proxy: unify filtering for local models and peers

This unifies the filtering capabilities for models and peers

- stripParams: removes params in the request
- setParams: sets params in the request

fixes #453

config.example.yaml

@@ -185,7 +185,7 @@ models:
 
     # filters: a dictionary of filter settings
     # - optional, default: empty dictionary
-    # - only stripParams is currently supported
+    # - same capabilities as peer filters (stripParams, setParams)
     filters:
       # stripParams: a comma separated list of parameters to remove from the request
       # - optional, default: ""
@@ -195,6 +195,16 @@ models:
       # - recommended to stick to sampling parameters
       stripParams: "temperature, top_p, top_k"
 
+      # setParams: a dictionary of parameters to set/override in requests
+      # - optional, default: empty dictionary
+      # - useful for enforcing specific parameter values
+      # - protected params like "model" cannot be overridden
+      # - values can be strings, numbers, booleans, arrays, or objects
+      setParams:
+        # Example: enforce specific sampling parameters
+        temperature: 0.7
+        top_p: 0.9
+
     # metadata: a dictionary of arbitrary values that are included in /v1/models
     # - optional, default: empty dictionary
     # - while metadata can contains complex types it is recommended to keep it simple
@@ -373,3 +383,23 @@ peers:
       - z-ai/glm-4.7
       - moonshotai/kimi-k2-0905
       - minimax/minimax-m2.1
+    # filters: a dictionary of filter settings for peer requests
+    # - optional, default: empty dictionary
+    # - same capabilities as model filters (stripParams, setParams)
+    filters:
+      # stripParams: a comma separated list of parameters to remove from the request
+      # - optional, default: ""
+      # - useful for removing parameters that the peer doesn't support
+      # - the `model` parameter can never be removed
+      stripParams: "temperature, top_p"
+
+      # setParams: a dictionary of parameters to set/override in requests to this peer
+      # - optional, default: empty dictionary
+      # - useful for injecting provider-specific settings like data retention policies
+      # - protected params like "model" cannot be overridden
+      # - values can be strings, numbers, booleans, arrays, or objects
+      setParams:
+        # Example: enforce zero-data-retention for OpenRouter
+        provider:
+          data_collection: "deny"
+          allow_fallbacks: false

proxy/config/filters.go

@@ -0,0 +1,81 @@
+package config
+
+import (
+	"slices"
+	"sort"
+	"strings"
+)
+
+// ProtectedParams is a list of parameters that cannot be set or stripped via filters
+// These are protected to prevent breaking the proxy's ability to route requests correctly
+var ProtectedParams = []string{"model"}
+
+// Filters contains filter settings for modifying request parameters
+// Used by both models and peers
+type Filters struct {
+	// StripParams is a comma-separated list of parameters to remove from requests
+	// The "model" parameter can never be removed
+	StripParams string `yaml:"stripParams"`
+
+	// SetParams is a dictionary of parameters to set/override in requests
+	// Protected params (like "model") cannot be set
+	SetParams map[string]any `yaml:"setParams"`
+}
+
+// SanitizedStripParams returns a sorted list of parameters to strip,
+// with duplicates, empty strings, and protected params removed
+func (f Filters) SanitizedStripParams() []string {
+	if f.StripParams == "" {
+		return nil
+	}
+
+	params := strings.Split(f.StripParams, ",")
+	cleaned := make([]string, 0, len(params))
+	seen := make(map[string]bool)
+
+	for _, param := range params {
+		trimmed := strings.TrimSpace(param)
+		// Skip protected params, empty strings, and duplicates
+		if slices.Contains(ProtectedParams, trimmed) || trimmed == "" || seen[trimmed] {
+			continue
+		}
+		seen[trimmed] = true
+		cleaned = append(cleaned, trimmed)
+	}
+
+	if len(cleaned) == 0 {
+		return nil
+	}
+
+	slices.Sort(cleaned)
+	return cleaned
+}
+
+// SanitizedSetParams returns a copy of SetParams with protected params removed
+// and keys sorted for consistent iteration order
+func (f Filters) SanitizedSetParams() (map[string]any, []string) {
+	if len(f.SetParams) == 0 {
+		return nil, nil
+	}
+
+	result := make(map[string]any, len(f.SetParams))
+	keys := make([]string, 0, len(f.SetParams))
+
+	for key, value := range f.SetParams {
+		// Skip protected params
+		if slices.Contains(ProtectedParams, key) {
+			continue
+		}
+		result[key] = value
+		keys = append(keys, key)
+	}
+
+	// Sort keys for consistent ordering
+	sort.Strings(keys)
+
+	if len(result) == 0 {
+		return nil, nil
+	}
+
+	return result, keys
+}

