Prelims
a) R34C5 = {17/26/35}, no 4,8,9
b) R5C23 = {29/38/47/56}, no 1
c) R5C78 = {29/38/47/56}, no 1
d) R67C5 = {29/38/47/56}, no 1
e) 11(3) cage at R1C7 = {128/137/146/236/245}, no 9
f) 11(3) cage at R2C1 = {128/137/146/236/245}, no 9
g) 20(3) cage at R2C3 = {389/479/569/578}, no 1,2
h) 8(3) cage at R2C7 = {125/134}
i) 23(3) cage at R2C8 = {689}
j) 20(3) cage at R5C4 = {389/479/569/578}, no 1,2
k) 8(3) cage at R6C2 = {125/134}
l) 11(3) cage at R7C3 = {128/137/146/236/245}, no 9
m) 22(3) cage at R7C8 = {589/679}
n) 11(3) cage at R9C7 = {128/137/146/236/245}, no 9
Steps Resulting From Prelims
1a. Naked triple {689} in 23(3) cage at R2C8, locked for N3
1b. 8(3) cage at R6C2 = {125/134}, 1 locked for R6
1c. 22(3) cage at R7C8 = {589/679}, 9 locked for N9
1d. 9 in C7 only in R456C7, locked for N6, clean-up: no 2 in R5C7
2a. 45 rule on R5 2 innies R5C19 = 3 = {12}, locked for R5, clean-up: no 9 in R5C23, no 9 in R5C7
2b. 9 in R5 only in 20(3) cage at R5C4, 9 locked for N5, clean-up: no 2 in R7C5
2c. 45 rule on R1 3 innies R1C456 = 22 = {589/679}, 9 locked for R1 and N2
2d. 45 rule on R1 3 outies R2C456 = 9 = {126/135/234}, no 7,8
2e. 45 rule on R123 3 innies R3C159 = 19 = {379/469/478/568} (cannot be {289} because 8,9 only in R3C1), no 1,2, clean-up: no 6,7 in R4C5
2f. 8,9 only in R3C1 -> R3C1 = {89}
2g. 45 rule on N1 1 innie R3C1 = 1 outie R3C4 + 2, R3C1 = {89} -> R3C4 = {67}
2h. 20(3) cage at R2C3 = {479/569/578} (cannot be {389} because R3C4 only contains 6,7), no 3
2i. R3C4 = {67] -> no 6,7 in R23C3
2j. Killer pair 8,9 in R3C1 and 20(3) cage, locked for N1
2k. 8 in R1 only in R1C456 = {589}, 5 locked for R1 and N2, clean-up: no 3 in R4C5
2l. R2C456 = 9 = {126/234}, 2 locked for R2 and N2
2m. 7 in N2 only in R3C45, locked for R3
2n. 45 rule on N3 1 innie R3C9 = 1 outie R3C6 + 3 -> R3C6 = 1, R3C9 = 4
2o. R2C456 = {234}, 3,4 locked for R2, 3 locked for N2 -> R2C7 = 5, R3C7 = 2 (cage sum), clean-up: no 5 in R4C5, no 6 in R5C8
2p. Naked pair {67} in R3C45, 6 locked for R3
2q. R3C23 = [35] (hidden pair in R3) -> R2C12 = 8 = {17}, locked for N1, clean-up: no 6 in R5C2, no 8 in R5C3
2r. 30(5) cage at R3C1 = {24789/25689} (cannot be {15789} which clashes with R2C1, cannot be {34689/35679/45678} because R5C1 only contained 1,2) -> R5C1 = 2, R3467C1 = {4789/5689}, no 1,3, 8,9 locked for C1
2s. Killer pair 4,6 in R1C1 and R3467C1, locked for C1
2t. 3 in C1 only in R89C1, locked for N7
2u. R3C9 = 4, R5C9 = 1 -> 19(5) cage at R3C9 = {12457/13456}, no 8, 5 locked for C9
2v. Killer pair 3,7 in R1C9 and 19(5) cage, locked for C9
2w. 11(3) cage at R9C7 = {128/146/236/245} (cannot be {137} because R9C9 only contains 2,6,8), no 7
2x. 45 rule on N9 3 innies R78C7 + R7C9 = 12 = {138/147/237/345} (cannot be {156/246} which clash with 11(3) cage), no 6
3a. 45 rule on N7 1 innie R7C1 = 1 outie R7C4 + 3 -> R7C4 = {123456}
3b. 45 rule on N9 1 outie R7C6 = 1 innie R7C9 + 2 -> R7C6 = {4579}
3c. 45 rule on R789 3 innies R7C159 = 17 = {269/278/359/368/458/467}
3d. R7C159 = {269/278/359/458/467} (cannot be {368} because [683] clashes with R7C14 = [63], CCC, cannot be [863] because R7C14 = [85] clashes with R7C69 = [53], CCC)
