diff --git a/crates/ruff_cli/src/cache.rs b/crates/ruff_cli/src/cache.rs
index 9b26c11809e4e..f71d26244a99e 100644
--- a/crates/ruff_cli/src/cache.rs
+++ b/crates/ruff_cli/src/cache.rs
@@ -25,10 +25,9 @@ use ruff_notebook::NotebookIndex;
 use ruff_python_ast::imports::ImportMap;
 use ruff_source_file::SourceFileBuilder;
 use ruff_text_size::{TextRange, TextSize};
-use ruff_workspace::resolver::{PyprojectConfig, PyprojectDiscoveryStrategy, Resolver};
+use ruff_workspace::resolver::Resolver;
 use ruff_workspace::Settings;
 
-use crate::cache;
 use crate::diagnostics::Diagnostics;
 
 /// [`Path`] that is relative to the package root in [`PackageCache`].
@@ -443,7 +442,7 @@ pub(super) struct CacheMessage {
 pub(crate) trait PackageCaches {
     fn get(&self, package_root: &Path) -> Option<&Cache>;
 
-    fn persist(self) -> anyhow::Result<()>;
+    fn persist(self) -> Result<()>;
 }
 
 impl<T> PackageCaches for Option<T>
@@ -469,27 +468,17 @@ pub(crate) struct PackageCacheMap<'a>(FxHashMap<&'a Path, Cache>);
 
 impl<'a> PackageCacheMap<'a> {
     pub(crate) fn init(
-        pyproject_config: &PyprojectConfig,
         package_roots: &FxHashMap<&'a Path, Option<&'a Path>>,
         resolver: &Resolver,
     ) -> Self {
         fn init_cache(path: &Path) {
-            if let Err(e) = cache::init(path) {
+            if let Err(e) = init(path) {
                 error!("Failed to initialize cache at {}: {e:?}", path.display());
             }
         }
 
-        match pyproject_config.strategy {
-            PyprojectDiscoveryStrategy::Fixed => {
-                init_cache(&pyproject_config.settings.cache_dir);
-            }
-            PyprojectDiscoveryStrategy::Hierarchical => {
-                for settings in
-                    std::iter::once(&pyproject_config.settings).chain(resolver.settings())
-                {
-                    init_cache(&settings.cache_dir);
-                }
-            }
+        for settings in resolver.settings() {
+            init_cache(&settings.cache_dir);
         }
 
         Self(
@@ -499,7 +488,7 @@ impl<'a> PackageCacheMap<'a> {
                 .unique()
                 .par_bridge()
                 .map(|cache_root| {
-                    let settings = resolver.resolve(cache_root, pyproject_config);
+                    let settings = resolver.resolve(cache_root);
                     let cache = Cache::open(cache_root.to_path_buf(), settings);
                     (cache_root, cache)
                 })
diff --git a/crates/ruff_cli/src/commands/add_noqa.rs b/crates/ruff_cli/src/commands/add_noqa.rs
index 541e40f2b78cf..4767e8c490278 100644
--- a/crates/ruff_cli/src/commands/add_noqa.rs
+++ b/crates/ruff_cli/src/commands/add_noqa.rs
@@ -38,7 +38,6 @@ pub(crate) fn add_noqa(
             .flatten()
             .map(ResolvedFile::path)
             .collect::<Vec<_>>(),
-        pyproject_config,
     );
 
     let start = Instant::now();
@@ -57,7 +56,7 @@ pub(crate) fn add_noqa(
                 .parent()
                 .and_then(|parent| package_roots.get(parent))
                 .and_then(|package| *package);
-            let settings = resolver.resolve(path, pyproject_config);
+            let settings = resolver.resolve(path);
             let source_kind = match SourceKind::from_path(path, source_type) {
                 Ok(Some(source_kind)) => source_kind,
                 Ok(None) => return None,
diff --git a/crates/ruff_cli/src/commands/check.rs b/crates/ruff_cli/src/commands/check.rs
index fb5332277ebab..71e38c5988bf0 100644
--- a/crates/ruff_cli/src/commands/check.rs
+++ b/crates/ruff_cli/src/commands/check.rs
@@ -57,16 +57,11 @@ pub(crate) fn check(
             .flatten()
             .map(ResolvedFile::path)
             .collect::<Vec<_>>(),
-        pyproject_config,
     );
 
