diff --git a/DESIGN.md b/DESIGN.md
index fec4cd1..4043566 100644
--- a/DESIGN.md
+++ b/DESIGN.md
@@ -7,7 +7,8 @@ Work is tracked in Gitea issues; the tracking epic links every piece in dependen
 ## Decisions
 
 - **Placement model:** freeform plops (not a square-foot grid), scaled by real plant spacing. Grid snapping may come later as a toggle.
-- **Spacing is a plant-to-plant rule, so bed edges get half of it.** A bed edge is not a competitor for soil, light or water, so the outer row owes it half the spacing rather than a full one. `FillRegion` centres its lattice accordingly, and lets a plop — a *clump* three spacings across — cross the edge by up to half a spacing so its outermost plants land at that half-spacing. The rule, the square-foot-chart arithmetic behind it, and the failure mode it prevents are written out once in `hexCenters`; #75 is what getting it wrong looked like.
+- **A fill is one of two operations (#77).** A plop is a *clump*, not a plant, which is the right primitive for SKETCHING ("a few plops of garlic in a corner") but can't draw a real planting — a filled bed comes out as ~15 blobs, not 8 rows of garlic. So `FillRegion`/`FillNamedRegion` take a `FillLayout`: `clump` (default; plop radius 1.5×spacing, ~7 plants each — quick coverage) or `grid` (radius spacing/2, pitch = spacing, ONE plant per plop — a layout you could plant from). Same `hexCenters` lattice and #75 edge rule for both; only the radius→spacing relationship differs. Surfaced on `POST /objects/:id/fill` (`layout`) and the agent's `fill_region` (`mode`). Same centered `hexCenters` lattice for both, but BOTH the plop radius (`plopRadiusFor`) and the edge inset (`edgeInset`) differ by layout: a grid plant sits at the plop's centre, so it insets a half-spacing; a clump's plants reach its rim, so it insets radius-less-a-half and overhangs the edge by that half — reusing the clump formula for grid would inset by zero and plant flush on the edge. A grid-filled bed approaches the low-hundreds-of-plops the SVG budget was sized for, which the semantic-zoom tiers already anticipate.
+- **Spacing is a plant-to-plant rule, so bed edges get half of it.** A bed edge is not a competitor for soil, light or water, so the outer row owes it half the spacing rather than a full one. `FillRegion` centres its lattice accordingly, and lets a plop — a *clump* three spacings across — cross the edge by up to half a spacing so its outermost plants land at that half-spacing. The rule, the square-foot-chart arithmetic behind it, and how it differs by layout are written out once in `edgeInset` (which `hexCenters` then honours); #75 is what getting it wrong looked like.
 - **Stack:** Go 1.26.x backend, module `gitea.stevedudenhoeffer.com/steve/pansy`; React + TypeScript + Vite + Tailwind frontend, production build embedded via `embed.FS` → one static binary (`CGO_ENABLED=0`).
 - **Users:** multi-user with ownership. Users own gardens; a garden can be shared with other users as viewer (read) or editor (edit content). Owner additionally shares/deletes. The first registered user is `is_admin` (set race-free inside the INSERT); admin gates instance-wide Settings (`requireAdmin`), the only thing that reads that flag.
 - **Auth:** OIDC-first (Authentik is the primary IdP), local argon2id passwords as an optional fallback.
diff --git a/internal/agent/runtime_test.go b/internal/agent/runtime_test.go
index 16791bd..a25945d 100644
--- a/internal/agent/runtime_test.go
+++ b/internal/agent/runtime_test.go
@@ -60,7 +60,7 @@ func TestTurnIsOneChangeSet(t *testing.T) {
 	if err != nil {
 		t.Fatalf("bed: %v", err)
 	}
-	if _, err := svc.FillNamedRegion(ctx, owner, bed.ID, "all", garlic.ID, nil); err != nil {
+	if _, err := svc.FillNamedRegion(ctx, owner, bed.ID, "all", garlic.ID, nil, service.FillClump); err != nil {
 		t.Fatalf("seed garlic: %v", err)
 	}
 
diff --git a/internal/agent/tools.go b/internal/agent/tools.go
index 9d59c7a..021a6d9 100644
--- a/internal/agent/tools.go
+++ b/internal/agent/tools.go
@@ -127,8 +127,9 @@ func (a *adapter) fillRegion(ctx context.Context, args struct {
 	Region          string   `json:"region" description:"nw|ne|sw|se corner, north|south|east|west (or top|bottom|left|right) half, or all"`
 	PlantID         int64    `json:"plantId" description:"plant to fill with"`
 	SpacingOverride *float64 `json:"spacingOverrideCm" description:"optional in-row spacing override in cm; omit to use the plant's spacing"`
+	Mode            string   `json:"mode" enum:"clump,grid" description:"clump (default) drops a few fat clumps for a quick sketch; grid lays out individual plants in rows at true spacing, a layout you could plant from"`
 }) (any, error) {
-	return a.svc.FillNamedRegion(ctx, a.actor, args.ObjectID, args.Region, args.PlantID, args.SpacingOverride)
+	return a.svc.FillNamedRegion(ctx, a.actor, args.ObjectID, args.Region, args.PlantID, args.SpacingOverride, service.FillLayout(args.Mode))
 }
 
