diff --git a/apps/api/src/lib/file-validation.ts b/apps/api/src/lib/file-validation.ts
index e86ca02e..18f94718 100644
--- a/apps/api/src/lib/file-validation.ts
+++ b/apps/api/src/lib/file-validation.ts
@@ -154,11 +154,13 @@ function detectMagicBytes(buffer: Buffer): string | null {
         const brand = buffer.slice(8, 12).toString("ascii");
         if (brand !== "avif" && brand !== "avis") continue;
       }
-      // For ftyp, verify HEIF/HEIC brand at bytes 8-11
+      // For ftyp, verify HEIF/HEIC brand at bytes 8-11.
+      // Covers HEVC still (heic/heix), HEVC sequence (hevc/hevx),
+      // generic HEIF still/sequence (mif1/msf1), and multi-layer profiles.
       if (entry.format === "heif") {
         if (buffer.length < 12) continue;
         const brand = buffer.slice(8, 12).toString("ascii");
-        if (brand !== "heic" && brand !== "heix" && brand !== "mif1") continue;
+        if (!["heic", "heix", "mif1", "msf1", "hevc", "hevx"].includes(brand)) continue;
       }
       return entry.format;
     }
diff --git a/apps/api/src/lib/heic-converter.ts b/apps/api/src/lib/heic-converter.ts
index b7f0d11d..7306dc88 100644
--- a/apps/api/src/lib/heic-converter.ts
+++ b/apps/api/src/lib/heic-converter.ts
@@ -8,9 +8,8 @@ import { promisify } from "node:util";
 const execFileAsync = promisify(execFile);
 
 /**
- * Find the HEIF decode command. macOS (Homebrew) provides `heif-dec`,
- * while Linux packages provide `heif-convert`. Both accept the same
- * `<input> <output>` argument syntax.
+ * Find the HEIF decode command. Both heif-convert and heif-dec accept
+ * `<input> <output>` positional arguments.
  */
 let cachedDecodeCmd: string | null = null;
 
@@ -32,20 +31,32 @@ async function findDecodeCmd(): Promise<string> {
  * Decode a HEIC/HEIF buffer to PNG using the system HEIF decoder CLI.
  * This is needed because Sharp's bundled libheif does not include the
  * HEVC decoder required for true HEIC files (iPhone photos).
+ *
+ * Multi-image HEIF files (common from iPhones) cause heif-convert/heif-dec
+ * to add numeric suffixes (-1, -2, ...) to the output filename. We try the
+ * exact path first, then fall back to the -1 suffixed path.
  */
 export async function decodeHeic(buffer: Buffer): Promise<Buffer> {
   const cmd = await findDecodeCmd();
   const id = randomUUID();
   const inputPath = join(tmpdir(), `heic-in-${id}.heic`);
   const outputPath = join(tmpdir(), `heic-out-${id}.png`);
+  const suffixedPath = outputPath.replace(/\.png$/, "-1.png");
 
   try {
     await writeFile(inputPath, buffer);
     await execFileAsync(cmd, [inputPath, outputPath], { timeout: 30_000 });
-    return await readFile(outputPath);
+
+    // Single-image HEIF: exact filename. Multi-image: -1 suffix on first image.
+    try {
+      return await readFile(outputPath);
+    } catch {
+      return await readFile(suffixedPath);
+    }
   } finally {
     await rm(inputPath, { force: true }).catch(() => {});
     await rm(outputPath, { force: true }).catch(() => {});
+    await rm(suffixedPath, { force: true }).catch(() => {});
   }
 }
 
diff --git a/apps/api/src/routes/files.ts b/apps/api/src/routes/files.ts
index 13c81916..cfd9645e 100644
--- a/apps/api/src/routes/files.ts
+++ b/apps/api/src/routes/files.ts
@@ -2,8 +2,10 @@ import { randomUUID } from "node:crypto";
 import { readFile, stat, writeFile } from "node:fs/promises";
 import { extname, join } from "node:path";
 import type { FastifyInstance, FastifyReply, FastifyRequest } from "fastify";
+import sharp from "sharp";
 import { validateImageBuffer } from "../lib/file-validation.js";
 import { sanitizeFilename } from "../lib/filename.js";
+import { decodeHeic } from "../lib/heic-converter.js";
 import { createWorkspace, getWorkspacePath } from "../lib/workspace.js";
 
 /**
@@ -120,6 +122,36 @@ export async function fileRoutes(app: FastifyInstance): Promise<void> {
         .send(buffer);
     },
   );
+
+  // ── POST /api/v1/preview ──────────────────────────────────────
+  // Returns a WebP preview for formats browsers can't display (HEIC/HEIF).
+  app.post("/api/v1/preview", async (request: FastifyRequest, reply: FastifyReply) => {
+    const data = await request.file();
+    if (!data) {
+      return reply.status(400).send({ error: "No file provided" });
+    }
+    let buffer = await data.toBuffer();
+
+    const validation = await validateImageBuffer(buffer);
+    if (!validation.valid) {
+      return reply.status(400).send({ error: validation.reason });
+    }
+
+    // Decode HEIC/HEIF via system decoder
+    if (validation.format === "heif") {
+      try {
+        buffer = await decodeHeic(buffer);
+      } catch {
+        return reply.status(422).send({ error: "Failed to decode HEIC/HEIF file" });
+      }
+    }
+
+    const webp = await sharp(buffer)
+      .resize(1200, 1200, { fit: "inside", withoutEnlargement: true })
+      .webp({ quality: 80 })
+      .toBuffer();
+    return reply.header("Content-Type", "image/webp").send(webp);
+  });
 }
 
 function getContentType(ext: string): string {
diff --git a/apps/api/src/routes/tool-factory.ts b/apps/api/src/routes/tool-factory.ts
index f17e3e32..af7e9750 100644
--- a/apps/api/src/routes/tool-factory.ts
+++ b/apps/api/src/routes/tool-factory.ts
@@ -149,11 +149,14 @@ export function createToolRoute<T>(app: FastifyInstance, config: ToolRouteConfig
       }
 
