Fix build_software tool stuck in planning mode loop

The builder would get stuck when the LLM returned JSON specs or planning
text instead of tool calls. The loop would continue for all iterations
without making progress, eventually timing out.

Changes:
- Make initial prompt directive: "Use write_file NOW" instead of passive
  "Start by creating the project structure"
- Add consecutive_text_responses counter to detect stuck state
- Fail fast after 2 consecutive text-only responses with clear error
- Send strong nudge on first text response: "STOP. Call write_file..."
- Reset counter once tools have been executed (completion phase)

Co-Authored-By: Claude Opus 4.5 <[email protected]>

src/tools/builder/core.rs

@@ -532,9 +532,12 @@ Create alongside the .wasm file to grant capabilities:
             .messages
             .push(ChatMessage::system(self.build_system_prompt(requirement)));
 
-        // Add initial user message
+        // Add initial user message - directive to force immediate tool use
         reason_ctx.messages.push(ChatMessage::user(format!(
-            "Build the {} in directory: {}\n\nRequirements:\n- {}\n\nStart by creating the project structure.",
+            "Build the {} in directory: {}\n\n\
+             Requirements:\n- {}\n\n\
+             IMPORTANT: Use the write_file tool NOW to create Cargo.toml. \
+             Do not explain, plan, or output JSON—immediately call write_file.",
             requirement.name,
             project_dir.display(),
             requirement.description
@@ -551,6 +554,7 @@ Create alongside the .wasm file to grant capabilities:
         let mut current_phase = BuildPhase::Scaffolding;
         let mut last_error: Option<String> = None;
         let mut tools_executed = false;
+        let mut consecutive_text_responses = 0;
 
         loop {
             iteration += 1;
@@ -593,27 +597,65 @@ Create alongside the .wasm file to grant capabilities:
 
             match result {
                 RespondResult::Text(response) => {
-                    // If no tools have been executed, prompt for tool use
-                    if !tools_executed && iteration < 3 {
+                    reason_ctx.messages.push(ChatMessage::assistant(&response));
+
+                    // If tools haven't been executed yet, we're stuck in planning mode
+                    if !tools_executed {
+                        consecutive_text_responses += 1;
+
+                        // Fail fast after 2 consecutive text-only responses
+                        if consecutive_text_responses >= 2 {
+                            logs.push(BuildLog {
+                                timestamp: Utc::now(),
+                                phase: BuildPhase::Failed,
+                                message: "Builder stuck in planning mode".into(),
+                                details: Some(format!(
+                                    "LLM returned {} consecutive text responses without calling tools. \
+                                     Try a more specific requirement.",
+                                    consecutive_text_responses
+                                )),
+                            });
+
+                            return Ok(BuildResult {
+                                build_id,
+                                requirement: requirement.clone(),
+                                artifact_path: project_dir.to_path_buf(),
+                                logs,
+                                success: false,
+                                error: Some(
+                                    "LLM not executing tools - stuck in planning mode".into(),
+                                ),
+                                started_at,
+                                completed_at: Utc::now(),
+                                iterations: iteration,
+                                validation_warnings: Vec::new(),
+                                tests_passed: 0,
+                                tests_failed: 0,
+                                registered: false,
+                            });
+                        }
+
                         tracing::debug!(
-                            "Builder: no tools executed yet (iteration {}), prompting for action",
-                            iteration
+                            "Builder: no tools executed (text response #{}/2), forcing tool use",
+                            consecutive_text_responses
                         );
-                        reason_ctx.messages.push(ChatMessage::assistant(&response));
                         reason_ctx.messages.push(ChatMessage::user(
-                            "Please use the available tools to implement this. Start by creating the necessary files.",
+                            "STOP. Do NOT output text, JSON specs, or explanations. \
+                             Call the write_file tool RIGHT NOW to create Cargo.toml. \
+                             Just call the tool—no commentary.",
                         ));
                         continue;
                     }
 
-                    reason_ctx.messages.push(ChatMessage::assistant(&response));
+                    // Reset counter when tools have been executed (we're in completion phase)
+                    consecutive_text_responses = 0;
 
                     // Check for completion signals
                     let response_lower = response.to_lowercase();
                     if response_lower.contains("build complete")
                         || response_lower.contains("successfully built")
                         || response_lower.contains("all tests pass")
-                        || (tools_executed && response_lower.contains("complete"))
+                        || response_lower.contains("complete")
                     {
                         logs.push(BuildLog {
                             timestamp: Utc::now(),