feat(go/plugin/anthropic): add Anthropic plugin

go/plugins/anthropic/anthropic.go

@@ -0,0 +1,145 @@
+// 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.
+//
+// SPDX-License-Identifier: Apache-2.0
+
+package anthropic
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"os"
+	"sync"
+
+	"github.com/anthropics/anthropic-sdk-go"
+	"github.com/anthropics/anthropic-sdk-go/option"
+	"github.com/firebase/genkit/go/ai"
+	"github.com/firebase/genkit/go/core"
+	"github.com/firebase/genkit/go/genkit"
+	ant "github.com/firebase/genkit/go/plugins/internal/anthropic"
+)
+
+const (
+	provider             = "anthropic"
+	anthropicLabelPrefix = "Anthropic"
+)
+
+type Anthropic struct {
+	APIKey  string           // If not provided, defaults to ANTHROPIC_API_KEY
+	aclient anthropic.Client // Anthropic client
+	mu      sync.Mutex       // Mutex to control access
+	initted bool             // Whether the plugin has been initialized
+}
+
+func (a *Anthropic) Name() string {
+	return provider
+}
+
+func (a *Anthropic) Init(ctx context.Context, g *genkit.Genkit) (err error) {
+	if a == nil {
+		a = &Anthropic{}
+	}
+
+	a.mu.Lock()
+	defer a.mu.Unlock()
+	if a.initted {
+		return errors.New("plugin already initialized")
+	}
+	defer func() {
+		if err != nil {
+			err = fmt.Errorf("Anthropic.Init: %w", err)
+		}
+	}()
+
+	apiKey := a.APIKey
+	if apiKey == "" {
+		apiKey = os.Getenv("ANTHROPIC_API_KEY")
+	}
+	if apiKey == "" {
+		return fmt.Errorf("Anthropic requires setting ANTHROPIC_API_KEY in the environment")
+	}
+
+	ac := anthropic.NewClient(
+		option.WithAPIKey(apiKey),
+	)
+	a.aclient = ac
+	a.initted = true
+
+	return nil
+}
+
+func (a *Anthropic) DefineModel(g *genkit.Genkit, name string, info *ai.ModelInfo) ai.Model {
+	return ant.DefineModel(g, a.aclient, provider, name, *info)
+}
+
+func (a *Anthropic) IsDefinedModel(g *genkit.Genkit, name string) bool {
+	return genkit.LookupModel(g, provider, name) != nil
+}
+
+func (a *Anthropic) ListActions(ctx context.Context) []core.ActionDesc {
+	actions := []core.ActionDesc{}
+
+	models, err := listModels(ctx, &a.aclient)
+	if err != nil {
+		return nil
+	}
+
+	for _, name := range models {
+		metadata := map[string]any{
+			"model": map[string]any{
+				"supports": map[string]any{
+					"media":       true,
+					"multiturn":   true,
+					"systemRole":  true,
+					"tools":       true,
+					"toolChoice":  true,
+					"constrained": "no-tools",
+				},
+			},
+			"versions": []string{},
+			"stage":    string(ai.ModelStageStable),
+		}
+		metadata["label"] = fmt.Sprintf("%s - %s", anthropicLabelPrefix, name)
+
+		actions = append(actions, core.ActionDesc{
+			Type:     core.ActionTypeModel,
+			Name:     fmt.Sprintf("%s/%s", provider, name),
+			Key:      fmt.Sprintf("/%s/%s/%s", core.ActionTypeModel, provider, name),
+			Metadata: metadata,
+		})
+
+	}
+	return actions
+}
+
+func (a *Anthropic) ResolveAction(g *genkit.Genkit, atype core.ActionType, name string) error {
+	switch atype {
+	case core.ActionTypeModel:
+		ant.DefineModel(g, a.aclient, provider, name, ai.ModelInfo{
+			Label:    fmt.Sprintf("%s - %s", anthropicLabelPrefix, name),
+			Stage:    ai.ModelStageStable,
+			Versions: []string{},
+			Supports: &ai.ModelSupports{
+				Media:       true,
+				Multiturn:   true,
+				SystemRole:  true,
+				Tools:       true,
+				ToolChoice:  true,
+				Constrained: ai.ConstrainedSupportNoTools,
+			},
+		})
+	}
+	return nil
+}

go/plugins/anthropic/models.go

@@ -0,0 +1,40 @@
+// 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.
+//
+// SPDX-License-Identifier: Apache-2.0
+
+package anthropic
+
+import (
+	"context"
+
+	"github.com/anthropics/anthropic-sdk-go"
+)
+
+// listModels returns a list of model names supported by the Anthropic client
+func listModels(ctx context.Context, client *anthropic.Client) ([]string, error) {
+	iter := client.Models.ListAutoPaging(ctx, anthropic.ModelListParams{})
+	models := []string{}
+
+	for iter.Next() {
+		m := iter.Current()
+		models = append(models, m.DisplayName)
+	}
+
+	if err := iter.Err(); err != nil {
+		panic(err.Error())
+	}
+
+	return models, nil
+}

go/plugins/googlegenai/googlegenai.go

@@ -330,7 +330,7 @@ func (ga *GoogleAI) ListActions(ctx context.Context) []core.ActionDesc {
 					"systemRole":  true,
 					"tools":       true,
 					"toolChoice":  true,
-					"constrained": true,
+					"constrained": "no-tools",
 				},
 				"versions": []string{},
 				"stage":    string(ai.ModelStageStable),
@@ -394,7 +394,7 @@ func (v *VertexAI) ListActions(ctx context.Context) []core.ActionDesc {
 					"systemRole":  true,
 					"tools":       true,
 					"toolChoice":  true,
-					"constrained": true,
+					"constrained": "no-tools",
 				},
 				"versions": []string{},
 				"stage":    string(ai.ModelStageStable),