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Auto Router v1.97: usage benchmarks and better quality for lower cost

Tin Lo
Tin Lo
AI Engineer, LiteLLM

LiteLLM Autorouter V2: routing accuracy on complex scenarios, 5.6x more accurate by reading the last N turns of the conversation before picking a model



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Already testing it? Share your results in discussion #32168.

v1.97 makes three changes to the auto router.

  • The LLM classifier now receives a window of prior conversation turns, defaulting to three. This improves accuracy of follow-up classifications from 14% to 78%, costs at most $0.61 per 1,000 requests, and no additional latency.
  • A new Benchmarks view prices routed traffic against an all-frontier baseline and reports the difference, and those savings now also appear in the Cost Optimization totals.
  • Session affinity is now off by default, following our previous post showing this was leading to worse quality without cost improvements.
Two defaults changed

classifier_context_window_size now defaults to 3 (LLM classifier only), and session_affinity now defaults to false (all routers). Config files are not modified, but the new defaults apply to any key left unset, so a config that never mentioned session_affinity will reclassify every turn after upgrading. Configs that set either key explicitly are unaffected.

Announcing Router Plugins: Customize Routing Signals

Krrish Dholakia
CEO, LiteLLM
Availability

Router plugins run on the proxy from v1.94.x. The design is still evolving; tell us how you'd use it and what you'd want next in the autorouter discussion on GitHub (#32168).

Router plugins are now available on LiteLLM. Each plugin receives the routing context, enriches it, and hands it to the next before the router makes the final decision.

The push came from the autorouter discussion (#32168): teams wanted to layer their own signals (language detection, domain classification, tenant policy, budget caps) onto routing without waiting for each one to land in core. This plugin extension lets teams make these changes while keeping LiteLLM's routing core stable.

Auto Router v2: one router for complexity, semantic, and adaptive routing

Krrish Dholakia
CEO, LiteLLM
Availability

Auto Router v2 ships in v1.94.x. The earliest dev release cuts Tuesday, 2026-07-14. Suggestions and feedback: discussion #32168.

Auto Router v2 collapses complexity, semantic, and adaptive routing into a single auto_router/complexity_router. One config now covers heuristic scoring, LLM classification, lexical or semantic keyword rules, and Thompson-sampled tier pools.

The push came from the community. On discussion #32168, users pointed out that all three routing strategies should converge into a single Auto Router. One router with configurable signals and weights keeps the API simple while letting the routing engine evolve internally, instead of forcing you to pick a mode up front.

The operational half came from discussion #32172: predictable beats clever for debuggability. A fixed, versioned mapping from capability class to model is what makes "why did this response cost 4x today" answerable after the fact.