3e. 5 of {359/458} must be in R7C9 (cannot be {59}3 which clashes with R7C69 = [53], CCC) -> no 5 in R7C15, no 3 in R7C9, clean-up: no 6 in R6C5, no 2 in R7C4, no 5 in R7C6
3f. {278} must be [872] (cannot be [782] because R7C14 = [74] clashes with R7C69 = [42], CCC), 7 of {467} must be in R7C9 -> no 7 in R7C1, clean-up: no 4 in R7C4
3g. 45 rule on N8 3 innies R7C456 = 16 = {169/178/349/367/457} (cannot be {358} because R7C6 only contains 4,7,9)
3h. R7C456 = {178/349/367/457} (cannot be {169} = [169] because R7C14 = [41] blocks 14(3) cage at R7C6 = 9{14})
3i. {367} must be [637] (cannot be [367] which clashes with R7C14 = [63], CCC) -> no 6 in R7C5, clean-up: no 5 in R6C5
3j. 45 rule on N7 3 innies R7C1 + R78C3 = 14 = {149/167/248}
3k. 6 of {167} must be in R7C1 -> no 6 in R78C3
3l. 18(3) cage at R9C1 = {369/378/459/567} (cannot be {189/279/468} which clash with R7C1 + R78C3), no 1,2
3m. 13(3) cage at R7C2 = {139/157/238/256} (cannot be {148/247} which clash with R7C1 + R78C3, cannot be {346} which clash with 18(3) cage), no 4
4a. R3C1 = R3C4 + 2 (step 2g) -> R3C14 = [86/97]
4b. R7C1 = R7C4 + 3 (step 3a) -> R7C14 = [41/63/85] (cannot be [96] which clashes with R3C14), no 9 in R7C1, no 6 in R7C4
[With hindsight I ought to have seen this after step 3a but I was specifically focussed on R7 at the time.]
4c. R7C456 (step 3h) = {178/349/457}
4d. 3 of {349} must be in R7C4 -> no 3 in R7C5, clean-up: no 8 in R6C5
4e. R7C1 + R78C3 (step 3j) = {167/248}
4f. 13(3) cage at R7C2 (step 3m) = {139/157/238} (cannot be {256} which clashes with R7C1 + R78C3), no 6
4g. 18(3) cage at R9C1 (step 3l) = {369/459/567} (cannot be {378} which clashes with R7C1 + R78C3), no 8
4h. 14(3) cage at R7C6 = 4{37}/7{34}/9{14}, no 8 in R78C7
4i. R78C7 + R7C9 (step 2x) = {147/237/345}
4j. 11(3) cage at R9C7 (step 2w) = {128/236} (cannot be {146} which clashes with 18(3) cage, cannot be {245} which clashes with R78C7 + R7C9), no 4,5, 2 locked for R9 and N9, clean-up: no 4 in R7C6 (step 3b)
4k. Killer pair 5,7 in 22(3) cage at R7C8 and R7C9, locked for N9
4l. 4 in N9 only in R78C7, locked for C7, clean-up: no 7 in R5C8
4m. R7C456 = {178/349} (cannot be {457} which clashes with R7C9), no 5, clean-up: no 8 in R7C1
4n. R7C6 = {79} -> no 7,9 in R7C5, clean-up: no 2,4 in R6C5
4o. Naked pair {46} in R17C1, locked for C1
4p. Killer pair 4,6 in R7C1 and 18(3) cage, locked for N7
5a. R7C69 (step 3b) = [75/97], 7 locked for R7
5b. R7C1457 (steps 3a and 4m) = [4183/6341], 1 locked for R7
5c. 11(3) cage at R7C3 = {128} (cannot be {137} because R7C3 only contains 2,8) -> R7C4 = 1, R7C1 = 4, R7C5 = 8, R6C5 = 3, R78C3 = [28], R7C6 = 7 (step 4m) -> R7C9 = 5, R7C28 = [96], R8C89 = [79]
5d. R2C3 = 9 -> R3C4 = 6 (cage sum)
5e. R7C2 = 9 -> R8C12 = 4 = [31] -> R78C7 = [34], clean-up: no 8 in R5C8
5f. R3C5 = 7 -> R4C5 = 1
5g. 8(3) cage at R6C2 = [512] (only remaining permutation)
5h. R3C1 = 8 -> R46C1 = {79}, 7 locked for C1 and N4
5i. R5C23 = [83] (only remaining permutation)
5j. Naked pair {46} in R4C23, locked for R4, R4C4 = 8 (cage sum)
[And maybe the neatest way to finish …]
5k. 45 rule on N6 4(2+2) outies R37C9 + R46C6 = 20, R37C9 = [45] = 9 -> R46C6 = 11 = [56]
5l. R8C4 = 5, R1C45 = [95] -> R2C4 = 3 (cage sum)
and the rest is naked singles.