Support echo "hello" | docker agent | cat

cmd/root/run.go

@@ -416,7 +416,10 @@ func (f *runExecFlags) createLocalRuntimeAndSession(ctx context.Context, loadRes
 
 func (f *runExecFlags) handleExecMode(ctx context.Context, out *cli.Printer, rt runtime.Runtime, sess *session.Session, args []string) error {
 	// args[0] is the agent file; args[1:] are user messages for multi-turn conversation
-	userMessages := args[1:]
+	var userMessages []string
+	if len(args) > 1 {
+		userMessages = args[1:]
+	}
 
 	err := cli.Run(ctx, out, cli.Config{
 		AppName:        AppName,

e2e/exec_test.go

@@ -9,7 +9,7 @@ import (
 func TestExec_OpenAI(t *testing.T) {
 	out := runCLI(t, "run", "--exec", "testdata/basic.yaml", "What's 2+2?")
 
-	require.Equal(t, "\n--- Agent: root ---\n2 + 2 equals 4.", out)
+	require.Equal(t, "2 + 2 equals 4.", out)
 }
 
 // TestExec_OpenAI_V3Config tests that v3 configs work correctly with thinking disabled by default.
@@ -18,7 +18,7 @@ func TestExec_OpenAI_V3Config(t *testing.T) {
 	out := runCLI(t, "run", "--exec", "testdata/basic_v3.yaml", "What's 2+2?")
 
 	// v3 config with gpt-5 should work correctly (thinking disabled by default for old configs)
-	require.Equal(t, "\n--- Agent: root ---\n4", out)
+	require.Equal(t, "4", out)
 }
 
 // TestExec_OpenAI_WithThinkingBudget tests that when thinking_budget is explicitly configured
@@ -28,57 +28,52 @@ func TestExec_OpenAI_WithThinkingBudget(t *testing.T) {
 
 	// With thinking_budget explicitly configured, response should include reasoning
 	// The output format includes the reasoning summary when thinking is enabled
-	require.Contains(t, out, "--- Agent: root ---")
 	require.Contains(t, out, "4")
 }
 
 func TestExec_OpenAI_ToolCall(t *testing.T) {
 	out := runCLI(t, "run", "--exec", "testdata/fs_tools.yaml", "How many files in testdata/working_dir? Only output the number.")
 
-	require.Equal(t, "\n--- Agent: root ---\n\nCalling list_directory(path: \"testdata/working_dir\")\n\nlist_directory response → \"FILE README.me\\n\"\n1", out)
+	require.Equal(t, "\nCalling list_directory(path: \"testdata/working_dir\")\n\nlist_directory response → \"FILE README.me\\n\"\n1", out)
 }
 
 func TestExec_OpenAI_HideToolCalls(t *testing.T) {
 	out := runCLI(t, "run", "--exec", "testdata/fs_tools.yaml", "--hide-tool-calls", "How many files in testdata/working_dir? Only output the number.")
 
-	require.Equal(t, "\n--- Agent: root ---\n1", out)
+	require.Equal(t, "1", out)
 }
 
 func TestExec_OpenAI_gpt5(t *testing.T) {
 	out := runCLI(t, "run", "--exec", "testdata/basic.yaml", "--model=openai/gpt-5", "What's 2+2?")
 
 	// With thinking enabled by default, response may include reasoning summary
-	require.Contains(t, out, "--- Agent: root ---")
 	require.Contains(t, out, "4")
 }
 
 func TestExec_OpenAI_gpt5_1(t *testing.T) {
 	out := runCLI(t, "run", "--exec", "testdata/basic.yaml", "--model=openai/gpt-5.1", "What's 2+2?")
 
-	require.Equal(t, "\n--- Agent: root ---\n2 + 2 = 4.", out)
+	require.Equal(t, "2 + 2 = 4.", out)
 }
 
 func TestExec_OpenAI_gpt5_codex(t *testing.T) {
 	out := runCLI(t, "run", "--exec", "testdata/basic.yaml", "--model=openai/gpt-5-codex", "What's 2+2?")
 
 	// Model reasoning summary varies, just check for the core response
-	require.Contains(t, out, "--- Agent: root ---")
 	require.Contains(t, out, "4")
 }
 
 func TestExec_Anthropic(t *testing.T) {
 	out := runCLI(t, "run", "--exec", "testdata/basic.yaml", "--model=anthropic/claude-sonnet-4-0", "What's 2+2?")
 
 	// With interleaved thinking enabled by default, Anthropic responses include thinking content
-	require.Contains(t, out, "--- Agent: root ---")
 	require.Contains(t, out, "2 + 2 = 4")
 }
 
 func TestExec_Anthropic_ToolCall(t *testing.T) {
 	out := runCLI(t, "run", "--exec", "testdata/fs_tools.yaml", "--model=anthropic/claude-sonnet-4-0", "How many files in testdata/working_dir? Only output the number.")
 
