diff --git a/.chronus/changes/python-nightly-fix-2026-1-6-9-19-9.md b/.chronus/changes/python-nightly-fix-2026-1-6-9-19-9.md
new file mode 100644
index 00000000000..271dc9d3c44
--- /dev/null
+++ b/.chronus/changes/python-nightly-fix-2026-1-6-9-19-9.md
@@ -0,0 +1,7 @@
+---
+changeKind: fix
+packages:
+  - "@typespec/http-client-python"
+---
+
+Fall back "Http.File" to "bytes" to avoid generation failure
\ No newline at end of file
diff --git a/packages/http-client-python/emitter/src/http.ts b/packages/http-client-python/emitter/src/http.ts
index 99184365d16..df1ee4702c3 100644
--- a/packages/http-client-python/emitter/src/http.ts
+++ b/packages/http-client-python/emitter/src/http.ts
@@ -480,6 +480,7 @@ function emitHttpHeaderParameter(
   parameter: SdkHeaderParameter,
   method: SdkServiceMethod<SdkHttpOperation>,
   serviceApiVersions: string[],
+  bodyParam?: SdkBodyParameter,
 ): Record<string, any> {
   const base = emitParamBase(context, parameter, method, serviceApiVersions);
   const [delimiter, explode] = getDelimiterAndExplode(parameter);
@@ -489,6 +490,16 @@ function emitHttpHeaderParameter(
     if (!clientDefaultValue && parameter.type.kind === "constant") {
       clientDefaultValue = parameter.type.value;
     }
+    // if still no default value, try to derive from body parameter's content types
+    if (!clientDefaultValue && bodyParam) {
+      const fileContentTypes = getHttpFileContentTypes(bodyParam);
+      const defaultContentType = fileContentTypes
+        ? fileContentTypes[0]
+        : bodyParam.defaultContentType;
+      if (defaultContentType) {
+        clientDefaultValue = defaultContentType;
+      }
+    }
     base.type = KnownTypes.string;
   }
   return {
@@ -571,7 +582,15 @@ function emitHttpParameters(
   for (const parameter of httpParameters) {
     switch (parameter.kind) {
       case "header":
-        parameters.push(emitHttpHeaderParameter(context, parameter, method, serviceApiVersions));
+        parameters.push(
+          emitHttpHeaderParameter(
+            context,
+            parameter,
+            method,
+            serviceApiVersions,
+            operation.bodyParam,
+          ),
+        );
         break;
       case "query":
         parameters.push(
@@ -587,21 +606,40 @@ function emitHttpParameters(
   return parameters;
 }
 
+function isHttpFileType(
+  type: { kind: string; crossLanguageDefinitionId?: string } | undefined,
+): boolean {
+  return type?.kind === "model" && type?.crossLanguageDefinitionId === "TypeSpec.Http.File";
+}
+
+function getHttpFileContentTypes(bodyParam: SdkBodyParameter): string[] | undefined {
+  if (bodyParam.type.kind === "model" && isHttpFileType(bodyParam.type)) {
+    const contentTypeProp = bodyParam.type.properties.find((p) => p.name === "contentType");
+    if (contentTypeProp && contentTypeProp.type.kind === "constant" && contentTypeProp.type.value) {
+      return [String(contentTypeProp.type.value)];
+    }
+  }
+  return undefined;
+}
+
 function emitHttpBodyParameter(
   context: PythonSdkContext,
   bodyParam?: SdkBodyParameter,
   serviceApiVersions: string[] = [],
 ): Record<string, any> | undefined {
   if (bodyParam === undefined) return undefined;
+  const fileContentTypes = getHttpFileContentTypes(bodyParam);
+  const contentTypes = fileContentTypes ?? bodyParam.contentTypes;
+  const defaultContentType = fileContentTypes ? fileContentTypes[0] : bodyParam.defaultContentType;
   return {
     ...emitParamBase(context, bodyParam, undefined, serviceApiVersions),
-    contentTypes: bodyParam.contentTypes,
+    contentTypes,
     location: bodyParam.kind,
     clientName: bodyParam.isGeneratedName ? "body" : camelToSnakeCase(bodyParam.name),
     wireName: bodyParam.isGeneratedName ? "body" : bodyParam.name,
     implementation: getImplementation(context, bodyParam),
     clientDefaultValue: bodyParam.clientDefaultValue,
-    defaultContentType: bodyParam.defaultContentType,
+    defaultContentType,
   };
 }
 
