fleetd #415: pin which UnsetMeaning Fleetd pairs with which pattern key

Review found a gap: the earlier tests all called CompletionResolver.coverage()
directly, supplying the UnsetMeaning themselves — proving the enum's wording,
never that Fleetd's two call sites pair the right meaning with the right key.
Swapping the two UnsetMeaning arguments at those call sites (recreating #415's
defect with exhaustedPattern and errorPattern exchanged) compiled with 0 errors
and left all 1506 tests green.

Extract the two coverage-line call sites out of main() into package-private
static factories (Fleetd.exhaustedPatternCoverageLine /
errorPatternCoverageLine), the same pattern already used for capacitySource
and worktreeBranchLookup. Add FleetdPatternCoverageLineTest, which calls both
factories directly and asserts the actual wording each produces for the same
empty-coverage input, including that the two differ.

Also recorded the swap-mutation measurement (0 errors, 1506 green) in
UnsetMeaning's javadoc so a future reader does not delete the new test as
redundant with CompletionResolverTest.

fleetd/src/main/java/dev/ltms/fleet/Fleetd.java

@@ -380,8 +380,7 @@ public final class Fleetd {
                 .map(session -> exhaustedPatternsByProfile.get(session.profile()))
                 .orElse(null);
         log.info("backend-exhausted classification (CB-578 stage A): {}",
-                CompletionResolver.coverage("exhaustedPattern", cfg.profiles().keySet(),
-                        exhaustedPatternsByProfile.keySet()));
+                exhaustedPatternCoverageLine(cfg.profiles().keySet(), exhaustedPatternsByProfile.keySet()));
         // fleetd #201 Unit 5: classify a completion-fallback scrape that matches a profile's
         // configured backend-error refusal (a credential outage, a provider 5xx) as a backend error
         // rather than handing it back as a real answer. Compiled once at startup, keyed by profile
@@ -401,8 +400,7 @@ public final class Fleetd {
         BackendErrorPatternLookup backendErrorPatterns = backendErrorPatternLookup(sessions::roster,
                 errorPatternsByProfile);
         log.info("backend-error classification (fleetd #201 Unit 5): {}",
-                CompletionResolver.coverage("errorPattern", cfg.profiles().keySet(),
-                        errorPatternsByProfile.keySet()));
+                errorPatternCoverageLine(cfg.profiles().keySet(), errorPatternsByProfile.keySet()));
         // 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
@@ -670,11 +668,8 @@ public final class Fleetd {
         }, outagePolicy);
 
         FleetMcp mcp = new FleetMcp(messages, workers, sessions, identity, presence,
-                primaryRegistry, callers, metrics, new FleetMcp.CapacitySource(profile -> liveCountRef.get().apply(profile),
-                profile -> {
-                    var configured = config.get().profiles().get(profile);
-                    return configured == null ? null : configured.maxLoad();
-                }, () -> config.get().profiles().keySet(), System::nanoTime),
+                primaryRegistry, callers, metrics,
+                capacitySource(config, cfg, profile -> liveCountRef.get().apply(profile)),
                 new FleetMcp.HealthCoverageSource(() -> {
                     var health = config.get().health();
                     return FleetHealthMonitor.coverage(health != null && health.isEnabled(),
@@ -810,6 +805,68 @@ public final class Fleetd {
         }, quarantine, profile -> startupExhaustedPatterns.containsKey(profile));
     }
 
