CB-578 stage B: quarantine the exhausted credential, not the profile

A BACKEND_EXHAUSTED classification (stage A) now puts that profile's
credential into a BackendQuarantine for a configurable cooldown. A spawn
onto a quarantined profile is refused naming the credential and roughly
when it lifts; weighted/round-robin/fixed placement skip a quarantined
candidate; the quarantine lifts itself on the injected clock; and it is
visible on bridge_profiles.

Keyed by credential, not by profile name, via the new Profile.credentialId
(profiles sharing one credential quarantine together — e.g. two models on
one account) and effectiveCredentialId() (unset ⇒ quarantines alone,
today's behaviour unchanged). Fixed a related gap along the way: a reload
changing exhaustedPattern was silently reported "applied" even though it's
deferred — sameLaunchSettings() now catches it too.

bridged/bridged.example.yaml

@@ -144,6 +144,17 @@ herdrSocket: ~/.config/herdr/herdr.sock
 #                      omit and this profile's completion fallback behaves exactly as before.
 #                      Every backend words its refusal differently, so this is config, never a
 #                      vendor string baked into bridged itself.
+#                      DEFERRED: compiled once into a startup pattern map — editing it needs a
+#                      daemon restart, same as this profile's model/baseUrl/argv.
+#   credentialId     → CB-578 stage B: the credential this profile quarantines WITH when a
+#                      BACKEND_EXHAUSTED classification fires. Two profiles that set the SAME
+#                      credentialId share one quarantine — the case this exists for is two models
+#                      on one account (e.g. sol and terra both billing one OpenAI credential): an
+#                      exhaustion on either one must lock out both, or the fleet just walks onto
+#                      the same dead account under the sibling's name. Opt-in — omit and this
+#                      profile quarantines alone, under its own name, exactly as if the field did
+#                      not exist. Cooldown length is the top-level quarantineCooldownSeconds below.
+#                      HOT: read live at every spawn/exhaustion check — no restart needed.
 #   env              → extra environment for this profile's workers, as a literal key/value map
 #                      (CB-511). Use it to give workers a toolchain.
 #
@@ -178,6 +189,7 @@ profiles:
     # gitTokenEnv: GITEA_TOKEN        # opt-in: let this profile's workers open their own PR (CB-302)
     # gitHostEnv: GITEA_HOST          # defaults to GITEA_HOST; injected only with gitTokenEnv
     # exhaustedPattern: "usage limit has been reached"   # opt-in: classify a usage-limit refusal (CB-578)
+    # credentialId: shared-openai   # opt-in: quarantine together with every other profile sharing this id (CB-578)
     # configDir: /Users/me/.ccs/instances/gx10   # CLAUDE_CONFIG_DIR — inherit that profile's skills/MCP
     # cwd: /Users/me/src/myrepo       # pin the working dir; omit to inherit the primary's
     # parityOverlay: [".claude/settings.local.json", ".env", ".envrc"]   # never add .mcp.json — see above
@@ -243,6 +255,15 @@ profiles:
 # round-robin, or weighted. Omitting this key is a strict no-op for existing configs.
 placement: weighted
 
+# How long a credential sits out after a BACKEND_EXHAUSTED classification (CB-578 stage B), in
+# seconds, before a spawn may land on it again. Applies to every profile's effective credential
+# (its own name, or its credentialId if set above) — there is no per-profile override. Default
+# 1800 (30 minutes) when omitted or non-positive.
+# DEFERRED: baked once into the BackendQuarantine built at startup — a running quarantine keeps
+# its original cooldown regardless; a new value only applies to a quarantine that starts after a
+# restart. Editing this needs a daemon restart to take effect.
+# quarantineCooldownSeconds: 1800
+
 # Re-read this file without restarting the daemon (CB-559). Off unless you add this block, so an
 # upgraded bridged keeps the old behaviour: the file is read once at boot and never again.
 #   enabled          → turn the watch on. bridged checks the file's modified time on a timer and
@@ -252,17 +273,20 @@ placement: weighted
 # Not every key can move under a running daemon, and the difference is about what already exists
 # when the reload happens — not about how important the key is:
 #   HOT       → takes effect on the next spawn: the whole `fleet:` block (every role pool,
-#               `charters`, and `tabLabel`), `placement:`, and an existing profile's weight / maxLoad. Those are
-#               hot because the placement policy reads them through a supplier — being config is
+#               `charters`, and `tabLabel`), `placement:`, and an existing profile's weight / maxLoad
+#               / credentialId. Those are hot because the placement policy (and, for credentialId,
+#               the CB-578 stage B quarantine check) reads them through a supplier — being config is
 #               not by itself enough to make a key hot.
 #   DEFERRED  → accepted into the new config, but the wiring built at startup keeps the old value
 #               until you restart: `lifecycle:`, `leadHeartbeat:`, `guard:`, `worktreeRoot:`,
-#               `spawnReadyTimeoutMs` / `spawnReadyPollMs`, ADDING or REMOVING a profile (a new
-#               backend needs its own launcher, and launchers are built once), AND an existing
-#               profile's launch settings — model, baseUrl, argv, env, configDir, mcpUrl, tabLabel.
-#               The launcher takes a copy of `profiles:` at startup and resolves every spawn out of
-#               that copy, so those never reach a launch until you restart. The reload logs them by
-#               name rather than pretending they applied.
+#               `spawnReadyTimeoutMs` / `spawnReadyPollMs`, `quarantineCooldownSeconds` (CB-578
+#               stage B — baked once into the quarantine tracker built at startup), ADDING or
+#               REMOVING a profile (a new backend needs its own launcher, and launchers are built
+#               once), AND an existing profile's launch settings — model, baseUrl, argv, env,
+#               configDir, mcpUrl, tabLabel, exhaustedPattern. The launcher takes a copy of
+#               `profiles:` at startup and resolves every spawn out of that copy, so those never
+#               reach a launch until you restart. The reload logs them by name rather than
+#               pretending they applied.
 #   COLD      → cannot change at all: `bind:`, `herdrSocket:`, `broker:` and `auth:`. The socket is
 #               bound, the broker connection is open, and the auth mode decides who may reach the
 #               port that is already listening.

bridged/src/main/java/dev/ltms/bridged/Bridged.java

@@ -14,6 +14,7 @@ import dev.ltms.bridged.herdr.UnixSocketHerdrClient;
 import dev.ltms.bridged.herdr.WorkspaceControl;
 import dev.ltms.bridged.inject.CompletionResolver;
 import dev.ltms.bridged.inject.ExhaustedPatternLookup;
+import dev.ltms.bridged.inject.ExhaustionSink;
 import dev.ltms.bridged.inject.Injector;
 import dev.ltms.bridged.inject.StatusPoller;
 import dev.ltms.bridged.inject.TurnListener;
@@ -37,6 +38,7 @@ import dev.ltms.bridged.msg.LeadHeartbeatLoop;
 import dev.ltms.bridged.msg.ReplyPushLoop;
 import dev.ltms.bridged.rest.BridgedApp;
 import dev.ltms.bridged.session.GitWorktrees;
+import dev.ltms.bridged.session.MemberSession;
 import dev.ltms.bridged.session.SessionManager;
 import dev.ltms.bridged.peer.PeerLauncher;
 import dev.ltms.bridged.session.SessionReaper;
@@ -44,6 +46,7 @@ import dev.ltms.bridged.member.ClaudeCodeLauncher;
 import dev.ltms.bridged.member.CompositePeerLauncher;
 import dev.ltms.bridged.member.HerdrPeerLauncher;
 import dev.ltms.bridged.member.OpenCodeLauncher;
+import dev.ltms.bridged.placement.BackendQuarantine;
 import io.javalin.Javalin;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
@@ -141,11 +144,18 @@ public final class Bridged {
                     () -> config.get().fleet()));
         }
         AtomicReference<Function<String, Integer>> liveCountRef = new AtomicReference<>(_ -> 0);
+        // CB-578 stage B: one quarantine tracker for the whole daemon, shared between the launcher
+        // (checked at spawn) and the exhaustion sink wired in below (written on BACKEND_EXHAUSTED).
+        // The cooldown is deferred (see BridgedConfig#quarantineCooldownSeconds): it is read once
+        // here, at startup, and a config reload only changes it for a daemon restart.
+        BackendQuarantine quarantine = new BackendQuarantine(System::nanoTime,
+                TimeUnit.SECONDS.toNanos(cfg.quarantineCooldownSeconds()));
         PeerLauncher workers = new CompositePeerLauncher(
                 adapters,
                 cfg.effectiveDefaultProfile(),
                 config,
-                profileName -> liveCountRef.get().apply(profileName));
+                profileName -> liveCountRef.get().apply(profileName),
+                quarantine);
         // CB-504: under supervision (launchd/systemd) bridged can start before herdr's socket
         // exists. The client itself is lazy — it connects per call — but the orphan reap below is
         // the first thing that actually talks to herdr, so without this wait a boot-order race
@@ -272,7 +282,23 @@ public final class Bridged {
                 .orElse(null);
         log.info("backend-exhausted classification (CB-578 stage A): {}",
                 CompletionResolver.coverage(cfg.profiles().keySet(), exhaustedPatternsByProfile.keySet()));
-        CompletionResolver completion = new CompletionResolver(agents, rendezvous, exhaustedPatterns);
+        // CB-578 stage B: on a classification that actually wins, quarantine the exhausted profile's
+        // CREDENTIAL — not the profile name — so a profile sharing that credential (e.g. two models
+        // on one OpenAI account) is refused too, not just the one that happened to report it. Reads
+        // the profile config live off `config`, so a credentialId edit is hot: no restart needed.
+        ExhaustionSink exhaustionSink = (target, reason) -> sessions.roster().stream()
+                .filter(session -> target.equals(session.terminalId()))
+                .findFirst()
+                .map(MemberSession::profile)
+                .map(profileName -> config.get().profiles().get(profileName))
+                .ifPresent(profile -> {
+                    String credentialId = profile.effectiveCredentialId();
+                    quarantine.quarantine(credentialId);
+                    log.warn("credential '{}' quarantined for {}s (profile '{}' classified "
+                                    + "BACKEND_EXHAUSTED): {}", credentialId,
+                            cfg.quarantineCooldownSeconds(), profile.profile(), reason);
+                });
+        CompletionResolver completion = new CompletionResolver(agents, rendezvous, exhaustedPatterns, exhaustionSink);
         // CB-113: deliver only to an available worker (its MCP is connected), never its boot window.
         // CB-301: the manager's presence bridge records availability and drives SPAWNING → READY.
         MemberPresence presence = sessions.asPresence();
@@ -440,7 +466,11 @@ public final class Bridged {
                     var health = config.get().health();
                     return FleetHealthMonitor.coverage(health != null && health.isEnabled(),
                             health != null && health.notifications() != null && health.notifications().configured());
-                }));
+                }),
+                new BridgeMcp.QuarantineSource(profile -> {
+                    var configured = config.get().profiles().get(profile);
+                    return configured == null ? null : configured.effectiveCredentialId();
+                }, quarantine));
 
         // CB-559: opt-in config reload. With no `configReload:` block nothing is constructed, so an
         // upgraded daemon behaves exactly as before — the file is read once at boot and never again.

bridged/src/main/java/dev/ltms/bridged/config/BridgedConfig.java

@@ -58,6 +58,12 @@ import java.util.Set;
  *                      {@code fixed} (default), {@code round-robin}, or {@code weighted}
  * @param auth          API authentication mode ({@code null} → {@code loopback-trust}, the
  *                      historical behaviour), CB-501
+ * @param quarantineCooldownSeconds  how long a credential stays quarantined after a
+ *                      {@code BACKEND_EXHAUSTED} classification (CB-578 stage B); {@code null}/{@code
+ *                      <=0} → {@link #DEFAULT_QUARANTINE_COOLDOWN_SECONDS}. Baked once into the
+ *                      {@code BackendQuarantine} built at startup, so it is DEFERRED: changing it
+ *                      needs a restart, and a quarantine already running keeps whatever cooldown was
+ *                      live when it started.
  */
 @JsonIgnoreProperties(ignoreUnknown = true)
 public record BridgedConfig(
@@ -76,7 +82,11 @@ public record BridgedConfig(
         Health health,
         String placement,
         Auth auth,
-        ConfigReload configReload) {
+        ConfigReload configReload,
+        Integer quarantineCooldownSeconds) {
+
+    /** Default cooldown (CB-578 stage B) when {@code quarantineCooldownSeconds} is absent/non-positive. */
+    public static final int DEFAULT_QUARANTINE_COOLDOWN_SECONDS = 1800;
 