@@ -637,8 +675,13 @@ function emitHttpResponse(
     type["referredByOperationType"] |= referredBy;
   }
 
+  const httpFile = isHttpFileType(response.type);
+  const headers = response.headers
+    .filter((x) => !httpFile || x.serializedName)
+    .map((x) => emitHttpResponseHeader(context, x));
+
   return {
-    headers: response.headers.map((x) => emitHttpResponseHeader(context, x)),
+    headers,
     statusCodes:
       typeof statusCodes === "object"
         ? [[(statusCodes as HttpStatusCodeRange).start, (statusCodes as HttpStatusCodeRange).end]]
diff --git a/packages/http-client-python/emitter/src/types.ts b/packages/http-client-python/emitter/src/types.ts
index 4bffbdbb2c6..81ed41428e1 100644
--- a/packages/http-client-python/emitter/src/types.ts
+++ b/packages/http-client-python/emitter/src/types.ts
@@ -260,6 +260,9 @@ function emitModel(context: PythonSdkContext, type: SdkModelType): Record<string
   if (typesMap.has(type)) {
     return typesMap.get(type)!;
   }
+  if (type.crossLanguageDefinitionId === "TypeSpec.Http.File") {
+    return getSimpleTypeResult({ type: "bytes" });
+  }
   if (type.crossLanguageDefinitionId === "Azure.Core.Foundations.Error") {
     return {
       type: "sdkcore",
diff --git a/packages/http-client-python/eng/scripts/ci/regenerate.ts b/packages/http-client-python/eng/scripts/ci/regenerate.ts
index 85a4a729eac..feececed164 100644
--- a/packages/http-client-python/eng/scripts/ci/regenerate.ts
+++ b/packages/http-client-python/eng/scripts/ci/regenerate.ts
@@ -49,8 +49,14 @@ const AZURE_EMITTER_OPTIONS: Record<string, Record<string, string> | Record<stri
   "azure/client-generator-core/api-version": {
     namespace: "specs.azure.clientgenerator.core.apiversion",
   },
-  "azure/client-generator-core/client-initialization": {
-    namespace: "specs.azure.clientgenerator.core.clientinitialization",
+  "azure/client-generator-core/client-initialization/default": {
+    namespace: "specs.azure.clientgenerator.core.clientinitialization.default",
+  },
+  "azure/client-generator-core/client-initialization/individually": {
+    namespace: "specs.azure.clientgenerator.core.clientinitialization.individually",
+  },
+  "azure/client-generator-core/client-initialization/individuallyParent": {
+    namespace: "specs.azure.clientgenerator.core.clientinitialization.individuallyparent",
   },
   "azure/client-generator-core/client-location": {
     namespace: "specs.azure.clientgenerator.core.clientlocation",
@@ -279,6 +285,10 @@ const EMITTER_OPTIONS: Record<string, Record<string, string> | Record<string, st
     "package-name": "typetest-discriminatedunion",
     namespace: "typetest.discriminatedunion",
   },
+  "type/file": {
+    "package-name": "typetest-file",
+    namespace: "typetest.file",
+  },
   documentation: {
     "package-name": "specs-documentation",
     namespace: "specs.documentation",
diff --git a/packages/http-client-python/generator/pygen/codegen/templates/utils.py.jinja2 b/packages/http-client-python/generator/pygen/codegen/templates/utils.py.jinja2
index 140f80638cd..8a4ed10f916 100644
--- a/packages/http-client-python/generator/pygen/codegen/templates/utils.py.jinja2
+++ b/packages/http-client-python/generator/pygen/codegen/templates/utils.py.jinja2
@@ -22,10 +22,14 @@ class ClientMixinABC(ABC, Generic[TClient, TConfig]):
 def raise_if_not_implemented(cls, abstract_methods):
     not_implemented = [f for f in abstract_methods if not callable(getattr(cls, f, None))]
     if not_implemented:
-        raise NotImplementedError("The following methods on operation group '{}' are not implemented: '{}'."
-        " Please refer to https://aka.ms/azsdk/python/dpcodegen/python/customize to learn how to customize.".format(
-        cls.__name__, '\', \''.join(not_implemented))
-        )
+        def _not_implemented(method_name, og_name):
+            def _raise(self, *args, **kwargs):
+                raise NotImplementedError("Method '{}' on operation group '{}' is not implemented."
