Chain Engine

Saved chain definitions, policies, local runtime endpoints, fallback, health, and traffic logs.

The Chain Engine turns saved proxy chains into local HTTP/CONNECT proxy endpoints.

What It Manages

Object	Purpose
Chain	A saved ordered list of proxy hops with labels, tags, and fallback chain IDs.
Policy	Runtime behavior such as validation, auth, timeout, health checks, retry budget, fallback, and bandwidth limit.
Runtime	A local endpoint bound to `127.0.0.1` that sends traffic through the saved chain route.
Traffic entry	Recent request/tunnel record with target, status, bytes, route, duration, and error details.

State	Meaning
Stopped	No listener is active.
Starting	Runtime is preparing routes and binding a local port.
Running	Runtime has an active local endpoint.
Degraded	Runtime started, but route health is not fully clean.
Error	Runtime could not start or continue.

Feature	Detail
Persistent definitions	Chains, policies, and runtime configs are stored locally as JSON-backed state.
Fallback graph	The engine validates missing fallback chains and fallback cycles before runtime use.
Port fallback	If the requested local port is busy, the runtime binds a random local port and records a notice.
Health loop	Routes are probed on the policy interval and can be marked unhealthy after the failure threshold.
Active route refresh	Runtime route selection refreshes after health updates.
Optional local auth	Basic proxy auth protects the local endpoint when enabled in policy.
Bandwidth cap	Chain runtime can enforce a bandwidth limit and return status `509` when reached.
Traffic memory	Latest 500 traffic entries include target, status, bytes, route, duration, success, error, and timestamps.

The Chain Engine is for durable local operation. Use Chain Tester first when you only need to evaluate chain candidates.