diff --git a/web/src/lib/components/files/DirectoryInput.svelte b/web/src/lib/components/files/DirectoryInput.svelte
index 556e32d..087dd12 100644
--- a/web/src/lib/components/files/DirectoryInput.svelte
+++ b/web/src/lib/components/files/DirectoryInput.svelte
@@ -26,6 +26,6 @@
     const mergedProps = mergeProps({ onclick }, restProps);
 </script>
 
-<Button.Root {...mergedProps}>
+<Button.Root type="button" {...mergedProps}>
     {@render children?.({ directory })}
 </Button.Root>
diff --git a/web/src/lib/components/files/FileTypeSelect.svelte b/web/src/lib/components/files/FileTypeSelect.svelte
new file mode 100644
index 0000000..8589e0a
--- /dev/null
+++ b/web/src/lib/components/files/FileTypeSelect.svelte
@@ -0,0 +1,59 @@
+<script lang="ts" module>
+    import { type BundledLanguage, bundledLanguages, type SpecialLanguage } from "shiki";
+
+    const languageKeys = [...Object.keys(bundledLanguages), "text", "ansi", "plaintext", "txt"] as BundledLanguage | SpecialLanguage[];
+</script>
+
+<script lang="ts">
+    import { Label, Select } from "bits-ui";
+
+    interface Props {
+        value?: BundledLanguage | SpecialLanguage | "auto";
+        allowAuto?: boolean;
+    }
+
+    let { value = $bindable("auto"), allowAuto = true }: Props = $props();
+
+    const uid = $props.id();
+    const fileTypeId = `file-type-${uid}`;
+    const fileTypeLabelId = `file-type-label-${uid}`;
+</script>
+
+<div class="flex items-center gap-1">
+    <!-- TODO Label gets active & hover styles, but doesn't open selector -->
+    <Label.Root id={fileTypeLabelId} for={fileTypeId} class="text-sm">File Type</Label.Root>
+    <Select.Root type="single" bind:value scrollAlignment="center">
+        <Select.Trigger id={fileTypeId} aria-labelledby={fileTypeLabelId} class="flex items-center gap-1 rounded-sm border btn-ghost px-2 text-sm">
+            {#if value === "auto"}
+                Infer Type
+            {:else}
+                {value}
+            {/if}
+            <span aria-hidden="true" class="iconify size-4 shrink-0 text-base text-em-disabled octicon--triangle-down-16"></span>
+        </Select.Trigger>
+        <Select.Portal>
+            <Select.Content class="z-100 mt-0.5 flex max-h-64 flex-col rounded-sm border bg-neutral p-1.5 shadow-md">
+                {#if allowAuto}
+                    <Select.Group class="mb-1">
+                        <Select.Item
+                            value="auto"
+                            class="cursor-default rounded-sm px-2 py-1 text-sm data-highlighted:bg-neutral-3 data-selected:bg-primary data-selected:text-white"
+                        >
+                            Infer Type
+                        </Select.Item>
+                    </Select.Group>
+                {/if}
+                <Select.Group class="flex grow flex-col gap-1 overflow-y-auto">
+                    {#each languageKeys as langKey (langKey)}
+                        <Select.Item
+                            value={langKey}
+                            class="cursor-default rounded-sm px-2 py-1 text-sm data-highlighted:bg-neutral-3 data-selected:bg-primary data-selected:text-white"
+                        >
+                            {langKey}
+                        </Select.Item>
+                    {/each}
+                </Select.Group>
+            </Select.Content>
+        </Select.Portal>
+    </Select.Root>
+</div>
diff --git a/web/src/lib/components/files/MultimodalFileInput.svelte b/web/src/lib/components/files/MultimodalFileInput.svelte
index fed02b5..219eb5d 100644
--- a/web/src/lib/components/files/MultimodalFileInput.svelte
+++ b/web/src/lib/components/files/MultimodalFileInput.svelte
@@ -3,13 +3,15 @@
     import { box } from "svelte-toolbelt";
     import { RadioGroup } from "bits-ui";
     import SingleFileInput from "$lib/components/files/SingleFileInput.svelte";
+    import FileTypeSelect from "$lib/components/files/FileTypeSelect.svelte";
 
