chore(release): v3.21.1 — concurrency queue + spawn-token + TUI session-scope fixes

Patch release bundling three merged bug fixes (no new cli.js wire behavior,
no new endpoint/header/env var):

- #148 fix(tui): session prefix + reap/kill-server scoped per-instance by port
- #150 fix(server): serialize -p real-HOME token fallback behind a mutex +
  30s TTL keychain read cache + de-staled isolation decision (new lib/spawn-auth.mjs)
- #149 fix: semaphore honors runtime-lowered maxConcurrent, queued requests
  cancelled on client disconnect, singleflight follower retry on leader
  disconnect, exact queued accounting, quiet disconnect handling

Release-kit walk (CLAUDE.md Iron Rule 5.5): package.json version bump,
CHANGELOG.md entry, one-sentence Troubleshooting note for the genuinely
operator-visible upgrade-overlap caveat from #148. No changes to
models.json / Available Models / API Endpoints / Environment Variables
tables — verified by diffing all three merged commits (2922d68..d96da46);
none add an endpoint, header, or env var.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

CHANGELOG.md

@@ -1,5 +1,15 @@
 # Changelog
 
+## v3.21.1 — 2026-07-07
+
+Patch release: three bug fixes from an independent concurrency/session-lifecycle audit, each its own PR with a fresh-context reviewer (Iron Rule 10). No new `cli.js` wire behavior, no new endpoint, header, or env var; the `/health` field set is unchanged (only value truthfulness improved).
+
+### Fixed
+
+- **TUI session-scope / boot-reap (#148)** — `lib/tui/session.mjs`'s tmux session prefix is now scoped per-instance by listen port (`ocp-tui-<port>-`) instead of a bare host-wide `ocp-tui-` constant, so a second OCP instance on the same host (e.g. a temporary verification instance) can no longer have its live TUI sessions reaped or `kill-server`'d by another instance's boot/periodic sweep. The one-time boot reap also claims exact-shape legacy `ocp-tui-<8hex>` sessions (pre-fix naming) once, to clean up zombies left behind across an in-place upgrade.
+- **`-p` spawn-token mutex + keychain caching (#150)** — the real-HOME token fallback used when the keychain token is within its 5-minute expiry window is now serialized behind a mutex, so concurrent `-p` spawns no longer race the same single-use refresh token against each other (the credential-fork hazard). Added a 30s TTL cache + last-good-label memoization for the keychain read, cutting per-spawn event-loop blocking. The isolation decision (`/health` isolated/real-home reporting) is now re-evaluated per spawn instead of memoized forever, so `/health` no longer misreports a stale decision. New module `lib/spawn-auth.mjs` extracts the pure, unit-testable primitives (mutex, TTL cache, expiry gate, label ordering).
+- **Concurrency queue / disconnect handling (#149)** — the shared semaphore now honors a runtime-lowered `maxConcurrent` immediately (previously a decrease was silently ignored until in-flight tasks finished on their own) and wakes queued waiters right away when the limit is raised. Queued `-p`/TUI requests are now linked to the client's HTTP connection via `AbortSignal`; a client that disconnects while queued is spliced out of the queue instead of still spawning `claude` once a slot frees. A singleflight follower whose leader disconnected now retries instead of inheriting a spurious 500, and a queued-then-disconnected request is no longer recorded as a usage failure or logged as an error (quiet disconnect handling).
+
 ## v3.21.0 — 2026-06-25
 
 Cleanup + docs release: TUI dead-code removal, docs honesty, and release prep. No new `cli.js` wire behavior; the default path (`CLAUDE_TUI_MODE` unset) is byte-for-byte unchanged.

README.md

@@ -894,6 +894,10 @@ node ~/ocp/scripts/sync-openclaw.mjs
 
 This is read-only at startup; the warning never blocks the gateway from running.
 
+### A TUI session vanished right after upgrading OCP
+
+If you ran a pre-3.21.1 OCP instance and a post-3.21.1 instance on the same host at the same time during an upgrade, the new instance's one-time boot reap can, once, kill an old-format (`ocp-tui-<8hex>`) live TUI session belonging to the still-running old instance — restart the affected session (`ocp restart` or re-run your TUI turn) and it will come back under the new instance's port-scoped naming.
+
 ### OpenClaw shows old models after `ocp update` (v3.10→v3.11 only)
 
 One-time bootstrap quirk for the v3.10.0 → v3.11.0 jump only — the running shell had the old `cmd_update` cached. Run once manually:

keys.mjs

@@ -382,11 +382,25 @@ export function getCacheStats() {
 // Per ADR 0005 / spec D4: in-process scope only (single Node process per host).
 const inflightMap = new Map();
 
-export function singleflight(hash, fn) {
+// `retryIf` (optional, audit finding M1): a predicate applied on the FOLLOWER path only.
+// When a follower joins an existing flight and the shared promise rejects with an error for
+// which retryIf(err) is true (in practice: the LEADER's client disconnected while queued —
+// an error that is personal to the leader, not a verdict about the upstream), the follower
+// does NOT inherit that rejection. Instead it re-enters singleflight with its OWN fn: it
+// either becomes the new leader (the map entry is already deleted — see the finally below,
+// which runs before any follower's catch because it is attached upstream of the promise the
+// followers await) or joins a flight another retrying follower just created. The leader's
+// own rejection is never retried here — its error belongs to it (leader path returns the
+// bare promise). Callers that pass no retryIf get the exact pre-M1 share-everything behavior.
+export function singleflight(hash, fn, retryIf) {
   const existing = inflightMap.get(hash);
   if (existing) {
     existing.requesters++;
-    return existing.promise;
+    if (!retryIf) return existing.promise;
+    return existing.promise.catch((err) => {
+      if (!retryIf(err)) throw err;
+      return singleflight(hash, fn, retryIf);
+    });
   }
   // Wrap fn() in Promise.resolve().then() so synchronous throws don't escape.
   const promise = Promise.resolve().then(fn).finally(() => {

lib/tui/semaphore.mjs

@@ -20,6 +20,15 @@
 //
 // Pure + importable so test-features.mjs can assert the bound directly (no server boot).
 
+// Thrown by acquire() when the caller-supplied AbortSignal fires before a slot was granted
+// (audit finding F2 — a client that disconnects while queued must never receive a slot; the
+// queue entry is spliced out, not just flagged, so `queued` accounting stays exact). Distinct
+// `name` lets callers (server.mjs acquireClaudeSlot) tell "client went away" apart from
+// "queue is full" without string-matching the message.
+export class SemaphoreAbortError extends Error {
+  constructor(message) { super(message); this.name = "SemaphoreAbortError"; }
+}
+
 export class TuiSemaphore {
   // limit: max concurrent slots. maxQueue: max waiters before run() rejects with backpressure.
   constructor(limit, { maxQueue } = {}) {
@@ -34,9 +43,30 @@ export class TuiSemaphore {
   get inflight() { return this._inflight; }
   get queued() { return this._waiters.length; }
 
+  // Runtime-adjust the concurrency limit (audit finding F1 — a PATCH /settings maxConcurrent
+  // change must actually take effect, not just be ignored until every currently-inflight task
+  // happens to finish). Lowering the limit is handled lazily by release() (see below) — it
+  // simply stops re-granting until inflight drains under the new, lower limit. Raising the
+  // limit has immediate headroom, so we wake as many queued waiters as now fit.
+  setLimit(limit) {
+    this.limit = Math.max(1, parseInt(limit, 10) || 1);
+    while (this._inflight < this.limit && this._waiters.length > 0) {
+      const next = this._waiters.shift();
+      this._inflight++;
+      next();
+    }
+  }
+
   // Acquire a slot. Resolves once a slot is free (immediately if under the limit, otherwise
   // when an in-flight task releases). Rejects synchronously-ish if the wait queue is full.
-  acquire() {
+  // `signal` (optional AbortSignal, F2) lets the caller cancel a QUEUED wait — e.g. wired to
+  // a client's socket "close" event so a request that disconnects before a slot is granted
+  // is removed from the queue instead of eventually being handed a slot for a dead socket.
+  // If `signal` is already aborted, reject immediately without ever touching the queue.
+  acquire(signal) {
+    if (signal?.aborted) {
+      return Promise.reject(new SemaphoreAbortError("acquire aborted before requesting a slot"));
+    }
     if (this._inflight < this.limit) {
       this._inflight++;
       return Promise.resolve();
@@ -46,24 +76,44 @@ export class TuiSemaphore {
         `tui_queue_full: TUI concurrency limit (${this.limit}) reached and wait queue ` +
         `(${this.maxQueue}) is full`));
     }
-    return new Promise((resolve) => { this._waiters.push(resolve); });
+    return new Promise((resolve, reject) => {
+      let waiter; // the FIFO entry — captured so onAbort can find + splice exactly this one
+      const onAbort = () => {
+        const idx = this._waiters.indexOf(waiter);
+        if (idx === -1) return; // already granted a slot (shifted out by release()/setLimit) — too late to cancel
+        this._waiters.splice(idx, 1); // remove, not just flag — keeps `queued` accounting exact
+        reject(new SemaphoreAbortError("acquire aborted while queued"));
+      };
+      waiter = () => {
+        signal?.removeEventListener("abort", onAbort);
+        resolve();
+      };
+      signal?.addEventListener("abort", onAbort, { once: true });
+      this._waiters.push(waiter);
+    });
   }
 
