fix(tracing): catch ValueError and RecursionError in _safe_json_serialize

[nileshpatil6]

Problem

_safe_json_serialize in telemetry/tracing.py only catches TypeError and OverflowError, but json.dumps can also raise:

• ValueError — e.g. circular references (json.dumps raises ValueError: Circular reference detected)
• RecursionError — e.g. deeply nested structures exceeding Python's recursion limit

Because this function is called inside finally blocks during tool execution telemetry, an uncaught exception here can interrupt normal execution flow and affect tool results.

Fixes #5411

Fix

Add ValueError and RecursionError to the existing except clause:

except (TypeError, OverflowError, ValueError, RecursionError):
    return '<not serializable>'

[nileshpatil6]

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[adk-bot]

Response from ADK Triaging Agent

Hello @nileshpatil6, thank you for creating this PR!

Could you please include a testing plan section in your PR to describe how you tested your changes? This will help reviewers to review your PR more efficiently. Thanks!

[nileshpatil6]

Testing Plan

Manual verification:

import json
from google.adk.telemetry.tracing import _safe_json_serialize

# Test 1: Circular reference (previously raised ValueError)
circular = {}
circular['self'] = circular
assert _safe_json_serialize(circular) == '<not serializable>'

# Test 2: Deeply nested structure (previously raised RecursionError)
deep = {}
node = deep
for _ in range(1000):
    node['child'] = {}
    node = node['child']
result = _safe_json_serialize(deep)
assert result == '<not serializable>'

# Test 3: Normal objects still serialize correctly
assert _safe_json_serialize({'key': 'value'}) == '{"key": "value"}'

print('All tests passed')

Before fix: _safe_json_serialize with a circular reference raises ValueError: Circular reference detected, which propagates out of the finally block and crashes tool execution.

After fix: Returns '<not serializable>' gracefully for all failure modes.