feat(v0.5): launch agent inside project subdirectory via launch_dir

LaunchOpts gains LaunchDir. session.Run resolves it via
workspace.ResolveLaunch, prints any fallback warning, and passes the
absolute path as the child process's working directory. Security
violations (absolute paths, .. escape) abort the session. The banner
gains a 'project dir: <name>/' line when launch_dir is set.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

cmd/new.go

@@ -128,6 +128,7 @@ func runNew(cmd *cobra.Command, args []string) error {
 		Mode:         ws.Meta.Mode,
 		Slug:         ws.Meta.Slug,
 		Shell:        newShell,
+		LaunchDir:    ws.Meta.LaunchDir,
 		NewlyCreated: true,
 	})
 }

cmd/open.go

@@ -45,12 +45,13 @@ func runOpen(cmd *cobra.Command, args []string) error {
 	envVars := config.EnvVars(ws.Meta.Slug, ws.Meta.Mode, ws.Root, ws.Path, ws.Meta.Category, workspace.EffectiveType(ws.Meta), ws.Meta.LaunchDir)
 
 	return session.Run(session.LaunchOpts{
-		WsDir:   ws.Path,
-		EnvVars: envVars,
-		Agent:   ws.Meta.Agent,
-		Mode:    ws.Meta.Mode,
-		Slug:    ws.Meta.Slug,
-		Shell:   true, // open always launches shell
-		Force:   openForce,
+		WsDir:     ws.Path,
+		EnvVars:   envVars,
+		Agent:     ws.Meta.Agent,
+		Mode:      ws.Meta.Mode,
+		Slug:      ws.Meta.Slug,
+		Shell:     true, // open always launches shell
+		LaunchDir: ws.Meta.LaunchDir,
+		Force:     openForce,
 	})
 }

cmd/resume.go

@@ -65,12 +65,13 @@ func doResume(query string, container, useShell, force bool, agentOverride strin
 	envVars := config.EnvVars(ws.Meta.Slug, ws.Meta.Mode, ws.Root, ws.Path, ws.Meta.Category, workspace.EffectiveType(ws.Meta), ws.Meta.LaunchDir)
 
 	return session.Run(session.LaunchOpts{
-		WsDir:   ws.Path,
-		EnvVars: envVars,
-		Agent:   agent,
-		Mode:    ws.Meta.Mode,
-		Slug:    ws.Meta.Slug,
-		Shell:   useShell,
-		Force:   force,
+		WsDir:     ws.Path,
+		EnvVars:   envVars,
+		Agent:     agent,
+		Mode:      ws.Meta.Mode,
+		Slug:      ws.Meta.Slug,
+		Shell:     useShell,
+		LaunchDir: ws.Meta.LaunchDir,
+		Force:     force,
 	})
 }

internal/session/run.go

@@ -9,6 +9,7 @@ import (
 
 	"github.com/warrenronsiek/ctask/internal/lockfile"
 	"github.com/warrenronsiek/ctask/internal/shell"
+	"github.com/warrenronsiek/ctask/internal/workspace"
 )
 
 // LaunchOpts configures a session launch.
@@ -20,6 +21,12 @@ type LaunchOpts struct {
 	Slug    string
 	Shell   bool // true = interactive shell, false = agent
 
+	// LaunchDir is the workspace-relative launch directory (v0.5). Empty for
+	// tasks and pre-v0.5 projects. When set, Run resolves the absolute path
+	// via workspace.ResolveLaunch and uses it as the child's working dir;
+	// a security violation (absolute path or .. escape) aborts the session.
+	LaunchDir string
+
 	// Force suppresses both the active-session warning (Layer 1) and the
 	// stale-workspace warning (Layer 3). It does NOT disable the metadata
 	// write lock or the session summary. Used for scripted/automated runs.
@@ -138,15 +145,27 @@ func Run(opts LaunchOpts) error {
 		hb = StartHeartbeat(leasePath, HeartbeatInterval)
 	}
 
