Skip to main content

​
Debugging

​
Enable debug logs

Set RUST_LOG before starting the proxy: 
RUST_LOG=litellm_rust=debug ./target/debug/lite --config config.yaml
For trace-level output (very verbose): 
RUST_LOG=litellm_rust=trace ./target/debug/lite --config config.yaml

​
Router resolution

Every request logs how the incoming model name was resolved to an upstream deployment. Exact match — model name matched a named route in model_list: 
router: exact match  model="claude" upstream_model="claude-sonnet-4-5" provider="anthropic"
Wildcard match — no exact match; fell through to the /* wildcard route. Provider prefix stripped if present: 
router: wildcard match — stripped provider prefix  model="anthropic/claude-opus-4-8" upstream_model="claude-opus-4-8" provider="anthropic"
No route — no exact match and no wildcard configured: 
router: no exact match and no wildcard route  model="gpt-4o"
Resolution is a single O(1) HashMap lookup — there is no retrying or brute-forcing.

​
Model cost map

On startup the proxy fetches the LiteLLM model pricing sheet. If the fetch fails it falls back to an embedded backup: 
WARN Failed to fetch model cost map from https://... — using backup
If both fail (parse error, network issue), the proxy continues with an empty cost map and logs: 
ERROR Failed to parse embedded backup model cost map: ...
Pricing data is used for cost tracking only — the proxy still routes requests normally with an empty map.

​
Config validation errors

Bad config exits immediately with a descriptive message:
ErrorCause
model must include provider prefixlitellm_params.model missing provider/ prefix
model missing name after provider prefixlitellm_params.model set to just anthropic/
unsupported provider: <id>Provider not registered (e.g. typo)
missing litellm_params.api_keyNo API key for that model entry
only one wildcard model route is supportedMore than one /* entry in model_list