feat: publish-ready overhaul — lints, tests, docs, CI, fuzzing, mutant testing

- Enable clippy pedantic + nursery lints; fix all warnings
- Add config validation (SF, CR, frequency range checks)
- Zeroize passphrase intermediates after key derivation
- Convert to lib+bin crate for fuzz target accessibility
- Replace Vec with VecDeque for O(1) log/bucket rotation
- Add TUI minimum terminal size guard

Testing:
- 145 unit + property tests (was 15)
- 6 proptest groups (frame roundtrip, hash, SNR, air time, peer list, padding)
- 2 cargo-fuzz targets (gossip frame decode, peer list decode)
- cargo-mutants: 0 missed, 241 caught, 54 unviable

Documentation:
- README with prerequisites, quick start, config reference, architecture
- Module-level and item-level rustdoc on all public items
- LICENSE (MIT), rustfmt.toml, .gitignore

Infrastructure:
- GitHub Actions CI (fmt, clippy, test, audit)
- cargo-mutants config (.cargo/mutants.toml)
- justfile for common tasks

src/config.rs

@@ -1,3 +1,8 @@
+//! TOML configuration loading and validation.
+//!
+//! Handles the `[radio]` and `[bridge]` sections with `MeshCore` US/Canada recommended
+//! defaults, and conversion to donglora-client `RadioConfig`.
+
 use std::path::{Path, PathBuf};
 
 use anyhow::{Context, Result, bail};
@@ -52,34 +57,34 @@ pub struct BridgeSection {
 
 // ── Defaults (MeshCore US/Canada Recommended) ────────────────────
 
-fn default_frequency() -> u32 {
+const fn default_frequency() -> u32 {
     910_525_000
 }
 fn default_bandwidth() -> String {
     "62.5kHz".into()
 }
-fn default_sf() -> u8 {
+const fn default_sf() -> u8 {
     7
 }
-fn default_cr() -> u8 {
+const fn default_cr() -> u8 {
     5
 }
-fn default_sync_word() -> u16 {
+const fn default_sync_word() -> u16 {
     0x3444
 }
 fn default_tx_power() -> String {
     "22".into()
 }
-fn default_preamble() -> u16 {
+const fn default_preamble() -> u16 {
     16
 }
-fn default_true() -> bool {
+const fn default_true() -> bool {
     true
 }
-fn default_dedup_window() -> u64 {
+const fn default_dedup_window() -> u64 {
     300
 }
-fn default_tx_queue_size() -> usize {
+const fn default_tx_queue_size() -> usize {
     32
 }
 
@@ -138,8 +143,20 @@ fn parse_tx_power(s: &str) -> Result<i8> {
 }
 
 impl RadioSection {
-    /// Convert to the donglora-client RadioConfig.
+    /// Convert to the donglora-client `RadioConfig`.
+    ///
+    /// Validates that all radio parameters are within hardware-supported ranges
+    /// before constructing the config.
     pub fn to_radio_config(&self) -> Result<RadioConfig> {
+        if !(7..=12).contains(&self.spreading_factor) {
+            bail!("spreading_factor must be 7-12, got {}", self.spreading_factor);
+        }
+        if !(5..=8).contains(&self.coding_rate) {
+            bail!("coding_rate must be 5-8 (meaning 4/5 to 4/8), got {}", self.coding_rate);
+        }
+        if self.frequency < 150_000_000 || self.frequency > 1_020_000_000 {
+            bail!("frequency {:.3} MHz out of range (150 MHz to 1.02 GHz)", f64::from(self.frequency) / 1_000_000.0);
+        }
         Ok(RadioConfig {
             freq_hz: self.frequency,
             bw: parse_bandwidth(&self.bandwidth)?,
@@ -157,9 +174,7 @@ impl RadioSection {
 
 /// Default config directory: `$XDG_CONFIG_HOME/donglora-bridge/` or `~/.config/donglora-bridge/`.
 pub fn config_dir() -> Result<PathBuf> {
-    let dir = dirs::config_dir()
-        .context("cannot determine config directory")?
-        .join("donglora-bridge");
+    let dir = dirs::config_dir().context("cannot determine config directory")?.join("donglora-bridge");
     Ok(dir)
 }
 
@@ -179,13 +194,241 @@ pub fn default_log_path() -> Result<PathBuf> {
 
 /// Load config from a TOML file. Returns None-passphrase error if not set.
 pub fn load_config(path: &Path) -> Result<Config> {
-    let text = std::fs::read_to_string(path)
-        .with_context(|| format!("reading config: {}", path.display()))?;
+    let text = std::fs::read_to_string(path).with_context(|| format!("reading config: {}", path.display()))?;
     let cfg: Config = toml::from_str(&text).context("parsing config TOML")?;
     if cfg.bridge.passphrase.is_empty() || cfg.bridge.passphrase == "change-me" {
-        bail!(
-            "passphrase is required — run `donglora-bridge config` to set it"
-        );
+        bail!("passphrase is required — run `donglora-bridge config` to set it");
     }
     Ok(cfg)
 }
+
+#[cfg(test)]
+#[allow(clippy::unwrap_used, clippy::expect_used)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn parse_bandwidth_canonical() {
+        assert!(matches!(parse_bandwidth("7.8kHz"), Ok(Bandwidth::Khz7)));
+        assert!(matches!(parse_bandwidth("62.5kHz"), Ok(Bandwidth::Khz62)));
+        assert!(matches!(parse_bandwidth("125kHz"), Ok(Bandwidth::Khz125)));
+        assert!(matches!(parse_bandwidth("500kHz"), Ok(Bandwidth::Khz500)));
+    }
+
+    #[test]
+    fn parse_bandwidth_aliases() {
+        assert!(matches!(parse_bandwidth("7khz"), Ok(Bandwidth::Khz7)));
+        assert!(matches!(parse_bandwidth("khz125"), Ok(Bandwidth::Khz125)));
+        assert!(matches!(parse_bandwidth("10khz"), Ok(Bandwidth::Khz10)));
+    }
+
+    #[test]
+    fn parse_bandwidth_case_insensitive() {
+        assert!(matches!(parse_bandwidth("125KHZ"), Ok(Bandwidth::Khz125)));
+        assert!(matches!(parse_bandwidth("62.5KHZ"), Ok(Bandwidth::Khz62)));
+    }
+
+    #[test]
+    fn parse_bandwidth_rejects_unknown() {
+        assert!(parse_bandwidth("999kHz").is_err());
+        assert!(parse_bandwidth("").is_err());
+        assert!(parse_bandwidth("not_a_bandwidth").is_err());
+    }
+
+    #[test]
+    fn parse_tx_power_numeric() {
+        assert_eq!(parse_tx_power("22").unwrap(), 22);
+        assert_eq!(parse_tx_power("-4").unwrap(), -4);
+        assert_eq!(parse_tx_power("0").unwrap(), 0);
+    }
+
+    #[test]
+    fn parse_tx_power_max_keyword() {
+        assert_eq!(parse_tx_power("max").unwrap(), TX_POWER_MAX);
+        assert_eq!(parse_tx_power("MAX").unwrap(), TX_POWER_MAX);
+        assert_eq!(parse_tx_power("Max").unwrap(), TX_POWER_MAX);
+    }
+
+    #[test]
+    fn parse_tx_power_rejects_garbage() {
+        assert!(parse_tx_power("abc").is_err());
+        assert!(parse_tx_power("").is_err());
+    }
+
+    #[test]
+    fn radio_section_defaults_to_radio_config() {
+        let section = RadioSection::default();
+        let config = section.to_radio_config().unwrap();
+        assert_eq!(config.freq_hz, 910_525_000);
+        assert_eq!(config.sf, 7);
+        assert_eq!(config.cr, 5);
+        assert_eq!(config.sync_word, 0x3444);
+        assert_eq!(config.preamble_len, 16);
+    }
+
+    #[test]
+    fn radio_section_max_power() {
+        let section = RadioSection { tx_power: "max".into(), ..RadioSection::default() };
+        let config = section.to_radio_config().unwrap();
+        assert_eq!(config.tx_power_dbm, TX_POWER_MAX);
+    }
+
+    #[test]
+    fn to_radio_config_rejects_invalid_sf() {
+        let section = RadioSection { spreading_factor: 6, ..RadioSection::default() };
+        assert!(section.to_radio_config().is_err());
+        let section = RadioSection { spreading_factor: 13, ..RadioSection::default() };
+        assert!(section.to_radio_config().is_err());
+    }
+
+    #[test]
+    fn to_radio_config_rejects_invalid_cr() {
+        let section = RadioSection { coding_rate: 4, ..RadioSection::default() };
+        assert!(section.to_radio_config().is_err());
+        let section = RadioSection { coding_rate: 9, ..RadioSection::default() };
+        assert!(section.to_radio_config().is_err());
+    }
+
+    #[test]
+    fn to_radio_config_rejects_invalid_frequency() {
+        let section = RadioSection { frequency: 0, ..RadioSection::default() };
+        assert!(section.to_radio_config().is_err());
+        let section = RadioSection { frequency: 2_000_000_000, ..RadioSection::default() };
+        assert!(section.to_radio_config().is_err());
+    }
+
+    #[test]
+    fn load_config_valid_minimal() {
+        let dir = tempfile::tempdir().unwrap();
+        let path = dir.path().join("config.toml");
+        std::fs::write(&path, "[bridge]\npassphrase = \"my-secret\"\n").unwrap();
+        let cfg = load_config(&path).unwrap();
+        assert_eq!(cfg.bridge.passphrase, "my-secret");
+        assert_eq!(cfg.radio.frequency, 910_525_000);
+    }
+
+    #[test]
+    fn load_config_empty_passphrase_rejected() {
+        let dir = tempfile::tempdir().unwrap();
+        let path = dir.path().join("config.toml");
+        std::fs::write(&path, "[bridge]\npassphrase = \"\"\n").unwrap();
+        assert!(load_config(&path).is_err());
+    }
+
+    #[test]
+    fn load_config_change_me_rejected() {
+        let dir = tempfile::tempdir().unwrap();
+        let path = dir.path().join("config.toml");
+        std::fs::write(&path, "[bridge]\npassphrase = \"change-me\"\n").unwrap();
+        assert!(load_config(&path).is_err());
+    }
+
+    #[test]
+    fn load_config_missing_file() {
+        assert!(load_config(std::path::Path::new("/nonexistent/config.toml")).is_err());
+    }
+
+    #[test]
+    fn load_config_invalid_toml() {
+        let dir = tempfile::tempdir().unwrap();
+        let path = dir.path().join("config.toml");
+        std::fs::write(&path, "not valid toml {{{{").unwrap();
+        assert!(load_config(&path).is_err());
+    }
+
+    // ── Mutant killers: default values (items 1-5) ─────────────────
+
+    #[test]
+    fn default_radio_cad_is_true() {
+        let radio = RadioSection::default();
+        assert!(radio.cad);
+        // Also test via serde (exercises the default_true function used by #[serde(default)])
+        let radio: RadioSection = toml::from_str("").unwrap();
+        assert!(radio.cad);
+    }
+
+    #[test]
+    fn default_dedup_window_is_300() {
+        let bridge = BridgeSection::default();
+        assert_eq!(bridge.dedup_window_secs, 300);
+    }
+
+    #[test]
+    fn default_tx_queue_size_is_32() {
+        let bridge = BridgeSection::default();
+        assert_eq!(bridge.tx_queue_size, 32);
+    }
+
+    // ── Mutant killers: missing bandwidth variants (items 6-10) ──
+
+    #[test]
+    fn parse_bandwidth_all_canonical_variants() {
+        assert!(matches!(parse_bandwidth("15.6kHz"), Ok(Bandwidth::Khz15)));
+        assert!(matches!(parse_bandwidth("20.8kHz"), Ok(Bandwidth::Khz20)));
+        assert!(matches!(parse_bandwidth("31.25kHz"), Ok(Bandwidth::Khz31)));
+        assert!(matches!(parse_bandwidth("41.7kHz"), Ok(Bandwidth::Khz41)));
+        assert!(matches!(parse_bandwidth("250kHz"), Ok(Bandwidth::Khz250)));
+    }
+
+    // ── Mutant killers: frequency boundary (items 11-12) ─────────
+
+    #[test]
+    fn to_radio_config_accepts_boundary_frequencies() {
+        let low = RadioSection { frequency: 150_000_000, ..RadioSection::default() };
+        assert!(low.to_radio_config().is_ok());
+
+        let high = RadioSection { frequency: 1_020_000_000, ..RadioSection::default() };
+        assert!(high.to_radio_config().is_ok());
+    }
+
+    // ── Mutant killers: path helpers (items 13-15) ───────────────
+
+    #[test]
+    fn config_dir_is_non_empty() {
+        let dir = config_dir().unwrap();
+        assert!(dir.components().count() > 0);
+    }
+
+    #[test]
+    fn config_path_ends_with_config_toml() {
+        let path = config_path().unwrap();
+        assert_eq!(path.file_name().unwrap(), "config.toml");
+    }
+
+    #[test]
+    fn default_log_path_ends_with_bridge_log() {
+        let path = default_log_path().unwrap();
+        assert_eq!(path.file_name().unwrap(), "bridge.log");
+    }
+
+    #[test]
+    fn load_config_full_round_trip() {
+        let dir = tempfile::tempdir().unwrap();
+        let path = dir.path().join("config.toml");
+        std::fs::write(
+            &path,
+            r#"
+[radio]
+frequency = 915000000
+bandwidth = "125kHz"
+spreading_factor = 12
+coding_rate = 8
+sync_word = 0x1234
+tx_power = "max"
+preamble = 8
+cad = false
+
+[bridge]
+passphrase = "test-phrase"
+dedup_window_secs = 600
+tx_queue_size = 64
+"#,
+        )
+        .unwrap();
+        let cfg = load_config(&path).unwrap();
+        assert_eq!(cfg.radio.frequency, 915_000_000);
+        assert_eq!(cfg.radio.spreading_factor, 12);
+        assert_eq!(cfg.bridge.dedup_window_secs, 600);
+        assert_eq!(cfg.bridge.tx_queue_size, 64);
+    }
+}

src/gossip.rs

@@ -1,3 +1,9 @@
+//! iroh-gossip swarm management and mainline DHT peer discovery.
+//!
+//! Derives cryptographic keys from a shared passphrase, manages the gossip
+//! subscription, and maintains a DHT heartbeat for zero-configuration peer
+//! bootstrapping.
+
 use std::collections::HashSet;
 use std::sync::atomic::{AtomicUsize, Ordering};
 use std::sync::{Arc, Mutex};
@@ -5,12 +11,12 @@ use std::time::{Duration, Instant};
 
 use anyhow::{Context, Result};
 use bytes::Bytes;
+use futures_lite::StreamExt;
 use iroh::endpoint::Incoming;
 use iroh::{Endpoint, PublicKey, SecretKey};
-use futures_lite::StreamExt;
-use iroh_gossip::api::Event;
-use iroh_gossip::net::{Gossip as GossipActor, GOSSIP_ALPN};
 use iroh_gossip::TopicId;
+use iroh_gossip::api::Event;
+use iroh_gossip::net::{GOSSIP_ALPN, Gossip as GossipActor};
 use mainline::async_dht::AsyncDht;
 use mainline::{Dht, MutableItem, SigningKey};
 use sha2::{Digest, Sha256};
@@ -25,13 +31,15 @@ use crate::packet::GossipFrame;
 /// Conservative cap to stay under BEP44's 1000-byte value limit.
 const MAX_DHT_PEERS: usize = 27;
 
-/// DHT heartbeat interval (base, before jitter).
+/// DHT heartbeat interval when connected (base, before jitter). 5 minutes
+/// balances freshness against DHT write amplification — connected nodes already
+/// have live gossip links and only need DHT for newcomer discovery.
 const DHT_HEARTBEAT_SECS: u64 = 300;
 