     /** Back-compat 14-arg form — no {@code configReload:} block, so file watching stays off. */
     public BridgedConfig(Bind bind, String herdrSocket, Map<String, Profile> profiles, Guard guard,
@@ -84,7 +94,7 @@ public record BridgedConfig(
                          Integer spawnReadyPollMs, Broker broker, Primary primary, Fleet fleet,
                          LeadHeartbeat leadHeartbeat, String placement, Auth auth) {
         this(bind, herdrSocket, profiles, guard, worktreeRoot, lifecycle, spawnReadyTimeoutMs,
-                spawnReadyPollMs, broker, primary, fleet, leadHeartbeat, null, placement, auth, null);
+                spawnReadyPollMs, broker, primary, fleet, leadHeartbeat, null, placement, auth, null, null);
     }
 
     /** Back-compat form before the optional {@code health:} block was added. */
@@ -93,7 +103,18 @@ public record BridgedConfig(
                          Integer spawnReadyPollMs, Broker broker, Primary primary, Fleet fleet,
                          LeadHeartbeat leadHeartbeat, String placement, Auth auth, ConfigReload configReload) {
         this(bind, herdrSocket, profiles, guard, worktreeRoot, lifecycle, spawnReadyTimeoutMs,
-                spawnReadyPollMs, broker, primary, fleet, leadHeartbeat, null, placement, auth, configReload);
+                spawnReadyPollMs, broker, primary, fleet, leadHeartbeat, null, placement, auth, configReload, null);
+    }
+
+    /** Back-compat form before the CB-578 stage B {@code quarantineCooldownSeconds} field was added. */
+    public BridgedConfig(Bind bind, String herdrSocket, Map<String, Profile> profiles, Guard guard,
+                         String worktreeRoot, Lifecycle lifecycle, Integer spawnReadyTimeoutMs,
+                         Integer spawnReadyPollMs, Broker broker, Primary primary, Fleet fleet,
+                         LeadHeartbeat leadHeartbeat, Health health, String placement, Auth auth,
+                         ConfigReload configReload) {
+        this(bind, herdrSocket, profiles, guard, worktreeRoot, lifecycle, spawnReadyTimeoutMs,
+                spawnReadyPollMs, broker, primary, fleet, leadHeartbeat, health, placement, auth,
+                configReload, null);
     }
 
     /**
@@ -187,6 +208,17 @@ public record BridgedConfig(
      *                       {@code null}/blank ⇒ the classification never fires for this profile and
      *                       today's completion-fallback behaviour is unchanged. Every backend words
      *                       its refusal differently, so this is config, never a vendor string in code.
+     * @param credentialId   the shared account this profile authenticates as (CB-578 stage B). Two
+     *                       or more profiles setting the <em>same</em> non-blank value are quarantined
+     *                       together by one {@code exhaustedPattern} classification on any one of
+     *                       them — the case a single OpenAI (or any other) credential backing several
+     *                       profiles ({@code sol}, {@code terra}, ...) needs, so a spawn does not walk
+     *                       straight onto the other profile sharing the same exhausted account.
+     *                       {@code null}/blank ⇒ this profile's {@link #effectiveCredentialId()} is
+     *                       its own name, so it quarantines alone — today's behaviour for every
+     *                       profile that does not opt in. Read live off the current config, so it is
+     *                       HOT: a change takes effect on the next exhaustion classification / spawn,
+     *                       no restart needed.
      */
     @JsonIgnoreProperties(ignoreUnknown = true)
     public record Profile(String profile, String baseUrl, String model,
@@ -200,7 +232,8 @@ public record BridgedConfig(
                          Float weight,
                          Integer maxLoad,
                          Boolean subscription,
-                         String exhaustedPattern) {
+                         String exhaustedPattern,
+                         String credentialId) {
 
         /** Peer kind spawned by {@link dev.ltms.bridged.member.ClaudeCodeLauncher} (the default). */
         public static final String KIND_CLAUDE_CODE = "claude-code";
@@ -246,6 +279,10 @@ public record BridgedConfig(
             // exhaustedPattern stays null when unset/blank (opt-in) — no defaulting, no vendor
             // wording: an unconfigured profile keeps today's completion-fallback behaviour exactly.
             exhaustedPattern = (exhaustedPattern == null || exhaustedPattern.isBlank()) ? null : exhaustedPattern;
+            // credentialId stays null when unset/blank — effectiveCredentialId() is where the
+            // "quarantines alone" fallback actually lives, so today's behaviour needs no defaulting
+            // here at all.
+            credentialId = (credentialId == null || credentialId.isBlank()) ? null : credentialId;
         }
 
         /**
@@ -290,7 +327,7 @@ public record BridgedConfig(
         public Profile withProfile(String p) {
             return new Profile(p, baseUrl, model, configDir, tokenEnv, argv, placement, workspace, tabLabel,
                     mcpUrl, cwd, parityOverlay, gitTokenEnv, gitHostEnv, kind, env, weight, maxLoad, subscription,
-                    exhaustedPattern);
+                    exhaustedPattern, credentialId);
         }
 
         /** True when this profile is served by the Claude Code adapter (the default kind). */
@@ -326,11 +363,38 @@ public record BridgedConfig(
                     mcpUrl, cwd, parityOverlay, gitTokenEnv, gitHostEnv, kind, env, weight, maxLoad, null, null);
         }
 
+        /**
+         * Backward-compatible constructor without the CB-578 stage B {@code credentialId} — the
+         * profile quarantines alone under its own name (see {@link #effectiveCredentialId()}). Keeps
+         * pre-stage-B call sites (and any YAML that omits the key) compiling and behaving identically.
+         */
+        public Profile(String profile, String baseUrl, String model,
+                      String configDir, String tokenEnv, List<String> argv,
+                      String placement, String workspace, String tabLabel, String mcpUrl,
+                      String cwd, List<String> parityOverlay, String gitTokenEnv, String gitHostEnv,
+                      String kind, Map<String, String> env, Float weight, Integer maxLoad,
+                      Boolean subscription, String exhaustedPattern) {
+            this(profile, baseUrl, model, configDir, tokenEnv, argv, placement, workspace, tabLabel,
+                    mcpUrl, cwd, parityOverlay, gitTokenEnv, gitHostEnv, kind, env, weight, maxLoad,
+                    subscription, exhaustedPattern, null);
+        }
+
         /** True when this profile's CB-578 stage A backend-exhausted classification is configured. */
         public boolean hasExhaustedPattern() {
             return exhaustedPattern != null;
         }
 
+        /**
+         * The credential group this profile quarantines with (CB-578 stage B): the configured
+         * {@link #credentialId} when set, else this profile's own name — so an unconfigured profile
+         * quarantines alone, exactly as it did before this field existed. Two profiles that set the
+         * same non-blank {@code credentialId} share one quarantine: a {@code BACKEND_EXHAUSTED}
+         * classification on either one quarantines both.
+         */
+        public String effectiveCredentialId() {
+            return (credentialId == null || credentialId.isBlank()) ? profile : credentialId;
+        }
+
         /** True when this profile's workers are granted a forge token to open their own PR (CB-302). */
         public boolean hasGitToken() {
             return gitTokenEnv != null && !gitTokenEnv.isBlank();
@@ -850,7 +914,7 @@ public record BridgedConfig(
     private static final Set<String> KNOWN_TOP_LEVEL_KEYS = Set.of(
             "bind", "herdrSocket", "profiles", "guard", "worktreeRoot",
             "lifecycle", "spawnReadyTimeoutMs", "spawnReadyPollMs", "broker", "primary", "fleet",
-            "leadHeartbeat", "health", "placement", "auth", "configReload");
+            "leadHeartbeat", "health", "placement", "auth", "configReload", "quarantineCooldownSeconds");
 
     /** Load and validate config from {@code path}. */
     public static BridgedConfig load(Path path) {
@@ -1157,8 +1221,15 @@ public record BridgedConfig(
         // configReload is left as-is: null is "off", and ConfigReload's own compact constructor
         // defaults the fields of a block that IS present. Defaulting it here would start watching
         // the file for every config that never asked to be watched.
+        // quarantineCooldownSeconds IS defaulted, unlike leadHeartbeat/configReload above: it has no
+        // separate on/off switch of its own (BackendQuarantine only ever quarantines a credential
+        // after a BACKEND_EXHAUSTED classification, which stays opt-in via exhaustedPattern), so a
+        // config that never mentions it should still get a sane cooldown rather than a null one.
+        Integer quarantineCooldown = (quarantineCooldownSeconds != null && quarantineCooldownSeconds > 0)
+                ? quarantineCooldownSeconds : DEFAULT_QUARANTINE_COOLDOWN_SECONDS;
         return new BridgedConfig(b, herdrSocket, profiles, g, worktreeRoot, l, timeout, pollMs,
-                broker, primary, f, leadHeartbeat, health, placementOrDefault, a, configReload);
+                broker, primary, f, leadHeartbeat, health, placementOrDefault, a, configReload,
+                quarantineCooldown);
     }
 
     /**

bridged/src/main/java/dev/ltms/bridged/config/ConfigRef.java

@@ -37,10 +37,15 @@ import java.util.function.Supplier;
  *       {@code fleet.leaders} needs a restart, the same as any deferred key below.</li>
  *   <li><strong>Deferred</strong> — accepted into the new snapshot, but the wiring built at startup
  *       keeps the old value until a restart: {@code lifecycle:}, {@code leadHeartbeat:},
- *       {@code spawnReadyTimeoutMs} / {@code spawnReadyPollMs}, {@code guard:},
- *       {@code worktreeRoot:}, adding or removing a profile (a new backend needs its own launcher,
+ *       {@code spawnReadyTimeoutMs} / {@code spawnReadyPollMs}, {@code quarantineCooldownSeconds}
+ *       (CB-578 stage B — baked once into the {@code BackendQuarantine} built at startup),
+ *       {@code guard:}, {@code worktreeRoot:}, adding or removing a profile (a new backend needs its own launcher,
  *       which is constructed once), <em>and an existing profile's launch settings</em> —
- *       {@code model}, {@code baseUrl}, {@code argv}, {@code env}, {@code mcpUrl} and the rest.
+ *       {@code model}, {@code baseUrl}, {@code argv}, {@code env}, {@code mcpUrl},
+ *       {@code exhaustedPattern} (CB-578 stage A — compiled once into {@code Bridged.main}'s
+ *       pattern map at startup), and the rest. {@code credentialId} (CB-578 stage B) is NOT on
+ *       this list — it is read live off the config supplier at every quarantine check and
+ *       exhaustion event, exactly like {@code weight} / {@code maxLoad}, so it is hot instead.
  *       {@code HerdrPeerLauncher} takes {@code Map.copyOf(profiles)} at construction and resolves
  *       each spawn out of that copy, so those never reach a launch until the daemon restarts. A
  *       reload logs these rather than pretending they applied.</li>
@@ -215,6 +220,12 @@ public final class ConfigRef implements Supplier<BridgedConfig> {
                 || !Objects.equals(old.spawnReadyPollMs(), fresh.spawnReadyPollMs())) {
             changed.add("spawnReady*");
         }
+        // CB-578 stage B: baked once into the BackendQuarantine built at startup — a running
+        // quarantine keeps its original cooldown regardless, and a new cooldown only applies to a
+        // quarantine that starts after a restart.
+        if (!Objects.equals(old.quarantineCooldownSeconds(), fresh.quarantineCooldownSeconds())) {
+            changed.add("quarantineCooldownSeconds");
+        }
         Map<String, BridgedConfig.Profile> before =
                 old.profiles() == null ? Map.of() : old.profiles();
         Map<String, BridgedConfig.Profile> after =
@@ -250,8 +261,10 @@ public final class ConfigRef implements Supplier<BridgedConfig> {
 
