Merge pull request #90 from lordmathis/feat/custom-args

feat: Add support for custom args

pkg/backends/builder.go

@@ -93,3 +93,22 @@ func BuildDockerCommand(backendConfig *config.BackendSettings, instanceArgs []st
 
 	return "docker", dockerArgs, nil
 }
+
+// convertExtraArgsToFlags converts map[string]string to command flags
+// Empty values become boolean flags: {"flag": ""} → ["--flag"]
+// Non-empty values: {"flag": "value"} → ["--flag", "value"]
+func convertExtraArgsToFlags(extraArgs map[string]string) []string {
+	var args []string
+
+	for key, value := range extraArgs {
+		if value == "" {
+			// Boolean flag
+			args = append(args, "--"+key)
+		} else {
+			// Value flag
+			args = append(args, "--"+key, value)
+		}
+	}
+
+	return args
+}

pkg/backends/llama.go

@@ -5,7 +5,6 @@ import (
 	"fmt"
 	"llamactl/pkg/validation"
 	"reflect"
-	"strconv"
 )
 
 // llamaMultiValuedFlags defines flags that should be repeated for each value rather than comma-separated
@@ -41,7 +40,7 @@ type LlamaServerOptions struct {
 	BatchSize               int      `json:"batch_size,omitempty"`
 	UBatchSize              int      `json:"ubatch_size,omitempty"`
 	Keep                    int      `json:"keep,omitempty"`
-	FlashAttn               bool     `json:"flash_attn,omitempty"`
+	FlashAttn               string   `json:"flash_attn,omitempty"`
 	NoPerf                  bool     `json:"no_perf,omitempty"`
 	Escape                  bool     `json:"escape,omitempty"`
 	NoEscape                bool     `json:"no_escape,omitempty"`
@@ -187,6 +186,10 @@ type LlamaServerOptions struct {
 	FIMQwen7BDefault      bool `json:"fim_qwen_7b_default,omitempty"`
 	FIMQwen7BSpec         bool `json:"fim_qwen_7b_spec,omitempty"`
 	FIMQwen14BSpec        bool `json:"fim_qwen_14b_spec,omitempty"`
+
+	// ExtraArgs are additional command line arguments.
+	// Example: {"verbose": "", "log-file": "/logs/llama.log"}
+	ExtraArgs map[string]string `json:"extra_args,omitempty"`
 }
 
 // UnmarshalJSON implements custom JSON unmarshaling to support multiple field names
@@ -209,6 +212,15 @@ func (o *LlamaServerOptions) UnmarshalJSON(data []byte) error {
 	// Copy to our struct
 	*o = LlamaServerOptions(temp)
 
+	// Track which fields we've processed
+	processedFields := make(map[string]bool)
+
+	// Get all known canonical field names from struct tags
+	knownFields := getKnownFieldNames(o)
+	for field := range knownFields {
+		processedFields[field] = true
+	}
+
 	// Handle alternative field names
 	fieldMappings := map[string]string{
 		// Common params
@@ -220,7 +232,7 @@ func (o *LlamaServerOptions) UnmarshalJSON(data []byte) error {
 		"Crb":           "cpu_range_batch", // -Crb, --cpu-range-batch lo-hi
 		"c":             "ctx_size",        // -c, --ctx-size N
 		"n":             "predict",         // -n, --predict N
-		"n-predict":     "predict",         // --n-predict N
+		"n_predict":     "predict",         // -n-predict N
 		"b":             "batch_size",      // -b, --batch-size N
 		"ub":            "ubatch_size",     // -ub, --ubatch-size N
 		"fa":            "flash_attn",      // -fa, --flash-attn
@@ -234,7 +246,7 @@ func (o *LlamaServerOptions) UnmarshalJSON(data []byte) error {
 		"dev":           "device",          // -dev, --device <dev1,dev2,..>
 		"ot":            "override_tensor", // --override-tensor, -ot
 		"ngl":           "gpu_layers",      // -ngl, --gpu-layers, --n-gpu-layers N
-		"n-gpu-layers":  "gpu_layers",      // --n-gpu-layers N
+		"n_gpu_layers":  "gpu_layers",      // --n-gpu-layers N
 		"sm":            "split_mode",      // -sm, --split-mode
 		"ts":            "tensor_split",    // -ts, --tensor-split N0,N1,N2,...
 		"mg":            "main_gpu",        // -mg, --main-gpu INDEX
@@ -250,9 +262,9 @@ func (o *LlamaServerOptions) UnmarshalJSON(data []byte) error {
 		"hffv":          "hf_file_v",       // -hffv, --hf-file-v FILE
 		"hft":           "hf_token",        // -hft, --hf-token TOKEN
 		"v":             "verbose",         // -v, --verbose, --log-verbose
-		"log-verbose":   "verbose",         // --log-verbose
+		"log_verbose":   "verbose",         // --log-verbose
 		"lv":            "verbosity",       // -lv, --verbosity, --log-verbosity N
-		"log-verbosity": "verbosity",       // --log-verbosity N
+		"log_verbosity": "verbosity",       // --log-verbosity N
 
 		// Sampling params
 		"s":  "seed",             // -s, --seed SEED
@@ -269,21 +281,23 @@ func (o *LlamaServerOptions) UnmarshalJSON(data []byte) error {
 		"rerank":             "reranking",              // --reranking
 		"to":                 "timeout",                // -to, --timeout N
 		"sps":                "slot_prompt_similarity", // -sps, --slot-prompt-similarity
-		"draft":              "draft-max",              // -draft, --draft-max N
+		"draft":              "draft_max",              // -draft, --draft-max N
-		"draft-n":            "draft-max",              // --draft-n-max N
+		"draft_n":            "draft_max",              // --draft-n-max N
-		"draft-n-min":        "draft_min",              // --draft-n-min N
+		"draft_n_min":        "draft_min",              // --draft-n-min N
 		"cd":                 "ctx_size_draft",         // -cd, --ctx-size-draft N
 		"devd":               "device_draft",           // -devd, --device-draft
 		"ngld":               "gpu_layers_draft",       // -ngld, --gpu-layers-draft
-		"n-gpu-layers-draft": "gpu_layers_draft",       // --n-gpu-layers-draft N
+		"n_gpu_layers_draft": "gpu_layers_draft",       // --n-gpu-layers-draft N
 		"md":                 "model_draft",            // -md, --model-draft FNAME
 		"ctkd":               "cache_type_k_draft",     // -ctkd, --cache-type-k-draft TYPE
 		"ctvd":               "cache_type_v_draft",     // -ctvd, --cache-type-v-draft TYPE
 		"mv":                 "model_vocoder",          // -mv, --model-vocoder FNAME
 	}
 
