Context Passport and Burst Guard
Context Passport persists bounded logical inference-session identity and best-effort affinity hints:
Send the returned ID as X-InferCrane-Context-Passport. The in-memory route snapshot prefers the hinted
binding or target only while it remains eligible; otherwise ordinary healthy routing wins and the response
reports X-InferCrane-Affinity: fallback.
Context Passport does not store conversation bodies and does not guarantee durable KV state. Logical
identity survives a worker; engine cache survival does not unless a separately qualified backend provides it.
Request survival
Request survival is a delegated capability contract. A runtime/backend may claim support only with a named
mechanism and local or real qualification evidence. Plain vLLM does not gain request migration from
InferCrane; unsupported and unknown states fail closed. InferCrane never implements distributed KV or token
migration.
Burst Guard
Burst Guard combines fresh queue evidence, sustained breach/recovery intervals, qualified external health,
and a hard incremental hourly cost ceiling:
It requires the existing governed external fallback policy, including privacy acknowledgement and its hard
request/cost budget. Stale signals, unavailable capacity, or cost above policy produce a fail-closed decision.
The evaluator persists evidence; route mutation remains owned by the existing policy controller.