[chrikrah]

Human Overview

Truncated SageMaker tool calls stop as max_tokens.

Description

Unstreamed, sagemaker.py:596 replaces inherited max_tokens for finish_reason: length with tool_calls, so the tool runs on truncated arguments, bypassing recover_message_on_max_tokens_reached.

# stub endpoint, stream False: get_weather(location="Pa") with finish_reason "length", then text
$ python repro_sagemaker.py   # base 15ca21f15
no exception
tool ran: ['Pa'] | invoke_endpoint calls: 2
$ python repro_sagemaker.py   # this branch
MaxTokensReachedException
tool ran: [] | invoke_endpoint calls: 1

Related Issues

Refs #5428

Documentation PR

None needed.

Type of Change

Bug fix

Testing

• I ran hatch run prepare
  • Steps run directly.

Additional Details

Output

# strands-py, python 3.12, base 15ca21f15
$ pytest -q -n 4 tests/strands/models tests/strands/event_loop
1094 passed, 3 warnings, 9 errors   # this branch
1091 passed, 3 warnings, 9 errors   # base; the 9 errors are provider SDKs not installed
$ pytest -q -n 4 tests/strands/models tests/strands/event_loop   # sagemaker.py reverted, tests kept
FAILED tests/strands/models/test_sagemaker.py::TestSageMakerAIModel::test_stream_non_streaming_tool_call_stop_reason[length-max_tokens]
1 failed, 1093 passed, 3 warnings, 9 errors
$ ruff format --check src/strands/models/sagemaker.py tests/strands/models/test_sagemaker.py && ruff check src/strands/models/sagemaker.py tests/strands/models/test_sagemaker.py   # ruff 0.17.3
2 files already formatted
All checks passed!
$ mypy src/strands/models/sagemaker.py   # mypy 2.3.1
Success: no issues found in 1 source file
# not run: hatch test --all on 3.10, 3.11, 3.13, 3.14; a live SageMaker endpoint

Checklist

• I have read the CONTRIBUTING document

• I have reviewed and understand every line of code in this PR, and I can explain why it works

• My change is focused and reasonably small; I have split unrelated work into separate PRs

• I have added any necessary tests that prove my fix is effective or my feature works

• I have updated the documentation accordingly

  • Nothing documented changes.

• I have added an appropriate example to the documentation to outline the feature, or no new docs are needed

• My changes generate no new warnings

• Any dependent changes have been merged and published

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@liramon2, stop beside a tool call still becomes tool_use. Right for your endpoints?

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

📢 Thoughts on this report? Let us know!

[liramon2]

Yes, stop beside another tool call should still run the tool and report tool_use.