[BUG] FILAMENT_CHANGE_RESUME_ON_INSERT does not automatically continue after filament insertion

[Dharmesh40]

Did you test the latest bugfix-2.1.x code?

Yes, and the problem still exists.

Bug Description

When FILAMENT_CHANGE_RESUME_ON_INSERT is enabled, Marlin still waits for the user to press the button after the "Insert filament" prompt. Reinserting filament changes the runout sensor state correctly, but the printer does not automatically continue or begin loading the filament.

The behavior is identical whether the filament change is initiated by:

• M600
• Automatic filament runout (FILAMENT_RUNOUT_SCRIPT "M600")

The feature comment says:

#define FILAMENT_CHANGE_RESUME_ON_INSERT
// Automatically continue / load filament when runout sensor is triggered again.

but this does not occur.

Configuration

Marlin branch: bugfix-2.1.x

Compiled: Jun 12 2026

Relevant configuration:

#define FILAMENT_RUNOUT_SENSOR
#define FIL_RUNOUT_STATE LOW
#define FIL_RUNOUT_PULLUP
#define FILAMENT_RUNOUT_SCRIPT "M600"

#define ADVANCED_PAUSE_FEATURE
#define FILAMENT_CHANGE_RESUME_ON_INSERT

Hardware

• Ender-3
• Single mechanical filament runout switch
• Single extruder
• Bowden setup

Bug Timeline

Compiled: Jun 12 2026

Expected behavior

When the runout sensor detects filament again, Marlin should automatically continue to the loading sequence without requiring the user to press the button.

Actual behavior

The LCD continues displaying the "Insert filament and press button" prompt.

The runout sensor changes state correctly, but Marlin waits indefinitely until the button is pressed.

Steps to Reproduce

Case 1

1. Start a print.
2. Execute M600.
3. Remove the filament.
4. Reinsert the filament.

Case 2

1. Start a print.
2. Allow the runout sensor to trigger M600.
3. Reinsert the filament.

Version of Marlin Firmware

bugfix-2.1.x

Printer model

Creality Ender-3

Electronics

Single mechanical filament runout switch and stock electronics (Creality board 4.2.2)

LCD/Controller

CR10_STOCKDISPLAY

Other add-ons

TouchMI auto bed levelling sensor

Bed Leveling

ABL Bilinear mesh

Your Slicer

Other (explain below)

Host Software

OctoPrint

Don't forget to include

• A ZIP file containing your Configuration.h and Configuration_adv.h.

Additional information & file uploads

Configuration.h and Configuration_adv.h..zip
i use Orca slicer and some times Cura

[Dharmesh40]

Additional investigation

After further debugging, I found that FILAMENT_CHANGE_RESUME_ON_INSERT never takes effect during the normal M600 flow because the firmware waits inside wait_for_confirmation() before reaching the existing auto-insert logic in load_filament().

As a test, I added a sensor check inside wait_for_confirmation(). This immediately enabled automatic loading, confirming that this is where the feature is missing.

On my Ender-3, the filament runout sensor is mounted approximately 10 mm before the extruder. This introduces a race condition because the old filament is still inside the sensor when wait_for_confirmation() begins.

As a temporary workaround, I delayed enabling the sensor check for a few seconds:

  // Wait for filament insert by user and press button
  KEEPALIVE_STATE(PAUSED_FOR_USER);
  TERN_(HOST_PROMPT_SUPPORT, hostui.continue_prompt(GET_TEXT_F(MSG_NOZZLE_PARKED)));
  TERN_(EXTENSIBLE_UI, ExtUI::onUserConfirmRequired(GET_TEXT_F(MSG_NOZZLE_PARKED)));
  
  const millis_t auto_insert_delay = millis() + 10000; // 10 seconds MY CODE DHARMESH STARTS 

  wait_for_user = true;    // LCD click or M108 will clear this
  while (wait_for_user) {
    
    // --- ADD THIS SENSOR CHECK BLOCK ---
    #if ALL(FILAMENT_CHANGE_RESUME_ON_INSERT, HAS_FILAMENT_SENSOR)

  // Ignore the runout sensor for a few seconds after unloading
  if (ELAPSED(millis(), auto_insert_delay)) {
    if (READ(FIL_RUNOUT_PIN) != FIL_RUNOUT_STATE)
      wait_for_user = false;
  }
    #endif
    // ---------------------------------------- MY CODE DHARMESH ENDS

With this change:

• Automatic resume works correctly.
• The printer waits while I remove the old filament.
• I can prepare a new filament.
• As soon as the new filament reaches the runout sensor, loading begins automatically.
• Manual button presses are no longer required.

I believe this demonstrates that the missing sensor check is inside wait_for_confirmation(). The fixed delay is only a workaround for my hardware placement; a proper upstream solution would ideally use an explicit state machine rather than a timeout.