**Overall Verdict:** Strong Accept — The submission is complete, internally consistent, professionally constructed, and end-to-end reachable with objective exact scoring and effective evaluator-data separation.

**Completeness Check:**
- Instruction: Complete — Clearly defines the transition semantics, retained-row boundaries, `null` behavior, JSONL schema, ordering rule, and exact scoring.
- Inputs: Complete — Provides 20 valid evaluation streams, ten person-disjoint worked examples, manifests, format documentation, and a submission template.
- Toolchain: Complete — Requires only Python 3.11 standard-library functionality on Linux and is feasible on an ordinary single machine.
- Reference output: Complete — Contains all 20 gold rows, original-marker provenance fields, selection records, construction logic, validation evidence, and scorer diagnostics.
- Rubric: Complete — Defines 40 independently scored exact decisions, rejects partial credit, validates value ranges and ordering, and includes coherent perfect, empty, uniform-thirds, and all-null controls.

**File and Task Reachability:**
Attachment classification: `reachable`. Task classification: `reachable`.

All three files were inspected: `pisa_variable_phase_transition_nearterm_20_v1_participant.zip`, `pisa_variable_phase_transition_nearterm_20_v1_reference_and_provenance.zip`, and `pisa_variable_phase_transition_nearterm_20_v1_selftest_evidence.zip`. Their byte counts match the manifest, all ZIP members pass integrity checks, and no encryption, traversal paths, links, device entries, or excessive expansion were found.

The participant archive contains 47 regular files. All JSON and JSONL parsed successfully, all 30 raw-file hashes matched their manifests, and every base64-gzip message was decoded and schema-checked. Retained-row counts match for all streams; removed marker names and source identifiers were absent even after decoding. The reference archive contains 72 readable files, including gold, provenance, scorer source, controls, rankings, and a byte-identical participant copy. The self-test archive contains three structurally valid 20-row submissions and one valid PNG; the reported 16/40, 22/40, and 20/40 results were independently reproduced from the supplied submissions and gold.

The completion path is clear: decode the streams, infer boundaries using the worked examples, produce the required 20-row JSONL, and evaluate it against the sealed gold. Uploaded programs were inspected as source rather than executed; published validation and scoring results were independently checked from the underlying data. No relevant attachment content remained unreviewed.

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. No affirmative evidence supports an AI-synthetic, public-benchmark, or synthetic-defect-fixture label for these protected session streams and task-specific gold.

**Recommended Changes:**
The package has strong input/reference separation, reproducible boundary derivation, consistent manifests, and credible blind difficulty evidence. No changes are required.