-	// Process alternative field names
+	// Process alternative field names and mark them as processed
 	for altName, canonicalName := range fieldMappings {
+		processedFields[altName] = true // Mark alternatives as known
+
 		if value, exists := raw[altName]; exists {
 			// Use reflection to set the field value
 			v := reflect.ValueOf(o).Elem()
@@ -294,36 +308,21 @@ func (o *LlamaServerOptions) UnmarshalJSON(data []byte) error {
 			})
 
 			if field.IsValid() && field.CanSet() {
-				switch field.Kind() {
+				setFieldValue(field, value)
-				case reflect.Int:
-					if intVal, ok := value.(float64); ok {
-						field.SetInt(int64(intVal))
-					} else if strVal, ok := value.(string); ok {
-						if intVal, err := strconv.Atoi(strVal); err == nil {
-							field.SetInt(int64(intVal))
-						}
-					}
-				case reflect.Float64:
-					if floatVal, ok := value.(float64); ok {
-						field.SetFloat(floatVal)
-					} else if strVal, ok := value.(string); ok {
-						if floatVal, err := strconv.ParseFloat(strVal, 64); err == nil {
-							field.SetFloat(floatVal)
-						}
-					}
-				case reflect.String:
-					if strVal, ok := value.(string); ok {
-						field.SetString(strVal)
-					}
-				case reflect.Bool:
-					if boolVal, ok := value.(bool); ok {
-						field.SetBool(boolVal)
-					}
-				}
 			}
 		}
 	}
 
+	// Collect unknown fields into ExtraArgs
+	if o.ExtraArgs == nil {
+		o.ExtraArgs = make(map[string]string)
+	}
+	for key, value := range raw {
+		if !processedFields[key] {
+			o.ExtraArgs[key] = fmt.Sprintf("%v", value)
+		}
+	}
+
 	return nil
 }
 
@@ -354,6 +353,18 @@ func (o *LlamaServerOptions) Validate() error {
 		return validation.ValidationError(fmt.Errorf("invalid port range: %d", o.Port))
 	}
 
+	// Validate extra_args keys and values
+	for key, value := range o.ExtraArgs {
+		if err := validation.ValidateStringForInjection(key); err != nil {
+			return validation.ValidationError(fmt.Errorf("extra_args key %q: %w", key, err))
+		}
+		if value != "" {
+			if err := validation.ValidateStringForInjection(value); err != nil {
+				return validation.ValidationError(fmt.Errorf("extra_args value for %q: %w", key, err))
+			}
+		}
+	}
+
 	return nil
 }
 
@@ -361,7 +372,12 @@ func (o *LlamaServerOptions) Validate() error {
 func (o *LlamaServerOptions) BuildCommandArgs() []string {
 	// Llama uses multiple flags for arrays by default (not comma-separated)
 	// Use package-level llamaMultiValuedFlags variable
-	return BuildCommandArgs(o, llamaMultiValuedFlags)
+	args := BuildCommandArgs(o, llamaMultiValuedFlags)
+
+	// Append extra args at the end
+	args = append(args, convertExtraArgsToFlags(o.ExtraArgs)...)
+
+	return args
 }
 
