diff --git a/src/vs/workbench/api/common/extHost.api.impl.ts b/src/vs/workbench/api/common/extHost.api.impl.ts
index 1b9c7eb2b08..8a99d63cb4c 100644
--- a/src/vs/workbench/api/common/extHost.api.impl.ts
+++ b/src/vs/workbench/api/common/extHost.api.impl.ts
@@ -1691,6 +1691,7 @@ export function createApiFactoryAndRegisterActors(accessor: ServicesAccessor): I
 			LanguageModelSystemMessage: extHostTypes.LanguageModelChatSystemMessage,
 			LanguageModelUserMessage: extHostTypes.LanguageModelChatUserMessage,
 			LanguageModelAssistantMessage: extHostTypes.LanguageModelChatAssistantMessage,
+			LanguageModelError: extHostTypes.LanguageModelError,
 			NewSymbolName: extHostTypes.NewSymbolName,
 			NewSymbolNameTag: extHostTypes.NewSymbolNameTag,
 			InlineEdit: extHostTypes.InlineEdit,
diff --git a/src/vs/workbench/api/common/extHostLanguageModels.ts b/src/vs/workbench/api/common/extHostLanguageModels.ts
index e51c875984d..ea10161e75f 100644
--- a/src/vs/workbench/api/common/extHostLanguageModels.ts
+++ b/src/vs/workbench/api/common/extHostLanguageModels.ts
@@ -8,6 +8,7 @@ import { IDisposable, toDisposable } from 'vs/base/common/lifecycle';
 import { ILogService } from 'vs/platform/log/common/log';
 import { ExtHostLanguageModelsShape, IMainContext, MainContext, MainThreadLanguageModelsShape } from 'vs/workbench/api/common/extHost.protocol';
 import * as typeConvert from 'vs/workbench/api/common/extHostTypeConverters';
+import { LanguageModelError } from 'vs/workbench/api/common/extHostTypes';
 import type * as vscode from 'vscode';
 import { Progress } from 'vs/platform/progress/common/progress';
 import { IChatMessage, IChatResponseFragment, ILanguageModelChatMetadata } from 'vs/workbench/contrib/chat/common/languageModels';
@@ -232,14 +233,14 @@ export class ExtHostLanguageModels implements ExtHostLanguageModelsShape {
 		const metadata = await this._proxy.$prepareChatAccess(from, languageModelId, options.justification);
 
 		if (!metadata || !this._languageModelIds.has(languageModelId)) {
-			throw new Error(`Language model '${languageModelId}' is unknown.`);
+			throw LanguageModelError.NotFound(`Language model '${languageModelId}' is unknown.`);
 		}
 
 		if (this._isUsingAuth(from, metadata)) {
 			const success = await this._getAuthAccess(extension, { identifier: metadata.extension, displayName: metadata.auth.providerLabel }, options.justification, options.silent);
 
 			if (!success || !this._modelAccessList.get(from)?.has(metadata.extension)) {
-				throw new Error(`Language model '${languageModelId}' cannot be used by '${from.value}'.`);
+				throw LanguageModelError.NoPermissions(`Language model '${languageModelId}' cannot be used by '${from.value}'.`);
 			}
 		}
 
@@ -270,7 +271,11 @@ export class ExtHostLanguageModels implements ExtHostLanguageModelsShape {
 		await barrier.wait();
 
 		if (error) {
-			throw new Error(`Language model '${languageModelId}' errored, check cause for more details`, { cause: error });
+			throw new LanguageModelError(
+				`Language model '${languageModelId}' errored, check cause for more details`,
+				'Unknown',
+				error
+			);
 		}
 
 		return res.apiObject;
diff --git a/src/vs/workbench/api/common/extHostTypes.ts b/src/vs/workbench/api/common/extHostTypes.ts
index 4eec0964cd2..2e1ff171d1f 100644
--- a/src/vs/workbench/api/common/extHostTypes.ts
+++ b/src/vs/workbench/api/common/extHostTypes.ts
@@ -4297,6 +4297,26 @@ export class LanguageModelChatAssistantMessage {
 	}
 }
 
+export class LanguageModelError extends Error {
+
+	static NotFound(message?: string): LanguageModelError {
+		return new LanguageModelError(message, LanguageModelError.NotFound.name);
+	}
+
+	static NoPermissions(message?: string): LanguageModelError {
+		return new LanguageModelError(message, LanguageModelError.NoPermissions.name);
+	}
+
+	readonly code: string;
+
+	constructor(message?: string, code?: string, cause?: Error) {
+		super(message, { cause });
+		this.name = 'LanguageModelError';
+		this.code = code ?? '';
+	}
+
+}
+
 //#endregion
 
 //#region ai
diff --git a/src/vscode-dts/vscode.proposed.languageModels.d.ts b/src/vscode-dts/vscode.proposed.languageModels.d.ts
index 59b053f149d..775e4d5e1dc 100644
--- a/src/vscode-dts/vscode.proposed.languageModels.d.ts
+++ b/src/vscode-dts/vscode.proposed.languageModels.d.ts
@@ -104,6 +104,36 @@ declare module 'vscode' {
 		readonly removed: readonly string[];
 	}
 
+	/**
+	 * An error type for language model specific errors.
+	 *
+	 * Consumers of language models should check the code property to determine specific
+	 * failure causes, like `if(someError.code === vscode.LanguageModelError.NotFound.name) {...}`
+	 * for the case of referring to an unknown language model.
+	 */
+	export class LanguageModelError extends Error {
+
+		/**
+		 * The language model does not exist.
+		 */
+		static NotFound(message?: string): LanguageModelError;
+
+		/**
+		 * The requestor does not have permissions to use this
+		 * language model
+		 */
+		static NoPermissions(message?: string): LanguageModelError;
+
+		/**
+		 * A code that identifies this error.
+		 *
+		 * Possible values are names of errors, like {@linkcode LanguageModelError.NotFound NotFound},
+		 * or `Unknown` for unspecified errors from the language model itself. In the latter case the
+		 * `cause`-property will contain the actual error.
+		 */
+		readonly code: string;
+	}
+
 	/**
 	 * Options for making a chat request using a language model.
 	 *
@@ -151,9 +181,9 @@ declare module 'vscode' {
 		 * @returns A thenable that resolves to a {@link LanguageModelChatResponse}. The promise will reject when making the request failed.
 		 */
 		// TODO@API refine doc
-		// TODO@API define specific error types?
-		// TODO@API NAME: sendChatRequest, fetchChatResponse, makeChatRequest, chat, chatRequest sendChatRequest
 		// TODO@API ExtensionContext#permission#languageModels: { languageModel: string: LanguageModelAccessInformation}
+		// TODO@API ✅ define specific error types?
+		// TODO@API ✅ NAME: sendChatRequest, fetchChatResponse, makeChatRequest, chat, chatRequest sendChatRequest
 		// TODO@API ✅ NAME: LanguageModelChatXYZMessage
 		// TODO@API ✅ errors on everything that prevents us to make the actual request
 		// TODO@API ✅ double auth