[System] You are a code execution simulator.

[User]
You are reasoning about concurrent Go program execution.

Here is a Go program:
<program>
// WEAVE_META
// outcome: race
// concurrency_pattern: mutex
// goroutine_count: 3
// expected_nondeterminism: medium
// description: Human-written GoBench bug kernel grpc_1748 (race)

package main

import (
	"os"
	"runtime/trace"
	"sync"
		"time"
)

var minConnectTimeout = 10 * time.Second

var balanceMutex sync.Mutex // We add this for avoiding other data race

type Balancer interface {
	HandleResolvedAddrs()
}

type Builder interface {
	Build(cc balancer_ClientConn) Balancer
}

func newPickfirstBuilder() Builder {
	return &pickfirstBuilder{}
}

type pickfirstBuilder struct{}

func (*pickfirstBuilder) Build(cc balancer_ClientConn) Balancer {
	return &pickfirstBalancer{cc: cc}
}

type SubConn interface {
	Connect()
}

type balancer_ClientConn interface {
	NewSubConn() SubConn
}

type pickfirstBalancer struct {
	cc balancer_ClientConn
	sc SubConn
}

func (b *pickfirstBalancer) HandleResolvedAddrs() {
	b.sc = b.cc.NewSubConn()
	b.sc.Connect()
}

type pickerWrapper struct {
	mu sync.Mutex
}

type acBalancerWrapper struct {
	mu sync.Mutex
	ac *addrConn
}

type addrConn struct {
	cc   *ClientConn
	acbw SubConn
	mu   sync.Mutex
}

func (ac *addrConn) resetTransport() {
	_ = minConnectTimeout
}

func (ac *addrConn) transportMonitor() {
	ac.resetTransport()
}

func (ac *addrConn) connect() {
	go func() {
		ac.transportMonitor()
	}()
}

func (acbw *acBalancerWrapper) Connect() {
	acbw.mu.Lock()
	defer acbw.mu.Unlock()
	acbw.ac.connect()
}

func newPickerWrapper() *pickerWrapper {
	return &pickerWrapper{}
}

type ClientConn struct {
	mu sync.Mutex
}

func (cc *ClientConn) switchBalancer() {
	builder := newPickfirstBuilder()
	newCCBalancerWrapper(cc, builder)
}

func (cc *ClientConn) newAddrConn() *addrConn {
	return &addrConn{cc: cc}
}

type ccBalancerWrapper struct {
	cc       *ClientConn
	balancer Balancer
}

func (ccb *ccBalancerWrapper) watcher() {
	for i := 0; i < 10; i++ {
		balanceMutex.Lock()
		if ccb.balancer != nil {
			balanceMutex.Unlock()
			ccb.balancer.HandleResolvedAddrs()
		} else {
			balanceMutex.Unlock()
		}
	}
}

func (ccb *ccBalancerWrapper) NewSubConn() SubConn {
	ac := ccb.cc.newAddrConn()
	acbw := &acBalancerWrapper{ac: ac}
	acbw.ac.mu.Lock()
	ac.acbw = acbw
	acbw.ac.mu.Unlock()
	return acbw
}

func newCCBalancerWrapper(cc *ClientConn, b Builder) {
	ccb := &ccBalancerWrapper{cc: cc}
	go ccb.watcher()
	balanceMutex.Lock()
	defer balanceMutex.Unlock()
	ccb.balancer = b.Build(ccb)
}

func main() {
	if tf := os.Getenv("WEAVE_TRACE_FILE"); tf != "" {
		f, err := os.Create(tf)
		if err == nil {
			if err := trace.Start(f); err == nil {
				defer func() { trace.Stop(); f.Close() }()
			}
		}
	}

	var wg sync.WaitGroup
	wg.Add(1)
	go func() {
		defer wg.Done()
		mctBkp := minConnectTimeout
		// Call this only after transportMonitor goroutine has ended.
		defer func() {
			minConnectTimeout = mctBkp
		}()
		cc := &ClientConn{}
		cc.switchBalancer()
	}()
	wg.Wait()
}

</program>

Here is a partial execution trace showing goroutine scheduler events so far:
<trace>
[
  {
    "event_id": 16,
    "timestamp_ns": 14759296253184,
    "event_type": "GoStart",
    "goroutine_id": 1,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 17,
    "timestamp_ns": 14759296254720,
    "event_type": "GoCreate",
    "goroutine_id": 9,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 18,
    "timestamp_ns": 14759296257472,
    "event_type": "GoCreate",
    "goroutine_id": 10,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 19,
    "timestamp_ns": 14759296260480,
    "event_type": "GoUnblock",
    "goroutine_id": 6,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 20,
    "timestamp_ns": 14759296260544,
    "event_type": "GoStart",
    "goroutine_id": 6,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 21,
    "timestamp_ns": 14759296261312,
    "event_type": "GoCreate",
    "goroutine_id": 11,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 22,
    "timestamp_ns": 14759296262464,
    "event_type": "GoBlock",
    "goroutine_id": 6,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 23,
    "timestamp_ns": 14759296263040,
    "event_type": "GoCreate",
    "goroutine_id": 12,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 24,
    "timestamp_ns": 14759296265408,
    "event_type": "GoStart",
    "goroutine_id": 6,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 25,
    "timestamp_ns": 14759296266176,
    "event_type": "GoBlock",
    "goroutine_id": 6,
    "goroutines": {
      "1": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "10": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "main.(*addrConn).connect"
      },
      "11": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "main.(*addrConn).connect"
      },
      "12": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "main.(*addrConn).connect"
      },
      "4": {
        "status": "blocked",
        "blocked_on": "chan receive",
        "locals_hint": "runtime.chanrecv1"
      },
      "5": {
        "status": "blocked",
        "blocked_on": "chan receive",
        "locals_hint": "runtime.chanrecv1"
      },
      "6": {
        "status": "blocked",
        "blocked_on": "system goroutine wait",
        "locals_hint": "runtime/trace.(*traceMultiplexer).startLocked.func1"
      },
      "8": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "9": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "main.(*addrConn).connect"
      }
    },
    "channels": {},
    "mutexes": {}
  }
]
</trace>

The current goroutine states are:
<current_state>
{
  "event_id": 25,
  "timestamp_ns": 14759296266176,
  "event_type": "GoBlock",
  "goroutine_id": 6,
  "goroutines": {
    "1": {
      "status": "running",
      "blocked_on": null,
      "locals_hint": "unknown"
    },
    "10": {
      "status": "runnable",
      "blocked_on": null,
      "locals_hint": "main.(*addrConn).connect"
    },
    "11": {
      "status": "runnable",
      "blocked_on": null,
      "locals_hint": "main.(*addrConn).connect"
    },
    "12": {
      "status": "runnable",
      "blocked_on": null,
      "locals_hint": "main.(*addrConn).connect"
    },
    "4": {
      "status": "blocked",
      "blocked_on": "chan receive",
      "locals_hint": "runtime.chanrecv1"
    },
    "5": {
      "status": "blocked",
      "blocked_on": "chan receive",
      "locals_hint": "runtime.chanrecv1"
    },
    "6": {
      "status": "blocked",
      "blocked_on": "system goroutine wait",
      "locals_hint": "runtime/trace.(*traceMultiplexer).startLocked.func1"
    },
    "8": {
      "status": "running",
      "blocked_on": null,
      "locals_hint": "unknown"
    },
    "9": {
      "status": "runnable",
      "blocked_on": null,
      "locals_hint": "main.(*addrConn).connect"
    }
  },
  "channels": {},
  "mutexes": {}
}
</current_state>

Predict the next scheduler event. What happens next?
Respond in JSON only — no markdown fences, no text outside the JSON object:
{"event_type":"GoStart|GoBlock|GoUnblock|GoCreate|GoEnd|GoSched","goroutine_id":<integer>,"reasoning":"<brief explanation>","confidence":"high|medium|low"}

[Assistant] {"event_type": "GoStart", "goroutine_id": 11}


[System] You are a code execution simulator.

[User]
You are reasoning about concurrent Go program execution.

Here is a Go program:
<program>
// WEAVE_META
// outcome: race
// concurrency_pattern: mutex
// goroutine_count: 3
// expected_nondeterminism: medium
// description: Human-written GoBench bug kernel grpc_1748 (race)

package main

import (
	"os"
	"runtime/trace"
	"sync"
		"time"
)

var minConnectTimeout = 10 * time.Second

var balanceMutex sync.Mutex // We add this for avoiding other data race

type Balancer interface {
	HandleResolvedAddrs()
}

type Builder interface {
	Build(cc balancer_ClientConn) Balancer
}

func newPickfirstBuilder() Builder {
	return &pickfirstBuilder{}
}

type pickfirstBuilder struct{}

func (*pickfirstBuilder) Build(cc balancer_ClientConn) Balancer {
	return &pickfirstBalancer{cc: cc}
}

type SubConn interface {
	Connect()
}

type balancer_ClientConn interface {
	NewSubConn() SubConn
}

type pickfirstBalancer struct {
	cc balancer_ClientConn
	sc SubConn
}

func (b *pickfirstBalancer) HandleResolvedAddrs() {
	b.sc = b.cc.NewSubConn()
	b.sc.Connect()
}

type pickerWrapper struct {
	mu sync.Mutex
}

type acBalancerWrapper struct {
	mu sync.Mutex
	ac *addrConn
}

type addrConn struct {
	cc   *ClientConn
	acbw SubConn
	mu   sync.Mutex
}

func (ac *addrConn) resetTransport() {
	_ = minConnectTimeout
}

func (ac *addrConn) transportMonitor() {
	ac.resetTransport()
}

func (ac *addrConn) connect() {
	go func() {
		ac.transportMonitor()
	}()
}

func (acbw *acBalancerWrapper) Connect() {
	acbw.mu.Lock()
	defer acbw.mu.Unlock()
	acbw.ac.connect()
}

func newPickerWrapper() *pickerWrapper {
	return &pickerWrapper{}
}

type ClientConn struct {
	mu sync.Mutex
}

func (cc *ClientConn) switchBalancer() {
	builder := newPickfirstBuilder()
	newCCBalancerWrapper(cc, builder)
}

func (cc *ClientConn) newAddrConn() *addrConn {
	return &addrConn{cc: cc}
}

type ccBalancerWrapper struct {
	cc       *ClientConn
	balancer Balancer
}

func (ccb *ccBalancerWrapper) watcher() {
	for i := 0; i < 10; i++ {
		balanceMutex.Lock()
		if ccb.balancer != nil {
			balanceMutex.Unlock()
			ccb.balancer.HandleResolvedAddrs()
		} else {
			balanceMutex.Unlock()
		}
	}
}

func (ccb *ccBalancerWrapper) NewSubConn() SubConn {
	ac := ccb.cc.newAddrConn()
	acbw := &acBalancerWrapper{ac: ac}
	acbw.ac.mu.Lock()
	ac.acbw = acbw
	acbw.ac.mu.Unlock()
	return acbw
}

func newCCBalancerWrapper(cc *ClientConn, b Builder) {
	ccb := &ccBalancerWrapper{cc: cc}
	go ccb.watcher()
	balanceMutex.Lock()
	defer balanceMutex.Unlock()
	ccb.balancer = b.Build(ccb)
}

func main() {
	if tf := os.Getenv("WEAVE_TRACE_FILE"); tf != "" {
		f, err := os.Create(tf)
		if err == nil {
			if err := trace.Start(f); err == nil {
				defer func() { trace.Stop(); f.Close() }()
			}
		}
	}

	var wg sync.WaitGroup
	wg.Add(1)
	go func() {
		defer wg.Done()
		mctBkp := minConnectTimeout
		// Call this only after transportMonitor goroutine has ended.
		defer func() {
			minConnectTimeout = mctBkp
		}()
		cc := &ClientConn{}
		cc.switchBalancer()
	}()
	wg.Wait()
}