-  // Release a slot. If a waiter is queued, hand the slot directly to it (inflight stays
+  // Release a slot. Always frees the caller's own slot first, then re-grants it to the next
-  // constant across the handoff); otherwise decrement.
+  // waiter ONLY if the (post-decrement) inflight count is still under the current limit (F1
+  // fix). This is what makes a runtime-lowered limit actually bite: if the limit was lowered
+  // while over-subscribed, releases stop re-granting and inflight drains toward the new limit
+  // instead of a freed slot being handed straight back out at the old, higher occupancy.
   release() {
-    const next = this._waiters.shift();
+    if (this._inflight > 0) this._inflight--;
-    if (next) {
+    if (this._inflight < this.limit) {
-      next(); // the woken waiter already "owns" the slot — inflight unchanged
+      const next = this._waiters.shift();
-    } else if (this._inflight > 0) {
+      if (next) {
-      this._inflight--;
+        this._inflight++;
+        next();
+      }
     }
   }
 
   // Run fn() under one slot. Releases in a finally so a throw (PR-A's honesty gates,
   // wallclock truncation, paste-not-landed, tmux spawn failure) NEVER leaks a slot.
-  async run(fn) {
+  // `signal` (optional, F2) is forwarded to acquire() so a queued run() can be cancelled.
-    await this.acquire();
+  async run(fn, signal) {
+    await this.acquire(signal);
     try {
       return await fn();
     } finally {

lib/tui/session.mjs

@@ -15,14 +15,48 @@ import { tmpdir } from "node:os";
 import { randomUUID } from "node:crypto";
 import { readTuiTranscript } from "./transcript.mjs";
 
-export const SESSION_PREFIX = "ocp-tui-"; // per-proxy namespace (coexistence rule)
+// F7 fix (audit finding, LOW): the prefix used to be a bare, host-wide constant
+// ("ocp-tui-"), so a SECOND OCP instance on the same host (e.g. a temporary
+// verification instance stood up alongside production — a real pattern used during
+// PR #144/#146 verification) would boot-reap and potentially kill-server the OTHER
+// instance's LIVE sessions: the coexistence guard below only ever spared foreign
+// PRODUCT prefixes (olp-tui-*), never a second ocp-tui-* instance on a different port.
+//
+// Fix: scope the prefix to the instance's own listen port. The port is the natural
+// stable per-instance discriminator on one host (two OCP instances cannot share a
+// port), so `ocp-tui-<port>-` uniquely namespaces this instance's sessions and makes
+// a same-host sibling OCP instance look exactly like a foreign product (olp-tui-*) to
+// the coexistence guard — its `ocp-tui-<otherPort>-*` sessions never match our own
+// prefix and are therefore never reaped/kill-server'd by us.
+//
+// LEGACY_SESSION_PREFIX / LEGACY_SESSION_NAME_RE describe the OLD bare-prefix shape
+// (pre-this-fix), retained ONLY for the boot-time legacy-zombie migration handled in
+// reapStaleTuiSessions (see comment there). No code path in this version ever CREATES
+// a legacy-shaped session name again — sessionPrefixForPort() is the only session-name
+// prefix constructor used going forward.
+export const LEGACY_SESSION_PREFIX = "ocp-tui-";
+// Exact legacy shape: LEGACY_SESSION_PREFIX + sessionId.slice(0, 8), where sessionId is
+// a randomUUID() — so the suffix is always exactly 8 lowercase hex characters with NO
+// further separator. The new port-scoped shape always inserts a "-" between the port
+// digits and the 8-hex suffix (see sessionPrefixForPort), so this regex can never match
+// a new-shape name: a new-shape suffix is `<port digits>-<8 hex>` (contains a literal
+// "-"), which `[0-9a-f]{8}$` anchored immediately after the prefix cannot satisfy.
+export const LEGACY_SESSION_NAME_RE = /^ocp-tui-[0-9a-f]{8}$/;
+
+// Build this instance's own session-name prefix, scoped by its listen port so a
+// second OCP instance on the same host (different port) is never mistaken for "ours".
+export function sessionPrefixForPort(port) {
+  return `ocp-tui-${port}-`;
+}
+
 const TMUX = process.env.OCP_TUI_TMUX_BIN || "tmux";
 
 const defaultTmux = (args, opts = {}) =>
   spawnSync(TMUX, args, { encoding: "utf8", ...opts });
 
-// Kill ONLY our own stale sessions. Scoped to SESSION_PREFIX so a co-hosted
+// Kill ONLY our own stale sessions. Scoped to sessionPrefixForPort(port) so a co-hosted
-// OLP test instance's `olp-tui-*` sessions are never touched.
+// OLP test instance's `olp-tui-*` sessions — AND a co-hosted second OCP instance's
+// `ocp-tui-<otherPort>-*` sessions — are never touched (F7 fix).
 //
 // Defunct-reaping (PI231 incident): the pane's `claude` process is a child of the
 // long-lived tmux SERVER daemon, NOT of the OCP node process — `tmux new-session -d`
@@ -36,23 +70,40 @@ const defaultTmux = (args, opts = {}) =>
 // merely re-signalling — is to stop the tmux server: when the server exits, the kernel
 // reparents its surviving children to init (PID 1), which reaps them immediately.
 //
-// So after killing our own sessions, if the server has NO sessions left of ANY prefix
+// `port` (required) is this instance's own listen port (server.mjs's PORT / lib/constants.mjs
-// (i.e. nothing we could disrupt — no co-hosted `olp-tui-*` or other instance), we
+// DEFAULT_PORT resolution) — the SPOT for "which sessions are ours."
-// `kill-server` to flush the defunct backlog. If ANY non-ocp session remains we leave the
+//
-// server running (coexistence rule, ADR 0007) and let the next boot/periodic sweep retry
+// `includeLegacy` (default false): when true, sessions matching the exact OLD bare-prefix
-// once the server is otherwise idle.
+// shape (LEGACY_SESSION_NAME_RE) are ALSO treated as ours for kill-session purposes. This is
-export function reapStaleTuiSessions({ tmux = defaultTmux } = {}) {
+// the boot-time legacy migration: an operator upgrading past this fix could otherwise be left
+// with orphaned bare-prefix zombie sessions from the PREVIOUS (pre-fix) process generation of
+// this SAME instance, since no live instance of the new version ever creates that shape again
+// — a legacy-shaped session found at boot is therefore presumed to be this instance's own
+// leftover, not a stranger's. Passed true ONLY from the one-time boot-reap call site in
+// server.mjs; the periodic idle-reap sweep does NOT set it, so a lingering legacy session
+// during steady-state is conservatively treated as foreign (correctly blocking kill-server)
+// rather than assumed to be ours on every 15-minute tick. Residual (accepted, documented):
+// if a genuinely-still-running PRE-FIX OCP instance is coexisting on the same host at the
+// exact moment a new instance boots, its live legacy-shaped session could be reaped — the
+// same class of residual risk the audit finding itself accepts ("no live instance of the new
+// version creates them"); this PR does not regress that scenario, it only removes the far
+// more common same-version collision (the actual F7 finding).
+export function reapStaleTuiSessions({ tmux = defaultTmux, port, includeLegacy = false } = {}) {
   const r = tmux(["list-sessions", "-F", "#{session_name}"]);
   if (!r || r.status !== 0) return 0; // no tmux server / no sessions
   const names = String(r.stdout || "").split("\n").map((s) => s.trim()).filter(Boolean);
+  const ownPrefix = sessionPrefixForPort(port);
   let killed = 0;
   let othersRemain = false;
   for (const name of names) {
-    if (name.startsWith(SESSION_PREFIX)) {
+    const isOwn = name.startsWith(ownPrefix);
+    const isLegacyOwn = includeLegacy && LEGACY_SESSION_NAME_RE.test(name);
+    if (isOwn || isLegacyOwn) {
       tmux(["kill-session", "-t", name]);
       killed++;
     } else {
-      othersRemain = true; // a session we do NOT own (e.g. olp-tui-*) — never kill-server
+      othersRemain = true; // a session we do NOT own (olp-tui-*, a sibling ocp-tui-<otherPort>-*,
+                            // or — outside includeLegacy — a legacy-shaped name) — never kill-server
     }
   }
   // Reap defunct `claude` zombies: safe ONLY when the server is now ours-only/empty.
@@ -358,12 +409,15 @@ export async function runTuiTurn({
   home,
   realHome,
   cwd,
+  port,
   wallclockMs = 120000,
   entrypointMode = "cli",
   tmux = defaultTmux,
 }) {
   const sessionId = randomUUID();
-  const tmuxName  = SESSION_PREFIX + sessionId.slice(0, 8);
+  // Port-scoped session name (F7 fix) — see sessionPrefixForPort / reapStaleTuiSessions
+  // for why this instance's own listen port is the namespace discriminator.
+  const tmuxName  = sessionPrefixForPort(port) + sessionId.slice(0, 8);
   const ehome     = home || process.env.HOME;       // HOME claude runs under (scratch or real)
   const rhome     = realHome || process.env.HOME;   // real home (OAuth + onboarded config source)
 

