The server now resolves source, identity, and style artifacts separately, emits role-labeled Gemini parts, and logs the effective request shape so deployed debugging can confirm which references reached upstream.
Constraint: The test deployment must stay on gemini-3.1-flash-image-preview while gaining better multi-image editing semantics
Rejected: Change the default model to gemini-3-pro-image-preview | test-server parity required keeping flash as default
Confidence: high
Scope-risk: moderate
Reversibility: clean
Directive: Preserve the source/identity/style logging until the upstream gateway exposes equivalent structured traces
Tested: go test ./internal/server
Tested: image img2img against http://101.42.99.35:18080/v1 (job_5af212df2c27)
Not-tested: Non-Gemini multi-image providers still fall back to the first reference only