fix(ui): skip image preview when input width is too small

- Return 0 from thumbCols when width <= 6 so a full-size thumbnail is
  no longer rendered for tiny or uninitialized (width 0) terminals;
  the caller falls back to the text pill

README.md

@@ -509,6 +509,8 @@ During an interactive session, use these slash commands:
 
 | Shortcut | Description |
 |----------|-------------|
+| `Ctrl+V` | Paste an image from the clipboard — shows an inline low-res thumbnail preview (tmux/zellij-safe) |
+| `Ctrl+U` | Clear all pending image attachments |
 | `Ctrl+X e` | Open `$VISUAL`/`$EDITOR` to compose or edit your prompt |
 | `Ctrl+X s` | Steer — inject a system-level instruction mid-turn |
 | `ESC ESC` | Cancel the current operation (tool call or streaming) |

go.mod

@@ -11,6 +11,7 @@ require (
 	github.com/alecthomas/chroma/v2 v2.26.1
 	github.com/atotto/clipboard v0.1.4
 	github.com/aymanbagabas/go-udiff v0.4.1
+	github.com/charmbracelet/colorprofile v0.4.3
 	github.com/charmbracelet/fang v1.0.0
 	github.com/charmbracelet/log v1.0.0
 	github.com/charmbracelet/openai-go v0.0.0-20260319145158-d0740cc34266
@@ -26,6 +27,7 @@ require (
 	github.com/spf13/cobra v1.10.2
 	github.com/spf13/viper v1.21.0
 	github.com/traefik/yaegi v0.16.1
+	golang.org/x/image v0.41.0
 	golang.org/x/term v0.43.0
 	gopkg.in/yaml.v3 v3.0.1
 )
@@ -55,7 +57,6 @@ require (
 	github.com/catppuccin/go v0.3.0 // indirect
 	github.com/cespare/xxhash/v2 v2.3.0 // indirect
 	github.com/charmbracelet/anthropic-sdk-go v0.0.0-20260223140439-63879b0b8dab // indirect
-	github.com/charmbracelet/colorprofile v0.4.3 // indirect
 	github.com/charmbracelet/harmonica v0.2.0 // indirect
 	github.com/charmbracelet/lipgloss v1.1.1-0.20250404203927-76690c660834 // indirect
 	github.com/charmbracelet/x/cellbuf v0.0.15 // indirect

go.sum

@@ -298,6 +298,8 @@ golang.org/x/crypto v0.52.0 h1:RMs7fP2rXdep0CftQlK8Uf+kibLm7qkCcradZWYz988=
 golang.org/x/crypto v0.52.0/go.mod h1:1QgfPxDqh0T2M/elOJtp9RvuR95kVjir0e6/BvEmGbc=
 golang.org/x/exp v0.0.0-20260528193900-50dc527dd6c7 h1:cHpkPjp4TILjdZxz/O4ykwCpeS+dDqNuDGse4zgQDCk=
 golang.org/x/exp v0.0.0-20260528193900-50dc527dd6c7/go.mod h1:d2fgXJLVs4dYDHUk5lwMIfzRzSrWCfGZb0ZqeLa/Vcw=
+golang.org/x/image v0.41.0 h1:8wS72eGJMJaBxK6okTzd4WaXumUlTVlb753MlsSvTCo=
+golang.org/x/image v0.41.0/go.mod h1:uIc348UZMSvS5Z65CVZ7iDPaNobNFEPeJ4kbqTOszmA=
 golang.org/x/net v0.55.0 h1:bcvxaJn3e1U6InsFWt1JUq1aSjnRxLzT2rtD2KfkDF8=
 golang.org/x/net v0.55.0/go.mod h1:L5U2KuzuOe1lY7Z+aWVIKK6qEeJXnXV9yzGA+WCHJww=
 golang.org/x/oauth2 v0.36.0 h1:peZ/1z27fi9hUOFCAZaHyrpWG5lwe0RJEEEeH0ThlIs=