 func (a *adapter) findPlant(ctx context.Context, args struct {
diff --git a/internal/agent/tools_test.go b/internal/agent/tools_test.go
index d599540..6e06ec8 100644
--- a/internal/agent/tools_test.go
+++ b/internal/agent/tools_test.go
@@ -169,7 +169,7 @@ func TestGarlicBedToCucumbers(t *testing.T) {
 	if err != nil {
 		t.Fatalf("bed: %v", err)
 	}
-	if _, err := svc.FillNamedRegion(ctx, owner, bed.ID, "all", garlic.ID, nil); err != nil {
+	if _, err := svc.FillNamedRegion(ctx, owner, bed.ID, "all", garlic.ID, nil, service.FillClump); err != nil {
 		t.Fatalf("seed the garlic: %v", err)
 	}
 
diff --git a/internal/api/ops.go b/internal/api/ops.go
index f212055..e152109 100644
--- a/internal/api/ops.go
+++ b/internal/api/ops.go
@@ -51,6 +51,10 @@ type objectFillRequest struct {
 	// SpacingOverrideCM plants tighter or looser than the plant's mature spacing
 	// without editing the catalog entry.
 	SpacingOverrideCM *float64 `json:"spacingOverrideCm"`
+	// Layout is "clump" (default; fat clumps for a quick sketch) or "grid"
+	// (individual plants in rows at true spacing). Empty = clump. An unknown value
+	// is refused by the service (#77).
+	Layout string `json:"layout"`
 }
 
 func (h *handlers) fillObject(c *gin.Context) {
@@ -84,9 +88,9 @@ func (h *handlers) fillObject(c *gin.Context) {
 			return
 		}
 		region := service.Region{MinX: rect.MinX, MinY: rect.MinY, MaxX: rect.MaxX, MaxY: rect.MaxY}
-		created, err = h.svc.FillRegion(c.Request.Context(), actor, id, region, req.PlantID, req.SpacingOverrideCM)
+		created, err = h.svc.FillRegion(c.Request.Context(), actor, id, region, req.PlantID, req.SpacingOverrideCM, service.FillLayout(req.Layout))
 	} else {
-		created, err = h.svc.FillNamedRegion(c.Request.Context(), actor, id, req.Region, req.PlantID, req.SpacingOverrideCM)
+		created, err = h.svc.FillNamedRegion(c.Request.Context(), actor, id, req.Region, req.PlantID, req.SpacingOverrideCM, service.FillLayout(req.Layout))
 	}
 	if err != nil {
 		writeServiceError(c, err)
diff --git a/internal/api/ops_test.go b/internal/api/ops_test.go
index bf317de..7a091ed 100644
--- a/internal/api/ops_test.go
+++ b/internal/api/ops_test.go
@@ -97,6 +97,44 @@ func TestFillAndClearAPI(t *testing.T) {
 	}
 }
 
+// TestFillLayoutAPI covers the layout selector (#77): grid packs denser than the
+// clump default, and an unknown layout is a 400 rather than a silent clump fill.
+func TestFillLayoutAPI(t *testing.T) {
+	r := authEngine(t, localCfg())
+	cookie := registerAndCookie(t, r, "layout@example.com")
+	_, objID, plantID := seedFillableBed(t, r, cookie, 200, 200, 20)
+
+	// Clump (default) for the baseline count.
+	w := doJSON(t, r, http.MethodPost, fillPath(objID), map[string]any{
+		"plantId": plantID, "region": "all",
+	}, cookie)
+	if w.Code != http.StatusOK {
+		t.Fatalf("clump fill: status %d, body %s", w.Code, w.Body.String())
+	}
+	clumpN := int(decodeMap(t, w.Body.Bytes())["created"].(float64))
+	if w := doJSON(t, r, http.MethodPost, clearPath(objID), nil, cookie); w.Code != http.StatusOK {
+		t.Fatalf("clear between fills: %d", w.Code)
+	}
+
+	// Grid packs individual plants at true spacing — many more, small plops.
+	w = doJSON(t, r, http.MethodPost, fillPath(objID), map[string]any{
+		"plantId": plantID, "region": "all", "layout": "grid",
+	}, cookie)
+	if w.Code != http.StatusOK {
+		t.Fatalf("grid fill: status %d, body %s", w.Code, w.Body.String())
+	}
+	if gridN := int(decodeMap(t, w.Body.Bytes())["created"].(float64)); gridN <= clumpN {
+		t.Errorf("grid fill created %d, want more than the clump fill's %d", gridN, clumpN)
+	}
+
+	// An unknown layout is a 400, not a silent clump fill.
+	if w := doJSON(t, r, http.MethodPost, fillPath(objID), map[string]any{
+		"plantId": plantID, "region": "all", "layout": "spiral",
+	}, cookie); w.Code != http.StatusBadRequest {
+		t.Errorf("unknown layout = %d, want 400", w.Code)
+	}
+}
+
 // TestFillRegionSelectionAPI: exactly one of region/rect, and a rect fills only
 // its own corner of the bed.
 func TestFillRegionSelectionAPI(t *testing.T) {
diff --git a/internal/service/ops.go b/internal/service/ops.go
index cc00a13..ec6e764 100644
--- a/internal/service/ops.go
+++ b/internal/service/ops.go
@@ -97,30 +97,106 @@ func defaultPlopRadius(spacingCM float64) float64 {
 	return math.Max(1.5*spacingCM, 15)
 }
 
