fix: handle missing optional fields in non-streaming citation conversion

[agent-of-mkmeral]

Non-streaming Bedrock responses with citationsContent crash with KeyError: 'title' when Nova grounding returns citations without optional fields.

Why

Nova's web grounding returns citations containing only location (with url and domain) but no title or sourceContent fields. The _convert_non_streaming_to_streaming method accesses these fields directly (citation["title"]), causing a KeyError.

The SDK's own CitationsDelta type is TypedDict(total=False) — all fields are optional. And the same file already handles this correctly in _format_request_message_content using if "title" in citation checks. The non-streaming conversion path was the only place that didn't follow this pattern.

What changed

src/strands/models/bedrock.py — Changed _convert_non_streaming_to_streaming to conditionally include citation fields only when present, matching the existing safe pattern elsewhere in the file.

tests/strands/models/test_bedrock.py — Added three test cases:

• Citations with missing optional fields (the Nova grounding case)
• Citations with all fields present (regression guard)
• Citations with only location (minimal citation)

Reproduction

from strands import Agent
from strands.models import BedrockModel

model = BedrockModel(
    model_id="us.amazon.nova-2-lite-v1:0",
    region_name="us-east-1",
    streaming=False,
    additional_args={
        "toolConfig": {"tools": [{"systemTool": {"name": "nova_grounding"}}]}
    },
)
agent = Agent(model=model, tools=[])
result = agent("top 5 shoe brands")  # KeyError: 'title'

Related: #1154, #1318, #1323

[codecov]

Codecov Report

❌ Patch coverage is 85.71429% with 1 line in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
src/strands/models/bedrock.py	85.71%	0 Missing and 1 partial ⚠️

📢 Thoughts on this report? Let us know!