[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: success
// concurrency_pattern: pipeline
// goroutine_count: 4
// expected_nondeterminism: medium
// description: Pipeline pipeline stages stage1 -> stage2 -> stage3, leak_bug=False

package main

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

func stage1(out chan<- int, wg *sync.WaitGroup) {
	defer wg.Done()
	for i := 0; i < 5; i++ {
		out <- i
		time.Sleep(time.Millisecond * 1)
	}
	close(out)
}

func stage2(in <-chan int, out chan<- int, wg *sync.WaitGroup) {
	defer wg.Done()
	for v := range in {
		out <- v * 2
		time.Sleep(time.Millisecond * 1)
	}
	close(out)
}

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 wg1, wg2, wg3 sync.WaitGroup
	ch1 := make(chan int)
	ch2 := make(chan int)

	wg1.Add(1)
	go stage1(ch1, &wg1)

	wg2.Add(1)
	go stage2(ch1, ch2, &wg2)

	wg3.Add(1)
	go func(inCh <-chan int) {
		defer wg3.Done()
		for range inCh { /* normal drain */ }
	}(ch2)

	// Exit harness
	done := make(chan struct{})
	go func() {
		wg1.Wait()
		wg2.Wait()
		wg3.Wait()
		close(done)
	}()

	select {
	case <-done:
		fmt.Println("pipeline done")
	case <-time.After(200 * time.Millisecond):
		fmt.Println("pipeline timeout")
	}
}

</program>

Here is a partial execution trace showing goroutine scheduler events so far:
<trace>
[
  {
    "event_id": 42,
    "timestamp_ns": 14735369388416,
    "event_type": "GoStart",
    "goroutine_id": 40,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 43,
    "timestamp_ns": 14735369388672,
    "event_type": "GoBlock",
    "goroutine_id": 40,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 44,
    "timestamp_ns": 14735370506944,
    "event_type": "GoUnblock",
    "goroutine_id": 38,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 45,
    "timestamp_ns": 14735370507200,
    "event_type": "GoUnblock",
    "goroutine_id": 39,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 46,
    "timestamp_ns": 14735370509120,
    "event_type": "GoStart",
    "goroutine_id": 38,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 47,
    "timestamp_ns": 14735370509824,
    "event_type": "GoBlock",
    "goroutine_id": 38,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 48,
    "timestamp_ns": 14735370509952,
    "event_type": "GoStart",
    "goroutine_id": 39,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 49,
    "timestamp_ns": 14735370510720,
    "event_type": "GoUnblock",
    "goroutine_id": 38,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 50,
    "timestamp_ns": 14735370511168,
    "event_type": "GoUnblock",
    "goroutine_id": 40,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 51,
    "timestamp_ns": 14735370511360,
    "event_type": "GoBlock",
    "goroutine_id": 39,
    "goroutines": {
      "1": {
        "status": "blocked",
        "blocked_on": "select",
        "locals_hint": "runtime.selectgo"
      },
      "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": "runnable",
        "blocked_on": null,
        "locals_hint": "runtime.chanrecv2"
      },
      "39": {
        "status": "blocked",
        "blocked_on": "sleep",
        "locals_hint": "time.Sleep"
      },
      "40": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "runtime.chansend1"
      },
      "41": {
        "status": "blocked",
        "blocked_on": "sync",
        "locals_hint": "sync.(*WaitGroup).Wait"
      }
    },
    "channels": {},
    "mutexes": {}
  }
]
</trace>

The current goroutine states are:
<current_state>
{
  "event_id": 51,
  "timestamp_ns": 14735370511360,
  "event_type": "GoBlock",
  "goroutine_id": 39,
  "goroutines": {
    "1": {
      "status": "blocked",
      "blocked_on": "select",
      "locals_hint": "runtime.selectgo"
    },
    "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": "runnable",
      "blocked_on": null,
      "locals_hint": "runtime.chanrecv2"
    },
    "39": {
      "status": "blocked",
      "blocked_on": "sleep",
      "locals_hint": "time.Sleep"
    },
    "40": {
      "status": "runnable",
      "blocked_on": null,
      "locals_hint": "runtime.chansend1"
    },
    "41": {
      "status": "blocked",
      "blocked_on": "sync",
      "locals_hint": "sync.(*WaitGroup).Wait"
    }
  },
  "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": 24}


[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: success
// concurrency_pattern: pipeline
// goroutine_count: 4
// expected_nondeterminism: medium
// description: Pipeline pipeline stages stage1 -> stage2 -> stage3, leak_bug=False

package main

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

func stage1(out chan<- int, wg *sync.WaitGroup) {
	defer wg.Done()
	for i := 0; i < 5; i++ {
		out <- i
		time.Sleep(time.Millisecond * 1)
	}
	close(out)
}

func stage2(in <-chan int, out chan<- int, wg *sync.WaitGroup) {
	defer wg.Done()
	for v := range in {
		out <- v * 2
		time.Sleep(time.Millisecond * 1)
	}
	close(out)
}

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 wg1, wg2, wg3 sync.WaitGroup
	ch1 := make(chan int)
	ch2 := make(chan int)

	wg1.Add(1)
	go stage1(ch1, &wg1)

	wg2.Add(1)
	go stage2(ch1, ch2, &wg2)

	wg3.Add(1)
	go func(inCh <-chan int) {
		defer wg3.Done()
		for range inCh { /* normal drain */ }
	}(ch2)

	// Exit harness
	done := make(chan struct{})
	go func() {
		wg1.Wait()
		wg2.Wait()
		wg3.Wait()
		close(done)
	}()

	select {
	case <-done:
		fmt.Println("pipeline done")
	case <-time.After(200 * time.Millisecond):
		fmt.Println("pipeline timeout")
	}
}

</program>

Here is a partial execution trace showing goroutine scheduler events so far:
<trace>
[
  {
    "event_id": 42,
    "timestamp_ns": 14735369388416,
    "event_type": "GoStart",
    "goroutine_id": 40,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 43,
    "timestamp_ns": 14735369388672,
    "event_type": "GoBlock",
    "goroutine_id": 40,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 44,
    "timestamp_ns": 14735370506944,
    "event_type": "GoUnblock",
    "goroutine_id": 38,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 45,
    "timestamp_ns": 14735370507200,
    "event_type": "GoUnblock",
    "goroutine_id": 39,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 46,
    "timestamp_ns": 14735370509120,
    "event_type": "GoStart",
    "goroutine_id": 38,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 47,
    "timestamp_ns": 14735370509824,
    "event_type": "GoBlock",
    "goroutine_id": 38,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 48,
    "timestamp_ns": 14735370509952,
    "event_type": "GoStart",
    "goroutine_id": 39,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 49,
    "timestamp_ns": 14735370510720,
    "event_type": "GoUnblock",
    "goroutine_id": 38,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 50,
    "timestamp_ns": 14735370511168,
    "event_type": "GoUnblock",
    "goroutine_id": 40,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 51,
    "timestamp_ns": 14735370511360,
    "event_type": "GoBlock",
    "goroutine_id": 39,
    "goroutines": {
      "1": {
        "status": "blocked",
        "blocked_on": "select",
        "locals_hint": "runtime.selectgo"
      },
      "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": "runnable",
        "blocked_on": null,
        "locals_hint": "runtime.chanrecv2"
      },
      "39": {
        "status": "blocked",
        "blocked_on": "sleep",
        "locals_hint": "time.Sleep"
      },
      "40": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "runtime.chansend1"
      },
      "41": {
        "status": "blocked",
        "blocked_on": "sync",
        "locals_hint": "sync.(*WaitGroup).Wait"
      }
    },
    "channels": {},
    "mutexes": {}
  }
]
</trace>

The current goroutine states are:
<current_state>
{
  "event_id": 51,
  "timestamp_ns": 14735370511360,
  "event_type": "GoBlock",
  "goroutine_id": 39,
  "goroutines": {
    "1": {
      "status": "blocked",
      "blocked_on": "select",
      "locals_hint": "runtime.selectgo"
    },
    "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": "runnable",
      "blocked_on": null,
      "locals_hint": "runtime.chanrecv2"
    },
    "39": {
      "status": "blocked",
      "blocked_on": "sleep",
      "locals_hint": "time.Sleep"
    },
    "40": {
      "status": "runnable",
      "blocked_on": null,
      "locals_hint": "runtime.chansend1"
    },
    "41": {
      "status": "blocked",
      "blocked_on": "sync",
      "locals_hint": "sync.(*WaitGroup).Wait"
    }
  },
  "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: success
// concurrency_pattern: pipeline
// goroutine_count: 4
// expected_nondeterminism: medium
// description: Pipeline pipeline stages stage1 -> stage2 -> stage3, leak_bug=False

package main

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

func stage1(out chan<- int, wg *sync.WaitGroup) {
	defer wg.Done()
	for i := 0; i < 5; i++ {
		out <- i
		time.Sleep(time.Millisecond * 1)
	}
	close(out)
}

func stage2(in <-chan int, out chan<- int, wg *sync.WaitGroup) {
	defer wg.Done()
	for v := range in {
		out <- v * 2
		time.Sleep(time.Millisecond * 1)
	}
	close(out)
}