</program>

Here is a partial execution trace showing goroutine scheduler events so far:
<trace>
[
  {
    "event_id": 16,
    "timestamp_ns": 14759296253184,
    "event_type": "GoStart",
    "goroutine_id": 1,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 17,
    "timestamp_ns": 14759296254720,
    "event_type": "GoCreate",
    "goroutine_id": 9,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 18,
    "timestamp_ns": 14759296257472,
    "event_type": "GoCreate",
    "goroutine_id": 10,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 19,
    "timestamp_ns": 14759296260480,
    "event_type": "GoUnblock",
    "goroutine_id": 6,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 20,
    "timestamp_ns": 14759296260544,
    "event_type": "GoStart",
    "goroutine_id": 6,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 21,
    "timestamp_ns": 14759296261312,
    "event_type": "GoCreate",
    "goroutine_id": 11,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 22,
    "timestamp_ns": 14759296262464,
    "event_type": "GoBlock",
    "goroutine_id": 6,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 23,
    "timestamp_ns": 14759296263040,
    "event_type": "GoCreate",
    "goroutine_id": 12,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 24,
    "timestamp_ns": 14759296265408,
    "event_type": "GoStart",
    "goroutine_id": 6,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 25,
    "timestamp_ns": 14759296266176,
    "event_type": "GoBlock",
    "goroutine_id": 6,
    "goroutines": {
      "1": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "10": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "main.(*addrConn).connect"
      },
      "11": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "main.(*addrConn).connect"
      },
      "12": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "main.(*addrConn).connect"
      },
      "4": {
        "status": "blocked",
        "blocked_on": "chan receive",
        "locals_hint": "runtime.chanrecv1"
      },
      "5": {
        "status": "blocked",
        "blocked_on": "chan receive",
        "locals_hint": "runtime.chanrecv1"
      },
      "6": {
        "status": "blocked",
        "blocked_on": "system goroutine wait",
        "locals_hint": "runtime/trace.(*traceMultiplexer).startLocked.func1"
      },
      "8": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "9": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "main.(*addrConn).connect"
      }
    },
    "channels": {},
    "mutexes": {}
  }
]
</trace>

The current goroutine states are:
<current_state>
{
  "event_id": 25,
  "timestamp_ns": 14759296266176,
  "event_type": "GoBlock",
  "goroutine_id": 6,
  "goroutines": {
    "1": {
      "status": "running",
      "blocked_on": null,
      "locals_hint": "unknown"
    },
    "10": {
      "status": "runnable",
      "blocked_on": null,
      "locals_hint": "main.(*addrConn).connect"
    },
    "11": {
      "status": "runnable",
      "blocked_on": null,
      "locals_hint": "main.(*addrConn).connect"
    },
    "12": {
      "status": "runnable",
      "blocked_on": null,
      "locals_hint": "main.(*addrConn).connect"
    },
    "4": {
      "status": "blocked",
      "blocked_on": "chan receive",
      "locals_hint": "runtime.chanrecv1"
    },
    "5": {
      "status": "blocked",
      "blocked_on": "chan receive",
      "locals_hint": "runtime.chanrecv1"
    },
    "6": {
      "status": "blocked",
      "blocked_on": "system goroutine wait",
      "locals_hint": "runtime/trace.(*traceMultiplexer).startLocked.func1"
    },
    "8": {
      "status": "running",
      "blocked_on": null,
      "locals_hint": "unknown"
    },
    "9": {
      "status": "runnable",
      "blocked_on": null,
      "locals_hint": "main.(*addrConn).connect"
    }
  },
  "channels": {},
  "mutexes": {}
}
</current_state>

Predict the next scheduler event. What happens next?
Respond in JSON only — no markdown fences, no text outside the JSON object:
{"event_type":"GoStart|GoBlock|GoUnblock|GoCreate|GoEnd|GoSched","goroutine_id":<integer>,"reasoning":"<brief explanation>","confidence":"high|medium|low"}

[Assistant] {"event_type": "GoStart", "goroutine_id": 37}


[System] You are a code execution simulator.

[User]
You are reasoning about concurrent Go program execution.

Here is a Go program:
<program>
// WEAVE_META
// outcome: race
// concurrency_pattern: mutex
// goroutine_count: 3
// expected_nondeterminism: medium
// description: Human-written GoBench bug kernel grpc_1748 (race)

package main

import (
	"os"
	"runtime/trace"
	"sync"
		"time"
)

var minConnectTimeout = 10 * time.Second

var balanceMutex sync.Mutex // We add this for avoiding other data race

type Balancer interface {
	HandleResolvedAddrs()
}

type Builder interface {
	Build(cc balancer_ClientConn) Balancer
}

func newPickfirstBuilder() Builder {
	return &pickfirstBuilder{}
}

type pickfirstBuilder struct{}

func (*pickfirstBuilder) Build(cc balancer_ClientConn) Balancer {
	return &pickfirstBalancer{cc: cc}
}

type SubConn interface {
	Connect()
}

type balancer_ClientConn interface {
	NewSubConn() SubConn
}

type pickfirstBalancer struct {
	cc balancer_ClientConn
	sc SubConn
}

func (b *pickfirstBalancer) HandleResolvedAddrs() {
	b.sc = b.cc.NewSubConn()
	b.sc.Connect()
}

type pickerWrapper struct {
	mu sync.Mutex
}

type acBalancerWrapper struct {
	mu sync.Mutex
	ac *addrConn
}

type addrConn struct {
	cc   *ClientConn
	acbw SubConn
	mu   sync.Mutex
}

func (ac *addrConn) resetTransport() {
	_ = minConnectTimeout
}

func (ac *addrConn) transportMonitor() {
	ac.resetTransport()
}

func (ac *addrConn) connect() {
	go func() {
		ac.transportMonitor()
	}()
}

func (acbw *acBalancerWrapper) Connect() {
	acbw.mu.Lock()
	defer acbw.mu.Unlock()
	acbw.ac.connect()
}

func newPickerWrapper() *pickerWrapper {
	return &pickerWrapper{}
}

type ClientConn struct {
	mu sync.Mutex
}

func (cc *ClientConn) switchBalancer() {
	builder := newPickfirstBuilder()
	newCCBalancerWrapper(cc, builder)
}

func (cc *ClientConn) newAddrConn() *addrConn {
	return &addrConn{cc: cc}
}

type ccBalancerWrapper struct {
	cc       *ClientConn
	balancer Balancer
}

func (ccb *ccBalancerWrapper) watcher() {
	for i := 0; i < 10; i++ {
		balanceMutex.Lock()
		if ccb.balancer != nil {
			balanceMutex.Unlock()
			ccb.balancer.HandleResolvedAddrs()
		} else {
			balanceMutex.Unlock()
		}
	}
}

func (ccb *ccBalancerWrapper) NewSubConn() SubConn {
	ac := ccb.cc.newAddrConn()
	acbw := &acBalancerWrapper{ac: ac}
	acbw.ac.mu.Lock()
	ac.acbw = acbw
	acbw.ac.mu.Unlock()
	return acbw
}

func newCCBalancerWrapper(cc *ClientConn, b Builder) {
	ccb := &ccBalancerWrapper{cc: cc}
	go ccb.watcher()
	balanceMutex.Lock()
	defer balanceMutex.Unlock()
	ccb.balancer = b.Build(ccb)
}

func main() {
	if tf := os.Getenv("WEAVE_TRACE_FILE"); tf != "" {
		f, err := os.Create(tf)
		if err == nil {
			if err := trace.Start(f); err == nil {
				defer func() { trace.Stop(); f.Close() }()
			}
		}
	}

	var wg sync.WaitGroup
	wg.Add(1)
	go func() {
		defer wg.Done()
		mctBkp := minConnectTimeout
		// Call this only after transportMonitor goroutine has ended.
		defer func() {
			minConnectTimeout = mctBkp
		}()
		cc := &ClientConn{}
		cc.switchBalancer()
	}()
	wg.Wait()
}

</program>

Here is a partial execution trace showing goroutine scheduler events so far:
<trace>
[
  {
    "event_id": 16,
    "timestamp_ns": 14759296253184,
    "event_type": "GoStart",
    "goroutine_id": 1,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 17,
    "timestamp_ns": 14759296254720,
    "event_type": "GoCreate",
    "goroutine_id": 9,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 18,
    "timestamp_ns": 14759296257472,
    "event_type": "GoCreate",
    "goroutine_id": 10,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 19,
    "timestamp_ns": 14759296260480,
    "event_type": "GoUnblock",
    "goroutine_id": 6,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 20,
    "timestamp_ns": 14759296260544,
    "event_type": "GoStart",
    "goroutine_id": 6,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 21,
    "timestamp_ns": 14759296261312,
    "event_type": "GoCreate",
    "goroutine_id": 11,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 22,
    "timestamp_ns": 14759296262464,
    "event_type": "GoBlock",
    "goroutine_id": 6,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 23,
    "timestamp_ns": 14759296263040,
    "event_type": "GoCreate",
    "goroutine_id": 12,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 24,
    "timestamp_ns": 14759296265408,
    "event_type": "GoStart",
    "goroutine_id": 6,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 25,
    "timestamp_ns": 14759296266176,
    "event_type": "GoBlock",
    "goroutine_id": 6,
    "goroutines": {
      "1": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "10": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "main.(*addrConn).connect"
      },
      "11": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "main.(*addrConn).connect"
      },
      "12": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "main.(*addrConn).connect"
      },
      "4": {
        "status": "blocked",
        "blocked_on": "chan receive",
        "locals_hint": "runtime.chanrecv1"
      },
      "5": {
        "status": "blocked",
        "blocked_on": "chan receive",
        "locals_hint": "runtime.chanrecv1"
      },
      "6": {
        "status": "blocked",
        "blocked_on": "system goroutine wait",
        "locals_hint": "runtime/trace.(*traceMultiplexer).startLocked.func1"
      },
      "8": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "9": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "main.(*addrConn).connect"
      }
    },
    "channels": {},
    "mutexes": {}
  }
]
</trace>

The current goroutine states are:
<current_state>
{
  "event_id": 25,
  "timestamp_ns": 14759296266176,
  "event_type": "GoBlock",
  "goroutine_id": 6,
  "goroutines": {
    "1": {
      "status": "running",
      "blocked_on": null,
      "locals_hint": "unknown"
    },
    "10": {
      "status": "runnable",
      "blocked_on": null,
      "locals_hint": "main.(*addrConn).connect"
    },
    "11": {
      "status": "runnable",
      "blocked_on": null,
      "locals_hint": "main.(*addrConn).connect"
    },
    "12": {
      "status": "runnable",
      "blocked_on": null,
      "locals_hint": "main.(*addrConn).connect"
    },
    "4": {
      "status": "blocked",
      "blocked_on": "chan receive",
      "locals_hint": "runtime.chanrecv1"
    },
    "5": {
      "status": "blocked",
      "blocked_on": "chan receive",
      "locals_hint": "runtime.chanrecv1"
    },
    "6": {
      "status": "blocked",
      "blocked_on": "system goroutine wait",
      "locals_hint": "runtime/trace.(*traceMultiplexer).startLocked.func1"
    },
    "8": {
      "status": "running",
      "blocked_on": null,
      "locals_hint": "unknown"
    },
    "9": {
      "status": "runnable",
      "blocked_on": null,
      "locals_hint": "main.(*addrConn).connect"
    }
  },
  "channels": {},
  "mutexes": {}
}
</current_state>

Predict the next scheduler event. What happens next?
Respond in JSON only — no markdown fences, no text outside the JSON object:
{"event_type":"GoStart|GoBlock|GoUnblock|GoCreate|GoEnd|GoSched","goroutine_id":<integer>,"reasoning":"<brief explanation>","confidence":"high|medium|low"}

[Assistant] {"event_type": "GoStart", "goroutine_id": 9}


[System] You are a code execution simulator.