package.json

@@ -1,6 +1,6 @@
 {
   "name": "open-claude-proxy",
-  "version": "3.21.0",
+  "version": "3.21.1",
   "description": "OCP (Open Claude Proxy) — use your Claude Pro/Max subscription as an OpenAI-compatible API for any IDE. Works with Cline, OpenCode, Aider, Continue.dev, OpenClaw, and more.",
   "type": "module",
   "bin": {

server.mjs

@@ -43,7 +43,7 @@ import { DEFAULT_PORT } from "./lib/constants.mjs";
 import { isLoopbackBind } from "./lib/net.mjs";
 import { runTuiTurn, reapStaleTuiSessions, resolveTuiHome } from "./lib/tui/session.mjs";
 import { detectTuiUpstreamError } from "./lib/tui/transcript.mjs";
-import { TuiSemaphore, recordTuiEntrypoint, buildTuiHealthBlock } from "./lib/tui/semaphore.mjs";
+import { TuiSemaphore, SemaphoreAbortError, recordTuiEntrypoint, buildTuiHealthBlock } from "./lib/tui/semaphore.mjs";
 import { createSerialMutex, createTtlCache, isTokenExpiring, orderLabelsLastGoodFirst } from "./lib/spawn-auth.mjs";
 
 const __dirname = dirname(fileURLToPath(import.meta.url));
@@ -507,16 +507,61 @@ class ConcurrencyOverflowError extends Error {
   constructor(message) { super(message); this.name = "ConcurrencyOverflowError"; this.httpStatus = 429; this.retryAfter = CLAUDE_QUEUE_RETRY_AFTER; }
 }
 