 func (o *LlamaServerOptions) BuildDockerArgs() []string {

pkg/backends/llama_test.go

@@ -33,12 +33,11 @@ func TestLlamaCppBuildCommandArgs_BooleanFields(t *testing.T) {
 		{
 			name: "multiple booleans",
 			options: backends.LlamaServerOptions{
-				Verbose:   true,
+				Verbose: true,
-				FlashAttn: true,
+				Mlock:   false,
-				Mlock:     false,
+				NoMmap:  true,
-				NoMmap:    true,
 			},
-			expected: []string{"--verbose", "--flash-attn", "--no-mmap"},
+			expected: []string{"--verbose", "--no-mmap"},
 			excluded: []string{"--mlock"},
 		},
 	}
@@ -346,7 +345,7 @@ func TestParseLlamaCommand(t *testing.T) {
 		},
 		{
 			name:      "multiple value types",
-			command:   "llama-server --model /test/model.gguf --gpu-layers 32 --temp 0.7 --verbose --no-mmap",
+			command:   "llama-server --model /test/model.gguf --n-gpu-layers 32 --temp 0.7 --verbose --no-mmap",
 			expectErr: false,
 			validate: func(t *testing.T, opts *backends.LlamaServerOptions) {
 				if opts.Model != "/test/model.gguf" {
@@ -434,3 +433,119 @@ func TestParseLlamaCommandArrays(t *testing.T) {
 		}
 	}
 }
+
+func TestLlamaCppBuildCommandArgs_ExtraArgs(t *testing.T) {
+	options := backends.LlamaServerOptions{
+		Model: "/models/test.gguf",
+		ExtraArgs: map[string]string{
+			"flash-attn": "",               // boolean flag
+			"log-file":   "/logs/test.log", // value flag
+		},
+	}
+
+	args := options.BuildCommandArgs()
+
+	// Check that extra args are present
+	if !testutil.Contains(args, "--flash-attn") {
+		t.Error("Expected --flash-attn flag not found")
+	}
+	if !testutil.Contains(args, "--log-file") || !testutil.Contains(args, "/logs/test.log") {
+		t.Error("Expected --log-file flag or value not found")
+	}
+}
+
+func TestParseLlamaCommand_ExtraArgs(t *testing.T) {
+	tests := []struct {
+		name      string
+		command   string
+		expectErr bool
+		validate  func(*testing.T, *backends.LlamaServerOptions)
+	}{
+		{
+			name:      "extra args with known fields",
+			command:   "llama-server --model /path/to/model.gguf --gpu-layers 32 --unknown-flag value --another-bool-flag",
+			expectErr: false,
+			validate: func(t *testing.T, opts *backends.LlamaServerOptions) {
+				if opts.Model != "/path/to/model.gguf" {
+					t.Errorf("expected model '/path/to/model.gguf', got '%s'", opts.Model)
+				}
+				if opts.GPULayers != 32 {
+					t.Errorf("expected gpu_layers 32, got %d", opts.GPULayers)
+				}
+				if opts.ExtraArgs == nil {
+					t.Fatal("expected extra_args to be non-nil")
+				}
+				if val, ok := opts.ExtraArgs["unknown_flag"]; !ok || val != "value" {
+					t.Errorf("expected extra_args[unknown_flag]='value', got '%s'", val)
+				}
+				if val, ok := opts.ExtraArgs["another_bool_flag"]; !ok || val != "true" {
+					t.Errorf("expected extra_args[another_bool_flag]='true', got '%s'", val)
+				}
+			},
+		},
+		{
+			name:      "extra args with alternative field names",
+			command:   "llama-server -m /model.gguf -ngl 16 --custom-arg test --new-feature",
+			expectErr: false,
+			validate: func(t *testing.T, opts *backends.LlamaServerOptions) {
+				// Check that alternative names worked for known fields
+				if opts.Model != "/model.gguf" {
+					t.Errorf("expected model '/model.gguf', got '%s'", opts.Model)
+				}
+				if opts.GPULayers != 16 {
+					t.Errorf("expected gpu_layers 16, got %d", opts.GPULayers)
+				}
+				// Check that unknown args went to ExtraArgs
+				if opts.ExtraArgs == nil {
+					t.Fatal("expected extra_args to be non-nil")
+				}
+				if val, ok := opts.ExtraArgs["custom_arg"]; !ok || val != "test" {
+					t.Errorf("expected extra_args[custom_arg]='test', got '%s'", val)
+				}
+				if val, ok := opts.ExtraArgs["new_feature"]; !ok || val != "true" {
+					t.Errorf("expected extra_args[new_feature]='true', got '%s'", val)
+				}
+			},
+		},
+		{
+			name:      "only extra args",
+			command:   "llama-server --experimental-feature --beta-mode enabled",
+			expectErr: false,
+			validate: func(t *testing.T, opts *backends.LlamaServerOptions) {
+				if opts.ExtraArgs == nil {
+					t.Fatal("expected extra_args to be non-nil")
+				}
+				if val, ok := opts.ExtraArgs["experimental_feature"]; !ok || val != "true" {
+					t.Errorf("expected extra_args[experimental_feature]='true', got '%s'", val)
+				}
+				if val, ok := opts.ExtraArgs["beta_mode"]; !ok || val != "enabled" {
+					t.Errorf("expected extra_args[beta_mode]='enabled', got '%s'", val)
+				}
+			},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			var opts backends.LlamaServerOptions
+			result, err := opts.ParseCommand(tt.command)
+
+			if tt.expectErr && err == nil {
+				t.Error("expected error but got none")
+				return
+			}
+			if !tt.expectErr && err != nil {
+				t.Errorf("unexpected error: %v", err)
+				return
+			}
+
+			if !tt.expectErr && tt.validate != nil {
+				llamaOpts, ok := result.(*backends.LlamaServerOptions)
+				if !ok {
+					t.Fatal("result is not *LlamaServerOptions")
+				}
+				tt.validate(t, llamaOpts)
+			}
+		})
+	}
+}

pkg/backends/mlx.go

@@ -1,6 +1,7 @@
 package backends
 
 import (
+	"encoding/json"
 	"fmt"
 	"llamactl/pkg/validation"
 )
@@ -29,6 +30,46 @@ type MlxServerOptions struct {
 	TopK      int     `json:"top_k,omitempty"`
 	MinP      float64 `json:"min_p,omitempty"`
 	MaxTokens int     `json:"max_tokens,omitempty"`
+
+	// ExtraArgs are additional command line arguments.
+	// Example: {"verbose": "", "log-file": "/logs/mlx.log"}
+	ExtraArgs map[string]string `json:"extra_args,omitempty"`
+}
+
+// UnmarshalJSON implements custom JSON unmarshaling to collect unknown fields into ExtraArgs
+func (o *MlxServerOptions) UnmarshalJSON(data []byte) error {
+	// First unmarshal into a map to capture all fields
+	var raw map[string]any
+	if err := json.Unmarshal(data, &raw); err != nil {
+		return err
+	}
+
+	// Create a temporary struct for standard unmarshaling
+	type tempOptions MlxServerOptions
+	temp := tempOptions{}
+
+	// Standard unmarshal first
+	if err := json.Unmarshal(data, &temp); err != nil {
+		return err
+	}
+
+	// Copy to our struct
+	*o = MlxServerOptions(temp)
+
+	// Get all known canonical field names from struct tags
+	knownFields := getKnownFieldNames(o)
+
+	// Collect unknown fields into ExtraArgs
+	if o.ExtraArgs == nil {
+		o.ExtraArgs = make(map[string]string)
+	}
+	for key, value := range raw {
+		if !knownFields[key] {
+			o.ExtraArgs[key] = fmt.Sprintf("%v", value)
+		}
+	}
+
+	return nil
 }
 
 func (o *MlxServerOptions) GetPort() int {
@@ -57,13 +98,30 @@ func (o *MlxServerOptions) Validate() error {
 		return validation.ValidationError(fmt.Errorf("invalid port range: %d", o.Port))
 	}
 
+	// Validate extra_args keys and values
+	for key, value := range o.ExtraArgs {
+		if err := validation.ValidateStringForInjection(key); err != nil {
+			return validation.ValidationError(fmt.Errorf("extra_args key %q: %w", key, err))
+		}
+		if value != "" {
+			if err := validation.ValidateStringForInjection(value); err != nil {
+				return validation.ValidationError(fmt.Errorf("extra_args value for %q: %w", key, err))
+			}
+		}
+	}
+
 	return nil
 }
 
