diff --git a/engine/engine_test.go b/engine/engine_test.go
index 4bc06fb..8c03690 100644
--- a/engine/engine_test.go
+++ b/engine/engine_test.go
@@ -32,16 +32,23 @@ func NewFsWrapper(path string, st *state.State) FsWrapper {
 	}
 }
 
-func(fs FsWrapper) one(sym string, input []byte, ctx context.Context) (string, error) {
-	return "one", nil
+func(fs FsWrapper) one(sym string, input []byte, ctx context.Context) (resource.Result, error) {
+	return resource.Result{
+		Content: "one",
+	}, nil
 }
 
-func(fs FsWrapper) inky(sym string, input []byte, ctx context.Context) (string, error) {
-	return "tinkywinky", nil
+func(fs FsWrapper) inky(sym string, input []byte, ctx context.Context) (resource.Result, error) {
+	return resource.Result{
+		Content: "tinkywinky",
+	}, nil
 }
 
-func(fs FsWrapper) pinky(sym string, input []byte, ctx context.Context) (string, error) {
-	return fmt.Sprintf("xyzzy: %x", input), nil
+func(fs FsWrapper) pinky(sym string, input []byte, ctx context.Context) (resource.Result, error) {
+	r := fmt.Sprintf("xyzzy: %x", input)
+	return resource.Result{
+		Content: r,
+	}, nil
 }
 
 func(fs FsWrapper) FuncFor(sym string) (resource.EntryFunc, error) {
diff --git a/render/size_test.go b/render/size_test.go
index e965775..db11bed 100644
--- a/render/size_test.go
+++ b/render/size_test.go
@@ -41,20 +41,28 @@ func funcFor(sym string) (resource.EntryFunc, error) {
 	return nil, fmt.Errorf("unknown func: %s", sym)
 }
 
-func getFoo(sym string, input []byte, ctx context.Context) (string, error) {
-	return "inky", nil
+func getFoo(sym string, input []byte, ctx context.Context) (resource.Result, error) {
+	return resource.Result{
+		Content: "inky",
+	}, nil
 }
 
-func getBar(sym string, input []byte, ctx context.Context) (string, error) {
-	return "pinky", nil
+func getBar(sym string, input []byte, ctx context.Context) (resource.Result, error) {
+	return resource.Result{
+		Content: "pinky",
+	}, nil
 }
 
-func getBaz(sym string, input []byte, ctx context.Context) (string, error) {
-	return "blinky", nil
+func getBaz(sym string, input []byte, ctx context.Context) (resource.Result, error) {
+	return resource.Result{
+		Content: "blinky",
+	}, nil
 }
 
-func getXyzzy(sym string, input []byte, ctx context.Context) (string, error) {
-	return "inky pinky\nblinky clyde sue\ntinkywinky dipsy\nlala poo\none two three four five six seven\neight nine ten\neleven twelve", nil
+func getXyzzy(sym string, input []byte, ctx context.Context) (resource.Result, error) {
+	return resource.Result{
+		Content: "inky pinky\nblinky clyde sue\ntinkywinky dipsy\nlala poo\none two three four five six seven\neight nine ten\neleven twelve",
+	}, nil
 }
 
 func TestSizeCheck(t *testing.T) {
diff --git a/resource/fs.go b/resource/fs.go
index 1b6bda6..82ab96d 100644
--- a/resource/fs.go
+++ b/resource/fs.go
@@ -55,18 +55,20 @@ func(fs FsResource) String() string {
 	return fmt.Sprintf("fs resource at path: %s", fs.Path)
 }
 
-func(fs FsResource) getFunc(sym string, input []byte, ctx context.Context) (string, error) {
+func(fs FsResource) getFunc(sym string, input []byte, ctx context.Context) (Result, error) {
 	return fs.getFuncNoCtx(sym, input)
 }
 