internal/ui/imagepreview/imagepreview.go

@@ -0,0 +1,233 @@
+// Package imagepreview renders low-resolution, in-terminal thumbnails of
+// images using Unicode upper half-block characters (U+2580, "▀") combined
+// with SGR foreground/background color codes.
+//
+// The technique stacks two vertical pixels into a single character cell: the
+// foreground color paints the top pixel and the background color paints the
+// bottom pixel. This produces pure styled text — no graphics escape sequences
+// — so the output survives terminal multiplexers (tmux, zellij) untouched.
+//
+// The Kitty graphics protocol, Sixel, and iTerm2 inline images are
+// deliberately NOT used: those are graphics escape-sequence protocols that
+// tmux and zellij strip or mangle by default.
+package imagepreview
+
+import (
+	"bytes"
+	"fmt"
+	"image"
+	"image/color"
+	"os"
+	"strings"
+
+	// Register the standard image decoders so image.Decode can handle the
+	// common clipboard / attachment formats.
+	_ "image/gif"
+	_ "image/jpeg"
+	_ "image/png"
+
+	"github.com/charmbracelet/colorprofile"
+	"github.com/charmbracelet/x/ansi"
+	xdraw "golang.org/x/image/draw"
+)
+
+// upperHalfBlock is U+2580 ("▀"). The glyph fills the top half of a cell,
+// letting the foreground color render the top pixel and the cell's background
+// color render the bottom pixel.
+const upperHalfBlock = "▀"
+
+// reset is the SGR reset sequence appended after each rendered row.
+const reset = "\x1b[0m"
+
+// maxImageDimension is the largest width or height, in pixels, that Render will
+// fully decode. Images larger than this in either axis are rejected before the
+// expensive image.Decode call to guard against decompression bombs (small
+// encoded payloads that expand to enormous pixel buffers).
+const maxImageDimension = 20000
+
+// Render returns a half-block ANSI thumbnail of the image, scaled to fit
+// within maxCols x maxRows terminal cells while preserving aspect ratio.
+//
+// Each terminal cell encodes two vertically-stacked pixels, so the effective
+// pixel resolution of the thumbnail is up to maxCols x (maxRows*2).
+//
+// Colors are emitted at the fidelity of the detected terminal color profile:
+// truecolor (24-bit) when available, degrading to 256-color. When the
+// terminal supports neither (no truecolor and no 256-color), Render returns
+// an empty string and a nil error so the caller can fall back to a text
+// indicator. A non-nil error is only returned when the image data cannot be
+// decoded.
+//
+// bg is the color used to composite transparent pixels (typically the
+// terminal background). A nil bg defaults to black.
+func Render(data []byte, mediaType string, maxCols, maxRows int, bg color.Color) (string, error) {
+	profile := colorprofile.Env(os.Environ())
+	return renderWithProfile(data, maxCols, maxRows, bg, profile)
+}
+
+// renderWithProfile is the testable core of Render. It accepts an explicit
+// color profile instead of detecting one from the environment.
+func renderWithProfile(data []byte, maxCols, maxRows int, bg color.Color, profile colorprofile.Profile) (string, error) {
+	// Half-block fidelity needs at least 256-color support. Anything less
+	// degrades to the caller's text fallback.
+	if profile < colorprofile.ANSI256 {
+		return "", nil
+	}
+	if maxCols < 1 || maxRows < 1 {
+		return "", nil
+	}
+	if bg == nil {
+		bg = color.Black
+	}
+
+	// Guard against decompression bombs: inspect the header dimensions before
+	// fully decoding, so a small malicious payload cannot expand into an
+	// enormous pixel buffer.
+	cfg, _, err := image.DecodeConfig(bytes.NewReader(data))
+	if err != nil {
+		return "", fmt.Errorf("decode image config: %w", err)
+	}
+	if cfg.Width > maxImageDimension || cfg.Height > maxImageDimension {
+		return "", fmt.Errorf("decode image: dimensions %dx%d exceed limit %d", cfg.Width, cfg.Height, maxImageDimension)
+	}
+
+	img, _, err := image.Decode(bytes.NewReader(data))
+	if err != nil {
+		return "", fmt.Errorf("decode image: %w", err)
+	}
+
