fix(navigation): back button on host detail returns to application when coming from there

- application_detail: host links now include ?back=/applications/:id
- host_detail: back_label handles /applications/ prefix → "← Application"

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Cargo.toml

@@ -6,6 +6,15 @@ edition = "2021"
 # Leptos nécessite deux formats de compilation :
 # - rlib   : bibliothèque normale, utilisée par le serveur Axum
 # - cdylib : bibliothèque dynamique compilée en WebAssembly pour le navigateur
+[[bin]]
+name = "rust-ipam"
+path = "src/main.rs"
+
+[[bin]]
+name = "seed"
+path = "src/bin/seed.rs"
+required-features = ["ssr"]
+
 [lib]
 crate-type = ["cdylib", "rlib"]
 

migrations/postgres/0008_create_host_applications.sql

@@ -0,0 +1,8 @@
+-- host_applications: direct association between a host and an application.
+-- Allows explicitly tagging a host with an application regardless of ports.
+-- One application can only be linked once to a given host.
+CREATE TABLE IF NOT EXISTS host_applications (
+    host_id        BIGINT NOT NULL REFERENCES hosts(id)        ON DELETE CASCADE,
+    application_id BIGINT NOT NULL REFERENCES applications(id) ON DELETE CASCADE,
+    PRIMARY KEY (host_id, application_id)
+);

migrations/sqlite/0008_create_host_applications.sql

@@ -0,0 +1,8 @@
+-- host_applications: direct association between a host and an application.
+-- Allows explicitly tagging a host with an application regardless of ports.
+-- One application can only be linked once to a given host.
+CREATE TABLE IF NOT EXISTS host_applications (
+    host_id        INTEGER NOT NULL REFERENCES hosts(id)        ON DELETE CASCADE,
+    application_id INTEGER NOT NULL REFERENCES applications(id) ON DELETE CASCADE,
+    PRIMARY KEY (host_id, application_id)
+);

seeds/postgres/dev_seed.sql

@@ -80,15 +80,25 @@ INSERT INTO ports (number, description) VALUES
     (993,   'IMAPS'),
     (1194,  'OpenVPN'),
     (2049,  'NFS'),
-    (3000, 'Grafana'),
+    (3000,  'Grafana / Gitea'),
+    (3306,  'MariaDB / MySQL'),
     (3389,  'RDP'),
     (4500,  'IPSec NAT-T'),
     (5044,  'Logstash Beats'),
     (5432,  'PostgreSQL'),
     (5601,  'Kibana'),
+    (6379,  'Redis'),
+    (8096,  'Jellyfin'),
+    (8123,  'Home Assistant'),
+    (8384,  'Syncthing UI'),
+    (8920,  'Jellyfin HTTPS'),
+    (9000,  'Portainer'),
     (9090,  'Prometheus'),
-    (9100, 'JetDirect'),
+    (9100,  'node_exporter / JetDirect'),
-    (9200, 'Elasticsearch')
+    (9200,  'Elasticsearch'),
+    (9443,  'Portainer HTTPS'),
+    (22000, 'Syncthing'),
+    (51820, 'WireGuard')
 ON CONFLICT (number) DO NOTHING;
 
 -- ── Host ports ────────────────────────────────────────────────────────────────
@@ -193,3 +203,84 @@ INSERT INTO host_ports (host_id, port_number)
 SELECT h.id, 22 FROM hosts h
 WHERE h.name = 'vpn-client-02' AND h.ip = '172.16.1.11'
 ON CONFLICT DO NOTHING;
+
+-- ── Applications ──────────────────────────────────────────────────────────────
+-- applications has no UNIQUE constraint on name, so we use WHERE NOT EXISTS.
+
+INSERT INTO applications (name)
+SELECT v.name FROM (VALUES
+    ('Nginx'),
+    ('Pi-hole'),
+    ('WireGuard'),
+    ('OpenVPN'),
+    ('PostgreSQL'),
+    ('MariaDB'),
+    ('Redis'),
+    ('Grafana'),
+    ('Prometheus'),
+    ('Elasticsearch'),
+    ('Kibana'),
+    ('Portainer'),
+    ('Jellyfin'),
+    ('Home Assistant'),
+    ('Syncthing'),
+    ('Vaultwarden')
+) AS v(name)
+WHERE NOT EXISTS (SELECT 1 FROM applications WHERE name = v.name);
+
+-- ── Application ports ─────────────────────────────────────────────────────────
+
+-- Nginx: HTTP, HTTPS
+INSERT INTO application_ports (application_id, port_number) SELECT id, 80  FROM applications WHERE name = 'Nginx' ON CONFLICT DO NOTHING;
+INSERT INTO application_ports (application_id, port_number) SELECT id, 443 FROM applications WHERE name = 'Nginx' ON CONFLICT DO NOTHING;
+
+-- Pi-hole: DNS, HTTP (admin UI), HTTPS
+INSERT INTO application_ports (application_id, port_number) SELECT id, 53  FROM applications WHERE name = 'Pi-hole' ON CONFLICT DO NOTHING;
+INSERT INTO application_ports (application_id, port_number) SELECT id, 80  FROM applications WHERE name = 'Pi-hole' ON CONFLICT DO NOTHING;
+INSERT INTO application_ports (application_id, port_number) SELECT id, 443 FROM applications WHERE name = 'Pi-hole' ON CONFLICT DO NOTHING;
+
+-- WireGuard
+INSERT INTO application_ports (application_id, port_number) SELECT id, 51820 FROM applications WHERE name = 'WireGuard' ON CONFLICT DO NOTHING;
+
+-- OpenVPN
+INSERT INTO application_ports (application_id, port_number) SELECT id, 1194 FROM applications WHERE name = 'OpenVPN' ON CONFLICT DO NOTHING;
+
+-- PostgreSQL
+INSERT INTO application_ports (application_id, port_number) SELECT id, 5432 FROM applications WHERE name = 'PostgreSQL' ON CONFLICT DO NOTHING;
+
+-- MariaDB
+INSERT INTO application_ports (application_id, port_number) SELECT id, 3306 FROM applications WHERE name = 'MariaDB' ON CONFLICT DO NOTHING;
+
+-- Redis
+INSERT INTO application_ports (application_id, port_number) SELECT id, 6379 FROM applications WHERE name = 'Redis' ON CONFLICT DO NOTHING;
+
+-- Grafana
+INSERT INTO application_ports (application_id, port_number) SELECT id, 3000 FROM applications WHERE name = 'Grafana' ON CONFLICT DO NOTHING;
+
+-- Prometheus
+INSERT INTO application_ports (application_id, port_number) SELECT id, 9090 FROM applications WHERE name = 'Prometheus' ON CONFLICT DO NOTHING;
+
+-- Elasticsearch
+INSERT INTO application_ports (application_id, port_number) SELECT id, 9200 FROM applications WHERE name = 'Elasticsearch' ON CONFLICT DO NOTHING;
+
+-- Kibana
+INSERT INTO application_ports (application_id, port_number) SELECT id, 5601 FROM applications WHERE name = 'Kibana' ON CONFLICT DO NOTHING;
+
+-- Portainer: HTTP, HTTPS
+INSERT INTO application_ports (application_id, port_number) SELECT id, 9000 FROM applications WHERE name = 'Portainer' ON CONFLICT DO NOTHING;
+INSERT INTO application_ports (application_id, port_number) SELECT id, 9443 FROM applications WHERE name = 'Portainer' ON CONFLICT DO NOTHING;
+
+-- Jellyfin: HTTP, HTTPS
+INSERT INTO application_ports (application_id, port_number) SELECT id, 8096 FROM applications WHERE name = 'Jellyfin' ON CONFLICT DO NOTHING;
+INSERT INTO application_ports (application_id, port_number) SELECT id, 8920 FROM applications WHERE name = 'Jellyfin' ON CONFLICT DO NOTHING;
+
+-- Home Assistant
+INSERT INTO application_ports (application_id, port_number) SELECT id, 8123 FROM applications WHERE name = 'Home Assistant' ON CONFLICT DO NOTHING;
+
+-- Syncthing: UI, data sync
+INSERT INTO application_ports (application_id, port_number) SELECT id, 8384  FROM applications WHERE name = 'Syncthing' ON CONFLICT DO NOTHING;
+INSERT INTO application_ports (application_id, port_number) SELECT id, 22000 FROM applications WHERE name = 'Syncthing' ON CONFLICT DO NOTHING;
+
+-- Vaultwarden: HTTP, HTTPS
+INSERT INTO application_ports (application_id, port_number) SELECT id, 80  FROM applications WHERE name = 'Vaultwarden' ON CONFLICT DO NOTHING;
+INSERT INTO application_ports (application_id, port_number) SELECT id, 443 FROM applications WHERE name = 'Vaultwarden' ON CONFLICT DO NOTHING;

seeds/sqlite/dev_seed.sql

@@ -60,15 +60,25 @@ INSERT OR IGNORE INTO ports (number, description) VALUES
     (993,   'IMAPS'),
     (1194,  'OpenVPN'),
     (2049,  'NFS'),
-    (3000, 'Grafana'),
+    (3000,  'Grafana / Gitea'),
+    (3306,  'MariaDB / MySQL'),
     (3389,  'RDP'),
     (4500,  'IPSec NAT-T'),
     (5044,  'Logstash Beats'),
     (5432,  'PostgreSQL'),
     (5601,  'Kibana'),
+    (6379,  'Redis'),
+    (8096,  'Jellyfin'),
+    (8123,  'Home Assistant'),
+    (8384,  'Syncthing UI'),
+    (8920,  'Jellyfin HTTPS'),
+    (9000,  'Portainer'),
     (9090,  'Prometheus'),
-    (9100, 'JetDirect'),
+    (9100,  'node_exporter / JetDirect'),
-    (9200, 'Elasticsearch');
+    (9200,  'Elasticsearch'),
+    (9443,  'Portainer HTTPS'),
+    (22000, 'Syncthing'),
+    (51820, 'WireGuard');
 