       // Decode HEIC/HEIF input via system heif-dec (Sharp's bundled libheif
-      // lacks the HEVC decoder needed for iPhone photos)
+      // lacks the HEVC decoder needed for iPhone photos).
+      // The decoded buffer is PNG, so update the filename extension to match.
       const isHeif = validation.format === "heif";
       if (isHeif) {
         try {
           fileBuffer = await decodeHeic(fileBuffer);
+          const ext = filename.match(/\.[^.]+$/)?.[0];
+          if (ext) filename = filename.slice(0, -ext.length) + ".png";
         } catch (err) {
           return reply.status(422).send({
             error: "Failed to decode HEIC file. Ensure libheif-examples is installed.",
@@ -240,6 +243,34 @@ export function createToolRoute<T>(app: FastifyInstance, config: ToolRouteConfig
         const outputPath = join(workspacePath, "output", result.filename);
         await writeFile(outputPath, result.buffer);
 
+        // Generate a browser-previewable WebP thumbnail for formats that
+        // browsers cannot render in <img> tags (HEIC, TIFF, etc.)
+        const BROWSER_PREVIEWABLE = new Set([
+          "image/jpeg",
+          "image/png",
+          "image/gif",
+          "image/webp",
+          "image/svg+xml",
+          "image/bmp",
+          "image/avif",
+        ]);
+        let previewUrl: string | undefined;
+        if (!BROWSER_PREVIEWABLE.has(result.contentType)) {
+          try {
+            let previewInput = result.buffer;
+            // Sharp can't decode HEIC - use system decoder first
+            if (result.contentType === "image/heic" || result.contentType === "image/heif") {
+              previewInput = await decodeHeic(result.buffer);
+            }
+            const previewBuffer = await sharp(previewInput).webp({ quality: 80 }).toBuffer();
+            const previewPath = join(workspacePath, "output", "preview.webp");
+            await writeFile(previewPath, previewBuffer);
+            previewUrl = `/api/v1/download/${jobId}/preview.webp`;
+          } catch {
+            // Non-fatal - frontend will show the success card fallback
+          }
+        }
+
         // Also save the original input for reference/download
         const inputPath = join(workspacePath, "input", filename);
         await writeFile(inputPath, fileBuffer);
@@ -296,6 +327,7 @@ export function createToolRoute<T>(app: FastifyInstance, config: ToolRouteConfig
         return reply.send({
           jobId,
           downloadUrl: `/api/v1/download/${jobId}/${encodeURIComponent(result.filename)}`,
+          previewUrl,
           originalSize: fileBuffer.length,
           processedSize: result.buffer.length,
           savedFileId,
diff --git a/apps/api/src/routes/tools/content-aware-resize.ts b/apps/api/src/routes/tools/content-aware-resize.ts
index 4fd240ad..bd7fd2b7 100644
--- a/apps/api/src/routes/tools/content-aware-resize.ts
+++ b/apps/api/src/routes/tools/content-aware-resize.ts
@@ -6,6 +6,7 @@ import type { FastifyInstance, FastifyReply, FastifyRequest } from "fastify";
 import { z } from "zod";
 import { autoOrient } from "../../lib/auto-orient.js";
 import { validateImageBuffer } from "../../lib/file-validation.js";
+import { decodeHeic } from "../../lib/heic-converter.js";
 import { createWorkspace } from "../../lib/workspace.js";
 import { registerToolProcessFn } from "../tool-factory.js";
 
@@ -59,6 +60,20 @@ export function registerContentAwareResize(app: FastifyInstance) {
         return reply.status(400).send({ error: `Invalid image: ${validation.reason}` });
       }
 
+      // Decode HEIC/HEIF input (caire can't read HEIF containers)
+      if (validation.format === "heif") {
+        try {
+          fileBuffer = await decodeHeic(fileBuffer);
+          const ext = filename.match(/\.[^.]+$/)?.[0];
+          if (ext) filename = filename.slice(0, -ext.length) + ".png";
+        } catch (err) {
+          return reply.status(422).send({
+            error: "Failed to decode HEIC/HEIF file",
+            details: err instanceof Error ? err.message : String(err),
+          });
+        }
+      }
+
       // Validate settings
       let settings: Settings;
       try {
@@ -143,7 +158,13 @@ export function registerContentAwareResize(app: FastifyInstance) {
     settingsSchema,
     process: async (inputBuffer, settings, filename) => {
       const s = settings as Settings;
-      const orientedBuffer = await autoOrient(inputBuffer);
+      // Decode HEIC/HEIF for pipeline/batch mode
+      const ext = filename.split(".").pop()?.toLowerCase() ?? "";
+      let buf = inputBuffer;
+      if (["heic", "heif", "hif"].includes(ext)) {
+        buf = await decodeHeic(buf);
+      }
+      const orientedBuffer = await autoOrient(buf);
       const jobId = randomUUID();
       const workspacePath = await createWorkspace(jobId);
       const result = await seamCarve(orientedBuffer, join(workspacePath, "output"), {
diff --git a/apps/api/src/routes/tools/convert.ts b/apps/api/src/routes/tools/convert.ts
index 98825ad5..38af3839 100644
--- a/apps/api/src/routes/tools/convert.ts
+++ b/apps/api/src/routes/tools/convert.ts
@@ -15,10 +15,11 @@ const FORMAT_CONTENT_TYPES: Record<string, string> = {
   tiff: "image/tiff",
   gif: "image/gif",
   heic: "image/heic",
+  heif: "image/heif",
 };
 
 const settingsSchema = z.object({
-  format: z.enum(["jpg", "png", "webp", "avif", "tiff", "gif", "heic"]),
+  format: z.enum(["jpg", "png", "webp", "avif", "tiff", "gif", "heic", "heif"]),
   quality: z.number().min(1).max(100).optional(),
 });
 
@@ -31,7 +32,7 @@ export function registerConvert(app: FastifyInstance) {
       const image = sharp(inputBuffer, sharpOpts);
 
       let buffer: Buffer;
-      if (settings.format === "heic") {
+      if (settings.format === "heic" || settings.format === "heif") {
         // Sharp cannot encode HEVC. Convert to PNG first, then use heif-enc.
         const pngBuffer = await image.png().toBuffer();
         buffer = await encodeHeic(pngBuffer, settings.quality);
diff --git a/apps/web/src/components/common/dropzone.tsx b/apps/web/src/components/common/dropzone.tsx
index f04d7217..250b16dd 100644
--- a/apps/web/src/components/common/dropzone.tsx
+++ b/apps/web/src/components/common/dropzone.tsx
@@ -10,7 +10,15 @@ interface DropzoneProps {
   currentFiles?: File[];
 }
 
