diff --git a/internal/landscape/compute.go b/internal/landscape/compute.go
index 4bc0e2f..4697fe0 100644
--- a/internal/landscape/compute.go
+++ b/internal/landscape/compute.go
@@ -3,6 +3,7 @@ package landscape
 import (
 	"context"
 	"fmt"
+	"os"
 	"path/filepath"
 	"runtime"
 	"sync"
@@ -15,9 +16,16 @@ import (
 // Compute runs one node over its input rasters. See the package doc for the
 // concurrency model: windows are processed by a worker pool; each worker owns
 // its own Reader handles (GDAL datasets are not goroutine-safe) and writes are
-// serialised per output. Window order does not affect the result.
+// serialised per output. Window order does not affect the result. On any
+// error, no output files are left behind: Compute best-effort removes every
+// output it created before returning.
 func Compute(ctx context.Context, rio raster.IO, node Node, inputs map[string]string, outDir string, p Params) (map[string]string, error) {
 	p = p.WithDefaults()
+	if p.WindowSize <= 0 {
+		// WithDefaults only fills in a zero value; guard against a negative
+		// one too, since raster.Windows would otherwise loop forever.
+		p.WindowSize = DefaultParams().WindowSize
+	}
 	paths := make([]string, len(node.Inputs))
 	for i, g := range node.Inputs {
 		path, ok := inputs[g]
@@ -35,30 +43,47 @@ func Compute(ctx context.Context, rio raster.IO, node Node, inputs map[string]st
 
 	outPaths := make(map[string]string, len(node.Outputs))
 	writers := make([]raster.Writer, len(node.Outputs))
+	createdPaths := make([]string, 0, len(node.Outputs))
 	for j, g := range node.Outputs {
 		path := filepath.Join(outDir, g+".tif")
 		w, err := rio.Create(ctx, path, grid, raster.DefaultWriterOptions())
 		if err != nil {
 			closeWriters(writers[:j])
+			removeOutputs(createdPaths)
 			return nil, fmt.Errorf("node %s: create output %s: %w", node.Code, g, err)
 		}
 		writers[j] = w
 		outPaths[g] = path
+		createdPaths = append(createdPaths, path)
 	}
 
 	windows := raster.Windows(grid.Width, grid.Height, p.WindowSize)
+	// The first window raster.Windows produces is always the largest: it
+	// starts at (0,0) so both its width and height are the un-clipped
+	// min(WindowSize, dimension). Size per-worker buffers off it instead of
+	// WindowSize*WindowSize, which would over-allocate whenever the raster is
+	// smaller than one window (the common case for small/test rasters, and
+	// for the last row/column of any raster).
+	var size int
+	if len(windows) > 0 {
+		size = windows[0].Width * windows[0].Height
+	}
 	jobs := make(chan raster.Window)
 	var writeMu sync.Mutex
 	eg, gctx := errgroup.WithContext(ctx)
-	workers := min(runtime.GOMAXPROCS(0), len(windows))
+	// Cap workers well below GOMAXPROCS too: each worker holds a full set of
+	// per-window input/output buffers, and nodes can have many inputs and
+	// outputs (e.g. node 20: 6 inputs, 5 outputs), so an unbounded worker
+	// count multiplies memory with core count and with concurrently running
+	// nodes.
+	workers := min(runtime.GOMAXPROCS(0), len(windows), 8)
 	for w := 0; w < workers; w++ {
 		eg.Go(func() error {
-			readers, err := openAll(gctx, rio, paths)
+			readers, err := openAll(gctx, rio, node, paths)
 			if err != nil {
 				return err
 			}
 			defer closeReaders(readers)
-			size := p.WindowSize * p.WindowSize
 			in := make([][]float64, len(paths))
 			for i := range in {
 				in[i] = make([]float64, size)
@@ -109,6 +134,7 @@ func Compute(ctx context.Context, rio raster.IO, node Node, inputs map[string]st
 		runErr = err
 	}
 	if runErr != nil {
+		removeOutputs(createdPaths)
 		return nil, runErr
 	}
 	return outPaths, nil
@@ -117,11 +143,14 @@ func Compute(ctx context.Context, rio raster.IO, node Node, inputs map[string]st
 // checkGrids opens every input once, verifies all grids match the first, and
 // returns that grid.
 func checkGrids(ctx context.Context, rio raster.IO, node Node, paths []string) (raster.Grid, error) {
-	readers, err := openAll(ctx, rio, paths)
+	readers, err := openAll(ctx, rio, node, paths)
 	if err != nil {
 		return raster.Grid{}, err
 	}
 	defer closeReaders(readers)
+	if len(readers) == 0 {
+		return raster.Grid{}, fmt.Errorf("node %s (%s): has no inputs", node.Code, node.Name)
+	}
 	ref := readers[0].Grid()
 	for i := 1; i < len(readers); i++ {
 		if g := readers[i].Grid(); !rio.SameGrid(ref, g) {
@@ -132,13 +161,20 @@ func checkGrids(ctx context.Context, rio raster.IO, node Node, paths []string) (
 	return ref, nil
 }
 
