diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 22581168..c0c75360 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -17,14 +17,14 @@ jobs:
       RUSTFLAGS: -D warnings
     steps:
       - uses: actions/checkout@93cb6efe18208431cddfb8368fd83d5badbf9bfd # v5.0.1
-      - uses: dtolnay/rust-toolchain@stable
+      - uses: dtolnay/rust-toolchain@4360b52568e2003a75bf9bc1d59f33a8e3fc893c # stable
         with:
           components: rustfmt, clippy
       - uses: Swatinem/rust-cache@98c8021b550208e191a6a3145459bfc9fb29c4c0 # v2.8.0
         with:
           key: partition-${{ matrix.partition }}
       - name: Install just, cargo-hack, and cargo-sync-rdme
-        uses: taiki-e/install-action@v2
+        uses: taiki-e/install-action@cb33e69fad06166ca28a42b2575e4dadabf62ee8 # v2
         with:
           tool: just,cargo-hack,cargo-sync-rdme
       - name: Lint (clippy)
@@ -35,7 +35,7 @@ jobs:
         run: just rustdoc
       # Pin to a specific nightly for compatibility with cargo-sync-rdme.
       - name: Install nightly toolchain for cargo-sync-rdme
-        uses: dtolnay/rust-toolchain@master
+        uses: dtolnay/rust-toolchain@6c977a6ca4077a0ceb28ffbe03f59d46e9ac8772 # master
         with:
           toolchain: nightly-2026-04-30
       - name: Regenerate readmes
@@ -56,15 +56,15 @@ jobs:
       RUSTFLAGS: -D warnings
     steps:
       - uses: actions/checkout@93cb6efe18208431cddfb8368fd83d5badbf9bfd # v5
-      - uses: dtolnay/rust-toolchain@master
+      - uses: dtolnay/rust-toolchain@6c977a6ca4077a0ceb28ffbe03f59d46e9ac8772 # master
         with:
           toolchain: ${{ matrix.rust-version }}
       - uses: Swatinem/rust-cache@98c8021b550208e191a6a3145459bfc9fb29c4c0 # v2.8.0
         with:
           key: partition-${{ matrix.partition }}
-      - uses: taiki-e/install-action@cargo-hack
-      - uses: taiki-e/install-action@just
-      - uses: taiki-e/install-action@nextest
+      - uses: taiki-e/install-action@78dfab2e8f19f714bfd9c6be6f5d54a483216ac7 # cargo-hack
+      - uses: taiki-e/install-action@6314fbb47f7230f3ddf154e8ffa886496186c6c2 # just
+      - uses: taiki-e/install-action@acdba816b0980ba6b63f1109f89a046e15fc301a # nextest
       - name: Build
         run: just powerset --partition ${{ matrix.partition }}/10 build
       - name: Run tests
@@ -86,15 +86,15 @@ jobs:
       RUSTFLAGS: -D warnings
     steps:
       - uses: actions/checkout@93cb6efe18208431cddfb8368fd83d5badbf9bfd # v5
-      - uses: dtolnay/rust-toolchain@master
+      - uses: dtolnay/rust-toolchain@6c977a6ca4077a0ceb28ffbe03f59d46e9ac8772 # master
         with:
           toolchain: ${{ matrix.rust-version }}
       - uses: Swatinem/rust-cache@98c8021b550208e191a6a3145459bfc9fb29c4c0 # v2.8.0
         with:
           key: partition-${{ matrix.partition }}-msrv
-      - uses: taiki-e/install-action@cargo-hack
-      - uses: taiki-e/install-action@just
-      - uses: taiki-e/install-action@nextest
+      - uses: taiki-e/install-action@78dfab2e8f19f714bfd9c6be6f5d54a483216ac7 # cargo-hack
+      - uses: taiki-e/install-action@6314fbb47f7230f3ddf154e8ffa886496186c6c2 # just
+      - uses: taiki-e/install-action@acdba816b0980ba6b63f1109f89a046e15fc301a # nextest
