From caa15491c3694dc4f003fe79ed0410ed85eef205 Mon Sep 17 00:00:00 2001
From: Kiss Lorand <50251547+kisslorand@users.noreply.github.com>
Date: Sat, 19 Sep 2026 19:19:54 +0300
Subject: [PATCH] Fix duplicate timelapse G-code on i3 printers (#15734)

---
 src/libslic3r/GCode.cpp        |  2 +-
 tests/fff_print/test_print.cpp | 49 ++++++++++++++++++++++++++++++++++
 2 files changed, 50 insertions(+), 1 deletion(-)

diff --git a/src/libslic3r/GCode.cpp b/src/libslic3r/GCode.cpp
index 81fc81b488..d9cc1d4a11 100644
--- a/src/libslic3r/GCode.cpp
+++ b/src/libslic3r/GCode.cpp
@@ -5628,7 +5628,7 @@ LayerResult GCode::process_layer(
     m_layer = &layer;
     m_object_layer_over_raft = false;
 
-    if (!m_config.time_lapse_gcode.value.empty() && !is_BBL_Printer()) {
+    if (!need_insert_timelapse_gcode_for_traditional && !m_config.time_lapse_gcode.value.empty() && !is_BBL_Printer()) {
         DynamicConfig config;
         config.set_key_value("layer_num", new ConfigOptionInt(m_layer_index));
         config.set_key_value("layer_z", new ConfigOptionFloat(print_z));
diff --git a/tests/fff_print/test_print.cpp b/tests/fff_print/test_print.cpp
index 6bff945fc3..d7cd965343 100644
--- a/tests/fff_print/test_print.cpp
+++ b/tests/fff_print/test_print.cpp
@@ -22,10 +22,59 @@
 #include <algorithm>
 #include <fstream>
 #include <iterator>
+#include <string_view>
 
 using namespace Slic3r;
 using namespace Slic3r::Test;
 
+TEST_CASE("Timelapse g-code is emitted once per layer for Bambu and non-Bambu printers", "[Print][Regression]")
+{
+    struct PrinterCase {
+        std::string name;
+        std::string structure;
+        bool        is_bbl;
+    };
+    const PrinterCase printer = GENERATE(from_range(std::vector<PrinterCase>{
+        { "non-BBL undefined", "undefine", false },
+        { "non-BBL CoreXY",    "corexy",   false },
+        { "non-BBL i3",        "i3",       false },
+        { "non-BBL H-Bot",     "hbot",     false },
+        { "non-BBL Delta",     "delta",    false },
+        { "Bambu CoreXY",      "corexy",   true },
+        { "Bambu i3",          "i3",       true },
+    }));
+    INFO("printer: " << printer.name);
+
+    DynamicPrintConfig config = DynamicPrintConfig::full_print_config();
+    config.set_deserialize_strict({
+        { "initial_layer_print_height", 0.2 },
+        { "layer_change_gcode",          ";TEST_LAYER_CHANGE" },
+        { "layer_height",                0.2 },
+        { "printer_structure",           printer.structure },
+        { "spiral_mode",                 false },
+        { "time_lapse_gcode",            "TIMELAPSE_TAKE_FRAME" },
+    });
+    Print print;
+    print.is_BBL_printer() = printer.is_bbl;
+    Model model;
+    init_print({ cube(20) }, print, model, config);
+    const std::string gcode = Slic3r::Test::gcode(print);
+
+    const auto count = [&gcode](std::string_view token) {
+        size_t occurrences = 0;
+        size_t pos = 0;
+        while ((pos = gcode.find(token, pos)) != std::string::npos) {
+            ++occurrences;
+            pos += token.size();
+        }
+        return occurrences;
+    };
+
+    const size_t layer_changes = count("\n;TEST_LAYER_CHANGE\n");
+    REQUIRE(layer_changes > 0);
+    CHECK(count("\nTIMELAPSE_TAKE_FRAME\n") == layer_changes);
+}
+
 SCENARIO("Changing the number of solid shell layers does not make all surfaces internal", "[Print]") {
     GIVEN("sliced 20mm cube and config with top_shell_layers = 2 and bottom_shell_layers = 1") {
         Slic3r::DynamicPrintConfig config = Slic3r::DynamicPrintConfig::full_print_config();