     // Load the caches.
     let caches = if bool::from(cache) {
-        Some(PackageCacheMap::init(
-            pyproject_config,
-            &package_roots,
-            &resolver,
-        ))
+        Some(PackageCacheMap::init(&package_roots, &resolver))
     } else {
         None
     };
@@ -81,7 +76,7 @@ pub(crate) fn check(
                     .and_then(|parent| package_roots.get(parent))
                     .and_then(|package| *package);
 
-                let settings = resolver.resolve(path, pyproject_config);
+                let settings = resolver.resolve(path);
 
                 if (settings.file_resolver.force_exclude || !resolved_file.is_root())
                     && match_exclusion(
@@ -128,7 +123,7 @@ pub(crate) fn check(
 
         Some(result.unwrap_or_else(|(path, message)| {
             if let Some(path) = &path {
-                let settings = resolver.resolve(path, pyproject_config);
+                let settings = resolver.resolve(path);
                 if settings.linter.rules.enabled(Rule::IOError) {
                     let dummy =
                         SourceFileBuilder::new(path.to_string_lossy().as_ref(), "").finish();
diff --git a/crates/ruff_cli/src/commands/check_stdin.rs b/crates/ruff_cli/src/commands/check_stdin.rs
index c2f1aaaafca5e..0471edd37804f 100644
--- a/crates/ruff_cli/src/commands/check_stdin.rs
+++ b/crates/ruff_cli/src/commands/check_stdin.rs
@@ -4,7 +4,7 @@ use anyhow::Result;
 
 use ruff_linter::packaging;
 use ruff_linter::settings::flags;
-use ruff_workspace::resolver::{match_exclusion, python_file_at_path, PyprojectConfig};
+use ruff_workspace::resolver::{match_exclusion, python_file_at_path, PyprojectConfig, Resolver};
 
 use crate::args::CliOverrides;
 use crate::diagnostics::{lint_stdin, Diagnostics};
@@ -18,20 +18,20 @@ pub(crate) fn check_stdin(
     noqa: flags::Noqa,
     fix_mode: flags::FixMode,
 ) -> Result<Diagnostics> {
-    if pyproject_config.settings.file_resolver.force_exclude {
+    let mut resolver = Resolver::new(pyproject_config);
+
+    if resolver.force_exclude() {
         if let Some(filename) = filename {
-            if !python_file_at_path(filename, pyproject_config, overrides)? {
+            if !python_file_at_path(filename, &mut resolver, overrides)? {
                 if fix_mode.is_apply() {
                     parrot_stdin()?;
                 }
                 return Ok(Diagnostics::default());
             }
 
-            let lint_settings = &pyproject_config.settings.linter;
-            if filename
-                .file_name()
-                .is_some_and(|name| match_exclusion(filename, name, &lint_settings.exclude))
-            {
+            if filename.file_name().is_some_and(|name| {
+                match_exclusion(filename, name, &resolver.base_settings().linter.exclude)
+            }) {
                 if fix_mode.is_apply() {
                     parrot_stdin()?;
                 }
@@ -41,13 +41,13 @@ pub(crate) fn check_stdin(
     }
     let stdin = read_from_stdin()?;
     let package_root = filename.and_then(Path::parent).and_then(|path| {
-        packaging::detect_package_root(path, &pyproject_config.settings.linter.namespace_packages)
+        packaging::detect_package_root(path, &resolver.base_settings().linter.namespace_packages)
     });
     let mut diagnostics = lint_stdin(
         filename,
         package_root,
         stdin,
-        &pyproject_config.settings,
+        resolver.base_settings(),
         noqa,
         fix_mode,
     )?;
diff --git a/crates/ruff_cli/src/commands/format.rs b/crates/ruff_cli/src/commands/format.rs
index 096cfeb43760c..c9287e459c431 100644
--- a/crates/ruff_cli/src/commands/format.rs
+++ b/crates/ruff_cli/src/commands/format.rs
@@ -25,9 +25,7 @@ use ruff_linter::warn_user_once;
 use ruff_python_ast::{PySourceType, SourceType};
 use ruff_python_formatter::{format_module_source, FormatModuleError, QuoteStyle};
 use ruff_text_size::{TextLen, TextRange, TextSize};
-use ruff_workspace::resolver::{
-    match_exclusion, python_files_in_path, PyprojectConfig, ResolvedFile, Resolver,
-};
+use ruff_workspace::resolver::{match_exclusion, python_files_in_path, ResolvedFile, Resolver};
 use ruff_workspace::FormatterSettings;
 