-// FillRegion lays a hex-packed field of plops of one plant across a region of a
-// plantable object the actor can edit. Plop radius comes from the plant's spacing
-// (or spacingOverride) via defaultPlopRadius; centers sit on a hex lattice at 2×
-// radius pitch, centered in the region, and set in from each edge by the plop's
-// radius less half a spacing — see hexCenters for why that half-spacing is what
-// the edge is owed. A candidate is skipped when its plop would sit entirely
-// inside an existing active plop (so re-filling doesn't stack duplicates).
-// Returns the plops it created.
-func (s *Service) FillRegion(ctx context.Context, actorID, objectID int64, region Region, plantID int64, spacingOverride *float64) ([]domain.Planting, error) {
+// FillLayout selects what a fill packs (#77).
+//
+// A plop is a CLUMP, not a plant, and that abstraction is the right primitive for
+// SKETCHING — "a few plops of garlic in one corner" — but it can't draw a real
+// planting: a filled 4×8ft bed comes out as ~15 blobs, not 8 rows of garlic. So
+// filling is now two operations. FillClump (the default, unchanged) drops fat
+// clumps for quick coverage; FillGrid lays out individual plants at true spacing,
+// producing a layout you could actually plant from.
+type FillLayout string
+
+const (
+	// FillClump packs fat clumps (radius 1.5×spacing). Each plop is ~7 plants.
+	FillClump FillLayout = "clump"
+	// FillGrid packs one plant per plop at true spacing (radius spacing/2, pitch
+	// = spacing). A bed becomes rows of individual plants.
+	FillGrid FillLayout = "grid"
+)
+
+// plopRadiusFor is the plop radius a fill uses, given the plant's spacing and the
+// layout. Grid mode is a plain spacing/2 (so the pitch is one spacing and each
+// plop's derived count is 1); clump mode keeps the 15cm floor that stops a
+// tiny-spacing plant from making invisibly small clumps — a floor grid mode
+// doesn't want, since its whole point is true spacing.
+func plopRadiusFor(spacingCM float64, layout FillLayout) float64 {
+	if layout == FillGrid {
+		return spacingCM / 2
+	}
+	return defaultPlopRadius(spacingCM)
+}
+
+// edgeInset is how far a plop's CENTRE must stay inside the region edge. It
+// differs by layout because the half-spacing rule is about where the PLANT lands,
+// and the plant sits in a different place within the plop.
+//
+// Spacing is a constraint between neighbouring plants competing for the same soil,
+// light and water; a bed edge is nobody's neighbour, so the outer plant owes it
+// only HALF the spacing — the half it would otherwise share. That is the
+// square-foot-chart arithmetic: garlic at 9-per-square sits 2" from the frame, not
+// 6".
+//
+//   - Grid: one plant, at the plop's centre. Put that centre a half-spacing in and
+//     the outer row lands exactly where the rule wants it — inset = spacing/2.
+//   - Clump: a fat plop (radius 1.5×spacing) whose plants fill out to its RIM.
+//     Insetting the whole circle would push the outer row a full 1.5 spacings in,
+//     three times the rule. Instead the clump may hang over by a half-spacing (rim
+//     at spacing/2 past the edge), landing its outermost plants that same
+//     half-spacing in — inset = radius − spacing/2. A grid plop reusing THAT
+//     formula would inset by radius − spacing/2 = 0 and plant flush on the edge,
+//     which is the bug this split fixes.
+func edgeInset(radius, spacing float64, layout FillLayout) float64 {
+	half := math.Max(0, spacing) / 2
+	if layout == FillGrid {
+		return half
+	}
+	return math.Max(0, radius-half)
+}
+
+// validFillLayout normalizes a layout: empty defaults to clump (so existing
+// callers are unchanged), a known value passes, anything else is rejected.
+func validFillLayout(l FillLayout) (FillLayout, bool) {
+	switch l {
+	case "", FillClump:
+		return FillClump, true
+	case FillGrid:
+		return FillGrid, true
+	default:
+		return "", false
+	}
+}
+
+// FillRegion lays a field of plops of one plant across a region of a plantable
+// object the actor can edit. The layout picks the primitive: FillClump drops fat
+// clumps for quick sketching, FillGrid lays out individual plants at true spacing
+// (see FillLayout). Plop radius comes from the plant's spacing (or spacingOverride)
+// via plopRadiusFor; centers sit on a centered hex lattice at 2×radius pitch, set
+// in from each edge by edgeInset — a half-spacing for grid, radius-less-a-half-
+// spacing for a clump (see edgeInset for the why). A candidate is skipped when its
+// plop would sit entirely inside an existing active plop (so re-filling doesn't
+// stack duplicates). Returns the plops it created.
+func (s *Service) FillRegion(ctx context.Context, actorID, objectID int64, region Region, plantID int64, spacingOverride *float64, layout FillLayout) ([]domain.Planting, error) {
 	o, _, err := s.objectForRole(ctx, actorID, objectID, roleEditor)
 	if err != nil {
 		return nil, err
 	}
-	return s.fillLoaded(ctx, actorID, o, region, plantID, spacingOverride)
+	return s.fillLoaded(ctx, actorID, o, region, plantID, spacingOverride, layout)
 }
 