 -- ── Host ports ────────────────────────────────────────────────────────────────
 -- INSERT OR IGNORE is safe: host_ports has a composite PRIMARY KEY (host_id, port_number).
@@ -124,7 +134,7 @@ INSERT OR IGNORE INTO host_ports (host_id, port_number) SELECT id, 993 FROM host
 INSERT OR IGNORE INTO host_ports (host_id, port_number) SELECT id, 22  FROM hosts WHERE name = 'core-switch-01'   AND ip = '10.0.0.1';
 INSERT OR IGNORE INTO host_ports (host_id, port_number) SELECT id, 161 FROM hosts WHERE name = 'core-switch-01'   AND ip = '10.0.0.1';
 
--- monitoring-01: SSH, HTTP, HTTPS, Prometheus, Grafana
+-- monitoring-01: SSH, HTTP, HTTPS, Grafana, Prometheus
 INSERT OR IGNORE INTO host_ports (host_id, port_number) SELECT id, 22   FROM hosts WHERE name = 'monitoring-01'    AND ip = '10.0.1.10';
 INSERT OR IGNORE INTO host_ports (host_id, port_number) SELECT id, 80   FROM hosts WHERE name = 'monitoring-01'    AND ip = '10.0.1.10';
 INSERT OR IGNORE INTO host_ports (host_id, port_number) SELECT id, 443  FROM hosts WHERE name = 'monitoring-01'    AND ip = '10.0.1.10';
@@ -152,3 +162,81 @@ INSERT OR IGNORE INTO host_ports (host_id, port_number) SELECT id, 4500 FROM hos
 -- vpn clients: SSH only
 INSERT OR IGNORE INTO host_ports (host_id, port_number) SELECT id, 22 FROM hosts WHERE name = 'vpn-client-01'  AND ip = '172.16.1.10';
 INSERT OR IGNORE INTO host_ports (host_id, port_number) SELECT id, 22 FROM hosts WHERE name = 'vpn-client-02'  AND ip = '172.16.1.11';
+
+-- ── Applications ──────────────────────────────────────────────────────────────
+-- applications has no UNIQUE constraint on name, so we use WHERE NOT EXISTS.
+
+INSERT INTO applications (name) SELECT 'Nginx'          WHERE NOT EXISTS (SELECT 1 FROM applications WHERE name = 'Nginx');
+INSERT INTO applications (name) SELECT 'Pi-hole'        WHERE NOT EXISTS (SELECT 1 FROM applications WHERE name = 'Pi-hole');
+INSERT INTO applications (name) SELECT 'WireGuard'      WHERE NOT EXISTS (SELECT 1 FROM applications WHERE name = 'WireGuard');
+INSERT INTO applications (name) SELECT 'OpenVPN'        WHERE NOT EXISTS (SELECT 1 FROM applications WHERE name = 'OpenVPN');
+INSERT INTO applications (name) SELECT 'PostgreSQL'     WHERE NOT EXISTS (SELECT 1 FROM applications WHERE name = 'PostgreSQL');
+INSERT INTO applications (name) SELECT 'MariaDB'        WHERE NOT EXISTS (SELECT 1 FROM applications WHERE name = 'MariaDB');
+INSERT INTO applications (name) SELECT 'Redis'          WHERE NOT EXISTS (SELECT 1 FROM applications WHERE name = 'Redis');
+INSERT INTO applications (name) SELECT 'Grafana'        WHERE NOT EXISTS (SELECT 1 FROM applications WHERE name = 'Grafana');
+INSERT INTO applications (name) SELECT 'Prometheus'     WHERE NOT EXISTS (SELECT 1 FROM applications WHERE name = 'Prometheus');
+INSERT INTO applications (name) SELECT 'Elasticsearch'  WHERE NOT EXISTS (SELECT 1 FROM applications WHERE name = 'Elasticsearch');
+INSERT INTO applications (name) SELECT 'Kibana'         WHERE NOT EXISTS (SELECT 1 FROM applications WHERE name = 'Kibana');
+INSERT INTO applications (name) SELECT 'Portainer'      WHERE NOT EXISTS (SELECT 1 FROM applications WHERE name = 'Portainer');
+INSERT INTO applications (name) SELECT 'Jellyfin'       WHERE NOT EXISTS (SELECT 1 FROM applications WHERE name = 'Jellyfin');
+INSERT INTO applications (name) SELECT 'Home Assistant' WHERE NOT EXISTS (SELECT 1 FROM applications WHERE name = 'Home Assistant');
+INSERT INTO applications (name) SELECT 'Syncthing'      WHERE NOT EXISTS (SELECT 1 FROM applications WHERE name = 'Syncthing');
+INSERT INTO applications (name) SELECT 'Vaultwarden'    WHERE NOT EXISTS (SELECT 1 FROM applications WHERE name = 'Vaultwarden');
+
+-- ── Application ports ─────────────────────────────────────────────────────────
+-- application_ports has a composite PRIMARY KEY, so INSERT OR IGNORE is safe.
+
+-- Nginx: HTTP, HTTPS
+INSERT OR IGNORE INTO application_ports (application_id, port_number) SELECT id, 80  FROM applications WHERE name = 'Nginx';
+INSERT OR IGNORE INTO application_ports (application_id, port_number) SELECT id, 443 FROM applications WHERE name = 'Nginx';
+
+-- Pi-hole: DNS, HTTP (admin UI), HTTPS
+INSERT OR IGNORE INTO application_ports (application_id, port_number) SELECT id, 53  FROM applications WHERE name = 'Pi-hole';
+INSERT OR IGNORE INTO application_ports (application_id, port_number) SELECT id, 80  FROM applications WHERE name = 'Pi-hole';
+INSERT OR IGNORE INTO application_ports (application_id, port_number) SELECT id, 443 FROM applications WHERE name = 'Pi-hole';
+
+-- WireGuard
+INSERT OR IGNORE INTO application_ports (application_id, port_number) SELECT id, 51820 FROM applications WHERE name = 'WireGuard';
+
+-- OpenVPN
+INSERT OR IGNORE INTO application_ports (application_id, port_number) SELECT id, 1194 FROM applications WHERE name = 'OpenVPN';
+
+-- PostgreSQL
+INSERT OR IGNORE INTO application_ports (application_id, port_number) SELECT id, 5432 FROM applications WHERE name = 'PostgreSQL';
+
+-- MariaDB
+INSERT OR IGNORE INTO application_ports (application_id, port_number) SELECT id, 3306 FROM applications WHERE name = 'MariaDB';
+
+-- Redis
+INSERT OR IGNORE INTO application_ports (application_id, port_number) SELECT id, 6379 FROM applications WHERE name = 'Redis';
+
+-- Grafana
+INSERT OR IGNORE INTO application_ports (application_id, port_number) SELECT id, 3000 FROM applications WHERE name = 'Grafana';
+
+-- Prometheus
+INSERT OR IGNORE INTO application_ports (application_id, port_number) SELECT id, 9090 FROM applications WHERE name = 'Prometheus';
+
+-- Elasticsearch
+INSERT OR IGNORE INTO application_ports (application_id, port_number) SELECT id, 9200 FROM applications WHERE name = 'Elasticsearch';
+
+-- Kibana
+INSERT OR IGNORE INTO application_ports (application_id, port_number) SELECT id, 5601 FROM applications WHERE name = 'Kibana';
+
+-- Portainer: HTTP, HTTPS
+INSERT OR IGNORE INTO application_ports (application_id, port_number) SELECT id, 9000 FROM applications WHERE name = 'Portainer';
+INSERT OR IGNORE INTO application_ports (application_id, port_number) SELECT id, 9443 FROM applications WHERE name = 'Portainer';
+
+-- Jellyfin: HTTP, HTTPS
+INSERT OR IGNORE INTO application_ports (application_id, port_number) SELECT id, 8096 FROM applications WHERE name = 'Jellyfin';
+INSERT OR IGNORE INTO application_ports (application_id, port_number) SELECT id, 8920 FROM applications WHERE name = 'Jellyfin';
+
+-- Home Assistant
+INSERT OR IGNORE INTO application_ports (application_id, port_number) SELECT id, 8123 FROM applications WHERE name = 'Home Assistant';
+
+-- Syncthing: UI, data sync
+INSERT OR IGNORE INTO application_ports (application_id, port_number) SELECT id, 8384  FROM applications WHERE name = 'Syncthing';
+INSERT OR IGNORE INTO application_ports (application_id, port_number) SELECT id, 22000 FROM applications WHERE name = 'Syncthing';
+
+-- Vaultwarden: HTTP, HTTPS
+INSERT OR IGNORE INTO application_ports (application_id, port_number) SELECT id, 80  FROM applications WHERE name = 'Vaultwarden';
+INSERT OR IGNORE INTO application_ports (application_id, port_number) SELECT id, 443 FROM applications WHERE name = 'Vaultwarden';

src/api/applications.rs

@@ -5,6 +5,24 @@ use serde::{Deserialize, Serialize};
 
 use crate::models::Application;
 
