diff --git a/llmcore.py b/llmcore.py
index 241cc8e..d911827 100644
--- a/llmcore.py
+++ b/llmcore.py
@@ -14,20 +14,19 @@ mykeys = _load_mykeys()
 proxy = mykeys.get("proxy", 'http://127.0.0.1:2082')
 proxies = {"http": proxy, "https": proxy} if proxy else None
 
-def compress_history_tags(messages, keep_recent=10, max_len=1000):
+def compress_history_tags(messages, keep_recent=10, max_len=800):
     """Compress <thinking>/<tool_use>/<tool_result> tags in older messages to save tokens.
     Supports both prompt-style (ClaudeSession/LLMSession) and content-style (NativeClaudeSession) messages."""
     compress_history_tags._cd = getattr(compress_history_tags, '_cd', 0) + 1
     if compress_history_tags._cd % 5 != 0: return messages
+    _before = sum(len(json.dumps(m)) for m in messages)
     _pats = {tag: re.compile(rf'(<{tag}>)([\s\S]*?)(</{tag}>)') for tag in ('thinking', 'tool_use', 'tool_result')}
     def _trunc(text):
         for pat in _pats.values(): text = pat.sub(lambda m: m.group(1) + m.group(2)[:max_len] + '...' + m.group(3) if len(m.group(2)) > max_len else m.group(0), text)
         return text
     for i, msg in enumerate(messages):
         if i >= len(messages) - keep_recent: break
-        if 'prompt' in msg and 'orig' not in msg:
-            msg['orig'] = msg['prompt']
-            msg['prompt'] = _trunc(msg['prompt'])
+        if 'prompt' in msg: msg['prompt'] = _trunc(msg['prompt'])
         elif 'content' in msg and 'prompt' not in msg:
             c = msg['content']
             if isinstance(c, str): msg['content'] = _trunc(c)
@@ -35,6 +34,7 @@ def compress_history_tags(messages, keep_recent=10, max_len=1000):
                 for block in c:
                     if isinstance(block, dict) and block.get('type') == 'text' and isinstance(block.get('text'), str):
                         block['text'] = _trunc(block['text'])
+    print(f"[Cut] {_before} -> {sum(len(json.dumps(m)) for m in messages)}")
     return messages
 
 def auto_make_url(base, path):
@@ -75,62 +75,171 @@ class SiderLLMSession:
         if stream: return iter([full_text])   # gen有奇怪的空回复或死循环行为，sider足够快
         return full_text   
 
+def _parse_claude_sse(resp_lines):
+    """Parse Anthropic SSE stream. Yields text chunks, returns list[content_block]."""
+    content_blocks = []; current_block = None; tool_json_buf = ""
+    for line in resp_lines:
+        if not line: continue
+        line = line.decode('utf-8') if isinstance(line, bytes) else line
+        if not line.startswith("data:"): continue
+        data_str = line[5:].lstrip()
+        if data_str == "[DONE]": break
+        try: evt = json.loads(data_str)
+        except: continue
+        evt_type = evt.get("type", "")
+        if evt_type == "message_start":
+            usage = evt.get("message", {}).get("usage", {})
+            ci, cr, inp = usage.get("cache_creation_input_tokens", 0), usage.get("cache_read_input_tokens", 0), usage.get("input_tokens", 0)
+            print(f"[Cache] input={inp} creation={ci} read={cr}")
+        elif evt_type == "content_block_start":
+            block = evt.get("content_block", {})
+            if block.get("type") == "text": current_block = {"type": "text", "text": ""}
+            elif block.get("type") == "tool_use":
+                current_block = {"type": "tool_use", "id": block.get("id", ""), "name": block.get("name", ""), "input": {}}
+                tool_json_buf = ""
+        elif evt_type == "content_block_delta":
+            delta = evt.get("delta", {})
+            if delta.get("type") == "text_delta":
+                text = delta.get("text", "")
+                if current_block and current_block.get("type") == "text": current_block["text"] += text
+                if text: yield text
+            elif delta.get("type") == "input_json_delta": tool_json_buf += delta.get("partial_json", "")
+        elif evt_type == "content_block_stop":
+            if current_block:
+                if current_block["type"] == "tool_use":
+                    try: current_block["input"] = json.loads(tool_json_buf) if tool_json_buf else {}
+                    except: current_block["input"] = {"_raw": tool_json_buf}
+                content_blocks.append(current_block)
+                current_block = None
+    return content_blocks
+
+def _parse_openai_sse(resp_lines, api_mode="chat_completions"):
+    """Parse OpenAI SSE stream (chat_completions or responses API).
