fix(bedrock): omit empty additionalModelRequestFields and system from Converse API payload

[roytev]

Relevant issues

Pre-Submission checklist

• I have added testing in the tests/test_litellm/ directory
• My PR's scope is as isolated as possible, it only solves 1 specific problem

What

Amazon Nova Pro (and other strict Bedrock models) return 400 Malformed input request when additionalModelRequestFields: {} or system: [] are present in the Converse API payload, even though both are semantically empty.

AmazonConverseConfig._transform_request_helper() was unconditionally writing both keys into every payload regardless of whether they carried any data.

Fix

Only include additionalModelRequestFields and system in the CommonRequestObject when they are non-empty. Both fields are already declared optional (total=False) in the TypedDict — this brings the runtime behaviour in line with the type definition.

# Before — always serialized, causes 400 on Nova Pro
data: CommonRequestObject = {
    "additionalModelRequestFields": additional_request_params,  # {} when empty
    "system": system_content_blocks,                            # [] when empty
    "inferenceConfig": ...,
}

# After — only included when non-empty
data: CommonRequestObject = {
    "inferenceConfig": ...,
}
if additional_request_params:
    data["additionalModelRequestFields"] = additional_request_params
if system_content_blocks:
    data["system"] = system_content_blocks

Tests

• test_nova_batch_jsonl_omits_empty_converse_fields — new regression test validating the exact payload shape AWS accepts for a Nova Pro batch record
• test_nova_text_only_uses_converse_format — extended to assert both empty fields are absent
• test_transform_request_with_function_tool — updated assertion: function tools produce no additionalModelRequestFields (confirmed by the test's own comment)
• test_bedrock_max_completion_tokens — removed assertion on empty fields

[greptile-apps]

Greptile Summary

This PR fixes a 400 Malformed input request error returned by Amazon Nova Pro (and similarly strict Bedrock models) when the Converse API payload includes additionalModelRequestFields: {} or system: []. Both fields were unconditionally written into every request by _transform_request_helper; they are now only emitted when non-empty, which aligns the runtime behaviour with their total=False TypedDict declarations.

• Core fix (converse_transformation.py): Two conditional guards replace the unconditional dict literal assignments for additionalModelRequestFields and system.
• Test updates: Existing tests that asserted the old (buggy) empty-field behaviour are corrected; new regression tests in test_bedrock_files_transformation.py verify the exact payload shape AWS accepts for a Nova Pro batch record.

Confidence Score: 5/5

Safe to merge — the change is minimal and targeted, and models that legitimately populate these fields will continue to have them included because non-empty values still pass through the new guards.

The two-line guard is a straightforward conditional around previously unconditional writes. All affected tests have been updated to match the corrected behaviour, and new regression tests cover the exact Nova Pro failure case. No downstream code paths depend on the empty dict/list being present — the TypedDict already declared both fields optional.

No files require special attention; the only minor item is redundant intermediate assertions in test_bedrock_files_transformation.py.

Important Files Changed

Filename	Overview
litellm/llms/bedrock/chat/converse_transformation.py	Omits additionalModelRequestFields and system from the Converse API payload when they are empty, preventing 400 errors from strict models like Amazon Nova Pro.
tests/llm_translation/test_bedrock_completion.py	Removes now-incorrect assertions that expected empty additionalModelRequestFields and system keys in the serialized payload.
tests/test_litellm/llms/bedrock/chat/test_converse_transformation.py	Flips test_transform_request_with_function_tool assertion to verify additionalModelRequestFields is absent for plain function tools, consistent with the new fix.
tests/test_litellm/llms/bedrock/files/test_bedrock_files_transformation.py	Adds regression tests verifying empty fields are omitted; the intermediate weaker assertions in test_nova_batch_jsonl_omits_empty_converse_fields are redundant before the final exact-equality check.

_{Reviews (1): Last reviewed commit: "fix(bedrock): omit empty additionalModel..." | Re-trigger Greptile}

[greptile-apps]

The two intermediate assertions check a weaker invariant ("absent or non-empty") but are immediately followed by an exact equality check that already implies both fields must be absent. They add noise without catching anything the final assertion doesn't already cover, and could mislead a future reader into thinking a non-empty additionalModelRequestFields would also be acceptable here.

Suggested change

	assert (
	"additionalModelRequestFields" not in model_input
	or model_input["additionalModelRequestFields"]
	), "additionalModelRequestFields must be absent or non-empty — Nova rejects {}"
	assert (
	"system" not in model_input or model_input["system"]
	), "system must be absent or non-empty — Nova rejects []"
	# Validate the exact shape AWS accepts
	assert model_input == {
	# Validate the exact shape AWS accepts — both empty fields must be absent
	assert model_input == {

Note: If this suggestion doesn't match your team's coding style, reply to this and let me know. I'll remember it for next time!

[Sameerlite]

LGTM