+// Tagged error for audit finding F2: the client disconnected while queued (or was already gone
+// before we even tried to queue it). Distinct from ConcurrencyOverflowError so callers never send
+// a response on this path — there is no socket left to write to.
+class RequestDisconnectedError extends Error {
+  constructor(message) { super(message); this.name = "RequestDisconnectedError"; }
+}
+
+// Build an AbortSignal that fires when `res` (an http.ServerResponse) closes — i.e. the client
+// disconnected. Used to cancel a QUEUED concurrency-slot wait (F2) so a client that gives up
+// before a slot is granted is spliced out of the wait queue instead of eventually spawning a
+// claude process for a dead socket. If `res` has already closed by the time we get here (its
+// underlying stream already torn down), the signal is returned pre-aborted so acquire() rejects
+// immediately without ever touching the queue — the "close already fired before we attach" case.
+// `detach()` MUST be called once the wait settles (granted or rejected) to avoid a listener leak.
+function closeSignalFor(res) {
+  const controller = new AbortController();
+  if (!res || typeof res.on !== "function") return { signal: controller.signal, detach() {} };
+  if (res.destroyed) {
+    controller.abort();
+    return { signal: controller.signal, detach() {} };
+  }
+  const onClose = () => controller.abort();
+  res.on("close", onClose);
+  return { signal: controller.signal, detach() { res.removeListener("close", onClose); } };
+}
+
 // Acquire a -p concurrency slot, queuing if all are busy (up to CLAUDE_MAX_QUEUE). Resolves to a
 // release() fn that MUST be called exactly once on every exit path (wired into ctx.cleanup()).
-// Rejects with ConcurrencyOverflowError when the wait-queue is full. Increments stats.queued while
+// Rejects with ConcurrencyOverflowError when the wait-queue is full, or with
-// waiting (decremented on acquire) and stats.queueRejections on overflow.
+// RequestDisconnectedError when `res` closes before a slot is granted (F2) — the caller must not
-async function acquireClaudeSlot() {
+// spawn claude in that case. `res` is optional (back-compat for any caller without a live response
-  stats.queued = claudeSemaphore.queued + 1; // reflect this waiter before we (maybe) block
+// object); omitting it just means a queued wait can't be cancelled early.
+//
+// F8 fix: stats.queued is set from claudeSemaphore.queued AFTER calling acquire() (not before) —
+// acquire() synchronously updates _inflight/_waiters before its Promise ever resolves, so reading
+// .queued right after the call already reflects reality. The old code set `queued + 1` BEFORE
+// calling acquire() to account for "this waiter", which over-reported by 1 whenever the slot was
+// granted immediately (the common case, not a queue at all).
+async function acquireClaudeSlot(res) {
+  const { signal, detach } = closeSignalFor(res);
+  const slot = claudeSemaphore.acquire(signal);
+  stats.queued = claudeSemaphore.queued; // accurate: acquire() already updated the queue synchronously
   try {
-    await claudeSemaphore.acquire();
+    await slot;
   } catch (e) {
+    detach();
     stats.queued = claudeSemaphore.queued;
+    if (e instanceof SemaphoreAbortError) {
+      // Client-driven cancellation, not backpressure — do NOT count it as a queueRejection or
+      // log it as concurrency_queue_full (that log/counter means "the queue itself is full").
+      logEvent("info", "concurrency_wait_cancelled", {
+        reason: "client_disconnected", inflight: claudeSemaphore.inflight, queued: claudeSemaphore.queued,
+      });
+      throw new RequestDisconnectedError("client disconnected while waiting for a concurrency slot");
+    }
     stats.queueRejections++;
     logEvent("warn", "concurrency_queue_full", {
       limit: claudeSemaphore.limit, maxQueue: claudeSemaphore.maxQueue,
@@ -526,6 +571,7 @@ async function acquireClaudeSlot() {
       `backpressure: concurrency limit (${claudeSemaphore.limit}) reached and wait queue ` +
       `(${claudeSemaphore.maxQueue}) is full — retry shortly`);
   }
+  detach();
   stats.queued = claudeSemaphore.queued;
   let released = false;
   return function releaseClaudeSlot() {
@@ -728,7 +774,13 @@ const TUI_REAP_INTERVAL_MS = 15 * 60 * 1000;
 const tuiReapInterval = TUI_MODE ? setInterval(() => {
   if (tuiSemaphore.inflight > 0 || tuiSemaphore.queued > 0) return; // a turn is live — defer
   try {
-    const n = reapStaleTuiSessions();
+    // F7 fix: scope to THIS instance's own port; a sibling ocp-tui-<otherPort>-* session
+    // (a second OCP instance on the same host) is treated as foreign, same as olp-tui-*.
+    // includeLegacy is NOT set here — see reapStaleTuiSessions' comment: the periodic sweep
+    // conservatively treats any lingering bare-prefix legacy session as foreign so it can
+    // never trigger kill-server on a steady-state tick; only the one-time boot reap below
+    // claims legacy-shaped zombies.
+    const n = reapStaleTuiSessions({ port: PORT });
     if (n) logEvent("info", "tui_reaped_stale_sessions", { count: n, trigger: "periodic" });
   } catch (e) { logEvent("error", "tui_periodic_reap_failed", { error: e.message }); }
 }, TUI_REAP_INTERVAL_MS) : null;
@@ -1129,14 +1181,29 @@ function spawnClaudeProcess(model, messages, conversationId, keyName, releaseSlo
 // We accumulate full text across all content_block_delta events plus the
 // assistant-aggregate fallback, then resolve with the assembled string.
 // Reference: OLP ADR 0009 Amendment 1 + commit 97e7d16.
-async function callClaude(model, messages, conversationId, keyName) {
+// `res` (optional, F2) is the client's http.ServerResponse — passed through so a queued wait
+// can be cancelled the moment the client disconnects, instead of spawning claude for a dead
+// socket once a slot finally frees up.
+async function callClaude(model, messages, conversationId, keyName, res) {
   // FIX ⑥: acquire a concurrency slot first (queues up to CLAUDE_MAX_QUEUE; rejects with a
-  // ConcurrencyOverflowError → 429 when the queue is full). The release fn is passed into the
+  // ConcurrencyOverflowError → 429 when the queue is full, or a RequestDisconnectedError (F2)
-  // spawn so the idempotent cleanup() frees it on every exit path. If the spawn itself throws
+  // if the client goes away first). The release fn is passed into the spawn so the idempotent
-  // synchronously (before cleanup is wired), release here so the slot never leaks.
+  // cleanup() frees it on every exit path. If the spawn itself throws synchronously (before
-  const releaseSlot = await acquireClaudeSlot();
+  // cleanup is wired), release here so the slot never leaks.
-  // F3: resolve the per-spawn HOME/token decision (may serialize on the real-HOME fallback mutex).
+  // F2×F3 composition: the slot acquire comes FIRST and is the cancellable step — a client
-  const spawnDecision = await resolveSpawnDecision();
+  // that disconnects while queued rejects here, BEFORE resolveSpawnDecision() runs, so a
+  // cancelled request can never acquire (or briefly hold) the real-HOME fallback mutex.
+  const releaseSlot = await acquireClaudeSlot(res);
+  // F3: resolve the per-spawn HOME/token decision (may serialize on the real-HOME fallback
+  // mutex). If it throws, release the just-acquired slot before propagating — cleanup() is
+  // not wired yet at this point.
+  let spawnDecision;
+  try {
+    spawnDecision = await resolveSpawnDecision();
+  } catch (err) {
+    releaseSlot();
+    throw err;
+  }
   return new Promise((resolve, reject) => {
     let ctx;
     try {
@@ -1215,26 +1282,50 @@ async function callClaude(model, messages, conversationId, keyName) {
 // flag that could perturb cc_entrypoint classification.
 // Authority: claude CLI v2.1.158 interactive mode (cc_entrypoint=cli).
 // SECURITY: A-path single-user ONLY — home is NOT isolation (see ADR 0007).
-function callClaudeTui(model, messages, _conversationId, _keyName) {
+// `res` (optional, F2) is the client's http.ServerResponse — see closeSignalFor.
+async function callClaudeTui(model, messages, _conversationId, _keyName, res) {
   const cliModel = MODEL_MAP[model] || model;
   const prompt = messagesToPrompt(messages); // includes system as [System] inline
   recordModelRequest(cliModel, prompt.length);
-  // C-4: gate the heavy interactive boot behind the TUI semaphore. run() acquires a slot
+  // C-4: gate the heavy interactive boot behind the TUI semaphore (queuing if all slots are
-  // (queuing if all are busy, up to maxQueue), then releases in a finally so any throw from
+  // busy, up to maxQueue). F2: `signal` (tied to `res` "close") cancels a QUEUED wait the
-  // runTuiTurn (tmux spawn failure, paste-not-landed) OR from the honesty gates below
+  // instant the client disconnects, so a dead socket never triggers a cold-boot tmux+claude
-  // (truncation / error banner) can NEVER leak a slot. tuiSemaphore.inflight feeds /health.
+  // spawn; detach() drops the "close" listener as soon as the wait settles rather than
-  return tuiSemaphore.run(() => runTuiTurn({
+  // holding it for the whole (up to 120s) turn.
-    prompt,
+  const { signal, detach } = closeSignalFor(res);
-    model: cliModel,
+  try {
-    claudeBin: CLAUDE,
+    await tuiSemaphore.acquire(signal);
-    home: TUI_HOME,
+  } catch (err) {
-    realHome: process.env.HOME,
+    detach();
-    cwd: TUI_CWD,
+    if (err instanceof SemaphoreAbortError) {
-    wallclockMs: TUI_WALLCLOCK_MS,
+      // L1: client-driven cancellation, not an upstream failure — info, not error (mirrors
-    entrypointMode: TUI_ENTRYPOINT,
+      // acquireClaudeSlot's concurrency_wait_cancelled on the -p path).
-  }).then(({ text, entrypoint, truncated }) => {
+      logEvent("info", "concurrency_wait_cancelled", {
+        reason: "client_disconnected", path: "tui", inflight: tuiSemaphore.inflight, queued: tuiSemaphore.queued,
+      });
+      throw new RequestDisconnectedError("client disconnected while waiting for a TUI concurrency slot");
+    }
+    throw err;
+  }
+  detach();
+  // release() runs in a finally so any throw from runTuiTurn (tmux spawn failure,
+  // paste-not-landed) OR from the honesty gates below (truncation / error banner) can NEVER
+  // leak a slot. tuiSemaphore.inflight feeds /health.
+  try {
+    const { text, entrypoint, truncated } = await runTuiTurn({
+      prompt,
+      model: cliModel,
+      claudeBin: CLAUDE,
+      home: TUI_HOME,
+      realHome: process.env.HOME,
+      cwd: TUI_CWD,
+      port: PORT, // F7 fix: port-scopes the tmux session name so a sibling OCP instance on a
+                  // different port never collides with this instance's reap/kill-server logic.
+      wallclockMs: TUI_WALLCLOCK_MS,
+      entrypointMode: TUI_ENTRYPOINT,
+    });
     // ── Honesty gates (issue #133) ─ run BEFORE recordModelSuccess / cache write-back.
-    // A throw here propagates to the .catch below (recordModelError + reject), so the
+    // A throw here propagates to the catch below (recordModelError + reject), so the
     // result never reaches the downstream setCachedResponse / singleflight / SUCCESS path.
 
     // C-2: the wall-clock cap hit with partial text and NO terminal marker — the turn
@@ -1269,10 +1360,12 @@ function callClaudeTui(model, messages, _conversationId, _keyName) {
       logEvent("warn", "tui_entrypoint_mismatch", { expected: "cli", got: entrypoint, model: cliModel });
     }
     return text;
-  }).catch((err) => {
+  } catch (err) {
     recordModelError(cliModel, false);
     throw err;
-  }));
+  } finally {
+    tuiSemaphore.release();
+  }
 }
 
 // ── SSE heartbeat (opt-in idle watchdog) ────────────────────────────────
@@ -1318,18 +1411,30 @@ async function callClaudeStreaming(model, messages, conversationId, res, authInf
   // FIX ⑥: acquire a concurrency slot first (queues up to CLAUDE_MAX_QUEUE). On overflow, surface
   // HTTP 429 + Retry-After (NOT 500). Release is wired into cleanup() for every exit path; if the
   // spawn throws synchronously before cleanup is wired, release here.
+  // F2: pass `res` so a queued wait is cancelled the instant this client disconnects — the client
+  // is already gone in that case, so there is no response to send back.
   let releaseSlot;
   try {
-    releaseSlot = await acquireClaudeSlot();
+    releaseSlot = await acquireClaudeSlot(res);
   } catch (err) {
+    if (err instanceof RequestDisconnectedError) return; // client gone — nothing to write to
     if (err instanceof ConcurrencyOverflowError) {
       return jsonResponse(res, 429, { error: { message: sanitizeError(err.message), type: "rate_limit_error" } }, { "Retry-After": String(err.retryAfter) });
     }
     return jsonResponse(res, 500, { error: { message: sanitizeError(err.message), type: "proxy_error" } });
   }
 