+    Yields text chunks, returns list[content_block].
+    content_block: {type:'text', text:str} | {type:'tool_use', id:str, name:str, input:dict}
+    """
+    content_text = ""
+    if api_mode == "responses":
+        seen_delta = False; fc_buf = {}; current_fc_idx = None
+        for line in resp_lines:
+            if not line: continue
+            line = line.decode('utf-8', errors='replace') if isinstance(line, bytes) else line
+            if not line.startswith("data:"): continue
+            data_str = line[5:].lstrip()
+            if data_str == "[DONE]": break
+            try: evt = json.loads(data_str)
+            except: continue
+            etype = evt.get("type", "")
+            if etype == "response.output_text.delta":
+                delta = evt.get("delta", "")
+                if delta: seen_delta = True; content_text += delta; yield delta
+            elif etype == "response.output_text.done" and not seen_delta:
+                text = evt.get("text", "")
+                if text: content_text += text; yield text
+            elif etype == "response.output_item.added":
+                item = evt.get("item", {})
+                if item.get("type") == "function_call":
+                    idx = evt.get("output_index", 0)
+                    fc_buf[idx] = {"id": item.get("call_id", item.get("id", "")), "name": item.get("name", ""), "args": ""}
+                    current_fc_idx = idx
+            elif etype == "response.function_call_arguments.delta":
+                idx = evt.get("output_index", current_fc_idx or 0)
+                if idx in fc_buf: fc_buf[idx]["args"] += evt.get("delta", "")
+            elif etype == "response.function_call_arguments.done":
+                idx = evt.get("output_index", current_fc_idx or 0)
+                if idx in fc_buf: fc_buf[idx]["args"] = evt.get("arguments", fc_buf[idx]["args"])
+            elif etype == "error":
+                err = evt.get("error", {})
+                emsg = err.get("message", str(err)) if isinstance(err, dict) else str(err)
+                if emsg: content_text += f"Error: {emsg}"; yield f"Error: {emsg}"
+                break
+            elif etype == "response.completed":
+                usage = evt.get("response", {}).get("usage", {})
+                cached = (usage.get("input_tokens_details") or {}).get("cached_tokens", 0)
+                inp = usage.get("input_tokens", 0)
+                if inp: print(f"[Cache] input={inp} cached={cached}")
+                break
+        blocks = []
+        if content_text: blocks.append({"type": "text", "text": content_text})
+        for idx in sorted(fc_buf):
+            fc = fc_buf[idx]
+            try: inp = json.loads(fc["args"]) if fc["args"] else {}
+            except: inp = {"_raw": fc["args"]}
+            blocks.append({"type": "tool_use", "id": fc["id"], "name": fc["name"], "input": inp})
+        return blocks
+    else:
+        tc_buf = {}  # index -> {id, name, args}
+        for line in resp_lines:
+            if not line: continue
+            line = line.decode('utf-8', errors='replace') if isinstance(line, bytes) else line
+            if not line.startswith("data:"): continue
+            data_str = line[5:].lstrip()
+            if data_str == "[DONE]": break
+            try: evt = json.loads(data_str)
+            except: continue
+            ch = (evt.get("choices") or [{}])[0]
+            delta = ch.get("delta", {})
+            if delta.get("content"):
+                text = delta["content"]; content_text += text; yield text
+            for tc in delta.get("tool_calls", []):
+                idx = tc.get("index", 0)
+                if idx not in tc_buf: tc_buf[idx] = {"id": tc.get("id", ""), "name": "", "args": ""}
+                if tc.get("function", {}).get("name"): tc_buf[idx]["name"] = tc["function"]["name"]
+                if tc.get("function", {}).get("arguments"): tc_buf[idx]["args"] += tc["function"]["arguments"]
+            usage = evt.get("usage")
+            if usage:
+                cached = (usage.get("prompt_tokens_details") or {}).get("cached_tokens", 0)
+                print(f"[Cache] input={usage.get('prompt_tokens',0)} cached={cached}")
+        blocks = []
+        if content_text: blocks.append({"type": "text", "text": content_text})
