diff --git a/src/chat-history.ts b/src/chat-history.ts
index 36f98f8..8f27b2f 100644
--- a/src/chat-history.ts
+++ b/src/chat-history.ts
@@ -99,6 +99,7 @@ export async function summarizeHistory(agentDir: string, branch: string): Promis
 			prompt,
 			dir: agentDir,
 			maxTurns: 1,
+			timeoutMs: 30_000,
 			replaceBuiltinTools: true,
 			tools: [],
 			systemPrompt: "You are a concise summarizer. Output only the summary, nothing else.",
diff --git a/src/sdk-types.ts b/src/sdk-types.ts
index 5ab79ca..be049ac 100644
--- a/src/sdk-types.ts
+++ b/src/sdk-types.ts
@@ -145,6 +145,8 @@ export interface QueryOptions {
 	hooks?: GCHooks;
 	maxTurns?: number;
 	abortController?: AbortController;
+	/** Maximum duration of each model turn before the query is aborted; this is not a whole-query timeout. */
+	timeoutMs?: number;
 	sessionId?: string;
 	/** MCP servers to connect to. Merged with manifest `mcp_servers` (these win on key collision). */
 	mcpServers?: Record<string, McpServerConfig>;
diff --git a/src/sdk.ts b/src/sdk.ts
index 55b941c..893391a 100644
--- a/src/sdk.ts
+++ b/src/sdk.ts
@@ -92,6 +92,10 @@ export function query(options: QueryOptions): Query {
 	const collectedMessages: GCMessage[] = [];
 	const ac = options.abortController ?? new AbortController();
 	const costTracker = new CostTracker();
+	let removeAbortForwarder: (() => void) | undefined;
+	const abortQuery = () => {
+		ac.abort();
+	};
 
 	// These are set once the agent is loaded (async init below)
 	let _sessionId = options.sessionId ?? "";
@@ -128,6 +132,11 @@ export function query(options: QueryOptions): Query {
 	// Async initialization + run
 	const runPromise = (async () => {
 		try {
+			if (options.timeoutMs !== undefined &&
+				(!Number.isFinite(options.timeoutMs) || options.timeoutMs <= 0)) {
+				throw new Error("timeoutMs must be a finite number greater than zero");
+			}
+
 		// Validate mutually exclusive options
 		if (options.repo && options.sandbox) {
 			throw new Error("repo and sandbox options are mutually exclusive");
@@ -315,6 +324,21 @@ export function query(options: QueryOptions): Query {
 				...modelOptions,
 			},
 		});
+		const forwardAbort = () => agent.abort();
+		ac.signal.addEventListener("abort", forwardAbort, { once: true });
+		removeAbortForwarder = () => ac.signal.removeEventListener("abort", forwardAbort);
+
+		const promptWithTimeout = async (prompt: string) => {
+			if (ac.signal.aborted) return;
+			const timer = options.timeoutMs === undefined
+				? undefined
+				: setTimeout(abortQuery, options.timeoutMs);
+			try {
+				await otelContext.with(_session.ctx, () => agent.prompt(prompt));
+			} finally {
+				if (timer !== undefined) clearTimeout(timer);
+			}
+		};
 
 		// 9. Subscribe to events and map to GCMessage
 		agent.subscribe((event: AgentEvent) => {
@@ -494,10 +518,42 @@ export function query(options: QueryOptions): Query {
 			}
 		});
 
+		const emitAbortedResponse = () => {
+			pushMsg({
+				type: "assistant",
+				content: "",
+				model: (loaded.model as any).id ?? "unknown",
+				provider: (loaded.model as any).provider ?? "unknown",
+				stopReason: "aborted",
+				usage: {
+					inputTokens: 0,
+					outputTokens: 0,
+					cacheReadTokens: 0,
+					cacheWriteTokens: 0,
+					totalTokens: 0,
+					costUsd: 0,
+				},
+			});
+		};
+		const finishAbortedQuery = () => {
+			emitAbortedResponse();
+			channel.finish();
+		};
+
 		// 10. Send prompt — run inside the session span's context so that
 		// gen_ai.chat and gitagent.tool.execute spans become children of
 		// gitagent.agent.session.
 		if (typeof options.prompt === "string") {
+			if (ac.signal.aborted) {
+				pushMsg({
+					type: "system",
+					subtype: "session_start",
+					content: `Agent ${loaded.manifest.name} initialized`,
+					metadata: { sessionId: _sessionId },
+				});
+				finishAbortedQuery();
+				return;
+			}
 			// Fire pre_query hook before sending to LLM
 			if (hooksConfig?.hooks.pre_query) {
 				const result = await runHooks(hooksConfig.hooks.pre_query, loaded.agentDir, {
@@ -515,12 +571,18 @@ export function query(options: QueryOptions): Query {
 					return;
 				}
 			}
-			await otelContext.with(_session.ctx, () =>
-				agent.prompt(options.prompt as string),
-			);
+			await promptWithTimeout(options.prompt as string);
+			if (ac.signal.aborted) {
+				finishAbortedQuery();
+				return;
+			}
 		} else {
 			// Multi-turn: iterate the async iterable
 			for await (const userMsg of options.prompt) {
+				if (ac.signal.aborted) {
+					finishAbortedQuery();
+					return;
+				}
 				pushMsg({ type: "user", content: userMsg.content });
 				// Fire pre_query hook for each turn
 				if (hooksConfig?.hooks.pre_query) {
@@ -539,9 +601,11 @@ export function query(options: QueryOptions): Query {
 						return;
 					}
 				}
-				await otelContext.with(_session.ctx, () =>
-					agent.prompt(userMsg.content),
-				);
+				await promptWithTimeout(userMsg.content);
+				if (ac.signal.aborted) {
+					finishAbortedQuery();
+					return;
+				}
 			}
 		}
 
