Python: Fix Bedrock parallel tool-call results rejected by Converse#14074
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kimnamu wants to merge 2 commits into
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Python: Fix Bedrock parallel tool-call results rejected by Converse#14074kimnamu wants to merge 2 commits into
kimnamu wants to merge 2 commits into
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When a model requests multiple tools in a single turn, the function-calling
loop appends one ChatMessageContent per tool call and one per tool result.
The Bedrock connector mapped each of these 1:1 to a Converse message, so N
parallel tool results became N separate user messages each with a single
toolResult block. Converse rejects this with:
Expected toolResult blocks at messages.X.content for the following
Ids: ... but found: ...
Merge consecutive messages that map to the same Bedrock role in
_prepare_chat_history_for_request, so all toolUse blocks for an assistant
turn land in one assistant message and all toolResult blocks land in one
user message. This mirrors the existing behavior of the sibling Anthropic
connector, which already groups parallel tool messages.
Python analogue of microsoft#13647 (reported for .NET).
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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Pull request overview
Note
Copilot was unable to run its full agentic suite in this review.
Adds Bedrock Converse compatibility by coalescing consecutive same-role messages (notably parallel tool calls/results) into single messages to avoid Bedrock request validation errors.
Changes:
- Update Bedrock chat history preparation to merge consecutive messages that map to the same Bedrock role.
- Add a unit test verifying parallel tool call + tool result messages are merged into the required Bedrock structure.
Reviewed changes
Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.
| File | Description |
|---|---|
| python/semantic_kernel/connectors/ai/bedrock/services/bedrock_chat_completion.py | Merge consecutive same-role Bedrock messages by concatenating content blocks. |
| python/tests/unit/connectors/ai/bedrock/services/test_bedrock_chat_completion.py | Add test coverage for merging parallel tool calls/results into single assistant/user messages. |
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| formatted_message = MESSAGE_CONVERTERS[message.role](message) | ||
| if messages and messages[-1][role_key] == formatted_message[role_key]: | ||
| # The Bedrock Converse API requires that consecutive messages with the same role be | ||
| # combined into a single message. In particular, SK emits one tool message per parallel | ||
| # tool result (all mapped to the "user" role), which Bedrock rejects unless every | ||
| # toolResult block for an assistant turn is grouped in a single user message. | ||
| messages[-1][content_key] += formatted_message[content_key] | ||
| else: | ||
| messages.append(formatted_message) |
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| @patch.object(boto3, "client", return_value=Mock()) | ||
| def test_prepare_chat_history_for_request_merges_parallel_tool_results(mock_client, bedrock_unit_test_env) -> None: | ||
| """Test that parallel tool calls and their results are merged into single Bedrock messages. | ||
|
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| When a model requests multiple tools in one turn, SK emits one assistant message per tool call | ||
| and one tool message per tool result. The Bedrock Converse API requires every toolUse block for a | ||
| turn to be in a single assistant message and every toolResult block to be in a single user message, | ||
| otherwise the request is rejected with an "Expected toolResult blocks ..." error. | ||
| """ |
![github-actions[bot]](https://avatars.githubusercontent.com/in/15368?s=60&v=4){kind=small}
- Build a new combined content list instead of in-place += (clearer type intent, no mutation of the previous message), per review feedback. - Add a regression test for merging consecutive non-tool same-role messages.
Author
|
Thanks for the review! Addressed both points in the latest commit:
Full bedrock connector suite passes (40 tests); |
Author
|
@microsoft-github-policy-service agree |
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Thanks to the SK maintainers for the Bedrock connector and the consistent connector design — this change just fills a gap the sibling Anthropic connector already handles.
Motivation and Context
Fixes #14073. Python analogue of #13647 (.NET).
When a model calls multiple tools in one turn, SK emits one
ChatMessageContentper tool call/result._prepare_chat_history_for_requestmapped each 1:1 to a Converse message, so paralleltoolResults landed in separate user messages → Converse rejects:Expected toolResult blocks at messages.X.content ....Description
Merge consecutive messages that map to the same Bedrock role, so all
toolUseblocks land in one assistant message and alltoolResultblocks in one user message. Mirrors the existing Anthropic connector (formatted_messages[-1][content_key] += ...).toolUsemessagestoolUseblockstoolResultmessages (Converse rejects)toolResultblocks_format_*converters, public API/argsContribution Checklist
test_prepare_chat_history_for_request_merges_parallel_tool_results. Reverting only the source makes it fail withassert 5 == 3(proving it catches the bug); with the fix the full bedrock unit suite passes (114 passed).ruff format/ruff check/mypyclean.This contribution was prepared with the help of an AI agent (Claude Code); a human reviewed the change, reasoning, and test results before submission.