+	// Target pixel dimensions: one pixel per column horizontally and two
+	// pixels per row vertically (the half-block trick).
+	cols, rows := fitDimensions(img.Bounds().Dx(), img.Bounds().Dy(), maxCols, maxRows)
+	if cols < 1 || rows < 1 {
+		return "", nil
+	}
+	pxW, pxH := cols, rows*2
+
+	scaled := image.NewRGBA(image.Rect(0, 0, pxW, pxH))
+	xdraw.CatmullRom.Scale(scaled, scaled.Bounds(), img, img.Bounds(), xdraw.Over, nil)
+
+	var b strings.Builder
+	for y := 0; y < pxH; y += 2 {
+		for x := range pxW {
+			top := composite(scaled.At(x, y), bg)
+			bottom := composite(scaled.At(x, y+1), bg)
+			b.WriteString(sgr(top, bottom, profile))
+			b.WriteString(upperHalfBlock)
+		}
+		b.WriteString(reset)
+		if y+2 < pxH {
+			b.WriteByte('\n')
+		}
+	}
+	return b.String(), nil
+}
+
+// fitDimensions returns the largest cell dimensions (cols, rows) that fit a
+// srcW x srcH image inside a maxCols x maxRows box while preserving aspect
+// ratio. Because each cell stacks two vertical pixels, a terminal cell is
+// treated as roughly twice as tall as it is wide, which keeps the thumbnail's
+// aspect ratio visually correct.
+func fitDimensions(srcW, srcH, maxCols, maxRows int) (cols, rows int) {
+	if srcW <= 0 || srcH <= 0 {
+		return 0, 0
+	}
+	// Work in pixel space: the box is maxCols wide and maxRows*2 tall.
+	maxPxW := float64(maxCols)
+	maxPxH := float64(maxRows * 2)
+	scale := maxPxW / float64(srcW)
+	if h := maxPxH / float64(srcH); h < scale {
+		scale = h
+	}
+	if scale > 1 {
+		scale = 1 // never upscale; keep the low-res look
+	}
+	pxW := int(float64(srcW) * scale)
+	pxH := int(float64(srcH) * scale)
+	if pxW < 1 {
+		pxW = 1
+	}
+	if pxH < 2 {
+		pxH = 2
+	}
+	// Convert back to cells; round the row count up to an even pixel height.
+	cols = pxW
+	rows = (pxH + 1) / 2
+	if cols > maxCols {
+		cols = maxCols
+	}
+	if rows > maxRows {
+		rows = maxRows
+	}
+	return cols, rows
+}
+
+// composite blends a (possibly translucent) pixel over the background color,
+// returning an opaque color. Fully opaque pixels are returned unchanged.
+func composite(c, bg color.Color) color.Color {
+	r, g, b, a := c.RGBA()
+	if a == 0xffff {
+		return c
+	}
+	br, bgc, bb, _ := bg.RGBA()
+	// Standard "over" alpha compositing in 16-bit space.
+	inv := 0xffff - a
+	out := color.RGBA64{
+		R: uint16(r + br*inv/0xffff),
+		G: uint16(g + bgc*inv/0xffff),
+		B: uint16(b + bb*inv/0xffff),
+		A: 0xffff,
+	}
+	return out
+}
+
+// sgr builds the SGR escape sequence that sets the foreground (top pixel) and
+// background (bottom pixel) colors at the fidelity of the given profile.
+func sgr(fg, bg color.Color, profile colorprofile.Profile) string {
+	if profile >= colorprofile.TrueColor {
+		fr, fgc, fb := rgb8(fg)
+		br, bgc, bb := rgb8(bg)
+		return fmt.Sprintf("\x1b[38;2;%d;%d;%d;48;2;%d;%d;%dm", fr, fgc, fb, br, bgc, bb)
+	}
+	return fmt.Sprintf("\x1b[38;5;%d;48;5;%dm", index256(fg, profile), index256(bg, profile))
+}
+
+// rgb8 reduces a color to 8-bit RGB components.
+func rgb8(c color.Color) (r, g, b uint8) {
+	cr, cg, cb, _ := c.RGBA()
+	return uint8(cr >> 8), uint8(cg >> 8), uint8(cb >> 8)
+}
+
+// index256 converts a color to its nearest 256-color palette index using the
+// supplied profile.
+func index256(c color.Color, profile colorprofile.Profile) uint8 {
+	cc := profile.Convert(c)
+	if idx, ok := cc.(ansi.IndexedColor); ok {
+		return uint8(idx)
+	}
+	if idx, ok := cc.(ansi.BasicColor); ok {
+		return uint8(idx)
+	}
+	// Fallback: derive an index directly if conversion produced an
+	// unexpected type.
+	r, g, b := rgb8(c)
+	return ansi256FromRGB(r, g, b)
+}
+
+// ansi256FromRGB maps an 8-bit RGB color to the xterm 256-color cube. It is a
+// best-effort fallback used only when profile.Convert does not yield a known
+// indexed color type.
+func ansi256FromRGB(r, g, b uint8) uint8 {
+	q := func(v uint8) int {
+		switch {
+		case v < 48:
+			return 0
+		case v < 115:
+			return 1
+		default:
+			return int((v - 35) / 40)
+		}
+	}
+	ri, gi, bi := q(r), q(g), q(b)
+	return uint8(16 + 36*ri + 6*gi + bi)
+}