-func(fs FsResource) getFuncNoCtx(sym string, input []byte) (string, error) {
+func(fs FsResource) getFuncNoCtx(sym string, input []byte) (Result, error) {
 	fb := sym + ".txt"
 	fp := path.Join(fs.Path, fb)
 	log.Printf("getfunc search dir %s %s for %s", fs.Path, fp, sym)
 	r, err := ioutil.ReadFile(fp)
 	if err != nil {
-		return "", fmt.Errorf("failed getting data for sym '%s': %v", sym, err)
+		return Result{}, fmt.Errorf("failed getting data for sym '%s': %v", sym, err)
 	}
 	s := string(r)
-	return strings.TrimSpace(s), nil
+	return Result{
+		Content: strings.TrimSpace(s),
+	}, nil
 }
diff --git a/resource/resource.go b/resource/resource.go
index c406c84..ee1bfed 100644
--- a/resource/resource.go
+++ b/resource/resource.go
@@ -4,8 +4,14 @@ import (
 	"context"
 )
 
+type Result struct {
+	Content string
+	FlagSet []uint32
+	FlagReset []uint32
+}
+
 // EntryFunc is a function signature for retrieving value for a key
-type EntryFunc func(sym string, input []byte, ctx context.Context) (string, error)
+type EntryFunc func(sym string, input []byte, ctx context.Context) (Result, error)
 type CodeFunc func(sym string) ([]byte, error)
 type TemplateFunc func(sym string) (string, error)
 type FuncForFunc func(sym string) (EntryFunc, error)
diff --git a/resource/resource_test.go b/resource/resource_test.go
index 66f5a21..7914759 100644
--- a/resource/resource_test.go
+++ b/resource/resource_test.go
@@ -37,18 +37,27 @@ func funcFor(sym string) (EntryFunc, error) {
 	return nil, fmt.Errorf("unknown func: %s", sym)
 }
 
-func get(sym string, input []byte, ctx context.Context) (string, error) {
+func get(sym string, input []byte, ctx context.Context) (Result, error) {
 	switch sym {
 	case "foo":
-		return "inky", nil
+		return Result{
+			Content: "inky",
+		}, nil
 	case "bar":
-		return "pinky", nil
+		return Result{
+			Content: "pinky",
+		}, nil
 	case "baz":
-		return "blinky", nil
+		return Result{
+			Content: "blinky",
+		}, nil
 	}
-	return "", fmt.Errorf("unknown sym: %s", sym)
+	return Result{}, fmt.Errorf("unknown sym: %s", sym)
 }
 
-func getXyzzy(sym string, input []byte, ctx context.Context) (string, error) {
-	return "inky pinky\nblinky clyde sue\ntinkywinky dipsy\nlala poo\none two three four five six seven\neight nine ten\neleven twelve", nil
+func getXyzzy(sym string, input []byte, ctx context.Context) (Result, error) {
+	r := "inky pinky\nblinky clyde sue\ntinkywinky dipsy\nlala poo\none two three four five six seven\neight nine ten\neleven twelve"
+	return Result{
+		Content: r,
+	}, nil
 }
diff --git a/state/flag.go b/state/flag.go
index b829415..295358c 100644
--- a/state/flag.go
+++ b/state/flag.go
@@ -5,4 +5,16 @@ const (
 	FLAG_INMATCH = 2
 	FLAG_TERMINATE = 3
 	FLAG_DIRTY = 4
+	FLAG_LOADFAIL = 5
+	//FLAG_WRITEABLE = FLAG_LOADFAIL
 )
+
+func IsWriteableFlag(flag uint32) bool {
+	if flag > 7 {
+		return true
+	}
+	//if flag & FLAG_WRITEABLE > 0 {
+	//	return true	
+	//}
+	return false
+}
diff --git a/state/state.go b/state/state.go
index 08abe72..39a64c6 100644
--- a/state/state.go
+++ b/state/state.go
@@ -112,6 +112,11 @@ func(st *State) ResetFlag(bitIndex uint32) (bool, error) {
 	return true, nil
 }
 
