tool calling chat template is broken
#4
by fullstack - opened
quick fix
cat > fix_and_test_template.py << 'EOF'
#!/usr/bin/env python3
import urllib.request
import re
import sys
# Step 1: Download
print("1. Downloading template...")
url = "https://huggingface.co/Qwen/Qwen3.5-35B-A3B/raw/main/chat_template.jinja"
try:
with urllib.request.urlopen(url) as response:
content = response.read().decode('utf-8')
print(" ✓ Downloaded successfully")
except Exception as e:
print(f" ✗ Download failed: {e}")
sys.exit(1)
# Step 2: Fix - replace the for loop line and add endif AFTER endfor
print("2. Fixing template...")
# Replace the for loop line
content = re.sub(
r'\{%-\s*for\s+args_name\s*,\s*args_value\s+in\s+tool_call\.arguments\s*\|\s*items\s*%\}',
'{%- if tool_call.arguments is mapping %}\n {%- for args_name in tool_call.arguments %}\n {%- set args_value = tool_call.arguments[args_name] %}',
content
)
# Find where to add the closing endif - right AFTER the endfor that closes the args loop
lines = content.split('\n')
new_lines = []
in_args_loop = False
for i, line in enumerate(lines):
# Detect when we enter the args iteration
if 'for args_name in tool_call.arguments' in line:
in_args_loop = True
new_lines.append(line)
# When we find the endfor that closes this loop, add endif AFTER it
if in_args_loop and '{%- endfor %}' in line:
# Check if previous lines have </parameter> - this is our loop
prev_lines = '\n'.join(lines[max(0, i-3):i+1])
if '</parameter>' in prev_lines:
new_lines.append(' {%- endif %}')
in_args_loop = False
content = '\n'.join(new_lines)
print(" ✓ Applied fix")
# Step 3: Lint
print("3. Linting template...")
try:
import jinja2
env = jinja2.Environment()
template = env.from_string(content)
print(" ✓ Template syntax is valid")
except ImportError:
print(" ⚠ jinja2 not installed, skipping lint")
except jinja2.exceptions.TemplateSyntaxError as e:
print(f" ✗ Syntax error at line {e.lineno}: {e.message}")
lines = content.split('\n')
start = max(0, e.lineno - 3)
end = min(len(lines), e.lineno + 2)
for i in range(start, end):
marker = " >>>" if i == e.lineno - 1 else " "
print(f"{marker} {i+1}: {lines[i]}")
sys.exit(1)
# Step 4: Save
print("4. Saving...")
with open('chat_template.jinja', 'w') as f:
f.write(content)
if '|items' not in content and 'arguments is mapping' in content:
print("✓ Template ready!")
else:
print("⚠ Warning: Fix may not be complete")
sys.exit(1)
EOF
python3 fix_and_test_template.py && ./llama.cpp/llama-server -hf unsloth/Qwen3.5-35B-A3B-GGUF:Q6_K_XL -fit on --ctx-size 220000 --jinja --chat-template-file chat_template.jinja
Thanks to @fullstack for the fix, You can use the fixed template below.
{%- set image_count = namespace(value=0) %}
{%- set video_count = namespace(value=0) %}
{%- macro render_content(content, do_vision_count, is_system_content=false) %}
{%- if content is string %}
{{- content }}
{%- elif content is iterable and content is not mapping %}
{%- for item in content %}
{%- if 'image' in item or 'image_url' in item or item.type == 'image' %}
{%- if is_system_content %}
{{- raise_exception('System message cannot contain images.') }}
{%- endif %}
{%- if do_vision_count %}
{%- set image_count.value = image_count.value + 1 %}
{%- endif %}
{%- if add_vision_id %}
{{- 'Picture ' ~ image_count.value ~ ': ' }}
{%- endif %}
{{- '<|vision_start|><|image_pad|><|vision_end|>' }}
{%- elif 'video' in item or item.type == 'video' %}
{%- if is_system_content %}
{{- raise_exception('System message cannot contain videos.') }}
{%- endif %}
{%- if do_vision_count %}
{%- set video_count.value = video_count.value + 1 %}
{%- endif %}
{%- if add_vision_id %}
{{- 'Video ' ~ video_count.value ~ ': ' }}
{%- endif %}
{{- '<|vision_start|><|video_pad|><|vision_end|>' }}
{%- elif 'text' in item %}
{{- item.text }}
{%- else %}
{{- raise_exception('Unexpected item type in content.') }}
{%- endif %}
{%- endfor %}
{%- elif content is none or content is undefined %}
{{- '' }}
{%- else %}
{{- raise_exception('Unexpected content type.') }}
{%- endif %}
{%- endmacro %}
{%- if not messages %}
{{- raise_exception('No messages provided.') }}
{%- endif %}
{%- if tools and tools is iterable and tools is not mapping %}
{{- '<|im_start|>system\n' }}
{{- "# Tools\n\nYou have access to the following functions:\n\n<tools>" }}
{%- for tool in tools %}
{{- "\n" }}
{{- tool | tojson }}
{%- endfor %}
{{- "\n</tools>" }}
{{- '\n\nIf you choose to call a function ONLY reply in the following format with NO suffix:\n\n<tool_call>\n<function=example_function_name>\n<parameter=example_parameter_1>\nvalue_1\n</parameter>\n<parameter=example_parameter_2>\nThis is the value for the second parameter\nthat can span\nmultiple lines\n</parameter>\n</function>\n</tool_call>\n\n<IMPORTANT>\nReminder:\n- Function calls MUST follow the specified format: an inner <function=...></function> block must be nested within <tool_call></tool_call> XML tags\n- Required parameters MUST be specified\n- You may provide optional reasoning for your function call in natural language BEFORE the function call, but NOT after\n- If there is no function call available, answer the question like normal with your current knowledge and do not tell the user about function calls\n</IMPORTANT>' }}
