diff --git a/crates/heph/src/service.rs b/crates/heph/src/service.rs
index 7b15865..1c90924 100644
--- a/crates/heph/src/service.rs
+++ b/crates/heph/src/service.rs
@@ -4,12 +4,18 @@
 //! be shared by the CLI, TUI, and `heph.nvim` without any one of them owning its
 //! lifecycle. macOS uses a launchd **LaunchAgent**, Linux a **systemd user
 //! service**. All verbs are idempotent.
+//!
+//! The service generator bakes the daemon's runtime config — mode, sync hub,
+//! and OIDC — into the unit so a spoke/hub can run under the managed service
+//! instead of a hand-written plist/unit. Regenerating (`start`/`restart`)
+//! **preserves any config already baked into the on-disk file**, so a bare
+//! invocation never silently drops flags a previous one set.
 
 use std::path::{Path, PathBuf};
 use std::process::Command;
 
 use anyhow::{bail, Context, Result};
-use clap::Subcommand;
+use clap::{Args, Subcommand};
 
 use hephd::{default_db_path, default_socket_path};
 
@@ -19,28 +25,106 @@ const LABEL: &str = "org.hephaestus.hephd";
 #[derive(Subcommand, Debug)]
 pub enum DaemonAction {
     /// Install (if needed) and start the daemon service.
-    Start {
-        /// Generate a service that runs with opt-in self-update enabled
-        /// (default off). The service gets a PATH that can find cargo.
-        #[arg(long)]
-        self_update: bool,
-    },
+    Start(ServiceArgs),
     /// Stop the daemon now (it may restart at next login; use `uninstall` to
     /// stop it for good).
     Stop,
     /// Restart the daemon — run this after upgrading the binary. Preserves the
-    /// existing self-update setting unless `--self-update` re-enables it.
-    Restart {
-        /// Force self-update on when regenerating the service definition.
-        #[arg(long)]
-        self_update: bool,
-    },
+    /// config already baked into the service file (pass flags to add/override).
+    Restart(ServiceArgs),
     /// Show whether the service is installed and running.
     Status,
     /// Stop and remove the service entirely.
     Uninstall,
 }
 