+    /**
+     * fleetd #415 (review follow-up): package-private factory for the CB-578 stage A {@code
+     * exhaustedPattern} startup coverage line, paired explicitly with {@link
+     * CompletionResolver.UnsetMeaning#OFF} — {@code exhaustedPattern} has no fallback, so a
+     * profile with none configured really does have the classification off.
+     *
+     * <p>Extracted out of {@code main} for the same reason {@link #capacitySource} and {@link
+     * #worktreeBranchLookup} were: {@code coverage()}'s own tests ({@code CompletionResolverTest})
+     * prove it words {@code OFF} and {@link CompletionResolver.UnsetMeaning#BUILT_IN_DEFAULT}
+     * correctly when a test supplies the meaning itself — they cannot prove {@code main} pairs the
+     * right meaning with the right key, which is the actual fleetd #415 defect. <b>Measured:</b>
+     * swapping the {@code UnsetMeaning} arguments between this method and {@link
+     * #errorPatternCoverageLine} — recreating #415's defect with the two keys exchanged — compiled
+     * with 0 errors and left all 1506 existing tests green before {@code
+     * FleetdPatternCoverageLineTest} was added to catch exactly that swap.
+     */
+    static String exhaustedPatternCoverageLine(Set<String> allProfiles, Set<String> configuredProfiles) {
+        return CompletionResolver.coverage("exhaustedPattern", CompletionResolver.UnsetMeaning.OFF,
+                allProfiles, configuredProfiles);
+    }
+
+    /**
+     * fleetd #415 (review follow-up): the {@code errorPattern} counterpart of {@link
+     * #exhaustedPatternCoverageLine}, paired explicitly with {@link
+     * CompletionResolver.UnsetMeaning#BUILT_IN_DEFAULT} — an unset {@code errorPattern} still runs
+     * backend-error classification against {@code CompletionResolver}'s built-in {@code
+     * BACKEND_ERROR} pattern, so the empty case is not "off". See {@link
+     * #exhaustedPatternCoverageLine}'s javadoc for the measured swap mutation this pairing guards
+     * against.
+     */
+    static String errorPatternCoverageLine(Set<String> allProfiles, Set<String> configuredProfiles) {
+        return CompletionResolver.coverage("errorPattern", CompletionResolver.UnsetMeaning.BUILT_IN_DEFAULT,
+                allProfiles, configuredProfiles);
+    }
+
+    /**
+     * fleetd #416: production source for {@code fleet_list}'s per-profile capacity facts.
+     *
+     * <p>The profile <em>set</em> ({@code configuredProfiles}) must come from {@code cfg} — the
+     * startup snapshot — not the live {@code config.get()}. {@code profiles} as a whole is a
+     * {@code DEFERRED} key ({@link ConfigRef#DEFERRED_KEYS}): {@code HerdrPeerLauncher} takes
+     * {@code Map.copyOf(profiles)} once at construction and a profile only added to the
+     * hot-reloaded map can never actually be spawned, so enumerating it live made {@code fleet_list}
+     * report a profile as available when {@code fleet_spawn} on that same profile fails with
+     * {@code unknown worker profile}. {@code fleet_list}'s own contract for {@code free} is "the
+     * same check the spawn gate itself runs" — the set the spawn gate can see is the startup one,
+     * so this must enumerate that one too, the same shape as {@code coordinator.peers} above.
+     *
+     * <p>{@code maxLoad} stays live on purpose: it is read off {@code config.get()} exactly like
+     * {@code credentialId} ({@link ConfigRef} documents both as hot), so an existing profile's
+     * {@code maxLoad} edit must still change what {@code fleet_list} reports without a restart.
+     */
+    static FleetMcp.CapacitySource capacitySource(ConfigRef config, FleetConfig cfg,
+            Function<String, Integer> liveCount) {
+        return new FleetMcp.CapacitySource(liveCount,
+                profile -> {
+                    var configured = config.get().profiles().get(profile);
+                    return configured == null ? null : configured.maxLoad();
+                },
+                cfg.profiles()::keySet, System::nanoTime);
+    }
+
     /**
      * fleetd #248: package-private factory for the member worktree/branch lookup {@link
      * CompletionResolver} uses to name a fallback report's worktree and branch (fleetd#241).

fleetd/src/main/java/dev/ltms/fleet/inject/CompletionResolver.java

@@ -698,17 +698,57 @@ public final class CompletionResolver implements TurnListener {
     }
 
