Problem

Claude Code clients poll GET / every second for MCP server availability checks. This creates significant log noise:

192.168.95.254 5c1e..f025 - - GET / 200 1ms | - - | - - | -

Solution

Add LOG_FILTER environment variable to filter out specific request patterns from access logs.

Format

JSON array of filter rules. A request is skipped if ALL conditions in a rule match:

LOG_FILTER='[{"method":"GET","path":"/","userAgent":"claude-code"}]'

Filter rule properties

All properties are optional. If a property is omitted, it matches any value.

Examples

Skip Claude Code polling (default):

LOG_FILTER='[{"method":"GET","path":"/","userAgent":"claude-code"}]'

Multiple filters - skip various polling sources:

LOG_FILTER='[
  {"method":"GET","path":"/","userAgent":"claude-code"},
  {"method":"GET","path":"/health"},
  {"method":"GET","path":"/","userAgent":"prometheus"},
  {"method":"HEAD","path":"/*"}
]'

Skip all GET requests to root (any User-Agent):

LOG_FILTER='[{"method":"GET","path":"/"}]'

Skip requests from specific monitoring tool:

LOG_FILTER='[{"userAgent":"datadog"}]'

Log all requests (disable filtering):

LOG_FILTER='[]'

Default behavior

• Default: Filters Claude Code polling requests ([{"method":"GET","path":"/","userAgent":"claude-code"}])
• Set LOG_FILTER='[]' to log all requests
• If set to invalid JSON: log warning at startup, log all requests

Implementation checklist

• Add LOG_FILTER parsing in src/config.ts with Zod schema validation
• Add filter check in access log middleware (src/server.ts) before opening request stack
• If request matches any filter rule, skip access logging but process request normally
• Log info at startup showing number of active filter rules
• Add unit tests for filter matching logic
• Update documentation:
  • Add to docs/CONFIGURATION.md under Logging section
  • Include all examples from this issue
  • Document that filtered requests are still processed, just not logged

Time estimate

1.5h (including documentation)