-  // F3: resolve the per-spawn HOME/token decision (may serialize on the real-HOME fallback mutex).
+  // F3: resolve the per-spawn HOME/token decision (may serialize on the real-HOME fallback
-  const spawnDecision = await resolveSpawnDecision();
+  // mutex). F2×F3 composition: this runs strictly AFTER the (cancellable) slot acquire, so a
+  // request cancelled while queued never touches the fallback mutex. If it throws, release
+  // the just-acquired slot before responding — cleanup() is not wired yet at this point.
+  let spawnDecision;
+  try {
+    spawnDecision = await resolveSpawnDecision();
+  } catch (err) {
+    releaseSlot();
+    return jsonResponse(res, 500, { error: { message: sanitizeError(err.message), type: "proxy_error" } });
+  }
   let ctx;
   try {
     ctx = spawnClaudeProcess(model, messages, conversationId, authInfo.keyName, releaseSlot, spawnDecision);
@@ -2001,9 +2106,12 @@ function applySettingUpdate(key, value) {
 
   switch (key) {
     case "timeout":          TIMEOUT = value; break;
-    // FIX ⑥: keep the -p wait-queue semaphore's limit in sync with the runtime MAX_CONCURRENT
+    // FIX ⑥ + F1: keep the -p wait-queue semaphore's limit in sync with the runtime MAX_CONCURRENT
-    // so a /settings change to maxConcurrent actually changes how many claude procs run at once.
+    // so a /settings change to maxConcurrent actually changes how many claude procs run at once —
-    case "maxConcurrent":    MAX_CONCURRENT = value; claudeSemaphore.limit = Math.max(1, value); break;
+    // in BOTH directions. setLimit() (not a bare `.limit =` assignment) is required: lowering
+    // needs release() to stop over-granting until inflight drains under the new cap, and raising
+    // needs queued waiters woken immediately to use the new headroom. See lib/tui/semaphore.mjs.
+    case "maxConcurrent":    MAX_CONCURRENT = value; claudeSemaphore.setLimit(value); break;
     case "sessionTTL":       SESSION_TTL = value; break;
     case "maxPromptChars":   MAX_PROMPT_CHARS = value; break;
     case "cacheTTL":         CACHE_TTL = value; break;
@@ -2160,7 +2268,7 @@ async function handleChatCompletions(req, res) {
       const t0TuiStream = Date.now();
       const promptCharsTuiStream = messages.reduce((a, m) => a + contentToText(m.content).length, 0);
       try {
-        const content = await callClaudeTui(model, messages, conversationId, req._authKeyName);
+        const content = await callClaudeTui(model, messages, conversationId, req._authKeyName, res);
         if (CACHE_TTL > 0 && req._cacheHash) {
           try { setCachedResponse(req._cacheHash, model, content); } catch (e) { logEvent("error", "cache_write_failed", { error: e.message }); }
         }
@@ -2197,15 +2305,27 @@ async function handleChatCompletions(req, res) {
         // will re-read the freshly-populated cache entry here rather than spawning.
         const recheck = getCachedResponse(req._cacheHash, CACHE_TTL);
         if (recheck) return recheck.response;
-        const c = await upstreamCall(model, messages, conversationId, req._authKeyName);
+        const c = await upstreamCall(model, messages, conversationId, req._authKeyName, res);
         try { setCachedResponse(req._cacheHash, model, c); } catch (e) { logEvent("error", "cache_write_failed", { error: e.message }); }
         return c;
-      });
+      },
+      // M1: if the LEADER disconnected while queued (F2), its RequestDisconnectedError is
+      // personal to the leader — a live follower must not inherit it as a spurious 500.
+      // retryIf makes this follower re-enter singleflight with its OWN fn (own res, own
+      // disconnect signal), becoming the new leader or joining a retrying sibling's flight —
+      // but only while OUR client is still connected. If our client is also gone, the
+      // rejection propagates and the RDE early-return in the catch below ends it quietly.
+      (err) => err instanceof RequestDisconnectedError && !res.destroyed);
       const id = `chatcmpl-${randomUUID()}`;
       completionResponse(res, id, model, content);
       try { recordUsage({ keyId: req._authKeyId, keyName: req._authKeyName, model, promptChars, responseChars: content.length, elapsedMs: Date.now() - t0Usage, success: true }); } catch (e) { logEvent("error", "usage_record_failed", { error: e.message }); }
       return;
     } catch (err) {
+      // L1: a client disconnect while queued is NOT an upstream failure — mirror the
+      // streaming path (which returns without recording anything): no usage-failure row,
+      // no [proxy] error log, no error response (the socket is gone). The disconnect is
+      // already logged at info level (concurrency_wait_cancelled) by acquireClaudeSlot.
+      if (err instanceof RequestDisconnectedError) { try { res.end(); } catch {} return; }
       try { recordUsage({ keyId: req._authKeyId, keyName: req._authKeyName, model, promptChars, responseChars: 0, elapsedMs: Date.now() - t0Usage, success: false }); } catch (e) { logEvent("error", "usage_record_failed", { error: e.message }); }
       console.error(`[proxy] error: ${err.message}`);
       if (res.headersSent || res.writableEnded || res.destroyed) {
@@ -2218,11 +2338,14 @@ async function handleChatCompletions(req, res) {
 
   // Fallback: cache disabled (CACHE_TTL=0) or no _cacheHash — original path untouched.
   try {
-    const content = await upstreamCall(model, messages, conversationId, req._authKeyName);
+    const content = await upstreamCall(model, messages, conversationId, req._authKeyName, res);
     const id = `chatcmpl-${randomUUID()}`;
     completionResponse(res, id, model, content);
     try { recordUsage({ keyId: req._authKeyId, keyName: req._authKeyName, model, promptChars, responseChars: content.length, elapsedMs: Date.now() - t0Usage, success: true }); } catch (e) { logEvent("error", "usage_record_failed", { error: e.message }); }
   } catch (err) {
+    // L1: disconnect-while-queued — same quiet non-error outcome as the singleflight
+    // path above and the streaming path (see acquireClaudeSlot's info-level log).
+    if (err instanceof RequestDisconnectedError) { try { res.end(); } catch {} return; }
     try { recordUsage({ keyId: req._authKeyId, keyName: req._authKeyName, model, promptChars, responseChars: 0, elapsedMs: Date.now() - t0Usage, success: false }); } catch (e) { logEvent("error", "usage_record_failed", { error: e.message }); }
     console.error(`[proxy] error: ${err.message}`);
     if (res.headersSent || res.writableEnded || res.destroyed) {
@@ -2744,7 +2867,11 @@ server.listen(PORT, BIND_ADDRESS, () => {
       : "credentials.json (no CLAUDE_CODE_OAUTH_TOKEN — see Troubleshooting #401)";
     console.log(`  TUI-mode: ON home=${TUI_HOME} cwd=${TUI_CWD} auth=${tuiAuth} wallclock=${TUI_WALLCLOCK_MS}ms maxConcurrent=${TUI_MAX_CONCURRENT}`);
     try {
-      const n = reapStaleTuiSessions();
+      // F7 fix: scope to THIS instance's own port (see reapStaleTuiSessions). includeLegacy:
+      // true ONLY here — the one-time boot reap is the designated point to claim orphaned
+      // bare-prefix ("ocp-tui-<uuid8>") zombie sessions left by a PRE-fix process generation
+      // of this same instance (no live post-fix instance ever creates that shape again).
+      const n = reapStaleTuiSessions({ port: PORT, includeLegacy: true });
       if (n) logEvent("info", "tui_reaped_stale_sessions", { count: n });
     } catch {}
   }

test-features.mjs

@@ -463,6 +463,52 @@ async function runSingleflightTests() {
     assert.equal(r1, 1);
     assert.equal(r2, 2);
   });
+
+  // 7. M1: leader disconnect while queued must not poison live followers. server.mjs passes
+  // retryIf = (err) => err instanceof RequestDisconnectedError && !res.destroyed — here we
+  // model that with a tagged error class. The leader (no retryIf on its own promise — the
+  // rejection is ITS OWN disconnect) sees the error; the live follower re-executes its OWN
+  // fn and gets a real result instead of a spurious inherited failure.
+  await asyncTest("M1: leader disconnects while queued → live follower re-executes and gets a real result", async () => {
+    class FakeDisconnectError extends Error {}
+    const leaderGate = Promise.withResolvers();
+    let leaderRuns = 0;
+    let followerRuns = 0;
+    const leaderFn = async () => { leaderRuns++; await leaderGate.promise; throw new FakeDisconnectError("leader client gone"); };
+    const followerFn = async () => { followerRuns++; return "real-execution"; };
+    const retryIf = (err) => err instanceof FakeDisconnectError;
+
+    const leaderP = singleflight("sf-m1-leader-dc", leaderFn);             // becomes leader
+    const followerP = singleflight("sf-m1-leader-dc", followerFn, retryIf); // joins as follower
+    leaderGate.resolve(); // leader "disconnects" while holding the flight
+
+    await assert.rejects(leaderP, FakeDisconnectError, "the leader itself still sees its own disconnect");
+    assert.equal(await followerP, "real-execution", "follower got a REAL execution, not the leader's disconnect");
+    assert.equal(leaderRuns, 1, "leader fn ran once");
+    assert.equal(followerRuns, 1, "follower re-executed exactly once (as the new leader)");
+    assert.equal(getInflightStats().inflight, 0, "map fully cleaned up after the retry flight settles");
+  });
+
+  // 8. M1 guard: a follower whose retryIf returns false (server.mjs: its OWN client is also
+  // gone) inherits the rejection unchanged — no retry, no masked error. And a follower with
+  // NO retryIf keeps the exact pre-M1 share-everything behavior (test 2 pins the fan-out;
+  // this pins the predicate=false path specifically for the disconnect error).
+  await asyncTest("M1: follower with retryIf=false (own client also gone) inherits the leader's rejection, no retry", async () => {
+    class FakeDisconnectError extends Error {}
+    const gate = Promise.withResolvers();
+    let followerRuns = 0;
+    const leaderFn = async () => { await gate.promise; throw new FakeDisconnectError("leader client gone"); };
+    const followerFn = async () => { followerRuns++; return "should-never-run"; };
+
+    const leaderP = singleflight("sf-m1-both-dc", leaderFn);
+    const followerP = singleflight("sf-m1-both-dc", followerFn, () => false); // own client dead → no retry
+    gate.resolve();
+
+    await assert.rejects(leaderP, FakeDisconnectError);
+    await assert.rejects(followerP, FakeDisconnectError, "rejection propagates unchanged when retryIf says no");
+    assert.equal(followerRuns, 0, "follower fn never executed — no wasted spawn for a dead client");
+    assert.equal(getInflightStats().inflight, 0);
+  });
 }
 
