diff --git a/packages/client/src/abort-signal.ts b/packages/client/src/abort-signal.ts
new file mode 100644
index 00000000..a76c0434
--- /dev/null
+++ b/packages/client/src/abort-signal.ts
@@ -0,0 +1,12 @@
+// React Native's AbortSignal polyfill (abort-controller@3) has neither
+// throwIfAborted() nor reason, so feature-detect before relying on them.
+export const throwIfAborted = (signal: AbortSignal | undefined) => {
+  if (!signal) return;
+  if (typeof signal.throwIfAborted === "function") {
+    signal.throwIfAborted();
+    return;
+  }
+  if (!signal.aborted) return;
+  if (signal.reason !== undefined) throw signal.reason;
+  throw Object.assign(new Error("The operation was aborted."), { name: "AbortError" });
+};
diff --git a/packages/client/src/ai-direct-stream.test.mjs b/packages/client/src/ai-direct-stream.test.mjs
index 90e2c8c2..504b0ddd 100644
--- a/packages/client/src/ai-direct-stream.test.mjs
+++ b/packages/client/src/ai-direct-stream.test.mjs
@@ -65,6 +65,36 @@ describe("direct AI generation client", () => {
  expect(events.some(e=>e.type==="text-delta"&&e.text==="Hello")).toBe(true);expect(paths).toEqual(["/api/v1/ai/generate/prepare"]);expect(calls).toBe(1);
 });
 
+  // React Native's abort-controller@3 polyfill exposes only `aborted` (#629).
+  const legacySignal = (aborted) => ({ aborted, addEventListener() {}, removeEventListener() {} });
+
+  test("streams with a React Native AbortSignal that lacks throwIfAborted", async () => {
+    const client = createEdgeEverClient({
+      directAiGeneration: true,
+      fetch: async () => Response.json({ provider: "openai-compatible", baseUrl: "https://model.example/v1", apiKey: "key", modelId: "model", system: "Summarize", prompt: "Body", maxOutputTokens: 32, resultBoundary: { start: "<r>", end: "</r>" } }),
+      providerFetch: async () => new Response('data: {"choices":[{"delta":{"content":"<r>Hello</r>"}}]}\n\ndata: [DONE]\n\n'),
+    });
+    const events = [];
+    await client.streamAiGeneration(
+      { action: "summarize", title: "Note", contentMarkdown: "Body" },
+      { signal: legacySignal(false), onEvent: (event) => events.push(event) },
+    );
+    expect(events.some((event) => event.type === "text-delta" && event.text === "Hello")).toBe(true);
+  });
+
+  test("rejects an aborted React Native AbortSignal with AbortError before preparing", async () => {
+    let prepared = false;
+    const client = createEdgeEverClient({
+      directAiGeneration: true,
+      fetch: async () => { prepared = true; return new Response("{}", { status: 404 }); },
+    });
+    await expect(client.streamAiGeneration(
+      { action: "summarize", title: "Note", contentMarkdown: "Body" },
+      { signal: legacySignal(true), onEvent() {} },
+    )).rejects.toMatchObject({ name: "AbortError" });
+    expect(prepared).toBe(false);
+  });
+
   test("fails without instance generation when direct prepare is missing", async () => {
     const urls = [];
     const client = createEdgeEverClient({
diff --git a/packages/client/src/companion-direct-stream.ts b/packages/client/src/companion-direct-stream.ts
index 6555e35e..2f51dee5 100644
--- a/packages/client/src/companion-direct-stream.ts
+++ b/packages/client/src/companion-direct-stream.ts
@@ -12,6 +12,7 @@ import type {
 } from "@edgeever/shared";
 import type { ModelMessage } from "ai";
 import { companionFailureDiagnostics, sealCompanionProcess } from "@edgeever/shared";
+import { throwIfAborted } from "./abort-signal";
 import { createClientAiModel } from "./ai-model";
 
 const asRecord = (value: unknown): Record<string, unknown> | null =>
@@ -232,7 +233,7 @@ export const streamDirectCompanion = async (
       abortSignal: options.signal,
     });
     for await (const part of result.fullStream) {
-      options.signal?.throwIfAborted();
+      throwIfAborted(options.signal);
       if (part.type === "error") throw part.error;
       if (part.type !== "text-delta") continue;
       const delta = typeof part.text === "string" ? part.text : "";
diff --git a/packages/client/src/index.ts b/packages/client/src/index.ts
index e261d8f8..e2694572 100644
--- a/packages/client/src/index.ts
+++ b/packages/client/src/index.ts
@@ -2,6 +2,7 @@ import {
   parsePreparedAiGeneration,
   streamDirectAiGeneration,
 } from "./ai-direct-stream";
+import { throwIfAborted } from "./abort-signal";
 
 import { createPluginCapabilities } from './plugin-capabilities';
 import type {
@@ -690,7 +691,7 @@ export const createEdgeEverClient = (options: EdgeEverClientOptions = {}) => {
     payload: unknown,
     streamOptions: { signal?: AbortSignal; onEvent: (event: CompanionEvent) => void },
   ) => {
-    streamOptions.signal?.throwIfAborted();
+    throwIfAborted(streamOptions.signal);
     const { context, response } = await send(preparePath, {
       method: "POST", body: JSON.stringify(payload), signal: streamOptions.signal,
     });
@@ -707,10 +708,10 @@ export const createEdgeEverClient = (options: EdgeEverClientOptions = {}) => {
     prepare: () => Promise<P | null>;
     run: (prepared: P) => Promise<T>;
   }): Promise<T> => {
-    args.signal?.throwIfAborted();
+    throwIfAborted(args.signal);
     const prepared = await args.prepare();
     if (prepared == null) throw directAiUnavailable();
-    args.signal?.throwIfAborted();
+    throwIfAborted(args.signal);
     return args.run(prepared);
   };
 
@@ -1077,7 +1078,7 @@ export const createEdgeEverClient = (options: EdgeEverClientOptions = {}) => {
     },
 
     streamAiGeneration: async (payload: AiGenerateInput, streamOptions: { signal?: AbortSignal; onEvent: (event: AiStreamEvent) => void }) => {
-      streamOptions.signal?.throwIfAborted();
+      throwIfAborted(streamOptions.signal);
       const { context, response } = await send("/api/v1/ai/generate/prepare", {
         method: "POST", body: JSON.stringify(payload), signal: streamOptions.signal,
       });
diff --git a/packages/client/src/infographic-direct.ts b/packages/client/src/infographic-direct.ts
index c3b988c4..ba586fbe 100644
--- a/packages/client/src/infographic-direct.ts
+++ b/packages/client/src/infographic-direct.ts
@@ -1,6 +1,7 @@
 import { isStepCount, tool, ToolLoopAgent, type LanguageModel } from "ai";
 import { z } from "zod";
 import { infographicRequestsTimeline, type InfographicAgentEvent, type InfographicAgentRequest } from "@edgeever/shared";
+import { throwIfAborted } from "./abort-signal";
 
 export const runInfographicAgent = async (args: {
   input: InfographicAgentRequest;
@@ -64,7 +65,7 @@ export const runInfographicAgent = async (args: {
   ];
   const result = await agent.stream({ messages, abortSignal: args.signal });
   for await (const part of result.fullStream) {
-    args.signal.throwIfAborted();
+    throwIfAborted(args.signal);
     if (part.type === "error") throw part.error;
     if (part.type !== "text-delta" || !part.text || !proposed || asked) continue;
     response += part.text;