-    let { state = $bindable(), label = "File", required = false }: MultimodalFileInputProps = $props();
+    let { state = $bindable(), label = "File", required = false, fileTypeOverride = true }: MultimodalFileInputProps = $props();
 
     const instance = new MultimodalFileInputState({
         state,
         label: box.with(() => label),
         required: box.with(() => required),
+        fileTypeOverride: box.with(() => fileTypeOverride),
     });
     state = instance;
 
@@ -74,12 +76,11 @@
 </script>
 
 {#snippet radioItem(name: string)}
-    <RadioGroup.Item value={name.toLowerCase()}>
-        {#snippet children({ checked })}
-            <span class="rounded-sm px-1 py-0.5 text-sm" class:btn-ghost={!checked} class:border={!checked} class:btn-primary={checked}>
-                {name}
-            </span>
-        {/snippet}
+    <RadioGroup.Item
+        value={name.toLowerCase()}
+        class="rounded-sm px-2 text-sm data-[state=checked]:btn-primary data-[state=unchecked]:border data-[state=unchecked]:btn-ghost"
+    >
+        {name}
     </RadioGroup.Item>
 {/snippet}
 
@@ -91,11 +92,16 @@
     ondrop={handleDrop}
     ondragleavecapture={handleDragLeave}
 >
-    <RadioGroup.Root class="mb-1 flex w-full gap-1" bind:value={instance.mode}>
-        {@render radioItem("File")}
-        {@render radioItem("URL")}
-        {@render radioItem("Text")}
-    </RadioGroup.Root>
+    <div class="mb-1 flex w-full flex-wrap items-center gap-1">
+        <RadioGroup.Root class="me-2 flex gap-1" bind:value={instance.mode}>
+            {@render radioItem("File")}
+            {@render radioItem("URL")}
+            {@render radioItem("Text")}
+        </RadioGroup.Root>
+        {#if fileTypeOverride}
+            <FileTypeSelect allowAuto={instance.mode !== "text"} bind:value={() => instance.getFileType(), (v) => instance.setFileType(v)} />
+        {/if}
+    </div>
     {#if instance.mode === "file"}
         {@render fileInput()}
     {:else if instance.mode === "url"}
diff --git a/web/src/lib/components/files/index.svelte.ts b/web/src/lib/components/files/index.svelte.ts
index 0aceded..946e102 100644
--- a/web/src/lib/components/files/index.svelte.ts
+++ b/web/src/lib/components/files/index.svelte.ts
@@ -1,5 +1,6 @@
 import { type ReadableBoxedValues } from "svelte-toolbelt";
-import { lazyPromise } from "$lib/util";
+import { getExtensionForLanguage, lazyPromise } from "$lib/util";
+import type { BundledLanguage, SpecialLanguage } from "shiki";
 
 export interface FileSystemEntry {
     fileName: string;
@@ -132,6 +133,8 @@ function filesToDirectory(files: FileList): DirectoryEntry {
     return ret;
 }
 
+export type FileType = SpecialLanguage | BundledLanguage | "auto";
+
 export type FileInputMode = "file" | "url" | "text";
 
 export type MultimodalFileInputValueMetadata = {
@@ -144,6 +147,7 @@ export type MultimodalFileInputProps = {
 
     label?: string | undefined;
     required?: boolean | undefined;
+    fileTypeOverride?: boolean | undefined;
 };
 
 export type MultimodalFileInputStateProps = {
@@ -151,14 +155,18 @@ export type MultimodalFileInputStateProps = {
 } & ReadableBoxedValues<{
     label: string;
     required: boolean;
+    fileTypeOverride: boolean;
 }>;
 
 export class MultimodalFileInputState {
     private readonly opts: MultimodalFileInputStateProps;
     mode: FileInputMode = $state("file");
     text: string = $state("");
+    textType: FileType = $state("plaintext");
     file: File | undefined = $state(undefined);
+    fileType: FileType = $state("auto");
     url: string = $state("");
+    urlType: FileType = $state("auto");
     private urlResolver = $derived.by(() => {
         const url = this.url;
         return lazyPromise(async () => {
@@ -185,22 +193,56 @@ export class MultimodalFileInputState {
         if (this.opts.state) {
             this.mode = this.opts.state.mode;
             this.text = this.opts.state.text;
+            this.textType = this.opts.state.textType;
             this.file = this.opts.state.file;
+            this.fileType = this.opts.state.fileType;
             this.url = this.opts.state.url;
+            this.urlType = this.opts.state.urlType;
             this.urlResolver = this.opts.state.urlResolver;
         }
     }
 
