diff --git a/packages/web/src/app/[domain]/chat/[id]/page.tsx b/packages/web/src/app/[domain]/chat/[id]/page.tsx
index d37076cd..4929589b 100644
--- a/packages/web/src/app/[domain]/chat/[id]/page.tsx
+++ b/packages/web/src/app/[domain]/chat/[id]/page.tsx
@@ -56,6 +56,7 @@ export default async function Page(props: PageProps) {
         <>
             <TopBar
                 domain={params.domain}
+                homePath={`/${params.domain}/chat`}
             >
                 <div className="flex flex-row gap-2 items-center">
                     <span className="text-muted mx-2 select-none">/</span>
diff --git a/packages/web/src/app/[domain]/chat/components/landingPageChatBox.tsx b/packages/web/src/app/[domain]/chat/components/landingPageChatBox.tsx
index b2080df3..7de6b928 100644
--- a/packages/web/src/app/[domain]/chat/components/landingPageChatBox.tsx
+++ b/packages/web/src/app/[domain]/chat/components/landingPageChatBox.tsx
@@ -9,6 +9,7 @@ import { RepositoryQuery, SearchContextQuery } from "@/lib/types";
 import { useState } from "react";
 import { useLocalStorage } from "usehooks-ts";
 import { SearchModeSelector } from "../../components/searchModeSelector";
+import { NotConfiguredErrorBanner } from "@/features/chat/components/notConfiguredErrorBanner";
 
 interface LandingPageChatBox {
     languageModels: LanguageModelInfo[];
@@ -24,9 +25,13 @@ export const LandingPageChatBox = ({
     const { createNewChatThread, isLoading } = useCreateNewChatThread();
     const [selectedSearchScopes, setSelectedSearchScopes] = useLocalStorage<SearchScope[]>("selectedSearchScopes", [], { initializeWithValue: false });
     const [isContextSelectorOpen, setIsContextSelectorOpen] = useState(false);
+    const isChatBoxDisabled = languageModels.length === 0;
+
     return (
-        <div className="flex flex-col items-center w-full">
-            <div className="mt-4 w-full border rounded-md shadow-sm max-w-[800px]">
+        <div className="w-full max-w-[800px] mt-4">
+           
+
+            <div className="border rounded-md w-full shadow-sm">
                 <ChatBox
                     onSubmit={(children) => {
                         createNewChatThread(children, selectedSearchScopes);
@@ -37,6 +42,7 @@ export const LandingPageChatBox = ({
                     selectedSearchScopes={selectedSearchScopes}
                     searchContexts={searchContexts}
                     onContextSelectorOpenChanged={setIsContextSelectorOpen}
+                    isDisabled={isChatBoxDisabled}
                 />
                 <Separator />
                 <div className="relative">
@@ -57,6 +63,10 @@ export const LandingPageChatBox = ({
                     </div>
                 </div>
             </div>
+
+            {isChatBoxDisabled && (
+                <NotConfiguredErrorBanner className="mt-4" />
+            )}
         </div >
     )
 }
\ No newline at end of file
diff --git a/packages/web/src/app/[domain]/components/topBar.tsx b/packages/web/src/app/[domain]/components/topBar.tsx
index 6661ae42..d9fadb89 100644
--- a/packages/web/src/app/[domain]/components/topBar.tsx
+++ b/packages/web/src/app/[domain]/components/topBar.tsx
@@ -8,18 +8,20 @@ import { Separator } from "@/components/ui/separator";
 interface TopBarProps {
     domain: string;
     children?: React.ReactNode;
+    homePath?: string;
 }
 
 export const TopBar = ({
     domain,
     children,
+    homePath = `/${domain}`,
 }: TopBarProps) => {
     return (
         <div className='sticky top-0 left-0 right-0 z-10'>
             <div className="flex flex-row justify-between items-center py-1.5 px-3 gap-4 bg-background">
                 <div className="grow flex flex-row gap-4 items-center">
                     <Link
-                        href={`/${domain}`}
+                        href={homePath}
                         className="shrink-0 cursor-pointer"
                     >
                         <Image
diff --git a/packages/web/src/app/[domain]/repos/layout.tsx b/packages/web/src/app/[domain]/repos/layout.tsx
index 85d607eb..6ff10adf 100644
--- a/packages/web/src/app/[domain]/repos/layout.tsx
+++ b/packages/web/src/app/[domain]/repos/layout.tsx
@@ -9,14 +9,8 @@ export default async function Layout(
     props: LayoutProps
 ) {
     const params = await props.params;
-
-    const {
-        domain
-    } = params;
-
-    const {
-        children
-    } = props;
+    const { domain } = params;
+    const { children } = props;
 
