Prelims
a) R12C5 = {16/25/34}, no 7,8,9
b) R12C6 = {16/25/34}, no 7,8,9
c) R34C5 = {18/27/36/45}, no 9
d) R45C1 = {18/27/36/45}, no 9
e) R4C89 = {16/25/34}, no 7,8,9
f) R5C34 = {14/23}
g) R5C67 = {39/48/57}, no 1,2,6
h) R67C5 = {29/38/47/56}, no 1
i) R67C8 = {16/25/34}, no 7,8,9
j) 20(3) cage at R1C7 = {389/479/569/578}, no 1,2
k) 21(5) cage at R8C3 = {489/579/678}, no 1,2,3
l) 6(3) cage at R8C6 = {123}
m) 32(5) cage at R4C4 = {26789/35789/45689}, no 1
1a. Naked triple {123} in 6(3) cage at R8C6, locked for N8, clean-up: no 8,9 in R6C5
1b. 32(5) cage at R4C4 = {26789/35789/45689}, 8,9 locked for N5, clean-up: no 1 in R3C5, no 3,4 in R5C7
1c. Killer triple 1,2,3 in R12C6 and R89C6, locked for C6, clean-up: no 9 in R5C7
1d. 45 rule on N8 3 innies R7C456 = 21 = {489/579/678}
1e. 45 rule on N4 3 innies R456C3 = 17 = {179/269/278/359/368/458/467}
1f. R5C3 = {1234} -> no 1,2,3,4 in R46C3
1g. 45 rule on N3 2 outies R3C6 + R4C7 = 15 = {69/78}
1h. R3C6 + R4C7 = 15 -> R1C9 + R2C8 + R3C7 = 13
1i. 45 rule on N7 2 outies R6C3 + R7C4 = 14 = {59/68}
1j. R6C3 + R7C4 = 14 -> R7C3 + R8C2 + R9C1 = 10 = {127/136/145/235}, no 8,9
1k. 45 rule on D/ 3 innies R4C6 + R5C5 + R6C4 = 22 = {589/679}, 9 locked for N5 and D/
1l. R4C6 + R5C5 + R6C4 = 22 -> R4C4 + R6C6 = 10 = [28/37/46/64]
1m. 45 rule on C5 3 innies R589C5 = 18 = {189/239/369/378} (cannot be {459/468/567} because R8C5 only contains 1,2,3), no 4,5
2a. 45 rule on R456789 3 innies R4C357 = 16 = {169/178/259/268/349/358/367/457}
2b. 1,2,3,4 only in R4C5 -> R4C5 = {1234}, clean-up: no 2,3,4 in R3C5
2c. 45 rule on N5 4 innies R46C5 + R5C46 = 13 = {1237/1246/1345}
2d. 7 of {1237} must be in R5C6 -> no 7 in R6C4, clean-up: no 4 in R7C5
2e. Consider placement for 5 in C5
R12C5 = {25}, 2 locked for C5, R46C5 cannot be [13] because R34C5 = [81] clashes with R67C5 = [38] (or, more simply, R46C5 = [13] clashes with R8C5) => R46C5 + R5C46 cannot be {1237}
or R34C5 = [54] => R46C5 + R5C46 = {1246/1345}
or R67C5 = {56} => R46C5 + R5C46 = {1246/1345}
-> R46C5 + R5C46 = {1246/1345}, no 7, 4 locked for N5, clean-up: no 6 in R4C4 + R6C6 (step 1l), no 5 in R5C7
2f. 45 rule on C789 3 outies R357C6 = 20 = {479/569} (cannot be {578} which clashes with R6C6), no 8, 9 locked for C6, clean-up: no 7 in R4C7 (step 1g)
2g. R5C6 = {45} -> no 4,5 in R7C6
2h. 8 in C6 only in R46C6, locked for N5
2i. Consider combinations for R357C6 = {479/569}
R357C6 = {479}, locked for C6 => R6C6 = 8, R4C6 + R5C5 + R6C4 (step 1k) = {679} => R4C6 = 6
or R357C6 = {569} => R5C6 = 5
-> R46C5 + R5C46 = {1345}, 3,5 locked for N5, clean-up: no 7 in R3C5, no 3 in R5C3, no 5,9 in R7C5
[Cracked. Fairly straightforward from here.]
