize"
            );
        }
        let removed = Self::sanitize_messages_for_llm(&mut messages);
        if removed > 0 {
            tracing::warn!(
                removed_count = removed,
                after_len = messages.len(),
                "Pre-process sanitize removed incomplete tool_call sequences"
            );
        }

        // Track tool calls for loop detection
        let mut loop_detector = LoopDetector::new(LoopDetectorConfig::default());
        let mut emitted_messages = Vec::new();

        // 工具集在 create_agent 时按当前专家 capability 过滤后注入（快照语义）。
        // 单次 process() 期间专家切换不影响当前 Arc<ToolRegistry> 引用，
        // 因此循环外构建一次 tool_defs，避免每轮重复读锁 + 全量 clone。
        // 注意：若未来支持 process() 中途热切换专家（当前不支持），需重新评估。
        let tool_defs = self.tools.get_definitions();
        let tools = if tool_defs.is_empty() {
            None
        } else {
            Some(tool_defs)
        };
        // 工具 token 估算在循环外算一次（tool_defs 在 process() 期间不变），
        // 避免每轮 serde_json::to_string 全量序列化工具定义。
        let tools_tokens = tools
            .as_ref()
            .map(|t| estimate_tokens_from_serialized_json(t))
            .unwrap_or_default();

        for iteration in 0..self.max_iterations {
            #[cfg(debug_assertions)]
            tracing::debug!(iteration, "Agent iteration started");

            // 检查取消信号
            // 使用 unwrap_or(true)：即使 watch channel 因异常关闭（sender drop 但未 send），
            // 也视为取消信号。defense-in-depth —— fail safe 而非 fail silent。
            if self.check_cancelled().await {
                tracing::info!(iteration, "Agent execution cancelled by user");
                let cancel = Self::build_cancel_result(iteration, emitted_messages);
                self.emit_live_tool_call_message(cancel.final_response.clone())
                    .await;
                return Ok(cancel);
            }

            // Defense-in-depth: sanitize incomplete tool call sequences
            // before EVERY LLM request, not just once at process() entry.
            // This catches edge cases where compression, persistence races,
            // or delta message merging may have introduced orphaned sequences
            // that survived the initial sanitization.
            let mid_loop_removed = Self::sanitize_messages_for_llm(&mut messages);
            if mid_loop_removed > 0 {
                tracing::warn!(
                    iteration = iteration,
                    removed_count = mid_loop_removed,
                    "Mid-loop sanitize removed incomplete tool call sequences before LLM request"
                );
            }

            let request = self.build_llm_request(
                &messages,
                system_prompt_context,
                tools.clone(),
                tools_tokens,
            );

            // Set up streaming delta consumer
            // Pre-generate the message ID so stream deltas and the final assistant
            // message share the same ID — this lets the front-end replace the
            // streamed message with the authoritative response.
            let streaming_message_id = uuid::Uuid::new_v4().to_string();
            if let Some(handler) = &self.emitted_message_handler {
                handler.set_stream_message_id(&streaming_message_id).await;
            }

            let max_retries = self.runtime_config.max_retries as usize;
            let mut response: Option<crate::providers::ChatCompletionResponse> = None;

            'retry: for attempt in 0..=max_retries {
                // 每次重试重建 channel + consumer：上次失败的 channel 可能已关闭。
                let (delta_tx, mut delta_rx) = tokio::sync::mpsc::channel::<StreamDelta>(256);
                let consumer_handler = self.emitted_message_handler.clone();
                let consumer_task = tokio::spawn(async move {
                    while let Some(delta) = delta_rx.recv().await {
                        if let Some(ref handler) = consumer_handler {
                            handler.handle_stream_delta(&delta).await;
                        }
                    }
                });
                // 跟踪是否已 emit delta：流式传输一旦开始（emit 过内容），
                // 重试会重复输出，此时不重试。
                let emitted = Arc::new(AtomicBool::new(false));
                let emitted_for_cb = emitted.clone();
                let stream_callback: StreamCallback = std::sync::Arc::new(move |delta: StreamDelta| {
                    emitted_for_cb.store(true, Ordering::SeqCst);
                    let _ = delta_tx.try_send(delta);
                });

                // LLM 调用与取消信号竞速：若取消信号到达，drop LLM future 以 abort HTTP 请求。
                let llm_result: Result<
                    crate::providers::ChatCompletionResponse,
                    Box<dyn std::error::Error + Send + Sync>,
                >;
                if self.cancel_token.is_some() {
                    tokio::select! {
                        _ = self.cancel_signal() => {
                            drop(stream_callback);
                            let _ = consumer_task.await;
                            let cancel = Self::build_cancel_result(iteration, emitted_messages);
                            self.emit_live_tool_call_message(cancel.final_response.clone()).await;
                            return Ok(cancel);
                        }
                        result = self.provider.chat_with_streaming(request.clone(), stream_callback.clone()) => {
                            llm_result = result;
                        }
                    }
                    drop(stream_callback);
                } else {
                    llm_result = self
                        .provider
                        .chat_with_streaming(request.clone(), stream_callback)
                        .await;
                }

                let _ = consumer_task.await;

                match llm_result {
                    Ok(resp) => {
                        response = Some(resp);
                        break 'retry;
                    }
                    Err(e) => {
                        let error_text = e.to_string();
                        let can_retry = attempt < max_retries
                            && !emitted.load(Ordering::SeqCst)
                            && is_recoverable_llm_error(&error_text);
                        if can_retry {
                            let delay = LLM_RETRY_DELAYS_MS
                                [attempt.min(LLM_RETRY_DELAYS_MS.len() - 1)];
                            tracing::warn!(
                                attempt = attempt + 1,
                                retry_in_ms = delay,
                                provider = %self.provider.name(),
                                model = %self.provider.model_id(),
                                error = %error_text,
                                "LLM streaming request failed, retrying"
                            );
                            // 退避等待期间也响应取消信号
                            if self.cancel_token.is_some() {
                                tokio::select! {
                                    _ = self.cancel_signal() => {
                                        let cancel = Self::build_cancel_result(iteration, emitted_messages);
                                        self.emit_live_tool_call_message(cancel.final_response.clone()).await;
                                        return Ok(cancel);
                                    }
                                    _ = tokio::time::sleep(Duration::from_millis(delay)) => {}
                                }
                            } else {
                                tokio::time::sleep(Duration::from_millis(delay)).await;
                            }
                            continue 'retry;
                        }
                        tracing::error!(
                            provider = %self.provider.name(),
                            model = %self.provider.model_id(),
                            error = %e,
                            error_details = %format_error_chain(e.as_ref()),
                            "LLM request failed"
                        );
                        let assistant_message =
                            ChatMessage::assistant(recoverable_llm_message(&error_text));
                        emitted_messages.push(assistant_message.clone());
                        self.emit_live_tool_call_message(assistant_message.clone())
                            .await;
                        return Ok(AgentProcessResult {
                            final_response: assistant_message,
                            emitted_messages,
                        });
                    }
                }
            }

            let response = response.expect("retry loop must set response or return");

            // Signal stream end if handler exists
            let had_streaming = self.emitted_message_handler.is_some();
            if had_streaming {
                let end_delta = StreamDelta {
                    content: String::new(),
                    reasoning_content: None,
                };
                if let Some(handler) = &self.emitted_message_handler {
                    handler.handle_stream_delta(&end_delta).await;
                }
            }

            #[cfg(debug_assertions)]
            tracing::debug!(
                iteration,
                response_len = response.content.len(),
                tool_calls_len = response.tool_calls.len(),
                "LLM response received"
            );

            // If no tool calls, this is the final response
            if response.tool_calls.is_empty() {
                let result = self
                    .build_final_response(
                        response,
                        &streaming_message_id,
                        had_streaming,
                        &mut emitted_messages,
                    )
                    .await;
                return Ok(result);
            }

            // Execute tool calls
            tracing::info!(
                iteration,
                count = response.tool_calls.len(),
                "Tool calls detected, executing tools"
            );

            // Add assistant message with tool calls
            let mut assistant_message =
                if let Some(reasoning_content) = response.reasoning_content.clone() {
                    ChatMessage::assistant_with_tool_calls_and_reasoning(
                        response.content.clone(),
                        response.tool_calls.clone(),
                        reasoning_content,
                    )
                } else {
                    ChatMessage::assistant_with_tool_calls(
                        response.content.clone(),
                        response.tool_calls.clone(),
                    )
                };
            // Use the same ID as stream deltas so the front-end can replace
            // the streamed message with this authoritative response.
            if had_streaming {
                assistant_message.id = streaming_message_id;
            }
            // 记录本次 LLM 调用的 token 用量（中间带 tool_calls 的调用也算消耗）
            assistant_message.usage = Some(
                crate::bus::message::MessageUsage::from_provider_usage(response.usage.clone())
                    .with_context_window(self.runtime_config.context_window_tokens),
            );
            messages.push(assistant_message.clone());
            emitted_messages.push(assistant_message);
            self.emit_live_tool_call_message(
                emitted_messages
                    .last()
                    .expect("assistant message just pushed")
                    .clone(),
            )
            .await;

