@@ -81,10 +81,9 @@ import {
   CLI,
   childEnv,
   E2E_SECRET_KEY,
-  portContentionError,
-  portDriftError,
+  KERNEL_ASSIGNED_PORT,
   probeThroughChild,
-  randomPort,
+  readKernelAssignedPort,
   TSX,
 } from './helpers/serve-process.js';
 import { defineStackSourceFromLiteral, linkSpec, writeDefineStackConfig } from './helpers/define-stack-fixture.js';
@@ -125,7 +124,7 @@ interface Live {
   output: () => string;
 }
 
-function boot(argv: string[], cwd: string, port: string, env: Record<string, string | undefined>): Promise<Live> {
+function boot(argv: string[], cwd: string, env: Record<string, string | undefined>): Promise<Live> {
   return new Promise((resolveBoot, rejectBoot) => {
     const child = spawn(TSX, [CLI, ...argv], {
       cwd,
@@ -147,26 +146,26 @@ function boot(argv: string[], cwd: string, port: string, env: Record<string, str
     groups.push(child);
     let out = '';
     let settled = false;
-    const settle = (err: Error | null) => {
+    const settle = (verdict: Error | number) => {
       if (settled) return;
       settled = true;
       clearTimeout(timer);
-      if (err) rejectBoot(err);
-      else resolveBoot({ child, base: `http://localhost:${port}`, output: () => out });
+      if (verdict instanceof Error) rejectBoot(verdict);
+      else resolveBoot({ child, base: `http://localhost:${verdict}`, output: () => out });
     };
     const timer = setTimeout(
       () => settle(new Error(`${argv[0]} never printed ${READY}\n--- output ---\n${out.slice(-4000)}`)),
       BOOT_TIMEOUT_MS,
     );
     const onData = (d: unknown) => {
       out += String(d);
-      if (READY.test(out)) settle(portDriftError(out, `os ${argv[0]}`, port));
+      // The child is the authority on the port it bound: a kernel-assigned one (#24342).
+      if (READY.test(out)) settle(readKernelAssignedPort(out, `os ${argv[0]}`));
     };
     child.stdout?.on('data', onData);
     child.stderr?.on('data', onData);
     child.on('exit', (code) =>
-      settle(portContentionError(out, `os ${argv[0]}`, port)
-        ?? new Error(`os ${argv[0]} exited ${String(code)} before ${READY}\n--- output ---\n${out.slice(-4000)}`)),
+      settle(new Error(`os ${argv[0]} exited ${String(code)} before ${READY}\n--- output ---\n${out.slice(-4000)}`)),
     );
   });
 }
@@ -250,10 +249,9 @@ interface Reading {
 }
 
 async function measure(argv: string[], cwd: string, env: Record<string, string | undefined> = {}): Promise<Reading> {
-  const port = randomPort();
   let live: Live | undefined;
   try {
-    live = await boot([...argv.slice(0, 1), '-p', port, ...argv.slice(1)], cwd, port, env);
+    live = await boot([...argv.slice(0, 1), '-p', KERNEL_ASSIGNED_PORT, ...argv.slice(1)], cwd, env);
     const signIn = await http(live, 'POST', '/api/v1/auth/sign-in/email', '', { email: EMAIL, password: PASSWORD });
     const token = signIn.body?.token;
     if (signIn.status !== 200 || typeof token !== 'string') {
 
@@ -58,7 +58,7 @@ import { fileURLToPath } from 'node:url';
 import {
   childEnv,
   E2E_SECRET_KEY,
-  randomPort,
+  KERNEL_ASSIGNED_PORT,
   requireBuiltCli,
   RUN_JS_RESOLVES_FROM_DIST,
 } from './helpers/serve-process.js';
@@ -115,10 +115,9 @@ function screenLines(raw: string): string[] {
 
 /** Boot `os dev` under a pty until the banner and the block have both printed, then Ctrl+C it. */
 function bootUnderPty(boot: number): Promise<string> {
-  const port = randomPort();
   const command = [
     `exec '${process.execPath}' '${CLI}' dev --no-watch`,
-    `-d 'file:boot${boot}.db' -p ${port}`,
+    `-d 'file:boot${boot}.db' -p ${KERNEL_ASSIGNED_PORT}`,
   ].join(' ');
   return new Promise((resolveBoot, rejectBoot) => {
     const child = spawn('script', ['-qfec', command, '/dev/null'], {
 