+/// Config flags baked into the generated service, shared by `start`/`restart`.
+/// Anything omitted falls back to what the on-disk service file already has, so
+/// regenerating is non-destructive.
+#[derive(Args, Debug)]
+pub struct ServiceArgs {
+    /// Runtime mode baked into the service (default `local`). Use `server` for a
+    /// sync hub, `client` for an online-only proxy.
+    #[arg(long, value_parser = ["local", "server", "client"])]
+    mode: Option<String>,
+    /// Hub to background-sync this replica's op-log with (makes it a spoke) —
+    /// bakes `--hub-url`.
+    #[arg(long)]
+    hub_url: Option<String>,
+    /// Hub HTTP listen address (server mode) — bakes `--http-addr`.
+    #[arg(long)]
+    http_addr: Option<String>,
+    /// OIDC issuer used to verify (server) or obtain (spoke) hub tokens — bakes
+    /// `--oidc-issuer`.
+    #[arg(long)]
+    oidc_issuer: Option<String>,
+    /// OIDC audience hub tokens must carry (server mode) — bakes
+    /// `--oidc-audience`.
+    #[arg(long)]
+    oidc_audience: Option<String>,
+    /// OIDC client id this device authenticates as (spoke) — bakes
+    /// `--oidc-client-id`.
+    #[arg(long)]
+    oidc_client_id: Option<String>,
+    /// Generate a service that runs with opt-in self-update enabled (default
+    /// off). The service gets a PATH that can find cargo.
+    #[arg(long)]
+    self_update: bool,
+    /// Override the self-update poll interval, in seconds (default: 6h). Only
+    /// meaningful with --self-update.
+    #[arg(long)]
+    self_update_interval_secs: Option<u64>,
+}
+
+/// The hephd flags the service generator bakes beyond the fixed `--db`/`--socket`.
+#[derive(Default, Clone, PartialEq, Debug)]
+struct DaemonConfig {
+    mode: Option<String>,
+    hub_url: Option<String>,
+    http_addr: Option<String>,
+    oidc_issuer: Option<String>,
+    oidc_audience: Option<String>,
+    oidc_client_id: Option<String>,
+    self_update: bool,
+    self_update_interval_secs: Option<u64>,
+}
+
+impl ServiceArgs {
+    fn to_config(&self) -> DaemonConfig {
+        DaemonConfig {
+            mode: self.mode.clone(),
+            hub_url: self.hub_url.clone(),
+            http_addr: self.http_addr.clone(),
+            oidc_issuer: self.oidc_issuer.clone(),
+            oidc_audience: self.oidc_audience.clone(),
+            oidc_client_id: self.oidc_client_id.clone(),
+            self_update: self.self_update,
+            self_update_interval_secs: self.self_update_interval_secs,
+        }
+    }
+}
+
+impl DaemonConfig {
+    /// CLI-provided values win; anything omitted falls back to `base` (the flags
+    /// already baked into the on-disk service file), so regenerating the service
+    /// never drops config a previous invocation set. `self_update` is sticky —
+    /// it stays on if either the CLI or the existing file enabled it.
+    fn fill_from(self, base: DaemonConfig) -> DaemonConfig {
+        DaemonConfig {
+            mode: self.mode.or(base.mode),
+            hub_url: self.hub_url.or(base.hub_url),
+            http_addr: self.http_addr.or(base.http_addr),
+            oidc_issuer: self.oidc_issuer.or(base.oidc_issuer),
+            oidc_audience: self.oidc_audience.or(base.oidc_audience),
+            oidc_client_id: self.oidc_client_id.or(base.oidc_client_id),
+            self_update: self.self_update || base.self_update,
+            self_update_interval_secs: self
+                .self_update_interval_secs
+                .or(base.self_update_interval_secs),
+        }
+    }
+}
+
 /// Resolved locations the service definition needs.
 struct Paths {
     hephd: PathBuf,
@@ -114,6 +198,105 @@ pub fn run(action: &DaemonAction) -> Result<()> {
     }
 }
 
+// --------------------------------------------------------------------------
+// hephd argument vector (pure — shared by both renderers and unit-tested)
+// --------------------------------------------------------------------------
+
+/// The full `hephd …` argument vector the service runs, given the resolved paths
+/// and baked config. `--mode` defaults to `local`; the optional flags appear in
+/// a stable order so regenerating an unchanged config produces an identical file.
+fn hephd_args(hephd: &Path, db: &Path, socket: &Path, cfg: &DaemonConfig) -> Vec<String> {
+    let mut a = vec![
+        hephd.to_string_lossy().into_owned(),
+        "--mode".into(),
+        cfg.mode.clone().unwrap_or_else(|| "local".into()),
+        "--db".into(),
+        db.to_string_lossy().into_owned(),
+        "--socket".into(),
+        socket.to_string_lossy().into_owned(),
+    ];
+    push_opt(&mut a, "--hub-url", &cfg.hub_url);
+    push_opt(&mut a, "--http-addr", &cfg.http_addr);
+    push_opt(&mut a, "--oidc-issuer", &cfg.oidc_issuer);
+    push_opt(&mut a, "--oidc-audience", &cfg.oidc_audience);
+    push_opt(&mut a, "--oidc-client-id", &cfg.oidc_client_id);
+    // Interval is only meaningful with --self-update, so it's nested under it.
+    if cfg.self_update {
+        a.push("--self-update".into());
+        if let Some(secs) = cfg.self_update_interval_secs {
+            a.push("--self-update-interval-secs".into());
+            a.push(secs.to_string());
+        }
+    }
+    a
+}
+
+fn push_opt(args: &mut Vec<String>, flag: &str, val: &Option<String>) {
+    if let Some(v) = val {
+        args.push(flag.to_string());
+        args.push(v.clone());
+    }
+}
+
+/// Parse a `hephd` argument vector back into a [`DaemonConfig`] — the inverse of
+/// [`hephd_args`], used to recover config already baked into an on-disk service
+/// file. Unrecognized args (the binary path, `--db`, `--socket`) are ignored.
+fn parse_hephd_args(args: &[String]) -> DaemonConfig {
+    let mut c = DaemonConfig::default();
+    let mut i = 0;
+    while i < args.len() {
+        let next = || args.get(i + 1).cloned();
+        match args[i].as_str() {
+            "--mode" => {
+                c.mode = next();
+                i += 2;
+            }
+            "--hub-url" => {
+                c.hub_url = next();
+                i += 2;
+            }
+            "--http-addr" => {
+                c.http_addr = next();
+                i += 2;
+            }
+            "--oidc-issuer" => {
+                c.oidc_issuer = next();
+                i += 2;
+            }
+            "--oidc-audience" => {
+                c.oidc_audience = next();
+                i += 2;
+            }
+            "--oidc-client-id" => {
+                c.oidc_client_id = next();
+                i += 2;
+            }
+            "--self-update" => {
+                c.self_update = true;
+                i += 1;
+            }
+            "--self-update-interval-secs" => {
+                c.self_update_interval_secs = next().and_then(|s| s.parse().ok());
+                i += 2;
+            }
+            _ => i += 1,
+        }
+    }
+    c
+}
+
+/// Recover the config baked into an existing service file (empty if absent).
+fn existing_config(path: &Path, mgr: &Manager) -> DaemonConfig {
+    let Ok(s) = std::fs::read_to_string(path) else {
+        return DaemonConfig::default();
+    };
+    let args = match mgr {
+        Manager::Launchd => launchd_program_args(&s),
+        Manager::Systemd => systemd_exec_args(&s),
+    };
+    parse_hephd_args(&args)
+}
+
 // --------------------------------------------------------------------------
 // Rendering (pure — unit-tested)
 // --------------------------------------------------------------------------
@@ -124,17 +307,22 @@ fn xml_escape(s: &str) -> String {
         .replace('>', "&gt;")
 }
 