            // Execute tools and add results to messages
            // 工具执行与取消信号竞速：取消时 drop join_all 或 sequential future，
            // 未完成的工具调用被丢弃。
            let tool_results = if self.cancel_token.is_some() {
                tokio::select! {
                    _ = self.cancel_signal() => {
                        // 为所有 tool_calls 补充取消结果，避免孤立 assistant(tool_calls)
                        for tool_call in &response.tool_calls {
                            let cancel_result = ChatMessage::tool_with_state(
                                tool_call.id.clone(),
                                tool_call.name.clone(),
                                "[Tool execution cancelled by user]".to_string(),
                                ToolMessageState::Completed,
                            );
                            messages.push(cancel_result.clone());
                            emitted_messages.push(cancel_result.clone());
                            self.emit_tool_result(cancel_result, Some(0)).await;
                        }
                        let cancel = Self::build_cancel_result(iteration, emitted_messages);
                        self.emit_live_tool_call_message(cancel.final_response.clone()).await;
                        return Ok(cancel);
                    }
                    results = self.execute_tools(&response.tool_calls) => {
                        results
                    }
                }
            } else {
                self.execute_tools(&response.tool_calls).await
            };

            self.process_tool_results(
                &response.tool_calls,
                &tool_results,
                &mut loop_detector,
                &mut messages,
                &mut emitted_messages,
            )
            .await;

            // Loop continues to next iteration with updated messages
            // PendingUserAction 工具的结果已在上方加入 messages，
            // 模型将在下一轮看到完整的终端输出并生成智能回复
            #[cfg(debug_assertions)]
            tracing::debug!(
                iteration,
                message_count = messages.len(),
                "Tool execution complete, continuing to next iteration"
            );
        }

        // Max iterations reached - request final summary from LLM
        Ok(self
            .run_final_summary(&mut messages, system_prompt_context, &mut emitted_messages)
            .await)
    }

    /// 等待取消信号。若未配置 cancel_token，永远不返回。
    ///
    /// 封装了与 watch channel 的交互：changed() 返回 Ok 表示收到信号，
    /// 返回 Err(Closed) 表示 sender 已 drop，两种情况都视为取消。
    async fn cancel_signal(&self) {
        if let Some(ref mutex) = self.cancel_token {
            let mut token = mutex.lock().await;
            let _ = token.changed().await;
        } else {
            std::future::pending::<()>().await;
        }
    }

    /// 净化消息中的不完整 tool_call 序列，返回移除数量。
    /// 日志由调用方负责，因为不同调用点需要不同的结构化字段。
    fn sanitize_messages_for_llm(messages: &mut Vec<ChatMessage>) -> usize {
        crate::bus::message::sanitize_incomplete_tool_call_sequences(messages)
    }

    /// 检查取消信号。返回 true 表示已取消。
    async fn check_cancelled(&self) -> bool {
        if let Some(ref mutex) = self.cancel_token {
            mutex.lock().await.has_changed().unwrap_or(true)
        } else {
            false
        }
    }

    /// 构建 LLM 请求：过滤图片、构建系统提示、转换消息格式。
    /// 统一了循环内调用和最终 summary 调用的请求构建逻辑。
    ///
    /// 优化：token 估算直接基于 ChatMessage 累加字段长度（轻量），
    /// 不再构造中间 text_only_messages: Vec<Message>（避免 N 条消息 × 5 字段双克隆）。
    /// 工具 token 估算在循环外预算后传入（tools_tokens）。
    fn build_llm_request(
        &self,
        messages: &[ChatMessage],
        system_prompt_context: Option<&SystemPromptContext>,
        tools: Option<Vec<crate::domain::tools::Tool>>,
        tools_tokens: usize,
    ) -> ChatCompletionRequest {
        let filtered_messages = filter_images_by_age_and_count(
            messages,
            self.runtime_config.max_image_age_rounds,
            self.runtime_config.max_images_in_context,
        );
        let filtered_messages_ref: &[ChatMessage] = &filtered_messages;
        let image_count = count_supported_image_media_refs(filtered_messages_ref);

        let system_prompt = system_prompt_context.and_then(|ctx| {
            self.system_prompt_provider
                .as_ref()
                .and_then(|provider| provider.build(ctx))
        });

        // 轻量 token 估算：直接从 ChatMessage 累加，无需构造中间 Vec<Message>
        let text_tokens = estimate_text_tokens_from_chat_messages(
            filtered_messages_ref,
            system_prompt.as_ref().map(|p| p.content.as_str()),
        );
        let image_tokens =
            image_token_budget_for_request(&self.runtime_config, text_tokens, tools_tokens);
        let mut image_budget = ImageInlineBudget::new(image_tokens, image_count);

        let mut messages_for_llm: Vec<Message> = Vec::with_capacity(filtered_messages_ref.len() + 2);
        if let Some(ref prompt) = system_prompt {
            messages_for_llm.push(Message::system(prompt.content.clone()));
        }
        messages_for_llm.extend(
            filtered_messages_ref
                .iter()
                .map(|message| chat_message_to_llm_message(message, &mut image_budget)),
        );

        ChatCompletionRequest {
            messages: messages_for_llm,
            temperature: None,
            max_tokens: None,
            tools,
        }
    }

    /// 构建 LLM 最终响应（无工具调用时）。调用方应先检查 `response.tool_calls.is_empty()`。
    async fn build_final_response(
        &self,
        response: crate::providers::ChatCompletionResponse,
        streaming_message_id: &str,
        had_streaming: bool,
        emitted_messages: &mut Vec<ChatMessage>,
    ) -> AgentProcessResult {
        let mut assistant_message = if let Some(reasoning_content) = response.reasoning_content {
            ChatMessage::assistant_with_reasoning(response.content, reasoning_content)
        } else {
            ChatMessage::assistant(response.content)
        };
        // Use the same ID as the stream deltas so the front-end can replace
        // the streamed message with this authoritative response.
        if had_streaming {
            assistant_message.id = streaming_message_id.to_string();
        }
        // 记录本次 LLM 调用的 token 用量（cost 累计 + context 瞬时）
        assistant_message.usage = Some(
            crate::bus::message::MessageUsage::from_provider_usage(response.usage)
                .with_context_window(self.runtime_config.context_window_tokens),
        );
        emitted_messages.push(assistant_message.clone());
        self.emit_live_tool_call_message(assistant_message.clone())
            .await;
        AgentProcessResult {
            final_response: assistant_message,
            emitted_messages: std::mem::take(emitted_messages),
        }
    }

    /// 处理工具执行结果，追加到 messages 和 emitted_messages，发出 tool_result 事件。
    /// 合并了 LoopDetectionResult::Warning 和 ::Ok 两个分支的逻辑。
    async fn process_tool_results(
        &self,
        tool_calls: &[ToolCall],
        tool_results: &[ToolExecutionOutcome],
        loop_detector: &mut LoopDetector,
        messages: &mut Vec<ChatMessage>,
        emitted_messages: &mut Vec<ChatMessage>,
    ) {
        for (tool_call, result) in tool_calls.iter().zip(tool_results.iter()) {
            let truncated_output =
                truncate_tool_result(&result.output, self.runtime_config.tool_result_max_chars);

            let loop_result = loop_detector.record(&tool_call.name, &tool_call.arguments);
            let prefix = match loop_result {
                LoopDetectionResult::Warning(msg) => {
                    tracing::warn!(tool = %tool_call.name, "Loop warning: {}", msg);
                    format!("{}\n\n[上一条结果]\n", msg)
                }
                LoopDetectionResult::Ok => String::new(),
            };

            let state = if result.state == ToolExecutionState::PendingUserAction {
                ToolMessageState::PendingUserAction
            } else {
                ToolMessageState::Completed
            };
            let tool_message = ChatMessage::tool_with_state(
                tool_call.id.clone(),
                tool_call.name.clone(),
                format!("{}{}", prefix, truncated_output),
                state,
            )
            .with_tool_duration(result.duration.as_millis() as u64);
            messages.push(tool_message.clone());
            emitted_messages.push(tool_message.clone());
            let duration_ms = Some(result.duration.as_millis() as u64);
            self.emit_tool_result(tool_message, duration_ms).await;
        }
    }

