starknet_transaction_prover: bump prover_panics_total on panic hook fire

Bumps the new `prover_panics_total` counter from the panic hook before
constructing the backtrace, so dashboards can alert on panic rate without
log search. The pre-registered zero observation in `install_exporter`
keeps the series visible at scrape time even before the first panic.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: avi-starkware

crates/starknet_transaction_prover/src/server/metrics.rs

@@ -27,6 +27,8 @@ pub const METRICS_PATH: &str = "/metrics";
 pub mod names {
     /// Build identity. Value is always 1; labels carry version + git_sha.
     pub const BUILD_INFO: &str = "prover_build_info";
+    /// Unhandled panics caught by the global panic hook.
+    pub const PANICS_TOTAL: &str = "prover_panics_total";
     /// Wall-clock duration of `prove_transaction` end-to-end. Bucketed.
     pub const PROVE_TRANSACTION_DURATION_SECONDS: &str =
         "prover_prove_transaction_duration_seconds";
@@ -71,6 +73,8 @@ pub fn install_exporter(version: &str, git_sha: &str) -> anyhow::Result<Promethe
         "git_sha" => git_sha.to_string(),
     )
     .set(1.0);
+    // Pre-register at zero so the series exists in scrapes before the first panic.
+    metrics::counter!(names::PANICS_TOTAL).increment(0);
     super::http_metrics::preregister_http_metrics();
     Ok(handle)
 }

crates/starknet_transaction_prover/src/server/panic.rs

@@ -1,12 +1,16 @@
 //! Process-wide panic hook: one structured `tracing` event with location +
 //! backtrace (indexable by log aggregators) instead of the default ad-hoc
-//! stderr output. Only logs — abort-on-panic behavior is preserved.
+//! stderr output, plus a `prover_panics_total` bump so alerts can fire on
+//! panic rate rather than log search. Only logs and counts — runtime
+//! abort-on-panic behavior is preserved.
 
 use std::backtrace::Backtrace;
 use std::panic::PanicHookInfo;
 
 use tracing::error;
 
+use crate::server::metrics::names::PANICS_TOTAL;
+
 #[cfg(test)]
 #[path = "panic_test.rs"]
 mod panic_test;
@@ -16,6 +20,9 @@ pub fn install_panic_hook() {
 }
 
 fn panic_hook(info: &PanicHookInfo<'_>) {
+    // Increment first — if `Backtrace::force_capture` or the `error!` macro
+    // panic recursively, the counter still reflects the original panic.
+    metrics::counter!(PANICS_TOTAL).increment(1);
     let message = extract_payload(info);
     let location = info
         .location()

crates/starknet_transaction_prover/src/server/panic_test.rs

@@ -1,6 +1,8 @@
 use std::sync::{Arc, Mutex};
 
-use crate::server::panic::extract_payload;
+use crate::server::metrics::names::PANICS_TOTAL;
+use crate::server::panic::{extract_payload, install_panic_hook};
+use crate::server::test_recorder::{metric_value, shared_handle};
 
 fn capture_payload<F: FnOnce() + std::panic::UnwindSafe>(f: F) -> String {
     let captured: Arc<Mutex<Option<String>>> = Arc::new(Mutex::new(None));
@@ -21,9 +23,23 @@ fn capture_payload<F: FnOnce() + std::panic::UnwindSafe>(f: F) -> String {
     payload
 }
 
-// The panic hook is global state — a single `#[test]` keeps captures serial.
+// Panic-capturing tests mutate the process-global panic hook.
 #[test]
 fn extracts_static_str_and_formatted_payloads() {
     assert_eq!(capture_payload(|| panic!("static literal")), "static literal");
     assert_eq!(capture_payload(|| panic!("formatted {}", 42)), "formatted 42");
 }
+
+#[test]
+fn panic_hook_bumps_panics_total_counter() {
+    let handle = shared_handle();
+    let before = metric_value(&handle.render(), PANICS_TOTAL);
+
+    let prev_hook = std::panic::take_hook();
+    install_panic_hook();
+    let _ = std::panic::catch_unwind(|| panic!("counter-test panic"));
+    std::panic::set_hook(prev_hook);
+
+    let after = metric_value(&handle.render(), PANICS_TOTAL);
+    assert_eq!(after - before, 1.0);
+}