Fix styled switch-back repaint

internal/harness/runner.go

@@ -3,6 +3,7 @@ package harness
 import (
 	"encoding/json"
 	"fmt"
+	"regexp"
 	"strings"
 )
 
@@ -74,6 +75,43 @@ func runStep(s *Session, step Step, results map[string]json.RawMessage) error {
 			return fmt.Errorf("screen does not contain %q:\n%s", step.Contains, screen)
 		}
 		return nil
+	case "assert_not_contains":
+		screen, err := s.Screen()
+		if err != nil {
+			return err
+		}
+		if strings.Contains(screen, step.Contains) {
+			return fmt.Errorf("screen contains %q:\n%s", step.Contains, screen)
+		}
+		return nil
+	case "mark_raw":
+		if step.SaveAs == "" {
+			return fmt.Errorf("mark_raw requires save_as")
+		}
+		raw, err := json.Marshal(s.RawOffset())
+		if err != nil {
+			return err
+		}
+		results[step.SaveAs] = raw
+		return nil
+	case "assert_raw_since_regex":
+		raw, ok := results[step.From]
+		if !ok {
+			return fmt.Errorf("no saved result %q", step.From)
+		}
+		var offset int
+		if err := json.Unmarshal(raw, &offset); err != nil {
+			return fmt.Errorf("saved result %q is not a raw offset: %w", step.From, err)
+		}
+		re, err := regexp.Compile(step.Regex)
+		if err != nil {
+			return err
+		}
+		b := s.RawSince(offset)
+		if !re.Match(b) {
+			return fmt.Errorf("raw output since %q does not match %q:\n%s", step.From, step.Regex, string(b))
+		}
+		return nil
 	case "assert_regex":
 		return s.WaitForRegex(step.Regex, timeoutMS(step.TimeoutMS))
 	case "wait_text":

internal/harness/scenarios/switch_replay_clears_viewport.json

@@ -0,0 +1,35 @@
+{
+  "name": "switch_replay_clears_viewport",
+  "cols": 80,
+  "rows": 24,
+  "scripts": [
+    {
+      "name": "blanktop",
+      "body": "#!/bin/sh\nprintf '\\033[2;1HFIRST-ROW-TWO\\n'\nsleep 5\n"
+    }
+  ],
+  "steps": [
+    {
+      "type": "mcp_call",
+      "method": "spawn_process",
+      "params": { "kind": "command", "argv": ["blanktop"], "name": "first" },
+      "save_as": "first"
+    },
+    { "type": "wait_text", "contains": "FIRST-ROW-TWO", "timeout_ms": 5000 },
+    {
+      "type": "mcp_call",
+      "method": "spawn_process",
+      "params": { "kind": "command", "argv": ["sh", "-lc", "echo SECOND READY; sleep 5"], "name": "second" },
+      "save_as": "second"
+    },
+    { "type": "wait_text", "contains": "SECOND READY", "timeout_ms": 5000 },
+    {
+      "type": "mcp_call",
+      "method": "select_process",
+      "params": { "process_id": "{{first.process_id}}" }
+    },
+    { "type": "wait_stable", "timeout_ms": 5000 },
+    { "type": "assert_contains", "contains": "FIRST-ROW-TWO" },
+    { "type": "assert_not_contains", "contains": "SECOND READY" }
+  ]
+}

internal/harness/scenarios/switch_replay_preserves_color.json

@@ -0,0 +1,36 @@
+{
+  "name": "switch_replay_preserves_color",
+  "cols": 80,
+  "rows": 24,
+  "scripts": [
+    {
+      "name": "color-frame",
+      "body": "#!/bin/sh\nprintf '\\033[31mREDMARK\\033[0m\\n'\nsleep 5\n"
+    }
+  ],
+  "steps": [
+    {
+      "type": "mcp_call",
+      "method": "spawn_process",
+      "params": { "kind": "command", "argv": ["color-frame"], "name": "color" },
+      "save_as": "color"
+    },
+    { "type": "wait_text", "contains": "REDMARK", "timeout_ms": 5000 },
+    {
+      "type": "mcp_call",
+      "method": "spawn_process",
+      "params": { "kind": "command", "argv": ["sh", "-lc", "echo SECOND READY; sleep 5"], "name": "second" },
+      "save_as": "second"
+    },
+    { "type": "wait_text", "contains": "SECOND READY", "timeout_ms": 5000 },
+    { "type": "mark_raw", "save_as": "before_switch_back" },
+    {
+      "type": "mcp_call",
+      "method": "select_process",
+      "params": { "process_id": "{{color.process_id}}" }
+    },
+    { "type": "wait_stable", "timeout_ms": 5000 },
+    { "type": "assert_contains", "contains": "REDMARK" },
+    { "type": "assert_raw_since_regex", "from": "before_switch_back", "regex": "\u001b\\[[0-9;]*38;2;[^m]*mREDMARK" }
+  ]
+}

internal/harness/session.go

@@ -262,3 +262,23 @@ func (s *Session) rawBytes() []byte {
 	copy(out, s.bytes)
 	return out
 }
+
+func (s *Session) RawOffset() int {
+	s.bytesMu.Lock()
+	defer s.bytesMu.Unlock()
+	return len(s.bytes)
+}
+
+func (s *Session) RawSince(offset int) []byte {
+	s.bytesMu.Lock()
+	defer s.bytesMu.Unlock()
+	if offset < 0 {
+		offset = 0
+	}
+	if offset > len(s.bytes) {
+		offset = len(s.bytes)
+	}
+	out := make([]byte, len(s.bytes)-offset)
+	copy(out, s.bytes[offset:])
+	return out
+}