     /**
      * Whether two versions of a profile would launch a peer identically. Compares every component
-     * the launcher reads at spawn; {@code weight} and {@code maxLoad} are excluded because those are
-     * read live by the placement policy and really do take effect on the next spawn.
+     * the launcher reads at spawn; {@code weight}, {@code maxLoad} and {@code credentialId} are
+     * excluded because those are read live (by the placement policy and, for credentialId, by
+     * {@code CompositePeerLauncher}/the CB-578 stage B exhaustion sink) and really do take effect on
+     * the next spawn.
      */
     private static boolean sameLaunchSettings(BridgedConfig.Profile a, BridgedConfig.Profile b) {
         return Objects.equals(a.baseUrl(), b.baseUrl())
@@ -269,6 +282,10 @@ public final class ConfigRef implements Supplier<BridgedConfig> {
                 && Objects.equals(a.gitHostEnv(), b.gitHostEnv())
                 && Objects.equals(a.kind(), b.kind())
                 && Objects.equals(a.env(), b.env())
-                && Objects.equals(a.subscription(), b.subscription());
+                && Objects.equals(a.subscription(), b.subscription())
+                // CB-578 stage B: exhaustedPattern is compiled once into Bridged.main's pattern map
+                // at startup (see ExhaustedPatternLookup wiring) — a reload never re-reads it, so a
+                // changed pattern must be reported as deferred, exactly like model/baseUrl/argv.
+                && Objects.equals(a.exhaustedPattern(), b.exhaustedPattern());
     }
 }

bridged/src/main/java/dev/ltms/bridged/inject/CompletionResolver.java

@@ -67,6 +67,7 @@ public final class CompletionResolver implements TurnListener {
     private final AgentControl agents;
     private final Rendezvous rendezvous;
     private final ExhaustedPatternLookup exhaustedPatterns;
+    private final ExhaustionSink exhaustionSink;
 
     /**
      * Per-target record of the turn currently in flight: the exact {@link Rendezvous} waiter its
@@ -89,11 +90,17 @@ public final class CompletionResolver implements TurnListener {
      *                          usage-limit refusal pattern. Required — there is deliberately no
      *                          defaulting overload; a caller that does not want the classification
      *                          must pass an explicit inert value ({@link ExhaustedPatternLookup#none()}).
+     * @param exhaustionSink    CB-578 stage B: notified when a {@code BACKEND_EXHAUSTED}
+     *                          classification actually resolves a waiter. Required for the same
+     *                          reason as {@code exhaustedPatterns} — pass {@link ExhaustionSink#none()}
+     *                          to opt out.
      */
-    public CompletionResolver(AgentControl agents, Rendezvous rendezvous, ExhaustedPatternLookup exhaustedPatterns) {
+    public CompletionResolver(AgentControl agents, Rendezvous rendezvous, ExhaustedPatternLookup exhaustedPatterns,
+                              ExhaustionSink exhaustionSink) {
         this.agents = agents;
         this.rendezvous = rendezvous;
         this.exhaustedPatterns = Objects.requireNonNull(exhaustedPatterns, "exhaustedPatterns");
+        this.exhaustionSink = Objects.requireNonNull(exhaustionSink, "exhaustionSink");
     }
 
     @Override
@@ -210,6 +217,9 @@ public final class CompletionResolver implements TurnListener {
                     inFlight.remove(target, turn);
                     log.warn("completion for {} classified BACKEND_EXHAUSTED (no bridge_reply; scrape "
                             + "matched the profile's exhausted pattern): {}", target, reason);
+                    // CB-578 stage B: only on the resolution that actually won the race — a late
+                    // duplicate must never quarantine a credential twice for one refusal.
+                    exhaustionSink.onExhausted(target, reason);
                 }
                 return;
             }

bridged/src/main/java/dev/ltms/bridged/inject/ExhaustionSink.java

@@ -0,0 +1,31 @@
+package dev.ltms.bridged.inject;
+
+/**
+ * Notified when {@link CompletionResolver} actually delivers a {@code BACKEND_EXHAUSTED}
+ * classification to a waiting send (CB-578 stage B) — never on a race that lost (see
+ * {@link CompletionResolver#resolve}, which only calls this after
+ * {@code Rendezvous.resolveExhausted} returns {@code true}).
+ *
+ * <p>{@link CompletionResolver} knows only {@code target} (a herdr terminal id); it has no notion of
+ * profiles or credentials, so mapping {@code target} to whatever should be quarantined is entirely
+ * the sink's job — see {@code Bridged.main}'s wiring, which resolves target → session → profile →
+ * {@code effectiveCredentialId()} and calls {@code BackendQuarantine.quarantine} on it.
+ */
+@FunctionalInterface
+public interface ExhaustionSink {
+
+    /**
+     * @param target the herdr terminal id whose turn was classified {@code BACKEND_EXHAUSTED}
+     * @param reason the matched-line reason carried by the classification
+     */
+    void onExhausted(String target, String reason);
+
+    /**
+     * Inert sink — nothing happens on exhaustion. The explicit stand-in a caller (or a test not
+     * exercising this feature) passes instead of a defaulting overload, exactly like
+     * {@link ExhaustedPatternLookup#none()}.
+     */
+    static ExhaustionSink none() {
+        return (target, reason) -> { };
+    }
+}

bridged/src/main/java/dev/ltms/bridged/mcp/BridgeMcp.java

@@ -14,6 +14,7 @@ import dev.ltms.bridged.herdr.HerdrException;
 import dev.ltms.bridged.msg.MessageService;
 import dev.ltms.bridged.msg.Rendezvous;
 import dev.ltms.bridged.peer.PeerUnreachableException;
+import dev.ltms.bridged.placement.BackendQuarantine;
 import dev.ltms.bridged.session.SessionManager;
 import dev.ltms.bridged.session.MemberSession;
 import dev.ltms.bridged.session.WorktreeRequest;
@@ -33,6 +34,7 @@ import jakarta.servlet.http.HttpServlet;
 import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.Objects;
 import java.util.Set;
 import java.util.function.Function;
 import java.util.function.LongSupplier;
@@ -78,6 +80,7 @@ public final class BridgeMcp {
     private final Metrics metrics;      // CB-502: null → auth failures not counted
     private final CapacitySource capacity;
     private final HealthCoverageSource healthCoverage;
+    private final QuarantineSource quarantine;
 
     /** Capacity facts used by {@code bridge_list}; production must supply the placement live count. */
     public record CapacitySource(Function<String, Integer> liveCount, Function<String, Integer> maxLoad,
@@ -90,17 +93,30 @@ public final class BridgeMcp {
     /** Coverage is supplied by the health wiring, not inferred from a missing dependency. */
     public record HealthCoverageSource(Supplier<String> value) { }
 
+    /**
+     * CB-578 stage B quarantine facts used by {@code bridge_profiles}: a profile → credential id
+     * lookup, plus the shared {@link BackendQuarantine} to read remaining cooldowns off.
+     */
+    public record QuarantineSource(Function<String, String> credentialIdFor, BackendQuarantine quarantine) {
+        /** Inert source — no profile is ever reported quarantined. Explicit stand-in, not a default. */
+        public static QuarantineSource none() { return new QuarantineSource(_ -> null, BackendQuarantine.none()); }
+    }
+
     /**
      * @param callers resolves each call's {@link Principal}; {@code null} disables authorization.
      *                This surface needs its own enforcement: {@code /mcp} is a raw servlet on
      *                Jetty's context handler and never passes through Javalin's {@code before}
      *                filter, so the REST guard does not cover it.
      * @param metrics registry for auth-failure counting; may be {@code null}
+     * @param quarantine CB-578 stage B facts for {@code bridge_profiles}; required — pass
+     *                   {@link QuarantineSource#none()} for a caller that does not want the feature
      */
     public BridgeMcp(MessageService messages, PeerLauncher workers, SessionManager sessions,
                      ConnectionIdentity identity, MemberPresence presence, PrimaryRegistry primaryRegistry,
-                      CallerResolver callers, Metrics metrics, CapacitySource capacity, HealthCoverageSource healthCoverage) {
+                      CallerResolver callers, Metrics metrics, CapacitySource capacity, HealthCoverageSource healthCoverage,
+                      QuarantineSource quarantine) {
         this.capacity = capacity;
+        this.quarantine = Objects.requireNonNull(quarantine, "quarantine");
         this.healthCoverage = healthCoverage;
         McpJsonMapper json = new JacksonMcpJsonMapperSupplier().get();
         this.transport = HttpServletStreamableServerTransportProvider.builder()
@@ -228,7 +244,7 @@ public final class BridgeMcp {
                 .toolCall(profilesTool(), (exchange, _) -> {
                     McpSchema.CallToolResult denied = deny(exchange, Authz.Action.READ, null);
                     if (denied != null) return denied;
-                    return profiles(workers);
+                    return profiles(workers, quarantine);
                 })
                 .toolCall(whoamiTool(), (exchange, _) -> {
                     McpSchema.CallToolResult denied = deny(exchange, Authz.Action.READ, null);
@@ -706,11 +722,33 @@ public final class BridgeMcp {
         return null;
     }
 
-    /** {@code bridge_profiles}: the configured worker profiles and the default. */
-    static McpSchema.CallToolResult profiles(PeerLauncher workers) {
-        return text(json(Map.of(
-                "profiles", workers.profiles(),
-                "default", workers.defaultProfile() == null ? "" : workers.defaultProfile())));
+    /**
+     * {@code bridge_profiles}: the configured worker profiles, the default, and — CB-578 stage B —
+     * which of them are currently quarantined (backend exhausted) and for how much longer. The
+     * {@code quarantined} key is present only when at least one profile is, so a fleet where nothing
+     * has ever been quarantined gets exactly the pre-stage-B shape.
+     */
+    static McpSchema.CallToolResult profiles(PeerLauncher workers, QuarantineSource quarantine) {
+        Map<String, Object> result = new LinkedHashMap<>();
+        result.put("profiles", workers.profiles());
+        result.put("default", workers.defaultProfile() == null ? "" : workers.defaultProfile());
+        Map<String, Object> quarantined = new LinkedHashMap<>();
+        for (String profile : workers.profiles()) {
+            String credentialId = quarantine.credentialIdFor().apply(profile);
+            if (credentialId == null) {
+                continue;
+            }
+            quarantine.quarantine().remainingSeconds(credentialId).ifPresent(remaining -> {
+                Map<String, Object> row = new LinkedHashMap<>();
+                row.put("credentialId", credentialId);
+                row.put("quarantinedForSeconds", remaining);
+                quarantined.put(profile, row);
+            });
+        }
+        if (!quarantined.isEmpty()) {
+            result.put("quarantined", quarantined);
+        }
+        return text(json(result));
     }
 
     /**
@@ -940,7 +978,10 @@ public final class BridgeMcp {
 
     private static McpSchema.Tool profilesTool() {
         return tool("bridge_profiles",
-                "List the configured worker profiles (backends) and which one bridge_spawn uses by default.",
+                "List the configured worker profiles (backends) and which one bridge_spawn uses by "
+                        + "default. A 'quarantined' map is present when a backend-exhausted refusal put "
+                        + "a profile's credential on cooldown — bridge_spawn onto it is refused until "
+                        + "quarantinedForSeconds elapses; a profile sharing that credential is listed too.",
                 objectSchema(Map.of(), List.of()));
     }
 

bridged/src/main/java/dev/ltms/bridged/member/CompositePeerLauncher.java

@@ -8,6 +8,7 @@ import dev.ltms.bridged.peer.PeerHandle;
 import dev.ltms.bridged.peer.PeerLauncher;
 import dev.ltms.bridged.peer.PeerUnreachableException;
 import dev.ltms.bridged.peer.SpawnRequest;
+import dev.ltms.bridged.placement.BackendQuarantine;
 import dev.ltms.bridged.placement.PlacementCandidate;
 import dev.ltms.bridged.placement.PlacementContext;
 import dev.ltms.bridged.placement.PlacementException;
@@ -23,10 +24,12 @@ import java.util.HashSet;
 import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.Objects;
 import java.util.Set;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.function.Function;
 import java.util.function.Supplier;
+import java.util.stream.Collectors;
 