     return (
         <div className="min-h-screen flex flex-col">
diff --git a/packages/web/src/app/api/(server)/chat/route.ts b/packages/web/src/app/api/(server)/chat/route.ts
index 2c9bced2..d7f9368b 100644
--- a/packages/web/src/app/api/(server)/chat/route.ts
+++ b/packages/web/src/app/api/(server)/chat/route.ts
@@ -1,8 +1,8 @@
 import { sew, withAuth, withOrgMembership } from "@/actions";
 import { _getConfiguredLanguageModelsFull, _getAISDKLanguageModelAndOptions, updateChatMessages } from "@/features/chat/actions";
 import { createAgentStream } from "@/features/chat/agent";
-import { additionalChatRequestParamsSchema, SBChatMessage, SearchScope } from "@/features/chat/types";
-import { getAnswerPartFromAssistantMessage } from "@/features/chat/utils";
+import { additionalChatRequestParamsSchema, LanguageModelInfo, SBChatMessage, SearchScope } from "@/features/chat/types";
+import { getAnswerPartFromAssistantMessage, getLanguageModelKey } from "@/features/chat/utils";
 import { ErrorCode } from "@/lib/errorCodes";
 import { notFound, schemaValidationError, serviceErrorResponse } from "@/lib/serviceError";
 import { isServiceError } from "@/lib/utils";
@@ -49,7 +49,11 @@ export async function POST(req: Request) {
         return serviceErrorResponse(schemaValidationError(parsed.error));
     }
 
-    const { messages, id, selectedSearchScopes, languageModelId } = parsed.data;
+    const { messages, id, selectedSearchScopes, languageModel: _languageModel } = parsed.data;
+    // @note: a bit of type massaging is required here since the
+    // zod schema does not enum on `model` or `provider`.
+    // @see: chat/types.ts
+    const languageModel = _languageModel as LanguageModelInfo;
 
     const response = await sew(() =>
         withAuth((userId) =>
@@ -78,13 +82,13 @@ export async function POST(req: Request) {
                 // corresponding config in `config.json`.
                 const languageModelConfig =
                     (await _getConfiguredLanguageModelsFull())
-                        .find((model) => model.model === languageModelId);
+                        .find((model) => getLanguageModelKey(model) === getLanguageModelKey(languageModel));
 
                 if (!languageModelConfig) {
                     return serviceErrorResponse({
                         statusCode: StatusCodes.BAD_REQUEST,
                         errorCode: ErrorCode.INVALID_REQUEST_BODY,
-                        message: `Language model ${languageModelId} is not configured.`,
+                        message: `Language model ${languageModel.model} is not configured.`,
                     });
                 }
 
diff --git a/packages/web/src/app/globals.css b/packages/web/src/app/globals.css
index 6ab78a86..ad3df7af 100644
--- a/packages/web/src/app/globals.css
+++ b/packages/web/src/app/globals.css
@@ -109,6 +109,7 @@
     --chat-citation-border: hsl(217, 91%, 60%);
 
     --warning: #ca8a04;
+    --error: #fc5c5c;
   }
 
   .dark {
@@ -201,6 +202,7 @@
     --chat-citation-border: hsl(217, 91%, 60%);
 
