diff --git a/cmd/gasm/main.go b/cmd/gasm/main.go
index 2f48e4d..89aa4c1 100644
--- a/cmd/gasm/main.go
+++ b/cmd/gasm/main.go
@@ -1067,6 +1067,7 @@ decoders) that crash on random input but should succeed on valid data.
 	sweepOne := fs.String("sweep-one", "", "") // hidden: smoke/abi a single function (subprocess mode)
 	call := fs.String("call", "", "call a single function with -buf instead of the sweeps")
 	bufSpec := fs.String("buf", "", "buffer spec for -call: name:size:pattern[,name:size:pattern] (zero, ones, seq, or hex)")
+	scalarSpec := fs.String("args", "", "scalar args for -call: name=value[,name=value] (decimal or 0x hex)")
 	repeat := fs.Int("repeat", 1, "number of times to repeat a -call invocation")
 	fs.Parse(args)
 	if fs.NArg() != 1 {
@@ -1105,7 +1106,7 @@ decoders) that crash on random input but should succeed on valid data.
 
 	// Single-function call mode: invoke one function with user-supplied buffers.
 	if *call != "" {
-		return cmdVerifyCall(k, path, *call, *bufSpec, *repeat)
+		return cmdVerifyCall(k, path, *call, *bufSpec, *scalarSpec, *repeat)
 	}
 
 	// Subprocess mode: fuzz a single function and exit.
@@ -1451,11 +1452,11 @@ func runSweepChecks(k *verify.Kernel, path, name string, fl asm.FuncLayout, smok
 	return msgs, failed
 }
 
-// cmdVerifyCall implements `gasm verify --call <func> [--buf spec] [--repeat n]`.
-// It invokes a single function with user-supplied buffers and prints the arg
-// block before and after the call, so the user can inspect return values and
-// any output written to the buffers.
-func cmdVerifyCall(k *verify.Kernel, path, funcName, bufSpec string, repeat int) int {
+// cmdVerifyCall implements `gasm verify --call <func> [--buf spec] [--args spec] [--repeat n]`.
+// It invokes a single function with user-supplied buffers and scalar
+// arguments and prints the arg block before and after the call, so the user
+// can inspect return values and any output written to the buffers.
+func cmdVerifyCall(k *verify.Kernel, path, funcName, bufSpec, scalarSpec string, repeat int) int {
 	fl, err := k.Func(funcName)
 	if err != nil {
 		fmt.Fprintf(os.Stderr, "gasm verify: %v\n", err)
@@ -1493,6 +1494,16 @@ func cmdVerifyCall(k *verify.Kernel, path, funcName, bufSpec string, repeat int)
 	defer pool.Close()
 	args := pool.BuildArgs(layout, fl.Args)
 
+	scalars, err := verify.ParseScalarArgs(scalarSpec)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "gasm verify: %v\n", err)
+		return 1
+	}
+	if err := verify.ApplyScalarArgs(args, layout, scalars); err != nil {
+		fmt.Fprintf(os.Stderr, "gasm verify: %v\n", err)
+		return 1
+	}
+
 	fmt.Printf("%s: %d bytes, args=%d\n", funcName, fl.Size, fl.Args)
 	fmt.Printf("  signature: func %s(%s) %s\n", sig.Name, formatParams(sig.Params), formatResults(sig.Results))
 	if len(specs) > 0 {
@@ -1501,6 +1512,17 @@ func cmdVerifyCall(k *verify.Kernel, path, funcName, bufSpec string, repeat int)
 			fmt.Printf("    %s: %d bytes, pattern=%s\n", s.Name, s.Size, s.Pattern)
 		}
 	}
+	if len(scalars) > 0 {
+		names := make([]string, 0, len(scalars))
+		for n := range scalars {
+			names = append(names, n)
+		}
+		sort.Strings(names)
+		fmt.Printf("  scalars:\n")
+		for _, n := range names {
+			fmt.Printf("    %s = %d\n", n, scalars[n])
+		}
+	}
 	fmt.Printf("  args before: %s\n", hexDump(args))
 
