[pull] main from fern-api:main

generators/python-v2/dynamic-snippets/src/context/DynamicSnippetsGeneratorContext.ts

@@ -101,12 +101,16 @@ export class DynamicSnippetsGeneratorContext extends AbstractDynamicSnippetsGene
         discriminantValue: FernIr.dynamic.NameAndWireValue;
     }): python.Reference {
         const unionClassName = this.getClassName(unionDeclaration.name);
-        const variantSuffix = discriminantValue.name.pascalCase.safeName;
+        const variantName = discriminantValue.name.pascalCase.safeName;
         const modulePath = [
             ...this.getRootModulePath(),
             ...unionDeclaration.fernFilepath.allParts.map((part) => part.snakeCase.safeName)
         ];
-        return python.reference({ name: `${unionClassName}_${variantSuffix}`, modulePath });
+        const name =
+            this.customConfig.pydantic_config?.union_naming === "v1"
+                ? `${variantName}${unionClassName}`
+                : `${unionClassName}_${variantName}`;
+        return python.reference({ name, modulePath });
     }
 
     public useTypedDictRequests(): boolean {

generators/python-v2/sdk/src/wire-tests/WireTestGenerator.ts

@@ -48,7 +48,10 @@ export class WireTestGenerator {
             config: {
                 organization: context.config.organization,
                 workspaceName: context.config.workspaceName,
-                customConfig: context.customConfig
+                // Pass the raw customConfig (not the parsed SdkCustomConfigSchema) so that
+                // fields consumed by the dynamic snippets generator (e.g. pydantic_config)
+                // are preserved. SdkCustomConfigSchema.parse() strips unknown keys.
+                customConfig: context.config.customConfig
             } as FernGeneratorExec.GeneratorConfig
         });
     }

generators/python/sdk/changes/5.5.2/fix-wire-test-union-naming-v1.yml

@@ -0,0 +1,8 @@
+# yaml-language-server: $schema=../../../../../fern-changes-yml.schema.json
+
+- summary: |
+    Fix generated wire tests and dynamic snippets to honor `pydantic_config.union_naming: v1`.
+    Previously, variant class names in wire tests and README/reference snippets were always
+    emitted with the v0 suffix style (e.g. `UnionName_Variant`), causing import errors when
+    the SDK types were generated with v1 prefix-style names (e.g. `VariantUnionName`).
+  type: fix

generators/python/sdk/versions.yml

@@ -1,4 +1,14 @@
 # yaml-language-server: $schema=../../../fern-versions-yml.schema.json
+- version: 5.5.2
+  changelogEntry:
+    - summary: |
+        Fix generated wire tests and dynamic snippets to honor `pydantic_config.union_naming: v1`.
+        Previously, variant class names in wire tests and README/reference snippets were always
+        emitted with the v0 suffix style (e.g. `UnionName_Variant`), causing import errors when
+        the SDK types were generated with v1 prefix-style names (e.g. `VariantUnionName`).
+      type: fix
+  createdAt: "2026-04-18"
+  irVersion: 66
 - version: 5.5.1
   changelogEntry:
     - summary: |

seed/python-sdk/seed.yml

@@ -386,6 +386,12 @@ fixtures:
           union_naming: v1
         use_inheritance_for_extended_models: false
       outputFolder: union-naming-v1
+    - customConfig:
+        enable_wire_tests: true
+        pydantic_config:
+          union_naming: v1
+        use_inheritance_for_extended_models: false
+      outputFolder: union-naming-v1-wire-tests
   websocket:
     - outputFolder: websocket-base
     - customConfig:
@@ -475,3 +481,9 @@ allowedFailures:
   - server-sent-event-examples:with-wire-tests # TODO: update wiretests geranation then remove it
   - trace
   - multi-url-environment-reference
+  # The unions API has two services (`union` and `bigunion`) that both expose
+  # `GET /{id}` on the root base-path, which causes a WireMock stub collision at
+  # test runtime. Code generation and imports are verified; one wire test
+  # assertion fails due to the colliding mocks. This is pre-existing and unrelated
+  # to the union_naming v1 fix this fixture regression-tests.
+  - unions:union-naming-v1-wire-tests