     --warning: #fde047;
+    --error: #f87171;
   }
 }
 
diff --git a/packages/web/src/features/chat/components/chatBox/atMentionButton.tsx b/packages/web/src/features/chat/components/chatBox/atMentionButton.tsx
new file mode 100644
index 00000000..fb17b4ee
--- /dev/null
+++ b/packages/web/src/features/chat/components/chatBox/atMentionButton.tsx
@@ -0,0 +1,38 @@
+'use client';
+
+import { Button } from "@/components/ui/button";
+import { Tooltip, TooltipContent, TooltipTrigger } from "@/components/ui/tooltip";
+import { AtSignIcon } from "lucide-react";
+import { useCallback } from "react";
+import { ReactEditor, useSlate } from "slate-react";
+import { AtMentionInfoCard } from "./atMentionInfoCard";
+
+// @note: we have this as a seperate component to avoid having to re-render the
+// entire toolbar whenever the user types (since we are using the useSlate hook
+// here).
+export const AtMentionButton = () => {
+    const editor = useSlate();
+
+    const onAddContext = useCallback(() => {
+        editor.insertText("@");
+        ReactEditor.focus(editor);
+    }, [editor]);
+
+    return (
+        <Tooltip>
+            <TooltipTrigger asChild>
+                <Button
+                    variant="ghost"
+                    size="icon"
+                    className="w-6 h-6 text-muted-foreground hover:text-primary"
+                    onClick={onAddContext}
+                >
+                    <AtSignIcon className="w-4 h-4" />
+                </Button>
+            </TooltipTrigger>
+            <TooltipContent side="bottom" className="p-0 border-0 bg-transparent shadow-none">
+                <AtMentionInfoCard />
+            </TooltipContent>
+        </Tooltip>
+    );
+}
\ No newline at end of file
diff --git a/packages/web/src/features/chat/components/chatBox/chatBox.tsx b/packages/web/src/features/chat/components/chatBox/chatBox.tsx
index 934199f2..8876bd69 100644
--- a/packages/web/src/features/chat/components/chatBox/chatBox.tsx
+++ b/packages/web/src/features/chat/components/chatBox/chatBox.tsx
@@ -27,6 +27,7 @@ interface ChatBoxProps {
     className?: string;
     isRedirecting?: boolean;
     isGenerating?: boolean;
+    isDisabled?: boolean;
     languageModels: LanguageModelInfo[];
     selectedSearchScopes: SearchScope[];
     searchContexts: SearchContextQuery[];
@@ -40,6 +41,7 @@ export const ChatBox = ({
     className,
     isRedirecting,
     isGenerating,
+    isDisabled,
     languageModels,
     selectedSearchScopes,
     searchContexts,
@@ -68,7 +70,7 @@ export const ChatBox = ({
         }).flat(),
     });
     const { selectedLanguageModel } = useSelectedLanguageModel({
-        initialLanguageModel: languageModels.length > 0 ? languageModels[0] : undefined,
+        languageModels,
     });
     const { toast } = useToast();
 
@@ -167,6 +169,13 @@ export const ChatBox = ({
                 onContextSelectorOpenChanged(true);
             }
 
+            if (isSubmitDisabledReason === "no-language-model-selected") {
+                toast({
+                    description: "⚠️ You must select a language model",
+                    variant: "destructive",
+                });
+            }
+
             return;
         }
 
@@ -287,6 +296,7 @@ export const ChatBox = ({
                 renderElement={renderElement}
                 renderLeaf={renderLeaf}
                 onKeyDown={onKeyDown}
+                readOnly={isDisabled}
             />
             <div className="ml-auto z-10">
                 {isRedirecting ? (
diff --git a/packages/web/src/features/chat/components/chatBox/chatBoxToolbar.tsx b/packages/web/src/features/chat/components/chatBox/chatBoxToolbar.tsx
index 8bb00cef..a0aae38c 100644
--- a/packages/web/src/features/chat/components/chatBox/chatBoxToolbar.tsx
+++ b/packages/web/src/features/chat/components/chatBox/chatBoxToolbar.tsx
@@ -1,18 +1,12 @@
 'use client';
 
-import { Button } from "@/components/ui/button";
 import { Separator } from "@/components/ui/separator";
-import { Tooltip, TooltipContent, TooltipTrigger } from "@/components/ui/tooltip";
 import { LanguageModelInfo, SearchScope } from "@/features/chat/types";
 import { RepositoryQuery, SearchContextQuery } from "@/lib/types";
-import { AtSignIcon } from "lucide-react";
-import { useCallback } from "react";
-import { ReactEditor, useSlate } from "slate-react";
 import { useSelectedLanguageModel } from "../../useSelectedLanguageModel";
+import { AtMentionButton } from "./atMentionButton";
 import { LanguageModelSelector } from "./languageModelSelector";
 import { SearchScopeSelector } from "./searchScopeSelector";
-import { SearchScopeInfoCard } from "@/features/chat/components/chatBox/searchScopeInfoCard";
-import { AtMentionInfoCard } from "@/features/chat/components/chatBox/atMentionInfoCard";
 