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 wg1, wg2, wg3 sync.WaitGroup
	ch1 := make(chan int)
	ch2 := make(chan int)

	wg1.Add(1)
	go stage1(ch1, &wg1)

	wg2.Add(1)
	go stage2(ch1, ch2, &wg2)

	wg3.Add(1)
	go func(inCh <-chan int) {
		defer wg3.Done()
		for range inCh { /* normal drain */ }
	}(ch2)

	// Exit harness
	done := make(chan struct{})
	go func() {
		wg1.Wait()
		wg2.Wait()
		wg3.Wait()
		close(done)
	}()

	select {
	case <-done:
		fmt.Println("pipeline done")
	case <-time.After(200 * time.Millisecond):
		fmt.Println("pipeline timeout")
	}
}

</program>

Here is a partial execution trace showing goroutine scheduler events so far:
<trace>
[
  {
    "event_id": 42,
    "timestamp_ns": 14735369388416,
    "event_type": "GoStart",
    "goroutine_id": 40,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 43,
    "timestamp_ns": 14735369388672,
    "event_type": "GoBlock",
    "goroutine_id": 40,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 44,
    "timestamp_ns": 14735370506944,
    "event_type": "GoUnblock",
    "goroutine_id": 38,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 45,
    "timestamp_ns": 14735370507200,
    "event_type": "GoUnblock",
    "goroutine_id": 39,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 46,
    "timestamp_ns": 14735370509120,
    "event_type": "GoStart",
    "goroutine_id": 38,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 47,
    "timestamp_ns": 14735370509824,
    "event_type": "GoBlock",
    "goroutine_id": 38,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 48,
    "timestamp_ns": 14735370509952,
    "event_type": "GoStart",
    "goroutine_id": 39,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 49,
    "timestamp_ns": 14735370510720,
    "event_type": "GoUnblock",
    "goroutine_id": 38,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 50,
    "timestamp_ns": 14735370511168,
    "event_type": "GoUnblock",
    "goroutine_id": 40,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 51,
    "timestamp_ns": 14735370511360,
    "event_type": "GoBlock",
    "goroutine_id": 39,
    "goroutines": {
      "1": {
        "status": "blocked",
        "blocked_on": "select",
        "locals_hint": "runtime.selectgo"
      },
      "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": "runnable",
        "blocked_on": null,
        "locals_hint": "runtime.chanrecv2"
      },
      "39": {
        "status": "blocked",
        "blocked_on": "sleep",
        "locals_hint": "time.Sleep"
      },
      "40": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "runtime.chansend1"
      },
      "41": {
        "status": "blocked",
        "blocked_on": "sync",
        "locals_hint": "sync.(*WaitGroup).Wait"
      }
    },
    "channels": {},
    "mutexes": {}
  }
]
</trace>

The current goroutine states are:
<current_state>
{
  "event_id": 51,
  "timestamp_ns": 14735370511360,
  "event_type": "GoBlock",
  "goroutine_id": 39,
  "goroutines": {
    "1": {
      "status": "blocked",
      "blocked_on": "select",
      "locals_hint": "runtime.selectgo"
    },
    "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": "runnable",
      "blocked_on": null,
      "locals_hint": "runtime.chanrecv2"
    },
    "39": {
      "status": "blocked",
      "blocked_on": "sleep",
      "locals_hint": "time.Sleep"
    },
    "40": {
      "status": "runnable",
      "blocked_on": null,
      "locals_hint": "runtime.chansend1"
    },
    "41": {
      "status": "blocked",
      "blocked_on": "sync",
      "locals_hint": "sync.(*WaitGroup).Wait"
    }
  },
  "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: success
// concurrency_pattern: pipeline
// goroutine_count: 4
// expected_nondeterminism: medium
// description: Pipeline pipeline stages stage1 -> stage2 -> stage3, leak_bug=False

package main

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

func stage1(out chan<- int, wg *sync.WaitGroup) {
	defer wg.Done()
	for i := 0; i < 5; i++ {
		out <- i
		time.Sleep(time.Millisecond * 1)
	}
	close(out)
}

func stage2(in <-chan int, out chan<- int, wg *sync.WaitGroup) {
	defer wg.Done()
	for v := range in {
		out <- v * 2
		time.Sleep(time.Millisecond * 1)
	}
	close(out)
}

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 wg1, wg2, wg3 sync.WaitGroup
	ch1 := make(chan int)
	ch2 := make(chan int)

	wg1.Add(1)
	go stage1(ch1, &wg1)

	wg2.Add(1)
	go stage2(ch1, ch2, &wg2)

	wg3.Add(1)
	go func(inCh <-chan int) {
		defer wg3.Done()
		for range inCh { /* normal drain */ }
	}(ch2)

	// Exit harness
	done := make(chan struct{})
	go func() {
		wg1.Wait()
		wg2.Wait()
		wg3.Wait()
		close(done)
	}()

	select {
	case <-done:
		fmt.Println("pipeline done")
	case <-time.After(200 * time.Millisecond):
		fmt.Println("pipeline timeout")
	}
}

</program>

Here is a partial execution trace showing goroutine scheduler events so far:
<trace>
[
  {
    "event_id": 62,
    "timestamp_ns": 14733323702272,
    "event_type": "GoBlock",
    "goroutine_id": 10,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 63,
    "timestamp_ns": 14733323702656,
    "event_type": "GoStart",
    "goroutine_id": 11,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 64,
    "timestamp_ns": 14733323703104,
    "event_type": "GoUnblock",
    "goroutine_id": 12,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 65,
    "timestamp_ns": 14733323703360,
    "event_type": "GoBlock",
    "goroutine_id": 11,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 66,
    "timestamp_ns": 14733323703552,
    "event_type": "GoStart",
    "goroutine_id": 12,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 67,
    "timestamp_ns": 14733323703872,
    "event_type": "GoBlock",
    "goroutine_id": 12,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 68,
    "timestamp_ns": 14733324831360,
    "event_type": "GoUnblock",
    "goroutine_id": 10,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 69,
    "timestamp_ns": 14733324831488,
    "event_type": "GoUnblock",
    "goroutine_id": 11,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 70,
    "timestamp_ns": 14733324832448,
    "event_type": "GoStart",
    "goroutine_id": 11,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 71,
    "timestamp_ns": 14733324833408,
    "event_type": "GoBlock",
    "goroutine_id": 11,
    "goroutines": {
      "1": {
        "status": "blocked",
        "blocked_on": "select",
        "locals_hint": "runtime.selectgo"
      },
      "10": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "11": {
        "status": "blocked",
        "blocked_on": "chan receive",
        "locals_hint": "runtime.chanrecv2"
      },
      "12": {
        "status": "blocked",
        "blocked_on": "chan receive",
        "locals_hint": "runtime.chanrecv2"
      },
      "13": {
        "status": "blocked",
        "blocked_on": "sync",
        "locals_hint": "sync.(*WaitGroup).Wait"
      },
      "7": {
        "status": "blocked",
        "blocked_on": "chan receive",
        "locals_hint": "runtime.chanrecv1"
      },
      "8": {
        "status": "blocked",
        "blocked_on": "chan receive",
        "locals_hint": "runtime.chanrecv1"
      },
      "9": {
        "status": "blocked",
        "blocked_on": "system goroutine wait",
        "locals_hint": "runtime/trace.(*traceMultiplexer).startLocked.func1"
      }
    },
    "channels": {},
    "mutexes": {}
  }
]
</trace>