@@ -182,8 +182,8 @@ function probeBind(want: number): number | null {
 
 /**
  * The released-port draw — a real bind probe, not a blind `Math.random()`
- * (#12441) — for the spawns that still take a number. ⛔ NOT for a spawn that
- * can reach production posture: those take {@link KERNEL_ASSIGNED_PORT}.
+ * (#12441) — for the few sites that still take a number. ⛔ NOT for a CLI
+ * spawn, in either posture: those take {@link KERNEL_ASSIGNED_PORT}.
  *
  * Listen on `0.0.0.0:0`, read the port the kernel assigned, close the listener,
  * return the port for the caller to hand to `os serve`.
@@ -224,21 +224,20 @@ function probeBind(want: number): number | null {
  * development-posture child hops instead, and `portDriftError()` reds the hop
  * just as surely, so that column closes the same way: `runServe()` hands its
  * child a kernel-assigned port whenever the caller passes no `--port`, and
- * returns the port the child bound (#24342).
+ * returns the port the child bound; every bespoke spawner reads its own
+ * kernel-assigned port back the same way (#24342).
  * `released-port-production-spawn.pin.test.ts` holds both: a file that spawns
  * the CLI may call this or `randomPort()` only as often as its ledger entry
  * there allows — zero without one.
  *
  * What may still call it, each with the race still real and unclosed there:
  *
- *   • the development-column spawners slice 2 of #24342 has yet to convert —
- *     the files that spawn `CLI` themselves (the `package-install-local-*`
- *     `os start` family among them) and the four `bin/run.js --dev` / `os dev`
- *     files, each ledgered in the pin with its exact count. A lost race there
- *     is a hop to the next port, and `portDriftError()` below turns it into a
- *     red on a correct tree;
  *   • instruments that need a number NOTHING is listening on (a closed-port
- *     probe), or that measure this draw itself (`serve-port-bind-probe`).
+ *     probe), or that measure this draw itself (`serve-port-bind-probe`);
+ *   • a CLI spawn whose SUBJECT is a non-zero request — a boot that must bind
+ *     exactly the port it asked for, which `--port 0` cannot ask. The pin's
+ *     ledger names each such file with its reason and exact count; a lost
+ *     race there is the residual this draw narrows and cannot close.
  *
  * `portContentionError()` below is what makes a residual loss SAY it is a port
  * race instead of `serve exited 1 before "Server is ready"`.
@@ -318,8 +317,8 @@ export function holdPort(): Promise<{ port: number; release: () => Promise<void>
  * ⚠️ The name is kept — and is now a slight misnomer, which is cheaper than the
  * alternative. It is `String(reservePort())` and nothing else; the draw, the
  * guarantees, the residual race and the callers it may still serve
- * (instruments, and the development-column files the pin's ledger names until
- * slice 2 of #24342 converts them — never another CLI spawn) are all
+ * (instruments, and the few CLI spawns the pin's ledger names with their
+ * reason — never another CLI spawn) are all
  * documented on `reservePort()` above, and there is no second mechanism hiding
  * behind this name.
  */
@@ -599,8 +598,9 @@ export function boundPortFromBanner(output: string): BannerPortReadback {
  * the port between this harness's bind probe and the child's `listen()`. The
  * production column would die loudly, which is why it no longer draws (it takes
  * {@link KERNEL_ASSIGNED_PORT}, #24295); the development column drifts and gets
- * this. `runServe()` without a `--port` no longer draws either (#24342); the
- * spawners still ledgered in the pin do, and this is what makes their race a red.
+ * this. `runServe()` without a `--port` no longer draws either, nor does any
+ * bespoke spawner (#24342): what reaches this now is an EXPLICIT port — one held
+ * on purpose to force the drift, or a draw the pin's ledger names.
  *
  * ## Why `unreadable` is an ERROR and not a skip
  *
 
@@ -55,10 +55,9 @@ import {
   CLI,
   childEnv,
   E2E_SECRET_KEY,
-  portContentionError,
-  portDriftError,
+  KERNEL_ASSIGNED_PORT,
   probeThroughChild,
-  randomPort,
+  readKernelAssignedPort,
   TSX,
 } from './helpers/serve-process.js';
 