+	// ---- Resolve launch directory (v0.5) ----
+	// Security violations (absolute path, ..-escape) abort the session
+	// before we hand control to the child. Missing/non-dir falls back to
+	// wsDir with a warning.
+	launchAbs, launchWarn, launchErr := workspace.ResolveLaunch(opts.WsDir, opts.LaunchDir)
+	if launchErr != nil {
+		return fmt.Errorf("resolving launch_dir: %w", launchErr)
+	}
+	if launchWarn != "" {
+		fmt.Fprintln(os.Stderr, launchWarn)
+	}
+
 	// ---- Run the child ----
 	var childErr error
 	if opts.Shell {
-		childErr = shell.ExecShell(opts.WsDir, opts.EnvVars, opts.Slug, opts.Mode)
+		childErr = shell.ExecShell(launchAbs, opts.EnvVars, opts.Slug, opts.Mode)
 	} else {
-		for _, line := range shell.BannerLines(opts.Mode, opts.Slug, opts.WsDir) {
+		for _, line := range shell.BannerLines(opts.Mode, opts.Slug, opts.WsDir, opts.LaunchDir) {
 			fmt.Println(line)
 		}
-		childErr = shell.ExecAgent(opts.Agent, opts.WsDir, opts.EnvVars)
+		childErr = shell.ExecAgent(opts.Agent, launchAbs, opts.EnvVars)
 	}
 
 	if hb != nil {

internal/shell/launch.go

@@ -37,11 +37,16 @@ func PromptPrefix(slug, mode string) string {
 }
 
 // BannerLines returns the launch banner lines for agent mode.
-func BannerLines(mode, slug, wsPath string) []string {
-	return []string{
+// Adds a "project dir:" line when launchDir is non-empty.
+func BannerLines(mode, slug, wsPath, launchDir string) []string {
+	lines := []string{
 		fmt.Sprintf("[ctask] %s :: %s", mode, slug),
 		fmt.Sprintf("[ctask] %s", wsPath),
 	}
+	if launchDir != "" {
+		lines = append(lines, fmt.Sprintf("[ctask] project dir: %s/", launchDir))
+	}
+	return lines
 }
 
 // ContainerNotice returns the v0.1 deferred container mode message.

internal/shell/launch_test.go

@@ -2,6 +2,7 @@ package shell
 
 import (
 	"runtime"
+	"strings"
 	"testing"
 )
 
@@ -44,7 +45,7 @@ func TestPromptPrefix(t *testing.T) {
 }
 
 func TestBannerLines(t *testing.T) {
-	lines := BannerLines("local", "my-task", "/home/user/ws/general/2026-04-05_my-task")
+	lines := BannerLines("local", "my-task", "/home/user/ws/general/2026-04-05_my-task", "")
 	if len(lines) != 2 {
 		t.Fatalf("expected 2 banner lines, got %d", len(lines))
 	}
@@ -56,6 +57,26 @@ func TestBannerLines(t *testing.T) {
 	}
 }
 
+func TestBannerLinesIncludesLaunchDirWhenSet(t *testing.T) {
+	lines := BannerLines("local", "demo", "/ws/2026-04-22_demo", "demo")
+	if len(lines) < 3 {
+		t.Fatalf("expected at least 3 lines when launch dir set, got %d: %v", len(lines), lines)
+	}
+	if !strings.Contains(lines[2], "project dir") {
+		t.Errorf("third line should mention 'project dir', got %q", lines[2])
+	}
+	if !strings.Contains(lines[2], "demo/") {
+		t.Errorf("third line should include 'demo/', got %q", lines[2])
+	}
+}
+
+func TestBannerLinesOmitsLaunchDirWhenEmpty(t *testing.T) {
+	lines := BannerLines("local", "demo", "/ws/2026-04-22_demo", "")
+	if len(lines) != 2 {
+		t.Errorf("expected 2 lines when launch dir empty, got %d: %v", len(lines), lines)
+	}
+}
+
 func TestContainerNotice(t *testing.T) {
 	msg := ContainerNotice()
 	expected := "[ctask] container mode is not available in v0.1. Use local mode or see docs for manual container setup."