+// Browsers may not map .heic/.heif to image/* in file pickers.
+// Append explicit extensions so they are selectable.
+function expandAccept(accept?: string): string | undefined {
+  if (!accept?.includes("image/*")) return accept;
+  return `${accept},.heic,.heif,.hif`;
+}
+
 export function Dropzone({ onFiles, accept, multiple = true, currentFiles = [] }: DropzoneProps) {
+  const resolvedAccept = expandAccept(accept);
   const [isDragging, setIsDragging] = useState(false);
 
   const handleDrag = useCallback((e: DragEvent) => {
@@ -35,7 +43,7 @@ export function Dropzone({ onFiles, accept, multiple = true, currentFiles = [] }
     const input = document.createElement("input");
     input.type = "file";
     input.multiple = multiple;
-    if (accept) input.accept = accept;
+    if (resolvedAccept) input.accept = resolvedAccept;
     input.onchange = (e) => {
       const files = Array.from((e.target as HTMLInputElement).files || []);
       if (files.length > 0) onFiles?.(files);
diff --git a/apps/web/src/components/common/multi-image-viewer.tsx b/apps/web/src/components/common/multi-image-viewer.tsx
index fd59753e..30fdbcc7 100644
--- a/apps/web/src/components/common/multi-image-viewer.tsx
+++ b/apps/web/src/components/common/multi-image-viewer.tsx
@@ -1,10 +1,27 @@
-import { ChevronLeft, ChevronRight } from "lucide-react";
+import { CheckCircle2, ChevronLeft, ChevronRight, Loader2 } from "lucide-react";
 import { useCallback } from "react";
 import { BeforeAfterSlider } from "@/components/common/before-after-slider";
 import { ImageViewer } from "@/components/common/image-viewer";
 import { ThumbnailStrip } from "@/components/common/thumbnail-strip";
 import { useFileStore } from "@/stores/file-store";
 
+const BROWSER_PREVIEWABLE_EXTS = new Set([
+  "jpg",
+  "jpeg",
+  "png",
+  "gif",
+  "webp",
+  "svg",
+  "bmp",
+  "ico",
+  "avif",
+]);
+
+function canBrowserPreview(url: string): boolean {
+  const ext = decodeURIComponent(url).split(".").pop()?.toLowerCase() ?? "";
+  return BROWSER_PREVIEWABLE_EXTS.has(ext);
+}
+
 export function MultiImageViewer() {
   const { entries, selectedIndex, setSelectedIndex, navigateNext, navigatePrev } = useFileStore();
 
@@ -29,6 +46,13 @@ export function MultiImageViewer() {
   const hasNext = selectedIndex < entries.length - 1;
 
   const hasProcessed = !!currentEntry.processedUrl;
+  const isPreviewable = hasProcessed && canBrowserPreview(currentEntry.processedUrl!);
+  const displayUrl = currentEntry.processedPreviewUrl ?? currentEntry.processedUrl;
+
+  const processedFilename = currentEntry.processedUrl
+    ? decodeURIComponent(currentEntry.processedUrl.split("/").pop() ?? "processed")
+    : "processed";
+  const processedExt = processedFilename.split(".").pop()?.toUpperCase() || "FILE";
 
   return (
     <section
@@ -49,13 +73,28 @@ export function MultiImageViewer() {
           </button>
         )}
         <div className="w-full h-full min-h-0">
-          {hasProcessed ? (
+          {hasProcessed && !isPreviewable && !currentEntry.processedPreviewUrl ? (
+            <div className="flex flex-col items-center justify-center h-full gap-3 text-center p-8">
+              <div className="w-12 h-12 rounded-full bg-green-100 dark:bg-green-900/30 flex items-center justify-center">
+                <CheckCircle2 className="h-6 w-6 text-green-600 dark:text-green-400" />
+              </div>
+              <p className="text-sm font-medium">{processedFilename}</p>
+              <p className="text-xs text-muted-foreground">
+                {processedExt} files cannot be previewed in the browser.
+              </p>
+            </div>
+          ) : hasProcessed ? (
             <BeforeAfterSlider
               beforeSrc={currentEntry.blobUrl}
-              afterSrc={currentEntry.processedUrl ?? ""}
+              afterSrc={displayUrl ?? ""}
               beforeSize={currentEntry.originalSize}
               afterSize={currentEntry.processedSize ?? undefined}
             />
+          ) : currentEntry.previewLoading ? (
+            <div className="flex flex-col items-center justify-center h-full gap-3 text-center">
+              <Loader2 className="h-8 w-8 text-muted-foreground animate-spin" />
+              <p className="text-sm text-muted-foreground">Generating preview...</p>
+            </div>
           ) : (
             <ImageViewer
               src={currentEntry.blobUrl}
diff --git a/apps/web/src/components/common/thumbnail-strip.tsx b/apps/web/src/components/common/thumbnail-strip.tsx
index f54bd90f..4d43e847 100644
--- a/apps/web/src/components/common/thumbnail-strip.tsx
+++ b/apps/web/src/components/common/thumbnail-strip.tsx
@@ -1,4 +1,4 @@
-import { CheckCircle2, XCircle } from "lucide-react";
+import { CheckCircle2, Loader2, XCircle } from "lucide-react";
 import { useEffect, useRef } from "react";
 import type { FileEntry } from "@/stores/file-store";
 