    /// 达到最大迭代次数后，请求 LLM 生成总结。
    async fn run_final_summary(
        &self,
        messages: &mut Vec<ChatMessage>,
        system_prompt_context: Option<&SystemPromptContext>,
        emitted_messages: &mut Vec<ChatMessage>,
    ) -> AgentProcessResult {
        tracing::warn!("Max iterations reached, requesting final summary from LLM");

        // Defense: sanitize before final summary request
        let removed = Self::sanitize_messages_for_llm(messages);
        if removed > 0 {
            tracing::warn!(
                removed_count = removed,
                "Sanitized before max-iterations summary"
            );
        }

        // Add a message asking for summary
        let summary_request = ChatMessage::user(
            "You have reached the maximum number of tool call iterations. \
            Please provide your best answer based on the work completed so far.",
        );
        messages.push(summary_request);

        let request = self.build_llm_request(messages, system_prompt_context, None, 0);
        let max_retries = self.runtime_config.max_retries as usize;

        for attempt in 0..=max_retries {
            // 最终 summary 调用也与取消信号竞速
            let final_result: Result<
                crate::providers::ChatCompletionResponse,
                Box<dyn std::error::Error + Send + Sync>,
            >;
            if self.cancel_token.is_some() {
                tokio::select! {
                    _ = self.cancel_signal() => {
                        let cancel = Self::build_cancel_result(self.max_iterations, std::mem::take(emitted_messages));
                        self.emit_live_tool_call_message(cancel.final_response.clone()).await;
                        return cancel;
                    }
                    result = self.provider.chat(request.clone()) => {
                        final_result = result;
                    }
                }
            } else {
                final_result = self.provider.chat(request.clone()).await;
            }

            match final_result {
                Ok(response) => {
                    let mut assistant_message = if let Some(reasoning_content) = response.reasoning_content
                    {
                        ChatMessage::assistant_with_reasoning(response.content, reasoning_content)
                    } else {
                        ChatMessage::assistant(response.content)
                    };
                    // 记录 summary 调用的 token 用量
                    assistant_message.usage = Some(
                        crate::bus::message::MessageUsage::from_provider_usage(response.usage)
                            .with_context_window(self.runtime_config.context_window_tokens),
                    );
                    emitted_messages.push(assistant_message.clone());
                    self.emit_live_tool_call_message(assistant_message.clone())
                        .await;
                    return AgentProcessResult {
                        final_response: assistant_message,
                        emitted_messages: std::mem::take(emitted_messages),
                    };
                }
                Err(e) => {
                    let error_text = e.to_string();
                    let can_retry = attempt < max_retries
                        && is_recoverable_llm_error(&error_text);
                    if can_retry {
                        let delay = LLM_RETRY_DELAYS_MS
                            [attempt.min(LLM_RETRY_DELAYS_MS.len() - 1)];
                        tracing::warn!(
                            attempt = attempt + 1,
                            retry_in_ms = delay,
                            provider = %self.provider.name(),
                            model = %self.provider.model_id(),
                            error = %error_text,
                            "Summary LLM request failed, retrying"
                        );
                        if self.cancel_token.is_some() {
                            tokio::select! {
                                _ = self.cancel_signal() => {
                                    let cancel = Self::build_cancel_result(self.max_iterations, std::mem::take(emitted_messages));
                                    self.emit_live_tool_call_message(cancel.final_response.clone()).await;
                                    return cancel;
                                }
                                _ = tokio::time::sleep(Duration::from_millis(delay)) => {}
                            }
                        } else {
                            tokio::time::sleep(Duration::from_millis(delay)).await;
                        }
                        continue;
                    }
                    tracing::error!(
                        provider = %self.provider.name(),
                        model = %self.provider.model_id(),
                        error = %e,
                        error_details = %format_error_chain(e.as_ref()),
                        "Failed to get summary from LLM"
                    );
                    let final_message = ChatMessage::assistant(recoverable_llm_message(&error_text));
                    emitted_messages.push(final_message.clone());
                    self.emit_live_tool_call_message(final_message.clone())
                        .await;
                    return AgentProcessResult {
                        final_response: final_message,
                        emitted_messages: std::mem::take(emitted_messages),
                    };
                }
            }
        }

        unreachable!("retry loop must return within its body")
    }

    /// 构建取消响应，包含已完成的迭代次数和已生成的消息数量。
    /// 构建取消响应，将取消通知追加到 `emitted_messages` 末尾后一并返回。
    /// 这样 finalize_result 会把中间消息加入内存历史，确保下一个 LLM 调用有完整上下文。
    fn build_cancel_result(
        iteration: usize,
        mut emitted_messages: Vec<ChatMessage>,
    ) -> AgentProcessResult {
        let emitted_count = emitted_messages.len();
        let cancel_message = format!(
            "\n\n[用户已取消执行。已迭代 {} 次，取消前共生成了 {} 条消息。]",
            iteration, emitted_count
        );
        let assistant_message = ChatMessage::assistant(cancel_message);
        emitted_messages.push(assistant_message.clone());
        AgentProcessResult {
            final_response: assistant_message,
            emitted_messages,
        }
    }

    async fn emit_live_tool_call_message(&self, message: ChatMessage) {
        if let Some(handler) = &self.emitted_message_handler {
            handler.handle(message).await;
        }
    }

    async fn emit_tool_result(&self, message: ChatMessage, duration_ms: Option<u64>) {
        if let Some(handler) = &self.emitted_message_handler {
            handler.handle_tool_result(message, duration_ms).await;
        }
    }

    /// Determine whether to execute tools in parallel or sequentially.
    ///
    /// Returns true if:
    /// - There are multiple tool calls
    /// - None of the tools require sequential execution (tool_search, non-concurrency-safe)
    fn should_execute_in_parallel(&self, tool_calls: &[ToolCall]) -> bool {
        if tool_calls.len() <= 1 {
            return false;
        }

        // tool_search must run sequentially to avoid MCP activation race conditions
        if tool_calls.iter().any(|tc| tc.name == "tool_search") {
            return false;
        }

        // Multiple Task tools can run in parallel
        // Task tools create independent subagents with isolated contexts, no shared state
        let task_count = tool_calls.iter().filter(|tc| tc.name == "task").count();
        if task_count > 1 && task_count == tool_calls.len() {
            return true;
        }

        // When Task is mixed with other tools, keep sequential to avoid complexity
        if task_count > 0 {
            return false;
        }

        // All tools must be concurrency-safe to run in parallel
        tool_calls.iter().all(|tc| {
            self.tools
                .get(&tc.name)
                .map(|t| t.concurrency_safe())
                .unwrap_or(false)
        })
    }

    /// Execute multiple tool calls, choosing parallel or sequential based on conditions.
    async fn execute_tools(&self, tool_calls: &[ToolCall]) -> Vec<ToolExecutionOutcome> {
        if self.should_execute_in_parallel(tool_calls) {
            tracing::debug!("Executing {} tools in parallel", tool_calls.len());
            self.execute_tools_parallel(tool_calls).await
        } else {
            tracing::debug!("Executing {} tools sequentially", tool_calls.len());
            self.execute_tools_sequential(tool_calls).await
        }
    }

    /// Execute tools in parallel using join_all.
    async fn execute_tools_parallel(&self, tool_calls: &[ToolCall]) -> Vec<ToolExecutionOutcome> {
        let futures: Vec<_> = tool_calls
            .iter()
            .map(|tc| self.execute_one_tool(tc))
            .collect();

        futures_util::future::join_all(futures).await
    }

    /// Execute tools sequentially.
    async fn execute_tools_sequential(&self, tool_calls: &[ToolCall]) -> Vec<ToolExecutionOutcome> {
        let mut outcomes = Vec::with_capacity(tool_calls.len());

        for tool_call in tool_calls {
            outcomes.push(self.execute_one_tool(tool_call).await);
        }

        outcomes
    }

    /// Execute a single tool and return the outcome with event tracking.
    async fn execute_one_tool(&self, tool_call: &ToolCall) -> ToolExecutionOutcome {
        let start = Instant::now();
        let tool_name = tool_call.name.clone();

        // Log function call with name and arguments before execution
        let args_str = match &tool_call.arguments {
            serde_json::Value::Object(obj) if obj.is_empty() => "{}".to_string(),
            other => serde_json::to_string_pretty(other).unwrap_or_else(|_| other.to_string()),
        };
        tracing::info!(tool = %tool_call.name, args = %args_str, "Calling tool");

        // Record ToolCallStart event
        if let Some(ref observer) = self.observer {
            observer.record_event(&ObserverEvent::ToolCallStart {
                tool: tool_name.clone(),
                arguments: Some(truncate_args(&tool_call.arguments, 300)),
            });
        }

        let result = self.execute_tool_internal(tool_call).await;
        let duration = start.elapsed();

