fix(gemma4): handle JSON-formatted keys in tool call parser

[afanty2021]

Summary

Gemma 4 models may output standard JSON format for tool call arguments:

call:func_name{"key": "value"}  ← Standard JSON

Instead of the Gemma 4-specific format:

call:func_name{key<|"|>value<|"|>}  ← Gemma 4 format

The parser's _parse_object function was directly using the raw key text,
which included the JSON quotes, resulting in keys like '"action"' instead
of 'action'.

Problem

When the parser received JSON-formatted input:

1. _parse_object extracted the key as "action" (with quotes)
2. This created a dict: {'"action"': 'add'}
3. json.dumps escaped the existing quotes: '{"\"action\"": "add"}'
4. Downstream tools received malformed parameter names

Solution

Modified _parse_object to detect and handle JSON-formatted keys:

if key.startswith('"') and key.endswith('"'):
    try:
        key = json.loads(key)  # Properly unescape
    except (json.JSONDecodeError, ValueError):
        key = key[1:-1]  # Fallback: strip quotes

Test Cases

Added comprehensive tests covering:

• ✅ Simple JSON-formatted keys
• ✅ Multiple JSON keys
• ✅ Nested objects/arrays with JSON keys
• ✅ Unicode escape sequences in keys
• ✅ Mixed Gemma 4 and JSON formats

All 12 tests pass.

Impact

• Fixes tool call parameter parsing for Gemma 4 models
• Maintains backward compatibility with existing Gemma 4 format
• No changes needed to model code or chat templates

Co-Authored-By: Claude Opus 4.6 [email protected]

[Blaizzy]

Hey @afanty2021, thanks!

Please open a issue first