diff --git a/CMakeLists.txt b/CMakeLists.txt
index 1a351cc..3870a3f 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -125,6 +125,7 @@ set(CST_CORE_SOURCES
   src/discover.c
   src/peer_auth.c
   src/parliament.c
+  src/parliament_daemon.c
   src/parliament_cli.c
   src/attach.c
   src/clipboard.c
diff --git a/Makefile b/Makefile
index 4bf76b6..34e1f78 100644
--- a/Makefile
+++ b/Makefile
@@ -106,7 +106,7 @@ CORE_SRC = \
 	src/extensions.c src/plugins.c src/mcp.c src/subagent.c src/attach.c src/clipboard.c \
 	src/pdf_text.c \
 	src/session.c src/runtime.c src/worktree.c src/realm.c src/discover.c \
-	src/peer_auth.c src/parliament.c src/parliament_cli.c \
+	src/peer_auth.c src/parliament.c src/parliament_daemon.c src/parliament_cli.c \
 	src/tools/tools.c \
 	src/tools/patch.c \
 	src/tools/registry.c \
diff --git a/include/cst_parliament.h b/include/cst_parliament.h
index e76bdb4..4f2f208 100644
--- a/include/cst_parliament.h
+++ b/include/cst_parliament.h
@@ -44,6 +44,28 @@ int cst_parliament_new_project(const char *project_id);
 int cst_parliament_context_put(const char *text);
 char *cst_parliament_context_get(void);
 
+/* Local login ticket: opens require a fresh chair session (or password env). */
+int cst_parliament_session_write(const char *instance_id);
+int cst_parliament_session_ok(char *instance_id_out, size_t n);
+void cst_parliament_session_clear(void);
+
+/* Apply a peer sync bundle (higher revision already selected by caller). */
+int cst_parliament_apply_sync(unsigned long revision, const char *parliament_id,
+                              const char *project_id, const char *chair,
+                              const char *context);
+
+/* Background parliament service: discover + peer listen + context sync. */
+int cst_parliament_daemon_pidfile(char *out, size_t n);
+int cst_parliament_daemon_running(void);
+/* Start in background (Unix fork). password unlocks Realm in the child.
+ * Returns 0 and writes pid. If already running, returns 0. */
+int cst_parliament_daemon_start(const char *password, const char *instance_id,
+                                int peer_port, char *err, size_t err_sz);
+int cst_parliament_daemon_stop(void);
+/* Foreground service loop (used by --service and the forked child). */
+int cst_parliament_daemon_run(const char *password, const char *instance_id,
+                              int peer_port, char *err, size_t err_sz);
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/include/cst_parliament_cli.h b/include/cst_parliament_cli.h
index 165963d..dab2052 100644
--- a/include/cst_parliament_cli.h
+++ b/include/cst_parliament_cli.h
@@ -11,6 +11,13 @@ int cst_parliament_cli_realm_new(void);
 int cst_parliament_cli_realm_password_init(const char *password);
 int cst_parliament_cli_login(const char *password, const char *instance_id,
                              const char *device_label);
+/* Login then ensure background parliament service (discover + sync). */
+int cst_parliament_cli_login_and_serve(const char *password,
+                                       const char *instance_id,
+                                       const char *device_label, int peer_port);
+int cst_parliament_cli_service(const char *password, const char *instance_id,
+                               int peer_port, int foreground);
+int cst_parliament_cli_service_stop(void);
 int cst_parliament_cli_new_project(const char *project_id);
 int cst_parliament_cli_realm_enroll(const char *instance_id, const char *label);
 int cst_parliament_cli_peer_listen(int port, const char *instance_id);
diff --git a/include/cst_peer.h b/include/cst_peer.h
index cf98973..0f7e7f1 100644
--- a/include/cst_peer.h
+++ b/include/cst_peer.h
@@ -15,9 +15,11 @@ typedef struct {
   cst_realm_cert_t remote;
   char host[64];
   int port;
+  intptr_t sock; /* open until cst_peer_close */
 } cst_peer_session_t;
 
-/* Dial host:port, prove our cert, verify theirs. 0 on success. */
+/* Dial host:port, prove our cert, verify theirs. 0 on success.
+ * Leaves sock open for post-handshake sync; call cst_peer_close. */
 int cst_peer_dial(const char *host, int port, const cst_realm_cert_t *self,
                   const uint8_t self_sk[64], const uint8_t realm_pk[32],
                   int timeout_ms, cst_peer_session_t *out, char *err,
@@ -29,6 +31,21 @@ int cst_peer_accept(intptr_t listen_sock, const cst_realm_cert_t *self,
                     int timeout_ms, cst_peer_session_t *out, char *err,
                     size_t err_sz);
 
+void cst_peer_close(cst_peer_session_t *s);
+
+/* After handshake: exchange parliament revision/context. Higher revision wins
+ * and is written locally via the callbacks. Returns 0 on success. */
+typedef struct {
+  unsigned long revision;
+  char parliament_id[64];
+  char project_id[64];
+  char chair_instance[64];
+  char *context; /* malloc'd when loading; freed by caller after sync */
+} cst_peer_sync_bundle_t;
+
+int cst_peer_sync(cst_peer_session_t *s, cst_peer_sync_bundle_t *local,
+                  int timeout_ms, char *err, size_t err_sz);
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/include/cst_version.h b/include/cst_version.h
index d9ce171..36ebcda 100644
--- a/include/cst_version.h
+++ b/include/cst_version.h
@@ -3,7 +3,7 @@
 