-/// Maximum random jitter added to heartbeat interval.
+/// Maximum random jitter added to heartbeat interval. Prevents synchronized
+/// publish storms when multiple bridges start simultaneously.
 const DHT_HEARTBEAT_JITTER_SECS: u64 = 60;
 
-
 // ── Key derivation ───────────────────────────────────────────────
 
 /// Cryptographic keys derived from a shared passphrase.
@@ -43,29 +51,44 @@ pub struct PassphraseKeys {
 
 impl PassphraseKeys {
     /// Derive all keys from a passphrase.
+    ///
+    /// Intermediate buffers containing the passphrase are zeroized after use to
+    /// minimize time sensitive material spends in memory.
+    #[must_use]
     pub fn derive(passphrase: &str) -> Self {
         // Application-specific prefix to avoid DHT collisions with other apps.
-        const APP_PREFIX: &str = "donglora-bridge:";
+        const APP_PREFIX: &[u8] = b"donglora-bridge:";
+
+        // Helper: build a zeroized buffer of [prefix | suffix | passphrase].
+        let keyed_buf = |suffix: &[u8]| -> Vec<u8> {
+            let mut buf = Vec::with_capacity(APP_PREFIX.len() + suffix.len() + passphrase.len());
+            buf.extend_from_slice(APP_PREFIX);
+            buf.extend_from_slice(suffix);
+            buf.extend_from_slice(passphrase.as_bytes());
+            buf
+        };
 
         // Topic ID: blake3 hash of prefixed passphrase.
-        let topic_bytes = *blake3::hash(format!("{APP_PREFIX}{passphrase}").as_bytes()).as_bytes();
+        let mut buf = keyed_buf(b"");
+        let topic_bytes = *blake3::hash(&buf).as_bytes();
         let topic_id = TopicId::from_bytes(topic_bytes);
+        zeroize::Zeroize::zeroize(&mut buf);
 
-        // DHT signing key: ed25519 from SHA-256 of prefixed passphrase + "sign".
-        let sign_seed = Sha256::digest(format!("{APP_PREFIX}sign:{passphrase}").as_bytes());
+        // DHT signing key: ed25519 from SHA-256 of prefixed passphrase + "sign:".
+        let mut buf = keyed_buf(b"sign:");
+        let sign_seed = Sha256::digest(&buf);
         let seed_bytes: [u8; 32] = sign_seed.into();
         let dht_signing_key = SigningKey::from_bytes(&seed_bytes);
+        zeroize::Zeroize::zeroize(&mut buf);
 
-        // DHT salt: first 20 bytes of SHA-256 of prefixed passphrase + "salt".
-        let salt_hash = Sha256::digest(format!("{APP_PREFIX}salt:{passphrase}").as_bytes());
+        // DHT salt: first 20 bytes of SHA-256 of prefixed passphrase + "salt:".
+        let mut buf = keyed_buf(b"salt:");
+        let salt_hash = Sha256::digest(&buf);
         let mut dht_salt = [0u8; 20];
         dht_salt.copy_from_slice(&salt_hash[..20]);
+        zeroize::Zeroize::zeroize(&mut buf);
 
-        Self {
-            topic_id,
-            dht_signing_key,
-            dht_salt,
-        }
+        Self { topic_id, dht_signing_key, dht_salt }
     }
 }
 
@@ -80,6 +103,7 @@ pub struct SwarmState {
     pub last_dht_publish: Option<Instant>,
 }
 
+/// Status of the mainline DHT connection.
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
 pub enum DhtStatus {
     Bootstrapping,
@@ -112,7 +136,9 @@ pub enum GossipEvent {
 /// Handle to the gossip swarm. Manages iroh endpoint, gossip subscription, and DHT.
 pub struct Gossip {
     endpoint: Endpoint,
-    gossip: GossipActor,
+    actor: GossipActor,
+    // std::sync::Mutex (not tokio::sync::Mutex) because locks are never held across
+    // .await points. This avoids async-aware mutex overhead for brief critical sections.
     state: Arc<Mutex<SwarmState>>,
     neighbors: Arc<Mutex<HashSet<PublicKey>>>,
     dht_signing_key: SigningKey,
@@ -147,7 +173,7 @@ impl Gossip {
         info!("iroh endpoint bound, id: {}", my_id.fmt_short());
 
         // Build gossip actor.
-        let gossip = GossipActor::builder().spawn(endpoint.clone());
+        let actor = GossipActor::builder().spawn(endpoint.clone());
 
         // Bootstrap from DHT.
         let bootstrap_peers = dht_get_peers(keys).await;
@@ -158,10 +184,7 @@ impl Gossip {
         }
 
         // Subscribe to gossip topic.
-        let topic = gossip
-            .subscribe(keys.topic_id, bootstrap_peers)
-            .await
-            .context("subscribing to gossip topic")?;
+        let topic = actor.subscribe(keys.topic_id, bootstrap_peers).await.context("subscribing to gossip topic")?;
 
         let (sender, receiver) = topic.split();
 
@@ -182,7 +205,7 @@ impl Gossip {
 
         let handle = Self {
             endpoint: endpoint.clone(),
-            gossip: gossip.clone(),
+            actor: actor.clone(),
             state: state.clone(),
             neighbors: neighbors.clone(),
             dht_signing_key: keys.dht_signing_key.clone(),
@@ -191,7 +214,7 @@ impl Gossip {
         };
 
         // Spawn accept loop.
-        spawn_accept_loop(endpoint.clone(), gossip.clone(), cancel.clone());
+        spawn_accept_loop(endpoint.clone(), actor.clone(), cancel.clone());
 
         // Spawn gossip receiver task.
         spawn_receiver(receiver, event_tx, state.clone(), neighbor_count.clone(), neighbors.clone(), cancel.clone());
@@ -221,8 +244,9 @@ impl Gossip {
     }
 
     /// Snapshot of swarm state for TUI.
+    #[must_use]
     pub fn swarm_state(&self) -> SwarmState {
-        self.state.lock().unwrap_or_else(|e| e.into_inner()).clone()
+        self.state.lock().unwrap_or_else(std::sync::PoisonError::into_inner).clone()
     }
 
     /// Graceful shutdown. Publishes neighbors (without ourselves) to DHT
@@ -232,7 +256,7 @@ impl Gossip {
         let neighbor_ids: Vec<[u8; 32]> = self
             .neighbors
             .lock()
-            .unwrap_or_else(|e| e.into_inner())
+            .unwrap_or_else(std::sync::PoisonError::into_inner)
             .iter()
             .map(|id| *id.as_bytes())
             .collect();
@@ -242,14 +266,9 @@ impl Gossip {
             let value = encode_peer_list(&neighbor_ids);
             let seq = std::time::SystemTime::now()
                 .duration_since(std::time::UNIX_EPOCH)
-                .map(|d| d.as_secs() as i64)
+                .map(|d| d.as_secs().cast_signed())
                 .unwrap_or(0);
-            let item = MutableItem::new(
-                self.dht_signing_key.clone(),
-                &value,
-                seq,
-                Some(self.dht_salt.as_ref()),
-            );
+            let item = MutableItem::new(self.dht_signing_key.clone(), &value, seq, Some(self.dht_salt.as_ref()));
             match dht.put_mutable(item, None).await {
                 Ok(_) => info!("shutdown: published {} neighbor(s) to DHT (removed self)", neighbor_ids.len()),
                 Err(e) => debug!("shutdown: DHT publish failed: {e:#}"),
@@ -257,7 +276,7 @@ impl Gossip {
         }
 
         self.cancel.cancel();
-        let _ = self.gossip.shutdown().await;
+        let _ = self.actor.shutdown().await;
         self.endpoint.close().await;
     }
 }
@@ -316,18 +335,29 @@ fn spawn_receiver(
                         debug!("received malformed gossip frame ({} bytes)", msg.content.len());
                     }
                 }
+                // Neighbor count is tracked in both AtomicUsize (for lock-free reads in DHT
+                // heartbeat) and SwarmState (for TUI snapshots). Brief inconsistency between
+                // the two is acceptable — the TUI polls at 250ms intervals.
                 Event::NeighborUp(id) => {
                     let count = neighbor_count.fetch_add(1, Ordering::Relaxed) + 1;
                     info!("neighbor up: {} (total: {count})", id.fmt_short());
-                    if let Ok(mut n) = neighbors.lock() { n.insert(id); }
-                    if let Ok(mut s) = state.lock() { s.neighbor_count = count; }
+                    if let Ok(mut n) = neighbors.lock() {
+                        n.insert(id);
+                    }
+                    if let Ok(mut s) = state.lock() {
+                        s.neighbor_count = count;
+                    }
                     let _ = event_tx.send(GossipEvent::NeighborChanged(count)).await;
                 }
                 Event::NeighborDown(id) => {
                     let count = neighbor_count.fetch_sub(1, Ordering::Relaxed).saturating_sub(1);
                     info!("neighbor down: {} (total: {count})", id.fmt_short());
-                    if let Ok(mut n) = neighbors.lock() { n.remove(&id); }
-                    if let Ok(mut s) = state.lock() { s.neighbor_count = count; }
+                    if let Ok(mut n) = neighbors.lock() {
+                        n.remove(&id);
+                    }
+                    if let Ok(mut s) = state.lock() {
+                        s.neighbor_count = count;
+                    }
                     let _ = event_tx.send(GossipEvent::NeighborChanged(count)).await;
                 }
                 Event::Lagged => {
@@ -361,11 +391,13 @@ fn spawn_broadcaster(
     });
 }
 
-/// DHT poll interval while alone (read frequently, publish infrequently).
+/// DHT poll interval while alone. 3 seconds is aggressive but reads are cheap
+/// (single DHT GET) and fast discovery matters when two nodes start together.
 const DHT_ALONE_READ_SECS: u64 = 3;
 
-/// How often a lonely node publishes (merge-only, never destructive).
-/// Slower than reads — publishing is heavier and a lonely node only adds itself.
+/// How often a lonely node publishes (merge-only, never destructive). 30 seconds
+/// is much slower than reads because DHT PUT is heavier and a lonely node only
+/// adds itself to the peer list.
 const DHT_ALONE_PUBLISH_SECS: u64 = 30;
 
 /// Periodically interact with the DHT to discover and share peers.
@@ -458,10 +490,7 @@ async fn dht_read_and_join(
 ) {
     if let Some(record) = dht.get_mutable_most_recent(pub_key_bytes, Some(salt)).await {
         let peers = decode_peer_list(record.value());
-        let new_peers: Vec<_> = peers
-            .into_iter()
-            .filter(|id| *id != *my_id)
-            .collect();
+        let new_peers: Vec<_> = peers.into_iter().filter(|id| *id != *my_id).collect();
         if !new_peers.is_empty() {
             info!("DHT discovered {} peer(s), feeding to gossip", new_peers.len());
             if let Err(e) = gossip_sender.join_peers(new_peers).await {
@@ -483,7 +512,7 @@ async fn dht_publish(
     neighbors: &Arc<Mutex<HashSet<PublicKey>>>,
     state: &Arc<Mutex<SwarmState>>,
 ) {
-    let has_neighbors = neighbors.lock().map(|n| !n.is_empty()).unwrap_or(false);
+    let has_neighbors = neighbors.lock().is_ok_and(|n| !n.is_empty());
 
     let mut seen = HashSet::new();
     let mut peer_list: Vec<[u8; 32]> = Vec::with_capacity(MAX_DHT_PEERS);
@@ -518,7 +547,7 @@ async fn dht_publish(
     let value = encode_peer_list(&peer_list);
     let seq = std::time::SystemTime::now()
         .duration_since(std::time::UNIX_EPOCH)
-        .map(|d| d.as_secs() as i64)
+        .map(|d| d.as_secs().cast_signed())
         .unwrap_or(0);
 
     let item = MutableItem::new(signing_key.clone(), &value, seq, Some(salt.as_ref()));
@@ -552,22 +581,24 @@ async fn dht_get_peers(keys: &PassphraseKeys) -> Vec<PublicKey> {
     };
 
     let pub_key_bytes = keys.dht_signing_key.verifying_key().to_bytes();
-    match dht.get_mutable_most_recent(&pub_key_bytes, Some(&keys.dht_salt)).await {
-        Some(record) => {
+    dht.get_mutable_most_recent(&pub_key_bytes, Some(&keys.dht_salt)).await.map_or_else(
+        || {
+            debug!("DHT bootstrap: no existing record");
+            vec![]
+        },
+        |record| {
             let peers = decode_peer_list(record.value());
             debug!("DHT bootstrap: found {} peer(s)", peers.len());
             peers
-        }
-        None => {
-            debug!("DHT bootstrap: no existing record");
-            vec![]
-        }
-    }
+        },
+    )
 }
 
 /// Encode a list of 32-byte peer IDs into bytes for DHT storage.
-/// Format: [count: u16 LE] [id_0: 32B] [id_1: 32B] ...
-fn encode_peer_list(peers: &[[u8; 32]]) -> Vec<u8> {
+/// Format: `[count: u16 LE] [id_0: 32B] [id_1: 32B] ...`
+#[must_use]
+pub fn encode_peer_list(peers: &[[u8; 32]]) -> Vec<u8> {
+    #[allow(clippy::cast_possible_truncation)] // MAX_DHT_PEERS (27) fits in u16
     let count = peers.len().min(MAX_DHT_PEERS) as u16;
     let mut buf = Vec::with_capacity(2 + (count as usize) * 32);
     buf.extend_from_slice(&count.to_le_bytes());
@@ -578,7 +609,8 @@ fn encode_peer_list(peers: &[[u8; 32]]) -> Vec<u8> {
 }
 
 /// Decode a peer list from DHT record value.
-fn decode_peer_list(data: &[u8]) -> Vec<PublicKey> {
+#[must_use]
+pub fn decode_peer_list(data: &[u8]) -> Vec<PublicKey> {
     if data.len() < 2 {
         return vec![];
     }
@@ -656,4 +688,82 @@ mod tests {
         let decoded = decode_peer_list(&data);
         assert_eq!(decoded.len(), 1);
     }
+
+    #[test]
+    fn dht_status_display() {
+        assert_eq!(format!("{}", DhtStatus::Bootstrapping), "Bootstrapping");
+        assert_eq!(format!("{}", DhtStatus::Ready), "Ready");
+        assert_eq!(format!("{}", DhtStatus::PublishFailed), "Failed");
+    }
+
+    #[test]
+    fn decode_peer_list_exact_boundary() {
+        // Build data with count=2 and exactly 2 + 32 + 32 = 66 bytes.
+        // Both peers should decode successfully.
+        let sk0 = iroh::SecretKey::generate(&mut rand::rng());
+        let sk1 = iroh::SecretKey::generate(&mut rand::rng());
+        let id0 = *sk0.public().as_bytes();
+        let id1 = *sk1.public().as_bytes();
+
+        let mut data = vec![2, 0]; // count = 2 (u16 LE)
+        data.extend_from_slice(&id0);
+        data.extend_from_slice(&id1);
+        assert_eq!(data.len(), 66);
+
+        let decoded = decode_peer_list(&data);
+        assert_eq!(decoded.len(), 2);
+        assert_eq!(*decoded[0].as_bytes(), id0);
+        assert_eq!(*decoded[1].as_bytes(), id1);
+    }
+
+    #[test]
+    fn decode_peer_list_one_byte_short() {
+        // Build data with count=2 but only 2 + 32 + 31 = 65 bytes.
+        // First peer decodes, second is truncated and skipped.
+        let sk0 = iroh::SecretKey::generate(&mut rand::rng());
+        let sk1 = iroh::SecretKey::generate(&mut rand::rng());
+        let id0 = *sk0.public().as_bytes();
+        let id1 = *sk1.public().as_bytes();
+
+        let mut data = vec![2, 0]; // count = 2 (u16 LE)
+        data.extend_from_slice(&id0);
+        data.extend_from_slice(&id1[..31]); // only 31 bytes of second peer
+        assert_eq!(data.len(), 65);
+
+        let decoded = decode_peer_list(&data);
+        assert_eq!(decoded.len(), 1);
+        assert_eq!(*decoded[0].as_bytes(), id0);
+    }
+
+    #[test]
+    fn decode_peer_list_count_header_only() {
+        // Data with exactly 2 bytes (count=0). Must not be rejected by the length check.
+        // Kills mutant: `data.len() < 2` → `data.len() <= 2`.
+        let data = [0u8, 0]; // count = 0
+        let decoded = decode_peer_list(&data);
+        assert!(decoded.is_empty());
+
+        // Data with 2 bytes but count=1 and no peer data — decodes 0 (truncated).
+        let data = [1u8, 0]; // count = 1 but no peer bytes
+        let decoded = decode_peer_list(&data);
+        assert!(decoded.is_empty());
+    }
+
+    mod proptests {
+        use super::*;
+        use proptest::prelude::*;
+
+        proptest! {
+            #[test]
+            fn peer_list_roundtrip_prop(count in 0usize..=30) {
+                let keys: Vec<[u8; 32]> = (0..count)
+                    .map(|_| *iroh::SecretKey::generate(&mut rand::rng()).public().as_bytes())
+                    .collect();
+                let encoded = encode_peer_list(&keys);
+                let decoded = decode_peer_list(&encoded);
+                let expected = count.min(MAX_DHT_PEERS);
+                prop_assert_eq!(decoded.len(), expected);
+            }
+        }
+    }
 }

