diff --git a/core/archipelago/src/fips/app_ports.rs b/core/archipelago/src/fips/app_ports.rs
new file mode 100644
index 00000000..2f8d25e5
--- /dev/null
+++ b/core/archipelago/src/fips/app_ports.rs
@@ -0,0 +1,44 @@
+//! Generated by scripts/generate-app-catalog.py. Do not edit manually.
+//!
+//! Catalog app launch ports (the web UIs the companion opens by direct
+//! port). Used to write the fips0 firewall allowance drop-in so app UIs
+//! are reachable over the mesh; ports of apps that aren't installed have
+//! no listener, so allowing them is inert.
+
+pub const APP_LAUNCH_PORTS: &[u16] = &[
+    2283,
+    2342,
+    3000,
+    3001,
+    3002,
+    4080,
+    5180,
+    7778,
+    8080,
+    8081,
+    8082,
+    8083,
+    8084,
+    8085,
+    8087,
+    8088,
+    8089,
+    8090,
+    8096,
+    8123,
+    8175,
+    8176,
+    8240,
+    8334,
+    8888,
+    8999,
+    9000,
+    9100,
+    10380,
+    11434,
+    18081,
+    18083,
+    23000,
+    32838,
+    50002,
+];
diff --git a/core/archipelago/src/fips/config.rs b/core/archipelago/src/fips/config.rs
index 29112ac1..3dff85ce 100644
--- a/core/archipelago/src/fips/config.rs
+++ b/core/archipelago/src/fips/config.rs
@@ -252,6 +252,29 @@ pub async fn install(identity_dir: &Path) -> Result<()> {
     let nft_install = sudo_install_file(&nft_stage, "/etc/fips/fips.d/80-web-ui.nft", "0644").await;
     let _ = tokio::fs::remove_file(&nft_stage).await;
     nft_install?;
+
+    // App launch ports: the companion opens catalog apps by direct port
+    // over the mesh. Ports of apps that aren't installed have no listener,
+    // so the allowance is inert until an app exists to answer.
+    let port_list = super::app_ports::APP_LAUNCH_PORTS
+        .iter()
+        .map(|p| p.to_string())
+        .collect::<Vec<_>>()
+        .join(", ");
+    let app_dropin = format!(
+        "# Written by archipelago on every daemon config install.\n\
+         # Catalog app launch ports (web UIs) allowed through the fips0\n\
+         # default-deny inbound baseline. Service/RPC ports stay closed.\n\
+         tcp dport {{ {port_list} }} accept\n"
+    );
+    let app_stage = std::env::temp_dir().join(format!("fips-appports-{}.nft", std::process::id()));
+    tokio::fs::write(&app_stage, app_dropin)
+        .await
+        .context("Failed to stage app-ports nft drop-in")?;
+    let app_install =
+        sudo_install_file(&app_stage, "/etc/fips/fips.d/85-app-ports.nft", "0644").await;
+    let _ = tokio::fs::remove_file(&app_stage).await;
+    app_install?;
     // Make the allowance live immediately; a no-op error when the
     // hardening baseline isn't installed on this node yet.
     if tokio::fs::try_exists("/etc/fips/fips.nft").await.unwrap_or(false) {
diff --git a/core/archipelago/src/fips/mod.rs b/core/archipelago/src/fips/mod.rs
index bbbcfa38..e8a26511 100644
--- a/core/archipelago/src/fips/mod.rs
+++ b/core/archipelago/src/fips/mod.rs
@@ -26,6 +26,7 @@
 #![allow(dead_code)]
 
 pub mod anchors;
+pub mod app_ports;
 pub mod config;
 pub mod dial;
 pub mod iface;
diff --git a/scripts/generate-app-catalog.py b/scripts/generate-app-catalog.py
index 6ee7a96e..09445b0b 100644
--- a/scripts/generate-app-catalog.py
+++ b/scripts/generate-app-catalog.py
@@ -141,6 +141,32 @@ def render_app_session_config(manifests: dict[str, dict[str, Any]]) -> str:
     return "\n".join(lines)
 
 
+def render_rust_ports(ports: dict[str, int], extra_ports: list[int]) -> str:
+    """Rust constant of catalog launch ports for the fips0 firewall drop-in
+    (core/archipelago/src/fips/app_ports.rs). Extra ports cover the frontend's
+    APP_PORTS overrides (companions/aliases) that have no manifest of their own.
+    """
+    distinct = sorted(set(list(ports.values()) + extra_ports))
+    lines = [
+        "//! Generated by scripts/generate-app-catalog.py. Do not edit manually.",
+        "//!",
+        "//! Catalog app launch ports (the web UIs the companion opens by direct",
+        "//! port). Used to write the fips0 firewall allowance drop-in so app UIs",
+        "//! are reachable over the mesh; ports of apps that aren\'t installed have",
+        "//! no listener, so allowing them is inert.",
+        "",
+        "pub const APP_LAUNCH_PORTS: &[u16] = &[",
+    ]
+    lines.extend(f"    {port}," for port in distinct)
+    lines.extend(["];", ""])
+    return "\n".join(lines)
+
+
+# Keep in lockstep with APP_PORTS overrides in
+# neode-ui/src/views/appSession/appSessionConfig.ts.
+RUST_EXTRA_PORTS = [8334, 50002, 18083, 11434, 8081, 8240, 8175, 8176, 8080]
+
+
 def sync_catalog(path: Path, manifests: dict[str, dict[str, Any]]) -> int:
     with path.open("r", encoding="utf-8") as fh:
         catalog = json.load(fh)
@@ -178,6 +204,11 @@ def main() -> int:
         default=[],
         help="Catalog JSON path to update. May be passed multiple times.",
     )
+    parser.add_argument(
+        "--rust-app-ports",
+        default="core/archipelago/src/fips/app_ports.rs",
+        help="Generated Rust launch-port list for the fips0 firewall drop-in. Empty string to skip.",
+    )
     parser.add_argument(
         "--app-session-config",
         default="neode-ui/src/views/appSession/generatedAppSessionConfig.ts",
@@ -201,6 +232,20 @@ def main() -> int:
             print(f"{path}: updated")
         else:
             print(f"{path}: updated 0 fields")
+    if args.rust_app_ports:
+        ports = {
+            app_id: port
+            for app_id, app in manifests.items()
+            if (port := manifest_launch_port(app))
+        }
+        rust_path = Path(args.rust_app_ports)
+        rust_content = render_rust_ports(ports, RUST_EXTRA_PORTS)
+        rust_old = rust_path.read_text(encoding="utf-8") if rust_path.exists() else ""
+        if rust_old != rust_content:
+            rust_path.write_text(rust_content, encoding="utf-8")
+            print(f"{rust_path}: updated")
+        else:
+            print(f"{rust_path}: updated 0 fields")
     print(f"total_updated={total}")
     return 0