@@ -44,12 +44,18 @@ export function ThumbnailStrip({ entries, selectedIndex, onSelect }: ThumbnailSt
             style={{ width: 52, height: 38 }}
             title={entry.file.name}
           >
-            <img
-              src={entry.processedUrl ?? entry.blobUrl}
-              alt={entry.file.name}
-              className="w-full h-full object-cover"
-              draggable={false}
-            />
+            {entry.previewLoading ? (
+              <div className="w-full h-full flex items-center justify-center bg-muted">
+                <Loader2 className="h-3.5 w-3.5 text-muted-foreground animate-spin" />
+              </div>
+            ) : (
+              <img
+                src={entry.processedPreviewUrl ?? entry.processedUrl ?? entry.blobUrl}
+                alt={entry.file.name}
+                className="w-full h-full object-cover"
+                draggable={false}
+              />
+            )}
             {isCompleted && (
               <div className="absolute -top-0.5 -right-0.5 w-3.5 h-3.5 bg-green-500 rounded-full flex items-center justify-center">
                 <CheckCircle2 className="h-2.5 w-2.5 text-white" />
diff --git a/apps/web/src/components/tools/convert-settings.tsx b/apps/web/src/components/tools/convert-settings.tsx
index 191fd9c1..16b0b09b 100644
--- a/apps/web/src/components/tools/convert-settings.tsx
+++ b/apps/web/src/components/tools/convert-settings.tsx
@@ -4,8 +4,8 @@ import { ProgressCard } from "@/components/common/progress-card";
 import { useToolProcessor } from "@/hooks/use-tool-processor";
 import { useFileStore } from "@/stores/file-store";
 
-const OUTPUT_FORMATS = ["jpg", "png", "webp", "avif", "tiff", "gif", "heic"] as const;
-const LOSSY_FORMATS = ["jpg", "jpeg", "webp", "avif", "heic"];
+const OUTPUT_FORMATS = ["jpg", "png", "webp", "avif", "tiff", "gif", "heic", "heif"] as const;
+const LOSSY_FORMATS = ["jpg", "jpeg", "webp", "avif", "heic", "heif"];
 
 export interface ConvertControlsProps {
   onChange?: (settings: Record<string, unknown>) => void;
@@ -132,10 +132,6 @@ export function ConvertSettings() {
         <div className="text-xs text-muted-foreground space-y-0.5">
           <p>Original: {(originalSize / 1024).toFixed(1)} KB</p>
           <p>Processed: {(processedSize / 1024).toFixed(1)} KB</p>
-          <p>
-            Savings:{" "}
-            {originalSize > 0 ? ((1 - processedSize / originalSize) * 100).toFixed(1) : "0"}%
-          </p>
         </div>
       )}
 
diff --git a/apps/web/src/components/tools/pipeline-builder.tsx b/apps/web/src/components/tools/pipeline-builder.tsx
index e782d44c..7a99e86c 100644
--- a/apps/web/src/components/tools/pipeline-builder.tsx
+++ b/apps/web/src/components/tools/pipeline-builder.tsx
@@ -146,7 +146,7 @@ export function PipelineBuilder({
   const handleFileSelect = useCallback(() => {
     const input = document.createElement("input");
     input.type = "file";
-    input.accept = "image/*";
+    input.accept = "image/*,.heic,.heif,.hif";
     input.onchange = (e) => {
       const f = (e.target as HTMLInputElement).files?.[0];
       if (f) setFile(f);
diff --git a/apps/web/src/components/tools/rotate-settings.tsx b/apps/web/src/components/tools/rotate-settings.tsx
index 6ceb0f87..84e0f23f 100644
--- a/apps/web/src/components/tools/rotate-settings.tsx
+++ b/apps/web/src/components/tools/rotate-settings.tsx
@@ -87,20 +87,45 @@ export function RotateControls({ onChange, onPreviewTransform, resetSignal }: Ro
 
   return (
     <div className="space-y-4">
-      {/* Quick rotate */}
+      {/* Quick rotate presets */}
       <div>
         <p className="text-xs text-muted-foreground">Rotate</p>
-        <div className="flex items-center gap-2 mt-1">
+        <div className="flex gap-1.5 mt-1">
           <button
             type="button"
             data-testid="rotate-left"
             onClick={rotateLeft}
-            className="flex-1 flex items-center justify-center gap-1.5 py-2.5 rounded-lg bg-muted text-muted-foreground hover:bg-primary hover:text-primary-foreground transition-colors text-sm font-medium"
+            className="flex-1 flex items-center justify-center gap-1 py-2 rounded-lg bg-muted text-muted-foreground hover:bg-primary hover:text-primary-foreground transition-colors text-xs font-medium"
             title="Rotate 90° counter-clockwise"
           >
-            <RotateCcw className="h-4 w-4" />
-            Left
+            <RotateCcw className="h-3.5 w-3.5" />
+            -90°
           </button>
+          <button
+            type="button"
+            onClick={() => setRotation((r) => r + 180)}
+            className="flex-1 flex items-center justify-center py-2 rounded-lg bg-muted text-muted-foreground hover:bg-primary hover:text-primary-foreground transition-colors text-xs font-medium"
+            title="Rotate 180°"
+          >
+            180°
+          </button>
+          <button
+            type="button"
+            data-testid="rotate-right"
+            onClick={rotateRight}
+            className="flex-1 flex items-center justify-center gap-1 py-2 rounded-lg bg-muted text-muted-foreground hover:bg-primary hover:text-primary-foreground transition-colors text-xs font-medium"
+            title="Rotate 90° clockwise"
+          >
+            +90°
+            <RotateCw className="h-3.5 w-3.5" />
+          </button>
+        </div>
+      </div>
+
+      {/* Custom angle */}
+      <div>
+        <p className="text-xs text-muted-foreground">Angle</p>
+        <div className="flex items-center justify-center gap-1.5 mt-1">
           <button
             type="button"
             onClick={() => setRotation((r) => r - 1)}
@@ -122,7 +147,7 @@ export function RotateControls({ onChange, onPreviewTransform, resetSignal }: Ro
                   commitAngleInput();
                 }
               }}
-              className="w-14 text-center text-sm font-mono font-medium tabular-nums py-1.5 rounded-md bg-background border border-border focus:outline-none focus:ring-2 focus:ring-primary/50 pr-4"
+              className="w-16 text-center text-sm font-mono font-medium tabular-nums py-1.5 rounded-md bg-background border border-border focus:outline-none focus:ring-2 focus:ring-primary/50 pr-4"
             />
             <span className="absolute right-2 text-sm font-mono text-muted-foreground pointer-events-none">
               °
@@ -136,16 +161,6 @@ export function RotateControls({ onChange, onPreviewTransform, resetSignal }: Ro
           >
             <Plus className="h-3.5 w-3.5" />
           </button>
-          <button
-            type="button"
-            data-testid="rotate-right"
-            onClick={rotateRight}
-            className="flex-1 flex items-center justify-center gap-1.5 py-2.5 rounded-lg bg-muted text-muted-foreground hover:bg-primary hover:text-primary-foreground transition-colors text-sm font-medium"
-            title="Rotate 90° clockwise"
-          >
-            Right
-            <RotateCw className="h-4 w-4" />
-          </button>
         </div>
       </div>
 