-fn launchd_plist(hephd: &Path, db: &Path, socket: &Path, log: &Path, self_update: bool) -> String {
-    let arg = |p: &Path| xml_escape(&p.to_string_lossy());
-    // Opt-in self-update: pass the flag, and give the service a PATH/HOME that
-    // can find cargo + the toolchain (a LaunchAgent's default env can't), since
-    // the apply path shells out to `cargo install`.
-    let self_update_arg = if self_update {
-        "\n    <string>--self-update</string>".to_string()
-    } else {
-        String::new()
-    };
-    let cargo_env = if self_update {
+fn xml_unescape(s: &str) -> String {
+    s.replace("&lt;", "<")
+        .replace("&gt;", ">")
+        .replace("&amp;", "&")
+}
+
+fn launchd_plist(hephd: &Path, db: &Path, socket: &Path, log: &Path, cfg: &DaemonConfig) -> String {
+    let args_xml = hephd_args(hephd, db, socket, cfg)
+        .iter()
+        .map(|a| format!("    <string>{}</string>", xml_escape(a)))
+        .collect::<Vec<_>>()
+        .join("\n");
+    // Opt-in self-update needs a PATH/HOME that can find cargo + the toolchain
+    // (a LaunchAgent's default env can't), since the apply path shells out to
+    // `cargo install`.
+    let cargo_env = if cfg.self_update {
         let (path, home) = cargo_env();
         format!(
             "\n    <key>PATH</key>\n    <string>{}</string>\n    <key>HOME</key>\n    <string>{}</string>",
@@ -153,13 +341,7 @@ fn launchd_plist(hephd: &Path, db: &Path, socket: &Path, log: &Path, self_update
   <string>{label}</string>
   <key>ProgramArguments</key>
   <array>
-    <string>{hephd}</string>
-    <string>--mode</string>
-    <string>local</string>
-    <string>--db</string>
-    <string>{db}</string>
-    <string>--socket</string>
-    <string>{socket}</string>{self_update_arg}
+{args_xml}
   </array>
   <key>RunAtLoad</key>
   <true/>
@@ -181,10 +363,7 @@ fn launchd_plist(hephd: &Path, db: &Path, socket: &Path, log: &Path, self_update
 </plist>
 "#,
         label = LABEL,
-        hephd = arg(hephd),
-        db = arg(db),
-        socket = arg(socket),
-        log = arg(log),
+        log = xml_escape(&log.to_string_lossy()),
     )
 }
 
