diff --git a/packages/coding-agent/CHANGELOG.md b/packages/coding-agent/CHANGELOG.md
index 3586ce0b6..a5a03faaa 100644
--- a/packages/coding-agent/CHANGELOG.md
+++ b/packages/coding-agent/CHANGELOG.md
@@ -43,6 +43,7 @@
 
 ### Fixed
 
+- Fixed an uncaught `questions.map is not a function` TUI crash in the ask tool's call renderer when a model double-encoded the `questions` array as a JSON string (a bare string passes a truthy `.length` check but has no `.map`): the renderer now normalizes untrusted call args — parsing double-encoded `questions`, dropping malformed entries/options, and falling back to the "No question provided" frame instead of throwing
 - Fixed model-provider detection for append-only mode, authoritative Vertex endpoint checks, and upstream-routing selection by switching from URL substring checks to catalog host-matching helpers
 - Fixed pasting into the ask tool's "Other (type your own)" text box (and hook input/editor dialogs) on terminals with OSC 5522 enhanced paste (kitty protocol): the enhanced-paste focus routing only targets components exposing a `pasteText` hook, and the dialog wrappers had none, so the payload was stuffed into the main prompt editor hidden behind the dialog. `HookEditorComponent` and `HookInputComponent` now forward `pasteText` to their inner editor/input (pasting also resets the input dialog's timeout countdown like any keystroke).
 - Fixed auto-retry giving up after one attempt ("Provider requested Xms wait, exceeds retry.maxDelayMs") on a usage-limit 429 when every sibling account was only momentarily blocked: the retry delay now waits for the earliest sibling unblock when that comes sooner than the provider's multi-hour retry-after, so the next attempt picks up the recovered account instead of failing fast.
diff --git a/packages/coding-agent/src/tools/ask.ts b/packages/coding-agent/src/tools/ask.ts
index 9230c0c8a..96a3853b6 100644
--- a/packages/coding-agent/src/tools/ask.ts
+++ b/packages/coding-agent/src/tools/ask.ts
@@ -641,6 +641,56 @@ interface AskRenderArgs {
 	}>;
 }
 
+/**
+ * Coerce an untrusted option list (streamed or model-mangled call args) into
+ * well-formed render options. Bare strings become labels; entries without a
+ * string label are dropped.
+ */
+function normalizeRenderOptions(raw: unknown): AskRenderOption[] | undefined {
+	if (!Array.isArray(raw)) return undefined;
+	const out: AskRenderOption[] = [];
+	for (const entry of raw) {
+		if (typeof entry === "string") {
+			out.push({ label: entry });
+			continue;
+		}
+		if (!entry || typeof entry !== "object") continue;
+		const { label, description } = entry as Partial<AskRenderOption>;
+		if (typeof label !== "string") continue;
+		out.push(typeof description === "string" ? { label, description } : { label });
+	}
+	return out;
+}
+
+/**
+ * Coerce untrusted `questions` call args into a renderable array. Models
+ * occasionally double-encode the array as a JSON string — a bare string passes
+ * a truthy `.length` check but has no `.map`, which used to crash the TUI
+ * render loop. Partially streamed args can also be missing fields.
+ */
+function normalizeRenderQuestions(raw: unknown): NonNullable<AskRenderArgs["questions"]> | undefined {
+	if (typeof raw === "string") {
+		try {
+			raw = JSON.parse(raw);
+		} catch {
+			return undefined;
+		}
+	}
+	if (!Array.isArray(raw)) return undefined;
+	const out: NonNullable<AskRenderArgs["questions"]> = [];
+	for (const entry of raw) {
+		if (!entry || typeof entry !== "object") continue;
+		const q = entry as Partial<NonNullable<AskRenderArgs["questions"]>[number]>;
+		out.push({
+			id: typeof q.id === "string" ? q.id : "?",
+			question: typeof q.question === "string" ? q.question : "",
+			options: normalizeRenderOptions(q.options) ?? [],
+			multi: q.multi === true,
+		});
+	}
+	return out;
+}
+
 /** Render a custom free-text answer as a status line plus indented continuation rows. */
 function renderCustomInputLines(uiTheme: Theme, customInput: string): string[] {
 	const lines = customInput.split("\n");
@@ -724,8 +774,10 @@ export const askToolRenderer = {
 			new Markdown(text, 1, 0, mdTheme, accentStyle).render(Math.max(1, width - 3 + 1));
 
