diff --git a/esphome/components/canbus/canbus.h b/esphome/components/canbus/canbus.h
index 122ccfe39e..f7b84111bd 100644
--- a/esphome/components/canbus/canbus.h
+++ b/esphome/components/canbus/canbus.h
@@ -115,14 +115,13 @@ template<typename... Ts> class CanbusSendAction : public Action<Ts...>, public P
   void set_data_template(std::vector<uint8_t> (*func)(Ts...)) {
     // Stateless lambdas (generated by ESPHome) implicitly convert to function pointers
     this->data_.func = func;
-    this->static_ = false;
+    this->len_ = -1;  // Sentinel value indicates template mode
   }
 
   // Store pointer to static data in flash (no RAM copy)
   void set_data_static(const uint8_t *data, size_t len) {
-    this->data_.static_data.ptr = data;
-    this->data_.static_data.len = len;
-    this->static_ = true;
+    this->data_.data = data;
+    this->len_ = len;  // Length >= 0 indicates static mode
   }
 
   void set_can_id(uint32_t can_id) { this->can_id_ = can_id; }
@@ -138,9 +137,11 @@ template<typename... Ts> class CanbusSendAction : public Action<Ts...>, public P
     auto use_extended_id =
         this->use_extended_id_.has_value() ? *this->use_extended_id_ : this->parent_->use_extended_id_;
     std::vector<uint8_t> data;
-    if (this->static_) {
-      data.assign(this->data_.static_data.ptr, this->data_.static_data.ptr + this->data_.static_data.len);
+    if (this->len_ >= 0) {
+      // Static mode: copy from flash to vector
+      data.assign(this->data_.data, this->data_.data + this->len_);
     } else {
+      // Template mode: call function
       data = this->data_.func(x...);
     }
     this->parent_->send_data(can_id, use_extended_id, this->remote_transmission_request_, data);
@@ -150,14 +151,11 @@ template<typename... Ts> class CanbusSendAction : public Action<Ts...>, public P
   optional<uint32_t> can_id_{};
   optional<bool> use_extended_id_{};
   bool remote_transmission_request_{false};
-  bool static_{true};  // Default to static mode (most common case)
+  ssize_t len_{-1};  // -1 = template mode, >=0 = static mode with length
   union Data {
-    std::vector<uint8_t> (*func)(Ts...);  // 4 bytes on 32-bit
-    struct {
-      const uint8_t *ptr;  // 4 bytes on 32-bit
-      size_t len;          // 4 bytes on 32-bit
-    } static_data;         // 8 bytes total on 32-bit
-  } data_;                 // Union size = 8 bytes (max of 4 and 8)
+    std::vector<uint8_t> (*func)(Ts...);  // Function pointer (stateless lambdas)
+    const uint8_t *data;                  // Pointer to static data in flash
+  } data_;
 };
 
 class CanbusTrigger : public Trigger<std::vector<uint8_t>, uint32_t, bool>, public Component {