@@ -199,20 +378,34 @@ fn cargo_env() -> (String, String) {
     (path, home)
 }
 
-/// Whether an already-installed service file opted into self-update — so
-/// `restart` (which regenerates the file) preserves the setting instead of
-/// silently turning it off.
-fn file_opts_into_self_update(path: &Path) -> bool {
-    std::fs::read_to_string(path)
-        .map(|s| s.contains("--self-update"))
-        .unwrap_or(false)
+/// Extract the `ProgramArguments` strings from an existing launchd plist.
+fn launchd_program_args(plist: &str) -> Vec<String> {
+    let Some(k) = plist.find("<key>ProgramArguments</key>") else {
+        return vec![];
+    };
+    let rest = &plist[k..];
+    let (Some(start), Some(end)) = (rest.find("<array>"), rest.find("</array>")) else {
+        return vec![];
+    };
+    let block = &rest[start..end];
+    let mut out = vec![];
+    let mut cur = block;
+    while let Some(o) = cur.find("<string>") {
+        let after = &cur[o + "<string>".len()..];
+        let Some(c) = after.find("</string>") else {
+            break;
+        };
+        out.push(xml_unescape(&after[..c]));
+        cur = &after[c + "</string>".len()..];
+    }
+    out
 }
 
-fn systemd_unit(hephd: &Path, db: &Path, socket: &Path, self_update: bool) -> String {
-    // Opt-in self-update: pass the flag and give the unit a PATH/HOME that can
-    // find cargo + the toolchain, since the apply path runs `cargo install`.
-    let su_arg = if self_update { " --self-update" } else { "" };
-    let cargo_env = if self_update {
+fn systemd_unit(hephd: &Path, db: &Path, socket: &Path, cfg: &DaemonConfig) -> String {
+    let exec = hephd_args(hephd, db, socket, cfg).join(" ");
+    // Opt-in self-update needs a PATH/HOME that can find cargo + the toolchain,
+    // since the apply path runs `cargo install`.
+    let cargo_env = if cfg.self_update {
         let (path, home) = cargo_env();
         format!("Environment=PATH={path}\nEnvironment=HOME={home}\n")
     } else {
@@ -224,19 +417,24 @@ fn systemd_unit(hephd: &Path, db: &Path, socket: &Path, self_update: bool) -> St
          After=default.target\n\
          \n\
          [Service]\n\
-         ExecStart={hephd} --mode local --db {db} --socket {socket}{su_arg}\n\
+         ExecStart={exec}\n\
          {cargo_env}\
          Restart=always\n\
          RestartSec=1\n\
          \n\
          [Install]\n\
          WantedBy=default.target\n",
-        hephd = hephd.display(),
-        db = db.display(),
-        socket = socket.display(),
     )
 }
 
+/// Extract the `ExecStart=` argument vector from an existing systemd unit.
+fn systemd_exec_args(unit: &str) -> Vec<String> {
+    unit.lines()
+        .find_map(|l| l.strip_prefix("ExecStart="))
+        .map(|rest| rest.split_whitespace().map(str::to_string).collect())
+        .unwrap_or_default()
+}
+
 // --------------------------------------------------------------------------
 // Shared helpers
 // --------------------------------------------------------------------------
@@ -303,10 +501,13 @@ fn launchd(action: &DaemonAction, p: &Paths) -> Result<()> {
     let target = format!("gui/{uid}/{LABEL}");
 
