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Can you add documentation for the COLOR_MODE config key in docs/rbtools/rbt/configuration/users.rst.

We can use the ColorMode type here.

The return statements make this a bit wonky to reason about. The code kind of backs this up, because we're checking late into it for a valid value when we've already ruled out one of them.
I'd suggest:

if options is None:
    color_mode = 'auto'
elif getattr(options, 'json_output', False):
    color_mode = 'never'
else:
    color_mode = getattr(options, 'color', 'auto')

    if color_mode not in {'always', 'auto', 'never'}:
        color_mode = 'auto'

if color_mode == 'auto':
    if os.environ.get('NO_COLOR');
        color_mode = 'never'
    elif os.environ.get('FORCE_COLOR');
        color_mode = 'always'

return color_mode


By the time we're at the return, we should have narrowed this to a valid type in all cases, and limited the conditions in which we've forced values.

This can be an if/else.

Can we use if config := self.config so we don't have to re-get the attribute?

We fetch these attributes twice. Let's pull them out.

The placement of the parents makes this read kind of funky.

We're accessing self.options.debug several times. Let's pull these out.

We can now do if output_stream := self.output_stream: here.

These can start on the Table( line, or could end with a ) on its own line.

Same here.

Same here.

This comparison should be in parens.

Can you swap these so they're in alphabetical order?

Since order is crucial here, let's make them keyword-only arguments.

Can we import this at the module level?

"Rich"

This is missing docs.

Your other docstrings elsewhere in the change refer to this as "Rich", so we should keep consistent with these. Or we could go the other way, avoid the capitalization if we want to say "rich" more generically.
This will apply to instances below as well, depending on the decision.

We should have a Prototype for this, so we can get proper typing and documentation on it.

Let's reference:

:py:class:`object.__len__`

Can we import this at the module level?

Private methods go below public.

We can reference ColorMode here.

We should never override _. This is a really big Claude smell (it's always trying to do this, even when I tell it not to) and not routine in our codebase due to our gettext usage.
Can just use [0] here or [:2] below, as needed.
Same below.

We should type this and use Final.
Also, maybe call it DEFAULT_RBTOOLS_STYLES?

Can we order these alphabetically?

We reference this somewhat-complex type here and elsewhere in the code. Can we get a TypeAlias for it?
If it's these specific types, maybe we'd also want a Literal of keys.

Missing Version Added.

We need a Version added for these.
We probably don't need the trailing comment.

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These should be using our standard multi-line form.