fix(cuprate): refuse to run on disks too small for the Monero chain

Cuprate has no pruning — verified against upstream main
(binaries/cuprated/src/config.rs): the 'pruning' crate is Monero's p2p
protocol pruning, not on-disk. Unlike the bitcoin apps, which branch on
DISK_GB in their entrypoint and self-prune, a disk-constrained cuprate
can only sync until the filesystem fills and take Archipelago down.

Translate the bitcoin disk-awareness into the only form cuprate can
honor — refuse rather than prune:
- install (sync + async RPC paths) and package.start fail with an
  actionable message below CUPRATE_MIN_DISK_GB (450 GB total: chain
  ~250 GiB + headroom; allows 500 GB-class, refuses the 250 GB VPS)
- boot reconcile skips an already-installed cuprate on a shrunken disk,
  recorded as Left("cuprate-insufficient-disk") before ensure_running
  so desired-state recovery can never undo it (same shape as
  requires-archival-bitcoin)
- df failure fail-opens at install (never block on an unreadable disk),
  fail-closes at boot (never start a doomed sync)

prod_orchestrator also registers cuprate-ui in UI_APP_IDS (its
companion commit follows).

core/archipelago/src/api/rpc/package/async_lifecycle.rs

@@ -55,6 +55,7 @@ impl RpcHandler {
             .to_string();
         super::validation::validate_app_id(&package_id)?;
         super::dependencies::check_bitcoin_pruning_compatibility(&package_id).await?;
+        super::dependencies::check_cuprate_disk_compatibility(&package_id).await?;
 
         // Reject if already in a transitional lifecycle (prevents double-click
         // queuing two installs on the same package).

core/archipelago/src/api/rpc/package/dependencies.rs

@@ -670,6 +670,54 @@ async fn detect_disk_gb() -> u64 {
         .unwrap_or(u64::MAX)
 }
 
+/// Smallest disk (GB, total) a cuprate node can live on. Monero mainnet is
+/// ~250 GiB of chain data in 2026 and grows ~60 GiB/year; cuprated's storage
+/// (block blobs + fjall index + logs) needs headroom above the raw chain.
+/// 450 lets a 500 GB-class disk work while refusing the 250 GB VPS class,
+/// where the chain does not fit at all.
+///
+/// Kept in lockstep with `prod_orchestrator::CUPRATE_MIN_DISK_GB` — same
+/// duplication pattern as `ARCHIVAL_BITCOIN_DISK_GB` above.
+pub(super) const CUPRATE_MIN_DISK_GB: u64 = 450;
+
+/// The bitcoin apps pick `-prune` automatically when disk is scarce, because
+/// bitcoind supports pruning. Cuprate CANNOT: upstream has no pruning config
+/// at all (the `pruning` crate in its workspace is Monero's p2p *protocol*
+/// pruning, not on-disk pruning), so the disk-scarce equivalent is to refuse
+/// to run cuprate at all rather than let it sync until the filesystem fills —
+/// which took Archipelago itself down on nodes with too little disk.
+fn cuprate_insufficient_disk_message(disk_gb: u64) -> String {
+    format!(
+        "Cuprate needs a disk of at least {} GB and this node has {} GB. \
+         A Monero node cannot run pruned — upstream cuprate has no pruning \
+         support — so the chain (~250 GB and growing) would fill the disk and \
+         take Archipelago down with it. Attach a larger disk (or move \
+         /var/lib/archipelago to one) and try again. Bitcoin apps CAN run \
+         pruned on smaller disks; Monero currently cannot.",
+        CUPRATE_MIN_DISK_GB, disk_gb
+    )
+}
+
+/// Pure decision half of the cuprate disk gate — testable without df.
+pub(super) fn cuprate_disk_gate(disk_gb: u64) -> Option<String> {
+    (disk_gb < CUPRATE_MIN_DISK_GB).then(|| cuprate_insufficient_disk_message(disk_gb))
+}
+
+/// Install/start-time pre-check: refuse cuprate on disks too small to hold
+/// the Monero chain. Mirrors `check_bitcoin_pruning_compatibility`'s
+/// fail-open-on-unknown-disk behaviour (`detect_disk_gb` returns u64::MAX
+/// when df fails, so an unreadable disk never blocks an install).
+pub(super) async fn check_cuprate_disk_compatibility(package_id: &str) -> Result<()> {
+    if package_id != "cuprate" {
+        return Ok(());
+    }
+    let disk_gb = detect_disk_gb().await;
+    if let Some(message) = cuprate_disk_gate(disk_gb) {
+        anyhow::bail!(message);
+    }
+    Ok(())
+}
+
 /// Log informational messages about optional dependencies.
 pub(super) fn log_optional_dep_info(package_id: &str, deps: &RunningDeps) {
     if matches!(package_id, "btcpay-server" | "btcpayserver") && !deps.has_lnd {
@@ -873,9 +921,9 @@ pub(super) fn configure_fedimint_lnd(
 #[cfg(test)]
 mod tests {
     use super::{
-        bitcoin_is_warming_up, dependency_list_declares_archival_bitcoin,
+        bitcoin_is_warming_up, cuprate_disk_gate, dependency_list_declares_archival_bitcoin,
         manifest_declares_archival_bitcoin, order_present_containers, requires_unpruned_bitcoin,
-        startup_order, BITCOIN_WARMUP_BUDGET,
+        startup_order, BITCOIN_WARMUP_BUDGET, CUPRATE_MIN_DISK_GB,
     };
     use archipelago_container::Dependency;
 
