[System] You are a code execution simulator.

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

Here is a Go program:
<program>
// WEAVE_META
// outcome: leak
// concurrency_pattern: select
// goroutine_count: 2
// expected_nondeterminism: low
// description: Select statement on unbuffered channel, leak_bug=True

package main

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

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() }()
			}
		}
	}

	ch := make(chan int)

	go func() {
		// Simulate processing delay
		time.Sleep(time.Millisecond * 10)
		ch <- 42
	}()

	select {
	case val := <-ch:
		fmt.Println("received:", val)
	case <-time.After(1 * time.Millisecond):
		fmt.Println("timeout occurred")
	}

	// Small delay to allow the leaked goroutine to lock into GoWaiting block
	time.Sleep(time.Millisecond * 20)
}

</program>

Here is a partial execution trace showing goroutine scheduler events so far:
<trace>
[
  {
    "event_id": 0,
    "timestamp_ns": 14726385218816,
    "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": 14726385223616,
    "event_type": "GoCreate",
    "goroutine_id": 8,
    "goroutines": {
      "1": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "7": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "runtime.traceStartReadCPU"
      },
      "8": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "runtime.(*traceAdvancerState).start"
      }
    },
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 2,
    "timestamp_ns": 14726385224448,
    "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"
      },
      "8": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "runtime.(*traceAdvancerState).start"
      }
    },
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 3,
    "timestamp_ns": 14726385235136,
    "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": {}
  },
  {
    "event_id": 4,
    "timestamp_ns": 14726385235648,
    "event_type": "GoCreate",
    "goroutine_id": 9,
    "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"
      },
      "9": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "runtime/trace.(*traceMultiplexer).startLocked"
      }
    },
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 5,
    "timestamp_ns": 14726385241280,
    "event_type": "GoCreate",
    "goroutine_id": 10,
    "goroutines": {
      "1": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "10": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "main.main"
      },
      "7": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "8": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "9": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "runtime/trace.(*traceMultiplexer).startLocked"
      }
    },
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 6,
    "timestamp_ns": 14726385258624,
    "event_type": "GoBlock",
    "goroutine_id": 1,
    "goroutines": {
      "1": {
        "status": "blocked",
        "blocked_on": "select",
        "locals_hint": "runtime.selectgo"
      },
      "10": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "main.main"
      },
      "7": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "8": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "9": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "runtime/trace.(*traceMultiplexer).startLocked"
      }
    },
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 7,
    "timestamp_ns": 14726385259008,
    "event_type": "GoStart",
    "goroutine_id": 10,
    "goroutines": {
      "1": {
        "status": "blocked",
        "blocked_on": "select",
        "locals_hint": "runtime.selectgo"
      },
      "10": {
        "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"
      },
      "9": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "runtime/trace.(*traceMultiplexer).startLocked"
      }
    },
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 8,
    "timestamp_ns": 14726385260608,
    "event_type": "GoBlock",
    "goroutine_id": 8,
    "goroutines": {
      "1": {
        "status": "blocked",
        "blocked_on": "select",
        "locals_hint": "runtime.selectgo"
      },
      "10": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "7": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "8": {
        "status": "blocked",
        "blocked_on": "chan receive",
        "locals_hint": "runtime.chanrecv1"
      },
      "9": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "runtime/trace.(*traceMultiplexer).startLocked"
      }
    },
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 9,
    "timestamp_ns": 14726385260992,
    "event_type": "GoStart",
    "goroutine_id": 9,
    "goroutines": {
      "1": {
        "status": "blocked",
        "blocked_on": "select",
        "locals_hint": "runtime.selectgo"
      },
      "10": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "7": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "8": {
        "status": "blocked",
        "blocked_on": "chan receive",
        "locals_hint": "runtime.chanrecv1"
      },
      "9": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      }
    },
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 10,
    "timestamp_ns": 14726385261376,
    "event_type": "GoBlock",
    "goroutine_id": 7,
    "goroutines": {
      "1": {
        "status": "blocked",
        "blocked_on": "select",
        "locals_hint": "runtime.selectgo"
      },
      "10": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "7": {
        "status": "blocked",
        "blocked_on": "chan receive",
        "locals_hint": "runtime.chanrecv1"
      },
      "8": {
        "status": "blocked",
        "blocked_on": "chan receive",
        "locals_hint": "runtime.chanrecv1"
      },
      "9": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      }
    },
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 11,
    "timestamp_ns": 14726385266048,
    "event_type": "GoBlock",
    "goroutine_id": 10,
    "goroutines": {
      "1": {
        "status": "blocked",
        "blocked_on": "select",
        "locals_hint": "runtime.selectgo"
      },
      "10": {
        "status": "blocked",
        "blocked_on": "sleep",
        "locals_hint": "time.Sleep"
      },
      "7": {
        "status": "blocked",
        "blocked_on": "chan receive",
        "locals_hint": "runtime.chanrecv1"
      },
      "8": {
        "status": "blocked",
        "blocked_on": "chan receive",
        "locals_hint": "runtime.chanrecv1"
      },
      "9": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      }
    },
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 12,
    "timestamp_ns": 14726385290368,
    "event_type": "GoBlock",
    "goroutine_id": 9,
    "goroutines": {
      "1": {
        "status": "blocked",
        "blocked_on": "select",
        "locals_hint": "runtime.selectgo"
      },
      "10": {
        "status": "blocked",
        "blocked_on": "sleep",
        "locals_hint": "time.Sleep"
      },
      "7": {
        "status": "blocked",
        "blocked_on": "chan receive",
        "locals_hint": "runtime.chanrecv1"
      },
      "8": {
        "status": "blocked",
        "blocked_on": "chan receive",
        "locals_hint": "runtime.chanrecv1"
      },
      "9": {
        "status": "running",
        "blocked_on": "syscall",
        "locals_hint": "syscall.syscall"
      }
    },
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 13,
    "timestamp_ns": 14726385332672,
    "event_type": "GoUnblock",
    "goroutine_id": 9,
    "goroutines": {
      "1": {
        "status": "blocked",
        "blocked_on": "select",
        "locals_hint": "runtime.selectgo"
      },
      "10": {
        "status": "blocked",
        "blocked_on": "sleep",
        "locals_hint": "time.Sleep"
      },
      "7": {
        "status": "blocked",
        "blocked_on": "chan receive",
        "locals_hint": "runtime.chanrecv1"
      },
      "8": {
        "status": "blocked",
        "blocked_on": "chan receive",
        "locals_hint": "runtime.chanrecv1"
      },
      "9": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "unknown"
      }
    },
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 14,
    "timestamp_ns": 14726385332736,
    "event_type": "GoStart",
    "goroutine_id": 9,
    "goroutines": {
      "1": {
        "status": "blocked",
        "blocked_on": "select",
        "locals_hint": "runtime.selectgo"
      },
      "10": {
        "status": "blocked",
        "blocked_on": "sleep",
        "locals_hint": "time.Sleep"
      },
      "7": {
        "status": "blocked",
        "blocked_on": "chan receive",
        "locals_hint": "runtime.chanrecv1"
      },
      "8": {
        "status": "blocked",
        "blocked_on": "chan receive",
        "locals_hint": "runtime.chanrecv1"
      },
      "9": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      }
    },
    "channels": {},
    "mutexes": {}
  }
]
</trace>

The current goroutine states are:
<current_state>
{
  "event_id": 14,
  "timestamp_ns": 14726385332736,
  "event_type": "GoStart",
  "goroutine_id": 9,
  "goroutines": {
    "1": {
      "status": "blocked",
      "blocked_on": "select",
      "locals_hint": "runtime.selectgo"
    },
    "10": {
      "status": "blocked",
      "blocked_on": "sleep",
      "locals_hint": "time.Sleep"
    },
    "7": {
      "status": "blocked",
      "blocked_on": "chan receive",
      "locals_hint": "runtime.chanrecv1"
    },
    "8": {
      "status": "blocked",
      "blocked_on": "chan receive",
      "locals_hint": "runtime.chanrecv1"
    },
    "9": {
      "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": "GoBlock", "goroutine_id": 8}


[System] You are a code execution simulator.

