fix: add float support to merge_dicts and merge_obj

[RoomWithOutRoof (Jah-yee)]

Summary

Fixes issue #36011: merge_dicts raises TypeError for float values during streaming chunk aggregation.

Changes

1. merge_dicts(): Changed isinstance(merged[right_k], int) to isinstance(merged[right_k], (int, float)) to handle float values the same way as integers.

2. merge_obj(): Added numeric type handling for int and float - now sums numeric values (consistent with merge_dicts behavior).

Root Cause

The function handled str, dict, list, equal values, and int types — but not float. When two dicts contain the same key with unequal float values (e.g., logprob, score, safety scores, cost fields in streaming), the function falls through to the final else branch and raises a TypeError.

Testing

This fix enables the following to work without errors:

from langchain_core.utils._merge import merge_dicts

# Now works!
merge_dicts({"score": 0.5}, {"score": 0.3})  # Returns {"score": 0.8}
merge_dicts({"logprob": -1.2}, {"logprob": -0.8})  # Returns {"logprob": -2.0}

Related

• Issue Bug: merge_dicts raises TypeError for float values during streaming chunk aggregation #36011
• Historical: Issue merge_dicts in _merge can't merge different values of instance float and raises a type error #17376 (2024) reported same bug for int
• PR langchain:Fix streaming error of TongYi model #16605 added int support but omitted float

[codspeed-hq]

Merging this PR will not alter performance

⚠️ Unknown Walltime execution environment detected

Using the Walltime instrument on standard Hosted Runners will lead to inconsistent data.

For the most accurate results, we recommend using CodSpeed Macro Runners: bare-metal machines fine-tuned for performance measurement consistency.

✅ 13 untouched benchmarks
⏩ 23 skipped benchmarks¹

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_{Comparing Jah-yee:fix/merge_dicts_float_support (397d11e) with master (07fa576)²}

Footnotes

1. 23 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

2. No successful run was found on master (2476f55) during the generation of this report, so 07fa576 was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩

[github-actions]

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