 /**
  * The {@link PeerLauncher} the core actually holds when more than one adapter is configured — a thin
@@ -78,6 +81,9 @@ public final class CompositePeerLauncher implements PeerLauncher {
     private final Supplier<Map<String, BridgedConfig.Profile>> profileConfigs;
     private final Supplier<PlacementPolicy> placementPolicy;
 
+    /** CB-578 stage B: credential cooldown, checked before an explicit spawn and filtered into placement. */
+    private final BackendQuarantine quarantine;
+
     /**
      * CB-557: the role pools an unqualified spawn draws its candidates from. A supplier that yields
      * {@code null}, and an empty pool for a role, both fall back to every configured profile — the
@@ -99,7 +105,10 @@ public final class CompositePeerLauncher implements PeerLauncher {
     }
 
     /**
-     * Production constructor with a placement policy and live-worker counter.
+     * Production constructor with a placement policy and live-worker counter. Quarantine (CB-578
+     * stage B) is off for this constructor — {@link BackendQuarantine#none()} — since it predates
+     * the feature and existing callers of this exact overload never exercised it; use the 7-arg
+     * overload below to wire a real {@link BackendQuarantine}.
      *
      * @param delegates      one adapter per configured peer kind; must be non-empty and declare
      *                       disjoint profile-name sets
@@ -113,13 +122,14 @@ public final class CompositePeerLauncher implements PeerLauncher {
                                  Map<String, BridgedConfig.Profile> profileConfigs,
                                  PlacementPolicy placementPolicy,
                                  Function<String, Integer> liveCount) {
-        this(delegates, defaultProfile, profileConfigs, placementPolicy, liveCount, null);
+        this(delegates, defaultProfile, profileConfigs, placementPolicy, liveCount, null, BackendQuarantine.none());
     }
 
     /**
      * Production constructor with role pools (CB-557). An unqualified spawn draws its candidates from
      * {@code fleet.<role>} instead of from every configured profile, so a reviewer is placed on a
-     * reviewer backend and never on, say, the architect-only one.
+     * reviewer backend and never on, say, the architect-only one. Quarantine is off for this
+     * constructor too, for the same reason as the 5-arg overload above.
      *
      * @param fleet the configured role pools; {@code null} ⇒ every profile is a candidate for every
      *              role, which is the pre-CB-557 behaviour
@@ -130,29 +140,50 @@ public final class CompositePeerLauncher implements PeerLauncher {
                                  PlacementPolicy placementPolicy,
                                  Function<String, Integer> liveCount,
                                  BridgedConfig.Fleet fleet) {
+        this(delegates, defaultProfile, profileConfigs, placementPolicy, liveCount, fleet, BackendQuarantine.none());
+    }
+
+    /**
+     * Production constructor with role pools and quarantine (CB-578 stage B). The full-featured
+     * non-reloading form; {@link #CompositePeerLauncher(List, String, Supplier, Function, BackendQuarantine)}
+     * is what {@code Bridged.main} actually wires up.
+     *
+     * @param quarantine required — pass {@link BackendQuarantine#none()} for a caller that does not
+     *                   want the feature, never a defaulting overload (CB-578 stage B's own rule).
+     */
+    public CompositePeerLauncher(List<HerdrPeerLauncher> delegates,
+                                 String defaultProfile,
+                                 Map<String, BridgedConfig.Profile> profileConfigs,
+                                 PlacementPolicy placementPolicy,
+                                 Function<String, Integer> liveCount,
+                                 BridgedConfig.Fleet fleet,
+                                 BackendQuarantine quarantine) {
         // LinkedHashMap, not Map.copyOf: candidates() promises definition order and the weighted
         // policy breaks exact-weight ties on it, so a salted iteration order would make placement
         // differ from one JVM run to the next.
         this(delegates, defaultProfile,
                 constant(Collections.unmodifiableMap(new LinkedHashMap<>(profileConfigs))),
-                constant(placementPolicy), liveCount, constant(fleet));
+                constant(placementPolicy), liveCount, constant(fleet), quarantine);
     }
 
     /**
      * Production constructor that re-reads its placement inputs per spawn (CB-559), so a config
      * reload retargets the next member without a restart.
      *
-     * @param config the live configuration — read at every spawn, never captured
+     * @param config     the live configuration — read at every spawn, never captured
+     * @param quarantine required — CB-578 stage B; pass {@link BackendQuarantine#none()} to opt out
      */
     public CompositePeerLauncher(List<HerdrPeerLauncher> delegates,
                                  String defaultProfile,
                                  Supplier<BridgedConfig> config,
-                                 Function<String, Integer> liveCount) {
+                                 Function<String, Integer> liveCount,
+                                 BackendQuarantine quarantine) {
         this(delegates, defaultProfile,
                 () -> config.get().profiles(),
                 () -> PlacementPolicies.fromName(config.get().placement()),
                 liveCount,
-                () -> config.get().fleet());
+                () -> config.get().fleet(),
+                quarantine);
     }
 
     /** The all-suppliers form every other constructor funnels into. */
@@ -161,8 +192,10 @@ public final class CompositePeerLauncher implements PeerLauncher {
                                   Supplier<Map<String, BridgedConfig.Profile>> profileConfigs,
                                   Supplier<PlacementPolicy> placementPolicy,
                                   Function<String, Integer> liveCount,
-                                  Supplier<BridgedConfig.Fleet> fleet) {
+                                  Supplier<BridgedConfig.Fleet> fleet,
+                                  BackendQuarantine quarantine) {
         this.fleet = fleet;
+        this.quarantine = Objects.requireNonNull(quarantine, "quarantine");
         if (delegates.isEmpty()) {
             throw new IllegalArgumentException("at least one peer adapter must be configured");
         }
@@ -225,6 +258,7 @@ public final class CompositePeerLauncher implements PeerLauncher {
             // the charter makes explicit-profile spawns the normal path — so skipping the check
             // here would leave the cap dead config in real operation.
             HerdrPeerLauncher d = route(requestedProfile);
+            enforceNotQuarantined(requestedProfile);
             enforceMaxLoad(requestedProfile);
             PeerHandle handle = d.spawn(req);
             spawnedBy.put(handle.id(), d);
@@ -238,7 +272,10 @@ public final class CompositePeerLauncher implements PeerLauncher {
         List<PlacementCandidate> candidates = candidates(req.role());
         String roleDefault = defaultProfileFor(req.role());
         Set<String> unreachable = new HashSet<>();
-        PlacementContext ctx = new PlacementContext(roleDefault, candidates, liveCount, unreachable);
+        // CB-578 stage B: computed once up front — a quarantine's expiry cannot pass within one spawn
+        // call, so re-deriving it per retry would only cost work, never change the answer.
+        Set<String> quarantined = quarantinedProfiles(candidates);
+        PlacementContext ctx = new PlacementContext(roleDefault, candidates, liveCount, unreachable, quarantined);
 
         int maxAttempts = candidates.isEmpty() ? 1 : candidates.size();
         for (int attempt = 0; attempt < maxAttempts; attempt++) {
@@ -268,7 +305,7 @@ public final class CompositePeerLauncher implements PeerLauncher {
                         chosen.profile(), e.getMessage());
                 unreachable.add(chosen.profile());
                 // Update the context for the next selection so the policy excludes this profile.
-                ctx = new PlacementContext(roleDefault, candidates, liveCount, unreachable);
+                ctx = new PlacementContext(roleDefault, candidates, liveCount, unreachable, quarantined);
             }
         }
 
@@ -298,6 +335,42 @@ public final class CompositePeerLauncher implements PeerLauncher {
      * @param profile the profile the caller explicitly named
      * @throws PlacementException when the profile is at capacity
      */
+    /**
+     * Refuse an explicit-profile spawn whose credential is quarantined (CB-578 stage B): a prior
+     * {@code BACKEND_EXHAUSTED} classification on this profile, or on another profile sharing its
+     * {@code credentialId}, is still on cooldown.
+     *
+     * <p>Checked before {@link #enforceMaxLoad}, and for the same reason that check exists: an
+     * explicit profile bypasses the placement policy's filtering entirely, so without this the cap
+     * (there, quarantine here) would be dead config on the very path the charter calls normal.
+     * Deliberately no fallback to another profile, matching {@link #enforceMaxLoad}'s own reasoning —
+     * the caller named this profile for a cost/model reason.
+     *
+     * @throws PlacementException naming the profile, its credential, and the remaining cooldown
+     */
+    private void enforceNotQuarantined(String profile) {
+        String credentialId = credentialIdFor(profile);
+        quarantine.remainingSeconds(credentialId).ifPresent(remaining -> {
+            throw new PlacementException("worker profile '" + profile + "' is quarantined "
+                    + "(credential '" + credentialId + "' exhausted; ~" + remaining
+                    + "s remaining) — refusing spawn");
+        });
+    }
+
+    /** {@code profile}'s credential group (CB-578 stage B), or the profile's own name if unconfigured. */
+    private String credentialIdFor(String profile) {
+        BridgedConfig.Profile cfg = profiles0().get(profile);
+        return cfg == null ? profile : cfg.effectiveCredentialId();
+    }
+
+    /** The subset of {@code candidates} whose credential is currently quarantined (CB-578 stage B). */
+    private Set<String> quarantinedProfiles(List<PlacementCandidate> candidates) {
+        return candidates.stream()
+                .map(PlacementCandidate::profile)
+                .filter(p -> quarantine.isQuarantined(credentialIdFor(p)))
+                .collect(Collectors.toSet());
+    }
+
     private void enforceMaxLoad(String profile) {
         // Absent config, or a config whose maxLoad normalized to null (non-positive ⇒ unlimited at
         // load), means no cap — never cap what wasn't configured.

bridged/src/main/java/dev/ltms/bridged/placement/BackendQuarantine.java

@@ -0,0 +1,99 @@
+package dev.ltms.bridged.placement;
+
+import java.util.LinkedHashMap;
+import java.util.Map;
+import java.util.Objects;
+import java.util.OptionalLong;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.function.LongSupplier;
+
+/**
+ * Where a credential (not a profile — see {@code BridgedConfig.Profile#effectiveCredentialId()})
+ * sits out a cooldown after a {@code BACKEND_EXHAUSTED} classification (CB-578 stage B), so a fresh
+ * spawn does not walk straight back onto the account that just refused on a usage limit.
+ *
+ * <p>Keyed by credential id, never by profile name: two profiles sharing one credential (e.g. two
+ * models on the same OpenAI account) share one quarantine — {@link #quarantine} one credential id
+ * and every profile whose {@code effectiveCredentialId()} equals it is quarantined too, without this
+ * class knowing anything about profiles at all. That mapping is the caller's job (see
+ * {@code CompositePeerLauncher} and {@code dev.ltms.bridged.inject.ExhaustionSink}).
+ *
+ * <p>The clock is injected ({@link LongSupplier}, conventionally {@code System::nanoTime} like
+ * {@code FleetHealthMonitor}), never read inline, so a quarantine's expiry is testable without a
+ * real sleep.
+ */
+public final class BackendQuarantine {
+
+    private final ConcurrentHashMap<String, Long> quarantinedUntilNanos = new ConcurrentHashMap<>();
+    private final LongSupplier nowNanos;
+    private final long cooldownNanos;
+
+    /**
+     * @param nowNanos      monotonic clock, injected for testability
+     * @param cooldownNanos how long a fresh {@link #quarantine} call blocks the credential for;
+     *                      must be positive
+     */
+    public BackendQuarantine(LongSupplier nowNanos, long cooldownNanos) {
+        this.nowNanos = Objects.requireNonNull(nowNanos, "nowNanos");
+        if (cooldownNanos <= 0) {
+            throw new IllegalArgumentException("cooldownNanos must be positive: " + cooldownNanos);
+        }
+        this.cooldownNanos = cooldownNanos;
+    }
+
+    /**
+     * Inert quarantine — nothing is ever quarantined unless {@link #quarantine} is actually called on
+     * this instance. The explicit stand-in a caller (or a test not exercising this feature) passes
+     * instead of a defaulting overload, exactly like {@code ExhaustedPatternLookup.none()}.
+     */
+    public static BackendQuarantine none() {
+        return new BackendQuarantine(() -> 0L, 1);
+    }
+
+    /**
+     * Quarantine {@code credentialId} for the configured cooldown, starting now. A repeat call while
+     * already quarantined restarts the cooldown at full length — a fresh refusal is fresh evidence the
+     * account is still exhausted, not a reason to let an earlier, shorter wait stand.
+     */
+    public void quarantine(String credentialId) {
+        Objects.requireNonNull(credentialId, "credentialId");
+        quarantinedUntilNanos.put(credentialId, nowNanos.getAsLong() + cooldownNanos);
+    }
+
+    /** Whether {@code credentialId} is quarantined right now. */
+    public boolean isQuarantined(String credentialId) {
+        return remainingNanos(credentialId) > 0;
+    }
+
+    /** Seconds left on {@code credentialId}'s quarantine, or empty when it is not quarantined. */
+    public OptionalLong remainingSeconds(String credentialId) {
+        long remaining = remainingNanos(credentialId);
+        return remaining > 0 ? OptionalLong.of(toSecondsRoundedUp(remaining)) : OptionalLong.empty();
+    }
+
+    /**
+     * Every currently-quarantined credential id and its remaining seconds (CB-578 stage B fleet
+     * reporting) — expired entries are never included. Not pruned from the backing map here: it stays
+     * small (bounded by the number of distinct credentials ever exhausted) and a lazily-stale entry is
+     * harmless, since every read already checks the deadline.
+     */
+    public Map<String, Long> activeRemainingSeconds() {
+        Map<String, Long> out = new LinkedHashMap<>();
+        quarantinedUntilNanos.forEach((credentialId, deadline) -> {
+            long remaining = deadline - nowNanos.getAsLong();
+            if (remaining > 0) {
+                out.put(credentialId, toSecondsRoundedUp(remaining));
+            }
+        });
+        return out;
+    }
+
+    private long remainingNanos(String credentialId) {
+        Long deadline = quarantinedUntilNanos.get(credentialId);
+        return deadline == null ? 0L : deadline - nowNanos.getAsLong();
+    }
+
+    private static long toSecondsRoundedUp(long nanos) {
+        return (nanos + 999_999_999L) / 1_000_000_000L;
+    }
+}