internal/ui/imagepreview/imagepreview_test.go

@@ -0,0 +1,193 @@
+package imagepreview
+
+import (
+	"bytes"
+	"image"
+	"image/color"
+	"image/png"
+	"strings"
+	"testing"
+
+	"github.com/charmbracelet/colorprofile"
+)
+
+// makePNG builds a simple w x h PNG filled with the given color and returns
+// its encoded bytes.
+func makePNG(t *testing.T, w, h int, c color.Color) []byte {
+	t.Helper()
+	img := image.NewRGBA(image.Rect(0, 0, w, h))
+	for y := range h {
+		for x := range w {
+			img.Set(x, y, c)
+		}
+	}
+	var buf bytes.Buffer
+	if err := png.Encode(&buf, img); err != nil {
+		t.Fatalf("encode png: %v", err)
+	}
+	return buf.Bytes()
+}
+
+func TestRenderTrueColor(t *testing.T) {
+	data := makePNG(t, 20, 20, color.RGBA{R: 255, A: 255})
+	out, err := renderWithProfile(data, 10, 5, color.Black, colorprofile.TrueColor)
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if out == "" {
+		t.Fatal("expected non-empty thumbnail for truecolor profile")
+	}
+	if !strings.Contains(out, upperHalfBlock) {
+		t.Error("output should contain upper half block glyphs")
+	}
+	if !strings.Contains(out, "\x1b[38;2;") || !strings.Contains(out, "48;2;") {
+		t.Errorf("expected truecolor SGR sequences, got %q", out)
+	}
+	// Red fill should appear as 255;0;0 somewhere.
+	if !strings.Contains(out, "255;0;0") {
+		t.Errorf("expected red color in output, got %q", out)
+	}
+}
+
+func TestRenderANSI256(t *testing.T) {
+	data := makePNG(t, 20, 20, color.RGBA{G: 255, A: 255})
+	out, err := renderWithProfile(data, 8, 4, color.Black, colorprofile.ANSI256)
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if out == "" {
+		t.Fatal("expected non-empty thumbnail for ANSI256 profile")
+	}
+	if !strings.Contains(out, "\x1b[38;5;") || !strings.Contains(out, "48;5;") {
+		t.Errorf("expected 256-color SGR sequences, got %q", out)
+	}
+	if strings.Contains(out, "38;2;") {
+		t.Errorf("ANSI256 output should not contain truecolor sequences, got %q", out)
+	}
+}
+
+func TestRenderDegradesBelowANSI256(t *testing.T) {
+	data := makePNG(t, 20, 20, color.RGBA{B: 255, A: 255})
+	for _, p := range []colorprofile.Profile{colorprofile.ANSI, colorprofile.ASCII, colorprofile.NoTTY} {
+		out, err := renderWithProfile(data, 10, 5, color.Black, p)
+		if err != nil {
+			t.Fatalf("profile %v: unexpected error: %v", p, err)
+		}
+		if out != "" {
+			t.Errorf("profile %v: expected empty fallback, got %q", p, out)
+		}
+	}
+}
+
+func TestRenderInvalidImage(t *testing.T) {
+	out, err := renderWithProfile([]byte("not an image"), 10, 5, color.Black, colorprofile.TrueColor)
+	if err == nil {
+		t.Fatal("expected error for invalid image data")
+	}
+	if out != "" {
+		t.Errorf("expected empty output on decode error, got %q", out)
+	}
+}
+
+func TestRenderRejectsOversizedImage(t *testing.T) {
+	// A header advertising dimensions beyond maxImageDimension must be
+	// rejected before full decode (decompression-bomb guard). image.RGBA
+	// allocation is avoided by only checking the config path here.
+	w := maxImageDimension + 1
+	data := makePNG(t, w, 1, color.White)