       - name: Build
         run: just powerset --partition ${{ matrix.partition }}/10 build
       # We don't run UI tests on the MSRV since compiler output varies by
@@ -118,11 +118,11 @@ jobs:
       RUSTFLAGS: -D warnings
     steps:
       - uses: actions/checkout@93cb6efe18208431cddfb8368fd83d5badbf9bfd # v5
-      - uses: dtolnay/rust-toolchain@master
+      - uses: dtolnay/rust-toolchain@6c977a6ca4077a0ceb28ffbe03f59d46e9ac8772 # master
         with:
           toolchain: ${{ matrix.rust-version }}
       - uses: Swatinem/rust-cache@98c8021b550208e191a6a3145459bfc9fb29c4c0 # v2.8.0
-      - uses: taiki-e/install-action@cross
+      - uses: taiki-e/install-action@416f12c0b8a4e67fa0a80513ef6c68fa59b355c3 # cross
       - name: Check
         run: cross check --target thumbv7em-none-eabi --no-default-features -p iddqd
 
@@ -153,15 +153,15 @@ jobs:
       MIRIFLAGS: ${{ matrix.miri-flags }}
     steps:
       - uses: actions/checkout@93cb6efe18208431cddfb8368fd83d5badbf9bfd # v5
-      - uses: dtolnay/rust-toolchain@master
+      - uses: dtolnay/rust-toolchain@6c977a6ca4077a0ceb28ffbe03f59d46e9ac8772 # master
         with:
           toolchain: nightly
           components: miri
       - uses: Swatinem/rust-cache@98c8021b550208e191a6a3145459bfc9fb29c4c0 # v2.8.0
         with:
           key: miri-${{ matrix.aliasing-model }}
-      - uses: taiki-e/install-action@cargo-hack
-      - uses: taiki-e/install-action@nextest
+      - uses: taiki-e/install-action@78dfab2e8f19f714bfd9c6be6f5d54a483216ac7 # cargo-hack
+      - uses: taiki-e/install-action@acdba816b0980ba6b63f1109f89a046e15fc301a # nextest
       # Run tests for all crates containing unsafe code. Currently, that's just
       # iddqd.
       - name: Run tests
@@ -174,12 +174,12 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@93cb6efe18208431cddfb8368fd83d5badbf9bfd # v5
-      - uses: dtolnay/rust-toolchain@stable
+      - uses: dtolnay/rust-toolchain@4360b52568e2003a75bf9bc1d59f33a8e3fc893c # stable
       - uses: Swatinem/rust-cache@98c8021b550208e191a6a3145459bfc9fb29c4c0 # v2.8.0
         with:
           key: soteria
-      - uses: taiki-e/install-action@just
-      - uses: taiki-e/install-action@nextest
+      - uses: taiki-e/install-action@6314fbb47f7230f3ddf154e8ffa886496186c6c2 # just
+      - uses: taiki-e/install-action@acdba816b0980ba6b63f1109f89a046e15fc301a # nextest
       # Soteria publishes only a single rolling `nightly` bundle, and `cargo
       # soteria setup` always installs whatever the tag points to. The cache
       # below is mainly for speed -- it (unfortunately) doesn't provide any
diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
index e9b80f08..0582a8da 100644
--- a/.github/workflows/release.yml
+++ b/.github/workflows/release.yml
@@ -21,7 +21,7 @@ jobs:
       - uses: rust-lang/crates-io-auth-action@v1
         id: auth
       - name: Install Rust
-        uses: dtolnay/rust-toolchain@stable
+        uses: dtolnay/rust-toolchain@4360b52568e2003a75bf9bc1d59f33a8e3fc893c # stable
       - name: Install cargo release
         uses: taiki-e/install-action@5ebac0d9522d786674368e47e92963ba13f2c376 # v2
         with: