Gemma 4 12B pi chat template (KV-cache-stable retain build for the pi coding agent + llama.cpp)

gemma-4-12b-pi.jinja

{#
  Template: Gemma 4 12B -- KV-cache-stable "retain" build  (WORKING / active)
  Base:     unsloth/gemma-4-12b-it tokenizer_config.json chat_template, fetched 2026-07-20.
            The 12B sibling of gemma-4-e4b-pi.jinja -- same pi communication-flow deltas
            ported onto the 12B base (NOT copied from the E4B pi file).

  Changes vs the 12B base (four, matching the E4B pi build):
    1. preserve_thinking now DEFAULTS TO true. llama.cpp does not pass this kwarg, and retaining
       reasoning across turns keeps the rendered prompt prefix byte-stable -- stops the KV-cache
       busting / full reprocessing described in ggml-org/llama.cpp#21912.
       Set preserve_thinking=false to restore upstream trim-on-new-turn behavior.
    2. Thinking gate broadened from "(preserve_thinking and message.tool_calls)" to just
       "preserve_thinking", so reasoning on prior FINAL answers is retained too, not only
       tool-call turns -- maximal prefix stability.
    3. Reasoning close-marker: '{reasoning}<channel|>' with NO newline before <channel|> (base
       emitted '\n<channel|>'). The model generates the close with no preceding newline, so the
       extra \n broke KV-cache prefix reuse at the reasoning->answer seam.
    4. format_tool_response_block: detect bash's "Command exited with code" failure signature in
       a non-mapping tool response and hoist it to a front-loaded structural flag
       ('{error:true,value:...}') the model can't miss. Interim heuristic; swap for a real marker
       once isError survives the wire.

  Kept from 12B base (do NOT regress): the add_generation_prompt empty-thought channel emitted
  when enable_thinking is false -- absent from the E4B base, which is why the E4B pi template
  cannot be reused verbatim here.

  Also kept from base (do NOT regress): string/JSON tool-arg tolerance, null handling, filter_keys
  tool-schema serialization, multimodal placeholders, O(1) turn-continuation tracking,
  strip_thinking on visible content.
#}
{%- 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 -%}
        {#- Interim: llama.cpp drops pi's isError at the wire, so detect bash's failure
            signature in-text and hoist it to a front-loaded structural flag the model
            can't miss. Swap this heuristic for a real marker once the tool-hook
            extension injects one (or once isError is forwarded on the wire). -#}
        {%- set rtext = response | string -%}
        {%- if 'Command exited with code' in rtext -%}
            {{- 'response:' + tool_name + '{error:true,value:' + format_argument(response, escape_keys=False) + '}' -}}
        {%- else -%}
            {{- 'response:' + tool_name + '{value:' + format_argument(response, escape_keys=False) + '}' -}}
        {%- endif -%}
    {%- 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(true) -%}  {#- WORKING BUILD: default true (base was false) so retention holds even when llama.cpp omits the kwarg -#}
{{- 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') -%}
    {#- WORKING BUILD: retain ALL prior-turn reasoning (base gated this on tool_calls) so the KV-cache prefix stays byte-stable across turns -#}
    {%- set thinking_gate = (loop.index0 > ns_turn.last_user_idx) or preserve_thinking -%}
    {%- if thinking_text and thinking_gate -%}
        {{- '<|channel>thought\n' + thinking_text + '<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 -%}
                    {%- elif function['arguments'] is string -%}
                        {#- Pre-serialized args (e.g. an OpenAI JSON string). We cannot JSON-parse
                            portably in-template, so render non-fatally instead of erroring. Strip an
                            outer {...} so it composes with the DSL braces rather than double-wrapping.
                            Prefer passing arguments as a mapping for exact Gemma DSL. -#}
                        {%- set argstr = function['arguments'] | trim -%}
                        {%- if argstr[:1] == '{' and argstr[-1:] == '}' -%}
                            {{- argstr[1:-1] -}}
                        {%- else -%}
                            {{- function['arguments'] -}}
                        {%- endif -%}
                    {%- 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|>' -}}
        {%- endif -%}
    {%- elif ns.prev_message_type == 'tool_response' and enable_thinking -%}
        {{- '<|channel>thought\n' -}}
    {%- endif -%}
{%- endif -%}