fix(go/plugins/compat_oai): add support for custom providers (#3617)

Author: hugoaguirre

go/plugins/compat_oai/README.md

@@ -1,6 +1,6 @@
 # OpenAI-Compatible Plugin Package
 
-This directory contains a package for building plugins that are compatible with the OpenAI API specification, along with plugins built on top of this package. 
+This directory contains a package for building plugins that are compatible with the OpenAI API specification, along with plugins built on top of this package.
 
 ## Package Overview
 
@@ -74,4 +74,4 @@ go test -v ./openai
 go test -v ./anthropic
 ```
 
-Note: Tests will be skipped if the required API keys are not set.
+Note: Tests will be skipped if the required API keys are not set.

go/plugins/compat_oai/compat_oai.go

@@ -17,7 +17,6 @@ package compat_oai
 import (
 	"context"
 	"fmt"
-	"strings"
 	"sync"
 
 	"github.com/firebase/genkit/go/ai"
@@ -68,6 +67,14 @@ type OpenAICompatible struct {
 	// This will be used as a prefix for model names (e.g., "myprovider/model-name").
 	// Should be lowercase and match the plugin's Name() method.
 	Provider string
+
+	// API key to use with the desired plugin.
+	APIKey string
+
+	// Base URL to use for custom endpoints.
+	// This should be used if you are running through a proxy or
+	// using a non-official endpoint
+	BaseURL string
 }
 
 // Init implements genkit.Plugin.
@@ -78,6 +85,14 @@ func (o *OpenAICompatible) Init(ctx context.Context) []api.Action {
 		panic("compat_oai.Init already called")
 	}
 
+	if o.APIKey != "" {
+		o.Opts = append([]option.RequestOption{option.WithAPIKey(o.APIKey)}, o.Opts...)
+	}
+
+	if o.BaseURL != "" {
+		o.Opts = append([]option.RequestOption{option.WithBaseURL(o.BaseURL)}, o.Opts...)
+	}
+
 	// create client
 	client := openai.NewClient(o.Opts...)
 	o.client = &client
@@ -99,16 +114,13 @@ func (o *OpenAICompatible) DefineModel(provider, id string, opts ai.ModelOptions
 		panic("OpenAICompatible.Init not called")
 	}
 
-	// Strip provider prefix if present to check against supportedModels
-	modelName := strings.TrimPrefix(id, provider+"/")
-
 	return ai.NewModel(api.NewName(provider, id), &opts, func(
 		ctx context.Context,
 		input *ai.ModelRequest,
 		cb func(context.Context, *ai.ModelResponseChunk) error,
 	) (*ai.ModelResponse, error) {
 		// Configure the response generator with input
-		generator := NewModelGenerator(o.client, modelName).WithMessages(input.Messages).WithConfig(input.Config).WithTools(input.Tools)
+		generator := NewModelGenerator(o.client, id).WithMessages(input.Messages).WithConfig(input.Config).WithTools(input.Tools)
 
 		// Generate response
 		resp, err := generator.Generate(ctx, input, cb)
@@ -197,7 +209,7 @@ func (o *OpenAICompatible) ListActions(ctx context.Context) []api.ActionDesc {
 					"systemRole":  true,
 					"tools":       true,
 					"toolChoice":  true,
-					"constrained": true,
+					"constrained": "all",
 				},
 			},
 			"versions": []string{},

go/plugins/compat_oai/generate.go

@@ -164,7 +164,7 @@ func (g *ModelGenerator) WithConfig(config any) *ModelGenerator {
 		openaiConfig = *cfg
 	case map[string]any:
 		if err := mapToStruct(cfg, &openaiConfig); err != nil {
-			g.err = fmt.Errorf("failed to convert config to OpenAIConfig: %w", err)
+			g.err = fmt.Errorf("failed to convert config to openai.ChatCompletionNewParams: %w", err)
 			return g
 		}
 	default:

go/samples/compat_oai/custom/main.go

@@ -0,0 +1,57 @@
+// Copyright 2025 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package main
+
+import (
+	"context"
+	"log"
+	"os"
+
+	"github.com/firebase/genkit/go/ai"
+	"github.com/firebase/genkit/go/genkit"
+
+	oai "github.com/firebase/genkit/go/plugins/compat_oai"
+	"github.com/openai/openai-go"
+)
+
+func main() {
+	ctx := context.Background()
+	apiKey := os.Getenv("OPENROUTER_API_KEY")
+	if apiKey == "" {
+		log.Fatalf("OPENROUTER_API_KEY environment variable not set")
+	}
+
+	g := genkit.Init(ctx, genkit.WithPlugins(&oai.OpenAICompatible{
+		Provider: "openrouter",
+		APIKey:   apiKey,
+		BaseURL:  "https://openrouter.ai/api/v1",
+	}),
+		genkit.WithDefaultModel("openrouter/tngtech/deepseek-r1t2-chimera:free"))
+
+	prompt := "tell me a joke"
+	config := &openai.ChatCompletionNewParams{
+		Temperature: openai.Float(0.7),
+		MaxTokens:   openai.Int(1000),
+		TopP:        openai.Float(0.9),
+	}
+
+	resp, err := genkit.Generate(context.Background(), g,
+		ai.WithConfig(config),
+		ai.WithPrompt(prompt))
+	if err != nil {
+		log.Fatalf("failed to generate contents: %v", err)
+	}
+	log.Println("Joke:", resp.Text())
+}