 // fillLoaded is the shared body of FillRegion/FillNamedRegion given an object
-// already loaded and authorized (roleEditor). It rejects a non-finite region,
-// clamps the region to the object's bounds, refuses fills over maxFillPlops, and
-// inserts the whole batch in one transaction rather than one round-trip per plop.
-func (s *Service) fillLoaded(ctx context.Context, actorID int64, o *domain.GardenObject, region Region, plantID int64, spacingOverride *float64) ([]domain.Planting, error) {
+// already loaded and authorized (roleEditor). It validates the layout, rejects a
+// non-finite region, clamps the region to the object's bounds, refuses fills over
+// maxFillPlops, and inserts the whole batch in one transaction rather than one
+// round-trip per plop.
+func (s *Service) fillLoaded(ctx context.Context, actorID int64, o *domain.GardenObject, region Region, plantID int64, spacingOverride *float64, layout FillLayout) ([]domain.Planting, error) {
 	if !o.Plantable {
 		return nil, domain.ErrInvalidInput
 	}
+	layout, ok := validFillLayout(layout)
+	if !ok {
+		return nil, domain.ErrInvalidInput
+	}
 	plant, err := s.visiblePlant(ctx, actorID, plantID)
 	if err != nil {
 		return nil, err
@@ -132,7 +208,7 @@ func (s *Service) fillLoaded(ctx context.Context, actorID int64, o *domain.Garde
 		}
 		spacing = *spacingOverride
 	}
-	radius := defaultPlopRadius(spacing)
+	radius := plopRadiusFor(spacing, layout)
 	if !isFinite(radius) || radius <= 0 {
 		return nil, domain.ErrInvalidInput
 	}
@@ -150,7 +226,7 @@ func (s *Service) fillLoaded(ctx context.Context, actorID int64, o *domain.Garde
 	}
 