+        for idx in sorted(tc_buf):
+            tc = tc_buf[idx]
+            try: inp = json.loads(tc["args"]) if tc["args"] else {}
+            except: inp = {"_raw": tc["args"]}
+            blocks.append({"type": "tool_use", "id": tc["id"], "name": tc["name"], "input": inp})
+        return blocks
+
 class ClaudeSession:
     def __init__(self, cfg):
         self.api_key = cfg['apikey']; self.api_base = cfg['apibase'].rstrip('/')
         self.default_model = cfg.get('model', 'claude-opus')
         self.context_win = cfg.get('context_win', 18000)
         self.raw_msgs, self.lock = [], threading.Lock()
-        self.prompt_cache = cfg.get('prompt_cache', False)
-    def _trim_messages(self, messages):
-        compress_history_tags(messages)
-        total = sum(len(m['prompt']) for m in messages)
-        if total <= self.context_win * 3: return messages
+        self.system = ""
+    def _trim_messages(self, raw_msgs):
+        compress_history_tags(raw_msgs)
+        total = sum(len(m['prompt']) for m in raw_msgs)
+        print(f'[Debug] Current context: {total} chars, {len(raw_msgs)} messages.')
+        if total <= self.context_win * 3: return raw_msgs
         target, current, result = self.context_win * 3 * 0.6, 0, []
-        for msg in reversed(messages):
+        for msg in reversed(raw_msgs):
             if (msg_len := len(msg['prompt'])) + current <= target:
                 result.append(msg); current += msg_len
-            else: break
-        if current > self.context_win * 2.7: print(f'[DEBUG] {len(result)} contexts, whole length {current//3} tokens.')
-        return result[::-1] or messages[-2:]
+            else: break    
+        print(f'[Debug] Trimmed context, current: {current} chars, {len(result)} messages.')
+        return result[::-1] or raw_msgs[-2:]
     def raw_ask(self, messages, model=None, temperature=0.5, max_tokens=6144):
         model = model or self.default_model
         if 'kimi' in model.lower() or 'moonshot' in model.lower(): temperature = 1.0  # kimi/moonshot only accepts temp 1.0
         headers = {"x-api-key": self.api_key, "Content-Type": "application/json", "anthropic-version": "2023-06-01", "anthropic-beta": "prompt-caching-2024-07-31"}
         payload = {"model": model, "messages": messages, "temperature": temperature, "max_tokens": max_tokens, "stream": True}
+        if self.system: payload["system"] = [{"type": "text", "text": self.system, "cache_control": {"type": "persistent"}}]
         try:
             with requests.post(auto_make_url(self.api_base, "messages"), headers=headers, json=payload, stream=True, timeout=(5,30)) as r:
                 r.raise_for_status()
-                for line in r.iter_lines():
-                    if not line: continue
-                    line = line.decode("utf-8") if isinstance(line, bytes) else line
-                    if not line.startswith("data:"): continue
-                    data = line[5:].lstrip()
-                    if data == "[DONE]": break
-                    try:
-                        obj = json.loads(data)
-                        if obj.get("type") == "message_start":
-                            usage = obj.get("message", {}).get("usage", {})
-                            ci, cr, inp = usage.get("cache_creation_input_tokens", 0), usage.get("cache_read_input_tokens", 0), usage.get("input_tokens", 0)
-                            print(f"[Cache] input={inp} creation={ci} read={cr}")
-                        elif obj.get("type") == "content_block_delta" and obj.get("delta", {}).get("type") == "text_delta":
-                            text = obj["delta"].get("text", "")
-                            if text: yield text
-                    except: pass
+                yield from _parse_claude_sse(r.iter_lines())
         except Exception as e: yield f"Error: {str(e)}"
     def make_messages(self, raw_list):
-        trimmed = self._trim_messages(raw_list)
-        msgs = [{"role": m['role'], "content": [{"type": "text", "text": m['prompt']}] if m['role'] == "assistant" else m['prompt']} for m in trimmed]
-        for i in range(len(msgs)-1, -1, -1):
-            if msgs[i]["role"] == "assistant":
-                msgs[i]["content"][-1]["cache_control"] = {"type": "ephemeral"}
