From c3004f87826e4e77aae8037bdaad545f06ee851d Mon Sep 17 00:00:00 2001
From: Qoder-AI <215799558+Qoder-AI@users.noreply.github.com>
Date: Sat, 24 Oct 2026 02:51:50 +0800
Subject: [PATCH 1/2] fix(web): keep export filenames valid when truncated

---
 web/src/v2/thread-export.test.ts | 6 ++++++
 web/src/v2/thread-export.ts      | 3 ++-
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/web/src/v2/thread-export.test.ts b/web/src/v2/thread-export.test.ts
index 0291cd39..5155838e 100644
--- a/web/src/v2/thread-export.test.ts
+++ b/web/src/v2/thread-export.test.ts
@@ -113,6 +113,12 @@ it("merges duplicate public assistant endings and labels pending and withdrawn i
   expect(filename).not.toMatch(/[\\/:*?"<>|\u0000-\u001f]/u);
 });
 
+it("truncates export filenames without splitting Unicode or ending in separators", () => {
+  const prefix = "a".repeat(99);
+  expect(threadExportFilename(`${prefix}😀suffix`, "markdown")).toBe(`conversation-${prefix}😀.md`);
+  expect(threadExportFilename(`${prefix} tail`, "text")).toBe(`conversation-${prefix}.txt`);
+});
+
 it("rejects missing full bodies instead of returning partial history", async () => {
   const get = vi.fn(async (path: string) => {
     if (path.endsWith("second")) throw new Error("body unavailable");
diff --git a/web/src/v2/thread-export.ts b/web/src/v2/thread-export.ts
index 36bed15a..792919a8 100644
--- a/web/src/v2/thread-export.ts
+++ b/web/src/v2/thread-export.ts
@@ -82,6 +82,7 @@ export function formatThreadExport(title: string, messages: ExportMessage[], for
 }
 
 export function threadExportFilename(title: string, format: ThreadExportFormat): string {
-  const name = title.replace(/[\\/:*?"<>|\u0000-\u001f]/gu, "_").trim().replace(/[. ]+$/u, "").slice(0, 100);
+  const clean = title.replace(/[\\/:*?"<>|\u0000-\u001f]/gu, "_").trim().replace(/[. ]+$/u, "");
+  const name = [...clean].slice(0, 100).join("").replace(/[. ]+$/u, "");
   return `conversation-${name || "export"}.${format === "markdown" ? "md" : "txt"}`;
 }

From d55a9cc4cc25c4bdb8a61e2b97c8d12765c908be Mon Sep 17 00:00:00 2001
From: Claude <claude@users.noreply.github.com>
Date: Wed, 28 Oct 2026 01:30:12 +0800
Subject: [PATCH 2/2] fix(web): truncate export filenames on grapheme
 boundaries

The code-point bound could still split a ZWJ emoji family or a combining
sequence into a broken fragment. Segment the title with Intl.Segmenter when
available (ES2023 baseline, code-point fallback otherwise) so the 100-unit
budget counts user-perceived characters and never lands inside one.
Extend the truncation test with a ZWJ family at the boundary.
---
 web/src/v2/thread-export.test.ts |  7 +++++++
 web/src/v2/thread-export.ts      | 20 +++++++++++++++++++-
 2 files changed, 26 insertions(+), 1 deletion(-)

diff --git a/web/src/v2/thread-export.test.ts b/web/src/v2/thread-export.test.ts
index 5155838e..9ecab880 100644
--- a/web/src/v2/thread-export.test.ts
+++ b/web/src/v2/thread-export.test.ts
@@ -119,6 +119,13 @@ it("truncates export filenames without splitting Unicode or ending in separators
   expect(threadExportFilename(`${prefix} tail`, "text")).toBe(`conversation-${prefix}.txt`);
 });
 
+it("keeps ZWJ emoji families whole when truncating export filenames", () => {
+  const family = "👨‍👩‍👧‍👦";
+  const prefix = "a".repeat(99);
+  expect(threadExportFilename(`${prefix}${family}tail`, "markdown")).toBe(`conversation-${prefix}${family}.md`);
+  expect(threadExportFilename(`${prefix}a${family}`, "text")).toBe(`conversation-${prefix}a.txt`);
+});
+
 it("rejects missing full bodies instead of returning partial history", async () => {
   const get = vi.fn(async (path: string) => {
     if (path.endsWith("second")) throw new Error("body unavailable");
diff --git a/web/src/v2/thread-export.ts b/web/src/v2/thread-export.ts
index 792919a8..c02cda78 100644
--- a/web/src/v2/thread-export.ts
+++ b/web/src/v2/thread-export.ts
@@ -81,8 +81,26 @@ export function formatThreadExport(title: string, messages: ExportMessage[], for
   return `${format === "markdown" ? "# " : ""}${heading}\n\n${sections.join("\n\n---\n\n")}\n`;
 }
 
+// Truncate by user-perceived character, not by code point: ZWJ emoji families,
+// skin-tone modifiers and combining marks each count as one grapheme, so the
+// bound can never split them into invalid or unrecognizable fragments. Runtimes
+// without Intl.Segmenter keep the code-point bound as a floor.
+function truncateExportTitleGraphemes(value: string, maxGraphemes: number): string {
+  if (typeof Intl === "undefined" || !("Segmenter" in Intl)) {
+    return [...value].slice(0, maxGraphemes).join("");
+  }
+  let name = "";
+  let count = 0;
+  for (const segment of new Intl.Segmenter(undefined, { granularity: "grapheme" }).segment(value)) {
+    if (count >= maxGraphemes) break;
+    name += segment.segment;
+    count += 1;
+  }
+  return name;
+}
+
 export function threadExportFilename(title: string, format: ThreadExportFormat): string {
   const clean = title.replace(/[\\/:*?"<>|\u0000-\u001f]/gu, "_").trim().replace(/[. ]+$/u, "");
-  const name = [...clean].slice(0, 100).join("").replace(/[. ]+$/u, "");
+  const name = truncateExportTitleGraphemes(clean, 100).replace(/[. ]+$/u, "");
   return `conversation-${name || "export"}.${format === "markdown" ? "md" : "txt"}`;
 }