+// Minimal host reference used by ApplicationDetail.
+#[derive(Clone, Debug, Serialize, Deserialize)]
+pub struct HostRef {
+    pub id:   i64,
+    pub name: String,
+    pub ip:   String,
+}
+
+// Full detail for a single application: identity, associated ports, and linked hosts.
+// Linked hosts are those that have at least one port matching an application_ports entry.
+#[derive(Clone, Debug, Serialize, Deserialize)]
+pub struct ApplicationDetail {
+    pub id:    i64,
+    pub name:  String,
+    pub ports: Vec<u16>,
+    pub hosts: Vec<HostRef>,
+}
+
 // Application row enriched with the number of hosts that use at least one of
 // its registered ports.  Host count is computed via the join:
 //   application_ports → host_ports (matched on port_number) → hosts
@@ -65,6 +83,52 @@ pub async fn get_applications() -> Result<Vec<Application>, ServerFnError> {
         .map_err(|e| ServerFnError::new(e.to_string()))
 }
 
+/// Returns full detail for a single application: identity, ports, and linked hosts.
+///
+/// Linked hosts are hosts that have at least one open port matching one of
+/// the application's registered port numbers (via application_ports ↔ host_ports).
+#[server]
+pub async fn get_application_detail(id: i64) -> Result<ApplicationDetail, ServerFnError> {
+    use sqlx::{AnyPool, Row};
+    use crate::server::repository::applications as repo;
+
+    let pool = use_context::<AnyPool>()
+        .ok_or_else(|| ServerFnError::new("Database pool not found in context"))?;
+
+    let app = repo::find_application(&pool, id)
+        .await
+        .map_err(|e| ServerFnError::new(e.to_string()))?
+        .ok_or_else(|| ServerFnError::new(format!("Application {id} not found")))?;
+
+    let ports = repo::list_ports_for_application(&pool, id)
+        .await
+        .map_err(|e| ServerFnError::new(e.to_string()))?;
+
+    let rows = sqlx::query(
+        "SELECT DISTINCT h.id, h.name, h.ip
+         FROM hosts h
+         JOIN host_ports hp        ON hp.host_id    = h.id
+         JOIN application_ports ap ON ap.port_number = hp.port_number
+         WHERE ap.application_id = $1
+         ORDER BY h.name",
+    )
+    .bind(id)
+    .fetch_all(&pool)
+    .await
+    .map_err(|e| ServerFnError::new(e.to_string()))?;
+
+    let hosts = rows
+        .iter()
+        .map(|row| HostRef {
+            id:   row.get("id"),
+            name: row.get("name"),
+            ip:   row.get("ip"),
+        })
+        .collect();
+
+    Ok(ApplicationDetail { id: app.id, name: app.name, ports, hosts })
+}
+
 /// Returns the port numbers associated with an application.
 #[server]
 pub async fn get_ports_for_application(
@@ -83,20 +147,55 @@ pub async fn get_ports_for_application(
 
 // ─── Mutations ────────────────────────────────────────────────────────────────
 
-/// Creates a new application and returns the created record.
+/// Updates the name of an application and returns the updated record.
 #[server]
-pub async fn create_application(name: String) -> Result<Application, ServerFnError> {
+pub async fn update_application(id: i64, name: String) -> Result<Application, ServerFnError> {
     use sqlx::AnyPool;
     use crate::server::repository::applications as repo;
 
     let pool = use_context::<AnyPool>()
         .ok_or_else(|| ServerFnError::new("Database pool not found in context"))?;
 
-    repo::create_application(&pool, &name)
+    if name.trim().is_empty() {
+        return Err(ServerFnError::new("Application name cannot be empty"));
+    }
+
+    repo::update_application(&pool, id, name.trim())
         .await
         .map_err(|e| ServerFnError::new(e.to_string()))
 }
 
+/// Creates a new application, then associates the given port numbers.
+///
+/// `ports` is a comma-separated list of port numbers (e.g. "80,443").
+/// An empty string means no ports are associated.
+#[server]
+pub async fn create_application(name: String, ports: String) -> Result<Application, ServerFnError> {
+    use sqlx::AnyPool;
+    use crate::server::repository::applications as repo;
+
+    let pool = use_context::<AnyPool>()
+        .ok_or_else(|| ServerFnError::new("Database pool not found in context"))?;
+
+    let app = repo::create_application(&pool, &name)
+        .await
+        .map_err(|e| ServerFnError::new(e.to_string()))?;
+
+    let port_numbers: Vec<u16> = ports
+        .split(',')
+        .filter_map(|s| s.trim().parse::<u16>().ok())
+        .filter(|&p| p >= 1)
+        .collect();
+
+    for port_number in port_numbers {
+        repo::add_port_to_application(&pool, app.id, port_number)
+            .await
+            .map_err(|e| ServerFnError::new(e.to_string()))?;
+    }
+
+    Ok(app)
+}
+
 /// Deletes an application and all its port associations.
 ///
 /// Returns `true` if the application existed and was deleted.

src/api/hosts.rs

@@ -3,9 +3,7 @@
 use leptos::prelude::*;
 use serde::{Deserialize, Serialize};
 
-use crate::models::Host;
+use crate::models::{Application, Host, Port};
-
-use crate::models::Port;
 
 // ─── Presentation types ───────────────────────────────────────────────────────
 
@@ -32,7 +30,7 @@ pub struct HostsPage {
     pub total_pages: i64, // ceil(total / per_page); always ≥ 1
 }
 
-// Full host detail: identity fields + resolved network + open ports.
+// Full host detail: identity fields + resolved network + open ports + linked applications.
 #[derive(Clone, Debug, Serialize, Deserialize)]
 pub struct HostDetail {
     pub id: i64,
@@ -42,6 +40,7 @@ pub struct HostDetail {
     pub network_name: String,
     pub network_cidr: String,
     pub ports: Vec<Port>,
+    pub applications: Vec<Application>,
 }
 
 // ─── Queries ──────────────────────────────────────────────────────────────────
@@ -50,7 +49,12 @@ pub struct HostDetail {
 #[server]
 pub async fn get_host_detail(id: i64) -> Result<HostDetail, ServerFnError> {
     use sqlx::AnyPool;
-    use crate::server::repository::{hosts as host_repo, networks, ports as port_repo};
+    use crate::server::repository::{
+        applications as app_repo,
+        hosts as host_repo,
+        networks,
+        ports as port_repo,
+    };
 
     let pool = use_context::<AnyPool>()
         .ok_or_else(|| ServerFnError::new("Database pool not found in context"))?;
@@ -69,6 +73,10 @@ pub async fn get_host_detail(id: i64) -> Result<HostDetail, ServerFnError> {
         .await
         .map_err(|e| ServerFnError::new(e.to_string()))?;
 
+    let applications = app_repo::list_applications_for_host(&pool, id)
+        .await
+        .map_err(|e| ServerFnError::new(e.to_string()))?;
+
     Ok(HostDetail {
         id: host.id,
         name: host.name,
@@ -77,6 +85,7 @@ pub async fn get_host_detail(id: i64) -> Result<HostDetail, ServerFnError> {
         network_name: network.name,
         network_cidr: network.cidr,
         ports,
+        applications,
     })
 }
 
@@ -343,6 +352,72 @@ pub async fn remove_host_port(host_id: i64, port_number: i64) -> Result<(), Serv
         .map_err(|e| ServerFnError::new(e.to_string()))
 }
 
