feat(csharp): add support for inferred authentication scheme

generators/browser-compatible-base/package.json

@@ -33,7 +33,7 @@
   },
   "dependencies": {
     "@fern-api/core-utils": "workspace:*",
-    "@fern-api/dynamic-ir-sdk": "^61.7.0",
+    "@fern-api/dynamic-ir-sdk": "^62.3.0",
     "@fern-api/fern-definition-schema": "workspace:*",
     "@fern-api/logger": "workspace:*",
     "@fern-api/path-utils": "workspace:*",

generators/csharp/base/package.json

@@ -37,7 +37,7 @@
     "@fern-api/csharp-codegen": "workspace:*",
     "@fern-api/fs-utils": "workspace:*",
     "@fern-api/logging-execa": "workspace:*",
-    "@fern-fern/ir-sdk": "^61.7.0",
+    "@fern-fern/ir-sdk": "^62.3.0",
     "@types/lodash-es": "^4.17.12",
     "@types/node": "18.15.3",
     "depcheck": "^1.4.7",

generators/csharp/codegen/package.json

@@ -33,8 +33,8 @@
   "dependencies": {
     "@fern-api/browser-compatible-base-generator": "workspace:*",
     "@fern-api/core-utils": "workspace:*",
-    "@fern-api/dynamic-ir-sdk": "^61.7.0",
-    "@fern-fern/ir-sdk": "^61.7.0",
+    "@fern-api/dynamic-ir-sdk": "^62.3.0",
+    "@fern-fern/ir-sdk": "^62.3.0",
     "zod": "^3.22.3"
   },
   "devDependencies": {

generators/csharp/codegen/src/context/generation-info.ts

@@ -384,7 +384,9 @@ export class Generation {
         }),
         methods: lazy({
             mockOauth: () => "MockOAuthEndpoint",
-            getAccessTokenAsync: () => "GetAccessTokenAsync"
+            mockInferredAuth: () => "MockInferredAuthEndpoint",
+            getAccessTokenAsync: () => "GetAccessTokenAsync",
+            getAuthHeadersAsync: () => "GetAuthHeadersAsync"
         }),
         variables: lazy({
             client: () => "client",
@@ -686,6 +688,12 @@ export class Generation {
                 origin: this.model.staticExplicit("OAuthTokenProvider"),
                 namespace: this.namespaces.core
             }),
+        /** Inferred auth token provider for authentication */
+        InferredAuthTokenProvider: () =>
+            this.csharp.classReference({
+                origin: this.model.staticExplicit("InferredAuthTokenProvider"),
+                namespace: this.namespaces.core
+            }),
         /** Converter for Protocol Buffer types */
         ProtoConverter: () =>
             this.csharp.classReference({

generators/csharp/dynamic-snippets/package.json

@@ -36,7 +36,7 @@
     "@fern-api/configs": "workspace:*",
     "@fern-api/core-utils": "workspace:*",
     "@fern-api/csharp-codegen": "workspace:*",
-    "@fern-api/dynamic-ir-sdk": "61.4.0",
+    "@fern-api/dynamic-ir-sdk": "^62.3.0",
     "@fern-api/path-utils": "workspace:*",
     "@types/lodash-es": "^4.17.12",
     "@types/node": "18.15.3",

generators/csharp/dynamic-snippets/src/EndpointSnippetGenerator.ts

@@ -175,6 +175,8 @@ export class EndpointSnippetGenerator extends WithGeneration {
         snippet: FernIr.dynamic.EndpointSnippetRequest;
     }): NamedArgument[] {
         const authArgs: NamedArgument[] = [];
+
+        // Check if the API uses inferred auth by looking for a token endpoint
         if (endpoint.auth != null) {
             if (snippet.auth != null) {
                 authArgs.push(...this.getConstructorAuthArgs({ auth: endpoint.auth, values: snippet.auth }));
@@ -324,8 +326,7 @@ export class EndpointSnippetGenerator extends WithGeneration {
             case "oauth":
                 return values.type === "oauth" ? this.getConstructorOAuthArgs({ auth, values }) : [];
             case "inferred":
-                this.addWarning("The C# SDK Generator does not support Inferred auth scheme yet");
-                return [];
+                return values.type === "inferred" ? this.getConstructorInferredAuthArgs({ auth, values }) : [];
             default:
                 assertNever(auth);
         }
@@ -411,6 +412,41 @@ export class EndpointSnippetGenerator extends WithGeneration {
         ];
     }
 