src/lib.rs

@@ -0,0 +1,18 @@
+//! Peer-to-peer `LoRa` bridge connecting `DongLoRa` USB dongles across the internet.
+//!
+//! Uses iroh-gossip for swarm-based packet broadcast and mainline DHT for
+//! zero-configuration peer discovery. Nodes sharing a passphrase automatically
+//! discover each other and relay radio packets through a gossip swarm.
+
+pub mod config;
+pub mod gossip;
+pub mod packet;
+pub mod radio;
+pub mod rate_limit;
+pub mod router;
+pub mod setup;
+
+// TUI is public only so its types are visible to the binary; not intended for
+// external consumption.
+#[doc(hidden)]
+pub mod tui;

src/main.rs

@@ -1,11 +1,4 @@
-mod config;
-mod gossip;
-mod packet;
-mod radio;
-mod rate_limit;
-mod router;
-mod setup;
-mod tui;
+use donglora_bridge::{config, gossip, radio, rate_limit, router, setup, tui};
 
 use std::sync::Arc;
 use std::time::Instant;
@@ -43,6 +36,7 @@ enum Commands {
 }
 
 #[tokio::main]
+#[allow(clippy::too_many_lines)]
 async fn main() -> Result<()> {
     let cli = Cli::parse();
 
@@ -53,12 +47,8 @@ async fn main() -> Result<()> {
     };
 
     // Config subcommand: run wizard with existing config as defaults.
-    if let Some(Commands::Config) = cli.command {
-        let existing = if config_path.exists() {
-            config::load_config(&config_path).ok()
-        } else {
-            None
-        };
+    if matches!(cli.command, Some(Commands::Config)) {
+        let existing = if config_path.exists() { config::load_config(&config_path).ok() } else { None };
         return setup::run_wizard(&config_path, existing.as_ref());
     }
 
@@ -69,39 +59,11 @@ async fn main() -> Result<()> {
     }
 
     // Load config.
-    let cfg = config::load_config(&config_path)
-        .with_context(|| format!("loading config from {}", config_path.display()))?;
+    let cfg =
+        config::load_config(&config_path).with_context(|| format!("loading config from {}", config_path.display()))?;
 
     // Set up logging.
-    if cli.log_only {
-        tracing_subscriber::fmt()
-            .with_env_filter(
-                tracing_subscriber::EnvFilter::try_from_default_env()
-                    .unwrap_or_else(|_| tracing_subscriber::EnvFilter::new("info")),
-            )
-            .init();
-    } else {
-        let log_path = cfg
-            .bridge
-            .log_file
-            .clone()
-            .unwrap_or_else(|| config::default_log_path().unwrap_or_else(|_| "/tmp/donglora-bridge.log".into()));
-        if let Some(parent) = log_path.parent() {
-            std::fs::create_dir_all(parent).ok();
-        }
-        let file_appender = tracing_appender::rolling::never(
-            log_path.parent().unwrap_or(std::path::Path::new("/tmp")),
-            log_path.file_name().unwrap_or(std::ffi::OsStr::new("donglora-bridge.log")),
-        );
-        tracing_subscriber::fmt()
-            .with_env_filter(
-                tracing_subscriber::EnvFilter::try_from_default_env()
-                    .unwrap_or_else(|_| tracing_subscriber::EnvFilter::new("info")),
-            )
-            .with_writer(file_appender)
-            .with_ansi(false)
-            .init();
-    }
+    setup_logging(cli.log_only, &cfg);
 
     // Ephemeral identity — fresh keypair each launch.
     let secret_key = SecretKey::generate(&mut rand::rng());
@@ -126,25 +88,22 @@ async fn main() -> Result<()> {
     info!("rate limiter: {:.1} pps", rate_limiter.rate_pps());
 
     // Create gossip network.
-    let (swarm, gossip_event_rx, gossip_frame_tx) =
-        gossip::Gossip::new(secret_key, &keys).await?;
+    let (swarm, gossip_event_rx, gossip_frame_tx) = gossip::Gossip::new(secret_key, &keys).await?;
     let swarm = Arc::new(swarm);
 
     // Start radio.
-    let (radio_event_rx, radio_tx) = radio::spawn(radio_config, cfg.radio.port.clone());
+    let (radio_event_rx, radio_tx) = radio::spawn(radio_config, cfg.radio.port.clone())?;
 
     // Stats + log channel + radio config watch.
     let stats = Arc::new(Stats::default());
     let (log_tx, log_rx) = mpsc::channel(512);
-    let (config_watch_tx, config_watch_rx) = tokio::sync::watch::channel(
-        router::RadioConfigInfo {
-            active: radio_config,
-            requested: radio_config,
-            source: radio::ConfigSource::Ours,
-            device: String::new(),
-            connected: false,
-        },
-    );
+    let (config_watch_tx, config_watch_rx) = tokio::sync::watch::channel(router::RadioConfigInfo {
+        active: radio_config,
+        requested: radio_config,
+        source: radio::ConfigSource::Ours,
+        device: String::new(),
+        connected: false,
+    });
 
     // Cancellation.
     let cancel = CancellationToken::new();
@@ -180,9 +139,7 @@ async fn main() -> Result<()> {
     {
         let cancel = cancel.clone();
         tokio::spawn(async move {
-            let sigterm = tokio::signal::unix::signal(
-                tokio::signal::unix::SignalKind::terminate(),
-            );
+            let sigterm = tokio::signal::unix::signal(tokio::signal::unix::SignalKind::terminate());
             match sigterm {
                 Ok(mut sigterm) => {
                     tokio::select! {
@@ -205,15 +162,7 @@ async fn main() -> Result<()> {
         info!("running in headless mode");
         cancel.cancelled().await;
     } else {
-        let terminal = tui::run(
-            config_watch_rx,
-            swarm.clone(),
-            stats,
-            log_rx,
-            cancel.clone(),
-            start_time,
-        )
-        .await;
+        let terminal = tui::run(config_watch_rx, swarm.clone(), stats, log_rx, cancel.clone(), start_time);
 
         cancel.cancel();
         swarm.shutdown().await;
@@ -232,3 +181,30 @@ async fn main() -> Result<()> {
 
     Ok(())
 }
+
+fn setup_logging(log_only: bool, cfg: &config::Config) {
+    let env_filter = || {
+        tracing_subscriber::EnvFilter::try_from_default_env()
+            .unwrap_or_else(|_| tracing_subscriber::EnvFilter::new("info"))
+    };
+
+    if log_only {
+        tracing_subscriber::fmt().with_env_filter(env_filter()).init();
+    } else {
+        let log_path = cfg
+            .bridge
+            .log_file
+            .clone()
+            .unwrap_or_else(|| config::default_log_path().unwrap_or_else(|_| "/tmp/donglora-bridge.log".into()));
+        if let Some(parent) = log_path.parent()
+            && let Err(e) = std::fs::create_dir_all(parent)
+        {
+            eprintln!("warning: failed to create log directory {}: {e}", parent.display());
+        }
+        let file_appender = tracing_appender::rolling::never(
+            log_path.parent().unwrap_or_else(|| std::path::Path::new("/tmp")),
+            log_path.file_name().unwrap_or_else(|| std::ffi::OsStr::new("donglora-bridge.log")),
+        );
+        tracing_subscriber::fmt().with_env_filter(env_filter()).with_writer(file_appender).with_ansi(false).init();
+    }
+}

src/packet.rs

@@ -1,7 +1,12 @@
-/// Gossip frame header size: sender(32) + rssi(2) + snr(2) + payload_len(2) = 38
+//! Wire format definitions for radio packets and gossip frames.
+//!
+//! Includes SNR quality grading against `LoRa` demodulation floors and blake3
+//! content hashing for deduplication.
+
+/// Gossip frame header size: `sender(32) + rssi(2) + snr(2) + payload_len(2) = 38`
 const FRAME_HEADER_SIZE: usize = 38;
 
-/// SNR quality grade for a received LoRa packet.
+/// SNR quality grade for a received `LoRa` packet.
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
 pub enum Grade {
     /// SNR well above demodulation floor (margin >= 3 dB).
@@ -16,7 +21,8 @@ pub enum Grade {
 
 impl Grade {
     /// Returns true if the packet is reliable enough to forward.
-    pub fn should_forward(self) -> bool {
+    #[must_use]
+    pub const fn should_forward(self) -> bool {
         matches!(self, Self::Good | Self::Marginal)
     }
 }
@@ -34,6 +40,7 @@ impl std::fmt::Display for Grade {
 
 /// Grade a received packet's SNR against the demodulation floor for the given
 /// spreading factor.
+#[must_use]
 pub fn snr_grade(snr: i16, sf: u8) -> Grade {
     if !(-32..=32).contains(&snr) {
         return Grade::Invalid;
@@ -62,33 +69,31 @@ pub struct RadioPacket {
 /// Wire format: `[sender: 32B] [rssi: i16 LE] [snr: i16 LE] [payload_len: u16 LE] [payload: NB]`
 #[derive(Debug, Clone)]
 pub struct GossipFrame {
-    /// EndpointId (PublicKey bytes) of the bridge that first heard this packet on radio.
+    /// `EndpointId` (`PublicKey` bytes) of the bridge that first heard this packet on radio.
     pub sender: [u8; 32],
     /// RSSI at the originating bridge (informational).
     pub rssi: i16,
     /// SNR at the originating bridge (informational).
     pub snr: i16,
-    /// Raw LoRa payload.
+    /// Raw `LoRa` payload.
     pub payload: Vec<u8>,
 }
 
 impl GossipFrame {
     /// Create a new gossip frame from a public key and radio packet data.
+    #[must_use]
     pub fn new(sender: &iroh::PublicKey, rssi: i16, snr: i16, payload: Vec<u8>) -> Self {
-        Self {
-            sender: *sender.as_bytes(),
-            rssi,
-            snr,
-            payload,
-        }
+        Self { sender: *sender.as_bytes(), rssi, snr, payload }
     }
 
     /// Encode this frame into bytes for gossip broadcast.
+    #[must_use]
     pub fn encode(&self) -> Vec<u8> {
         let mut buf = Vec::with_capacity(FRAME_HEADER_SIZE + self.payload.len());
         buf.extend_from_slice(&self.sender);
         buf.extend_from_slice(&self.rssi.to_le_bytes());
         buf.extend_from_slice(&self.snr.to_le_bytes());
+        #[allow(clippy::cast_possible_truncation)] // LoRa payloads never exceed 256 bytes
         let len = self.payload.len() as u16;
         buf.extend_from_slice(&len.to_le_bytes());
         buf.extend_from_slice(&self.payload);
@@ -96,6 +101,7 @@ impl GossipFrame {
     }
 
     /// Decode a gossip frame from bytes received from the swarm.
+    #[must_use]
     pub fn decode(data: &[u8]) -> Option<Self> {
         if data.len() < FRAME_HEADER_SIZE {
             return None;
@@ -107,21 +113,18 @@ impl GossipFrame {
         if data.len() != FRAME_HEADER_SIZE + payload_len {
             return None;
         }
-        Some(Self {
-            sender,
-            rssi,
-            snr,
-            payload: data[FRAME_HEADER_SIZE..].to_vec(),
-        })
+        Some(Self { sender, rssi, snr, payload: data[FRAME_HEADER_SIZE..].to_vec() })
     }
 }
 
 /// Compute a 32-byte blake3 content hash for deduplication.
+#[must_use]
 pub fn content_hash(payload: &[u8]) -> [u8; 32] {
     *blake3::hash(payload).as_bytes()
 }
 
 #[cfg(test)]
+#[allow(clippy::unwrap_used, clippy::expect_used)]
 mod tests {
     use super::*;
 
@@ -156,6 +159,17 @@ mod tests {
         assert!(GossipFrame::decode(&[0u8; 10]).is_none());
     }
 
+    #[test]
+    fn gossip_frame_decode_empty_payload() {
+        // Exactly FRAME_HEADER_SIZE (38) bytes with payload_len=0 must decode.
+        // Kills mutant: `data.len() < 38` → `data.len() <= 38`.
+        let mut data = vec![0u8; 38];
+        data[36..38].copy_from_slice(&0u16.to_le_bytes()); // payload_len = 0
+        let frame = GossipFrame::decode(&data);
+        assert!(frame.is_some(), "38-byte frame with 0-length payload must decode");
+        assert!(frame.unwrap().payload.is_empty());
+    }
+
     #[test]
     fn gossip_frame_reject_wrong_length() {
         // Header says payload_len=5 but only 3 bytes follow.
@@ -164,6 +178,43 @@ mod tests {
         assert!(GossipFrame::decode(&data).is_none());
     }
 
+    #[test]
+    fn should_forward_true_for_good_and_marginal() {
+        assert!(Grade::Good.should_forward());
+        assert!(Grade::Marginal.should_forward());
+    }
+
+    #[test]
+    fn should_forward_false_for_unreliable_and_invalid() {
+        assert!(!Grade::Unreliable.should_forward());
+        assert!(!Grade::Invalid.should_forward());
+    }
+
+    #[test]
+    fn grade_display() {
+        assert_eq!(format!("{}", Grade::Good), "GOOD");
+        assert_eq!(format!("{}", Grade::Marginal), "MARG");
+        assert_eq!(format!("{}", Grade::Unreliable), "UNRL");
+        assert_eq!(format!("{}", Grade::Invalid), "INVL");
+    }
+
+    #[test]
+    fn snr_grade_exact_boundaries() {
+        // SF12: min_snr = -2.5 * (12 - 4) = -20.0
+        //
+        // At snr=-20, margin = -20 - (-20.0) = 0.0 exactly.
+        // The code uses `margin < 0.0`, so 0.0 is NOT < 0.0 → Marginal (not Unreliable).
+        assert_eq!(snr_grade(-20, 12), Grade::Marginal);
+        // One below: snr=-21, margin = -1.0 → Unreliable.
+        assert_eq!(snr_grade(-21, 12), Grade::Unreliable);
+
+        // At snr=-17, margin = -17 - (-20.0) = 3.0 exactly.
+        // The code uses `margin < 3.0`, so 3.0 is NOT < 3.0 → Good (not Marginal).
+        assert_eq!(snr_grade(-17, 12), Grade::Good);
+        // One below: snr=-18, margin = 2.0 → Marginal.
+        assert_eq!(snr_grade(-18, 12), Grade::Marginal);
+    }
+
     #[test]
     fn content_hash_deterministic() {
         let h1 = content_hash(b"hello");
@@ -172,4 +223,36 @@ mod tests {
         let h3 = content_hash(b"world");
         assert_ne!(h1, h3);
     }
+
+    mod proptests {
+        use super::*;
+        use proptest::prelude::*;
+
+        proptest! {
+            #[test]
+            fn gossip_frame_roundtrip_prop(
+                rssi in -200i16..=200i16,
+                snr in -32i16..=32i16,
+                payload in proptest::collection::vec(any::<u8>(), 0..256),
+            ) {
+                let key = iroh::SecretKey::generate(&mut rand::rng());
+                let frame = GossipFrame::new(&key.public(), rssi, snr, payload.clone());
+                let encoded = frame.encode();
+                let decoded = GossipFrame::decode(&encoded).unwrap();
+                prop_assert_eq!(decoded.rssi, rssi);
+                prop_assert_eq!(decoded.snr, snr);
+                prop_assert_eq!(decoded.payload, payload);
+            }
+
+            #[test]
+            fn content_hash_deterministic_prop(data in proptest::collection::vec(any::<u8>(), 0..1024)) {
+                prop_assert_eq!(content_hash(&data), content_hash(&data));
+            }
+
+            #[test]
+            fn snr_grade_never_panics(snr in i16::MIN..=i16::MAX, sf in 5u8..=12u8) {
+                let _ = snr_grade(snr, sf);
+            }
+        }
+    }
 }

src/radio.rs

@@ -1,6 +1,11 @@
+//! `DongLoRa` hardware communication on a blocking thread.
+//!
+//! Handles connection, config negotiation, RX/TX, liveness pings, and
+//! exponential backoff reconnection.
+
 use std::time::Duration;
 
