1 files changed, 31 insertions, 7 deletions

diff --git a/src/Agent.Core/Runtime/PlannerService.cs b/src/Agent.Core/Runtime/PlannerService.cs
index 3591259..756cc41 100644
--- a/src/Agent.Core/Runtime/PlannerService.cs
+++ b/src/Agent.Core/Runtime/PlannerService.cs
@@ -31,12 +31,13 @@ public sealed class PlannerService(IOllamaClient ollama, AgentRuntimeSettings se
 
         var messages = new List<OllamaMessage>
         {
-            new("system", FixedPrompt.Load()),
-            new("system", _settings.UserSystemPrompt),
+            // Planning has a dedicated read-only contract. Execution prompts contain instructions
+            // to inspect files and call tools, so mixing them here creates contradictory system
+            // instructions and causes models to execute narratively instead of returning a graph.
+            new("system", BuildPlanningInstruction()),
             new("system", $"Respond in locale: {_settings.Locale}."),
             new("system", ComposeSkillCatalog(_settings.Skills)),
             new("system", _settings.SandboxCapabilitySummary),
-            new("system", BuildPlanningInstruction()),
             new("user", request, images)
         };
 
@@ -58,11 +59,9 @@ public sealed class PlannerService(IOllamaClient ollama, AgentRuntimeSettings se
 
         var messages = new List<OllamaMessage>
         {
-            new("system", FixedPrompt.Load()),
-            new("system", _settings.UserSystemPrompt),
+            new("system", BuildReplanInstruction(existing, replanReason)),
             new("system", $"Respond in locale: {_settings.Locale}."),
             new("system", _settings.SandboxCapabilitySummary),
-            new("system", BuildReplanInstruction(existing, replanReason)),
             new("user", request)
         };
 
@@ -74,6 +73,7 @@ public sealed class PlannerService(IOllamaClient ollama, AgentRuntimeSettings se
 
     private TaskGraph BuildTaskGraph(PlanResult plan, string originalRequest)
     {
+        ValidatePlanStructure(plan);
         var graph = new TaskGraph(_settings.MaxTasks);
         var idMap = new List<Guid>();
 
@@ -105,6 +105,7 @@ public sealed class PlannerService(IOllamaClient ollama, AgentRuntimeSettings se
 
     private TaskGraph RebuildTaskGraph(TaskGraph existing, PlanResult plan, string originalRequest)
     {
+        ValidatePlanStructure(plan);
         PlannerTask[] completed = existing.Tasks.Where(static t => t.State == PlannerTaskState.Completed).ToArray();
         var completedByDescription = completed.GroupBy(static t => t.Description, StringComparer.Ordinal)
             .ToDictionary(static group => group.Key, static group => group.First(), StringComparer.Ordinal);
@@ -182,6 +183,29 @@ public sealed class PlannerService(IOllamaClient ollama, AgentRuntimeSettings se
         return tools;
     }
 
+    private static void ValidatePlanStructure(PlanResult plan)
+    {
+        for (int index = 0; index < plan.Tasks.Count; index++)
+        {
+            PlannedTask task = plan.Tasks[index];
+            if (!task.RequiredTools.Contains("file_edit", StringComparer.Ordinal) ||
+                !task.RequiredTools.Contains("process_run", StringComparer.Ordinal)) continue;
+
+            var pending = new Stack<int>(task.Dependencies);
+            var visited = new HashSet<int>();
+            while (pending.TryPop(out int dependency))
+            {
+                if (dependency < 0 || dependency >= index || !visited.Add(dependency)) continue;
+                PlannedTask ancestor = plan.Tasks[dependency];
+                if (ancestor.RequiredTools.Contains("file_edit", StringComparer.Ordinal))
+                    throw new PlannerValidationException(
+                        "A coding implementation-and-verification Task cannot depend on a separate file_edit Task. " +
+                        "Combine the edits, optional corrections, and process verification in one Task requiring file_edit and process_run.");
+                foreach (int parent in ancestor.Dependencies) pending.Push(parent);
+            }
+        }
+    }
+
     private static PlanResult? ParsePlan(string content)
     {
         try
@@ -266,7 +290,7 @@ public sealed class PlannerService(IOllamaClient ollama, AgentRuntimeSettings se
                 {
                     attemptMessages = messages.Concat([
                         new OllamaMessage("system",
-                            "The previous response was not a valid TaskGraph JSON object. Do not call or execute any Tool while planning. " +
+                            $"The previous response was not a valid TaskGraph: {ex.Message} Do not call or execute any Tool while planning. " +
                             "Return only one JSON object that matches the supplied schema, beginning with {\"tasks\":[ and containing no Markdown or commentary.")
                     ]).ToArray();
                 }