fix(bedrock): fold streaming tool input deltas back into tool args (#6149)

[tsushanth]

Closes #6149. Streaming twin of #4972 (non-streaming case already fixed by #5415).

_handle_streaming_converse and _ahandle_streaming_converse accumulate Bedrock Converse's contentBlockDelta JSON chunks into a local accumulated_tool_input string but never fold that string back into current_tool_use["input"]. At contentBlockStop the code reads current_tool_use.get("input", {}), which the start event left as the empty dict, so every streaming tool call reaches _handle_tool_execution with {} and pydantic raises Field required [type=missing].

The fix is a focused parse-on-stop, shared between the sync and async paths:

• new module-level _parse_streaming_tool_input(accumulated, fallback) that returns json.loads(accumulated) when deltas arrived, falls back to the start-block's input dict otherwise (some providers send the full input up front), and degrades to {} on JSONDecodeError so a malformed partial doesn't crash the stream
• both contentBlockStop branches now call the helper instead of reading current_tool_use["input"] directly

current_tool_use["input"] is intentionally left untouched in the dict that's later re-appended to messages ({"toolUse": current_tool_use}) — the assistant turn echoed back to the model uses Bedrock's own start-block payload, not the parsed args, and changing that shape is out of scope here.

Regression test

lib/crewai/tests/llms/bedrock/test_bedrock.py::test_streaming_tool_call_accumulates_input_deltas:

• Builds a synthetic Converse stream — contentBlockStart(toolUse) → contentBlockDelta('{"city":') → contentBlockDelta(' "Paris"}') → contentBlockStop → messageStop — exactly the shape the issue describes.
• Stubs an available_functions["get_weather"] that records its city arg.
• Asserts the captured arg is {"city": "Paris"}.

Verified locally — fails against main with AssertionError: {} == {'city': 'Paris'} and the WARNING ... Bedrock streaming returned empty content log; passes with the fix.

No async regression test added: the existing test_bedrock_async.py cases are all skipped in CI (VCR doesn't play back aiobotocore), and the parsing logic is shared with the sync path through _parse_streaming_tool_input, so the sync test exercises the relevant code in both call sites.

Summary by CodeRabbit

Release Notes

• Bug Fixes
  • Fixed tool call argument reconstruction in Bedrock Converse streaming to properly accumulate fragmented inputs into complete function arguments instead of returning incomplete or empty values.

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📥 Commits

Reviewing files that changed from the base of the PR and between d80719d and cdc145a.

📒 Files selected for processing (2)

• lib/crewai/src/crewai/llms/providers/bedrock/completion.py
• lib/crewai/tests/llms/bedrock/test_bedrock.py

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📝 Walkthrough

Walkthrough

This PR fixes a streaming bug where Bedrock tool calls receive empty arguments. The fix introduces a helper function to parse accumulated streaming deltas, applies it to both sync and async streaming handlers at content-block termination, and validates the behavior with regression tests.

Changes

Bedrock streaming tool-call argument accumulation

Layer / File(s)	Summary
Streaming tool input parsing helper lib/crewai/src/crewai/llms/providers/bedrock/completion.py	Introduces _parse_streaming_tool_input helper that JSON-parses accumulated delta text with fallback to a provided default dictionary on decode failure or empty accumulation.
Streaming content block stop handlers lib/crewai/src/crewai/llms/providers/bedrock/completion.py	Both sync and async streaming handlers now invoke _parse_streaming_tool_input(accumulated_tool_input, current_tool_use["input"]) at contentBlockStop instead of reading the empty initial input block directly.
Regression test for accumulated input deltas lib/crewai/tests/llms/bedrock/test_bedrock.py	Adds _make_streaming_tool_use_events mock-event generator and test_streaming_tool_call_accumulates_input_deltas regression test that verifies fragmented tool-use input chunks are reassembled into final arguments and the tool is invoked with the reconstructed payload.

🐰 A streaming bug we did find,
Empty args left behind,
Now deltas stack with parsed JSON back,
Tool calls work—no empty pack! ✨

🎯 3 (Moderate) | ⏱️ ~25 minutes

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 75.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly describes the main fix: folding streaming tool input deltas back into tool arguments for Bedrock, matching the changeset's core objective.
Linked Issues check	✅ Passed	All coding objectives from #6149 are met: the helper function parses accumulated JSON deltas, both sync/async contentBlockStop handlers use it, and a regression test validates streaming tool-call argument reconstruction.
Out of Scope Changes check	✅ Passed	All changes are scoped to the streaming Bedrock tool-call argument fix; no unrelated modifications to other providers, tool-use payload shapes, or unrelated modules were introduced.

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[tsushanth]

Apologies @kimnamu — your #6150 was open ~9 hours before this and addresses the same root cause in the same file (bedrock/completion.py). I missed it because the Fixes: keyword didn't auto-link it to issue #6149 in the sidebar. Closing in favor of yours. The streaming-mock test I added here (_make_streaming_tool_use_events helper + test_streaming_tool_call_accumulates_input_deltas) is a different shape from your tests; happy for you to lift it if useful, otherwise feel free to ignore.