diff --git a/coworker/server/app.py b/coworker/server/app.py
index 3b054945..c9fdaa48 100644
--- a/coworker/server/app.py
+++ b/coworker/server/app.py
@@ -445,14 +445,21 @@ def install_persona(body: dict) -> dict[str, Any]:
                         "error": "gallery requires cloud sign-in (or the cloud is unreachable)",
                     }
                 markdown = manifest.get("manifest_markdown", "")
-                digest = "sha256:" + hashlib.sha256(markdown.encode()).hexdigest()
+                digest = (
+                    "sha256:" + hashlib.sha256(markdown.encode("utf-8")).hexdigest()
+                )
                 if (
                     manifest.get("manifest_hash")
                     and manifest["manifest_hash"] != digest
                 ):
                     return {"ok": False, "error": "manifest hash mismatch"}
                 with tempfile.TemporaryDirectory() as td:
-                    (Path(td) / f"{slug}.md").write_text(markdown)
+                    # UTF-8 explicitly: the hash above and `load_manifest_file` both
+                    # treat this markdown as UTF-8, so the file between them must match.
+                    # Defaulting to the locale encoding breaks on Windows (cp1252),
+                    # where CJK/emoji fail to encode and an em-dash writes as a byte the
+                    # UTF-8 read then rejects.
+                    (Path(td) / f"{slug}.md").write_text(markdown, encoding="utf-8")
                     summaries = reg.install_from_dir(td)
                 cloud.gallery_install_event(manager.secrets, load_config(), slug)
             else:
diff --git a/tests/test_cloud_server.py b/tests/test_cloud_server.py
index 12f33e7d..29a9aff7 100644
--- a/tests/test_cloud_server.py
+++ b/tests/test_cloud_server.py
@@ -174,6 +174,36 @@ def test_gallery_install_runs_consent_flow(client, monkeypatch):
     assert events == ["sales"]  # install event fired
 
 
+NON_ASCII_MANIFEST = """---
+id: sales
+name: Sales Coworker — 销售
+icon: chart
+tagline: It’s a “quality” pitch — 你好
+family: knowledge
+workspace: deliverable
+tools: [files, search, todo]
+description: d
+---
+You are the Sales Coworker. \U0001f680"""
+
+
+def test_gallery_install_handles_non_ascii_manifest(client, monkeypatch):
+    """Gallery copy carries em-dashes, curly quotes, CJK and emoji.
+
+    The install path hashes the markdown as UTF-8 and `personas/manifest.py` reads it
+    back as UTF-8, so the temp file in between must be written as UTF-8 too. Writing it
+    with the locale encoding works on Linux/macOS but not on Windows, where the default
+    is cp1252: CJK and emoji fail to encode outright, while an em-dash silently writes
+    as a single cp1252 byte that the UTF-8 read then rejects.
+    """
+    _stub_gallery(monkeypatch, markdown=NON_ASCII_MANIFEST)
+    body = client.post("/v1/personas/install", json={"gallery_slug": "sales"}).json()
+    assert body["ok"], body
+    installed = {p["id"]: p for p in body["personas"]}
+    assert installed["sales"]["name"] == "Sales Coworker — 销售"
+    assert installed["sales"]["tagline"] == "It’s a “quality” pitch — 你好"
+
+
 def test_gallery_install_rejects_hash_mismatch(client, monkeypatch):
     _stub_gallery(monkeypatch, hash_ok=False)
     body = client.post("/v1/personas/install", json={"gallery_slug": "sales"}).json()