fix(runner): a terminal process result always persists as valid content

src/runner/workflow_state.lua

@@ -1171,12 +1171,27 @@ function methods:handle_process_exit(pid, success, result)
         }
     })
 
+    -- A process can die with any value the runtime hands back — a raw error,
+    -- userdata, a coroutine. The node.result row must always carry persistable
+    -- content: a value that binds SQL NULL poisons the whole completion batch
+    -- and strands the run, so anything that is not plain data persists as its
+    -- string form.
+    local result_content = result
+    local content_kind = type(result_content)
+    if content_kind ~= "string" and content_kind ~= "number"
+        and content_kind ~= "boolean" and content_kind ~= "table" then
+        result_content = result_content ~= nil and tostring(result_content) or nil
+    end
+    if result_content == nil then
+        result_content = success and "Completed" or "Failed"
+    end
+
     table.insert(self.queued_commands, {
         type = consts.COMMAND_TYPES.CREATE_DATA,
         payload = {
             data_id = result_data_id,
             data_type = consts.DATA_TYPE.NODE_RESULT,
-            content = result or (success and "Completed" or "Failed"),
+            content = result_content,
             node_id = exited_node_id,
             discriminator = discriminator
         }

src/runner/workflow_state_test.lua

@@ -837,6 +837,48 @@ local function define_tests()
 
                 test.is_nil(exit_info)
             end)
+
+            -- A process can die with a raw error value (userdata, function —
+            -- anything the runtime hands back). The queued node.result must
+            -- always carry persistable, non-nil content: a row that binds SQL
+            -- NULL poisons the whole completion batch and strands the run.
+            it("persists a non-encodable terminal result as its string form", function()
+                local ws = workflow_state.new(test_ctx.dataflow_id) :: any
+                ws.nodes["node-1"] = { status = consts.STATUS.RUNNING, type = "test_node" }
+                ws:track_process("node-1", "pid-123")
+
+                local weird = coroutine.create(function() end)
+                local exit_info = ws:handle_process_exit("pid-123", false, weird) :: any
+                test.not_nil(exit_info)
+
+                local content = nil
+                for _, cmd in ipairs(ws.queued_commands) do
+                    local p = (cmd :: any).payload or {}
+                    if p.data_type == consts.DATA_TYPE.NODE_RESULT then content = p.content end
+                end
+                test.not_nil(content)
+                test.eq(type(content), "string")
+            end)
+
+            it("persists a table result whose values cannot encode as its string form", function()
+                local ws = workflow_state.new(test_ctx.dataflow_id) :: any
+                ws.nodes["node-1"] = { status = consts.STATUS.RUNNING, type = "test_node" }
+                ws:track_process("node-1", "pid-123")
+
+                local poison = { message = "boom", raw = coroutine.create(function() end) }
+                local exit_info = ws:handle_process_exit("pid-123", false, poison) :: any
+                test.not_nil(exit_info)
+
+                local content = nil
+                for _, cmd in ipairs(ws.queued_commands) do
+                    local p = (cmd :: any).payload or {}
+                    if p.data_type == consts.DATA_TYPE.NODE_RESULT then content = p.content end
+                end
+                test.not_nil(content)
+                local encoded, encode_err = json.encode(content)
+                test.is_nil(encode_err)
+                test.not_nil(encoded)
+            end)
         end)
 
         describe("Yield Tracking", function()