+	out, err := renderWithProfile(data, 10, 5, color.Black, colorprofile.TrueColor)
+	if err == nil {
+		t.Fatal("expected error for oversized image dimensions")
+	}
+	if out != "" {
+		t.Errorf("expected empty output for oversized image, got %q", out)
+	}
+}
+
+func TestRenderZeroBox(t *testing.T) {
+	data := makePNG(t, 20, 20, color.White)
+	out, err := renderWithProfile(data, 0, 0, color.Black, colorprofile.TrueColor)
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if out != "" {
+		t.Errorf("expected empty output for zero-sized box, got %q", out)
+	}
+}
+
+func TestRenderNilBackgroundDefaults(t *testing.T) {
+	data := makePNG(t, 10, 10, color.RGBA{R: 10, G: 20, B: 30, A: 255})
+	out, err := renderWithProfile(data, 6, 3, nil, colorprofile.TrueColor)
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if out == "" {
+		t.Fatal("expected output with nil background (defaults to black)")
+	}
+}
+
+func TestRowCountWithinBounds(t *testing.T) {
+	// A tall image should be capped at maxRows cells.
+	data := makePNG(t, 10, 100, color.White)
+	out, err := renderWithProfile(data, 20, 6, color.Black, colorprofile.TrueColor)
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	rows := strings.Count(out, "\n") + 1
+	if rows > 6 {
+		t.Errorf("expected at most 6 rows, got %d", rows)
+	}
+}
+
+func TestColumnCountWithinBounds(t *testing.T) {
+	// A wide image should be capped at maxCols cells per row.
+	data := makePNG(t, 100, 10, color.White)
+	out, err := renderWithProfile(data, 8, 20, color.Black, colorprofile.TrueColor)
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	firstRow := strings.SplitN(out, "\n", 2)[0]
+	cols := strings.Count(firstRow, upperHalfBlock)
+	if cols > 8 {
+		t.Errorf("expected at most 8 columns, got %d", cols)
+	}
+	if cols == 0 {
+		t.Error("expected at least one column")
+	}
+}
+
+func TestFitDimensionsPreservesAspect(t *testing.T) {
+	// 2:1 (wide) image into a 40x20 box. Pixel box is 40x40; width-bound.
+	cols, rows := fitDimensions(200, 100, 40, 20)
+	if cols != 40 {
+		t.Errorf("expected 40 cols, got %d", cols)
+	}
+	// pxH = 100 * (40/200) = 20 → 10 rows.
+	if rows != 10 {
+		t.Errorf("expected 10 rows, got %d", rows)
+	}
+}
+
+func TestFitDimensionsNeverUpscales(t *testing.T) {
+	cols, rows := fitDimensions(4, 4, 40, 20)
+	if cols != 4 || rows != 2 {
+		t.Errorf("expected 4x2 (no upscale), got %dx%d", cols, rows)
+	}
+}
+
+func TestCompositeOpaquePassthrough(t *testing.T) {
+	c := color.RGBA{R: 1, G: 2, B: 3, A: 255}
+	got := composite(c, color.White)
+	if got != color.Color(c) {
+		t.Errorf("opaque color should pass through unchanged, got %v", got)
+	}
+}
+
+func TestCompositeTransparentOverBackground(t *testing.T) {
+	// Fully transparent pixel over red background should yield red.
+	got := composite(color.RGBA{}, color.RGBA{R: 255, A: 255})
+	r, g, b, a := got.RGBA()
+	if r>>8 != 255 || g>>8 != 0 || b>>8 != 0 || a != 0xffff {
+		t.Errorf("expected opaque red, got r=%d g=%d b=%d a=%d", r>>8, g>>8, b>>8, a)
+	}
+}

internal/ui/input.go

@@ -2,6 +2,7 @@ package ui
 
 import (
 	"fmt"
+	"image/color"
 	"sort"
 	"strings"
 