-use anyhow::Result;
+use anyhow::{Context, Result};
 use donglora_client::{RadioConfig, Response, Transport};
 use tokio::sync::mpsc;
 use tracing::{debug, error, info, warn};
@@ -29,21 +34,19 @@ pub enum RadioEvent {
 /// Spawn the blocking radio thread.
 ///
 /// Returns a receiver for radio events and a sender for TX payloads.
-pub fn spawn(
-    config: RadioConfig,
-    port: Option<String>,
-) -> (mpsc::Receiver<RadioEvent>, mpsc::Sender<Vec<u8>>) {
+pub fn spawn(config: RadioConfig, port: Option<String>) -> Result<(mpsc::Receiver<RadioEvent>, mpsc::Sender<Vec<u8>>)> {
     let (event_tx, event_rx) = mpsc::channel::<RadioEvent>(256);
     let (tx_send, tx_recv) = mpsc::channel::<Vec<u8>>(64);
 
     std::thread::Builder::new()
         .name("radio".into())
         .spawn(move || radio_loop(config, port, event_tx, tx_recv))
-        .ok();
+        .context("failed to spawn radio thread")?;
 
-    (event_rx, tx_send)
+    Ok((event_rx, tx_send))
 }
 
+#[allow(clippy::needless_pass_by_value)] // values moved across thread boundary in spawn()
 fn radio_loop(
     config: RadioConfig,
     port: Option<String>,
@@ -56,7 +59,7 @@ fn radio_loop(
 
     loop {
         let started = std::time::Instant::now();
-        match connect_and_run(&config, &port, &event_tx, &mut tx_recv) {
+        match connect_and_run(&config, port.as_deref(), &event_tx, &mut tx_recv) {
             Ok(()) => {
                 info!("radio thread exiting");
                 return;
@@ -81,16 +84,16 @@ fn radio_loop(
 
 fn connect_and_run(
     config: &RadioConfig,
-    port: &Option<String>,
+    port: Option<&str>,
     event_tx: &mpsc::Sender<RadioEvent>,
     tx_recv: &mut mpsc::Receiver<Vec<u8>>,
 ) -> Result<()> {
     // Long initial timeout: the mux serializes commands through the dongle,
-    // so our GetConfig might have to wait behind other clients' commands.
+    // so our `GetConfig` might have to wait behind other clients' commands.
     let timeout = Duration::from_secs(10);
 
     info!("connecting to dongle...");
-    let (mut client, device) = if let Some(port) = &port {
+    let (mut client, device) = if let Some(port) = port {
         let c = donglora_client::connect(Some(port), timeout)?;
         (c, shorten_path(port))
     } else {
@@ -132,9 +135,7 @@ fn connect_and_run(
     let _ = event_tx.blocking_send(RadioEvent::Connected(active_config, config_source, device));
 
     // Set a short timeout so we can interleave RX and TX.
-    client
-        .transport_mut()
-        .set_timeout(Duration::from_millis(100))?;
+    client.transport_mut().set_timeout(Duration::from_millis(100))?;
     info!("[radio] entering main loop");
 
     // Liveness: ping the mux periodically when idle to detect a dead connection.
@@ -159,19 +160,13 @@ fn connect_and_run(
                 last_activity = std::time::Instant::now();
                 let grade = snr_grade(snr, active_config.sf);
                 if grade.should_forward() {
-                    debug!(
-                        "RX {} bytes rssi={rssi} snr={snr} grade={grade}",
-                        payload.len()
-                    );
+                    debug!("RX {} bytes rssi={rssi} snr={snr} grade={grade}", payload.len());
                     let pkt = RadioPacket { rssi, snr, payload };
                     if event_tx.blocking_send(RadioEvent::Packet(pkt)).is_err() {
                         return Ok(());
                     }
                 } else {
-                    debug!(
-                        "RX drop {} bytes rssi={rssi} snr={snr} grade={grade}",
-                        payload.len()
-                    );
+                    debug!("RX drop {} bytes rssi={rssi} snr={snr} grade={grade}", payload.len());
                 }
             }
             Ok(Some(_)) => {
@@ -208,13 +203,13 @@ fn connect_and_run(
 /// Negotiate radio config with the dongle/mux.
 ///
 /// Strategy:
-/// 1. GetConfig first to read what's active (caches the result).
-/// 2. If it matches our desired config, use it — no SetConfig needed.
-/// 3. If it differs, only try SetConfig if we haven't been rejected before.
-/// 4. If SetConfig is rejected, set the flag IMMEDIATELY (before the mux can
-///    disconnect us and lose this state), then return the cached GetConfig result.
+/// 1. `GetConfig` first to read what's active (caches the result).
+/// 2. If it matches our desired config, use it — no `SetConfig` needed.
+/// 3. If it differs, only try `SetConfig` if we haven't been rejected before.
+/// 4. If `SetConfig` is rejected, set the flag IMMEDIATELY (before the mux can
+///    disconnect us and lose this state), then return the cached `GetConfig` result.
 ///
-/// On reconnect, the flag ensures we never retry SetConfig.
+/// On reconnect, the flag ensures we never retry `SetConfig`.
 fn negotiate_config<T: Transport>(
     client: &mut donglora_client::Client<T>,
     desired: &RadioConfig,
@@ -251,10 +246,7 @@ fn negotiate_config<T: Transport>(
 
 /// Shorten a device path to just the filename for display.
 fn shorten_path(path: &str) -> String {
-    std::path::Path::new(path)
-        .file_name()
-        .map(|f| f.to_string_lossy().into_owned())
-        .unwrap_or_else(|| path.to_string())
+    std::path::Path::new(path).file_name().map_or_else(|| path.to_string(), |f| f.to_string_lossy().into_owned())
 }
 
 fn configs_match(a: &RadioConfig, b: &RadioConfig) -> bool {
@@ -269,18 +261,13 @@ fn configs_match(a: &RadioConfig, b: &RadioConfig) -> bool {
 }
 
 fn is_timeout_error(e: &anyhow::Error) -> bool {
-    if let Some(io_err) = e.downcast_ref::<std::io::Error>() {
-        matches!(
-            io_err.kind(),
-            std::io::ErrorKind::WouldBlock | std::io::ErrorKind::TimedOut
-        )
-    } else {
-        false
-    }
+    e.downcast_ref::<std::io::Error>()
+        .is_some_and(|io_err| matches!(io_err.kind(), std::io::ErrorKind::WouldBlock | std::io::ErrorKind::TimedOut))
 }
 
 /// Format a bandwidth value for display.
-pub fn format_bandwidth(bw: donglora_client::Bandwidth) -> &'static str {
+#[must_use]
+pub const fn format_bandwidth(bw: donglora_client::Bandwidth) -> &'static str {
     match bw {
         donglora_client::Bandwidth::Khz7 => "7.8 kHz",
         donglora_client::Bandwidth::Khz10 => "10.4 kHz",
@@ -295,23 +282,156 @@ pub fn format_bandwidth(bw: donglora_client::Bandwidth) -> &'static str {
     }
 }
 
-/// Format a RadioConfig for display.
+/// Format a `RadioConfig` for display.
+#[must_use]
 pub fn format_radio_config(config: &RadioConfig) -> String {
-    let freq_mhz = config.freq_hz as f64 / 1_000_000.0;
+    let freq_mhz = f64::from(config.freq_hz) / 1_000_000.0;
     let bw = format_bandwidth(config.bw);
     let power = if config.tx_power_dbm == donglora_client::TX_POWER_MAX {
         "max".to_string()
     } else {
         format!("{} dBm", config.tx_power_dbm)
     };
-    let preamble = if config.preamble_len == 0 {
-        16
-    } else {
-        config.preamble_len
-    };
+    let preamble = if config.preamble_len == 0 { 16 } else { config.preamble_len };
     let cad = if config.cad != 0 { "on" } else { "off" };
     format!(
         "{freq_mhz:.3}MHz SF{} BW{bw} CR4/{} SW0x{:04X} TX:{power} Pre:{preamble} CAD:{cad}",
         config.sf, config.cr, config.sync_word
     )
 }
+
+#[cfg(test)]
+#[allow(clippy::unwrap_used, clippy::expect_used)]
+mod tests {
+    use super::*;
+
+    fn default_config() -> RadioConfig {
+        RadioConfig {
+            freq_hz: 910_525_000,
+            bw: donglora_client::Bandwidth::Khz62,
+            sf: 7,
+            cr: 5,
+            sync_word: 0x3444,
+            tx_power_dbm: 22,
+            preamble_len: 16,
+            cad: 1,
+        }
+    }
+
+    #[test]
+    fn configs_match_identical() {
+        let a = default_config();
+        let b = default_config();
+        assert!(configs_match(&a, &b));
+    }
+
+    #[test]
+    fn configs_match_differs_each_field() {
+        let base = default_config();
+
+        let mut c = base;
+        c.freq_hz = 915_000_000;
+        assert!(!configs_match(&base, &c));
+
+        let mut c = base;
+        c.sf = 12;
+        assert!(!configs_match(&base, &c));
+
+        let mut c = base;
+        c.cr = 8;
+        assert!(!configs_match(&base, &c));
+
+        let mut c = base;
+        c.sync_word = 0x1234;
+        assert!(!configs_match(&base, &c));
+
+        let mut c = base;
+        c.tx_power_dbm = 10;
+        assert!(!configs_match(&base, &c));
+
+        let mut c = base;
+        c.preamble_len = 8;
+        assert!(!configs_match(&base, &c));
+
+        let mut c = base;
+        c.cad = 0;
+        assert!(!configs_match(&base, &c));
+    }
+
+    #[test]
+    fn is_timeout_would_block() {
+        let e = anyhow::Error::from(std::io::Error::new(std::io::ErrorKind::WouldBlock, "test"));
+        assert!(is_timeout_error(&e));
+    }
+
+    #[test]
+    fn is_timeout_timed_out() {
+        let e = anyhow::Error::from(std::io::Error::new(std::io::ErrorKind::TimedOut, "test"));
+        assert!(is_timeout_error(&e));
+    }
+
+    #[test]
+    fn is_timeout_false_for_other() {
+        let e = anyhow::Error::from(std::io::Error::new(std::io::ErrorKind::ConnectionReset, "test"));
+        assert!(!is_timeout_error(&e));
+    }
+
+    #[test]
+    fn shorten_path_extracts_filename() {
+        assert_eq!(shorten_path("/dev/ttyACM0"), "ttyACM0");
+        assert_eq!(shorten_path("ttyACM0"), "ttyACM0");
+    }
+
+    #[test]
+    fn format_bandwidth_all_variants() {
+        assert_eq!(format_bandwidth(donglora_client::Bandwidth::Khz7), "7.8 kHz");
+        assert_eq!(format_bandwidth(donglora_client::Bandwidth::Khz125), "125 kHz");
+        assert_eq!(format_bandwidth(donglora_client::Bandwidth::Khz500), "500 kHz");
+    }
+
+    #[test]
+    fn format_radio_config_typical() {
+        let cfg = default_config();
+        let s = format_radio_config(&cfg);
+        assert!(s.contains("910.525MHz"));
+        assert!(s.contains("SF7"));
+        assert!(s.contains("CR4/5"));
+        assert!(s.contains("0x3444"));
+        assert!(s.contains("CAD:on"), "cad=1 should show CAD:on: {s}");
+    }
+
+    #[test]
+    fn format_radio_config_cad_off() {
+        let mut cfg = default_config();
+        cfg.cad = 0;
+        let s = format_radio_config(&cfg);
+        assert!(s.contains("CAD:off"), "cad=0 should show CAD:off: {s}");
+    }
+
+    #[test]
+    fn format_radio_config_max_power() {
+        let mut cfg = default_config();
+        cfg.tx_power_dbm = donglora_client::TX_POWER_MAX;
+        let s = format_radio_config(&cfg);
+        assert!(s.contains("TX:max"));
+        assert!(!s.contains("dBm"), "max power should not contain 'dBm': {s}");
+    }
+
+    #[test]
+    fn format_radio_config_non_max_power() {
+        let mut cfg = default_config();
+        cfg.tx_power_dbm = 22;
+        assert_ne!(cfg.tx_power_dbm, donglora_client::TX_POWER_MAX);
+        let s = format_radio_config(&cfg);
+        assert!(s.contains("22 dBm"), "non-max power should contain '22 dBm': {s}");
+        assert!(!s.contains("max"), "non-max power should not contain 'max': {s}");
+    }
+
+    #[test]
+    fn format_radio_config_zero_preamble() {
+        let mut cfg = default_config();
+        cfg.preamble_len = 0;
+        let s = format_radio_config(&cfg);
+        assert!(s.contains("Pre:16"));
+    }
+}

src/rate_limit.rs

@@ -1,10 +1,15 @@
+//! `LoRa` air-time-aware token bucket rate limiter.
+//!
+//! Calculates transmit rate from the Semtech `LoRa` air time formula and
+//! enforces it with a configurable burst allowance.
+
 use std::time::{Duration, Instant};
 
 use donglora_client::Bandwidth;
 
 /// Token-bucket rate limiter for radio transmissions.
 ///
-/// Calculates a safe transmit rate from the LoRa radio configuration (spreading factor,
+/// Calculates a safe transmit rate from the `LoRa` radio configuration (spreading factor,
 /// bandwidth, coding rate) and enforces it with a token bucket that allows short bursts.
 pub struct RateLimiter {
     tokens: f64,
@@ -13,43 +18,33 @@ pub struct RateLimiter {
     last_refill: Instant,
 }
 
-/// Default burst size (max tokens).
+/// Default burst size (max tokens). Allows short bursts of 3 back-to-back packets
+/// to handle bursty mesh traffic without triggering rate limiting on every packet.
 const DEFAULT_BURST: f64 = 3.0;
 
 /// Reference payload size (bytes) used to estimate air time for rate calculation.
+/// 50 bytes is a representative `MeshCore` packet size (header + small payload).
 const REFERENCE_PAYLOAD_BYTES: usize = 50;
 
