What

Add a recover() to the stage goroutine in clstages.StartWithStage so a panic in any Caplin stage's ActionFunc is converted into a stage error (logged at Error with a stack trace) instead of propagating out of the unrecovered goroutine and terminating the whole erigon process.

Why

Caplin stages process peer-controlled req/resp responses. A malformed response that trips a nil-pointer dereference — or any other panic — inside a stage currently crashes the entire node, because the goroutine in StartWithStage has no defer recover():

go func() {
    select {
    case errch <- currentStage.ActionFunc(ctx, lg, cfg, args):
    case <-ctx.Done():
        errch <- ctx.Err()
    }
}()

An unrecovered panic in this goroutine is a remote, unauthenticated crash (DoS) vector. This change is defense-in-depth that covers every current and future stage, not just whichever call site happens to be reachable today. It matches the recover() patterns already used elsewhere in Caplin (cl/sentinel/handlers, cl/phase1/network/gossip) and the stage loop's own stated intent — "caplin is designed to always be able to recover regardless of db state".

Change

// Recover so a panic in a stage (e.g. from a malformed peer response) degrades
// to a stage error instead of terminating the whole node.
defer func() {
    if r := recover(); r != nil {
        lg.Error("[Caplin] panic in clstage", "err", r, "stack", dbg.Stack())
        errch <- fmt.Errorf("panic in clstage: %v", r)
    }
}()

The recovered panic is surfaced to the stage's TransitionFunc as an error, so the stage loop continues exactly as it would for any other stage error.

Test

TestStartWithStageRecoversFromActionFuncPanic (added TDD red→green): a stage whose ActionFunc panics. Without the recover the test binary crashes with panic: kaboom (out of the goroutine at clstages.go:50); with it, the panic is surfaced as a stage error and StartWithStage returns normally.

Verification

• go test ./cl/clstages/ ✅
• make lint ✅ (0 issues)
• make erigon integration ✅

🤖 Generated with Claude Code