The current goroutine states are:
<current_state>
{
  "event_id": 71,
  "timestamp_ns": 14733324833408,
  "event_type": "GoBlock",
  "goroutine_id": 11,
  "goroutines": {
    "1": {
      "status": "blocked",
      "blocked_on": "select",
      "locals_hint": "runtime.selectgo"
    },
    "10": {
      "status": "runnable",
      "blocked_on": null,
      "locals_hint": "unknown"
    },
    "11": {
      "status": "blocked",
      "blocked_on": "chan receive",
      "locals_hint": "runtime.chanrecv2"
    },
    "12": {
      "status": "blocked",
      "blocked_on": "chan receive",
      "locals_hint": "runtime.chanrecv2"
    },
    "13": {
      "status": "blocked",
      "blocked_on": "sync",
      "locals_hint": "sync.(*WaitGroup).Wait"
    },
    "7": {
      "status": "blocked",
      "blocked_on": "chan receive",
      "locals_hint": "runtime.chanrecv1"
    },
    "8": {
      "status": "blocked",
      "blocked_on": "chan receive",
      "locals_hint": "runtime.chanrecv1"
    },
    "9": {
      "status": "blocked",
      "blocked_on": "system goroutine wait",
      "locals_hint": "runtime/trace.(*traceMultiplexer).startLocked.func1"
    }
  },
  "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": 10}


[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: success
// concurrency_pattern: pipeline
// goroutine_count: 4
// expected_nondeterminism: medium
// description: Pipeline pipeline stages stage1 -> stage2 -> stage3, leak_bug=False

package main

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

func stage1(out chan<- int, wg *sync.WaitGroup) {
	defer wg.Done()
	for i := 0; i < 5; i++ {
		out <- i
		time.Sleep(time.Millisecond * 1)
	}
	close(out)
}

func stage2(in <-chan int, out chan<- int, wg *sync.WaitGroup) {
	defer wg.Done()
	for v := range in {
		out <- v * 2
		time.Sleep(time.Millisecond * 1)
	}
	close(out)
}

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 wg1, wg2, wg3 sync.WaitGroup
	ch1 := make(chan int)
	ch2 := make(chan int)

	wg1.Add(1)
	go stage1(ch1, &wg1)

	wg2.Add(1)
	go stage2(ch1, ch2, &wg2)

	wg3.Add(1)
	go func(inCh <-chan int) {
		defer wg3.Done()
		for range inCh { /* normal drain */ }
	}(ch2)

	// Exit harness
	done := make(chan struct{})
	go func() {
		wg1.Wait()
		wg2.Wait()
		wg3.Wait()
		close(done)
	}()

	select {
	case <-done:
		fmt.Println("pipeline done")
	case <-time.After(200 * time.Millisecond):
		fmt.Println("pipeline timeout")
	}
}

</program>

Here is a partial execution trace showing goroutine scheduler events so far:
<trace>
[
  {
    "event_id": 62,
    "timestamp_ns": 14733323702272,
    "event_type": "GoBlock",
    "goroutine_id": 10,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 63,
    "timestamp_ns": 14733323702656,
    "event_type": "GoStart",
    "goroutine_id": 11,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 64,
    "timestamp_ns": 14733323703104,
    "event_type": "GoUnblock",
    "goroutine_id": 12,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 65,
    "timestamp_ns": 14733323703360,
    "event_type": "GoBlock",
    "goroutine_id": 11,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 66,
    "timestamp_ns": 14733323703552,
    "event_type": "GoStart",
    "goroutine_id": 12,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 67,
    "timestamp_ns": 14733323703872,
    "event_type": "GoBlock",
    "goroutine_id": 12,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 68,
    "timestamp_ns": 14733324831360,
    "event_type": "GoUnblock",
    "goroutine_id": 10,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 69,
    "timestamp_ns": 14733324831488,
    "event_type": "GoUnblock",
    "goroutine_id": 11,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 70,
    "timestamp_ns": 14733324832448,
    "event_type": "GoStart",
    "goroutine_id": 11,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 71,
    "timestamp_ns": 14733324833408,
    "event_type": "GoBlock",
    "goroutine_id": 11,
    "goroutines": {
      "1": {
        "status": "blocked",
        "blocked_on": "select",
        "locals_hint": "runtime.selectgo"
      },
      "10": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "11": {
        "status": "blocked",
        "blocked_on": "chan receive",
        "locals_hint": "runtime.chanrecv2"
      },
      "12": {
        "status": "blocked",
        "blocked_on": "chan receive",
        "locals_hint": "runtime.chanrecv2"
      },
      "13": {
        "status": "blocked",
        "blocked_on": "sync",
        "locals_hint": "sync.(*WaitGroup).Wait"
      },
      "7": {
        "status": "blocked",
        "blocked_on": "chan receive",
        "locals_hint": "runtime.chanrecv1"
      },
      "8": {
        "status": "blocked",
        "blocked_on": "chan receive",
        "locals_hint": "runtime.chanrecv1"
      },
      "9": {
        "status": "blocked",
        "blocked_on": "system goroutine wait",
        "locals_hint": "runtime/trace.(*traceMultiplexer).startLocked.func1"
      }
    },
    "channels": {},
    "mutexes": {}
  }
]
</trace>

The current goroutine states are:
<current_state>
{
  "event_id": 71,
  "timestamp_ns": 14733324833408,
  "event_type": "GoBlock",
  "goroutine_id": 11,
  "goroutines": {
    "1": {
      "status": "blocked",
      "blocked_on": "select",
      "locals_hint": "runtime.selectgo"
    },
    "10": {
      "status": "runnable",
      "blocked_on": null,
      "locals_hint": "unknown"
    },
    "11": {
      "status": "blocked",
      "blocked_on": "chan receive",
      "locals_hint": "runtime.chanrecv2"
    },
    "12": {
      "status": "blocked",
      "blocked_on": "chan receive",
      "locals_hint": "runtime.chanrecv2"
    },
    "13": {
      "status": "blocked",
      "blocked_on": "sync",
      "locals_hint": "sync.(*WaitGroup).Wait"
    },
    "7": {
      "status": "blocked",
      "blocked_on": "chan receive",
      "locals_hint": "runtime.chanrecv1"
    },
    "8": {
      "status": "blocked",
      "blocked_on": "chan receive",
      "locals_hint": "runtime.chanrecv1"
    },
    "9": {
      "status": "blocked",
      "blocked_on": "system goroutine wait",
      "locals_hint": "runtime/trace.(*traceMultiplexer).startLocked.func1"
    }
  },
  "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": 10}


[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: success
// concurrency_pattern: pipeline
// goroutine_count: 4
// expected_nondeterminism: medium
// description: Pipeline pipeline stages stage1 -> stage2 -> stage3, leak_bug=False

package main

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

func stage1(out chan<- int, wg *sync.WaitGroup) {
	defer wg.Done()
	for i := 0; i < 5; i++ {
		out <- i
		time.Sleep(time.Millisecond * 1)
	}
	close(out)
}

func stage2(in <-chan int, out chan<- int, wg *sync.WaitGroup) {
	defer wg.Done()
	for v := range in {
		out <- v * 2
		time.Sleep(time.Millisecond * 1)
	}
	close(out)
}

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 wg1, wg2, wg3 sync.WaitGroup
	ch1 := make(chan int)
	ch2 := make(chan int)

	wg1.Add(1)
	go stage1(ch1, &wg1)

	wg2.Add(1)
	go stage2(ch1, ch2, &wg2)

	wg3.Add(1)
	go func(inCh <-chan int) {
		defer wg3.Done()
		for range inCh { /* normal drain */ }
	}(ch2)

	// Exit harness
	done := make(chan struct{})
	go func() {
		wg1.Wait()
		wg2.Wait()
		wg3.Wait()
		close(done)
	}()

	select {
	case <-done:
		fmt.Println("pipeline done")
	case <-time.After(200 * time.Millisecond):
		fmt.Println("pipeline timeout")
	}
}

</program>

Here is a partial execution trace showing goroutine scheduler events so far:
<trace>
[
  {
    "event_id": 62,
    "timestamp_ns": 14733323702272,
    "event_type": "GoBlock",
    "goroutine_id": 10,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 63,
    "timestamp_ns": 14733323702656,
    "event_type": "GoStart",
    "goroutine_id": 11,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 64,
    "timestamp_ns": 14733323703104,
    "event_type": "GoUnblock",
    "goroutine_id": 12,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 65,
    "timestamp_ns": 14733323703360,
    "event_type": "GoBlock",
    "goroutine_id": 11,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 66,
    "timestamp_ns": 14733323703552,
    "event_type": "GoStart",
    "goroutine_id": 12,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 67,
    "timestamp_ns": 14733323703872,
    "event_type": "GoBlock",
    "goroutine_id": 12,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 68,
    "timestamp_ns": 14733324831360,
    "event_type": "GoUnblock",
    "goroutine_id": 10,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 69,
    "timestamp_ns": 14733324831488,
    "event_type": "GoUnblock",
    "goroutine_id": 11,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 70,
    "timestamp_ns": 14733324832448,
    "event_type": "GoStart",
    "goroutine_id": 11,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 71,
    "timestamp_ns": 14733324833408,
    "event_type": "GoBlock",
    "goroutine_id": 11,
    "goroutines": {
      "1": {
        "status": "blocked",
        "blocked_on": "select",
        "locals_hint": "runtime.selectgo"
      },
      "10": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "11": {
        "status": "blocked",
        "blocked_on": "chan receive",
        "locals_hint": "runtime.chanrecv2"
      },
      "12": {
        "status": "blocked",
        "blocked_on": "chan receive",
        "locals_hint": "runtime.chanrecv2"
      },
      "13": {
        "status": "blocked",
        "blocked_on": "sync",
        "locals_hint": "sync.(*WaitGroup).Wait"
      },
      "7": {
        "status": "blocked",
        "blocked_on": "chan receive",
        "locals_hint": "runtime.chanrecv1"
      },
      "8": {
        "status": "blocked",
        "blocked_on": "chan receive",
        "locals_hint": "runtime.chanrecv1"
      },
      "9": {
        "status": "blocked",
        "blocked_on": "system goroutine wait",
        "locals_hint": "runtime/trace.(*traceMultiplexer).startLocked.func1"
      }
    },
    "channels": {},
    "mutexes": {}
  }
]
</trace>