 	region = region.clampTo(o.WidthCM/2, o.HeightCM/2)
-	centers, total := hexCenters(region, radius, spacing, maxFillPlops)
+	centers, total := hexCenters(region, radius, edgeInset(radius, spacing, layout), maxFillPlops)
 	if total > maxFillPlops {
 		return nil, domain.ErrInvalidInput // region too large for this spacing; ask for less
 	}
@@ -161,13 +237,17 @@ func (s *Service) fillLoaded(ctx context.Context, actorID int64, o *domain.Garde
 	}
 	today := s.now().UTC().Format(dateLayout)
 	batch := make([]*domain.Planting, 0, len(centers))
+	// Only the plops that were ALREADY here can cover a candidate: every plop this
+	// fill makes shares one radius and sits on a distinct lattice point, and a plop
+	// is "covered" only when it lies entirely inside another — impossible between
+	// two equal-radius circles at different centres. So skip against `existing` as
+	// loaded and don't grow it per plop, which made an empty-bed grid fill's check
+	// needlessly quadratic.
 	for _, c := range centers {
 		if coveredByExisting(c.x, c.y, radius, existing) {
 			continue
 		}
-		p := &domain.Planting{ObjectID: o.ID, PlantID: plantID, XCM: c.x, YCM: c.y, RadiusCM: radius, PlantedAt: &today}
-		batch = append(batch, p)
-		existing = append(existing, *p) // so later candidates in THIS fill don't stack on it
+		batch = append(batch, &domain.Planting{ObjectID: o.ID, PlantID: plantID, XCM: c.x, YCM: c.y, RadiusCM: radius, PlantedAt: &today})
 	}
 	created, err := s.store.CreatePlantings(ctx, batch)
 	if err != nil {
@@ -196,24 +276,14 @@ type localPoint struct{ x, y float64 }
 //
 // # How close to the edge the outer row goes
 //
-// Spacing is a constraint BETWEEN NEIGHBOURING PLANTS competing for the same
-// soil, light and water. A bed edge is not a competitor, so the outer row only
-// owes it HALF the spacing — the half it would otherwise share with a neighbour.
-// That is the arithmetic inside every square-foot-gardening chart: 4 per square
-// is 6" apart and 3" from the square's edge; 9 per square is 4" apart and 2"
-// from the edge. Garlic at 9 per square goes in 2" from the frame, not 6".
+// The caller passes `inset`: the margin the outer row keeps from every edge. It
+// encodes the half-spacing rule (spacing is owed between neighbouring plants, and
+// a bed edge is nobody's neighbour) and differs by layout — see edgeInset, which
+// derives it. hexCenters just honours it on all four sides.
 //
-// A plop is a CLUMP, not a plant — defaultPlopRadius makes it 1.5×spacing, so
-// three spacings across — and its plants sit out to its rim. So keeping the whole
-// circle inside the bed would inset the outer row by a full 1.5 spacings, three
-// times what the rule allows. Instead the clump may hang over the edge by up to
-// half a spacing, which puts its outermost plants exactly the half-spacing from
-// the edge that the rule asks for. Overhang is capped there and nowhere near the
-// full radius: a clump mostly outside the bed is a drawing of plants in the path.
-//
-// Do not "simplify" this back to anchoring at the region's min corner. That is
-// what #75 was: staggered rows start a full pitch in, and the leftover all lands
-// on the far edge, where clumps hang outside a bed that nothing clips them to.
+// Do not "simplify" the centering back to anchoring at the region's min corner.
+// That is what #75 was: staggered rows start a full pitch in, and the leftover all
+// lands on the far edge, where clumps hang outside a bed that nothing clips them to.
 //
 // # Counting before building
 //
@@ -221,7 +291,7 @@ type localPoint struct{ x, y float64 }
 // BEFORE building anything: a fill large enough to be refused shouldn't allocate
 // its whole lattice first just to be counted and thrown away. Over `limit` it
 // returns (nil, total), so the caller can still refuse with the real number.
-func hexCenters(r Region, radius, spacing float64, limit int) ([]localPoint, int) {
+func hexCenters(r Region, radius, inset float64, limit int) ([]localPoint, int) {
 	if radius <= 0 {
 		return nil, 0
 	}
@@ -234,11 +304,6 @@ func hexCenters(r Region, radius, spacing float64, limit int) ([]localPoint, int
 	pitch := 2 * radius
 	rowH := pitch * math.Sqrt(3) / 2
 
-	// How far a clump's centre must stay inside the edge: its own radius, less the
-	// half-spacing of overhang the rule allows. Never negative, and never past the
-	// centre of the clump.
-	inset := math.Max(0, radius-math.Max(0, spacing)/2)
-
 	rows, y0 := fitAxis(r.MaxY-r.MinY, rowH, inset)
 	cols, x0 := fitAxis(r.MaxX-r.MinX, pitch, inset)
 
@@ -311,7 +376,7 @@ func coveredByExisting(x, y, radius float64, existing []domain.Planting) bool {
 // FillNamedRegion is FillRegion addressed by a compass name ("ne", "south half")
 // instead of a resolved Region — the ergonomic form for agent tools, which don't
 // hold the object's geometry. It resolves the name against the object, then fills.
-func (s *Service) FillNamedRegion(ctx context.Context, actorID, objectID int64, regionName string, plantID int64, spacingOverride *float64) ([]domain.Planting, error) {
+func (s *Service) FillNamedRegion(ctx context.Context, actorID, objectID int64, regionName string, plantID int64, spacingOverride *float64, layout FillLayout) ([]domain.Planting, error) {
 	o, _, err := s.objectForRole(ctx, actorID, objectID, roleEditor)
 	if err != nil {
 		return nil, err
@@ -320,7 +385,7 @@ func (s *Service) FillNamedRegion(ctx context.Context, actorID, objectID int64,
 	if err != nil {
 		return nil, err
 	}
-	return s.fillLoaded(ctx, actorID, o, region, plantID, spacingOverride)
+	return s.fillLoaded(ctx, actorID, o, region, plantID, spacingOverride, layout)
 }
 