 use crate::args::{CliOverrides, FormatArguments};
@@ -79,7 +77,7 @@ pub(crate) fn format(
         return Ok(ExitStatus::Success);
     }
 
-    warn_incompatible_formatter_settings(&pyproject_config, Some(&resolver));
+    warn_incompatible_formatter_settings(&resolver);
 
     // Discover the package root for each Python file.
     let package_roots = resolver.package_roots(
@@ -88,7 +86,6 @@ pub(crate) fn format(
             .flatten()
             .map(ResolvedFile::path)
             .collect::<Vec<_>>(),
-        &pyproject_config,
     );
 
     let caches = if cli.no_cache {
@@ -99,11 +96,7 @@ pub(crate) fn format(
         #[cfg(debug_assertions)]
         crate::warn_user!("Detected debug build without --no-cache.");
 
-        Some(PackageCacheMap::init(
-            &pyproject_config,
-            &package_roots,
-            &resolver,
-        ))
+        Some(PackageCacheMap::init(&package_roots, &resolver))
     };
 
     let start = Instant::now();
@@ -118,7 +111,7 @@ pub(crate) fn format(
                         return None;
                     };
 
-                    let settings = resolver.resolve(path, &pyproject_config);
+                    let settings = resolver.resolve(path);
 
                     // Ignore files that are excluded from formatting
                     if (settings.file_resolver.force_exclude || !resolved_file.is_root())
@@ -723,15 +716,10 @@ impl Display for FormatCommandError {
     }
 }
 
-pub(super) fn warn_incompatible_formatter_settings(
-    pyproject_config: &PyprojectConfig,
-    resolver: Option<&Resolver>,
-) {
+pub(super) fn warn_incompatible_formatter_settings(resolver: &Resolver) {
     // First, collect all rules that are incompatible regardless of the linter-specific settings.
     let mut incompatible_rules = FxHashSet::default();
-    for setting in std::iter::once(&pyproject_config.settings)
-        .chain(resolver.iter().flat_map(|resolver| resolver.settings()))
-    {
+    for setting in resolver.settings() {
         for rule in [
             // The formatter might collapse implicit string concatenation on a single line.
             Rule::SingleLineImplicitStringConcatenation,
@@ -760,9 +748,7 @@ pub(super) fn warn_incompatible_formatter_settings(
     }
 
     // Next, validate settings-specific incompatibilities.
-    for setting in std::iter::once(&pyproject_config.settings)
-        .chain(resolver.iter().flat_map(|resolver| resolver.settings()))
-    {
+    for setting in resolver.settings() {
         // Validate all rules that rely on tab styles.
         if setting.linter.rules.enabled(Rule::TabIndentation)
             && setting.formatter.indent_style.is_tab()
diff --git a/crates/ruff_cli/src/commands/format_stdin.rs b/crates/ruff_cli/src/commands/format_stdin.rs
index 01c6e29b141a4..33fa5160424fe 100644
--- a/crates/ruff_cli/src/commands/format_stdin.rs
+++ b/crates/ruff_cli/src/commands/format_stdin.rs
@@ -6,7 +6,7 @@ use log::error;
 
 use ruff_linter::source_kind::SourceKind;
 use ruff_python_ast::{PySourceType, SourceType};
-use ruff_workspace::resolver::{match_exclusion, python_file_at_path};
+use ruff_workspace::resolver::{match_exclusion, python_file_at_path, Resolver};
 use ruff_workspace::FormatterSettings;
 
 use crate::args::{CliOverrides, FormatArguments};
@@ -27,24 +27,23 @@ pub(crate) fn format_stdin(cli: &FormatArguments, overrides: &CliOverrides) -> R
         cli.stdin_filename.as_deref(),
     )?;
 
