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<|channel>thought\n must be prefilled for thinking.
{#
Template: Google Gemma 4 Canonical Chat Template
Author: Google Gemma Engineering Team
Published: 2026-07-09
Context: Fixed tool-calling loops, turn closures, and thinking content-ordering.
#}
{%- macro format_parameters(properties, required, filter_keys=false) -%}
{%- set standard_keys = ['description', 'type', 'properties', 'required', 'nullable'] -%}
{%- set ns = namespace(found_first=false) -%}
{%- for key, value in properties | dictsort -%}
{%- set add_comma = false -%}
{%- if not filter_keys or key not in standard_keys -%}
{%- if ns.found_first %},{% endif -%}
{%- set ns.found_first = true -%}
{{ key }}:{
{%- if value['description'] -%}
description:<|"|>{{ value['description'] }}<|"|>
{%- set add_comma = true -%}
{%- endif -%}
{%- if value['type'] | upper == 'STRING' -%}
{%- if value['enum'] -%}
{%- if add_comma %},{%- else -%} {%- set add_comma = true -%} {% endif -%}
enum:{{ format_argument(value['enum']) }}
{%- endif -%}
{%- elif value['type'] | upper == 'ARRAY' -%}
{%- if value['items'] is mapping and value['items'] -%}
{%- if add_comma %},{%- else -%} {%- set add_comma = true -%} {% endif -%}
items:{
{%- set ns_items = namespace(found_first=false) -%}
{%- for item_key, item_value in value['items'] | dictsort -%}
{%- if item_value is not none -%}
{%- if ns_items.found_first %},{% endif -%}
{%- set ns_items.found_first = true -%}
{%- if item_key == 'properties' -%}
properties:{
{%- if item_value is mapping -%}
{{- format_parameters(item_value, value['items']['required'] | default([])) -}}
{%- endif -%}
}
{%- elif item_key == 'required' -%}
required:[
{%- for req_item in item_value -%}
<|"|>{{- req_item -}}<|"|>
{%- if not loop.last %},{% endif -%}
{%- endfor -%}
]
{%- elif item_key == 'type' -%}
{%- if item_value is string -%}
type:{{ format_argument(item_value | upper) }}
{%- else -%}
type:{{ format_argument(item_value | map('upper') | list) }}
{%- endif -%}
{%- else -%}
{{ item_key }}:{{ format_argument(item_value) }}
{%- endif -%}
{%- endif -%}
{%- endfor -%}
}
{%- endif -%}
{%- endif -%}
{%- if value['nullable'] %}
{%- if add_comma %},{%- else -%} {%- set add_comma = true -%} {% endif -%}
nullable:true
{%- endif -%}
{%- if value['type'] | upper == 'OBJECT' -%}
{%- if value['properties'] is defined and value['properties'] is mapping -%}
{%- if add_comma %},{%- else -%} {%- set add_comma = true -%} {% endif -%}
properties:{
{{- format_parameters(value['properties'], value['required'] | default([])) -}}
}
{%- elif value is mapping -%}
{%- if add_comma %},{%- else -%} {%- set add_comma = true -%} {% endif -%}
properties:{
{{- format_parameters(value, value['required'] | default([]), filter_keys=true) -}}
}
{%- endif -%}
{%- if value['required'] -%}
{%- if add_comma %},{%- else -%} {%- set add_comma = true -%} {% endif -%}
required:[
{%- for item in value['required'] | default([]) -%}
<|"|>{{- item -}}<|"|>
{%- if not loop.last %},{% endif -%}
{%- endfor -%}
]
{%- endif -%}
{%- endif -%}
{%- if add_comma %},{%- else -%} {%- set add_comma = true -%} {% endif -%}
type:<|"|>{{ value['type'] | upper }}<|"|>}
{%- endif -%}
{%- endfor -%}
{%- endmacro -%}
{%- macro format_function_declaration(tool_data) -%}
declaration:{{- tool_data['function']['name'] -}}{description:<|"|>{{- tool_data['function']['description'] -}}<|"|>