@@ -558,6 +622,8 @@ export function query(options: QueryOptions): Query {
 		// Ensure channel finishes even if no agent_end event
 		channel.finish();
 		} finally {
+			removeAbortForwarder?.();
+			removeAbortForwarder = undefined;
 			// Tear down MCP servers on every exit path — success, hook-block
 			// early-return, abort, and error (this finally runs before the
 			// .catch() handler below). cleanup() is idempotent.
@@ -604,7 +670,7 @@ export function query(options: QueryOptions): Query {
 	// Build the Query object (AsyncGenerator + helpers)
 	const generator: Query = {
 		abort() {
-			ac.abort();
+			abortQuery();
 		},
 
 		steer(_message: string) {
diff --git a/test/sdk.test.ts b/test/sdk.test.ts
index a71fcc6..1e4f0cd 100644
--- a/test/sdk.test.ts
+++ b/test/sdk.test.ts
@@ -1,5 +1,8 @@
 import { describe, it, before } from "node:test";
 import assert from "node:assert/strict";
+import { mkdtempSync, rmSync, writeFileSync } from "node:fs";
+import { join } from "node:path";
+import { tmpdir } from "node:os";
 
 // Dynamic imports since the project is ESM
 let query: typeof import("../dist/exports.js").query;
@@ -204,6 +207,65 @@ describe("wrapToolWithProgrammaticHooks()", () => {
 // ── query() error handling ─────────────────────────────────────────────
 
 describe("query()", () => {
+	it("reports invalid timeout values without loading an agent", async () => {
+		const messages: any[] = [];
+		for await (const msg of query({
+			prompt: "hello",
+			dir: "/nonexistent/path",
+			timeoutMs: 0,
+		})) {
+			messages.push(msg);
+		}
+
+		const errorMsg = messages.find((m) => m.type === "system" && m.subtype === "error");
+		assert.match(errorMsg?.content ?? "", /timeoutMs must be a finite number greater than zero/);
+	});
+
+	it("honors an already-aborted controller before starting the model", async () => {
+		const agentDir = mkdtempSync(join(tmpdir(), "gitagent-abort-"));
+		try {
+			writeFileSync(join(agentDir, "agent.yaml"), `spec_version: "1.0"\nname: test\nversion: "1.0.0"\ndescription: test\nmodel:\n  preferred: openai:gpt-4o-mini\n  fallback: []\ntools: []\nruntime:\n  max_turns: 1\n`);
+			const controller = new AbortController();
+			controller.abort();
+			const messages: any[] = [];
+			const drain = (async () => {
+				for await (const msg of query({
+					prompt: "hello",
+					dir: agentDir,
+					abortController: controller,
+					timeoutMs: 100,
+				})) {
+					messages.push(msg);
+				}
+			})();
+			let deadlineTimer: ReturnType<typeof setTimeout>;
+			const deadline = new Promise((_, reject) => {
+				deadlineTimer = setTimeout(
+					() => reject(new Error("aborted query did not settle")),
+					2000,
+				);
+			});
+			try {
+				await Promise.race([drain, deadline]);
+			} finally {
+				clearTimeout(deadlineTimer!);
+			}
+			assert.ok(messages.some((m) => m.type === "system"));
+			const assistantMessages = messages.filter((m) => m.type === "assistant");
+			assert.equal(messages.some((m) => m.type === "delta"), false);
+			assert.equal(assistantMessages.length, 1);
+			assert.equal(assistantMessages[0].stopReason, "aborted");
+			assert.equal(assistantMessages[0].usage.totalTokens, 0);
+			assert.equal(
+				assistantMessages[0].content,
+				"",
+				"a pre-aborted query must not produce model content",
+			);
+		} finally {
+			rmSync(agentDir, { recursive: true, force: true });
+		}
+	});
+
 	it("emits error system message when agent dir is invalid", async () => {
 		const messages: any[] = [];
 		for await (const msg of query({