+                " Please refer to https://aka.ms/azsdk/python/dpcodegen/python/customize to learn how to customize.".format(
+                method_name, og_name))
+            return _raise
+        for method in not_implemented:
+            setattr(cls, method, _not_implemented(method, cls.__name__))
 {% endif %}
 
 {% if code_model.need_utils_etag(client_namespace) %}
diff --git a/packages/http-client-python/generator/test/azure/mock_api_tests/asynctests/test_azure_client_generator_core_client_initialization_async.py b/packages/http-client-python/generator/test/azure/mock_api_tests/asynctests/test_azure_client_generator_core_client_initialization_async.py
index abaf9179c90..156f87a9a01 100644
--- a/packages/http-client-python/generator/test/azure/mock_api_tests/asynctests/test_azure_client_generator_core_client_initialization_async.py
+++ b/packages/http-client-python/generator/test/azure/mock_api_tests/asynctests/test_azure_client_generator_core_client_initialization_async.py
@@ -4,15 +4,14 @@
 # license information.
 # --------------------------------------------------------------------------
 import pytest
-from specs.azure.clientgenerator.core.clientinitialization.aio import (
+from specs.azure.clientgenerator.core.clientinitialization.default.aio import (
     HeaderParamClient,
     MultipleParamsClient,
     MixedParamsClient,
     PathParamClient,
     ParamAliasClient,
-    ParentClient,
 )
-from specs.azure.clientgenerator.core.clientinitialization.models import Input
+from specs.azure.clientgenerator.core.clientinitialization.default.models import Input
 
 
 @pytest.mark.asyncio
diff --git a/packages/http-client-python/generator/test/azure/mock_api_tests/test_azure_client_generator_core_client_initialization.py b/packages/http-client-python/generator/test/azure/mock_api_tests/test_azure_client_generator_core_client_initialization.py
index 569a765af43..602332210f5 100644
--- a/packages/http-client-python/generator/test/azure/mock_api_tests/test_azure_client_generator_core_client_initialization.py
+++ b/packages/http-client-python/generator/test/azure/mock_api_tests/test_azure_client_generator_core_client_initialization.py
@@ -3,15 +3,14 @@
 # Licensed under the MIT License. See License.txt in the project root for
 # license information.
 # --------------------------------------------------------------------------
-from specs.azure.clientgenerator.core.clientinitialization import (
+from specs.azure.clientgenerator.core.clientinitialization.default import (
     HeaderParamClient,
     MultipleParamsClient,
     MixedParamsClient,
     PathParamClient,
     ParamAliasClient,
-    ParentClient,
 )
-from specs.azure.clientgenerator.core.clientinitialization.models import Input
+from specs.azure.clientgenerator.core.clientinitialization.default.models import Input
 
 
 def test_header_param_client():
diff --git a/packages/http-client-python/generator/test/azure/requirements.txt b/packages/http-client-python/generator/test/azure/requirements.txt
index 8c9d1fd91a9..424beb3a176 100644
--- a/packages/http-client-python/generator/test/azure/requirements.txt
+++ b/packages/http-client-python/generator/test/azure/requirements.txt
@@ -7,7 +7,9 @@ azure-mgmt-core==1.6.0
 -e ./generated/azure-client-generator-core-api-version-header
 -e ./generated/azure-client-generator-core-api-version-path
 -e ./generated/azure-client-generator-core-api-version-query
--e ./generated/azure-client-generator-core-client-initialization
+-e ./generated/azure-client-generator-core-client-initialization-default
+-e ./generated/azure-client-generator-core-client-initialization-individually
+-e ./generated/azure-client-generator-core-client-initialization-individuallyparent
 -e ./generated/azure-client-generator-core-deserialize-empty-string-as-null
 -e ./generated/azure-client-generator-core-flatten-property
 -e ./generated/azure-client-generator-core-hierarchy-building
@@ -82,6 +84,7 @@ azure-mgmt-core==1.6.0
 -e ./generated/typetest-dictionary
 -e ./generated/typetest-enum-extensible
 -e ./generated/typetest-enum-fixed
+-e ./generated/typetest-file
 -e ./generated/typetest-model-enumdiscriminator
 -e ./generated/typetest-model-nesteddiscriminator
 -e ./generated/typetest-model-notdiscriminated
diff --git a/packages/http-client-python/generator/test/generic_mock_api_tests/asynctests/test_typetest_file_async.py b/packages/http-client-python/generator/test/generic_mock_api_tests/asynctests/test_typetest_file_async.py
new file mode 100644
index 00000000000..aba1bf14d98
--- /dev/null
+++ b/packages/http-client-python/generator/test/generic_mock_api_tests/asynctests/test_typetest_file_async.py
@@ -0,0 +1,55 @@
+# -------------------------------------------------------------------------
+# Copyright (c) Microsoft Corporation. All rights reserved.
+# Licensed under the MIT License. See License.txt in the project root for
+# license information.