        // Record ToolCall event
        if let Some(ref observer) = self.observer {
            observer.record_event(&ObserverEvent::ToolCall {
                tool: tool_name.clone(),
                duration,
                success: result.success,
            });
        }

        // Apply duration
        ToolExecutionOutcome { duration, ..result }
    }

    /// Internal tool execution without event tracking.
    async fn execute_tool_internal(&self, tool_call: &ToolCall) -> ToolExecutionOutcome {
        let normalized_arguments = normalize_tool_arguments(&tool_call.arguments);

        let tool = match self.tools.get(&tool_call.name) {
            Some(t) => t,
            None => {
                tracing::warn!(tool = %tool_call.name, "Tool not found");
                let skill_hint = self
                    .skills
                    .as_ref()
                    .and_then(|s| s.matching_skill_summary(&tool_call.name));
                let error = match skill_hint {
                    Some(summary) => format!(
                        "Tool '{}' not found. A skill with the same name exists: {}. Skills are not tools. Call skill_activate with {{\"name\": \"{}\"}} first.",
                        tool_call.name, summary, tool_call.name
                    ),
                    None => format!("Tool '{}' not found", tool_call.name),
                };
                return ToolExecutionOutcome::failure(format!("Error: {}", error), Some(error));
            }
        };

        match tool
            .execute_with_context(
                &{
                    let mut ctx = self.tool_context.clone();
                    ctx.tool_call_id = Some(tool_call.id.clone());
                    ctx
                },
                normalized_arguments.clone(),
            )
            .await
        {
            Ok(result) => {
                if result.success {
                    if let Some(pending_output) = parse_pending_tool_output(&result.output) {
                        ToolExecutionOutcome::pending(pending_output)
                    } else {
                        ToolExecutionOutcome::success(result.output)
                    }
                } else {
                    let error = result.error.unwrap_or_default();
                    tracing::error!(
                        tool = %tool_call.name,
                        args = %truncate_args(&tool_call.arguments, 4_000),
                        normalized_args = %truncate_args(&normalized_arguments, 4_000),
                        error = %error,
                        output = %result.output,
                        "Tool returned an error result"
                    );
                    // task 工具在失败时提供结构化 JSON output（含 task_id），直接透传；
                    // 其他工具 output 为空，走纯文本 "Error: {error}" 回退。
                    let failure_output = if !result.output.is_empty() {
                        result.output
                    } else {
                        format!("Error: {}", error)
                    };
                    ToolExecutionOutcome::failure(failure_output, Some(error))
                }
            }
            Err(e) => {
                tracing::error!(
                    tool = %tool_call.name,
                    args = %truncate_args(&tool_call.arguments, 4_000),
                    normalized_args = %truncate_args(&normalized_arguments, 4_000),
                    error = %e,
                    error_details = %format!("{:#}", e),
                    "Tool execution failed"
                );
                ToolExecutionOutcome::failure(format!("Error: {}", e), Some(e.to_string()))
            }
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::config::LLMProviderConfig;
    use crate::observability::{MultiObserver, Observer};
    use crate::providers::{ChatCompletionResponse, Usage};
    use tempfile::tempdir;

    struct TestObserver {
        events: std::sync::Mutex<Vec<ObserverEvent>>,
    }

    impl TestObserver {
        fn new() -> Self {
            Self {
                events: std::sync::Mutex::new(Vec::new()),
            }
        }
    }

    impl Observer for TestObserver {
        fn record_event(&self, event: &ObserverEvent) {
            self.events.lock().unwrap().push(event.clone());
        }

        fn name(&self) -> &str {
            "test_observer"
        }
    }

    struct TestSkillProvider;

    impl SkillProvider for TestSkillProvider {
        fn system_index_prompt(&self) -> Option<String> {
            None
        }

        fn matching_skill_summary(&self, name: &str) -> Option<String> {
            (name == "baidu-search").then(|| "用于百度搜索和天气查询的技能".to_string())
        }
    }

    fn test_runtime_config() -> LLMProviderConfig {
        LLMProviderConfig {
            provider_type: "openai".to_string(),
            name: "test".to_string(),
            base_url: "http://localhost".to_string(),
            api_key: "test-key".to_string(),
            extra_headers: std::collections::HashMap::new(),
            llm_timeout_secs: 120,
            memory_maintenance_timeout_secs: 600,
            max_retries: 3,
            model_id: "test-model".to_string(),
            temperature: Some(0.0),
            max_tokens: Some(32),
            context_window_tokens: None,
            model_extra: std::collections::HashMap::new(),
            max_tool_iterations: 1,
            tool_result_max_chars: 100_000,
            context_tool_result_trim_chars: 100_000,
            max_images_in_context: 1,
            max_image_age_rounds: 10,
        }
    }

    #[tokio::test]
    async fn test_missing_tool_with_same_name_skill_returns_activation_hint() {
        let loop_instance = AgentLoop::with_tools_and_skill_provider(
            test_runtime_config(),
            Arc::new(ToolRegistry::new()),
            Arc::new(TestSkillProvider),
        )
        .unwrap();

        let outcome = loop_instance
            .execute_tool_internal(&ToolCall {
                id: "call-1".to_string(),
                name: "baidu-search".to_string(),
                arguments: serde_json::json!({
                    "queries": "佛山今天几点下雨"
                }),
            })
            .await;

        assert_eq!(outcome.state, ToolExecutionState::Completed);
        assert!(!outcome.success);
        assert!(outcome.output.contains("技能"));
        assert!(outcome.output.contains("skill_activate"));
        assert!(outcome.output.contains("baidu-search"));
    }

    #[tokio::test]
    async fn test_observer_receives_tool_events() {
        // Verify MultiObserver works
        let mut multi = MultiObserver::new();
        multi.add_observer(Box::new(TestObserver::new()));

        let event = ObserverEvent::ToolCallStart {
            tool: "test".to_string(),
            arguments: Some("{}".to_string()),
        };
        multi.record_event(&event);

        // Just verify the structure works
        assert_eq!(multi.len(), 1);
    }

    #[test]
    fn test_should_execute_in_parallel_single_tool() {
        // Would need a proper setup with AgentLoop to test fully
        // For now, just verify the logic: single tool should return false
        let calls = vec![ToolCall {
            id: "1".to_string(),
            name: "test".to_string(),
            arguments: serde_json::json!({}),
        }];

        // If there's only 1 tool, should return false regardless
        assert_eq!(calls.len() <= 1, true);
    }

    #[test]
    fn test_chat_message_to_llm_message_preserves_assistant_tool_calls() {
        let chat_message = ChatMessage::assistant_with_tool_calls(
            "calling tool",
            vec![ToolCall {
                id: "call_1".to_string(),
                name: "calculator".to_string(),
                arguments: serde_json::json!({ "expression": "2+2" }),
            }],
        );

        let mut image_budget = ImageInlineBudget::new(0, 0);
        let provider_message = chat_message_to_llm_message(&chat_message, &mut image_budget);

        assert_eq!(provider_message.role, "assistant");
        assert_eq!(provider_message.tool_calls.as_ref().unwrap().len(), 1);
        assert_eq!(
            provider_message.tool_calls.as_ref().unwrap()[0].id,
            "call_1"
        );
        assert_eq!(
            provider_message.tool_calls.as_ref().unwrap()[0].name,
            "calculator"
        );
    }

    #[test]
    fn test_chat_message_to_llm_message_preserves_reasoning_content() {
        let chat_message =
            ChatMessage::assistant_with_reasoning("final answer", "hidden chain of thought");

        let mut image_budget = ImageInlineBudget::new(0, 0);
        let provider_message = chat_message_to_llm_message(&chat_message, &mut image_budget);

        assert_eq!(provider_message.role, "assistant");
        assert_eq!(
            provider_message.reasoning_content.as_deref(),
            Some("hidden chain of thought")
        );
    }

    #[test]
    fn test_truncate_tool_result_handles_utf8_char_boundaries() {
        let input = "范".repeat(100_500);

        let output = truncate_tool_result(&input, 100_000);

        assert!(output.contains("Output truncated"));
        assert!(output.is_char_boundary(output.len()));
    }

    #[test]
    fn test_parse_pending_tool_output() {
        let output = parse_pending_tool_output("__PICOBOT_PENDING_USER_ACTION__\n请完成授权");
        assert_eq!(output.as_deref(), Some("请完成授权"));
        assert!(parse_pending_tool_output("normal output").is_none());
    }