 // ClearObject soft-removes every active plop in an object the actor can edit (one
diff --git a/internal/service/ops_test.go b/internal/service/ops_test.go
index 1a003a1..ba2810a 100644
--- a/internal/service/ops_test.go
+++ b/internal/service/ops_test.go
@@ -59,7 +59,7 @@ func TestFillRegionCappedForHugeArea(t *testing.T) {
 	bed := seedFillBed(t, s, owner, g.ID, 6000, 6000) // ~46k lattice points at radius 15 → over the cap
 	plant := seedOwnPlant(t, s, owner, 10)
 	region, _ := NamedRegion(bed, "all")
-	if _, err := s.FillRegion(ctx, owner, bed.ID, region, plant.ID, nil); !errors.Is(err, domain.ErrInvalidInput) {
+	if _, err := s.FillRegion(ctx, owner, bed.ID, region, plant.ID, nil, FillClump); !errors.Is(err, domain.ErrInvalidInput) {
 		t.Errorf("oversized fill err = %v, want ErrInvalidInput (over maxFillPlops)", err)
 	}
 }
@@ -96,7 +96,7 @@ func TestHexCentersEdgeInset(t *testing.T) {
 	} {
 		t.Run(tc.name, func(t *testing.T) {
 			r := rect(-tc.w/2, -tc.h/2, tc.w/2, tc.h/2)
-			pts, total := hexCenters(r, tc.radius, tc.spacing, maxFillPlops)
+			pts, total := hexCenters(r, tc.radius, edgeInset(tc.radius, tc.spacing, FillClump), maxFillPlops)
 			if len(pts) == 0 {
 				t.Fatal("no centers")
 			}
@@ -173,7 +173,7 @@ func TestHexCentersTinyRegion(t *testing.T) {
 		{"off in a corner", rect(20, -40, 30, -30), 25, -35},
 	} {
 		t.Run(tc.name, func(t *testing.T) {
-			pts, _ := hexCenters(tc.r, 15, 10, maxFillPlops)
+			pts, _ := hexCenters(tc.r, 15, edgeInset(15, 10, FillClump), maxFillPlops)
 			if len(pts) != 1 || pts[0].x != tc.wantX || pts[0].y != tc.wantY {
 				t.Errorf("got %+v, want one plop at (%v,%v)", pts, tc.wantX, tc.wantY)
 			}
@@ -199,7 +199,7 @@ func TestFillRegionRejectsNonFiniteRegion(t *testing.T) {
 		{MinX: nan, MinY: -50, MaxX: 50, MaxY: 50},
 		{MinX: -50, MinY: -50, MaxX: 50, MaxY: math.Inf(1)},
 	} {
-		created, err := s.FillRegion(ctx, owner, bed.ID, r, plant.ID, nil)
+		created, err := s.FillRegion(ctx, owner, bed.ID, r, plant.ID, nil, FillClump)
 		if !errors.Is(err, domain.ErrInvalidInput) {
 			t.Errorf("FillRegion(%+v) err = %v, want ErrInvalidInput", r, err)
 		}
@@ -223,7 +223,7 @@ func TestFillRegionOutsideObjectPlantsNothing(t *testing.T) {
 	plant := seedOwnPlant(t, s, owner, 10)
 
 	// Wholly east of the bed: clampTo gives MinX=500, MaxX=50.
-	created, err := s.FillRegion(ctx, owner, bed.ID, rect(500, -50, 600, 50), plant.ID, nil)
+	created, err := s.FillRegion(ctx, owner, bed.ID, rect(500, -50, 600, 50), plant.ID, nil, FillClump)
 	if err != nil {
 		t.Fatalf("FillRegion: %v", err)
 	}
@@ -256,7 +256,7 @@ func TestFillRegionDeterministicPacking(t *testing.T) {
 	plant := seedOwnPlant(t, s, owner, 10)        // radius = max(15,15) = 15
 
 	region, _ := NamedRegion(bed, "all")
-	created, err := s.FillRegion(ctx, owner, bed.ID, region, plant.ID, nil)
+	created, err := s.FillRegion(ctx, owner, bed.ID, region, plant.ID, nil, FillClump)
 	if err != nil {
 		t.Fatalf("FillRegion: %v", err)
 	}
@@ -283,7 +283,7 @@ func TestFillRegionDeterministicPacking(t *testing.T) {
 
 	// Re-filling the same region skips everything (each candidate sits exactly on
 	// an existing plop → entirely inside it).
-	again, err := s.FillRegion(ctx, owner, bed.ID, region, plant.ID, nil)
+	again, err := s.FillRegion(ctx, owner, bed.ID, region, plant.ID, nil, FillClump)
 	if err != nil {
 		t.Fatalf("second FillRegion: %v", err)
 	}
@@ -292,6 +292,70 @@ func TestFillRegionDeterministicPacking(t *testing.T) {
 	}
 }
 