 #define CST_VERSION_MAJOR 0
 #define CST_VERSION_MINOR 9
-#define CST_VERSION_PATCH 12
+#define CST_VERSION_PATCH 13
 
 #define CST_VERSION_STR_(x) #x
 #define CST_VERSION_STR(x) CST_VERSION_STR_(x)
diff --git a/src/main.c b/src/main.c
index 8a3cfcb..ca7e99c 100644
--- a/src/main.c
+++ b/src/main.c
@@ -1,7 +1,9 @@
 #include "cst_agent.h"
 #include "cst_ext.h"
 #include "cst_models.h"
+#include "cst_parliament.h"
 #include "cst_parliament_cli.h"
+#include "cst_realm.h"
 #include "cst_tools.h"
 #include "cst_version.h"
 #include "cst_webui.h"
@@ -50,7 +52,10 @@ static void usage(const char *argv0) {
           "      --no-orchestrate  override workspace orchestration setting\n"
           "      --realm-new       create Realm file keys (legacy/dev)\n"
           "      --realm-password-init  create password-derived Realm (no sk on disk)\n"
-          "      --login           unlock with password; this device becomes chair\n"
+          "      --login           unlock; claim chair; start parliament service\n"
+          "      --service         run parliament service (discover+context sync)\n"
+          "      --service-fg      same as --service, stay in foreground\n"
+          "      --service-stop    stop the parliament background service\n"
           "      --new-project ID  replace all parliament context for a new project\n"
           "      --realm-enroll ID enroll this instance under the Realm\n"
           "      --realm-label S   display label for enroll/login\n"
@@ -374,7 +379,8 @@ int main(int argc, char **argv) {
   int new_session = 0, do_list = 0, do_migrate = 0;
   const char *resume_id = NULL;
   int do_realm_new = 0, do_realm_enroll = 0, do_peer_listen = 0, do_peer_dial = 0,
-      do_discover = 0, do_realm_pw_init = 0, do_login = 0, do_new_project = 0;
+      do_discover = 0, do_realm_pw_init = 0, do_login = 0, do_new_project = 0,
+      do_service = 0, do_service_fg = 0, do_service_stop = 0;
   const char *realm_enroll_id = NULL, *realm_label = NULL;
   const char *peer_dial_spec = NULL, *parliament_instance = NULL;
   const char *new_project_id = NULL;
@@ -439,6 +445,9 @@ int main(int argc, char **argv) {
       {"realm-password-init", no_argument, 0, 0x118},
       {"login", no_argument, 0, 0x119},
       {"new-project", required_argument, 0, 0x11a},
+      {"service", no_argument, 0, 0x11b},
+      {"service-fg", no_argument, 0, 0x11c},
+      {"service-stop", no_argument, 0, 0x11d},
       {0, 0, 0, 0}};
   int c;
   while ((c = getopt_long(argc, argv, "w:s:b:k:m:P:r:n:T:Hp:dahVNcR:LyA:C:e:M:",
@@ -492,6 +501,15 @@ int main(int argc, char **argv) {
       do_new_project = 1;
       new_project_id = optarg;
       break;
+    case 0x11b:
+      do_service = 1;
+      break;
+    case 0x11c:
+      do_service_fg = 1;
+      break;
+    case 0x11d:
+      do_service_stop = 1;
+      break;
     case 'w':
       snprintf(cfg.workspace_root, sizeof(cfg.workspace_root), "%s", optarg);
       break;
@@ -675,6 +693,22 @@ int main(int argc, char **argv) {
     curl_global_cleanup();
     return rc;
   }
+  if (do_service_stop) {
+    int rc = cst_parliament_cli_service_stop();
+    curl_global_cleanup();
+    return rc;
+  }
+  if (do_service || do_service_fg) {
+    const char *pw = getenv("CST_REALM_PASSWORD");
+    const char *iid = parliament_instance ? parliament_instance
+                                          : getenv("CST_INSTANCE_ID");
+    if (!iid || !iid[0])
+      iid = "chair-local";
+    int rc = cst_parliament_cli_service(pw, iid, discover_peer_port,
+                                        do_service_fg);
+    curl_global_cleanup();
+    return rc;
+  }
   if (do_realm_enroll) {
     int rc = cst_parliament_cli_realm_enroll(realm_enroll_id, realm_label);
     curl_global_cleanup();
@@ -715,6 +749,38 @@ int main(int argc, char **argv) {
     return rc;
   }
 