The current goroutine states are:
<current_state>
{
  "event_id": 71,
  "timestamp_ns": 14733324833408,
  "event_type": "GoBlock",
  "goroutine_id": 11,
  "goroutines": {
    "1": {
      "status": "blocked",
      "blocked_on": "select",
      "locals_hint": "runtime.selectgo"
    },
    "10": {
      "status": "runnable",
      "blocked_on": null,
      "locals_hint": "unknown"
    },
    "11": {
      "status": "blocked",
      "blocked_on": "chan receive",
      "locals_hint": "runtime.chanrecv2"
    },
    "12": {
      "status": "blocked",
      "blocked_on": "chan receive",
      "locals_hint": "runtime.chanrecv2"
    },
    "13": {
      "status": "blocked",
      "blocked_on": "sync",
      "locals_hint": "sync.(*WaitGroup).Wait"
    },
    "7": {
      "status": "blocked",
      "blocked_on": "chan receive",
      "locals_hint": "runtime.chanrecv1"
    },
    "8": {
      "status": "blocked",
      "blocked_on": "chan receive",
      "locals_hint": "runtime.chanrecv1"
    },
    "9": {
      "status": "blocked",
      "blocked_on": "system goroutine wait",
      "locals_hint": "runtime/trace.(*traceMultiplexer).startLocked.func1"
    }
  },
  "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": "GoBlock", "goroutine_id": 10}


[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: success
// concurrency_pattern: pipeline
// goroutine_count: 4
// expected_nondeterminism: medium
// description: Pipeline pipeline stages stage1 -> stage2 -> stage3, leak_bug=False

package main

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

func stage1(out chan<- int, wg *sync.WaitGroup) {
	defer wg.Done()
	for i := 0; i < 5; i++ {
		out <- i
		time.Sleep(time.Millisecond * 1)
	}
	close(out)
}

func stage2(in <-chan int, out chan<- int, wg *sync.WaitGroup) {
	defer wg.Done()
	for v := range in {
		out <- v * 2
		time.Sleep(time.Millisecond * 1)
	}
	close(out)
}

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 wg1, wg2, wg3 sync.WaitGroup
	ch1 := make(chan int)
	ch2 := make(chan int)

	wg1.Add(1)
	go stage1(ch1, &wg1)

	wg2.Add(1)
	go stage2(ch1, ch2, &wg2)

	wg3.Add(1)
	go func(inCh <-chan int) {
		defer wg3.Done()
		for range inCh { /* normal drain */ }
	}(ch2)

	// Exit harness
	done := make(chan struct{})
	go func() {
		wg1.Wait()
		wg2.Wait()
		wg3.Wait()
		close(done)
	}()

	select {
	case <-done:
		fmt.Println("pipeline done")
	case <-time.After(200 * time.Millisecond):
		fmt.Println("pipeline timeout")
	}
}

</program>

Here is a partial execution trace showing goroutine scheduler events so far:
<trace>
[
  {
    "event_id": 62,
    "timestamp_ns": 14733323702272,
    "event_type": "GoBlock",
    "goroutine_id": 10,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 63,
    "timestamp_ns": 14733323702656,
    "event_type": "GoStart",
    "goroutine_id": 11,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 64,
    "timestamp_ns": 14733323703104,
    "event_type": "GoUnblock",
    "goroutine_id": 12,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 65,
    "timestamp_ns": 14733323703360,
    "event_type": "GoBlock",
    "goroutine_id": 11,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 66,
    "timestamp_ns": 14733323703552,
    "event_type": "GoStart",
    "goroutine_id": 12,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 67,
    "timestamp_ns": 14733323703872,
    "event_type": "GoBlock",
    "goroutine_id": 12,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 68,
    "timestamp_ns": 14733324831360,
    "event_type": "GoUnblock",
    "goroutine_id": 10,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 69,
    "timestamp_ns": 14733324831488,
    "event_type": "GoUnblock",
    "goroutine_id": 11,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 70,
    "timestamp_ns": 14733324832448,
    "event_type": "GoStart",
    "goroutine_id": 11,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 71,
    "timestamp_ns": 14733324833408,
    "event_type": "GoBlock",
    "goroutine_id": 11,
    "goroutines": {
      "1": {
        "status": "blocked",
        "blocked_on": "select",
        "locals_hint": "runtime.selectgo"
      },
      "10": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "11": {
        "status": "blocked",
        "blocked_on": "chan receive",
        "locals_hint": "runtime.chanrecv2"
      },
      "12": {
        "status": "blocked",
        "blocked_on": "chan receive",
        "locals_hint": "runtime.chanrecv2"
      },
      "13": {
        "status": "blocked",
        "blocked_on": "sync",
        "locals_hint": "sync.(*WaitGroup).Wait"
      },
      "7": {
        "status": "blocked",
        "blocked_on": "chan receive",
        "locals_hint": "runtime.chanrecv1"
      },
      "8": {
        "status": "blocked",
        "blocked_on": "chan receive",
        "locals_hint": "runtime.chanrecv1"
      },
      "9": {
        "status": "blocked",
        "blocked_on": "system goroutine wait",
        "locals_hint": "runtime/trace.(*traceMultiplexer).startLocked.func1"
      }
    },
    "channels": {},
    "mutexes": {}
  }
]
</trace>

The current goroutine states are:
<current_state>
{
  "event_id": 71,
  "timestamp_ns": 14733324833408,
  "event_type": "GoBlock",
  "goroutine_id": 11,
  "goroutines": {
    "1": {
      "status": "blocked",
      "blocked_on": "select",
      "locals_hint": "runtime.selectgo"
    },
    "10": {
      "status": "runnable",
      "blocked_on": null,
      "locals_hint": "unknown"
    },
    "11": {
      "status": "blocked",
      "blocked_on": "chan receive",
      "locals_hint": "runtime.chanrecv2"
    },
    "12": {
      "status": "blocked",
      "blocked_on": "chan receive",
      "locals_hint": "runtime.chanrecv2"
    },
    "13": {
      "status": "blocked",
      "blocked_on": "sync",
      "locals_hint": "sync.(*WaitGroup).Wait"
    },
    "7": {
      "status": "blocked",
      "blocked_on": "chan receive",
      "locals_hint": "runtime.chanrecv1"
    },
    "8": {
      "status": "blocked",
      "blocked_on": "chan receive",
      "locals_hint": "runtime.chanrecv1"
    },
    "9": {
      "status": "blocked",
      "blocked_on": "system goroutine wait",
      "locals_hint": "runtime/trace.(*traceMultiplexer).startLocked.func1"
    }
  },
  "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": "GoBlock", "goroutine_id": 23}


[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: success
// concurrency_pattern: pipeline
// goroutine_count: 4
// expected_nondeterminism: medium
// description: Pipeline pipeline stages stage1 -> stage2 -> stage3, leak_bug=False

package main

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

func stage1(out chan<- int, wg *sync.WaitGroup) {
	defer wg.Done()
	for i := 0; i < 5; i++ {
		out <- i
		time.Sleep(time.Millisecond * 1)
	}
	close(out)
}

func stage2(in <-chan int, out chan<- int, wg *sync.WaitGroup) {
	defer wg.Done()
	for v := range in {
		out <- v * 2
		time.Sleep(time.Millisecond * 1)
	}
	close(out)
}