+/// Returns all applications not yet directly linked to a host.
+///
+/// Used to populate the "add applications" modal on the host detail page.
+#[server]
+pub async fn get_applications_not_on_host(
+    host_id: i64,
+) -> Result<Vec<Application>, ServerFnError> {
+    use sqlx::AnyPool;
+    use crate::server::repository::applications as repo;
+
+    let pool = use_context::<AnyPool>()
+        .ok_or_else(|| ServerFnError::new("Database pool not found in context"))?;
+
+    repo::list_applications_not_on_host(&pool, host_id)
+        .await
+        .map_err(|e| ServerFnError::new(e.to_string()))
+}
+
+/// Links one or more applications to a host.
+///
+/// `application_ids` is a comma-separated string of application IDs (e.g. "1,3,7").
+/// Already-linked applications are silently skipped (no-op).
+#[server]
+pub async fn add_host_applications(
+    host_id: i64,
+    application_ids: String,
+) -> Result<(), ServerFnError> {
+    use sqlx::AnyPool;
+    use crate::server::repository::applications as repo;
+
+    let pool = use_context::<AnyPool>()
+        .ok_or_else(|| ServerFnError::new("Database pool not found in context"))?;
+
+    let ids: Vec<i64> = application_ids
+        .split(',')
+        .filter_map(|s| s.trim().parse::<i64>().ok())
+        .collect();
+
+    for application_id in ids {
+        repo::add_application_to_host(&pool, host_id, application_id)
+            .await
+            .map_err(|e| ServerFnError::new(e.to_string()))?;
+    }
+
+    Ok(())
+}
+
+/// Removes the direct link between a host and an application.
+///
+/// Returns `true` if the association existed and was removed.
+#[server]
+pub async fn remove_host_application(
+    host_id: i64,
+    application_id: i64,
+) -> Result<bool, ServerFnError> {
+    use sqlx::AnyPool;
+    use crate::server::repository::applications as repo;
+
+    let pool = use_context::<AnyPool>()
+        .ok_or_else(|| ServerFnError::new("Database pool not found in context"))?;
+
+    repo::remove_application_from_host(&pool, host_id, application_id)
+        .await
+        .map_err(|e| ServerFnError::new(e.to_string()))
+}
+
 /// Deletes a host by id.
 ///
 /// Also removes all its port associations (via `ON DELETE CASCADE`).

src/app.rs

@@ -12,6 +12,7 @@ use leptos_router::{
 };
 
 use crate::client::{
+    application_detail::ApplicationDetailPage,
     applications::ApplicationsPage,
     home::HomePage,
     host_detail::HostDetailPage,
@@ -115,6 +116,7 @@ pub fn App() -> impl IntoView {
                     <Route path=path!("/hosts") view=HostsPage/>
                     <Route path=path!("/hosts/:id") view=HostDetailPage/>
                     <Route path=path!("/applications") view=ApplicationsPage/>
+                    <Route path=path!("/applications/:id") view=ApplicationDetailPage/>
                 </Routes>
             </main>
         </Router>

src/bin/seed.rs

@@ -85,5 +85,13 @@ async fn main() {
         .await
         .unwrap_or(0);
 
-    tracing::info!("Database now contains {} network(s) and {} host(s).", network_count, host_count);
+    let application_count: i64 = sqlx::query_scalar("SELECT COUNT(*) FROM applications")
+        .fetch_one(&pool)
+        .await
+        .unwrap_or(0);
+
+    tracing::info!(
+        "Database now contains {} network(s), {} host(s) and {} application(s).",
+        network_count, host_count, application_count
+    );
 }

src/client/application_detail.rs

@@ -0,0 +1,311 @@
+// client/application_detail.rs — Application detail page
+//
+// Shows all information for a single application:
+//   - Identity form  : name — editable, saved with "Save changes"
+//   - Ports section  : ports associated with this application + Add/Remove per port
+//   - Hosts section  : hosts sharing at least one port with this application (read-only)
+//   - Delete button  : confirmation modal, then navigates back to /applications
+
+use leptos::prelude::*;
+use leptos_router::hooks::{use_navigate, use_params_map, use_query_map};
+
+use crate::api::applications::{
+    AddPortToApplication, DeleteApplication, RemovePortFromApplication,
+    UpdateApplication, get_application_detail,
+};
+
+// ─── Delete confirmation modal ────────────────────────────────────────────────
+
+#[component]
+fn DeleteModal(
+    app_name: String,
+    delete_action: ServerAction<DeleteApplication>,
+    app_id: i64,
+    show_modal: RwSignal<bool>,
+) -> impl IntoView {
+    view! {
+        <div class="modal-backdrop" on:click=move |_| show_modal.set(false)>
+            <div class="modal" on:click=move |e| e.stop_propagation()>
+                <div class="modal__header">
+                    <h2>"Delete application"</h2>
+                    <button class="modal__close" type="button" aria-label="Close"
+                        on:click=move |_| show_modal.set(false)>
+                        "×"
+                    </button>
+                </div>
+                <div class="modal__body">
+                    <p class="warning">
+                        "Are you sure you want to delete "
+                        <strong>{app_name}</strong>
+                        "? All port associations will also be removed."
+                    </p>
+                </div>
+                <div class="modal__actions">
+                    <button class="btn-secondary" type="button"
+                        on:click=move |_| show_modal.set(false)>
+                        "Cancel"
+                    </button>
+                    <button class="btn-danger" type="button"
+                        on:click=move |_| { delete_action.dispatch(DeleteApplication { id: app_id }); }>
+                        "Delete"
+                    </button>
+                </div>
+            </div>
+        </div>
+    }.into_any()
+}
+
+// ─── Main page component ──────────────────────────────────────────────────────
+
+#[component]
+pub fn ApplicationDetailPage() -> impl IntoView {
+    let params = use_params_map();
+    let app_id = move || {
+        params.read().get("id")
+            .and_then(|s| s.parse::<i64>().ok())
+            .unwrap_or(0)
+    };
+
+    let query = use_query_map();
+    let back_url = move || {
+        query.read().get("back")
+            .map(|s| s.to_string())
+            .unwrap_or_else(|| "/applications".to_string())
+    };
+    let back_label = move || {
+        if back_url().starts_with("/hosts/") { "← Host" } else { "← Applications" }
+    };
+
+    let update_action      = ServerAction::<UpdateApplication>::new();
+    let add_port_action    = ServerAction::<AddPortToApplication>::new();
+    let remove_port_action = ServerAction::<RemovePortFromApplication>::new();
+    let delete_action      = ServerAction::<DeleteApplication>::new();
+
+    let show_delete_modal = RwSignal::new(false);
+
+    let app = LocalResource::new(move || {
+        let _ = update_action.version().get();
+        let _ = add_port_action.version().get();
+        let _ = remove_port_action.version().get();
+        get_application_detail(app_id())
+    });
+
+    let name_sig = RwSignal::new(String::new());
+    let new_port = RwSignal::new(String::new());
+
+    // Sync the editable name whenever fresh data arrives.
+    Effect::new(move |_| {
+        if let Some(r) = app.get() {
+            if let Ok(ref detail) = *r {
+                name_sig.set(detail.name.clone());
+            }
+        }
+    });
+
+    let navigate = use_navigate();
+    Effect::new(move |_| {
+        if let Some(Ok(true)) = delete_action.value().get() {
+            navigate("/applications", Default::default());
+        }
+    });
+
+    view! {
+        <div class="application-detail-page">
+            // Delete modal lives OUTSIDE <Suspense> so it is not unmounted when
+            // the application resource re-fetches.
+            {move || show_delete_modal.get().then(|| view! {
+                <DeleteModal
+                    app_name=name_sig.get()
+                    delete_action=delete_action
+                    app_id=app_id()
+                    show_modal=show_delete_modal
+                />
+            })}
+
+            <Suspense fallback=|| view! { <p class="empty">"Loading application…"</p> }>
+                {move || app.get().map(|r| match (*r).clone() {
+                    Err(e) => view! {
+                        <p class="error">"Could not load application: " {e.to_string()}</p>
+                    }.into_any(),
+
+                    Ok(detail) => {
+                        let id         = detail.id;
+                        let port_count = detail.ports.len();
+                        let host_count = detail.hosts.len();
+                        let ports      = detail.ports;
+                        let hosts      = detail.hosts;
+
+                        let ports_list = if ports.is_empty() {
+                            view! {
+                                <p class="empty">"No ports associated with this application."</p>
+                            }.into_any()
+                        } else {
+                            view! {
+                                <div class="port-list">
+                                    {ports.into_iter().map(|num| {
+                                        view! {
+                                            <div class="port-row">
+                                                <span class="port-row__number">{num}</span>
+                                                <button
+                                                    class="btn-danger"
+                                                    type="button"
+                                                    on:click=move |_| {
+                                                        remove_port_action.dispatch(
+                                                            RemovePortFromApplication {
+                                                                application_id: id,
+                                                                port_number: num,
+                                                            }
+                                                        );
+                                                    }
+                                                >
+                                                    "Remove"
+                                                </button>
+                                            </div>
+                                        }
+                                    }).collect_view()}
+                                </div>
+                            }.into_any()
+                        };
+
+                        let hosts_list = if hosts.is_empty() {
+                            view! {
+                                <p class="empty">"No hosts share a port with this application."</p>
+                            }.into_any()
+                        } else {
+                            view! {
+                                <div class="app-list">
+                                    {hosts.into_iter().map(|host| {
+                                        view! {
+                                            <div class="app-row">
+                                                <a class="table-link"
+                                                    href=format!("/hosts/{}?back=/applications/{}", host.id, id)>
+                                                    {host.name}
+                                                </a>
+                                                <span class="cell-mono">{host.ip}</span>
+                                            </div>
+                                        }
+                                    }).collect_view()}
+                                </div>
+                            }.into_any()
+                        };
+
+                        view! {
+                            // ── Page header ───────────────────────────────────
+                            <div class="page-header detail-page-header">
+                                <a class="back-btn" href=move || back_url()>
+                                    {move || back_label()}
+                                </a>
+                                <h1 class="detail-page-title">{move || name_sig.get()}</h1>
+                            </div>
+
+                            // ── Identity form ─────────────────────────────────
+                            <section class="detail-section">
+                                <h2 class="detail-section__title">"Identity"</h2>
+                                <div class="detail-form">
+                                    <label class="detail-field">
+                                        "Name"
+                                        <input
+                                            type="text"
+                                            prop:value=move || name_sig.get()
+                                            on:input=move |e| name_sig.set(event_target_value(&e))
+                                        />
+                                    </label>
+
+                                    {move || update_action.value().get()
+                                        .and_then(|r| r.err())
+                                        .map(|e| view! { <p class="error">{e.to_string()}</p> })
+                                    }
+
+                                    <div class="form-actions">
+                                        <button
+                                            class="btn-primary"
+                                            type="button"
+                                            on:click=move |_| {
+                                                update_action.dispatch(UpdateApplication {
+                                                    id,
+                                                    name: name_sig.get_untracked(),
+                                                });
+                                            }
+                                        >
+                                            "Save changes"
+                                        </button>
+                                    </div>
+                                </div>
+                            </section>
+
+                            // ── Ports section ─────────────────────────────────
+                            <section class="detail-section">
+                                <h2 class="detail-section__title">
+                                    {format!("Associated ports ({})", port_count)}
+                                </h2>
+
+                                {ports_list}
+
+                                {move || remove_port_action.value().get()
+                                    .and_then(|r| r.err())
+                                    .map(|e| view! {
+                                        <p class="error">"Remove failed: " {e.to_string()}</p>
+                                    })
+                                }
+
+                                <div class="port-add-row">
+                                    <input
+                                        type="number"
+                                        min="1"
+                                        max="65535"
+                                        placeholder="Port number (1–65535)"
+                                        prop:value=move || new_port.get()
+                                        on:input=move |e| new_port.set(event_target_value(&e))
+                                    />
+                                    <button
+                                        class="btn-primary"
+                                        type="button"
+                                        on:click=move |_| {
+                                            let raw = new_port.get_untracked();
+                                            if let Ok(n) = raw.trim().parse::<i64>() {
+                                                if (1..=65535).contains(&n) {
+                                                    add_port_action.dispatch(AddPortToApplication {
+                                                        application_id: id,
+                                                        port_number: n as u16,
+                                                    });
+                                                    new_port.set(String::new());
+                                                }
+                                            }
+                                        }
+                                    >
+                                        "Add port"
+                                    </button>
+                                    {move || add_port_action.value().get()
+                                        .and_then(|r| r.err())
+                                        .map(|e| view! {
+                                            <p class="error">"Add failed: " {e.to_string()}</p>
+                                        })
+                                    }
+                                </div>
+                            </section>
+
+                            // ── Hosts section (read-only — linked via shared ports) ──
+                            <section class="detail-section">
+                                <h2 class="detail-section__title">
+                                    {format!("Linked hosts ({})", host_count)}
+                                </h2>
+                                {hosts_list}
+                            </section>
+
+                            // ── Danger zone ───────────────────────────────────
+                            <div class="danger-zone">
+                                <button
+                                    class="btn-danger-solid"
+                                    type="button"
+                                    on:click=move |_| show_delete_modal.set(true)
+                                >
+                                    "Delete application"
+                                </button>
+                            </div>
+                        }.into_any()
+                    }
+                })}
+            </Suspense>
+        </div>
+    }.into_any()
+}

