diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index b03f069..4faa843 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -18,10 +18,7 @@ jobs:
     - uses: actions/checkout@v4
 
     - name: Install Rust
-      uses: dtolnay/rust-toolchain@stable
-      with:
-        toolchain: 1.90.0
-        components: rustfmt, clippy
+      run: rustup install
 
     - name: Cache cargo registry
       uses: actions/cache@v4
@@ -30,9 +27,9 @@ jobs:
           ~/.cargo/registry
           ~/.cargo/git
           target
-        key: ${{ runner.os }}-cargo-${{ hashFiles('**/Cargo.lock') }}
+        key: ${{ runner.os }}-${{ hashFiles('rust-toolchain.toml') }}-cargo-${{ hashFiles('**/Cargo.lock') }}
         restore-keys: |
-          ${{ runner.os }}-cargo-
+          ${{ runner.os }}-${{ hashFiles('rust-toolchain.toml') }}-cargo-
 
     - name: Check formatting
       run: cargo fmt --all -- --check
@@ -99,14 +96,11 @@ jobs:
     strategy:
       matrix:
         os: [ubuntu-latest, windows-latest, macos-latest]
-        rust: [1.90.0]
     steps:
     - uses: actions/checkout@v4
 
     - name: Install Rust
-      uses: dtolnay/rust-toolchain@master
-      with:
-        toolchain: ${{ matrix.rust }}
+      run: rustup install
 
     - name: Cache cargo registry
       uses: actions/cache@v4
@@ -115,10 +109,9 @@ jobs:
           ~/.cargo/registry
           ~/.cargo/git
           target
-        key: ${{ runner.os }}-${{ matrix.rust }}-cargo-${{ hashFiles('**/Cargo.lock') }}
+        key: ${{ runner.os }}-${{ hashFiles('rust-toolchain.toml') }}-cargo-${{ hashFiles('**/Cargo.lock') }}
         restore-keys: |
-          ${{ runner.os }}-${{ matrix.rust }}-cargo-
-          ${{ runner.os }}-cargo-
+          ${{ runner.os }}-${{ hashFiles('rust-toolchain.toml') }}-cargo-
 
     - name: Build
       run: cargo build --verbose
@@ -231,9 +224,7 @@ jobs:
     - uses: actions/checkout@v4
 
     - name: Install Rust
-      uses: dtolnay/rust-toolchain@stable
-      with:
-        toolchain: 1.90.0
+      run: rustup install
 
     - name: Cache cargo registry
       uses: actions/cache@v4
@@ -242,7 +233,7 @@ jobs:
           ~/.cargo/registry
           ~/.cargo/git
           target
-        key: windows-latest-cargo-${{ hashFiles('**/Cargo.lock') }}
+        key: windows-latest-${{ hashFiles('rust-toolchain.toml') }}-cargo-${{ hashFiles('**/Cargo.lock') }}
 
     - name: Build Ruby Butler
       run: cargo build --release
@@ -305,12 +296,10 @@ jobs:
     - uses: actions/checkout@v4
 
     - name: Install Rust
-      uses: dtolnay/rust-toolchain@stable
-      with:
-        toolchain: 1.90.0
+      run: rustup install
 
     - name: Install cargo-audit
-      run: cargo install --force cargo-audit
+      run: cargo install --locked --force cargo-audit
 
     - name: Run security audit
       run: cargo audit
@@ -323,10 +312,10 @@ jobs:
     - uses: actions/checkout@v4
 
     - name: Install Rust
-      uses: dtolnay/rust-toolchain@stable
-      with:
-        toolchain: 1.90.0
-        components: llvm-tools-preview
+      run: rustup install
+
+    - name: Install coverage tools
+      run: rustup component add llvm-tools-preview
 
     - name: Cache cargo registry
       uses: actions/cache@v4
@@ -335,7 +324,7 @@ jobs:
           ~/.cargo/registry
           ~/.cargo/git
           target
-        key: coverage-cargo-${{ hashFiles('**/Cargo.lock') }}
+        key: coverage-${{ hashFiles('rust-toolchain.toml') }}-cargo-${{ hashFiles('**/Cargo.lock') }}
 
     - name: Install cargo-llvm-cov
       run: cargo install --force cargo-llvm-cov
diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
index e97e566..73bf187 100644
--- a/.github/workflows/release.yml
+++ b/.github/workflows/release.yml
@@ -81,10 +81,10 @@ jobs:
         fetch-depth: 0  # Need full history for git info
 