 export interface ChatBoxToolbarProps {
     languageModels: LanguageModelInfo[];
@@ -33,67 +27,29 @@ export const ChatBoxToolbar = ({
     isContextSelectorOpen,
     onContextSelectorOpenChanged,
 }: ChatBoxToolbarProps) => {
-    const editor = useSlate();
-    
-    const onAddContext = useCallback(() => {
-        editor.insertText("@");
-        ReactEditor.focus(editor);
-    }, [editor]);
-
     const { selectedLanguageModel, setSelectedLanguageModel } = useSelectedLanguageModel({
-        initialLanguageModel: languageModels.length > 0 ? languageModels[0] : undefined,
+        languageModels,
     });
 
     return (
         <>
-            <Tooltip>
-                <TooltipTrigger asChild>
-                    <Button
-                        variant="ghost"
-                        size="icon"
-                        className="w-6 h-6 text-muted-foreground hover:text-primary"
-                        onClick={onAddContext}
-                    >
-                        <AtSignIcon className="w-4 h-4" />
-                    </Button>
-                </TooltipTrigger>
-                <TooltipContent side="bottom" className="p-0 border-0 bg-transparent shadow-none">
-                    <AtMentionInfoCard />
-                </TooltipContent>
-            </Tooltip>
+            <AtMentionButton />
             <Separator orientation="vertical" className="h-3 mx-1" />
-            <Tooltip>
-                <TooltipTrigger asChild>
-                    <SearchScopeSelector
-                        className="bg-inherit w-fit h-6 min-h-6"
-                        repos={repos}
-                        searchContexts={searchContexts}
-                        selectedSearchScopes={selectedSearchScopes}
-                        onSelectedSearchScopesChange={onSelectedSearchScopesChange}
-                        isOpen={isContextSelectorOpen}
-                        onOpenChanged={onContextSelectorOpenChanged}
-                    />
-                </TooltipTrigger>
-                <TooltipContent side="bottom" className="p-0 border-0 bg-transparent shadow-none">
-                    <SearchScopeInfoCard />
-                </TooltipContent>
-            </Tooltip>
-            {languageModels.length > 0 && (
-                <>
-                    <Separator orientation="vertical" className="h-3 ml-1 mr-2" />
-                    <Tooltip>
-                        <TooltipTrigger asChild>
-                            <div>
-                                <LanguageModelSelector
-                                    languageModels={languageModels}
-                                    onSelectedModelChange={setSelectedLanguageModel}
-                                    selectedModel={selectedLanguageModel}
-                                />
-                            </div>
-                        </TooltipTrigger>
-                    </Tooltip>
-                </>
-            )}
+            <SearchScopeSelector
+                className="bg-inherit w-fit h-6 min-h-6"
+                repos={repos}
+                searchContexts={searchContexts}
+                selectedSearchScopes={selectedSearchScopes}
+                onSelectedSearchScopesChange={onSelectedSearchScopesChange}
+                isOpen={isContextSelectorOpen}
+                onOpenChanged={onContextSelectorOpenChanged}
+            />
+            <Separator orientation="vertical" className="h-3 ml-1 mr-2" />
+            <LanguageModelSelector
+                languageModels={languageModels}
+                onSelectedModelChange={setSelectedLanguageModel}
+                selectedModel={selectedLanguageModel}
+            />
         </>
     )
 }
diff --git a/packages/web/src/features/chat/components/chatBox/languageModelInfoCard.tsx b/packages/web/src/features/chat/components/chatBox/languageModelInfoCard.tsx
new file mode 100644
index 00000000..7b24a42d
--- /dev/null
+++ b/packages/web/src/features/chat/components/chatBox/languageModelInfoCard.tsx
@@ -0,0 +1,16 @@
+import { BotIcon } from "lucide-react";
+import Link from "next/link";
+
+export const LanguageModelInfoCard = () => {
+    return (
+        <div className="bg-popover border border-border rounded-lg shadow-lg p-4 w-80 max-w-[90vw]">
+            <div className="flex items-center gap-2 mb-3 pb-2 border-b border-border/50">
+                <BotIcon className="h-4 w-4 text-primary" />
+                <h4 className="text-sm font-semibold text-popover-foreground">Language Model</h4>
+            </div>
+            <div className="text-sm text-popover-foreground leading-relaxed">
+                Select the language model to use for the chat. <Link href="https://docs.sourcebot.dev/docs/configuration/language-model-providers" target="_blank" className="text-link">Configuration docs.</Link>
+            </div>
+        </div>
+    );
+}; 
\ No newline at end of file
diff --git a/packages/web/src/features/chat/components/chatBox/languageModelSelector.tsx b/packages/web/src/features/chat/components/chatBox/languageModelSelector.tsx
index 791fa8c8..c8fc0196 100644
--- a/packages/web/src/features/chat/components/chatBox/languageModelSelector.tsx
+++ b/packages/web/src/features/chat/components/chatBox/languageModelSelector.tsx
@@ -23,6 +23,9 @@ import {
 } from "lucide-react";
 import { useMemo, useState } from "react";
 import { ModelProviderLogo } from "./modelProviderLogo";
+import { getLanguageModelKey } from "../../utils";
+import { Tooltip, TooltipContent, TooltipTrigger } from "@/components/ui/tooltip";
+import { LanguageModelInfoCard } from "./languageModelInfoCard";
 