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

Here is a Go program:
<program>
// WEAVE_META
// outcome: leak
// concurrency_pattern: select
// goroutine_count: 2
// expected_nondeterminism: low
// description: Select statement on unbuffered channel, leak_bug=True

package main

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

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() }()
			}
		}
	}

	ch := make(chan int)

	go func() {
		// Simulate processing delay
		time.Sleep(time.Millisecond * 10)
		ch <- 42
	}()

	select {
	case val := <-ch:
		fmt.Println("received:", val)
	case <-time.After(1 * time.Millisecond):
		fmt.Println("timeout occurred")
	}

	// Small delay to allow the leaked goroutine to lock into GoWaiting block
	time.Sleep(time.Millisecond * 20)
}

</program>

Here is a partial execution trace showing goroutine scheduler events so far:
<trace>
[
  {
    "event_id": 0,
    "timestamp_ns": 14726385218816,
    "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": 14726385223616,
    "event_type": "GoCreate",
    "goroutine_id": 8,
    "goroutines": {
      "1": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "7": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "runtime.traceStartReadCPU"
      },
      "8": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "runtime.(*traceAdvancerState).start"
      }
    },
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 2,
    "timestamp_ns": 14726385224448,
    "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"
      },
      "8": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "runtime.(*traceAdvancerState).start"
      }
    },
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 3,
    "timestamp_ns": 14726385235136,
    "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": {}
  },
  {
    "event_id": 4,
    "timestamp_ns": 14726385235648,
    "event_type": "GoCreate",
    "goroutine_id": 9,
    "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"
      },
      "9": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "runtime/trace.(*traceMultiplexer).startLocked"
      }
    },
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 5,
    "timestamp_ns": 14726385241280,
    "event_type": "GoCreate",
    "goroutine_id": 10,
    "goroutines": {
      "1": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "10": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "main.main"
      },
      "7": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "8": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "9": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "runtime/trace.(*traceMultiplexer).startLocked"
      }
    },
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 6,
    "timestamp_ns": 14726385258624,
    "event_type": "GoBlock",
    "goroutine_id": 1,
    "goroutines": {
      "1": {
        "status": "blocked",
        "blocked_on": "select",
        "locals_hint": "runtime.selectgo"
      },
      "10": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "main.main"
      },
      "7": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "8": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "9": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "runtime/trace.(*traceMultiplexer).startLocked"
      }
    },
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 7,
    "timestamp_ns": 14726385259008,
    "event_type": "GoStart",
    "goroutine_id": 10,
    "goroutines": {
      "1": {
        "status": "blocked",
        "blocked_on": "select",
        "locals_hint": "runtime.selectgo"
      },
      "10": {
        "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"
      },
      "9": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "runtime/trace.(*traceMultiplexer).startLocked"
      }
    },
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 8,
    "timestamp_ns": 14726385260608,
    "event_type": "GoBlock",
    "goroutine_id": 8,
    "goroutines": {
      "1": {
        "status": "blocked",
        "blocked_on": "select",
        "locals_hint": "runtime.selectgo"
      },
      "10": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "7": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "8": {
        "status": "blocked",
        "blocked_on": "chan receive",
        "locals_hint": "runtime.chanrecv1"
      },
      "9": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "runtime/trace.(*traceMultiplexer).startLocked"
      }
    },
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 9,
    "timestamp_ns": 14726385260992,
    "event_type": "GoStart",
    "goroutine_id": 9,
    "goroutines": {
      "1": {
        "status": "blocked",
        "blocked_on": "select",
        "locals_hint": "runtime.selectgo"
      },
      "10": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "7": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "8": {
        "status": "blocked",
        "blocked_on": "chan receive",
        "locals_hint": "runtime.chanrecv1"
      },
      "9": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      }
    },
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 10,
    "timestamp_ns": 14726385261376,
    "event_type": "GoBlock",
    "goroutine_id": 7,
    "goroutines": {
      "1": {
        "status": "blocked",
        "blocked_on": "select",
        "locals_hint": "runtime.selectgo"
      },
      "10": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "7": {
        "status": "blocked",
        "blocked_on": "chan receive",
        "locals_hint": "runtime.chanrecv1"
      },
      "8": {
        "status": "blocked",
        "blocked_on": "chan receive",
        "locals_hint": "runtime.chanrecv1"
      },
      "9": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      }
    },
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 11,
    "timestamp_ns": 14726385266048,
    "event_type": "GoBlock",
    "goroutine_id": 10,
    "goroutines": {
      "1": {
        "status": "blocked",
        "blocked_on": "select",
        "locals_hint": "runtime.selectgo"
      },
      "10": {
        "status": "blocked",
        "blocked_on": "sleep",
        "locals_hint": "time.Sleep"
      },
      "7": {
        "status": "blocked",
        "blocked_on": "chan receive",
        "locals_hint": "runtime.chanrecv1"
      },
      "8": {
        "status": "blocked",
        "blocked_on": "chan receive",
        "locals_hint": "runtime.chanrecv1"
      },
      "9": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      }
    },
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 12,
    "timestamp_ns": 14726385290368,
    "event_type": "GoBlock",
    "goroutine_id": 9,
    "goroutines": {
      "1": {
        "status": "blocked",
        "blocked_on": "select",
        "locals_hint": "runtime.selectgo"
      },
      "10": {
        "status": "blocked",
        "blocked_on": "sleep",
        "locals_hint": "time.Sleep"
      },
      "7": {
        "status": "blocked",
        "blocked_on": "chan receive",
        "locals_hint": "runtime.chanrecv1"
      },
      "8": {
        "status": "blocked",
        "blocked_on": "chan receive",
        "locals_hint": "runtime.chanrecv1"
      },
      "9": {
        "status": "running",
        "blocked_on": "syscall",
        "locals_hint": "syscall.syscall"
      }
    },
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 13,
    "timestamp_ns": 14726385332672,
    "event_type": "GoUnblock",
    "goroutine_id": 9,
    "goroutines": {
      "1": {
        "status": "blocked",
        "blocked_on": "select",
        "locals_hint": "runtime.selectgo"
      },
      "10": {
        "status": "blocked",
        "blocked_on": "sleep",
        "locals_hint": "time.Sleep"
      },
      "7": {
        "status": "blocked",
        "blocked_on": "chan receive",
        "locals_hint": "runtime.chanrecv1"
      },
      "8": {
        "status": "blocked",
        "blocked_on": "chan receive",
        "locals_hint": "runtime.chanrecv1"
      },
      "9": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "unknown"
      }
    },
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 14,
    "timestamp_ns": 14726385332736,
    "event_type": "GoStart",
    "goroutine_id": 9,
    "goroutines": {
      "1": {
        "status": "blocked",
        "blocked_on": "select",
        "locals_hint": "runtime.selectgo"
      },
      "10": {
        "status": "blocked",
        "blocked_on": "sleep",
        "locals_hint": "time.Sleep"
      },
      "7": {
        "status": "blocked",
        "blocked_on": "chan receive",
        "locals_hint": "runtime.chanrecv1"
      },
      "8": {
        "status": "blocked",
        "blocked_on": "chan receive",
        "locals_hint": "runtime.chanrecv1"
      },
      "9": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      }
    },
    "channels": {},
    "mutexes": {}
  }
]
</trace>

