fix: strip query parameters from request path before parser resolution (llm-d#1585)

* fix: strip query parameters from request path before parser resolution

The HTTP/2 :path pseudo-header includes query parameters (e.g.
/v1/messages?beta=true), which caused parser suffix matching and
per-parser endpoint validation to fail for clients that append query
strings. Strip query parameters at header ingestion in
HandleRequestHeaders so all downstream consumers see a clean path.

Signed-off-by: greg pereira <gpereira@redhat.com>
Co-Authored-By: Claude <noreply@anthropic.com>
Signed-off-by: greg pereira <grpereir@redhat.com>

* fix: add comment explaining query parameter stripping from :path

Signed-off-by: greg pereira <grpereir@redhat.com>

* make implementation non mutating

Signed-off-by: greg pereira <grpereir@redhat.com>

---------

Signed-off-by: greg pereira <gpereira@redhat.com>
Signed-off-by: greg pereira <grpereir@redhat.com>
Co-authored-by: Claude <noreply@anthropic.com>

Author: Gregory-Pereira

pkg/epp/framework/common/request/headers.go

@@ -33,20 +33,26 @@ func GetHeader(headers map[string]string, key string) string {
 }
 
 // GetRequestPath extracts the request path from headers with fallback priority.
+// Query parameters are stripped because the path is used only for parser routing.
 func GetRequestPath(headers map[string]string) string {
 	if path := headers[":path"]; path != "" {
-		return path
+		return stripQuery(path)
 	}
 	if path := headers["x-original-path"]; path != "" {
-		return path
+		return stripQuery(path)
 	}
 	if path := headers["x-forwarded-path"]; path != "" {
-		return path
+		return stripQuery(path)
 	}
 	// Default to completions API for backward compatibility with existing clients and integration tests
 	return "/v1/completions"
 }
 
+func stripQuery(path string) string {
+	clean, _, _ := strings.Cut(path, "?")
+	return clean
+}
+
 // MatchPathSuffix checks if the path matches the suffix.
 func MatchPathSuffix(path, suffix string) bool {
 	path = strings.TrimSuffix(strings.TrimSpace(path), "/")

pkg/epp/framework/common/request/headers_test.go

@@ -51,6 +51,21 @@ func TestGetRequestPath(t *testing.T) {
 			headers: map[string]string{"x-forwarded-path": "/baz"},
 			want:    "/baz",
 		},
+		{
+			name:    "query parameters stripped from :path",
+			headers: map[string]string{":path": "/v1/messages?beta=true"},
+			want:    "/v1/messages",
+		},
+		{
+			name:    "query parameters stripped from x-original-path",
+			headers: map[string]string{"x-original-path": "/v1/messages?foo=bar&baz=1"},
+			want:    "/v1/messages",
+		},
+		{
+			name:    "query parameters stripped from x-forwarded-path",
+			headers: map[string]string{"x-forwarded-path": "/v1/chat/completions?stream=true"},
+			want:    "/v1/chat/completions",
+		},
 		{
 			name:    "fallback to completions",
 			headers: map[string]string{},

pkg/epp/framework/plugins/requesthandling/parsers/anthropic/anthropic.go

@@ -25,9 +25,9 @@ import (
 
 	v1 "sigs.k8s.io/gateway-api-inference-extension/api/v1"
 
+	"github.com/llm-d/llm-d-router/pkg/epp/framework/common/request"
 	fwkplugin "github.com/llm-d/llm-d-router/pkg/epp/framework/interface/plugin"
 	fwkrh "github.com/llm-d/llm-d-router/pkg/epp/framework/interface/requesthandling"
-	"github.com/llm-d/llm-d-router/pkg/epp/framework/plugins/requesthandling/parsers"
 )
 
 const (
@@ -79,7 +79,7 @@ func (p *AnthropicParser) WithName(name string) *AnthropicParser {
 }
 
 func (p *AnthropicParser) ParseRequest(_ context.Context, body []byte, headers map[string]string) (*fwkrh.ParseResult, error) {
-	path := getRequestPath(headers)
+	path := request.GetRequestPath(headers)
 
 	// The count_tokens endpoint returns only a token count and gains nothing from
 	// structured parsing or response interception; forward the body unchanged.
@@ -141,19 +141,6 @@ func (p *AnthropicParser) ParseResponse(_ context.Context, body []byte, headers
 	return &fwkrh.ParsedResponse{Usage: usage}, nil
 }
 
-func getRequestPath(headers map[string]string) string {
-	if path := headers[parsers.MethodPathKey]; path != "" {
-		return path
-	}
-	if path := headers["x-original-path"]; path != "" {
-		return path
-	}
-	if path := headers["x-forwarded-path"]; path != "" {
-		return path
-	}
-	return ""
-}
-
 func extractUsage(responseBytes []byte) (*fwkrh.Usage, error) {
 	var responseBody map[string]any
 	if err := json.Unmarshal(responseBytes, &responseBody); err != nil {