src/client/applications.rs

@@ -8,6 +8,7 @@
 
 use leptos::prelude::*;
 use leptos::form::ActionForm;
+use leptos::html::Input;
 
 use crate::api::applications::{
     ApplicationWithCounts, CreateApplication, DeleteApplication,
@@ -21,19 +22,33 @@ fn AddApplicationModal(
     create_action: ServerAction<CreateApplication>,
     show_modal: RwSignal<bool>,
 ) -> impl IntoView {
-    Effect::new(move |_| {
+    use leptos::task::spawn_local;
-        if let Some(Ok(_)) = create_action.value().get() {
+
-            show_modal.set(false);
+    let name_ref = NodeRef::<Input>::new();
+
+    // Defer focus to the next microtask so the element is in the DOM.
+    // Using get_untracked() avoids subscribing to NodeRef's reactive signal,
+    // which would otherwise re-trigger during modal unmount and cause
+    // "closure invoked after being dropped" in wasm-bindgen.
+    spawn_local(async move {
+        if let Some(el) = name_ref.get_untracked() {
+            let _ = el.focus();
         }
     });
 
+    // close() defers show_modal.set(false) to the next microtask.
+    // Without this, setting the signal synchronously inside a click handler
+    // unmounts the modal (and frees its closures) while the handler is still
+    // on the call stack, causing wasm-bindgen to panic.
+    let close = move || spawn_local(async move { show_modal.set(false) });
+
     view! {
-        <div class="modal-backdrop" on:click=move |_| show_modal.set(false)>
+        <div class="modal-backdrop" on:click=move |_| close()>
             <div class="modal" on:click=move |e| e.stop_propagation()>
                 <div class="modal__header">
                     <h2>"Add an application"</h2>
                     <button class="modal__close" type="button" aria-label="Close"
-                        on:click=move |_| show_modal.set(false)>
+                        on:click=move |_| close()>
                         "×"
                     </button>
                 </div>
@@ -43,17 +58,27 @@ fn AddApplicationModal(
                         <label>
                             "Name"
                             <input
+                                node_ref=name_ref
                                 type="text"
                                 name="name"
                                 placeholder="e.g. Nginx, PostgreSQL, Prometheus"
                                 required
                             />
                         </label>
+                        <label>
+                            "Associated ports"
+                            <input
+                                type="text"
+                                name="ports"
+                                placeholder="e.g. 22, 80, 443"
+                            />
+                            <span class="field-hint">"Comma-separated port numbers"</span>
+                        </label>
                     </div>
 
                     <div class="modal__actions">
                         <button class="btn-secondary" type="button"
-                            on:click=move |_| show_modal.set(false)>
+                            on:click=move |_| close()>
                             "Cancel"
                         </button>
                         <button type="submit">"Add application"</button>
@@ -132,6 +157,19 @@ pub fn ApplicationsPage() -> impl IntoView {
     // Name filter (client-side — list is typically small)
     let name_filter = RwSignal::new(String::new());
 
+    // Close the add modal when the action transitions pending→done with Ok.
+    // Lives in the parent so it is never recreated across modal open/close cycles,
+    // which avoids the stale-value re-trigger bug.
+    Effect::new(move |was_pending: Option<bool>| {
+        let is_pending = create_action.pending().get();
+        if was_pending == Some(true) && !is_pending {
+            if let Some(Ok(_)) = create_action.value().get() {
+                show_modal.set(false);
+            }
+        }
+        is_pending
+    });
+
     // Close the delete modal automatically after a successful deletion.
     Effect::new(move |_| {
         if let Some(Ok(_)) = delete_action.value().get() {
@@ -225,10 +263,15 @@ pub fn ApplicationsPage() -> impl IntoView {
                                                     let app_clone = app.clone();
                                                     view! {
                                                         <tr>
-                                                            <td>{app.name}</td>
+                                                            <td>
+                                                                <a class="table-link"
+                                                                    href=format!("/applications/{}", app.id)>
+                                                                    {app.name}
+                                                                </a>
+                                                            </td>
                                                             <td class="col-count">{app.host_count}</td>
                                                             <td class="col-actions">
-                                                                <button on:click=move |_| {
+                                                                <button class="btn-danger" on:click=move |_| {
                                                                     pending_delete.set(Some(app_clone.clone()));
                                                                 }>
                                                                     "Delete"

src/client/host_detail.rs

@@ -3,15 +3,175 @@
 // Shows all information for a single host:
 //   - Identity form     : name, IP, network dropdown — editable, saved with "Save changes"
 //   - Ports section     : full list with Remove per port + Add port input
+//   - Applications      : directly linked apps with Remove + modal multi-select to add
 //   - Delete button     : opens a confirmation modal, then navigates back to /hosts
 
 use leptos::prelude::*;
 use leptos_router::hooks::{use_navigate, use_params_map, use_query_map};
 