    #[test]
    fn test_normalize_tool_arguments_parses_stringified_json() {
        let normalized = normalize_tool_arguments(&serde_json::Value::String(
            "{\"command\":\"ls -la\"}".to_string(),
        ));

        assert_eq!(normalized, serde_json::json!({ "command": "ls -la" }));
    }

    #[test]
    fn test_normalize_tool_arguments_keeps_plain_string() {
        let normalized =
            normalize_tool_arguments(&serde_json::Value::String("plain text".to_string()));

        assert_eq!(
            normalized,
            serde_json::Value::String("plain text".to_string())
        );
    }

    #[test]
    fn test_build_content_blocks_skips_non_image_media_refs() {
        let temp_dir = tempdir().unwrap();
        let pdf_path = temp_dir.path().join("demo.pdf");
        std::fs::write(&pdf_path, b"%PDF-1.4").unwrap();

        let mut budget = ImageInlineBudget::new(1_000, 0);
        let blocks = build_content_blocks(
            "hello",
            &[pdf_path.to_string_lossy().to_string()],
            &mut budget,
        );

        assert_eq!(blocks.len(), 1);
        assert!(matches!(&blocks[0], ContentBlock::Text { text } if text == "hello"));
    }

    #[test]
    fn test_build_content_blocks_keeps_supported_images() {
        let temp_dir = tempdir().unwrap();
        let jpg_path = temp_dir.path().join("demo.jpg");
        let image = image::DynamicImage::new_rgb8(8, 8);
        image.save(&jpg_path).unwrap();

        let mut budget = ImageInlineBudget::new(10_000, 1);
        let blocks = build_content_blocks(
            "hello",
            &[jpg_path.to_string_lossy().to_string()],
            &mut budget,
        );

        assert_eq!(blocks.len(), 2);
        assert!(matches!(&blocks[0], ContentBlock::Text { text } if text == "hello"));
        assert!(
            matches!(&blocks[1], ContentBlock::ImageUrl { image_url } if image_url.url.starts_with("data:image/jpeg;base64,"))
        );
    }

    #[test]
    fn test_build_content_blocks_compresses_images_to_budget() {
        let temp_dir = tempdir().unwrap();
        let png_path = temp_dir.path().join("large.png");
        let image = image::DynamicImage::new_rgb8(512, 512);
        image.save(&png_path).unwrap();

        let mut budget = ImageInlineBudget::new(512, 1);
        let blocks = build_content_blocks(
            "hello",
            &[png_path.to_string_lossy().to_string()],
            &mut budget,
        );

        assert_eq!(blocks.len(), 2);
        assert!(matches!(&blocks[0], ContentBlock::Text { text } if text == "hello"));
        assert!(
            matches!(&blocks[1], ContentBlock::ImageUrl { image_url } if image_url.url.starts_with("data:image/jpeg;base64,"))
        );
    }

    #[test]
    fn test_build_content_blocks_adds_user_visible_notice_when_image_cannot_be_sent() {
        let temp_dir = tempdir().unwrap();
        let jpg_path = temp_dir.path().join("demo.jpg");
        let image = image::DynamicImage::new_rgb8(8, 8);
        image.save(&jpg_path).unwrap();

        let mut budget = ImageInlineBudget::new(0, 1);
        let blocks = build_content_blocks(
            "hello",
            &[jpg_path.to_string_lossy().to_string()],
            &mut budget,
        );

        assert_eq!(blocks.len(), 2);
        assert!(matches!(&blocks[0], ContentBlock::Text { text } if text == "hello"));
        assert!(matches!(
            &blocks[1],
            ContentBlock::Text { text }
                if text.contains("图片未能成功入模") && text.contains("demo.jpg")
        ));
    }

    #[test]
    fn test_filter_images_by_age_and_count_no_images() {
        let messages = vec![
            ChatMessage::user("hello"),
            ChatMessage::assistant("hi"),
            ChatMessage::user("how are you"),
        ];

        let filtered = filter_images_by_age_and_count(&messages, 10, 5);
        assert_eq!(filtered.len(), 3);
        assert_eq!(filtered[0].content, "hello");
        assert_eq!(filtered[1].content, "hi");
        assert_eq!(filtered[2].content, "how are you");
    }

    #[test]
    fn test_filter_images_by_age_limit() {
        let temp_dir = tempdir().unwrap();
        let jpg_path = temp_dir.path().join("test.jpg");
        let image = image::DynamicImage::new_rgb8(8, 8);
        image.save(&jpg_path).unwrap();

        // 创建 12 条消息，第 0 条（最旧）有图片
        let messages: Vec<ChatMessage> = (0..12)
            .map(|i| {
                if i == 0 {
                    ChatMessage::user_with_media(
                        "first message with image",
                        vec![jpg_path.to_string_lossy().to_string()],
                    )
                } else if i % 2 == 0 {
                    ChatMessage::user(format!("user message {}", i))
                } else {
                    ChatMessage::assistant(format!("assistant message {}", i))
                }
            })
            .collect();

        // max_age_rounds = 10，第一条消息（索引 0）距离最新消息（索引 11）有 11 条消息
        // 所以第一条消息的图片应该被过滤
        let filtered = filter_images_by_age_and_count(&messages, 10, 100);

        // 检查第一条消息的图片被过滤
        assert_eq!(filtered[0].media_refs.len(), 0);
        assert!(filtered[0].content.contains("图片已过期"));
    }

    #[test]
    fn test_filter_images_by_count_limit() {
        let temp_dir = tempdir().unwrap();

        // 创建 3 张不同的图片
        let jpg_paths: Vec<String> = (0..3)
            .map(|i| {
                let path = temp_dir.path().join(format!("test{}.jpg", i));
                let image = image::DynamicImage::new_rgb8(8, 8);
                image.save(&path).unwrap();
                path.to_string_lossy().to_string()
            })
            .collect();

        // 创建 3 条消息，每条都有图片
        let messages: Vec<ChatMessage> = (0..3)
            .map(|i| {
                ChatMessage::user_with_media(format!("message {}", i), vec![jpg_paths[i].clone()])
            })
            .collect();

        // max_images = 1，只保留最新的图片（索引 2）
        let filtered = filter_images_by_age_and_count(&messages, 100, 1);

        // 检查最新的消息保留图片，旧消息的图片被过滤
        assert_eq!(filtered[2].media_refs.len(), 1); // 最新保留
        assert_eq!(filtered[1].media_refs.len(), 0); // 被过滤
        assert!(filtered[1].content.contains("超出最大图片数量限制"));
        assert_eq!(filtered[0].media_refs.len(), 0); // 被过滤
        assert!(filtered[0].content.contains("超出最大图片数量限制"));
    }

    #[test]
    fn test_filter_images_combined_limits() {
        let temp_dir = tempdir().unwrap();

        // 创建 5 张图片
        let jpg_paths: Vec<String> = (0..5)
            .map(|i| {
                let path = temp_dir.path().join(format!("test{}.jpg", i));
                let image = image::DynamicImage::new_rgb8(8, 8);
                image.save(&path).unwrap();
                path.to_string_lossy().to_string()
            })
            .collect();

        // 创建 20 条消息，在特定位置添加图片
        let messages: Vec<ChatMessage> = (0..20)
            .map(|i| {
                // 在索引 0, 5, 10, 15, 19 添加图片
                if i == 0 || i == 5 || i == 10 || i == 15 || i == 19 {
                    let image_idx = i / 5;
                    ChatMessage::user_with_media(
                        format!("message {} with image", i),
                        vec![jpg_paths[image_idx.clamp(0, 4)].clone()],
                    )
                } else if i % 2 == 0 {
                    ChatMessage::user(format!("user message {}", i))
                } else {
                    ChatMessage::assistant(format!("assistant message {}", i))
                }
            })
            .collect();

        // max_age_rounds = 10（保留最近 10 条消息内的图片）
        // max_images = 3（最多 3 张图片）
        // 最新消息索引 19 (age=0)，索引 15 (age=4)，索引 10 (age=9)，索引 5 (age=14)，索引 0 (age=19)
        // 索引 5 和 0 超出 age 限制
        // 索引 19, 15, 10 的图片应该保留（共 3 张，不超过 max_images）
        let filtered = filter_images_by_age_and_count(&messages, 10, 3);

        // 检查结果
        assert!(filtered[19].media_refs.len() > 0, "最新消息应保留图片");
        assert!(filtered[15].media_refs.len() > 0, "age=4 的消息应保留图片");
        assert!(filtered[10].media_refs.len() > 0, "age=9 的消息应保留图片");
        assert_eq!(filtered[5].media_refs.len(), 0, "age=14 的消息图片应被过滤");
        assert!(filtered[5].content.contains("超出 10 条消息范围"));
        assert_eq!(filtered[0].media_refs.len(), 0, "age=19 的消息图片应被过滤");
        assert!(filtered[0].content.contains("超出 10 条消息范围"));
    }