 interface LanguageModelSelectorProps {
     languageModels: LanguageModelInfo[];
@@ -59,7 +62,7 @@ export const LanguageModelSelector = ({
     // De-duplicate models
     const languageModels = useMemo(() => {
         return _languageModels.filter((model, selfIndex, selfArray) =>
-            selfIndex === selfArray.findIndex((t) => t.model === model.model)
+            selfIndex === selfArray.findIndex((t) => getLanguageModelKey(t) === getLanguageModelKey(model))
         );
     }, [_languageModels]);
 
@@ -68,81 +71,89 @@ export const LanguageModelSelector = ({
             open={isPopoverOpen}
             onOpenChange={setIsPopoverOpen}
         >
-            <PopoverTrigger asChild>
-                <Button
-                    onClick={handleTogglePopover}
-                    className={cn(
-                        "flex p-1 rounded-md items-center justify-between bg-inherit h-6",
-                        className
-                    )}
-                >
-                    <div className="flex items-center justify-between mx-auto max-w-64 overflow-hidden">
-                        {selectedModel ? (
-                            <ModelProviderLogo 
-                                provider={selectedModel.provider} 
-                                className="mr-1" 
-                            />
-                        ) : (
-                            <Bot className="h-4 w-4 text-muted-foreground mr-1" />
-                        )}
-                        <span
+            <Tooltip>
+                <PopoverTrigger asChild>
+                    <TooltipTrigger asChild>
+                        <Button
+                            onClick={handleTogglePopover}
                             className={cn(
-                                "text-sm text-muted-foreground mx-1 text-ellipsis overflow-hidden whitespace-nowrap",
-                                selectedModel ? "font-medium" : "font-normal"
+                                "flex p-1 rounded-md items-center justify-between bg-inherit h-6",
+                                className
                             )}
                         >
-                            {selectedModel ? (selectedModel.displayName ?? selectedModel.model) : "Select model"}
-                        </span>
-                        <ChevronDown className="h-4 cursor-pointer text-muted-foreground" />
-                    </div>
-                </Button>
-            </PopoverTrigger>
-            <PopoverContent
-                className="w-auto p-0"
-                align="start"
-                onEscapeKeyDown={() => setIsPopoverOpen(false)}
-            >
-                <Command>
-                    <CommandInput
-                        placeholder="Search models..."
-                        onKeyDown={handleInputKeyDown}
-                    />
-                    <CommandList>
-                        <CommandEmpty>No models found.</CommandEmpty>
-                        <CommandGroup>
-                            {languageModels
-                                .map((model, index) => {
-                                const isSelected = selectedModel?.model === model.model;
-                                return (
-                                    <CommandItem
-                                        key={`${model.model}-${index}`}
-                                        onSelect={() => {
-                                            selectModel(model)
-                                        }}
-                                        className="cursor-pointer"
-                                    >
-                                        <div
-                                            className={cn(
-                                                "mr-2 flex h-4 w-4 items-center justify-center rounded-sm border border-primary",
-                                                isSelected
-                                                    ? "bg-primary text-primary-foreground"
-                                                    : "opacity-50 [&_svg]:invisible"
-                                            )}
-                                        >
-                                            <CheckIcon className="h-4 w-4" />
-                                        </div>
-                                        <ModelProviderLogo 
-                                            provider={model.provider} 
-                                            className="mr-2" 
-                                        />
-                                        <span>{model.displayName ?? model.model}</span>
-                                    </CommandItem>
-                                );
-                            })}
-                        </CommandGroup>
-                    </CommandList>
-                </Command>
-            </PopoverContent>
+                            <div className="flex items-center justify-between mx-auto max-w-64 overflow-hidden">
+                                {selectedModel ? (
+                                    <ModelProviderLogo
+                                        provider={selectedModel.provider}
+                                        className="mr-1"