+    getFileType(): FileType {
+        if (this.mode === "file") {
+            return this.fileType;
+        } else if (this.mode === "url") {
+            return this.urlType;
+        } else if (this.mode === "text") {
+            return this.textType;
+        }
+        throw new Error("Invalid mode");
+    }
+
+    setFileType(fileType: FileType) {
+        if (this.mode === "file") {
+            this.fileType = fileType;
+        } else if (this.mode === "url") {
+            this.urlType = fileType;
+        } else if (this.mode === "text") {
+            this.textType = fileType;
+        } else {
+            throw new Error("Invalid mode");
+        }
+    }
+
+    private getExtensionOrBlank() {
+        const fileType = this.getFileType();
+        if (fileType === "auto") {
+            return "";
+        }
+        return getExtensionForLanguage(fileType);
+    }
+
     get metadata(): MultimodalFileInputValueMetadata | null {
         const mode = this.mode;
         const label = this.opts.label.current;
         if (mode === "file" && this.file !== undefined) {
             const file = this.file;
-            return { type: "file", name: file.name };
+            return { type: "file", name: `${file.name}${this.getExtensionOrBlank()}` };
         } else if (mode === "url" && this.url !== "") {
-            return { type: "url", name: this.url };
+            return { type: "url", name: `${this.url}${this.getExtensionOrBlank()}` };
         } else if (mode === "text" && this.text !== "") {
-            return { type: "text", name: `${label} (Text Input)` };
+            return { type: "text", name: `${label}${this.getExtensionOrBlank()}` };
         } else {
             return null;
         }
@@ -228,20 +270,29 @@ export class MultimodalFileInputState {
     swapState(other: MultimodalFileInputState) {
         const mode = this.mode;
         const text = this.text;
+        const textType = this.textType;
         const file = this.file;
+        const fileType = this.fileType;
         const url = this.url;
+        const urlType = this.urlType;
         const urlResolver = this.urlResolver;
 
         this.mode = other.mode;
         this.text = other.text;
+        this.textType = other.textType;
         this.file = other.file;
+        this.fileType = other.fileType;
         this.url = other.url;
+        this.urlType = other.urlType;
         this.urlResolver = other.urlResolver;
 
         other.mode = mode;
         other.text = text;
+        other.textType = textType;
         other.file = file;
+        other.fileType = fileType;
         other.url = url;
+        other.urlType = urlType;
         other.urlResolver = urlResolver;
     }
 }
diff --git a/web/src/lib/components/settings-popover/ShikiThemeSelector.svelte b/web/src/lib/components/settings-popover/ShikiThemeSelector.svelte
index 40e945a..099b34c 100644
--- a/web/src/lib/components/settings-popover/ShikiThemeSelector.svelte
+++ b/web/src/lib/components/settings-popover/ShikiThemeSelector.svelte
@@ -22,14 +22,14 @@
     <Select.Trigger aria-labelledby={labelId} id={triggerId} class="group flex cursor-pointer items-center justify-between gap-1 px-2 py-1">
         <Label.Root id={labelId} for={triggerId} class="cursor-pointer text-sm">{capitalizeFirstLetter(mode)} theme</Label.Root>
         <div
-            class="flex w-44 items-center gap-1 rounded-sm border btn-ghost bg-neutral px-1 py-0.5 text-sm select-none group-hover:btn-ghost-hover group-active:btn-ghost-active"
+            class="flex w-44 items-center gap-1 rounded-sm border btn-ghost bg-neutral px-2 py-0.5 text-sm select-none group-hover:btn-ghost-hover group-active:btn-ghost-active"
             bind:this={anchor}
         >
             <div bind:clientWidth={triggerLabelContainerW} class="flex grow overflow-hidden" class:reveal-right={scrollDistance !== 0}>
                 <div
                     use:resizeObserver={(e) => (triggerLabelW = e[0].target.scrollWidth)}
                     aria-label="Current {mode} syntax highlighting theme"
-                    class="scrolling-text grow text-center text-nowrap"
+                    class="scrolling-text grow text-left text-nowrap"
                     style="--scroll-distance: -{scrollDistance}px;"
                 >
                     {value}
diff --git a/web/src/lib/diff-viewer-multi-file.svelte.ts b/web/src/lib/diff-viewer-multi-file.svelte.ts
index ca980b0..78afdf4 100644
--- a/web/src/lib/diff-viewer-multi-file.svelte.ts
+++ b/web/src/lib/diff-viewer-multi-file.svelte.ts
@@ -282,9 +282,7 @@ export class MultiFileDiffViewerState {
     private static readonly context = new Context<MultiFileDiffViewerState>("MultiFileDiffViewerState");
 