    // ====================
    // sanitize_incomplete_tool_call_sequences tests
    // ====================

    #[test]
    fn test_sanitize_removes_trailing_incomplete_tool_call_sequence() {
        let mut messages = vec![
            ChatMessage::user("hello"),
            ChatMessage::assistant_with_tool_calls(
                "calling tool",
                vec![ToolCall {
                    id: "call_1".to_string(),
                    name: "calculator".to_string(),
                    arguments: serde_json::json!({"expression": "1+1"}),
                }],
            ),
            // Tool result for call_1 is MISSING — incomplete sequence
        ];

        let removed = crate::bus::message::sanitize_incomplete_tool_call_sequences(&mut messages);
        assert_eq!(removed, 1);
        assert_eq!(messages.len(), 1);
        assert_eq!(messages[0].role, "user");
    }

    #[test]
    fn test_sanitize_preserves_complete_tool_call_sequence() {
        let mut messages = vec![
            ChatMessage::user("hello"),
            ChatMessage::assistant_with_tool_calls(
                "calling tool",
                vec![ToolCall {
                    id: "call_1".to_string(),
                    name: "calculator".to_string(),
                    arguments: serde_json::json!({"expression": "1+1"}),
                }],
            ),
            ChatMessage::tool("call_1", "calculator", "2"),
        ];

        let removed = crate::bus::message::sanitize_incomplete_tool_call_sequences(&mut messages);
        assert_eq!(removed, 0);
        assert_eq!(messages.len(), 3);
    }

    #[test]
    fn test_sanitize_removes_multiple_incomplete_sequences() {
        let mut messages = vec![
            ChatMessage::user("hello"),
            ChatMessage::assistant_with_tool_calls(
                "first tool call",
                vec![ToolCall {
                    id: "call_1".to_string(),
                    name: "calculator".to_string(),
                    arguments: serde_json::json!({"expression": "1+1"}),
                }],
            ),
            // Missing tool result for call_1
            ChatMessage::user("second question"),
            ChatMessage::assistant_with_tool_calls(
                "second tool call",
                vec![ToolCall {
                    id: "call_2".to_string(),
                    name: "read".to_string(),
                    arguments: serde_json::json!({"path": "README.md"}),
                }],
            ),
            // Also missing tool result for call_2
        ];

        let removed = crate::bus::message::sanitize_incomplete_tool_call_sequences(&mut messages);
        // Should remove both trailing assistant messages with incomplete tool calls
        assert_eq!(removed, 2);
        assert_eq!(messages.len(), 2);
        assert_eq!(messages[0].role, "user");
        assert_eq!(messages[0].content, "hello");
        assert_eq!(messages[1].role, "user");
        assert_eq!(messages[1].content, "second question");
    }

    #[test]
    fn test_sanitize_removes_assistant_when_partial_tool_results() {
        // Assistant makes 2 tool calls, but only 1 tool result exists
        let mut messages = vec![
            ChatMessage::user("hello"),
            ChatMessage::assistant_with_tool_calls(
                "calling two tools",
                vec![
                    ToolCall {
                        id: "call_1".to_string(),
                        name: "calculator".to_string(),
                        arguments: serde_json::json!({"expression": "1+1"}),
                    },
                    ToolCall {
                        id: "call_2".to_string(),
                        name: "read".to_string(),
                        arguments: serde_json::json!({"path": "README.md"}),
                    },
                ],
            ),
            ChatMessage::tool("call_1", "calculator", "2"),
            // Missing tool result for call_2
        ];

        let removed_count =
            crate::bus::message::sanitize_incomplete_tool_call_sequences(&mut messages);
        // Phase 1 removes the assistant message (call_2 has no result).
        // Phase 2 removes the orphaned tool result for call_1 (its parent
        // assistant was removed).
        assert_eq!(removed_count, 2);
        assert_eq!(messages.len(), 1);
        assert_eq!(messages[0].role, "user");
    }

    #[test]
    fn test_sanitize_preserves_messages_without_tool_calls() {
        let mut messages = vec![
            ChatMessage::user("hello"),
            ChatMessage::assistant("hi there"),
            ChatMessage::user("how are you"),
        ];

        let removed = crate::bus::message::sanitize_incomplete_tool_call_sequences(&mut messages);
        assert_eq!(removed, 0);
        assert_eq!(messages.len(), 3);
    }

    #[test]
    fn test_sanitize_handles_empty_messages() {
        let mut messages: Vec<ChatMessage> = vec![];
        let removed = crate::bus::message::sanitize_incomplete_tool_call_sequences(&mut messages);
        assert_eq!(removed, 0);
    }

    #[test]
    fn test_sanitize_removes_orphaned_tool_messages() {
        // A lone tool message without a preceding assistant tool_calls
        // is orphaned and should be removed.
        let mut messages = vec![ChatMessage::tool("call_1", "calculator", "2")];

        let removed = crate::bus::message::sanitize_incomplete_tool_call_sequences(&mut messages);
        assert_eq!(removed, 1);
        assert!(messages.is_empty());
    }

    #[test]
    fn test_sanitize_preserves_complete_sequence_with_multiple_tool_calls() {
        let mut messages = vec![
            ChatMessage::user("do two things"),
            ChatMessage::assistant_with_tool_calls(
                "calling two tools",
                vec![
                    ToolCall {
                        id: "call_1".to_string(),
                        name: "calculator".to_string(),
                        arguments: serde_json::json!({"expression": "1+1"}),
                    },
                    ToolCall {
                        id: "call_2".to_string(),
                        name: "read".to_string(),
                        arguments: serde_json::json!({"path": "README.md"}),
                    },
                ],
            ),
            ChatMessage::tool("call_1", "calculator", "2"),
            ChatMessage::tool("call_2", "read", "contents of README"),
        ];

        let removed = crate::bus::message::sanitize_incomplete_tool_call_sequences(&mut messages);
        assert_eq!(removed, 0);
        assert_eq!(messages.len(), 4);
    }

    #[test]
    fn test_sanitize_only_trims_trailing_incomplete_sequence() {
        // Complete sequence followed by an incomplete one — only the
        // trailing incomplete one should be removed
        let mut messages = vec![
            ChatMessage::user("first question"),
            ChatMessage::assistant_with_tool_calls(
                "first tool call",
                vec![ToolCall {
                    id: "call_1".to_string(),
                    name: "calculator".to_string(),
                    arguments: serde_json::json!({"expression": "1+1"}),
                }],
            ),
            ChatMessage::tool("call_1", "calculator", "2"),
            ChatMessage::assistant("the answer is 2"),
            ChatMessage::user("second question"),
            ChatMessage::assistant_with_tool_calls(
                "second tool call",
                vec![ToolCall {
                    id: "call_2".to_string(),
                    name: "read".to_string(),
                    arguments: serde_json::json!({"path": "README.md"}),
                }],
            ),
            // Missing tool result for call_2 — only THIS sequence should be trimmed
        ];

        let removed = crate::bus::message::sanitize_incomplete_tool_call_sequences(&mut messages);
        assert_eq!(removed, 1);
        // First complete sequence preserved (5 messages), user message for second
        // question preserved
        assert_eq!(messages.len(), 5);
        assert_eq!(messages[0].content, "first question");
        assert_eq!(messages[3].content, "the answer is 2");
        assert_eq!(messages[4].content, "second question");
    }

    #[test]
    fn test_sanitize_removes_mid_history_orphaned_tool_calls() {
        // Bug scenario: orphaned tool_calls in the MIDDLE of history,
        // followed by a complete sequence. The old trailing-only sanitizer
        // would stop at the complete sequence and never remove the orphan.
        let mut messages = vec![
            ChatMessage::user("first question"),
            ChatMessage::assistant_with_tool_calls(
                "orphaned tool call",
                vec![ToolCall {
                    id: "call_1".to_string(),
                    name: "calculator".to_string(),
                    arguments: serde_json::json!({"expression": "1+1"}),
                }],
            ),
            // Missing tool result for call_1 — ORPHAN in the middle
            ChatMessage::user("second question"),
            ChatMessage::assistant_with_tool_calls(
                "valid tool call",
                vec![ToolCall {
                    id: "call_2".to_string(),
                    name: "read".to_string(),
                    arguments: serde_json::json!({"path": "README.md"}),
                }],
            ),
            ChatMessage::tool("call_2", "read", "file contents"),
        ];

        let removed = crate::bus::message::sanitize_incomplete_tool_call_sequences(&mut messages);
        // call_1 assistant removed (1), rest preserved (4)
        assert_eq!(removed, 1);
        assert_eq!(messages.len(), 4);
        assert_eq!(messages[0].role, "user");
        assert_eq!(messages[0].content, "first question");
        assert_eq!(messages[1].role, "user");
        assert_eq!(messages[1].content, "second question");
        // The complete call_2 sequence is preserved
        assert_eq!(messages[2].role, "assistant");
        assert_eq!(messages[3].role, "tool");
    }