-    warn_incompatible_formatter_settings(&pyproject_config, None);
+    let mut resolver = Resolver::new(&pyproject_config);
+    warn_incompatible_formatter_settings(&resolver);
 
     let mode = FormatMode::from_cli(cli);
 
-    if pyproject_config.settings.file_resolver.force_exclude {
+    if resolver.force_exclude() {
         if let Some(filename) = cli.stdin_filename.as_deref() {
-            if !python_file_at_path(filename, &pyproject_config, overrides)? {
+            if !python_file_at_path(filename, &mut resolver, overrides)? {
                 if mode.is_write() {
                     parrot_stdin()?;
                 }
                 return Ok(ExitStatus::Success);
             }
 
-            let format_settings = &pyproject_config.settings.formatter;
-            if filename
-                .file_name()
-                .is_some_and(|name| match_exclusion(filename, name, &format_settings.exclude))
-            {
+            if filename.file_name().is_some_and(|name| {
+                match_exclusion(filename, name, &resolver.base_settings().formatter.exclude)
+            }) {
                 if mode.is_write() {
                     parrot_stdin()?;
                 }
@@ -63,12 +62,7 @@ pub(crate) fn format_stdin(cli: &FormatArguments, overrides: &CliOverrides) -> R
     };
 
     // Format the file.
-    match format_source_code(
-        path,
-        &pyproject_config.settings.formatter,
-        source_type,
-        mode,
-    ) {
+    match format_source_code(path, &resolver.base_settings().formatter, source_type, mode) {
         Ok(result) => match mode {
             FormatMode::Write => Ok(ExitStatus::Success),
             FormatMode::Check | FormatMode::Diff => {
diff --git a/crates/ruff_cli/src/commands/show_settings.rs b/crates/ruff_cli/src/commands/show_settings.rs
index baeed55a08f36..2e27fb344ada3 100644
--- a/crates/ruff_cli/src/commands/show_settings.rs
+++ b/crates/ruff_cli/src/commands/show_settings.rs
@@ -29,7 +29,7 @@ pub(crate) fn show_settings(
         bail!("No files found under the given path");
     };
 
-    let settings = resolver.resolve(&path, pyproject_config);
+    let settings = resolver.resolve(&path);
 
     writeln!(writer, "Resolved settings for: {path:?}")?;
     if let Some(settings_path) = pyproject_config.path.as_ref() {
diff --git a/crates/ruff_dev/src/format_dev.rs b/crates/ruff_dev/src/format_dev.rs
index 2de483ffe00ea..be52ec863e467 100644
--- a/crates/ruff_dev/src/format_dev.rs
+++ b/crates/ruff_dev/src/format_dev.rs
@@ -27,7 +27,7 @@ use tracing_subscriber::layer::SubscriberExt;
 use tracing_subscriber::util::SubscriberInitExt;
 use tracing_subscriber::EnvFilter;
 
-use ruff_cli::args::{FormatCommand, LogLevelArgs};
+use ruff_cli::args::{CliOverrides, FormatArguments, FormatCommand, LogLevelArgs};
 use ruff_cli::resolve::resolve;
 use ruff_formatter::{FormatError, LineWidth, PrintError};
 use ruff_linter::logging::LogLevel;
@@ -38,24 +38,24 @@ use ruff_python_formatter::{
 use ruff_python_parser::ParseError;
 use ruff_workspace::resolver::{python_files_in_path, PyprojectConfig, ResolvedFile, Resolver};
 