     - name: Install Rust
-      uses: dtolnay/rust-toolchain@stable
-      with:
-        toolchain: 1.90.0
-        targets: ${{ matrix.target }}
+      run: rustup install
+
+    - name: Install target
+      run: rustup target add ${{ matrix.target }}
 
     - name: Cache cargo registry
       uses: actions/cache@v4
@@ -93,9 +93,9 @@ jobs:
           ~/.cargo/registry
           ~/.cargo/git
           target
-        key: ${{ matrix.os }}-1.90.0-cargo-${{ hashFiles('**/Cargo.lock') }}
+        key: ${{ matrix.os }}-${{ hashFiles('rust-toolchain.toml') }}-cargo-${{ hashFiles('**/Cargo.lock') }}
         restore-keys: |
-          ${{ matrix.os }}-1.90.0-cargo-
+          ${{ matrix.os }}-${{ hashFiles('rust-toolchain.toml') }}-cargo-
           ${{ matrix.os }}-cargo-
 
     - name: Build release binary
diff --git a/crates/rb-cli/src/config/mod.rs b/crates/rb-cli/src/config/mod.rs
index fab081f..11ec6a1 100644
--- a/crates/rb-cli/src/config/mod.rs
+++ b/crates/rb-cli/src/config/mod.rs
@@ -86,11 +86,8 @@ impl RbConfig {
                 debug!("  Using rubies-dir from config file: {}", dir.display());
                 self.rubies_dir = other.rubies_dir;
             }
-        } else {
-            debug!(
-                "  Using rubies-dir from CLI arguments: {}",
-                self.rubies_dir.as_ref().unwrap().display()
-            );
+        } else if let Some(dir) = &self.rubies_dir {
+            debug!("  Using rubies-dir from CLI arguments: {}", dir.display());
         }
 
         if self.ruby_version.is_none() {
@@ -98,11 +95,8 @@ impl RbConfig {
                 debug!("  Using ruby-version from config file: {}", version);
                 self.ruby_version = other.ruby_version;
             }
-        } else {
-            debug!(
-                "  Using ruby-version from CLI arguments: {}",
-                self.ruby_version.as_ref().unwrap()
-            );
+        } else if let Some(version) = &self.ruby_version {
+            debug!("  Using ruby-version from CLI arguments: {}", version);
         }
 
         if self.gem_home.is_none() {
@@ -110,11 +104,8 @@ impl RbConfig {
                 debug!("  Using gem-home from config file: {}", home.display());
                 self.gem_home = other.gem_home;
             }
-        } else {
-            debug!(
-                "  Using gem-home from CLI arguments: {}",
-                self.gem_home.as_ref().unwrap().display()
-            );
+        } else if let Some(home) = &self.gem_home {
+            debug!("  Using gem-home from CLI arguments: {}", home.display());
         }
 
         if self.no_bundler.is_none() {
@@ -122,11 +113,8 @@ impl RbConfig {
                 debug!("  Using no-bundler from config file: {}", no_bundler);
                 self.no_bundler = Some(no_bundler);
             }
-        } else {
-            debug!(
-                "  Using no-bundler from CLI arguments: {}",
-                self.no_bundler.unwrap()
-            );
+        } else if let Some(no_bundler) = &self.no_bundler {
+            debug!("  Using no-bundler from CLI arguments: {}", no_bundler);
         }
 
         if self.work_dir.is_none() {
@@ -134,11 +122,8 @@ impl RbConfig {
                 debug!("  Using work-dir from config file: {}", dir.display());
                 self.work_dir = other.work_dir;
             }
-        } else {
-            debug!(
-                "  Using work-dir from CLI arguments: {}",
-                self.work_dir.as_ref().unwrap().display()
-            );
+        } else if let Some(dir) = &self.work_dir {
+            debug!("  Using work-dir from CLI arguments: {}", dir.display());
         }
     }
 }
diff --git a/rust-toolchain.toml b/rust-toolchain.toml
new file mode 100644
index 0000000..c3f67b6
--- /dev/null
+++ b/rust-toolchain.toml
@@ -0,0 +1,4 @@
+[toolchain]
+channel = "1.98.1"
+profile = "minimal"
+components = ["rustfmt", "clippy"]