-func openAll(ctx context.Context, rio raster.IO, paths []string) ([]raster.Reader, error) {
+// openAll opens paths in order, wrapping any failure with the node code and
+// the input group name (paths is always node.Inputs resolved to files, in
+// the same order) for context.
+func openAll(ctx context.Context, rio raster.IO, node Node, paths []string) ([]raster.Reader, error) {
 	readers := make([]raster.Reader, 0, len(paths))
-	for _, p := range paths {
+	for i, p := range paths {
 		r, err := rio.Open(ctx, p)
 		if err != nil {
 			closeReaders(readers)
-			return nil, err
+			name := p
+			if i < len(node.Inputs) {
+				name = node.Inputs[i]
+			}
+			return nil, fmt.Errorf("node %s: input %s: %w", node.Code, name, err)
 		}
 		readers = append(readers, r)
 	}
@@ -165,3 +201,11 @@ func closeWriters(ws []raster.Writer) error {
 	}
 	return first
 }
+
+// removeOutputs best-effort deletes every path in paths, ignoring errors. It
+// is used to leave no partially-written output behind after a failed run.
+func removeOutputs(paths []string) {
+	for _, p := range paths {
+		_ = os.Remove(p)
+	}
+}
diff --git a/internal/landscape/compute_test.go b/internal/landscape/compute_test.go
index 9f39ae4..5754366 100644
--- a/internal/landscape/compute_test.go
+++ b/internal/landscape/compute_test.go
@@ -2,6 +2,8 @@ package landscape
 
 import (
 	"context"
+	"fmt"
+	"os"
 	"path/filepath"
 	"testing"
 