-/// Target duty cycle fraction (0.5 = 50%).
+/// Target duty cycle fraction. 50% leaves headroom for other radio traffic sharing
+/// the channel while still forwarding bridge traffic aggressively.
 const TARGET_DUTY_CYCLE: f64 = 0.5;
 
 impl RateLimiter {
     /// Create a rate limiter derived from radio config.
     ///
     /// If `override_pps` is `Some`, use that rate directly instead of calculating.
-    pub fn from_radio_config(
-        sf: u8,
-        bw: Bandwidth,
-        cr: u8,
-        preamble: u16,
-        override_pps: Option<f64>,
-    ) -> Self {
-        let refill_rate = if let Some(pps) = override_pps {
-            pps.max(0.01)
-        } else {
-            let air_time = lora_air_time(REFERENCE_PAYLOAD_BYTES, sf, bw, cr, preamble);
-            let secs = air_time.as_secs_f64();
-            if secs > 0.0 {
-                TARGET_DUTY_CYCLE / secs
-            } else {
-                10.0 // fallback
-            }
-        };
-        Self {
-            tokens: DEFAULT_BURST,
-            max_tokens: DEFAULT_BURST,
-            refill_rate,
-            last_refill: Instant::now(),
-        }
+    #[must_use]
+    pub fn from_radio_config(sf: u8, bw: Bandwidth, cr: u8, preamble: u16, override_pps: Option<f64>) -> Self {
+        let refill_rate = override_pps.map_or_else(
+            || {
+                let air_time = lora_air_time(REFERENCE_PAYLOAD_BYTES, sf, bw, cr, preamble);
+                let secs = air_time.as_secs_f64();
+                if secs > 0.0 { TARGET_DUTY_CYCLE / secs } else { 10.0 }
+            },
+            |pps| pps.max(0.01),
+        );
+        Self { tokens: DEFAULT_BURST, max_tokens: DEFAULT_BURST, refill_rate, last_refill: Instant::now() }
     }
 
     /// Try to consume one token. Returns `true` if the transmission is allowed.
@@ -64,19 +59,20 @@ impl RateLimiter {
     }
 
     /// Current rate in packets per second.
-    pub fn rate_pps(&self) -> f64 {
+    #[must_use]
+    pub const fn rate_pps(&self) -> f64 {
         self.refill_rate
     }
 
     fn refill(&mut self) {
         let now = Instant::now();
         let elapsed = now.duration_since(self.last_refill).as_secs_f64();
-        self.tokens = (self.tokens + elapsed * self.refill_rate).min(self.max_tokens);
+        self.tokens = elapsed.mul_add(self.refill_rate, self.tokens).min(self.max_tokens);
         self.last_refill = now;
     }
 }
 
-/// Estimate LoRa packet air time using the Semtech SX1276 formula.
+/// Estimate `LoRa` packet air time using the Semtech `LoRa` time-on-air formula.
 ///
 /// Parameters:
 /// - `payload_bytes`: payload size in bytes
@@ -84,28 +80,27 @@ impl RateLimiter {
 /// - `bw`: bandwidth
 /// - `cr`: coding rate denominator (5–8, meaning 4/5 to 4/8)
 /// - `preamble`: preamble length in symbols (0 = firmware default of 16)
+#[must_use]
 pub fn lora_air_time(payload_bytes: usize, sf: u8, bw: Bandwidth, cr: u8, preamble: u16) -> Duration {
     let sf_f = f64::from(sf);
     let bw_hz = bandwidth_hz(bw);
     let preamble_symbols = if preamble == 0 { 16.0 } else { f64::from(preamble) };
 
     // Symbol time in seconds.
-    let t_sym = 2.0_f64.powf(sf_f) / bw_hz;
+    let t_sym = sf_f.exp2() / bw_hz;
 
     // Preamble time.
     let t_preamble = (preamble_symbols + 4.25) * t_sym;
 
     // Low data rate optimize: enabled when SF >= 11 and BW <= 125 kHz.
-    let de: f64 = if sf >= 11 && bw_hz <= 125_000.0 {
-        1.0
-    } else {
-        0.0
-    };
+    let de: f64 = if sf >= 11 && bw_hz <= 125_000.0 { 1.0 } else { 0.0 };
 
     // Payload symbol count (Semtech formula with CRC enabled, explicit header).
-    let numerator = 8.0 * payload_bytes as f64 - 4.0 * sf_f + 28.0 + 16.0;
-    let denominator = 4.0 * (sf_f - 2.0 * de);
-    let n_payload = 8.0 + (numerator / denominator).ceil().max(0.0) * f64::from(cr);
+    #[allow(clippy::cast_precision_loss)] // payload_bytes is always < 256
+    let payload_f = payload_bytes as f64;
+    let numerator = 8.0f64.mul_add(payload_f, (-4.0f64).mul_add(sf_f, 44.0));
+    let denominator = 4.0f64.mul_add(sf_f, -8.0 * de);
+    let n_payload = (numerator / denominator).ceil().max(0.0).mul_add(f64::from(cr), 8.0);
 
     let t_payload = n_payload * t_sym;
     let total = t_preamble + t_payload;
@@ -113,7 +108,7 @@ pub fn lora_air_time(payload_bytes: usize, sf: u8, bw: Bandwidth, cr: u8, preamb
     Duration::from_secs_f64(total)
 }
 
-fn bandwidth_hz(bw: Bandwidth) -> f64 {
+const fn bandwidth_hz(bw: Bandwidth) -> f64 {
     match bw {
         Bandwidth::Khz7 => 7_800.0,
         Bandwidth::Khz10 => 10_400.0,
@@ -171,4 +166,178 @@ mod tests {
         let t_explicit = lora_air_time(50, 7, Bandwidth::Khz125, 5, 16);
         assert_eq!(t_default, t_explicit);
     }
+
+    // ── Mutant-killing tests for from_radio_config (items 1-5) ────────
+
+    #[test]
+    fn from_radio_config_calculates_reasonable_rate() {
+        // SF7/BW125/CR5/preamble16 with 50-byte reference payload:
+        // air time ~105.7ms, so rate = 0.5 / 0.1057 ~= 4.73 pps.
+        let rl = RateLimiter::from_radio_config(7, Bandwidth::Khz125, 5, 16, None);
+        let rate = rl.rate_pps();
+        // Must be between 0.1 and 100 (rules out fallback of 10.0 indirectly,
+        // and catches if secs<=0 path is taken or division is wrong).
+        assert!(rate > 0.1, "rate too low: {rate}");
+        assert!(rate < 100.0, "rate too high: {rate}");
+        // Specifically verify it is NOT the 10.0 fallback, proving secs > 0.0 was true.
+        assert!((rate - 10.0).abs() > 0.5, "rate should not be the 10.0 fallback: {rate}");
+        // Tight check around the expected ~4.73 pps.
+        assert!(rate > 4.0, "rate should be near 4.73: {rate}");
+        assert!(rate < 5.5, "rate should be near 4.73: {rate}");
+    }
+
+    #[test]
+    fn from_radio_config_sf12_rate_much_slower() {
+        // SF12/BW125: air time ~2564ms, rate = 0.5 / 2.564 ~= 0.195 pps.
+        let rl = RateLimiter::from_radio_config(12, Bandwidth::Khz125, 5, 16, None);
+        let rate = rl.rate_pps();
+        assert!(rate > 0.1, "rate too low: {rate}");
+        assert!(rate < 0.5, "rate too high: {rate}");
+        // Definitely not 10.0 fallback.
+        assert!((rate - 10.0).abs() > 1.0, "rate should not be the fallback: {rate}");
+    }
+
+    // ── Mutant-killing tests for refill (item 6) ───────────────────
+
+    #[test]
+    fn rate_limiter_refills_after_waiting() {
+        // Use override_pps for predictable timing: 10 pps = 1 token per 100ms.
+        let mut rl = RateLimiter::from_radio_config(7, Bandwidth::Khz125, 5, 16, Some(10.0));
+        // Exhaust all burst tokens.
+        assert!(rl.try_acquire());
+        assert!(rl.try_acquire());
+        assert!(rl.try_acquire());
+        assert!(!rl.try_acquire(), "burst should be exhausted");
+
+        // Sleep enough for at least 1 token to refill (10 pps -> 100ms per token).
+        std::thread::sleep(Duration::from_millis(200));
+
+        // After sleeping, refill should have added tokens, so acquire succeeds.
+        assert!(rl.try_acquire(), "should succeed after refill");
+    }
+
+    // ── Mutant-killing tests for lora_air_time (items 7-14) ────────
+
+    #[test]
+    fn air_time_exact_sf7_bw125() {
+        // SF7, BW125kHz, CR4/5, preamble=16, payload=50 bytes.
+        // Expected: 105.728 ms (computed from Semtech formula).
+        let t = lora_air_time(50, 7, Bandwidth::Khz125, 5, 16);
+        let ms = t.as_secs_f64() * 1000.0;
+        assert!((ms - 105.728).abs() < 0.01, "SF7/BW125 air time should be ~105.728ms, got {ms:.3}ms");
+    }
+
+    #[test]
+    fn air_time_exact_sf12_bw125() {
+        // SF12, BW125kHz, CR4/5, preamble=16, payload=50 bytes.
+        // Expected: 2564.096 ms.
+        let t = lora_air_time(50, 12, Bandwidth::Khz125, 5, 16);
+        let ms = t.as_secs_f64() * 1000.0;
+        assert!((ms - 2564.096).abs() < 0.01, "SF12/BW125 air time should be ~2564.096ms, got {ms:.3}ms");
+    }
+
+    #[test]
+    fn air_time_ldro_sf11_bw125_vs_sf10_bw125() {
+        // SF>=11 && BW<=125kHz triggers LDRO. SF10 does not.
+        // SF11/BW125: 1445.888 ms (de=1), SF10/BW125: 681.984 ms (de=0).
+        let t11 = lora_air_time(50, 11, Bandwidth::Khz125, 5, 16);
+        let t10 = lora_air_time(50, 10, Bandwidth::Khz125, 5, 16);
+
+        let ms11 = t11.as_secs_f64() * 1000.0;
+        let ms10 = t10.as_secs_f64() * 1000.0;
+
+        // Verify exact values.
+        assert!((ms11 - 1445.888).abs() < 0.01, "SF11/BW125 should be ~1445.888ms, got {ms11:.3}ms");
+        assert!((ms10 - 681.984).abs() < 0.01, "SF10/BW125 should be ~681.984ms, got {ms10:.3}ms");
+
+        // SF11 must be more than double SF10 due to LDRO + SF increase.
+        // (Kills mutant: replace >= with < in sf >= 11 check.)
+        assert!(t11 > t10 * 2, "SF11 with LDRO should be >2x SF10");
+    }
+
+    #[test]
+    fn air_time_ldro_not_triggered_high_bw() {
+        // SF11/BW250: LDRO should NOT be active (BW > 125kHz).
+        // Expected: 641.024 ms (de=0).
+        let t11_250 = lora_air_time(50, 11, Bandwidth::Khz250, 5, 16);
+        let ms = t11_250.as_secs_f64() * 1000.0;
+        assert!((ms - 641.024).abs() < 0.01, "SF11/BW250 should be ~641.024ms (no LDRO), got {ms:.3}ms");
+
+        // Compare with SF11/BW125 which HAS LDRO.
+        let t11_125 = lora_air_time(50, 11, Bandwidth::Khz125, 5, 16);
+        // Even accounting for halved BW doubling the base time, the LDRO effect
+        // on SF11/BW125 makes it much longer than simply 2x SF11/BW250.
+        assert!(t11_125 > t11_250 * 2, "SF11/BW125 (LDRO on) should be >2x SF11/BW250 (LDRO off)");
+    }
+
+    #[test]
+    fn air_time_preamble_scaling() {
+        // Changing preamble by N symbols changes air time by N * t_sym.
+        // t_sym for SF7/BW125 = 2^7 / 125000 = 1.024 ms.
+        let t8 = lora_air_time(50, 7, Bandwidth::Khz125, 5, 8);
+        let t16 = lora_air_time(50, 7, Bandwidth::Khz125, 5, 16);
+        let t32 = lora_air_time(50, 7, Bandwidth::Khz125, 5, 32);
+
+        let diff_8_to_16 = t16.as_secs_f64() - t8.as_secs_f64();
+        let diff_16_to_32 = t32.as_secs_f64() - t16.as_secs_f64();
+
+        let t_sym = 128.0 / 125_000.0; // 1.024 ms
+
+        // 8 -> 16: 8 symbols difference.
+        let expected_8 = 8.0f64.mul_add(t_sym, -diff_8_to_16).abs();
+        assert!(expected_8 < 1e-9, "preamble 8->16 should add 8*t_sym, got {diff_8_to_16:.6}s");
+
+        // 16 -> 32: 16 symbols difference.
+        let expected_16 = 16.0f64.mul_add(t_sym, -diff_16_to_32).abs();
+        assert!(expected_16 < 1e-9, "preamble 16->32 should add 16*t_sym, got {diff_16_to_32:.6}s");
+    }
+
+    #[test]
+    fn air_time_sensible_range_all_sf_bw() {
+        // Verify reasonable bounds for all SF/BW combos with 50-byte payload.
+        // This catches gross formula errors (e.g. division replaced with modulo).
+        let bandwidths = [
+            Bandwidth::Khz7,
+            Bandwidth::Khz10,
+            Bandwidth::Khz15,
+            Bandwidth::Khz20,
+            Bandwidth::Khz31,
+            Bandwidth::Khz41,
+            Bandwidth::Khz62,
+            Bandwidth::Khz125,
+            Bandwidth::Khz250,
+            Bandwidth::Khz500,
+        ];
+        for sf in 7..=12u8 {
+            for &bw in &bandwidths {
+                let t = lora_air_time(50, sf, bw, 5, 16);
+                let ms = t.as_secs_f64() * 1000.0;
+                // Fastest: SF7/BW500 ~26ms. Slowest: SF12/BW7.8kHz ~many seconds.
+                // All should be > 1ms and < 300s.
+                assert!(ms > 1.0, "SF{sf}/BW{bw:?}: air time too short: {ms:.3}ms");
+                assert!(ms < 300_000.0, "SF{sf}/BW{bw:?}: air time too long: {ms:.3}ms");
+            }
+        }
+    }
+
+    mod proptests {
+        use super::*;
+        use proptest::prelude::*;
+
+        proptest! {
+            #[test]
+            fn air_time_always_positive(
+                payload in 0usize..256,
+                sf in 7u8..=12u8,
+                cr in 5u8..=8u8,
+                preamble in 0u16..=64u16,
+            ) {
+                for bw in [Bandwidth::Khz7, Bandwidth::Khz62, Bandwidth::Khz125, Bandwidth::Khz500] {
+                    let t = lora_air_time(payload, sf, bw, cr, preamble);
+                    prop_assert!(t > Duration::ZERO, "air time must be positive");
+                    prop_assert!(t < Duration::from_secs(600), "air time should be < 600s");
+                }
+            }
+        }
+    }
 }

src/router.rs

@@ -1,3 +1,8 @@
+//! Central packet bus bridging radio and gossip swarm.
+//!
+//! Applies blake3 content-hash deduplication, token bucket rate limiting,
+//! and TX queue management.
+
 use std::collections::{HashMap, VecDeque};
 use std::sync::atomic::{AtomicU64, Ordering};
 use std::time::{Duration, Instant};
@@ -81,6 +86,7 @@ pub struct Stats {
 }
 
 impl Stats {
+    #[must_use]
     pub fn snapshot(&self) -> StatsSnapshot {
         StatsSnapshot {
             radio_rx: self.radio_rx.load(Ordering::Relaxed),
@@ -96,6 +102,7 @@ impl Stats {
     }
 }
 
+/// Point-in-time snapshot of bridge statistics, cloned from atomic counters.
 #[derive(Debug, Clone)]
 pub struct StatsSnapshot {
     pub radio_rx: u64,
@@ -117,10 +124,7 @@ struct DedupCache {
 
 impl DedupCache {
     fn new(ttl: Duration) -> Self {
-        Self {
-            entries: HashMap::new(),
-            ttl,
-        }
+        Self { entries: HashMap::new(), ttl }
     }
 
