loop: per-step budgets — replan gate (8 rounds) and stall detection (5 rounds)

pkg/agent/loop.go

@@ -28,6 +28,14 @@ const (
 	consecutiveErrorHardLimit = 10
 )
 
+// replanGate is the max consecutive tool rounds without a PLAN: block before
+// a mandatory replan nudge is injected.
+const replanGate = 8
+
+// stallThreshold is the number of consecutive rounds where LastAction doesn't
+// change before injecting a stall nudge.
+const stallThreshold = 5
+
 // planReinjectInterval is the number of tool-call rounds between periodic
 // task state re-injection into the conversation.
 const planReinjectInterval = 10
@@ -65,6 +73,9 @@ type agentConfig struct {
 func run(ctx context.Context, cfg agentConfig, state state) error {
 	var step int
 	var consecutiveErrors int // rounds where every tool call returned an error
+	var roundsWithoutPlan int // consecutive tool rounds without a PLAN: block
+	var lastAction string     // previous round's LastAction for stall detection
+	var stallRounds int       // consecutive rounds with unchanged LastAction
 	// resultCache stores outputs of read-safe tool calls keyed by name+args.
 	// Only tools classified as parallel-safe (immutable reads) are cached.
 	// sync.Map is required because execOne may run in concurrent goroutines.
@@ -492,6 +503,39 @@ func run(ctx context.Context, cfg agentConfig, state state) error {
 			}, nil)
 		}
 
+		// Replan gate: if the model has been calling tools without emitting a
+		// PLAN: block, force it to replan before continuing.
+		if strings.Contains(msg.Content, "PLAN:") {
+			roundsWithoutPlan = 0
+		} else {
+			roundsWithoutPlan++
+		}
+		if roundsWithoutPlan >= replanGate {
+			state.update(backend.Message{
+				Role:    "user",
+				Content: "[system: you have executed " + fmt.Sprintf("%d", replanGate) + " tool rounds without replanning. Stop and write a PLAN: block showing your current checklist before calling any more tools. Update s/$OLLIE_SESSION_ID/plan.]",
+			}, nil)
+			roundsWithoutPlan = 0
+		}
+
+		// Stall detection: if LastAction hasn't changed across rounds, the
+		// model is likely stuck in a loop.
+		if ts := state.taskState(); ts != nil {
+			if ts.LastAction == lastAction && lastAction != "" {
+				stallRounds++
+			} else {
+				stallRounds = 0
+			}
+			lastAction = ts.LastAction
+			if stallRounds >= stallThreshold {
+				state.update(backend.Message{
+					Role:    "user",
+					Content: "[system: stall detected — you have repeated the same action for " + fmt.Sprintf("%d", stallRounds) + " rounds. Step back, reassess your approach, and try something different. Update your plan.]",
+				}, nil)
+				stallRounds = 0
+			}
+		}
+
 		// Soft step-budget guardrail: when MaxSteps is set and the budget is
 		// exhausted, nudge the model to wrap up and exit cleanly. This is not
 		// a hard abort — the model gets one final turn without tools to emit