+    private getConstructorInferredAuthArgs({
+        auth,
+        values
+    }: {
+        auth: FernIr.dynamic.InferredAuth;
+        values: FernIr.dynamic.InferredAuthValues;
+    }): NamedArgument[] {
+        const args: NamedArgument[] = [];
+
+        // Use parameters from the IR
+        if (auth.parameters != null) {
+            for (const param of auth.parameters) {
+                const wireValue = param.name.wireValue;
+                const value = values.values?.[wireValue];
+
+                args.push({
+                    name: this.context.getParameterName(param.name.name),
+                    assignment: this.context.dynamicLiteralMapper.convert({
+                        typeReference: param.typeReference,
+                        value: value,
+                        fallbackToDefault: wireValue
+                    })
+                });
+            }
+        } else {
+            this.context.errors.add({
+                severity: Severity.Critical,
+                message:
+                    "Inferred auth parameters are not defined in the IR. Please ensure you're using IR version 62.3.0 or later."
+            });
+        }
+
+        return args;
+    }
+
     private getConstructorHeaderArgs({
         headers,
         values

generators/csharp/model/package.json

@@ -46,7 +46,7 @@
     "@fern-api/csharp-codegen": "workspace:*",
     "@fern-api/csharp-formatter": "workspace:*",
     "@fern-api/fs-utils": "workspace:*",
-    "@fern-fern/ir-sdk": "^61.7.0",
+    "@fern-fern/ir-sdk": "^62.3.0",
     "@types/node": "18.15.3",
     "depcheck": "^1.4.7",
     "typescript": "5.9.3",

generators/csharp/model/versions.yml

@@ -1,4 +1,11 @@
 # yaml-language-server: $schema=../../../fern-versions-yml.schema.json
+- version: 0.0.6
+  changelogEntry:
+    - type: internal
+      summary: Upgrade to IR version 61.
+  createdAt: "2025-12-11"
+  irVersion: 62
+
 - version: 0.0.5
   changelogEntry:
     - type: chore

generators/csharp/sdk/package.json

@@ -50,7 +50,7 @@
     "@fern-api/logger": "workspace:*",
     "@fern-fern/generator-cli-sdk": "^0.1.5",
     "@fern-fern/generator-exec-sdk": "^0.0.1167",
-    "@fern-fern/ir-sdk": "^61.7.0",
+    "@fern-fern/ir-sdk": "^62.3.0",
     "@types/node": "18.15.3",
     "@types/url-join": "4.0.1",
     "depcheck": "^1.4.7",

generators/csharp/sdk/src/SdkGeneratorCli.ts

@@ -20,6 +20,7 @@ import { BaseExceptionGenerator } from "./error/BaseExceptionGenerator";
 import { CustomExceptionInterceptorGenerator } from "./error/CustomExceptionInterceptorGenerator";
 import { ErrorGenerator } from "./error/ErrorGenerator";
 import { generateSdkTests } from "./generateSdkTests";
+import { InferredAuthTokenProviderGenerator } from "./inferred-auth/InferredAuthTokenProviderGenerator";
 import { OauthTokenProviderGenerator } from "./oauth/OauthTokenProviderGenerator";
 import { BaseOptionsGenerator } from "./options/BaseOptionsGenerator";
 import { ClientOptionsGenerator } from "./options/ClientOptionsGenerator";
@@ -242,6 +243,15 @@ export class SdkGeneratorCLI extends AbstractCsharpGeneratorCli {
             context.project.addSourceFiles(oauthTokenProvider.generate());
         }
 
+        const inferred = context.getInferredAuth();
+        if (inferred != null) {
+            const inferredAuthTokenProvider = new InferredAuthTokenProviderGenerator({
+                context,
+                scheme: inferred
+            });
+            context.project.addSourceFiles(inferredAuthTokenProvider.generate());
+        }
+
         const testGenerator = new TestFileGenerator(context);
         const test = testGenerator.generate();
         context.project.addTestFiles(test);
@@ -282,7 +292,10 @@ export class SdkGeneratorCLI extends AbstractCsharpGeneratorCli {
             context.logger.debug("No snippets were produced; skipping README.md generation.");
             return;
         }
-        const content = await context.generatorAgent.generateReadme({ context, endpointSnippets });
+        const content = await context.generatorAgent.generateReadme({
+            context,
+            endpointSnippets
+        });
         const otherPath = context.settings.outputPath.other;
         context.project.addRawFiles(
             new File(context.generatorAgent.README_FILENAME, RelativeFilePath.of(otherPath), content)