{%- set params = tool_data['function']['parameters'] -%}
{%- if params -%}
,parameters:{
{%- if params['properties'] -%}
properties:{ {{- format_parameters(params['properties'], params['required']) -}} },
{%- endif -%}
{%- if params['required'] -%}
required:[
{%- for item in params['required'] -%}
<|"|>{{- item -}}<|"|>
{{- ',' if not loop.last -}}
{%- endfor -%}
],
{%- endif -%}
{%- if params['type'] -%}
type:<|"|>{{- params['type'] | upper -}}<|"|>}
{%- endif -%}
{%- endif -%}
{%- if 'response' in tool_data['function'] -%}
{%- set response_declaration = tool_data['function']['response'] -%}
,response:{
{%- if response_declaration['description'] -%}
description:<|"|>{{- response_declaration['description'] -}}<|"|>,
{%- endif -%}
{%- if response_declaration['type'] | upper == 'OBJECT' -%}
type:<|"|>{{- response_declaration['type'] | upper -}}<|"|>}
{%- endif -%}
{%- endif -%}
}
{%- endmacro -%}
{%- macro format_argument(argument, escape_keys=True) -%}
{%- if argument is none -%}
{{- 'null' -}}
{%- elif argument is string -%}
{{- '<|"|>' + argument + '<|"|>' -}}
{%- elif argument is boolean -%}
{{- 'true' if argument else 'false' -}}
{%- elif argument is mapping -%}
{{- '{' -}}
{%- set ns = namespace(found_first=false) -%}
{%- for key, value in argument | dictsort -%}
{%- if ns.found_first %},{% endif -%}
{%- set ns.found_first = true -%}
{%- if escape_keys -%}
{{- '<|"|>' + key + '<|"|>' -}}
{%- else -%}
{{- key -}}
{%- endif -%}
:{{- format_argument(value, escape_keys=escape_keys) -}}
{%- endfor -%}
{{- '}' -}}
{%- elif argument is sequence -%}
{{- '[' -}}
{%- for item in argument -%}
{{- format_argument(item, escape_keys=escape_keys) -}}
{%- if not loop.last %},{% endif -%}
{%- endfor -%}
{{- ']' -}}
{%- else -%}
{{- argument -}}
{%- endif -%}
{%- endmacro -%}
{%- macro strip_thinking(text) -%}
{%- set ns = namespace(result='') -%}
{%- for part in text.split('<channel|>') -%}
{%- if '<|channel>' in part -%}
{%- set ns.result = ns.result + part.split('<|channel>')[0] -%}
{%- else -%}
{%- set ns.result = ns.result + part -%}
{%- endif -%}
{%- endfor -%}
{{- ns.result | trim -}}
{%- endmacro -%}
{%- macro format_tool_response_block(tool_name, response) -%}
{{- '<|tool_response>' -}}
{%- if response is mapping -%}
{{- 'response:' + tool_name + '{' -}}
{%- for key, value in response | dictsort -%}
{{- key -}}:{{- format_argument(value, escape_keys=False) -}}
{%- if not loop.last %},{% endif -%}
{%- endfor -%}
{{- '}' -}}
{%- else -%}
{{- 'response:' + tool_name + '{value:' + format_argument(response, escape_keys=False) + '}' -}}
{%- endif -%}
{{- '<tool_response|>' -}}
{%- endmacro -%}
{#- ===== SETUP ===== -#}
{%- set ns = namespace(prev_message_type=None, prev_non_tool_role=None) -%}
{%- set loop_messages = messages -%}
{%- set enable_thinking = enable_thinking | default(false) -%}
{%- set preserve_thinking = preserve_thinking | default(false) -%}
{{- bos_token -}}
{#- Handle System/Tool Definitions Block -#}
{%- if enable_thinking or tools or (messages and messages[0]['role'] in ['system', 'developer']) -%}
{{- '<|turn>system\n' -}}
{#- Inject Thinking token at the very top of the FIRST system turn -#}
{%- if enable_thinking -%}
{{- '<|think|>\n' -}}
{%- set ns.prev_message_type = 'think' -%}
{%- endif -%}
{%- if messages and messages[0]['role'] in ['system', 'developer'] -%}
{%- if messages[0]['content'] is string -%}
