diff --git a/internal/tmux/tmux.go b/internal/tmux/tmux.go
index fe2b097c..749106ea 100644
--- a/internal/tmux/tmux.go
+++ b/internal/tmux/tmux.go
@@ -9,12 +9,18 @@ import (
 	"os/exec"
 	"regexp"
 	"strings"
+	"sync"
 	"time"
 
 	"github.com/steveyegge/gastown/internal/config"
 	"github.com/steveyegge/gastown/internal/constants"
 )
 
+// sessionNudgeLocks serializes nudges to the same session.
+// This prevents interleaving when multiple nudges arrive concurrently,
+// which can cause garbled input and missed Enter keys.
+var sessionNudgeLocks sync.Map // map[string]*sync.Mutex
+
 // versionPattern matches Claude Code version numbers like "2.0.76"
 var versionPattern = regexp.MustCompile(`^\d+\.\d+\.\d+$`)
 
@@ -420,11 +426,28 @@ func (t *Tmux) SendKeysDelayedDebounced(session, keys string, preDelayMs, deboun
 	return t.SendKeysDebounced(session, keys, debounceMs)
 }
 
+// getSessionNudgeLock returns the mutex for serializing nudges to a session.
+// Creates a new mutex if one doesn't exist for this session.
+func getSessionNudgeLock(session string) *sync.Mutex {
+	actual, _ := sessionNudgeLocks.LoadOrStore(session, &sync.Mutex{})
+	return actual.(*sync.Mutex)
+}
+
 // NudgeSession sends a message to a Claude Code session reliably.
 // This is the canonical way to send messages to Claude sessions.
 // Uses: literal mode + 500ms debounce + ESC (for vim mode) + separate Enter.
 // Verification is the Witness's job (AI), not this function.
+//
+// IMPORTANT: Nudges to the same session are serialized to prevent interleaving.
+// If multiple goroutines try to nudge the same session concurrently, they will
+// queue up and execute one at a time. This prevents garbled input when
+// SessionStart hooks and nudges arrive simultaneously.
 func (t *Tmux) NudgeSession(session, message string) error {
+	// Serialize nudges to this session to prevent interleaving
+	lock := getSessionNudgeLock(session)
+	lock.Lock()
+	defer lock.Unlock()
+
 	// 1. Send text in literal mode (handles special characters)
 	if _, err := t.run("send-keys", "-t", session, "-l", message); err != nil {
 		return err
@@ -455,7 +478,13 @@ func (t *Tmux) NudgeSession(session, message string) error {
 
 // NudgePane sends a message to a specific pane reliably.
 // Same pattern as NudgeSession but targets a pane ID (e.g., "%9") instead of session name.
+// Nudges to the same pane are serialized to prevent interleaving.
 func (t *Tmux) NudgePane(pane, message string) error {
+	// Serialize nudges to this pane to prevent interleaving
+	lock := getSessionNudgeLock(pane)
+	lock.Lock()
+	defer lock.Unlock()
+
 	// 1. Send text in literal mode (handles special characters)
 	if _, err := t.run("send-keys", "-t", pane, "-l", message); err != nil {
 		return err