proxy/config/filters_test.go

@@ -0,0 +1,168 @@
+package config
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestFilters_SanitizedStripParams(t *testing.T) {
+	tests := []struct {
+		name        string
+		stripParams string
+		want        []string
+	}{
+		{
+			name:        "empty string",
+			stripParams: "",
+			want:        nil,
+		},
+		{
+			name:        "single param",
+			stripParams: "temperature",
+			want:        []string{"temperature"},
+		},
+		{
+			name:        "multiple params",
+			stripParams: "temperature, top_p, top_k",
+			want:        []string{"temperature", "top_k", "top_p"}, // sorted
+		},
+		{
+			name:        "model param filtered",
+			stripParams: "model, temperature, top_p",
+			want:        []string{"temperature", "top_p"},
+		},
+		{
+			name:        "only model param",
+			stripParams: "model",
+			want:        nil,
+		},
+		{
+			name:        "duplicates removed",
+			stripParams: "temperature, top_p, temperature",
+			want:        []string{"temperature", "top_p"},
+		},
+		{
+			name:        "extra whitespace",
+			stripParams: "  temperature  ,  top_p  ",
+			want:        []string{"temperature", "top_p"},
+		},
+		{
+			name:        "empty values filtered",
+			stripParams: "temperature,,top_p,",
+			want:        []string{"temperature", "top_p"},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			f := Filters{StripParams: tt.stripParams}
+			got := f.SanitizedStripParams()
+			assert.Equal(t, tt.want, got)
+		})
+	}
+}
+
+func TestFilters_SanitizedSetParams(t *testing.T) {
+	tests := []struct {
+		name       string
+		setParams  map[string]any
+		wantParams map[string]any
+		wantKeys   []string
+	}{
+		{
+			name:       "empty setParams",
+			setParams:  nil,
+			wantParams: nil,
+			wantKeys:   nil,
+		},
+		{
+			name:       "empty map",
+			setParams:  map[string]any{},
+			wantParams: nil,
+			wantKeys:   nil,
+		},
+		{
+			name: "normal params",
+			setParams: map[string]any{
+				"temperature": 0.7,
+				"top_p":       0.9,
+			},
+			wantParams: map[string]any{
+				"temperature": 0.7,
+				"top_p":       0.9,
+			},
+			wantKeys: []string{"temperature", "top_p"},
+		},
+		{
+			name: "protected model param filtered",
+			setParams: map[string]any{
+				"model":       "should-be-filtered",
+				"temperature": 0.7,
+			},
+			wantParams: map[string]any{
+				"temperature": 0.7,
+			},
+			wantKeys: []string{"temperature"},
+		},
+		{
+			name: "only protected param",
+			setParams: map[string]any{
+				"model": "should-be-filtered",
+			},
+			wantParams: nil,
+			wantKeys:   nil,
+		},
+		{
+			name: "complex nested values",
+			setParams: map[string]any{
+				"provider": map[string]any{
+					"data_collection": "deny",
+					"allow_fallbacks": false,
+				},
+				"transforms": []string{"middle-out"},
+			},
+			wantParams: map[string]any{
+				"provider": map[string]any{
+					"data_collection": "deny",
+					"allow_fallbacks": false,
+				},
+				"transforms": []string{"middle-out"},
+			},
+			wantKeys: []string{"provider", "transforms"},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			f := Filters{SetParams: tt.setParams}
+			gotParams, gotKeys := f.SanitizedSetParams()
+
+			assert.Equal(t, len(tt.wantKeys), len(gotKeys), "keys length mismatch")
+			for i, key := range gotKeys {
+				assert.Equal(t, tt.wantKeys[i], key, "key mismatch at %d", i)
+			}
+
+			if tt.wantParams == nil {
+				assert.Nil(t, gotParams, "expected nil params")
+				return
+			}
+
+			assert.Equal(t, len(tt.wantParams), len(gotParams), "params length mismatch")
+			for key, wantValue := range tt.wantParams {
+				gotValue, exists := gotParams[key]
+				assert.True(t, exists, "missing key: %s", key)
+				// Simple comparison for basic types
+				switch v := wantValue.(type) {
+				case string, int, float64, bool:
+					assert.Equal(t, v, gotValue, "value mismatch for key %s", key)
+				}
+			}
+		})
+	}
+}
+
+func TestProtectedParams(t *testing.T) {
+	// Verify that "model" is protected
+	assert.Contains(t, ProtectedParams, "model")
+}

proxy/config/model_config.go

@@ -3,8 +3,6 @@ package config
 import (
 	"errors"
 	"runtime"
-	"slices"
-	"strings"
 )
 
 type ModelConfig struct {
@@ -74,16 +72,15 @@ func (m *ModelConfig) SanitizedCommand() ([]string, error) {
 	return SanitizeCommand(m.Cmd)
 }
 
