update README

Author: voocel

README.md

@@ -55,14 +55,23 @@ Each layer has one job. No layer knows about the layers above it.
 ## Quick Start
 
 ```bash
-# Install globally
+# Install
 go install github.com/voocel/codebot/cmd/codebot@latest
 
-# Or build from source
+# Set API key and run
+export ANTHROPIC_API_KEY=sk-ant-...
+codebot
+```
+
+Or build from source:
+
+```bash
 git clone https://github.com/voocel/codebot.git
 cd codebot && go build -o codebot ./cmd/codebot
 ```
 
+Supported environment variables: `ANTHROPIC_API_KEY`, `OPENAI_API_KEY`, `GEMINI_API_KEY`. For more options see [settings.example.jsonc](settings.example.jsonc).
+
 ## Usage
 
 ```bash

README_zh.md

@@ -55,14 +55,23 @@
 ## 快速开始
 
 ```bash
-# 全局安装
+# 安装
 go install github.com/voocel/codebot/cmd/codebot@latest
 
-# 或从源码构建
+# 设置 API Key 并运行
+export ANTHROPIC_API_KEY=sk-ant-...
+codebot
+```
+
+或从源码构建：
+
+```bash
 git clone https://github.com/voocel/codebot.git
 cd codebot && go build -o codebot ./cmd/codebot
 ```
 
+支持的环境变量：`ANTHROPIC_API_KEY`、`OPENAI_API_KEY`、`GEMINI_API_KEY`。更多配置项参考 [settings.example.jsonc](settings.example.jsonc)。
+
 ## 使用
 
 ```bash

internal/agent/session.go

@@ -1,6 +1,7 @@
 package agent
 
 import (
+	"encoding/json"
 	"fmt"
 	"strings"
 	"sync"
@@ -743,9 +744,17 @@ func (s *Session) persistMessage(msg agentcore.Message) {
 	s.mu.Unlock()
 	if store != nil {
 		if err := store.AppendMessage(msg); err != nil {
+			// Enrich error with tool call details for diagnosis.
+			detail := err.Error()
+			for _, tc := range msg.ToolCalls() {
+				if !json.Valid(tc.Args) {
+					detail = fmt.Sprintf("%s [invalid args in %s(%s): %s]",
+						detail, tc.Name, tc.ID, truncateBytes(tc.Args, 200))
+				}
+			}
 			s.emit(SessionEvent{
 				Type:  SEError,
-				Error: fmt.Errorf("persist message: %w", err),
+				Error: fmt.Errorf("persist message: %s", detail),
 			})
 		}
 	}
@@ -763,6 +772,14 @@ func (s *Session) flushPendingMessages() {
 	}
 }
 
+// truncateBytes returns at most n bytes from b, appending "..." if truncated.
+func truncateBytes(b []byte, n int) string {
+	if len(b) <= n {
+		return string(b)
+	}
+	return string(b[:n]) + "..."
+}
+
 // reclampThinking re-clamps the current thinking level to the new model's capabilities.
 func (s *Session) reclampThinking() {
 	if s.registry == nil {