diff --git a/codeagent-wrapper/backend.go b/codeagent-wrapper/backend.go
index aed8617..ac7f617 100644
--- a/codeagent-wrapper/backend.go
+++ b/codeagent-wrapper/backend.go
@@ -36,19 +36,13 @@ func (ClaudeBackend) BuildArgs(cfg *Config, targetArg string) []string {
 		args = append(args, "--dangerously-skip-permissions")
 	}
 
-	workdir := cfg.WorkDir
-	if workdir == "" {
-		workdir = defaultWorkdir
-	}
-
 	if cfg.Mode == "resume" {
 		if cfg.SessionID != "" {
 			// Claude CLI uses -r <session_id> for resume.
 			args = append(args, "-r", cfg.SessionID)
 		}
-	} else {
-		args = append(args, "-C", workdir)
 	}
+	// Note: claude CLI doesn't support -C flag; workdir set via cmd.Dir
 
 	args = append(args, "--output-format", "stream-json", "--verbose", targetArg)
 
@@ -67,18 +61,12 @@ func (GeminiBackend) BuildArgs(cfg *Config, targetArg string) []string {
 	}
 	args := []string{"-o", "stream-json", "-y"}
 
-	workdir := cfg.WorkDir
-	if workdir == "" {
-		workdir = defaultWorkdir
-	}
-
 	if cfg.Mode == "resume" {
 		if cfg.SessionID != "" {
 			args = append(args, "-r", cfg.SessionID)
 		}
-	} else {
-		args = append(args, "-C", workdir)
 	}
+	// Note: gemini CLI doesn't support -C flag; workdir set via cmd.Dir
 
 	args = append(args, "-p", targetArg)
 
diff --git a/codeagent-wrapper/backend_test.go b/codeagent-wrapper/backend_test.go
index a74e35c..c16779e 100644
--- a/codeagent-wrapper/backend_test.go
+++ b/codeagent-wrapper/backend_test.go
@@ -11,7 +11,7 @@ func TestClaudeBuildArgs_ModesAndPermissions(t *testing.T) {
 	t.Run("new mode uses workdir without skip by default", func(t *testing.T) {
 		cfg := &Config{Mode: "new", WorkDir: "/repo"}
 		got := backend.BuildArgs(cfg, "todo")
-		want := []string{"-p", "-C", "/repo", "--output-format", "stream-json", "--verbose", "todo"}
+		want := []string{"-p", "--output-format", "stream-json", "--verbose", "todo"}
 		if !reflect.DeepEqual(got, want) {
 			t.Fatalf("got %v, want %v", got, want)
 		}
@@ -20,7 +20,7 @@ func TestClaudeBuildArgs_ModesAndPermissions(t *testing.T) {
 	t.Run("new mode opt-in skip permissions with default workdir", func(t *testing.T) {
 		cfg := &Config{Mode: "new", SkipPermissions: true}
 		got := backend.BuildArgs(cfg, "-")
-		want := []string{"-p", "--dangerously-skip-permissions", "-C", defaultWorkdir, "--output-format", "stream-json", "--verbose", "-"}
+		want := []string{"-p", "--dangerously-skip-permissions", "--output-format", "stream-json", "--verbose", "-"}
 		if !reflect.DeepEqual(got, want) {
 			t.Fatalf("got %v, want %v", got, want)
 		}
@@ -56,7 +56,7 @@ func TestClaudeBuildArgs_GeminiAndCodexModes(t *testing.T) {
 		backend := GeminiBackend{}
 		cfg := &Config{Mode: "new", WorkDir: "/workspace"}
 		got := backend.BuildArgs(cfg, "task")
-		want := []string{"-o", "stream-json", "-y", "-C", "/workspace", "-p", "task"}
+		want := []string{"-o", "stream-json", "-y", "-p", "task"}
 		if !reflect.DeepEqual(got, want) {
 			t.Fatalf("got %v, want %v", got, want)
 		}
diff --git a/codeagent-wrapper/executor.go b/codeagent-wrapper/executor.go
index 4ea2fe5..d49a14f 100644
--- a/codeagent-wrapper/executor.go
+++ b/codeagent-wrapper/executor.go
@@ -23,6 +23,7 @@ type commandRunner interface {
 	StdoutPipe() (io.ReadCloser, error)
 	StdinPipe() (io.WriteCloser, error)
 	SetStderr(io.Writer)
+	SetDir(string)
 	Process() processHandle
 }
 