[User]
You are reasoning about concurrent Go program execution.

Here is a Go program:
<program>
// WEAVE_META
// outcome: race
// concurrency_pattern: mutex
// goroutine_count: 3
// expected_nondeterminism: medium
// description: Human-written GoBench bug kernel grpc_1748 (race)

package main

import (
	"os"
	"runtime/trace"
	"sync"
		"time"
)

var minConnectTimeout = 10 * time.Second

var balanceMutex sync.Mutex // We add this for avoiding other data race

type Balancer interface {
	HandleResolvedAddrs()
}

type Builder interface {
	Build(cc balancer_ClientConn) Balancer
}

func newPickfirstBuilder() Builder {
	return &pickfirstBuilder{}
}

type pickfirstBuilder struct{}

func (*pickfirstBuilder) Build(cc balancer_ClientConn) Balancer {
	return &pickfirstBalancer{cc: cc}
}

type SubConn interface {
	Connect()
}

type balancer_ClientConn interface {
	NewSubConn() SubConn
}

type pickfirstBalancer struct {
	cc balancer_ClientConn
	sc SubConn
}

func (b *pickfirstBalancer) HandleResolvedAddrs() {
	b.sc = b.cc.NewSubConn()
	b.sc.Connect()
}

type pickerWrapper struct {
	mu sync.Mutex
}

type acBalancerWrapper struct {
	mu sync.Mutex
	ac *addrConn
}

type addrConn struct {
	cc   *ClientConn
	acbw SubConn
	mu   sync.Mutex
}

func (ac *addrConn) resetTransport() {
	_ = minConnectTimeout
}

func (ac *addrConn) transportMonitor() {
	ac.resetTransport()
}

func (ac *addrConn) connect() {
	go func() {
		ac.transportMonitor()
	}()
}

func (acbw *acBalancerWrapper) Connect() {
	acbw.mu.Lock()
	defer acbw.mu.Unlock()
	acbw.ac.connect()
}

func newPickerWrapper() *pickerWrapper {
	return &pickerWrapper{}
}

type ClientConn struct {
	mu sync.Mutex
}

func (cc *ClientConn) switchBalancer() {
	builder := newPickfirstBuilder()
	newCCBalancerWrapper(cc, builder)
}

func (cc *ClientConn) newAddrConn() *addrConn {
	return &addrConn{cc: cc}
}

type ccBalancerWrapper struct {
	cc       *ClientConn
	balancer Balancer
}

func (ccb *ccBalancerWrapper) watcher() {
	for i := 0; i < 10; i++ {
		balanceMutex.Lock()
		if ccb.balancer != nil {
			balanceMutex.Unlock()
			ccb.balancer.HandleResolvedAddrs()
		} else {
			balanceMutex.Unlock()
		}
	}
}

func (ccb *ccBalancerWrapper) NewSubConn() SubConn {
	ac := ccb.cc.newAddrConn()
	acbw := &acBalancerWrapper{ac: ac}
	acbw.ac.mu.Lock()
	ac.acbw = acbw
	acbw.ac.mu.Unlock()
	return acbw
}

func newCCBalancerWrapper(cc *ClientConn, b Builder) {
	ccb := &ccBalancerWrapper{cc: cc}
	go ccb.watcher()
	balanceMutex.Lock()
	defer balanceMutex.Unlock()
	ccb.balancer = b.Build(ccb)
}

func main() {
	if tf := os.Getenv("WEAVE_TRACE_FILE"); tf != "" {
		f, err := os.Create(tf)
		if err == nil {
			if err := trace.Start(f); err == nil {
				defer func() { trace.Stop(); f.Close() }()
			}
		}
	}

	var wg sync.WaitGroup
	wg.Add(1)
	go func() {
		defer wg.Done()
		mctBkp := minConnectTimeout
		// Call this only after transportMonitor goroutine has ended.
		defer func() {
			minConnectTimeout = mctBkp
		}()
		cc := &ClientConn{}
		cc.switchBalancer()
	}()
	wg.Wait()
}

</program>

Here is a partial execution trace showing goroutine scheduler events so far:
<trace>
[
  {
    "event_id": 16,
    "timestamp_ns": 14759296253184,
    "event_type": "GoStart",
    "goroutine_id": 1,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 17,
    "timestamp_ns": 14759296254720,
    "event_type": "GoCreate",
    "goroutine_id": 9,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 18,
    "timestamp_ns": 14759296257472,
    "event_type": "GoCreate",
    "goroutine_id": 10,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 19,
    "timestamp_ns": 14759296260480,
    "event_type": "GoUnblock",
    "goroutine_id": 6,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 20,
    "timestamp_ns": 14759296260544,
    "event_type": "GoStart",
    "goroutine_id": 6,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 21,
    "timestamp_ns": 14759296261312,
    "event_type": "GoCreate",
    "goroutine_id": 11,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 22,
    "timestamp_ns": 14759296262464,
    "event_type": "GoBlock",
    "goroutine_id": 6,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 23,
    "timestamp_ns": 14759296263040,
    "event_type": "GoCreate",
    "goroutine_id": 12,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 24,
    "timestamp_ns": 14759296265408,
    "event_type": "GoStart",
    "goroutine_id": 6,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 25,
    "timestamp_ns": 14759296266176,
    "event_type": "GoBlock",
    "goroutine_id": 6,
    "goroutines": {
      "1": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "10": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "main.(*addrConn).connect"
      },
      "11": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "main.(*addrConn).connect"
      },
      "12": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "main.(*addrConn).connect"
      },
      "4": {
        "status": "blocked",
        "blocked_on": "chan receive",
        "locals_hint": "runtime.chanrecv1"
      },
      "5": {
        "status": "blocked",
        "blocked_on": "chan receive",
        "locals_hint": "runtime.chanrecv1"
      },
      "6": {
        "status": "blocked",
        "blocked_on": "system goroutine wait",
        "locals_hint": "runtime/trace.(*traceMultiplexer).startLocked.func1"
      },
      "8": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "9": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "main.(*addrConn).connect"
      }
    },
    "channels": {},
    "mutexes": {}
  }
]
</trace>

The current goroutine states are:
<current_state>
{
  "event_id": 25,
  "timestamp_ns": 14759296266176,
  "event_type": "GoBlock",
  "goroutine_id": 6,
  "goroutines": {
    "1": {
      "status": "running",
      "blocked_on": null,
      "locals_hint": "unknown"
    },
    "10": {
      "status": "runnable",
      "blocked_on": null,
      "locals_hint": "main.(*addrConn).connect"
    },
    "11": {
      "status": "runnable",
      "blocked_on": null,
      "locals_hint": "main.(*addrConn).connect"
    },
    "12": {
      "status": "runnable",
      "blocked_on": null,
      "locals_hint": "main.(*addrConn).connect"
    },
    "4": {
      "status": "blocked",
      "blocked_on": "chan receive",
      "locals_hint": "runtime.chanrecv1"
    },
    "5": {
      "status": "blocked",
      "blocked_on": "chan receive",
      "locals_hint": "runtime.chanrecv1"
    },
    "6": {
      "status": "blocked",
      "blocked_on": "system goroutine wait",
      "locals_hint": "runtime/trace.(*traceMultiplexer).startLocked.func1"
    },
    "8": {
      "status": "running",
      "blocked_on": null,
      "locals_hint": "unknown"
    },
    "9": {
      "status": "runnable",
      "blocked_on": null,
      "locals_hint": "main.(*addrConn).connect"
    }
  },
  "channels": {},
  "mutexes": {}
}
</current_state>

Predict the next scheduler event. What happens next?
Respond in JSON only — no markdown fences, no text outside the JSON object:
{"event_type":"GoStart|GoBlock|GoUnblock|GoCreate|GoEnd|GoSched","goroutine_id":<integer>,"reasoning":"<brief explanation>","confidence":"high|medium|low"}

[Assistant] {"event_type": "GoStart", "goroutine_id": 9}


[System] You are a code execution simulator.

[User]
You are reasoning about concurrent Go program execution.

Here is a Go program:
<program>
// WEAVE_META
// outcome: race
// concurrency_pattern: mutex
// goroutine_count: 3
// expected_nondeterminism: medium
// description: Human-written GoBench bug kernel grpc_1748 (race)

package main

import (
	"os"
	"runtime/trace"
	"sync"
		"time"
)

var minConnectTimeout = 10 * time.Second

var balanceMutex sync.Mutex // We add this for avoiding other data race

type Balancer interface {
	HandleResolvedAddrs()
}

type Builder interface {
	Build(cc balancer_ClientConn) Balancer
}

func newPickfirstBuilder() Builder {
	return &pickfirstBuilder{}
}

type pickfirstBuilder struct{}

func (*pickfirstBuilder) Build(cc balancer_ClientConn) Balancer {
	return &pickfirstBalancer{cc: cc}
}

type SubConn interface {
	Connect()
}

type balancer_ClientConn interface {
	NewSubConn() SubConn
}

type pickfirstBalancer struct {
	cc balancer_ClientConn
	sc SubConn
}

func (b *pickfirstBalancer) HandleResolvedAddrs() {
	b.sc = b.cc.NewSubConn()
	b.sc.Connect()
}

type pickerWrapper struct {
	mu sync.Mutex
}

type acBalancerWrapper struct {
	mu sync.Mutex
	ac *addrConn
}

type addrConn struct {
	cc   *ClientConn
	acbw SubConn
	mu   sync.Mutex
}

func (ac *addrConn) resetTransport() {
	_ = minConnectTimeout
}

func (ac *addrConn) transportMonitor() {
	ac.resetTransport()
}

func (ac *addrConn) connect() {
	go func() {
		ac.transportMonitor()
	}()
}

func (acbw *acBalancerWrapper) Connect() {
	acbw.mu.Lock()
	defer acbw.mu.Unlock()
	acbw.ac.connect()
}

func newPickerWrapper() *pickerWrapper {
	return &pickerWrapper{}
}

type ClientConn struct {
	mu sync.Mutex
}

func (cc *ClientConn) switchBalancer() {
	builder := newPickfirstBuilder()
	newCCBalancerWrapper(cc, builder)
}

func (cc *ClientConn) newAddrConn() *addrConn {
	return &addrConn{cc: cc}
}

type ccBalancerWrapper struct {
	cc       *ClientConn
	balancer Balancer
}

func (ccb *ccBalancerWrapper) watcher() {
	for i := 0; i < 10; i++ {
		balanceMutex.Lock()
		if ccb.balancer != nil {
			balanceMutex.Unlock()
			ccb.balancer.HandleResolvedAddrs()
		} else {
			balanceMutex.Unlock()
		}
	}
}

func (ccb *ccBalancerWrapper) NewSubConn() SubConn {
	ac := ccb.cc.newAddrConn()
	acbw := &acBalancerWrapper{ac: ac}
	acbw.ac.mu.Lock()
	ac.acbw = acbw
	acbw.ac.mu.Unlock()
	return acbw
}

func newCCBalancerWrapper(cc *ClientConn, b Builder) {
	ccb := &ccBalancerWrapper{cc: cc}
	go ccb.watcher()
	balanceMutex.Lock()
	defer balanceMutex.Unlock()
	ccb.balancer = b.Build(ccb)
}

func main() {
	if tf := os.Getenv("WEAVE_TRACE_FILE"); tf != "" {
		f, err := os.Create(tf)
		if err == nil {
			if err := trace.Start(f); err == nil {
				defer func() { trace.Stop(); f.Close() }()
			}
		}
	}

	var wg sync.WaitGroup
	wg.Add(1)
	go func() {
		defer wg.Done()
		mctBkp := minConnectTimeout
		// Call this only after transportMonitor goroutine has ended.
		defer func() {
			minConnectTimeout = mctBkp
		}()
		cc := &ClientConn{}
		cc.switchBalancer()
	}()
	wg.Wait()
}