-/// Find files that ruff would check so we can format them. Adapted from `ruff_cli`.
-#[allow(clippy::type_complexity)]
-fn ruff_check_paths(
-    dirs: &[PathBuf],
-) -> anyhow::Result<(
-    Vec<Result<ResolvedFile, ignore::Error>>,
-    Resolver,
-    PyprojectConfig,
-)> {
+fn parse_cli(dirs: &[PathBuf]) -> anyhow::Result<(FormatArguments, CliOverrides)> {
     let args_matches = FormatCommand::command()
         .no_binary_name(true)
         .get_matches_from(dirs);
     let arguments: FormatCommand = FormatCommand::from_arg_matches(&args_matches)?;
     let (cli, overrides) = arguments.partition();
+    Ok((cli, overrides))
+}
+
+/// Find the [`PyprojectConfig`] to use for formatting.
+fn find_pyproject_config(
+    cli: &FormatArguments,
+    overrides: &CliOverrides,
+) -> anyhow::Result<PyprojectConfig> {
     let mut pyproject_config = resolve(
         cli.isolated,
         cli.config.as_deref(),
-        &overrides,
+        overrides,
         cli.stdin_filename.as_deref(),
     )?;
     // We don't want to format pyproject.toml
@@ -64,11 +64,18 @@ fn ruff_check_paths(
         FilePattern::Builtin("*.pyi"),
     ])
     .unwrap();
-    let (paths, resolver) = python_files_in_path(&cli.files, &pyproject_config, &overrides)?;
-    if paths.is_empty() {
-        bail!("no python files in {:?}", dirs)
-    }
-    Ok((paths, resolver, pyproject_config))
+    Ok(pyproject_config)
+}
+
+/// Find files that ruff would check so we can format them. Adapted from `ruff_cli`.
+#[allow(clippy::type_complexity)]
+fn ruff_check_paths<'a>(
+    pyproject_config: &'a PyprojectConfig,
+    cli: &FormatArguments,
+    overrides: &CliOverrides,
+) -> anyhow::Result<(Vec<Result<ResolvedFile, ignore::Error>>, Resolver<'a>)> {
+    let (paths, resolver) = python_files_in_path(&cli.files, pyproject_config, overrides)?;
+    Ok((paths, resolver))
 }
 
 /// Collects statistics over the formatted files to compute the Jaccard index or the similarity
@@ -452,11 +459,17 @@ fn format_dev_project(
         files[0].display()
     );
 
-    // TODO(konstin): black excludes
+    // TODO(konstin): Respect black's excludes.
 
     // Find files to check (or in this case, format twice). Adapted from ruff_cli
     // First argument is ignored
-    let (paths, resolver, pyproject_config) = ruff_check_paths(files)?;
+    let (cli, overrides) = parse_cli(files)?;
+    let pyproject_config = find_pyproject_config(&cli, &overrides)?;
+    let (paths, resolver) = ruff_check_paths(&pyproject_config, &cli, &overrides)?;
+
+    if paths.is_empty() {
+        bail!("No Python files found under the given path(s)");
+    }
 
     let results = {
         let pb_span =
@@ -469,14 +482,7 @@ fn format_dev_project(
         #[cfg(feature = "singlethreaded")]
         let iter = { paths.into_iter() };
         iter.map(|path| {
-            let result = format_dir_entry(
-                path,
-                stability_check,
-                write,
-                &black_options,
-                &resolver,
-                &pyproject_config,
-            );
+            let result = format_dir_entry(path, stability_check, write, &black_options, &resolver);
             pb_span.pb_inc(1);
             result
         })
@@ -526,14 +532,13 @@ fn format_dev_project(
     })
 }
 
-/// Error handling in between walkdir and `format_dev_file`
+/// Error handling in between walkdir and `format_dev_file`.
 fn format_dir_entry(
     resolved_file: Result<ResolvedFile, ignore::Error>,
     stability_check: bool,
     write: bool,
     options: &BlackOptions,
     resolver: &Resolver,
-    pyproject_config: &PyprojectConfig,
 ) -> anyhow::Result<(Result<Statistics, CheckFileError>, PathBuf), Error> {
     let resolved_file = resolved_file.context("Iterating the files in the repository failed")?;
     // For some reason it does not filter in the beginning
@@ -544,7 +549,7 @@ fn format_dir_entry(
     let path = resolved_file.into_path();
     let mut options = options.to_py_format_options(&path);
 