@@ -43,6 +45,9 @@ func TestCompute_E_TilesWindowsAndWritesEveryPixel(t *testing.T) {
 	if res.grid != g {
 		t.Fatal("output grid must copy the first input's grid")
 	}
+	if res.opts != raster.DefaultWriterOptions() {
+		t.Fatalf("output created with %+v, want raster.DefaultWriterOptions() = %+v", res.opts, raster.DefaultWriterOptions())
+	}
 	for i, v := range res.data {
 		want := 4.0
 		if i == 0 {
@@ -99,3 +104,116 @@ func TestCompute_MultiOutputNode(t *testing.T) {
 		t.Fatal("min(P, E) not applied per output")
 	}
 }
+
+// TestCompute_MultiOutputNode_TiledWindows runs the 6-input/5-output node 20
+// with a window size much smaller than the raster, so per-worker output
+// buffers are reused across windows of differing pixel counts (partial
+// windows at the raster's right/bottom edges).
+func TestCompute_MultiOutputNode_TiledWindows(t *testing.T) {
+	fio := newFakeIO()
+	w, h := 5, 3
+	g := grid(w, h)
+	paths := map[string]string{}
+	for i, s := range []string{SlotPIrrigation, SlotPSnow, SlotPCrop, SlotPPasture, SlotPTourism} {
+		paths[s] = s + ".tif"
+		fio.put(paths[s], g, constRaster(w, h, float64(i+1)))
+	}
+	paths[OutE] = "e.tif"
+	fio.put("e.tif", g, constRaster(w, h, 3))
+	node, _ := NodeByCode("20")
+	p := DefaultParams()
+	p.WindowSize = 2 // 5x3 with 2x2 tiles: several differently-sized windows
+	out, err := Compute(context.Background(), fio, node, paths, "/o2", p)
+	if err != nil {
+		t.Fatal(err)
+	}
+	codes := []string{OutCIrrigation, OutCSnow, OutCCrop, OutCPasture, OutCTourism}
+	for i, code := range codes {
+		want := min(i+1, 3) // min(P_sector, E=3)
+		res := fio.files[out[code]]
+		for px, v := range res.data {
+			if v != float64(want) {
+				t.Fatalf("%s pixel %d = %v want %v", code, px, v, want)
+			}
+		}
+	}
+}
+
+// TestCompute_ZeroParamsUsesDefaults exercises Compute with a completely
+// zero-valued Params, relying on WithDefaults to fill in WindowSize and the
+// other node-independent knobs.
+func TestCompute_ZeroParamsUsesDefaults(t *testing.T) {
+	fio := newFakeIO()
+	g := grid(4, 4)
+	fio.put("z.tif", g, constRaster(4, 4, 2))
+	fio.put("u.tif", g, constRaster(4, 4, 3))
+	node, _ := NodeByCode("10")
+	out, err := Compute(context.Background(), fio, node, map[string]string{OutZIntegrated: "z.tif", OutUIntegrated: "u.tif"}, "/z", Params{})
+	if err != nil {
+		t.Fatal(err)
+	}
+	for _, v := range fio.files[out[OutE]].data {
+		if v != 3 {
+			t.Fatalf("pixel = %v want 3", v)
+		}
+	}
+}
+
+// TestCompute_NegativeWindowSizeClampedToDefault guards against
+// raster.Windows looping forever on a non-positive window size: WithDefaults
+// only fills in a zero value, so Compute must clamp negatives itself.
+func TestCompute_NegativeWindowSizeClampedToDefault(t *testing.T) {
+	fio := newFakeIO()
+	g := grid(2, 2)
+	fio.put("z.tif", g, constRaster(2, 2, 2))
+	fio.put("u.tif", g, constRaster(2, 2, 3))
+	node, _ := NodeByCode("10")
+	p := DefaultParams()
+	p.WindowSize = -5
+	out, err := Compute(context.Background(), fio, node, map[string]string{OutZIntegrated: "z.tif", OutUIntegrated: "u.tif"}, "/neg", p)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if fio.files[out[OutE]].data[0] != 3 {
+		t.Fatal("unexpected result")
+	}
+}
+
+// TestCompute_FailureMidRunReturnsError simulates a read failure partway
+// through a run (the fake fails every ReadFloat64 against u.tif from the
+// first call on) and checks Compute surfaces the error instead of returning
+// a partial result.
+func TestCompute_FailureMidRunReturnsError(t *testing.T) {
+	fio := newFakeIO()
+	g := grid(10, 7)
+	fio.put("z.tif", g, constRaster(10, 7, 2))
+	fio.put("u.tif", g, constRaster(10, 7, 4))
+	fio.failReadAfterN("u.tif", 0) // fail starting from the very first read
+	node, _ := NodeByCode("10")
+	p := DefaultParams()
+	p.WindowSize = 4
+	if _, err := Compute(context.Background(), fio, node, map[string]string{OutZIntegrated: "z.tif", OutUIntegrated: "u.tif"}, "/out-fail", p); err == nil {
+		t.Fatal("expected error from simulated read failure")
+	}
+}
+
+// TestRemoveOutputs_DeletesFiles unit-tests the cleanup helper Compute uses
+// after a failed run, against the real filesystem (the fake IO above has no
+// on-disk files to assert against).
+func TestRemoveOutputs_DeletesFiles(t *testing.T) {
+	dir := t.TempDir()
+	var paths []string
+	for i := 0; i < 3; i++ {
+		p := filepath.Join(dir, fmt.Sprintf("out%d.tif", i))
+		if err := os.WriteFile(p, []byte("data"), 0o644); err != nil {
+			t.Fatal(err)
+		}
+		paths = append(paths, p)
+	}
+	removeOutputs(paths)
+	for _, p := range paths {
+		if _, err := os.Stat(p); !os.IsNotExist(err) {
+			t.Fatalf("expected %s to be removed, stat err = %v", p, err)
+		}
+	}
+}
diff --git a/internal/landscape/fakeio_test.go b/internal/landscape/fakeio_test.go
index 7aca385..61e1ce8 100644
--- a/internal/landscape/fakeio_test.go
+++ b/internal/landscape/fakeio_test.go
@@ -12,11 +12,19 @@ import (
 type fakeIO struct {
 	mu    sync.Mutex
 	files map[string]*fakeRaster
+
+	// failReadAfter, when set for a path, makes every ReadFloat64 call
+	// against that path fail once the cumulative read count (across all
+	// readers/workers) exceeds the configured threshold. Used to simulate a
+	// mid-run I/O failure.
+	failReadAfter map[string]int
+	readCounts    map[string]int
 }
 