+// ResetBaseFlags restes all builtin flags not writeable by client.
+func(st *State) ResetBaseFlags() {
+	st.Flags[0] = 0	
+}
+
 // GetFlag returns the state of the flag at the given bit field index.
 //
 // Fails if bit field index is out of range.
diff --git a/vm/runner.go b/vm/runner.go
index 1fe00f4..92463ee 100644
--- a/vm/runner.go
+++ b/vm/runner.go
@@ -60,6 +60,7 @@ func(vm *Vm) Run(b []byte, ctx context.Context) ([]byte, error) {
 			log.Printf("terminate set! bailing!")
 			return []byte{}, nil
 		}
+		vm.st.ResetBaseFlags()
 		_, err = vm.st.SetFlag(state.FLAG_DIRTY)
 		if err != nil {
 			panic(err)
@@ -179,7 +180,8 @@ func(vm *Vm) RunCatch(b []byte, ctx context.Context) ([]byte, error) {
 		log.Printf("catch at flag %v, moving to %v", sig, sym) //bitField, d)
 		vm.st.Down(sym)
 		vm.Reset()
-		b = []byte{}
+		bh := NewLine(nil, HALT, nil, nil, nil)
+		b = append(bh, b...)
 	} 
 	return b, nil
 }
@@ -430,6 +432,33 @@ func(vm *Vm) refresh(key string, rs resource.Resource, ctx context.Context) (str
 		return "", fmt.Errorf("no retrieve function for external symbol %v", key)
 	}
 	input, _ := vm.st.GetInput()
-	return fn(key, input, ctx)
-}
+	r, err := fn(key, input, ctx)
+	if err != nil {
+		var perr error
+		_, perr = vm.st.SetFlag(state.FLAG_LOADFAIL)
+		if perr != nil {
+			panic(err)
+		}
+		return "", err
+	}
+	for _, flag := range r.FlagSet {
+		if !state.IsWriteableFlag(flag) {
+			continue
+		}
+		_, err = vm.st.SetFlag(flag)
+		if err != nil {
+			panic(err)
+		}
+	}
+	for _, flag := range r.FlagReset {
+		if !state.IsWriteableFlag(flag) {
+			continue
+		}
+		_, err = vm.st.ResetFlag(flag)
+		if err != nil {
+			panic(err)
+		}
+	}
 
+	return r.Content, err
+}
diff --git a/vm/runner_test.go b/vm/runner_test.go
index 4f78f8d..7da7ef4 100644
--- a/vm/runner_test.go
+++ b/vm/runner_test.go
@@ -20,16 +20,45 @@ type TestResource struct {
 	state *state.State
 }
 
-func getOne(sym string, input []byte, ctx context.Context) (string, error) {
-	return "one", nil
+func getOne(sym string, input []byte, ctx context.Context) (resource.Result, error) {
+	return resource.Result{
+		Content: "one",
+	}, nil
 }
 
-func getTwo(sym string, input []byte, ctx context.Context) (string, error) {
-	return "two", nil
+func getTwo(sym string, input []byte, ctx context.Context) (resource.Result, error) {
+	return resource.Result{
+		Content: "two",
+	}, nil
 }
 
-func getDyn(sym string, input []byte, ctx context.Context) (string, error) {
-	return dynVal, nil
+func getDyn(sym string, input []byte, ctx context.Context) (resource.Result, error) {
+	return resource.Result{
+		Content: dynVal,
+	}, nil
+}
+
+func getEcho(sym string, input []byte, ctx context.Context) (resource.Result, error) {
+	r := fmt.Sprintf("echo: %s", input)
+	return resource.Result{
+		Content: r,
+	}, nil
+}
+
+func setFlag(sym string, input []byte, ctx context.Context) (resource.Result, error) {
+	s := fmt.Sprintf("ping")
+	r := resource.Result{
+		Content: s,
+	}
+	if len(input) > 0 {
+		r.FlagSet = append(r.FlagSet, uint32(input[0]))
+	}
+	if len(input) > 1 {
+		r.FlagReset = append(r.FlagReset, uint32(input[1]))
+	}
+	log.Printf("setflag %v", r)
+	return r, nil 
+
 }
 