+# --------------------------------------------------------------------------
+import json
+
+import pytest
+from typetest.file.aio import FileClient
+
+
+@pytest.fixture
+async def client():
+    async with FileClient(endpoint="http://localhost:3000") as client:
+        yield client
+
+
+@pytest.mark.asyncio
+async def test_upload_file_specific_content_type(client: FileClient, png_data: bytes):
+    await client.body.upload_file_specific_content_type(png_data)
+
+
+# Do not support this case for now
+# @pytest.mark.asyncio
+# async def test_upload_file_json_content_type(client: FileClient):
+#     await client.body.upload_file_json_content_type(json.dumps({"message": "test file content"}).encode())
+
+
+@pytest.mark.asyncio
+async def test_download_file_json_content_type(client: FileClient):
+    result = await client.body.download_file_json_content_type()
+    assert result is not None
+
+
+@pytest.mark.asyncio
+async def test_download_file_specific_content_type(client: FileClient, png_data: bytes):
+    result = b"".join([d async for d in (await client.body.download_file_specific_content_type())])
+    assert result == png_data
+
+
+@pytest.mark.asyncio
+async def test_download_file_multiple_content_types(client: FileClient, png_data: bytes):
+    result = b"".join([d async for d in (await client.body.download_file_multiple_content_types())])
+    assert result == png_data
+
+
+@pytest.mark.asyncio
+async def test_upload_file_default_content_type(client: FileClient, png_data: bytes):
+    await client.body.upload_file_default_content_type(png_data, content_type="image/png")
+
+
+@pytest.mark.asyncio
+async def test_download_file_default_content_type(client: FileClient, png_data: bytes):
+    result = b"".join([d async for d in (await client.body.download_file_default_content_type())])
+    assert result == png_data
diff --git a/packages/http-client-python/generator/test/generic_mock_api_tests/test_typetest_file.py b/packages/http-client-python/generator/test/generic_mock_api_tests/test_typetest_file.py
new file mode 100644
index 00000000000..7e87a52ff75
--- /dev/null
+++ b/packages/http-client-python/generator/test/generic_mock_api_tests/test_typetest_file.py
@@ -0,0 +1,48 @@
+# -------------------------------------------------------------------------
+# Copyright (c) Microsoft Corporation. All rights reserved.
+# Licensed under the MIT License. See License.txt in the project root for
+# license information.
+# --------------------------------------------------------------------------
+import json
+
+import pytest
+from typetest.file import FileClient
+
+
+@pytest.fixture
+def client():
+    with FileClient(endpoint="http://localhost:3000") as client:
+        yield client
+
+
+def test_upload_file_specific_content_type(client: FileClient, png_data: bytes):
+    client.body.upload_file_specific_content_type(png_data)
+
+
+# Do not support this case for now
+# def test_upload_file_json_content_type(client: FileClient):
+#     client.body.upload_file_json_content_type(json.dumps({"message": "test file content"}).encode())
+
+
+def test_download_file_json_content_type(client: FileClient):
+    result = client.body.download_file_json_content_type()
+    assert result is not None
+
+
+def test_download_file_specific_content_type(client: FileClient, png_data: bytes):
+    result = b"".join(client.body.download_file_specific_content_type())
+    assert result == png_data
+
+
+def test_download_file_multiple_content_types(client: FileClient, png_data: bytes):
+    result = b"".join(client.body.download_file_multiple_content_types())
+    assert result == png_data
+
+
+def test_upload_file_default_content_type(client: FileClient, png_data: bytes):
+    client.body.upload_file_default_content_type(png_data, content_type="image/png")
+
+
+def test_download_file_default_content_type(client: FileClient, png_data: bytes):
+    result = b"".join(client.body.download_file_default_content_type())
+    assert result == png_data
