Fix working_dir failures: validate path early, remove hardcoded /root

executor/claude.go: stat working_dir before cmd.Start() so a missing
or inaccessible directory surfaces as a clear error
("working_dir \"/bad/path\": no such file or directory") rather than
an opaque chdir failure wrapped in "starting claude".

api/elaborate.go: replace the hardcoded /root/workspace/claudomator
path with buildElaboratePrompt(workDir) which injects the server's
actual working directory (from os.Getwd() at startup). Empty workDir
tells the model to leave working_dir blank.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

5 files changed, 62 insertions, 5 deletions

diff --git a/internal/api/elaborate.go b/internal/api/elaborate.go
index 357bf3c..d275d61 100644
--- a/internal/api/elaborate.go
+++ b/internal/api/elaborate.go
@@ -13,12 +13,15 @@ import (
 
 const elaborateTimeout = 30 * time.Second
 
-const elaborateSystemPrompt = `You are a task configuration assistant for Claudomator, an AI task runner that executes tasks by running Claude as a subprocess.
+func buildElaboratePrompt(workDir string) string {
+	workDirLine := `    "working_dir":     string  — leave empty unless you have a specific reason to set it,`
+	if workDir != "" {
+		workDirLine = fmt.Sprintf(`    "working_dir":     string  — use %q for tasks that operate on this codebase, empty string otherwise,`, workDir)
+	}
+	return `You are a task configuration assistant for Claudomator, an AI task runner that executes tasks by running Claude as a subprocess.
 
 Your ONLY job is to convert any user request into a Claudomator task JSON object. You MUST always output valid JSON. Never ask clarifying questions. Never explain. Never refuse. Make reasonable assumptions and produce the JSON.
 
-If the request is about Claudomator itself (e.g. "add a feature", "fix a bug", "hide completed tasks"), treat it as a software engineering task to be implemented in the Claudomator codebase at /root/workspace/claudomator.
-
 Output ONLY a valid JSON object matching this schema (no markdown fences, no prose, no explanation):
 
 {
@@ -27,7 +30,7 @@ Output ONLY a valid JSON object matching this schema (no markdown fences, no pro
   "claude": {
     "model":           string  — "sonnet" unless the task obviously needs opus,
     "instructions":    string  — detailed, step-by-step instructions for Claude,
-    "working_dir":     string  — use "/root/workspace/claudomator" for Claudomator tasks, empty string otherwise,
+` + workDirLine + `
     "max_budget_usd":  number  — conservative estimate (0.25–5.00),
     "allowed_tools":   array   — only tools the task genuinely needs
   },
@@ -35,6 +38,7 @@ Output ONLY a valid JSON object matching this schema (no markdown fences, no pro
   "priority": string  — "normal" | "high" | "low",
   "tags":     array   — relevant lowercase tags
 }`
+}
 
 // elaboratedTask mirrors the task creation schema for elaboration responses.
 type elaboratedTask struct {
@@ -98,7 +102,7 @@ func (s *Server) handleElaborateTask(w http.ResponseWriter, r *http.Request) {
 
 	cmd := exec.CommandContext(ctx, s.claudeBinaryPath(),
 		"-p", input.Prompt,
-		"--system-prompt", elaborateSystemPrompt,
+		"--system-prompt", buildElaboratePrompt(s.workDir),
 		"--output-format", "json",
 		"--model", "haiku",
 	)
diff --git a/internal/api/elaborate_test.go b/internal/api/elaborate_test.go
index ff158a8..52f7fdf 100644
--- a/internal/api/elaborate_test.go
+++ b/internal/api/elaborate_test.go
@@ -8,6 +8,7 @@ import (
 	"net/http/httptest"
 	"os"
 	"path/filepath"
+	"strings"
 	"testing"
 )
 
@@ -28,6 +29,23 @@ func createFakeClaude(t *testing.T, output string, exitCode int) string {
 	return script
 }
 
