From f881f086bb75efb171de0372951bf9913e3e2668 Mon Sep 17 00:00:00 2001
From: Vincent Koc <vincentkoc@ieee.org>
Date: Mon, 13 Apr 2026 16:05:50 +0100
Subject: [PATCH] fix(line): make webhook replay retries explicit

---
 extensions/line/src/bot-handlers.test.ts | 35 ++++++++++++++++++++----
 extensions/line/src/bot-handlers.ts      | 13 ++++++++-
 2 files changed, 41 insertions(+), 7 deletions(-)

diff --git a/extensions/line/src/bot-handlers.test.ts b/extensions/line/src/bot-handlers.test.ts
index b9122666d9a..71a0221f537 100644
--- a/extensions/line/src/bot-handlers.test.ts
+++ b/extensions/line/src/bot-handlers.test.ts
@@ -237,6 +237,7 @@ vi.mock("./bot-message-context.js", () => ({
 
 let handleLineWebhookEvents: typeof import("./bot-handlers.js").handleLineWebhookEvents;
 let createLineWebhookReplayCache: typeof import("./bot-handlers.js").createLineWebhookReplayCache;
+let LineRetryableWebhookError: typeof import("./bot-handlers.js").LineRetryableWebhookError;
 type LineWebhookContext = Parameters<typeof import("./bot-handlers.js").handleLineWebhookEvents>[1];
 
 const createRuntime = () => ({ log: vi.fn(), error: vi.fn(), exit: vi.fn() });
@@ -367,7 +368,8 @@ async function startInflightReplayDuplicate(params: {
 
 describe("handleLineWebhookEvents", () => {
   beforeAll(async () => {
-    ({ handleLineWebhookEvents, createLineWebhookReplayCache } = await import("./bot-handlers.js"));
+    ({ handleLineWebhookEvents, createLineWebhookReplayCache, LineRetryableWebhookError } =
+      await import("./bot-handlers.js"));
   });
 
   beforeEach(() => {
@@ -733,7 +735,7 @@ describe("handleLineWebhookEvents", () => {
     expect(processMessage).toHaveBeenCalledTimes(1);
   });
 
-  it("mirrors in-flight replay failures so concurrent duplicates also fail", async () => {
+  it("mirrors in-flight retryable replay failures so concurrent duplicates also fail", async () => {
     let rejectFirst: ((err: Error) => void) | undefined;
     const firstDone = new Promise<void>((_, reject) => {
       rejectFirst = reject;
@@ -751,7 +753,7 @@ describe("handleLineWebhookEvents", () => {
     const { firstRun, secondRun } = await startInflightReplayDuplicate({ event, processMessage });
     const firstFailure = expect(firstRun).rejects.toThrow("transient inflight failure");
     const secondFailure = expect(secondRun).rejects.toThrow("transient inflight failure");
-    rejectFirst?.(new Error("transient inflight failure"));
+    rejectFirst?.(new LineRetryableWebhookError("transient inflight failure"));
 
     await Promise.all([firstFailure, secondFailure]);
     expect(processMessage).toHaveBeenCalledTimes(1);
@@ -1039,7 +1041,7 @@ describe("handleLineWebhookEvents", () => {
     expect(processMessage).not.toHaveBeenCalled();
   });
 
-  it("does not mark replay cache when event processing fails", async () => {
+  it("keeps replay cache committed after a non-retryable event failure", async () => {
     const processMessage = vi
       .fn()
       .mockRejectedValueOnce(new Error("transient failure"))
@@ -1056,10 +1058,31 @@ describe("handleLineWebhookEvents", () => {
     await expect(handleLineWebhookEvents([event], context)).rejects.toThrow("transient failure");
     await handleLineWebhookEvents([event], context);
 
-    expect(buildLineMessageContextMock).toHaveBeenCalledTimes(2);
-    expect(processMessage).toHaveBeenCalledTimes(2);
+    expect(buildLineMessageContextMock).toHaveBeenCalledTimes(1);
+    expect(processMessage).toHaveBeenCalledTimes(1);
     expect(context.runtime.error).toHaveBeenCalledWith(
       expect.stringContaining("line: event handler failed: Error: transient failure"),
     );
   });
+
+  it("reopens replay after an explicit retryable event failure", async () => {
+    const processMessage = vi
+      .fn()
+      .mockRejectedValueOnce(new LineRetryableWebhookError("retry me"))
+      .mockResolvedValueOnce(undefined);
+    const event = createReplayMessageEvent({
+      messageId: "m-fail-then-retryable",
+      groupId: "group-retry",
+      userId: "user-retry",
+      webhookEventId: "evt-fail-then-retryable",
+      isRedelivery: false,
+    });
+    const context = createOpenGroupReplayContext(processMessage, createLineWebhookReplayCache());
+
+    await expect(handleLineWebhookEvents([event], context)).rejects.toThrow("retry me");
+    await handleLineWebhookEvents([event], context);
+
+    expect(buildLineMessageContextMock).toHaveBeenCalledTimes(2);
+    expect(processMessage).toHaveBeenCalledTimes(2);
+  });
 });
diff --git a/extensions/line/src/bot-handlers.ts b/extensions/line/src/bot-handlers.ts
index 98917868ab0..df58515b6ff 100644
--- a/extensions/line/src/bot-handlers.ts
+++ b/extensions/line/src/bot-handlers.ts
@@ -87,6 +87,13 @@ const LINE_WEBHOOK_REPLAY_WINDOW_MS = 10 * 60 * 1000;
 const LINE_WEBHOOK_REPLAY_MAX_ENTRIES = 4096;
 export type LineWebhookReplayCache = ClaimableDedupe;
 
+export class LineRetryableWebhookError extends Error {
+  constructor(message: string, options?: ErrorOptions) {
+    super(message, options);
+    this.name = "LineRetryableWebhookError";
+  }
+}
+
 export function createLineWebhookReplayCache(): LineWebhookReplayCache {
   return createClaimableDedupe({
     ttlMs: LINE_WEBHOOK_REPLAY_WINDOW_MS,
@@ -617,7 +624,11 @@ export async function handleLineWebhookEvents(
       }
     } catch (err) {
       if (replayCandidate) {
-        replayCandidate.cache.release(replayCandidate.key, { error: err });
+        if (err instanceof LineRetryableWebhookError) {
+          replayCandidate.cache.release(replayCandidate.key, { error: err });
+        } else {
+          await replayCandidate.cache.commit(replayCandidate.key);
+        }
       }
       context.runtime.error?.(danger(`line: event handler failed: ${String(err)}`));
       firstError ??= err;