fix(engine): a client that leaves must not kill the daemon, and a long round must say it started

Round 9.1, spec §3 D + ADR 0006 items 2 and 4. Two small changes, both proven
by measurement, both E2E-verified locally against a rebuilt brain.

D1 — SIGPIPE/EPIPE survival (vendor/el-runtime el_runtime.c).
Root cause, at the layer that owns it: the whole HTTP server lives in the C
runtime; .el has no socket primitive. http_send_all() called send() with flags
0 and nothing anywhere in the runtime set a SIGPIPE disposition, so the default
disposition — terminate the process — applied. When a handler finished after
its client had gone (Tim's VM: reply at 116.9 s, client cancelled at 25.0 s),
the second of the four sends that write one reply raised SIGPIPE and the daemon
died: `exited due to SIGPIPE ... ran for 361177ms`, launchd respawn 4 ms later,
every other in-flight session's work lost, user never told.

Fix: SIGPIPE -> SIG_IGN at runtime init and at each http_serve* entry, plus
per-connection SO_NOSIGPIPE / MSG_NOSIGNAL so the guard survives an embedder
resetting dispositions. http_send_all now retries EINTR and preserves errno;
http_send_response classifies it once — a departure is logged as routine
("client left before the reply was written ... reply discarded") and ANY other
errno is logged as a real "send failed: <strerror>". Spec §5.3: the routine
case must not mask a genuine write fault, and it does not.

Proof (scratch HOME + free port, 3 disconnects mid-reply):
  round-9 shipped brain 4402179554… — DIED, exit 141 (128+13 = SIGPIPE), round 1
  round-9 sources rebuilt with this exact recipe — DIED, exit 141, round 1
  this build — SURVIVED 3/3, /health 200 after, still serving the full graph,
  three honest "client left" lines in the log naming Broken pipe / Connection
  reset by peer.

D2 — the round-start marker (chat.el, agentic_loop).
The ledger only ever appended AFTER a round returned, so a healthy first leg
produced zero progress by construction; since server-side web_search moved
inside the outbound call that leg is 60-120 s of silence, which is how a 25 s
client watchdog came to kill a healthy mission. One entry,
{"i":N,"t":"","tool":"__working__"}, written to the existing
run_progress_<session_id> ledger BEFORE each round's outbound call — the wire
shape ChatView.kt:1148 has handled as a life signal since 2026-07-13 and never
received. No new key, no new route, no new lifecycle: a strict subset of WS3
item 3. WS3's run registry is untouched and stays Will's.

Proof (live Anthropic key, real research mission, scratch HOME + free port):
  round-9 baseline — ledger EMPTY for the whole 59.7 s leg
  this build       — {"i":0,"t":"","tool":"__working__"} visible at 18.6 s of a
                     70.0 s leg; both builds returned correct ~4.9 KB answers

Regression: prompt-matrix gate 32/32 on this build (round-9 baseline also 32/32
under the same recipe, so the score is not a build artifact). Soul contract
gate PASS — 27/27 routes, immutability clean. neuron#111 miscompile guard: 0
sites in the generated amalgam this binary was compiled from.

NOT included, deliberately: the regenerated dist/soul.c. CI compiles that file,
so production stays exposed until it is regenerated — the same open ask as
neuron#111 / ui#209. The regen recipe is now known and recorded; landing it is
Will's call, per BUILD-HYGIENE.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

chat.el

@@ -2837,6 +2837,30 @@ fn agentic_loop(session_id: String, model: String, safe_sys: String, tools_json:
             + ",\"messages\":" + messages
             + "}"
 
+        // ── ROUND-START MARKER (2026-08-06, round 9.1 D2 / ADR 0006 item 2) ──────────
+        // The ledger below only ever appended AFTER a round returned, so a healthy
+        // first leg produced ZERO progress by construction. Since server-side
+        // web_search moved inside the outbound call (2026-08-04) that leg measures
+        // 84-117 s, and the client had no way to tell "working" from "dead" — which is
+        // how a 25 s client-side watchdog came to kill a healthy mission.
+        //
+        // Only this loop knows a round has started, so only this loop can say so. One
+        // entry, written BEFORE the call goes out, using the ledger and the wire shape
+        // that already exist: the app has handled tool == "__working__" as an
+        // Activity-only life signal since 2026-07-13 (ChatView.kt:1148) and never
+        // received one. Narration is deliberately empty - the marker means "a round
+        // started", nothing more, and the client renders it as a heartbeat, not prose.
+        //
+        // This is a strict subset of WS3 item 3 (push/poll progress). It builds none of
+        // WS3's run registry: no new state key, no new route, no new lifecycle.
+        if !str_eq(session_id, "") {
+            let start_key: String = "run_progress_" + session_id
+            let start_prev: String = state_get(start_key)
+            let start_entry: String = "{\"i\":" + int_to_str(iteration) + ",\"t\":\"\",\"tool\":\"__working__\"}"
+            let start_next: String = if str_eq(start_prev, "") { start_entry } else { start_prev + "," + start_entry }
+            state_set(start_key, start_next)
+        }
+
         let raw_resp: String = http_post_with_headers(api_url, req_body, h)
 