{%- if messages[0].role == 'system' %}
{%- set content = render_content(messages[0].content, false, true)|trim %}
{%- if content %}
{{- '\n\n' + content }}
{%- endif %}
{%- endif %}
{{- '<|im_end|>\n' }}
{%- else %}
{%- if messages[0].role == 'system' %}
{%- set content = render_content(messages[0].content, false, true)|trim %}
{{- '<|im_start|>system\n' + content + '<|im_end|>\n' }}
{%- endif %}
{%- endif %}
{%- set ns = namespace(multi_step_tool=true, last_query_index=messages|length - 1) %}
{%- for message in messages[::-1] %}
{%- set index = (messages|length - 1) - loop.index0 %}
{%- if ns.multi_step_tool and message.role == "user" %}
{%- set content = render_content(message.content, false)|trim %}
{%- if not(content.startswith('<tool_response>') and content.endswith('</tool_response>')) %}
{%- set ns.multi_step_tool = false %}
{%- set ns.last_query_index = index %}
{%- endif %}
{%- endif %}
{%- endfor %}
{%- if ns.multi_step_tool %}
{{- raise_exception('No user query found in messages.') }}
{%- endif %}
{%- for message in messages %}
{%- set content = render_content(message.content, true)|trim %}
{%- if message.role == "system" %}
{%- if not loop.first %}
{{- raise_exception('System message must be at the beginning.') }}
{%- endif %}
{%- elif message.role == "user" %}
{{- '<|im_start|>' + message.role + '\n' + content + '<|im_end|>' + '\n' }}
{%- elif message.role == "assistant" %}
{%- set reasoning_content = '' %}
{%- if message.reasoning_content is string %}
{%- set reasoning_content = message.reasoning_content %}
{%- else %}
{%- if '</think>' in content %}
{%- set reasoning_content = content.split('</think>')[0].rstrip('\n').split('<think>')[-1].lstrip('\n') %}
{%- set content = content.split('</think>')[-1].lstrip('\n') %}
{%- endif %}
{%- endif %}
{%- set reasoning_content = reasoning_content|trim %}
{%- if loop.index0 > ns.last_query_index %}
{{- '<|im_start|>' + message.role + '\n<think>\n' + reasoning_content + '\n</think>\n\n' + content }}
{%- else %}
{{- '<|im_start|>' + message.role + '\n' + content }}
{%- endif %}
{%- if message.tool_calls and message.tool_calls is iterable and message.tool_calls is not mapping %}
{%- for tool_call in message.tool_calls %}
{%- if tool_call.function is defined %}
{%- set tool_call = tool_call.function %}
{%- endif %}
{%- if loop.first %}
{%- if content|trim %}
{{- '\n\n<tool_call>\n<function=' + tool_call.name + '>\n' }}
{%- else %}
{{- '<tool_call>\n<function=' + tool_call.name + '>\n' }}
{%- endif %}
{%- else %}
{{- '\n<tool_call>\n<function=' + tool_call.name + '>\n' }}
{%- endif %}
{%- if tool_call.arguments is mapping %}
{%- for args_name in tool_call.arguments %}
{%- set args_value = tool_call.arguments[args_name] %}
{{- '<parameter=' + args_name + '>\n' }}
{%- set args_value = args_value | tojson | safe if args_value is mapping or (args_value is iterable and args_value is not string) else args_value | string %}
{{- args_value }}
{{- '\n</parameter>\n' }}
{%- endfor %}
{%- endif %}
{{- '</function>\n</tool_call>' }}
{%- endfor %}
{%- endif %}
{{- '<|im_end|>\n' }}
{%- elif message.role == "tool" %}
{%- if loop.previtem and loop.previtem.role != "tool" %}
{{- '<|im_start|>user' }}
{%- endif %}
{{- '\n<tool_response>\n' }}
{{- content }}
{{- '\n</tool_response>' }}
{%- if not loop.last and loop.nextitem.role != "tool" %}
{{- '<|im_end|>\n' }}
{%- elif loop.last %}
{{- '<|im_end|>\n' }}
{%- endif %}
{%- else %}
{{- raise_exception('Unexpected message role.') }}
{%- endif %}
{%- endfor %}
{%- if add_generation_prompt %}
{{- '<|im_start|>assistant\n' }}
{%- if enable_thinking is defined and enable_thinking is false %}
{{- '<think>\n\n</think>\n\n' }}
{%- else %}
{{- '<think>\n' }}
{%- endif %}
{%- endif %}
it is not working, LM Studio is throwing an error I'm on qwen3.5 27B
What is with the newest version? Doe it also need that template?
What is with the newest version? Doe it also need that template?
I have corrected the template and now it's working good for me. If you need I can share it, I have already made a template bug report in LM Studio Discord
I've implemented a comprehensive fix for this and 20 other bugs in the official template.
Fix 6 in my template uses arguments.items() with proper mapping checks, plus adds configurable truncation for massive tool arguments (Fix 16) and proper parallel tool call separation (Fix 15).
Full template with all 21 fixes: https://huggingface.co/barubary/qwen3.5-barubary-attuned-chat-template
Drop-in replacement — just swap chat_template.jinja and it works on llama.cpp, Open WebUI, vLLM, etc.