     match action {
-        DaemonAction::Start { self_update } => {
+        DaemonAction::Start(args) => {
+            let cfg = args
+                .to_config()
+                .fill_from(existing_config(&plist, &Manager::Launchd));
             write_if_changed(
                 &plist,
-                &launchd_plist(&p.hephd, &p.db, &p.socket, &p.log, *self_update),
+                &launchd_plist(&p.hephd, &p.db, &p.socket, &p.log, &cfg),
             )?;
             if launchd_loaded(&target) {
                 println!("heph daemon already running ({LABEL}).");
@@ -322,11 +523,13 @@ fn launchd(action: &DaemonAction, p: &Paths) -> Result<()> {
             let (_ok, _err) = run_cmd("launchctl", &["bootout", &target])?;
             println!("heph daemon stopped (still installed; `uninstall` to remove).");
         }
-        DaemonAction::Restart { self_update } => {
-            let su = *self_update || file_opts_into_self_update(&plist);
+        DaemonAction::Restart(args) => {
+            let cfg = args
+                .to_config()
+                .fill_from(existing_config(&plist, &Manager::Launchd));
             write_if_changed(
                 &plist,
-                &launchd_plist(&p.hephd, &p.db, &p.socket, &p.log, su),
+                &launchd_plist(&p.hephd, &p.db, &p.socket, &p.log, &cfg),
             )?;
             let _ = run_cmd("launchctl", &["bootout", &target])?;
             let (ok, err) = run_cmd("launchctl", &["bootstrap", &domain, &plist_str(&plist)?])?;
@@ -380,11 +583,11 @@ fn sc(args: &[&str]) -> Result<(bool, String)> {
 fn systemd(action: &DaemonAction, p: &Paths) -> Result<()> {
     let unit = systemd_unit_path()?;
     match action {
-        DaemonAction::Start { self_update } => {
-            write_if_changed(
-                &unit,
-                &systemd_unit(&p.hephd, &p.db, &p.socket, *self_update),
-            )?;
+        DaemonAction::Start(args) => {
+            let cfg = args
+                .to_config()
+                .fill_from(existing_config(&unit, &Manager::Systemd));
+            write_if_changed(&unit, &systemd_unit(&p.hephd, &p.db, &p.socket, &cfg))?;
             sc(&["daemon-reload"])?;
             let (ok, err) = sc(&["enable", "--now", UNIT])?;
             if !ok {
@@ -396,9 +599,11 @@ fn systemd(action: &DaemonAction, p: &Paths) -> Result<()> {
             sc(&["stop", UNIT])?;
             println!("heph daemon stopped (still enabled; `uninstall` to remove).");
         }
-        DaemonAction::Restart { self_update } => {
-            let su = *self_update || file_opts_into_self_update(&unit);
-            write_if_changed(&unit, &systemd_unit(&p.hephd, &p.db, &p.socket, su))?;
+        DaemonAction::Restart(args) => {
+            let cfg = args
+                .to_config()
+                .fill_from(existing_config(&unit, &Manager::Systemd));
+            write_if_changed(&unit, &systemd_unit(&p.hephd, &p.db, &p.socket, &cfg))?;
             sc(&["daemon-reload"])?;
             let (ok, err) = sc(&["restart", UNIT])?;
             if !ok {
@@ -440,6 +645,18 @@ fn print_status(installed: bool, running: bool, p: &Paths, service_file: &Path)
 mod tests {
     use super::*;
 
+    fn spoke_cfg() -> DaemonConfig {
+        DaemonConfig {
+            mode: Some("local".into()),
+            hub_url: Some("http://hub.example:8787".into()),
+            oidc_issuer: Some("https://idp.example/o/heph/".into()),
+            oidc_client_id: Some("heph".into()),
+            self_update: true,
+            self_update_interval_secs: Some(600),
+            ..Default::default()
+        }
+    }
+
     #[test]
     fn launchd_plist_has_label_args_and_paths() {
         let plist = launchd_plist(
@@ -447,19 +664,21 @@ mod tests {
             Path::new("/home/e/.local/share/heph/heph.db"),
             Path::new("/tmp/heph/hephd.sock"),
             Path::new("/home/e/.local/share/heph/hephd.log"),
-            false,
+            &DaemonConfig::default(),
         );
         assert!(plist.contains("<string>org.hephaestus.hephd</string>"));
         assert!(plist.contains("<string>/usr/local/bin/hephd</string>"));
         assert!(plist.contains("<string>--mode</string>"));
+        assert!(plist.contains("<string>local</string>"));
         assert!(plist.contains("<string>/home/e/.local/share/heph/heph.db</string>"));
         assert!(plist.contains("<string>/tmp/heph/hephd.sock</string>"));
         assert!(plist.contains("<key>RunAtLoad</key>"));
         assert!(plist.contains("<key>KeepAlive</key>"));
         assert!(plist.contains("hephd.log"));
-        // Default (no self-update): no flag, no cargo PATH baked in.
+        // Default (no self-update, no spoke/hub config): none of those flags.
         assert!(!plist.contains("--self-update"));
         assert!(!plist.contains(".cargo/bin"));
+        assert!(!plist.contains("--hub-url"));
     }
 