     /// Returns true if the key was already present (i.e., duplicate).
@@ -144,7 +148,7 @@ impl DedupCache {
 /// Run the router — the central packet bus.
 ///
 /// Bridges radio packets to/from the gossip swarm with deduplication and rate limiting.
-#[allow(clippy::too_many_arguments)]
+#[allow(clippy::too_many_arguments, clippy::too_many_lines)]
 pub async fn run(
     our_id: PublicKey,
     dedup_window: Duration,
@@ -294,6 +298,7 @@ pub async fn run(
                         }).await;
                     }
                     GossipEvent::NeighborChanged(count) => {
+                        #[allow(clippy::cast_possible_truncation)]
                         stats.neighbor_count.store(count as u64, Ordering::Relaxed);
                     }
                 }
@@ -309,3 +314,111 @@ pub async fn run(
         }
     }
 }
+
+#[cfg(test)]
+#[allow(clippy::unwrap_used, clippy::expect_used)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn dedup_cache_new_key_not_duplicate() {
+        let mut cache = DedupCache::new(Duration::from_secs(10));
+        assert!(!cache.check_and_insert([0u8; 32]));
+    }
+
+    #[test]
+    fn dedup_cache_duplicate_detected() {
+        let mut cache = DedupCache::new(Duration::from_secs(10));
+        cache.check_and_insert([1u8; 32]);
+        assert!(cache.check_and_insert([1u8; 32]));
+    }
+
+    #[test]
+    fn dedup_cache_different_keys_independent() {
+        let mut cache = DedupCache::new(Duration::from_secs(10));
+        cache.check_and_insert([1u8; 32]);
+        assert!(!cache.check_and_insert([2u8; 32]));
+    }
+
+    #[test]
+    fn dedup_cache_expired_entry_not_duplicate() {
+        let mut cache = DedupCache::new(Duration::from_millis(1));
+        cache.check_and_insert([1u8; 32]);
+        std::thread::sleep(Duration::from_millis(5));
+        assert!(!cache.check_and_insert([1u8; 32]));
+    }
+
+    #[test]
+    fn dedup_cache_prune_removes_expired() {
+        let mut cache = DedupCache::new(Duration::from_millis(1));
+        cache.check_and_insert([1u8; 32]);
+        cache.check_and_insert([2u8; 32]);
+        std::thread::sleep(Duration::from_millis(5));
+        cache.prune();
+        assert!(cache.entries.is_empty());
+    }
+
+    #[test]
+    fn dedup_cache_prune_keeps_fresh() {
+        let mut cache = DedupCache::new(Duration::from_secs(10));
+        cache.check_and_insert([1u8; 32]);
+        cache.prune();
+        assert_eq!(cache.entries.len(), 1);
+    }
+
+    #[test]
+    fn stats_snapshot_reflects_increments() {
+        let stats = Stats::default();
+        stats.radio_rx.fetch_add(5, Ordering::Relaxed);
+        stats.gossip_tx.fetch_add(3, Ordering::Relaxed);
+        stats.radio_connected.store(1, Ordering::Relaxed);
+        let snap = stats.snapshot();
+        assert_eq!(snap.radio_rx, 5);
+        assert_eq!(snap.gossip_tx, 3);
+        assert!(snap.radio_connected);
+    }
+
+    #[test]
+    fn stats_default_is_zeroed() {
+        let snap = Stats::default().snapshot();
+        assert_eq!(snap.radio_rx, 0);
+        assert_eq!(snap.gossip_rx, 0);
+        assert!(!snap.radio_connected);
+    }
+
+    #[test]
+    fn packet_action_display() {
+        assert_eq!(format!("{}", PacketAction::Bridged), "");
+        assert_eq!(format!("{}", PacketAction::DroppedDedup), "DUP");
+        assert_eq!(format!("{}", PacketAction::DroppedQueueFull), "FULL");
+        assert_eq!(format!("{}", PacketAction::DroppedRateLimit), "RATE");
+    }
+
+    #[test]
+    fn dedup_cache_ttl_boundary_check_and_insert() {
+        // Force an entry's timestamp to be exactly TTL ago. With `< ttl`, the entry
+        // at exactly TTL is NOT a duplicate. With `<= ttl` (the mutant), it would
+        // wrongly be treated as still live.
+        let ttl = Duration::from_secs(10);
+        let mut cache = DedupCache::new(ttl);
+        cache.check_and_insert([9u8; 32]);
+        // Backdate the entry to exactly TTL ago.
+        let exactly_ttl_ago = Instant::now().checked_sub(ttl).unwrap();
+        cache.entries.insert([9u8; 32], exactly_ttl_ago);
+        // duration_since(exactly_ttl_ago) == ttl, so `< ttl` is false → not duplicate.
+        // The mutant `<= ttl` would say true → duplicate. This catches it.
+        assert!(!cache.check_and_insert([9u8; 32]), "entry at exact TTL must be treated as expired");
+    }
+
+    #[test]
+    fn dedup_cache_ttl_boundary_prune() {
+        let ttl = Duration::from_secs(10);
+        let mut cache = DedupCache::new(ttl);
+        cache.check_and_insert([8u8; 32]);
+        // Backdate to exactly TTL ago.
+        let exactly_ttl_ago = Instant::now().checked_sub(ttl).unwrap();
+        cache.entries.insert([8u8; 32], exactly_ttl_ago);
+        cache.prune();
+        assert!(cache.entries.is_empty(), "entry at exact TTL must be pruned");
+    }
+}

src/setup.rs

@@ -17,10 +17,8 @@ const RESET: &str = "\x1b[0m";
 
 /// Run the interactive setup wizard. If `existing` is Some, use those values as defaults.
 pub fn run_wizard(config_path: &Path, existing: Option<&Config>) -> Result<()> {
-    let defaults = existing.map_or_else(
-        || (RadioSection::default(), BridgeSection::default()),
-        |c| (c.radio.clone(), c.bridge.clone()),
-    );
+    let defaults = existing
+        .map_or_else(|| (RadioSection::default(), BridgeSection::default()), |c| (c.radio.clone(), c.bridge.clone()));
     let (radio, bridge) = defaults;
 
     println!();
@@ -43,8 +41,9 @@ pub fn run_wizard(config_path: &Path, existing: Option<&Config>) -> Result<()> {
 
     // ── Radio ────────────────────────────────────────────────────
 
-    let freq_default = format!("{:.3}", radio.frequency as f64 / 1_000_000.0);
+    let freq_default = format!("{:.3}", f64::from(radio.frequency) / 1_000_000.0);
     let freq_mhz: f64 = prompt_parse("Frequency (MHz)", &freq_default)?;
+    #[allow(clippy::cast_possible_truncation, clippy::cast_sign_loss)] // validated by prompt_parse
     let frequency = (freq_mhz * 1_000_000.0) as u32;
 
     let bandwidth = prompt_default("Bandwidth", &radio.bandwidth)?;
@@ -70,11 +69,7 @@ pub fn run_wizard(config_path: &Path, existing: Option<&Config>) -> Result<()> {
 
     let port_default = radio.port.as_deref().unwrap_or("auto");
     let port_str = prompt_default("Serial Port", port_default)?;
-    let port = if port_str == "auto" || port_str.is_empty() {
-        None
-    } else {
-        Some(port_str)
-    };
+    let port = if port_str == "auto" || port_str.is_empty() { None } else { Some(port_str) };
 
     // ── Build and save ───────────────────────────────────────────
 
@@ -111,12 +106,10 @@ pub fn run_wizard(config_path: &Path, existing: Option<&Config>) -> Result<()> {
 
 fn write_config(path: &Path, cfg: &Config) -> Result<()> {
     if let Some(parent) = path.parent() {
-        std::fs::create_dir_all(parent)
-            .with_context(|| format!("creating directory: {}", parent.display()))?;
+        std::fs::create_dir_all(parent).with_context(|| format!("creating directory: {}", parent.display()))?;
     }
     let content = toml::to_string_pretty(cfg).context("serializing config")?;
-    std::fs::write(path, content)
-        .with_context(|| format!("writing config: {}", path.display()))?;
+    std::fs::write(path, content).with_context(|| format!("writing config: {}", path.display()))?;
     Ok(())
 }
 
@@ -128,20 +121,12 @@ fn prompt_default(label: &str, default: &str) -> Result<String> {
     let mut input = String::new();
     io::stdin().read_line(&mut input)?;
     let trimmed = input.trim();
-    if trimmed.is_empty() {
-        Ok(default.to_string())
-    } else {
-        Ok(trimmed.to_string())
-    }
+    if trimmed.is_empty() { Ok(default.to_string()) } else { Ok(trimmed.to_string()) }
 }
 
 fn prompt_required(label: &str, default: Option<&str>) -> Result<String> {
     loop {
-        let prompt = if let Some(d) = default {
-            format!("  {label} {DIM}[{d}]{RESET}: ")
-        } else {
-            format!("  {label}: ")
-        };
+        let prompt = default.map_or_else(|| format!("  {label}: "), |d| format!("  {label} {DIM}[{d}]{RESET}: "));
         print!("{prompt}");
         io::stdout().flush()?;
         let mut input = String::new();
@@ -175,3 +160,35 @@ fn parse_sync_word(s: &str) -> Result<u16> {
     let s = s.strip_prefix("0x").unwrap_or(&s);
     u16::from_str_radix(s, 16).with_context(|| format!("invalid sync word: {s}"))
 }
+
+#[cfg(test)]
+#[allow(clippy::unwrap_used, clippy::expect_used)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn parse_sync_word_hex_prefix() {
+        assert_eq!(parse_sync_word("0x3444").unwrap(), 0x3444);
+    }
+
+    #[test]
+    fn parse_sync_word_no_prefix() {
+        assert_eq!(parse_sync_word("3444").unwrap(), 0x3444);
+    }
+
+    #[test]
+    fn parse_sync_word_case_insensitive() {
+        assert_eq!(parse_sync_word("0xABCD").unwrap(), 0xABCD);
+    }
+
+    #[test]
+    fn parse_sync_word_whitespace() {
+        assert_eq!(parse_sync_word("  0x3444  ").unwrap(), 0x3444);
+    }
+
+    #[test]
+    fn parse_sync_word_invalid() {
+        assert!(parse_sync_word("ZZZZ").is_err());
+        assert!(parse_sync_word("").is_err());
+    }
+}

src/tui.rs

@@ -1,19 +1,23 @@
+//! Ratatui terminal user interface.
+//!
+//! Displays network status, radio configuration, aggregate statistics,
+//! a scrolling packet log, and real-time activity sparklines.
+
+use std::collections::VecDeque;
 use std::io::{self, Stdout};
 use std::sync::Arc;
 use std::time::{Duration, Instant};
 
-use crossterm::event::{self, Event, KeyCode, KeyEventKind};
-use crossterm::terminal::{
-    EnterAlternateScreen, LeaveAlternateScreen, disable_raw_mode, enable_raw_mode,
-};
 use crossterm::ExecutableCommand;
+use crossterm::event::{self, Event, KeyCode, KeyEventKind};
+use crossterm::terminal::{EnterAlternateScreen, LeaveAlternateScreen, disable_raw_mode, enable_raw_mode};
+use ratatui::Terminal;
 use ratatui::backend::CrosstermBackend;
 use ratatui::layout::{Alignment, Constraint, Direction, Layout, Rect};
 use ratatui::style::{Color, Modifier, Style};
 use ratatui::symbols;
 use ratatui::text::{Line, Span};
 use ratatui::widgets::{Block, Borders, Clear, Paragraph, Sparkline};
-use ratatui::Terminal;
 use tokio::sync::mpsc;
 use tokio_util::sync::CancellationToken;
 
@@ -53,7 +57,7 @@ struct Bucket {
 }
 
 struct TimeSeries {
-    buckets: Vec<Bucket>,
+    buckets: VecDeque<Bucket>,
     last_snap: StatsSnapshot,
     last_bucket_time: Instant,
 }
@@ -61,7 +65,7 @@ struct TimeSeries {
 impl TimeSeries {
     fn new(snap: &StatsSnapshot) -> Self {
         Self {
-            buckets: vec![Bucket::default(); MAX_BUCKETS],
+            buckets: VecDeque::from(vec![Bucket::default(); MAX_BUCKETS]),
             last_snap: snap.clone(),
             last_bucket_time: Instant::now(),
         }
@@ -78,9 +82,9 @@ impl TimeSeries {
                 snr_sum,
                 snr_count,
             };
-            self.buckets.push(bucket);
+            self.buckets.push_back(bucket);
             if self.buckets.len() > MAX_BUCKETS {
-                self.buckets.remove(0);
+                self.buckets.pop_front();
             }
             self.last_snap = snap.clone();
             self.last_bucket_time = now;
@@ -98,8 +102,8 @@ impl TimeSeries {
             .iter()
             .map(|b| {
                 if b.snr_count > 0 {
-                    let avg = b.snr_sum / b.snr_count as i64;
-                    (avg + 30).max(0) as u64
+                    let avg = b.snr_sum / b.snr_count.cast_signed();
+                    (avg + 30).max(0).cast_unsigned()
                 } else {
                     0
                 }
@@ -114,7 +118,7 @@ impl TimeSeries {
         self.buckets.iter().map(|b| b.radio_tx).max().unwrap_or(0)
     }
     fn latest_avg_snr(&self) -> Option<i64> {
-        self.buckets.iter().rev().find(|b| b.snr_count > 0).map(|b| b.snr_sum / b.snr_count as i64)
+        self.buckets.iter().rev().find(|b| b.snr_count > 0).map(|b| b.snr_sum / b.snr_count.cast_signed())
     }
 }
 
@@ -137,7 +141,9 @@ fn snr_stats_since(entries: &[PacketLogEntry], since: Instant) -> (i64, u64) {
 
 type Term = Terminal<CrosstermBackend<Stdout>>;
 
-pub async fn run(
+/// Start the terminal UI event loop. Returns the terminal handle for cleanup on exit.
+#[allow(clippy::needless_pass_by_value)] // Arc/CancellationToken are cheaply cloned and owned by this scope
+pub fn run(
     config_watch: tokio::sync::watch::Receiver<RadioConfigInfo>,
     gossip: Arc<Gossip>,
     stats: Arc<Stats>,
@@ -150,26 +156,34 @@ pub async fn run(
     let backend = CrosstermBackend::new(io::stdout());
     let mut terminal = Terminal::new(backend)?;
 
-    let mut log_entries: Vec<PacketLogEntry> = Vec::with_capacity(MAX_LOG_ENTRIES);
+    let mut log_entries: VecDeque<PacketLogEntry> = VecDeque::with_capacity(MAX_LOG_ENTRIES);
     let mut series = TimeSeries::new(&stats.snapshot());
 
     let _result = tui_loop(
-        &mut terminal, config_watch, &gossip, &stats,
-        &mut log_rx, &cancel, start_time, &mut log_entries, &mut series,
-    ).await;
+        &mut terminal,
+        config_watch,
+        &gossip,
+        &stats,
+        &mut log_rx,
+        &cancel,
+        start_time,
+        &mut log_entries,
+        &mut series,
+    );
 
     terminal.draw(|frame| draw_shutdown_overlay(frame, frame.area()))?;
     Ok(terminal)
 }
 
+/// Restore the terminal to its normal state (disable raw mode, leave alternate screen).
 pub fn restore_terminal(terminal: &mut Term) {
     let _ = disable_raw_mode();
     let _ = io::stdout().execute(LeaveAlternateScreen);
     let _ = terminal.show_cursor();
 }
 