 	rc := 0
diff --git a/verify/buffers.go b/verify/buffers.go
index b355d19..1489087 100644
--- a/verify/buffers.go
+++ b/verify/buffers.go
@@ -148,3 +148,73 @@ func fillBuffer(buf []byte, pattern string) {
 		}
 	}
 }
+
+// ApplyScalarArgs writes user-supplied scalar argument values into an ABI0
+// argument block after BuildArgs.  Each name=value pair addresses the layout
+// entry of that parameter name; only word-sized scalar parameters (int,
+// int64, uint64, and their named spellings) accept values, so a typo'd name
+// or a slice parameter fails loudly instead of silently corrupting the call.
+func ApplyScalarArgs(args []byte, layout []ArgOffset, scalars map[string]uint64) error {
+	if len(scalars) == 0 {
+		return nil
+	}
+	byName := make(map[string]ArgOffset, len(layout))
+	for _, l := range layout {
+		byName[l.Name] = l
+	}
+	for name, val := range scalars {
+		l, ok := byName[name]
+		if !ok {
+			return fmt.Errorf("scalar arg %q: no such parameter", name)
+		}
+		if l.IsPtr || l.Size != 8 {
+			return fmt.Errorf("scalar arg %q: parameter has type %s; only word-sized scalars accept values", name, l.Typ)
+		}
+		if l.Offset+8 > len(args) {
+			return fmt.Errorf("scalar arg %q: offset %d outside the %d-byte arg block", name, l.Offset, len(args))
+		}
+		binary.LittleEndian.PutUint64(args[l.Offset:], val)
+	}
+	return nil
+}
+
+// ParseScalarArgs parses a "name=value[,name=value...]" spec into a map.
+// Values are decimal or 0x-prefixed hex.
+func ParseScalarArgs(spec string) (map[string]uint64, error) {
+	out := map[string]uint64{}
+	if strings.TrimSpace(spec) == "" {
+		return out, nil
+	}
+	for _, part := range strings.Split(spec, ",") {
+		part = strings.TrimSpace(part)
+		if part == "" {
+			continue
+		}
+		name, val, err := splitScalar(part)
+		if err != nil {
+			return nil, err
+		}
+		out[name] = val
+	}
+	return out, nil
+}
+
+func splitScalar(part string) (string, uint64, error) {
+	eq := strings.Index(part, "=")
+	if eq <= 0 {
+		return "", 0, fmt.Errorf("scalar arg spec %q: want name=value", part)
+	}
+	name := strings.TrimSpace(part[:eq])
+	valStr := strings.TrimSpace(part[eq+1:])
+	var val uint64
+	var err error
+	if strings.HasPrefix(valStr, "0x") || strings.HasPrefix(valStr, "0X") {
+		_, err = fmt.Sscanf(valStr, "0x%x", &val)
+	} else {
+		_, err = fmt.Sscanf(valStr, "%d", &val)
+	}
+	if err != nil || name == "" {
+		return "", 0, fmt.Errorf("scalar arg spec %q: bad value", part)
+	}
+	return name, val, nil
+}
diff --git a/verify/buffers_test.go b/verify/buffers_test.go
index 5b0fbf9..862c51b 100644
--- a/verify/buffers_test.go
+++ b/verify/buffers_test.go
@@ -156,3 +156,41 @@ func TestBufPoolBuildArgs(t *testing.T) {
 		t.Errorf("src.len = %d, want 128", args[32])
 	}
 }
+
+func TestParseScalarArgs(t *testing.T) {
+	m, err := ParseScalarArgs("n=57,base=0x1f,x= 12 ")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if m["n"] != 57 || m["base"] != 0x1f || m["x"] != 12 {
+		t.Fatalf("parsed %+v", m)
+	}
+	if _, err := ParseScalarArgs("n"); err == nil {
+		t.Error("name-only spec must fail")
+	}
+	if _, err := ParseScalarArgs("n=zz"); err == nil {
+		t.Error("bad value must fail")
+	}
+}
+
+func TestApplyScalarArgs(t *testing.T) {
+	layout := []ArgOffset{
+		{Name: "text", Typ: "*byte", Offset: 0, Size: 8, IsPtr: true},
+		{Name: "n", Typ: "int", Offset: 8, Size: 8, IsPtr: false},
+	}
+	args := make([]byte, 16)
+	if err := ApplyScalarArgs(args, layout, map[string]uint64{"n": 0x1f}); err != nil {
+		t.Fatal(err)
+	}
+	if got := args[8]; got != 0x1f {
+		t.Fatalf("args[8] = %d, want 31", got)
+	}
+	// Pointer parameters reject scalar writes.
+	if err := ApplyScalarArgs(args, layout, map[string]uint64{"text": 5}); err == nil {
+		t.Fatal("pointer param must reject a scalar write")
+	}
+	// Unknown names reject.
+	if err := ApplyScalarArgs(args, layout, map[string]uint64{"nope": 1}); err == nil {
+		t.Fatal("unknown param must reject")
+	}
+}