fix: support nested tmux sessions with correct detach hints

cmd/sidecar/main.go

@@ -60,7 +60,7 @@ func main() {
 	// Unset TMUX so sidecar's internal tmux sessions are independent of any
 	// outer tmux session. This allows prefix+d to detach from the workspace's
 	// inner session rather than the user's outer tmux.
-	os.Unsetenv("TMUX")
+	_ = os.Unsetenv("TMUX")
 
 	// Start pprof server if enabled (for memory profiling)
 	if pprofPort := os.Getenv("SIDECAR_PPROF"); pprofPort != "" {

internal/plugins/workspace/shell.go

@@ -2,6 +2,7 @@ package workspace
 
 import (
 	"fmt"
+	"os"
 	"os/exec"
 	"path/filepath"
 	"regexp"
@@ -22,6 +23,11 @@ const (
 	shellSessionPrefix = "sidecar-sh-" // Distinct from worktree prefix "sidecar-ws-"
 )
 
+// launchedInsideTmux is true if sidecar was started from within an existing
+// tmux session (i.e. TMUX env var was set at process start). This is captured
+// at package init time, before main() unsets TMUX for nested session support.
+var launchedInsideTmux = os.Getenv("TMUX") != ""
+
 // tmuxInstalled caches whether tmux is available in PATH.
 // Checked once and cached to avoid repeated exec calls.
 var (
@@ -70,6 +76,18 @@ func getTmuxPrefix() string {
 	return tmuxPrefixCached
 }
 
+// getTmuxDetachHint returns the key sequence hint for detaching from a nested
+// tmux session. When sidecar was launched inside an existing tmux session, the
+// user needs to press the prefix twice (once to reach the inner session) before
+// pressing d. Otherwise a single prefix + d suffices.
+func getTmuxDetachHint() string {
+	prefix := getTmuxPrefix()
+	if launchedInsideTmux {
+		return prefix + " " + prefix + " d"
+	}
+	return prefix + " d"
+}
+
 // tmuxNotationToHuman converts tmux key notation to human-readable format.
 // Examples: C-b → Ctrl-b, C-a → Ctrl-a, M-x → Alt-x
 func tmuxNotationToHuman(notation string) string {

internal/plugins/workspace/view_preview.go

@@ -229,11 +229,11 @@ func (p *Plugin) renderOutputContent(width, height int) string {
 		hint = interactiveStyle.Render("INTERACTIVE") + " " + dimText(p.getInteractiveExitKey()+" exit • "+p.getInteractiveAttachKey()+" attach")
 	} else {
 		// Only show "E for interactive" hint if feature flag is enabled
-		prefix := getTmuxPrefix()
+		detach := getTmuxDetachHint()
 		if features.IsEnabled(features.TmuxInteractiveInput.Name) {
-			hint = dimText(fmt.Sprintf("t to attach • E for interactive • %s d to detach", prefix))
+			hint = dimText(fmt.Sprintf("t to attach • E for interactive • %s to detach", detach))
 		} else {
-			hint = dimText(fmt.Sprintf("t to attach • %s d to detach", prefix))
+			hint = dimText(fmt.Sprintf("t to attach • %s to detach", detach))
 		}
 	}
 	height-- // Reserve line for hint
@@ -432,11 +432,11 @@ func (p *Plugin) renderShellOutput(width, height int) string {
 		hint = interactiveStyle.Render("INTERACTIVE") + " " + dimText(p.getInteractiveExitKey()+" exit")
 	} else {
 		// Only show "E for interactive" hint if feature flag is enabled
-		prefix := getTmuxPrefix()
+		detach := getTmuxDetachHint()
 		if features.IsEnabled(features.TmuxInteractiveInput.Name) {
-			hint = dimText(fmt.Sprintf("t to attach • E for interactive • %s d to detach", prefix))
+			hint = dimText(fmt.Sprintf("t to attach • E for interactive • %s to detach", detach))
 		} else {
-			hint = dimText(fmt.Sprintf("t to attach • %s d to detach", prefix))
+			hint = dimText(fmt.Sprintf("t to attach • %s to detach", detach))
 		}
 	}
 	height-- // Reserve line for hint