fix: set inline disposition for renderable blob elements

[axelray-dev]

Fixes #2946

Summary

SQLAlchemyDataLayer.create_element never passed content_disposition to storage_provider.upload_file. Azure Blob Storage defaults to Content-Disposition: attachment in this case, which causes browser-renderable elements (PDF, images, audio, video) to render blank on chat resume because iframes and media tags refuse to display content served with an attachment disposition.

This fix sets content_disposition='inline' for browser-renderable MIME types while preserving the existing behavior for non-renderable uploads.

Scope

Only browser-renderable MIME types are affected:

• application/pdf
• image/*
• audio/*
• video/*

All other element types (generic files, text/plain, application/octet-stream, etc.) keep content_disposition=None, preserving the existing download behavior.

Changes

• backend/chainlit/data/sql_alchemy.py: determine content_disposition before upload_file call based on element.mime
• backend/tests/data/test_sql_alchemy.py: 3 new tests verifying disposition behavior for PDF, image, and text/plain elements

Testing

Backend tests run locally:

• tests/data/test_sql_alchemy.py: 18/18 passed (including 3 new tests)
• tests/data/: 71/71 passed, 1 pre-existing error (test_get_data_layer fails without built frontend)
• ruff check: all passed
• ruff format --check: all passed
• git diff --check: clean

Note: pre-commit hooks could not run locally (frontend build OOMs on VPS). CI will verify lint and format.

Backward Compatibility

This change is fully backward-compatible per AGENTS.md requirements:

• Non-renderable element types are unaffected
• The content_disposition parameter was already accepted by all storage clients but never used by SQLAlchemyDataLayer
• The fix follows the same pattern used in chainlit_data_layer.py

---

Summary by cubic

Force inline Content-Disposition for renderable blob uploads so PDFs, images, audio, and video display correctly in iframes/media on chat resume. Leaves non-renderable files unchanged.

• Bug Fixes
  • Pass content_disposition='inline' for application/pdf, image/*, audio/*, video/* in SQLAlchemyDataLayer.create_element.
  • Keep content_disposition=None for others (e.g., text/plain, application/octet-stream) to preserve download behavior.
  • Added tests for PDF inline, image inline, and text default cases.

^{Written for commit afe6d49. Summary will update on new commits.}

[cubic-dev-ai]

No issues found across 2 files

_{Re-trigger cubic}