</program>

Here is a partial execution trace showing goroutine scheduler events so far:
<trace>
[
  {
    "event_id": 16,
    "timestamp_ns": 14759296253184,
    "event_type": "GoStart",
    "goroutine_id": 1,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 17,
    "timestamp_ns": 14759296254720,
    "event_type": "GoCreate",
    "goroutine_id": 9,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 18,
    "timestamp_ns": 14759296257472,
    "event_type": "GoCreate",
    "goroutine_id": 10,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 19,
    "timestamp_ns": 14759296260480,
    "event_type": "GoUnblock",
    "goroutine_id": 6,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 20,
    "timestamp_ns": 14759296260544,
    "event_type": "GoStart",
    "goroutine_id": 6,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 21,
    "timestamp_ns": 14759296261312,
    "event_type": "GoCreate",
    "goroutine_id": 11,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 22,
    "timestamp_ns": 14759296262464,
    "event_type": "GoBlock",
    "goroutine_id": 6,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 23,
    "timestamp_ns": 14759296263040,
    "event_type": "GoCreate",
    "goroutine_id": 12,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 24,
    "timestamp_ns": 14759296265408,
    "event_type": "GoStart",
    "goroutine_id": 6,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 25,
    "timestamp_ns": 14759296266176,
    "event_type": "GoBlock",
    "goroutine_id": 6,
    "goroutines": {
      "1": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "10": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "main.(*addrConn).connect"
      },
      "11": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "main.(*addrConn).connect"
      },
      "12": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "main.(*addrConn).connect"
      },
      "4": {
        "status": "blocked",
        "blocked_on": "chan receive",
        "locals_hint": "runtime.chanrecv1"
      },
      "5": {
        "status": "blocked",
        "blocked_on": "chan receive",
        "locals_hint": "runtime.chanrecv1"
      },
      "6": {
        "status": "blocked",
        "blocked_on": "system goroutine wait",
        "locals_hint": "runtime/trace.(*traceMultiplexer).startLocked.func1"
      },
      "8": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "9": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "main.(*addrConn).connect"
      }
    },
    "channels": {},
    "mutexes": {}
  }
]
</trace>

The current goroutine states are:
<current_state>
{
  "event_id": 25,
  "timestamp_ns": 14759296266176,
  "event_type": "GoBlock",
  "goroutine_id": 6,
  "goroutines": {
    "1": {
      "status": "running",
      "blocked_on": null,
      "locals_hint": "unknown"
    },
    "10": {
      "status": "runnable",
      "blocked_on": null,
      "locals_hint": "main.(*addrConn).connect"
    },
    "11": {
      "status": "runnable",
      "blocked_on": null,
      "locals_hint": "main.(*addrConn).connect"
    },
    "12": {
      "status": "runnable",
      "blocked_on": null,
      "locals_hint": "main.(*addrConn).connect"
    },
    "4": {
      "status": "blocked",
      "blocked_on": "chan receive",
      "locals_hint": "runtime.chanrecv1"
    },
    "5": {
      "status": "blocked",
      "blocked_on": "chan receive",
      "locals_hint": "runtime.chanrecv1"
    },
    "6": {
      "status": "blocked",
      "blocked_on": "system goroutine wait",
      "locals_hint": "runtime/trace.(*traceMultiplexer).startLocked.func1"
    },
    "8": {
      "status": "running",
      "blocked_on": null,
      "locals_hint": "unknown"
    },
    "9": {
      "status": "runnable",
      "blocked_on": null,
      "locals_hint": "main.(*addrConn).connect"
    }
  },
  "channels": {},
  "mutexes": {}
}
</current_state>

Predict the next scheduler event. What happens next?
Respond in JSON only — no markdown fences, no text outside the JSON object:
{"event_type":"GoStart|GoBlock|GoUnblock|GoCreate|GoEnd|GoSched","goroutine_id":<integer>,"reasoning":"<brief explanation>","confidence":"high|medium|low"}

[Assistant] {"event_type": "GoStart", "goroutine_id": 37}


[System] You are a code execution simulator.

[User]
You are reasoning about concurrent Go program execution.

Here is a Go program:
<program>
// WEAVE_META
// outcome: race
// concurrency_pattern: mutex
// goroutine_count: 3
// expected_nondeterminism: medium
// description: Human-written GoBench bug kernel grpc_1748 (race)

package main

import (
	"os"
	"runtime/trace"
	"sync"
		"time"
)

var minConnectTimeout = 10 * time.Second

var balanceMutex sync.Mutex // We add this for avoiding other data race

type Balancer interface {
	HandleResolvedAddrs()
}

type Builder interface {
	Build(cc balancer_ClientConn) Balancer
}

func newPickfirstBuilder() Builder {
	return &pickfirstBuilder{}
}

type pickfirstBuilder struct{}

func (*pickfirstBuilder) Build(cc balancer_ClientConn) Balancer {
	return &pickfirstBalancer{cc: cc}
}

type SubConn interface {
	Connect()
}

type balancer_ClientConn interface {
	NewSubConn() SubConn
}

type pickfirstBalancer struct {
	cc balancer_ClientConn
	sc SubConn
}

func (b *pickfirstBalancer) HandleResolvedAddrs() {
	b.sc = b.cc.NewSubConn()
	b.sc.Connect()
}

type pickerWrapper struct {
	mu sync.Mutex
}

type acBalancerWrapper struct {
	mu sync.Mutex
	ac *addrConn
}

type addrConn struct {
	cc   *ClientConn
	acbw SubConn
	mu   sync.Mutex
}

func (ac *addrConn) resetTransport() {
	_ = minConnectTimeout
}

func (ac *addrConn) transportMonitor() {
	ac.resetTransport()
}

func (ac *addrConn) connect() {
	go func() {
		ac.transportMonitor()
	}()
}

func (acbw *acBalancerWrapper) Connect() {
	acbw.mu.Lock()
	defer acbw.mu.Unlock()
	acbw.ac.connect()
}

func newPickerWrapper() *pickerWrapper {
	return &pickerWrapper{}
}

type ClientConn struct {
	mu sync.Mutex
}

func (cc *ClientConn) switchBalancer() {
	builder := newPickfirstBuilder()
	newCCBalancerWrapper(cc, builder)
}

func (cc *ClientConn) newAddrConn() *addrConn {
	return &addrConn{cc: cc}
}

type ccBalancerWrapper struct {
	cc       *ClientConn
	balancer Balancer
}

func (ccb *ccBalancerWrapper) watcher() {
	for i := 0; i < 10; i++ {
		balanceMutex.Lock()
		if ccb.balancer != nil {
			balanceMutex.Unlock()
			ccb.balancer.HandleResolvedAddrs()
		} else {
			balanceMutex.Unlock()
		}
	}
}

func (ccb *ccBalancerWrapper) NewSubConn() SubConn {
	ac := ccb.cc.newAddrConn()
	acbw := &acBalancerWrapper{ac: ac}
	acbw.ac.mu.Lock()
	ac.acbw = acbw
	acbw.ac.mu.Unlock()
	return acbw
}

func newCCBalancerWrapper(cc *ClientConn, b Builder) {
	ccb := &ccBalancerWrapper{cc: cc}
	go ccb.watcher()
	balanceMutex.Lock()
	defer balanceMutex.Unlock()
	ccb.balancer = b.Build(ccb)
}

func main() {
	if tf := os.Getenv("WEAVE_TRACE_FILE"); tf != "" {
		f, err := os.Create(tf)
		if err == nil {
			if err := trace.Start(f); err == nil {
				defer func() { trace.Stop(); f.Close() }()
			}
		}
	}

	var wg sync.WaitGroup
	wg.Add(1)
	go func() {
		defer wg.Done()
		mctBkp := minConnectTimeout
		// Call this only after transportMonitor goroutine has ended.
		defer func() {
			minConnectTimeout = mctBkp
		}()
		cc := &ClientConn{}
		cc.switchBalancer()
	}()
	wg.Wait()
}

</program>

Here is a partial execution trace showing goroutine scheduler events so far:
<trace>
[
  {
    "event_id": 8,
    "timestamp_ns": 14761361312896,
    "event_type": "GoBlock",
    "goroutine_id": 35,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 9,
    "timestamp_ns": 14761361317568,
    "event_type": "GoBlock",
    "goroutine_id": 36,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 10,
    "timestamp_ns": 14761361330496,
    "event_type": "GoBlock",
    "goroutine_id": 37,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 11,
    "timestamp_ns": 14761361366656,
    "event_type": "GoUnblock",
    "goroutine_id": 37,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 12,
    "timestamp_ns": 14761361366720,
    "event_type": "GoStart",
    "goroutine_id": 37,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 13,
    "timestamp_ns": 14761361369984,
    "event_type": "GoBlock",
    "goroutine_id": 37,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 14,
    "timestamp_ns": 14761361372416,
    "event_type": "GoStart",
    "goroutine_id": 38,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 15,
    "timestamp_ns": 14761361375232,
    "event_type": "GoStart",
    "goroutine_id": 37,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 16,
    "timestamp_ns": 14761361376512,
    "event_type": "GoBlock",
    "goroutine_id": 37,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 17,
    "timestamp_ns": 14761361397824,
    "event_type": "GoCreate",
    "goroutine_id": 49,
    "goroutines": {
      "1": {
        "status": "blocked",
        "blocked_on": "sync",
        "locals_hint": "sync.(*WaitGroup).Wait"
      },
      "35": {
        "status": "blocked",
        "blocked_on": "chan receive",
        "locals_hint": "runtime.chanrecv1"
      },
      "36": {
        "status": "blocked",
        "blocked_on": "chan receive",
        "locals_hint": "runtime.chanrecv1"
      },
      "37": {
        "status": "blocked",
        "blocked_on": "system goroutine wait",
        "locals_hint": "runtime/trace.(*traceMultiplexer).startLocked.func1"
      },
      "38": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "49": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "main.newCCBalancerWrapper"
      }
    },
    "channels": {},
    "mutexes": {}
  }
]
</trace>

The current goroutine states are:
<current_state>
{
  "event_id": 17,
  "timestamp_ns": 14761361397824,
  "event_type": "GoCreate",
  "goroutine_id": 49,
  "goroutines": {
    "1": {
      "status": "blocked",
      "blocked_on": "sync",
      "locals_hint": "sync.(*WaitGroup).Wait"
    },
    "35": {
      "status": "blocked",
      "blocked_on": "chan receive",
      "locals_hint": "runtime.chanrecv1"
    },
    "36": {
      "status": "blocked",
      "blocked_on": "chan receive",
      "locals_hint": "runtime.chanrecv1"
    },
    "37": {
      "status": "blocked",
      "blocked_on": "system goroutine wait",
      "locals_hint": "runtime/trace.(*traceMultiplexer).startLocked.func1"
    },
    "38": {
      "status": "running",
      "blocked_on": null,
      "locals_hint": "unknown"
    },
    "49": {
      "status": "runnable",
      "blocked_on": null,
      "locals_hint": "main.newCCBalancerWrapper"
    }
  },
  "channels": {},
  "mutexes": {}
}
</current_state>

Predict the next scheduler event. What happens next?
Respond in JSON only — no markdown fences, no text outside the JSON object:
{"event_type":"GoStart|GoBlock|GoUnblock|GoCreate|GoEnd|GoSched","goroutine_id":<integer>,"reasoning":"<brief explanation>","confidence":"high|medium|low"}

[Assistant] {"event_type": "GoUnblock", "goroutine_id": 1}


[System] You are a code execution simulator.

