diff --git a/cmd/entire/cli/agent/opencode/entire_plugin.ts b/cmd/entire/cli/agent/opencode/entire_plugin.ts
index 8544aa59a..a8a30d274 100644
--- a/cmd/entire/cli/agent/opencode/entire_plugin.ts
+++ b/cmd/entire/cli/agent/opencode/entire_plugin.ts
@@ -75,11 +75,11 @@ export const EntirePlugin: Plugin = async ({ directory }) => {
               seenUserMessages.clear()
               messageStore.clear()
               currentModel = null
+              await callHook("session-start", {
+                session_id: session.id,
+              })
             }
             currentSessionID = session.id
-            await callHook("session-start", {
-              session_id: session.id,
-            })
             break
           }
 
diff --git a/cmd/entire/cli/agent/opencode/hooks_test.go b/cmd/entire/cli/agent/opencode/hooks_test.go
index 744714b26..aaf39a593 100644
--- a/cmd/entire/cli/agent/opencode/hooks_test.go
+++ b/cmd/entire/cli/agent/opencode/hooks_test.go
@@ -101,6 +101,45 @@ func TestInstallHooks_LocalDev(t *testing.T) {
 	}
 }
 
+func TestInstallHooks_SessionStartIsGuardedBySessionSwitch(t *testing.T) {
+	dir := t.TempDir()
+	t.Chdir(dir)
+	ag := &OpenCodeAgent{}
+
+	if _, err := ag.InstallHooks(context.Background(), false, false); err != nil {
+		t.Fatalf("install failed: %v", err)
+	}
+
+	pluginPath := filepath.Join(dir, ".opencode", "plugins", "entire.ts")
+	data, err := os.ReadFile(pluginPath)
+	if err != nil {
+		t.Fatalf("plugin file not created: %v", err)
+	}
+
+	content := string(data)
+	guard := "if (currentSessionID !== session.id) {"
+	hook := `await callHook("session-start", {`
+	currentSessionAssignment := "currentSessionID = session.id"
+
+	guardIdx := strings.Index(content, guard)
+	hookIdx := strings.Index(content, hook)
+	assignIdx := strings.Index(content, currentSessionAssignment)
+
+	if guardIdx == -1 {
+		t.Fatalf("plugin file missing guard %q", guard)
+	}
+	if hookIdx == -1 {
+		t.Fatalf("plugin file missing session-start hook call %q", hook)
+	}
+	if assignIdx == -1 {
+		t.Fatalf("plugin file missing current session assignment %q", currentSessionAssignment)
+	}
+	if !(guardIdx < hookIdx && hookIdx < assignIdx) {
+		t.Fatalf("expected guarded session-start call before session assignment, got guard=%d hook=%d assignment=%d",
+			guardIdx, hookIdx, assignIdx)
+	}
+}
+
 func TestInstallHooks_ForceReinstall(t *testing.T) {
 	dir := t.TempDir()
 	t.Chdir(dir)