christophevg / yoker / 28653731816

85%

push

github

fix(backends): prevent LiteLLM backend from mutating caller messages

LitellmBackend.chat_stream converted tool-call arguments from dict to
JSON string in place, corrupting the shared context dicts. After the
first LiteLLM turn with tool calls, the context's argument dicts were
permanently replaced with JSON strings, breaking the generic-format
invariant and corrupting saved context/replays. Cross-backend session
resumption would also fail (Ollama requires dict arguments).

Fix: deep-copy messages before the dict→JSON conversion, so only the
local copy passed to litellm.acompletion is affected.

Investigation confirmed:
- Ollama backend requires dict arguments (Message.model_validate
  rejects strings), so standardizing on JSON everywhere is not viable
- Ollama backend does not mutate input messages at all
- The generic-format invariant (context stores dicts) is preserved

Tests:
- test_chat_stream_does_not_mutate_caller_messages
- test_chat_stream_passes_json_string_arguments_to_litellm

Fixes #38

🤖 Implemented together with a coding agent.

912 of 1052 branches covered (86.69%)

Branch coverage included in aggregate %.

5092 of 6129 relevant lines covered (83.08%)

0.83 hits per line