 use crate::api::{
-    hosts::{AddHostPort, DeleteHost, RemoveHostPort, UpdateHost, get_host_detail},
+    hosts::{
+        AddHostApplications, AddHostPort, DeleteHost, RemoveHostApplication,
+        RemoveHostPort, UpdateHost, get_applications_not_on_host, get_host_detail,
+    },
     networks::get_networks,
 };
+use crate::models::Application;
+
+// ─── Add applications modal ───────────────────────────────────────────────────
+
+// Scrollable pick list + selected tags:
+//   - Top: scrollable list of available apps; clicking one moves it to the
+//     selected section and removes it from the list.
+//   - Bottom: selected apps shown as removable tags; clicking × puts the app
+//     back in the list.
+//
+// The auto-close Effect lives in the PARENT to avoid the re-trigger bug
+// (an Effect inside a conditionally-rendered component fires on mount and
+// would immediately close the modal if the action already held a past Ok value).
+#[component]
+fn AddAppModal(
+    host_id: i64,
+    available_apps_res: LocalResource<Result<Vec<Application>, ServerFnError>>,
+    add_action: ServerAction<AddHostApplications>,
+    show_modal: RwSignal<bool>,
+) -> impl IntoView {
+    // Full Application structs so names are available in the selected tag list.
+    let selected: RwSignal<Vec<Application>> = RwSignal::new(vec![]);
+
+    view! {
+        <div class="modal-backdrop" on:click=move |_| show_modal.set(false)>
+            <div class="modal" on:click=move |e| e.stop_propagation()>
+                <div class="modal__header">
+                    <h2>"Add applications"</h2>
+                    <button class="modal__close" type="button" aria-label="Close"
+                        on:click=move |_| show_modal.set(false)>
+                        "×"
+                    </button>
+                </div>
+
+                <div class="modal__body">
+
+                    // ── Scrollable pick list ──────────────────────────────────
+                    {move || match available_apps_res.get() {
+                        None => view! { <p class="empty">"Loading…"</p> }.into_any(),
+                        Some(r) => match (*r).clone() {
+                            Err(e) => view! {
+                                <p class="error">
+                                    "Could not load applications: " {e.to_string()}
+                                </p>
+                            }.into_any(),
+                            Ok(apps) => {
+                                // Exclude already-selected apps from the displayed list.
+                                let sel_ids: Vec<i64> = selected.get()
+                                    .iter().map(|a| a.id).collect();
+                                let displayed: Vec<Application> = apps.into_iter()
+                                    .filter(|a| !sel_ids.contains(&a.id))
+                                    .collect();
+
+                                if displayed.is_empty() && sel_ids.is_empty() {
+                                    view! {
+                                        <p class="empty">
+                                            "All applications are already linked to this host."
+                                        </p>
+                                    }.into_any()
+                                } else if displayed.is_empty() {
+                                    view! {
+                                        <p class="empty">
+                                            "All available applications have been selected."
+                                        </p>
+                                    }.into_any()
+                                } else {
+                                    view! {
+                                        <ul class="app-pick-list">
+                                            {displayed.into_iter().map(|app| {
+                                                let app_clone = app.clone();
+                                                view! {
+                                                    <li class="app-pick-item"
+                                                        on:click=move |_| {
+                                                            selected.update(|v| {
+                                                                v.push(app_clone.clone());
+                                                            });
+                                                        }
+                                                    >
+                                                        <span>{app.name}</span>
+                                                        <span class="app-pick-item__add">"+"</span>
+                                                    </li>
+                                                }
+                                            }).collect_view()}
+                                        </ul>
+                                    }.into_any()
+                                }
+                            }
+                        }
+                    }}
+
+                    // ── Selected tags (shown once at least one app is chosen) ─
+                    {move || (!selected.get().is_empty()).then(|| {
+                        let sel = selected.get();
+                        view! {
+                            <div class="app-selected-section">
+                                <span class="app-selected-label">"Selected:"</span>
+                                <div class="app-selected-list">
+                                    {sel.into_iter().map(|app| {
+                                        let app_id = app.id;
+                                        view! {
+                                            <span class="app-selected-tag">
+                                                {app.name}
+                                                <button
+                                                    class="app-selected-tag__remove"
+                                                    type="button"
+                                                    aria-label="Remove"
+                                                    on:click=move |_| {
+                                                        selected.update(|v| {
+                                                            v.retain(|x| x.id != app_id);
+                                                        });
+                                                    }
+                                                >"×"</button>
+                                            </span>
+                                        }
+                                    }).collect_view()}
+                                </div>
+                            </div>
+                        }
+                    })}
+
+                    {move || add_action.value().get()
+                        .and_then(|r| r.err())
+                        .map(|e| view! { <p class="error">{e.to_string()}</p> })
+                    }
+                </div>
+
+                <div class="modal__actions">
+                    <button class="btn-secondary" type="button"
+                        on:click=move |_| show_modal.set(false)>
+                        "Cancel"
+                    </button>
+                    <button
+                        class="btn-primary"
+                        type="button"
+                        disabled={move || selected.get().is_empty()}
+                        on:click=move |_| {
+                            let ids_str = selected.get_untracked()
+                                .iter()
+                                .map(|a| a.id.to_string())
+                                .collect::<Vec<_>>()
+                                .join(",");
+                            if !ids_str.is_empty() {
+                                add_action.dispatch(AddHostApplications {
+                                    host_id,
+                                    application_ids: ids_str,
+                                });
+                            }
+                        }
+                    >
+                        "Add selected"
+                    </button>
+                </div>
+            </div>
+        </div>
+    }.into_any()
+}
 
 // ─── Delete confirmation modal ────────────────────────────────────────────────
 
@@ -36,7 +196,7 @@ fn DeleteModal(
                     <p class="warning">
                         "Are you sure you want to delete "
                         <strong>{host_name}</strong>
-                        "? All port associations will also be removed."
+                        "? All port and application associations will also be removed."
                     </p>
                 </div>
                 <div class="modal__actions">
@@ -58,8 +218,6 @@ fn DeleteModal(
 
 #[component]
 pub fn HostDetailPage() -> impl IntoView {
-    // Read the `:id` segment from the URL.
-    // `use_params_map()` returns a reactive map of all URL path parameters.
     let params = use_params_map();
     let host_id = move || {
         params.read().get("id")
@@ -67,8 +225,6 @@ pub fn HostDetailPage() -> impl IntoView {
             .unwrap_or(0)
     };
 
-    // Optional `?back=<url>` query parameter — used when arriving from a network
-    // detail page so the back button returns there instead of the hosts list.
     let query = use_query_map();
     let back_url = move || {
         query.read().get("back")
@@ -76,53 +232,74 @@ pub fn HostDetailPage() -> impl IntoView {
             .unwrap_or_else(|| "/hosts".to_string())
     };
     let back_label = move || {
-        if back_url().starts_with("/networks/") { "← Network" } else { "← Hosts" }
+        if back_url().starts_with("/networks/")     { "← Network" }
+        else if back_url().starts_with("/applications/") { "← Application" }
+        else { "← Hosts" }
     };
 
     let update_action      = ServerAction::<UpdateHost>::new();
     let add_port_action    = ServerAction::<AddHostPort>::new();
     let remove_port_action = ServerAction::<RemoveHostPort>::new();
+    let add_app_action     = ServerAction::<AddHostApplications>::new();
+    let remove_app_action  = ServerAction::<RemoveHostApplication>::new();
     let delete_action      = ServerAction::<DeleteHost>::new();
 
     let show_delete_modal  = RwSignal::new(false);
+    let show_add_app_modal = RwSignal::new(false);
 
-    // Reload detail after any mutation that touches this host.
+    // Auto-close the add-app modal when the action completes successfully.
-    // The resource key includes action versions so it invalidates automatically.
+    // Lives here (not inside AddAppModal) so it is never recreated across modal open/close cycles.
-    let host = Resource::new(
+    Effect::new(move |was_pending: Option<bool>| {
-        move || (
+        let is_pending = add_app_action.pending().get();
-            host_id(),
+        if was_pending == Some(true) && !is_pending {
-            update_action.version().get(),
+            if let Some(Ok(_)) = add_app_action.value().get() {
-            add_port_action.version().get(),
+                show_add_app_modal.set(false);
-            remove_port_action.version().get(),
+            }
-        ),
+        }
-        |(id, _, _, _)| get_host_detail(id),
+        is_pending
-    );
+    });
+
+    // LocalResource avoids reading the resource outside <Suspense> during hydration,
+    // which would cause a mismatch between the SSR-rendered fallback and the content
+    // the WASM expects to find after the resource resolves.
+    let host = LocalResource::new(move || {
+        let _ = update_action.version().get();
+        let _ = add_port_action.version().get();
+        let _ = remove_port_action.version().get();
+        let _ = add_app_action.version().get();
+        let _ = remove_app_action.version().get();
+        get_host_detail(host_id())
+    });
 
     // Networks dropdown — LocalResource avoids SSR/hydration mismatch.
     let networks_res = LocalResource::new(|| get_networks());
 
-    // Edit-field signals, populated once by the Effect below.
+    // Available apps for the modal: re-fetched whenever add/remove completes.
-    // Using signals (rather than local variables) keeps them stable across
+    let add_app_ver    = add_app_action.version();
-    // re-renders and lets the user edit without triggering a resource reload.
+    let remove_app_ver = remove_app_action.version();
+    let available_apps_res = LocalResource::new(move || {
+        let _ = add_app_ver.get();
+        let _ = remove_app_ver.get();
+        get_applications_not_on_host(host_id())
+    });
+
     let name_sig   = RwSignal::new(String::new());
     let ip_sig     = RwSignal::new(String::new());
     let net_id_sig = RwSignal::new(0i64);
-
-    // Input value for the "add port" row.
     let new_port   = RwSignal::new(String::new());
 