@@ -1017,6 +1065,37 @@ mod tests {
         assert!(!manifest_declares_archival_bitcoin("does-not-exist"));
     }
 
+    #[test]
+    fn cuprate_disk_gate_refuses_disks_too_small_for_the_monero_chain() {
+        // 250 GB VPS class: the ~250 GiB chain does not fit, full stop.
+        assert!(cuprate_disk_gate(0).is_some());
+        assert!(cuprate_disk_gate(250).is_some());
+        assert!(cuprate_disk_gate(CUPRATE_MIN_DISK_GB - 1).is_some());
+        assert!(cuprate_disk_gate(CUPRATE_MIN_DISK_GB).is_none());
+        assert!(cuprate_disk_gate(1000).is_none());
+        // df failure reads as u64::MAX — an unreadable disk must not block.
+        assert!(cuprate_disk_gate(u64::MAX).is_none());
+    }
+
+    #[test]
+    fn cuprate_disk_gate_message_names_the_fix_not_just_the_problem() {
+        let msg = cuprate_disk_gate(250).expect("250 GB must be refused");
+        assert!(msg.contains("cannot run pruned"), "{msg}");
+        assert!(msg.contains("larger disk"), "{msg}");
+        assert!(msg.contains("250 GB"), "{msg}");
+    }
+
+    #[tokio::test]
+    async fn cuprate_disk_gate_only_applies_to_cuprate() {
+        // Every other package passes regardless of disk — including the
+        // bitcoin apps, which self-prune via their manifest entrypoint.
+        for package_id in ["bitcoin-knots", "bitcoin-core", "electrumx", "mempool"] {
+            super::check_cuprate_disk_compatibility(package_id)
+                .await
+                .expect("non-cuprate installs must not be gated here");
+        }
+    }
+
     mod dep_wait {
         use super::super::{wait_for_install_deps, DepProbe, DependencyGateError, RunningDeps};
         use std::sync::atomic::{AtomicU32, Ordering};

core/archipelago/src/api/rpc/package/install.rs

@@ -3,10 +3,10 @@ use super::config::{
     is_readonly_compatible, is_valid_docker_image,
 };
 use super::dependencies::{
-    check_bitcoin_pruning_compatibility, configure_fedimint_lnd, detect_existing_containers,
-    detect_running_deps, detect_running_deps_from_package_data, log_optional_dep_info,
-    needs_archy_net, wait_for_install_deps, DepProbe, RunningDeps, DEP_WAIT_INTERVAL,
-    DEP_WAIT_MAX_ATTEMPTS,
+    check_bitcoin_pruning_compatibility, check_cuprate_disk_compatibility, configure_fedimint_lnd,
+    detect_existing_containers, detect_running_deps, detect_running_deps_from_package_data,
+    log_optional_dep_info, needs_archy_net, wait_for_install_deps, DepProbe, RunningDeps,
+    DEP_WAIT_INTERVAL, DEP_WAIT_MAX_ATTEMPTS,
 };
 use super::progress::parse_pull_progress;
 use super::validation::validate_app_id;
@@ -374,6 +374,7 @@ impl RpcHandler {
         // failing instantly.
         let deps = self.gate_install_deps(package_id).await?;
         check_bitcoin_pruning_compatibility(package_id).await?;
+        check_cuprate_disk_compatibility(package_id).await?;
         log_optional_dep_info(package_id, &deps);
         if matches!(package_id, "bitcoin" | "bitcoin-core" | "bitcoin-knots") {
             // Materialise the RPC password file before any install path

core/archipelago/src/api/rpc/package/runtime.rs

@@ -60,6 +60,12 @@ impl RpcHandler {
             .and_then(|v| v.as_str())
             .ok_or_else(|| anyhow::anyhow!("Missing package id"))?;
         validate_app_id(package_id)?;
+        // A cuprate node that starts on a too-small disk fills it and takes
+        // Archipelago down with it (no upstream pruning — see
+        // dependencies::check_cuprate_disk_compatibility). Fail the start
+        // before clearing user-stopped or flipping state, so the app stays
+        // cleanly stopped and the error carries the actionable message.
+        super::dependencies::check_cuprate_disk_compatibility(package_id).await?;
 