@@ -185,26 +200,26 @@ export function RotateControls({ onChange, onPreviewTransform, resetSignal }: Ro
             type="button"
             data-testid="rotate-flip-h"
             onClick={() => setFlipH(!flipH)}
-            className={`flex-1 flex items-center justify-center gap-1.5 py-2.5 rounded-lg text-sm font-medium transition-colors ${
+            className={`flex-1 flex items-center justify-center gap-1.5 py-2 rounded-lg text-xs font-medium transition-colors ${
               flipH
                 ? "bg-primary text-primary-foreground"
                 : "bg-muted text-muted-foreground hover:bg-primary/10"
             }`}
           >
-            <FlipHorizontal className="h-4 w-4" />
+            <FlipHorizontal className="h-3.5 w-3.5" />
             Horizontal
           </button>
           <button
             type="button"
             data-testid="rotate-flip-v"
             onClick={() => setFlipV(!flipV)}
-            className={`flex-1 flex items-center justify-center gap-1.5 py-2.5 rounded-lg text-sm font-medium transition-colors ${
+            className={`flex-1 flex items-center justify-center gap-1.5 py-2 rounded-lg text-xs font-medium transition-colors ${
               flipV
                 ? "bg-primary text-primary-foreground"
                 : "bg-muted text-muted-foreground hover:bg-primary/10"
             }`}
           >
-            <FlipVertical className="h-4 w-4" />
+            <FlipVertical className="h-3.5 w-3.5" />
             Vertical
           </button>
         </div>
diff --git a/apps/web/src/hooks/use-tool-processor.ts b/apps/web/src/hooks/use-tool-processor.ts
index ebf1535d..b98bfc1b 100644
--- a/apps/web/src/hooks/use-tool-processor.ts
+++ b/apps/web/src/hooks/use-tool-processor.ts
@@ -7,6 +7,7 @@ import { useFileStore } from "@/stores/file-store";
 interface ProcessResult {
   jobId: string;
   downloadUrl: string;
+  previewUrl?: string;
   originalSize: number;
   processedSize: number;
   savedFileId?: string;
@@ -31,7 +32,7 @@ const AI_PYTHON_TOOLS = new Set<string>(PYTHON_SIDECAR_TOOLS);
 
 // Tools that take a few seconds (not instant like Sharp, not minutes like AI).
 // Uses a smoother progress: upload 0-40%, then a gradual fill during processing.
-const MEDIUM_TOOLS = new Set(["content-aware-resize"]);
+const MEDIUM_TOOLS = new Set(["content-aware-resize", "convert"]);
 
 export function useToolProcessor(toolId: string) {
   const {
@@ -141,8 +142,8 @@ export function useToolProcessor(toolId: string) {
       const xhr = new XMLHttpRequest();
       xhrRef.current = xhr;
 
-      // Timeout: 60s for fast/medium tools, 5 min for AI tools
-      xhr.timeout = isAiTool ? 300_000 : 60_000;
+      // Timeout: 60s for fast tools, 3 min for medium (seam carving), 5 min for AI
+      xhr.timeout = isAiTool ? 300_000 : isMediumTool ? 180_000 : 60_000;
 
       // For AI tools: upload = 0-15%, processing = 15-100% (SSE-driven)
       // For medium tools: upload = 0-40%, processing = 40-95% (gradual fill)
@@ -167,11 +168,11 @@ export function useToolProcessor(toolId: string) {
           stage: isAiTool ? "Starting..." : "Processing...",
         }));
 
-        // Medium tools: gradually fill from upload weight to 95% over ~15s
+        // Medium tools: gradually fill from upload weight to 95% over ~45s
         if (isMediumTool) {
           const start = UPLOAD_WEIGHT;
           const target = 95;
-          const step = (target - start) / 30; // 30 ticks over ~15s
+          const step = (target - start) / 90; // 90 ticks over ~45s
           processingTimerRef.current = setInterval(() => {
             setProgress((prev) => {
               if (prev.phase !== "processing") return prev;
@@ -194,7 +195,7 @@ export function useToolProcessor(toolId: string) {
           try {
             const result: ProcessResult = JSON.parse(xhr.responseText);
             setJobId(result.jobId);
-            setProcessedUrl(result.downloadUrl);
+            setProcessedUrl(result.downloadUrl, result.previewUrl);
             setSizes(result.originalSize, result.processedSize);
             // Update serverFileId if a new version was saved
             if (result.savedFileId) {
diff --git a/apps/web/src/pages/home-page.tsx b/apps/web/src/pages/home-page.tsx
index 71421b05..79658471 100644
--- a/apps/web/src/pages/home-page.tsx
+++ b/apps/web/src/pages/home-page.tsx
@@ -1,5 +1,6 @@
 import { CATEGORIES, TOOLS } from "@stirling-image/shared";
 import * as icons from "lucide-react";
+import { Loader2 } from "lucide-react";
 import { useCallback, useEffect } from "react";
 import { useNavigate } from "react-router-dom";
 import { ImageViewer } from "@/components/common/image-viewer";
@@ -12,8 +13,15 @@ import { useSettingsStore } from "@/stores/settings-store";
 const QUICK_ACTION_IDS = ["resize", "compress", "convert", "remove-background"];
 
 export function HomePage() {
-  const { setFiles, files, reset, originalBlobUrl, selectedFileName, selectedFileSize } =
-    useFileStore();
+  const {
+    setFiles,
+    files,
+    reset,
+    originalBlobUrl,
+    selectedFileName,
+    selectedFileSize,
+    currentEntry,
+  } = useFileStore();
   const navigate = useNavigate();
   const { fetch: fetchSettings } = useSettingsStore();
 