 await runSingleflightTests();
@@ -1664,12 +1710,23 @@ await asyncTest("readTuiTranscript throws when no text and cap elapses", async (
 });
 
 // ── TUI session reaper ───────────────────────────────────────────────────
-import { reapStaleTuiSessions, SESSION_PREFIX, buildTuiCmd } from "./lib/tui/session.mjs";
+import { reapStaleTuiSessions, sessionPrefixForPort, LEGACY_SESSION_PREFIX, LEGACY_SESSION_NAME_RE, buildTuiCmd } from "./lib/tui/session.mjs";
 
 console.log("\nTUI session reaper:");
 
-test("SESSION_PREFIX is ocp-tui-", () => {
+// F7 fix: the session prefix is instance-scoped by listen port so a second OCP
-  assert.equal(SESSION_PREFIX, "ocp-tui-");
+// instance on the same host (different port) is never mistaken for "ours".
+test("sessionPrefixForPort embeds the port (F7 instance scoping)", () => {
+  assert.equal(sessionPrefixForPort(3456), "ocp-tui-3456-");
+  assert.equal(sessionPrefixForPort(4000), "ocp-tui-4000-");
+  assert.notEqual(sessionPrefixForPort(3456), sessionPrefixForPort(4000));
+});
+
+test("LEGACY_SESSION_NAME_RE matches only the exact old bare-prefix shape, never the new shape", () => {
+  assert.ok(LEGACY_SESSION_NAME_RE.test(`${LEGACY_SESSION_PREFIX}a1b2c3d4`), "legacy 8-hex shape matches");
+  assert.ok(!LEGACY_SESSION_NAME_RE.test("ocp-tui-3456-a1b2c3d4"), "new port-scoped shape must NOT match legacy regex");
+  assert.ok(!LEGACY_SESSION_NAME_RE.test("ocp-tui-a1b2c3"), "too-short suffix must not match");
+  assert.ok(!LEGACY_SESSION_NAME_RE.test("ocp-tui-a1b2c3d4extra"), "trailing extra chars must not match");
 });
 
 console.log("\nTUI command construction (proxy-purity / #4):");
@@ -1776,22 +1833,40 @@ test("buildTuiCmd OCP_TUI_FULL_TOOLS=1 grants -p-equivalent tool surface (single
   }
 });
 
-test("reaper kills ONLY ocp-tui- sessions, never olp-tui-", () => {
+test("reaper kills ONLY this instance's own port-scoped sessions, never olp-tui-", () => {
   const killed = [];
   const fakeTmux = (args) => {
-    if (args[0] === "list-sessions") return { status: 0, stdout: "ocp-tui-aaaa\nolp-tui-bbbb\nmisc\nocp-tui-cccc\n" };
+    if (args[0] === "list-sessions") return { status: 0, stdout: "ocp-tui-3456-aaaa\nolp-tui-bbbb\nmisc\nocp-tui-3456-cccc\n" };
     if (args[0] === "kill-session") { killed.push(args[args.indexOf("-t") + 1]); return { status: 0 }; }
     return { status: 0, stdout: "" };
   };
-  const n = reapStaleTuiSessions({ tmux: fakeTmux });
+  const n = reapStaleTuiSessions({ tmux: fakeTmux, port: 3456 });
   assert.equal(n, 2);
-  assert.equal(killed.join(","), "ocp-tui-aaaa,ocp-tui-cccc");
+  assert.equal(killed.join(","), "ocp-tui-3456-aaaa,ocp-tui-3456-cccc");
   assert.ok(!killed.includes("olp-tui-bbbb"), "olp-tui-bbbb must never be killed");
 });
 
+// F7 fix: a second OCP instance on the same host (different port) must be treated exactly
+// like a foreign product prefix — never reaped, never allowed to trigger kill-server.
+test("reaper treats a sibling OCP instance on a DIFFERENT port as foreign (F7)", () => {
+  const killed = [];
+  const calls = [];
+  const fakeTmux = (args) => {
+    calls.push(args.join(" "));
+    if (args[0] === "list-sessions") return { status: 0, stdout: "ocp-tui-3456-aaaa\nocp-tui-9999-bbbb\n" };
+    if (args[0] === "kill-session") { killed.push(args[args.indexOf("-t") + 1]); return { status: 0 }; }
+    return { status: 0, stdout: "" };
+  };
+  const n = reapStaleTuiSessions({ tmux: fakeTmux, port: 3456 });
+  assert.equal(n, 1, "killed only the own-port session");
+  assert.equal(killed.join(","), "ocp-tui-3456-aaaa");
+  assert.ok(!killed.includes("ocp-tui-9999-bbbb"), "sibling instance's session (port 9999) must NEVER be killed");
+  assert.ok(!calls.includes("kill-server"), "kill-server MUST NOT fire — sibling instance's session still live");
+});
+
 test("reaper returns 0 when tmux status !== 0 (no server)", () => {
   const fakeTmux = (_args) => ({ status: 1, stdout: "" });
-  const n = reapStaleTuiSessions({ tmux: fakeTmux });
+  const n = reapStaleTuiSessions({ tmux: fakeTmux, port: 3456 });
   assert.equal(n, 0);
 });
 
@@ -1802,7 +1877,7 @@ test("reaper returns 0 for empty session list", () => {
     if (args[0] === "kill-session") { killed.push(args[args.indexOf("-t") + 1]); return { status: 0 }; }
     return { status: 0, stdout: "" };
   };
-  const n = reapStaleTuiSessions({ tmux: fakeTmux });
+  const n = reapStaleTuiSessions({ tmux: fakeTmux, port: 3456 });
   assert.equal(n, 0);
   assert.equal(killed.length, 0);
 });
@@ -1815,10 +1890,10 @@ test("reaper kill-servers when the server is ours-only (flush defunct claude zom
   const calls = [];
   const fakeTmux = (args) => {
     calls.push(args.join(" "));
-    if (args[0] === "list-sessions") return { status: 0, stdout: "ocp-tui-aaaa\nocp-tui-bbbb\n" };
+    if (args[0] === "list-sessions") return { status: 0, stdout: "ocp-tui-3456-aaaa\nocp-tui-3456-bbbb\n" };
     return { status: 0, stdout: "" };
   };
-  const n = reapStaleTuiSessions({ tmux: fakeTmux });
+  const n = reapStaleTuiSessions({ tmux: fakeTmux, port: 3456 });
   assert.equal(n, 2, "killed both of our sessions");
   assert.ok(calls.includes("kill-server"), "kill-server fired — reaps the defunct backlog");
 });
@@ -1827,10 +1902,10 @@ test("reaper does NOT kill-server when a foreign (non-ocp) session remains (coex
   const calls = [];
   const fakeTmux = (args) => {
     calls.push(args.join(" "));
-    if (args[0] === "list-sessions") return { status: 0, stdout: "ocp-tui-aaaa\nolp-tui-bbbb\n" };
+    if (args[0] === "list-sessions") return { status: 0, stdout: "ocp-tui-3456-aaaa\nolp-tui-bbbb\n" };
     return { status: 0, stdout: "" };
   };
-  const n = reapStaleTuiSessions({ tmux: fakeTmux });
+  const n = reapStaleTuiSessions({ tmux: fakeTmux, port: 3456 });
   assert.equal(n, 1, "killed only our own session");
   assert.ok(!calls.includes("kill-server"), "kill-server MUST NOT fire — would disrupt olp-tui-*");
 });
@@ -1838,10 +1913,61 @@ test("reaper does NOT kill-server when a foreign (non-ocp) session remains (coex
 test("reaper does NOT kill-server when there is no server (status !== 0)", () => {
   const calls = [];
   const fakeTmux = (args) => { calls.push(args.join(" ")); return { status: 1, stdout: "" }; };
-  reapStaleTuiSessions({ tmux: fakeTmux });
+  reapStaleTuiSessions({ tmux: fakeTmux, port: 3456 });
   assert.ok(!calls.includes("kill-server"), "no server → no kill-server (early return)");
 });
 