bridged/src/main/java/dev/ltms/bridged/placement/FixedPlacementPolicy.java

@@ -4,18 +4,28 @@ package dev.ltms.bridged.placement;
  * Backward-compatible placement: an unqualified spawn always resolves to the configured default
  * profile, exactly as {@code CompositePeerLauncher} did before CB-518. This ignores caps and
  * reachability so that a pre-existing config behaves identically after upgrade.
+ *
+ * <p>Quarantine (CB-578 stage B) is the one exception: a quarantined default is a credential that
+ * just refused on a usage limit, not a transient capacity or reachability concern, so {@code fixed}
+ * steps to the first non-quarantined candidate instead of walking straight back onto it. A fleet
+ * where nothing is ever quarantined never exercises this path, so today's behaviour is unchanged.
  */
 final class FixedPlacementPolicy implements PlacementPolicy {
 
     @Override
     public PlacementCandidate select(PlacementContext ctx) {
         String d = ctx.defaultProfile();
-        if (d != null && !d.isBlank()) {
+        if (d != null && !d.isBlank() && !ctx.quarantined().contains(d)) {
             return new PlacementCandidate(d, null, 1.0f, null);
         }
-        if (!ctx.candidates().isEmpty()) {
-            PlacementCandidate first = ctx.candidates().getFirst();
-            return new PlacementCandidate(first.profile(), null, first.weight(), first.maxLoad());
+        for (PlacementCandidate c : ctx.candidates()) {
+            if (!ctx.quarantined().contains(c.profile())) {
+                return new PlacementCandidate(c.profile(), null, c.weight(), c.maxLoad());
+            }
+        }
+        if (d != null && !d.isBlank()) {
+            throw new PlacementException("worker profile '" + d + "' is quarantined (backend "
+                    + "exhausted) and no un-quarantined candidate is available");
         }
         throw new PlacementException("no worker profiles configured");
     }

bridged/src/main/java/dev/ltms/bridged/placement/PlacementContext.java

@@ -11,9 +11,13 @@ import java.util.function.Function;
  * @param candidates     every configured candidate; the policy filters out those at cap or unreachable
  * @param liveCount      current live worker count per profile (from the session registry)
  * @param unreachable    profiles already known to have failed in this spawn attempt
+ * @param quarantined    profiles whose credential is currently quarantined (CB-578 stage B) — a
+ *                       {@code BACKEND_EXHAUSTED} classification put it, or a profile it shares a
+ *                       credential with, on cooldown. Filtered the same way as {@code unreachable}.
  */
 public record PlacementContext(String defaultProfile,
                                List<PlacementCandidate> candidates,
                                Function<String, Integer> liveCount,
-                               Set<String> unreachable) {
+                               Set<String> unreachable,
+                               Set<String> quarantined) {
 }

bridged/src/main/java/dev/ltms/bridged/placement/PlacementPolicyUtil.java

@@ -12,13 +12,13 @@ final class PlacementPolicyUtil {
     }
 
     /**
-     * Candidates that are not known-unreachable and have not reached their maxLoad.
-     * A {@code null} maxLoad means unlimited.
+     * Candidates that are not known-unreachable, not quarantined (CB-578 stage B), and have not
+     * reached their maxLoad. A {@code null} maxLoad means unlimited.
      */
     static List<PlacementCandidate> available(PlacementContext ctx) {
         List<PlacementCandidate> out = new ArrayList<>();
         for (PlacementCandidate c : ctx.candidates()) {
-            if (ctx.unreachable().contains(c.profile())) {
+            if (ctx.unreachable().contains(c.profile()) || ctx.quarantined().contains(c.profile())) {
                 continue;
             }
             Integer cap = c.maxLoad();
@@ -35,14 +35,17 @@ final class PlacementPolicyUtil {
 
     /**
      * Build a clear exception describing why every candidate was dropped: all at capacity,
-     * all unreachable, or a mix.
+     * all unreachable, all quarantined, or a mix.
      */
     static PlacementException emptyException(PlacementContext ctx) {
         int atCap = 0;
         int unreachable = 0;
+        int quarantined = 0;
         for (PlacementCandidate c : ctx.candidates()) {
             Integer cap = c.maxLoad();
-            if (ctx.unreachable().contains(c.profile())) {
+            if (ctx.quarantined().contains(c.profile())) {
+                quarantined++;
+            } else if (ctx.unreachable().contains(c.profile())) {
                 unreachable++;
             } else if (cap != null && ctx.liveCount().apply(c.profile()) >= cap) {
                 atCap++;
@@ -53,6 +56,9 @@ final class PlacementPolicyUtil {
         if (total == 0) {
             return new PlacementException("no worker profiles configured");
         }
+        if (quarantined == total) {
+            return new PlacementException("all worker profiles are quarantined (backend exhausted)");
+        }
         if (atCap == total) {
             return new PlacementException("all worker profiles are at maxLoad");
         }
@@ -60,6 +66,7 @@ final class PlacementPolicyUtil {
             return new PlacementException("all worker profiles are unreachable");
         }
         return new PlacementException("no worker profile available: " + atCap + " at maxLoad, "
-                + unreachable + " unreachable, " + (total - atCap - unreachable) + " remaining");
+                + unreachable + " unreachable, " + quarantined + " quarantined, "
+                + (total - atCap - unreachable - quarantined) + " remaining");
     }
 }

bridged/src/test/java/dev/ltms/bridged/config/ConfigRefTest.java

@@ -338,6 +338,54 @@ class ConfigRefTest {
         assertEquals("deepseek-v4-flash", ref.get().profiles().get("sonnet").model());
     }
 
+    /**
+     * CB-578 stage B: exhaustedPattern is compiled once into Bridged.main's pattern map at startup
+     * (see ExhaustedPatternLookup), so a reload never re-reads it — a changed pattern must be
+     * reported deferred exactly like model/baseUrl, not silently claimed as applied.
+     */
+    @Test
+    void changingAProfilesExhaustedPatternIsReportedAsDeferred(@TempDir Path dir) throws Exception {
+        Path f = dir.resolve("bridged.yaml");
+        Files.writeString(f, """
+                bind:
+                  host: 127.0.0.1
+                  port: 8765
+                herdrSocket: ~/.config/herdr/herdr.sock
+                profiles:
+                  sonnet:
+                    baseUrl: http://gx00.gw:8000
+                    model: sonnet
+                    exhaustedPattern: "usage limit has been reached"
+                guard:
+                  offSubscriptionHosts:
+                    - gx00.gw
+                """);
+        ConfigRef ref = refFor(f);
+
+        Files.writeString(f, """
+                bind:
+                  host: 127.0.0.1
+                  port: 8765
+                herdrSocket: ~/.config/herdr/herdr.sock
+                profiles:
+                  sonnet:
+                    baseUrl: http://gx00.gw:8000
+                    model: sonnet
+                    exhaustedPattern: "rate limit exceeded"
+                guard:
+                  offSubscriptionHosts:
+                    - gx00.gw
+                """);
+        ConfigRef.Outcome out = ref.reload();
+
+        assertTrue(out.applied());
+        assertEquals(1, out.deferred().size(), out.deferred().toString());
+        assertTrue(out.deferred().getFirst().contains("sonnet"), out.deferred().toString());
+        assertTrue(out.deferred().getFirst().contains("launch settings"), out.deferred().toString());
+        // The snapshot still carries the new value — a restart is what makes it take effect.
+        assertEquals("rate limit exceeded", ref.get().profiles().get("sonnet").exhaustedPattern());
+    }
+
     @Test
     void aFixedRefHasNoFileAndRefusesToReload() {
         BridgedConfig cfg = new BridgedConfig(null, null, null, null, null, null,

bridged/src/test/java/dev/ltms/bridged/inject/CompletionResolverTest.java

@@ -26,7 +26,7 @@ class CompletionResolverTest {
     void skipsTheScrapeWhenNoSendIsWaiting() {
         FakeHerdr herdr = new FakeHerdr();
         Rendezvous rendezvous = new Rendezvous(); // no waiter opened
-        CompletionResolver resolver = new CompletionResolver(new AgentControl(herdr), rendezvous, ExhaustedPatternLookup.none());
+        CompletionResolver resolver = new CompletionResolver(new AgentControl(herdr), rendezvous, ExhaustedPatternLookup.none(), ExhaustionSink.none());
 
         resolver.resolve("term_a", null); // no in-flight turn captured for this target
 
@@ -38,7 +38,7 @@ class CompletionResolverTest {
     void failSkipsTheScrapeWhenNoSendIsWaiting() {
         FakeHerdr herdr = new FakeHerdr();
         Rendezvous rendezvous = new Rendezvous(); // no waiter opened
-        CompletionResolver resolver = new CompletionResolver(new AgentControl(herdr), rendezvous, ExhaustedPatternLookup.none());
+        CompletionResolver resolver = new CompletionResolver(new AgentControl(herdr), rendezvous, ExhaustedPatternLookup.none(), ExhaustionSink.none());
 
         resolver.fail("term_a", null); // no in-flight turn, and no registered waiter to fall back to
 
@@ -50,7 +50,7 @@ class CompletionResolverTest {
     void captureBaselineSkipsTheReadWhenNoSendIsWaiting() {
         FakeHerdr herdr = new FakeHerdr().readText("⏺ X\n❯ ");
         Rendezvous rendezvous = new Rendezvous(); // no waiter opened
-        CompletionResolver resolver = new CompletionResolver(new AgentControl(herdr), rendezvous, ExhaustedPatternLookup.none());
+        CompletionResolver resolver = new CompletionResolver(new AgentControl(herdr), rendezvous, ExhaustedPatternLookup.none(), ExhaustionSink.none());
 
         resolver.captureBaseline("term_a", TestTurnTokens.inert("term_a")); // no send to attribute a later completion to
 