+  /* Password Realm: interactive/agent open requires a chair login session. */
+  {
+    char rdir[OS_PATH_MAX];
+    if (cst_realm_dir(rdir, sizeof(rdir)) == 0 &&
+        cst_realm_is_password_mode(rdir) && !cst_parliament_session_ok(NULL, 0)) {
+      const char *pw = getenv("CST_REALM_PASSWORD");
+      if (pw && pw[0]) {
+        const char *iid = parliament_instance ? parliament_instance
+                                              : getenv("CST_INSTANCE_ID");
+        if (!iid || !iid[0])
+          iid = "chair-local";
+        char err[256];
+        char *hand =
+            cst_parliament_login(pw, iid, realm_label, err, sizeof(err));
+        if (!hand) {
+          fprintf(stderr, "%s\n", err[0] ? err : "login required");
+          curl_global_cleanup();
+          return 1;
+        }
+        free(hand);
+        (void)cst_parliament_daemon_start(pw, iid, discover_peer_port, err,
+                                          sizeof(err));
+      } else {
+        fprintf(stderr,
+                "password Realm active: run --login (or set "
+                "CST_REALM_PASSWORD) before opening the agent\n");
+        curl_global_cleanup();
+        return 1;
+      }
+    }
+  }
+
   if (do_list) {
     int rc = list_sessions(cfg.workspace_root);
     curl_global_cleanup();
diff --git a/src/parliament.c b/src/parliament.c
index 3e749f2..b6867bb 100644
--- a/src/parliament.c
+++ b/src/parliament.c
@@ -165,7 +165,7 @@ int cst_parliament_claim_chair(const char *instance_id,
   return cst_parliament_save(&m);
 }
 
-int cst_parliament_context_put(const char *text) {
+static int context_write_file(const char *text) {
   char path[OS_PATH_MAX], tmp[OS_PATH_MAX + 8];
   if (context_path(path, sizeof(path)) != 0)
     return -1;
@@ -185,6 +185,12 @@ int cst_parliament_context_put(const char *text) {
     remove(tmp);
     return -1;
   }
+  return 0;
+}
+
+int cst_parliament_context_put(const char *text) {
+  if (context_write_file(text) != 0)
+    return -1;
   cst_parliament_meta_t m;
   if (cst_parliament_load(&m) == 0) {
     m.revision++;
@@ -290,8 +296,115 @@ char *cst_parliament_login(const char *password, const char *instance_id,
   cst_buf_puts(&hand, ctx ? ctx : "");
   free(ctx);
   free(dev);
+  if (cst_parliament_session_write(instance_id) != 0) {
+    if (err && err_sz)
+      snprintf(err, err_sz, "session ticket write failed");
+    crypto_wipe(keys.seed, sizeof(keys.seed));
+    crypto_wipe(keys.sk, sizeof(keys.sk));
+    crypto_wipe(sk, sizeof(sk));
+    cst_buf_free(&hand);
+    return NULL;
+  }
   crypto_wipe(keys.seed, sizeof(keys.seed));
   crypto_wipe(keys.sk, sizeof(keys.sk));
   crypto_wipe(sk, sizeof(sk));
   return cst_buf_steal(&hand);
 }
+
+static int session_path(char *out, size_t n) {
+  char dir[OS_PATH_MAX];
+  if (cst_realm_dir(dir, sizeof(dir)) != 0)
+    return -1;
+  return os_path_join(out, n, dir, "chair.session");
+}
+
+int cst_parliament_session_write(const char *instance_id) {
+  if (!instance_id || !instance_id[0])
+    return -1;
+  char path[OS_PATH_MAX], tmp[OS_PATH_MAX + 8];
+  if (session_path(path, sizeof(path)) != 0)
+    return -1;
+  if (snprintf(tmp, sizeof(tmp), "%s.tmp", path) >= (int)sizeof(tmp))
+    return -1;
+  FILE *f = fopen(tmp, "wb");
+  if (!f)
+    return -1;
+  int ok = fprintf(f, "instance=%s\nissued=%ld\n", instance_id,
+                   (long)time(NULL)) > 0;
+  if (fclose(f) != 0)
+    ok = 0;
+  if (!ok) {
+    remove(tmp);
+    return -1;
+  }
+  if (os_rename_replace(tmp, path) != 0) {
+    remove(tmp);
+    return -1;
+  }
+  return 0;
+}
+
+int cst_parliament_session_ok(char *instance_id_out, size_t n) {
+  char path[OS_PATH_MAX];
+  if (session_path(path, sizeof(path)) != 0)
+    return 0;
+  FILE *f = fopen(path, "rb");
+  if (!f)
+    return 0;
+  char line[256], iid[64] = {0};
+  long issued = 0;
+  while (fgets(line, sizeof(line), f)) {
+    if (!strncmp(line, "instance=", 9)) {
+      const char *p = line + 9;
+      size_t i = 0;
+      while (p[i] && p[i] != '\n' && p[i] != '\r' && i + 1 < sizeof(iid)) {
+        iid[i] = p[i];
+        i++;
+      }
+      iid[i] = 0;
+    } else if (!strncmp(line, "issued=", 7))
+      issued = atol(line + 7);
+  }
+  fclose(f);
+  if (!iid[0] || issued <= 0)
+    return 0;
+  /* Ticket valid for 24h of wall clock. */
+  long now = (long)time(NULL);
+  if (now < issued || now - issued > 86400)
+    return 0;
+  cst_parliament_meta_t m;
+  if (cst_parliament_load(&m) != 0)
+    return 0;
+  if (!m.chair_instance[0] || strcmp(m.chair_instance, iid) != 0)
+    return 0;
+  if (instance_id_out && n)
+    snprintf(instance_id_out, n, "%s", iid);
+  return 1;
+}
+
+void cst_parliament_session_clear(void) {
+  char path[OS_PATH_MAX];
+  if (session_path(path, sizeof(path)) == 0)
+    remove(path);
+}
+
+int cst_parliament_apply_sync(unsigned long revision, const char *parliament_id,
+                              const char *project_id, const char *chair,
+                              const char *context) {
+  cst_parliament_meta_t m;
+  if (cst_parliament_load(&m) != 0)
+    return -1;
+  if (revision <= m.revision)
+    return 0;
+  if (parliament_id && parliament_id[0])
+    snprintf(m.parliament_id, sizeof(m.parliament_id), "%s", parliament_id);
+  if (project_id)
+    snprintf(m.project_id, sizeof(m.project_id), "%s", project_id);
+  if (chair)
+    snprintf(m.chair_instance, sizeof(m.chair_instance), "%s", chair);
+  m.revision = revision;
+  snprintf(m.status, sizeof(m.status), "%s", "open");
+  if (context_write_file(context ? context : "") != 0)
+    return -1;
+  return cst_parliament_save(&m);
+}
diff --git a/src/parliament_cli.c b/src/parliament_cli.c
index 34cce18..e3eebd5 100644
--- a/src/parliament_cli.c
+++ b/src/parliament_cli.c
@@ -69,6 +69,13 @@ int cst_parliament_cli_realm_password_init(const char *password) {
 