-                break
+        msgs = [{"role": m['role'], "content": [{"type": "text", "text": m['prompt']}]} for m in raw_list]
+        c = msgs[-1]["content"]
+        c[-1] = dict(c[-1], cache_control={"type": "ephemeral"})
         return msgs
     def ask(self, prompt, model=None, stream=False):
         def _ask_gen():
             content = ''
             with self.lock:
                 self.raw_msgs.append({"role": "user", "prompt": prompt})
+                self.raw_msgs = self._trim_messages(self.raw_msgs)
                 messages = self.make_messages(self.raw_msgs)
             for chunk in self.raw_ask(messages, model):
                 content += chunk; yield chunk
@@ -145,7 +254,6 @@ class LLMSession:
         self.raw_msgs, self.messages = [], []
         proxy = cfg.get('proxy')
         self.proxies = {"http": proxy, "https": proxy} if proxy else None
-        self.prompt_cache = cfg.get('prompt_cache', False)
         self.lock = threading.Lock()
         self.max_retries = max(0, int(cfg.get('max_retries', 2)))
         self.connect_timeout = max(1, int(cfg.get('connect_timeout', 10)))
@@ -201,7 +309,7 @@ class LLMSession:
             if self.reasoning_effort: payload["reasoning"] = {"effort": self.reasoning_effort}
         else:
             url = auto_make_url(self.api_base, "chat/completions")
-            payload = {"model": model, "messages": messages, "temperature": temperature, "stream": True}
+            payload = {"model": model, "messages": messages, "temperature": temperature, "stream": True, "stream_options": {"include_usage": True}}
             if self.reasoning_effort: payload["reasoning_effort"] = self.reasoning_effort
         for attempt in range(self.max_retries + 1):
             streamed_any = False
@@ -216,42 +324,9 @@ class LLMSession:
                             time.sleep(delay)
                             continue
                     r.raise_for_status()
-                    buffer = ''; seen_delta = False
-                    for line in r.iter_lines():
-                        line = line.decode("utf-8") if isinstance(line, bytes) else line
-                        if not line or not line.startswith("data:"): continue
-                        data = line[5:].lstrip()
-                        if data == "[DONE]": break
-                        try: obj = json.loads(data)
-                        except: continue
-                        if self.api_mode == "responses":
-                            etype = obj.get("type", "")
-                            delta = obj.get("delta", "") if etype == "response.output_text.delta" else ""
-                            if delta:
-                                streamed_any = True; seen_delta = True
-                                yield delta; buffer += delta
-                            elif etype == "response.output_text.done" and not seen_delta:
-                                text = obj.get("text", "")
-                                if text:
-                                    streamed_any = True
-                                    yield text; buffer += text
-                            elif etype == "error":
-                                err = obj.get("error", {})
-                                emsg = err.get("message", str(err)) if isinstance(err, dict) else str(err)
-                                if emsg:
-                                    yield f"Error: {emsg}"
-                                    return
-                            elif etype == "response.completed":
-                                break
-                        else:
-                            ch = (obj.get("choices") or [{}])[0]
-                            finish_reason = ch.get("finish_reason")
-                            delta = (ch.get("delta") or {}).get("content")
-                            if delta:
-                                streamed_any = True
-                                yield delta; buffer += delta
-                            if finish_reason: break
-                        #if '</tool_use>' in buffer[-30:]: break
+                    for chunk in _parse_openai_sse(r.iter_lines(), self.api_mode):
+                        streamed_any = True
+                        yield chunk
                     return