@@ -139,7 +139,7 @@ class CompletionResolverTest {
         // send must NOT be resolved with the stale answer.
         FakeHerdr herdr = new FakeHerdr().readText("⏺ 391\n❯ ");
         Rendezvous rendezvous = new Rendezvous();
-        CompletionResolver resolver = new CompletionResolver(new AgentControl(herdr), rendezvous, ExhaustedPatternLookup.none());
+        CompletionResolver resolver = new CompletionResolver(new AgentControl(herdr), rendezvous, ExhaustedPatternLookup.none(), ExhaustionSink.none());
 
         var waiter = rendezvous.open("term_a");   // a send is blocked on this turn
         // The turn as captured at delivery: its waiter, and the previous turn's answer still on screen.
@@ -154,7 +154,7 @@ class CompletionResolverTest {
     void resolvesACompletionWhoseScrapeChangedSinceDelivery() {
         FakeHerdr herdr = new FakeHerdr().readText("⏺ No, 391 = 17 × 23.\n❯ "); // the worker's real answer
         Rendezvous rendezvous = new Rendezvous();
-        CompletionResolver resolver = new CompletionResolver(new AgentControl(herdr), rendezvous, ExhaustedPatternLookup.none());
+        CompletionResolver resolver = new CompletionResolver(new AgentControl(herdr), rendezvous, ExhaustedPatternLookup.none(), ExhaustionSink.none());
 
         var waiter = rendezvous.open("term_a");
         // Delivery baseline was the previous turn's "391"; the scrape now differs → resolve.
@@ -171,7 +171,7 @@ class CompletionResolverTest {
         String block = "⏺ " + "x".repeat(CompletionResolver.MAX_SCRAPE_CHARS + 1) + "\n❯ ";
         FakeHerdr herdr = new FakeHerdr().readText(block);
         Rendezvous rendezvous = new Rendezvous();
-        CompletionResolver resolver = new CompletionResolver(new AgentControl(herdr), rendezvous, ExhaustedPatternLookup.none());
+        CompletionResolver resolver = new CompletionResolver(new AgentControl(herdr), rendezvous, ExhaustedPatternLookup.none(), ExhaustionSink.none());
 
         var waiter = rendezvous.open("term_a");
         resolver.resolve("term_a", new CompletionResolver.InFlight(waiter, null));
@@ -185,7 +185,7 @@ class CompletionResolverTest {
     void leavesAnUnclippedCompletionPaneTailUnmarked() {
         FakeHerdr herdr = new FakeHerdr().readText("⏺ complete report\n❯ ");
         Rendezvous rendezvous = new Rendezvous();
-        CompletionResolver resolver = new CompletionResolver(new AgentControl(herdr), rendezvous, ExhaustedPatternLookup.none());
+        CompletionResolver resolver = new CompletionResolver(new AgentControl(herdr), rendezvous, ExhaustedPatternLookup.none(), ExhaustionSink.none());
 
         var waiter = rendezvous.open("term_a");
         resolver.resolve("term_a", new CompletionResolver.InFlight(waiter, null));
@@ -197,7 +197,7 @@ class CompletionResolverTest {
     void resolvesSynchronouslyBeforePostTurnContextClearing() {
         FakeHerdr herdr = new FakeHerdr().readText("⏺ previous answer\n❯ ");
         Rendezvous rendezvous = new Rendezvous();
-        CompletionResolver resolver = new CompletionResolver(new AgentControl(herdr), rendezvous, ExhaustedPatternLookup.none());
+        CompletionResolver resolver = new CompletionResolver(new AgentControl(herdr), rendezvous, ExhaustedPatternLookup.none(), ExhaustionSink.none());
         var waiter = rendezvous.open("term_a");
         resolver.captureBaseline("term_a", new TurnToken("term_a", waiter));
         herdr.readText("⏺ answer that /clear would erase\n❯ ");
@@ -219,7 +219,7 @@ class CompletionResolverTest {
         String longBlock = "⏺ " + "x".repeat(CompletionResolver.MAX_SCRAPE_CHARS + 500) + "\n❯ ";
         FakeHerdr herdr = new FakeHerdr().readText(longBlock);
         Rendezvous rendezvous = new Rendezvous();
-        CompletionResolver resolver = new CompletionResolver(new AgentControl(herdr), rendezvous, ExhaustedPatternLookup.none());
+        CompletionResolver resolver = new CompletionResolver(new AgentControl(herdr), rendezvous, ExhaustedPatternLookup.none(), ExhaustionSink.none());
 
         var waiter = rendezvous.open("term_a");        // a send is blocked on this turn
         resolver.captureBaseline("term_a", new TurnToken("term_a", waiter)); // baseline is the clipped >cap block
@@ -239,7 +239,7 @@ class CompletionResolverTest {
         // No delivery baseline (e.g. the pre-turn read failed) ⇒ never suppress; the completion resolves.
         FakeHerdr herdr = new FakeHerdr().readText("⏺ hello\n❯ ");
         Rendezvous rendezvous = new Rendezvous();
-        CompletionResolver resolver = new CompletionResolver(new AgentControl(herdr), rendezvous, ExhaustedPatternLookup.none());
+        CompletionResolver resolver = new CompletionResolver(new AgentControl(herdr), rendezvous, ExhaustedPatternLookup.none(), ExhaustionSink.none());
 
         var waiter = rendezvous.open("term_a");
         resolver.resolve("term_a", new CompletionResolver.InFlight(waiter, null));
@@ -257,7 +257,7 @@ class CompletionResolverTest {
         // byte-identical guard would wrongly match the empty tail and suppress.
         FakeHerdr herdr = new FakeHerdr().healthy(false); // agent.read throws HerdrException
         Rendezvous rendezvous = new Rendezvous();
-        CompletionResolver resolver = new CompletionResolver(new AgentControl(herdr), rendezvous, ExhaustedPatternLookup.none());
+        CompletionResolver resolver = new CompletionResolver(new AgentControl(herdr), rendezvous, ExhaustedPatternLookup.none(), ExhaustionSink.none());
 
         var waiter = rendezvous.open("term_a");
         var turn = new CompletionResolver.InFlight(waiter, ""); // empty pane baselined at delivery
@@ -277,7 +277,7 @@ class CompletionResolverTest {
         // fail must not overwrite that value, and must not even scrape the worker — nobody needs it.
         FakeHerdr herdr = new FakeHerdr().readText("an error screen");
         Rendezvous rendezvous = new Rendezvous();
-        CompletionResolver resolver = new CompletionResolver(new AgentControl(herdr), rendezvous, ExhaustedPatternLookup.none());
+        CompletionResolver resolver = new CompletionResolver(new AgentControl(herdr), rendezvous, ExhaustedPatternLookup.none(), ExhaustionSink.none());
 
         var waiter = rendezvous.open("term_a");
         var turn = new CompletionResolver.InFlight(waiter, null);
@@ -298,7 +298,7 @@ class CompletionResolverTest {
         // fail falls back to the waiter currently registered on the Rendezvous and fails it.
         FakeHerdr herdr = new FakeHerdr().readText("stuck on an error screen");
         Rendezvous rendezvous = new Rendezvous();
-        CompletionResolver resolver = new CompletionResolver(new AgentControl(herdr), rendezvous, ExhaustedPatternLookup.none());
+        CompletionResolver resolver = new CompletionResolver(new AgentControl(herdr), rendezvous, ExhaustedPatternLookup.none(), ExhaustionSink.none());
 
         var waiter = rendezvous.open("term_a"); // send registered, but no captureBaseline ever ran
         resolver.fail("term_a", null);          // no in-flight turn → fall back to the registered waiter
@@ -324,7 +324,7 @@ class CompletionResolverTest {
         try {
             FakeHerdr herdr = new FakeHerdr().readText("stuck on an error screen");
             Rendezvous rendezvous = new Rendezvous();
-            CompletionResolver resolver = new CompletionResolver(new AgentControl(herdr), rendezvous, ExhaustedPatternLookup.none());
+            CompletionResolver resolver = new CompletionResolver(new AgentControl(herdr), rendezvous, ExhaustedPatternLookup.none(), ExhaustionSink.none());
             var waiter = rendezvous.open("term_a");
 
             resolver.fail("term_a", null);
@@ -352,7 +352,7 @@ class CompletionResolverTest {
         // scrape to turn N+1; targeting turn N's captured waiter makes the late completion a no-op.
         FakeHerdr herdr = new FakeHerdr().readText("⏺ turn N answer\n❯ ");
         Rendezvous rendezvous = new Rendezvous();
-        CompletionResolver resolver = new CompletionResolver(new AgentControl(herdr), rendezvous, ExhaustedPatternLookup.none());
+        CompletionResolver resolver = new CompletionResolver(new AgentControl(herdr), rendezvous, ExhaustedPatternLookup.none(), ExhaustionSink.none());
 
         var waiterN = rendezvous.open("term_a"); // turn N's send
         // The turn as the injector captured it at delivery (waiter + pre-turn baseline).
@@ -382,7 +382,7 @@ class CompletionResolverTest {
         FakeHerdr herdr = new FakeHerdr().readText(block);
         Rendezvous rendezvous = new Rendezvous();
         ExhaustedPatternLookup patterns = target -> Pattern.compile("usage limit has been reached");
-        CompletionResolver resolver = new CompletionResolver(new AgentControl(herdr), rendezvous, patterns);
+        CompletionResolver resolver = new CompletionResolver(new AgentControl(herdr), rendezvous, patterns, ExhaustionSink.none());
 
         var waiter = rendezvous.open("term_a");
         resolver.resolve("term_a", new CompletionResolver.InFlight(waiter, null));
@@ -398,7 +398,7 @@ class CompletionResolverTest {
         FakeHerdr herdr = new FakeHerdr().readText(block);
         Rendezvous rendezvous = new Rendezvous();
         ExhaustedPatternLookup patterns = target -> Pattern.compile("usage limit has been reached");
-        CompletionResolver resolver = new CompletionResolver(new AgentControl(herdr), rendezvous, patterns);
+        CompletionResolver resolver = new CompletionResolver(new AgentControl(herdr), rendezvous, patterns, ExhaustionSink.none());
 
         var waiter = rendezvous.open("term_a");
         resolver.resolve("term_a", new CompletionResolver.InFlight(waiter, null));
@@ -407,12 +407,53 @@ class CompletionResolverTest {
                 waiter.getNow(null).text(), "the reason names the real cause and carries the matched line");
     }
 
+    @Test
+    void aWinningBackendExhaustedClassificationNotifiesTheExhaustionSink() {
+        String block = "⏺ Working on it...\nThe usage limit has been reached. Try again later.\n❯ ";
+        FakeHerdr herdr = new FakeHerdr().readText(block);
+        Rendezvous rendezvous = new Rendezvous();
+        ExhaustedPatternLookup patterns = target -> Pattern.compile("usage limit has been reached");
+        java.util.List<String> notified = new java.util.ArrayList<>();
+        ExhaustionSink sink = (target, reason) -> notified.add(target + ": " + reason);
+        CompletionResolver resolver = new CompletionResolver(new AgentControl(herdr), rendezvous, patterns, sink);
+
+        var waiter = rendezvous.open("term_a");
+        resolver.resolve("term_a", new CompletionResolver.InFlight(waiter, null));
+
+        assertEquals(1, notified.size(), "the sink is notified exactly once for the winning classification");
+        assertTrue(notified.get(0).startsWith("term_a: "), "the sink is told which target exhausted");
+        assertTrue(notified.get(0).contains("The usage limit has been reached"),
+                "the sink is told the matched reason: " + notified.get(0));
+    }
+
+    @Test
+    void aLosingBackendExhaustedClassificationNeverNotifiesTheExhaustionSink() {
+        // The waiter was already resolved (e.g. by the worker's own reply) before this scrape landed —
+        // resolveExhausted loses the race and must return false, so the sink must not fire either.
+        String block = "⏺ Working on it...\nThe usage limit has been reached. Try again later.\n❯ ";
+        FakeHerdr herdr = new FakeHerdr().readText(block);
+        Rendezvous rendezvous = new Rendezvous();
+        ExhaustedPatternLookup patterns = target -> Pattern.compile("usage limit has been reached");
+        java.util.List<String> notified = new java.util.ArrayList<>();
+        ExhaustionSink sink = (target, reason) -> notified.add(target + ": " + reason);
+        CompletionResolver resolver = new CompletionResolver(new AgentControl(herdr), rendezvous, patterns, sink);
+
+        var waiter = rendezvous.open("term_a");
+        var turn = new CompletionResolver.InFlight(waiter, null);
+        assertTrue(rendezvous.resolveCompletion(waiter, "already replied"));
+
+        resolver.resolve("term_a", turn);
+
+        assertTrue(notified.isEmpty(), "a classification that loses the race must not quarantine anything");
+        assertEquals("already replied", waiter.getNow(null).text(), "the earlier resolution stands untouched");
+    }
+
     @Test
     void aNonMatchingScrapeResolvesAsAnOrdinaryCompletion() {
         FakeHerdr herdr = new FakeHerdr().readText("⏺ complete report\n❯ ");
         Rendezvous rendezvous = new Rendezvous();
         ExhaustedPatternLookup patterns = target -> Pattern.compile("usage limit has been reached");
-        CompletionResolver resolver = new CompletionResolver(new AgentControl(herdr), rendezvous, patterns);
+        CompletionResolver resolver = new CompletionResolver(new AgentControl(herdr), rendezvous, patterns, ExhaustionSink.none());
 