[User]
You are reasoning about concurrent Go program execution.

Here is a Go program:
<program>
// WEAVE_META
// outcome: race
// concurrency_pattern: mutex
// goroutine_count: 3
// expected_nondeterminism: medium
// description: Human-written GoBench bug kernel grpc_1748 (race)

package main

import (
	"os"
	"runtime/trace"
	"sync"
		"time"
)

var minConnectTimeout = 10 * time.Second

var balanceMutex sync.Mutex // We add this for avoiding other data race

type Balancer interface {
	HandleResolvedAddrs()
}

type Builder interface {
	Build(cc balancer_ClientConn) Balancer
}

func newPickfirstBuilder() Builder {
	return &pickfirstBuilder{}
}

type pickfirstBuilder struct{}

func (*pickfirstBuilder) Build(cc balancer_ClientConn) Balancer {
	return &pickfirstBalancer{cc: cc}
}

type SubConn interface {
	Connect()
}

type balancer_ClientConn interface {
	NewSubConn() SubConn
}

type pickfirstBalancer struct {
	cc balancer_ClientConn
	sc SubConn
}

func (b *pickfirstBalancer) HandleResolvedAddrs() {
	b.sc = b.cc.NewSubConn()
	b.sc.Connect()
}

type pickerWrapper struct {
	mu sync.Mutex
}

type acBalancerWrapper struct {
	mu sync.Mutex
	ac *addrConn
}

type addrConn struct {
	cc   *ClientConn
	acbw SubConn
	mu   sync.Mutex
}

func (ac *addrConn) resetTransport() {
	_ = minConnectTimeout
}

func (ac *addrConn) transportMonitor() {
	ac.resetTransport()
}

func (ac *addrConn) connect() {
	go func() {
		ac.transportMonitor()
	}()
}

func (acbw *acBalancerWrapper) Connect() {
	acbw.mu.Lock()
	defer acbw.mu.Unlock()
	acbw.ac.connect()
}

func newPickerWrapper() *pickerWrapper {
	return &pickerWrapper{}
}

type ClientConn struct {
	mu sync.Mutex
}

func (cc *ClientConn) switchBalancer() {
	builder := newPickfirstBuilder()
	newCCBalancerWrapper(cc, builder)
}

func (cc *ClientConn) newAddrConn() *addrConn {
	return &addrConn{cc: cc}
}

type ccBalancerWrapper struct {
	cc       *ClientConn
	balancer Balancer
}

func (ccb *ccBalancerWrapper) watcher() {
	for i := 0; i < 10; i++ {
		balanceMutex.Lock()
		if ccb.balancer != nil {
			balanceMutex.Unlock()
			ccb.balancer.HandleResolvedAddrs()
		} else {
			balanceMutex.Unlock()
		}
	}
}

func (ccb *ccBalancerWrapper) NewSubConn() SubConn {
	ac := ccb.cc.newAddrConn()
	acbw := &acBalancerWrapper{ac: ac}
	acbw.ac.mu.Lock()
	ac.acbw = acbw
	acbw.ac.mu.Unlock()
	return acbw
}

func newCCBalancerWrapper(cc *ClientConn, b Builder) {
	ccb := &ccBalancerWrapper{cc: cc}
	go ccb.watcher()
	balanceMutex.Lock()
	defer balanceMutex.Unlock()
	ccb.balancer = b.Build(ccb)
}

func main() {
	if tf := os.Getenv("WEAVE_TRACE_FILE"); tf != "" {
		f, err := os.Create(tf)
		if err == nil {
			if err := trace.Start(f); err == nil {
				defer func() { trace.Stop(); f.Close() }()
			}
		}
	}

	var wg sync.WaitGroup
	wg.Add(1)
	go func() {
		defer wg.Done()
		mctBkp := minConnectTimeout
		// Call this only after transportMonitor goroutine has ended.
		defer func() {
			minConnectTimeout = mctBkp
		}()
		cc := &ClientConn{}
		cc.switchBalancer()
	}()
	wg.Wait()
}

</program>

Here is a partial execution trace showing goroutine scheduler events so far:
<trace>
[
  {
    "event_id": 8,
    "timestamp_ns": 14761361312896,
    "event_type": "GoBlock",
    "goroutine_id": 35,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 9,
    "timestamp_ns": 14761361317568,
    "event_type": "GoBlock",
    "goroutine_id": 36,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 10,
    "timestamp_ns": 14761361330496,
    "event_type": "GoBlock",
    "goroutine_id": 37,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 11,
    "timestamp_ns": 14761361366656,
    "event_type": "GoUnblock",
    "goroutine_id": 37,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 12,
    "timestamp_ns": 14761361366720,
    "event_type": "GoStart",
    "goroutine_id": 37,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 13,
    "timestamp_ns": 14761361369984,
    "event_type": "GoBlock",
    "goroutine_id": 37,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 14,
    "timestamp_ns": 14761361372416,
    "event_type": "GoStart",
    "goroutine_id": 38,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 15,
    "timestamp_ns": 14761361375232,
    "event_type": "GoStart",
    "goroutine_id": 37,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 16,
    "timestamp_ns": 14761361376512,
    "event_type": "GoBlock",
    "goroutine_id": 37,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 17,
    "timestamp_ns": 14761361397824,
    "event_type": "GoCreate",
    "goroutine_id": 49,
    "goroutines": {
      "1": {
        "status": "blocked",
        "blocked_on": "sync",
        "locals_hint": "sync.(*WaitGroup).Wait"
      },
      "35": {
        "status": "blocked",
        "blocked_on": "chan receive",
        "locals_hint": "runtime.chanrecv1"
      },
      "36": {
        "status": "blocked",
        "blocked_on": "chan receive",
        "locals_hint": "runtime.chanrecv1"
      },
      "37": {
        "status": "blocked",
        "blocked_on": "system goroutine wait",
        "locals_hint": "runtime/trace.(*traceMultiplexer).startLocked.func1"
      },
      "38": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "49": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "main.newCCBalancerWrapper"
      }
    },
    "channels": {},
    "mutexes": {}
  }
]
</trace>

The current goroutine states are:
<current_state>
{
  "event_id": 17,
  "timestamp_ns": 14761361397824,
  "event_type": "GoCreate",
  "goroutine_id": 49,
  "goroutines": {
    "1": {
      "status": "blocked",
      "blocked_on": "sync",
      "locals_hint": "sync.(*WaitGroup).Wait"
    },
    "35": {
      "status": "blocked",
      "blocked_on": "chan receive",
      "locals_hint": "runtime.chanrecv1"
    },
    "36": {
      "status": "blocked",
      "blocked_on": "chan receive",
      "locals_hint": "runtime.chanrecv1"
    },
    "37": {
      "status": "blocked",
      "blocked_on": "system goroutine wait",
      "locals_hint": "runtime/trace.(*traceMultiplexer).startLocked.func1"
    },
    "38": {
      "status": "running",
      "blocked_on": null,
      "locals_hint": "unknown"
    },
    "49": {
      "status": "runnable",
      "blocked_on": null,
      "locals_hint": "main.newCCBalancerWrapper"
    }
  },
  "channels": {},
  "mutexes": {}
}
</current_state>

Predict the next scheduler event. What happens next?
Respond in JSON only — no markdown fences, no text outside the JSON object:
{"event_type":"GoStart|GoBlock|GoUnblock|GoCreate|GoEnd|GoSched","goroutine_id":<integer>,"reasoning":"<brief explanation>","confidence":"high|medium|low"}

[Assistant] {"event_type": "GoUnblock", "goroutine_id": 1}


[System] You are a code execution simulator.

[User]
You are reasoning about concurrent Go program execution.

Here is a Go program:
<program>
// WEAVE_META
// outcome: race
// concurrency_pattern: mutex
// goroutine_count: 3
// expected_nondeterminism: medium
// description: Human-written GoBench bug kernel grpc_1748 (race)

package main

import (
	"os"
	"runtime/trace"
	"sync"
		"time"
)

var minConnectTimeout = 10 * time.Second

var balanceMutex sync.Mutex // We add this for avoiding other data race

type Balancer interface {
	HandleResolvedAddrs()
}

type Builder interface {
	Build(cc balancer_ClientConn) Balancer
}

func newPickfirstBuilder() Builder {
	return &pickfirstBuilder{}
}

type pickfirstBuilder struct{}

func (*pickfirstBuilder) Build(cc balancer_ClientConn) Balancer {
	return &pickfirstBalancer{cc: cc}
}

type SubConn interface {
	Connect()
}

type balancer_ClientConn interface {
	NewSubConn() SubConn
}

type pickfirstBalancer struct {
	cc balancer_ClientConn
	sc SubConn
}

func (b *pickfirstBalancer) HandleResolvedAddrs() {
	b.sc = b.cc.NewSubConn()
	b.sc.Connect()
}

type pickerWrapper struct {
	mu sync.Mutex
}

type acBalancerWrapper struct {
	mu sync.Mutex
	ac *addrConn
}

type addrConn struct {
	cc   *ClientConn
	acbw SubConn
	mu   sync.Mutex
}

func (ac *addrConn) resetTransport() {
	_ = minConnectTimeout
}

func (ac *addrConn) transportMonitor() {
	ac.resetTransport()
}

func (ac *addrConn) connect() {
	go func() {
		ac.transportMonitor()
	}()
}

func (acbw *acBalancerWrapper) Connect() {
	acbw.mu.Lock()
	defer acbw.mu.Unlock()
	acbw.ac.connect()
}

func newPickerWrapper() *pickerWrapper {
	return &pickerWrapper{}
}

type ClientConn struct {
	mu sync.Mutex
}

func (cc *ClientConn) switchBalancer() {
	builder := newPickfirstBuilder()
	newCCBalancerWrapper(cc, builder)
}

func (cc *ClientConn) newAddrConn() *addrConn {
	return &addrConn{cc: cc}
}

type ccBalancerWrapper struct {
	cc       *ClientConn
	balancer Balancer
}

func (ccb *ccBalancerWrapper) watcher() {
	for i := 0; i < 10; i++ {
		balanceMutex.Lock()
		if ccb.balancer != nil {
			balanceMutex.Unlock()
			ccb.balancer.HandleResolvedAddrs()
		} else {
			balanceMutex.Unlock()
		}
	}
}

func (ccb *ccBalancerWrapper) NewSubConn() SubConn {
	ac := ccb.cc.newAddrConn()
	acbw := &acBalancerWrapper{ac: ac}
	acbw.ac.mu.Lock()
	ac.acbw = acbw
	acbw.ac.mu.Unlock()
	return acbw
}

func newCCBalancerWrapper(cc *ClientConn, b Builder) {
	ccb := &ccBalancerWrapper{cc: cc}
	go ccb.watcher()
	balanceMutex.Lock()
	defer balanceMutex.Unlock()
	ccb.balancer = b.Build(ccb)
}

func main() {
	if tf := os.Getenv("WEAVE_TRACE_FILE"); tf != "" {
		f, err := os.Create(tf)
		if err == nil {
			if err := trace.Start(f); err == nil {
				defer func() { trace.Stop(); f.Close() }()
			}
		}
	}

	var wg sync.WaitGroup
	wg.Add(1)
	go func() {
		defer wg.Done()
		mctBkp := minConnectTimeout
		// Call this only after transportMonitor goroutine has ended.
		defer func() {
			minConnectTimeout = mctBkp
		}()
		cc := &ClientConn{}
		cc.switchBalancer()
	}()
	wg.Wait()
}