             except requests.HTTPError as e:
                 resp = getattr(e, "response", None)
@@ -420,64 +495,46 @@ class NativeOAISession:
         self.api_key = cfg['apikey']; self.api_base = cfg['apibase'].rstrip('/')
         self.default_model = cfg.get('model', 'gpt-4o')
         self.context_win = cfg.get('context_win', 28000)
+        self.reasoning_effort = cfg.get('reasoning_effort')
         proxy = cfg.get('proxy')
         self.proxies = {"http": proxy, "https": proxy} if proxy else None
-        self.history = []; self.system = None; self.lock = threading.Lock()
-    def set_system(self, system_text): self.system = system_text
+        self.history = []; self.system = ''; self.lock = threading.Lock()
 
     def raw_ask(self, messages, tools=None, system=None, model=None, temperature=0.5, max_tokens=6144, **kw):
         """OpenAI streaming. yields text chunks, generator return = list[content_block]"""
         model = model or self.default_model
         headers = {"Authorization": f"Bearer {self.api_key}", "Content-Type": "application/json"}
         msgs = ([{"role": "system", "content": system}] if system else []) + messages
-        payload = {"model": model, "messages": msgs, "temperature": temperature, "max_tokens": max_tokens, "stream": True}
+        payload = {"model": model, "messages": msgs, "temperature": temperature, "max_tokens": max_tokens, "stream": True, "stream_options": {"include_usage": True}}
         if tools: payload["tools"] = tools
+        if self.reasoning_effort: payload["reasoning_effort"] = self.reasoning_effort
         try:
             resp = requests.post(auto_make_url(self.api_base, "chat/completions"), headers=headers, json=payload, stream=True, timeout=120, proxies=self.proxies)
             if resp.status_code != 200:
                 err = f"Error: HTTP {resp.status_code} {resp.text[:500]}"; yield err; return [{"type": "text", "text": err}]
         except Exception as e:
             err = f"Error: {e}"; yield err; return [{"type": "text", "text": err}]
-        content_text = ""; tc_buf = {}  # index -> {id, name, args_str}
-        for line in resp.iter_lines():
-            if not line: continue
-            line = line.decode('utf-8', errors='replace') if isinstance(line, bytes) else line
-            if not line.startswith("data: "): continue
-            data_str = line[6:]
-            if data_str.strip() == "[DONE]": break
-            try: evt = json.loads(data_str)
-            except: continue
-            delta = evt.get("choices", [{}])[0].get("delta", {})
-            if delta.get("content"):
-                text = delta["content"]; content_text += text; yield text
-            for tc in delta.get("tool_calls", []):
-                idx = tc.get("index", 0)
-                if idx not in tc_buf: tc_buf[idx] = {"id": tc.get("id", ""), "name": "", "args": ""}
-                if tc.get("function", {}).get("name"): tc_buf[idx]["name"] = tc["function"]["name"]
-                if tc.get("function", {}).get("arguments"): tc_buf[idx]["args"] += tc["function"]["arguments"]
-        blocks = []
-        if content_text: blocks.append({"type": "text", "text": content_text})
-        for idx in sorted(tc_buf):
-            tc = tc_buf[idx]
-            try: inp = json.loads(tc["args"]) if tc["args"] else {}
-            except: inp = {"_raw": tc["args"]}
-            blocks.append({"type": "tool_use", "id": tc["id"], "name": tc["name"], "input": inp})
-        return blocks
+        gen = _parse_openai_sse(resp.iter_lines(), "chat_completions")
+        try:
+            while True: yield next(gen)
+        except StopIteration as e:
+            return e.value or []
 
     def ask(self, msg, tools=None, model=None, **kw):
-        """Managed ask with history. yields text chunks, return MockResponse"""
-        if isinstance(msg, str): msg = {"role": "user", "content": msg}
-        elif isinstance(msg, list): msg = {"role": "user", "content": msg}
+        assert type(msg) is dict
         with self.lock:
             self.history.append(msg)
             compress_history_tags(self.history)
             cost = sum(len(json.dumps(m, ensure_ascii=False)) for m in self.history) 
+            print(f'[Debug] Current context: {cost} chars, {len(self.history)} messages.')