         let is_error: Bool = str_starts_with(raw_resp, "{\"error\"")

vendor/el-runtime/v1.0.0-20260501/el_runtime.c

@@ -41,6 +41,7 @@
 #include <fcntl.h>
 #include <dirent.h>
 #include <errno.h>
+#include <signal.h>     /* SIGPIPE disposition — see el_runtime_ignore_sigpipe */
 #include <pthread.h>
 #include <curl/curl.h>
 
@@ -1238,16 +1239,77 @@ static const char* http_reason_phrase(int status) {
     }
 }
 
-/* Best-effort send with retry on partial writes. */
+/* ── A departing client MUST NOT be able to kill the daemon ──────────────────
+ * (2026-08-06, round 9.1 / ADR 0006 item 4.)
+ *
+ * Measured field failure: a client cancelled its request at 25 s; the handler
+ * finished its work at 116.9 s and wrote the reply into the departed client's
+ * socket. The second send() on a reset connection raised SIGPIPE, whose DEFAULT
+ * disposition terminates the process — `exited due to SIGPIPE ... ran for
+ * 361177ms`. launchd respawned 4 ms later, so EVERY other in-flight request on
+ * that daemon lost its work, silently.
+ *
+ * Two independent guards, because one of them can be undone from outside this
+ * file (an embedder may reset signal dispositions) and the other cannot:
+ *   1. process-wide SIGPIPE -> SIG_IGN, installed at runtime init;
+ *   2. per-send suppression at the syscall (MSG_NOSIGNAL where the platform has
+ *      it, SO_NOSIGPIPE on the accepted socket on macOS/BSD).
+ * With either in force, send() reports the peer's departure as EPIPE and the
+ * caller decides — which is the point: this is an ordinary I/O outcome, not a
+ * fatal condition.
+ *
+ * It deliberately does NOT swallow the error. http_send_response() below
+ * classifies the errno and logs: "client left" for a departure, and a real
+ * "send failed: <strerror>" for anything else, so a genuine write fault is
+ * still visible in the log (spec round-9.1 §5.3).                            */
+
+#ifndef MSG_NOSIGNAL
+#define MSG_NOSIGNAL 0
+#endif
+
+void el_runtime_ignore_sigpipe(void) {
+    static int done = 0;
+    if (done) return;
+    done = 1;
+    struct sigaction sa;
+    memset(&sa, 0, sizeof(sa));
+    sa.sa_handler = SIG_IGN;
+    sigemptyset(&sa.sa_mask);
+    sigaction(SIGPIPE, &sa, NULL);
+}
+
+/* Suppress SIGPIPE for one accepted connection (macOS/BSD have no
+ * MSG_NOSIGNAL; they have the socket option instead). Best effort. */
+static void http_socket_nosigpipe(int fd) {
+#ifdef SO_NOSIGPIPE
+    int on = 1;
+    setsockopt(fd, SOL_SOCKET, SO_NOSIGPIPE, &on, sizeof(on));
+#else
+    (void)fd;
+#endif
+}
+
+/* Best-effort send with retry on partial writes.
+ * Returns 0 on success, -1 on failure with errno preserved for the caller. */
 static int http_send_all(int fd, const char* p, size_t left) {
     while (left > 0) {
-        ssize_t w = send(fd, p, left, 0);
-        if (w <= 0) return -1;
+        ssize_t w = send(fd, p, left, MSG_NOSIGNAL);
+        if (w < 0) {
+            if (errno == EINTR) continue;       /* not an error — retry */
+            return -1;                          /* errno stays set for caller */
+        }
+        if (w == 0) { errno = EPIPE; return -1; }
         p += w; left -= (size_t)w;
     }
     return 0;
 }
 
+/* Did this write fail because the client is gone, or because something is
+ * actually wrong with the socket? Only the first is routine. */
+static int http_write_err_is_client_gone(int e) {
+    return e == EPIPE || e == ECONNRESET || e == ENOTCONN || e == ESHUTDOWN;
+}
+
 /* Discriminator that http_response() embeds at the start of its envelope.
  * A handler returning a string starting with this exact prefix is treated
  * as a structured response; anything else is treated as a raw body. */
@@ -1468,14 +1530,30 @@ static void http_send_response(int fd, const char* body) {
         free(env_body); free(hdrs.buf); return;
     }
 