</program>

Here is a partial execution trace showing goroutine scheduler events so far:
<trace>
[
  {
    "event_id": 8,
    "timestamp_ns": 14761361312896,
    "event_type": "GoBlock",
    "goroutine_id": 35,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 9,
    "timestamp_ns": 14761361317568,
    "event_type": "GoBlock",
    "goroutine_id": 36,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 10,
    "timestamp_ns": 14761361330496,
    "event_type": "GoBlock",
    "goroutine_id": 37,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 11,
    "timestamp_ns": 14761361366656,
    "event_type": "GoUnblock",
    "goroutine_id": 37,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 12,
    "timestamp_ns": 14761361366720,
    "event_type": "GoStart",
    "goroutine_id": 37,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 13,
    "timestamp_ns": 14761361369984,
    "event_type": "GoBlock",
    "goroutine_id": 37,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 14,
    "timestamp_ns": 14761361372416,
    "event_type": "GoStart",
    "goroutine_id": 38,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 15,
    "timestamp_ns": 14761361375232,
    "event_type": "GoStart",
    "goroutine_id": 37,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 16,
    "timestamp_ns": 14761361376512,
    "event_type": "GoBlock",
    "goroutine_id": 37,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 17,
    "timestamp_ns": 14761361397824,
    "event_type": "GoCreate",
    "goroutine_id": 49,
    "goroutines": {
      "1": {
        "status": "blocked",
        "blocked_on": "sync",
        "locals_hint": "sync.(*WaitGroup).Wait"
      },
      "35": {
        "status": "blocked",
        "blocked_on": "chan receive",
        "locals_hint": "runtime.chanrecv1"
      },
      "36": {
        "status": "blocked",
        "blocked_on": "chan receive",
        "locals_hint": "runtime.chanrecv1"
      },
      "37": {
        "status": "blocked",
        "blocked_on": "system goroutine wait",
        "locals_hint": "runtime/trace.(*traceMultiplexer).startLocked.func1"
      },
      "38": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "49": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "main.newCCBalancerWrapper"
      }
    },
    "channels": {},
    "mutexes": {}
  }
]
</trace>

The current goroutine states are:
<current_state>
{
  "event_id": 17,
  "timestamp_ns": 14761361397824,
  "event_type": "GoCreate",
  "goroutine_id": 49,
  "goroutines": {
    "1": {
      "status": "blocked",
      "blocked_on": "sync",
      "locals_hint": "sync.(*WaitGroup).Wait"
    },
    "35": {
      "status": "blocked",
      "blocked_on": "chan receive",
      "locals_hint": "runtime.chanrecv1"
    },
    "36": {
      "status": "blocked",
      "blocked_on": "chan receive",
      "locals_hint": "runtime.chanrecv1"
    },
    "37": {
      "status": "blocked",
      "blocked_on": "system goroutine wait",
      "locals_hint": "runtime/trace.(*traceMultiplexer).startLocked.func1"
    },
    "38": {
      "status": "running",
      "blocked_on": null,
      "locals_hint": "unknown"
    },
    "49": {
      "status": "runnable",
      "blocked_on": null,
      "locals_hint": "main.newCCBalancerWrapper"
    }
  },
  "channels": {},
  "mutexes": {}
}
</current_state>

Predict the next scheduler event. What happens next?
Respond in JSON only — no markdown fences, no text outside the JSON object:
{"event_type":"GoStart|GoBlock|GoUnblock|GoCreate|GoEnd|GoSched","goroutine_id":<integer>,"reasoning":"<brief explanation>","confidence":"high|medium|low"}

[Assistant] {"event_type": "GoStart", "goroutine_id": 17}


[System] You are a code execution simulator.

[User]
You are reasoning about concurrent Go program execution.

Here is a Go program:
<program>
// WEAVE_META
// outcome: race
// concurrency_pattern: mutex
// goroutine_count: 3
// expected_nondeterminism: medium
// description: Human-written GoBench bug kernel grpc_1748 (race)

package main

import (
	"os"
	"runtime/trace"
	"sync"
		"time"
)

var minConnectTimeout = 10 * time.Second

var balanceMutex sync.Mutex // We add this for avoiding other data race

type Balancer interface {
	HandleResolvedAddrs()
}

type Builder interface {
	Build(cc balancer_ClientConn) Balancer
}

func newPickfirstBuilder() Builder {
	return &pickfirstBuilder{}
}

type pickfirstBuilder struct{}

func (*pickfirstBuilder) Build(cc balancer_ClientConn) Balancer {
	return &pickfirstBalancer{cc: cc}
}

type SubConn interface {
	Connect()
}

type balancer_ClientConn interface {
	NewSubConn() SubConn
}

type pickfirstBalancer struct {
	cc balancer_ClientConn
	sc SubConn
}

func (b *pickfirstBalancer) HandleResolvedAddrs() {
	b.sc = b.cc.NewSubConn()
	b.sc.Connect()
}

type pickerWrapper struct {
	mu sync.Mutex
}

type acBalancerWrapper struct {
	mu sync.Mutex
	ac *addrConn
}

type addrConn struct {
	cc   *ClientConn
	acbw SubConn
	mu   sync.Mutex
}

func (ac *addrConn) resetTransport() {
	_ = minConnectTimeout
}

func (ac *addrConn) transportMonitor() {
	ac.resetTransport()
}

func (ac *addrConn) connect() {
	go func() {
		ac.transportMonitor()
	}()
}

func (acbw *acBalancerWrapper) Connect() {
	acbw.mu.Lock()
	defer acbw.mu.Unlock()
	acbw.ac.connect()
}

func newPickerWrapper() *pickerWrapper {
	return &pickerWrapper{}
}

type ClientConn struct {
	mu sync.Mutex
}

func (cc *ClientConn) switchBalancer() {
	builder := newPickfirstBuilder()
	newCCBalancerWrapper(cc, builder)
}

func (cc *ClientConn) newAddrConn() *addrConn {
	return &addrConn{cc: cc}
}

type ccBalancerWrapper struct {
	cc       *ClientConn
	balancer Balancer
}

func (ccb *ccBalancerWrapper) watcher() {
	for i := 0; i < 10; i++ {
		balanceMutex.Lock()
		if ccb.balancer != nil {
			balanceMutex.Unlock()
			ccb.balancer.HandleResolvedAddrs()
		} else {
			balanceMutex.Unlock()
		}
	}
}

func (ccb *ccBalancerWrapper) NewSubConn() SubConn {
	ac := ccb.cc.newAddrConn()
	acbw := &acBalancerWrapper{ac: ac}
	acbw.ac.mu.Lock()
	ac.acbw = acbw
	acbw.ac.mu.Unlock()
	return acbw
}

func newCCBalancerWrapper(cc *ClientConn, b Builder) {
	ccb := &ccBalancerWrapper{cc: cc}
	go ccb.watcher()
	balanceMutex.Lock()
	defer balanceMutex.Unlock()
	ccb.balancer = b.Build(ccb)
}

func main() {
	if tf := os.Getenv("WEAVE_TRACE_FILE"); tf != "" {
		f, err := os.Create(tf)
		if err == nil {
			if err := trace.Start(f); err == nil {
				defer func() { trace.Stop(); f.Close() }()
			}
		}
	}

	var wg sync.WaitGroup
	wg.Add(1)
	go func() {
		defer wg.Done()
		mctBkp := minConnectTimeout
		// Call this only after transportMonitor goroutine has ended.
		defer func() {
			minConnectTimeout = mctBkp
		}()
		cc := &ClientConn{}
		cc.switchBalancer()
	}()
	wg.Wait()
}

</program>

Here is a partial execution trace showing goroutine scheduler events so far:
<trace>
[
  {
    "event_id": 8,
    "timestamp_ns": 14761361312896,
    "event_type": "GoBlock",
    "goroutine_id": 35,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 9,
    "timestamp_ns": 14761361317568,
    "event_type": "GoBlock",
    "goroutine_id": 36,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 10,
    "timestamp_ns": 14761361330496,
    "event_type": "GoBlock",
    "goroutine_id": 37,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 11,
    "timestamp_ns": 14761361366656,
    "event_type": "GoUnblock",
    "goroutine_id": 37,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 12,
    "timestamp_ns": 14761361366720,
    "event_type": "GoStart",
    "goroutine_id": 37,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 13,
    "timestamp_ns": 14761361369984,
    "event_type": "GoBlock",
    "goroutine_id": 37,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 14,
    "timestamp_ns": 14761361372416,
    "event_type": "GoStart",
    "goroutine_id": 38,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 15,
    "timestamp_ns": 14761361375232,
    "event_type": "GoStart",
    "goroutine_id": 37,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 16,
    "timestamp_ns": 14761361376512,
    "event_type": "GoBlock",
    "goroutine_id": 37,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 17,
    "timestamp_ns": 14761361397824,
    "event_type": "GoCreate",
    "goroutine_id": 49,
    "goroutines": {
      "1": {
        "status": "blocked",
        "blocked_on": "sync",
        "locals_hint": "sync.(*WaitGroup).Wait"
      },
      "35": {
        "status": "blocked",
        "blocked_on": "chan receive",
        "locals_hint": "runtime.chanrecv1"
      },
      "36": {
        "status": "blocked",
        "blocked_on": "chan receive",
        "locals_hint": "runtime.chanrecv1"
      },
      "37": {
        "status": "blocked",
        "blocked_on": "system goroutine wait",
        "locals_hint": "runtime/trace.(*traceMultiplexer).startLocked.func1"
      },
      "38": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "49": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "main.newCCBalancerWrapper"
      }
    },
    "channels": {},
    "mutexes": {}
  }
]
</trace>

The current goroutine states are:
<current_state>
{
  "event_id": 17,
  "timestamp_ns": 14761361397824,
  "event_type": "GoCreate",
  "goroutine_id": 49,
  "goroutines": {
    "1": {
      "status": "blocked",
      "blocked_on": "sync",
      "locals_hint": "sync.(*WaitGroup).Wait"
    },
    "35": {
      "status": "blocked",
      "blocked_on": "chan receive",
      "locals_hint": "runtime.chanrecv1"
    },
    "36": {
      "status": "blocked",
      "blocked_on": "chan receive",
      "locals_hint": "runtime.chanrecv1"
    },
    "37": {
      "status": "blocked",
      "blocked_on": "system goroutine wait",
      "locals_hint": "runtime/trace.(*traceMultiplexer).startLocked.func1"
    },
    "38": {
      "status": "running",
      "blocked_on": null,
      "locals_hint": "unknown"
    },
    "49": {
      "status": "runnable",
      "blocked_on": null,
      "locals_hint": "main.newCCBalancerWrapper"
    }
  },
  "channels": {},
  "mutexes": {}
}
</current_state>

Predict the next scheduler event. What happens next?
Respond in JSON only — no markdown fences, no text outside the JSON object:
{"event_type":"GoStart|GoBlock|GoUnblock|GoCreate|GoEnd|GoSched","goroutine_id":<integer>,"reasoning":"<brief explanation>","confidence":"high|medium|low"}

[Assistant] {"event_type": "GoSched", "goroutine_id": 39}


[System] You are a code execution simulator.

