From 32453d3946a868faea75f891008a6cf3eacfb7ec Mon Sep 17 00:00:00 2001
From: Cursor Agent <cursoragent@cursor.com>
Date: Fri, 18 Sep 2026 06:20:52 +0000
Subject: [PATCH] Skip non-object rows when decoding session message JSON

decode_messages_json only skipped null shared_ptrs, so JSON null,
strings, numbers, and arrays in a session history became empty-role
Message rows on TUI restore. Skip any element that is not a JSON
object, matching tool_trace_from_json.

Co-authored-by: Tyler Reckart <tylerreckart@users.noreply.github.com>
---
 CHANGELOG.md                 |  7 +++++++
 CMakeLists.txt               | 13 ++++++++++++
 src/message_codec.cpp        |  9 ++++++++-
 tests/test_message_codec.cpp | 39 ++++++++++++++++++++++++++++++++++++
 4 files changed, 67 insertions(+), 1 deletion(-)
 create mode 100644 tests/test_message_codec.cpp

diff --git a/CHANGELOG.md b/CHANGELOG.md
index dae12b43..af883b7a 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,13 @@ loosely while pre-1.0 (breaking changes can land on minor bumps).
 
 ## [Unreleased]
 
+### Fixed
+- **Session restore skips non-object message rows.** `decode_messages_json`
+  only skipped null `shared_ptr`s, so JSON `null` / strings / numbers /
+  arrays in a session history became empty-`role` `Message` rows on TUI
+  restore. Skip any element that is not a JSON object, matching
+  `tool_trace_from_json`.
+
 ## [0.13.4] — 2026-09-10
 
 ### Fixed
diff --git a/CMakeLists.txt b/CMakeLists.txt
index ee7a9662..508e6fbe 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1145,6 +1145,19 @@ if(INDEX_BUILD_TESTS)
     endif()
     add_test(NAME unit_message_replay_roundtrip COMMAND unit_message_replay_roundtrip)
 
+    # Session JSON message array decode (no OpenTUI).
+    add_executable(unit_message_codec
+        tests/test_message_codec.cpp
+        src/message_codec.cpp
+        src/json.cpp
+    )
+    target_include_directories(unit_message_codec PRIVATE
+        ${CMAKE_SOURCE_DIR}/include
+        ${CMAKE_SOURCE_DIR}/third_party/doctest
+        ${OPENSSL_INCLUDE_DIR}  # message_codec.h → api_client.h → openssl/ssl.h
+    )
+    add_test(NAME unit_message_codec COMMAND unit_message_codec)
+
     # --- Unit tests for the natural-language schedule parser ---
     add_executable(unit_schedule_parser
         tests/test_schedule_parser.cpp
diff --git a/src/message_codec.cpp b/src/message_codec.cpp
index e5c05ac0..57fb87c6 100644
--- a/src/message_codec.cpp
+++ b/src/message_codec.cpp
@@ -66,7 +66,14 @@ std::vector<Message> decode_messages_json(const std::string& json) {
         auto root = json_parse(json);
         if (!root || !root->is_array()) return out;
         for (auto& v : root->as_array()) {
-            if (!v) continue;
+            // get_string() on a non-object is a silent empty default, so a
+            // JSON null / string / number / array would otherwise become a
+            // Message with empty role.  Those rows then go back into the
+            // model view on TUI/session restore and providers reject them.
+            // Skip the same way tool_trace_from_json already skips
+            // non-object trace entries.  Null shared_ptr (sparse arrays)
+            // is the same class of invalid element.
+            if (!v || !v->is_object()) continue;
             Message msg;
             msg.role = v->get_string("role");
             msg.content = v->get_string("content");
diff --git a/tests/test_message_codec.cpp b/tests/test_message_codec.cpp
new file mode 100644
index 00000000..db80d115
--- /dev/null
+++ b/tests/test_message_codec.cpp
@@ -0,0 +1,39 @@
+#define DOCTEST_CONFIG_IMPLEMENT_WITH_MAIN
+#include "doctest.h"
+
+#include "message_codec.h"
+
+using namespace arbiter;
+
+TEST_CASE("decode_messages_json skips JSON null and other non-objects") {
+    const auto restored = decode_messages_json(
+        R"([null,"skip",1,true,[],{"role":"user","content":"keep"},{"role":"assistant","content":"also"}])");
+    REQUIRE(restored.size() == 2);
+    CHECK(restored[0].role == "user");
+    CHECK(restored[0].content == "keep");
+    CHECK(restored[0].thinking.empty());
+    CHECK(restored[0].tool_trace.empty());
+    CHECK(restored[1].role == "assistant");
+    CHECK(restored[1].content == "also");
+}
+
+TEST_CASE("decode_messages_json all-non-object array is empty, not empty-role rows") {
+    const auto restored = decode_messages_json(R"([null, "x", 0])");
+    CHECK(restored.empty());
+}
+
+TEST_CASE("decode_messages_json still round-trips object rows") {
+    Message user;
+    user.role = "user";
+    user.content = "do the thing";
+    Message asst;
+    asst.role = "assistant";
+    asst.content = "done";
+    asst.thinking = "step";
+    const auto back = decode_messages_json(encode_messages_json({user, asst}));
+    REQUIRE(back.size() == 2);
+    CHECK(back[0].role == "user");
+    CHECK(back[0].content == "do the thing");
+    CHECK(back[1].role == "assistant");
+    CHECK(back[1].thinking == "step");
+}