-    // Sync edit signals whenever the host resource delivers fresh data.
+    // Sync edit signals whenever fresh host data arrives.
-    // This runs on initial load and after every successful mutation.
+    // LocalResource wraps its value in SendWrapper, so we dereference with `*r`.
     Effect::new(move |_| {
-        if let Some(Ok(ref detail)) = host.get() {
+        if let Some(r) = host.get() {
+            if let Ok(ref detail) = *r {
                 name_sig.set(detail.name.clone());
                 ip_sig.set(detail.ip.clone());
                 net_id_sig.set(detail.network_id);
             }
+        }
     });
 
-    // Navigate back to the list after a successful delete.
-    // `use_navigate()` must be called during component setup (not inside a closure).
     let navigate = use_navigate();
     Effect::new(move |_| {
         if let Some(Ok(true)) = delete_action.value().get() {
@@ -132,17 +309,37 @@ pub fn HostDetailPage() -> impl IntoView {
 
     view! {
         <div class="host-detail-page">
+            // Modals live OUTSIDE <Suspense> so they are not unmounted when the
+            // host resource re-fetches (which would kill their reactive subscriptions).
+            {move || show_add_app_modal.get().then(|| view! {
+                <AddAppModal
+                    host_id=host_id()
+                    available_apps_res=available_apps_res
+                    add_action=add_app_action
+                    show_modal=show_add_app_modal
+                />
+            })}
+            {move || show_delete_modal.get().then(|| view! {
+                <DeleteModal
+                    host_name=name_sig.get()
+                    delete_action=delete_action
+                    host_id=host_id()
+                    show_modal=show_delete_modal
+                />
+            })}
+
             <Suspense fallback=|| view! { <p class="empty">"Loading host…"</p> }>
-                {move || host.get().map(|result| match result {
+                {move || host.get().map(|r| match (*r).clone() {
                     Err(e) => view! {
                         <p class="error">"Could not load host: " {e.to_string()}</p>
                     }.into_any(),
 
                     Ok(detail) => {
                         let id           = detail.id;
-                        let modal_name  = detail.name.clone();
                         let port_count   = detail.ports.len();
+                        let app_count    = detail.applications.len();
                         let ports        = detail.ports;
+                        let applications = detail.applications;
 
                         // Pre-built ports view — consumes `ports` once, not reactively.
                         let ports_list = if ports.is_empty() {
@@ -178,6 +375,40 @@ pub fn HostDetailPage() -> impl IntoView {
                             }.into_any()
                         };
 
+                        // Pre-built applications view.
+                        let apps_list = if applications.is_empty() {
+                            view! {
+                                <p class="empty">"No applications linked to this host."</p>
+                            }.into_any()
+                        } else {
+                            view! {
+                                <div class="app-list">
+                                    {applications.into_iter().map(|app| {
+                                        let app_id = app.id;
+                                        view! {
+                                            <div class="app-row">
+                                                <a class="table-link app-row__name"
+                                                    href=format!("/applications/{}?back=/hosts/{}", app_id, id)>
+                                                    {app.name}
+                                                </a>
+                                                <button
+                                                    class="btn-danger"
+                                                    type="button"
+                                                    on:click=move |_| {
+                                                        remove_app_action.dispatch(
+                                                            RemoveHostApplication { host_id: id, application_id: app_id }
+                                                        );
+                                                    }
+                                                >
+                                                    "Remove"
+                                                </button>
+                                            </div>
+                                        }
+                                    }).collect_view()}
+                                </div>
+                            }.into_any()
+                        };
+
                         view! {
                             // ── Page header ──────────────────────────────────
                             <div class="page-header detail-page-header">
@@ -223,7 +454,7 @@ pub fn HostDetailPage() -> impl IntoView {
                                                         view! {
                                                             <option
                                                                 value=n.id.to_string()
-                                                                selected=(n.id == current)
+                                                                selected=n.id == current
                                                             >
                                                                 {label}
                                                             </option>
@@ -273,7 +504,6 @@ pub fn HostDetailPage() -> impl IntoView {
                                     })
                                 }
 
-                                // Add port row
                                 <div class="port-add-row">
                                     <input
                                         type="number"
@@ -310,7 +540,33 @@ pub fn HostDetailPage() -> impl IntoView {
                                 </div>
                             </section>
 
-                            // ── Danger zone ──────────────────────────────────
+                            // ── Applications section ──────────────────────────
+                            <section class="detail-section">
+                                <h2 class="detail-section__title">
+                                    {format!("Applications ({})", app_count)}
+                                </h2>
+
+                                {apps_list}
+
+                                {move || remove_app_action.value().get()
+                                    .and_then(|r| r.err())
+                                    .map(|e| view! {
+                                        <p class="error">"Remove failed: " {e.to_string()}</p>
+                                    })
+                                }
+
+                                <div class="port-add-row">
+                                    <button
+                                        class="btn-primary"
+                                        type="button"
+                                        on:click=move |_| show_add_app_modal.set(true)
+                                    >
+                                        "+ Add applications"
+                                    </button>
+                                </div>
+                            </section>
+
+                            // ── Danger zone ───────────────────────────────────
                             <div class="danger-zone">
                                 <button
                                     class="btn-danger-solid"
@@ -320,16 +576,6 @@ pub fn HostDetailPage() -> impl IntoView {
                                     "Delete host"
                                 </button>
                             </div>
-
-                            // ── Delete modal (conditional) ────────────────────
-                            {move || show_delete_modal.get().then(|| view! {
-                                <DeleteModal
-                                    host_name=modal_name.clone()
-                                    delete_action=delete_action
-                                    host_id=id
-                                    show_modal=show_delete_modal
-                                />
-                            })}
                         }.into_any()
                     }
                 })}

src/client/hosts.rs

@@ -12,6 +12,7 @@
 
 use leptos::prelude::*;
 use leptos::form::ActionForm;
+use leptos::html::Input;
 
 use crate::api::{
     applications::get_applications,
@@ -76,15 +77,20 @@ fn AddHostModal(
     networks_res: LocalResource<Result<Vec<crate::models::Network>, ServerFnError>>,
     show_modal: RwSignal<bool>,
 ) -> impl IntoView {
-    // Close the modal automatically after a successful creation.
+    use leptos::task::spawn_local;
-    Effect::new(move |_| {
+
-        if let Some(Ok(_)) = create_action.value().get() {
+    let name_ref = NodeRef::<Input>::new();
-            show_modal.set(false);
+
+    spawn_local(async move {
+        if let Some(el) = name_ref.get_untracked() {
+            let _ = el.focus();
         }
     });
 
+    let close = move || spawn_local(async move { show_modal.set(false) });
+
     view! {
-        <div class="modal-backdrop" on:click=move |_| show_modal.set(false)>
+        <div class="modal-backdrop" on:click=move |_| close()>
             <div class="modal" on:click=move |e| e.stop_propagation()>
                 <div class="modal__header">
                     <h2>"Add a host"</h2>
@@ -92,7 +98,7 @@ fn AddHostModal(
                         class="modal__close"
                         type="button"
                         aria-label="Close"
-                        on:click=move |_| show_modal.set(false)
+                        on:click=move |_| close()
                     >"×"</button>
                 </div>
 
@@ -100,7 +106,7 @@ fn AddHostModal(
                     <div class="add-form__fields">
                         <label>
                             "Name"
-                            <input type="text" name="name" placeholder="e.g. web-server-01" required/>
+                            <input node_ref=name_ref type="text" name="name" placeholder="e.g. web-server-01" required/>
                         </label>
                         <label>
                             "IP address"
@@ -134,7 +140,7 @@ fn AddHostModal(
                         <button
                             class="btn-secondary"
                             type="button"
-                            on:click=move |_| show_modal.set(false)
+                            on:click=move |_| close()
                         >"Cancel"</button>
                         <button type="submit">"Add host"</button>
                     </div>
@@ -287,12 +293,12 @@ fn PaginationBar(
 
 #[component]
 fn HostTable(
-    hosts: Resource<Result<HostsPageData, ServerFnError>>,
+    hosts: LocalResource<Result<HostsPageData, ServerFnError>>,
     pending_delete: RwSignal<Option<(i64, String)>>,
 ) -> impl IntoView {
     view! {
         <Suspense fallback=|| view! { <p class="empty">"Loading hosts…"</p> }>
-            {move || hosts.get().map(|result| match result {
+            {move || hosts.get().map(|r| match (*r).clone() {
                 Err(e) => view! {
                     <p class="error">"Could not load hosts: " {e.to_string()}</p>
                 }.into_any(),
@@ -364,6 +370,17 @@ pub fn HostsPage() -> impl IntoView {
     // None = no modal, Some((id, name)) = delete confirmation open.
     let pending_delete: RwSignal<Option<(i64, String)>> = RwSignal::new(None);
 
+    // Close the add modal on pending→done with Ok (lives in parent to avoid stale-value re-trigger).
+    Effect::new(move |was_pending: Option<bool>| {
+        let is_pending = create_action.pending().get();
+        if was_pending == Some(true) && !is_pending {
+            if let Some(Ok(_)) = create_action.value().get() {
+                show_modal.set(false);
+            }
+        }
+        is_pending
+    });
+
     // Close the delete modal automatically after a successful deletion.
     Effect::new(move |_| {
         if let Some(Ok(_)) = delete_action.value().get() {
@@ -380,28 +397,30 @@ pub fn HostsPage() -> impl IntoView {
     let page     = RwSignal::new(1i64);
     let per_page = RwSignal::new(15i64);
 