-// ModelFilters see issue #174
+// ModelFilters embeds Filters and adds legacy support for strip_params field
+// See issue #174
 type ModelFilters struct {
-	StripParams string `yaml:"stripParams"`
+	Filters `yaml:",inline"`
 }
 
 func (m *ModelFilters) UnmarshalYAML(unmarshal func(interface{}) error) error {
 	type rawModelFilters ModelFilters
-	defaults := rawModelFilters{
-		StripParams: "",
-	}
+	defaults := rawModelFilters{}
 
 	if err := unmarshal(&defaults); err != nil {
 		return err
@@ -104,25 +101,8 @@ func (m *ModelFilters) UnmarshalYAML(unmarshal func(interface{}) error) error {
 	return nil
 }
 
+// SanitizedStripParams wraps Filters.SanitizedStripParams for backwards compatibility
+// Returns ([]string, error) to match existing API
 func (f ModelFilters) SanitizedStripParams() ([]string, error) {
-	if f.StripParams == "" {
-		return nil, nil
-	}
-
-	params := strings.Split(f.StripParams, ",")
-	cleaned := make([]string, 0, len(params))
-	seen := make(map[string]bool)
-
-	for _, param := range params {
-		trimmed := strings.TrimSpace(param)
-		if trimmed == "model" || trimmed == "" || seen[trimmed] {
-			continue
-		}
-		seen[trimmed] = true
-		cleaned = append(cleaned, trimmed)
-	}
-
-	// sort cleaned
-	slices.Sort(cleaned)
-	return cleaned, nil
+	return f.Filters.SanitizedStripParams(), nil
 }

proxy/config/model_config_test.go

@@ -72,3 +72,35 @@ models:
 		assert.True(t, *config.Models["model2"].SendLoadingState)
 	}
 }
+
+func TestConfig_ModelFiltersWithSetParams(t *testing.T) {
+	content := `
+models:
+  model1:
+    cmd: path/to/cmd --port ${PORT}
+    filters:
+      stripParams: "top_k"
+      setParams:
+        temperature: 0.7
+        top_p: 0.9
+        stop:
+          - "<|end|>"
+          - "<|stop|>"
+`
+	config, err := LoadConfigFromReader(strings.NewReader(content))
+	assert.NoError(t, err)
+
+	modelConfig := config.Models["model1"]
+
+	// Check stripParams
+	stripParams, err := modelConfig.Filters.SanitizedStripParams()
+	assert.NoError(t, err)
+	assert.Equal(t, []string{"top_k"}, stripParams)
+
+	// Check setParams
+	setParams, keys := modelConfig.Filters.SanitizedSetParams()
+	assert.NotNil(t, setParams)
+	assert.Equal(t, []string{"stop", "temperature", "top_p"}, keys)
+	assert.Equal(t, 0.7, setParams["temperature"])
+	assert.Equal(t, 0.9, setParams["top_p"])
+}

proxy/config/peer.go

@@ -11,14 +11,16 @@ type PeerConfig struct {
 	ProxyURL *url.URL `yaml:"-"`
 	ApiKey   string   `yaml:"apiKey"`
 	Models   []string `yaml:"models"`
+	Filters  Filters  `yaml:"filters"`
 }
 
 func (c *PeerConfig) UnmarshalYAML(unmarshal func(interface{}) error) error {
 	type rawPeerConfig PeerConfig
 	defaults := rawPeerConfig{
-		Proxy:  "",
-		ApiKey: "",
-		Models: []string{},
+		Proxy:   "",
+		ApiKey:  "",
+		Models:  []string{},
+		Filters: Filters{},
 	}
 
 	if err := unmarshal(&defaults); err != nil {

proxy/config/peer_test.go

@@ -137,3 +137,73 @@ func searchSubstring(s, substr string) bool {
 	}
 	return false
 }
+
+func TestPeerConfig_WithFilters(t *testing.T) {
+	yamlData := `
+proxy: https://openrouter.ai/api
+apiKey: sk-test
+models:
+  - model_a
+filters:
+  setParams:
+    temperature: 0.7
+    provider:
+      data_collection: deny
+`
+	var config PeerConfig
+	err := yaml.Unmarshal([]byte(yamlData), &config)
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+
+	if config.Filters.SetParams == nil {
+		t.Fatal("Filters.SetParams should not be nil")
+	}
+
+	if config.Filters.SetParams["temperature"] != 0.7 {
+		t.Errorf("expected temperature 0.7, got %v", config.Filters.SetParams["temperature"])
+	}
+
+	provider, ok := config.Filters.SetParams["provider"].(map[string]any)
+	if !ok {
+		t.Fatal("provider should be a map")
+	}
+	if provider["data_collection"] != "deny" {
+		t.Errorf("expected data_collection deny, got %v", provider["data_collection"])
+	}
+}
+
+func TestPeerConfig_WithBothFilters(t *testing.T) {
+	yamlData := `
+proxy: https://openrouter.ai/api
+apiKey: sk-test
+models:
+  - model_a
+filters:
+  stripParams: "temperature, top_p"
+  setParams:
+    max_tokens: 1000
+`
+	var config PeerConfig
+	err := yaml.Unmarshal([]byte(yamlData), &config)
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+
+	// Check stripParams
+	stripParams := config.Filters.SanitizedStripParams()
+	if len(stripParams) != 2 {
+		t.Errorf("expected 2 strip params, got %d", len(stripParams))
+	}
+	if stripParams[0] != "temperature" || stripParams[1] != "top_p" {
+		t.Errorf("unexpected strip params: %v", stripParams)
+	}
+
+	// Check setParams
+	if config.Filters.SetParams == nil {
+		t.Fatal("Filters.SetParams should not be nil")
+	}
+	if config.Filters.SetParams["max_tokens"] != 1000 {
+		t.Errorf("expected max_tokens 1000, got %v", config.Filters.SetParams["max_tokens"])
+	}
+}