 		// Multi-part questions: one divider-labelled section per question.
-		if (args.questions && args.questions.length > 0) {
-			const questions = args.questions;
+		// Call args are untrusted (partially streamed or model-mangled) and a
+		// throw here takes down the whole TUI render loop — normalize first.
+		const questions = normalizeRenderQuestions(args.questions);
+		if (questions && questions.length > 0) {
 			const header = `${label} ${uiTheme.fg("muted", `${questions.length} questions`)}`;
 			return framedBlock(uiTheme, width => {
 				const sections = questions.map(q => {
@@ -742,7 +794,7 @@ export const askToolRenderer = {
 		}
 
 		// Single question
-		if (!args.question) {
+		if (typeof args.question !== "string" || !args.question) {
 			const errorLine = formatErrorMessage("No question provided", uiTheme);
 			return framedBlock(uiTheme, width => ({
 				header: errorLine,
@@ -756,9 +808,9 @@ export const askToolRenderer = {
 		const question = args.question;
 		const meta: string[] = [];
 		if (args.multi) meta.push("multi");
-		if (args.options?.length) meta.push(`options:${args.options.length}`);
+		const questionOptions = normalizeRenderOptions(args.options);
+		if (questionOptions?.length) meta.push(`options:${questionOptions.length}`);
 		const header = `${label}${formatMeta(meta, uiTheme)}`;
-		const questionOptions = args.options;
 		const multi = args.multi;
 		return framedBlock(uiTheme, width => {
 			const bodyLines = md(question, width);
diff --git a/packages/coding-agent/test/tools/ask.test.ts b/packages/coding-agent/test/tools/ask.test.ts
index 832b4b2ae..475c4fb61 100644
--- a/packages/coding-agent/test/tools/ask.test.ts
+++ b/packages/coding-agent/test/tools/ask.test.ts
@@ -1237,3 +1237,59 @@ describe("AskTool option markers", () => {
 		expect(text).not.toContain(theme!.radio.selected);
 	});
 });
+
+describe("askToolRenderer malformed call args", () => {
+	it("renders double-encoded questions string instead of crashing the TUI", async () => {
+		const theme = await getThemeByName("dark");
+		expect(theme).toBeDefined();
+		// Models occasionally JSON-encode the questions array as a string; a bare
+		// string passes a truthy `.length` check but has no `.map` (TUI crash).
+		const doubleEncoded = JSON.stringify([
+			{ id: "q1", question: "Pick one", options: [{ label: "Alpha" }, { label: "Beta" }] },
+		]);
+		const rendered = askToolRenderer.renderCall(
+			{ questions: doubleEncoded } as never,
+			{ expanded: true, isPartial: false },
+			theme!,
+		);
+		const text = stripAnsi(rendered.render(120).join("\n"));
+		expect(text).toContain("[q1]");
+		expect(text).toContain("Pick one");
+		expect(text).toContain("Alpha");
+	});
+
+	it("falls back to the error frame for unparseable questions without throwing", async () => {
+		const theme = await getThemeByName("dark");
+		expect(theme).toBeDefined();
+		for (const questions of ["[{trunc", 42, { 0: { id: "x" } }]) {
+			const rendered = askToolRenderer.renderCall(
+				{ questions } as never,
+				{ expanded: true, isPartial: true },
+				theme!,
+			);
+			const text = stripAnsi(rendered.render(120).join("\n"));
+			expect(text).toContain("No question provided");
+		}
+	});
+
+	it("drops malformed question entries and option items while keeping valid ones", async () => {
+		const theme = await getThemeByName("dark");
+		expect(theme).toBeDefined();
+		const rendered = askToolRenderer.renderCall(
+			{
+				questions: [
+					null,
+					"garbage",
+					{ id: "ok", question: "Real question", options: ["BareString", { label: "Proper" }, { nope: 1 }, 7] },
+				],
+			} as never,
+			{ expanded: true, isPartial: true },
+			theme!,
+		);
+		const text = stripAnsi(rendered.render(120).join("\n"));
+		expect(text).toContain("[ok]");
+		expect(text).toContain("Real question");
+		expect(text).toContain("BareString");
+		expect(text).toContain("Proper");
+	});
+});