         let to_start = if self.orchestrator.is_some() && uses_single_orchestrator_app(package_id) {
             vec![orchestrator_app_id(package_id).to_string()]

core/archipelago/src/container/prod_orchestrator.rs

@@ -47,8 +47,21 @@ use crate::update::host_sudo;
 ///
 /// Keep in sync with the running fixture on .116. Centralized as a constant
 /// so the rule is visible in one place and unit-testable.
-const UI_APP_IDS: &[&str] = &["bitcoin-ui", "electrs-ui", "lnd-ui"];
+const UI_APP_IDS: &[&str] = &["bitcoin-ui", "electrs-ui", "lnd-ui", "cuprate-ui"];
 const ARCHIVAL_BITCOIN_DISK_GB: u64 = 1000;
+/// Smallest disk (GB, total) a cuprate node may run on. Cuprate cannot prune
+/// (upstream has no on-disk pruning — the bitcoin apps self-prune via their
+/// entrypoint, cuprated has no equivalent flag), so a node too small for the
+/// ~250 GiB Monero chain must not sync it at all: left running, it fills the
+/// filesystem and takes Archipelago down. Install/start carry the same gate
+/// (`dependencies::CUPRATE_MIN_DISK_GB`); this one covers boot reconcile, so
+/// an already-installed cuprate on a shrunken/remounted disk stays down
+/// instead of resuming a doomed sync.
+const CUPRATE_MIN_DISK_GB: u64 = 450;
+
+fn requires_cuprate_disk(app_id: &str, disk_gb: u64) -> bool {
+    app_id == "cuprate" && disk_gb < CUPRATE_MIN_DISK_GB
+}
 
 /// Apps expected to exist from first boot on every node — the ONLY apps the
 /// boot reconciler may install from nothing. Every other app needs
@@ -1944,6 +1957,23 @@ impl ProdContainerOrchestrator {
                 crate::crash_recovery::pending_boot_start_done(&container_name);
                 continue;
             }
+            // Same shape as the archival-bitcoin skip above: recorded BEFORE
+            // ensure_running_with_mode, so the "absent" desired-state recovery
+            // below can never fire on this reason and undo it.
+            if mode == ReconcileMode::ExistingOnly && requires_cuprate_disk(&app_id, disk_gb) {
+                tracing::warn!(
+                    app_id = %app_id,
+                    disk_gb,
+                    "cuprate needs a larger disk (no pruning support) — skipping start"
+                );
+                report.record(
+                    &app_id,
+                    ReconcileAction::Left("cuprate-insufficient-disk".into()),
+                );
+                crate::crash_recovery::pending_boot_start_done(&app_id);
+                crate::crash_recovery::pending_boot_start_done(&container_name);
+                continue;
+            }
             match self.ensure_running_with_mode(&lm, mode).await {
                 // Desired-state recovery: the app has no container and was left
                 // "absent" by boot reconcile, BUT it was running at the last
@@ -5365,6 +5395,27 @@ app:
         assert_eq!(compute_container_name(&m), "archy-electrs-ui");
         let m = pull_manifest("lnd-ui", "foo:1");
         assert_eq!(compute_container_name(&m), "archy-lnd-ui");
+        let m = pull_manifest("cuprate-ui", "foo:1");
+        assert_eq!(compute_container_name(&m), "archy-cuprate-ui");
+    }
+
+    #[test]
+    fn cuprate_disk_gate_blocks_only_cuprate_on_small_disks() {
+        // 250 GB VPS class: the ~250 GiB Monero chain cannot fit and cuprate
+        // has no pruning — boot reconcile must leave it down.
+        assert!(requires_cuprate_disk("cuprate", 250));
+        assert!(requires_cuprate_disk("cuprate", CUPRATE_MIN_DISK_GB - 1));
+        assert!(!requires_cuprate_disk("cuprate", CUPRATE_MIN_DISK_GB));
+        assert!(!requires_cuprate_disk("cuprate", 1000));
+        // df failure in detect_disk_gb reads as 0 → fail closed at boot: a
+        // doomed sync is worse than a node that stays down until it can
+        // measure (same direction as the archival-bitcoin skip).
+        assert!(requires_cuprate_disk("cuprate", 0));
+        // Nothing else is gated here: bitcoin apps self-prune, everything
+        // else is irrelevant to the Monero chain.
+        for app_id in ["bitcoin-knots", "bitcoin-core", "electrumx", "mempool"] {
+            assert!(!requires_cuprate_disk(app_id, 0), "{app_id}");
+        }
     }
 
     #[test]