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MAX_CALLBACKS Limit

Error Message​

Cannot add callback - would exceed MAX_CALLBACKS limit of 30. Current callbacks: 30

What This Means​

LiteLLM limits the number of callbacks that can be registered to prevent performance degradation. Each callback runs on every LLM request, so having too many callbacks can cause exponential CPU usage and slow down your proxy.

The default limit is 30 callbacks.

When You Might Hit This Limit​

  • Large enterprise deployments with many teams, each having their own guardrails
  • Multiple logging integrations combined with custom callbacks
  • Per-team callback configurations that add up across your organization

How to Override​

Set the LITELLM_MAX_CALLBACKS environment variable to increase the limit:

# Docker
docker run -e LITELLM_MAX_CALLBACKS=100 ...

# Docker Compose
environment:
  - LITELLM_MAX_CALLBACKS=100

# Kubernetes
env:
  - name: LITELLM_MAX_CALLBACKS
    value: "100"

# Direct
export LITELLM_MAX_CALLBACKS=100
litellm --config config.yaml

Recommendations​

  1. Start conservative - Only increase as much as you need. If you have 60 teams with guardrails, try LITELLM_MAX_CALLBACKS=75 to leave headroom.

  2. Monitor performance - More callbacks means more processing per request. Watch your CPU usage and response latency after increasing the limit.

  3. Consolidate where possible - If multiple teams use identical guardrails, consider using shared callback configurations rather than per-team duplicates.

Example: Large Enterprise Setup​

For an organization with 60+ teams, each with a guardrail callback:

# config.yaml
litellm_settings:
  callbacks: ["prometheus", "langfuse"]  # 2 global callbacks

# Each team adds 1 guardrail callback = 60+ callbacks
# Total: 62+ callbacks needed

Set the environment variable:

export LITELLM_MAX_CALLBACKS=100