The current goroutine states are:
<current_state>
{
  "event_id": 14,
  "timestamp_ns": 14726385332736,
  "event_type": "GoStart",
  "goroutine_id": 9,
  "goroutines": {
    "1": {
      "status": "blocked",
      "blocked_on": "select",
      "locals_hint": "runtime.selectgo"
    },
    "10": {
      "status": "blocked",
      "blocked_on": "sleep",
      "locals_hint": "time.Sleep"
    },
    "7": {
      "status": "blocked",
      "blocked_on": "chan receive",
      "locals_hint": "runtime.chanrecv1"
    },
    "8": {
      "status": "blocked",
      "blocked_on": "chan receive",
      "locals_hint": "runtime.chanrecv1"
    },
    "9": {
      "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": "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: select
// goroutine_count: 2
// expected_nondeterminism: low
// description: Select statement on unbuffered channel, leak_bug=True

package main

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

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() }()
			}
		}
	}

	ch := make(chan int)

	go func() {
		// Simulate processing delay
		time.Sleep(time.Millisecond * 10)
		ch <- 42
	}()

	select {
	case val := <-ch:
		fmt.Println("received:", val)
	case <-time.After(1 * time.Millisecond):
		fmt.Println("timeout occurred")
	}

	// Small delay to allow the leaked goroutine to lock into GoWaiting block
	time.Sleep(time.Millisecond * 20)
}

</program>

Here is a partial execution trace showing goroutine scheduler events so far:
<trace>
[
  {
    "event_id": 12,
    "timestamp_ns": 14728460491072,
    "event_type": "GoUnblock",
    "goroutine_id": 9,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 13,
    "timestamp_ns": 14728460491136,
    "event_type": "GoStart",
    "goroutine_id": 9,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 14,
    "timestamp_ns": 14728460494080,
    "event_type": "GoBlock",
    "goroutine_id": 9,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 15,
    "timestamp_ns": 14728460498368,
    "event_type": "GoBlock",
    "goroutine_id": 8,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 16,
    "timestamp_ns": 14728460501248,
    "event_type": "GoStart",
    "goroutine_id": 9,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 17,
    "timestamp_ns": 14728460502080,
    "event_type": "GoBlock",
    "goroutine_id": 9,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 18,
    "timestamp_ns": 14728461603648,
    "event_type": "GoUnblock",
    "goroutine_id": 1,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 19,
    "timestamp_ns": 14728461609984,
    "event_type": "GoStart",
    "goroutine_id": 1,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 20,
    "timestamp_ns": 14728461649024,
    "event_type": "GoBlock",
    "goroutine_id": 1,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 21,
    "timestamp_ns": 14728461653312,
    "event_type": "GoStart",
    "goroutine_id": 1,
    "goroutines": {
      "1": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "10": {
        "status": "blocked",
        "blocked_on": "sleep",
        "locals_hint": "time.Sleep"
      },
      "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": 21,
  "timestamp_ns": 14728461653312,
  "event_type": "GoStart",
  "goroutine_id": 1,
  "goroutines": {
    "1": {
      "status": "running",
      "blocked_on": null,
      "locals_hint": "unknown"
    },
    "10": {
      "status": "blocked",
      "blocked_on": "sleep",
      "locals_hint": "time.Sleep"
    },
    "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": 1}


[System] You are a code execution simulator.

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

Here is a Go program:
<program>
// WEAVE_META
// outcome: leak
// concurrency_pattern: select
// goroutine_count: 2
// expected_nondeterminism: low
// description: Select statement on unbuffered channel, leak_bug=True

package main

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

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() }()
			}
		}
	}

	ch := make(chan int)

	go func() {
		// Simulate processing delay
		time.Sleep(time.Millisecond * 10)
		ch <- 42
	}()

	select {
	case val := <-ch:
		fmt.Println("received:", val)
	case <-time.After(1 * time.Millisecond):
		fmt.Println("timeout occurred")
	}

	// Small delay to allow the leaked goroutine to lock into GoWaiting block
	time.Sleep(time.Millisecond * 20)
}

</program>

Here is a partial execution trace showing goroutine scheduler events so far:
<trace>
[
  {
    "event_id": 12,
    "timestamp_ns": 14728460491072,
    "event_type": "GoUnblock",
    "goroutine_id": 9,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 13,
    "timestamp_ns": 14728460491136,
    "event_type": "GoStart",
    "goroutine_id": 9,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 14,
    "timestamp_ns": 14728460494080,
    "event_type": "GoBlock",
    "goroutine_id": 9,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 15,
    "timestamp_ns": 14728460498368,
    "event_type": "GoBlock",
    "goroutine_id": 8,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 16,
    "timestamp_ns": 14728460501248,
    "event_type": "GoStart",
    "goroutine_id": 9,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 17,
    "timestamp_ns": 14728460502080,
    "event_type": "GoBlock",
    "goroutine_id": 9,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 18,
    "timestamp_ns": 14728461603648,
    "event_type": "GoUnblock",
    "goroutine_id": 1,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 19,
    "timestamp_ns": 14728461609984,
    "event_type": "GoStart",
    "goroutine_id": 1,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 20,
    "timestamp_ns": 14728461649024,
    "event_type": "GoBlock",
    "goroutine_id": 1,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 21,
    "timestamp_ns": 14728461653312,
    "event_type": "GoStart",
    "goroutine_id": 1,
    "goroutines": {
      "1": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "10": {
        "status": "blocked",
        "blocked_on": "sleep",
        "locals_hint": "time.Sleep"
      },
      "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": 21,
  "timestamp_ns": 14728461653312,
  "event_type": "GoStart",
  "goroutine_id": 1,
  "goroutines": {
    "1": {
      "status": "running",
      "blocked_on": null,
      "locals_hint": "unknown"
    },
    "10": {
      "status": "blocked",
      "blocked_on": "sleep",
      "locals_hint": "time.Sleep"
    },
    "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": 1}


[System] You are a code execution simulator.