-    let settings = resolver.resolve(&path, pyproject_config);
+    let settings = resolver.resolve(&path);
     // That's a bad way of doing this but it's not worth doing something better for format_dev
     if settings.formatter.line_width != LineWidth::default() {
         options = options.with_line_width(settings.formatter.line_width);
diff --git a/crates/ruff_workspace/src/resolver.rs b/crates/ruff_workspace/src/resolver.rs
index 2c6108f828974..590eb3e2d7f83 100644
--- a/crates/ruff_workspace/src/resolver.rs
+++ b/crates/ruff_workspace/src/resolver.rs
@@ -11,7 +11,7 @@ use anyhow::Result;
 use anyhow::{anyhow, bail};
 use globset::{Candidate, GlobSet};
 use ignore::{WalkBuilder, WalkState};
-use itertools::Itertools;
+use itertools::{Either, Itertools};
 use log::debug;
 use path_absolutize::path_dedot;
 use rustc_hash::{FxHashMap, FxHashSet};
@@ -25,6 +25,7 @@ use crate::pyproject::settings_toml;
 use crate::settings::Settings;
 
 /// The configuration information from a `pyproject.toml` file.
+#[derive(Debug)]
 pub struct PyprojectConfig {
     /// The strategy used to discover the relevant `pyproject.toml` file for
     /// each Python file.
@@ -63,10 +64,12 @@ pub enum PyprojectDiscoveryStrategy {
 }
 
 impl PyprojectDiscoveryStrategy {
+    #[inline]
     pub const fn is_fixed(self) -> bool {
         matches!(self, PyprojectDiscoveryStrategy::Fixed)
     }
 
+    #[inline]
     pub const fn is_hierarchical(self) -> bool {
         matches!(self, PyprojectDiscoveryStrategy::Hierarchical)
     }
@@ -94,40 +97,68 @@ impl Relativity {
     }
 }
 
-#[derive(Default)]
-pub struct Resolver {
+#[derive(Debug)]
+pub struct Resolver<'a> {
+    pyproject_config: &'a PyprojectConfig,
     settings: BTreeMap<PathBuf, Settings>,
 }
 
-impl Resolver {
+impl<'a> Resolver<'a> {
+    /// Create a new [`Resolver`] for the given [`PyprojectConfig`].
+    pub fn new(pyproject_config: &'a PyprojectConfig) -> Self {
+        Self {
+            pyproject_config,
+            settings: BTreeMap::new(),
+        }
+    }
+
+    /// Return the [`Settings`] from the [`PyprojectConfig`].
+    #[inline]
+    pub fn base_settings(&self) -> &Settings {
+        &self.pyproject_config.settings
+    }
+
+    /// Return `true` if the [`Resolver`] is using a hierarchical discovery strategy.
+    #[inline]
+    pub fn is_hierarchical(&self) -> bool {
+        self.pyproject_config.strategy.is_hierarchical()
+    }
+
+    /// Return `true` if the [`Resolver`] should force-exclude files passed directly to the CLI.
+    #[inline]
+    pub fn force_exclude(&self) -> bool {
+        self.pyproject_config.settings.file_resolver.force_exclude
+    }
+
+    /// Return `true` if the [`Resolver`] should respect `.gitignore` files.
+    #[inline]
+    pub fn respect_gitignore(&self) -> bool {
+        self.pyproject_config
+            .settings
+            .file_resolver
+            .respect_gitignore
+    }
+
     /// Add a resolved [`Settings`] under a given [`PathBuf`] scope.
     fn add(&mut self, path: PathBuf, settings: Settings) {
         self.settings.insert(path, settings);
     }
 
     /// Return the appropriate [`Settings`] for a given [`Path`].
-    pub fn resolve<'a>(
-        &'a self,
-        path: &Path,
-        pyproject_config: &'a PyprojectConfig,
-    ) -> &'a Settings {
-        match pyproject_config.strategy {
-            PyprojectDiscoveryStrategy::Fixed => &pyproject_config.settings,
+    pub fn resolve(&self, path: &Path) -> &Settings {
+        match self.pyproject_config.strategy {
+            PyprojectDiscoveryStrategy::Fixed => &self.pyproject_config.settings,
             PyprojectDiscoveryStrategy::Hierarchical => self
                 .settings
                 .iter()
                 .rev()
                 .find_map(|(root, settings)| path.starts_with(root).then_some(settings))
-                .unwrap_or(&pyproject_config.settings),
+                .unwrap_or(&self.pyproject_config.settings),
         }
     }
 