+                                    />
+                                ) : (
+                                    <Bot className="h-4 w-4 text-muted-foreground mr-1" />
+                                )}
+                                <span
+                                    className={cn(
+                                        "text-sm text-muted-foreground mx-1 text-ellipsis overflow-hidden whitespace-nowrap font-medium",
+                                    )}
+                                >
+                                    {selectedModel ? (selectedModel.displayName ?? selectedModel.model) : "Select model"}
+                                </span>
+                                <ChevronDown className="h-4 cursor-pointer text-muted-foreground" />
+                            </div>
+                        </Button>
+                    </TooltipTrigger>
+                </PopoverTrigger>
+                <TooltipContent side="bottom" className="p-0 border-0 bg-transparent shadow-none">
+                    <LanguageModelInfoCard />
+                </TooltipContent>
+                <PopoverContent
+                    className="w-auto p-0"
+                    align="start"
+                    onEscapeKeyDown={() => setIsPopoverOpen(false)}
+                >
+                    <Command>
+                        <CommandInput
+                            placeholder="Search models..."
+                            onKeyDown={handleInputKeyDown}
+                        />
+                        <CommandList>
+                            <CommandEmpty>
+                                <p>No models found.</p>
+                            </CommandEmpty>
+                            <CommandGroup>
+                                {languageModels
+                                    .map((model) => {
+                                        const isSelected = selectedModel && getLanguageModelKey(selectedModel) === getLanguageModelKey(model);
+                                        return (
+                                            <CommandItem
+                                                key={getLanguageModelKey(model)}
+                                                onSelect={() => {
+                                                    selectModel(model)
+                                                }}
+                                                className="cursor-pointer"
+                                            >
+                                                <div
+                                                    className={cn(
+                                                        "mr-2 flex h-4 w-4 items-center justify-center rounded-sm border border-primary",
+                                                        isSelected
+                                                            ? "bg-primary text-primary-foreground"
+                                                            : "opacity-50 [&_svg]:invisible"
+                                                    )}
+                                                >
+                                                    <CheckIcon className="h-4 w-4" />
+                                                </div>
+                                                <ModelProviderLogo
+                                                    provider={model.provider}
+                                                    className="mr-2"
+                                                />
+                                                <span>{model.displayName ?? model.model}</span>
+                                            </CommandItem>
+                                        );
+                                    })}
+                            </CommandGroup>
+                        </CommandList>
+                    </Command>
+                </PopoverContent>
+            </Tooltip>
         </Popover>
     );
 };
diff --git a/packages/web/src/features/chat/components/chatThread/chatThread.tsx b/packages/web/src/features/chat/components/chatThread/chatThread.tsx
index 0c58ae67..e7a49ba9 100644
--- a/packages/web/src/features/chat/components/chatThread/chatThread.tsx
+++ b/packages/web/src/features/chat/components/chatThread/chatThread.tsx
@@ -25,6 +25,7 @@ import { usePrevious } from '@uidotdev/usehooks';
 import { RepositoryQuery, SearchContextQuery } from '@/lib/types';
 import { generateAndUpdateChatNameFromMessage } from '../../actions';
 import { isServiceError } from '@/lib/utils';
+import { NotConfiguredErrorBanner } from '../notConfiguredErrorBanner';
 
 type ChatHistoryState = {
     scrollOffset?: number;
@@ -73,7 +74,7 @@ export const ChatThread = ({
     );
 
     const { selectedLanguageModel } = useSelectedLanguageModel({
-        initialLanguageModel: languageModels.length > 0 ? languageModels[0] : undefined,
+        languageModels,
     });
 
     const {
@@ -118,7 +119,7 @@ export const ChatThread = ({
         _sendMessage(message, {
             body: {
                 selectedSearchScopes,
-                languageModelId: selectedLanguageModel.model,
+                languageModel: selectedLanguageModel,
             } satisfies AdditionalChatRequestParams,
         });
 