+func TestElaboratePrompt_ContainsWorkDir(t *testing.T) {
+	prompt := buildElaboratePrompt("/some/custom/path")
+	if !strings.Contains(prompt, "/some/custom/path") {
+		t.Error("prompt should contain the provided workDir")
+	}
+	if strings.Contains(prompt, "/root/workspace/claudomator") {
+		t.Error("prompt should not hardcode /root/workspace/claudomator")
+	}
+}
+
+func TestElaboratePrompt_EmptyWorkDir(t *testing.T) {
+	prompt := buildElaboratePrompt("")
+	if strings.Contains(prompt, "/root") {
+		t.Error("prompt should not reference /root when workDir is empty")
+	}
+}
+
 func TestElaborateTask_Success(t *testing.T) {
 	srv, _ := testServer(t)
 
diff --git a/internal/api/server.go b/internal/api/server.go
index 315b64b..8415b28 100644
--- a/internal/api/server.go
+++ b/internal/api/server.go
@@ -6,6 +6,7 @@ import (
 	"fmt"
 	"log/slog"
 	"net/http"
+	"os"
 	"time"
 
 	"github.com/thepeterstone/claudomator/internal/executor"
@@ -25,9 +26,11 @@ type Server struct {
 	mux              *http.ServeMux
 	claudeBinPath    string // path to claude binary; defaults to "claude"
 	elaborateCmdPath string // overrides claudeBinPath; used in tests
+	workDir          string // working directory injected into elaborate system prompt
 }
 
 func NewServer(store *storage.DB, pool *executor.Pool, logger *slog.Logger, claudeBinPath string) *Server {
+	wd, _ := os.Getwd()
 	s := &Server{
 		store:         store,
 		logStore:      store,
@@ -36,6 +39,7 @@ func NewServer(store *storage.DB, pool *executor.Pool, logger *slog.Logger, clau
 		logger:        logger,
 		mux:           http.NewServeMux(),
 		claudeBinPath: claudeBinPath,
+		workDir:       wd,
 	}
 	s.routes()
 	return s
diff --git a/internal/executor/claude.go b/internal/executor/claude.go
index 8486427..7b3884c 100644
--- a/internal/executor/claude.go
+++ b/internal/executor/claude.go
@@ -40,6 +40,9 @@ func (r *ClaudeRunner) Run(ctx context.Context, t *task.Task, e *storage.Executi
 		"CLAUDOMATOR_TASK_ID="+t.ID,
 	)
 	if t.Claude.WorkingDir != "" {
+		if _, err := os.Stat(t.Claude.WorkingDir); err != nil {
+			return fmt.Errorf("working_dir %q: %w", t.Claude.WorkingDir, err)
+		}
 		cmd.Dir = t.Claude.WorkingDir
 	}
 
diff --git a/internal/executor/claude_test.go b/internal/executor/claude_test.go
index fa81b09..ac6aabf 100644
--- a/internal/executor/claude_test.go
+++ b/internal/executor/claude_test.go
@@ -1,9 +1,13 @@
 package executor
 
 import (
+	"context"
+	"io"
+	"log/slog"
 	"strings"
 	"testing"
 
+	"github.com/thepeterstone/claudomator/internal/storage"
 	"github.com/thepeterstone/claudomator/internal/task"
 )
 
@@ -166,6 +170,30 @@ func TestClaudeRunner_BuildArgs_PreambleBashNotDuplicated(t *testing.T) {
 	}
 }
 
+func TestClaudeRunner_Run_InaccessibleWorkingDir_ReturnsError(t *testing.T) {
+	r := &ClaudeRunner{
+		BinaryPath: "true", // would succeed if it ran
+		Logger:     slog.New(slog.NewTextHandler(io.Discard, nil)),
+		LogDir:     t.TempDir(),
+	}
+	tk := &task.Task{
+		Claude: task.ClaudeConfig{
+			WorkingDir:   "/nonexistent/path/does/not/exist",
+			SkipPlanning: true,
+		},
+	}
+	exec := &storage.Execution{ID: "test-exec"}
+
+	err := r.Run(context.Background(), tk, exec)
+
+	if err == nil {
+		t.Fatal("expected error for inaccessible working_dir, got nil")
+	}
+	if !strings.Contains(err.Error(), "working_dir") {
+		t.Errorf("expected 'working_dir' in error, got: %v", err)
+	}
+}
+
 func TestClaudeRunner_BinaryPath_Default(t *testing.T) {
 	r := &ClaudeRunner{}
 	if r.binaryPath() != "claude" {