-#[allow(clippy::too_many_arguments)]
-async fn tui_loop(
+#[allow(clippy::too_many_arguments, clippy::needless_pass_by_value)]
+fn tui_loop(
     terminal: &mut Term,
     config_watch: tokio::sync::watch::Receiver<RadioConfigInfo>,
     gossip: &Gossip,
@@ -177,26 +191,27 @@ async fn tui_loop(
     log_rx: &mut mpsc::Receiver<PacketLogEntry>,
     cancel: &CancellationToken,
     start_time: Instant,
-    log_entries: &mut Vec<PacketLogEntry>,
+    log_entries: &mut VecDeque<PacketLogEntry>,
     series: &mut TimeSeries,
 ) -> anyhow::Result<()> {
     let mut last_tick = Instant::now();
     loop {
         while let Ok(entry) = log_rx.try_recv() {
             if log_entries.len() >= MAX_LOG_ENTRIES {
-                log_entries.remove(0);
+                log_entries.pop_front();
             }
-            log_entries.push(entry);
+            log_entries.push_back(entry);
         }
         if cancel.is_cancelled() {
             return Ok(());
         }
         let snap = stats.snapshot();
-        series.update(&snap, log_entries);
+        let log_slice = log_entries.make_contiguous();
+        series.update(&snap, log_slice);
         let swarm_state = gossip.swarm_state();
         let config_info = config_watch.borrow().clone();
         terminal.draw(|frame| {
-            draw_ui(frame, frame.area(), &config_info, &snap, &swarm_state, log_entries, start_time, series);
+            draw_ui(frame, frame.area(), &config_info, &snap, &swarm_state, log_slice, start_time, series);
         })?;
         let timeout = TICK_RATE.checked_sub(last_tick.elapsed()).unwrap_or(Duration::ZERO);
         if event::poll(timeout)?
@@ -204,8 +219,7 @@ async fn tui_loop(
             && key.kind == KeyEventKind::Press
             && matches!(
                 (key.code, key.modifiers),
-                (KeyCode::Char('q'), _)
-                    | (KeyCode::Char('c'), crossterm::event::KeyModifiers::CONTROL)
+                (KeyCode::Char('q'), _) | (KeyCode::Char('c'), crossterm::event::KeyModifiers::CONTROL)
             )
         {
             cancel.cancel();
@@ -230,6 +244,16 @@ fn draw_ui(
     start_time: Instant,
     series: &TimeSeries,
 ) {
+    // Minimum terminal size for the 3-column layout.
+    if area.width < 86 || area.height < 12 {
+        let msg = format!("Terminal too small ({}x{}), need 86x12+", area.width, area.height);
+        frame.render_widget(
+            Paragraph::new(msg).alignment(Alignment::Center).style(Style::default().fg(C_RATE_DROP)),
+            area,
+        );
+        return;
+    }
+
     // Header row + body.
     let rows = Layout::default()
         .direction(Direction::Vertical)
@@ -248,11 +272,7 @@ fn draw_ui(
     // Left column: Network, Radio, Stats stacked.
     let left = Layout::default()
         .direction(Direction::Vertical)
-        .constraints([
-            Constraint::Length(6),
-            Constraint::Length(12),
-            Constraint::Min(5),
-        ])
+        .constraints([Constraint::Length(6), Constraint::Length(12), Constraint::Min(5)])
         .split(cols[0]);
 
     draw_network(frame, left[0], swarm_state);
@@ -269,7 +289,7 @@ fn draw_header(frame: &mut ratatui::Frame, area: Rect, stats: &StatsSnapshot) {
         .direction(Direction::Horizontal)
         .constraints([
             Constraint::Length(14), // pills
-            Constraint::Min(0),    // fill
+            Constraint::Min(0),     // fill
         ])
         .split(area);
 
@@ -283,19 +303,12 @@ fn draw_header(frame: &mut ratatui::Frame, area: Rect, stats: &StatsSnapshot) {
     frame.render_widget(Paragraph::new(pills), cols[0]);
 
     // Right: clock with timezone.
-    let clock = Line::from(Span::styled(
-        format!("{} ", chrono_time()),
-        Style::default().fg(C_LABEL),
-    ));
+    let clock = Line::from(Span::styled(format!("{} ", chrono_time()), Style::default().fg(C_LABEL)));
     frame.render_widget(Paragraph::new(clock).alignment(Alignment::Right), cols[1]);
 }
 
 fn status_pill(label: &str, ok: bool) -> Span<'static> {
-    let (fg, bg) = if ok {
-        (Color::Black, Color::Green)
-    } else {
-        (Color::White, C_LABEL)
-    };
+    let (fg, bg) = if ok { (Color::Black, Color::Green) } else { (Color::White, C_LABEL) };
     Span::styled(format!(" {label} "), Style::default().fg(fg).bg(bg))
 }
 
@@ -310,10 +323,7 @@ fn draw_network(frame: &mut ratatui::Frame, area: Rect, state: &crate::gossip::S
         crate::gossip::DhtStatus::PublishFailed => C_QUEUE_DROP,
     };
     let neighbor_color = if state.neighbor_count > 0 { Color::Green } else { C_RATE_DROP };
-    let last_pub = state
-        .last_dht_publish
-        .map(|t| format!("{}s ago", t.elapsed().as_secs()))
-        .unwrap_or_else(|| "-".into());
+    let last_pub = state.last_dht_publish.map_or_else(|| "-".into(), |t| format!("{}s ago", t.elapsed().as_secs()));
 
     let lines = vec![
         kv_line("ID", &state.topic_hash, C_ACCENT),
@@ -347,17 +357,14 @@ fn draw_radio(frame: &mut ratatui::Frame, area: Rect, config_info: &RadioConfigI
     };
 
     let block = Block::default()
-        .title(Span::styled(
-            title,
-            Style::default().fg(C_TITLE).add_modifier(Modifier::BOLD),
-        ))
+        .title(Span::styled(title, Style::default().fg(C_TITLE).add_modifier(Modifier::BOLD)))
         .borders(Borders::ALL)
         .border_style(Style::default().fg(border_color));
 
     let a = &config_info.active;
     let r = &config_info.requested;
 
-    let freq_mhz = a.freq_hz as f64 / 1_000_000.0;
+    let freq_mhz = f64::from(a.freq_hz) / 1_000_000.0;
     let bw_str = crate::radio::format_bandwidth(a.bw);
     let power_str = if a.tx_power_dbm == donglora_client::TX_POWER_MAX {
         "max".to_string()
@@ -429,6 +436,7 @@ fn draw_stats(frame: &mut ratatui::Frame, area: Rect, stats: &StatsSnapshot, sta
 
 // ── Packet log ───────────────────────────────────────────────────
 
+#[allow(clippy::option_if_let_else)] // match is more readable for RSSI/SNR formatting
 fn draw_log(frame: &mut ratatui::Frame, area: Rect, entries: &[PacketLogEntry]) {
     let block = panel_block(" Packet Log ");
 
@@ -472,18 +480,10 @@ fn draw_log(frame: &mut ratatui::Frame, area: Rect, entries: &[PacketLogEntry])
         let (rf_col, net_col) = match e.direction {
             PacketDirection::RadioIn => (
                 Span::styled(format!("{:>4}", "RX"), Style::default().fg(C_RADIO_RX)),
-                if bridged {
-                    Span::styled(format!("{:>4}", "TX"), Style::default().fg(C_NET_TX))
-                } else {
-                    dash
-                },
+                if bridged { Span::styled(format!("{:>4}", "TX"), Style::default().fg(C_NET_TX)) } else { dash },
             ),
             PacketDirection::GossipIn => (
-                if bridged {
-                    Span::styled(format!("{:>4}", "TX"), Style::default().fg(C_RADIO_TX))
-                } else {
-                    dash
-                },
+                if bridged { Span::styled(format!("{:>4}", "TX"), Style::default().fg(C_RADIO_TX)) } else { dash },
                 Span::styled(format!("{:>4}", "RX"), Style::default().fg(C_NET_RX)),
             ),
         };
@@ -510,15 +510,15 @@ fn draw_log(frame: &mut ratatui::Frame, area: Rect, entries: &[PacketLogEntry])
             PacketAction::DroppedQueueFull => "FULL",
             PacketAction::DroppedRateLimit => "RATE",
         };
-        let action_span = Span::styled(format!(" {:>4}", action_str), Style::default().fg(action_color));
+        let action_span = Span::styled(format!(" {action_str:>4}"), Style::default().fg(action_color));
 
         let size_str = format!("{}B", e.size);
         lines.push(Line::from(vec![
-            Span::styled(format!("{:>5}", age), Style::default().fg(C_LABEL)),
+            Span::styled(format!("{age:>5}"), Style::default().fg(C_LABEL)),
             hash_span,
             rf_col,
             net_col,
-            Span::styled(format!("{:>6}", size_str), Style::default().fg(C_VALUE)),
+            Span::styled(format!("{size_str:>6}"), Style::default().fg(C_VALUE)),
             rssi_span,
             snr_span,
             action_span,
@@ -541,11 +541,7 @@ fn draw_activity(frame: &mut ratatui::Frame, area: Rect, series: &TimeSeries) {
 
     let rows = Layout::default()
         .direction(Direction::Vertical)
-        .constraints([
-            Constraint::Ratio(1, 3),
-            Constraint::Ratio(1, 3),
-            Constraint::Ratio(1, 3),
-        ])
+        .constraints([Constraint::Ratio(1, 3), Constraint::Ratio(1, 3), Constraint::Ratio(1, 3)])
         .split(inner);
 
     let spark_w = inner.width as usize;
@@ -556,10 +552,7 @@ fn draw_activity(frame: &mut ratatui::Frame, area: Rect, series: &TimeSeries) {
 
     let peak_rx = series.peak_rx();
     let peak_tx = series.peak_tx();
-    let snr_label = series
-        .latest_avg_snr()
-        .map(|s| format!("{s}dB"))
-        .unwrap_or_else(|| "-".into());
+    let snr_label = series.latest_avg_snr().map_or_else(|| "-".into(), |s| format!("{s}dB"));
 
     draw_sparkline_section(frame, rows[0], "RX", &format!("pk:{peak_rx}"), &rx_data, C_RADIO_RX);
     draw_sparkline_section(frame, rows[1], "TX", &format!("pk:{peak_tx}"), &tx_data, C_RADIO_TX);
@@ -590,10 +583,7 @@ fn draw_sparkline_section(
     ]);
     frame.render_widget(Paragraph::new(label_line), rows[0]);
 
-    let spark = Sparkline::default()
-        .data(data)
-        .bar_set(symbols::bar::NINE_LEVELS)
-        .style(Style::default().fg(color));
+    let spark = Sparkline::default().data(data).bar_set(symbols::bar::NINE_LEVELS).style(Style::default().fg(color));
     frame.render_widget(spark, rows[1]);
 }
 
@@ -619,9 +609,7 @@ fn draw_shutdown_overlay(frame: &mut ratatui::Frame, area: Rect) {
     let popup = Rect::new(x, y, w.min(area.width), h.min(area.height));
 
     frame.render_widget(Clear, popup);
-    let block = Block::default()
-        .borders(Borders::ALL)
-        .border_style(Style::default().fg(C_BORDER));
+    let block = Block::default().borders(Borders::ALL).border_style(Style::default().fg(C_BORDER));
     let text = Paragraph::new(Line::from(vec![
         Span::styled(" Shutting down", Style::default().fg(C_RATE_DROP)),
         Span::styled(" — updating DHT...", Style::default().fg(C_LABEL)),
@@ -635,20 +623,29 @@ fn draw_shutdown_overlay(frame: &mut ratatui::Frame, area: Rect) {
 
 fn panel_block(title: &str) -> Block<'static> {
     Block::default()
-        .title(Span::styled(
-            title.to_string(),
-            Style::default().fg(C_TITLE).add_modifier(Modifier::BOLD),
-        ))
+        .title(Span::styled(title.to_string(), Style::default().fg(C_TITLE).add_modifier(Modifier::BOLD)))
         .borders(Borders::ALL)
         .border_style(Style::default().fg(C_BORDER))
 }
 
-fn rssi_color(rssi: i16) -> Color {
-    if rssi >= -70 { Color::Green } else if rssi >= -90 { C_RATE_DROP } else { C_QUEUE_DROP }
+const fn rssi_color(rssi: i16) -> Color {
+    if rssi >= -70 {
+        Color::Green
+    } else if rssi >= -90 {
+        C_RATE_DROP
+    } else {
+        C_QUEUE_DROP
+    }
 }
 
-fn snr_color(snr: i16) -> Color {
-    if snr >= 5 { Color::Green } else if snr >= 0 { C_RATE_DROP } else { C_QUEUE_DROP }
+const fn snr_color(snr: i16) -> Color {
+    if snr >= 5 {
+        Color::Green
+    } else if snr >= 0 {
+        C_RATE_DROP
+    } else {
+        C_QUEUE_DROP
+    }
 }
 
 fn kv_line(label: &str, value: &str, color: Color) -> Line<'static> {
@@ -661,18 +658,496 @@ fn kv_line(label: &str, value: &str, color: Color) -> Line<'static> {
 
 fn format_duration(d: Duration) -> String {
     let secs = d.as_secs();
-    if secs < 60 { format!("{secs}s") }
-    else if secs < 3600 { format!("{}m{}s", secs / 60, secs % 60) }
-    else { format!("{}h{}m", secs / 3600, (secs % 3600) / 60) }
+    if secs < 60 {
+        format!("{secs}s")
+    } else if secs < 3600 {
+        format!("{}m{}s", secs / 60, secs % 60)
+    } else {
+        format!("{}h{}m", secs / 3600, (secs % 3600) / 60)
+    }
 }
 
 fn format_short_duration(d: Duration) -> String {
     let secs = d.as_secs();
-    if secs < 60 { format!("{secs}s") }
-    else if secs < 3600 { format!("{}m", secs / 60) }
-    else { format!("{}h", secs / 3600) }
+    if secs < 60 {
+        format!("{secs}s")
+    } else if secs < 3600 {
+        format!("{}m", secs / 60)
+    } else {
+        format!("{}h", secs / 3600)
+    }
 }
 