{{- messages[0]['content'] | trim -}}
{%- elif messages[0]['content'] is sequence -%}
{%- for item in messages[0]['content'] -%}
{{- item['text'] | trim + ' '-}}
{%- endfor -%}
{%- endif -%}
{%- set loop_messages = messages[1:] -%}
{%- endif -%}
{%- if tools -%}
{%- for tool in tools %}
{{- '<|tool>' -}}
{{- format_function_declaration(tool) | trim -}}
{{- '<tool|>' -}}
{%- endfor %}
{%- set ns.prev_message_type = 'tool' -%}
{%- endif -%}
{{- '<turn|>\n' -}}
{%- endif %}
{#- Pre-scan: find last user message index for reasoning guard -#}
{%- set ns_turn = namespace(last_user_idx=-1) -%}
{%- for i in range(loop_messages | length) -%}
{%- if loop_messages[i]['role'] == 'user' -%}
{%- set ns_turn.last_user_idx = i -%}
{%- endif -%}
{%- endfor -%}
{#- Loop through messages -#}
{%- for message in loop_messages -%}
{%- if message['role'] != 'tool' -%}
{%- set ns.prev_message_type = None -%}
{%- set role = 'model' if message['role'] == 'assistant' else message['role'] -%}
{#- Detect continuation using tracked state — O(1) instead of O(n) backward scan -#}
{%- set continue_same_model_turn = (role == 'model' and ns.prev_non_tool_role == 'assistant') -%}
{%- if not continue_same_model_turn -%}
{{- '<|turn>' + role + '\n' }}
{%- endif -%}
{#- Render reasoning/reasoning_content as thinking channel -#}
{%- set thinking_text = message.get('reasoning') or message.get('reasoning_content') -%}
{%- set thinking_gate = (loop.index0 > ns_turn.last_user_idx) or (preserve_thinking and message.get('tool_calls')) -%}
{%- if thinking_text and thinking_gate -%}
{{- '<|channel>thought\n' + thinking_text + '\n<channel|>' -}}
{%- endif -%}
{%- if message.get('tool_calls') -%}
{%- for tool_call in message.get('tool_calls') -%}
{%- set function = tool_call['function'] -%}
{{- '<|tool_call>call:' + function['name'] + '{' -}}
{%- if function['arguments'] is mapping -%}
{%- set ns_args = namespace(found_first=false) -%}
{%- for key, value in function['arguments'] | dictsort -%}
{%- if ns_args.found_first %},{% endif -%}
{%- set ns_args.found_first = true -%}
{{- key -}}:{{- format_argument(value, escape_keys=False) -}}
{%- endfor -%}
{%- elif function['arguments'] is none -%}
{%- else -%}
{{- raise_exception(
"chat_template: tool_calls[].function.arguments must be a "
"JSON object (mapping), not a string. Deserialize arguments "
"before passing to the template."
) -}}
{%- endif -%}
{{- '}<tool_call|>' -}}
{%- endfor -%}
{%- set ns.prev_message_type = 'tool_call' -%}
{%- endif -%}
{%- set ns_tr_out = namespace(flag=false) -%}
{%- if message.get('tool_responses') -%}
{#- Legacy: tool_responses embedded on the assistant message (Google/Gemma native) -#}
{%- for tool_response in message.get('tool_responses') -%}
{{- format_tool_response_block(tool_response['name'] | default('unknown', true), tool_response['response']) -}}
{%- set ns_tr_out.flag = true -%}
{%- set ns.prev_message_type = 'tool_response' -%}
{%- endfor -%}
{%- elif message.get('tool_calls') -%}
{#- OpenAI Chat Completions: forward-scan consecutive role:tool messages -#}
{%- set ns_tool_scan = namespace(stopped=false) -%}
{%- for k in range(loop.index0 + 1, loop_messages | length) -%}
{%- if ns_tool_scan.stopped -%}
{%- elif loop_messages[k]['role'] != 'tool' -%}
{%- set ns_tool_scan.stopped = true -%}
{%- else -%}
{%- set follow = loop_messages[k] -%}
{#- Resolve tool_call_id to function name -#}