     #[test]
@@ -469,12 +688,64 @@ mod tests {
             Path::new("/db"),
             Path::new("/sock"),
             Path::new("/log"),
-            true,
+            &DaemonConfig {
+                self_update: true,
+                ..Default::default()
+            },
         );
         assert!(plist.contains("<string>--self-update</string>"));
         assert!(plist.contains("<key>PATH</key>"));
         assert!(plist.contains(".cargo/bin"));
         assert!(plist.contains("<key>HOME</key>"));
+        // No interval given → no interval flag.
+        assert!(!plist.contains("--self-update-interval-secs"));
+    }
+
+    #[test]
+    fn launchd_plist_self_update_interval_is_baked_under_self_update() {
+        let with = launchd_plist(
+            Path::new("/hephd"),
+            Path::new("/db"),
+            Path::new("/sock"),
+            Path::new("/log"),
+            &DaemonConfig {
+                self_update: true,
+                self_update_interval_secs: Some(3600),
+                ..Default::default()
+            },
+        );
+        assert!(with.contains("<string>--self-update-interval-secs</string>"));
+        assert!(with.contains("<string>3600</string>"));
+        // Interval is meaningless without --self-update, so it's not emitted.
+        let without = launchd_plist(
+            Path::new("/hephd"),
+            Path::new("/db"),
+            Path::new("/sock"),
+            Path::new("/log"),
+            &DaemonConfig {
+                self_update: false,
+                self_update_interval_secs: Some(3600),
+                ..Default::default()
+            },
+        );
+        assert!(!without.contains("--self-update-interval-secs"));
+    }
+
+    #[test]
+    fn launchd_plist_bakes_spoke_config() {
+        let plist = launchd_plist(
+            Path::new("/hephd"),
+            Path::new("/db"),
+            Path::new("/sock"),
+            Path::new("/log"),
+            &spoke_cfg(),
+        );
+        assert!(plist.contains("<string>--hub-url</string>"));
+        assert!(plist.contains("<string>http://hub.example:8787</string>"));
+        assert!(plist.contains("<string>--oidc-issuer</string>"));
+        assert!(plist.contains("<string>https://idp.example/o/heph/</string>"));
+        assert!(plist.contains("<string>--oidc-client-id</string>"));
+        assert!(plist.contains("<string>heph</string>"));
     }
 
     #[test]
@@ -483,7 +754,7 @@ mod tests {
             Path::new("/usr/local/bin/hephd"),
             Path::new("/home/e/.local/share/heph/heph.db"),
             Path::new("/run/user/1000/heph/hephd.sock"),
-            false,
+            &DaemonConfig::default(),
         );
         assert!(unit.contains(
             "ExecStart=/usr/local/bin/hephd --mode local \
@@ -507,17 +778,96 @@ mod tests {
             Path::new("/usr/local/bin/hephd"),
             Path::new("/db"),
             Path::new("/sock"),
-            true,
+            &DaemonConfig {
+                self_update: true,
+                self_update_interval_secs: Some(3600),
+                ..Default::default()
+            },
         );
-        assert!(unit.contains("--self-update"));
+        assert!(unit.contains("--self-update --self-update-interval-secs 3600"));
         assert!(unit.contains("Environment=PATH="));
         assert!(unit.contains(".cargo/bin"));
         assert!(unit.contains("Environment=HOME="));
     }
 