 int cst_parliament_cli_login(const char *password, const char *instance_id,
                              const char *device_label) {
+  return cst_parliament_cli_login_and_serve(password, instance_id, device_label,
+                                            9100);
+}
+
+int cst_parliament_cli_login_and_serve(const char *password,
+                                       const char *instance_id,
+                                       const char *device_label, int peer_port) {
   char err[256];
   char *hand = cst_parliament_login(password, instance_id, device_label, err,
                                     sizeof(err));
@@ -78,6 +85,49 @@ int cst_parliament_cli_login(const char *password, const char *instance_id,
   }
   fputs(hand, stdout);
   free(hand);
+  if (cst_parliament_daemon_start(password, instance_id,
+                                  peer_port > 0 ? peer_port : 9100, err,
+                                  sizeof(err)) != 0) {
+    fprintf(stderr, "service: %s\n", err[0] ? err : "start failed");
+    return 1;
+  }
+  if (cst_parliament_daemon_running())
+    printf("service=running\n");
+  return 0;
+}
+
+int cst_parliament_cli_service(const char *password, const char *instance_id,
+                               int peer_port, int foreground) {
+  char err[256];
+  if (!instance_id || !instance_id[0]) {
+    fprintf(stderr, "instance id required\n");
+    return 1;
+  }
+  if (foreground) {
+    if (cst_parliament_daemon_run(password, instance_id,
+                                  peer_port > 0 ? peer_port : 9100, err,
+                                  sizeof(err)) != 0) {
+      fprintf(stderr, "%s\n", err[0] ? err : "service failed");
+      return 1;
+    }
+    return 0;
+  }
+  if (cst_parliament_daemon_start(password, instance_id,
+                                  peer_port > 0 ? peer_port : 9100, err,
+                                  sizeof(err)) != 0) {
+    fprintf(stderr, "%s\n", err[0] ? err : "service start failed");
+    return 1;
+  }
+  printf("service=running\n");
+  return 0;
+}
+
+int cst_parliament_cli_service_stop(void) {
+  if (cst_parliament_daemon_stop() != 0) {
+    fprintf(stderr, "service stop failed\n");
+    return 1;
+  }
+  printf("service=stopped\n");
   return 0;
 }
 
@@ -116,6 +166,19 @@ int cst_parliament_cli_realm_enroll(const char *instance_id, const char *label)
   return 0;
 }
 
+static int load_realm_for_cli(cst_realm_keys_t *realm) {
+  char dir[OS_PATH_MAX];
+  if (cst_realm_dir(dir, sizeof(dir)) != 0)
+    return -1;
+  if (cst_realm_is_password_mode(dir)) {
+    const char *pw = getenv("CST_REALM_PASSWORD");
+    if (!pw || !pw[0])
+      return -1;
+    return cst_realm_unlock_password(dir, pw, realm);
+  }
+  return cst_realm_load(dir, realm);
+}
+
 int cst_parliament_cli_peer_listen(int port, const char *instance_id) {
   if (!instance_id || !instance_id[0]) {
     fprintf(stderr, "instance id required\n");
@@ -125,7 +188,7 @@ int cst_parliament_cli_peer_listen(int port, const char *instance_id) {
   cst_realm_keys_t realm;
   cst_realm_cert_t cert;
   uint8_t sk[64];
-  if (cst_realm_dir(dir, sizeof(dir)) != 0 || cst_realm_load(dir, &realm) != 0 ||
+  if (cst_realm_dir(dir, sizeof(dir)) != 0 || load_realm_for_cli(&realm) != 0 ||
       cst_realm_instance_load(instance_id, &cert, sk) != 0) {
     fprintf(stderr, "cannot load realm/instance %s\n", instance_id);
     return 1;
@@ -151,6 +214,7 @@ int cst_parliament_cli_peer_listen(int port, const char *instance_id) {
     return 1;
   }
   printf("peer_ok remote=%s host=%s\n", sess.remote.instance_id, sess.host);
+  cst_peer_close(&sess);
   os_net_close(ls);
   return 0;
 }
@@ -165,7 +229,7 @@ int cst_parliament_cli_peer_dial(const char *host, int port,
   cst_realm_keys_t realm;
   cst_realm_cert_t cert;
   uint8_t sk[64];
-  if (cst_realm_dir(dir, sizeof(dir)) != 0 || cst_realm_load(dir, &realm) != 0 ||
+  if (cst_realm_dir(dir, sizeof(dir)) != 0 || load_realm_for_cli(&realm) != 0 ||
       cst_realm_instance_load(instance_id, &cert, sk) != 0) {
     fprintf(stderr, "cannot load realm/instance %s\n", instance_id);
     return 1;
@@ -177,6 +241,7 @@ int cst_parliament_cli_peer_dial(const char *host, int port,
     return 1;
   }
   printf("peer_ok remote=%s\n", sess.remote.instance_id);
+  cst_peer_close(&sess);
   return 0;
 }
 
