diff --git a/models.go b/models.go
index 7624be7..87a5c5e 100644
--- a/models.go
+++ b/models.go
@@ -68,6 +68,8 @@ const (
 	ZapScriptCmdProfile      = "profile"
 	ZapScriptCmdProfileClear = "profile.clear"
 
+	ZapScriptCmdPlaytimeExtend = "playtime.extend"
+
 	ZapScriptCmdInputKey = "input.key" // DEPRECATED
 	ZapScriptCmdKey      = "key"       // DEPRECATED
 	ZapScriptCmdCoinP1   = "coinp1"    // DEPRECATED
diff --git a/playtime_test.go b/playtime_test.go
new file mode 100644
index 0000000..ff0b827
--- /dev/null
+++ b/playtime_test.go
@@ -0,0 +1,169 @@
+// Copyright 2026 The Zaparoo Project Contributors.
+// SPDX-License-Identifier: Apache-2.0
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package zapscript_test
+
+import (
+	"reflect"
+	"testing"
+
+	"github.com/ZaparooProject/go-zapscript"
+	"github.com/google/go-cmp/cmp"
+)
+
+// TestParsePlaytimeExtend covers both amount forms the command accepts, plus
+// the argument combinations a written card is likely to carry.
+func TestParsePlaytimeExtend(t *testing.T) {
+	t.Parallel()
+
+	tests := []struct {
+		name  string
+		input string
+		want  zapscript.Script
+	}{
+		{
+			name:  "duration amount",
+			input: `**playtime.extend:15m?profile=abc123`,
+			want: zapscript.Script{
+				Cmds: []zapscript.Command{
+					{
+						Name:    zapscript.ZapScriptCmdPlaytimeExtend,
+						Args:    []string{"15m"},
+						AdvArgs: zapscript.NewAdvArgs(map[string]string{"profile": "abc123"}),
+					},
+				},
+			},
+		},
+		{
+			name:  "compound duration amount",
+			input: `**playtime.extend:1h30m?profile=abc123`,
+			want: zapscript.Script{
+				Cmds: []zapscript.Command{
+					{
+						Name:    zapscript.ZapScriptCmdPlaytimeExtend,
+						Args:    []string{"1h30m"},
+						AdvArgs: zapscript.NewAdvArgs(map[string]string{"profile": "abc123"}),
+					},
+				},
+			},
+		},
+		{
+			name:  "today amount",
+			input: `**playtime.extend:today?profile=abc123`,
+			want: zapscript.Script{
+				Cmds: []zapscript.Command{
+					{
+						Name:    zapscript.ZapScriptCmdPlaytimeExtend,
+						Args:    []string{zapscript.PlaytimeExtendToday},
+						AdvArgs: zapscript.NewAdvArgs(map[string]string{"profile": "abc123"}),
+					},
+				},
+			},
+		},
+		{
+			// The when argument is global, so it has to survive alongside a
+			// command-specific one.
+			name:  "with global when argument",
+			input: `**playtime.extend:15m?profile=abc123&when=true`,
+			want: zapscript.Script{
+				Cmds: []zapscript.Command{
+					{
+						Name: zapscript.ZapScriptCmdPlaytimeExtend,
+						Args: []string{"15m"},
+						AdvArgs: zapscript.NewAdvArgs(map[string]string{
+							"profile": "abc123",
+							"when":    "true",
+						}),
+					},
+				},
+			},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+			p := zapscript.NewParser(tt.input)
+			got, err := p.ParseScript()
+			if err != nil {
+				t.Fatalf("ParseScript() error = %v", err)
+			}
+			if diff := cmp.Diff(tt.want, got, cmp.AllowUnexported(zapscript.AdvArgs{})); diff != "" {
+				t.Errorf("ParseScript() mismatch (-want +got):\n%s", diff)
+			}
+		})
+	}
+}
+
+// TestPlaytimeExtendRoundTrip checks a parsed command survives String() and
+// reparsing unchanged, so tooling that rewrites a card cannot alter the
+// amount or drop the authorizing profile.
+func TestPlaytimeExtendRoundTrip(t *testing.T) {
+	t.Parallel()
+
+	inputs := []string{
+		`**playtime.extend:15m?profile=abc123`,
+		`**playtime.extend:1h30m?profile=abc123`,
+		`**playtime.extend:today?profile=abc123`,
+	}
+
+	for _, input := range inputs {
+		t.Run(input, func(t *testing.T) {
+			t.Parallel()
+
+			first, err := zapscript.NewParser(input).ParseScript()
+			if err != nil {
+				t.Fatalf("ParseScript() error = %v", err)
+			}
+			if len(first.Cmds) != 1 {
+				t.Fatalf("expected 1 command, got %d", len(first.Cmds))
+			}
+
+			second, err := zapscript.NewParser(first.Cmds[0].String()).ParseScript()
+			if err != nil {
+				t.Fatalf("reparse error = %v", err)
+			}
+
+			if diff := cmp.Diff(first, second, cmp.AllowUnexported(zapscript.AdvArgs{})); diff != "" {
+				t.Errorf("round-trip mismatch (-original +reparsed):\n  string(): %s\n%s",
+					first.Cmds[0].String(), diff)
+			}
+		})
+	}
+}
+
+// TestPlaytimeExtendArgsContract pins the parts of PlaytimeExtendArgs that
+// consumers bind against. This library only declares the tags; the decoding
+// lives in the consumer, so a tag that stops matching its key constant would
+// otherwise fail silently and far from here.
+func TestPlaytimeExtendArgsContract(t *testing.T) {
+	t.Parallel()
+
+	argsType := reflect.TypeOf(zapscript.PlaytimeExtendArgs{})
+
+	profile, ok := argsType.FieldByName("Profile")
+	if !ok {
+		t.Fatal("PlaytimeExtendArgs.Profile is missing")
+	}
+	if got, want := profile.Tag.Get("advarg"), string(zapscript.KeyProfile); got != want {
+		t.Errorf("Profile advarg tag = %q, want %q", got, want)
+	}
+
+	// GlobalArgs has to stay embedded or the global when argument silently
+	// stops reaching the command.
+	if _, ok := argsType.FieldByName("When"); !ok {
+		t.Error("PlaytimeExtendArgs does not embed GlobalArgs")
+	}
+}
diff --git a/types.go b/types.go
index c59e44e..eacbb06 100644
--- a/types.go
+++ b/types.go
@@ -51,6 +51,15 @@ const (
 	KeyName           Key = "name"
 	KeyPreNotice      Key = "pre_notice"
 	KeyHidden         Key = "hidden"
+	KeyProfile        Key = "profile"
+)
+
+// Playtime extension amounts for the playtime.extend command.
+const (
+	// PlaytimeExtendToday waives the session limit for the rest of the
+	// local day instead of adding a fixed amount of time. Any other value
+	// is a Go duration.
+	PlaytimeExtendToday = "today"
 )
 
 // Action values for the action advanced argument.
@@ -187,3 +196,13 @@ type MisterScriptArgs struct {
 	// Hidden controls whether the script window is hidden.
 	Hidden string `advarg:"hidden"`
 }
+
+// PlaytimeExtendArgs contains advanced arguments for the playtime.extend
+// command.
+type PlaytimeExtendArgs struct {
+	GlobalArgs
+	// Profile is the switch ID authorizing the extension, the same value
+	// the profile command takes. It names who permits the grant, not who
+	// receives it.
+	Profile string `advarg:"profile"`
+}