     static init() {
-        const state = new MultiFileDiffViewerState();
-        MultiFileDiffViewerState.context.set(state);
-        return state;
+        return MultiFileDiffViewerState.context.set(new MultiFileDiffViewerState());
     }
 
     static get() {
diff --git a/web/src/lib/util.ts b/web/src/lib/util.ts
index 59635b1..a20c9ea 100644
--- a/web/src/lib/util.ts
+++ b/web/src/lib/util.ts
@@ -373,6 +373,12 @@ const languageMap: { [key: string]: BundledLanguage | SpecialLanguage } = {
     ".yml": "yaml",
 };
 
+const reverseLanguageMap = Object.fromEntries(Object.entries(languageMap).map(([ext, lang]) => [lang, ext]));
+
+export function getExtensionForLanguage(language: BundledLanguage | SpecialLanguage): string {
+    return reverseLanguageMap[language] || ".txt";
+}
+
 export function guessLanguageFromExtension(fileName: string): BundledLanguage | SpecialLanguage {
     const lowerFileName = fileName.toLowerCase();
     const extensionIndex = lowerFileName.lastIndexOf(".");
diff --git a/web/src/routes/LoadDiffDialog.svelte b/web/src/routes/LoadDiffDialog.svelte
index 5928a05..04f2334 100644
--- a/web/src/routes/LoadDiffDialog.svelte
+++ b/web/src/routes/LoadDiffDialog.svelte
@@ -382,7 +382,7 @@
     <Dialog.Portal>
         <Dialog.Overlay class="fixed inset-0 z-50 bg-black/50 dark:bg-white/20" />
         <Dialog.Content
-            class="fixed top-1/2 left-1/2 z-50 max-h-svh w-192 max-w-[95%] -translate-x-1/2 -translate-y-1/2 overflow-y-auto rounded-md bg-neutral shadow-md"
+            class="fixed top-1/2 left-1/2 z-50 max-h-svh w-192 max-w-full -translate-x-1/2 -translate-y-1/2 overflow-y-auto rounded-md bg-neutral shadow-md sm:max-w-[95%]"
         >
             <header class="sticky top-0 z-10 flex flex-row items-center justify-between rounded-t-md bg-neutral-2 p-4">
                 <Dialog.Title class="text-xl font-semibold">Load a diff</Dialog.Title>
@@ -464,7 +464,7 @@
                     <span class="iconify size-6 shrink-0 octicon--file-diff-24"></span>
                     From Patch File
                 </h3>
-                <MultimodalFileInput bind:state={patchFile} required label="Patch File" />
+                <MultimodalFileInput bind:state={patchFile} required fileTypeOverride={false} label="Patch File" />
                 <Button.Root type="submit" class="mt-1 rounded-md btn-primary px-2 py-1">Go</Button.Root>
             </form>
 
@@ -533,7 +533,7 @@
                             <span class="iconify size-4 shrink-0 octicon--filter-16" aria-hidden="true"></span>
                         </Popover.Trigger>
                         <Popover.Portal>
-                            <Popover.Content side="top" class="z-50 overflow-hidden rounded-md border bg-neutral">
+                            <Popover.Content side="top" class="z-50 mx-2 overflow-hidden rounded-md border bg-neutral">
                                 {@render blacklistPopoverContent()}
                                 <Popover.Arrow class="text-edge" />
                             </Popover.Content>