@@ -188,7 +253,7 @@ int cst_parliament_cli_discover(const char *instance_id, int peer_port,
   }
   char dir[OS_PATH_MAX], fp[33];
   cst_realm_keys_t realm;
-  if (cst_realm_dir(dir, sizeof(dir)) != 0 || cst_realm_load(dir, &realm) != 0 ||
+  if (cst_realm_dir(dir, sizeof(dir)) != 0 || load_realm_for_cli(&realm) != 0 ||
       cst_realm_fingerprint(realm.pk, fp) != 0) {
     fprintf(stderr, "cannot load realm\n");
     return 1;
diff --git a/src/parliament_daemon.c b/src/parliament_daemon.c
new file mode 100644
index 0000000..673bb2e
--- /dev/null
+++ b/src/parliament_daemon.c
@@ -0,0 +1,321 @@
+#ifndef _DEFAULT_SOURCE
+#define _DEFAULT_SOURCE
+#endif
+#include "cst_parliament.h"
+#include "cst_discover.h"
+#include "cst_net.h"
+#include "cst_peer.h"
+#include "cst_realm.h"
+#include "cst_util.h"
+#include "monocypher.h"
+#include "os_compat.h"
+
+#include <errno.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <time.h>
+
+#ifdef _WIN32
+#include <windows.h>
+#else
+#include <fcntl.h>
+#include <signal.h>
+#include <sys/stat.h>
+#include <unistd.h>
+#endif
+
+static volatile int g_stop;
+
+#ifndef _WIN32
+static void on_sig(int sig) {
+  (void)sig;
+  g_stop = 1;
+}
+#endif
+
+int cst_parliament_daemon_pidfile(char *out, size_t n) {
+  char dir[OS_PATH_MAX];
+  if (cst_realm_dir(dir, sizeof(dir)) != 0)
+    return -1;
+  return os_path_join(out, n, dir, "parliament.pid");
+}
+
+static int read_pid(void) {
+  char path[OS_PATH_MAX];
+  if (cst_parliament_daemon_pidfile(path, sizeof(path)) != 0)
+    return -1;
+  FILE *f = fopen(path, "rb");
+  if (!f)
+    return -1;
+  int pid = -1;
+  if (fscanf(f, "%d", &pid) != 1)
+    pid = -1;
+  fclose(f);
+  return pid;
+}
+
+static int write_pid(int pid) {
+  char path[OS_PATH_MAX], tmp[OS_PATH_MAX + 8];
+  if (cst_parliament_daemon_pidfile(path, sizeof(path)) != 0)
+    return -1;
+  if (snprintf(tmp, sizeof(tmp), "%s.tmp", path) >= (int)sizeof(tmp))
+    return -1;
+  FILE *f = fopen(tmp, "wb");
+  if (!f)
+    return -1;
+  int ok = fprintf(f, "%d\n", pid) > 0;
+  if (fclose(f) != 0)
+    ok = 0;
+  if (!ok) {
+    remove(tmp);
+    return -1;
+  }
+  return os_rename_replace(tmp, path);
+}
+
+static void clear_pid(void) {
+  char path[OS_PATH_MAX];
+  if (cst_parliament_daemon_pidfile(path, sizeof(path)) == 0)
+    remove(path);
+}
+
+int cst_parliament_daemon_running(void) {
+  int pid = read_pid();
+  if (pid <= 0)
+    return 0;
+#ifdef _WIN32
+  HANDLE h = OpenProcess(PROCESS_QUERY_LIMITED_INFORMATION, FALSE, (DWORD)pid);
+  if (!h)
+    return 0;
+  CloseHandle(h);
+  return 1;
+#else
+  return kill(pid, 0) == 0;
+#endif
+}
+
+static void sleep_ms(int ms) {
+#ifdef _WIN32
+  Sleep((DWORD)ms);
+#else
+  struct timespec ts = {ms / 1000, (ms % 1000) * 1000000L};
+  nanosleep(&ts, NULL);
+#endif
+}
+
+static int load_local_bundle(cst_peer_sync_bundle_t *b) {
+  memset(b, 0, sizeof(*b));
+  cst_parliament_meta_t m;
+  if (cst_parliament_load(&m) != 0)
+    return -1;
+  b->revision = m.revision;
+  snprintf(b->parliament_id, sizeof(b->parliament_id), "%s", m.parliament_id);
+  snprintf(b->project_id, sizeof(b->project_id), "%s", m.project_id);
+  snprintf(b->chair_instance, sizeof(b->chair_instance), "%s",
+           m.chair_instance);
+  b->context = cst_parliament_context_get();
+  return b->context ? 0 : -1;
+}
+
+static int apply_if_newer(cst_peer_sync_bundle_t *b, unsigned long before) {
+  if (b->revision <= before)
+    return 0;
+  return cst_parliament_apply_sync(b->revision, b->parliament_id, b->project_id,
+                                   b->chair_instance, b->context);
+}
+
+static int sync_on_session(cst_peer_session_t *sess) {
+  cst_peer_sync_bundle_t local;
+  if (load_local_bundle(&local) != 0)
+    return -1;
+  unsigned long before = local.revision;
+  char err[128];
+  int rc = cst_peer_sync(sess, &local, 15000, err, sizeof(err));
+  if (rc == 0)
+    apply_if_newer(&local, before);
+  free(local.context);
+  return rc;
+}
+
+static int unlock_realm(const char *password, cst_realm_keys_t *keys) {
+  char dir[OS_PATH_MAX];
+  if (cst_realm_dir(dir, sizeof(dir)) != 0)
+    return -1;
+  if (cst_realm_is_password_mode(dir))
+    return cst_realm_unlock_password(dir, password, keys);
+  return cst_realm_load(dir, keys);
+}
+
+int cst_parliament_daemon_run(const char *password, const char *instance_id,
+                              int peer_port, char *err, size_t err_sz) {
+  if (err && err_sz)
+    err[0] = 0;
+  if (!instance_id || !instance_id[0]) {
+    if (err && err_sz)
+      snprintf(err, err_sz, "instance id required");
+    return -1;
+  }
+  cst_realm_keys_t realm;
+  if (unlock_realm(password, &realm) != 0) {
+    if (err && err_sz)
+      snprintf(err, err_sz, "cannot unlock realm");
