Fix audit middleware transport detection to use actual transport type instead of hardcoded paths

[amirejaz]

Summary

This PR fixes the audit middleware's transport detection mechanism to use the actual transport type passed from the command line instead of relying on hardcoded path patterns like /sse.

Problem

The audit middleware was using hardcoded path checking (strings.Contains(path, "/sse")) to determine if a request was using SSE transport. This approach was problematic because:

1. Inflexible: Different MCP servers use different SSE endpoint paths or may not use any path (e.g., /v1/sse, /sse, /api/sse)
2. Unreliable: The middleware couldn't correctly identify transport type for varying endpoint structures
3. Hardcoded: Required manual updates for each new endpoint pattern

Solution

Refactored the audit middleware to:

1. Accept transport type directly: The middleware now receives the actual transport type (sse, streamable-http) from the run configuration
2. Remove hardcoded path checks: Eliminated all strings.Contains(path, "/sse") logic
3. Detect sticky MCP streams on the request: classify as sticky only for GET with Accept containing text/event-stream (covers SSE + Streamable HTTP stream).
4. Update all constructors: Modified NewAuditorWithTransport to require transport type parameter

Changes

Core Changes

• pkg/audit/auditor.go:

  • Added transportType field to Auditor struct
  • Updated NewAuditorWithTransport to require transport type
  • Simplified isSSETransport() to use direct transport type comparison
  • Removed all hardcoded path checking in determineEventType and addMetadata

• pkg/audit/config.go:

  • Updated CreateMiddlewareWithTransport to require transport type
  • Modified GetMiddlewareFromFile to accept transport type parameter

• pkg/audit/middleware.go:

  • Updated MiddlewareParams to include TransportType field
  • Modified CreateMiddleware to always use transport-aware constructor
  • Add isMCPStreamOpenRequest (GET + Accept: text/event-stream) and log connection-open immediately for those; remove path checks and isMCPMessagePost; no ResponseWriter changes.

• pkg/runner/config_builder.go & pkg/runner/middleware.go:

  • Updated middleware configuration to pass actual transport type

Test Updates

• pkg/audit/auditor_test.go & pkg/audit/config_test.go:
  • Updated all test calls to use NewAuditorWithTransport with appropriate transport types
  • Fixed TestDetermineEventType to use correct transport types for each test case

Benefits

1. Accurate transport detection: Works with any SSE endpoint path structure
2. Maintainable: No more hardcoded path patterns to maintain
3. Flexible: Supports any transport type passed from command line
4. Reliable: Uses the actual transport configuration instead of guessing

Testing

• All existing tests updated and passing
• Transport detection now works correctly for different endpoint patterns
• No breaking changes to existing functionality

Original identified issue: #1957 (comment)

[codecov]

Codecov Report

❌ Patch coverage is 67.56757% with 12 lines in your changes missing coverage. Please review.
✅ Project coverage is 48.19%. Comparing base (6929a52) to head (168b930).
⚠️ Report is 4 commits behind head on main.

Files with missing lines	Patch %	Lines
pkg/runner/config_builder.go	0.00%	4 Missing ⚠️
pkg/runner/middleware.go	0.00%	4 Missing ⚠️
pkg/audit/auditor.go	87.50%	2 Missing and 1 partial ⚠️
pkg/audit/config.go	75.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1974      +/-   ##
==========================================
+ Coverage   48.13%   48.19%   +0.06%     
==========================================
  Files         233      233              
  Lines       29229    29240      +11     
==========================================
+ Hits        14069    14093      +24     
+ Misses      14129    14111      -18     
- Partials     1031     1036       +5     

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