    #[test]
    fn test_sanitize_removes_multiple_mid_history_orphans() {
        // Multiple orphaned tool_calls scattered throughout history
        let mut messages = vec![
            ChatMessage::user("first"),
            ChatMessage::assistant_with_tool_calls(
                "orphan 1",
                vec![ToolCall {
                    id: "orphan_1".to_string(),
                    name: "tool_a".to_string(),
                    arguments: serde_json::json!({}),
                }],
            ),
            // Missing result for orphan_1
            ChatMessage::user("second"),
            ChatMessage::assistant_with_tool_calls(
                "orphan 2",
                vec![ToolCall {
                    id: "orphan_2".to_string(),
                    name: "tool_b".to_string(),
                    arguments: serde_json::json!({}),
                }],
            ),
            // Missing result for orphan_2
            ChatMessage::user("third"),
        ];

        let removed = crate::bus::message::sanitize_incomplete_tool_call_sequences(&mut messages);
        assert_eq!(removed, 2);
        assert_eq!(messages.len(), 3);
        assert_eq!(messages[0].content, "first");
        assert_eq!(messages[1].content, "second");
        assert_eq!(messages[2].content, "third");
    }

    #[test]
    fn test_sanitize_removes_orphaned_tool_results_for_removed_mid_assistant() {
        // When removing a mid-history assistant with partial tool results,
        // both the assistant AND its orphaned tool results must be removed.
        // Assistant has 2 tool calls, only 1 has a result → assistant is
        // incomplete → both assistant and its lone tool result removed.
        let mut messages = vec![
            ChatMessage::user("first question"),
            ChatMessage::assistant_with_tool_calls(
                "two tool calls, only one has result",
                vec![
                    ToolCall {
                        id: "call_has_result".to_string(),
                        name: "tool_a".to_string(),
                        arguments: serde_json::json!({}),
                    },
                    ToolCall {
                        id: "call_no_result".to_string(),
                        name: "tool_b".to_string(),
                        arguments: serde_json::json!({}),
                    },
                ],
            ),
            ChatMessage::tool("call_has_result", "tool_a", "some result"),
            // Missing tool result for call_no_result → incomplete sequence
            ChatMessage::user("second question"),
            ChatMessage::assistant_with_tool_calls(
                "valid tool call",
                vec![ToolCall {
                    id: "call_valid".to_string(),
                    name: "good_tool".to_string(),
                    arguments: serde_json::json!({}),
                }],
            ),
            ChatMessage::tool("call_valid", "good_tool", "valid result"),
        ];

        let removed = crate::bus::message::sanitize_incomplete_tool_call_sequences(&mut messages);
        // call_has_result/call_no_result assistant (1) + its orphaned tool result (1) = 2 removed
        assert_eq!(removed, 2);
        assert_eq!(messages.len(), 4);
        assert_eq!(messages[0].content, "first question");
        assert_eq!(messages[1].content, "second question");
        assert_eq!(messages[2].role, "assistant");
        assert_eq!(messages[3].role, "tool");
        // Verify the remaining tool belongs to call_valid
        assert_eq!(messages[3].tool_call_id.as_deref(), Some("call_valid"));
    }

    #[test]
    fn test_sanitize_handles_complex_interleaved_history() {
        // Complete → Orphaned → Complete: a realistic scenario after
        // history compaction
        let mut messages = vec![
            ChatMessage::user("task 1"),
            ChatMessage::assistant_with_tool_calls(
                "doing task 1",
                vec![ToolCall {
                    id: "t1_call".to_string(),
                    name: "read".to_string(),
                    arguments: serde_json::json!({"path": "a.txt"}),
                }],
            ),
            ChatMessage::tool("t1_call", "read", "content A"),
            ChatMessage::assistant("task 1 is done"),
            // End of task 1 — complete sequence
            ChatMessage::user("task 2"),
            ChatMessage::assistant_with_tool_calls(
                "doing task 2 — this got interrupted",
                vec![
                    ToolCall {
                        id: "t2_call_1".to_string(),
                        name: "write".to_string(),
                        arguments: serde_json::json!({"path": "b.txt"}),
                    },
                    ToolCall {
                        id: "t2_call_2".to_string(),
                        name: "calculator".to_string(),
                        arguments: serde_json::json!({"expression": "2+2"}),
                    },
                ],
            ),
            // Missing BOTH tool results — process was killed here
            // End of task 2 — orphaned sequence in the middle
            ChatMessage::user("task 3"),
            ChatMessage::assistant_with_tool_calls(
                "doing task 3",
                vec![ToolCall {
                    id: "t3_call".to_string(),
                    name: "search".to_string(),
                    arguments: serde_json::json!({"query": "hello"}),
                }],
            ),
            ChatMessage::tool("t3_call", "search", "found results"),
            ChatMessage::assistant("task 3 is done"),
        ];

        let removed = crate::bus::message::sanitize_incomplete_tool_call_sequences(&mut messages);
        // Removed: assistant with t2_call_1/t2_call_2 (1 message)
        assert_eq!(removed, 1);
        // Original 10 messages - 1 = 9
        assert_eq!(messages.len(), 9);
        assert_eq!(messages[4].content, "task 2");
        assert_eq!(messages[5].content, "task 3");
    }

    #[test]
    fn test_sanitize_removes_orphaned_tool_results_without_any_assistant_tool_calls() {
        // After heavy compaction, all assistant tool_calls messages may be
        // summarized into plain text, leaving only orphaned tool results.
        // Phase 2 must still clean them even when no assistant has tool_calls.
        let mut messages = vec![
            ChatMessage::user("do something"),
            ChatMessage::assistant("I used a tool to help you"), // plain text, no tool_calls
            ChatMessage::tool("orphan_call", "search", "some result"), // orphaned!
            ChatMessage::user("thanks"),
            ChatMessage::assistant("you're welcome"),
        ];

        let removed = crate::bus::message::sanitize_incomplete_tool_call_sequences(&mut messages);
        assert_eq!(removed, 1, "should remove the orphaned tool result");
        assert_eq!(messages.len(), 4);
        assert_eq!(messages[0].role, "user");
        assert_eq!(messages[1].role, "assistant");
        assert_eq!(messages[2].role, "user");
        assert_eq!(messages[2].content, "thanks");
        assert_eq!(messages[3].role, "assistant");
    }

    #[test]
    fn test_sanitize_handles_empty_tool_calls_vector() {
        // An assistant message with tool_calls: Some(vec![]) — edge case
        // that shouldn't crash or cause API errors.
        let mut msg = ChatMessage::assistant("thinking...");
        msg.tool_calls = Some(vec![]); // Some but empty

        let mut messages = vec![
            ChatMessage::user("hello"),
            msg,
            ChatMessage::assistant("here is my answer"),
        ];

        let removed = crate::bus::message::sanitize_incomplete_tool_call_sequences(&mut messages);
        assert_eq!(removed, 0, "empty tool_calls vec should not be removed");
        assert_eq!(messages.len(), 3);
    }

    #[test]
    fn test_sanitize_removes_multiple_orphaned_tool_results_after_compaction() {
        // Simulates a scenario where compaction summarized all tool call
        // sequences, leaving multiple orphaned tool results scattered.
        let mut messages = vec![
            ChatMessage::user("task 1"),
            ChatMessage::assistant("completed task 1"), // summary text, no tool_calls
            ChatMessage::tool("old_call_1", "read", "file contents"), // orphaned
            ChatMessage::user("task 2"),
            ChatMessage::assistant("completed task 2"), // summary text
            ChatMessage::tool("old_call_2", "bash", "command output"), // orphaned
            ChatMessage::user("task 3"),
            ChatMessage::assistant("final answer"),
        ];

        let removed = crate::bus::message::sanitize_incomplete_tool_call_sequences(&mut messages);
        assert_eq!(removed, 2, "should remove both orphaned tool results");
        assert_eq!(messages.len(), 6);
        // Verify no tool messages remain
        assert!(messages.iter().all(|m| m.role != "tool"));
    }

