[script] Fix parallel mode scripts with delays cancelling each other (#10324)

esphome/core/base_automation.h

@@ -5,6 +5,8 @@
 #include "esphome/core/hal.h"
 #include "esphome/core/defines.h"
 #include "esphome/core/preferences.h"
+#include "esphome/core/scheduler.h"
+#include "esphome/core/application.h"
 
 #include <vector>
 
@@ -158,7 +160,16 @@ template<typename... Ts> class DelayAction : public Action<Ts...>, public Compon
   void play_complex(Ts... x) override {
     auto f = std::bind(&DelayAction<Ts...>::play_next_, this, x...);
     this->num_running_++;
-    this->set_timeout("delay", this->delay_.value(x...), f);
+
+    // If num_running_ > 1, we have multiple instances running in parallel
+    // In single/restart/queued modes, only one instance runs at a time
+    // Parallel mode uses skip_cancel=true to allow multiple delays to coexist
+    // WARNING: This can accumulate delays if scripts are triggered faster than they complete!
+    // Users should set max_runs on parallel scripts to limit concurrent executions.
+    // Issue #10264: This is a workaround for parallel script delays interfering with each other.
+    App.scheduler.set_timer_common_(this, Scheduler::SchedulerItem::TIMEOUT,
+                                    /* is_static_string= */ true, "delay", this->delay_.value(x...), std::move(f),
+                                    /* is_retry= */ false, /* skip_cancel= */ this->num_running_ > 1);
   }
   float get_setup_priority() const override { return setup_priority::HARDWARE; }
 

esphome/core/scheduler.cpp

@@ -65,14 +65,17 @@ static void validate_static_string(const char *name) {
 
 // Common implementation for both timeout and interval
 void HOT Scheduler::set_timer_common_(Component *component, SchedulerItem::Type type, bool is_static_string,
-                                      const void *name_ptr, uint32_t delay, std::function<void()> func, bool is_retry) {
+                                      const void *name_ptr, uint32_t delay, std::function<void()> func, bool is_retry,
+                                      bool skip_cancel) {
   // Get the name as const char*
   const char *name_cstr = this->get_name_cstr_(is_static_string, name_ptr);
 
   if (delay == SCHEDULER_DONT_RUN) {
     // Still need to cancel existing timer if name is not empty
-    LockGuard guard{this->lock_};
-    this->cancel_item_locked_(component, name_cstr, type);
+    if (!skip_cancel) {
+      LockGuard guard{this->lock_};
+      this->cancel_item_locked_(component, name_cstr, type);
+    }
     return;
   }
 
@@ -97,7 +100,9 @@ void HOT Scheduler::set_timer_common_(Component *component, SchedulerItem::Type
   if (delay == 0 && type == SchedulerItem::TIMEOUT) {
     // Put in defer queue for guaranteed FIFO execution
     LockGuard guard{this->lock_};
-    this->cancel_item_locked_(component, name_cstr, type);
+    if (!skip_cancel) {
+      this->cancel_item_locked_(component, name_cstr, type);
+    }
     this->defer_queue_.push_back(std::move(item));
     return;
   }
@@ -150,9 +155,11 @@ void HOT Scheduler::set_timer_common_(Component *component, SchedulerItem::Type
     return;
   }
 
-  // If name is provided, do atomic cancel-and-add
+  // If name is provided, do atomic cancel-and-add (unless skip_cancel is true)
   // Cancel existing items
-  this->cancel_item_locked_(component, name_cstr, type);
+  if (!skip_cancel) {
+    this->cancel_item_locked_(component, name_cstr, type);
+  }
   // Add new item directly to to_add_
   // since we have the lock held
   this->to_add_.push_back(std::move(item));

esphome/core/scheduler.h

@@ -21,8 +21,13 @@ struct RetryArgs;
 void retry_handler(const std::shared_ptr<RetryArgs> &args);
 
 class Scheduler {
-  // Allow retry_handler to access protected members
+  // Allow retry_handler to access protected members for internal retry mechanism
   friend void ::esphome::retry_handler(const std::shared_ptr<RetryArgs> &args);
+  // Allow DelayAction to call set_timer_common_ with skip_cancel=true for parallel script delays.
+  // This is needed to fix issue #10264 where parallel scripts with delays interfere with each other.
+  // We use friend instead of a public API because skip_cancel is dangerous - it can cause delays
+  // to accumulate and overload the scheduler if misused.
+  template<typename... Ts> friend class DelayAction;
 
  public:
   // Public API - accepts std::string for backward compatibility
@@ -184,7 +189,7 @@ class Scheduler {
 
   // Common implementation for both timeout and interval
   void set_timer_common_(Component *component, SchedulerItem::Type type, bool is_static_string, const void *name_ptr,
-                         uint32_t delay, std::function<void()> func, bool is_retry = false);
+                         uint32_t delay, std::function<void()> func, bool is_retry = false, bool skip_cancel = false);
 
   // Common implementation for retry
   void set_retry_common_(Component *component, bool is_static_string, const void *name_ptr, uint32_t initial_wait_time,