@@ -153,9 +152,9 @@ interface LiveStart {
   output: () => string;
 }
 
-function bootStart(cwd: string, home: string, port: string, extra: string[] = []): Promise<LiveStart> {
+function bootStart(cwd: string, home: string, extra: string[] = []): Promise<LiveStart> {
   return new Promise((resolveBoot, rejectBoot) => {
-    const child = spawn(TSX, [CLI, 'start', '-p', port, '--home', home, '--auth-secret', E2E_SECRET_KEY, '--no-ui', ...extra], {
+    const child = spawn(TSX, [CLI, 'start', '-p', KERNEL_ASSIGNED_PORT, '--home', home, '--auth-secret', E2E_SECRET_KEY, '--no-ui', ...extra], {
       cwd,
       // `childEnv`, never a bare `...process.env` — see its header.
       env: childEnv({ NO_COLOR: '1', OS_CLOUD_URL: 'off', OS_LOG_LEVEL: 'warn', OS_SECRET_KEY: E2E_SECRET_KEY }),
@@ -166,27 +165,26 @@ function bootStart(cwd: string, home: string, port: string, extra: string[] = []
     groups.push(child);
     let out = '';
     let settled = false;
-    const settle = (err: Error | null) => {
+    const settle = (verdict: Error | number) => {
       if (settled) return;
       settled = true;
       clearTimeout(timer);
-      if (err) rejectBoot(err);
-      else resolveBoot({ child, base: `http://localhost:${port}`, output: () => out });
+      if (verdict instanceof Error) rejectBoot(verdict);
+      else resolveBoot({ child, base: `http://localhost:${verdict}`, output: () => out });
     };
     const timer = setTimeout(
       () => settle(new Error(`os start never printed ${READY}\n--- output ---\n${out.slice(-4000)}`)),
       BOOT_TIMEOUT_MS,
     );
     const onData = (d: unknown) => {
       out += String(d);
-      // The child is the authority on the port it bound.
-      if (READY.test(out)) settle(portDriftError(out, 'os start', port));
+      // The child is the authority on the port it bound: a kernel-assigned one (#24342).
+      if (READY.test(out)) settle(readKernelAssignedPort(out, 'os start'));
     };
     child.stdout?.on('data', onData);
     child.stderr?.on('data', onData);
     child.on('exit', (code) =>
-      settle(portContentionError(out, 'os start', port)
-        ?? new Error(`os start exited ${String(code)} before ${READY}\n--- output ---\n${out.slice(-4000)}`)),
+      settle(new Error(`os start exited ${String(code)} before ${READY}\n--- output ---\n${out.slice(-4000)}`)),
     );
   });
 }
@@ -320,24 +318,23 @@ beforeAll(async () => {
   const hostArtifact = join(runtimeDir, 'host.json');
   writeFileSync(hostArtifact, JSON.stringify(HOST_ARTIFACT, null, 2), 'utf8');
   const home = join(runtimeDir, 'home');
-  const port = randomPort();
 
   // ── boot 1: the host, hot install, probe ───────────────────────────────
-  const first = await bootStart(runtimeDir, home, port, ['--artifact', hostArtifact]);
+  const first = await bootStart(runtimeDir, home, ['--artifact', hostArtifact]);
   const token = await authenticate(first);
   installs.push(await packageInstall(appDir, first));
   phases.install = await probe(first, token);
   await stopGroup(first.child);
 
   // ── boot 2: same host, home and cwd — the ledger rehydrates on kernel:ready ──
-  const second = await bootStart(runtimeDir, home, port, ['--artifact', hostArtifact]);
+  const second = await bootStart(runtimeDir, home, ['--artifact', hostArtifact]);
   phases.restart = await probe(second, await authenticate(second));
   await stopGroup(second.child);
 
   // ── boot 3: the CONTROL — the same file as the boot artifact ───────────
   const controlDir = join(root, 'control');
   mkdirSync(controlDir, { recursive: true });
-  const third = await bootStart(controlDir, join(controlDir, 'home'), port, ['--artifact', join(appDir, 'dist', 'objectstack.json')]);
+  const third = await bootStart(controlDir, join(controlDir, 'home'), ['--artifact', join(appDir, 'dist', 'objectstack.json')]);
   phases.control = await probe(third, await authenticate(third));
   await stopGroup(third.child);
 }, 4 * BOOT_TIMEOUT_MS);
 
@@ -40,9 +40,9 @@
  *
  * The tsx source entry (`bin/run-dev.js`), as every `runServe()` caller spawns
  * it, for `os start` and for `os package install` alike. It pins
- * `NODE_ENV=development`, which lets `serve` auto-shift off a port taken
- * between the probe and the bind, so the ready banner is read back
- * (`portDriftError`) before any request is addressed to the port. The CLI runs
+ * `NODE_ENV=development`, where a taken port is a hop rather than an exit, so
+ * each boot takes a kernel-assigned port and reads it back off its own ready
+ * banner (`readKernelAssignedPort`) before any request is addressed to it. The CLI runs
  * from `src/`, but every workspace package it loads — `@objectstack/runtime`
  * and `@objectstack/cloud-connection` included — resolves through its
  * `exports` to `dist/`: an ablation of either package's source reaches this
@@ -60,10 +60,9 @@ import {
   CLI,
   childEnv,
   E2E_SECRET_KEY,
-  portContentionError,
-  portDriftError,
+  KERNEL_ASSIGNED_PORT,
   probeThroughChild,
-  randomPort,
+  readKernelAssignedPort,
   TSX,
 } from './helpers/serve-process.js';
 