 type TestStatefulResolver struct {
@@ -50,6 +79,8 @@ func (r TestResource) GetTemplate(sym string) (string, error) {
 		return "root", nil
 	case "_catch":
 		return "aiee", nil
+	case "flagCatch":
+		return "flagiee", nil
 	}
 	panic(fmt.Sprintf("unknown symbol %s", sym))
 	return "", fmt.Errorf("unknown symbol %s", sym)
@@ -65,21 +96,32 @@ func (r TestResource) FuncFor(sym string) (resource.EntryFunc, error) {
 		return getDyn, nil
 	case "arg":
 		return r.getInput, nil
+	case "echo":
+		return getEcho, nil
+	case "setFlagOne":
+		return setFlag, nil
 	}
 	return nil, fmt.Errorf("invalid function: '%s'", sym)
 }
 
-func(r TestResource) getInput(sym string, input []byte, ctx context.Context) (string, error) {
+func(r TestResource) getInput(sym string, input []byte, ctx context.Context) (resource.Result, error) {
 	v, err := r.state.GetInput()
-	return string(v), err
+	return resource.Result{
+		Content: string(v),
+	}, err
 }
 
 func(r TestResource) GetCode(sym string) ([]byte, error) {
 	var b []byte
-	if sym == "_catch" {
+	switch sym {
+	case "_catch":
+		b = NewLine(b, MOUT, []string{"0", "repent"}, nil, nil)
+		b = NewLine(b, HALT, nil, nil, nil)
+	case "flagCatch":
 		b = NewLine(b, MOUT, []string{"0", "repent"}, nil, nil)
 		b = NewLine(b, HALT, nil, nil, nil)
 	}
+
 	return b, nil
 }
 
@@ -409,3 +451,73 @@ func TestRunReturn(t *testing.T) {
 		t.Fatalf("expected location 'root', got '%s'", location)
 	}
 }
+
+
+func TestRunLoadInput(t *testing.T) {
+	st := state.NewState(5)
+	rs := TestResource{}
+	ca := cache.NewCache()
+	vm := NewVm(&st, &rs, ca, nil)
+
+	var err error
+
+	st.Down("root")
+	st.SetInput([]byte("foobar"))
+
+	b := NewLine(nil, LOAD, []string{"echo"}, []byte{0x00}, nil)
+	b = NewLine(b, HALT, nil, nil, nil)
+
+	ctx := context.TODO()
+
+	b, err = vm.Run(b, ctx)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	r, err := ca.Get("echo")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if r != "echo: foobar" {
+		t.Fatalf("expected 'echo: foobar', got %s", r)
+	}
+}
+
+func TestInputBranch(t *testing.T) {
+	st := state.NewState(5)
+	rs := TestResource{}
+	ca := cache.NewCache()
+	vm := NewVm(&st, &rs, ca, nil)
+
+	var err error
+
+	st.Down("root")
+
+	b := NewLine(nil, LOAD, []string{"setFlagOne"}, []byte{0x00}, nil)
+	b = NewLine(b, CATCH, []string{"flagCatch"}, []byte{8}, []uint8{0})
+	b = NewLine(b, RELOAD, []string{"setFlagOne"}, nil, nil)
+	b = NewLine(b, CATCH, []string{"flagCatch"}, []byte{8}, []uint8{0})
+	b = NewLine(b, CATCH, []string{"one"}, []byte{9}, []uint8{0})
+
+	ctx := context.TODO()
+
+	st.SetInput([]byte{0x08})
+	b, err = vm.Run(b, ctx)
+	if err != nil {
+		t.Fatal(err)
+	}
+	location, _ := st.Where()
+	if location != "flagCatch" {
+		t.Fatalf("expected 'flagCatch', got %s", location)
+	}
+
+	st.SetInput([]byte{0x09, 0x08})
+	b, err = vm.Run(b, ctx)
+	if err != nil {
+		t.Fatal(err)
+	}
+	location, _ = st.Where()
+	if location != "one" {
+		t.Fatalf("expected 'one', got %s", location)
+	}
+}