+// TestFillGridLaysOutIndividualPlants is the #77 grid mode: a grid fill packs one
+// plant per plop at true spacing, so a bed becomes rows of plants rather than a
+// few fat clumps. On the same bed it produces many more, smaller plops, each a
+// single plant.
+func TestFillGridLaysOutIndividualPlants(t *testing.T) {
+	ctx := context.Background()
+	s := newTestService(t, openConfig())
+	owner := seedUser(t, s, "a@example.com")
+	g, _ := s.CreateGarden(ctx, owner, GardenInput{Name: "Big", WidthCM: 2000, HeightCM: 2000})
+	bed := seedFillBed(t, s, owner, g.ID, 60, 60)
+	plant := seedOwnPlant(t, s, owner, 10) // spacing 10
+
+	region, _ := NamedRegion(bed, "all")
+	clump, err := s.FillRegion(ctx, owner, bed.ID, region, plant.ID, nil, FillClump)
+	if err != nil {
+		t.Fatalf("clump: %v", err)
+	}
+	if _, err := s.ClearObject(ctx, owner, bed.ID); err != nil {
+		t.Fatalf("clear: %v", err)
+	}
+	grid, err := s.FillRegion(ctx, owner, bed.ID, region, plant.ID, nil, FillGrid)
+	if err != nil {
+		t.Fatalf("grid: %v", err)
+	}
+
+	// Grid packs at spacing 10 (radius 5, pitch 10); clump at radius 15 (pitch 30).
+	// Grid must produce many more plops.
+	if len(grid) <= len(clump) {
+		t.Errorf("grid produced %d plops, clump %d — grid should be denser", len(grid), len(clump))
+	}
+	// Each grid plop is one plant at radius spacing/2 = 5.
+	maxAbs := 0.0
+	for _, p := range grid {
+		if p.RadiusCM != 5 {
+			t.Errorf("grid plop radius = %v, want 5 (spacing/2)", p.RadiusCM)
+		}
+		if p.DerivedCount != 1 {
+			t.Errorf("grid plop derived count = %d, want 1 (one plant per plop)", p.DerivedCount)
+		}
+		maxAbs = math.Max(maxAbs, math.Max(math.Abs(p.XCM), math.Abs(p.YCM)))
+	}
+	// The half-spacing edge rule: a grid plant sits AT the plop centre, so the
+	// outer row is inset a half-spacing (spacing/2 = 5) — at ±25 on this 60cm bed,
+	// not flush on ±30. Regression guard: the clump inset formula (radius − half)
+	// collapses to 0 for grid and would plant one on the very edge.
+	if edge := 30.0; maxAbs > edge-5+1e-6 {
+		t.Errorf("outermost grid plop at |coord|=%.2f — only %.2fcm from the edge; want a half-spacing (5cm) in", maxAbs, edge-maxAbs)
+	}
+}
+
+// TestFillRejectsUnknownLayout: a layout that isn't clump/grid is ErrInvalidInput.
+func TestFillRejectsUnknownLayout(t *testing.T) {
+	ctx := context.Background()
+	s := newTestService(t, openConfig())
+	owner := seedUser(t, s, "a@example.com")
+	g, _ := s.CreateGarden(ctx, owner, GardenInput{Name: "Big", WidthCM: 2000, HeightCM: 2000})
+	bed := seedFillBed(t, s, owner, g.ID, 60, 60)
+	plant := seedOwnPlant(t, s, owner, 10)
+	region, _ := NamedRegion(bed, "all")
+	if _, err := s.FillRegion(ctx, owner, bed.ID, region, plant.ID, nil, FillLayout("spiral")); !errors.Is(err, domain.ErrInvalidInput) {
+		t.Errorf("unknown layout err = %v, want ErrInvalidInput", err)
+	}
+}
+
 func TestFillRegionRotatedBedUsesLocalFrame(t *testing.T) {
 	ctx := context.Background()
 	s := newTestService(t, openConfig())
@@ -304,7 +368,7 @@ func TestFillRegionRotatedBedUsesLocalFrame(t *testing.T) {
 	plant := seedOwnPlant(t, s, owner, 20)
 
 	region, _ := NamedRegion(bed, "ne")
-	created, err := s.FillRegion(ctx, owner, bed.ID, region, plant.ID, nil)
+	created, err := s.FillRegion(ctx, owner, bed.ID, region, plant.ID, nil, FillClump)
 	if err != nil {
 		t.Fatalf("FillRegion: %v", err)
 	}
@@ -327,7 +391,7 @@ func TestClearObject(t *testing.T) {
 	bed := seedBed(t, s, owner, g.ID)
 	plant := seedOwnPlant(t, s, owner, 10)
 	region, _ := NamedRegion(bed, "all")
-	if _, err := s.FillRegion(ctx, owner, bed.ID, region, plant.ID, nil); err != nil {
+	if _, err := s.FillRegion(ctx, owner, bed.ID, region, plant.ID, nil, FillClump); err != nil {
 		t.Fatalf("fill: %v", err)
 	}
 
