fix(agent): detect repeated tool call loops and make max_iterations configurable

Local LLMs often get stuck calling the same tool repeatedly because they
lack the sophistication to synthesize results. The agent loop had no
safeguard — it re-executed whatever the model requested up to 10 times.

Add fingerprint-based loop detection: if the same tool+args combination
repeats 3 consecutive times, break the loop and return the last results.
Also add agents.max_iterations to the config schema so the iteration
limit is user-configurable (default: 10).

src/backends/native/agent.ts

@@ -143,6 +143,13 @@ export class NativeAgent {
       content: m.content,
     }));
 
+    // Track consecutive identical tool call fingerprints to detect loops.
+    // Local LLMs are especially prone to repeatedly requesting the same tool call.
+    let lastFingerprint: string | undefined;
+    let consecutiveRepeats = 0;
+    const maxConsecutiveRepeats = 3;
+    let lastToolResults: string[] = [];
+
     for (let iteration = 0; iteration < this.maxIterations; iteration++) {
       // Build request — cast loopMessages to Message[] because the underlying
       // model client will pass them through to the API which accepts structured content.
@@ -170,6 +177,19 @@ export class NativeAgent {
         return finalContent;
       }
 
+      // Check for repeated tool calls — build a fingerprint from tool names + args
+      const fingerprint = response.toolCalls
+        .map(tc => `${tc.name}:${JSON.stringify(tc.args)}`)
+        .sort()
+        .join('|');
+
+      if (fingerprint === lastFingerprint) {
+        consecutiveRepeats++;
+      } else {
+        consecutiveRepeats = 1;
+        lastFingerprint = fingerprint;
+      }
+
       // Build the assistant message with tool_use content blocks
       const assistantContent: unknown[] = [];
       if (response.content) {
@@ -187,6 +207,7 @@ export class NativeAgent {
 
       // Execute each tool call and collect results
       const toolResultBlocks: unknown[] = [];
+      lastToolResults = [];
       for (const tc of response.toolCalls) {
         const internalName = this.toolRegistry!.getByApiName(tc.name)?.name ?? tc.name;
         this.onToolUse?.({ type: 'start', tool: internalName, args: tc.args });
@@ -195,16 +216,31 @@ export class NativeAgent {
 
         this.onToolUse?.({ type: 'end', tool: internalName, result });
 
+        const resultContent = result.success ? result.output : (result.error ?? 'Unknown error');
         toolResultBlocks.push({
           type: 'tool_result',
           tool_use_id: tc.id,
-          content: result.success ? result.output : (result.error ?? 'Unknown error'),
+          content: resultContent,
           is_error: !result.success,
         });
+        if (result.success && result.output) {
+          lastToolResults.push(result.output);
+        }
       }
 
       // Add tool results as a user message
       loopMessages.push({ role: 'user', content: toolResultBlocks });
+
+      // Break out if the model is stuck in a repeated tool call loop
+      if (consecutiveRepeats >= maxConsecutiveRepeats) {
+        const toolOutput = lastToolResults.length > 0
+          ? lastToolResults.join('\n\n')
+          : 'No results available.';
+        const breakMsg = `Tool loop detected (same tool called ${consecutiveRepeats} times). Returning last results:\n\n${toolOutput}`;
+        const assistantMsg: Message = { role: 'assistant', content: breakMsg };
+        this.addToHistory(assistantMsg);
+        return breakMsg;
+      }
     }
 
     // Max iterations reached