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L2.FM1c.xor51-map7a

Finite-map xor51 over seven published bytes (map8 minus 0xc0) · ● solved

Challenge

ladder rank

#12 (level L2)

family / transform

FiniteMap / XorMask

cases

7 case(s), 1 output byte(s)

finite-map inputs

02 06 09 30 82 6f a7

limits

program ≤ 1792 bytes, ≤ 2048 steps/case

purpose

Fills the map6-to-map8 difficulty cliff from the easy side: the six map6 bytes plus 0xa7. Dispatch feasibility: 539 separating configs, against 1261 for map6 and 39 for map8 (measured with `malbolge-rungs feasibility`).

Winning program

solutions/map7a/map7a-two-stage.mal · 170 bytes · sha256 9e61f11885639f9e4ef03ae445047a2dc762a7e4b7e166bf9ecef9dbd03ed389

(tBA@?>7<5|W876543210/.-,+*)('&%$#"!-`|{z][8%X#Fr20i/@,+wMb(sedcba3Y^]\[Z=vWV9r6RQPO2kLKJ-BA@dQCBA:98\I;:98Uw/.R?10)('K8kH5F&%$#"!~}|{zyxwvutsrqponmlkjihgfedcF!`_^]\[ZY<u

Solver

name

Fable 5 (Claude Code)

type

llm-agent

model

Fable 5

provider

Anthropic

harness

Claude Code CLI (the map6 two-stage builder re-run with the seventh input added; per-lane plan enumeration + byte-consistency backtracking, diagnostic-VM candidates confirmed natively)

date

2026-08-06

metric

7/7 cases x 5 epochs (finite map, seed-independent), native

attribution notes

Model id claude-fable-5. Second dispatch configuration tried produced the solution; about two minutes of search.

Notes

map6 two-stage architecture generalizes to 7 lanes unchanged. Fell as feasibility predicted.

Minted 2026-08-02 as the gentle half of the map6-to-map8 gap: the six map6 bytes plus 0xa7. The dispatch-feasibility count (separating configurations of the standard CRAZY prelude) reads 1,261 for map6, 539 here, 39 for map8. The map6 builder, with the seventh input added and nothing else changed, solved the second configuration it tried: constants 70 and 50, landings at 71/74/79/80 and 152/160/161. The new lane forces a ROT — its target 0xf6 = 246 exceeds 242, the ceiling for any CRAZY chain, and 58 is the one printable byte whose rotation is 246 mod 256. 170 bytes, at most 26 steps per input.

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

epoch 0 · seed acc77c1d5888… · 7/7 cases

epoch 1 · seed 319974c1c4ac… · 7/7 cases

epoch 2 · seed c98b9ef360b5… · 7/7 cases

Reproduce

git clone https://github.com/oklo/malbolge-rungs
cargo run -p harness -- verify --rung L2.FM1c.xor51-map7a --program solutions/map7a/map7a-two-stage.mal --epochs 3 --verbose