diff --git a/packages/types/src/provider-settings.ts b/packages/types/src/provider-settings.ts
index a05e3f6b50..636214e9a1 100644
--- a/packages/types/src/provider-settings.ts
+++ b/packages/types/src/provider-settings.ts
@@ -353,7 +353,7 @@ const fakeAiSchema = baseProviderSettingsSchema.extend({
 
 const xaiSchema = apiModelIdProviderModelSchema.extend({
 	xaiApiKey: z.string().optional(),
-	xaiModelContextWindow: z.number().optional(),
+	xaiModelContextWindow: z.number().int().min(1).optional(),
 })
 
 const groqSchema = apiModelIdProviderModelSchema.extend({
diff --git a/src/api/providers/fetchers/xai.ts b/src/api/providers/fetchers/xai.ts
index 5f12eb03a0..4ca861864d 100644
--- a/src/api/providers/fetchers/xai.ts
+++ b/src/api/providers/fetchers/xai.ts
@@ -77,7 +77,7 @@ export async function getXaiModels(apiKey?: string, baseUrl?: string): Promise<R
 				inputPrice: centsToDollars(m.prompt_text_token_price),
 				outputPrice: centsToDollars(m.completion_text_token_price),
 				cacheReadsPrice,
-				cacheWritesPrice: cacheReadsPrice, // xAI uses same price for reads and writes
+				cacheWritesPrice: undefined, // Leave undefined unless API exposes a distinct write price
 				description: staticInfo?.description,
 				supportsReasoningEffort:
 					staticInfo && "supportsReasoningEffort" in staticInfo
diff --git a/src/api/providers/xai.ts b/src/api/providers/xai.ts
index 4eefe48745..e019a44b3d 100644
--- a/src/api/providers/xai.ts
+++ b/src/api/providers/xai.ts
@@ -89,7 +89,7 @@ export class XAIHandler extends BaseProvider implements SingleCompletionHandler
 		try {
 			stream = await this.client.chat.completions.create({
 				model: modelId,
-				max_tokens: modelInfo.maxTokens,
+				...(typeof modelInfo.maxTokens === "number" ? { max_tokens: modelInfo.maxTokens } : {}),
 				temperature: this.options.modelTemperature ?? XAI_DEFAULT_TEMPERATURE,
 				messages: [{ role: "system", content: systemPrompt }, ...convertToOpenAiMessages(messages)],
 				stream: true,
diff --git a/webview-ui/src/components/settings/providers/XAI.tsx b/webview-ui/src/components/settings/providers/XAI.tsx
index 1b584aee99..39e289934e 100644
--- a/webview-ui/src/components/settings/providers/XAI.tsx
+++ b/webview-ui/src/components/settings/providers/XAI.tsx
@@ -166,9 +166,9 @@ export const XAI = ({
 									<VSCodeTextField
 										value={apiConfiguration?.xaiModelContextWindow?.toString() || ""}
 										onInput={handleInputChange("xaiModelContextWindow", (e) => {
-											const target = e.target as HTMLInputElement
-											const value = target.value
-											return value ? parseInt(value, 10) : undefined
+											const v = (e.target as HTMLInputElement).value.trim()
+											const n = Number(v)
+											return Number.isFinite(n) && n > 0 ? Math.floor(n) : undefined
 										})}
 										placeholder="e.g., 256000"
 										className="w-full mt-4">
diff --git a/webview-ui/src/components/ui/hooks/useSelectedModel.ts b/webview-ui/src/components/ui/hooks/useSelectedModel.ts
index d4cd9275c8..1ef1a1f079 100644
--- a/webview-ui/src/components/ui/hooks/useSelectedModel.ts
+++ b/webview-ui/src/components/ui/hooks/useSelectedModel.ts
@@ -184,10 +184,11 @@ function getSelectedModel({
 			const id = apiConfiguration.apiModelId ?? xaiDefaultModelId
 			const dynamicInfo = routerModels.xai?.[id]
 			if (dynamicInfo) {
-				// If router-provided model lacks contextWindow, apply manual override when provided
+				// If router-provided contextWindow is missing or invalid (<= 0), apply manual override when provided
 				const overrideCw = apiConfiguration.xaiModelContextWindow
 				const info =
-					dynamicInfo.contextWindow === undefined && typeof overrideCw === "number"
+					!(typeof dynamicInfo.contextWindow === "number" && dynamicInfo.contextWindow > 0) &&
+					typeof overrideCw === "number"
 						? { ...dynamicInfo, contextWindow: overrideCw }
 						: dynamicInfo
 				return { id, info }