@@ -355,31 +356,38 @@ export const ChatThread = ({
                 }
             </ScrollArea>
             {!isChatReadonly && (
-                <div className="border rounded-md w-full max-w-3xl mx-auto mb-8 shadow-sm">
-                    <CustomSlateEditor>
-                        <ChatBox
-                            onSubmit={onSubmit}
-                            className="min-h-[80px]"
-                            preferredSuggestionsBoxPlacement="top-start"
-                            isGenerating={status === "streaming" || status === "submitted"}
-                            onStop={stop}
-                            languageModels={languageModels}
-                            selectedSearchScopes={selectedSearchScopes}
-                            searchContexts={searchContexts}
-                            onContextSelectorOpenChanged={setIsContextSelectorOpen}
-                        />
-                        <div className="w-full flex flex-row items-center bg-accent rounded-b-md px-2">
-                            <ChatBoxToolbar
+                <div className="w-full max-w-3xl mx-auto mb-8">
+                    {languageModels.length === 0 && (
+                        <NotConfiguredErrorBanner className="mb-2" />
+                    )}
+
+                    <div className="border rounded-md w-full shadow-sm">
+                        <CustomSlateEditor>
+                            <ChatBox
+                                onSubmit={onSubmit}
+                                className="min-h-[80px]"
+                                preferredSuggestionsBoxPlacement="top-start"
+                                isGenerating={status === "streaming" || status === "submitted"}
+                                onStop={stop}
                                 languageModels={languageModels}
-                                repos={repos}
-                                searchContexts={searchContexts}
                                 selectedSearchScopes={selectedSearchScopes}
-                                onSelectedSearchScopesChange={onSelectedSearchScopesChange}
-                                isContextSelectorOpen={isContextSelectorOpen}
+                                searchContexts={searchContexts}
                                 onContextSelectorOpenChanged={setIsContextSelectorOpen}
+                                isDisabled={languageModels.length === 0}
                             />
-                        </div>
-                    </CustomSlateEditor>
+                            <div className="w-full flex flex-row items-center bg-accent rounded-b-md px-2">
+                                <ChatBoxToolbar
+                                    languageModels={languageModels}
+                                    repos={repos}
+                                    searchContexts={searchContexts}
+                                    selectedSearchScopes={selectedSearchScopes}
+                                    onSelectedSearchScopesChange={onSelectedSearchScopesChange}
+                                    isContextSelectorOpen={isContextSelectorOpen}
+                                    onContextSelectorOpenChanged={setIsContextSelectorOpen}
+                                />
+                            </div>
+                        </CustomSlateEditor>
+                    </div>
                 </div>
             )}
         </>
diff --git a/packages/web/src/features/chat/components/notConfiguredErrorBanner.tsx b/packages/web/src/features/chat/components/notConfiguredErrorBanner.tsx
new file mode 100644
index 00000000..3b142bf1
--- /dev/null
+++ b/packages/web/src/features/chat/components/notConfiguredErrorBanner.tsx
@@ -0,0 +1,18 @@
+import { TriangleAlertIcon } from "lucide-react"
+import Link from "next/link"
+import { cn } from "@/lib/utils";
+
+const DOCS_URL = "https://docs.sourcebot.dev/docs/configuration/language-model-providers"; 
+
+interface NotConfiguredErrorBannerProps {
+    className?: string;
+}
+
+export const NotConfiguredErrorBanner = ({ className }: NotConfiguredErrorBannerProps) => {
+    return (
+        <div className={cn("flex flex-row items-center bg-error rounded-md p-2", className)}>
+            <TriangleAlertIcon className="h-4 w-4 text-accent mr-1.5" />
+            <span className="text-sm font-medium text-accent"><span className="font-bold">Ask unavailable:</span> no language model configured. See the <Link href={DOCS_URL} target="_blank" className="underline">configuration docs</Link> for more information.</span>
+        </div>
+    )
+}
\ No newline at end of file
diff --git a/packages/web/src/features/chat/types.ts b/packages/web/src/features/chat/types.ts
index 524f14f8..8d543b1a 100644
--- a/packages/web/src/features/chat/types.ts
+++ b/packages/web/src/features/chat/types.ts
@@ -170,6 +170,13 @@ export type LanguageModelProvider = LanguageModel['provider'];
 