     #[test]
-    fn xml_escape_escapes_markup() {
+    fn systemd_unit_bakes_hub_config() {
+        let unit = systemd_unit(
+            Path::new("/hephd"),
+            Path::new("/db"),
+            Path::new("/sock"),
+            &DaemonConfig {
+                mode: Some("server".into()),
+                http_addr: Some("0.0.0.0:8787".into()),
+                oidc_issuer: Some("https://idp.example/o/heph/".into()),
+                oidc_audience: Some("heph".into()),
+                ..Default::default()
+            },
+        );
+        assert!(unit.contains("--mode server"));
+        assert!(unit.contains("--http-addr 0.0.0.0:8787"));
+        assert!(unit.contains("--oidc-issuer https://idp.example/o/heph/"));
+        assert!(unit.contains("--oidc-audience heph"));
+    }
+
+    #[test]
+    fn launchd_config_round_trips_through_the_plist() {
+        let cfg = spoke_cfg();
+        let plist = launchd_plist(
+            Path::new("/hephd"),
+            Path::new("/db"),
+            Path::new("/sock"),
+            Path::new("/log"),
+            &cfg,
+        );
+        let parsed = parse_hephd_args(&launchd_program_args(&plist));
+        assert_eq!(parsed, cfg);
+    }
+
+    #[test]
+    fn systemd_config_round_trips_through_the_unit() {
+        let cfg = DaemonConfig {
+            mode: Some("server".into()),
+            http_addr: Some("0.0.0.0:8787".into()),
+            oidc_issuer: Some("https://idp.example/o/heph/".into()),
+            oidc_audience: Some("heph".into()),
+            self_update: true,
+            self_update_interval_secs: Some(600),
+            ..Default::default()
+        };
+        let unit = systemd_unit(
+            Path::new("/hephd"),
+            Path::new("/db"),
+            Path::new("/sock"),
+            &cfg,
+        );
+        let parsed = parse_hephd_args(&systemd_exec_args(&unit));
+        assert_eq!(parsed, cfg);
+    }
+
+    #[test]
+    fn fill_from_preserves_existing_and_lets_cli_override() {
+        let existing = spoke_cfg();
+        // A bare invocation (no flags) preserves everything baked in the file.
+        assert_eq!(
+            DaemonConfig::default().fill_from(existing.clone()),
+            existing
+        );
+        // A CLI-provided value overrides; self_update stays sticky.
+        let overridden = DaemonConfig {
+            self_update_interval_secs: Some(60),
+            ..Default::default()
+        }
+        .fill_from(existing.clone());
+        assert_eq!(overridden.self_update_interval_secs, Some(60));
+        assert_eq!(overridden.hub_url, existing.hub_url);
+        assert!(overridden.self_update);
+    }
+
+    #[test]
+    fn xml_escape_round_trips() {
         assert_eq!(xml_escape("a & b < c > d"), "a &amp; b &lt; c &gt; d");
+        assert_eq!(xml_unescape("a &amp; b &lt; c &gt; d"), "a & b < c > d");
     }
 
     #[test]
diff --git a/docs/changelog.d/daemon-self-update-interval.feature.md b/docs/changelog.d/daemon-self-update-interval.feature.md
new file mode 100644
index 0000000..b5ec9b8
--- /dev/null
+++ b/docs/changelog.d/daemon-self-update-interval.feature.md
@@ -0,0 +1 @@
+`heph daemon start`/`restart` can now bake the daemon's full runtime config into the managed service — `--mode`, `--hub-url`, `--http-addr`, `--oidc-issuer`/`--oidc-audience`/`--oidc-client-id`, and `--self-update-interval-secs` (previously only the bare `--self-update` bool was wired). Regenerating preserves whatever is already baked into the on-disk plist/unit, so a bare `start`/`restart` no longer silently drops spoke/hub or self-update config.
diff --git a/docs/how-to/run-the-daemon.md b/docs/how-to/run-the-daemon.md
index 2b00dff..cb9e56d 100644
--- a/docs/how-to/run-the-daemon.md
+++ b/docs/how-to/run-the-daemon.md
@@ -36,14 +36,47 @@ when it's already stopped is fine.
 > exits cleanly to hand off to the new binary) wouldn't come back on Linux. Run
 > `heph daemon restart` once (it regenerates the unit) to pick up `Restart=always`.
 
