diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index c32c21ee..566d3bbf 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -11,7 +11,7 @@ env:
   RUST_BACKTRACE: full
 jobs:
   Clippy:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-24.04
     timeout-minutes: 2
     steps:
     - uses: actions/checkout@v4
@@ -21,7 +21,7 @@ jobs:
     - name: Run Clippy
       run: make clippy_all
   Rustfmt:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-24.04
     timeout-minutes: 2
     steps:
     - uses: actions/checkout@v4
@@ -31,7 +31,7 @@ jobs:
     - name: Check formatting
       run: cargo fmt --all -- --check
   Docs:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-24.04
     timeout-minutes: 2
     steps:
     - uses: actions/checkout@v4
diff --git a/.github/workflows/heph.yml b/.github/workflows/heph.yml
index 2e585ffb..9b0ec29f 100644
--- a/.github/workflows/heph.yml
+++ b/.github/workflows/heph.yml
@@ -23,31 +23,34 @@ env:
   RUST_BACKTRACE: full
 jobs:
   Test:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-24.04
     timeout-minutes: 10
-    if: false # FIXME.
     steps:
     - uses: actions/checkout@v4
     - uses: ./.github/workflows/test
       with:
         working-directory: ./
   Miri:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-24.04
     timeout-minutes: 10
-    if: false # FIXME.
+    # TODO: enable <https://github.com/Thomasdezeeuw/heph/issues/644>.
+    if: false
     steps:
     - uses: actions/checkout@v4
     - uses: ./.github/workflows/test_miri
       with:
         working-directory: ./
   Sanitiser:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-24.04
     timeout-minutes: 10
-    if: false # FIXME.
+    # TODO: enable <https://github.com/Thomasdezeeuw/heph/issues/645>.
+    if: false
     strategy:
       fail-fast: false
       matrix:
-        sanitiser: [address, leak, memory, thread]
+        # LeakSanitizer is broken, see
+        # <https://github.com/rust-lang/rust/issues/111073>.
+        sanitiser: [address, memory, thread] # leak
     steps:
     - uses: actions/checkout@v4
     - uses: ./.github/workflows/test_sanitizer
diff --git a/.github/workflows/http.yml b/.github/workflows/http.yml
index 6b01bed0..1c44b631 100644
--- a/.github/workflows/http.yml
+++ b/.github/workflows/http.yml
@@ -17,22 +17,26 @@ env:
   RUST_BACKTRACE: full
 jobs:
   Test:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-24.04
     timeout-minutes: 10
-    if: false # FIXME.
+    # TODO: enable <https://github.com/Thomasdezeeuw/heph/issues/647>.
+    if: false
     steps:
     - uses: actions/checkout@v4
     - uses: ./.github/workflows/test
       with:
         working-directory: http
   Sanitiser:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-24.04
     timeout-minutes: 10
-    if: false # FIXME.
+    # TODO: enable <https://github.com/Thomasdezeeuw/heph/issues/647>.
+    if: false
     strategy:
       fail-fast: false
       matrix:
-        sanitiser: [address, leak, memory, thread]
+        # LeakSanitizer is broken, see
+        # <https://github.com/rust-lang/rust/issues/111073>.
+        sanitiser: [address, memory, thread] # leak
     steps:
     - uses: actions/checkout@v4
     - uses: ./.github/workflows/test_sanitizer
diff --git a/.github/workflows/inbox.yml b/.github/workflows/inbox.yml
index 87e24616..faccd325 100644
--- a/.github/workflows/inbox.yml
+++ b/.github/workflows/inbox.yml
@@ -17,7 +17,7 @@ env:
   RUST_BACKTRACE: full
 jobs:
   Test:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-24.04
     timeout-minutes: 10
     # This often run too many iterations on CI, which is not a real error.
     continue-on-error: ${{ matrix.release == 'release' }}
@@ -32,7 +32,7 @@ jobs:
         test-flags: ${{ matrix.release }}
         working-directory: inbox
   Miri:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-24.04
     timeout-minutes: 10
     steps:
     - uses: actions/checkout@v4
@@ -40,12 +40,14 @@ jobs:
       with:
         working-directory: inbox
   Sanitiser:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-24.04
     timeout-minutes: 10
     strategy:
       fail-fast: false
       matrix:
-        sanitiser: [address, leak, memory, thread]
+        # LeakSanitizer is broken, see
+        # <https://github.com/rust-lang/rust/issues/111073>.
+        sanitiser: [address, memory, thread] # leak
     steps:
     - uses: actions/checkout@v4
     - uses: ./.github/workflows/test_sanitizer
diff --git a/.github/workflows/remote.yml b/.github/workflows/remote.yml
index 2cc1285c..101466ee 100644
--- a/.github/workflows/remote.yml
+++ b/.github/workflows/remote.yml
@@ -17,22 +17,24 @@ env:
   RUST_BACKTRACE: full
 jobs:
   Test:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-24.04
     timeout-minutes: 10
-    if: false # FIXME.
     steps:
     - uses: actions/checkout@v4
+    - name: Install Cargo-hack
+      run: cargo install --debug cargo-hack
     - uses: ./.github/workflows/test
       with:
         working-directory: remote
   Sanitiser:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-24.04
     timeout-minutes: 10
-    if: false # FIXME.
     strategy:
       fail-fast: false
       matrix:
-        sanitiser: [address, leak, memory, thread]
+        # LeakSanitizer is broken, see
+        # <https://github.com/rust-lang/rust/issues/111073>.
+        sanitiser: [address, memory, thread] # leak
     steps:
     - uses: actions/checkout@v4
     - uses: ./.github/workflows/test_sanitizer
diff --git a/.github/workflows/rt.yml b/.github/workflows/rt.yml
index 3e675467..3fce043d 100644
--- a/.github/workflows/rt.yml
+++ b/.github/workflows/rt.yml
@@ -17,22 +17,24 @@ env:
   RUST_BACKTRACE: full
 jobs:
   Test:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-24.04
     timeout-minutes: 10
-    if: false # FIXME.
     steps:
     - uses: actions/checkout@v4
     - uses: ./.github/workflows/test
       with:
         working-directory: rt
   Sanitiser:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-24.04
     timeout-minutes: 10
-    if: false # FIXME.
+    # TODO: enable <https://github.com/Thomasdezeeuw/heph/issues/646>.
+    if: false
     strategy:
       fail-fast: false
       matrix:
-        sanitiser: [address, leak, memory, thread]
+        # LeakSanitizer is broken, see
+        # <https://github.com/rust-lang/rust/issues/111073>.
+        sanitiser: [address, memory, thread] # leak
     steps:
     - uses: actions/checkout@v4
     - uses: ./.github/workflows/test_sanitizer
diff --git a/Makefile.include b/Makefile.include
index e62231ff..8afd53f6 100644
--- a/Makefile.include
+++ b/Makefile.include
@@ -26,7 +26,9 @@ test:
 
 test_sanitizers:
 	$(MAKE) test_sanitizer sanitizer=address
-	$(MAKE) test_sanitizer sanitizer=leak
+	# LeakSanitizer is broken, see
+	# <https://github.com/rust-lang/rust/issues/111073>.
+	#$(MAKE) test_sanitizer sanitizer=leak
 	$(MAKE) test_sanitizer sanitizer=memory
 	$(MAKE) test_sanitizer sanitizer=thread