Pattern Proposal: Pluggable Provider Adapter

Summary

Isolates external API communications behind swappable client implementations for testing and runtime flexibility.

Candidate Pattern

• ID: pluggable-provider-adapter
• Classification: architectural
• Maturity: strategic_direction
• Type: emerging

Observed Signals

No specific signals listed.

Evidence

Supporting Evidence

• src/cas_runner/llm/litellm_client.py (LiteLLMClient) - Production integration with LiteLLM library.
• src/cas_runner/llm/mock_client.py (MockLLMClient) - Deterministic in-memory mock client enabling decoupled test execution.

Scope Assessment

• Evidence Strength: high
• Confidence: high
• Applies to: ideas-to-life-cas

Rationale

• Intent: Allow execution in disconnected or automated test environments by swapping real external services with mock equivalents.
• Context: The system relies on external LLM services (LiteLLM) during normal operation, but integration pipelines and tests require local deterministic responses without network calls or secrets.
• Force: Automated tests must not require API keys or incur network latencies.
• Force: Execution layer should remain unaware of whether an online or mock backend is in use.

Traceability

Artifact source: proposed-patterns