From 6235720c8aee5eb7547f2d7028192cf004d4e66b Mon Sep 17 00:00:00 2001
From: Peter Steinberger <steipete@gmail.com>
Date: Fri, 29 May 2026 08:40:37 -0400
Subject: [PATCH] fix(slack): validate inbound timestamp parsing

---
 .../monitor/message-handler/prepare.test.ts    | 12 ++++++++++++
 .../src/monitor/message-handler/prepare.ts     | 18 ++++++++++++++----
 2 files changed, 26 insertions(+), 4 deletions(-)

diff --git a/extensions/slack/src/monitor/message-handler/prepare.test.ts b/extensions/slack/src/monitor/message-handler/prepare.test.ts
index b0600a5ece2..c56ea897e5b 100644
--- a/extensions/slack/src/monitor/message-handler/prepare.test.ts
+++ b/extensions/slack/src/monitor/message-handler/prepare.test.ts
@@ -707,6 +707,18 @@ describe("slack prepareSlackMessage inbound contract", () => {
     expect(prepared?.ackReactionPromise).toBeNull();
   });
 
+  it("does not coerce malformed Slack timestamps into inbound event times", async () => {
+    const prepared = await prepareWithDefaultCtx(
+      createSlackMessage({
+        ts: "0x10",
+      }),
+    );
+
+    assertPrepared(prepared);
+    expect(prepared.ctxPayload.Timestamp).toBeUndefined();
+    expect(prepared.ctxPayload.MessageSid).toBe("0x10");
+  });
+
   it("primes Slack status reactions when channel replies are message-tool-only", async () => {
     const slackCtx = createInboundSlackCtx({
       cfg: {
diff --git a/extensions/slack/src/monitor/message-handler/prepare.ts b/extensions/slack/src/monitor/message-handler/prepare.ts
index 8c055d3b9f9..6f2debe1500 100644
--- a/extensions/slack/src/monitor/message-handler/prepare.ts
+++ b/extensions/slack/src/monitor/message-handler/prepare.ts
@@ -83,6 +83,7 @@ const SLACK_HISTORY_MEDIA_MAX_ATTACHMENTS = 4;
 const SLACK_HISTORY_MEDIA_MAX_BYTES = 10 * 1024 * 1024;
 const SLACK_HISTORY_MEDIA_IDLE_TIMEOUT_MS = 1_000;
 const SLACK_HISTORY_MEDIA_TOTAL_TIMEOUT_MS = 3_000;
+const SLACK_TIMESTAMP_RE = /^\d+(?:\.\d+)?$/;
 
 function recordString(
   record: Record<string, unknown> | undefined,
@@ -104,6 +105,15 @@ function recordNullableString(
   return normalizeOptionalString(record[key]);
 }
 
+function resolveSlackTimestampMs(ts: string | undefined): number | undefined {
+  const trimmed = ts?.trim();
+  if (!trimmed || !SLACK_TIMESTAMP_RE.test(trimmed)) {
+    return undefined;
+  }
+  const parsed = Number(trimmed);
+  return Number.isFinite(parsed) ? Math.round(parsed * 1000) : undefined;
+}
+
 function mergeSlackAssistantThreadContext(
   primary: Omit<SlackAssistantThreadContext, "updatedAt"> | undefined,
   fallback: Omit<SlackAssistantThreadContext, "updatedAt"> | undefined,
@@ -969,7 +979,7 @@ export async function prepareSlackMessage(params: {
             client: ctx.app.client,
           })
         : null;
-    const timestamp = message.ts ? Math.round(Number(message.ts) * 1000) : undefined;
+    const timestamp = resolveSlackTimestampMs(message.ts);
     const senderName = pendingBody ? await resolveSenderName() : undefined;
     await recordDroppedChannelInboundHistory({
       input: {
@@ -1145,7 +1155,7 @@ export async function prepareSlackMessage(params: {
   const body = formatInboundEnvelope({
     channel: "Slack",
     from: envelopeFrom,
-    timestamp: message.ts ? Math.round(Number(message.ts) * 1000) : undefined,
+    timestamp: resolveSlackTimestampMs(message.ts),
     body: textWithId,
     chatType,
     sender: { name: senderName, id: senderId },
@@ -1238,7 +1248,7 @@ export async function prepareSlackMessage(params: {
     channel: "slack",
     accountId: route.accountId,
     messageId: message.ts,
-    timestamp: message.ts ? Math.round(Number(message.ts) * 1000) : undefined,
+    timestamp: resolveSlackTimestampMs(message.ts),
     from: slackFrom,
     sender: {
       id: senderId,
@@ -1335,7 +1345,7 @@ export async function prepareSlackMessage(params: {
       entry: {
         sender: senderName,
         body: rawBody,
-        timestamp: message.ts ? Math.round(Number(message.ts) * 1000) : undefined,
+        timestamp: resolveSlackTimestampMs(message.ts),
         messageId: message.ts,
       },
     });