             if cost > self.context_win * 3: 
                 target = self.context_win * 3 * 0.6
                 while len(self.history) > 2 and cost > target:
                     self.history.pop(0); self.history.pop(0)
                     cost = sum(len(json.dumps(m, ensure_ascii=False)) for m in self.history)
+                print(f'[Debug] Trimmed context, current: {cost} chars, {len(self.history)} messages.')
             messages = list(self.history)
+
         content_blocks = None
         gen = self.raw_ask(messages, tools, self.system, model)
         try:
@@ -495,14 +552,10 @@ class NativeClaudeSession:
     def __init__(self, cfg):
         self.api_key = cfg['apikey']; self.api_base = cfg['apibase'].rstrip('/')
         self.default_model = cfg.get('model', 'claude-opus')
-        self.context_win = cfg.get('context_win', 32000)
-        self.history = []  
-        self.system = None
-        self.lock = threading.Lock()
-    def set_system(self, system_text): self.system = system_text
+        self.context_win = cfg.get('context_win', 30000)
+        self.history = []; self.system = ''; self.lock = threading.Lock()
 
     def raw_ask(self, messages, tools=None, system=None, model=None, temperature=0.5, max_tokens=6144):
-        """底层API调用。yields text chunks，generator return = list[content_block]"""
         model = model or self.default_model
         headers = {"x-api-key": self.api_key, "Content-Type": "application/json", "anthropic-version": "2023-06-01", "anthropic-beta": "prompt-caching-2024-07-31"}
         payload = {"model": model, "messages": messages, "temperature": temperature, "max_tokens": max_tokens, "stream": True}
@@ -510,12 +563,8 @@ class NativeClaudeSession:
             tools = [dict(t) for t in tools]; tools[-1]["cache_control"] = {"type": "ephemeral"}
             payload["tools"] = tools
         if system: payload["system"] = [{"type": "text", "text": system, "cache_control": {"type": "ephemeral"}}]
-        # 历史消息缓存：最后一个assistant消息加cache_control
-        for i in range(len(messages) - 1, -1, -1):
-            if messages[i]["role"] == "assistant":
-                c = messages[i].get("content", [])
-                if isinstance(c, list) and c: messages[i] = {**messages[i], "content": [*c[:-1], {**c[-1], "cache_control": {"type": "ephemeral"}}]}
-                break
+        messages[-1] = {**messages[-1], "content": list(messages[-1]["content"])}
+        messages[-1]["content"][-1] = dict(messages[-1]["content"][-1], cache_control={"type": "ephemeral"})
         try:
             resp = requests.post(auto_make_url(self.api_base, "messages"), headers=headers, json=payload, stream=True, timeout=120)
             if resp.status_code != 200:
@@ -526,51 +575,22 @@ class NativeClaudeSession:
             error_msg = f"Error: {e}"
             yield error_msg
             return [{"type": "text", "text": error_msg}]
-
-        content_blocks = []; current_block = None; tool_json_buf = ""
-        for line in resp.iter_lines():
-            if not line: continue
-            line = line.decode('utf-8') if isinstance(line, bytes) else line
-            data_str = line[6:]
-            if data_str.strip() == "[DONE]": break
-            try: evt = json.loads(data_str)
-            except: continue
-            evt_type = evt.get("type", "")
-            if evt_type == "content_block_start":
-                block = evt.get("content_block", {})
-                if block.get("type") == "text": current_block = {"type": "text", "text": ""}
-                elif block.get("type") == "tool_use":
-                    current_block = {"type": "tool_use", "id": block.get("id", ""), "name": block.get("name", ""), "input": {}}
-                    tool_json_buf = ""
-            elif evt_type == "content_block_delta":
-                delta = evt.get("delta", {})
-                if delta.get("type") == "text_delta":
-                    text = delta.get("text", "")
-                    if current_block: current_block["text"] += text
-                    yield text
-                elif delta.get("type") == "input_json_delta": tool_json_buf += delta.get("partial_json", "")
-            elif evt_type == "content_block_stop":
-                if current_block:
-                    if current_block["type"] == "tool_use":
-                        try: current_block["input"] = json.loads(tool_json_buf) if tool_json_buf else {}
-                        except: current_block["input"] = {"_raw": tool_json_buf}
-                    content_blocks.append(current_block)
-                    current_block = None
-        return content_blocks
+        content_blocks = yield from _parse_claude_sse(resp.iter_lines())
+        return content_blocks or []
 
     def ask(self, msg, tools=None, model=None):
-        """增量ask。msg: str|list[content_block]|dict。yields text chunks, return MockResponse"""
-        if isinstance(msg, str): msg = {"role": "user", "content": msg}
-        elif isinstance(msg, list): msg = {"role": "user", "content": msg}  
+        assert type(msg) is dict
         with self.lock:
             self.history.append(msg)
             compress_history_tags(self.history)
             cost = sum(len(json.dumps(m, ensure_ascii=False)) for m in self.history) 
+            print(f'[Debug] Current context: {cost} chars, {len(self.history)} messages.')