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 wg1, wg2, wg3 sync.WaitGroup
	ch1 := make(chan int)
	ch2 := make(chan int)

	wg1.Add(1)
	go stage1(ch1, &wg1)

	wg2.Add(1)
	go stage2(ch1, ch2, &wg2)

	wg3.Add(1)
	go func(inCh <-chan int) {
		defer wg3.Done()
		for range inCh { /* normal drain */ }
	}(ch2)

	// Exit harness
	done := make(chan struct{})
	go func() {
		wg1.Wait()
		wg2.Wait()
		wg3.Wait()
		close(done)
	}()

	select {
	case <-done:
		fmt.Println("pipeline done")
	case <-time.After(200 * time.Millisecond):
		fmt.Println("pipeline timeout")
	}
}

</program>

Here is a partial execution trace showing goroutine scheduler events so far:
<trace>
[
  {
    "event_id": 62,
    "timestamp_ns": 14733323702272,
    "event_type": "GoBlock",
    "goroutine_id": 10,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 63,
    "timestamp_ns": 14733323702656,
    "event_type": "GoStart",
    "goroutine_id": 11,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 64,
    "timestamp_ns": 14733323703104,
    "event_type": "GoUnblock",
    "goroutine_id": 12,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 65,
    "timestamp_ns": 14733323703360,
    "event_type": "GoBlock",
    "goroutine_id": 11,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 66,
    "timestamp_ns": 14733323703552,
    "event_type": "GoStart",
    "goroutine_id": 12,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 67,
    "timestamp_ns": 14733323703872,
    "event_type": "GoBlock",
    "goroutine_id": 12,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 68,
    "timestamp_ns": 14733324831360,
    "event_type": "GoUnblock",
    "goroutine_id": 10,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 69,
    "timestamp_ns": 14733324831488,
    "event_type": "GoUnblock",
    "goroutine_id": 11,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 70,
    "timestamp_ns": 14733324832448,
    "event_type": "GoStart",
    "goroutine_id": 11,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 71,
    "timestamp_ns": 14733324833408,
    "event_type": "GoBlock",
    "goroutine_id": 11,
    "goroutines": {
      "1": {
        "status": "blocked",
        "blocked_on": "select",
        "locals_hint": "runtime.selectgo"
      },
      "10": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "11": {
        "status": "blocked",
        "blocked_on": "chan receive",
        "locals_hint": "runtime.chanrecv2"
      },
      "12": {
        "status": "blocked",
        "blocked_on": "chan receive",
        "locals_hint": "runtime.chanrecv2"
      },
      "13": {
        "status": "blocked",
        "blocked_on": "sync",
        "locals_hint": "sync.(*WaitGroup).Wait"
      },
      "7": {
        "status": "blocked",
        "blocked_on": "chan receive",
        "locals_hint": "runtime.chanrecv1"
      },
      "8": {
        "status": "blocked",
        "blocked_on": "chan receive",
        "locals_hint": "runtime.chanrecv1"
      },
      "9": {
        "status": "blocked",
        "blocked_on": "system goroutine wait",
        "locals_hint": "runtime/trace.(*traceMultiplexer).startLocked.func1"
      }
    },
    "channels": {},
    "mutexes": {}
  }
]
</trace>

The current goroutine states are:
<current_state>
{
  "event_id": 71,
  "timestamp_ns": 14733324833408,
  "event_type": "GoBlock",
  "goroutine_id": 11,
  "goroutines": {
    "1": {
      "status": "blocked",
      "blocked_on": "select",
      "locals_hint": "runtime.selectgo"
    },
    "10": {
      "status": "runnable",
      "blocked_on": null,
      "locals_hint": "unknown"
    },
    "11": {
      "status": "blocked",
      "blocked_on": "chan receive",
      "locals_hint": "runtime.chanrecv2"
    },
    "12": {
      "status": "blocked",
      "blocked_on": "chan receive",
      "locals_hint": "runtime.chanrecv2"
    },
    "13": {
      "status": "blocked",
      "blocked_on": "sync",
      "locals_hint": "sync.(*WaitGroup).Wait"
    },
    "7": {
      "status": "blocked",
      "blocked_on": "chan receive",
      "locals_hint": "runtime.chanrecv1"
    },
    "8": {
      "status": "blocked",
      "blocked_on": "chan receive",
      "locals_hint": "runtime.chanrecv1"
    },
    "9": {
      "status": "blocked",
      "blocked_on": "system goroutine wait",
      "locals_hint": "runtime/trace.(*traceMultiplexer).startLocked.func1"
    }
  },
  "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": 40}


[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: mutex
// goroutine_count: 3
// expected_nondeterminism: medium
// description: Human-written GoBench bug kernel cockroach_1055 (leak)

package main

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

type Stopper struct {
	stopper  chan struct{}
	stop     sync.WaitGroup
	mu       sync.Mutex
	draining int32
	drain    sync.WaitGroup
}

func (s *Stopper) AddWorker() {
	s.stop.Add(1)
}

func (s *Stopper) ShouldStop() <-chan struct{} {
	if s == nil {
		return nil
	}
	return s.stopper
}

func (s *Stopper) SetStopped() {
	if s != nil {
		s.stop.Done()
	}
}

func (s *Stopper) Quiesce() {
	s.mu.Lock()
	defer s.mu.Unlock()
	s.draining = 1
	s.drain.Wait()
	s.draining = 0
}

func (s *Stopper) Stop() {
	s.mu.Lock()
	defer s.mu.Unlock()
	atomic.StoreInt32(&s.draining, 1)
	s.drain.Wait()
	close(s.stopper)
	s.stop.Wait()
}

func (s *Stopper) StartTask() bool {
	if atomic.LoadInt32(&s.draining) == 0 {
		s.mu.Lock()
		defer s.mu.Unlock()
		s.drain.Add(1)
		return true
	}
	return false
}

func NewStopper() *Stopper {
	return &Stopper{
		stopper: make(chan struct{}),
	}
}

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 stoppers []*Stopper
	for i := 0; i < 3; i++ {
		stoppers = append(stoppers, NewStopper())
	}

	for i := range stoppers {
		s := stoppers[i]
		s.AddWorker()
		go func() {
			s.StartTask()
			<-s.ShouldStop()
			s.SetStopped()
		}()
	}

	done := make(chan struct{})
	go func() {
		for _, s := range stoppers {
			s.Quiesce()
		}
		for _, s := range stoppers {
			s.Stop()
		}
		close(done)
	}()

	<-done
}

</program>

Here is a partial execution trace showing goroutine scheduler events so far:
<trace>
[
  {
    "event_id": 0,
    "timestamp_ns": 14735628596672,
    "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": 14735628618368,
    "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"
      }
    },
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 2,
    "timestamp_ns": 14735628619392,
    "event_type": "GoCreate",
    "goroutine_id": 20,
    "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": 14735628642496,
    "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": 14735628656768,
    "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": 14735628674176,
    "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": {}
  },
  {
    "event_id": 6,
    "timestamp_ns": 14735628674368,
    "event_type": "GoCreate",
    "goroutine_id": 22,
    "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"
      },
      "22": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "main.main"
      }
    },
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 7,
    "timestamp_ns": 14735628676736,
    "event_type": "GoCreate",
    "goroutine_id": 23,
    "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"
      },
      "22": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "main.main"
      },
      "23": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "main.main"
      }
    },
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 8,
    "timestamp_ns": 14735628677952,
    "event_type": "GoCreate",
    "goroutine_id": 24,
    "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"
      },
      "22": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "main.main"
      },
      "23": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "main.main"
      },
      "24": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "main.main"
      }
    },
    "channels": {},
    "mutexes": {}
  }
]
</trace>

The current goroutine states are:
<current_state>
{
  "event_id": 8,
  "timestamp_ns": 14735628677952,
  "event_type": "GoCreate",
  "goroutine_id": 24,
  "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"
    },
    "22": {
      "status": "runnable",
      "blocked_on": null,
      "locals_hint": "main.main"
    },
    "23": {
      "status": "runnable",
      "blocked_on": null,
      "locals_hint": "main.main"
    },
    "24": {
      "status": "runnable",
      "blocked_on": null,
      "locals_hint": "main.main"
    }
  },
  "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": 25}