-    let hosts = Resource::new(
+    // LocalResource avoids reading a resource outside <Suspense> during hydration.
-        move || (
+    // All dependencies (filters, pagination, action versions) are client-side only,
+    // so there is no benefit to SSR for this resource.
+    let hosts = LocalResource::new(move || {
+        let _ = create_action.version().get();
+        let _ = delete_action.version().get();
+        get_hosts_page(
             name_filter.get(),
             network_id_filter.get(),
             port_filter.get(),
             app_id_filter.get(),
             page.get(),
             per_page.get(),
-            create_action.version().get(),
+        )
-            delete_action.version().get(),
+    });
-        ),
-        |(name, net, port, app, p, pp, _, _)| get_hosts_page(name, net, port, app, p, pp),
-    );
 
     let networks_res     = LocalResource::new(|| get_networks());
     let applications_res = LocalResource::new(|| get_applications());
 
     let total_pages = Signal::derive(move || {
-        hosts.get().and_then(|r| r.ok()).map(|p| p.total_pages).unwrap_or(1)
+        hosts.get().and_then(|r| (*r).clone().ok()).map(|p| p.total_pages).unwrap_or(1)
     });
     let total = Signal::derive(move || {
-        hosts.get().and_then(|r| r.ok()).map(|p| p.total).unwrap_or(0)
+        hosts.get().and_then(|r| (*r).clone().ok()).map(|p| p.total).unwrap_or(0)
     });
 
     view! {

src/client/mod.rs

@@ -9,6 +9,7 @@
 // Do not place code here that requires browser-only APIs (window, document...)
 // without guarding it with `#[cfg(target_arch = "wasm32")]`.
 
+pub mod application_detail; // Application detail: identity, ports, linked hosts, delete
 pub mod applications;       // Applications list and creation
 pub mod home;               // Home page
 pub mod host_detail;        // Host detail: identity, ports, edit, delete

src/server/repository/applications.rs

@@ -42,6 +42,18 @@ pub async fn create_application(pool: &AnyPool, name: &str) -> Result<Applicatio
     Ok(row_to_application(&row))
 }
 
+/// Updates the name of an application. Returns the updated record.
+pub async fn update_application(pool: &AnyPool, id: i64, name: &str) -> Result<Application, DbError> {
+    let row = sqlx::query(
+        "UPDATE applications SET name = $1 WHERE id = $2 RETURNING id, name",
+    )
+    .bind(name)
+    .bind(id)
+    .fetch_one(pool)
+    .await?;
+    Ok(row_to_application(&row))
+}
+
 /// Deletes an application and its port associations (via `ON DELETE CASCADE`).
 ///
 /// Returns `true` if a row was deleted, `false` if the id did not exist.
@@ -54,6 +66,84 @@ pub async fn delete_application(pool: &AnyPool, id: i64) -> Result<bool, DbError
     Ok(result.rows_affected() > 0)
 }
 
+// ─── Host-application associations ───────────────────────────────────────────
+
+/// Returns all applications linked directly to a host, ordered by name.
+pub async fn list_applications_for_host(
+    pool: &AnyPool,
+    host_id: i64,
+) -> Result<Vec<Application>, DbError> {
+    let rows = sqlx::query(
+        "SELECT a.id, a.name
+         FROM applications a
+         JOIN host_applications ha ON ha.application_id = a.id
+         WHERE ha.host_id = $1
+         ORDER BY a.name",
+    )
+    .bind(host_id)
+    .fetch_all(pool)
+    .await?;
+    Ok(rows.iter().map(row_to_application).collect())
+}
+
+/// Returns all applications NOT yet linked to a host, ordered by name.
+pub async fn list_applications_not_on_host(
+    pool: &AnyPool,
+    host_id: i64,
+) -> Result<Vec<Application>, DbError> {
+    let rows = sqlx::query(
+        "SELECT id, name FROM applications
+         WHERE id NOT IN (
+             SELECT application_id FROM host_applications WHERE host_id = $1
+         )
+         ORDER BY name",
+    )
+    .bind(host_id)
+    .fetch_all(pool)
+    .await?;
+    Ok(rows.iter().map(row_to_application).collect())
+}
+
+/// Links an application directly to a host.
+///
+/// If the link already exists, this is a no-op (not an error).
+pub async fn add_application_to_host(
+    pool: &AnyPool,
+    host_id: i64,
+    application_id: i64,
+) -> Result<(), DbError> {
+    let result = sqlx::query(
+        "INSERT INTO host_applications (host_id, application_id) VALUES ($1, $2)",
+    )
+    .bind(host_id)
+    .bind(application_id)
+    .execute(pool)
+    .await;
+    match result {
+        Ok(_) => Ok(()),
+        Err(sqlx::Error::Database(ref e)) if e.is_unique_violation() => Ok(()),
+        Err(e) => Err(DbError::Connection(e)),
+    }
+}
+
+/// Removes the direct link between a host and an application.
+///
+/// Returns `true` if the association existed and was removed.
+pub async fn remove_application_from_host(
+    pool: &AnyPool,
+    host_id: i64,
+    application_id: i64,
+) -> Result<bool, DbError> {
+    let result = sqlx::query(
+        "DELETE FROM host_applications WHERE host_id = $1 AND application_id = $2",
+    )
+    .bind(host_id)
+    .bind(application_id)
+    .execute(pool)
+    .await?;
+    Ok(result.rows_affected() > 0)
+}
+
 // ─── Application-port associations ───────────────────────────────────────────
 
 /// Returns all port numbers associated with an application, sorted numerically.

style/rust-ipam.css

@@ -1223,3 +1223,125 @@ td.col-actions {
   color: var(--text-secondary);
   margin: 0;
 }
+
+/* ============================================================
+   HOST DETAIL — APPLICATIONS SECTION
+   ============================================================ */
+
+/* List of applications linked to a host (mirrors .port-list) */
+.app-list {
+  display: flex;
+  flex-direction: column;
+  margin-bottom: var(--size-md);
+  border-top: 1px solid var(--border);
+}
+
+.app-row {
+  display: flex;
+  align-items: center;
+  gap: var(--size-md);
+  padding: var(--size-sm) var(--size-xs);
+  border-bottom: 1px solid var(--border);
+}
+
+.app-row__name {
+  flex: 1;
+  font-size: var(--font-sm);
+}
+
+/* ── Pick list (scrollable, click to select) ── */
+.app-pick-list {
+  list-style: none;
+  margin: 0 0 var(--size-sm);
+  padding: 0;
+  max-height: 220px;
+  overflow-y: auto;
+  border: 1px solid var(--border);
+  border-radius: 6px;
+}
+
+.app-pick-item {
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+  padding: var(--size-sm) var(--size-md);
+  cursor: pointer;
+  font-size: var(--font-sm);
+  border-bottom: 1px solid var(--border);
+  transition: background 0.1s;
+}
+
+.app-pick-item:last-child {
+  border-bottom: none;
+}
+
+.app-pick-item:hover {
+  background: color-mix(in srgb, var(--accent) 10%, transparent);
+  color: var(--accent);
+}
+
+.app-pick-item__add {
+  font-size: 1.1rem;
+  font-weight: 600;
+  color: var(--accent);
+  opacity: 0.7;
+}
+
+.app-pick-item:hover .app-pick-item__add {
+  opacity: 1;
+}
+
+/* ── Selected tags (shown below the pick list) ── */
+.app-selected-section {
+  display: flex;
+  flex-direction: column;
+  gap: var(--size-xs);
+  padding-top: var(--size-sm);
+  border-top: 1px solid var(--border);
+  margin-top: var(--size-xs);
+}
+
+.app-selected-label {
+  font-size: var(--font-xs, 0.75rem);
+  font-weight: 600;
+  text-transform: uppercase;
+  letter-spacing: 0.05em;
+  color: var(--text-secondary);
+}
+
+.app-selected-list {
+  display: flex;
+  flex-wrap: wrap;
+  gap: var(--size-xs);
+}
+
+.app-selected-tag {
+  display: inline-flex;
+  align-items: center;
+  gap: 4px;
+  padding: 2px 8px 2px 10px;
+  border-radius: 999px;
+  background: color-mix(in srgb, var(--accent) 15%, transparent);
+  border: 1px solid color-mix(in srgb, var(--accent) 40%, transparent);
+  color: var(--accent);
+  font-size: var(--font-sm);
+  font-weight: 500;
+}
+
+.app-selected-tag__remove {
+  display: inline-flex;
+  align-items: center;
+  justify-content: center;
+  background: none;
+  border: none;
+  padding: 0 2px;
+  cursor: pointer;
+  font-size: 0.9rem;
+  color: var(--accent);
+  opacity: 0.7;
+  line-height: 1;
+}
+
+.app-selected-tag__remove:hover {
+  opacity: 1;
+}