feat(go): add OAuth token override support

generators/go-v2/ast/src/custom-config/BaseGoCustomConfigSchema.ts

@@ -24,7 +24,8 @@ export const baseGoCustomConfigSchema = z.object({
     enableWireTests: z.boolean().optional(),
     exportAllRequestsAtRoot: z.boolean().optional(),
     customReadmeSections: z.array(CustomReadmeSectionSchema).optional(),
-    customPagerName: z.string().optional()
+    customPagerName: z.string().optional(),
+    oauthTokenOverride: z.boolean().optional()
 });
 
 export type BaseGoCustomConfigSchema = z.infer<typeof baseGoCustomConfigSchema>;

generators/go/cmd/fern-go-fiber/main.go

@@ -34,6 +34,7 @@ func run(config *cmd.Config, coordinator *coordinator.Client) ([]*generator.File
 		config.UseReaderForBytesRequest,
 		config.GettersPassByValue,
 		config.ExportAllRequestsAtRoot,
+		config.OAuthTokenOverride,
 		config.Organization,
 		config.Version,
 		config.IrFilepath,

generators/go/cmd/fern-go-model/main.go

@@ -34,6 +34,7 @@ func run(config *cmd.Config, coordinator *coordinator.Client) ([]*generator.File
 		config.UseReaderForBytesRequest,
 		config.GettersPassByValue,
 		config.ExportAllRequestsAtRoot,
+		config.OAuthTokenOverride,
 		config.Organization,
 		config.Version,
 		config.IrFilepath,

generators/go/cmd/fern-go-sdk/main.go

@@ -34,6 +34,7 @@ func run(config *cmd.Config, coordinator *coordinator.Client) ([]*generator.File
 		config.UseReaderForBytesRequest,
 		config.GettersPassByValue,
 		config.ExportAllRequestsAtRoot,
+		config.OAuthTokenOverride,
 		config.Organization,
 		config.Version,
 		config.IrFilepath,

generators/go/internal/cmd/cmd.go

@@ -64,6 +64,7 @@ type Config struct {
 	UseReaderForBytesRequest     bool
 	GettersPassByValue           bool
 	ExportAllRequestsAtRoot      bool
+	OAuthTokenOverride           bool
 	Organization                 string
 	CoordinatorURL               string
 	CoordinatorTaskID            string
@@ -235,6 +236,7 @@ func newConfig(configFilename string) (*Config, error) {
 		UseReaderForBytesRequest:     *customConfig.UseReaderForBytesRequest,
 		GettersPassByValue:           *customConfig.GettersPassByValue,
 		ExportAllRequestsAtRoot:      *customConfig.ExportAllRequestsAtRoot,
+		OAuthTokenOverride:           *customConfig.OAuthTokenOverride,
 		Organization:                 config.Organization,
 		AlwaysSendRequiredProperties: *customConfig.AlwaysSendRequiredProperties,
 		Whitelabel:                   config.Whitelabel,
@@ -299,6 +301,7 @@ type customConfig struct {
 	UseReaderForBytesRequest     *bool         `json:"useReaderForBytesRequest,omitempty"`
 	GettersPassByValue           *bool         `json:"gettersPassByValue,omitempty"`
 	ExportAllRequestsAtRoot      *bool         `json:"exportAllRequestsAtRoot,omitempty"`
+	OAuthTokenOverride           *bool         `json:"oauthTokenOverride,omitempty"`
 	ClientName                   string        `json:"clientName,omitempty"`
 	ClientConstructorName        string        `json:"clientConstructorName,omitempty"`
 	ImportPath                   string        `json:"importPath,omitempty"`
@@ -459,6 +462,9 @@ func applyCustomConfigDefaultsForV1(customConfig *customConfig) *customConfig {
 	if customConfig.ExportAllRequestsAtRoot == nil {
 		customConfig.ExportAllRequestsAtRoot = gospec.Ptr(false)
 	}
+	if customConfig.OAuthTokenOverride == nil {
+		customConfig.OAuthTokenOverride = gospec.Ptr(false)
+	}
 	if customConfig.UnionVersion == "" {
 		customConfig.UnionVersion = "v1"
 	}