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

Here is a Go program:
<program>
// WEAVE_META
// outcome: leak
// concurrency_pattern: select
// goroutine_count: 2
// expected_nondeterminism: low
// description: Select statement on unbuffered channel, leak_bug=True

package main

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

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() }()
			}
		}
	}

	ch := make(chan int)

	go func() {
		// Simulate processing delay
		time.Sleep(time.Millisecond * 10)
		ch <- 42
	}()

	select {
	case val := <-ch:
		fmt.Println("received:", val)
	case <-time.After(1 * time.Millisecond):
		fmt.Println("timeout occurred")
	}

	// Small delay to allow the leaked goroutine to lock into GoWaiting block
	time.Sleep(time.Millisecond * 20)
}

</program>

Here is a partial execution trace showing goroutine scheduler events so far:
<trace>
[
  {
    "event_id": 12,
    "timestamp_ns": 14728460491072,
    "event_type": "GoUnblock",
    "goroutine_id": 9,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 13,
    "timestamp_ns": 14728460491136,
    "event_type": "GoStart",
    "goroutine_id": 9,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 14,
    "timestamp_ns": 14728460494080,
    "event_type": "GoBlock",
    "goroutine_id": 9,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 15,
    "timestamp_ns": 14728460498368,
    "event_type": "GoBlock",
    "goroutine_id": 8,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 16,
    "timestamp_ns": 14728460501248,
    "event_type": "GoStart",
    "goroutine_id": 9,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 17,
    "timestamp_ns": 14728460502080,
    "event_type": "GoBlock",
    "goroutine_id": 9,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 18,
    "timestamp_ns": 14728461603648,
    "event_type": "GoUnblock",
    "goroutine_id": 1,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 19,
    "timestamp_ns": 14728461609984,
    "event_type": "GoStart",
    "goroutine_id": 1,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 20,
    "timestamp_ns": 14728461649024,
    "event_type": "GoBlock",
    "goroutine_id": 1,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 21,
    "timestamp_ns": 14728461653312,
    "event_type": "GoStart",
    "goroutine_id": 1,
    "goroutines": {
      "1": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "10": {
        "status": "blocked",
        "blocked_on": "sleep",
        "locals_hint": "time.Sleep"
      },
      "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": 21,
  "timestamp_ns": 14728461653312,
  "event_type": "GoStart",
  "goroutine_id": 1,
  "goroutines": {
    "1": {
      "status": "running",
      "blocked_on": null,
      "locals_hint": "unknown"
    },
    "10": {
      "status": "blocked",
      "blocked_on": "sleep",
      "locals_hint": "time.Sleep"
    },
    "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": 1}


[System] You are a code execution simulator.

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

Here is a Go program:
<program>
// WEAVE_META
// outcome: leak
// concurrency_pattern: select
// goroutine_count: 2
// expected_nondeterminism: low
// description: Select statement on unbuffered channel, leak_bug=True

package main

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

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() }()
			}
		}
	}

	ch := make(chan int)

	go func() {
		// Simulate processing delay
		time.Sleep(time.Millisecond * 10)
		ch <- 42
	}()

	select {
	case val := <-ch:
		fmt.Println("received:", val)
	case <-time.After(1 * time.Millisecond):
		fmt.Println("timeout occurred")
	}

	// Small delay to allow the leaked goroutine to lock into GoWaiting block
	time.Sleep(time.Millisecond * 20)
}

</program>

Here is a partial execution trace showing goroutine scheduler events so far:
<trace>
[
  {
    "event_id": 12,
    "timestamp_ns": 14728460491072,
    "event_type": "GoUnblock",
    "goroutine_id": 9,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 13,
    "timestamp_ns": 14728460491136,
    "event_type": "GoStart",
    "goroutine_id": 9,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 14,
    "timestamp_ns": 14728460494080,
    "event_type": "GoBlock",
    "goroutine_id": 9,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 15,
    "timestamp_ns": 14728460498368,
    "event_type": "GoBlock",
    "goroutine_id": 8,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 16,
    "timestamp_ns": 14728460501248,
    "event_type": "GoStart",
    "goroutine_id": 9,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 17,
    "timestamp_ns": 14728460502080,
    "event_type": "GoBlock",
    "goroutine_id": 9,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 18,
    "timestamp_ns": 14728461603648,
    "event_type": "GoUnblock",
    "goroutine_id": 1,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 19,
    "timestamp_ns": 14728461609984,
    "event_type": "GoStart",
    "goroutine_id": 1,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 20,
    "timestamp_ns": 14728461649024,
    "event_type": "GoBlock",
    "goroutine_id": 1,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 21,
    "timestamp_ns": 14728461653312,
    "event_type": "GoStart",
    "goroutine_id": 1,
    "goroutines": {
      "1": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "10": {
        "status": "blocked",
        "blocked_on": "sleep",
        "locals_hint": "time.Sleep"
      },
      "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": 21,
  "timestamp_ns": 14728461653312,
  "event_type": "GoStart",
  "goroutine_id": 1,
  "goroutines": {
    "1": {
      "status": "running",
      "blocked_on": null,
      "locals_hint": "unknown"
    },
    "10": {
      "status": "blocked",
      "blocked_on": "sleep",
      "locals_hint": "time.Sleep"
    },
    "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": 1}


[System] You are a code execution simulator.

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

Here is a Go program:
<program>
// WEAVE_META
// outcome: leak
// concurrency_pattern: select
// goroutine_count: 2
// expected_nondeterminism: low
// description: Select statement on unbuffered channel, leak_bug=True

package main

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

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() }()
			}
		}
	}

	ch := make(chan int)

	go func() {
		// Simulate processing delay
		time.Sleep(time.Millisecond * 10)
		ch <- 42
	}()

	select {
	case val := <-ch:
		fmt.Println("received:", val)
	case <-time.After(1 * time.Millisecond):
		fmt.Println("timeout occurred")
	}

	// Small delay to allow the leaked goroutine to lock into GoWaiting block
	time.Sleep(time.Millisecond * 20)
}

</program>

Here is a partial execution trace showing goroutine scheduler events so far:
<trace>
[
  {
    "event_id": 12,
    "timestamp_ns": 14728460491072,
    "event_type": "GoUnblock",
    "goroutine_id": 9,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 13,
    "timestamp_ns": 14728460491136,
    "event_type": "GoStart",
    "goroutine_id": 9,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 14,
    "timestamp_ns": 14728460494080,
    "event_type": "GoBlock",
    "goroutine_id": 9,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 15,
    "timestamp_ns": 14728460498368,
    "event_type": "GoBlock",
    "goroutine_id": 8,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 16,
    "timestamp_ns": 14728460501248,
    "event_type": "GoStart",
    "goroutine_id": 9,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 17,
    "timestamp_ns": 14728460502080,
    "event_type": "GoBlock",
    "goroutine_id": 9,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 18,
    "timestamp_ns": 14728461603648,
    "event_type": "GoUnblock",
    "goroutine_id": 1,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 19,
    "timestamp_ns": 14728461609984,
    "event_type": "GoStart",
    "goroutine_id": 1,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 20,
    "timestamp_ns": 14728461649024,
    "event_type": "GoBlock",
    "goroutine_id": 1,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 21,
    "timestamp_ns": 14728461653312,
    "event_type": "GoStart",
    "goroutine_id": 1,
    "goroutines": {
      "1": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      },
      "10": {
        "status": "blocked",
        "blocked_on": "sleep",
        "locals_hint": "time.Sleep"
      },
      "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": 21,
  "timestamp_ns": 14728461653312,
  "event_type": "GoStart",
  "goroutine_id": 1,
  "goroutines": {
    "1": {
      "status": "running",
      "blocked_on": null,
      "locals_hint": "unknown"
    },
    "10": {
      "status": "blocked",
      "blocked_on": "sleep",
      "locals_hint": "time.Sleep"
    },
    "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": 1}


[System] You are a code execution simulator.

