fix: preserve message tags when restoring from dictionaries

WT
19d ago
+13-0

Summary

MessageBase.from_dict() drops tags even though Message.__init__() accepts them and to_dict() serializes them. Forward the stored tags when reconstructing a message, including through the chat-resume path. Dictionaries without the field continue to produce tags=None.

This is a source finding on current main. No matching existing issue was found; no issue has been published.

Validation

  • Added round-trip coverage for a non-empty tag list, an empty list and None, plus a compatibility assertion for a legacy dictionary without tags.
  • Unmodified implementation with the regression tests: 2 failed, 51 passed in backend/tests/test_message.py; both failures reproduce dropped tags.
  • Patched implementation: 70 passed across backend/tests/test_message.py and backend/tests/test_modes.py.
  • PYTHONPATH=backend python -m pytest backend/tests/test_message.py backend/tests/test_modes.py -q --tb=short --allow-hosts=127.0.0.1,::1; remote sockets are blocked, with loopback allowed for the Windows asyncio loop. The verification harness asserts the loaded source path for both baseline and patched runs.
  • python scripts/lint.py backend/chainlit/message.py backend/tests/test_message.py and python scripts/format.py --check backend/chainlit/message.py backend/tests/test_message.py pass using Ruff 0.13.3.
  • git diff --check passes. No new dependencies.

Validation limits

  • Windows / Python 3.11.0, within the supported package range; the development target is Python 3.13. The source backend is loaded directly in an isolated environment to avoid the frontend build hook.
  • A prior complete scripts/type_check.py --no-incremental comparison reported the same 38 diagnostics in 16 files on unmodified main and the patch (109 files checked), including missing optional integration dependencies. This is not a passing whole-backend type check.
  • The targeted test run reports 11 warnings, including existing dependency deprecation, asyncio marker and AsyncMock warnings.
  • A prior source hello-app launch failed because frontend assets were not built. Browser workflows, frontend lint/format, the full backend suite and Cypress E2E remain unverified.

AI assistance

Codex assisted with investigation, the one-line fix and regression tests. Verification results and limitations are listed above.

Summary by cubic

Fixes MessageBase.from_dict() dropping tags when reconstructing messages, even though Message.__init__() accepts them and to_dict() serializes them. The stored tags are now forwarded when restoring, including through the chat-resume path, while dictionaries without the field still produce tags=None.

Adds regression tests covering round-trip preservation for a non-empty tag list, an empty list, and None, plus a compatibility assertion for legacy dictionaries without the tags field.