{%- set ns_tname = namespace(name=follow.get('name') or 'unknown') -%}
{%- for tc in message.get('tool_calls') -%}
{%- if tc.get('id') == follow.get('tool_call_id') -%}
{%- set ns_tname.name = tc['function']['name'] -%}
{%- endif -%}
{%- endfor -%}
{#- Handle content as string or content-parts array -#}
{%- set tool_body = follow.get('content') -%}
{%- if tool_body is string -%}
{{- format_tool_response_block(ns_tname.name, tool_body) -}}
{%- elif tool_body is sequence and tool_body is not string -%}
{%- set ns_txt = namespace(s='') -%}
{%- for part in tool_body -%}
{%- if part.get('type') == 'text' -%}
{%- set ns_txt.s = ns_txt.s + (part.get('text') | default('')) -%}
{%- endif -%}
{%- endfor -%}
{{- format_tool_response_block(ns_tname.name, ns_txt.s) -}}
{%- for part in tool_body -%}
{%- if part.get('type') in ['image', 'image_url'] -%}
{{- '<|image|>' -}}
{%- elif part.get('type') in ['audio', 'input_audio'] -%}
{{- '<|audio|>' -}}
{%- elif part.get('type') == 'video' -%}
{{- '<|video|>' -}}
{%- endif -%}
{%- endfor -%}
{%- else -%}
{{- format_tool_response_block(ns_tname.name, tool_body) -}}
{%- endif -%}
{%- set ns_tr_out.flag = true -%}
{%- set ns.prev_message_type = 'tool_response' -%}
{%- endif -%}
{%- endfor -%}
{%- endif -%}
{%- set captured_content -%}
{%- if message.get('content') is string -%}
{%- if role == 'model' -%}
{{- strip_thinking(message['content']) -}}
{%- else -%}
{{- message['content'] | trim -}}
{%- endif -%}
{%- elif message.get('content') is sequence -%}
{%- for item in message['content'] -%}
{%- if item.get('type') == 'text' -%}
{%- if role == 'model' -%}
{{- strip_thinking(item['text']) -}}
{%- else -%}
{{- item['text'] | trim -}}
{%- endif -%}
{%- elif item.get('type') in ['image', 'image_url'] -%}
{{- '<|image|>' -}}
{%- elif item.get('type') in ['audio', 'input_audio'] -%}
{{- '<|audio|>' -}}
{%- elif item.get('type') == 'video' -%}
{{- '<|video|>' -}}
{%- endif -%}
{%- endfor -%}
{%- endif -%}
{%- endset -%}
{{- captured_content -}}
{%- set has_content = captured_content | trim | length > 0 -%}
{#- Forward-scan: find next non-tool message role for continuation detection -#}
{%- set next_nt = namespace(role=None, found=false) -%}
{%- for j in range(loop.index0 + 1, loop_messages | length) -%}
{%- if not next_nt.found -%}
{%- if loop_messages[j]['role'] != 'tool' -%}
{%- set next_nt.role = loop_messages[j]['role'] -%}
{%- set next_nt.found = true -%}
{%- endif -%}
{%- endif -%}
{%- endfor -%}
{%- set continues_into_next = (
role == 'model'
and next_nt.role == 'assistant'
and (not message.get('tool_calls') or ns_tr_out.flag)
) -%}
{%- if ns.prev_message_type == 'tool_call' and not ns_tr_out.flag -%}
{{- '<|tool_response>' -}}
{%- elif continues_into_next -%}
{%- elif not (ns_tr_out.flag and not has_content and not next_nt.found) -%}
{{- '<turn|>\n' -}}
{%- endif -%}
{#- Track previous non-tool role for next iteration (avoids O(n) backward scan) -#}
{%- set ns.prev_non_tool_role = message['role'] -%}
{%- endif -%}
{%- endfor -%}
{%- if add_generation_prompt -%}
{%- if ns.prev_message_type != 'tool_response' and ns.prev_message_type != 'tool_call' -%}
{{- '<|turn>model\n' -}}
{%- if not enable_thinking -%}
{{- '<|channel>thought\n<channel|>' -}}
{%- else -%}
{{- '<|channel>thought\n' -}}
{%- endif -%}
{%- elif ns.prev_message_type == 'tool_response' and enable_thinking -%}
{{- '<|channel>thought\n' -}}
{%- endif -%}
{%- endif -%}