@@ -141,6 +149,12 @@ export function HomePage() {
         <div className="flex-1 flex items-center justify-center p-6 min-h-0">
           {files.length > 1 ? (
             <MultiImageViewer />
+          ) : currentEntry?.previewLoading ? (
+            <div className="flex flex-col items-center justify-center h-full gap-3 text-center">
+              <Loader2 className="h-8 w-8 text-muted-foreground animate-spin" />
+              <p className="text-sm text-muted-foreground">Generating preview...</p>
+              <p className="text-xs text-muted-foreground/60">{selectedFileName}</p>
+            </div>
           ) : originalBlobUrl ? (
             <ImageViewer
               src={originalBlobUrl}
diff --git a/apps/web/src/pages/tool-page.tsx b/apps/web/src/pages/tool-page.tsx
index 91024d73..5661f331 100644
--- a/apps/web/src/pages/tool-page.tsx
+++ b/apps/web/src/pages/tool-page.tsx
@@ -1,6 +1,6 @@
 import { TOOLS } from "@stirling-image/shared";
 import * as icons from "lucide-react";
-import { CheckCircle2, ChevronLeft, ChevronRight, Download } from "lucide-react";
+import { CheckCircle2, ChevronLeft, ChevronRight, Download, Loader2 } from "lucide-react";
 import { Suspense, useCallback, useEffect, useMemo, useRef, useState } from "react";
 import type { Crop } from "react-image-crop";
 import { useParams } from "react-router-dom";
@@ -20,6 +20,24 @@ import { formatFileSize } from "@/lib/download";
 import { getToolRegistryEntry } from "@/lib/tool-registry";
 import { useFileStore } from "@/stores/file-store";
 
+/** Formats that browsers can render in <img> tags. */
+const BROWSER_PREVIEWABLE_EXTS = new Set([
+  "jpg",
+  "jpeg",
+  "png",
+  "gif",
+  "webp",
+  "svg",
+  "bmp",
+  "ico",
+  "avif",
+]);
+
+function canBrowserPreview(url: string): boolean {
+  const ext = decodeURIComponent(url).split(".").pop()?.toLowerCase() ?? "";
+  return BROWSER_PREVIEWABLE_EXTS.has(ext);
+}
+
 /** File selection indicator shown in left panel */
 function FileSelectionInfo({
   files,
@@ -84,6 +102,7 @@ export function ToolPage() {
     addFiles,
     reset,
     processedUrl,
+    processedPreviewUrl,
     originalBlobUrl,
     originalSize,
     processedSize,
@@ -170,7 +189,7 @@ export function ToolPage() {
     const input = document.createElement("input");
     input.type = "file";
     input.multiple = true;
-    input.accept = "image/*";
+    input.accept = "image/*,.heic,.heif,.hif";
     input.onchange = (e) => {
       const newFiles = Array.from((e.target as HTMLInputElement).files || []);
       if (newFiles.length > 0) addFiles(newFiles);
@@ -208,11 +227,15 @@ export function ToolPage() {
   const isNoDropzone = displayMode === "no-dropzone";
   const isLivePreview = registryEntry.livePreview ?? false;
 
-  // Derive processed file info from context
-  const processedFileName = selectedFileName ? `processed-${selectedFileName}` : "processed-image";
-  const processedFileType = selectedFileName
-    ? selectedFileName.split(".").pop()?.toUpperCase() || "IMAGE"
-    : "IMAGE";
+  // Derive processed file info from the actual download URL (has correct extension)
+  const processedFileName = processedUrl
+    ? decodeURIComponent(processedUrl.split("/").pop() ?? "processed-image")
+    : "processed-image";
+  const processedFileType = processedFileName.split(".").pop()?.toUpperCase() || "IMAGE";
+  const isProcessedPreviewable = processedUrl ? canBrowserPreview(processedUrl) : false;
+  // Use server-generated preview for non-previewable formats (HEIC, TIFF).
+  // Always a string when hasProcessed is true (processedUrl is non-null).
+  const displayUrl = (processedPreviewUrl ?? processedUrl) as string;
 
   // Build settings props
   const settingsProps = {
@@ -287,6 +310,30 @@ export function ToolPage() {
       );
     }
 
+    // Non-previewable format with no server-generated preview - show success card
+    if (hasProcessed && !isProcessedPreviewable && !processedPreviewUrl) {
+      return (
+        <div className="flex flex-col items-center justify-center h-full gap-4 text-center p-8">
+          <div className="w-16 h-16 rounded-full bg-green-100 dark:bg-green-900/30 flex items-center justify-center">
+            <CheckCircle2 className="h-8 w-8 text-green-600 dark:text-green-400" />
+          </div>
+          <div>
+            <p className="text-sm font-medium">Conversion complete</p>
+            <p className="text-xs text-muted-foreground mt-1">{processedFileName}</p>
+            {processedSize != null && (
+              <p className="text-xs text-muted-foreground">
+                {formatFileSize(processedSize)} · {processedFileType}
+              </p>
+            )}
+          </div>
+          <p className="text-xs text-muted-foreground max-w-xs">
+            {processedFileType} files cannot be previewed in the browser. Use the download button to
+            save your file.
+          </p>
+        </div>
+      );
+    }
+
     if (
       hasProcessed &&
       originalBlobUrl &&
@@ -295,7 +342,7 @@ export function ToolPage() {
       return (
         <SideBySideComparison
           beforeSrc={originalBlobUrl}
-          afterSrc={processedUrl}
+          afterSrc={displayUrl}
           beforeSize={originalSize ?? undefined}
           afterSize={processedSize ?? undefined}
         />
@@ -308,11 +355,7 @@ export function ToolPage() {
       (displayMode === "live-preview" || displayMode === "no-comparison")
     ) {
       return (
-        <ImageViewer
-          src={processedUrl}
-          filename={processedFileName}
-          fileSize={processedSize ?? 0}
-        />
+        <ImageViewer src={displayUrl} filename={processedFileName} fileSize={processedSize ?? 0} />
       );
     }
 