 	// With interleaved thinking enabled by default, Anthropic responses include thinking content
-	require.Contains(t, out, "--- Agent: root ---")
 	require.Contains(t, out, `Calling list_directory(path: "testdata/working_dir")`)
 	require.Contains(t, out, `list_directory response → "FILE README.me\n"`)
 	// The response should end with "1" (the count)
@@ -89,15 +84,13 @@ func TestExec_Anthropic_AgentsMd(t *testing.T) {
 	out := runCLI(t, "run", "--exec", "testdata/agents-md.yaml", "--model=anthropic/claude-sonnet-4-0", "What's 2+2?")
 
 	// With interleaved thinking enabled by default, Anthropic responses include thinking content
-	require.Contains(t, out, "--- Agent: root ---")
 	require.Contains(t, out, "2 + 2 = 4")
 }
 
 func TestExec_Gemini(t *testing.T) {
 	out := runCLI(t, "run", "--exec", "testdata/basic.yaml", "--model=google/gemini-2.5-flash", "What's 2+2?")
 
 	// With thinking enabled by default (dynamic thinking for Gemini 2.5), responses may include thinking content
-	require.Contains(t, out, "--- Agent: root ---")
 	// The response should contain the answer "4" somewhere
 	require.Contains(t, out, "4")
 }
@@ -106,7 +99,6 @@ func TestExec_Gemini_ToolCall(t *testing.T) {
 	out := runCLI(t, "run", "--exec", "testdata/fs_tools.yaml", "--model=google/gemini-2.5-flash", "How many files in testdata/working_dir? Only output the number.")
 
 	// With thinking enabled by default (dynamic thinking for Gemini 2.5), responses include thinking content
-	require.Contains(t, out, "--- Agent: root ---")
 	require.Contains(t, out, `Calling list_directory(path: "testdata/working_dir")`)
 	require.Contains(t, out, `list_directory response → "FILE README.me\n"`)
 	// The response should end with "1" (the count)
@@ -116,13 +108,13 @@ func TestExec_Gemini_ToolCall(t *testing.T) {
 func TestExec_Mistral(t *testing.T) {
 	out := runCLI(t, "run", "--exec", "testdata/basic.yaml", "--model=mistral/mistral-small", "What's 2+2?")
 
-	require.Equal(t, "\n--- Agent: root ---\nThe sum of 2 + 2 is 4.", out)
+	require.Equal(t, "The sum of 2 + 2 is 4.", out)
 }
 
 func TestExec_Mistral_ToolCall(t *testing.T) {
 	out := runCLI(t, "run", "--exec", "testdata/fs_tools.yaml", "--model=mistral/mistral-small", "How many files in testdata/working_dir? Only output the number.")
 
-	require.Equal(t, "\n--- Agent: root ---\n\nCalling list_directory(path: \"testdata/working_dir\")\n\nlist_directory response → \"FILE README.me\\n\"\n1", out)
+	require.Equal(t, "\nCalling list_directory(path: \"testdata/working_dir\")\n\nlist_directory response → \"FILE README.me\\n\"\n1", out)
 }
 
 func TestExec_ToolCallsNeedAcceptance(t *testing.T) {

pkg/cli/printer.go

@@ -30,12 +30,18 @@ const (
 var bold = color.New(color.Bold).SprintfFunc()
 
 type Printer struct {
-	out io.Writer
+	out      io.Writer
+	isTTYOut bool
 }
 
 func NewPrinter(out io.Writer) *Printer {
+	isTTY := false
+	if f, ok := out.(*os.File); ok {
+		isTTY = isatty.IsTerminal(f.Fd())
+	}
 	return &Printer{
-		out: out,
+		out:      out,
+		isTTYOut: isTTY,
 	}
 }
 
@@ -63,6 +69,9 @@ func (p *Printer) PrintError(err error) {
 
 // PrintAgentName prints the agent name header
 func (p *Printer) PrintAgentName(agentName string) {
+	if !p.isTTYOut {
+		return
+	}
 	p.Printf("\n--- Agent: %s ---\n", bold(agentName))
 }
 

pkg/cli/runner.go

@@ -12,6 +12,8 @@ import (
 	"path/filepath"
 	"strings"
 
+	"github.com/mattn/go-isatty"
+
 	"github.com/docker/docker-agent/pkg/chat"
 	"github.com/docker/docker-agent/pkg/input"
 	"github.com/docker/docker-agent/pkg/runtime"
@@ -267,6 +269,16 @@ func Run(ctx context.Context, out *Printer, cfg Config, rt runtime.Runtime, sess
 				return err
 			}
 		}
+	case !isatty.IsTerminal(os.Stdin.Fd()):
+		// Stdin is not a terminal: read all input from stdin
+		buf, err := io.ReadAll(os.Stdin)
+		if err != nil {
+			return fmt.Errorf("failed to read from stdin: %w", err)
+		}
+
+		if err := oneLoop(string(buf), os.Stdin); err != nil {
+			return err
+		}
 	default:
 		// No messages: interactive prompt loop
 		out.PrintWelcomeMessage(cfg.AppName)