 // This is a subset of information about a configured
 // language model that we can safely send to the client.
+// @note: ensure this is in sync with the LanguageModelInfo type.
+export const languageModelInfoSchema = z.object({
+    provider: z.string(),
+    model: z.string(),
+    displayName: z.string().optional(),
+});
+
 export type LanguageModelInfo = {
     provider: LanguageModelProvider,
     model: LanguageModel['model'],
@@ -178,7 +185,7 @@ export type LanguageModelInfo = {
 
 // Additional request body data that we send along to the chat API.
 export const additionalChatRequestParamsSchema = z.object({
-    languageModelId: z.string(),
+    languageModel: languageModelInfoSchema,
     selectedSearchScopes: z.array(searchScopeSchema),
 });
 export type AdditionalChatRequestParams = z.infer<typeof additionalChatRequestParamsSchema>;
\ No newline at end of file
diff --git a/packages/web/src/features/chat/useSelectedLanguageModel.ts b/packages/web/src/features/chat/useSelectedLanguageModel.ts
index 7cdc79e4..a22b5940 100644
--- a/packages/web/src/features/chat/useSelectedLanguageModel.ts
+++ b/packages/web/src/features/chat/useSelectedLanguageModel.ts
@@ -2,22 +2,40 @@
 
 import { useLocalStorage } from "usehooks-ts";
 import { LanguageModelInfo } from "./types";
+import { useEffect } from "react";
+import { getLanguageModelKey } from "./utils";
 
 type Props = {
-    initialLanguageModel?: LanguageModelInfo;
+    languageModels: LanguageModelInfo[];
 }
 
 export const useSelectedLanguageModel = ({
-    initialLanguageModel,
-}: Props = {}) => {
+    languageModels,
+}: Props) => {
+    const fallbackLanguageModel = languageModels.length > 0 ? languageModels[0] : undefined;
     const [selectedLanguageModel, setSelectedLanguageModel] = useLocalStorage<LanguageModelInfo | undefined>(
         "selectedLanguageModel",
-        initialLanguageModel,
+        fallbackLanguageModel,
         {
             initializeWithValue: false,
         }
     );
 
+    // Handle the case where the selected language model is no longer
+    // available. Reset to the fallback language model in this case.
+    useEffect(() => {
+        if (!selectedLanguageModel || !languageModels.find(
+            (model) => getLanguageModelKey(model) === getLanguageModelKey(selectedLanguageModel)
+        )) {
+            setSelectedLanguageModel(fallbackLanguageModel);
+        }
+    }, [
+        fallbackLanguageModel,
+        languageModels,
+        selectedLanguageModel,
+        setSelectedLanguageModel,
+    ]);
+
     return {
         selectedLanguageModel,
         setSelectedLanguageModel,
diff --git a/packages/web/src/features/chat/utils.ts b/packages/web/src/features/chat/utils.ts
index c57f3fd5..f339b872 100644
--- a/packages/web/src/features/chat/utils.ts
+++ b/packages/web/src/features/chat/utils.ts
@@ -6,6 +6,7 @@ import {
     CustomText,
     FileReference,
     FileSource,
+    LanguageModelInfo,
     MentionData,
     MentionElement,
     ParagraphElement,
@@ -365,4 +366,11 @@ export const buildSearchQuery = (options: {
     }
 
     return query;
-}
\ No newline at end of file
+}
+
+/**
+ * Generates a unique key given a LanguageModelInfo object.
+ */
+export const getLanguageModelKey = (model: LanguageModelInfo) => {
+    return `${model.provider}-${model.model}-${model.displayName}`;
+}
diff --git a/packages/web/tailwind.config.ts b/packages/web/tailwind.config.ts
index 1f7acf4d..c2859825 100644
--- a/packages/web/tailwind.config.ts
+++ b/packages/web/tailwind.config.ts
@@ -67,6 +67,7 @@ const config = {
                     ring: 'var(--sidebar-ring)'
                 },
                 warning: 'var(--warning)',
+                error: 'var(--error)',
                 editor: {
                     background: 'var(--editor-background)',
                     foreground: 'var(--editor-foreground)',