    #[test]
    fn test_sanitize_strips_tool_calls_when_tool_results_not_immediately_following() {
        // [assistant(tool_calls=[A]), user, tool(A)]
        // Tool result exists but is NOT immediately after assistant → strip tool_calls
        // This is the scenario that triggers DeepSeek 400 "insufficient tool messages
        // following tool_calls message" — the reverse scan sees tool(A) as resolved,
        // but the API requires it to be IMMEDIATELY after the assistant.
        let mut messages = vec![
            ChatMessage::assistant_with_tool_calls(
                "calling tool",
                vec![ToolCall {
                    id: "call_A".to_string(),
                    name: "search".to_string(),
                    arguments: serde_json::json!({}),
                }],
            ),
            ChatMessage::user("interrupting message"),
            ChatMessage::tool("call_A", "search", "result"),
        ];

        let removed = crate::bus::message::sanitize_incomplete_tool_call_sequences(&mut messages);
        // The assistant should be removed (tool_calls stripped via removal)
        // and the orphaned tool(A) should also be removed
        assert!(
            removed >= 2,
            "should remove both the assistant and orphaned tool message, got {}",
            removed
        );
        assert_eq!(messages.len(), 1, "only the user message should remain");
        assert_eq!(messages[0].role, "user");
        assert!(
            messages
                .iter()
                .all(|m| m.tool_calls.as_ref().map_or(true, |c| c.is_empty())),
            "no assistant should have tool_calls remaining"
        );
    }

    #[test]
    fn test_sanitize_preserves_tool_calls_when_immediately_followed() {
        // [assistant(tool_calls=[A]), tool(A), user] — valid, tool result is immediate
        let mut messages = vec![
            ChatMessage::assistant_with_tool_calls(
                "calling tool",
                vec![ToolCall {
                    id: "call_A".to_string(),
                    name: "search".to_string(),
                    arguments: serde_json::json!({}),
                }],
            ),
            ChatMessage::tool("call_A", "search", "result"),
            ChatMessage::user("next message after tool result"),
        ];

        let removed = crate::bus::message::sanitize_incomplete_tool_call_sequences(&mut messages);
        assert_eq!(
            removed, 0,
            "should not remove anything — tool result immediately follows"
        );
        assert_eq!(messages.len(), 3);
    }

    // ===== LLM 重试机制测试 =====

    #[test]
    fn test_is_recoverable_llm_error_detects_transient_errors() {
        // 429 限流
        assert!(is_recoverable_llm_error("HTTP 429 Too Many Requests"));
        assert!(is_recoverable_llm_error("rate limited (429)"));
        // 502/503/504 网关错误
        assert!(is_recoverable_llm_error("502 Bad Gateway"));
        assert!(is_recoverable_llm_error("503 Service Unavailable"));
        assert!(is_recoverable_llm_error("504 Gateway Timeout"));
        // timeout
        assert!(is_recoverable_llm_error("request timed out"));
        assert!(is_recoverable_llm_error("stream timeout"));
        assert!(is_recoverable_llm_error("operation timed out after 30s"));
        // 连接错误
        assert!(is_recoverable_llm_error("connection reset by peer"));
        assert!(is_recoverable_llm_error("connection refused"));
    }

    #[test]
    fn test_is_recoverable_llm_error_rejects_fatal_errors() {
        assert!(!is_recoverable_llm_error("401 Unauthorized"));
        assert!(!is_recoverable_llm_error("403 Forbidden"));
        assert!(!is_recoverable_llm_error("400 Bad Request"));
        assert!(!is_recoverable_llm_error("404 Not Found: model not found"));
        assert!(!is_recoverable_llm_error("Invalid API key"));
        assert!(!is_recoverable_llm_error("content filter blocked the request"));
    }

    #[test]
    fn test_is_recoverable_llm_error_case_insensitive() {
        assert!(is_recoverable_llm_error("GATEWAY TIMEOUT"));
        assert!(is_recoverable_llm_error("Timed Out"));
        assert!(is_recoverable_llm_error("CONNECTION RESET"));
    }

    /// 简单 mock provider：按预设序列依次返回响应/错误。
    /// chat_with_streaming 不 emit delta（保持 emitted=false），以便测试重试逻辑。
    struct MockProvider {
        responses: std::sync::Mutex<Vec<Result<ChatCompletionResponse, String>>>,
    }

    impl MockProvider {
        fn new(responses: Vec<Result<ChatCompletionResponse, String>>) -> Self {
            Self {
                responses: std::sync::Mutex::new(responses),
            }
        }
    }

    #[async_trait]
    impl LLMProvider for MockProvider {
        async fn chat(
            &self,
            _request: ChatCompletionRequest,
        ) -> Result<ChatCompletionResponse, Box<dyn std::error::Error + Send + Sync>> {
            let mut responses = self.responses.lock().unwrap();
            if responses.is_empty() {
                return Err("no more mock responses".into());
            }
            match responses.remove(0) {
                Ok(r) => Ok(r),
                Err(e) => Err(e.into()),
            }
        }

        fn ptype(&self) -> &str {
            "mock"
        }
        fn name(&self) -> &str {
            "mock"
        }
        fn model_id(&self) -> &str {
            "mock-model"
        }
    }

    fn mock_success_response(content: &str) -> ChatCompletionResponse {
        ChatCompletionResponse {
            id: "test-id".to_string(),
            model: "test-model".to_string(),
            content: content.to_string(),
            reasoning_content: None,
            tool_calls: vec![],
            usage: Usage {
                prompt_tokens: 10,
                completion_tokens: 10,
                total_tokens: 20,
            },
        }
    }

    fn make_loop_with_provider(provider: Box<dyn LLMProvider>, max_retries: u32) -> AgentLoop {
        let config = test_runtime_config();
        let mut runtime_config: AgentRuntimeConfig = config.into();
        runtime_config.max_retries = max_retries;
        AgentLoop {
            runtime_config,
            provider,
            tools: Arc::new(ToolRegistry::new()),
            system_prompt_provider: None,
            skills: None,
            tool_context: ToolContext::default(),
            observer: None,
            emitted_message_handler: None,
            cancel_token: None,
            max_iterations: 1,
        }
    }

    #[tokio::test]
    async fn test_retry_recovers_on_transient_error() {
        // 前 2 次返回 504（可恢复），第 3 次成功
        let loop_instance =
            make_loop_with_provider(Box::new(MockProvider::new(vec![
                Err("504 Gateway Timeout".to_string()),
                Err("504 Gateway Timeout".to_string()),
                Ok(mock_success_response("recovered")),
            ])), 3);

        let result = loop_instance
            .process(vec![ChatMessage::user("hello")], None)
            .await
            .unwrap();

        assert_eq!(result.final_response.content, "recovered");
    }

    #[tokio::test]
    async fn test_retry_skipped_on_fatal_error() {
        // 401 不可恢复 → 立即失败，不重试
        let loop_instance =
            make_loop_with_provider(Box::new(MockProvider::new(vec![
                Err("401 Unauthorized: invalid api key".to_string()),
                // 如果错误地重试了，第二次会返回成功，但我们期望不会到达
                Ok(mock_success_response("should not reach")),
            ])), 3);

        let result = loop_instance
            .process(vec![ChatMessage::user("hello")], None)
            .await
            .unwrap();

        // 应返回错误消息而非成功内容
        assert_ne!(result.final_response.content, "should not reach");
        assert!(result.final_response.content.contains("暂时不可用") || result.final_response.content.contains("401"));
    }

    #[tokio::test]
    async fn test_no_retry_when_max_retries_zero() {
        // max_retries=0 → 不重试，第一次失败即返回
        let loop_instance =
            make_loop_with_provider(Box::new(MockProvider::new(vec![
                Err("504 Gateway Timeout".to_string()),
                Ok(mock_success_response("should not reach")),
            ])), 0);

        let result = loop_instance
            .process(vec![ChatMessage::user("hello")], None)
            .await
            .unwrap();

        // 504 是可恢复错误，但 max_retries=0 不重试 → 返回错误消息
        assert_ne!(result.final_response.content, "should not reach");
    }

    #[tokio::test]
    async fn test_retry_exhausted_returns_error_message() {
        // max_retries=1，两次都返回 504 → 重试1次后仍失败
        let loop_instance =
            make_loop_with_provider(Box::new(MockProvider::new(vec![
                Err("504 Gateway Timeout".to_string()),
                Err("504 Gateway Timeout".to_string()),
            ])), 1);

        let result = loop_instance
            .process(vec![ChatMessage::user("hello")], None)
            .await
            .unwrap();

        // 重试用完，返回可恢复错误消息
        assert_eq!(result.final_response.content, RECOVERABLE_LLM_ERROR_MESSAGE);
    }
}

#[derive(Debug)]
pub enum AgentError {
    ProviderCreation(String),
    LlmError(String),
    Other(String),
}

impl std::fmt::Display for AgentError {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        match self {
            AgentError::ProviderCreation(e) => write!(f, "Provider creation error: {}", e),
            AgentError::LlmError(e) => write!(f, "LLM error: {}", e),
            AgentError::Other(e) => write!(f, "{}", e),
        }
    }
}

impl std::error::Error for AgentError {}