[User]
You are reasoning about concurrent Go program execution.

Here is a Go program:
<program>
// WEAVE_META
// outcome: race
// concurrency_pattern: mutex
// goroutine_count: 3
// expected_nondeterminism: medium
// description: Human-written GoBench bug kernel grpc_1748 (race)

package main

import (
	"os"
	"runtime/trace"
	"sync"
		"time"
)

var minConnectTimeout = 10 * time.Second

var balanceMutex sync.Mutex // We add this for avoiding other data race

type Balancer interface {
	HandleResolvedAddrs()
}

type Builder interface {
	Build(cc balancer_ClientConn) Balancer
}

func newPickfirstBuilder() Builder {
	return &pickfirstBuilder{}
}

type pickfirstBuilder struct{}

func (*pickfirstBuilder) Build(cc balancer_ClientConn) Balancer {
	return &pickfirstBalancer{cc: cc}
}

type SubConn interface {
	Connect()
}

type balancer_ClientConn interface {
	NewSubConn() SubConn
}

type pickfirstBalancer struct {
	cc balancer_ClientConn
	sc SubConn
}

func (b *pickfirstBalancer) HandleResolvedAddrs() {
	b.sc = b.cc.NewSubConn()
	b.sc.Connect()
}

type pickerWrapper struct {
	mu sync.Mutex
}

type acBalancerWrapper struct {
	mu sync.Mutex
	ac *addrConn
}

type addrConn struct {
	cc   *ClientConn
	acbw SubConn
	mu   sync.Mutex
}

func (ac *addrConn) resetTransport() {
	_ = minConnectTimeout
}

func (ac *addrConn) transportMonitor() {
	ac.resetTransport()
}

func (ac *addrConn) connect() {
	go func() {
		ac.transportMonitor()
	}()
}

func (acbw *acBalancerWrapper) Connect() {
	acbw.mu.Lock()
	defer acbw.mu.Unlock()
	acbw.ac.connect()
}

func newPickerWrapper() *pickerWrapper {
	return &pickerWrapper{}
}

type ClientConn struct {
	mu sync.Mutex
}

func (cc *ClientConn) switchBalancer() {
	builder := newPickfirstBuilder()
	newCCBalancerWrapper(cc, builder)
}

func (cc *ClientConn) newAddrConn() *addrConn {
	return &addrConn{cc: cc}
}

type ccBalancerWrapper struct {
	cc       *ClientConn
	balancer Balancer
}

func (ccb *ccBalancerWrapper) watcher() {
	for i := 0; i < 10; i++ {
		balanceMutex.Lock()
		if ccb.balancer != nil {
			balanceMutex.Unlock()
			ccb.balancer.HandleResolvedAddrs()
		} else {
			balanceMutex.Unlock()
		}
	}
}

func (ccb *ccBalancerWrapper) NewSubConn() SubConn {
	ac := ccb.cc.newAddrConn()
	acbw := &acBalancerWrapper{ac: ac}
	acbw.ac.mu.Lock()
	ac.acbw = acbw
	acbw.ac.mu.Unlock()
	return acbw
}

func newCCBalancerWrapper(cc *ClientConn, b Builder) {
	ccb := &ccBalancerWrapper{cc: cc}
	go ccb.watcher()
	balanceMutex.Lock()
	defer balanceMutex.Unlock()
	ccb.balancer = b.Build(ccb)
}

func main() {
	if tf := os.Getenv("WEAVE_TRACE_FILE"); tf != "" {
		f, err := os.Create(tf)
		if err == nil {
			if err := trace.Start(f); err == nil {
				defer func() { trace.Stop(); f.Close() }()
			}
		}
	}

	var wg sync.WaitGroup
	wg.Add(1)
	go func() {
		defer wg.Done()
		mctBkp := minConnectTimeout
		// Call this only after transportMonitor goroutine has ended.
		defer func() {
			minConnectTimeout = mctBkp
		}()
		cc := &ClientConn{}
		cc.switchBalancer()
	}()
	wg.Wait()
}

</program>

Here is a partial execution trace showing goroutine scheduler events so far:
<trace>
[
  {
    "event_id": 8,
    "timestamp_ns": 14761361312896,
    "event_type": "GoBlock",
    "goroutine_id": 35,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 9,
    "timestamp_ns": 14761361317568,
    "event_type": "GoBlock",
    "goroutine_id": 36,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 10,
    "timestamp_ns": 14761361330496,
    "event_type": "GoBlock",
    "goroutine_id": 37,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 11,
    "timestamp_ns": 14761361366656,
    "event_type": "GoUnblock",
    "goroutine_id": 37,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 12,
    "timestamp_ns": 14761361366720,
    "event_type": "GoStart",
    "goroutine_id": 37,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 13,
    "timestamp_ns": 14761361369984,
    "event_type": "GoBlock",
    "goroutine_id": 37,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 14,
    "timestamp_ns": 14761361372416,
    "event_type": "GoStart",
    "goroutine_id": 38,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 15,
    "timestamp_ns": 14761361375232,
    "event_type": "GoStart",
    "goroutine_id": 37,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 16,
    "timestamp_ns": 14761361376512,
    "event_type": "GoBlock",
    "goroutine_id": 37,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 17,
    "timestamp_ns": 14761361397824,
    "event_type": "GoCreate",
    "goroutine_id": 49,
    "goroutines": {
      "1": {
        "status": "blocked",
        "blocked_on": "sync",
        "locals_hint": "sync.(*WaitGroup).Wait"
      },
      "35": {
        "status": "blocked",
        "blocked_on": "chan receive",
        "locals_hint": "runtime.chanrecv1"
      },
      "36": {
        "status": "blocked",
        "blocked_on": "chan receive",
        "locals_hint": "runtime.chanrecv1"
      },
      "37": {
        "status": "blocked",
        "blocked_on": "system goroutine wait",
        "locals_hint": "runtime/trace.(*traceMultiplexer).startLocked.func1"
      },
      "38": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "49": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "main.newCCBalancerWrapper"
      }
    },
    "channels": {},
    "mutexes": {}
  }
]
</trace>

The current goroutine states are:
<current_state>
{
  "event_id": 17,
  "timestamp_ns": 14761361397824,
  "event_type": "GoCreate",
  "goroutine_id": 49,
  "goroutines": {
    "1": {
      "status": "blocked",
      "blocked_on": "sync",
      "locals_hint": "sync.(*WaitGroup).Wait"
    },
    "35": {
      "status": "blocked",
      "blocked_on": "chan receive",
      "locals_hint": "runtime.chanrecv1"
    },
    "36": {
      "status": "blocked",
      "blocked_on": "chan receive",
      "locals_hint": "runtime.chanrecv1"
    },
    "37": {
      "status": "blocked",
      "blocked_on": "system goroutine wait",
      "locals_hint": "runtime/trace.(*traceMultiplexer).startLocked.func1"
    },
    "38": {
      "status": "running",
      "blocked_on": null,
      "locals_hint": "unknown"
    },
    "49": {
      "status": "runnable",
      "blocked_on": null,
      "locals_hint": "main.newCCBalancerWrapper"
    }
  },
  "channels": {},
  "mutexes": {}
}
</current_state>

Predict the next scheduler event. What happens next?
Respond in JSON only — no markdown fences, no text outside the JSON object:
{"event_type":"GoStart|GoBlock|GoUnblock|GoCreate|GoEnd|GoSched","goroutine_id":<integer>,"reasoning":"<brief explanation>","confidence":"high|medium|low"}

[Assistant] {"event_type": "GoStart", "goroutine_id": 11}


[System] You are a code execution simulator.

[User]
You are reasoning about concurrent Go program execution.

Here is a Go program:
<program>
// WEAVE_META
// outcome: leak
// concurrency_pattern: select
// goroutine_count: 3
// expected_nondeterminism: medium
// description: Human-written GoBench bug kernel grpc_660 (leak)

/*
 * Project: grpc-go
 * Issue or PR  : https://github.com/grpc/grpc-go/pull/660
 * Buggy version: db85417dd0de6cc6f583672c6175a7237e5b5dd2
 * fix commit-id: ceacfbcbc1514e4e677932fd55938ac455d182fb
 * Flaky: 100/100
 * Description:
 *   The parent function could return without draining the done channel.
 */
package main

import (
	"os"
	"runtime/trace"
	"math/rand"
	)

type benchmarkClient struct {
	stop chan bool
}

func (bc *benchmarkClient) doCloseLoopUnary() {
	for {
		done := make(chan bool)
		go func() { // G2
			if rand.Intn(10) > 7 {
				done <- false
				return
			}
			done <- true
		}()
		select {
		case <-bc.stop:
			return
		case <-done:
		}
	}
}

///
/// G1 						G2 				helper goroutine
/// doCloseLoopUnary()
///											bc.stop <- true
/// <-bc.stop
/// return
/// 						done <-
/// ----------------------G2 leak--------------------------
///

func main() {
	if tf := os.Getenv("WEAVE_TRACE_FILE"); tf != "" {
		f, err := os.Create(tf)
		if err == nil {
			if err := trace.Start(f); err == nil {
				defer func() { trace.Stop(); f.Close() }()
			}
		}
	}

	bc := &benchmarkClient{
		stop: make(chan bool),
	}
	go bc.doCloseLoopUnary() // G1
	go func() {              // helper goroutine
		bc.stop <- true
	}()
}

