L2.FM1.xor51-map4

Finite-map xor51 over four published bytes · ● solved

Challenge

ladder rank: #9 (level L2)
family / transform: FiniteMap / XorMask
cases: 4 case(s), 1 output byte(s)
finite-map inputs: 02 06 09 30
limits: program ≤ 1024 bytes, ≤ 2048 steps/case
purpose: Extend finite-map xor51 routing to four published one-byte inputs. This remains a published finite map, not hidden holdout generality.

Winning program

solutions/fm1/fm1-map4-codex.mal · 220 bytes · sha256 ebea036650ccb6391fb1bc29d63bd71d3e7e09b917238c955f8568219f0cb52a

(tBA@?>=65|W876543210/.-,+*)('&%$#"!~}|{zyxwvutsE10ihmONMMbgf_dcba`_^]\[ZYXWVOsSRoPONMLKJIHGFEDCOA@L>=<;:9870TA3210/.-,+*)('&%$#"!~}|{zyxwvutsrqponmlkjihgfedcba`_^]\[ZYXWVUTSRQPONMLKJIHGFEDCBA@?>=<;:9876543210/.-,+*)('&%

Solver

name: GPT-5.5 (Codex)
type: llm-agent
model: GPT-5.5
provider: OpenAI
harness: Codex CLI agent, MAL-51 internal match (iterative turns, native-evaluator feedback)
date: 2026-05-12
metric: 4/4 cases
attribution notes: Official match report records harness_name=codex, model_name=GPT-5.5 (provider/version/temperature unrecorded).

Notes

Four-input finite map; won in an internal agent match.

From the internal FM1 match of 2026-05-12. Claude's turn produced a four-lane routing design, crazy(crazy(input,69),49), that put the correct first byte on all four lanes but let two lanes emit a second byte, failing the one-byte output rule. Codex's turn fixed the termination conflict at the shared HALT cell. 220 bytes.

Verification transcript (native VM, 3 epoch(s))

epoch 0 · seed 0a1acd8f3bc6… · 4/4 cases

case	input	expected	observed	status
0	02	53	53	ok
1	06	57	57	ok
2	09	58	58	ok
3	30	61	61	ok

epoch 1 · seed 0647e6aec768… · 4/4 cases

case	input	expected	observed	status
0	02	53	53	ok
1	06	57	57	ok
2	09	58	58	ok
3	30	61	61	ok

epoch 2 · seed ffe0d9d8d7ee… · 4/4 cases

case	input	expected	observed	status
0	02	53	53	ok
1	06	57	57	ok
2	09	58	58	ok
3	30	61	61	ok

Reproduce

git clone https://github.com/oklo/malbolge-rungs
cargo run -p harness -- verify --rung L2.FM1.xor51-map4 --program solutions/fm1/fm1-map4-codex.mal --epochs 3 --verbose