2j. R4C6 + R5C5 + R6C4 = {679}, 6,7 locked for D/, 7 locked for N5
2k. R4C4 = 2, R6C6 = 8, both placed for D\, clean-up: no 5 in R4C89, no 7 in R5C1, no 6 in R7C4 (step 1i)
2l. Naked triple {679} in R347C6, 6 locked for C6, clean-up: no 1 in R12C6
2m. 1 in C6 only in R89C6, locked for N8
2n. 8 on D/ only in R1C9 + R2C8 + R3C7, locked for N3 and 28(5) cage at R1C9, clean-up: no 7 in R3C6 (step 1g)
2o. Naked pair {69} in R3C6 + R4C7, CPE no 6 in R4C6 -> R4C6 = 7, clean-up: no 2 in R5C1
2p. R37C6 = {69} -> R5C6 = 5, R5C7 = 7, clean-up: no 2 in R12C6, no 4 in R4C1, no 6 in R7C5
2q. 20(3) cage at R1C7 = {479/569}, no 3, 9 locked for N3
2r. 7 of {479} must be in R1C8 -> no 4 in R1C8
2s. R7C3 + R8C2 + R9C1 (step 1j) = 10 = {145/235}, 5 locked for N7 and D/
2t. Naked pair {34} in R12C6, locked for N2, 3 locked for C6
2u. R8C5 = 3 (hidden single in N8), R6C5 = 4 -> R7C6 = 7, R4C5 = 1 -> R3C5 = 8, R5C4 = 3 -> R5C3 = 2, clean-up: no 6 in R12C5, no 6 in R4C1, no 6 in R4C89, no 8 in R5C1, no 3 in R7C8
2v. Naked pair {25} in R12C5, 5 locked for N2
2w. R456C3 (step 1e) = 17, R5C3 = 2 -> R46C3 = 15 = {69}, locked for C3 and N4, clean-up: no 3 in R4C1, no 9 in R7C4 (step 1i)
2x. Naked pair {34} in R4C89, locked for R4 and N6, clean-up: no 4 in R7C8
2y. Naked pair {69} in R7C6 + R9C5, locked for N8
2z. 21(3) cage at R8C3 = {489/678} -> R9C2 = {69}, R89C3 = {478}, 8 locked for C3 and N8
2aa. Naked pair {69} in R9C25, locked for R9
2ab. Naked pair {58} in R4C12, locked for N4
2ac. Naked pair {14} in R5C12, 1 locked for R5 and N4
2ad. Naked pair {69} in R6C34, 6 locked for R6, clean-up: no 1 in R7C8
2ae. 8 in N6 only in R5C89, locked for 29(5) cage at R5C8
2af. 8 in N9 only in 18(3) cage at R8C7 = {189/378/468}, no 2,5
2ag. 6,9 of {189/468} must be in R8C7 -> no 1,4 in R8C7
2ah. 7 of {378} must be in R9C8 -> no 3 in R9C8
3a. R7C4 = 8 (hidden single in R7) -> R6C3 = 6 (step 1i), R4C3 = 9, R6C4 = 9 -> R5C5 = 6, placed for D\, R4C7 = 6 -> R3C6 = 9, R7C6 = 6, R9C5 = 9, clean-up: no 1 in R6C8
3b. R9C2 = 6 -> R89C3 = 15 = {78}, 7 locked for C3 and N7
3c. Naked pair {89} in R5C89, 9 locked for 29(5) cage at R5C8
3d. R5C9 = 9 (hidden single in C9) -> R5C8 = 8
3e. R8C9 = 6 (hidden single in R8), R5C89 = 17 -> R67C9 = 6 = [15/24/51]
3f. R7C8 = 2 (hidden single in N9) -> R6C8 = 5 -> R67C9 = [15/24]
3g. Naked pair {12} in R6C79, CPE no 1 in R9C9
3h. R8C7 = {89} -> R9C78 = 9,10 = {18}/[37], no 4
3i. Killer pair 7,8 in R9C3 and R9C78, locked for R9
3j. Naked triple {345} in R479C9, locked for C9
3k. R1C9 = 8 (hidden single in C9)
3l. R2C1 = 8 (hidden single in N1), R4C1 = 5 -> R5C1 = 4, R5C2 = 1
3m. 7 in C9 only in R23C9, locked for N3
3n. R23C9 = {17/27} -> R3C8 = {34}
3o. 20(3) cage at R1C7 = {569} (only remaining combination) -> R12C7 = {59}, locked for C7
3p. R8C7 = 8 -> R9C78 = 10 = [37]
4a. Naked pair {34} in R34C8, locked for R8 -> R2C8 = 1, R3C7 = 4 (cage sum), both placed for D/
4b. R67C7 = [21], R8C8 = 9, R9C9 = 4 (cage sum), 1,4,9 placed for D\
and the rest is naked singles.