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

Here is a Go program:
<program>
// WEAVE_META
// outcome: success
// concurrency_pattern: channel
// goroutine_count: 4
// expected_nondeterminism: low
// description: Producer-consumer queue with P=2, Cap=2, leak_bug=False

package main

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

func producer(id int, ch chan<- int, wg *sync.WaitGroup) {
	defer wg.Done()
	for i := 0; i < 3; i++ {
		ch <- id*10 + i
		time.Sleep(time.Millisecond * 1)
	}
}

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() }()
			}
		}
	}

	ch := make(chan int, 2)
	var pwg sync.WaitGroup
	var cwg sync.WaitGroup

	// Start producers
	for p := 1; p <= 2; p++ {
		pwg.Add(1)
		go producer(p, ch, &pwg)
	}

	// Start consumer
	cwg.Add(1)
	go func() {
		defer cwg.Done()
		for val := range ch {
			_ = val
		}
	}()

	// Closer goroutine
	go func() {
		pwg.Wait()
		close(ch)
	}()

	// Monitor
	done := make(chan struct{})
	go func() {
		cwg.Wait()
		close(done)
	}()

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

</program>

Here is a partial execution trace showing goroutine scheduler events so far:
<trace>
[
  {
    "event_id": 8,
    "timestamp_ns": 14730523132224,
    "event_type": "GoCreate",
    "goroutine_id": 13,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 9,
    "timestamp_ns": 14730523134336,
    "event_type": "GoCreate",
    "goroutine_id": 14,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 10,
    "timestamp_ns": 14730523141056,
    "event_type": "GoBlock",
    "goroutine_id": 7,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 11,
    "timestamp_ns": 14730523141568,
    "event_type": "GoStart",
    "goroutine_id": 13,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 12,
    "timestamp_ns": 14730523141569,
    "event_type": "GoBlock",
    "goroutine_id": 8,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 13,
    "timestamp_ns": 14730523141952,
    "event_type": "GoStart",
    "goroutine_id": 9,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 14,
    "timestamp_ns": 14730523143488,
    "event_type": "GoBlock",
    "goroutine_id": 1,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 15,
    "timestamp_ns": 14730523143872,
    "event_type": "GoStart",
    "goroutine_id": 14,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 16,
    "timestamp_ns": 14730523150656,
    "event_type": "GoBlock",
    "goroutine_id": 14,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 17,
    "timestamp_ns": 14730523150720,
    "event_type": "GoBlock",
    "goroutine_id": 13,
    "goroutines": {
      "1": {
        "status": "blocked",
        "blocked_on": "select",
        "locals_hint": "runtime.selectgo"
      },
      "10": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "main.main"
      },
      "11": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "main.main"
      },
      "12": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "main.main"
      },
      "13": {
        "status": "blocked",
        "blocked_on": "sync",
        "locals_hint": "sync.(*WaitGroup).Wait"
      },
      "14": {
        "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": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      }
    },
    "channels": {},
    "mutexes": {}
  }
]
</trace>

The current goroutine states are:
<current_state>
{
  "event_id": 17,
  "timestamp_ns": 14730523150720,
  "event_type": "GoBlock",
  "goroutine_id": 13,
  "goroutines": {
    "1": {
      "status": "blocked",
      "blocked_on": "select",
      "locals_hint": "runtime.selectgo"
    },
    "10": {
      "status": "runnable",
      "blocked_on": null,
      "locals_hint": "main.main"
    },
    "11": {
      "status": "runnable",
      "blocked_on": null,
      "locals_hint": "main.main"
    },
    "12": {
      "status": "runnable",
      "blocked_on": null,
      "locals_hint": "main.main"
    },
    "13": {
      "status": "blocked",
      "blocked_on": "sync",
      "locals_hint": "sync.(*WaitGroup).Wait"
    },
    "14": {
      "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": "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": "GoStart", "goroutine_id": 12}


[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: channel
// goroutine_count: 4
// expected_nondeterminism: low
// description: Producer-consumer queue with P=2, Cap=2, leak_bug=False

package main

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

func producer(id int, ch chan<- int, wg *sync.WaitGroup) {
	defer wg.Done()
	for i := 0; i < 3; i++ {
		ch <- id*10 + i
		time.Sleep(time.Millisecond * 1)
	}
}

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() }()
			}
		}
	}

	ch := make(chan int, 2)
	var pwg sync.WaitGroup
	var cwg sync.WaitGroup

	// Start producers
	for p := 1; p <= 2; p++ {
		pwg.Add(1)
		go producer(p, ch, &pwg)
	}

	// Start consumer
	cwg.Add(1)
	go func() {
		defer cwg.Done()
		for val := range ch {
			_ = val
		}
	}()

	// Closer goroutine
	go func() {
		pwg.Wait()
		close(ch)
	}()

	// Monitor
	done := make(chan struct{})
	go func() {
		cwg.Wait()
		close(done)
	}()

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

</program>

Here is a partial execution trace showing goroutine scheduler events so far:
<trace>
[
  {
    "event_id": 8,
    "timestamp_ns": 14730523132224,
    "event_type": "GoCreate",
    "goroutine_id": 13,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 9,
    "timestamp_ns": 14730523134336,
    "event_type": "GoCreate",
    "goroutine_id": 14,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 10,
    "timestamp_ns": 14730523141056,
    "event_type": "GoBlock",
    "goroutine_id": 7,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 11,
    "timestamp_ns": 14730523141568,
    "event_type": "GoStart",
    "goroutine_id": 13,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 12,
    "timestamp_ns": 14730523141569,
    "event_type": "GoBlock",
    "goroutine_id": 8,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 13,
    "timestamp_ns": 14730523141952,
    "event_type": "GoStart",
    "goroutine_id": 9,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 14,
    "timestamp_ns": 14730523143488,
    "event_type": "GoBlock",
    "goroutine_id": 1,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 15,
    "timestamp_ns": 14730523143872,
    "event_type": "GoStart",
    "goroutine_id": 14,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 16,
    "timestamp_ns": 14730523150656,
    "event_type": "GoBlock",
    "goroutine_id": 14,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 17,
    "timestamp_ns": 14730523150720,
    "event_type": "GoBlock",
    "goroutine_id": 13,
    "goroutines": {
      "1": {
        "status": "blocked",
        "blocked_on": "select",
        "locals_hint": "runtime.selectgo"
      },
      "10": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "main.main"
      },
      "11": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "main.main"
      },
      "12": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "main.main"
      },
      "13": {
        "status": "blocked",
        "blocked_on": "sync",
        "locals_hint": "sync.(*WaitGroup).Wait"
      },
      "14": {
        "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": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      }
    },
    "channels": {},
    "mutexes": {}
  }
]
</trace>

The current goroutine states are:
<current_state>
{
  "event_id": 17,
  "timestamp_ns": 14730523150720,
  "event_type": "GoBlock",
  "goroutine_id": 13,
  "goroutines": {
    "1": {
      "status": "blocked",
      "blocked_on": "select",
      "locals_hint": "runtime.selectgo"
    },
    "10": {
      "status": "runnable",
      "blocked_on": null,
      "locals_hint": "main.main"
    },
    "11": {
      "status": "runnable",
      "blocked_on": null,
      "locals_hint": "main.main"
    },
    "12": {
      "status": "runnable",
      "blocked_on": null,
      "locals_hint": "main.main"
    },
    "13": {
      "status": "blocked",
      "blocked_on": "sync",
      "locals_hint": "sync.(*WaitGroup).Wait"
    },
    "14": {
      "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": "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": "GoStart", "goroutine_id": 12}