@@ -13,6 +14,7 @@ import (
 	"github.com/mark3labs/kit/internal/clipboard"
 	"github.com/mark3labs/kit/internal/ui/commands"
 	"github.com/mark3labs/kit/internal/ui/core"
+	"github.com/mark3labs/kit/internal/ui/imagepreview"
 	"github.com/mark3labs/kit/internal/ui/style"
 )
 
@@ -80,6 +82,23 @@ type InputComponent struct {
 	// Images are added via Ctrl+V and cleared on submit or Ctrl+U.
 	pendingImages []core.ImageAttachment
 
+	// imageThumbs caches the rendered half-block thumbnail for each entry in
+	// pendingImages (1:1 index correspondence). Thumbnails are rendered
+	// asynchronously off the Bubble Tea event loop (decode + resample is too
+	// slow to run inside Update), so an entry starts as the empty string
+	// placeholder and is filled in when the matching thumbnailReadyMsg
+	// arrives. An entry stays empty when the terminal cannot display a
+	// half-block preview, in which case the text pill is shown alone.
+	// See internal/ui/imagepreview.
+	imageThumbs []string
+
+	// imageGen is a monotonic generation counter incremented whenever the
+	// pending image set is cleared. Async thumbnail results carry the
+	// generation they were enqueued under and are discarded if it no longer
+	// matches, preventing a stale thumbnail from landing on the wrong slot
+	// after a clear + re-attach.
+	imageGen int
+
 	// history stores previously submitted prompts (most recent last).
 	// Limited to maxHistory entries; duplicates of the previous entry are
 	// skipped. Empty strings are never stored.
@@ -105,6 +124,16 @@ type clipboardImageMsg struct {
 	err   error
 }
 
+// thumbnailReadyMsg carries the result of an async thumbnail render back to
+// the Update loop. gen and index identify the pendingImages slot the
+// thumbnail belongs to; the result is dropped if the generation no longer
+// matches (the pending set was cleared) or the index is out of range.
+type thumbnailReadyMsg struct {
+	gen   int
+	index int
+	thumb string
+}
+
 // NewInputComponent creates a new InputComponent with the given width and
 // optional AppController. If appCtrl is nil the component still works but
 // /clear and /clear-queue are no-ops.
@@ -193,7 +222,23 @@ func (s *InputComponent) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
 			return s, nil
 		}
 		if msg.image != nil {
-			s.pendingImages = append(s.pendingImages, *msg.image)
+			img := *msg.image
+			index := len(s.pendingImages)
+			s.pendingImages = append(s.pendingImages, img)
+			// Reserve a placeholder; the async render fills it in via
+			// thumbnailReadyMsg so Update never blocks on decode/resample.
+			s.imageThumbs = append(s.imageThumbs, "")
+			cols := s.thumbCols()
+			if cols < 1 {
+				return s, nil
+			}
+			return s, renderThumbnailCmd(img, cols, thumbMaxRows, style.GetTheme().Background, s.imageGen, index)
+		}
+		return s, nil
+
+	case thumbnailReadyMsg:
+		if msg.gen == s.imageGen && msg.index >= 0 && msg.index < len(s.imageThumbs) {
+			s.imageThumbs[msg.index] = msg.thumb
 		}
 		return s, nil
 
@@ -250,6 +295,8 @@ func (s *InputComponent) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
 				// Clear all pending image attachments.
 				if len(s.pendingImages) > 0 {
 					s.pendingImages = nil
+					s.imageThumbs = nil
+					s.imageGen++
 					return s, nil
 				}
 			}
@@ -486,6 +533,8 @@ func (s *InputComponent) handleSubmit(value string) tea.Cmd {
 	// images and clear them.
 	images := s.pendingImages
 	s.pendingImages = nil
+	s.imageThumbs = nil
+	s.imageGen++
 	return func() tea.Msg {
 		return core.SubmitMsg{Text: trimmed, Images: images}
 	}
@@ -519,6 +568,42 @@ func (s *InputComponent) resetHistoryBrowsing() {
 	s.savedInput = ""
 }
 