@@ -361,7 +425,7 @@ func TestOpsForbiddenForViewer(t *testing.T) {
 	}
 	region, _ := NamedRegion(bed, "all")
 
-	if _, err := s.FillRegion(ctx, viewer, bed.ID, region, plant.ID, nil); !errors.Is(err, domain.ErrForbidden) {
+	if _, err := s.FillRegion(ctx, viewer, bed.ID, region, plant.ID, nil, FillClump); !errors.Is(err, domain.ErrForbidden) {
 		t.Errorf("viewer fill = %v, want ErrForbidden", err)
 	}
 	if _, err := s.ClearObject(ctx, viewer, bed.ID); !errors.Is(err, domain.ErrForbidden) {
@@ -391,7 +455,7 @@ func TestFillScenario(t *testing.T) {
 		if err != nil {
 			t.Fatalf("region %q: %v", name, err)
 		}
-		if _, err := s.FillRegion(ctx, owner, bed.ID, region, plantID, nil); err != nil {
+		if _, err := s.FillRegion(ctx, owner, bed.ID, region, plantID, nil, FillClump); err != nil {
 			t.Fatalf("fill %q: %v", name, err)
 		}
 	}
diff --git a/internal/service/revisions_test.go b/internal/service/revisions_test.go
index f83c008..ecc500c 100644
--- a/internal/service/revisions_test.go
+++ b/internal/service/revisions_test.go
@@ -73,7 +73,7 @@ func TestFillRegionIsOneChangeSet(t *testing.T) {
 	plant := seedOwnPlant(t, s, owner, 15)
 	ctx := context.Background()
 
-	created, err := s.FillNamedRegion(ctx, owner, bed.ID, "all", plant.ID, nil)
+	created, err := s.FillNamedRegion(ctx, owner, bed.ID, "all", plant.ID, nil, FillClump)
 	if err != nil {
 		t.Fatalf("FillNamedRegion: %v", err)
 	}
@@ -320,7 +320,7 @@ func TestRevertClearObject(t *testing.T) {
 	plant := seedOwnPlant(t, s, owner, 15)
 	ctx := context.Background()
 
-	if _, err := s.FillNamedRegion(ctx, owner, bed.ID, "all", plant.ID, nil); err != nil {
+	if _, err := s.FillNamedRegion(ctx, owner, bed.ID, "all", plant.ID, nil, FillClump); err != nil {
 		t.Fatalf("fill: %v", err)
 	}
 	before, _ := s.store.ListActivePlantingsForObject(ctx, bed.ID)
@@ -688,7 +688,7 @@ func TestClearObjectOnlyClearsWhatItSnapshotted(t *testing.T) {
 	plant := seedOwnPlant(t, s, owner, 15)
 	ctx := context.Background()
 
-	if _, err := s.FillNamedRegion(ctx, owner, bed.ID, "all", plant.ID, nil); err != nil {
+	if _, err := s.FillNamedRegion(ctx, owner, bed.ID, "all", plant.ID, nil, FillClump); err != nil {
 		t.Fatalf("fill: %v", err)
 	}
 	before, _ := s.store.ListActivePlantingsForObject(ctx, bed.ID)
@@ -725,7 +725,7 @@ func TestRevertResultCarriesItsCounts(t *testing.T) {
 	plant := seedOwnPlant(t, s, owner, 15)
 	ctx := context.Background()
 
-	if _, err := s.FillNamedRegion(ctx, owner, bed.ID, "all", plant.ID, nil); err != nil {
+	if _, err := s.FillNamedRegion(ctx, owner, bed.ID, "all", plant.ID, nil, FillClump); err != nil {
 		t.Fatalf("fill: %v", err)
 	}
 	// A second, different kind of change, so the breakdown has more than one row
@@ -830,7 +830,7 @@ func TestSucceededTurnRecordsEvenIfTheCallerWentAway(t *testing.T) {
 	cs, err := s.WithChangeSet(ctx, owner, g.ID, ChangeSetOptions{
 		Source: domain.SourceAgent, Summary: "plant beans in the second bed",
 	}, func(ctx context.Context) error {
-		if _, err := s.FillNamedRegion(ctx, owner, bed.ID, "all", plant.ID, nil); err != nil {
+		if _, err := s.FillNamedRegion(ctx, owner, bed.ID, "all", plant.ID, nil, FillClump); err != nil {
 			return err
 		}
 		cancel() // the client disconnects, mid-turn, after the work landed