[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: mutex
// goroutine_count: 3
// expected_nondeterminism: medium
// description: Human-written GoBench bug kernel cockroach_1055 (leak)

package main

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

type Stopper struct {
	stopper  chan struct{}
	stop     sync.WaitGroup
	mu       sync.Mutex
	draining int32
	drain    sync.WaitGroup
}

func (s *Stopper) AddWorker() {
	s.stop.Add(1)
}

func (s *Stopper) ShouldStop() <-chan struct{} {
	if s == nil {
		return nil
	}
	return s.stopper
}

func (s *Stopper) SetStopped() {
	if s != nil {
		s.stop.Done()
	}
}

func (s *Stopper) Quiesce() {
	s.mu.Lock()
	defer s.mu.Unlock()
	s.draining = 1
	s.drain.Wait()
	s.draining = 0
}

func (s *Stopper) Stop() {
	s.mu.Lock()
	defer s.mu.Unlock()
	atomic.StoreInt32(&s.draining, 1)
	s.drain.Wait()
	close(s.stopper)
	s.stop.Wait()
}

func (s *Stopper) StartTask() bool {
	if atomic.LoadInt32(&s.draining) == 0 {
		s.mu.Lock()
		defer s.mu.Unlock()
		s.drain.Add(1)
		return true
	}
	return false
}

func NewStopper() *Stopper {
	return &Stopper{
		stopper: make(chan struct{}),
	}
}

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 stoppers []*Stopper
	for i := 0; i < 3; i++ {
		stoppers = append(stoppers, NewStopper())
	}

	for i := range stoppers {
		s := stoppers[i]
		s.AddWorker()
		go func() {
			s.StartTask()
			<-s.ShouldStop()
			s.SetStopped()
		}()
	}

	done := make(chan struct{})
	go func() {
		for _, s := range stoppers {
			s.Quiesce()
		}
		for _, s := range stoppers {
			s.Stop()
		}
		close(done)
	}()

	<-done
}

</program>

Here is a partial execution trace showing goroutine scheduler events so far:
<trace>
[
  {
    "event_id": 0,
    "timestamp_ns": 14735628596672,
    "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": 14735628618368,
    "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"
      }
    },
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 2,
    "timestamp_ns": 14735628619392,
    "event_type": "GoCreate",
    "goroutine_id": 20,
    "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": 14735628642496,
    "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": 14735628656768,
    "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": 14735628674176,
    "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": {}
  },
  {
    "event_id": 6,
    "timestamp_ns": 14735628674368,
    "event_type": "GoCreate",
    "goroutine_id": 22,
    "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"
      },
      "22": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "main.main"
      }
    },
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 7,
    "timestamp_ns": 14735628676736,
    "event_type": "GoCreate",
    "goroutine_id": 23,
    "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"
      },
      "22": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "main.main"
      },
      "23": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "main.main"
      }
    },
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 8,
    "timestamp_ns": 14735628677952,
    "event_type": "GoCreate",
    "goroutine_id": 24,
    "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"
      },
      "22": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "main.main"
      },
      "23": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "main.main"
      },
      "24": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "main.main"
      }
    },
    "channels": {},
    "mutexes": {}
  }
]
</trace>

The current goroutine states are:
<current_state>
{
  "event_id": 8,
  "timestamp_ns": 14735628677952,
  "event_type": "GoCreate",
  "goroutine_id": 24,
  "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"
    },
    "22": {
      "status": "runnable",
      "blocked_on": null,
      "locals_hint": "main.main"
    },
    "23": {
      "status": "runnable",
      "blocked_on": null,
      "locals_hint": "main.main"
    },
    "24": {
      "status": "runnable",
      "blocked_on": null,
      "locals_hint": "main.main"
    }
  },
  "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": 40}


[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: mutex
// goroutine_count: 3
// expected_nondeterminism: medium
// description: Human-written GoBench bug kernel cockroach_1055 (leak)

package main

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

type Stopper struct {
	stopper  chan struct{}
	stop     sync.WaitGroup
	mu       sync.Mutex
	draining int32
	drain    sync.WaitGroup
}

func (s *Stopper) AddWorker() {
	s.stop.Add(1)
}

func (s *Stopper) ShouldStop() <-chan struct{} {
	if s == nil {
		return nil
	}
	return s.stopper
}

func (s *Stopper) SetStopped() {
	if s != nil {
		s.stop.Done()
	}
}

func (s *Stopper) Quiesce() {
	s.mu.Lock()
	defer s.mu.Unlock()
	s.draining = 1
	s.drain.Wait()
	s.draining = 0
}

func (s *Stopper) Stop() {
	s.mu.Lock()
	defer s.mu.Unlock()
	atomic.StoreInt32(&s.draining, 1)
	s.drain.Wait()
	close(s.stopper)
	s.stop.Wait()
}

func (s *Stopper) StartTask() bool {
	if atomic.LoadInt32(&s.draining) == 0 {
		s.mu.Lock()
		defer s.mu.Unlock()
		s.drain.Add(1)
		return true
	}
	return false
}

func NewStopper() *Stopper {
	return &Stopper{
		stopper: make(chan struct{}),
	}
}

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 stoppers []*Stopper
	for i := 0; i < 3; i++ {
		stoppers = append(stoppers, NewStopper())
	}

	for i := range stoppers {
		s := stoppers[i]
		s.AddWorker()
		go func() {
			s.StartTask()
			<-s.ShouldStop()
			s.SetStopped()
		}()
	}

	done := make(chan struct{})
	go func() {
		for _, s := range stoppers {
			s.Quiesce()
		}
		for _, s := range stoppers {
			s.Stop()
		}
		close(done)
	}()

	<-done
}

</program>

Here is a partial execution trace showing goroutine scheduler events so far:
<trace>
[
  {
    "event_id": 9,
    "timestamp_ns": 11912665772736,
    "event_type": "GoCreate",
    "goroutine_id": 40,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 10,
    "timestamp_ns": 11912665779072,
    "event_type": "GoBlock",
    "goroutine_id": 1,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 11,
    "timestamp_ns": 11912665779776,
    "event_type": "GoStart",
    "goroutine_id": 40,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 12,
    "timestamp_ns": 11912665794368,
    "event_type": "GoBlock",
    "goroutine_id": 36,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 13,
    "timestamp_ns": 11912665809984,
    "event_type": "GoBlock",
    "goroutine_id": 40,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 14,
    "timestamp_ns": 11912665810304,
    "event_type": "GoStart",
    "goroutine_id": 37,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 15,
    "timestamp_ns": 11912665818560,
    "event_type": "GoUnblock",
    "goroutine_id": 40,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 16,
    "timestamp_ns": 11912665820352,
    "event_type": "GoEnd",
    "goroutine_id": 37,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 17,
    "timestamp_ns": 11912665821056,
    "event_type": "GoStart",
    "goroutine_id": 40,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 18,
    "timestamp_ns": 11912665822976,
    "event_type": "GoBlock",
    "goroutine_id": 40,
    "goroutines": {
      "1": {
        "status": "blocked",
        "blocked_on": "chan receive",
        "locals_hint": "runtime.chanrecv1"
      },
      "34": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "35": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "36": {
        "status": "running",
        "blocked_on": "syscall",
        "locals_hint": "syscall.syscall"
      },
      "38": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "main.main"
      },
      "39": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "main.main"
      },
      "40": {
        "status": "blocked",
        "blocked_on": "sync",
        "locals_hint": "sync.(*WaitGroup).Wait"
      }
    },
    "channels": {},
    "mutexes": {}
  }
]
</trace>

The current goroutine states are:
<current_state>
{
  "event_id": 18,
  "timestamp_ns": 11912665822976,
  "event_type": "GoBlock",
  "goroutine_id": 40,
  "goroutines": {
    "1": {
      "status": "blocked",
      "blocked_on": "chan receive",
      "locals_hint": "runtime.chanrecv1"
    },
    "34": {
      "status": "running",
      "blocked_on": null,
      "locals_hint": "unknown"
    },
    "35": {
      "status": "running",
      "blocked_on": null,
      "locals_hint": "unknown"
    },
    "36": {
      "status": "running",
      "blocked_on": "syscall",
      "locals_hint": "syscall.syscall"
    },
    "38": {
      "status": "runnable",
      "blocked_on": null,
      "locals_hint": "main.main"
    },
    "39": {
      "status": "runnable",
      "blocked_on": null,
      "locals_hint": "main.main"
    },
    "40": {
      "status": "blocked",
      "blocked_on": "sync",
      "locals_hint": "sync.(*WaitGroup).Wait"
    }
  },
  "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": 38}


