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gemma-4-E2B-it-ONNX

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Bug

chat_template.jinja calls value['type'] | upper on every property in a tool's
parameters.properties, in four places inside the format_parameters macro.

JSON Schema (and the OpenAI Chat Completions API) both allow a property without an
explicit type field — a property with only a description is valid. Several popular
OpenAI-compatible clients emit schemas like that (for example, agent frameworks such
as Hermes and OpenClaw).

When such a schema is passed through Gemma's chat template, Jinja raises:

Cannot apply filter "upper" to type: UndefinedValue

and generation fails before any tokens are produced.

Minimal repro

curl http://localhost:8000/v1/chat/completions \
  -H "Content-Type: application/json" \
  -d '{
    "model": "onnx-community/gemma-4-E4B-it-ONNX",
    "messages": [{"role":"user","content":"hi"}],
    "tools": [{"type":"function","function":{"name":"test","parameters":{
      "type":"object","properties":{"a":{"description":"a value"}}
    }}}],
    "max_tokens": 10
  }'

(Reproduced against transformers.js inference; the same template is loaded by
@huggingface/transformers under Node.)

Fix

Default the missing type to 'string' before applying | upper. String is the most
common and safest default for a described but untyped property. Same fix pattern, four
call sites:

- value['type'] | upper
+ (value['type'] | default('string')) | upper

This does not change behavior for any property that already sets type.

Scope

• Only touches format_parameters in chat_template.jinja.
• Same fix applies to onnx-community/gemma-4-E2B-it-ONNX (identical template) — a
  companion PR is opened there.