generators/go/internal/generator/config.go

@@ -28,6 +28,7 @@ type Config struct {
 	UseReaderForBytesRequest     bool
 	GettersPassByValue           bool
 	ExportAllRequestsAtRoot      bool
+	OAuthTokenOverride           bool
 	Organization                 string
 	Version                      string
 	IRFilepath                   string
@@ -74,6 +75,7 @@ func NewConfig(
 	useReaderForBytesRequest bool,
 	gettersPassByValue bool,
 	exportAllRequestsAtRoot bool,
+	oauthTokenOverride bool,
 	organization string,
 	version string,
 	irFilepath string,
@@ -105,6 +107,7 @@ func NewConfig(
 		UseReaderForBytesRequest:     useReaderForBytesRequest,
 		GettersPassByValue:           gettersPassByValue,
 		ExportAllRequestsAtRoot:      exportAllRequestsAtRoot,
+		OAuthTokenOverride:           oauthTokenOverride,
 		Version:                      version,
 		IRFilepath:                   irFilepath,
 		SnippetFilepath:              snippetFilepath,

generators/go/internal/generator/generator.go

@@ -382,6 +382,7 @@ func (g *Generator) generate(ir *fernir.IntermediateRepresentation, mode Mode) (
 			ir.SdkConfig,
 			g.config.ModuleConfig,
 			g.config.Version,
+			g.config.OAuthTokenOverride,
 		); err != nil {
 			return nil, err
 		}

generators/go/internal/generator/sdk.go

@@ -290,6 +290,7 @@ func (f *fileWriter) WriteRequestOptionsDefinition(
 	sdkConfig *ir.SdkConfig,
 	moduleConfig *ModuleConfig,
 	sdkVersion string,
+	oauthTokenOverride bool,
 ) error {
 	importPath := path.Join(f.baseImportPath, "core")
 	f.P("// RequestOption adapts the behavior of the client or an individual request.")
@@ -329,6 +330,9 @@ func (f *fileWriter) WriteRequestOptionsDefinition(
 				typeReferenceToGoType(authScheme.Header.ValueType, f.types, f.scope, f.baseImportPath, importPath, false),
 			)
 		}
+		if authScheme.Oauth != nil && oauthTokenOverride {
+			f.P("Token string")
+		}
 	}
 	for _, header := range headers {
 		if !shouldGenerateHeader(header, f.types) {
@@ -370,7 +374,7 @@ func (f *fileWriter) WriteRequestOptionsDefinition(
 			return err
 		}
 		f.P()
-		return f.writeRequestOptionStructs(auth, headers, len(idempotencyHeaders) > 0)
+		return f.writeRequestOptionStructs(auth, headers, len(idempotencyHeaders) > 0, oauthTokenOverride)
 	}
 
 	// Generate the ToHeader method.
@@ -417,6 +421,11 @@ func (f *fileWriter) WriteRequestOptionsDefinition(
 			f.P(`header.Set("`, header.Name.WireValue, `", fmt.Sprintf("`, prefix, `%v",`, value, "))")
 			f.P("}")
 		}
+		if authScheme.Oauth != nil && oauthTokenOverride {
+			f.P(`if r.Token != "" {`)
+			f.P(`header.Set("Authorization", "Bearer " + r.Token)`)
+			f.P("}")
+		}
 	}
 	for _, header := range headers {
 		valueTypeFormat := formatForValueType(header.ValueType, f.types)
@@ -455,7 +464,7 @@ func (f *fileWriter) WriteRequestOptionsDefinition(
 
 	f.P()
 
-	if err := f.writeRequestOptionStructs(auth, headers, len(idempotencyHeaders) > 0); err != nil {
+	if err := f.writeRequestOptionStructs(auth, headers, len(idempotencyHeaders) > 0, oauthTokenOverride); err != nil {
 		return err
 	}
 
@@ -493,6 +502,7 @@ func (f *fileWriter) writeRequestOptionStructs(
 	auth *ir.ApiAuth,
 	headers []*ir.HttpHeader,
 	asIdempotentRequestOption bool,
+	oauthTokenOverride bool,
 ) error {
 	if err := f.writeOptionStruct("BaseURL", "string", true, asIdempotentRequestOption); err != nil {
 		return err
@@ -557,6 +567,11 @@ func (f *fileWriter) writeRequestOptionStructs(
 					return err
 				}
 			}
+			if authScheme.Oauth != nil && oauthTokenOverride {
+				if err := f.writeOptionStruct("Token", "string", true, asIdempotentRequestOption); err != nil {
+					return err
+				}
+			}
 		}
 	}
 

generators/go/sdk/versions.yml

@@ -1,5 +1,15 @@
 # yaml-language-server: $schema=../../../fern-versions-yml.schema.json
 
+- version: 1.19.0
+  changelogEntry:
+    - summary: |
+        Add support for OAuth token override via the `oauthTokenOverride` config option.
+        When enabled, users can provide a pre-generated bearer token directly via the `WithToken`
+        option function, bypassing the OAuth client credentials flow.
+      type: feat
+  createdAt: "2025-12-08"
+  irVersion: 60
+
 - version: 1.18.4
   changelogEntry:
     - summary: |