Tools and debugging

Beyond viewing and analyzing, the Custom G-code Editor provides tools for modifying G-code precisely, reordering sections safely, and debugging execution step by step.

Precision editing tools

Select any range of lines (in the editor or via the Outline Panel) and apply targeted modifications. Every operation shows you exactly what will change before you confirm.

Selection operations

Tool	What it does	Example
Change speed	Multiply or set feedrate for all moves in the selection	Multiply all `F` values by 0.8 to slow a section by 20%
Change flow	Scale E values by a multiplier	Multiply all `E` values by 1.1 for 10% more extrusion
Insert temperature	Add a temperature command at the start of the selection	Insert `M104 S210` before a specific layer
Insert fan	Add a fan speed command at the start of the selection	Insert `M106 S200` to increase cooling
Insert pause	Insert a firmware-aware pause (Marlin `M0`, Prusa `M601`, Klipper `PAUSE`, Bambu `M400 U1` — never `M600` on Bambu)	Insert a pause at the current line
Insert custom G-code	Insert any G-code snippet at the cursor	Add a custom priming sequence or retraction routine

Each tool has an input field for the value and an Apply button. Confirm opens a Monaco diff of current vs proposed text. After Apply you can undo typing with Ctrl+Z in the editor, or restore a snapshot.

Batch operations

These apply to the entire file with one click:

Operation	What it does
Normalize feedrate	Ensures every `G1` move has an explicit `F` parameter (inherits from the last set feedrate)
Merge redundant temps	Removes consecutive `M104` commands with the same target temperature
Remove no-ops	Removes `G1` commands that don't change any coordinates
Toggle extrusion mode	Switches between `M82` (absolute) and `M83` (relative) extrusion

Spatial operations

These are geometry-aware operations that modify the toolpath structure:

Operation	What it does
Linearize Arcs	Converts G2/G3 arc commands into G1 linear segments at a configurable chord length (0.1–2.0mm). Makes arcs editable as individual points. E values are distributed evenly across generated segments.
Fit arcs	Inverse of linearize: weld stable G1 runs into G2/G3 within a tolerance (default 0.05 mm). Refused when the printer profile has `arcSupport` off.
Redistribute	Re-spaces points evenly along their paths at a target spacing while preserving corners sharper than the threshold angle. Total extrusion per path segment is conserved.

Both operations can target the current selection or the entire file.

Safe reordering

The reorder engine lets you rearrange sections of G-code (layers, regions within layers) while checking for dependency breaks — problems that would occur if the machine state isn't correct at section boundaries.

How it works

Initiate — drag sections in the Outline Panel or select a reorder from the context menu
Analyze — the system simulates machine state at every boundary and checks for breaks
Preview — a dialog shows:
Approve — toggle which transitions to include, then confirm or cancel
Apply — the source is updated with sections in the new order and approved transitions inserted

Dependency break types

Break type	What's wrong	Auto-fixable?
Temperature	Nozzle not at expected temperature	Yes (inserts `M109`)
Homing	Motion before G28 in new order	Yes (inserts `G28`, requires approval)
Extrusion mode	M82/M83 mismatch at boundary	Yes (inserts mode switch)
Motion mode	G90/G91 mismatch at boundary	Yes (inserts mode switch)
Retraction	Retracted/unretracted state mismatch	Yes (inserts `G10`/`G11`)
Fan	Fan speed differs at boundary	Yes (inserts `M106`/`M107`)
Position	Large XY jump without travel	Yes (inserts `G0` travel)
Z collision	Z decreases after reorder	No (requires manual decision)

Use cases

Print infill before perimeters for strength optimization
Reorder islands to reduce travel distance
Group similar features for thermal consistency
Move support sections for better surface quality

Bed array

The Array card in the Custom G-code dock copies the motion body across the bed (grid or polar). Startup and shutdown stay once. Optional snippet between copies (for example M0 ; pause). A bed-fit warning appears if copies leave the machine volume. This is a tool, not a separate app: use </> from a vase module, then array.

Snapshots

Snapshots let you save named versions of your G-code as you work. Think of them as manual save points.

Creating a snapshot

Open the Snapshots tab in the dock
Type a name (e.g. "Before speed change" or "Original import")
Click Save

The snapshot stores the full G-code source text with a timestamp and line count.

Managing snapshots

Restore — click to replace the current source with the snapshot's content
Delete — remove a snapshot you no longer need
Compare — opens a Monaco diff of the snapshot versus the current source

Debugger

The G-code debugger lets you step through commands one at a time and inspect the complete machine state at every line — like a debugger for code, but for printer instructions.

Machine state inspector

At the current debug line, you can see every tracked value:

Field	Description
X, Y, Z	Current nozzle position (mm)
E	Current E position (mm)
F	Current feedrate (mm/min)
Total extruded	Cumulative filament used (mm)
Nozzle target	Target nozzle temperature (°C)
Bed target	Target bed temperature (°C)
Fan speed	Fan PWM value (0-255)
Flow	Volumetric flow rate (mm3/s)
Move distance	Distance of current move (mm)
Elapsed time	Estimated time from start (s)
Extrusion mode	Absolute or relative
Motion mode	Absolute or relative
Retracted	Yes or No
Acceleration	Current acceleration (mm/s2)

Step controls

Control	Action
Step Forward	Advance one line
Step Backward	Go back one line
Next Command	Skip blank lines and comments
To Breakpoint	Run until the next breakpoint
Layer	Jump to next layer change
Retract	Jump to next retraction
Temp	Jump to next temperature change

Breakpoints

Click Add BP to set a breakpoint at the current line. Breakpoints show as red badges in the sidebar. During playback, execution pauses automatically when a breakpoint is reached.

Set breakpoints on any line
Clear individual breakpoints or all at once
Click a breakpoint badge to jump to that line

Watch expressions

Select which machine state fields to monitor in the Watch panel. Watched values update in real time as you step through commands. This is useful for tracking how a specific value (like temperature or flow) changes over the course of the file.

Viewport actions

Click a toolpath in the 3D view to select a line, then use the action HUD:

Pause — firmware-aware (M0 / M601 / PAUSE / Bambu M400 U1)
Filament change — dialect snippet (never M600 on Bambu)
Slow 50% — insert a feedrate override at the selection
Fan — insert M106 / dialect equivalent
Skip layer — jump the remaining body of the current layer
Copy line — copy the raw command

The Outline panel context menu offers the same pause / filament / slow / fan actions.

Resume from Z

If a print failed part-way, Resume from Z keeps the startup sequence, drops motion below the chosen Z, then splices a firmware-aware recover block (G90, M82, G92 E0). It does not emit G28 Z. Klipper uses SET_KINEMATIC_POSITION; Marlin homes X/Y only.