[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: channel
// goroutine_count: 4
// expected_nondeterminism: low
// description: Producer-consumer queue with P=2, Cap=2, leak_bug=False

package main

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

func producer(id int, ch chan<- int, wg *sync.WaitGroup) {
	defer wg.Done()
	for i := 0; i < 3; i++ {
		ch <- id*10 + i
		time.Sleep(time.Millisecond * 1)
	}
}

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() }()
			}
		}
	}

	ch := make(chan int, 2)
	var pwg sync.WaitGroup
	var cwg sync.WaitGroup

	// Start producers
	for p := 1; p <= 2; p++ {
		pwg.Add(1)
		go producer(p, ch, &pwg)
	}

	// Start consumer
	cwg.Add(1)
	go func() {
		defer cwg.Done()
		for val := range ch {
			_ = val
		}
	}()

	// Closer goroutine
	go func() {
		pwg.Wait()
		close(ch)
	}()

	// Monitor
	done := make(chan struct{})
	go func() {
		cwg.Wait()
		close(done)
	}()

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

</program>

Here is a partial execution trace showing goroutine scheduler events so far:
<trace>
[
  {
    "event_id": 8,
    "timestamp_ns": 14730523132224,
    "event_type": "GoCreate",
    "goroutine_id": 13,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 9,
    "timestamp_ns": 14730523134336,
    "event_type": "GoCreate",
    "goroutine_id": 14,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 10,
    "timestamp_ns": 14730523141056,
    "event_type": "GoBlock",
    "goroutine_id": 7,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 11,
    "timestamp_ns": 14730523141568,
    "event_type": "GoStart",
    "goroutine_id": 13,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 12,
    "timestamp_ns": 14730523141569,
    "event_type": "GoBlock",
    "goroutine_id": 8,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 13,
    "timestamp_ns": 14730523141952,
    "event_type": "GoStart",
    "goroutine_id": 9,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 14,
    "timestamp_ns": 14730523143488,
    "event_type": "GoBlock",
    "goroutine_id": 1,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 15,
    "timestamp_ns": 14730523143872,
    "event_type": "GoStart",
    "goroutine_id": 14,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 16,
    "timestamp_ns": 14730523150656,
    "event_type": "GoBlock",
    "goroutine_id": 14,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 17,
    "timestamp_ns": 14730523150720,
    "event_type": "GoBlock",
    "goroutine_id": 13,
    "goroutines": {
      "1": {
        "status": "blocked",
        "blocked_on": "select",
        "locals_hint": "runtime.selectgo"
      },
      "10": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "main.main"
      },
      "11": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "main.main"
      },
      "12": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "main.main"
      },
      "13": {
        "status": "blocked",
        "blocked_on": "sync",
        "locals_hint": "sync.(*WaitGroup).Wait"
      },
      "14": {
        "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": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      }
    },
    "channels": {},
    "mutexes": {}
  }
]
</trace>

The current goroutine states are:
<current_state>
{
  "event_id": 17,
  "timestamp_ns": 14730523150720,
  "event_type": "GoBlock",
  "goroutine_id": 13,
  "goroutines": {
    "1": {
      "status": "blocked",
      "blocked_on": "select",
      "locals_hint": "runtime.selectgo"
    },
    "10": {
      "status": "runnable",
      "blocked_on": null,
      "locals_hint": "main.main"
    },
    "11": {
      "status": "runnable",
      "blocked_on": null,
      "locals_hint": "main.main"
    },
    "12": {
      "status": "runnable",
      "blocked_on": null,
      "locals_hint": "main.main"
    },
    "13": {
      "status": "blocked",
      "blocked_on": "sync",
      "locals_hint": "sync.(*WaitGroup).Wait"
    },
    "14": {
      "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": "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": "GoBlock", "goroutine_id": 1}


[System] You are a code execution simulator.

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

Here is a Go program:
<program>
// WEAVE_META
// outcome: success
// concurrency_pattern: channel
// goroutine_count: 4
// expected_nondeterminism: low
// description: Producer-consumer queue with P=2, Cap=2, leak_bug=False

package main

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

func producer(id int, ch chan<- int, wg *sync.WaitGroup) {
	defer wg.Done()
	for i := 0; i < 3; i++ {
		ch <- id*10 + i
		time.Sleep(time.Millisecond * 1)
	}
}

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() }()
			}
		}
	}

	ch := make(chan int, 2)
	var pwg sync.WaitGroup
	var cwg sync.WaitGroup

	// Start producers
	for p := 1; p <= 2; p++ {
		pwg.Add(1)
		go producer(p, ch, &pwg)
	}

	// Start consumer
	cwg.Add(1)
	go func() {
		defer cwg.Done()
		for val := range ch {
			_ = val
		}
	}()

	// Closer goroutine
	go func() {
		pwg.Wait()
		close(ch)
	}()

	// Monitor
	done := make(chan struct{})
	go func() {
		cwg.Wait()
		close(done)
	}()

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

</program>

Here is a partial execution trace showing goroutine scheduler events so far:
<trace>
[
  {
    "event_id": 8,
    "timestamp_ns": 14730523132224,
    "event_type": "GoCreate",
    "goroutine_id": 13,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 9,
    "timestamp_ns": 14730523134336,
    "event_type": "GoCreate",
    "goroutine_id": 14,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 10,
    "timestamp_ns": 14730523141056,
    "event_type": "GoBlock",
    "goroutine_id": 7,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 11,
    "timestamp_ns": 14730523141568,
    "event_type": "GoStart",
    "goroutine_id": 13,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 12,
    "timestamp_ns": 14730523141569,
    "event_type": "GoBlock",
    "goroutine_id": 8,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 13,
    "timestamp_ns": 14730523141952,
    "event_type": "GoStart",
    "goroutine_id": 9,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 14,
    "timestamp_ns": 14730523143488,
    "event_type": "GoBlock",
    "goroutine_id": 1,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 15,
    "timestamp_ns": 14730523143872,
    "event_type": "GoStart",
    "goroutine_id": 14,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 16,
    "timestamp_ns": 14730523150656,
    "event_type": "GoBlock",
    "goroutine_id": 14,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 17,
    "timestamp_ns": 14730523150720,
    "event_type": "GoBlock",
    "goroutine_id": 13,
    "goroutines": {
      "1": {
        "status": "blocked",
        "blocked_on": "select",
        "locals_hint": "runtime.selectgo"
      },
      "10": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "main.main"
      },
      "11": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "main.main"
      },
      "12": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "main.main"
      },
      "13": {
        "status": "blocked",
        "blocked_on": "sync",
        "locals_hint": "sync.(*WaitGroup).Wait"
      },
      "14": {
        "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": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      }
    },
    "channels": {},
    "mutexes": {}
  }
]
</trace>

