I wrote a TOML 1.1 parser that passes the test suite, but my parser behaves differently than tomli 2.4.0 which also passes the test suite.

Here's a minimal reproducer to trigger the bug (modified from invalid/table/append-with-dotted-keys-01.toml):

[a.b.c]
z = 9

[[totally_unrelated]]
x = 123

[a]
b.c.t = "this should NOT be allowed"

My parser --> valid
tomli 2.4.0 --> invalid

I think tomli is correct here and this should be considered invalid. The bug in my parser is that the code that handles array tables like [[totally_unrelated]] doesn't mark the old table as done when it switches to the new table.