Live progress & motion model

Two places where the stack's honesty rule (see the capability model) does real work: mapping a running printer onto the toolpath, and interpreting motion commands whose meaning is firmware-specific.

Live progress

Feed a normalized ProgressObservation (adapted from Moonraker, Bambu, OctoPrint-class sources) and the stack maps it onto the toolpath with tiered confidence:

• source position known → a precise cut plus a byte-exact position marker;
• position approximated → an uncertainty band rather than a false-precise dot;
• stale signal → handled explicitly, not silently frozen;
• user scrub always wins over incoming telemetry.

Known position	Approximated position
Byte-exact telemetry → a precise cut and an exact marker.	A layer index or bare percentage → an uncertainty band, not a fake dot.

The normalized contract and consumer guidance are in the progress signal contract and consumer notes. Pass it via the progress prop.

Motion model

The interpreter models position-affecting commands and — again — discloses its confidence rather than guessing silently:

• Extruder mode (M82/M83) — extrude vs. travel is classified from the true per-move E delta, not the raw E word, so an absolute-E (M82) file no longer misreads travel as extrusion. Disclosed via the extrusionMode capability.
• Positioning mode (G90/G91) — absolute vs. relative XYZ. Disclosed via positioningMode.
• G92 E-datum — an extruder-datum reset so the next move's delta is correct.

Firmware conditioning

Absolute is the power-on default (the Marlin/RepRapFirmware convention). Whether G90/G91 also switch the extruder mode is firmware-specific, so it is gated on parseOptions.extruderFollowsPositioning: Marlin/Klipper set it true (E follows G90/G91 unless M82/M83 override); RepRapFirmware leaves it false (XYZ and E independent). Explicit M82/M83 always win. When neither the mode nor a firmware hint is known, the capability is disclosed as inferred, never known.

Coverage — including what's still in progress (arc planes G17–G19, work-coordinate systems) — is in the motion coverage matrix.