The current goroutine states are:
<current_state>
{
  "event_id": 17,
  "timestamp_ns": 14730523150720,
  "event_type": "GoBlock",
  "goroutine_id": 13,
  "goroutines": {
    "1": {
      "status": "blocked",
      "blocked_on": "select",
      "locals_hint": "runtime.selectgo"
    },
    "10": {
      "status": "runnable",
      "blocked_on": null,
      "locals_hint": "main.main"
    },
    "11": {
      "status": "runnable",
      "blocked_on": null,
      "locals_hint": "main.main"
    },
    "12": {
      "status": "runnable",
      "blocked_on": null,
      "locals_hint": "main.main"
    },
    "13": {
      "status": "blocked",
      "blocked_on": "sync",
      "locals_hint": "sync.(*WaitGroup).Wait"
    },
    "14": {
      "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": "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": "GoBlock", "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: channel
// goroutine_count: 4
// expected_nondeterminism: low
// description: Producer-consumer queue with P=2, Cap=2, leak_bug=False

package main

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

func producer(id int, ch chan<- int, wg *sync.WaitGroup) {
	defer wg.Done()
	for i := 0; i < 3; i++ {
		ch <- id*10 + i
		time.Sleep(time.Millisecond * 1)
	}
}

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() }()
			}
		}
	}

	ch := make(chan int, 2)
	var pwg sync.WaitGroup
	var cwg sync.WaitGroup

	// Start producers
	for p := 1; p <= 2; p++ {
		pwg.Add(1)
		go producer(p, ch, &pwg)
	}

	// Start consumer
	cwg.Add(1)
	go func() {
		defer cwg.Done()
		for val := range ch {
			_ = val
		}
	}()

	// Closer goroutine
	go func() {
		pwg.Wait()
		close(ch)
	}()

	// Monitor
	done := make(chan struct{})
	go func() {
		cwg.Wait()
		close(done)
	}()

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

</program>

Here is a partial execution trace showing goroutine scheduler events so far:
<trace>
[
  {
    "event_id": 8,
    "timestamp_ns": 14730523132224,
    "event_type": "GoCreate",
    "goroutine_id": 13,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 9,
    "timestamp_ns": 14730523134336,
    "event_type": "GoCreate",
    "goroutine_id": 14,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 10,
    "timestamp_ns": 14730523141056,
    "event_type": "GoBlock",
    "goroutine_id": 7,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 11,
    "timestamp_ns": 14730523141568,
    "event_type": "GoStart",
    "goroutine_id": 13,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 12,
    "timestamp_ns": 14730523141569,
    "event_type": "GoBlock",
    "goroutine_id": 8,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 13,
    "timestamp_ns": 14730523141952,
    "event_type": "GoStart",
    "goroutine_id": 9,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 14,
    "timestamp_ns": 14730523143488,
    "event_type": "GoBlock",
    "goroutine_id": 1,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 15,
    "timestamp_ns": 14730523143872,
    "event_type": "GoStart",
    "goroutine_id": 14,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 16,
    "timestamp_ns": 14730523150656,
    "event_type": "GoBlock",
    "goroutine_id": 14,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 17,
    "timestamp_ns": 14730523150720,
    "event_type": "GoBlock",
    "goroutine_id": 13,
    "goroutines": {
      "1": {
        "status": "blocked",
        "blocked_on": "select",
        "locals_hint": "runtime.selectgo"
      },
      "10": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "main.main"
      },
      "11": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "main.main"
      },
      "12": {
        "status": "runnable",
        "blocked_on": null,
        "locals_hint": "main.main"
      },
      "13": {
        "status": "blocked",
        "blocked_on": "sync",
        "locals_hint": "sync.(*WaitGroup).Wait"
      },
      "14": {
        "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": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      }
    },
    "channels": {},
    "mutexes": {}
  }
]
</trace>

The current goroutine states are:
<current_state>
{
  "event_id": 17,
  "timestamp_ns": 14730523150720,
  "event_type": "GoBlock",
  "goroutine_id": 13,
  "goroutines": {
    "1": {
      "status": "blocked",
      "blocked_on": "select",
      "locals_hint": "runtime.selectgo"
    },
    "10": {
      "status": "runnable",
      "blocked_on": null,
      "locals_hint": "main.main"
    },
    "11": {
      "status": "runnable",
      "blocked_on": null,
      "locals_hint": "main.main"
    },
    "12": {
      "status": "runnable",
      "blocked_on": null,
      "locals_hint": "main.main"
    },
    "13": {
      "status": "blocked",
      "blocked_on": "sync",
      "locals_hint": "sync.(*WaitGroup).Wait"
    },
    "14": {
      "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": "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": "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: channel
// goroutine_count: 4
// expected_nondeterminism: low
// description: Producer-consumer queue with P=2, Cap=2, leak_bug=False

package main

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

func producer(id int, ch chan<- int, wg *sync.WaitGroup) {
	defer wg.Done()
	for i := 0; i < 3; i++ {
		ch <- id*10 + i
		time.Sleep(time.Millisecond * 1)
	}
}

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() }()
			}
		}
	}

	ch := make(chan int, 2)
	var pwg sync.WaitGroup
	var cwg sync.WaitGroup

	// Start producers
	for p := 1; p <= 2; p++ {
		pwg.Add(1)
		go producer(p, ch, &pwg)
	}

	// Start consumer
	cwg.Add(1)
	go func() {
		defer cwg.Done()
		for val := range ch {
			_ = val
		}
	}()

	// Closer goroutine
	go func() {
		pwg.Wait()
		close(ch)
	}()

	// Monitor
	done := make(chan struct{})
	go func() {
		cwg.Wait()
		close(done)
	}()

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

</program>

Here is a partial execution trace showing goroutine scheduler events so far:
<trace>
[
  {
    "event_id": 28,
    "timestamp_ns": 14726452436544,
    "event_type": "GoUnblock",
    "goroutine_id": 6,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 29,
    "timestamp_ns": 14726452436608,
    "event_type": "GoStart",
    "goroutine_id": 6,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 30,
    "timestamp_ns": 14726452440064,
    "event_type": "GoBlock",
    "goroutine_id": 6,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 31,
    "timestamp_ns": 14726452447104,
    "event_type": "GoStart",
    "goroutine_id": 6,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 32,
    "timestamp_ns": 14726452448192,
    "event_type": "GoBlock",
    "goroutine_id": 6,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 33,
    "timestamp_ns": 14726453333696,
    "event_type": "GoUnblock",
    "goroutine_id": 8,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 34,
    "timestamp_ns": 14726453340480,
    "event_type": "GoStart",
    "goroutine_id": 8,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 35,
    "timestamp_ns": 14726453342784,
    "event_type": "GoUnblock",
    "goroutine_id": 9,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 36,
    "timestamp_ns": 14726453343040,
    "event_type": "GoBlock",
    "goroutine_id": 8,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 37,
    "timestamp_ns": 14726453347648,
    "event_type": "GoStart",
    "goroutine_id": 9,
    "goroutines": {
      "1": {
        "status": "blocked",
        "blocked_on": "select",
        "locals_hint": "runtime.selectgo"
      },
      "10": {
        "status": "blocked",
        "blocked_on": "sync",
        "locals_hint": "sync.(*WaitGroup).Wait"
      },
      "11": {
        "status": "blocked",
        "blocked_on": "sync",
        "locals_hint": "sync.(*WaitGroup).Wait"
      },
      "4": {
        "status": "blocked",
        "blocked_on": "chan receive",
        "locals_hint": "runtime.chanrecv1"
      },
      "5": {
        "status": "blocked",
        "blocked_on": "chan receive",
        "locals_hint": "runtime.chanrecv1"
      },
      "6": {
        "status": "blocked",
        "blocked_on": "system goroutine wait",
        "locals_hint": "runtime/trace.(*traceMultiplexer).startLocked.func1"
      },
      "7": {
        "status": "blocked",
        "blocked_on": "sleep",
        "locals_hint": "time.Sleep"
      },
      "8": {
        "status": "blocked",
        "blocked_on": "sleep",
        "locals_hint": "time.Sleep"
      },
      "9": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      }
    },
    "channels": {},
    "mutexes": {}
  }
]
</trace>

