diff --git a/tests/test_tui_gateway_server.py b/tests/test_tui_gateway_server.py
index a25d713b80a..24075884acd 100644
--- a/tests/test_tui_gateway_server.py
+++ b/tests/test_tui_gateway_server.py
@@ -219,6 +219,44 @@ def test_tui_verbose_tool_events_omit_details_when_redaction_fails(monkeypatch):
     assert "result_text" not in events[1][2]
 
 
+def test_tool_complete_emits_full_unified_diff(monkeypatch):
+    events: list[tuple[str, str, dict]] = []
+    monkeypatch.setattr(
+        server, "_emit", lambda event_type, sid, payload: events.append((event_type, sid, payload))
+    )
+    monkeypatch.setitem(
+        server._sessions,
+        "diff-test",
+        {"tool_progress_mode": "concise", "tool_started_at": {}, "edit_snapshots": {}},
+    )
+
+    diff = "--- a/x.py\n+++ b/x.py\n@@ -1 +1 @@\n-a = 1\n+a = 2\n"
+    result = json.dumps({"success": True, "diff": diff})
+    server._on_tool_complete("diff-test", "tool-1", "patch", {"mode": "replace", "path": "x.py"}, result)
+
+    assert events and events[0][0] == "tool.complete"
+    payload = events[0][2]
+    # the raw unified diff rides alongside the pretty/capped inline_diff
+    assert payload["diff_unified"] == diff
+    assert "inline_diff" in payload
+
+
+def test_cap_diff_unified_truncates_at_line_boundary():
+    line = "+" + "x" * 63  # 64 bytes per line incl. newline
+    diff = "\n".join([line] * 100)
+
+    capped = server._cap_diff_unified(diff, max_bytes=1000)
+
+    body, _, marker = capped.rpartition("\n")
+    assert marker.startswith("# … diff truncated (")
+    assert marker.endswith(" more bytes)")
+    assert len(body.encode("utf-8")) <= 1000
+    # cut on a line boundary: every surviving line is intact
+    assert all(l == line for l in body.split("\n"))
+    # under the cap → untouched
+    assert server._cap_diff_unified("small", max_bytes=1000) == "small"
+
+
 def test_dispatch_rejects_non_object_request():
     resp = server.dispatch([])
 
diff --git a/tui_gateway/server.py b/tui_gateway/server.py
index 018d2b8b9f4..a67dbe5bfb4 100644
--- a/tui_gateway/server.py
+++ b/tui_gateway/server.py
@@ -1950,6 +1950,28 @@ def _cap_tui_verbose_text(text: str) -> str:
     return f"{label}{tail}"
 
 
+# The FULL raw unified diff shipped on file-edit tool.complete (`diff_unified`,
+# for clients with a native diff renderer — ui-opentui). Unlike the verbose
+# trail above this is rendered COLLAPSED by default and only on edit tools, so
+# it gets a far larger budget; 512KB is still a hard ceiling so a runaway
+# multi-megabyte edit can't flood the pipe.
+_DIFF_UNIFIED_MAX_BYTES = 512 * 1024
+
+
+def _cap_diff_unified(diff: str, max_bytes: int = _DIFF_UNIFIED_MAX_BYTES) -> str:
+    raw = diff.encode("utf-8")
+    if len(raw) <= max_bytes:
+        return diff
+    head = raw[:max_bytes].decode("utf-8", errors="ignore")
+    # Truncate at a line boundary so the surviving diff stays parseable, then
+    # append an honest marker line (never send more than the cap + marker).
+    cut = head.rfind("\n")
+    if cut > 0:
+        head = head[:cut]
+    omitted = len(raw) - len(head.encode("utf-8"))
+    return f"{head}\n# … diff truncated ({omitted} more bytes)"
+
+
 def _redact_tui_verbose_text(text: str) -> str:
     try:
         from agent.redact import redact_sensitive_text
@@ -2096,7 +2118,23 @@ def _on_tool_complete(sid: str, tool_call_id: str, name: str, args: dict, result
             payload["inline_diff"] = "\n".join(rendered)
     except Exception:
         pass
-    if _tool_progress_enabled(sid) or payload.get("inline_diff"):
+    # Alongside the pretty-rendered/capped `inline_diff` (Ink consumes that), ship
+    # the RAW unified diff for clients with a native diff renderer (ui-opentui's
+    # file-tool view). Capped at _DIFF_UNIFIED_MAX_BYTES with an honest marker.
+    try:
+        from agent.display import extract_edit_diff
+
+        diff_unified = extract_edit_diff(
+            name,
+            result,
+            function_args=args,
+            snapshot=snapshot,
+        )
+        if diff_unified:
+            payload["diff_unified"] = _cap_diff_unified(diff_unified)
+    except Exception:
+        pass
+    if _tool_progress_enabled(sid) or payload.get("inline_diff") or payload.get("diff_unified"):
         _emit("tool.complete", sid, payload)