 // BuildCommandArgs converts to command line arguments
 func (o *MlxServerOptions) BuildCommandArgs() []string {
 	multipleFlags := map[string]struct{}{} // MLX doesn't currently have []string fields
-	return BuildCommandArgs(o, multipleFlags)
+	args := BuildCommandArgs(o, multipleFlags)
+
+	// Append extra args at the end
+	args = append(args, convertExtraArgsToFlags(o.ExtraArgs)...)
+
+	return args
 }
 
 func (o *MlxServerOptions) BuildDockerArgs() []string {

pkg/backends/mlx_test.go

@@ -202,3 +202,75 @@ func TestMlxBuildCommandArgs_ZeroValues(t *testing.T) {
 		}
 	}
 }
+
+func TestParseMlxCommand_ExtraArgs(t *testing.T) {
+	tests := []struct {
+		name      string
+		command   string
+		expectErr bool
+		validate  func(*testing.T, *backends.MlxServerOptions)
+	}{
+		{
+			name:      "extra args with known fields",
+			command:   "mlx_lm.server --model /path/to/model --port 8080 --unknown-flag value --new-bool-flag",
+			expectErr: false,
+			validate: func(t *testing.T, opts *backends.MlxServerOptions) {
+				if opts.Model != "/path/to/model" {
+					t.Errorf("expected model '/path/to/model', got '%s'", opts.Model)
+				}
+				if opts.Port != 8080 {
+					t.Errorf("expected port 8080, got %d", opts.Port)
+				}
+				if opts.ExtraArgs == nil {
+					t.Fatal("expected extra_args to be non-nil")
+				}
+				if val, ok := opts.ExtraArgs["unknown_flag"]; !ok || val != "value" {
+					t.Errorf("expected extra_args[unknown_flag]='value', got '%s'", val)
+				}
+				if val, ok := opts.ExtraArgs["new_bool_flag"]; !ok || val != "true" {
+					t.Errorf("expected extra_args[new_bool_flag]='true', got '%s'", val)
+				}
+			},
+		},
+		{
+			name:      "only extra args",
+			command:   "mlx_lm.server --experimental-feature --custom-param test",
+			expectErr: false,
+			validate: func(t *testing.T, opts *backends.MlxServerOptions) {
+				if opts.ExtraArgs == nil {
+					t.Fatal("expected extra_args to be non-nil")
+				}
+				if val, ok := opts.ExtraArgs["experimental_feature"]; !ok || val != "true" {
+					t.Errorf("expected extra_args[experimental_feature]='true', got '%s'", val)
+				}
+				if val, ok := opts.ExtraArgs["custom_param"]; !ok || val != "test" {
+					t.Errorf("expected extra_args[custom_param]='test', got '%s'", val)
+				}
+			},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			var opts backends.MlxServerOptions
+			result, err := opts.ParseCommand(tt.command)
+
+			if tt.expectErr && err == nil {
+				t.Error("expected error but got none")
+				return
+			}
+			if !tt.expectErr && err != nil {
+				t.Errorf("unexpected error: %v", err)
+				return
+			}
+
+			if !tt.expectErr && tt.validate != nil {
+				mlxOpts, ok := result.(*backends.MlxServerOptions)
+				if !ok {
+					t.Fatal("result is not *MlxServerOptions")
+				}
+				tt.validate(t, mlxOpts)
+			}
+		})
+	}
+}

pkg/backends/parser.go

@@ -4,6 +4,7 @@ import (
 	"encoding/json"
 	"fmt"
 	"path/filepath"
+	"reflect"
 	"regexp"
 	"strconv"
 	"strings"
@@ -211,3 +212,65 @@ func parseValue(value string) any {
 	// Return as string
 	return value
 }
+
+// setFieldValue sets a field value using reflection, handling type conversions
+// Used by UnmarshalJSON implementations to handle alternative field names
+func setFieldValue(field reflect.Value, value any) {
+	switch field.Kind() {
+	case reflect.Int:
+		if intVal, ok := value.(float64); ok {
+			field.SetInt(int64(intVal))
+		} else if strVal, ok := value.(string); ok {
+			if intVal, err := strconv.Atoi(strVal); err == nil {
+				field.SetInt(int64(intVal))
+			}
+		}
+	case reflect.Float64:
+		if floatVal, ok := value.(float64); ok {
+			field.SetFloat(floatVal)
+		} else if strVal, ok := value.(string); ok {
+			if floatVal, err := strconv.ParseFloat(strVal, 64); err == nil {
+				field.SetFloat(floatVal)
+			}
+		}
+	case reflect.String:
+		if strVal, ok := value.(string); ok {
+			field.SetString(strVal)
+		}
+	case reflect.Bool:
+		if boolVal, ok := value.(bool); ok {
+			field.SetBool(boolVal)
+		}
+	case reflect.Slice:
+		// Handle string slices
+		if field.Type().Elem().Kind() == reflect.String {
+			if slice, ok := value.([]any); ok {
+				strSlice := make([]string, 0, len(slice))
+				for _, v := range slice {
+					if s, ok := v.(string); ok {
+						strSlice = append(strSlice, s)
+					}
+				}
+				field.Set(reflect.ValueOf(strSlice))
+			}
+		}
+	}
+}
+
+// getKnownFieldNames extracts all known field names from struct json tags
+// Used by UnmarshalJSON implementations to identify unknown fields for ExtraArgs
+func getKnownFieldNames(v any) map[string]bool {
+	fields := make(map[string]bool)
+	t := reflect.TypeOf(v).Elem()
+
+	for i := 0; i < t.NumField(); i++ {
+		field := t.Field(i)
+		jsonTag := field.Tag.Get("json")
+		if jsonTag != "" && jsonTag != "-" {
+			// Handle "name,omitempty" format
+			name := strings.Split(jsonTag, ",")[0]
+			fields[name] = true
+		}
+	}
+	return fields
+}

