Skip non-object rows when decoding session message JSON

CHANGELOG.md

@@ -8,11 +8,11 @@ loosely while pre-1.0 (breaking changes can land on minor bumps).
 ## [Unreleased]
 
 ### Fixed
-- **Lesson search is a literal substring.** `search_lessons` (`GET /v1/lessons?q=`
-  and `/lesson search`) wrapped the query in `LIKE %q%` without escaping `%` /
-  `_`, so those characters acted as SQL wildcards. A search for `100%` matched
-  `1000`, and `foo_bar` matched `fooXbar`. Patterns now escape LIKE
-  metacharacters (`ESCAPE '\'`).
+- **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`.
 - **Unreadable TUI sessions are not empty.** `session_json_is_empty` no
 - **Advise-gate cancel is not a bad bearer.** `POST /v1/advise/gate`
 - **MCP string JSON-RPC ids.** `parse_response` now accepts a decimal-string
@@ -34,6 +34,7 @@ loosely while pre-1.0 (breaking changes can land on minor bumps).
 - **Loop `/kill` wakes the inter-iteration pause.** After each turn,
 - **Memory `tag=` LIKE wildcards are literals.** `/mem entries tag=` and
 - **Dispatch of stored agents past newest-200.** `GET /v1/agents/:id` already
+- **Lesson search is a literal substring.** `search_lessons` (`GET /v1/lessons?q=`
 
 ## [0.13.7] — 2026-09-21
 

CMakeLists.txt

@@ -1146,6 +1146,19 @@ 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

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");

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");
+}