feat: recommend the official Slack plugin to Claude Code users

cmd/help/help.go

@@ -21,6 +21,7 @@ import (
 	"github.com/slackapi/slack-cli/internal/experiment"
 	"github.com/slackapi/slack-cli/internal/shared"
 	"github.com/slackapi/slack-cli/internal/style"
+	"github.com/slackapi/slack-cli/internal/useragent"
 	"github.com/spf13/cobra"
 )
 
@@ -75,6 +76,9 @@ func PrintHelpTemplate(cmd *cobra.Command, data style.TemplateData) {
 	if err != nil {
 		cmd.PrintErrln(err)
 	}
+
+	// Recommend the official Slack plugin when running inside Claude Code
+	useragent.EmitClaudeCodePluginHint(cmd.ErrOrStderr())
 }
 
 // ════════════════════════════════════════════════════════════════════════════════

cmd/help/help_test.go

@@ -28,9 +28,11 @@ import (
 
 func TestHelpFunc(t *testing.T) {
 	tests := map[string]struct {
-		exampleCommands []style.ExampleCommand
-		experiments     []string
-		expectedOutput  []string
+		exampleCommands     []style.ExampleCommand
+		experiments         []string
+		envVars             map[string]string
+		expectedOutput      []string
+		expectedErrorOutput []string
 	}{
 		"basic command information is included": {
 			expectedOutput: []string{
@@ -63,6 +65,10 @@ func TestHelpFunc(t *testing.T) {
 				"unknown (invalid)",
 			},
 		},
+		"the claude code plugin hint is emitted inside claude code": {
+			envVars:             map[string]string{"CLAUDECODE": "1"},
+			expectedErrorOutput: []string{"claude-code-hint"},
+		},
 	}
 
 	for name, tc := range tests {
@@ -74,6 +80,9 @@ func TestHelpFunc(t *testing.T) {
 				// Restore original EnabledExperiments
 				experiment.EnabledExperiments = _EnabledExperiments
 			}()
+			for name, value := range tc.envVars {
+				t.Setenv(name, value)
+			}
 
 			ctx := slackcontext.MockContext(t.Context())
 			clientsMock := shared.NewClientsMock()
@@ -102,6 +111,9 @@ func TestHelpFunc(t *testing.T) {
 			for _, expectedString := range tc.expectedOutput {
 				assert.Contains(t, clientsMock.GetStdoutOutput(), expectedString)
 			}
+			for _, expectedString := range tc.expectedErrorOutput {
+				assert.Contains(t, clientsMock.GetStderrOutput(), expectedString)
+			}
 		})
 	}
 }

cmd/root.go

@@ -129,6 +129,9 @@ func NewRootCommand(clients *shared.ClientFactory, updateNotification *update.Up
 			// Check for an CLI update in the background while the command runs
 			updateNotification = update.New(clients, version.Raw(), "SLACK_SKIP_UPDATE")
 			updateNotification.CheckForUpdateInBackground(ctx, false)
+
+			// Recommend the official Slack plugin when running inside Claude Code
+			useragent.EmitClaudeCodePluginHint(clients.IO.WriteErr())
 			return nil
 		},
 		PersistentPostRunE: func(cmd *cobra.Command, args []string) error {

internal/useragent/hint.go

@@ -0,0 +1,37 @@
+// Copyright 2022-2026 Salesforce, Inc.
+//
+// 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 useragent
+
+import (
+	"fmt"
+	"io"
+	"os"
+)
+
+// claudeCodePluginHint is the marker to recommend the official Slack plugin to
+// users of Claude Code.
+//
+// https://code.claude.com/docs/en/plugin-hints
+const claudeCodePluginHint = `<claude-code-hint v="1" type="plugin" value="slack@claude-plugins-official" />`
+
+// EmitClaudeCodePluginHint writes the Claude Code plugin recommendation marker
+// to a writer that must be stderr to prompt installation without an appearance
+// in actual outputs.
+func EmitClaudeCodePluginHint(w io.Writer) {
+	if os.Getenv("CLAUDECODE") == "" {
+		return
+	}
+	fmt.Fprintln(w, claudeCodePluginHint)
+}

internal/useragent/hint_test.go

@@ -0,0 +1,53 @@
+// Copyright 2022-2026 Salesforce, Inc.
+//
+// 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 useragent
+
+import (
+	"bytes"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func Test_EmitClaudeCodePluginHint(t *testing.T) {
+	tests := map[string]struct {
+		claudeCode string
+		expected   string
+	}{
+		"emits the hint on its own line inside claude code": {
+			claudeCode: "1",
+			expected:   claudeCodePluginHint + "\n",
+		},
+		"emits the hint for any non-empty CLAUDECODE value": {
+			claudeCode: "true",
+			expected:   claudeCodePluginHint + "\n",
+		},
+		"emits nothing when CLAUDECODE is unset": {
+			claudeCode: "",
+			expected:   "",
+		},
+	}
+	for name, tc := range tests {
+		t.Run(name, func(t *testing.T) {
+			clearEnvVars(t)
+			t.Setenv("CLAUDECODE", tc.claudeCode)
+
+			var buf bytes.Buffer
+			EmitClaudeCodePluginHint(&buf)
+
+			assert.Equal(t, tc.expected, buf.String())
+		})
+	}
+}