diff --git a/.github/workflows/nightlies.yml b/.github/workflows/nightlies.yml
index d5ca6d2..e6a7a01 100644
--- a/.github/workflows/nightlies.yml
+++ b/.github/workflows/nightlies.yml
@@ -129,12 +129,12 @@ jobs:
           # to make. Without this, make.ps1 falls back to "<VERSION>-<sha>".
           $cloudsmithVersion = (Get-Date).ToString("yyyyMMdd")
           $applicationVersion = "nightly-$cloudsmithVersion"
-          # Pin cloudsmith-cli below 1.19.0: 1.19.0 added a PyJWT[crypto]
-          # dependency that pulls in cryptography, which has no prebuilt
-          # win_arm64 wheel and fails to build from source on this runner.
-          # Remove once arm64 Windows can install the latest cloudsmith-cli
-          # again.
-          python.exe -m pip install --upgrade "cloudsmith-cli<1.19.0"
+          # Pin cloudsmith-cli below 1.18.0 on arm64 Windows:
+          # - 1.18.0 added mcp==1.9.1 which imports a pydantic internal
+          #   that was removed in pydantic 2.14.
+          # - 1.19.0 added PyJWT[crypto] which pulls in cryptography,
+          #   which has no prebuilt win_arm64 wheel.
+          python.exe -m pip install --upgrade "cloudsmith-cli<1.18.0"
           Invoke-WebRequest https://dl.cloudsmith.io/public/ponylang/releases/raw/versions/latest/ponyc-arm64-pc-windows-msvc.zip -OutFile C:\ponyc.zip;
           Expand-Archive -Path C:\ponyc.zip -DestinationPath C:\ponyc;
           $env:PATH = 'C:\ponyc\bin;' + $env:PATH;
diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
index e34b5f5..d33ef19 100644
--- a/.github/workflows/release.yml
+++ b/.github/workflows/release.yml
@@ -178,12 +178,12 @@ jobs:
           # the Linux/macOS release scripts, which pass `version=` to make.
           # Without this, make.ps1 falls back to "<VERSION>-<sha>".
           $applicationVersion = (Get-Content .\VERSION)
-          # Pin cloudsmith-cli below 1.19.0: 1.19.0 added a PyJWT[crypto]
-          # dependency that pulls in cryptography, which has no prebuilt
-          # win_arm64 wheel and fails to build from source on this runner.
-          # Remove once arm64 Windows can install the latest cloudsmith-cli
-          # again.
-          python.exe -m pip install --upgrade "cloudsmith-cli<1.19.0"
+          # Pin cloudsmith-cli below 1.18.0 on arm64 Windows:
+          # - 1.18.0 added mcp==1.9.1 which imports a pydantic internal
+          #   that was removed in pydantic 2.14.
+          # - 1.19.0 added PyJWT[crypto] which pulls in cryptography,
+          #   which has no prebuilt win_arm64 wheel.
+          python.exe -m pip install --upgrade "cloudsmith-cli<1.18.0"
           Invoke-WebRequest https://dl.cloudsmith.io/public/ponylang/releases/raw/versions/latest/ponyc-arm64-pc-windows-msvc.zip -OutFile C:\ponyc.zip;
           Expand-Archive -Path C:\ponyc.zip -DestinationPath C:\ponyc;
           $env:PATH = 'C:\ponyc\bin;' + $env:PATH;