diff --git a/.github/workflows/size-report.yml b/.github/workflows/size-report.yml
index 383f23b..9313da5 100644
--- a/.github/workflows/size-report.yml
+++ b/.github/workflows/size-report.yml
@@ -27,7 +27,10 @@ jobs:
       - name: setup deno
         uses: denoland/setup-deno@667a34cdef165d8d2b2e98dde39547c9daac7282 # v2.0.4
         with:
-          deno-version: v2.x
+          # Pinned to v2.8.3 to avoid https://github.com/denoland/deno/issues/35529
+          # (v2.9.0 rejects JSR files without a manifest checksum on warm cache).
+          # Restore to v2.x once v2.9.1 ships.
+          deno-version: v2.8.3
 
       - name: setup node
         uses: actions/setup-node@48b55a011bda9f5d6aeb4c2d9c7362e8dae4041e # v4
diff --git a/.github/workflows/verify.yaml b/.github/workflows/verify.yaml
index 1bce582..5937e13 100644
--- a/.github/workflows/verify.yaml
+++ b/.github/workflows/verify.yaml
@@ -29,7 +29,10 @@ jobs:
       - name: setup deno
         uses: denoland/setup-deno@667a34cdef165d8d2b2e98dde39547c9daac7282 # v2.0.4
         with:
-          deno-version: v2.x
+          # Pinned to v2.8.3 to avoid https://github.com/denoland/deno/issues/35529
+          # (v2.9.0 rejects JSR files without a manifest checksum on warm cache).
+          # Restore to v2.x once v2.9.1 ships.
+          deno-version: v2.8.3
 
       - name: format
         run: deno task fmt:check
@@ -71,7 +74,10 @@ jobs:
       - name: setup deno
         uses: denoland/setup-deno@667a34cdef165d8d2b2e98dde39547c9daac7282 # v2.0.4
         with:
-          deno-version: v2.x
+          # Pinned to v2.8.3 to avoid https://github.com/denoland/deno/issues/35529
+          # (v2.9.0 rejects JSR files without a manifest checksum on warm cache).
+          # Restore to v2.x once v2.9.1 ships.
+          deno-version: v2.8.3
 
       - name: download wasm artifact
         uses: actions/download-artifact@3e5f45b2cfb9172054b4087a40e8e0b5a5461e7c # v8.0.1
@@ -95,7 +101,10 @@ jobs:
       - name: setup deno
         uses: denoland/setup-deno@667a34cdef165d8d2b2e98dde39547c9daac7282 # v2.0.4
         with:
-          deno-version: v2.x
+          # Pinned to v2.8.3 to avoid https://github.com/denoland/deno/issues/35529
+          # (v2.9.0 rejects JSR files without a manifest checksum on warm cache).
+          # Restore to v2.x once v2.9.1 ships.
+          deno-version: v2.8.3
 
       - name: Setup Node
         uses: actions/setup-node@48b55a011bda9f5d6aeb4c2d9c7362e8dae4041e # v6.4.0