-Either way it runs `hephd --mode local` against the default store
+By default it runs `hephd --mode local` against the default store
 (`~/.local/share/heph/heph.db`) and socket, with logs at
-`~/.local/share/heph/hephd.log`.
+`~/.local/share/heph/hephd.log`. Pass flags to `start`/`restart` to bake a
+different runtime config into the service (see below).
 
 > **`stop` vs `uninstall`:** `stop` halts the daemon now, but the service is
 > still installed, so on macOS it starts again at next login. Use `uninstall`
 > to stop it persistently.
 
+## Baking sync config (spoke / hub)
+
+By default the service runs a standalone `--mode local` daemon. To make the
+managed service a **spoke** (background-syncs to a hub) or a **hub** (`--mode
+server`), pass the corresponding `hephd` flags to `start` (or `restart`) — they
+get baked into the generated plist/unit:
+
+```bash
+# Spoke: sync to a hub, authenticating with OIDC
+heph daemon start \
+  --hub-url http://hub.example:8787 \
+  --oidc-issuer https://idp.example/application/o/heph/ \
+  --oidc-client-id heph
+
+# Hub: expose the authenticated sync endpoint
+heph daemon start --mode server \
+  --http-addr 0.0.0.0:8787 \
+  --oidc-issuer https://idp.example/application/o/heph/ \
+  --oidc-audience heph
+```
+
+Bakeable flags: `--mode`, `--hub-url`, `--http-addr`, `--oidc-issuer`,
+`--oidc-audience`, `--oidc-client-id`, `--self-update`,
+`--self-update-interval-secs`. **Regenerating preserves what's already baked
+in** — `start`/`restart` read the existing service file and carry over any flags
+you don't pass, so a bare `heph daemon restart` never drops your spoke/hub or
+self-update config. Pass a flag again to add or override it.
+
+> Spoke sync is HTTP-only today (`hephd`'s sync client doesn't speak HTTPS) — a
+> `--hub-url` over the tailnet or behind a TLS-terminating proxy is the usual
+> setup.
+
 ## After upgrading
 
 When you rebuild/reinstall (`cargo install … --force`), the running daemon is
@@ -59,9 +92,11 @@ heph daemon restart
 service that polls the forge for newer releases and, when one appears, rebuilds
 via `cargo install` (anonymous HTTPS clone of the public repo — no credentials)
 and restarts onto the new binary. It is **off by default**; the generated
-service also gets a `PATH` that can find cargo. `heph daemon restart` preserves
-the setting (pass `--self-update` again to turn it on later). Requires the Rust
-toolchain (`cargo`) installed for the service user.
+service also gets a `PATH` that can find cargo. Override the 6h poll cadence with
+`--self-update-interval-secs <secs>`. Both `start` and `restart` preserve an
+already-baked self-update setting (and its interval), so a bare invocation won't
+silently disable it — pass `--self-update` again only to turn it on later.
+Requires the Rust toolchain (`cargo`) installed for the service user.
 
 ## Development isolation
 
diff --git a/docs/how-to/self-update.md b/docs/how-to/self-update.md
index d4dda1f..e7d0627 100644
--- a/docs/how-to/self-update.md
+++ b/docs/how-to/self-update.md
@@ -20,9 +20,17 @@ heph daemon start --self-update
 ```
 
 That generates a launchd/systemd service that runs `hephd --self-update` and
-gives it a `PATH` that can find `cargo`. `heph daemon restart` preserves the
-setting (pass `--self-update` again to turn it on later). To run the daemon
-directly instead:
+gives it a `PATH` that can find `cargo`. Override the 6h poll cadence with
+`--self-update-interval-secs <secs>`:
+
+```bash
+heph daemon start --self-update                              # default: poll every 6h
+heph daemon start --self-update --self-update-interval-secs 3600
+```
+
+Both `start` and `restart` preserve an already-baked setting (the flag and its
+interval), so a bare invocation won't silently disable it — pass `--self-update`
+again only to turn it on later. To run the daemon directly instead:
 
 ```bash
 hephd --self-update                              # default: poll every 6h