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.

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.