fix(ci): narrow --prerelease=allow to wheels in cross-platform instal… (#13303)

fix(ci): narrow --prerelease=allow to wheels in cross-platform install tests

Nightly cross-platform install tests were failing on Python 3.12/3.13 with
a pydantic ValidationError at langchain_core import time:

  File ".../langchain_core/runnables/passthrough.py", line 349, in <module>
      _graph_passthrough: RunnablePassthrough = RunnablePassthrough()
  pydantic_core._pydantic_core.ValidationError: 1 validation error for
  RunnablePassthrough
  name
    Field required ...

Cause: --prerelease=allow was pulling pydantic 2.14.0a1 as a transitive
dep, which is incompatible with langchain-core 1.4.0's top-level
RunnablePassthrough() initialization.

We need pre-releases enabled for the nightly langflow* .dev wheels we
pass on the command line, but not for transitive deps. Switch to
--prerelease=if-necessary-or-explicit, which keeps the explicit .dev
wheel installs working while resolving stable pydantic for everything
else.

Author: erichare

.github/workflows/cross-platform-test.yml

@@ -293,7 +293,12 @@ jobs:
             printf 'Installing %s wheel(s):\n' "$label"
             printf '%s\n' "$@"
             refresh_find_links
-            uv pip install --prerelease=allow --python "$PYTHON" "${FIND_LINKS[@]}" "$@"
+            # Use `if-necessary-or-explicit` (not `allow`): nightly langflow* wheels
+            # are .dev pre-releases so we need to allow them explicitly, but `allow`
+            # leaks to transitive deps and resolves pre-release pydantic alphas
+            # (e.g. 2.14.0a1) which break langchain-core's module-level
+            # `RunnablePassthrough()` call at import time.
+            uv pip install --prerelease=if-necessary-or-explicit --python "$PYTHON" "${FIND_LINKS[@]}" "$@"
           }
 
           SDK_WHEELS=(./sdk-dist/*.whl)
@@ -581,7 +586,8 @@ jobs:
             printf 'Installing %s wheel(s):\n' "$label"
             printf '%s\n' "$@"
             refresh_find_links
-            uv pip install --prerelease=allow --python "$PYTHON" "${FIND_LINKS[@]}" "$@"
+            # See stable job above for rationale on --prerelease=if-necessary-or-explicit.
+            uv pip install --prerelease=if-necessary-or-explicit --python "$PYTHON" "${FIND_LINKS[@]}" "$@"
           }
 
           SDK_WHEELS=(./sdk-dist/*.whl)
@@ -631,7 +637,7 @@ jobs:
               if [ "${{ inputs.pre_release }}" = "true" ]; then
                 NO_DEPS=""
               fi
-              uv pip install --force-reinstall $NO_DEPS --prerelease=allow --python ./test-env/Scripts/python.exe "${INSTALL_WHEELS[@]}"
+              uv pip install --force-reinstall $NO_DEPS --prerelease=if-necessary-or-explicit --python ./test-env/Scripts/python.exe "${INSTALL_WHEELS[@]}"
             fi
           fi
 
@@ -643,7 +649,7 @@ jobs:
             if [ "${{ inputs.pre_release }}" = "true" ]; then
               NO_DEPS=""
             fi
-            uv pip install --force-reinstall $NO_DEPS --prerelease=allow --python ./test-env/Scripts/python.exe "$BASE_WHEEL"
+            uv pip install --force-reinstall $NO_DEPS --prerelease=if-necessary-or-explicit --python ./test-env/Scripts/python.exe "$BASE_WHEEL"
           fi
         shell: bash
 
@@ -668,7 +674,7 @@ jobs:
               if [ "${{ inputs.pre_release }}" = "true" ]; then
                 NO_DEPS=""
               fi
-              uv pip install --force-reinstall $NO_DEPS --prerelease=allow --python ./test-env/bin/python "${INSTALL_WHEELS[@]}"
+              uv pip install --force-reinstall $NO_DEPS --prerelease=if-necessary-or-explicit --python ./test-env/bin/python "${INSTALL_WHEELS[@]}"
             fi
           fi
 
@@ -680,7 +686,7 @@ jobs:
             if [ "${{ inputs.pre_release }}" = "true" ]; then
               NO_DEPS=""
             fi
-            uv pip install --force-reinstall $NO_DEPS --prerelease=allow --python ./test-env/bin/python "$BASE_WHEEL"
+            uv pip install --force-reinstall $NO_DEPS --prerelease=if-necessary-or-explicit --python ./test-env/bin/python "$BASE_WHEEL"
           fi
         shell: bash