             if cost > self.context_win * 3: 
                 target = self.context_win * 3 * 0.6
                 while len(self.history) > 2 and cost > target:
                     self.history.pop(0); self.history.pop(0)
                     cost = sum(len(json.dumps(m, ensure_ascii=False)) for m in self.history)
+                print(f'[Debug] Trimmed context, current: {cost} chars, {len(self.history)} messages.')
             messages = list(self.history)
 
         content_blocks = None
@@ -619,10 +639,8 @@ class MockResponse:
         return f"<MockResponse thinking={bool(self.thinking)}, content='{self.content}', tools={bool(self.tool_calls)}>"
 
 class ToolClient:
-    def __init__(self, backends, auto_save_tokens=True):
-        if isinstance(backends, list): self.backends = backends
-        else: self.backends = [backends]
-        self.backend = self.backends[0]
+    def __init__(self, backend, auto_save_tokens=True):
+        self.backend = backend
         self.auto_save_tokens = auto_save_tokens
         self.last_tools = ''
         self.total_cd_tokens = 0
@@ -726,19 +744,17 @@ class ToolClient:
         system_content = next((m['content'] for m in messages if m['role'].lower() == 'system'), "")
         history_msgs = [m for m in messages if m['role'].lower() != 'system']
         tool_instruction = self._prepare_tool_instruction(tools)
-            
-        prompt = ""
-        if system_content: prompt += f"=== SYSTEM ===\n{system_content}\n"
-        prompt += f"{tool_instruction}\n\n"
+        system = ""
+        if system_content: system += f"{system_content}\n"
+        system += f"{tool_instruction}"
+        user = ""
         for m in history_msgs:
             role = "USER" if m['role'] == 'user' else "ASSISTANT"
-            prompt += f"=== {role} ===\n{m['content']}\n\n"
-            self.total_cd_tokens += self._estimate_content_len(m['content'])
-            
+            user += f"=== {role} ===\n{m['content']}\n\n"
+            self.total_cd_tokens += self._estimate_content_len(m['content'])           
         if self.total_cd_tokens > 6000: self.last_tools = ''
-
-        prompt += "=== ASSISTANT ===\n" 
-        return prompt
+        user += "=== ASSISTANT ===\n" 
+        return system + user
 
     def _parse_mixed_response(self, text):
         remaining_text = text; thinking = ''
@@ -830,8 +846,10 @@ class NativeToolClient:
         combined_content = []; resp = None
         for msg in messages:
             c = msg.get('content', '')
+            if msg['role'] == 'system': 
+                self.set_system(c); continue
             if isinstance(c, str): combined_content.append({"type": "text", "text": c})
-            elif isinstance(c, list) or isinstance(c, dict): combined_content.extend(c)
+            elif isinstance(c, list): combined_content.extend(c)
         if self._pending_tool_ids and isinstance(self.backend, NativeClaudeSession):
             tool_result_blocks = [{"type": "tool_result", "tool_use_id": tid, "content": ""} for tid in self._pending_tool_ids]
             combined_content = tool_result_blocks + combined_content