What causes "cannot restart process Delve did not create" in go-delve/delve?

Detach and relaunch the program under 'dlv debug' or 'dlv exec' instead of attaching.

cannot restart process Delve did not create

Error message

cannot restart process Delve did not create

What it means

RPCServer.Restart refuses to restart a target process that Delve attached to rather than launched. Restart requires re-executing the program, which is only possible when Delve created the process itself; an attached (already-running) process cannot be relaunched.

Source

Thrown at service/rpc2/server.go:96

	// When Rerecord is set the target will be rerecorded
	Rerecord bool

	// When Rebuild is set the process will be build again
	Rebuild bool

	NewRedirects [3]string
}

type RestartOut struct {
	DiscardedBreakpoints []api.DiscardedBreakpoint
}

// Restart restarts program.
func (s *RPCServer) Restart(arg RestartIn, cb service.RPCCallback) {
	close(cb.SetupDoneChan())
	if s.config.Debugger.AttachPid != 0 {
		cb.Return(nil, errors.New("cannot restart process Delve did not create"))
		return
	}
	var out RestartOut
	var err error
	out.DiscardedBreakpoints, err = s.debugger.Restart(arg.Rerecord, arg.Position, arg.ResetArgs, arg.NewArgs, arg.NewRedirects, arg.Rebuild)
	cb.Return(out, err)
}

type StateIn struct {
	// If NonBlocking is true State will return immediately even if the target process is running.
	NonBlocking bool
}

type StateOut struct {
	State *api.DebuggerState
}

// State returns the current debugger state.

View on GitHub (pinned to a23773e6c3)

Solutions

Detach and relaunch the program under 'dlv debug' or 'dlv exec' instead of attaching.
Exit the debug session, rebuild/restart the process, and attach to the new PID.
Use rerun workflows only for processes Delve launched.
Check AttachPid in your client before offering a restart option in the UI.

Example fix

// before (client always shows restart)
call := svc.Restart(restartIn)
// after
if debuggerAttachPid == 0 {
    call := svc.Restart(restartIn)
} else {
    fmt.Println("restart unavailable: attached to an existing process")
}

Defensive patterns

Strategy: validation

Validate before calling

if attachPid != 0 {
    return errors.New("restart not available for attached processes")
}

Try / catch

var out rpc2.RestartOut
err := client.Call("RPCServer.Restart", in, &out)
if err != nil && strings.Contains(err.Error(), "Delve did not create") {
    // fall back to relaunch workflow outside Delve
}

Prevention

Track whether the session was launched (debug/exec/test) or attached.
Disable restart UI/actions when AttachPid != 0.
Document restart semantics for embedded Delve users.

When it happens

Trigger: Calling the RPC Restart method (or 'restart' in a client) when the server was started with dlv attach, i.e. config.Debugger.AttachPid != 0.

Common situations: Developers debugging a running service via 'dlv attach <pid>' then issuing a restart command in the terminal or IDE expecting a re-launch.

Related errors

AI-assisted analysis of go-delve/delve@a23773e6c3 (2026-08-31). Data as JSON: /api/errors/1a748f7ee433c1ac. Report an issue: GitHub.