 type fakeRaster struct {
 	grid raster.Grid
 	data []float64 // row-major
+	opts raster.WriterOptions
 }
 
 func newFakeIO() *fakeIO { return &fakeIO{files: map[string]*fakeRaster{}} }
@@ -25,12 +33,39 @@ func (f *fakeIO) put(path string, g raster.Grid, data []float64) {
 	f.files[path] = &fakeRaster{grid: g, data: data}
 }
 
-type fakeReader struct{ r *fakeRaster }
+// failReadAfterN makes ReadFloat64 against path fail starting from the
+// (n+1)-th call to it.
+func (f *fakeIO) failReadAfterN(path string, n int) {
+	f.mu.Lock()
+	defer f.mu.Unlock()
+	if f.failReadAfter == nil {
+		f.failReadAfter = map[string]int{}
+		f.readCounts = map[string]int{}
+	}
+	f.failReadAfter[path] = n
+}
+
+type fakeReader struct {
+	f    *fakeIO
+	path string
+	r    *fakeRaster
+}
 
 func (r *fakeReader) Grid() raster.Grid       { return r.r.grid }
 func (r *fakeReader) NoData() (float64, bool) { return -9999, true }
 func (r *fakeReader) Close() error            { return nil }
 func (r *fakeReader) ReadFloat64(w raster.Window, dst []float64) error {
+	if r.f != nil {
+		r.f.mu.Lock()
+		if n, ok := r.f.failReadAfter[r.path]; ok {
+			r.f.readCounts[r.path]++
+			if r.f.readCounts[r.path] > n {
+				r.f.mu.Unlock()
+				return fmt.Errorf("fake: simulated read failure for %s", r.path)
+			}
+		}
+		r.f.mu.Unlock()
+	}
 	for y := 0; y < w.Height; y++ {
 		copy(dst[y*w.Width:(y+1)*w.Width], r.r.data[(w.Y+y)*r.r.grid.Width+w.X:(w.Y+y)*r.r.grid.Width+w.X+w.Width])
 	}
@@ -61,13 +96,13 @@ func (f *fakeIO) Open(_ context.Context, path string) (raster.Reader, error) {
 	if !ok {
 		return nil, fmt.Errorf("fake: %s not found", path)
 	}
-	return &fakeReader{r: r}, nil
+	return &fakeReader{f: f, path: path, r: r}, nil
 }
 
-func (f *fakeIO) Create(_ context.Context, path string, g raster.Grid, _ raster.WriterOptions) (raster.Writer, error) {
+func (f *fakeIO) Create(_ context.Context, path string, g raster.Grid, o raster.WriterOptions) (raster.Writer, error) {
 	f.mu.Lock()
 	defer f.mu.Unlock()
-	r := &fakeRaster{grid: g, data: make([]float64, g.Width*g.Height)}
+	r := &fakeRaster{grid: g, data: make([]float64, g.Width*g.Height), opts: o}
 	f.files[path] = r
 	return &fakeWriter{f: f, r: r}, nil
 }