+    return -1;
+  }
+  cst_realm_cert_t cert;
+  uint8_t sk[64];
+  if (cst_realm_instance_load(instance_id, &cert, sk) != 0) {
+    if (err && err_sz)
+      snprintf(err, err_sz, "instance not enrolled; login first");
+    crypto_wipe(realm.seed, sizeof(realm.seed));
+    crypto_wipe(realm.sk, sizeof(realm.sk));
+    return -1;
+  }
+  char fp[33];
+  cst_realm_fingerprint(realm.pk, fp);
+  os_net_init();
+  char nerr[128];
+  os_socket_t ls =
+      os_net_listen("0.0.0.0", peer_port > 0 ? peer_port : 0, nerr, sizeof(nerr));
+  if (ls == OS_SOCKET_BAD) {
+    if (err && err_sz)
+      snprintf(err, err_sz, "listen failed: %s", nerr);
+    crypto_wipe(sk, sizeof(sk));
+    crypto_wipe(realm.seed, sizeof(realm.seed));
+    crypto_wipe(realm.sk, sizeof(realm.sk));
+    return -1;
+  }
+  int bound = os_net_port(ls);
+  cst_discover_t *disc =
+      cst_discover_start(fp, instance_id, instance_id, bound);
+  write_pid(
+#ifdef _WIN32
+      (int)GetCurrentProcessId()
+#else
+      (int)getpid()
+#endif
+  );
+  fprintf(stderr, "parliament_service pid=%d port=%d id=%s realm=%s\n",
+#ifdef _WIN32
+          (int)GetCurrentProcessId(),
+#else
+          (int)getpid(),
+#endif
+          bound, instance_id, fp);
+  fflush(stderr);
+
+#ifndef _WIN32
+  signal(SIGTERM, on_sig);
+  signal(SIGINT, on_sig);
+  signal(SIGHUP, on_sig);
+#endif
+  g_stop = 0;
+  int tick = 0;
+  while (!g_stop) {
+    cst_peer_session_t sess;
+    char herr[128];
+    if (cst_peer_accept((intptr_t)ls, &cert, sk, realm.pk, 500, &sess, herr,
+                        sizeof(herr)) == 0) {
+      sync_on_session(&sess);
+      cst_peer_close(&sess);
+    }
+    if (++tick % 10 == 0 && disc) {
+      cst_peer_info_t peers[16];
+      int n = cst_discover_peers(disc, peers, 16);
+      for (int i = 0; i < n; i++) {
+        if (peers[i].port <= 0)
+          continue;
+        if (cst_peer_dial(peers[i].host, peers[i].port, &cert, sk, realm.pk,
+                          3000, &sess, herr, sizeof(herr)) == 0) {
+          sync_on_session(&sess);
+          cst_peer_close(&sess);
+        }
+      }
+    }
+    sleep_ms(200);
+  }
+  if (disc)
+    cst_discover_stop(disc);
+  os_net_close(ls);
+  clear_pid();
+  crypto_wipe(sk, sizeof(sk));
+  crypto_wipe(realm.seed, sizeof(realm.seed));
+  crypto_wipe(realm.sk, sizeof(realm.sk));
+  return 0;
+}
+
+int cst_parliament_daemon_stop(void) {
+  int pid = read_pid();
+  if (pid <= 0)
+    return 0;
+#ifdef _WIN32
+  HANDLE h = OpenProcess(PROCESS_TERMINATE, FALSE, (DWORD)pid);
+  if (h) {
+    TerminateProcess(h, 0);
+    CloseHandle(h);
+  }
+#else
+  if (kill(pid, SIGTERM) != 0 && errno != ESRCH)
+    return -1;
+  for (int i = 0; i < 25; i++) {
+    if (kill(pid, 0) != 0)
+      break;
+    sleep_ms(100);
+  }
+  if (kill(pid, 0) == 0)
+    kill(pid, SIGKILL);
+#endif
+  clear_pid();
+  return 0;
+}
+
+int cst_parliament_daemon_start(const char *password, const char *instance_id,
+                                int peer_port, char *err, size_t err_sz) {
+  if (err && err_sz)
+    err[0] = 0;
+  if (cst_parliament_daemon_running())
+    return 0;
+#ifdef _WIN32
+  /* Windows: run in-process foreground loop under a detached console is
+   * deferred; callers should use --service in a service manager. */
+  if (err && err_sz)
+    snprintf(err, err_sz, "background daemon requires --service on Windows");
+  return -1;
+#else
+  if (!password || !password[0]) {
+    if (err && err_sz)
+      snprintf(err, err_sz, "password required to start service");
+    return -1;
+  }
+  pid_t pid = fork();
+  if (pid < 0) {
+    if (err && err_sz)
+      snprintf(err, err_sz, "fork failed");
+    return -1;
+  }
+  if (pid > 0) {
+    /* Parent: wait briefly for pidfile. */
+    for (int i = 0; i < 50; i++) {
+      if (cst_parliament_daemon_running())
+        return 0;
+      sleep_ms(50);
+    }
+    if (err && err_sz)
+      snprintf(err, err_sz, "service did not start");
+    return -1;
+  }
+  /* Child: detach. */
+  setsid();
+  int fd = open("/dev/null", O_RDWR);
+  if (fd >= 0) {
+    dup2(fd, 0);
+    /* Keep stderr for service banner until closed by operator logs. */
+    if (fd > 2)
+      close(fd);
+  }
+  char derr[256];
+  (void)cst_parliament_daemon_run(password, instance_id, peer_port, derr,
+                                  sizeof(derr));
+  _exit(0);
+#endif
+}
diff --git a/src/peer_auth.c b/src/peer_auth.c
index c63f0d3..9fe03e8 100644
--- a/src/peer_auth.c
+++ b/src/peer_auth.c
@@ -298,7 +298,7 @@ int cst_peer_dial(const char *host, int port, const cst_realm_cert_t *self,
   out->remote = remote;
   snprintf(out->host, sizeof(out->host), "%s", host);
   out->port = port;
-  os_net_close(s);
+  out->sock = (intptr_t)s;
   return 0;
 }
 