@@ -320,13 +363,23 @@ export function ToolPage() {
       return (
         <BeforeAfterSlider
           beforeSrc={originalBlobUrl}
-          afterSrc={processedUrl}
+          afterSrc={displayUrl}
           beforeSize={originalSize ?? undefined}
           afterSize={processedSize ?? undefined}
         />
       );
     }
 
+    if (hasFile && currentEntry?.previewLoading) {
+      return (
+        <div className="flex flex-col items-center justify-center h-full gap-3 text-center">
+          <Loader2 className="h-8 w-8 text-muted-foreground animate-spin" />
+          <p className="text-sm text-muted-foreground">Generating preview...</p>
+          <p className="text-xs text-muted-foreground/60">{selectedFileName}</p>
+        </div>
+      );
+    }
+
     if (hasFile && originalBlobUrl) {
       return (
         <ImageViewer
@@ -413,7 +466,7 @@ export function ToolPage() {
             fileSize={processedSize}
             fileType={processedFileType}
             downloadUrl={processedUrl}
-            previewUrl={processedUrl}
+            previewUrl={isProcessedPreviewable ? processedUrl : (processedPreviewUrl ?? undefined)}
             onUndo={handleUndo}
             currentToolId={tool?.id ?? ""}
           />
diff --git a/apps/web/src/stores/file-store.ts b/apps/web/src/stores/file-store.ts
index b438ac52..207b51eb 100644
--- a/apps/web/src/stores/file-store.ts
+++ b/apps/web/src/stores/file-store.ts
@@ -1,9 +1,12 @@
 import { create } from "zustand";
+import { formatHeaders } from "@/lib/api";
 
 export interface FileEntry {
   file: File;
   blobUrl: string;
+  previewLoading: boolean;
   processedUrl: string | null;
+  processedPreviewUrl: string | null;
   processedSize: number | null;
   originalSize: number;
   status: "pending" | "processing" | "completed" | "failed";
@@ -19,7 +22,9 @@ function createEntry(file: File): FileEntry {
   return {
     file,
     blobUrl: URL.createObjectURL(file),
+    previewLoading: needsServerPreview(file),
     processedUrl: null,
+    processedPreviewUrl: null,
     processedSize: null,
     originalSize: file.size,
     status: "pending",
@@ -51,6 +56,7 @@ function deriveSelected(entries: FileEntry[], selectedIndex: number) {
     selectedFileSize: entry ? entry.file.size : null,
     originalBlobUrl: entry ? entry.blobUrl : null,
     processedUrl: entry ? entry.processedUrl : null,
+    processedPreviewUrl: entry ? entry.processedPreviewUrl : null,
     originalSize: entry ? entry.originalSize : null,
     processedSize: entry ? entry.processedSize : null,
   };
@@ -69,6 +75,34 @@ function deriveFiles(entries: FileEntry[]): File[] {
   return prevFiles;
 }
 
+// ---------------------------------------------------------------------------
+// HEIC/HEIF preview helpers
+// ---------------------------------------------------------------------------
+
+const HEIF_EXTENSIONS = new Set(["heic", "heif", "hif"]);
+
+function needsServerPreview(file: File): boolean {
+  const ext = file.name.split(".").pop()?.toLowerCase() ?? "";
+  return HEIF_EXTENSIONS.has(ext);
+}
+
+async function fetchDecodedPreview(file: File): Promise<string | null> {
+  try {
+    const formData = new FormData();
+    formData.append("file", file);
+    const res = await fetch("/api/v1/preview", {
+      method: "POST",
+      headers: formatHeaders(),
+      body: formData,
+    });
+    if (!res.ok) return null;
+    const blob = await res.blob();
+    return URL.createObjectURL(blob);
+  } catch {
+    return null;
+  }
+}
+
 // ---------------------------------------------------------------------------
 // Store
 // ---------------------------------------------------------------------------
@@ -88,6 +122,7 @@ interface FileState {
   readonly selectedFileSize: number | null;
   readonly originalBlobUrl: string | null;
   readonly processedUrl: string | null;
+  readonly processedPreviewUrl: string | null;
   readonly originalSize: number | null;
   readonly processedSize: number | null;
 
@@ -103,7 +138,7 @@ interface FileState {
   setProcessing: (v: boolean) => void;
   setError: (e: string | null) => void;
   setJobId: (id: string) => void;
-  setProcessedUrl: (url: string | null) => void;
+  setProcessedUrl: (url: string | null, previewUrl?: string | null) => void;
   setSizes: (original: number, processed: number) => void;
   undoProcessing: () => void;
   reset: () => void;
@@ -133,12 +168,41 @@ export const useFileStore = create<FileState>((set, get) => ({
       files: deriveFiles(entries),
       ...deriveSelected(entries, 0),
     });
+    // Async: decode HEIC/HEIF files for browser preview
+    for (let i = 0; i < entries.length; i++) {
+      if (needsServerPreview(entries[i].file)) {
+        const file = entries[i].file;
+        fetchDecodedPreview(file).then((url) => {
+          const state = get();
+          if (state.entries[i]?.file !== file) return;
+          const updated = [...state.entries];
+          updated[i] = { ...updated[i], previewLoading: false, ...(url ? { blobUrl: url } : {}) };
+          set({ entries: updated, ...deriveSelected(updated, state.selectedIndex) });
+        });
+      }
+    }
   },
 
   addFiles: (files) => {
-    const entries = [...get().entries, ...files.map(createEntry)];
+    const oldLen = get().entries.length;
+    const newEntries = files.map(createEntry);
+    const entries = [...get().entries, ...newEntries];
     const idx = get().selectedIndex;
     set({ entries, files: deriveFiles(entries), ...deriveSelected(entries, idx) });
+    // Async: decode HEIC/HEIF files for browser preview
+    for (let j = 0; j < newEntries.length; j++) {
+      const i = oldLen + j;
+      if (needsServerPreview(newEntries[j].file)) {
+        const file = newEntries[j].file;
+        fetchDecodedPreview(file).then((url) => {
+          const state = get();
+          if (state.entries[i]?.file !== file) return;
+          const updated = [...state.entries];
+          updated[i] = { ...updated[i], previewLoading: false, ...(url ? { blobUrl: url } : {}) };
+          set({ entries: updated, ...deriveSelected(updated, state.selectedIndex) });
+        });
+      }
+    }
   },
 
   removeFile: (index) => {
@@ -207,7 +271,7 @@ export const useFileStore = create<FileState>((set, get) => ({
     // no-op for backward compat
   },
 
