**Overall Verdict:** Accept — The task is complete, objectively evaluable, and supported by a compliant reference circuit and substantial proof evidence.

**Completeness Check:**

- Instruction: Complete — Deliverables, permitted gates, wire ordering, budgets, theorem types, and prohibited proof shortcuts are explicit.
- Inputs: Complete — The table contains 256 valid sixteen-bit outputs and matches the unchanged Lean specification; all duplicated inputs agree.
- Toolchain: Complete — Lean 4.19.0, a pinned Mathlib revision, and build instructions establish a suitable open-source Linux workflow.
- Reference output: Complete — Independent checks confirm 490 total gates, including 96 AND gates, exact agreement on all 256 inputs, and identical ordered Lean and JSON circuit data.
- Rubric: Complete — The 20/30/50-point allocation clearly separates functional correctness, budget compliance, and formal verification.

**File and Task Reachability:**

Attachment classification: `reachable`. Inspected `paired_substitution_inputs.zip`, `paired_substitution_reference.zip`, and `paired_substitution_evidence.zip`, including their specifications, tables, circuits, proof sources, checking instructions, scripts, configurations, licensing notice, and logs. All three archives match manifest sizes, pass archive integrity checks, and contain safe member paths without encryption. Text members are readable UTF-8.

All 256 reference proof traces independently match recomputed gate values. The proof sources cover every input, and supplied build logs report successful Lean checking with only permitted axiom dependencies. Lean compilation was not independently repeated. Bundled executables and compiled Lean objects received format-level inspection only and were not executed or trusted.

Task classification: `reachable`. A single-machine workflow supports synthesis, exhaustive circuit testing, ordered data comparison, source compilation, and theorem-type and axiom inspection. Supplied records report approximately 27 minutes for reference proof checking. The self-test correctly documents an unsuccessful 20/100 attempt, not a compliant solution. Solver inputs contain no reference implementation.

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. BearSSL-derived AES components are disclosed with a license notice, but this does not establish that the generated paired target or complete answer is a public benchmark. Public availability of the exact task could not be independently checked; AI fabrication is not established.

**Recommended Changes:**

The precise specification, independently validated reference circuit, and detailed verification evidence support readiness. No changes are required.