[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: mutex
// goroutine_count: 3
// expected_nondeterminism: medium
// description: Human-written GoBench bug kernel cockroach_1055 (leak)

package main

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

type Stopper struct {
	stopper  chan struct{}
	stop     sync.WaitGroup
	mu       sync.Mutex
	draining int32
	drain    sync.WaitGroup
}

func (s *Stopper) AddWorker() {
	s.stop.Add(1)
}

func (s *Stopper) ShouldStop() <-chan struct{} {
	if s == nil {
		return nil
	}
	return s.stopper
}

func (s *Stopper) SetStopped() {
	if s != nil {
		s.stop.Done()
	}
}

func (s *Stopper) Quiesce() {
	s.mu.Lock()
	defer s.mu.Unlock()
	s.draining = 1
	s.drain.Wait()
	s.draining = 0
}

func (s *Stopper) Stop() {
	s.mu.Lock()
	defer s.mu.Unlock()
	atomic.StoreInt32(&s.draining, 1)
	s.drain.Wait()
	close(s.stopper)
	s.stop.Wait()
}

func (s *Stopper) StartTask() bool {
	if atomic.LoadInt32(&s.draining) == 0 {
		s.mu.Lock()
		defer s.mu.Unlock()
		s.drain.Add(1)
		return true
	}
	return false
}

func NewStopper() *Stopper {
	return &Stopper{
		stopper: make(chan struct{}),
	}
}

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 stoppers []*Stopper
	for i := 0; i < 3; i++ {
		stoppers = append(stoppers, NewStopper())
	}

	for i := range stoppers {
		s := stoppers[i]
		s.AddWorker()
		go func() {
			s.StartTask()
			<-s.ShouldStop()
			s.SetStopped()
		}()
	}

	done := make(chan struct{})
	go func() {
		for _, s := range stoppers {
			s.Quiesce()
		}
		for _, s := range stoppers {
			s.Stop()
		}
		close(done)
	}()

	<-done
}

</program>

Here is a partial execution trace showing goroutine scheduler events so far:
<trace>
[
  {
    "event_id": 9,
    "timestamp_ns": 11912665772736,
    "event_type": "GoCreate",
    "goroutine_id": 40,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 10,
    "timestamp_ns": 11912665779072,
    "event_type": "GoBlock",
    "goroutine_id": 1,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 11,
    "timestamp_ns": 11912665779776,
    "event_type": "GoStart",
    "goroutine_id": 40,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 12,
    "timestamp_ns": 11912665794368,
    "event_type": "GoBlock",
    "goroutine_id": 36,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 13,
    "timestamp_ns": 11912665809984,
    "event_type": "GoBlock",
    "goroutine_id": 40,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 14,
    "timestamp_ns": 11912665810304,
    "event_type": "GoStart",
    "goroutine_id": 37,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 15,
    "timestamp_ns": 11912665818560,
    "event_type": "GoUnblock",
    "goroutine_id": 40,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 16,
    "timestamp_ns": 11912665820352,
    "event_type": "GoEnd",
    "goroutine_id": 37,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 17,
    "timestamp_ns": 11912665821056,
    "event_type": "GoStart",
    "goroutine_id": 40,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 18,
    "timestamp_ns": 11912665822976,
    "event_type": "GoBlock",
    "goroutine_id": 40,
    "goroutines": {
      "1": {
        "status": "blocked",
        "blocked_on": "chan receive",
        "locals_hint": "runtime.chanrecv1"
      },
      "34": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "35": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "36": {
        "status": "running",
        "blocked_on": "syscall",
        "locals_hint": "syscall.syscall"
      },
      "38": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "main.main"
      },
      "39": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "main.main"
      },
      "40": {
        "status": "blocked",
        "blocked_on": "sync",
        "locals_hint": "sync.(*WaitGroup).Wait"
      }
    },
    "channels": {},
    "mutexes": {}
  }
]
</trace>

The current goroutine states are:
<current_state>
{
  "event_id": 18,
  "timestamp_ns": 11912665822976,
  "event_type": "GoBlock",
  "goroutine_id": 40,
  "goroutines": {
    "1": {
      "status": "blocked",
      "blocked_on": "chan receive",
      "locals_hint": "runtime.chanrecv1"
    },
    "34": {
      "status": "running",
      "blocked_on": null,
      "locals_hint": "unknown"
    },
    "35": {
      "status": "running",
      "blocked_on": null,
      "locals_hint": "unknown"
    },
    "36": {
      "status": "running",
      "blocked_on": "syscall",
      "locals_hint": "syscall.syscall"
    },
    "38": {
      "status": "runnable",
      "blocked_on": null,
      "locals_hint": "main.main"
    },
    "39": {
      "status": "runnable",
      "blocked_on": null,
      "locals_hint": "main.main"
    },
    "40": {
      "status": "blocked",
      "blocked_on": "sync",
      "locals_hint": "sync.(*WaitGroup).Wait"
    }
  },
  "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": "GoBlock", "goroutine_id": 25}


[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: mutex
// goroutine_count: 3
// expected_nondeterminism: medium
// description: Human-written GoBench bug kernel cockroach_1055 (leak)

package main

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

type Stopper struct {
	stopper  chan struct{}
	stop     sync.WaitGroup
	mu       sync.Mutex
	draining int32
	drain    sync.WaitGroup
}

func (s *Stopper) AddWorker() {
	s.stop.Add(1)
}

func (s *Stopper) ShouldStop() <-chan struct{} {
	if s == nil {
		return nil
	}
	return s.stopper
}

func (s *Stopper) SetStopped() {
	if s != nil {
		s.stop.Done()
	}
}

func (s *Stopper) Quiesce() {
	s.mu.Lock()
	defer s.mu.Unlock()
	s.draining = 1
	s.drain.Wait()
	s.draining = 0
}

func (s *Stopper) Stop() {
	s.mu.Lock()
	defer s.mu.Unlock()
	atomic.StoreInt32(&s.draining, 1)
	s.drain.Wait()
	close(s.stopper)
	s.stop.Wait()
}

func (s *Stopper) StartTask() bool {
	if atomic.LoadInt32(&s.draining) == 0 {
		s.mu.Lock()
		defer s.mu.Unlock()
		s.drain.Add(1)
		return true
	}
	return false
}

func NewStopper() *Stopper {
	return &Stopper{
		stopper: make(chan struct{}),
	}
}

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 stoppers []*Stopper
	for i := 0; i < 3; i++ {
		stoppers = append(stoppers, NewStopper())
	}

	for i := range stoppers {
		s := stoppers[i]
		s.AddWorker()
		go func() {
			s.StartTask()
			<-s.ShouldStop()
			s.SetStopped()
		}()
	}

	done := make(chan struct{})
	go func() {
		for _, s := range stoppers {
			s.Quiesce()
		}
		for _, s := range stoppers {
			s.Stop()
		}
		close(done)
	}()

	<-done
}

</program>

Here is a partial execution trace showing goroutine scheduler events so far:
<trace>
[
  {
    "event_id": 18,
    "timestamp_ns": 14735628714240,
    "event_type": "GoBlock",
    "goroutine_id": 20,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 19,
    "timestamp_ns": 14735628714368,
    "event_type": "GoBlock",
    "goroutine_id": 25,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 20,
    "timestamp_ns": 14735628714432,
    "event_type": "GoStart",
    "goroutine_id": 23,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 21,
    "timestamp_ns": 14735628717824,
    "event_type": "GoUnblock",
    "goroutine_id": 25,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 22,
    "timestamp_ns": 14735628718080,
    "event_type": "GoEnd",
    "goroutine_id": 23,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 23,
    "timestamp_ns": 14735628718208,
    "event_type": "GoStart",
    "goroutine_id": 25,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 24,
    "timestamp_ns": 14735628719552,
    "event_type": "GoBlock",
    "goroutine_id": 25,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 25,
    "timestamp_ns": 14735628739072,
    "event_type": "GoUnblock",
    "goroutine_id": 21,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 26,
    "timestamp_ns": 14735628739136,
    "event_type": "GoStart",
    "goroutine_id": 21,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 27,
    "timestamp_ns": 14735628741824,
    "event_type": "GoBlock",
    "goroutine_id": 21,
    "goroutines": {
      "1": {
        "status": "blocked",
        "blocked_on": "chan receive",
        "locals_hint": "runtime.chanrecv1"
      },
      "19": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "20": {
        "status": "blocked",
        "blocked_on": "chan receive",
        "locals_hint": "runtime.chanrecv1"
      },
      "21": {
        "status": "running",
        "blocked_on": "syscall",
        "locals_hint": "syscall.syscall"
      },
      "24": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "main.main"
      },
      "25": {
        "status": "blocked",
        "blocked_on": "sync",
        "locals_hint": "sync.(*WaitGroup).Wait"
      }
    },
    "channels": {},
    "mutexes": {}
  }
]
</trace>