         var waiter = rendezvous.open("term_a");
         resolver.resolve("term_a", new CompletionResolver.InFlight(waiter, null));
@@ -430,7 +471,7 @@ class CompletionResolverTest {
         FakeHerdr herdr = new FakeHerdr().readText(block);
         Rendezvous rendezvous = new Rendezvous();
         CompletionResolver resolver =
-                new CompletionResolver(new AgentControl(herdr), rendezvous, ExhaustedPatternLookup.none());
+                new CompletionResolver(new AgentControl(herdr), rendezvous, ExhaustedPatternLookup.none(), ExhaustionSink.none());
 
         var waiter = rendezvous.open("term_a");
         resolver.resolve("term_a", new CompletionResolver.InFlight(waiter, null));

bridged/src/test/java/dev/ltms/bridged/mcp/BridgeMcpAuthzTest.java

@@ -72,7 +72,8 @@ class BridgeMcpAuthzTest {
                 new PrimaryRegistry(null),
                 enforce ? CallerResolver.withLeadsAndMembers(identity, false, null,
                 Map::of, new MemberRegistry(null)) : null,
-                metrics, BridgeMcp.CapacitySource.none(), new BridgeMcp.HealthCoverageSource(() -> "off"));
+                metrics, BridgeMcp.CapacitySource.none(), new BridgeMcp.HealthCoverageSource(() -> "off"),
+                BridgeMcp.QuarantineSource.none());
         return mcp;
     }
 

bridged/src/test/java/dev/ltms/bridged/mcp/BridgeMcpTest.java

@@ -16,6 +16,7 @@ import dev.ltms.bridged.inject.MemberPresence;
 import dev.ltms.bridged.session.MemberSession;
 import dev.ltms.bridged.session.WorktreeRequest;
 import dev.ltms.bridged.member.ClaudeCodeLauncher;
+import dev.ltms.bridged.placement.BackendQuarantine;
 import io.modelcontextprotocol.spec.McpSchema;
 import dev.ltms.bridged.msg.InMemoryReplyInbox;
 import org.junit.jupiter.api.BeforeEach;
@@ -437,11 +438,29 @@ class BridgeMcpTest {
     @Test
     void profilesListsConfiguredProfilesAndDefault() {
         FakeHerdr h = new FakeHerdr();
-        McpSchema.CallToolResult res = BridgeMcp.profiles(workerService(h, "http://gx00.gw:8000", Set.of("gx00.gw")));
+        McpSchema.CallToolResult res = BridgeMcp.profiles(
+                workerService(h, "http://gx00.gw:8000", Set.of("gx00.gw")), BridgeMcp.QuarantineSource.none());
         assertNotEquals(Boolean.TRUE, res.isError());
         String out = textOf(res);
         assertTrue(out.contains("ltms-local"), out);
         assertTrue(out.contains("\"default\":\"ltms-local\""), out);
+        assertFalse(out.contains("quarantined"), "no profile is quarantined, so the key is omitted: " + out);
+    }
+
+    @Test
+    void profilesReportsAQuarantinedCredential() {
+        FakeHerdr h = new FakeHerdr();
+        BackendQuarantine quarantine = new BackendQuarantine(() -> 0L, TimeUnit.MINUTES.toNanos(30));
+        quarantine.quarantine("shared-openai");
+        BridgeMcp.QuarantineSource source = new BridgeMcp.QuarantineSource(
+                profile -> "ltms-local".equals(profile) ? "shared-openai" : null, quarantine);
+        McpSchema.CallToolResult res = BridgeMcp.profiles(
+                workerService(h, "http://gx00.gw:8000", Set.of("gx00.gw")), source);
+        assertNotEquals(Boolean.TRUE, res.isError());
+        String out = textOf(res);
+        assertTrue(out.contains("\"quarantined\""), out);
+        assertTrue(out.contains("shared-openai"), out);
+        assertTrue(out.contains("\"quarantinedForSeconds\":1800"), out);
     }
 
     @Test

bridged/src/test/java/dev/ltms/bridged/member/CompositePeerLauncherTest.java

@@ -16,6 +16,7 @@ import dev.ltms.bridged.peer.PeerHandle;
 import dev.ltms.bridged.peer.PeerLauncher;
 import dev.ltms.bridged.peer.PeerUnreachableException;
 import dev.ltms.bridged.peer.SpawnRequest;
+import dev.ltms.bridged.placement.BackendQuarantine;
 import dev.ltms.bridged.placement.PlacementException;
 import dev.ltms.bridged.placement.PlacementPolicies;
 import org.junit.jupiter.api.Test;
@@ -27,6 +28,8 @@ import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicLong;
 
 import static org.junit.jupiter.api.Assertions.*;
 
@@ -128,6 +131,13 @@ class CompositePeerLauncherTest {
                 weight, maxLoad);
     }
 
+    private static BridgedConfig.Profile stubWorker(String profile, String credentialId) {
+        return new BridgedConfig.Profile(profile, "http://gx00.gw:8000", "coder",
+                null, "BRIDGED_WORKER_TOKEN", List.of("claude"), "tab", "bridged-workers",
+                "w #{n}", null, null, null, null, null, null, null, null, null,
+                null, null, credentialId);
+    }
+
     /**
      * An <em>order-preserving</em> profile map. Never {@code Map.of} here: its iteration order is
      * salted per JVM run, and the weighted policy breaks an exact-weight tie on candidate order —
@@ -554,4 +564,105 @@ class CompositePeerLauncherTest {
                 new SpawnRequest(null, null, null, null, null, MemberRole.DEV)));
         assertTrue(e.getMessage().contains("maxLoad"), e.getMessage());
     }
+
+    // ── CB-578 stage B: a BACKEND_EXHAUSTED classification quarantines the credential ──────────
+
+    @Test
+    void explicitSpawnOntoAQuarantinedProfileIsRefusedNamingTheCredentialAndRemainingTime() {
+        FakeHerdr herdr = new FakeHerdr();
+        Map<String, BridgedConfig.Profile> profiles = ordered(
+                "sol", stubWorker("sol", "shared-openai"),
+                "terra", stubWorker("terra", "shared-openai"));
+        StubLauncher adapter = new StubLauncher("claude", herdr, profiles, "sol", Set.of());
+        BackendQuarantine quarantine = new BackendQuarantine(() -> 0L, TimeUnit.MINUTES.toNanos(30));
+        quarantine.quarantine("shared-openai");
+        CompositePeerLauncher composite = new CompositePeerLauncher(List.of(adapter), "sol", profiles,
+                PlacementPolicies.fixed(), _ -> 0, null, quarantine);
+
+        PlacementException e = assertThrows(PlacementException.class,
+                () -> composite.spawn(new SpawnRequest("sol", null, null)));
+        assertTrue(e.getMessage().contains("sol"), "message names the profile: " + e.getMessage());
+        assertTrue(e.getMessage().contains("shared-openai"), "message names the credential: " + e.getMessage());
+        assertTrue(e.getMessage().contains("1800"), "message names roughly when it lifts: " + e.getMessage());
+        assertEquals(0, adapter.spawnCount("sol"), "the quarantined profile is never delegated to");
+    }
+
+    /**
+     * The part CB-578 stage B calls out as easy to get wrong: sol and terra are two different
+     * profiles sharing one OpenAI credential. Quarantining because of an exhaustion classified on
+     * ONE of them must lock out the other too, or the fleet just walks onto the same dead account
+     * under the sibling's name.
+     */
+    @Test
+    void twoProfilesSharingACredentialAreBothQuarantinedByOneExhaustionEvent() {
+        FakeHerdr herdr = new FakeHerdr();
+        Map<String, BridgedConfig.Profile> profiles = ordered(
+                "sol", stubWorker("sol", "shared-openai"),
+                "terra", stubWorker("terra", "shared-openai"));
+        StubLauncher adapter = new StubLauncher("claude", herdr, profiles, "sol", Set.of());
+        BackendQuarantine quarantine = new BackendQuarantine(() -> 0L, TimeUnit.MINUTES.toNanos(30));
+        // Only "sol" was classified BACKEND_EXHAUSTED — but the two profiles share one credential.
+        quarantine.quarantine("shared-openai");
+        CompositePeerLauncher composite = new CompositePeerLauncher(List.of(adapter), "sol", profiles,
+                PlacementPolicies.fixed(), _ -> 0, null, quarantine);
+
+        assertThrows(PlacementException.class, () -> composite.spawn(new SpawnRequest("sol", null, null)),
+                "sol was the one classified exhausted");
+        assertThrows(PlacementException.class, () -> composite.spawn(new SpawnRequest("terra", null, null)),
+                "terra shares sol's credential, so it must be locked out too");
+        assertEquals(0, adapter.spawnCount("sol"));
+        assertEquals(0, adapter.spawnCount("terra"));
+    }
+
+    @Test
+    void placementSkipsAQuarantinedProfileAndRoutesToAnUnquarantinedOne() {
+        FakeHerdr herdr = new FakeHerdr();
+        Map<String, BridgedConfig.Profile> profiles = ordered(
+                "sol", stubWorker("sol", "shared-openai"),
+                "b", stubWorker("b"));
+        StubLauncher adapter = new StubLauncher("claude", herdr, profiles, "sol", Set.of());
+        BackendQuarantine quarantine = new BackendQuarantine(() -> 0L, TimeUnit.MINUTES.toNanos(30));
+        quarantine.quarantine("shared-openai");
+        CompositePeerLauncher composite = new CompositePeerLauncher(List.of(adapter), "sol", profiles,
+                PlacementPolicies.weighted(), _ -> 0, null, quarantine);
+
+        PeerHandle h = composite.spawn(new SpawnRequest(null, null, null));
+        assertEquals("b", h.profile(), "sol is quarantined, so an unqualified spawn must land on b");
+        assertEquals(0, adapter.spawnCount("sol"));
+    }
+
+    @Test
+    void aQuarantineLiftsOnTheInjectedClockAndTheProfileBecomesSpawnableAgain() {
+        FakeHerdr herdr = new FakeHerdr();
+        Map<String, BridgedConfig.Profile> profiles = ordered(
+                "sol", stubWorker("sol", "shared-openai"),
+                "b", stubWorker("b"));
+        StubLauncher adapter = new StubLauncher("claude", herdr, profiles, "sol", Set.of());
+        AtomicLong nowNanos = new AtomicLong(0L);
+        BackendQuarantine quarantine = new BackendQuarantine(nowNanos::get, TimeUnit.MINUTES.toNanos(30));
+        quarantine.quarantine("shared-openai");
+        CompositePeerLauncher composite = new CompositePeerLauncher(List.of(adapter), "sol", profiles,
+                PlacementPolicies.fixed(), _ -> 0, null, quarantine);
+
+        assertThrows(PlacementException.class, () -> composite.spawn(new SpawnRequest("sol", null, null)),
+                "still inside the cooldown");
+
+        nowNanos.set(TimeUnit.MINUTES.toNanos(31));
+
+        PeerHandle h = composite.spawn(new SpawnRequest("sol", null, null));
+        assertEquals("sol", h.profile(), "the cooldown expired on the injected clock — sol is spawnable again");
+        assertEquals(1, adapter.spawnCount("sol"));
+    }
+
+    @Test
+    void aFleetWithNoExhaustedPatternAnywhereBehavesExactlyAsBeforeQuarantineExisted() {
+        // BackendQuarantine.none() is the inert stand-in every constructor already defaults to when
+        // no quarantine is wired — the 2/5/6-arg constructors used throughout this file all exercise
+        // it. This test pins that an explicit .none() also never refuses a spawn, for any profile.
+        FakeHerdr herdr = new FakeHerdr();
+        PeerLauncher composite = composite(herdr);
+
+        assertDoesNotThrow(() -> composite.spawn(new SpawnRequest("claude", null, null)));
+        assertDoesNotThrow(() -> composite.spawn(new SpawnRequest("gemini", null, null)));
+    }
 }

