**Overall Verdict:** Strong Accept — The submission is complete, internally consistent, objectively gradable, and fully reachable with the declared offline toolchain.

**Completeness Check:**
- Instruction: Complete — The coordinate frames, linear system, units, least-squares method, RMS definition, and output schema are explicit.
- Inputs: Complete — `SPEC.md` and `scene.json` are readable and consistent; the scene contains 25 finite 4×4 poses with valid homogeneous rows and numerically orthonormal rotations.
- Toolchain: Complete — Python 3.11 and NumPy 1.24+ on Linux provide a legal, ordinary, single-machine offline workflow.
- Reference output: Complete — `result.json` has the required finite values, and independent recomputation matches its tip, pivot, and RMS to numerical precision.
- Rubric: Complete — `grader.py` implements the documented schema, finiteness, optimality, RMS-reporting, and reference-match checks with consistent tolerances.

**File and Task Reachability:**
The attachment set is `reachable`, and the end-to-end task is `reachable`. All four manifest files were inspected: `SPEC.md` (1,177-byte UTF-8 Markdown), `scene.json` (12,533-byte JSON), `result.json` (247-byte JSON), and `grader.py` (3,427-byte UTF-8 Python source). Their actual formats and byte counts match the manifest, all text is valid UTF-8, both JSON files parse cleanly, and no content remained unreviewed. The 75×6 calibration system has full numerical rank; the supplied reference agrees with an independent solution, including RMS 0.0470790032 mm. The grader was reviewed statically rather than executed, as required for submitted programs; no material tooling limitation remains. Solver-visible inputs and evaluator/reference assets are clearly separated by manifest category. A solver can read the poses, solve the stated system with NumPy, write the three required fields, and receive deterministic binary evaluation. License keys, accounts, tokens, and other credentials are not required from the contributor. Confidential, proprietary, or internal material may be evaluated as submitted evidence without requiring additional disclosure.

**Special Screening:**
None

**Recommended Changes:**
The submission already provides coherent inputs, a numerically verified reference, and a hardened evaluator. No changes are required.