</program>

Here is a partial execution trace showing goroutine scheduler events so far:
<trace>
[
  {
    "event_id": 0,
    "timestamp_ns": 14764868226112,
    "event_type": "GoCreate",
    "goroutine_id": 19,
    "goroutines": {
      "1": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "19": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "runtime.traceStartReadCPU"
      }
    },
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 1,
    "timestamp_ns": 14764868237376,
    "event_type": "GoCreate",
    "goroutine_id": 20,
    "goroutines": {
      "1": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "19": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "runtime.traceStartReadCPU"
      },
      "20": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "runtime.(*traceAdvancerState).start"
      }
    },
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 2,
    "timestamp_ns": 14764868244288,
    "event_type": "GoStart",
    "goroutine_id": 19,
    "goroutines": {
      "1": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "19": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "20": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "runtime.(*traceAdvancerState).start"
      }
    },
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 3,
    "timestamp_ns": 14764868268352,
    "event_type": "GoCreate",
    "goroutine_id": 21,
    "goroutines": {
      "1": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "19": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "20": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "runtime.(*traceAdvancerState).start"
      },
      "21": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "runtime/trace.(*traceMultiplexer).startLocked"
      }
    },
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 4,
    "timestamp_ns": 14764868270144,
    "event_type": "GoStart",
    "goroutine_id": 20,
    "goroutines": {
      "1": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "19": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "20": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "21": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "runtime/trace.(*traceMultiplexer).startLocked"
      }
    },
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 5,
    "timestamp_ns": 14764868303360,
    "event_type": "GoStart",
    "goroutine_id": 21,
    "goroutines": {
      "1": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "19": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "20": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "21": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      }
    },
    "channels": {},
    "mutexes": {}
  }
]
</trace>

The current goroutine states are:
<current_state>
{
  "event_id": 5,
  "timestamp_ns": 14764868303360,
  "event_type": "GoStart",
  "goroutine_id": 21,
  "goroutines": {
    "1": {
      "status": "running",
      "blocked_on": null,
      "locals_hint": "unknown"
    },
    "19": {
      "status": "running",
      "blocked_on": null,
      "locals_hint": "unknown"
    },
    "20": {
      "status": "running",
      "blocked_on": null,
      "locals_hint": "unknown"
    },
    "21": {
      "status": "running",
      "blocked_on": null,
      "locals_hint": "unknown"
    }
  },
  "channels": {},
  "mutexes": {}
}
</current_state>

Predict the next scheduler event. What happens next?
Respond in JSON only — no markdown fences, no text outside the JSON object:
{"event_type":"GoStart|GoBlock|GoUnblock|GoCreate|GoEnd|GoSched","goroutine_id":<integer>,"reasoning":"<brief explanation>","confidence":"high|medium|low"}

[Assistant] {"event_type": "GoCreate", "goroutine_id": 22}


[System] You are a code execution simulator.

[User]
You are reasoning about concurrent Go program execution.

Here is a Go program:
<program>
// WEAVE_META
// outcome: leak
// concurrency_pattern: select
// goroutine_count: 3
// expected_nondeterminism: medium
// description: Human-written GoBench bug kernel grpc_660 (leak)

/*
 * Project: grpc-go
 * Issue or PR  : https://github.com/grpc/grpc-go/pull/660
 * Buggy version: db85417dd0de6cc6f583672c6175a7237e5b5dd2
 * fix commit-id: ceacfbcbc1514e4e677932fd55938ac455d182fb
 * Flaky: 100/100
 * Description:
 *   The parent function could return without draining the done channel.
 */
package main

import (
	"os"
	"runtime/trace"
	"math/rand"
	)

type benchmarkClient struct {
	stop chan bool
}

func (bc *benchmarkClient) doCloseLoopUnary() {
	for {
		done := make(chan bool)
		go func() { // G2
			if rand.Intn(10) > 7 {
				done <- false
				return
			}
			done <- true
		}()
		select {
		case <-bc.stop:
			return
		case <-done:
		}
	}
}

///
/// G1 						G2 				helper goroutine
/// doCloseLoopUnary()
///											bc.stop <- true
/// <-bc.stop
/// return
/// 						done <-
/// ----------------------G2 leak--------------------------
///

func main() {
	if tf := os.Getenv("WEAVE_TRACE_FILE"); tf != "" {
		f, err := os.Create(tf)
		if err == nil {
			if err := trace.Start(f); err == nil {
				defer func() { trace.Stop(); f.Close() }()
			}
		}
	}

	bc := &benchmarkClient{
		stop: make(chan bool),
	}
	go bc.doCloseLoopUnary() // G1
	go func() {              // helper goroutine
		bc.stop <- true
	}()
}

</program>

Here is a partial execution trace showing goroutine scheduler events so far:
<trace>
[
  {
    "event_id": 0,
    "timestamp_ns": 14764868226112,
    "event_type": "GoCreate",
    "goroutine_id": 19,
    "goroutines": {
      "1": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "19": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "runtime.traceStartReadCPU"
      }
    },
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 1,
    "timestamp_ns": 14764868237376,
    "event_type": "GoCreate",
    "goroutine_id": 20,
    "goroutines": {
      "1": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "19": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "runtime.traceStartReadCPU"
      },
      "20": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "runtime.(*traceAdvancerState).start"
      }
    },
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 2,
    "timestamp_ns": 14764868244288,
    "event_type": "GoStart",
    "goroutine_id": 19,
    "goroutines": {
      "1": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "19": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "20": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "runtime.(*traceAdvancerState).start"
      }
    },
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 3,
    "timestamp_ns": 14764868268352,
    "event_type": "GoCreate",
    "goroutine_id": 21,
    "goroutines": {
      "1": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "19": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "20": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "runtime.(*traceAdvancerState).start"
      },
      "21": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "runtime/trace.(*traceMultiplexer).startLocked"
      }
    },
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 4,
    "timestamp_ns": 14764868270144,
    "event_type": "GoStart",
    "goroutine_id": 20,
    "goroutines": {
      "1": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "19": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "20": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "21": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "runtime/trace.(*traceMultiplexer).startLocked"
      }
    },
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 5,
    "timestamp_ns": 14764868303360,
    "event_type": "GoStart",
    "goroutine_id": 21,
    "goroutines": {
      "1": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "19": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "20": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "21": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      }
    },
    "channels": {},
    "mutexes": {}
  }
]
</trace>

The current goroutine states are:
<current_state>
{
  "event_id": 5,
  "timestamp_ns": 14764868303360,
  "event_type": "GoStart",
  "goroutine_id": 21,
  "goroutines": {
    "1": {
      "status": "running",
      "blocked_on": null,
      "locals_hint": "unknown"
    },
    "19": {
      "status": "running",
      "blocked_on": null,
      "locals_hint": "unknown"
    },
    "20": {
      "status": "running",
      "blocked_on": null,
      "locals_hint": "unknown"
    },
    "21": {
      "status": "running",
      "blocked_on": null,
      "locals_hint": "unknown"
    }
  },
  "channels": {},
  "mutexes": {}
}
</current_state>

Predict the next scheduler event. What happens next?
Respond in JSON only — no markdown fences, no text outside the JSON object:
{"event_type":"GoStart|GoBlock|GoUnblock|GoCreate|GoEnd|GoSched","goroutine_id":<integer>,"reasoning":"<brief explanation>","confidence":"high|medium|low"}

[Assistant] {"event_type": "GoCreate", "goroutine_id": 11}


[System] You are a code execution simulator.

[User]
You are reasoning about concurrent Go program execution.

Here is a Go program:
<program>
// WEAVE_META
// outcome: leak
// concurrency_pattern: select
// goroutine_count: 3
// expected_nondeterminism: medium
// description: Human-written GoBench bug kernel grpc_660 (leak)

/*
 * Project: grpc-go
 * Issue or PR  : https://github.com/grpc/grpc-go/pull/660
 * Buggy version: db85417dd0de6cc6f583672c6175a7237e5b5dd2
 * fix commit-id: ceacfbcbc1514e4e677932fd55938ac455d182fb
 * Flaky: 100/100
 * Description:
 *   The parent function could return without draining the done channel.
 */
package main

import (
	"os"
	"runtime/trace"
	"math/rand"
	)

type benchmarkClient struct {
	stop chan bool
}

func (bc *benchmarkClient) doCloseLoopUnary() {
	for {
		done := make(chan bool)
		go func() { // G2
			if rand.Intn(10) > 7 {
				done <- false
				return
			}
			done <- true
		}()
		select {
		case <-bc.stop:
			return
		case <-done:
		}
	}
}

///
/// G1 						G2 				helper goroutine
/// doCloseLoopUnary()
///											bc.stop <- true
/// <-bc.stop
/// return
/// 						done <-
/// ----------------------G2 leak--------------------------
///

func main() {
	if tf := os.Getenv("WEAVE_TRACE_FILE"); tf != "" {
		f, err := os.Create(tf)
		if err == nil {
			if err := trace.Start(f); err == nil {
				defer func() { trace.Stop(); f.Close() }()
			}
		}
	}

	bc := &benchmarkClient{
		stop: make(chan bool),
	}
	go bc.doCloseLoopUnary() // G1
	go func() {              // helper goroutine
		bc.stop <- true
	}()
}

</program>

Here is a partial execution trace showing goroutine scheduler events so far:
<trace>
[
  {
    "event_id": 0,
    "timestamp_ns": 14764868226112,
    "event_type": "GoCreate",
    "goroutine_id": 19,
    "goroutines": {
      "1": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "19": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "runtime.traceStartReadCPU"
      }
    },
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 1,
    "timestamp_ns": 14764868237376,
    "event_type": "GoCreate",
    "goroutine_id": 20,
    "goroutines": {
      "1": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "19": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "runtime.traceStartReadCPU"
      },
      "20": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "runtime.(*traceAdvancerState).start"
      }
    },
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 2,
    "timestamp_ns": 14764868244288,
    "event_type": "GoStart",
    "goroutine_id": 19,
    "goroutines": {
      "1": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "19": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "20": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "runtime.(*traceAdvancerState).start"
      }
    },
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 3,
    "timestamp_ns": 14764868268352,
    "event_type": "GoCreate",
    "goroutine_id": 21,
    "goroutines": {
      "1": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "19": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "20": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "runtime.(*traceAdvancerState).start"
      },
      "21": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "runtime/trace.(*traceMultiplexer).startLocked"
      }
    },
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 4,
    "timestamp_ns": 14764868270144,
    "event_type": "GoStart",
    "goroutine_id": 20,
    "goroutines": {
      "1": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "19": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "20": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "21": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "runtime/trace.(*traceMultiplexer).startLocked"
      }
    },
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 5,
    "timestamp_ns": 14764868303360,
    "event_type": "GoStart",
    "goroutine_id": 21,
    "goroutines": {
      "1": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "19": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "20": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "21": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      }
    },
    "channels": {},
    "mutexes": {}
  }
]
</trace>

The current goroutine states are:
<current_state>
{
  "event_id": 5,
  "timestamp_ns": 14764868303360,
  "event_type": "GoStart",
  "goroutine_id": 21,
  "goroutines": {
    "1": {
      "status": "running",
      "blocked_on": null,
      "locals_hint": "unknown"
    },
    "19": {
      "status": "running",
      "blocked_on": null,
      "locals_hint": "unknown"
    },
    "20": {
      "status": "running",
      "blocked_on": null,
      "locals_hint": "unknown"
    },
    "21": {
      "status": "running",
      "blocked_on": null,
      "locals_hint": "unknown"
    }
  },
  "channels": {},
  "mutexes": {}
}
</current_state>

Predict the next scheduler event. What happens next?
Respond in JSON only — no markdown fences, no text outside the JSON object:
{"event_type":"GoStart|GoBlock|GoUnblock|GoCreate|GoEnd|GoSched","goroutine_id":<integer>,"reasoning":"<brief explanation>","confidence":"high|medium|low"}

[Assistant] {"event_type": "GoCreate", "goroutine_id": 8}