Gateway Route Explanations

Route explanations make dry-run decisions auditable for humans and machines.

Explanation Shape

summary
strategy
selected
hard_requirements
score_breakdown
rejected
fallbacks
warnings
policy_source
preset_id
deterministic_tie_break

Language Rules

Explanations use planning language:

• selected for planning
• recommended candidate
• fallback plan
• dry-run decision

They avoid wording that implies a request was transmitted, a provider was invoked, an upstream answer came back, or failover actually ran.

Redaction Boundary

Explanations must not include:

• prompt bodies
• API keys
• authorization headers
• credential values
• sensitive environment values
• absolute local machine paths

Determinism

Equivalent inputs produce equivalent explanations when the caller supplies the same request ID and decision timestamp.

Sprint D adds resilience explanations for simulated failure chains. They keep the same redaction and planning-language boundaries.