@@ -329,6 +329,136 @@ int cst_peer_accept(intptr_t listen_sock, const cst_realm_cert_t *self,
   out->remote = remote;
   os_net_peer(s, out->host, sizeof(out->host));
   out->port = 0;
-  os_net_close(s);
+  out->sock = (intptr_t)s;
+  return 0;
+}
+
+void cst_peer_close(cst_peer_session_t *s) {
+  if (!s)
+    return;
+  if (s->sock != 0 && s->sock != (intptr_t)OS_SOCKET_BAD)
+    os_net_close((os_socket_t)s->sock);
+  s->sock = (intptr_t)OS_SOCKET_BAD;
+}
+
+static int send_sync_hdr(os_socket_t s, const cst_peer_sync_bundle_t *b,
+                         int timeout_ms) {
+  cJSON *o = cJSON_CreateObject();
+  if (!o)
+    return -1;
+  cJSON_AddNumberToObject(o, "v", 1);
+  cJSON_AddStringToObject(o, "op", "sync");
+  cJSON_AddNumberToObject(o, "revision", (double)b->revision);
+  cJSON_AddStringToObject(o, "parliament_id", b->parliament_id);
+  cJSON_AddStringToObject(o, "project_id", b->project_id);
+  cJSON_AddStringToObject(o, "chair", b->chair_instance);
+  size_t clen = b->context ? strlen(b->context) : 0;
+  cJSON_AddNumberToObject(o, "context_len", (double)clen);
+  char *line = cJSON_PrintUnformatted(o);
+  cJSON_Delete(o);
+  if (!line)
+    return -1;
+  int rc = send_line(s, line, timeout_ms);
+  free(line);
+  if (rc != 0)
+    return -1;
+  if (clen > 0 &&
+      os_net_send_all(s, b->context, clen, timeout_ms) != 0)
+    return -1;
+  return 0;
+}
+
+static int read_sync_hdr(os_socket_t s, cst_peer_sync_bundle_t *b,
+                         int timeout_ms) {
+  memset(b, 0, sizeof(*b));
+  char *line = recv_line(s, timeout_ms);
+  if (!line)
+    return -1;
+  cJSON *o = cJSON_Parse(line);
+  free(line);
+  if (!o)
+    return -1;
+  const cJSON *op = cJSON_GetObjectItemCaseSensitive(o, "op");
+  if (!cJSON_IsString(op) || strcmp(op->valuestring, "sync") != 0) {
+    cJSON_Delete(o);
+    return -1;
+  }
+  const cJSON *v;
+  v = cJSON_GetObjectItemCaseSensitive(o, "revision");
+  if (cJSON_IsNumber(v))
+    b->revision = (unsigned long)v->valuedouble;
+  v = cJSON_GetObjectItemCaseSensitive(o, "parliament_id");
+  if (cJSON_IsString(v))
+    snprintf(b->parliament_id, sizeof(b->parliament_id), "%s", v->valuestring);
+  v = cJSON_GetObjectItemCaseSensitive(o, "project_id");
+  if (cJSON_IsString(v))
+    snprintf(b->project_id, sizeof(b->project_id), "%s", v->valuestring);
+  v = cJSON_GetObjectItemCaseSensitive(o, "chair");
+  if (cJSON_IsString(v))
+    snprintf(b->chair_instance, sizeof(b->chair_instance), "%s",
+             v->valuestring);
+  size_t clen = 0;
+  v = cJSON_GetObjectItemCaseSensitive(o, "context_len");
+  if (cJSON_IsNumber(v) && v->valuedouble >= 0)
+    clen = (size_t)v->valuedouble;
+  cJSON_Delete(o);
+  if (clen > 2 * 1024 * 1024)
+    return -1;
+  if (clen == 0) {
+    b->context = strdup("");
+    return b->context ? 0 : -1;
+  }
+  char *ctx = malloc(clen + 1);
+  if (!ctx)
+    return -1;
+  size_t got = 0;
+  while (got < clen) {
+    long r = os_net_recv(s, ctx + got, clen - got, timeout_ms);
+    if (r <= 0) {
+      free(ctx);
+      return -1;
+    }
+    got += (size_t)r;
+  }
+  ctx[clen] = 0;
+  b->context = ctx;
+  return 0;
+}
+
+int cst_peer_sync(cst_peer_session_t *s, cst_peer_sync_bundle_t *local,
+                  int timeout_ms, char *err, size_t err_sz) {
+  if (err && err_sz)
+    err[0] = 0;
+  if (!s || !local || s->sock == (intptr_t)OS_SOCKET_BAD) {
+    if (err && err_sz)
+      snprintf(err, err_sz, "bad peer session");
+    return -1;
+  }
+  os_socket_t sock = (os_socket_t)s->sock;
+  if (send_sync_hdr(sock, local, timeout_ms) != 0) {
+    if (err && err_sz)
+      snprintf(err, err_sz, "sync send failed");
+    return -1;
+  }
+  cst_peer_sync_bundle_t remote;
+  if (read_sync_hdr(sock, &remote, timeout_ms) != 0) {
+    if (err && err_sz)
+      snprintf(err, err_sz, "sync recv failed");
+    return -1;
+  }
+  if (remote.revision > local->revision) {
+    free(local->context);
+    local->context = remote.context;
+    remote.context = NULL;
+    local->revision = remote.revision;
+    snprintf(local->parliament_id, sizeof(local->parliament_id), "%s",
+             remote.parliament_id);
+    snprintf(local->project_id, sizeof(local->project_id), "%s",
+             remote.project_id);
+    snprintf(local->chair_instance, sizeof(local->chair_instance), "%s",
+             remote.chair_instance);
+  } else {
+    free(remote.context);
+  }
   return 0;
 }
diff --git a/tests/test_parliament.c b/tests/test_parliament.c
index a1d0f8d..2d488e5 100644
--- a/tests/test_parliament.c
+++ b/tests/test_parliament.c
@@ -44,6 +44,8 @@ int main(void) {
   assert(cst_parliament_load(&m) == 0);
   assert(!strcmp(m.chair_instance, "laptop-2"));
 
