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SOFAI (Slow and Fast AI) Sampling Strategy. This module implements a two-solver sampling strategy that uses:
  1. S1 Solver (fast model) - Iterative solving with feedback-based repair
  2. S2 Solver (slow model) - Single attempt escalation when S1 fails or shows no improvement
The strategy leverages ValidationResult.reason fields to provide targeted feedback for repair, enabling more effective iterative improvement.

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Classes

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CLASS SOFAISamplingStrategy

SOFAI (Slow and Fast AI) two-solver sampling strategy. Uses S1 Solver (fast model) in a loop with targeted feedback from validation results. If S1 Solver fails after exhausting the budget or shows no improvement, escalates to a single attempt with S2 Solver (slow model). The strategy leverages ValidationResult.reason fields to provide targeted feedback for repair, enabling more effective iterative improvement. Args:
  • s1_solver_backend: Backend for the fast S1 solver used in the iterative repair loop.
  • s2_solver_backend: Backend for the slow S2 solver used as a final escalation step.
  • s2_solver_mode: How to invoke the S2 solver when S1 fails.
  • loop_budget: Maximum number of S1 repair attempts before escalating to S2. Must be greater than 0. Defaults to 3.
  • judge_backend: Optional backend for LLM-as-Judge validation. If None, falls back to the session backend.
  • feedback_strategy: Detail level of repair feedback provided to the S1 solver.
Methods:

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FUNC repair 

repair(old_ctx: Context, new_ctx: Context, past_actions: list[Component], past_results: list[ModelOutputThunk], past_val: list[list[tuple[Requirement, ValidationResult]]]) -> tuple[Component, Context]
Create targeted feedback message from validation results. Extracts failed requirements and uses their ValidationResult.reason fields to provide specific, actionable feedback for the next attempt. Args:
  • old_ctx: The context WITHOUT the last action + output.
  • new_ctx: The context including the last action + output.
  • past_actions: List of actions executed.
  • past_results: List of generation results.
  • past_val: List of validation results.
Returns:
  • Tuple of (Message component with repair feedback, new context).

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FUNC select_from_failure 

select_from_failure(sampled_actions: list[Component], sampled_results: list[ModelOutputThunk], sampled_val: list[list[tuple[Requirement, ValidationResult]]]) -> int
Select the most informed attempt (last) when all fail. Returns the last attempt as it has benefited from the most feedback. Args:
  • sampled_actions: List of actions that have been executed (without success).
  • sampled_results: List of (unsuccessful) generation results for these actions.
  • sampled_val: List of validation results for the results.
Returns:
  • The index of the result that should be selected as .value.

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FUNC sample 

sample(self, action: Component[S], context: Context, backend: Backend, requirements: list[Requirement] | None) -> SamplingResult[S]
Execute SOFAI two-solver sampling strategy.

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SOFAI Flow Overview:

  1. PHASE 1 - S1 Solver Loop:
    • Generate candidate solution with fast S1 model
    • Validate against requirements
    • If success: return immediately
    • If failure: generate repair feedback and iterate
    • If no improvement detected: early exit to Phase 2
  2. PHASE 2 - S2 Solver Escalation:
    • Prepare context based on s2_solver_mode:
      • fresh_start: clean slate with original prompt
      • continue_chat: full S1 conversation history
      • best_attempt: best S1 result with feedback summary
    • Generate single attempt with slow S2 model
    • Validate and return result (success or failure)
Args:
  • action: The component to sample (Instruction, Message, etc.).
  • context: The session context (must be ChatContext).
  • backend: Session backend (used for validation fallback).
  • requirements: Requirements to validate against.
  • validation_ctx: Optional separate validation context (unused).
  • format: Output format for structured outputs.
  • model_options: Model options to pass to backends.
  • tool_calls: True if tool calls should be used.
Returns:
  • SamplingResult with success status and all generation history.