     /// Return a mapping from Python package to its package root.
-    pub fn package_roots<'a>(
-        &'a self,
-        files: &[&'a Path],
-        pyproject_config: &'a PyprojectConfig,
-    ) -> FxHashMap<&'a Path, Option<&'a Path>> {
+    pub fn package_roots(&'a self, files: &[&'a Path]) -> FxHashMap<&'a Path, Option<&'a Path>> {
         // Pre-populate the module cache, since the list of files could (but isn't
         // required to) contain some `__init__.py` files.
         let mut package_cache: FxHashMap<&Path, bool> = FxHashMap::default();
@@ -154,10 +185,7 @@ impl Resolver {
                     std::collections::hash_map::Entry::Occupied(_) => continue,
                     std::collections::hash_map::Entry::Vacant(entry) => {
                         let namespace_packages = if has_namespace_packages {
-                            self.resolve(file, pyproject_config)
-                                .linter
-                                .namespace_packages
-                                .as_slice()
+                            self.resolve(file).linter.namespace_packages.as_slice()
                         } else {
                             &[]
                         };
@@ -176,7 +204,12 @@ impl Resolver {
 
     /// Return an iterator over the resolved [`Settings`] in this [`Resolver`].
     pub fn settings(&self) -> impl Iterator<Item = &Settings> {
-        self.settings.values()
+        match self.pyproject_config.strategy {
+            PyprojectDiscoveryStrategy::Fixed => {
+                Either::Left(std::iter::once(&self.pyproject_config.settings))
+            }
+            PyprojectDiscoveryStrategy::Hierarchical => Either::Right(self.settings.values()),
+        }
     }
 }
 
@@ -288,18 +321,18 @@ pub fn resolve_root_settings(
 }
 
 /// Find all Python (`.py`, `.pyi` and `.ipynb` files) in a set of paths.
-pub fn python_files_in_path(
+pub fn python_files_in_path<'a>(
     paths: &[PathBuf],
-    pyproject_config: &PyprojectConfig,
+    pyproject_config: &'a PyprojectConfig,
     transformer: &dyn ConfigurationTransformer,
-) -> Result<(Vec<Result<ResolvedFile, ignore::Error>>, Resolver)> {
+) -> Result<(Vec<Result<ResolvedFile, ignore::Error>>, Resolver<'a>)> {
     // Normalize every path (e.g., convert from relative to absolute).
     let mut paths: Vec<PathBuf> = paths.iter().map(fs::normalize_path).unique().collect();
 
     // Search for `pyproject.toml` files in all parent directories.
-    let mut resolver = Resolver::default();
+    let mut resolver = Resolver::new(pyproject_config);
     let mut seen = FxHashSet::default();
-    if pyproject_config.strategy.is_hierarchical() {
+    if resolver.is_hierarchical() {
         for path in &paths {
             for ancestor in path.ancestors() {
                 if seen.insert(ancestor) {
@@ -315,8 +348,8 @@ pub fn python_files_in_path(
     }
 
     // Check if the paths themselves are excluded.
-    if pyproject_config.settings.file_resolver.force_exclude {
-        paths.retain(|path| !is_file_excluded(path, &resolver, pyproject_config));
+    if resolver.force_exclude() {
+        paths.retain(|path| !is_file_excluded(path, &resolver));
         if paths.is_empty() {
             return Ok((vec![], resolver));
         }
@@ -330,11 +363,12 @@ pub fn python_files_in_path(
     for path in rest_paths {
         builder.add(path);
     }
-    builder.standard_filters(pyproject_config.settings.file_resolver.respect_gitignore);
+    builder.standard_filters(resolver.respect_gitignore());
     builder.hidden(false);
     let walker = builder.build_parallel();
 
