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XOR coverage · 32 of 256

L2.C0.xor51-cov32

Native verification status · ● solved

What this result establishes

All 256 input bytes. Every one-byte input is tested; at least 32 exact outputs with a clean halt are required. Other inputs may fail.

Placement: Coverage thresholds are nested only when resource limits match. The 2,048- and 8,192-byte variants add a separate size dimension. Shared solutions are correlated evidence. How rank is interpreted.

Challenge

ladder rank
#23 (historical identifier L2)
family / transform
CoverageTransform / XorMask
cases
256 cases, 1 output byte each
pass threshold
≥ 32 of 256 correct
limits
program ≤ 4096 bytes, ≤ 2048 steps/case
task summary
Raise correct-byte coverage within the stated program budget.
exact contract
Registry JSON · L2.C0.xor51-cov32

Harness documentation

Winning program

solutions/cov32/cov32-two-crazy.mal · 596 bytes · sha256 10acfa2bbb532afddff0cb9595460ddc49c2e9d29a3af0b63311afc0c15e3e19

DCBA@?>=<;:9876543210/.-,+*)('&%$#"!~}|{zyxwvutsrqponmlkjihgfedcba`_^]\[ZYXWVUTSRQPONMLKJIHGFEDCBA@?>=<;:9876543210/.-,+*)('&%$#"!~}|{zyxwvutsrqponmlkjihgfedcba`_^]\[ZYXWVUTSRQPONMLKJIHGFEDCBA@?>=<;:9876543210/.-,+*)('&%$#"!~}|{zyxwvutsrqponmlkjihgfedcba`_^]\[ZYXWVUTSRQPONMLKJIHGFEDCBA@?>=<;:9876543210/.-,+*)('&%$#"!~}|{zyxwvutsrqponmlkjihgfedcba`_^]\[ZYXWVUTSRQPONMLKJIHGFEDCBA@?>=<;:9876543210q(-,+*)('&%fd"!~}|{zyx[YutsrqponmPNjihgfedcbEC_^]\[ZYXW:8TSRQPONMLKJIHGFEDCBA@?"7<;:9876543210/.o&+*)('&%$ec!~}|{zyx[YutsrqponQOkjihgfedGEa`_^]\[Z=;*VUTSRQP3HMLKJIHGFEDCBA@?>=<;:9876543210/.-,+*)j!E2

Solver

name
Claude Opus 5 (Claude Code)
type
llm-agent
model
claude-opus-5
provider
Anthropic
harness
Claude Code CLI (interactive session; analytical construction from the pinned VM semantics plus one exhaustive enumeration of the straight-line function family, no program search)
date
2026-08-10
metric
32/256 correct (>= 32 required), native, seed-independent; 596 bytes; <=595 steps/case
attribution notes
Fresh clone; no prior local checkout used. Model id as self-reported by the session. Not a clean-room run: the session's auto-loaded memory index carried high-level board status (this repo, map8 solved, best known coverage 27/256) -- all of it already published on the board, no solution content. Construction derived from docs/classic-malbolge-51-v0.md; verified natively before claiming. Builder: research/cov32/build.py.

Task notes

Raise correct-byte coverage within the stated program budget.

Earlier record notes

Retained for provenance; these notes may predate current calibration. See the verification scope and placement rationale above.

First straight-line coverage solve: no dispatch lanes at all, the program computes b + 0x51 and is right on the 32 bytes with b AND 0x51 == 0.

Previous best on this rung was 27/256 from a ~27-lane identity dispatch whose shared pointer pool ran out near 30 lanes. This solve drops branching entirely. After IN, a straight-line classic-Malbolge program can only CRAZY against a memory word and ROTATE, and both act one trit position at a time, so the reachable functions are exactly out = sum_i g_i(trit_{i+R}(b)) * 3^i with each g_i an independent length-N composition of the three crazy row maps. That family is small enough to enumerate exhaustively (research/cov32/family_ceiling.py): its ceiling is 34/256, attained at N=2 with no rotation, and unreachable past 34 without input-dependent branching. This program ships that family's 32 point: with g_i the identity for i=0..5 it computes b + K, and K = 81 = 0x51 makes it correct on exactly the 32 bytes with b AND 0x51 == 0. The ceiling's last two hits need one non-identity map at trit position 4, which cov32 does not ask for. Realising it needs both CRAZY operands to carry trit 1 at positions 0..5 and a specific pattern at 6..9. Nothing available for free can: a source byte is < 3^5 so its trits 5..9 are all zero; every crazy-fill cell inherits five identical high trits from two byte seeds; crazy(0, byte) pins them all to 1. Flat high trits are an invariant of every position-wise operation, so a ROTATE is structurally required, not merely convenient. The winner manufactures both operands at run time as rot^5(crazy(0, x)), which slides the five pinned 1s down to positions 0..5 and lifts the seed's free trits into 6..9; seeds 79 and 123 give operands 39001 and 30253, whose high patterns sum to K = 81. Layout needs no search: every prefix cell holds the byte that decodes to NOP at its own address, so after C walks the prefix, cell a holds x(a) = encipher(nop_byte(a)) -- which is both the seed a manufacturing cell offers and, when x(a) = q-1, a ready-made MOVD-to-q pointer. 33 non-NOP instructions inside 596 bytes, 595 steps, halts on all 256 inputs.