bridged/src/test/java/dev/ltms/bridged/msg/MessageServiceTest.java

@@ -6,6 +6,7 @@ import dev.ltms.bridged.herdr.FakeHerdr;
 import dev.ltms.bridged.herdr.HerdrException;
 import dev.ltms.bridged.inject.CompletionResolver;
 import dev.ltms.bridged.inject.ExhaustedPatternLookup;
+import dev.ltms.bridged.inject.ExhaustionSink;
 import dev.ltms.bridged.mcp.PrimaryRegistry;
 import dev.ltms.bridged.inject.Injector;
 import org.junit.jupiter.api.BeforeEach;
@@ -33,7 +34,7 @@ class MessageServiceTest {
     private final AgentControl agents = new AgentControl(herdr);
     private final Rendezvous rendezvous = new Rendezvous();
     private final CompletionResolver completion =
-            new CompletionResolver(agents, rendezvous, ExhaustedPatternLookup.none());
+            new CompletionResolver(agents, rendezvous, ExhaustedPatternLookup.none(), ExhaustionSink.none());
     private final Injector injector = new Injector(agents, completion);
     private final InMemoryReplyInbox inbox = new InMemoryReplyInbox();
     private final MessageService messages = new MessageService(agents, injector, rendezvous, inbox);

bridged/src/test/java/dev/ltms/bridged/placement/BackendQuarantineTest.java

@@ -0,0 +1,108 @@
+package dev.ltms.bridged.placement;
+
+import org.junit.jupiter.api.Test;
+
+import java.util.Map;
+import java.util.OptionalLong;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicLong;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+/**
+ * CB-578 stage B: the credential-keyed quarantine tracker itself, isolated from placement/spawn
+ * wiring (that's {@code CompositePeerLauncherTest}). The clock is a plain {@link AtomicLong} of
+ * nanos so expiry is exercised without a real sleep.
+ */
+class BackendQuarantineTest {
+
+    @Test
+    void aFreshCredentialIsNotQuarantined() {
+        BackendQuarantine q = new BackendQuarantine(() -> 0L, TimeUnit.MINUTES.toNanos(30));
+        assertFalse(q.isQuarantined("shared-openai"));
+        assertEquals(OptionalLong.empty(), q.remainingSeconds("shared-openai"));
+    }
+
+    @Test
+    void quarantineBlocksTheCredentialForTheFullCooldown() {
+        BackendQuarantine q = new BackendQuarantine(() -> 0L, TimeUnit.MINUTES.toNanos(30));
+        q.quarantine("shared-openai");
+
+        assertTrue(q.isQuarantined("shared-openai"));
+        assertEquals(OptionalLong.of(1800L), q.remainingSeconds("shared-openai"));
+    }
+
+    @Test
+    void onlyTheQuarantinedCredentialIsAffected() {
+        BackendQuarantine q = new BackendQuarantine(() -> 0L, TimeUnit.MINUTES.toNanos(30));
+        q.quarantine("shared-openai");
+
+        assertFalse(q.isQuarantined("some-other-credential"),
+                "an unrelated credential must not be swept into the quarantine");
+    }
+
+    @Test
+    void expiresOnTheInjectedClock() {
+        AtomicLong now = new AtomicLong(0L);
+        BackendQuarantine q = new BackendQuarantine(now::get, TimeUnit.MINUTES.toNanos(30));
+        q.quarantine("shared-openai");
+        assertTrue(q.isQuarantined("shared-openai"));
+
+        now.set(TimeUnit.MINUTES.toNanos(29));
+        assertTrue(q.isQuarantined("shared-openai"), "still inside the cooldown");
+
+        now.set(TimeUnit.MINUTES.toNanos(31));
+        assertFalse(q.isQuarantined("shared-openai"), "the cooldown has elapsed on the injected clock");
+        assertEquals(OptionalLong.empty(), q.remainingSeconds("shared-openai"));
+    }
+
+    @Test
+    void aRepeatQuarantineCallRestartsTheCooldownAtFullLength() {
+        AtomicLong now = new AtomicLong(0L);
+        BackendQuarantine q = new BackendQuarantine(now::get, TimeUnit.MINUTES.toNanos(30));
+        q.quarantine("shared-openai");
+
+        now.set(TimeUnit.MINUTES.toNanos(20));
+        q.quarantine("shared-openai");
+
+        now.set(TimeUnit.MINUTES.toNanos(45)); // 25 min after the second call, 45 after the first
+        assertTrue(q.isQuarantined("shared-openai"),
+                "a fresh exhaustion resets the cooldown to full length, not the earlier shorter wait");
+    }
+
+    @Test
+    void activeRemainingSecondsListsOnlyStillQuarantinedCredentials() {
+        AtomicLong now = new AtomicLong(0L);
+        BackendQuarantine q = new BackendQuarantine(now::get, TimeUnit.MINUTES.toNanos(30));
+        q.quarantine("shared-openai");
+        q.quarantine("another-credential");
+
+        now.set(TimeUnit.MINUTES.toNanos(31));
+        q.quarantine("shared-openai"); // re-quarantined after the first one expired
+
+        Map<String, Long> active = q.activeRemainingSeconds();
+        assertEquals(Map.of("shared-openai", 1800L), active,
+                "the expired credential is dropped; the re-quarantined one is reported");
+    }
+
+    @Test
+    void noneReportsNothingQuarantinedWhenNeverToldTo() {
+        // .none() is the stand-in for a caller whose code path never calls #quarantine at all (e.g.
+        // the 2/5/6-arg CompositePeerLauncher constructors) — not a guarantee that a call to
+        // #quarantine on it is a no-op. Left alone, as those call sites leave it, nothing is ever
+        // quarantined.
+        BackendQuarantine q = BackendQuarantine.none();
+
+        assertFalse(q.isQuarantined("anything"));
+        assertTrue(q.activeRemainingSeconds().isEmpty());
+    }
+
+    @Test
+    void aNonPositiveCooldownIsRejected() {
+        assertThrows(IllegalArgumentException.class, () -> new BackendQuarantine(() -> 0L, 0L));
+        assertThrows(IllegalArgumentException.class, () -> new BackendQuarantine(() -> 0L, -1L));
+    }
+}

bridged/src/test/java/dev/ltms/bridged/placement/PlacementPolicyTest.java

@@ -24,7 +24,13 @@ class PlacementPolicyTest {
     private static PlacementContext ctx(List<PlacementCandidate> candidates,
                                         Function<String, Integer> liveCount,
                                         Set<String> unreachable) {
-        return new PlacementContext("b", candidates, liveCount, unreachable);
+        return ctx(candidates, liveCount, unreachable, Set.of());
+    }
+
+    private static PlacementContext ctx(List<PlacementCandidate> candidates,
+                                        Function<String, Integer> liveCount,
+                                        Set<String> unreachable, Set<String> quarantined) {
+        return new PlacementContext("b", candidates, liveCount, unreachable, quarantined);
     }
 
     private static PlacementContext ctx(List<PlacementCandidate> candidates,
@@ -46,17 +52,37 @@ class PlacementPolicyTest {
         PlacementPolicy policy = PlacementPolicies.fixed();
         PlacementContext ctx = new PlacementContext(null,
                 List.of(PlacementCandidate.profile("a"), PlacementCandidate.profile("b")),
-                noSessions(), Set.of());
+                noSessions(), Set.of(), Set.of());
         assertEquals("a", policy.select(ctx).profile());
     }
 
     @Test
     void fixedThrowsWhenNoProfilesAndNoDefault() {
         PlacementPolicy policy = PlacementPolicies.fixed();
-        PlacementContext ctx = new PlacementContext(null, List.of(), noSessions(), Set.of());
+        PlacementContext ctx = new PlacementContext(null, List.of(), noSessions(), Set.of(), Set.of());
         assertThrows(PlacementException.class, () -> policy.select(ctx));
     }
 
+    @Test
+    void fixedSkipsQuarantinedDefault() {
+        PlacementPolicy policy = PlacementPolicies.fixed();
+        PlacementContext ctx = new PlacementContext("b",
+                List.of(PlacementCandidate.profile("a"), PlacementCandidate.profile("b")),
+                noSessions(), Set.of(), Set.of("b"));
+        assertEquals("a", policy.select(ctx).profile(),
+                "the default 'b' is quarantined, so fixed falls through to the first un-quarantined candidate");
+    }
+
+    @Test
+    void fixedThrowsWhenDefaultAndEveryCandidateQuarantined() {
+        PlacementPolicy policy = PlacementPolicies.fixed();
+        PlacementContext ctx = new PlacementContext("b",
+                List.of(PlacementCandidate.profile("a"), PlacementCandidate.profile("b")),
+                noSessions(), Set.of(), Set.of("a", "b"));
+        PlacementException e = assertThrows(PlacementException.class, () -> policy.select(ctx));
+        assertTrue(e.getMessage().contains("quarantined"), e.getMessage());
+    }
+
     @Test
     void roundRobinCyclesThroughAvailableProfiles() {
         PlacementPolicy policy = PlacementPolicies.roundRobin();
@@ -82,6 +108,18 @@ class PlacementPolicyTest {
         }
     }
 
+    @Test
+    void roundRobinSkipsQuarantinedProfiles() {
+        PlacementPolicy policy = PlacementPolicies.roundRobin();
+        List<PlacementCandidate> candidates = List.of(
+                PlacementCandidate.profile("a"),
+                PlacementCandidate.profile("b"));
+        PlacementContext ctx = ctx(candidates, noSessions(), Set.of(), Set.of("a"));
+        for (int i = 0; i < 5; i++) {
+            assertEquals("b", policy.select(ctx).profile(), "a is quarantined, so every pick lands on b");
+        }
+    }
+
     @Test
     void roundRobinThrowsWhenAllAtMaxLoad() {
         PlacementPolicy policy = PlacementPolicies.roundRobin();
@@ -150,6 +188,29 @@ class PlacementPolicyTest {
         assertTrue(e.getMessage().contains("maxLoad"), e.getMessage());
     }
 
+    @Test
+    void weightedSkipsQuarantinedProfile() {
+        PlacementPolicy policy = PlacementPolicies.weighted();
+        List<PlacementCandidate> candidates = List.of(
+                PlacementCandidate.profile("a", 1.0f, null),
+                PlacementCandidate.profile("b", 1.0f, null));
+        PlacementContext ctx = ctx(candidates, noSessions(), Set.of(), Set.of("a"));
+        for (int i = 0; i < 5; i++) {
+            assertEquals("b", policy.select(ctx).profile(), "a is quarantined, so every pick lands on b");
+        }
+    }
+
+    @Test
+    void weightedThrowsWhenAllQuarantined() {
+        PlacementPolicy policy = PlacementPolicies.weighted();
+        List<PlacementCandidate> candidates = List.of(
+                PlacementCandidate.profile("a"),
+                PlacementCandidate.profile("b"));
+        PlacementException e = assertThrows(PlacementException.class,
+                () -> policy.select(ctx(candidates, noSessions(), Set.of(), Set.of("a", "b"))));
+        assertTrue(e.getMessage().contains("quarantined"), e.getMessage());
+    }
+
     @Test
     void weightedThrowsWhenAllUnreachable() {
         PlacementPolicy policy = PlacementPolicies.weighted();