The current goroutine states are:
<current_state>
{
  "event_id": 37,
  "timestamp_ns": 14726453347648,
  "event_type": "GoStart",
  "goroutine_id": 9,
  "goroutines": {
    "1": {
      "status": "blocked",
      "blocked_on": "select",
      "locals_hint": "runtime.selectgo"
    },
    "10": {
      "status": "blocked",
      "blocked_on": "sync",
      "locals_hint": "sync.(*WaitGroup).Wait"
    },
    "11": {
      "status": "blocked",
      "blocked_on": "sync",
      "locals_hint": "sync.(*WaitGroup).Wait"
    },
    "4": {
      "status": "blocked",
      "blocked_on": "chan receive",
      "locals_hint": "runtime.chanrecv1"
    },
    "5": {
      "status": "blocked",
      "blocked_on": "chan receive",
      "locals_hint": "runtime.chanrecv1"
    },
    "6": {
      "status": "blocked",
      "blocked_on": "system goroutine wait",
      "locals_hint": "runtime/trace.(*traceMultiplexer).startLocked.func1"
    },
    "7": {
      "status": "blocked",
      "blocked_on": "sleep",
      "locals_hint": "time.Sleep"
    },
    "8": {
      "status": "blocked",
      "blocked_on": "sleep",
      "locals_hint": "time.Sleep"
    },
    "9": {
      "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": "GoBlock", "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: channel
// goroutine_count: 4
// expected_nondeterminism: low
// description: Producer-consumer queue with P=2, Cap=2, leak_bug=False

package main

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

func producer(id int, ch chan<- int, wg *sync.WaitGroup) {
	defer wg.Done()
	for i := 0; i < 3; i++ {
		ch <- id*10 + i
		time.Sleep(time.Millisecond * 1)
	}
}

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() }()
			}
		}
	}

	ch := make(chan int, 2)
	var pwg sync.WaitGroup
	var cwg sync.WaitGroup

	// Start producers
	for p := 1; p <= 2; p++ {
		pwg.Add(1)
		go producer(p, ch, &pwg)
	}

	// Start consumer
	cwg.Add(1)
	go func() {
		defer cwg.Done()
		for val := range ch {
			_ = val
		}
	}()

	// Closer goroutine
	go func() {
		pwg.Wait()
		close(ch)
	}()

	// Monitor
	done := make(chan struct{})
	go func() {
		cwg.Wait()
		close(done)
	}()

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

</program>

Here is a partial execution trace showing goroutine scheduler events so far:
<trace>
[
  {
    "event_id": 28,
    "timestamp_ns": 14726452436544,
    "event_type": "GoUnblock",
    "goroutine_id": 6,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 29,
    "timestamp_ns": 14726452436608,
    "event_type": "GoStart",
    "goroutine_id": 6,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 30,
    "timestamp_ns": 14726452440064,
    "event_type": "GoBlock",
    "goroutine_id": 6,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 31,
    "timestamp_ns": 14726452447104,
    "event_type": "GoStart",
    "goroutine_id": 6,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 32,
    "timestamp_ns": 14726452448192,
    "event_type": "GoBlock",
    "goroutine_id": 6,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 33,
    "timestamp_ns": 14726453333696,
    "event_type": "GoUnblock",
    "goroutine_id": 8,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 34,
    "timestamp_ns": 14726453340480,
    "event_type": "GoStart",
    "goroutine_id": 8,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 35,
    "timestamp_ns": 14726453342784,
    "event_type": "GoUnblock",
    "goroutine_id": 9,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 36,
    "timestamp_ns": 14726453343040,
    "event_type": "GoBlock",
    "goroutine_id": 8,
    "goroutines": "... [TRUNCATED FOR LENGTH] ...",
    "channels": {},
    "mutexes": {}
  },
  {
    "event_id": 37,
    "timestamp_ns": 14726453347648,
    "event_type": "GoStart",
    "goroutine_id": 9,
    "goroutines": {
      "1": {
        "status": "blocked",
        "blocked_on": "select",
        "locals_hint": "runtime.selectgo"
      },
      "10": {
        "status": "blocked",
        "blocked_on": "sync",
        "locals_hint": "sync.(*WaitGroup).Wait"
      },
      "11": {
        "status": "blocked",
        "blocked_on": "sync",
        "locals_hint": "sync.(*WaitGroup).Wait"
      },
      "4": {
        "status": "blocked",
        "blocked_on": "chan receive",
        "locals_hint": "runtime.chanrecv1"
      },
      "5": {
        "status": "blocked",
        "blocked_on": "chan receive",
        "locals_hint": "runtime.chanrecv1"
      },
      "6": {
        "status": "blocked",
        "blocked_on": "system goroutine wait",
        "locals_hint": "runtime/trace.(*traceMultiplexer).startLocked.func1"
      },
      "7": {
        "status": "blocked",
        "blocked_on": "sleep",
        "locals_hint": "time.Sleep"
      },
      "8": {
        "status": "blocked",
        "blocked_on": "sleep",
        "locals_hint": "time.Sleep"
      },
      "9": {
        "status": "running",
        "blocked_on": null,
        "locals_hint": "unknown"
      }
    },
    "channels": {},
    "mutexes": {}
  }
]
</trace>

The current goroutine states are:
<current_state>
{
  "event_id": 37,
  "timestamp_ns": 14726453347648,
  "event_type": "GoStart",
  "goroutine_id": 9,
  "goroutines": {
    "1": {
      "status": "blocked",
      "blocked_on": "select",
      "locals_hint": "runtime.selectgo"
    },
    "10": {
      "status": "blocked",
      "blocked_on": "sync",
      "locals_hint": "sync.(*WaitGroup).Wait"
    },
    "11": {
      "status": "blocked",
      "blocked_on": "sync",
      "locals_hint": "sync.(*WaitGroup).Wait"
    },
    "4": {
      "status": "blocked",
      "blocked_on": "chan receive",
      "locals_hint": "runtime.chanrecv1"
    },
    "5": {
      "status": "blocked",
      "blocked_on": "chan receive",
      "locals_hint": "runtime.chanrecv1"
    },
    "6": {
      "status": "blocked",
      "blocked_on": "system goroutine wait",
      "locals_hint": "runtime/trace.(*traceMultiplexer).startLocked.func1"
    },
    "7": {
      "status": "blocked",
      "blocked_on": "sleep",
      "locals_hint": "time.Sleep"
    },
    "8": {
      "status": "blocked",
      "blocked_on": "sleep",
      "locals_hint": "time.Sleep"
    },
    "9": {
      "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": "GoStart", "goroutine_id": 24}