feat: implement Langfuse Prompt client with CRUD operations

libs/acl/langfuse/README.md

@@ -0,0 +1,8 @@
+# Langfuse ACL Extension
+
+This module provides the Langfuse adapter used by Eino for event and prompt management against the Langfuse public API.
+
+- `prompt.go` implements the prompt client, including typed request/response models and helpers to list, fetch, and create prompts.
+- A minimal usage sample lives in `examples/prompt/main.go`, showing how to initialize a Langfuse client and load a prompt by name.
+
+Run `go test ./...` before submitting changes to ensure the package continues to build and the existing suites pass.

libs/acl/langfuse/examples/prompt/main.go

@@ -0,0 +1,46 @@
+/*
+ * Copyright 2025 CloudWeGo Authors
+ *
+ * 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 examples
+
+import (
+	"context"
+	"fmt"
+	"log"
+
+	"github.com/cloudwego/eino-ext/libs/acl/langfuse"
+)
+
+func main() {
+	ctx := context.Background()
+
+	lf := langfuse.NewLangfuse(
+		"https://cloud.your-langfuse-instance.com",
+		"your-public-key",
+		"your-secret-key",
+	)
+
+	promptClient := lf.Prompt()
+
+	prompt, err := promptClient.GetPrompt(ctx, langfuse.GetParams{
+		Name: "welcome-message",
+	})
+	if err != nil {
+		log.Fatalf("failed to fetch prompt: %v", err)
+	}
+
+	fmt.Printf("Loaded prompt %q version %d\n", prompt.Name, prompt.Version)
+}

libs/acl/langfuse/langfuse.go

@@ -38,6 +38,7 @@ type Langfuse interface {
 	EndGeneration(body *GenerationEventBody) error
 	CreateEvent(body *EventEventBody) (string, error)
 	Flush()
+	Prompt() *PromptClient
 }
 
 // NewLangfuse creates a Langfuse client instance
@@ -68,9 +69,10 @@ func NewLangfuse(
 		opt(o)
 	}
 
+	httpCli := &http.Client{Timeout: o.timeout}
 	tm := newTaskManager(
 		o.threads,
-		&http.Client{Timeout: o.timeout},
+		httpCli,
 		host,
 		o.maxTaskQueueSize,
 		o.flushAt,
@@ -85,11 +87,14 @@ func NewLangfuse(
 		secretKey,
 		o.maxRetry,
 	)
-	return &langfuseIns{tm: tm}
+	langfuseCli := newClient(httpCli, host, publicKey, secretKey, sdkVersion)
+	promptCli := &PromptClient{cli: langfuseCli}
+	return &langfuseIns{tm: tm, promptCli: promptCli}
 }
 
 type langfuseIns struct {
-	tm *taskManager
+	tm        *taskManager
+	promptCli *PromptClient
 }
 
 // CreateTrace creates a new trace in Langfuse
@@ -215,3 +220,9 @@ func (l *langfuseIns) CreateEvent(body *EventEventBody) (string, error) {
 func (l *langfuseIns) Flush() {
 	l.tm.flush()
 }
+
+// Prompt provides access to the prompt client for managing prompts.
+// Use the returned PromptClient to create, retrieve and list prompts.
+func (l *langfuseIns) Prompt() *PromptClient {
+	return l.promptCli
+}