Deep dive into grammar rule: All cases when consonants are soft

Always soft consonants:

• й, ч, щ — always soft.

Consonants are soft:

• if followed by the letters е, ё, и, ю, я (they trigger palatalization /ʸ/ on the preceding consonant);
• if followed by the soft sign ь.

When paired hard consonants soften before soft consonants:

• /z, s, n/ become /zʸ, sʸ, nʸ/ before /dʸ, tʸ, zʸ, sʸ, nʸ/, e.g.: месть [mʸesʸtʸ], здесь [zʸdʸesʸ], бантик [ˈbanʸtʸɪk]. /n/ also softens before /t͡ɕ/, /ɕː/, e.g.: кончик [ˈkonʸchɪk], гонщик [ˈgonʸshchːɪk].
• /z, s, n/ become /zʸ, sʸ, nʸ/ before /bʸ, pʸ, vʸ, fʸ/, e.g.: зверь [zʸvʸerʸ], свет often [sʸvʸet] (though sometimes [svʸet]).