+// Legacy migration (F7): pre-fix versions created bare-prefix `ocp-tui-<uuid8>` sessions with
+// no port segment. includeLegacy is the boot-only opt-in that claims these as our own leftover
+// zombies; the periodic sweep never sets it, so a lingering legacy session cannot trigger
+// kill-server on a routine 15-minute tick.
+console.log("\nTUI legacy-prefix migration (boot-only reap, F7):");
+
+test("reaper leaves legacy bare-prefix sessions untouched by default (includeLegacy unset)", () => {
+  const killed = [];
+  const calls = [];
+  const fakeTmux = (args) => {
+    calls.push(args.join(" "));
+    if (args[0] === "list-sessions") return { status: 0, stdout: "ocp-tui-3456-aaaa\nocp-tui-deadbeef\n" };
+    if (args[0] === "kill-session") { killed.push(args[args.indexOf("-t") + 1]); return { status: 0 }; }
+    return { status: 0, stdout: "" };
+  };
+  const n = reapStaleTuiSessions({ tmux: fakeTmux, port: 3456 });
+  assert.equal(n, 1, "killed only the own-port session");
+  assert.ok(!killed.includes("ocp-tui-deadbeef"), "legacy session must NOT be reaped without includeLegacy");
+  assert.ok(!calls.includes("kill-server"), "legacy session blocks kill-server when not claimed");
+});
+
+test("reaper claims legacy bare-prefix sessions when includeLegacy=true (boot-time migration)", () => {
+  const killed = [];
+  const calls = [];
+  const fakeTmux = (args) => {
+    calls.push(args.join(" "));
+    if (args[0] === "list-sessions") return { status: 0, stdout: "ocp-tui-3456-aaaa\nocp-tui-deadbeef\n" };
+    if (args[0] === "kill-session") { killed.push(args[args.indexOf("-t") + 1]); return { status: 0 }; }
+    return { status: 0, stdout: "" };
+  };
+  const n = reapStaleTuiSessions({ tmux: fakeTmux, port: 3456, includeLegacy: true });
+  assert.equal(n, 2, "both own-port and legacy sessions reaped");
+  assert.ok(killed.includes("ocp-tui-deadbeef"), "legacy session claimed as our own leftover");
+  assert.ok(calls.includes("kill-server"), "kill-server fires once no foreign/unclaimed session remains");
+});
+
+test("reaper with includeLegacy=true still spares a sibling instance's port-scoped session", () => {
+  const killed = [];
+  const calls = [];
+  const fakeTmux = (args) => {
+    calls.push(args.join(" "));
+    if (args[0] === "list-sessions") return { status: 0, stdout: "ocp-tui-3456-aaaa\nocp-tui-deadbeef\nocp-tui-9999-zzzz\n" };
+    if (args[0] === "kill-session") { killed.push(args[args.indexOf("-t") + 1]); return { status: 0 }; }
+    return { status: 0, stdout: "" };
+  };
+  const n = reapStaleTuiSessions({ tmux: fakeTmux, port: 3456, includeLegacy: true });
+  assert.equal(n, 2, "own-port + legacy reaped, sibling instance untouched");
+  assert.ok(!killed.includes("ocp-tui-9999-zzzz"), "sibling instance session must never be claimed as legacy");
+  assert.ok(!calls.includes("kill-server"), "sibling instance's live session still blocks kill-server");
+});
+
 // ── TUI home preparation (scratch vs real) ───────────────────────────────
 import { prepareTuiHome, ensureTuiCwdTrusted } from "./lib/tui/session.mjs";
 import { mkdtempSync as hMkdtemp, mkdirSync as hMkdir, writeFileSync as hWrite, readFileSync as hRead, existsSync as hExists, readlinkSync as hReadlink } from "node:fs";
@@ -1925,7 +2051,7 @@ test("resolveTuiHome: explicit OCP_TUI_HOME wins regardless of env token (back-c
 });
 
 // ── TUI concurrency limiter + drift observability (PR-B: audit C-4 / C-5) ──
-import { TuiSemaphore, recordTuiEntrypoint, buildTuiHealthBlock } from "./lib/tui/semaphore.mjs";
+import { TuiSemaphore, SemaphoreAbortError, recordTuiEntrypoint, buildTuiHealthBlock } from "./lib/tui/semaphore.mjs";
 
 console.log("\nTUI concurrency limiter (C-4):");
 
@@ -2030,6 +2156,226 @@ await asyncTest("FIX ⑥: slot released on normal completion is immediately reus
   assert.equal(sem.inflight, 0);
 });
 