diff --git a/packages/http-client-python/generator/test/unbranded/requirements.txt b/packages/http-client-python/generator/test/unbranded/requirements.txt
index 9a5c309bffa..7dc3b37522d 100644
--- a/packages/http-client-python/generator/test/unbranded/requirements.txt
+++ b/packages/http-client-python/generator/test/unbranded/requirements.txt
@@ -29,6 +29,7 @@
 -e ./generated/typetest-dictionary
 -e ./generated/typetest-enum-extensible
 -e ./generated/typetest-enum-fixed
+-e ./generated/typetest-file
 -e ./generated/typetest-model-enumdiscriminator
 -e ./generated/typetest-model-nesteddiscriminator
 -e ./generated/typetest-model-notdiscriminated
diff --git a/packages/http-client-python/package-lock.json b/packages/http-client-python/package-lock.json
index 4e173ed3521..d4650c20712 100644
--- a/packages/http-client-python/package-lock.json
+++ b/packages/http-client-python/package-lock.json
@@ -17,7 +17,7 @@
         "tsx": "~4.19.1"
       },
       "devDependencies": {
-        "@azure-tools/azure-http-specs": "0.1.0-alpha.37-dev.1",
+        "@azure-tools/azure-http-specs": "0.1.0-alpha.37-dev.3",
         "@azure-tools/typespec-autorest": "~0.64.1",
         "@azure-tools/typespec-azure-core": "~0.64.0",
         "@azure-tools/typespec-azure-resource-manager": "~0.64.1",
@@ -29,7 +29,7 @@
         "@typespec/compiler": "^1.8.0",
         "@typespec/events": "~0.78.0",
         "@typespec/http": "^1.8.0",
-        "@typespec/http-specs": "0.1.0-alpha.32-dev.5",
+        "@typespec/http-specs": "0.1.0-alpha.32-dev.6",
         "@typespec/openapi": "^1.8.0",
         "@typespec/rest": "~0.78.0",
         "@typespec/spec-api": "0.1.0-alpha.12",
@@ -66,9 +66,9 @@
       }
     },
     "node_modules/@azure-tools/azure-http-specs": {
-      "version": "0.1.0-alpha.37-dev.1",
-      "resolved": "https://registry.npmjs.org/@azure-tools/azure-http-specs/-/azure-http-specs-0.1.0-alpha.37-dev.1.tgz",
-      "integrity": "sha512-lGu4bBoN8ghpHWUwRJK2auHcY+AUpPkcVbD18Z06FBi66vR8m7e0dczOl40YpUKUlbjlGjZon9QT2iSp9hKoWA==",
+      "version": "0.1.0-alpha.37-dev.3",
+      "resolved": "https://registry.npmjs.org/@azure-tools/azure-http-specs/-/azure-http-specs-0.1.0-alpha.37-dev.3.tgz",
+      "integrity": "sha512-XCNift6HBDFgF63tIOyYOyis82b+tOgNNMuLMNzz+c7lCGGLjfRicFh3YgIlh69YMzKYREbXfHkx3JZ4nlsN0g==",
       "dev": true,
       "license": "MIT",
       "dependencies": {
@@ -2318,9 +2318,9 @@
       }
     },
     "node_modules/@typespec/http-specs": {
-      "version": "0.1.0-alpha.32-dev.5",
-      "resolved": "https://registry.npmjs.org/@typespec/http-specs/-/http-specs-0.1.0-alpha.32-dev.5.tgz",
-      "integrity": "sha512-MD1nWHuste79REtadDyPGTTAZwgGCGD/kB9K8zNX2nTTbAMiWzUTBhpztZtQ+A08G3Snn1ZwSFy4OTyYkHCg6g==",
+      "version": "0.1.0-alpha.32-dev.6",
+      "resolved": "https://registry.npmjs.org/@typespec/http-specs/-/http-specs-0.1.0-alpha.32-dev.6.tgz",
+      "integrity": "sha512-0YlxxbmBuOeyVjrLWFNb+6VG36M+WpnKbogLHrm1xvpWhPGaj1OriRCWv4Cxof+Vx0az4xRHPxhpINb7+uq7rw==",
       "dev": true,
       "license": "MIT",
       "dependencies": {
diff --git a/packages/http-client-python/package.json b/packages/http-client-python/package.json
index 081ffab2d4e..48b70df2bf0 100644
--- a/packages/http-client-python/package.json
+++ b/packages/http-client-python/package.json
@@ -82,7 +82,7 @@
     "@azure-tools/typespec-azure-resource-manager": "~0.64.1",
     "@azure-tools/typespec-azure-rulesets": "~0.64.0",
     "@azure-tools/typespec-client-generator-core": "~0.64.6",
-    "@azure-tools/azure-http-specs": "0.1.0-alpha.37-dev.1",
+    "@azure-tools/azure-http-specs": "0.1.0-alpha.37-dev.3",
     "@typespec/compiler": "^1.8.0",
     "@typespec/http": "^1.8.0",
     "@typespec/openapi": "^1.8.0",
@@ -94,7 +94,7 @@
     "@typespec/sse": "~0.78.0",
     "@typespec/streams": "~0.78.0",
     "@typespec/xml": "~0.78.0",
-    "@typespec/http-specs": "0.1.0-alpha.32-dev.5",
+    "@typespec/http-specs": "0.1.0-alpha.32-dev.6",
     "@types/js-yaml": "~4.0.5",
     "@types/node": "~24.1.0",
     "@types/semver": "7.5.8",