pkg/backends/vllm.go

@@ -1,6 +1,7 @@
 package backends
 
 import (
+	"encoding/json"
 	"fmt"
 	"llamactl/pkg/validation"
 )
@@ -142,6 +143,46 @@ type VllmServerOptions struct {
 	OverridePoolingConfig     string `json:"override_pooling_config,omitempty"`
 	OverrideNeuronConfig      string `json:"override_neuron_config,omitempty"`
 	OverrideKVCacheALIGNSize  int    `json:"override_kv_cache_align_size,omitempty"`
+
+	// ExtraArgs are additional command line arguments.
+	// Example: {"verbose": "", "log-file": "/logs/vllm.log"}
+	ExtraArgs map[string]string `json:"extra_args,omitempty"`
+}
+
+// UnmarshalJSON implements custom JSON unmarshaling to collect unknown fields into ExtraArgs
+func (o *VllmServerOptions) UnmarshalJSON(data []byte) error {
+	// First unmarshal into a map to capture all fields
+	var raw map[string]any
+	if err := json.Unmarshal(data, &raw); err != nil {
+		return err
+	}
+
+	// Create a temporary struct for standard unmarshaling
+	type tempOptions VllmServerOptions
+	temp := tempOptions{}
+
+	// Standard unmarshal first
+	if err := json.Unmarshal(data, &temp); err != nil {
+		return err
+	}
+
+	// Copy to our struct
+	*o = VllmServerOptions(temp)
+
+	// Get all known canonical field names from struct tags
+	knownFields := getKnownFieldNames(o)
+
+	// Collect unknown fields into ExtraArgs
+	if o.ExtraArgs == nil {
+		o.ExtraArgs = make(map[string]string)
+	}
+	for key, value := range raw {
+		if !knownFields[key] {
+			o.ExtraArgs[key] = fmt.Sprintf("%v", value)
+		}
+	}
+
+	return nil
 }
 
 func (o *VllmServerOptions) GetPort() int {
@@ -171,6 +212,18 @@ func (o *VllmServerOptions) Validate() error {
 		return validation.ValidationError(fmt.Errorf("invalid port range: %d", o.Port))
 	}
 
+	// Validate extra_args keys and values
+	for key, value := range o.ExtraArgs {
+		if err := validation.ValidateStringForInjection(key); err != nil {
+			return validation.ValidationError(fmt.Errorf("extra_args key %q: %w", key, err))
+		}
+		if value != "" {
+			if err := validation.ValidateStringForInjection(value); err != nil {
+				return validation.ValidationError(fmt.Errorf("extra_args value for %q: %w", key, err))
+			}
+		}
+	}
+
 	return nil
 }
 
@@ -193,6 +246,9 @@ func (o *VllmServerOptions) BuildCommandArgs() []string {
 	flagArgs := BuildCommandArgs(&optionsCopy, vllmMultiValuedFlags)
 	args = append(args, flagArgs...)
 
+	// Append extra args at the end
+	args = append(args, convertExtraArgsToFlags(o.ExtraArgs)...)
+
 	return args
 }
 
@@ -203,6 +259,9 @@ func (o *VllmServerOptions) BuildDockerArgs() []string {
 	flagArgs := BuildCommandArgs(o, vllmMultiValuedFlags)
 	args = append(args, flagArgs...)
 
+	// Append extra args at the end
+	args = append(args, convertExtraArgsToFlags(o.ExtraArgs)...)
+
 	return args
 }
 

pkg/backends/vllm_test.go

@@ -321,3 +321,94 @@ func TestVllmBuildCommandArgs_PositionalModel(t *testing.T) {
 		t.Errorf("Expected --port 8080 not found in %v", args)
 	}
 }
+
+func TestParseVllmCommand_ExtraArgs(t *testing.T) {
+	tests := []struct {
+		name      string
+		command   string
+		expectErr bool
+		validate  func(*testing.T, *backends.VllmServerOptions)
+	}{
+		{
+			name:      "extra args with known fields",
+			command:   "vllm serve llama-model --tensor-parallel-size 2 --unknown-flag value --new-bool-flag",
+			expectErr: false,
+			validate: func(t *testing.T, opts *backends.VllmServerOptions) {
+				if opts.Model != "llama-model" {
+					t.Errorf("expected model 'llama-model', got '%s'", opts.Model)
+				}
+				if opts.TensorParallelSize != 2 {
+					t.Errorf("expected tensor_parallel_size 2, got %d", opts.TensorParallelSize)
+				}
+				if opts.ExtraArgs == nil {
+					t.Fatal("expected extra_args to be non-nil")
+				}
+				if val, ok := opts.ExtraArgs["unknown_flag"]; !ok || val != "value" {
+					t.Errorf("expected extra_args[unknown_flag]='value', got '%s'", val)
+				}
+				if val, ok := opts.ExtraArgs["new_bool_flag"]; !ok || val != "true" {
+					t.Errorf("expected extra_args[new_bool_flag]='true', got '%s'", val)
+				}
+			},
+		},
+		{
+			name:      "only extra args",
+			command:   "vllm serve model --experimental-feature --custom-param test",
+			expectErr: false,
+			validate: func(t *testing.T, opts *backends.VllmServerOptions) {
+				if opts.ExtraArgs == nil {
+					t.Fatal("expected extra_args to be non-nil")
+				}
+				if val, ok := opts.ExtraArgs["experimental_feature"]; !ok || val != "true" {
+					t.Errorf("expected extra_args[experimental_feature]='true', got '%s'", val)
+				}
+				if val, ok := opts.ExtraArgs["custom_param"]; !ok || val != "test" {
+					t.Errorf("expected extra_args[custom_param]='test', got '%s'", val)
+				}
+			},
+		},
+		{
+			name:      "extra args without model positional",
+			command:   "vllm serve --model my-model --new-feature enabled --beta-flag",
+			expectErr: false,
+			validate: func(t *testing.T, opts *backends.VllmServerOptions) {
+				if opts.Model != "my-model" {
+					t.Errorf("expected model 'my-model', got '%s'", opts.Model)
+				}
+				if opts.ExtraArgs == nil {
+					t.Fatal("expected extra_args to be non-nil")
+				}
+				if val, ok := opts.ExtraArgs["new_feature"]; !ok || val != "enabled" {
+					t.Errorf("expected extra_args[new_feature]='enabled', got '%s'", val)
+				}
+				if val, ok := opts.ExtraArgs["beta_flag"]; !ok || val != "true" {
+					t.Errorf("expected extra_args[beta_flag]='true', got '%s'", val)
+				}
+			},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			var opts backends.VllmServerOptions
+			result, err := opts.ParseCommand(tt.command)
+
+			if tt.expectErr && err == nil {
+				t.Error("expected error but got none")
+				return
+			}
+			if !tt.expectErr && err != nil {
+				t.Errorf("unexpected error: %v", err)
+				return
+			}
+
+			if !tt.expectErr && tt.validate != nil {
+				vllmOpts, ok := result.(*backends.VllmServerOptions)
+				if !ok {
+					t.Fatal("result is not *VllmServerOptions")
+				}
+				tt.validate(t, vllmOpts)
+			}
+		})
+	}
+}

