feat: add stuck loop detection and exponential backoff infrastructure for agent polling (#17118)

Merged via /review-pr -> /prepare-pr -> /merge-pr.

Prepared head SHA: eebabf679b
Co-authored-by: akramcodez <179671552+akramcodez@users.noreply.github.com>
Co-authored-by: gumadeiras <5599352+gumadeiras@users.noreply.github.com>
Reviewed-by: @gumadeiras

src/logging/diagnostic-session-state.ts

@@ -6,6 +6,17 @@ export type SessionState = {
   lastActivity: number;
   state: SessionStateValue;
   queueDepth: number;
+  toolCallHistory?: ToolCallRecord[];
+  toolLoopWarningBuckets?: Map<string, number>;
+  commandPollCounts?: Map<string, { count: number; lastPollAt: number }>;
+};
+
+export type ToolCallRecord = {
+  toolName: string;
+  argsHash: string;
+  toolCallId?: string;
+  resultHash?: string;
+  timestamp: number;
 };
 
 export type SessionRef = {

src/logging/diagnostic.ts

@@ -256,6 +256,42 @@ export function logRunAttempt(params: SessionRef & { runId: string; attempt: num
   markActivity();
 }
 
+export function logToolLoopAction(
+  params: SessionRef & {
+    toolName: string;
+    level: "warning" | "critical";
+    action: "warn" | "block";
+    detector: "generic_repeat" | "known_poll_no_progress" | "global_circuit_breaker" | "ping_pong";
+    count: number;
+    message: string;
+    pairedToolName?: string;
+  },
+) {
+  const payload = `tool loop: sessionId=${params.sessionId ?? "unknown"} sessionKey=${
+    params.sessionKey ?? "unknown"
+  } tool=${params.toolName} level=${params.level} action=${params.action} detector=${
+    params.detector
+  } count=${params.count}${params.pairedToolName ? ` pairedTool=${params.pairedToolName}` : ""} message="${params.message}"`;
+  if (params.level === "critical") {
+    diag.error(payload);
+  } else {
+    diag.warn(payload);
+  }
+  emitDiagnosticEvent({
+    type: "tool.loop",
+    sessionId: params.sessionId,
+    sessionKey: params.sessionKey,
+    toolName: params.toolName,
+    level: params.level,
+    action: params.action,
+    detector: params.detector,
+    count: params.count,
+    message: params.message,
+    pairedToolName: params.pairedToolName,
+  });
+  markActivity();
+}
+
 export function logActiveRuns() {
   const activeSessions = Array.from(diagnosticSessionStates.entries())
     .filter(([, s]) => s.state === "processing")
@@ -314,6 +350,16 @@ export function startDiagnosticHeartbeat() {
       queued: totalQueued,
     });
 
+    import("../agents/command-poll-backoff.js")
+      .then(({ pruneStaleCommandPolls }) => {
+        for (const [, state] of diagnosticSessionStates) {
+          pruneStaleCommandPolls(state);
+        }
+      })
+      .catch((err) => {
+        diag.debug(`command-poll-backoff prune failed: ${String(err)}`);
+      });
+
     for (const [, state] of diagnosticSessionStates) {
       const ageMs = now - state.lastActivity;
       if (state.state === "processing" && ageMs > 120_000) {