diff --git a/src/handler-dispatcher.test.ts b/src/handler-dispatcher.test.ts
index 95833d2..2559d98 100644
--- a/src/handler-dispatcher.test.ts
+++ b/src/handler-dispatcher.test.ts
@@ -113,6 +113,18 @@ describe("HandlerDispatcher", () => {
 			expect(coder.getCoderUserByGitHubId).toHaveBeenCalledWith(67890);
 		});
 
+		test("resolves coder user from sender (assigner), not issue author", async () => {
+			// senderId represents the person who assigned the bot, not the issue author
+			const ctx = {
+				...createTaskContext,
+				senderLogin: "org-maintainer",
+				senderId: 99999,
+			};
+			const result = makeDispatchedResult("create_task", ctx);
+			await dispatcher.dispatch(result);
+			expect(coder.getCoderUserByGitHubId).toHaveBeenCalledWith(99999);
+		});
+
 		test("creates a task and returns ActionOutputs", async () => {
 			coder.getTask.mockResolvedValue(null);
 			coder.createTask.mockResolvedValue(mockTask);
diff --git a/src/handlers/create-task.test.ts b/src/handlers/create-task.test.ts
index f1f558a..02ae8f5 100644
--- a/src/handlers/create-task.test.ts
+++ b/src/handlers/create-task.test.ts
@@ -80,6 +80,63 @@ describe("CreateTaskHandler", () => {
 		expect(coder.createTask).not.toHaveBeenCalled();
 	});
 
+	// Permission check must use the sender (assigner), not the issue author.
+	// This covers the case where an external user without write access creates
+	// the issue and a maintainer with write access assigns the bot.
+	test("checks permission for senderLogin (the assigner)", async () => {
+		github.checkActorPermission.mockResolvedValue(true);
+		coder.getTask.mockResolvedValue(null);
+		coder.createTask.mockResolvedValue(mockTask);
+
+		const ctx = {
+			...issueContext,
+			senderLogin: "maintainer-who-assigned",
+		};
+		const handler = new CreateTaskHandler(
+			coder,
+			github as unknown as import("../github-client").GitHubClient,
+			baseInputs,
+			ctx,
+			logger,
+		);
+		await handler.run();
+
+		expect(github.checkActorPermission).toHaveBeenCalledWith(
+			ctx.owner,
+			ctx.repo,
+			"maintainer-who-assigned",
+		);
+	});
+
+	test("creates task when assigner has write access regardless of issue author", async () => {
+		github.checkActorPermission.mockResolvedValue(true);
+		coder.getTask.mockResolvedValue(null);
+		coder.createTask.mockResolvedValue(mockTask);
+
+		// senderLogin is the maintainer who assigned the bot, not the issue author
+		const ctx = {
+			...issueContext,
+			senderLogin: "org-maintainer",
+		};
+		const handler = new CreateTaskHandler(
+			coder,
+			github as unknown as import("../github-client").GitHubClient,
+			baseInputs,
+			ctx,
+			logger,
+		);
+		const result = await handler.run();
+
+		expect(result.skipped).toBe(false);
+		expect(coder.createTask).toHaveBeenCalledTimes(1);
+		// Verify permission was checked for the assigner, not anyone else
+		expect(github.checkActorPermission).toHaveBeenCalledWith(
+			"xmtp",
+			"libxmtp",
+			"org-maintainer",
+		);
+	});
+
 	// AC #4: Issue URL appended to prompt
 	test("appends issue URL to prompt", async () => {
 		github.checkActorPermission.mockResolvedValue(true);
diff --git a/src/webhook-router.test.ts b/src/webhook-router.test.ts
index 26f24ce..b554309 100644
--- a/src/webhook-router.test.ts
+++ b/src/webhook-router.test.ts
@@ -75,6 +75,29 @@ describe("WebhookRouter", () => {
 		expect(ctx.senderId).toBe(65710);
 	});
 
+	test("issues.assigned extracts senderLogin from sender, not issue author", async () => {
+		// Simulate: external user created the issue, maintainer assigned the bot
+		const payload = {
+			...issuesAssigned,
+			issue: {
+				...issuesAssigned.issue,
+				user: { login: "external-user", id: 11111 },
+			},
+			sender: { login: "org-maintainer", id: 22222 },
+		};
+		const result = await router.handleWebhook(
+			"issues",
+			"delivery-001b",
+			payload,
+		);
+
+		expect(result.dispatched).toBe(true);
+		if (!result.dispatched) throw new Error("expected dispatched");
+		const ctx = result.context as CreateTaskContext;
+		expect(ctx.senderLogin).toBe("org-maintainer");
+		expect(ctx.senderId).toBe(22222);
+	});
+
 	test("issues.assigned with non-matching assignee login → skipped", async () => {
 		const payload = {
 			...issuesAssigned,