 fn chrono_time() -> String {
     jiff::Zoned::now().strftime("%H:%M:%S %Z").to_string()
 }
+
+#[cfg(test)]
+#[allow(clippy::unwrap_used, clippy::expect_used)]
+mod tests {
+    use super::*;
+
+    // ── Helpers ──────────────────────────────────────────────────
+
+    fn make_snapshot(radio_rx: u64, radio_tx: u64) -> StatsSnapshot {
+        StatsSnapshot {
+            radio_rx,
+            radio_tx,
+            gossip_rx: 0,
+            gossip_tx: 0,
+            dedup_hits: 0,
+            rate_limit_drops: 0,
+            dropped_queue: 0,
+            neighbor_count: 0,
+            radio_connected: true,
+        }
+    }
+
+    fn make_log_entry(timestamp: Instant, snr: Option<i16>) -> PacketLogEntry {
+        PacketLogEntry {
+            timestamp,
+            hash: [0u8; 32],
+            direction: PacketDirection::RadioIn,
+            size: 10,
+            snr,
+            rssi: Some(-80),
+            action: PacketAction::Bridged,
+        }
+    }
+
+    // ── format_duration tests ───────────────────────────────────
+
+    #[test]
+    fn format_duration_seconds() {
+        assert_eq!(format_duration(Duration::from_secs(45)), "45s");
+    }
+
+    #[test]
+    fn format_duration_minutes() {
+        assert_eq!(format_duration(Duration::from_secs(125)), "2m5s");
+    }
+
+    #[test]
+    fn format_duration_hours() {
+        assert_eq!(format_duration(Duration::from_secs(7500)), "2h5m");
+    }
+
+    #[test]
+    fn format_duration_zero() {
+        assert_eq!(format_duration(Duration::ZERO), "0s");
+    }
+
+    #[test]
+    fn format_duration_boundary_59s() {
+        assert_eq!(format_duration(Duration::from_secs(59)), "59s");
+    }
+
+    #[test]
+    fn format_duration_boundary_60s() {
+        assert_eq!(format_duration(Duration::from_secs(60)), "1m0s");
+    }
+
+    #[test]
+    fn format_duration_boundary_3599s() {
+        assert_eq!(format_duration(Duration::from_secs(3599)), "59m59s");
+    }
+
+    #[test]
+    fn format_duration_boundary_3600s() {
+        assert_eq!(format_duration(Duration::from_secs(3600)), "1h0m");
+    }
+
+    // ── format_short_duration tests ─────────────────────────────
+
+    #[test]
+    fn format_short_duration_rounds() {
+        assert_eq!(format_short_duration(Duration::from_secs(30)), "30s");
+        assert_eq!(format_short_duration(Duration::from_secs(90)), "1m");
+        assert_eq!(format_short_duration(Duration::from_secs(7500)), "2h");
+    }
+
+    #[test]
+    fn format_short_duration_boundary_59s() {
+        assert_eq!(format_short_duration(Duration::from_secs(59)), "59s");
+    }
+
+    #[test]
+    fn format_short_duration_boundary_60s() {
+        assert_eq!(format_short_duration(Duration::from_secs(60)), "1m");
+    }
+
+    #[test]
+    fn format_short_duration_boundary_3599s() {
+        assert_eq!(format_short_duration(Duration::from_secs(3599)), "59m");
+    }
+
+    #[test]
+    fn format_short_duration_boundary_3600s() {
+        assert_eq!(format_short_duration(Duration::from_secs(3600)), "1h");
+    }
+
+    // ── chrono_time tests ───────────────────────────────────────
+
+    #[test]
+    fn chrono_time_returns_non_empty_string() {
+        let t = chrono_time();
+        assert!(!t.is_empty(), "chrono_time() should not be empty");
+    }
+
+    #[test]
+    fn chrono_time_contains_colons() {
+        // HH:MM:SS format should have at least two colons
+        let t = chrono_time();
+        assert!(t.matches(':').count() >= 2, "chrono_time() should contain HH:MM:SS, got: {t}");
+    }
+
+    // ── rssi_color tests ────────────────────────────────────────
+
+    #[test]
+    fn rssi_color_green_at_minus_70() {
+        assert_eq!(rssi_color(-70), Color::Green);
+    }
+
+    #[test]
+    fn rssi_color_yellow_at_minus_71() {
+        assert_eq!(rssi_color(-71), C_RATE_DROP);
+    }
+
+    #[test]
+    fn rssi_color_yellow_at_minus_90() {
+        assert_eq!(rssi_color(-90), C_RATE_DROP);
+    }
+
+    #[test]
+    fn rssi_color_red_at_minus_91() {
+        assert_eq!(rssi_color(-91), C_QUEUE_DROP);
+    }
+
+    #[test]
+    fn rssi_color_green_at_zero() {
+        assert_eq!(rssi_color(0), Color::Green);
+    }
+
+    // ── snr_color tests ─────────────────────────────────────────
+
+    #[test]
+    fn snr_color_green_at_5() {
+        assert_eq!(snr_color(5), Color::Green);
+    }
+
+    #[test]
+    fn snr_color_yellow_at_4() {
+        assert_eq!(snr_color(4), C_RATE_DROP);
+    }
+
+    #[test]
+    fn snr_color_yellow_at_0() {
+        assert_eq!(snr_color(0), C_RATE_DROP);
+    }
+
+    #[test]
+    fn snr_color_red_at_minus_1() {
+        assert_eq!(snr_color(-1), C_QUEUE_DROP);
+    }
+
+    #[test]
+    fn snr_color_green_at_high_value() {
+        assert_eq!(snr_color(20), Color::Green);
+    }
+
+    // ── snr_stats_since tests ───────────────────────────────────
+
+    #[test]
+    fn snr_stats_since_empty() {
+        assert_eq!(snr_stats_since(&[], Instant::now()), (0, 0));
+    }
+
+    #[test]
+    fn snr_stats_since_sums_and_counts_correctly() {
+        let now = Instant::now();
+        let entries = vec![
+            make_log_entry(now + Duration::from_secs(1), Some(10)),
+            make_log_entry(now + Duration::from_secs(2), Some(20)),
+            make_log_entry(now + Duration::from_secs(3), Some(-5)),
+        ];
+        let (sum, count) = snr_stats_since(&entries, now);
+        assert_eq!(sum, 25); // 10 + 20 + (-5)
+        assert_eq!(count, 3);
+    }
+
+    #[test]
+    fn snr_stats_since_respects_cutoff() {
+        let now = Instant::now();
+        let entries = vec![
+            make_log_entry(now + Duration::from_secs(1), Some(10)),
+            make_log_entry(now + Duration::from_secs(2), Some(20)),
+            make_log_entry(now + Duration::from_secs(5), Some(30)),
+        ];
+        // Use a cutoff after the first two entries
+        let cutoff = now + Duration::from_secs(3);
+        let (sum, count) = snr_stats_since(&entries, cutoff);
+        assert_eq!(sum, 30);
+        assert_eq!(count, 1);
+    }
+
+    #[test]
+    fn snr_stats_since_skips_none_snr() {
+        let now = Instant::now();
+        let entries = vec![
+            make_log_entry(now + Duration::from_secs(1), Some(10)),
+            make_log_entry(now + Duration::from_secs(2), None),
+            make_log_entry(now + Duration::from_secs(3), Some(20)),
+        ];
+        let (sum, count) = snr_stats_since(&entries, now);
+        assert_eq!(sum, 30); // 10 + 20, skipping None
+        assert_eq!(count, 2);
+    }
+
+    #[test]
+    fn snr_stats_since_all_before_cutoff() {
+        let now = Instant::now();
+        let entries = vec![make_log_entry(now, Some(10)), make_log_entry(now, Some(20))];
+        // Cutoff at `now` means entries at exactly `now` are <= since, so excluded
+        let (sum, count) = snr_stats_since(&entries, now);
+        assert_eq!(sum, 0);
+        assert_eq!(count, 0);
+    }
+
+    #[test]
+    fn snr_stats_since_all_none_snr() {
+        let now = Instant::now();
+        let entries = vec![
+            make_log_entry(now + Duration::from_secs(1), None),
+            make_log_entry(now + Duration::from_secs(2), None),
+        ];
+        let (sum, count) = snr_stats_since(&entries, now);
+        assert_eq!(sum, 0);
+        assert_eq!(count, 0);
+    }
+
+    // ── TimeSeries tests ────────────────────────────────────────
+
+    #[test]
+    fn time_series_new_has_max_buckets() {
+        let snap = make_snapshot(0, 0);
+        let ts = TimeSeries::new(&snap);
+        assert_eq!(ts.buckets.len(), MAX_BUCKETS);
+    }
+
+    #[test]
+    fn time_series_radio_rx_returns_bucket_data() {
+        let snap = make_snapshot(0, 0);
+        let mut ts = TimeSeries::new(&snap);
+        // Manually push a bucket with known data
+        ts.buckets.push_back(Bucket { radio_rx: 42, radio_tx: 0, snr_sum: 0, snr_count: 0 });
+        let rx = ts.radio_rx();
+        assert_eq!(*rx.last().unwrap(), 42);
+    }
+
+    #[test]
+    fn time_series_radio_tx_returns_bucket_data() {
+        let snap = make_snapshot(0, 0);
+        let mut ts = TimeSeries::new(&snap);
+        ts.buckets.push_back(Bucket { radio_rx: 0, radio_tx: 99, snr_sum: 0, snr_count: 0 });
+        let tx = ts.radio_tx();
+        assert_eq!(*tx.last().unwrap(), 99);
+    }
+
+    #[test]
+    fn time_series_avg_snr_with_data() {
+        let snap = make_snapshot(0, 0);
+        let mut ts = TimeSeries::new(&snap);
+        // Push bucket: snr_sum=10, snr_count=2 -> avg=5 -> shifted = 5+30 = 35
+        ts.buckets.push_back(Bucket { radio_rx: 0, radio_tx: 0, snr_sum: 10, snr_count: 2 });
+        let snr = ts.avg_snr();
+        assert_eq!(*snr.last().unwrap(), 35);
+    }
+
+    #[test]
+    fn time_series_avg_snr_zero_count() {
+        let snap = make_snapshot(0, 0);
+        let ts = TimeSeries::new(&snap);
+        // All default buckets have snr_count=0, so avg_snr should be all zeros
+        let snr = ts.avg_snr();
+        assert!(snr.iter().all(|&v| v == 0));
+    }
+
+    #[test]
+    fn time_series_avg_snr_negative_clamps_to_zero() {
+        let snap = make_snapshot(0, 0);
+        let mut ts = TimeSeries::new(&snap);
+        // avg = -50, shifted = -50+30 = -20, clamped to 0
+        ts.buckets.push_back(Bucket { radio_rx: 0, radio_tx: 0, snr_sum: -50, snr_count: 1 });
+        let snr = ts.avg_snr();
+        assert_eq!(*snr.last().unwrap(), 0);
+    }
+
+    #[test]
+    fn time_series_peak_rx() {
+        let snap = make_snapshot(0, 0);
+        let mut ts = TimeSeries::new(&snap);
+        ts.buckets.push_back(Bucket { radio_rx: 5, radio_tx: 0, snr_sum: 0, snr_count: 0 });
+        ts.buckets.push_back(Bucket { radio_rx: 15, radio_tx: 0, snr_sum: 0, snr_count: 0 });
+        ts.buckets.push_back(Bucket { radio_rx: 3, radio_tx: 0, snr_sum: 0, snr_count: 0 });
+        assert_eq!(ts.peak_rx(), 15);
+    }
+
+    #[test]
+    fn time_series_peak_tx() {
+        let snap = make_snapshot(0, 0);
+        let mut ts = TimeSeries::new(&snap);
+        ts.buckets.push_back(Bucket { radio_rx: 0, radio_tx: 7, snr_sum: 0, snr_count: 0 });
+        ts.buckets.push_back(Bucket { radio_rx: 0, radio_tx: 22, snr_sum: 0, snr_count: 0 });
+        assert_eq!(ts.peak_tx(), 22);
+    }
+
+    #[test]
+    fn time_series_peak_rx_default_is_zero() {
+        let snap = make_snapshot(0, 0);
+        let ts = TimeSeries::new(&snap);
+        assert_eq!(ts.peak_rx(), 0);
+    }
+
+    #[test]
+    fn time_series_peak_tx_default_is_zero() {
+        let snap = make_snapshot(0, 0);
+        let ts = TimeSeries::new(&snap);
+        assert_eq!(ts.peak_tx(), 0);
+    }
+
+    #[test]
+    fn time_series_latest_avg_snr_with_data() {
+        let snap = make_snapshot(0, 0);
+        let mut ts = TimeSeries::new(&snap);
+        // Push an older bucket with different SNR
+        ts.buckets.push_back(Bucket { radio_rx: 0, radio_tx: 0, snr_sum: 100, snr_count: 10 });
+        // Push the latest bucket with known SNR: sum=20, count=4 -> avg=5
+        ts.buckets.push_back(Bucket { radio_rx: 0, radio_tx: 0, snr_sum: 20, snr_count: 4 });
+        assert_eq!(ts.latest_avg_snr(), Some(5));
+    }
+
+    #[test]
+    fn time_series_latest_avg_snr_none_when_no_data() {
+        let snap = make_snapshot(0, 0);
+        let ts = TimeSeries::new(&snap);
+        // All default buckets have snr_count=0
+        assert_eq!(ts.latest_avg_snr(), None);
+    }
+
+    #[test]
+    fn time_series_latest_avg_snr_skips_trailing_empty() {
+        let snap = make_snapshot(0, 0);
+        let mut ts = TimeSeries::new(&snap);
+        // A bucket with data followed by an empty bucket
+        ts.buckets.push_back(Bucket { radio_rx: 0, radio_tx: 0, snr_sum: -12, snr_count: 3 });
+        ts.buckets.push_back(Bucket::default()); // snr_count = 0
+        // latest_avg_snr scans backwards, skips the empty one, finds -12/3 = -4
+        assert_eq!(ts.latest_avg_snr(), Some(-4));
+    }
+
+    #[test]
+    fn time_series_update_creates_bucket() {
+        let snap0 = make_snapshot(10, 5);
+        let mut ts = TimeSeries::new(&snap0);
+        // Force the last_bucket_time to be old enough to trigger a new bucket
+        ts.last_bucket_time = Instant::now().checked_sub(Duration::from_secs(BUCKET_SECS + 1)).unwrap();
+        let initial_len = ts.buckets.len();
+
+        let snap1 = make_snapshot(15, 8);
+        let entries = vec![make_log_entry(Instant::now(), Some(10))];
+        ts.update(&snap1, &entries);
+
+        // A new bucket should have been pushed
+        assert!(ts.buckets.len() >= initial_len);
+        let last = ts.buckets.back().unwrap();
+        assert_eq!(last.radio_rx, 5); // 15 - 10
+        assert_eq!(last.radio_tx, 3); // 8 - 5
+    }
+
+    #[test]
+    fn time_series_update_does_not_create_bucket_when_interval_not_elapsed() {
+        let snap0 = make_snapshot(10, 5);
+        let mut ts = TimeSeries::new(&snap0);
+        // last_bucket_time is now, so interval has NOT elapsed
+        let len_before = ts.buckets.len();
+
+        let snap1 = make_snapshot(20, 10);
+        ts.update(&snap1, &[]);
+
+        // No new bucket should be added
+        assert_eq!(ts.buckets.len(), len_before);
+    }
+
+    #[test]
+    fn time_series_update_rotates_when_exceeding_max() {
+        let snap0 = make_snapshot(0, 0);
+        let mut ts = TimeSeries::new(&snap0);
+        assert_eq!(ts.buckets.len(), MAX_BUCKETS);
+
+        // Force old timestamp so update triggers
+        ts.last_bucket_time = Instant::now().checked_sub(Duration::from_secs(BUCKET_SECS + 1)).unwrap();
+        let snap1 = make_snapshot(1, 1);
+        ts.update(&snap1, &[]);
+
+        // Should still be at MAX_BUCKETS (the front was popped)
+        assert_eq!(ts.buckets.len(), MAX_BUCKETS);
+        // The last bucket should be our new one
+        let last = ts.buckets.back().unwrap();
+        assert_eq!(last.radio_rx, 1);
+    }
+
+    #[test]
+    fn time_series_update_no_pop_at_exactly_max() {
+        // Start with MAX_BUCKETS - 1 entries. Push one to reach exactly MAX_BUCKETS.
+        // With `> MAX_BUCKETS`: 300 is NOT > 300, so no pop → len stays 300. (correct)
+        // With `>= MAX_BUCKETS`: 300 IS >= 300, so pop → len becomes 299. (wrong)
+        let snap0 = make_snapshot(0, 0);
+        let mut ts = TimeSeries::new(&snap0);
+        ts.buckets.pop_front(); // now MAX_BUCKETS - 1
+        assert_eq!(ts.buckets.len(), MAX_BUCKETS - 1);
+
+        ts.last_bucket_time = Instant::now().checked_sub(Duration::from_secs(BUCKET_SECS + 1)).unwrap();
+        let snap1 = make_snapshot(1, 0);
+        ts.update(&snap1, &[]);
+
+        assert_eq!(ts.buckets.len(), MAX_BUCKETS, "should be exactly MAX_BUCKETS, not popped");
+    }
+
+    // ── pad_right_align tests ───────────────────────────────────
+
+    #[test]
+    fn pad_right_align_shorter_than_width() {
+        assert_eq!(pad_right_align(&[1, 2, 3], 5), vec![0, 0, 1, 2, 3]);
+    }
+
+    #[test]
+    fn pad_right_align_longer_than_width() {
+        assert_eq!(pad_right_align(&[1, 2, 3, 4, 5], 3), vec![3, 4, 5]);
+    }
+
+    #[test]
+    fn pad_right_align_exact() {
+        assert_eq!(pad_right_align(&[1, 2, 3], 3), vec![1, 2, 3]);
+    }
+
+    #[test]
+    fn pad_right_align_empty() {
+        assert_eq!(pad_right_align(&[], 3), vec![0, 0, 0]);
+    }
+
+    mod proptests {
+        use super::*;
+        use proptest::prelude::*;
+
+        proptest! {
+            #[test]
+            fn pad_right_align_output_length(
+                data in proptest::collection::vec(0u64..100, 0..500),
+                width in 1usize..200,
+            ) {
+                let result = pad_right_align(&data, width);
+                prop_assert_eq!(result.len(), width);
+            }
+        }
+    }
+}