     // Run the `WalkParallel` to collect all Python files.
+    let is_hierarchical = resolver.is_hierarchical();
     let error: std::sync::Mutex<Result<()>> = std::sync::Mutex::new(Ok(()));
     let resolver: RwLock<Resolver> = RwLock::new(resolver);
     let files: std::sync::Mutex<Vec<Result<ResolvedFile, ignore::Error>>> =
@@ -346,7 +380,7 @@ pub fn python_files_in_path(
                 if entry.depth() > 0 {
                     let path = entry.path();
                     let resolver = resolver.read().unwrap();
-                    let settings = resolver.resolve(path, pyproject_config);
+                    let settings = resolver.resolve(path);
                     if let Some(file_name) = path.file_name() {
                         let file_path = Candidate::new(path);
                         let file_basename = Candidate::new(file_name);
@@ -374,7 +408,7 @@ pub fn python_files_in_path(
 
             // Search for the `pyproject.toml` file in this directory, before we visit any
             // of its contents.
-            if pyproject_config.strategy.is_hierarchical() {
+            if is_hierarchical {
                 if let Ok(entry) = &result {
                     if entry
                         .file_type()
@@ -416,7 +450,7 @@ pub fn python_files_in_path(
                         // Otherwise, check if the file is included.
                         let path = entry.path();
                         let resolver = resolver.read().unwrap();
-                        let settings = resolver.resolve(path, pyproject_config);
+                        let settings = resolver.resolve(path);
                         if settings.file_resolver.include.is_match(path) {
                             debug!("Included path via `include`: {:?}", path);
                             Some(ResolvedFile::Nested(entry.into_path()))
@@ -494,15 +528,14 @@ impl Ord for ResolvedFile {
 /// Return `true` if the Python file at [`Path`] is _not_ excluded.
 pub fn python_file_at_path(
     path: &Path,
-    pyproject_config: &PyprojectConfig,
+    resolver: &mut Resolver,
     transformer: &dyn ConfigurationTransformer,
 ) -> Result<bool> {
     // Normalize the path (e.g., convert from relative to absolute).
     let path = fs::normalize_path(path);
 
     // Search for `pyproject.toml` files in all parent directories.
-    let mut resolver = Resolver::default();
-    if pyproject_config.strategy.is_hierarchical() {
+    if resolver.is_hierarchical() {
         for ancestor in path.ancestors() {
             if let Some(pyproject) = settings_toml(ancestor)? {
                 let (root, settings) =
@@ -514,18 +547,14 @@ pub fn python_file_at_path(
     }
 
     // Check exclusions.
-    Ok(!is_file_excluded(&path, &resolver, pyproject_config))
+    Ok(!is_file_excluded(&path, resolver))
 }
 
 /// Return `true` if the given top-level [`Path`] should be excluded.
-fn is_file_excluded(
-    path: &Path,
-    resolver: &Resolver,
-    pyproject_strategy: &PyprojectConfig,
-) -> bool {
+fn is_file_excluded(path: &Path, resolver: &Resolver) -> bool {
     // TODO(charlie): Respect gitignore.
     for path in path.ancestors() {
-        let settings = resolver.resolve(path, pyproject_strategy);
+        let settings = resolver.resolve(path);
         if let Some(file_name) = path.file_name() {
             let file_path = Candidate::new(path);
             let file_basename = Candidate::new(file_name);
@@ -618,7 +647,6 @@ mod tests {
     #[test]
     fn rooted_exclusion() -> Result<()> {
         let package_root = test_resource_path("package");
-        let resolver = Resolver::default();
         let pyproject_config = PyprojectConfig::new(
             PyprojectDiscoveryStrategy::Hierarchical,
             resolve_root_settings(
@@ -628,20 +656,19 @@ mod tests {
             )?,
             None,
         );
+        let resolver = Resolver::new(&pyproject_config);
         // src/app.py should not be excluded even if it lives in a hierarchy that should
         // be excluded by virtue of the pyproject.toml having `resources/*` in
         // it.
         assert!(!is_file_excluded(
             &package_root.join("src/app.py"),
             &resolver,
-            &pyproject_config,
         ));
         // However, resources/ignored.py should be ignored, since that `resources` is
         // beneath the package root.
         assert!(is_file_excluded(
             &package_root.join("resources/ignored.py"),
             &resolver,
-            &pyproject_config,
         ));
         Ok(())
     }