@@ -142,9 +141,9 @@ interface LiveStart {
   output: () => string;
 }
 
-function bootStart(cwd: string, home: string, port: string, extra: string[] = []): Promise<LiveStart> {
+function bootStart(cwd: string, home: string, extra: string[] = []): Promise<LiveStart> {
   return new Promise((resolveBoot, rejectBoot) => {
-    const child = spawn(TSX, [CLI, 'start', '-p', port, '--home', home, '--auth-secret', E2E_SECRET_KEY, '--no-ui', ...extra], {
+    const child = spawn(TSX, [CLI, 'start', '-p', KERNEL_ASSIGNED_PORT, '--home', home, '--auth-secret', E2E_SECRET_KEY, '--no-ui', ...extra], {
       cwd,
       // `childEnv`, never a bare `...process.env` — see its header.
       env: childEnv({ NO_COLOR: '1', OS_CLOUD_URL: 'off', OS_LOG_LEVEL: 'warn', OS_SECRET_KEY: E2E_SECRET_KEY }),
@@ -155,27 +154,26 @@ function bootStart(cwd: string, home: string, port: string, extra: string[] = []
     groups.push(child);
     let out = '';
     let settled = false;
-    const settle = (err: Error | null) => {
+    const settle = (verdict: Error | number) => {
       if (settled) return;
       settled = true;
       clearTimeout(timer);
-      if (err) rejectBoot(err);
-      else resolveBoot({ child, base: `http://localhost:${port}`, output: () => out });
+      if (verdict instanceof Error) rejectBoot(verdict);
+      else resolveBoot({ child, base: `http://localhost:${verdict}`, output: () => out });
     };
     const timer = setTimeout(
       () => settle(new Error(`os start never printed ${READY}\n--- output ---\n${out.slice(-4000)}`)),
       BOOT_TIMEOUT_MS,
     );
     const onData = (d: unknown) => {
       out += String(d);
-      // The child is the authority on the port it bound.
-      if (READY.test(out)) settle(portDriftError(out, 'os start', port));
+      // The child is the authority on the port it bound: a kernel-assigned one (#24342).
+      if (READY.test(out)) settle(readKernelAssignedPort(out, 'os start'));
     };
     child.stdout?.on('data', onData);
     child.stderr?.on('data', onData);
     child.on('exit', (code) =>
-      settle(portContentionError(out, 'os start', port)
-        ?? new Error(`os start exited ${String(code)} before ${READY}\n--- output ---\n${out.slice(-4000)}`)),
+      settle(new Error(`os start exited ${String(code)} before ${READY}\n--- output ---\n${out.slice(-4000)}`)),
     );
   });
 }
@@ -327,10 +325,9 @@ beforeAll(async () => {
   const runtimeDir = join(root, 'runtime');
   mkdirSync(runtimeDir, { recursive: true });
   const home = join(runtimeDir, 'home');
-  const port = randomPort();
 
   // ── boot 1: empty `os start`, install, probe, reinstall, probe ─────────
-  const first = await bootStart(runtimeDir, home, port);
+  const first = await bootStart(runtimeDir, home);
   const token = await authenticate(first);
   installs.push(await packageInstall(appDir, first));
   phases.install = await probe(first, token);
@@ -339,14 +336,14 @@ beforeAll(async () => {
   await stopGroup(first.child);
 
   // ── boot 2: same home and cwd — the ledger rehydrates on kernel:ready ──
-  const second = await bootStart(runtimeDir, home, port);
+  const second = await bootStart(runtimeDir, home);
   phases.restart = await probe(second, await authenticate(second));
   await stopGroup(second.child);
 
   // ── boot 3: the CONTROL — the same file as the boot artifact ───────────
   const controlDir = join(root, 'control');
   mkdirSync(controlDir, { recursive: true });
-  const third = await bootStart(controlDir, join(controlDir, 'home'), port, ['--artifact', join(appDir, 'dist', 'objectstack.json')]);
+  const third = await bootStart(controlDir, join(controlDir, 'home'), ['--artifact', join(appDir, 'dist', 'objectstack.json')]);
   phases.control = await probe(third, await authenticate(third));
   await stopGroup(third.child);
 }, 4 * BOOT_TIMEOUT_MS);