+  assert(cst_parliament_session_ok(NULL, 0));
+
   assert(cst_parliament_new_project("proj-b") == 0);
   char *ctx = cst_parliament_context_get();
   assert(ctx && ctx[0] == 0);
@@ -51,6 +53,16 @@ int main(void) {
   assert(cst_parliament_load(&m) == 0);
   assert(!strcmp(m.project_id, "proj-b"));
   assert(m.chair_instance[0] == 0);
+  assert(!cst_parliament_session_ok(NULL, 0));
+
+  assert(cst_parliament_apply_sync(9, "parl-x", "proj-c", "chair-z",
+                                   "synced-body") == 0);
+  ctx = cst_parliament_context_get();
+  assert(ctx && strstr(ctx, "synced-body"));
+  free(ctx);
+  assert(cst_parliament_load(&m) == 0);
+  assert(m.revision == 9);
+  assert(!strcmp(m.chair_instance, "chair-z"));
 
   test_rmrf(dir);
   puts("test_parliament: OK");
diff --git a/tests/test_peer_auth.c b/tests/test_peer_auth.c
index fe25d96..9df03bd 100644
--- a/tests/test_peer_auth.c
+++ b/tests/test_peer_auth.c
@@ -24,8 +24,10 @@ static void *server_main(void *p) {
   char err[128];
   s->ok = cst_peer_accept((intptr_t)s->listen, &s->cert, s->sk, s->realm_pk,
                           5000, &sess, err, sizeof(err)) == 0;
-  if (s->ok)
+  if (s->ok) {
     snprintf(s->remote_id, sizeof(s->remote_id), "%s", sess.remote.instance_id);
+    cst_peer_close(&sess);
+  }
   return NULL;
 }
 
@@ -55,6 +57,7 @@ int main(void) {
   assert(cst_peer_dial("127.0.0.1", port, &ca, ska, realm.pk, 5000, &sess, err,
                        sizeof(err)) == 0);
   assert(!strcmp(sess.remote.instance_id, "peer-b"));
+  cst_peer_close(&sess);
   pthread_join(th, NULL);
   assert(srv.ok);
   assert(!strcmp(srv.remote_id, "peer-a"));