fix(cartesia): keep plain-string search results and skip malformed messages - #1683

Summary

src/supermemory_cartesia/utils.py and src/supermemory_pipecat/utils.py are copies of the same file. #1434 hardened two spots in the pipecat copy and missed the cartesia one. This brings the two hunks back to parity and adds regression tests.

Bug 1 — plain-string search results are silently dropped

deduplicate_memories → unique_search calls _field(r, "memory", "chunk", "content", default="") on every result. For a plain str that finds no attribute, falls back to "", and the entry never reaches the prompt.

format_memories_to_text in the same file already has an isinstance(item, str) branch for search results, so that branch is currently unreachable — nothing can get past dedup as a string.

Reproduced against the pipecat copy as the reference:

cartesia  search_results -> []
cartesia  rendered       -> ''
pipecat   search_results -> ['User prefers tea']
pipecat   rendered       -> 'Based on previous conversations, I recall:\n\n\n## Relevant Memories\n\n- User prefers tea'

Bug 2 — get_last_user_message raises KeyError

It indexed msg["role"] and msg["content"] positionally, so a tool-call turn or provider event missing either key raised instead of being skipped. Non-string content was also returned verbatim despite the -> str | None annotation.

user with no content   cartesia  -> KeyError: 'content'
user with no content   pipecat   -> 'hello'
entry with no role     cartesia  -> KeyError: 'role'
entry with no role     pipecat   -> 'hello'
non-string content     cartesia  -> [{'type': 'text', 'text': 'hello'}]
non-string content     pipecat   -> None

Changes

• src/supermemory_cartesia/utils.py — both hunks now match the pipecat implementation exactly.
• tests/test_utils.py — new, 6 tests.

Test plan

• 3 of the 6 new tests fail on unmodified main and pass with the fix:

  FAILED tests/test_utils.py::TestGetLastUserMessage::test_skips_entries_without_role_or_content
  FAILED tests/test_utils.py::TestGetLastUserMessage::test_skips_non_string_content
  FAILED tests/test_utils.py::TestDeduplicateMemories::test_keeps_plain_string_search_results
  3 failed, 5 passed
  

• Full suite with the fix: 8 passed.
• ci-python.yml already path-filters packages/cartesia-sdk-python/**, so these run in CI with no workflow change.

No behaviour change for dict or Stainless-model search results — covered by test_still_reads_the_memory_field_of_models_and_dicts.