generators/csharp/sdk/src/SdkGeneratorContext.ts

@@ -13,6 +13,7 @@ import {
     FernFilepath,
     HttpEndpoint,
     HttpService,
+    InferredAuthScheme,
     IntermediateRepresentation,
     Name,
     NameAndWireValue,
@@ -323,6 +324,15 @@ export class SdkGeneratorContext extends GeneratorContext {
         return undefined;
     }
 
+    public getInferredAuth(): InferredAuthScheme | undefined {
+        for (const scheme of this.ir.auth.schemes) {
+            if (scheme.type === "inferred") {
+                return scheme;
+            }
+        }
+        return undefined;
+    }
+
     public resolveEndpoint(service: HttpService, endpointId: EndpointId): HttpEndpoint {
         const httpEndpoint = service.endpoints.find((endpoint) => endpoint.id === endpointId);
         if (httpEndpoint == null) {

generators/csharp/sdk/src/endpoint/AbstractEndpointGenerator.ts

@@ -8,7 +8,9 @@ import { EndpointSignatureInfo } from "./EndpointSignatureInfo";
 import { getEndpointRequest } from "./utils/getEndpointRequest";
 import { getEndpointReturnType } from "./utils/getEndpointReturnType";
 
-type PagingEndpoint = HttpEndpoint & { pagination: NonNullable<HttpEndpoint["pagination"]> };
+type PagingEndpoint = HttpEndpoint & {
+    pagination: NonNullable<HttpEndpoint["pagination"]>;
+};
 
 export abstract class AbstractEndpointGenerator extends WithGeneration {
     private exampleGenerator: ExampleGenerator;
@@ -69,10 +71,17 @@ export abstract class AbstractEndpointGenerator extends WithGeneration {
         endpoint: HttpEndpoint;
         endpointType: "unpaged" | "paged";
     }): EndpointSignatureInfo {
-        const request = getEndpointRequest({ context: this.context, endpoint, serviceId });
+        const request = getEndpointRequest({
+            context: this.context,
+            endpoint,
+            serviceId
+        });
         const requestParameter =
             request != null
-                ? this.csharp.parameter({ type: request.getParameterType(), name: request.getParameterName() })
+                ? this.csharp.parameter({
+                      type: request.getParameterType(),
+                      name: request.getParameterName()
+                  })
                 : undefined;
         const { pathParameters, pathParameterReferences } = this.getAllPathParameters({
             endpoint,
@@ -154,7 +163,9 @@ export abstract class AbstractEndpointGenerator extends WithGeneration {
                     this.csharp.parameter({
                         docs: pathParam.docs,
                         name: parameterName,
-                        type: this.context.csharpTypeMapper.convert({ reference: pathParam.valueType })
+                        type: this.context.csharpTypeMapper.convert({
+                            reference: pathParam.valueType
+                        })
                     })
                 );
             }

generators/csharp/sdk/src/endpoint/grpc/GrpcEndpointGenerator.ts

@@ -24,7 +24,10 @@ export class GrpcEndpointGenerator extends AbstractEndpointGenerator {
         cls: ast.Class,
         { serviceId, endpoint, rawGrpcClientReference, grpcClientInfo }: GrpcEndpointGenerator.Args
     ) {
-        const endpointSignatureInfo = this.getEndpointSignatureInfo({ serviceId, endpoint });
+        const endpointSignatureInfo = this.getEndpointSignatureInfo({
+            serviceId,
+            endpoint
+        });
         const parameters = [...endpointSignatureInfo.baseParameters];
         parameters.push(
             this.csharp.parameter({
@@ -57,7 +60,10 @@ export class GrpcEndpointGenerator extends AbstractEndpointGenerator {
             summary: endpoint.docs,
             return_: endpointSignatureInfo.returnType,
             body: this.settings.includeExceptionHandler
-                ? this.wrapWithExceptionHandler({ body, returnType: endpointSignatureInfo.returnType })
+                ? this.wrapWithExceptionHandler({
+                      body,
+                      returnType: endpointSignatureInfo.returnType
+                  })
                 : body,
             codeExample: snippet?.endpointCall
         });