diff --git a/.github/actions/checkout-rust/action.yml b/.github/actions/checkout-rust/action.yml
new file mode 100644
index 00000000000..67140523f20
--- /dev/null
+++ b/.github/actions/checkout-rust/action.yml
@@ -0,0 +1,31 @@
+name: Check out rust-lang/rust
+description: >
+  Checks out the rust-lang/rust commit of the toolchain into `<path>/build/rust`, where y.sh runs
+  the rustc tests. Unlike the anonymous full clone y.sh would do, this checkout is authenticated
+  and shallow, so GitHub does not rate-limit it.
+
+inputs:
+  path:
+    description: The cg_gcc directory.
+    default: .
+
+runs:
+  using: composite
+  steps:
+    - id: toolchain
+      shell: bash
+      working-directory: ${{ inputs.path }}
+      run: |
+        commit="$(rustc -vV | sed -n 's/^commit-hash: //p')"
+        if [ -z "$commit" ]; then
+          echo "::error::could not find the commit of the toolchain"
+          exit 1
+        fi
+        echo "commit=$commit" >> "$GITHUB_OUTPUT"
+
+    - uses: actions/checkout@v7
+      with:
+        repository: rust-lang/rust
+        ref: ${{ steps.toolchain.outputs.commit }}
+        path: ${{ inputs.path }}/build/rust
+        persist-credentials: false
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 66362e27ce4..fc45d1a60f8 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -173,6 +173,10 @@ jobs:
       if: ${{ matrix.libgccjit_version.gcc == 'gcc-15-without-int128' }}
       run: cat tests/failing-ui-tests-without-128bit-integers.txt >> tests/failing-ui-tests.txt
 
+    - name: Check out rust-lang/rust
+      if: ${{ contains(matrix.commands, '-rustc') }}
+      uses: ./.github/actions/checkout-rust
+
     - name: Run tests
       run: |
         ./y.sh test --release --clean --build-sysroot --no-builtins-tests ${{ matrix.commands }}
diff --git a/.github/workflows/failures.yml b/.github/workflows/failures.yml
index cd218ee0b2e..23411645931 100644
--- a/.github/workflows/failures.yml
+++ b/.github/workflows/failures.yml
@@ -100,6 +100,10 @@ jobs:
       if: matrix.libgccjit_version.gcc != 'libgccjit12.so'
       run: ./y.sh prepare
 
+    - name: Check out rust-lang/rust
+      if: matrix.libgccjit_version.gcc != 'libgccjit12.so'
+      uses: ./.github/actions/checkout-rust
+
     - name: Run tests
       # FIXME: re-enable those tests for libgccjit 12.
       if: matrix.libgccjit_version.gcc != 'libgccjit12.so'
diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
index 43885125278..cc91ea2b666 100644
--- a/.github/workflows/release.yml
+++ b/.github/workflows/release.yml
@@ -83,6 +83,9 @@ jobs:
     - name: Add more failing tests (some panic and debuginfo tests fail)
       run: cat tests/failing-lto-tests.txt >> tests/failing-ui-tests.txt
 
+    - name: Check out rust-lang/rust
+      uses: ./.github/actions/checkout-rust
+
     - name: Run tests
       run: |
         # FIXME(antoyo): we cannot enable LTO for stdarch tests currently because of some failing LTO tests using proc-macros.
diff --git a/.github/workflows/rustup.yml b/.github/workflows/rustup.yml
index 0309ccbad54..13fb592fc2b 100644
--- a/.github/workflows/rustup.yml
+++ b/.github/workflows/rustup.yml
@@ -111,6 +111,12 @@ jobs:
         git config --global user.name "User"
         ./y.sh prepare
 
+    - name: Check out rust-lang/rust
+      if: ${{ contains(matrix.commands, '-rustc') }}
+      uses: ./.github/actions/checkout-rust
+      with:
+        path: rust/compiler/rustc_codegen_gcc
+
     - name: Run tests
       run: |
         ./y.sh test --release --clean --build-sysroot --no-builtins-tests ${{ matrix.commands }}
@@ -252,6 +258,11 @@ jobs:
         git config --global user.name "User"
         ./y.sh prepare
 
+    - name: Check out rust-lang/rust
+      uses: ./.github/actions/checkout-rust
+      with:
+        path: rust/compiler/rustc_codegen_gcc
+
     - name: Run tests
       run: |
         # Without this, `tee` masks the exit status of `y.sh test`.
diff --git a/build_system/src/test.rs b/build_system/src/test.rs
index 79eae8afa14..2880108825b 100644
--- a/build_system/src/test.rs
+++ b/build_system/src/test.rs
@@ -559,18 +559,33 @@ fn setup_rustc(env: &mut Env, args: &TestArg) -> Result<PathBuf, String> {
     let _ = git_clone("https://github.com/rust-lang/rust.git", Some(&rust_dir_path), false);
     let rust_dir: Option<&Path> = Some(&rust_dir_path);
     run_command(&[&"git", &"checkout", &"--", &"tests/"], rust_dir)?;
-    run_command_with_output_and_env(&[&"git", &"fetch"], rust_dir, Some(env))?;
     let rustc_commit = match rustc_version_info(env.get("RUSTC").map(|s| s.as_str()))?.commit_hash {
         Some(commit_hash) => commit_hash,
         None => return Err("Couldn't retrieve rustc commit hash".to_string()),
     };
     if rustc_commit != "unknown" {
+        // GitHub rate-limits a fetch right after a full clone, so only fetch a missing commit.
+        let commit_object = format!("{rustc_commit}^{{commit}}");
+        let has_commit = run_command_with_output_and_env_no_err(
+            &[&"git", &"rev-parse", &"--quiet", &"--verify", &commit_object],
+            rust_dir,
+            Some(env),
+        )
+        .is_ok();
+        if !has_commit {
+            run_command_with_output_and_env(
+                &[&"git", &"fetch", &"origin", &rustc_commit],
+                rust_dir,
+                Some(env),
+            )?;
+        }
         run_command_with_output_and_env(
             &[&"git", &"checkout", &rustc_commit],
             rust_dir,
             Some(env),
         )?;
     } else {
+        run_command_with_output_and_env(&[&"git", &"fetch"], rust_dir, Some(env))?;
         run_command_with_output_and_env(&[&"git", &"checkout"], rust_dir, Some(env))?;
     }
 
diff --git a/rust-toolchain.toml b/rust-toolchain.toml
index 5750754596b..16d6ab86704 100644
--- a/rust-toolchain.toml
+++ b/rust-toolchain.toml
@@ -1,3 +1,3 @@
 [toolchain]
-channel = "nightly-2026-10-24"
+channel = "nightly-2026-10-26"
 components = ["rust-src", "rustc-dev", "llvm-tools-preview"]