-    if (http_send_all(fd, status_line, (size_t)sl) == 0
-     && http_send_all(fd, hdrs.buf,    hdrs.len)   == 0
-     && http_send_all(fd, tail,        (size_t)tl) == 0
-     && (head_only
-         /* HEAD requests echo headers + Content-Length but no body. */
-         ? 1
-         : http_send_all(fd, eff_body, blen) == 0)) {
-        /* sent successfully */
+    /* The reply is written in four pieces; any of them can find the client
+     * already gone. errno is captured at the first failure, before any later
+     * library call can clobber it, and classified once below. */
+    errno = 0;
+    int send_err = 0;
+    if (http_send_all(fd, status_line, (size_t)sl) != 0) send_err = errno;
+    else if (http_send_all(fd, hdrs.buf, hdrs.len) != 0) send_err = errno;
+    else if (http_send_all(fd, tail, (size_t)tl) != 0) send_err = errno;
+    else if (!head_only /* HEAD echoes headers + Content-Length, no body. */
+             && http_send_all(fd, eff_body, blen) != 0) send_err = errno;
+
+    if (send_err) {
+        if (http_write_err_is_client_gone(send_err)) {
+            /* ROUTINE. The user closed the window, quit the app, or cancelled.
+             * The work is done and the daemon keeps serving everyone else. */
+            fprintf(stderr, "[http] client left before the reply was written "
+                            "(%zu-byte body, %s) - request completed, reply discarded\n",
+                    blen, strerror(send_err));
+        } else {
+            /* NOT routine — a real write fault. Never let the client-gone case
+             * above hide this one. */
+            fprintf(stderr, "[http] send failed: %s (%zu-byte body)\n",
+                    strerror(send_err), blen);
+        }
     }
 
     if (env_parsed_root) el_release(env_parsed_root);
@@ -1491,6 +1569,7 @@ static void* http_worker(void* arg) {
     HttpWorkerArg* a = (HttpWorkerArg*)arg;
     int fd = a->fd;
     free(a);
+    http_socket_nosigpipe(fd);
     char *method = NULL, *path = NULL, *body = NULL;
     if (http_read_request(fd, &method, &path, &body, NULL) == 0) {
         http_handler_fn h = http_lookup_active();
@@ -1531,6 +1610,7 @@ static void* http_worker(void* arg) {
 }
 
 void http_serve(el_val_t port, el_val_t handler) {
+    el_runtime_ignore_sigpipe();   /* serving implies clients that leave */
     /* If `handler` looks like a string name, register it as the active handler. */
     const char* hname = EL_CSTR(handler);
     if (hname && looks_like_string(handler)) {
@@ -1634,6 +1714,7 @@ static void* _http_serve_async_loop(void* raw) {
 }
 
 void http_serve_async(el_val_t port, el_val_t handler) {
+    el_runtime_ignore_sigpipe();   /* serving implies clients that leave */
     const char* hname = EL_CSTR(handler);
     if (hname && looks_like_string(handler)) {
         http_set_handler(handler);
@@ -1821,6 +1902,7 @@ static void* http_worker_v2(void* arg) {
     HttpWorkerArg* a = (HttpWorkerArg*)arg;
     int fd = a->fd;
     free(a);
+    http_socket_nosigpipe(fd);
     char *method = NULL, *path = NULL, *body = NULL, *hdr_block = NULL;
     if (http_read_request(fd, &method, &path, &body, &hdr_block) == 0) {
         http_handler4_fn h = http_lookup_active_v2();
@@ -1858,6 +1940,7 @@ static void* http_worker_v2(void* arg) {
 }
 
 void http_serve_v2(el_val_t port, el_val_t handler) {
+    el_runtime_ignore_sigpipe();   /* serving implies clients that leave */
     const char* hname = EL_CSTR(handler);
     if (hname && looks_like_string(handler)) {
         http_set_handler_v2(handler);
@@ -5511,6 +5594,9 @@ el_val_t getpid_now(void) {
 static el_val_t _el_args_list = 0;
 
 void el_runtime_init_args(int argc, char** argv) {
+    /* First line of every generated main(): a client that leaves must never be
+     * able to signal this process to death. See el_runtime_ignore_sigpipe. */
+    el_runtime_ignore_sigpipe();
     _el_args_list = el_list_empty();
     for (int i = 1; i < argc; i++) {
         _el_args_list = el_list_append(_el_args_list, EL_STR(argv[i]));