+// ── Audit F1 — runtime-lowered/raised limit must actually bite ──────────────
+// server.mjs reuses this same TuiSemaphore as `claudeSemaphore`; a PATCH /settings
+// maxConcurrent update now calls `claudeSemaphore.setLimit(value)` (see applySettingUpdate's
+// "maxConcurrent" case). These tests pin the semaphore-level contract that fix depends on.
+console.log("\nF1 — runtime concurrency-limit changes (setLimit / release honoring the current limit):");
+
+await asyncTest("F1: lowering the limit mid-load — release() stops re-granting until inflight drains under the new limit", async () => {
+  const sem = new TuiSemaphore(3, { maxQueue: 16 });
+  const g = [deferred(), deferred(), deferred()];
+  const held = g.map((d) => sem.run(async () => { await d.p; }));
+  await new Promise((r) => setImmediate(r));
+  assert.equal(sem.inflight, 3, "3 tasks hold the 3 slots");
+  // A 4th arrives while at capacity — it queues.
+  const g4 = deferred();
+  const queued4 = sem.run(async () => { await g4.p; });
+  await new Promise((r) => setImmediate(r));
+  assert.equal(sem.queued, 1, "4th request queued");
+
+  // Operator lowers maxConcurrent from 3 to 1 while all 3 original slots are still inflight
+  // (mirrors a PATCH /settings maxConcurrent=1 hitting server.mjs mid-burst).
+  sem.setLimit(1);
+  assert.equal(sem.limit, 1);
+
+  // Releasing one of the 3 original holders must NOT hand the freed slot to the queued 4th
+  // request — before the F1 fix, release() handed slots off unconditionally, so inflight
+  // would have stayed pinned at the OLD higher occupancy forever.
+  g[0].resolve();
+  await held[0];
+  await new Promise((r) => setImmediate(r));
+  assert.equal(sem.inflight, 2, "inflight drains toward the new limit, not re-granted");
+  assert.equal(sem.queued, 1, "4th request is STILL queued — not over-admitted");
+
+  g[1].resolve();
+  await held[1];
+  await new Promise((r) => setImmediate(r));
+  assert.equal(sem.inflight, 1, "inflight now exactly at the new limit (1)");
+  assert.equal(sem.queued, 1, "still queued — inflight(1) is not < limit(1), so no grant yet");
+
+  // Releasing the LAST original holder finally drops inflight under the new limit — only
+  // now does the queued 4th request get granted.
+  g[2].resolve();
+  await held[2];
+  await new Promise((r) => setImmediate(r));
+  assert.equal(sem.inflight, 1, "queued 4th request now holds the single slot");
+  assert.equal(sem.queued, 0, "queue drained");
+  g4.resolve();
+  await queued4;
+  assert.equal(sem.inflight, 0);
+});
+
+await asyncTest("F1: raising the limit wakes queued waiters immediately, up to the new headroom", async () => {
+  const sem = new TuiSemaphore(1, { maxQueue: 16 });
+  const g1 = deferred();
+  const t1 = sem.run(async () => { await g1.p; }); // holds the only slot
+  await new Promise((r) => setImmediate(r));
+  const started = [];
+  const g2 = deferred(), g3 = deferred();
+  const t2 = sem.run(async () => { started.push(2); await g2.p; });
+  const t3 = sem.run(async () => { started.push(3); await g3.p; });
+  await new Promise((r) => setImmediate(r));
+  assert.equal(sem.queued, 2, "both queue behind the single holder");
+  assert.deepEqual(started, [], "neither queued task has started");
+
+  // Operator raises maxConcurrent from 1 to 3 (2 units of new headroom) — BOTH queued
+  // waiters must be woken immediately, without waiting for t1 to release.
+  sem.setLimit(3);
+  await new Promise((r) => setImmediate(r));
+  assert.equal(sem.inflight, 3, "t1 + both newly-woken waiters now hold slots");
+  assert.equal(sem.queued, 0, "queue drained by the limit raise");
+  assert.deepEqual(started.sort(), [2, 3], "both queued tasks started without waiting for t1's release");
+
+  g1.resolve(); g2.resolve(); g3.resolve();
+  await Promise.all([t1, t2, t3]);
+  assert.equal(sem.inflight, 0);
+});
+
+await asyncTest("F1: raising the limit wakes only as many waiters as the new headroom allows (FIFO)", async () => {
+  const sem = new TuiSemaphore(1, { maxQueue: 16 });
+  const g1 = deferred();
+  const t1 = sem.run(async () => { await g1.p; });
+  await new Promise((r) => setImmediate(r));
+  const started = [];
+  const g2 = deferred(), g3 = deferred();
+  const t2 = sem.run(async () => { started.push(2); await g2.p; });
+  const t3 = sem.run(async () => { started.push(3); await g3.p; });
+  await new Promise((r) => setImmediate(r));
+  assert.equal(sem.queued, 2);
+
+  sem.setLimit(2); // only 1 unit of new headroom (1 -> 2) — exactly one queued waiter wakes
+  await new Promise((r) => setImmediate(r));
+  assert.equal(sem.inflight, 2);
+  assert.equal(sem.queued, 1, "one waiter still queued — only one slot of headroom existed");
+  assert.deepEqual(started, [2], "FIFO: the earlier-queued waiter (t2) wakes, not t3");
+
+  // Freeing t1's slot afterward still honors the (now current) limit of 2 via release()'s
+  // normal path — the still-queued t3 gets in once a slot actually frees.
+  g1.resolve();
+  await t1;
+  await new Promise((r) => setImmediate(r));
+  assert.deepEqual(started, [2, 3], "t3 granted once a slot frees, honoring the raised limit");
+  assert.equal(sem.queued, 0);
+
+  g2.resolve(); g3.resolve();
+  await t2; await t3;
+  assert.equal(sem.inflight, 0);
+});
+
+// ── Audit F2 — queued waiters must be cancellable on client disconnect ──────
+// server.mjs wires an AbortSignal derived from the client's res "close" event into
+// claudeSemaphore.acquire()/tuiSemaphore.acquire() (see closeSignalFor + acquireClaudeSlot /
+// callClaudeTui). These tests pin the semaphore-level cancellation contract that depends on.
+console.log("\nF2 — queued-wait cancellation via AbortSignal (client disconnect while queued):");
+
+await asyncTest("F2: aborting a QUEUED waiter rejects with SemaphoreAbortError and SPLICES it out (queued drops immediately, not just flagged)", async () => {
+  const sem = new TuiSemaphore(1, { maxQueue: 16 });
+  const g1 = deferred();
+  const t1 = sem.run(async () => { await g1.p; }); // holds the only slot
+  await new Promise((r) => setImmediate(r));
+  const controller = new AbortController();
+  const acquire2 = sem.acquire(controller.signal); // queues behind t1
+  await new Promise((r) => setImmediate(r));
+  assert.equal(sem.queued, 1, "second acquire queued");
+
+  controller.abort(); // simulates the client disconnecting while still queued
+  await assert.rejects(acquire2, SemaphoreAbortError, "cancelled waiter rejects with SemaphoreAbortError");
+  assert.equal(sem.queued, 0, "cancelled waiter is REMOVED — queue length drops immediately");
+  assert.equal(sem.inflight, 1, "t1's slot is untouched by the cancellation");
+
+  // Prove the cancelled waiter never later acquires a slot: free t1's slot and confirm
+  // nobody is waiting to receive it (the queue is genuinely empty, not just decremented).
+  g1.resolve();
+  await t1;
+  assert.equal(sem.inflight, 0, "slot freed with nobody queued — the cancelled waiter never got it");
+});
+
+await asyncTest("F2: an already-aborted signal rejects acquire() immediately, never touching the wait queue", async () => {
+  const sem = new TuiSemaphore(1, { maxQueue: 16 });
+  const g1 = deferred();
+  const t1 = sem.run(async () => { await g1.p; }); // holds the only slot
+  await new Promise((r) => setImmediate(r));
+
+  const controller = new AbortController();
+  controller.abort(); // client already gone before this request ever tries to acquire
+  await assert.rejects(sem.acquire(controller.signal), SemaphoreAbortError);
+  assert.equal(sem.queued, 0, "never entered the wait queue at all");
+
+  g1.resolve(); await t1;
+});
+
+await asyncTest("F2: cancelling one queued waiter preserves FIFO order for the others", async () => {
+  const sem = new TuiSemaphore(1, { maxQueue: 16 });
+  const g1 = deferred();
+  const t1 = sem.run(async () => { await g1.p; });
+  await new Promise((r) => setImmediate(r));
+
+  const started = [];
+  const cA = new AbortController();
+  const cB = new AbortController();
+  const accA = sem.acquire(cA.signal).then(() => started.push("A"));
+  const accB = sem.acquire(cB.signal).then(() => started.push("B"));
+  const g3 = deferred();
+  const t3 = sem.run(async () => { started.push("C"); await g3.p; });
+  await new Promise((r) => setImmediate(r));
+  assert.equal(sem.queued, 3, "A, B, C all queued behind t1");
+
+  cB.abort(); // B (the middle waiter) disconnects
+  await assert.rejects(accB, SemaphoreAbortError);
+  assert.equal(sem.queued, 2, "B removed; A and C remain, in original relative order");
+
+  g1.resolve();
+  await t1;
+  await new Promise((r) => setImmediate(r));
+  assert.deepEqual(started, ["A"], "A (queued first, still present) is granted next — FIFO preserved after B's removal");
+  assert.equal(sem.inflight, 1);
+  assert.equal(sem.queued, 1, "C still waiting");
+
+  sem.release(); // A was acquired directly (not via run()) — free its slot manually
+  await new Promise((r) => setImmediate(r));
+  assert.deepEqual(started, ["A", "C"], "C granted next");
+  g3.resolve();
+  await t3;
+  assert.equal(sem.inflight, 0);
+});
+
+await asyncTest("F2/L2: abort AFTER grant is a no-op — waiter keeps its slot, no rejection, slot released exactly once", async () => {
+  const sem = new TuiSemaphore(1, { maxQueue: 16 });
+  const g1 = deferred();
+  const t1 = sem.run(async () => { await g1.p; }); // holds the only slot
+  await new Promise((r) => setImmediate(r));
+
+  const controller = new AbortController();
+  let granted = false;
+  const acq = sem.acquire(controller.signal).then(() => { granted = true; });
+  await new Promise((r) => setImmediate(r));
+  assert.equal(sem.queued, 1, "waiter queued behind t1");
+
+  // t1 finishes → release() shifts the waiter out and grants it the slot (waiter() detaches
+  // the abort listener before resolving).
+  g1.resolve();
+  await t1;
+  await acq;
+  assert.equal(granted, true, "waiter was granted the slot");
+  assert.equal(sem.inflight, 1, "granted waiter holds the slot");
+  assert.equal(sem.queued, 0);
+
+  // The client disconnects AFTER the grant — the abort-after-grant race. onAbort must be a
+  // no-op (the waiter is no longer in _waiters; idx===-1 guard): no rejection materializes,
+  // the queue is untouched, and the slot is still owned by the (already-resolved) acquirer.
+  controller.abort();
+  await new Promise((r) => setImmediate(r));
+  assert.equal(sem.inflight, 1, "abort after grant did NOT revoke or double-free the slot");
+  assert.equal(sem.queued, 0, "abort after grant did not corrupt queue accounting");
+
+  // The slot is released exactly once via the normal path and is immediately reusable.
+  sem.release();
+  assert.equal(sem.inflight, 0, "slot released exactly once via the normal path");
+  await sem.run(async () => {}); // prove the semaphore is fully healthy afterward
+  assert.equal(sem.inflight, 0);
+});
+
 console.log("\nTUI drift observability (C-5):");
 
 test("recordTuiEntrypoint: observed 'cli' is NOT a mismatch and sets lastEntrypoint", () => {