     /**
-     * Coverage summary for the CB-578 stage A exhausted-pattern classification, logged at startup
+     * What an unset pattern key means for the classification it configures (fleetd#415).
+     * {@code coverage()} cannot infer this from the key's name — the two keys it currently
+     * describes disagree on it, and a string comparison on the name would just move the same bug
+     * to a new spot — so every caller must state it explicitly.
+     *
+     * <p><strong>This alone does not prove a caller passes the right one for its key.</strong> A
+     * test that calls {@code coverage()} directly and supplies the meaning itself only proves this
+     * enum is worded correctly, never that {@code Fleetd}'s two call sites pair each key with its
+     * true meaning — that pairing is #415's actual defect. Measured on review: swapping the two
+     * {@code UnsetMeaning} arguments at those call sites (giving {@code exhaustedPattern} the
+     * built-in-default wording and {@code errorPattern} the off wording — #415's exact defect with
+     * the keys exchanged) compiled with 0 errors and left all 1506 existing tests green. See
+     * {@code dev.ltms.fleet.Fleetd#exhaustedPatternCoverageLine}/{@code #errorPatternCoverageLine}
+     * and {@code FleetdPatternCoverageLineTest}, which exists specifically to catch that swap.
+     */
+    public enum UnsetMeaning {
+        /** No fallback exists: a profile with no configured pattern truly has this classification off. */
+        OFF,
+        /** A built-in pattern applies when unset: the classification still runs for that profile. */
+        BUILT_IN_DEFAULT
+    }
+
+    /**
+     * Coverage summary for a fleetd#201/CB-578-style pattern-key classification, logged at startup
      * the way {@link dev.ltms.fleet.health.FleetHealthMonitor#coverage} is — so an operator can
      * see whether the classification is on, and for which profiles, without reading every
      * profile's config by hand.
      *
+     * <p>fleetd#415: this method measures <em>pattern coverage</em> — how many profiles set the
+     * key — which is not the same thing as <em>feature state</em> for a key with a fallback. For
+     * {@code errorPattern}, an empty {@code configuredProfiles} still runs the classification
+     * against {@code CompletionResolver}'s built-in compatibility pattern ({@link #BACKEND_ERROR}
+     * at line ~84); for {@code exhaustedPattern} there is no fallback, so empty really does mean
+     * off. {@code unsetMeaning} is the single, required source of that fact — see
+     * {@link dev.ltms.fleet.config.FleetConfig#rejectMalformedProfilePatterns} lines ~2029-2032 for
+     * where it is documented for config authors. It is a required parameter, not a defaulted
+     * overload: a third pattern key added later must supply one to compile at all, rather than
+     * silently inheriting whichever wording this method happened to default to.
+     *
      * @param allProfiles        every configured profile name
-     * @param configuredProfiles the subset of {@code allProfiles} that carry an exhausted pattern
+     * @param configuredProfiles the subset of {@code allProfiles} that carry the pattern
      */
-    public static String coverage(String patternKey, Set<String> allProfiles, Set<String> configuredProfiles) {
+    public static String coverage(String patternKey, UnsetMeaning unsetMeaning, Set<String> allProfiles,
+                                   Set<String> configuredProfiles) {
         if (configuredProfiles.isEmpty()) {
-            return "off (no profile has an " + patternKey + " configured; profiles: " + sorted(allProfiles) + ")";
+            return switch (unsetMeaning) {
+                case OFF -> "off (no profile has an " + patternKey + " configured; profiles: "
+                        + sorted(allProfiles) + ")";
+                case BUILT_IN_DEFAULT -> "built-in default for all profiles (no profile customises "
+                        + patternKey + "; profiles: " + sorted(allProfiles) + ")";
+            };
         }
         Set<String> unconfigured = new TreeSet<>(allProfiles);
         unconfigured.removeAll(configuredProfiles);

