# Concept 27 R2 source provenance

This is a local integration of the actual BRep builder supplied by Adam MCP task
`da122c5a-e392-47b7-a53f-a52d949eabb7`. The unmodified checkpoint is preserved as
`Adam_checkpoint_build_Concept_27_R2.py.reference`, SHA-256
`314c4b3db5402d2ea1a9cad1017c10e3a8c85a0aa207fc605b105e101a91fd51`.

The builder imports the checksum-locked, published Concept 27 R1 STEP. It does
not recreate the exterior from an image or replace it with the 5.2 shell.
Supplied electronic component geometry is transformed rigidly and remains
separate from the manufactured parts.

The local parameter file was authored from measured hardware and R1 datums; it
is not presented as an Adam-delivered parameter file. Its provenance field
separates measurements from selected prototype dimensions. PCB registration to
the first Adam hardware checkpoint used all 306 corresponding solid centroids,
with a maximum residual of 2.64e-9 mm. This registration is not itself a fit
or full surface-congruence test.

Local corrections to the checkpoint:

- Move only the hidden side-carrier drive pads to the actual plungers' Z=-11.3
  plane. Keep visible faces, carrier capture flanges and stops unchanged.
- Add coordinated clearance through the new LED cradle and keeper; relieve the
  light coupler around the actual LED dome by 0.20 mm. Cut the new cradle before
  joining it to the original shell so the existing lens interface is retained.
- Name the two disconnected pieces of the notched left battery pad separately,
  in both installed and free states. No pad bridges the protection module.
- Create output directories in the builder so the source is portable.
- Correct the audit's side-plunger selection to the third solid of each
  supplied switch, require actual carrier contact, and limit allowed screw
  overlaps to their matching nominal thread regions. Preserve and quantify the
  original lens press fit instead of masking arbitrary lens/shell clashes.

Use the final validation records for acceptance. Source code and source PASS
labels alone do not establish assembly fit. Foam force, switch overtravel,
return force, optical performance, harness routing, RF performance and physical
prototype durability require qualification on real parts.

Final measured corrections also include:

- Four paired PCB support sites on verified bare-board edges; remove old rear
  overhangs that contacted SMD geometry and relieve the left front web in the
  inherited cable channel. The lower support clears the switch clamp and rear stop.
- Broad battery pads, side/end liners, split protection-module pad and support
  rails ending below the front closure bosses.
- Speaker mounting-ear keepers in place of the SR2 magnet bridge; correct the
  microphone ring/membrane to the existing raised acoustic nozzle.
- Nonmetal LTE frame with header clearance, PET seat pocket and two 3 mm internal
  driver approach reliefs. Fit upper battery liners after the antenna screws.
- Nominal M2.5x12 closure screws on Z=-17.9 head seats; flexible rim installed
  last. Complete front-clamp pilot cavities through the intervening 0.2 mm web.
  The original main pilot was already accessible with the board removed.
- USB bridge clearance for the actual signal pins and matching side-actuator
  passages. Preserve the original lens press-fit volume.
- Serial OCC topology validation. ShapeFix repairs an inherited cut-face wire
  orientation only when bounds and volume are unchanged. STL export removes
  only triangles collapsed to repeated vertices by float32 quantization; it
  keeps thin nonzero triangles and requires a watertight result.

The last change removes 29.443954 mm3 from the rear shell for driver approach.
Reconstruction from the saved pre-relief BRep by two cylinder cuts matches final
volume, area and face count. A coincident-solid Boolean gave an invalid result
and was rejected as proof. Final static and cover checks are rerun; affected
retention contacts and access gauges are rechecked. Control geometry remains
unchanged. See final_change_review.json for the scope of each check.

Fastener representation correction: bd-warehouse simple=True exports the minor-diameter core and the head/drive, not a full major-diameter body. The unchanged reference geometry is labeled accordingly. A separate 18-screw major-diameter envelope audit checks matching thread-pilot intersections and off-axis clearance. Mating helical threads and fastening force remain unmodeled.