The current goroutine states are:
<current_state>
{
  "event_id": 27,
  "timestamp_ns": 14735628741824,
  "event_type": "GoBlock",
  "goroutine_id": 21,
  "goroutines": {
    "1": {
      "status": "blocked",
      "blocked_on": "chan receive",
      "locals_hint": "runtime.chanrecv1"
    },
    "19": {
      "status": "running",
      "blocked_on": null,
      "locals_hint": "unknown"
    },
    "20": {
      "status": "blocked",
      "blocked_on": "chan receive",
      "locals_hint": "runtime.chanrecv1"
    },
    "21": {
      "status": "running",
      "blocked_on": "syscall",
      "locals_hint": "syscall.syscall"
    },
    "24": {
      "status": "runnable",
      "blocked_on": null,
      "locals_hint": "main.main"
    },
    "25": {
      "status": "blocked",
      "blocked_on": "sync",
      "locals_hint": "sync.(*WaitGroup).Wait"
    }
  },
  "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": 21}


[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: mutex
// goroutine_count: 3
// expected_nondeterminism: medium
// description: Human-written GoBench bug kernel cockroach_1055 (leak)

package main

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

type Stopper struct {
	stopper  chan struct{}
	stop     sync.WaitGroup
	mu       sync.Mutex
	draining int32
	drain    sync.WaitGroup
}

func (s *Stopper) AddWorker() {
	s.stop.Add(1)
}

func (s *Stopper) ShouldStop() <-chan struct{} {
	if s == nil {
		return nil
	}
	return s.stopper
}

func (s *Stopper) SetStopped() {
	if s != nil {
		s.stop.Done()
	}
}

func (s *Stopper) Quiesce() {
	s.mu.Lock()
	defer s.mu.Unlock()
	s.draining = 1
	s.drain.Wait()
	s.draining = 0
}

func (s *Stopper) Stop() {
	s.mu.Lock()
	defer s.mu.Unlock()
	atomic.StoreInt32(&s.draining, 1)
	s.drain.Wait()
	close(s.stopper)
	s.stop.Wait()
}

func (s *Stopper) StartTask() bool {
	if atomic.LoadInt32(&s.draining) == 0 {
		s.mu.Lock()
		defer s.mu.Unlock()
		s.drain.Add(1)
		return true
	}
	return false
}

func NewStopper() *Stopper {
	return &Stopper{
		stopper: make(chan struct{}),
	}
}

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 stoppers []*Stopper
	for i := 0; i < 3; i++ {
		stoppers = append(stoppers, NewStopper())
	}

	for i := range stoppers {
		s := stoppers[i]
		s.AddWorker()
		go func() {
			s.StartTask()
			<-s.ShouldStop()
			s.SetStopped()
		}()
	}

	done := make(chan struct{})
	go func() {
		for _, s := range stoppers {
			s.Quiesce()
		}
		for _, s := range stoppers {
			s.Stop()
		}
		close(done)
	}()

	<-done
}

</program>

Here is a partial execution trace showing goroutine scheduler events so far:
<trace>
[
  {
    "event_id": 18,
    "timestamp_ns": 14735628714240,
    "event_type": "GoBlock",
    "goroutine_id": 20,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 19,
    "timestamp_ns": 14735628714368,
    "event_type": "GoBlock",
    "goroutine_id": 25,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 20,
    "timestamp_ns": 14735628714432,
    "event_type": "GoStart",
    "goroutine_id": 23,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 21,
    "timestamp_ns": 14735628717824,
    "event_type": "GoUnblock",
    "goroutine_id": 25,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 22,
    "timestamp_ns": 14735628718080,
    "event_type": "GoEnd",
    "goroutine_id": 23,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 23,
    "timestamp_ns": 14735628718208,
    "event_type": "GoStart",
    "goroutine_id": 25,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 24,
    "timestamp_ns": 14735628719552,
    "event_type": "GoBlock",
    "goroutine_id": 25,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 25,
    "timestamp_ns": 14735628739072,
    "event_type": "GoUnblock",
    "goroutine_id": 21,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 26,
    "timestamp_ns": 14735628739136,
    "event_type": "GoStart",
    "goroutine_id": 21,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 27,
    "timestamp_ns": 14735628741824,
    "event_type": "GoBlock",
    "goroutine_id": 21,
    "goroutines": {
      "1": {
        "status": "blocked",
        "blocked_on": "chan receive",
        "locals_hint": "runtime.chanrecv1"
      },
      "19": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "20": {
        "status": "blocked",
        "blocked_on": "chan receive",
        "locals_hint": "runtime.chanrecv1"
      },
      "21": {
        "status": "running",
        "blocked_on": "syscall",
        "locals_hint": "syscall.syscall"
      },
      "24": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "main.main"
      },
      "25": {
        "status": "blocked",
        "blocked_on": "sync",
        "locals_hint": "sync.(*WaitGroup).Wait"
      }
    },
    "channels": {},
    "mutexes": {}
  }
]
</trace>

The current goroutine states are:
<current_state>
{
  "event_id": 27,
  "timestamp_ns": 14735628741824,
  "event_type": "GoBlock",
  "goroutine_id": 21,
  "goroutines": {
    "1": {
      "status": "blocked",
      "blocked_on": "chan receive",
      "locals_hint": "runtime.chanrecv1"
    },
    "19": {
      "status": "running",
      "blocked_on": null,
      "locals_hint": "unknown"
    },
    "20": {
      "status": "blocked",
      "blocked_on": "chan receive",
      "locals_hint": "runtime.chanrecv1"
    },
    "21": {
      "status": "running",
      "blocked_on": "syscall",
      "locals_hint": "syscall.syscall"
    },
    "24": {
      "status": "runnable",
      "blocked_on": null,
      "locals_hint": "main.main"
    },
    "25": {
      "status": "blocked",
      "blocked_on": "sync",
      "locals_hint": "sync.(*WaitGroup).Wait"
    }
  },
  "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": "GoBlock", "goroutine_id": 36}


[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: channel
// goroutine_count: 3
// expected_nondeterminism: medium
// description: Human-written GoBench bug kernel cockroach_13755 (leak)

/*
 * Project: cockroach
 * Issue or PR  : https://github.com/cockroachdb/cockroach/pull/13755
 * Buggy version: 7acb881bbb8f23e87b69fce9568d9a3316b5259c
 * fix commit-id: ef906076adc1d0e3721944829cfedfed51810088
 * Flaky: 100/100
 * Description: The buggy code does not close the db query result (rows),
 * so that one goroutine running (*Rows).awaitDone is blocked forever.
 * The blocking goroutine is waiting for cancel signal from context.
 */

package main

import (
	"os"
	"runtime/trace"
	"context"
	)

type Rows struct {
	cancel context.CancelFunc
}

func (rs *Rows) initContextClose(ctx context.Context) {
	ctx, rs.cancel = context.WithCancel(ctx)
	go rs.awaitDone(ctx)
}

func (rs *Rows) awaitDone(ctx context.Context) {
	<-ctx.Done()
	rs.close(ctx.Err())
}

func (rs *Rows) close(err error) {
	// rs.cancel()
}

/// G1 						G2
/// initContextClose()
/// 						awaitDone()
/// 						<-tx.ctx.Done()
/// return
/// ---------------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() }()
			}
		}
	}

	rs := &Rows{}
	rs.initContextClose(context.Background())
	// FIX: rs.close()
}

</program>

Here is a partial execution trace showing goroutine scheduler events so far:
<trace>
[
  {
    "event_id": 0,
    "timestamp_ns": 14737606999168,
    "event_type": "GoCreate",
    "goroutine_id": 7,
    "goroutines": {
      "1": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "7": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "runtime.traceStartReadCPU"
      }
    },
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 1,
    "timestamp_ns": 14737607005120,
    "event_type": "GoStart",
    "goroutine_id": 7,
    "goroutines": {
      "1": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "7": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      }
    },
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 2,
    "timestamp_ns": 14737607013376,
    "event_type": "GoCreate",
    "goroutine_id": 8,
    "goroutines": {
      "1": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "7": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "8": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "runtime.(*traceAdvancerState).start"
      }
    },
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 3,
    "timestamp_ns": 14737607022400,
    "event_type": "GoStart",
    "goroutine_id": 8,
    "goroutines": {
      "1": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "7": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "8": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      }
    },
    "channels": {},
    "mutexes": {}
  }
]
</trace>

The current goroutine states are:
<current_state>
{
  "event_id": 3,
  "timestamp_ns": 14737607022400,
  "event_type": "GoStart",
  "goroutine_id": 8,
  "goroutines": {
    "1": {
      "status": "running",
      "blocked_on": null,
      "locals_hint": "unknown"
    },
    "7": {
      "status": "running",
      "blocked_on": null,
      "locals_hint": "unknown"
    },
    "8": {
      "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": 9}