Fixes a real bug: with `filter_incomplete_user_turns` enabled, the
smart-turn detector's tentative stop was firing `on_user_turn_stopped`
before the LLM had a chance to veto it. Observers, transcript
appenders and UI indicators received an early — and sometimes
duplicated — signal.
Decomposes the single stop concern into two events:
- `on_user_turn_inference_triggered` fires when a stop strategy has
enough signal to start LLM inference. The aggregator pushes the
context here, kicking off the LLM call.
- `on_user_turn_stopped` fires only when the user turn is semantically
final. Built-in strategies fire both events at the same call site,
preserving today's behavior for the common case.
Adds `LLMTurnCompletionUserTurnStopStrategy`, which gates
finalization on a `UserTurnCompletedFrame` (a fieldless system frame
emitted by any component judging turn completeness — currently the
`UserTurnCompletionLLMServiceMixin` on `✓`).
Adds `deferred(strategy)` / `DeferredUserTurnStopStrategy`, a thin
wrapper that forwards an inner strategy's events except
`on_user_turn_stopped`. Use this to install a stop strategy as an
inference trigger only, leaving finalization to a peer (e.g. the LLM
completion strategy).
Adds `llm_completion_user_turn_stop_strategies()` for the common
case:
UserTurnStrategies(
stop=llm_completion_user_turn_stop_strategies(),
)
Deprecates `LLMUserAggregatorParams.filter_incomplete_user_turns`.
The aggregator emits a `DeprecationWarning`, wraps existing stop
strategies with `deferred(...)`, and appends
`LLMTurnCompletionUserTurnStopStrategy` automatically.
Turn completion instructions were being injected as a system message in
the LLM context, which caused warning spam when system_instruction was
also set, did not persist across full context updates, and broke LLMs
that do not support consecutive system messages.
Instead, compose the turn completion instructions into the LLM service
system_instruction field. This is managed via _base_system_instruction
which stores the original value for restoration when turn completion is
disabled.
