From 93660e6f1d925a0400a495e3352e8d7944fc207a Mon Sep 17 00:00:00 2001
From: Hugo Dutka <hugo@coder.com>
Date: Tue, 24 Feb 2026 10:54:14 +0100
Subject: [PATCH] fix(slack): correct auto-formatting of slack ids

---
 packages/slack/src/message.test.ts | 104 +++++++++++++++++++++++++++++
 packages/slack/src/message.ts      |  19 +++++-
 2 files changed, 121 insertions(+), 2 deletions(-)
 create mode 100644 packages/slack/src/message.test.ts

diff --git a/packages/slack/src/message.test.ts b/packages/slack/src/message.test.ts
new file mode 100644
index 00000000..04ad6f6a
--- /dev/null
+++ b/packages/slack/src/message.test.ts
@@ -0,0 +1,104 @@
+import { describe, expect, test } from "bun:test";
+import { formatMessage } from "./message";
+
+describe("formatMessage", () => {
+  describe("markdown to Slack formatting", () => {
+    test("converts markdown links to Slack format", () => {
+      expect(formatMessage("[click here](https://example.com)")).toBe(
+        "<https://example.com|click here>"
+      );
+    });
+
+    test("converts double-star bold to single-star bold", () => {
+      expect(formatMessage("**hello**")).toBe("*hello*");
+    });
+  });
+
+  describe("user ID mention wrapping", () => {
+    test("wraps @-prefixed Slack user IDs", () => {
+      expect(formatMessage("@U02UD2WE3HA")).toBe("<@U02UD2WE3HA>");
+    });
+
+    test("wraps bare Slack user IDs", () => {
+      expect(formatMessage("user U02UD2WE3HA said")).toBe(
+        "user <@U02UD2WE3HA> said"
+      );
+    });
+
+    test("wraps workspace IDs starting with W", () => {
+      expect(formatMessage("@W01AB2CD3EF")).toBe("<@W01AB2CD3EF>");
+    });
+
+    test("does not double-wrap already bracketed IDs", () => {
+      expect(formatMessage("<@U02UD2WE3HA>")).toBe("<@U02UD2WE3HA>");
+    });
+
+    test("removes brackets from non-ID @handles", () => {
+      expect(formatMessage("<@john.doe>")).toBe("@john.doe");
+    });
+  });
+
+  describe("false-positive prevention", () => {
+    test("does not match pure-alpha words like WORKSPACE", () => {
+      const input = "CODER_WORKSPACE_IS_PREBUILD_CLAIM=true";
+      expect(formatMessage(input)).toBe(input);
+    });
+
+    test("does not match UPPERCASE without digits", () => {
+      expect(formatMessage("UNDEFINED")).toBe("UNDEFINED");
+      expect(formatMessage("WORKSPACEID")).toBe("WORKSPACEID");
+    });
+
+    test("does not match short IDs", () => {
+      expect(formatMessage("U1234")).toBe("U1234");
+    });
+  });
+
+  describe("code block preservation", () => {
+    test("does not format IDs inside inline code", () => {
+      const input = "`U02UD2WE3HA`";
+      expect(formatMessage(input)).toBe(input);
+    });
+
+    test("does not format IDs inside code blocks", () => {
+      const input = "```\nU02UD2WE3HA\n```";
+      expect(formatMessage(input)).toBe(input);
+    });
+
+    test("formats IDs outside code but preserves code content", () => {
+      const input = "user U02UD2WE3HA said `U02UD2WE3HA`";
+      expect(formatMessage(input)).toBe(
+        "user <@U02UD2WE3HA> said `U02UD2WE3HA`"
+      );
+    });
+
+    test("preserves markdown links inside code blocks", () => {
+      const input = "```\n[text](url)\n```";
+      expect(formatMessage(input)).toBe(input);
+    });
+
+    test("preserves bold syntax inside inline code", () => {
+      const input = "`**not bold**`";
+      expect(formatMessage(input)).toBe(input);
+    });
+
+    test("handles multiple code blocks", () => {
+      const input = "`U02UD2WE3HA` and U02UD2WE3HA and ```U02UD2WE3HA```";
+      expect(formatMessage(input)).toBe(
+        "`U02UD2WE3HA` and <@U02UD2WE3HA> and ```U02UD2WE3HA```"
+      );
+    });
+
+    test("does not format IDs inside code blocks with more than 3 backticks", () => {
+      const input = "````\nU02UD2WE3HA\n````";
+      expect(formatMessage(input)).toBe(input);
+    });
+  });
+
+  describe("truncation", () => {
+    test("truncates text longer than 3000 characters", () => {
+      const input = "a".repeat(4000);
+      expect(formatMessage(input).length).toBe(3000);
+    });
+  });
+});
diff --git a/packages/slack/src/message.ts b/packages/slack/src/message.ts
index 0a278d1a..19d8d0e1 100644
--- a/packages/slack/src/message.ts
+++ b/packages/slack/src/message.ts
@@ -30,6 +30,14 @@ export function formatMessage(text: string): string {
     text = text.slice(0, maxLength);
   }
 
+  // Preserve code blocks and inline code from formatting
+  const preserved: string[] = [];
+  const placeholder = (i: number) => `\x00CODE${i}\x00`;
+  text = text.replace(/```[\s\S]*?```|`[^`]+`/g, (match) => {
+    preserved.push(match);
+    return placeholder(preserved.length - 1);
+  });
+
   // Manual formatting fixes for Slack compatibility
   // Convert markdown links [text](url) to Slack format <url|text>
   text = text.replace(/\[([^\]]+)\]\(([^)]+)\)/g, "<$2|$1>");
@@ -39,15 +47,17 @@ export function formatMessage(text: string): string {
 
   // Replace non-bracketed user IDs with Slack format <@user_id>
   // Only wrap when not already inside angle brackets
+  // Require at least one digit to avoid matching pure-alpha words like WORKSPACE
   text = text.replace(
-    /(?<!<)@(U|W)[A-Z0-9]{8,}(?!>)/g,
+    /(?<!<)@(?:U|W)(?=[A-Z0-9]*\d)[A-Z0-9]{8,}(?!>)/g,
     (match) => `<${match}>`
   );
 
   // Also handle bare user IDs that start with U or W (LLMs often omit @ and <>)
   // Ensure we don't match within a larger alphanumeric token and avoid already bracketed forms
+  // Require at least one digit to avoid matching pure-alpha words like WORKSPACE
   text = text.replace(
-    /(^|[^A-Z0-9<@])((?:U|W)[A-Z0-9]{8,})(?![A-Z0-9>])/g,
+    /(^|[^A-Z0-9<@])((?:U|W)(?=[A-Z0-9]*\d)[A-Z0-9]{8,})(?![A-Z0-9>])/g,
     (m, prefix, id) => `${prefix}<@${id}>`
   );
 
@@ -56,6 +66,11 @@ export function formatMessage(text: string): string {
     /^[UW][A-Z0-9]{8,}$/.test(u) ? m : `@${u}`
   );
 
+  // Restore preserved code blocks
+  for (let i = 0; i < preserved.length; i++) {
+    text = text.replace(placeholder(i), preserved[i] ?? "");
+  }
+
   return text;
 }