@@ -72,6 +73,12 @@ func (r *realCmd) SetStderr(w io.Writer) {
 	}
 }
 
+func (r *realCmd) SetDir(dir string) {
+	if r.cmd != nil {
+		r.cmd.Dir = dir
+	}
+}
+
 func (r *realCmd) Process() processHandle {
 	if r == nil || r.cmd == nil || r.cmd.Process == nil {
 		return nil
@@ -577,6 +584,12 @@ func runCodexTaskWithContext(parentCtx context.Context, taskSpec TaskSpec, backe
 
 	cmd := newCommandRunner(ctx, commandName, codexArgs...)
 
+	// For backends that don't support -C flag (claude, gemini), set working directory via cmd.Dir
+	// Codex passes workdir via -C flag, so we skip setting Dir for it to avoid conflicts
+	if cfg.Mode != "resume" && commandName != "codex" && cfg.WorkDir != "" {
+		cmd.SetDir(cfg.WorkDir)
+	}
+
 	stderrWriters := []io.Writer{stderrBuf}
 	if stderrLogger != nil {
 		stderrWriters = append(stderrWriters, stderrLogger)
diff --git a/codeagent-wrapper/executor_concurrent_test.go b/codeagent-wrapper/executor_concurrent_test.go
index 57aed24..4c56961 100644
--- a/codeagent-wrapper/executor_concurrent_test.go
+++ b/codeagent-wrapper/executor_concurrent_test.go
@@ -117,6 +117,7 @@ func (f *execFakeRunner) StdinPipe() (io.WriteCloser, error) {
 	return &writeCloserStub{}, nil
 }
 func (f *execFakeRunner) SetStderr(io.Writer) {}
+func (f *execFakeRunner) SetDir(string)      {}
 func (f *execFakeRunner) Process() processHandle {
 	if f.process != nil {
 		return f.process
diff --git a/codeagent-wrapper/main_test.go b/codeagent-wrapper/main_test.go
index 99bfc4a..40172d1 100644
--- a/codeagent-wrapper/main_test.go
+++ b/codeagent-wrapper/main_test.go
@@ -250,6 +250,10 @@ func (d *drainBlockingCmd) SetStderr(w io.Writer) {
 	d.inner.SetStderr(w)
 }
 
+func (d *drainBlockingCmd) SetDir(dir string) {
+	d.inner.SetDir(dir)
+}
+
 func (d *drainBlockingCmd) Process() processHandle {
 	return d.inner.Process()
 }
@@ -504,6 +508,8 @@ func (f *fakeCmd) SetStderr(w io.Writer) {
 	f.stderr = w
 }
 
+func (f *fakeCmd) SetDir(string) {}
+
 func (f *fakeCmd) Process() processHandle {
 	if f == nil {
 		return nil
@@ -1371,7 +1377,7 @@ func TestBackendBuildArgs_ClaudeBackend(t *testing.T) {
 	backend := ClaudeBackend{}
 	cfg := &Config{Mode: "new", WorkDir: defaultWorkdir}
 	got := backend.BuildArgs(cfg, "todo")
-	want := []string{"-p", "-C", defaultWorkdir, "--output-format", "stream-json", "--verbose", "todo"}
+	want := []string{"-p", "--output-format", "stream-json", "--verbose", "todo"}
 	if len(got) != len(want) {
 		t.Fatalf("length mismatch")
 	}
@@ -1411,7 +1417,7 @@ func TestBackendBuildArgs_GeminiBackend(t *testing.T) {
 	backend := GeminiBackend{}
 	cfg := &Config{Mode: "new"}
 	got := backend.BuildArgs(cfg, "task")
-	want := []string{"-o", "stream-json", "-y", "-C", defaultWorkdir, "-p", "task"}
+	want := []string{"-o", "stream-json", "-y", "-p", "task"}
 	if len(got) != len(want) {
 		t.Fatalf("length mismatch")
 	}