pkg/validation/validation_test.go

@@ -239,25 +239,3 @@ func TestValidateInstanceOptions_MultipleFieldInjection(t *testing.T) {
 		})
 	}
 }
-
-func TestValidateInstanceOptions_NonStringFields(t *testing.T) {
-	// Test that non-string fields don't interfere with validation
-	options := backends.Options{
-		BackendType: backends.BackendTypeLlamaCpp,
-		LlamaServerOptions: &backends.LlamaServerOptions{
-			Port:        8080,
-			GPULayers:   32,
-			CtxSize:     4096,
-			Temperature: 0.7,
-			TopK:        40,
-			TopP:        0.9,
-			Verbose:     true,
-			FlashAttn:   false,
-		},
-	}
-
-	err := options.ValidateInstanceOptions()
-	if err != nil {
-		t.Errorf("ValidateInstanceOptions with non-string fields should not error, got: %v", err)
-	}
-}

webui/src/components/BackendFormField.tsx

@@ -3,17 +3,31 @@ import { Input } from '@/components/ui/input'
 import { Label } from '@/components/ui/label'
 import { Checkbox } from '@/components/ui/checkbox'
 import { getBackendFieldType, basicBackendFieldsConfig } from '@/lib/zodFormUtils'
+import ExtraArgsInput from '@/components/form/ExtraArgsInput'
 
 interface BackendFormFieldProps {
   fieldKey: string
-  value: string | number | boolean | string[] | undefined
+  value: string | number | boolean | string[] | Record<string, string> | undefined
-  onChange: (key: string, value: string | number | boolean | string[] | undefined) => void
+  onChange: (key: string, value: string | number | boolean | string[] | Record<string, string> | undefined) => void
 }
 
 const BackendFormField: React.FC<BackendFormFieldProps> = ({ fieldKey, value, onChange }) => {
+  // Special handling for extra_args
+  if (fieldKey === 'extra_args') {
+    return (
+      <ExtraArgsInput
+        id={fieldKey}
+        label="Extra Arguments"
+        value={value as Record<string, string> | undefined}
+        onChange={(newValue) => onChange(fieldKey, newValue)}
+        description="Additional command line arguments to pass to the backend"
+      />
+    )
+  }
+
   // Get configuration for basic fields, or use field name for advanced fields
   const config = basicBackendFieldsConfig[fieldKey] || { label: fieldKey }
-  
+
   // Get type from Zod schema
   const fieldType = getBackendFieldType(fieldKey)
 

webui/src/components/form/EnvVarsInput.tsx

@@ -0,0 +1,27 @@
+import React from 'react'
+import KeyValueInput from './KeyValueInput'
+
+interface EnvVarsInputProps {
+  id: string
+  label: string
+  value: Record<string, string> | undefined
+  onChange: (value: Record<string, string> | undefined) => void
+  description?: string
+  disabled?: boolean
+  className?: string
+}
+
+const EnvVarsInput: React.FC<EnvVarsInputProps> = (props) => {
+  return (
+    <KeyValueInput
+      {...props}
+      keyPlaceholder="Variable name"
+      valuePlaceholder="Variable value"
+      addButtonText="Add Variable"
+      helperText="Environment variables that will be passed to the backend process"
+      allowEmptyValues={false}
+    />
+  )
+}
+
+export default EnvVarsInput

webui/src/components/form/EnvironmentVariablesInput.tsx

@@ -1,144 +0,0 @@
-import React, { useState } from 'react'
-import { Input } from '@/components/ui/input'
-import { Label } from '@/components/ui/label'
-import { Button } from '@/components/ui/button'
-import { X, Plus } from 'lucide-react'
-
-interface EnvironmentVariablesInputProps {
-  id: string
-  label: string
-  value: Record<string, string> | undefined
-  onChange: (value: Record<string, string> | undefined) => void
-  description?: string
-  disabled?: boolean
-  className?: string
-}
-
-interface EnvVar {
-  key: string
-  value: string
-}
-
-const EnvironmentVariablesInput: React.FC<EnvironmentVariablesInputProps> = ({
-  id,
-  label,
-  value,
-  onChange,
-  description,
-  disabled = false,
-  className
-}) => {
-  // Convert the value object to an array of key-value pairs for editing
-  const envVarsFromValue = value
-    ? Object.entries(value).map(([key, val]) => ({ key, value: val }))
-    : []
-
-  const [envVars, setEnvVars] = useState<EnvVar[]>(
-    envVarsFromValue.length > 0 ? envVarsFromValue : [{ key: '', value: '' }]
-  )
-
-  // Update parent component when env vars change
-  const updateParent = (newEnvVars: EnvVar[]) => {
-    // Filter out empty entries
-    const validVars = newEnvVars.filter(env => env.key.trim() !== '' && env.value.trim() !== '')
-
-    if (validVars.length === 0) {
-      onChange(undefined)
-    } else {
-      const envObject = validVars.reduce((acc, env) => {
-        acc[env.key.trim()] = env.value.trim()
-        return acc
-      }, {} as Record<string, string>)
-      onChange(envObject)
-    }
-  }
-
-  const handleKeyChange = (index: number, newKey: string) => {
-    const newEnvVars = [...envVars]
-    newEnvVars[index].key = newKey
-    setEnvVars(newEnvVars)
-    updateParent(newEnvVars)
-  }
-
-  const handleValueChange = (index: number, newValue: string) => {
-    const newEnvVars = [...envVars]
-    newEnvVars[index].value = newValue
-    setEnvVars(newEnvVars)
-    updateParent(newEnvVars)
-  }
-
-  const addEnvVar = () => {
-    const newEnvVars = [...envVars, { key: '', value: '' }]
-    setEnvVars(newEnvVars)
-  }
-
-  const removeEnvVar = (index: number) => {
-    if (envVars.length === 1) {
-      // Reset to empty if it's the last one
-      const newEnvVars = [{ key: '', value: '' }]
-      setEnvVars(newEnvVars)
-      updateParent(newEnvVars)
-    } else {
-      const newEnvVars = envVars.filter((_, i) => i !== index)
-      setEnvVars(newEnvVars)
-      updateParent(newEnvVars)
-    }
-  }
-
-  return (
-    <div className={`grid gap-2 ${className || ''}`}>
-      <Label htmlFor={id}>
-        {label}
-      </Label>
-      <div className="space-y-2">
-        {envVars.map((envVar, index) => (
-          <div key={index} className="flex gap-2 items-center">
-            <Input
-              placeholder="Variable name"
-              value={envVar.key}
-              onChange={(e) => handleKeyChange(index, e.target.value)}
-              disabled={disabled}
-              className="flex-1"
-            />
-            <Input
-              placeholder="Variable value"
-              value={envVar.value}
-              onChange={(e) => handleValueChange(index, e.target.value)}
-              disabled={disabled}
-              className="flex-1"
-            />
-            <Button
-              type="button"
-              variant="outline"
-              size="sm"
-              onClick={() => removeEnvVar(index)}
-              disabled={disabled}
-              className="shrink-0"
-            >
-              <X className="h-4 w-4" />
-            </Button>
-          </div>
-        ))}
-        <Button
-          type="button"
-          variant="outline"
-          size="sm"
-          onClick={addEnvVar}
-          disabled={disabled}
-          className="w-fit"
-        >
-          <Plus className="h-4 w-4 mr-2" />
-          Add Variable
-        </Button>
-      </div>
-      {description && (
-        <p className="text-sm text-muted-foreground">{description}</p>
-      )}
-      <p className="text-xs text-muted-foreground">
-        Environment variables that will be passed to the backend process
-      </p>
-    </div>
-  )
-}
-
-export default EnvironmentVariablesInput