proxy/peerproxy.go

@@ -106,6 +106,20 @@ func (p *PeerProxy) HasPeerModel(modelID string) bool {
 	return found
 }
 
+// GetPeerFilters returns the filters for a peer model, or empty filters if not found
+func (p *PeerProxy) GetPeerFilters(modelID string) config.Filters {
+	pp, found := p.proxyMap[modelID]
+	if !found {
+		return config.Filters{}
+	}
+	// Get the peer config using the peerID
+	peer, found := p.peers[pp.peerID]
+	if !found {
+		return config.Filters{}
+	}
+	return peer.Filters
+}
+
 func (p *PeerProxy) ListPeers() config.PeerDictionaryConfig {
 	return p.peers
 }

proxy/proxymanager.go

@@ -650,13 +650,49 @@ func (pm *ProxyManager) proxyInferenceHandler(c *gin.Context) {
 			}
 		}
 
+		// issue #453 set/override parameters in the JSON body
+		setParams, setParamKeys := pm.config.Models[modelID].Filters.SanitizedSetParams()
+		for _, key := range setParamKeys {
+			pm.proxyLogger.Debugf("<%s> setting param: %s", modelID, key)
+			bodyBytes, err = sjson.SetBytes(bodyBytes, key, setParams[key])
+			if err != nil {
+				pm.sendErrorResponse(c, http.StatusInternalServerError, fmt.Sprintf("error setting parameter %s in request", key))
+				return
+			}
+		}
+
 		pm.proxyLogger.Debugf("ProxyManager using local Process for model: %s", requestedModel)
 		nextHandler = processGroup.ProxyRequest
 	} else if pm.peerProxy != nil && pm.peerProxy.HasPeerModel(requestedModel) {
 		pm.proxyLogger.Debugf("ProxyManager using ProxyPeer for model: %s", requestedModel)
 		modelID = requestedModel
-		nextHandler = pm.peerProxy.ProxyRequest
 
+		// issue #453 apply filters for peer requests
+		peerFilters := pm.peerProxy.GetPeerFilters(requestedModel)
+
+		// Apply stripParams - remove specified parameters from request
+		stripParams := peerFilters.SanitizedStripParams()
+		for _, param := range stripParams {
+			pm.proxyLogger.Debugf("<%s> stripping param: %s", requestedModel, param)
+			bodyBytes, err = sjson.DeleteBytes(bodyBytes, param)
+			if err != nil {
+				pm.sendErrorResponse(c, http.StatusInternalServerError, fmt.Sprintf("error stripping parameter %s from request", param))
+				return
+			}
+		}
+
+		// Apply setParams - set/override specified parameters in request
+		setParams, setParamKeys := peerFilters.SanitizedSetParams()
+		for _, key := range setParamKeys {
+			pm.proxyLogger.Debugf("<%s> setting param: %s", requestedModel, key)
+			bodyBytes, err = sjson.SetBytes(bodyBytes, key, setParams[key])
+			if err != nil {
+				pm.sendErrorResponse(c, http.StatusInternalServerError, fmt.Sprintf("error setting parameter %s in request", key))
+				return
+			}
+		}
+
+		nextHandler = pm.peerProxy.ProxyRequest
 	}
 
 	if nextHandler == nil {

proxy/proxymanager_test.go

@@ -966,7 +966,9 @@ func TestProxyManager_ChatContentLength(t *testing.T) {
 func TestProxyManager_FiltersStripParams(t *testing.T) {
 	modelConfig := getTestSimpleResponderConfig("model1")
 	modelConfig.Filters = config.ModelFilters{
-		StripParams: "temperature, model, stream",
+		Filters: config.Filters{
+			StripParams: "temperature, model, stream",
+		},
 	}
 
 	config := config.AddDefaultGroupToConfig(config.Config{