+// thumbMaxCols and thumbMaxRows cap the size, in terminal cells, of pending
+// image previews. Kept small for the low-res look and to keep scrollback
+// light.
+const (
+	thumbMaxCols = 40
+	thumbMaxRows = 12
+)
+
+// thumbCols returns the thumbnail width in terminal cells given the current
+// input width, or 0 when there is no room to render a preview.
+func (s *InputComponent) thumbCols() int {
+	if s.width <= 6 {
+		return 0
+	}
+	cols := min(thumbMaxCols, s.width-6)
+	if cols < 1 {
+		return 0
+	}
+	return cols
+}
+
+// renderThumbnailCmd returns a tea.Cmd that renders a half-block ANSI preview
+// off the Bubble Tea event loop. The decode + resample work runs in the Cmd
+// goroutine, and the result is delivered as a thumbnailReadyMsg tagged with
+// the generation and slot index it was enqueued for. An empty thumbnail
+// (terminal unsupported or render error) leaves the text pill in place.
+func renderThumbnailCmd(img core.ImageAttachment, cols, rows int, bg color.Color, gen, index int) tea.Cmd {
+	return func() tea.Msg {
+		thumb, err := imagepreview.Render(img.Data, img.MediaType, cols, rows, bg)
+		if err != nil {
+			thumb = ""
+		}
+		return thumbnailReadyMsg{gen: gen, index: index, thumb: thumb}
+	}
+}
+
 // View implements tea.Model. Renders the textarea, autocomplete popup
 // (if visible), and help text.
 func (s *InputComponent) View() tea.View {
@@ -544,7 +629,9 @@ func (s *InputComponent) View() tea.View {
 	// Popup is now rendered as a centered overlay in AppModel.View()
 	// instead of inline here to prevent bottom overflow
 
-	// Show image attachment indicator when images are pending.
+	// Show image attachment previews when images are pending. A cached
+	// half-block thumbnail is rendered when the terminal supports it;
+	// otherwise the text pill alone is shown.
 	if len(s.pendingImages) > 0 {
 		imgStyle := lipgloss.NewStyle().
 			Foreground(theme.Secondary).
@@ -553,6 +640,14 @@ func (s *InputComponent) View() tea.View {
 		label := fmt.Sprintf("[%d image(s) attached] ctrl+u to clear", len(s.pendingImages))
 		view.WriteString("\n")
 		view.WriteString(imgStyle.Render(label))
+
+		thumbStyle := lipgloss.NewStyle().PaddingLeft(3)
+		for i := range s.pendingImages {
+			if i < len(s.imageThumbs) && s.imageThumbs[i] != "" {
+				view.WriteString("\n")
+				view.WriteString(thumbStyle.Render(s.imageThumbs[i]))
+			}
+		}
 	}
 
 	if !s.hideHint {
@@ -844,6 +939,8 @@ func readClipboardImageCmd() tea.Cmd {
 func (s *InputComponent) ClearPendingImages() []core.ImageAttachment {
 	images := s.pendingImages
 	s.pendingImages = nil
+	s.imageThumbs = nil
+	s.imageGen++
 	return images
 }
 

www/pages/cli/commands.md

@@ -110,6 +110,23 @@ Press **Ctrl+X s** during streaming to inject a system-level instruction mid-tur
 
 Example: While the model is writing code, press Ctrl+X s and type "Use async/await instead" to change the implementation approach.
 
+### Image attachments
+
+Attach images to your next prompt straight from the clipboard:
+
+- Copy an image (e.g. a screenshot) to the system clipboard, then press **Ctrl+V** in the input to attach it.
+- Press **Ctrl+U** to clear all pending image attachments.
+- Attachments are sent alongside your text when you submit, and cleared afterward.
+
+When a terminal supports color, Kit renders a small low-resolution **thumbnail preview** of each pending image directly in the input, below the `[N image(s) attached]` indicator, so you can confirm the right image was attached before sending.
+
+The preview is drawn with Unicode half-block characters and ordinary terminal colors — not a graphics protocol — so it renders correctly inside terminal multiplexers like **tmux** and **zellij**. Thumbnails are capped to a small cell box for a glanceable, low-res look.
+
+- Best fidelity needs a **truecolor** terminal (`COLORTERM=truecolor`); Kit degrades to 256-color where truecolor is unavailable.
+- On terminals with neither, the preview is skipped and the `[N image(s) attached]` text indicator is shown alone.
+
+You can also attach image files by referencing them with `@path/to/image.png` — binary files are auto-detected by MIME type. See [Quick Start](/quick-start) for the `@` attachment syntax.
+
 ## Prompt templates
 
 ### Creating templates