webui/src/components/form/ExtraArgsInput.tsx

@@ -0,0 +1,27 @@
+import React from 'react'
+import KeyValueInput from './KeyValueInput'
+
+interface ExtraArgsInputProps {
+  id: string
+  label: string
+  value: Record<string, string> | undefined
+  onChange: (value: Record<string, string> | undefined) => void
+  description?: string
+  disabled?: boolean
+  className?: string
+}
+
+const ExtraArgsInput: React.FC<ExtraArgsInputProps> = (props) => {
+  return (
+    <KeyValueInput
+      {...props}
+      keyPlaceholder="Flag name (without --)"
+      valuePlaceholder="Value (empty for boolean flags)"
+      addButtonText="Add Argument"
+      helperText="Additional command line arguments to pass to the backend. Leave value empty for boolean flags."
+      allowEmptyValues={true}
+    />
+  )
+}
+
+export default ExtraArgsInput

webui/src/components/form/KeyValueInput.tsx

@@ -0,0 +1,171 @@
+import React, { useState, useEffect } from 'react'
+import { Input } from '@/components/ui/input'
+import { Label } from '@/components/ui/label'
+import { Button } from '@/components/ui/button'
+import { X, Plus } from 'lucide-react'
+
+interface KeyValueInputProps {
+  id: string
+  label: string
+  value: Record<string, string> | undefined
+  onChange: (value: Record<string, string> | undefined) => void
+  description?: string
+  disabled?: boolean
+  className?: string
+  keyPlaceholder?: string
+  valuePlaceholder?: string
+  addButtonText?: string
+  helperText?: string
+  allowEmptyValues?: boolean // If true, entries with empty values are considered valid
+}
+
+interface KeyValuePair {
+  key: string
+  value: string
+}
+
+const KeyValueInput: React.FC<KeyValueInputProps> = ({
+  id,
+  label,
+  value,
+  onChange,
+  description,
+  disabled = false,
+  className,
+  keyPlaceholder = 'Key',
+  valuePlaceholder = 'Value',
+  addButtonText = 'Add Entry',
+  helperText,
+  allowEmptyValues = false
+}) => {
+  // Convert the value object to an array of key-value pairs for editing
+  const pairsFromValue = value
+    ? Object.entries(value).map(([key, val]) => ({ key, value: val }))
+    : []
+
+  const [pairs, setPairs] = useState<KeyValuePair[]>(
+    pairsFromValue.length > 0 ? pairsFromValue : [{ key: '', value: '' }]
+  )
+
+  // Sync internal state when value prop changes
+  useEffect(() => {
+    const newPairsFromValue = value
+      ? Object.entries(value).map(([key, val]) => ({ key, value: val }))
+      : []
+
+    if (newPairsFromValue.length > 0) {
+      setPairs(newPairsFromValue)
+    } else if (!value) {
+      // Reset to single empty row if value is explicitly undefined/null
+      setPairs([{ key: '', value: '' }])
+    }
+    // eslint-disable-next-line react-hooks/exhaustive-deps
+  }, [value])
+
+  // Update parent component when pairs change
+  const updateParent = (newPairs: KeyValuePair[]) => {
+    // Filter based on validation rules
+    const validPairs = allowEmptyValues
+      ? newPairs.filter(pair => pair.key.trim() !== '')
+      : newPairs.filter(pair => pair.key.trim() !== '' && pair.value.trim() !== '')
+
+    if (validPairs.length === 0) {
+      onChange(undefined)
+    } else {
+      const pairsObject = validPairs.reduce((acc, pair) => {
+        acc[pair.key.trim()] = pair.value.trim()
+        return acc
+      }, {} as Record<string, string>)
+      onChange(pairsObject)
+    }
+  }
+
+  const handleKeyChange = (index: number, newKey: string) => {
+    const newPairs = [...pairs]
+    newPairs[index].key = newKey
+    setPairs(newPairs)
+    updateParent(newPairs)
+  }
+
+  const handleValueChange = (index: number, newValue: string) => {
+    const newPairs = [...pairs]
+    newPairs[index].value = newValue
+    setPairs(newPairs)
+    updateParent(newPairs)
+  }
+
+  const addPair = () => {
+    const newPairs = [...pairs, { key: '', value: '' }]
+    setPairs(newPairs)
+  }
+
+  const removePair = (index: number) => {
+    if (pairs.length === 1) {
+      // Reset to empty if it's the last one
+      const newPairs = [{ key: '', value: '' }]
+      setPairs(newPairs)
+      updateParent(newPairs)
+    } else {
+      const newPairs = pairs.filter((_, i) => i !== index)
+      setPairs(newPairs)
+      updateParent(newPairs)
+    }
+  }
+
+  return (
+    <div className={`grid gap-2 ${className || ''}`}>
+      <Label htmlFor={id}>
+        {label}
+      </Label>
+      <div className="space-y-2">
+        {pairs.map((pair, index) => (
+          <div key={index} className="flex gap-2 items-center">
+            <Input
+              placeholder={keyPlaceholder}
+              value={pair.key}
+              onChange={(e) => handleKeyChange(index, e.target.value)}
+              disabled={disabled}
+              className="flex-1"
+            />
+            <Input
+              placeholder={valuePlaceholder}
+              value={pair.value}
+              onChange={(e) => handleValueChange(index, e.target.value)}
+              disabled={disabled}
+              className="flex-1"
+            />
+            <Button
+              type="button"
+              variant="outline"
+              size="sm"
+              onClick={() => removePair(index)}
+              disabled={disabled}
+              className="shrink-0"
+            >
+              <X className="h-4 w-4" />
+            </Button>
+          </div>
+        ))}
+        <Button
+          type="button"
+          variant="outline"
+          size="sm"
+          onClick={addPair}
+          disabled={disabled}
+          className="w-fit"
+        >
+          <Plus className="h-4 w-4 mr-2" />
+          {addButtonText}
+        </Button>
+      </div>
+      {description && (
+        <p className="text-sm text-muted-foreground">{description}</p>
+      )}
+      {helperText && (
+        <p className="text-xs text-muted-foreground">{helperText}</p>
+      )}
+    </div>
+  )
+}
+
+export default KeyValueInput

