[management,proxy] Add agentgateway integration (#7274)

* [management] Add agentgateway provider catalog entry

Allow Agent Network providers to target an operator-supplied agentgateway proxy while stamping trusted NetBird identity headers.

Signed-off-by: Daneyon Hansen <daneyon.hansen@solo.io>

* [proxy] Allow trusted Agent Network identity headers

Permit only the built-in identity injector to replace the two reserved agentgateway attribution headers while keeping them blocked for every other middleware.

Signed-off-by: Daneyon Hansen <daneyon.hansen@solo.io>

* [management,proxy] Add multi-vendor gateway routing

Let one Agent Network route declare multiple parser surfaces while preserving the existing singular vendor wire field.

Signed-off-by: Daneyon Hansen <daneyon.hansen@solo.io>

* [management] Update router test for model policies

Signed-off-by: Daneyon Hansen <daneyon.hansen@solo.io>

* [proxy] Cover reserved header policy

Signed-off-by: Daneyon Hansen <daneyon.hansen@solo.io>

* [management] Add agentgateway model discovery

Use agentgateway's OpenAI-compatible models endpoint and omit wildcard patterns until NetBird can authorize and price them consistently.

Signed-off-by: Daneyon Hansen <daneyon.hansen@solo.io>

---------

Signed-off-by: Daneyon Hansen <daneyon.hansen@solo.io>

proxy/internal/middleware/builtin/llm_router/factory.go

@@ -36,7 +36,10 @@ type ProviderRoute struct {
 	// request on a same-vendor route so catch-all gateways of a different
 	// vendor can't swallow it. Empty disables vendor filtering for this
 	// route.
-	Vendor          string   `json:"vendor,omitempty"`
+	Vendor string `json:"vendor,omitempty"`
+	// Vendors lists every parser surface a multi-surface gateway accepts.
+	// Vendor remains supported for existing single-surface configurations.
+	Vendors         []string `json:"vendors,omitempty"`
 	Models          []string `json:"models"`
 	UpstreamScheme  string   `json:"upstream_scheme"`
 	UpstreamHost    string   `json:"upstream_host"`

proxy/internal/middleware/builtin/llm_router/middleware.go

@@ -409,7 +409,7 @@ func stripBedrockNamespace(out *middleware.Output) {
 //     peer, return matchOutcomeUnauthorised so the caller can emit
 //     the dedicated no_authorised_provider deny code.
 //  3. Vendor precedence: when the request carries a detected vendor
-//     (llm.provider) and at least one candidate is the same vendor,
+//     (llm.provider) and at least one candidate declares that vendor,
 //     drop the rest — a vendor-tagged request must never cross to
 //     another vendor's route (e.g. an Anthropic call landing on an
 //     OpenAI-compatible gateway that also claims the model).
@@ -432,9 +432,9 @@ func (m *Middleware) matchRoute(model, vendor, reqPath string, userGroups []stri
 
 	// Vendor pinning runs BEFORE the group filter so a request the parser
 	// tagged with a vendor can never cross to another vendor's route — not
-	// even an authorised one. Narrow to same-vendor routes when any
-	// model-matched route declares that vendor; setups with no vendor tag on
-	// any route fall through unchanged. After narrowing, if no same-vendor
+	// even an authorised one. Narrow to supporting routes when any
+	// model-matched route declares that vendor; setups with no matching vendor
+	// declaration fall through unchanged. After narrowing, if no supporting
 	// route authorises the caller, that's matchOutcomeUnauthorised (no
 	// cross-vendor fallback).
 	if vendor != "" {
@@ -805,21 +805,31 @@ func authorisingGroupsCSV(routeGroups, userGroups []string) string {
 	return strings.Join(out, ",")
 }
 
-// matchingVendor returns the subset of routes whose Vendor equals the
-// request's detected vendor. Routes with an empty Vendor never match — an
-// untagged route can't be asserted to speak the request's surface, so it
-// stays out of the vendor-filtered set (but remains eligible via the
-// fall-through when no route matches the vendor at all).
+// matchingVendor returns the routes that declare the request's detected
+// vendor through either the legacy singular field or the multi-vendor field.
+// Untagged routes remain eligible only when no route declares the vendor.
 func matchingVendor(routes []ProviderRoute, vendor string) []ProviderRoute {
 	var out []ProviderRoute
 	for _, r := range routes {
-		if r.Vendor == vendor {
+		if routeSupportsVendor(r, vendor) {
 			out = append(out, r)
 		}
 	}
 	return out
 }
 