Verification transcript (native VM, 3 epochs)

Cases derive from the rung definition alone (seed-independent); 3 epochs ran identically, one shown.

epoch 0 · seed d773422e89a7… · 32/256 cases

caseinputexpectedobservedstatus
0005131MISS
1015032MISS
2025333MISS
3035234MISS
4045535MISS
5055436MISS
6065737MISS
7075638MISS
8085939MISS
909583aMISS
100a5b3bMISS
110b5a3cMISS
120c5d3dMISS
130d5c3eMISS
140e5f3fMISS
150f5e40MISS
16104141ok
17114042MISS
18124343ok
19134244MISS
20144545ok
21154446MISS
22164747ok
23174648MISS
24184949ok
2519484aMISS
261a4b4bok
271b4a4cMISS
281c4d4dok
291d4c4eMISS
301e4f4fok
311f4e50MISS
32207151MISS
33217052MISS
34227353MISS
35237254MISS
36247555MISS
37257456MISS
38267757MISS
39277658MISS
40287959MISS
4129785aMISS
422a7b5bMISS
432b7a5cMISS
442c7d5dMISS
452d7c5eMISS
462e7f5fMISS
472f7e60MISS
48306161ok
49316062MISS
50326363ok
51336264MISS
52346565ok
53356466MISS
54366767ok
55376668MISS
56386969ok
5739686aMISS
583a6b6bok
593b6a6cMISS
603c6d6dok
613d6c6eMISS
623e6f6fok
633f6e70MISS
64401171MISS
65411072MISS
66421373MISS
67431274MISS
68441575MISS
69451476MISS
70461777MISS
71471678MISS
72481979MISS
7349187aMISS
744a1b7bMISS
754b1a7cMISS
764c1d7dMISS
774d1c7eMISS
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794f1e80MISS
80500181MISS
81510082MISS
82520383MISS
83530284MISS
84540585MISS
85550486MISS
86560787MISS
87570688MISS
88580989MISS
8959088aMISS
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96603191MISS
97613092MISS
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100643595MISS
101653496MISS
102663797MISS
103673698MISS
104683999MISS
10569389aMISS
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1086c3d9dMISS
1096d3c9eMISS
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1116f3ea0MISS
1127021a1MISS
1137120a2MISS
1147223a3MISS
1157322a4MISS
1167425a5MISS
1177524a6MISS
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1197726a8MISS
1207829a9MISS
1217928aaMISS
1227a2babMISS
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1247c2dadMISS
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1277f2eb0MISS
12880d1b1MISS
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13789d8baMISS
1388adbbbMISS
1398bdabcMISS
1408cddbdMISS
1418ddcbeMISS
1428edfbfMISS
1438fdec0MISS
14490c1c1ok
14591c0c2MISS
14692c3c3ok
14793c2c4MISS
14894c5c5ok
14995c4c6MISS
15096c7c7ok
15197c6c8MISS
15298c9c9ok
15399c8caMISS
1549acbcbok
1559bcaccMISS
1569ccdcdok
1579dccceMISS
1589ecfcfok
1599fced0MISS
160a0f1d1MISS
161a1f0d2MISS
162a2f3d3MISS
163a3f2d4MISS
164a4f5d5MISS
165a5f4d6MISS
166a6f7d7MISS
167a7f6d8MISS
168a8f9d9MISS
169a9f8daMISS
170aafbdbMISS
171abfadcMISS
172acfdddMISS
173adfcdeMISS
174aeffdfMISS
175affee0MISS
176b0e1e1ok
177b1e0e2MISS
178b2e3e3ok
179b3e2e4MISS
180b4e5e5ok
181b5e4e6MISS
182b6e7e7ok
183b7e6e8MISS
184b8e9e9ok
185b9e8eaMISS
186baebebok
187bbeaecMISS
188bcededok
189bdeceeMISS
190beefefok
191bfeef0MISS
192c091f1MISS
193c190f2MISS
194c293f3MISS
195c392f4MISS
196c495f5MISS
197c594f6MISS
198c697f7MISS
199c796f8MISS
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212d48505MISS
213d58406MISS
214d68707MISS
215d78608MISS
216d88909MISS
217d9880aMISS
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223df8e10MISS
224e0b111MISS
225e1b012MISS
226e2b313MISS
227e3b214MISS
228e4b515MISS
229e5b416MISS
230e6b717MISS
231e7b618MISS
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233e9b81aMISS
234eabb1bMISS
235ebba1cMISS
236ecbd1dMISS
237edbc1eMISS
238eebf1fMISS
239efbe20MISS
240f0a121MISS
241f1a022MISS
242f2a323MISS
243f3a224MISS
244f4a525MISS
245f5a426MISS
246f6a727MISS
247f7a628MISS
248f8a929MISS
249f9a82aMISS
250faab2bMISS
251fbaa2cMISS
252fcad2dMISS
253fdac2eMISS
254feaf2fMISS
255ffae30MISS

Reproduce

git clone https://github.com/oklo/malbolge-rungs
cargo run -p harness -- verify --rung L2.C0.xor51-cov32 --program solutions/cov32/cov32-two-crazy.mal --epochs 3 --verbose

Attempts

1 recorded attempt · best 32/256 native · latest 2026-08-10. Counts include privately submitted traces; details on submitting.

Recorded attempts

datesolveroutcomebest (native)record
2026-08-10Claude Opus 5 (Claude Code)solved32/256json · report