-  setProcessedUrl: (url) => {
+  setProcessedUrl: (url, previewUrl) => {
     const { entries, selectedIndex } = get();
     if (!entries[selectedIndex]) return;
     const updated = [...entries];
@@ -215,12 +279,14 @@ export const useFileStore = create<FileState>((set, get) => ({
       updated[selectedIndex] = {
         ...updated[selectedIndex],
         processedUrl: url,
+        processedPreviewUrl: previewUrl ?? null,
         status: "completed",
       };
     } else {
       updated[selectedIndex] = {
         ...updated[selectedIndex],
         processedUrl: null,
+        processedPreviewUrl: null,
         status: "pending",
       };
     }
@@ -247,6 +313,7 @@ export const useFileStore = create<FileState>((set, get) => ({
     const resetEntries = entries.map((e) => ({
       ...e,
       processedUrl: null,
+      processedPreviewUrl: null,
       processedSize: null,
       status: "pending" as const,
       error: null,
diff --git a/packages/ai/src/seam-carving.ts b/packages/ai/src/seam-carving.ts
index 69ad6dd8..1b1b070c 100644
--- a/packages/ai/src/seam-carving.ts
+++ b/packages/ai/src/seam-carving.ts
@@ -47,9 +47,17 @@ async function findCaire(): Promise<string> {
   );
 }
 
+/** Max pixels on the longest edge before downscaling for caire. */
+const MAX_CAIRE_DIMENSION = 1200;
+
 /**
  * Content-aware resize using caire (Go seam carving engine).
  * Supports both shrinking and enlarging via seam removal/insertion.
+ *
+ * Large images (>1200px longest edge) are downscaled first because
+ * seam carving is O(width * height * seams) and becomes impractical
+ * on high-resolution inputs. JPEG intermediate is used because Go's
+ * JPEG decoder is significantly faster than PNG for large images.
  */
 export async function seamCarve(
   inputBuffer: Buffer,
@@ -58,38 +66,71 @@ export async function seamCarve(
 ): Promise<SeamCarveResult> {
   const cairePath = await findCaire();
   const id = randomUUID();
-  const inputPath = join(outputDir, `caire-in-${id}.png`);
+  // Use JPEG for input (fast decode in Go) and PNG for output (lossless)
+  const inputPath = join(outputDir, `caire-in-${id}.jpg`);
   const outputPath = join(outputDir, `caire-out-${id}.png`);
 
   try {
-    await writeFile(inputPath, inputBuffer);
+    // Downscale large images and convert to JPEG for fast caire processing
+    const meta = await sharp(inputBuffer).metadata();
+    const origWidth = meta.width ?? 0;
+    const origHeight = meta.height ?? 0;
+    const longest = Math.max(origWidth, origHeight);
+
+    let width = origWidth;
+    let height = origHeight;
+
+    if (longest > MAX_CAIRE_DIMENSION) {
+      const scale = MAX_CAIRE_DIMENSION / longest;
+      width = Math.round(origWidth * scale);
+      height = Math.round(origHeight * scale);
+    }
+
+    // Always output JPEG for caire input (Go decodes JPEG 3-5x faster than PNG)
+    const processBuffer = await sharp(inputBuffer)
+      .resize(width, height, { fit: "fill" })
+      .jpeg({ quality: 95 })
+      .toBuffer();
+
+    await writeFile(inputPath, processBuffer);
 
     // Build caire arguments
     const args = ["-in", inputPath, "-out", outputPath, "-preview=false"];
 
     if (options.square) {
-      // Caire -square requires -width and -height set to the shortest edge
-      const meta = await sharp(inputBuffer).metadata();
-      const shortest = Math.min(meta.width ?? 0, meta.height ?? 0);
+      const shortest = Math.min(width, height);
       args.push("-square", "-width", String(shortest), "-height", String(shortest));
     } else {
-      if (options.width) args.push("-width", String(options.width));
-      if (options.height) args.push("-height", String(options.height));
+      if (options.width) {
+        // Scale user-specified dimensions proportionally if image was downscaled
+        const targetW =
+          longest > MAX_CAIRE_DIMENSION
+            ? Math.round(options.width * (MAX_CAIRE_DIMENSION / longest))
+            : options.width;
+        args.push("-width", String(targetW));
+      }
+      if (options.height) {
+        const targetH =
+          longest > MAX_CAIRE_DIMENSION
+            ? Math.round(options.height * (MAX_CAIRE_DIMENSION / longest))
+            : options.height;
+        args.push("-height", String(targetH));
+      }
     }
 
     if (options.protectFaces) args.push("-face");
     if (options.blurRadius !== undefined) args.push("-blur", String(options.blurRadius));
     if (options.sobelThreshold !== undefined) args.push("-sobel", String(options.sobelThreshold));
 
-    await execFileAsync(cairePath, args, { timeout: 60_000 });
+    await execFileAsync(cairePath, args, { timeout: 120_000 });
 
     const buffer = await readFile(outputPath);
-    const meta = await sharp(buffer).metadata();
+    const outMeta = await sharp(buffer).metadata();
 
     return {
       buffer,
-      width: meta.width ?? 0,
-      height: meta.height ?? 0,
+      width: outMeta.width ?? 0,
+      height: outMeta.height ?? 0,
     };
   } finally {
     await rm(inputPath, { force: true }).catch(() => {});
diff --git a/packages/image-engine/src/types.ts b/packages/image-engine/src/types.ts
index 416ec1d5..8f660748 100644
--- a/packages/image-engine/src/types.ts
+++ b/packages/image-engine/src/types.ts
@@ -17,7 +17,7 @@ export interface OperationResult {
   info: ImageInfo;
 }
 
-export type OutputFormat = "jpg" | "png" | "webp" | "avif" | "tiff" | "gif" | "heic";
+export type OutputFormat = "jpg" | "png" | "webp" | "avif" | "tiff" | "gif" | "heic" | "heif";
 
 export interface ResizeOptions {
   width?: number;