Filter 3: file_resolve

[leseb]

Purpose

Resolve file_id, file_data, file_url, and image_url references in input messages to inline content.

Behavior

• Walk all messages in responses.messages
• For file_id: fetch file content + MIME type from file store, base64 encode, build data URL
• For file_data: wrap in data URL format
• For file_url: pass through as-is
• For input_file.filename: preserve original filename through resolution (needed for citations)
• For image_url with file_id: resolve to data URL
• For input_image.detail: preserve detail level enum (low|high|auto, default auto) and pass to inference
• For tool outputs containing images/files: resolve file references in-place, preserve multi-modal content as-is
• Update responses.messages

Praxis trait methods

• on_request — walk messages, resolve file references

Dependencies

• File store (read)

Reference

• Proposal: Responses API Filters — Filter 3
• Part of Epic: Responses API and Agentic Loop Orchestration #93