webui/src/components/instance/BackendConfiguration.tsx

@@ -47,8 +47,18 @@ const BackendConfiguration: React.FC<BackendConfigurationProps> = ({
             ))}
         </div>
       )}
+
+      {/* Extra Args - Always visible as a separate section */}
+      <div className="space-y-4">
+        <BackendFormField
+          key="extra_args"
+          fieldKey="extra_args"
+          value={(formData.backend_options as any)?.extra_args}
+          onChange={onBackendFieldChange}
+        />
+      </div>
     </div>
   )
 }
 
-export default BackendConfiguration
+export default BackendConfiguration

webui/src/components/instance/BackendConfigurationCard.tsx

@@ -109,6 +109,16 @@ const BackendConfigurationCard: React.FC<BackendConfigurationCardProps> = ({
             )}
           </div>
         )}
+
+        {/* Extra Arguments - Always visible */}
+        <div className="space-y-4">
+          <BackendFormField
+            key="extra_args"
+            fieldKey="extra_args"
+            value={(formData.backend_options as Record<string, unknown>)?.extra_args as Record<string, string> | undefined}
+            onChange={onBackendFieldChange}
+          />
+        </div>
       </CardContent>
     </Card>
   )

webui/src/components/instance/InstanceSettingsCard.tsx

@@ -6,7 +6,7 @@ import { Input } from '@/components/ui/input'
 import AutoRestartConfiguration from '@/components/instance/AutoRestartConfiguration'
 import NumberInput from '@/components/form/NumberInput'
 import CheckboxInput from '@/components/form/CheckboxInput'
-import EnvironmentVariablesInput from '@/components/form/EnvironmentVariablesInput'
+import EnvVarsInput from '@/components/form/EnvVarsInput'
 import SelectInput from '@/components/form/SelectInput'
 import { nodesApi, type NodesMap } from '@/lib/api'
 
@@ -132,7 +132,7 @@ const InstanceSettingsCard: React.FC<InstanceSettingsCardProps> = ({
             description="Start instance only when needed"
           />
 
-          <EnvironmentVariablesInput
+          <EnvVarsInput
             id="environment"
             label="Environment Variables"
             value={formData.environment}

webui/src/lib/zodFormUtils.ts

@@ -126,7 +126,7 @@ export function getAdvancedBackendFields(backendType?: string): string[] {
   const fieldGetter = backendFieldGetters[normalizedType] || getAllLlamaCppFieldKeys
   const basicConfig = backendFieldConfigs[normalizedType] || basicLlamaCppFieldsConfig
 
-  return fieldGetter().filter(key => !(key in basicConfig))
+  return fieldGetter().filter(key => !(key in basicConfig) && key !== 'extra_args')
 }
 
 // Combined backend fields config for use in BackendFormField

webui/src/schemas/backends/llamacpp.ts

@@ -167,6 +167,9 @@ export const LlamaCppBackendOptionsSchema = z.object({
   fim_qwen_7b_default: z.boolean().optional(),
   fim_qwen_7b_spec: z.boolean().optional(),
   fim_qwen_14b_spec: z.boolean().optional(),
+
+  // Extra args
+  extra_args: z.record(z.string(), z.string()).optional(),
 })
 
 // Infer the TypeScript type from the schema

webui/src/schemas/backends/mlx.ts

@@ -25,6 +25,9 @@ export const MlxBackendOptionsSchema = z.object({
   top_k: z.number().optional(),
   min_p: z.number().optional(),
   max_tokens: z.number().optional(),
+
+  // Extra args
+  extra_args: z.record(z.string(), z.string()).optional(),
 })
 
 // Infer the TypeScript type from the schema

webui/src/schemas/backends/vllm.ts

@@ -125,6 +125,9 @@ export const VllmBackendOptionsSchema = z.object({
   override_pooling_config: z.string().optional(),
   override_neuron_config: z.string().optional(),
   override_kv_cache_align_size: z.number().optional(),
+
+  // Extra args
+  extra_args: z.record(z.string(), z.string()).optional(),
 })
 
 // Infer the TypeScript type from the schema