+func routeSupportsVendor(route ProviderRoute, vendor string) bool {
+	if route.Vendor == vendor {
+		return true
+	}
+	for _, candidate := range route.Vendors {
+		if candidate == vendor {
+			return true
+		}
+	}
+	return false
+}
+
 // explicitlyClaiming returns the subset of routes whose Models list
 // names the model exactly. Catch-all routes (empty Models) are excluded,
 // so callers can prefer a provider that genuinely declares the model over

proxy/internal/middleware/builtin/llm_router/middleware_test.go

@@ -412,6 +412,50 @@ func TestRouter_VendorKeepsOpenAIOffAnthropic(t *testing.T) {
 	assert.Equal(t, "api.openai.com", out.Mutations.RewriteUpstream.Host, "openai vendor must pin to the openai route despite anthropic being declared first")
 }
 
+func TestRouter_MultiVendorGatewayAcceptsBothSurfaces(t *testing.T) {
+	gateway := ProviderRoute{
+		ID:              "agentgateway",
+		Vendors:         []string{"openai", "anthropic"},
+		Models:          nil,
+		AllowedGroupIDs: []string{defaultTestGroup},
+		UpstreamScheme:  "https",
+		UpstreamHost:    "gateway.example.com",
+	}
+	other := ProviderRoute{
+		ID:              "other-vendor",
+		Vendor:          "mistral",
+		Models:          nil,
+		AllowedGroupIDs: []string{defaultTestGroup},
+		UpstreamScheme:  "https",
+		UpstreamHost:    "mistral.example.com",
+	}
+	mw := New(Config{Providers: []ProviderRoute{other, gateway}})
+
+	for _, tc := range []struct {
+		name   string
+		vendor string
+		model  string
+		path   string
+	}{
+		{name: "OpenAI", vendor: "openai", model: "gpt-4o-mini", path: "/v1/chat/completions"},
+		{name: "Anthropic", vendor: "anthropic", model: "claude-sonnet-4-5", path: "/v1/messages"},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			out, err := mw.Invoke(context.Background(), newInputVendorModelURL(tc.vendor, tc.model, tc.path))
+			require.NoError(t, err)
+			require.NotNil(t, out)
+			assert.Equal(t, middleware.DecisionAllow, out.Decision,
+				"supported vendor must route through the multi-surface gateway")
+			require.NotNil(t, out.Mutations)
+			require.NotNil(t, out.Mutations.RewriteUpstream)
+			assert.Equal(t, "gateway.example.com", out.Mutations.RewriteUpstream.Host)
+
+			provider, _ := metaValue(t, out.Metadata, middleware.KeyLLMResolvedProviderID)
+			assert.Equal(t, "agentgateway", provider)
+		})
+	}
+}
+
 // TestRouter_VendorAbsentFallsBackToModelPath confirms vendor filtering is
 // inert when the request carries no detected vendor: routing then relies on
 // model/path as before.
@@ -692,6 +736,23 @@ func TestRouter_FactoryRejectsBadJSON(t *testing.T) {
 	require.Error(t, err, "malformed JSON config must be rejected at chain build time")
 }
 
+func TestRouter_FactoryDecodesLegacyAndMultiVendorFields(t *testing.T) {
+	raw := []byte(`{"providers":[` +
+		`{"id":"legacy","vendor":"openai","models":[],"upstream_scheme":"https","upstream_host":"openai.example.com","auth_header_name":"Authorization","auth_header_value":"Bearer legacy","allowed_group_ids":["group"]},` +
+		`{"id":"multi","vendors":["openai","anthropic"],"models":[],"upstream_scheme":"https","upstream_host":"gateway.example.com","auth_header_name":"Authorization","auth_header_value":"Bearer multi","allowed_group_ids":["group"]}` +
+		`]}`)
+
+	resolved, err := Factory{}.New(raw)
+	require.NoError(t, err)
+	router, ok := resolved.(*Middleware)
+	require.True(t, ok, "factory must return the concrete router middleware")
+	require.Len(t, router.cfg.Providers, 2)
+	assert.Equal(t, "openai", router.cfg.Providers[0].Vendor,
+		"the legacy singular field must keep decoding")
+	assert.Equal(t, []string{"openai", "anthropic"}, router.cfg.Providers[1].Vendors,
+		"the multi-vendor field must decode both supported surfaces")
+}
+
 func TestRouter_FactoryAcceptsEmptyShapes(t *testing.T) {
 	cases := [][]byte{nil, []byte(""), []byte(" "), []byte("null"), []byte("{}"), []byte("[]")}
 	for _, raw := range cases {