fleetd/src/test/java/dev/ltms/fleet/FleetdCapacitySourceWiringTest.java

@@ -0,0 +1,155 @@
+package dev.ltms.fleet;
+
+import dev.ltms.fleet.config.ConfigRef;
+import dev.ltms.fleet.config.FleetConfig;
+import dev.ltms.fleet.mcp.FleetMcp;
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.io.TempDir;
+
+import java.nio.file.Files;
+import java.nio.file.Path;
+
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+/**
+ * fleetd #416: {@code fleet_list}'s {@code CapacitySource.configuredProfiles} must enumerate the
+ * <em>startup</em> profile set, not the live, hot-reloaded one.
+ *
+ * <p>{@code profiles} as a whole is a {@code DEFERRED} key ({@link ConfigRef#DEFERRED_KEYS}):
+ * {@code HerdrPeerLauncher} takes {@code Map.copyOf(profiles)} once at construction, so a profile
+ * only added to the hot-reloaded map can never actually be spawned. Before this fix, {@code
+ * Fleetd.main} built {@code CapacitySource} with {@code () -> config.get().profiles().keySet()} —
+ * the live map — so {@code fleet_list} would report a freshly hot-reloaded profile as available
+ * ({@code free > 0}) while {@code fleet_spawn} on that same profile failed with
+ * {@code unknown worker profile}. Measured on another host: adding a throwaway profile and letting
+ * it hot-reload gave {@code fleet_list} -> {@code free: 3} and {@code fleet_spawn} ->
+ * {@code error: unknown worker profile}.
+ *
+ * <p>This test needs a reload, the same reason {@link FleetdExhaustionDetectionArmedWiringTest}
+ * does: at startup the two snapshots agree, so a test of only a newly started daemon would not
+ * detect a live {@code config.get()} lookup for the set.
+ *
+ * <p><b>maxLoad must stay hot.</b> It is read off {@code config.get()} exactly like
+ * {@code credentialId} ({@link ConfigRef} documents both as hot, "read live off the config
+ * supplier ... exactly like weight/maxLoad"), so a reload that only changes an existing profile's
+ * {@code maxLoad} — no add/remove — must still change what {@code fleet_list} reports without a
+ * restart. A fix that freezes the whole {@code CapacitySource} against {@code cfg} (rather than
+ * only its {@code configuredProfiles} set) would trade this bug for its mirror image and is pinned
+ * wrong by {@link #reloadedMaxLoadStillChangesWhatFleetListReports}.
+ */
+class FleetdCapacitySourceWiringTest {
+
+    private static final String STARTUP = """
+            bind:
+              host: 127.0.0.1
+              port: 8765
+            herdrSocket: ~/.config/herdr/herdr.sock
+            profiles:
+              terra:
+                baseUrl: http://gx00.gw:8000
+                model: terra
+                maxLoad: 3
+            guard:
+              offSubscriptionHosts:
+                - gx00.gw
+            """;
+
+    private static final String WITH_NEW_PROFILE = """
+            bind:
+              host: 127.0.0.1
+              port: 8765
+            herdrSocket: ~/.config/herdr/herdr.sock
+            profiles:
+              terra:
+                baseUrl: http://gx00.gw:8000
+                model: terra
+                maxLoad: 3
+              ghost404:
+                baseUrl: http://gx00.gw:8001
+                model: ghost404
+                maxLoad: 3
+            guard:
+              offSubscriptionHosts:
+                - gx00.gw
+            """;
+
+    private static final String WITH_CHANGED_MAX_LOAD = """
+            bind:
+              host: 127.0.0.1
+              port: 8765
+            herdrSocket: ~/.config/herdr/herdr.sock
+            profiles:
+              terra:
+                baseUrl: http://gx00.gw:8000
+                model: terra
+                maxLoad: 9
+            guard:
+              offSubscriptionHosts:
+                - gx00.gw
+            """;
+
+    @Test
+    @DisplayName("a profile present only in the live (hot-reloaded) config is NOT listed")
+    void liveOnlyProfileIsNotListed(@TempDir Path dir) throws Exception {
+        Path file = dir.resolve("fleetd.yaml");
+        Files.writeString(file, STARTUP);
+        FleetConfig cfg = FleetConfig.load(file);
+        ConfigRef config = new ConfigRef(file, cfg);
+
+        Files.writeString(file, WITH_NEW_PROFILE);
+        assertTrue(config.reload().applied());
+        // The live snapshot now has the new profile — proves the reload really happened and this
+        // test is not accidentally passing because nothing changed.
+        assertTrue(config.get().profiles().containsKey("ghost404"));
+
+        FleetMcp.CapacitySource source = Fleetd.capacitySource(config, cfg, _ -> 0);
+
+        assertFalse(source.configuredProfiles().get().contains("ghost404"),
+                "a profile added only to the hot-reloaded config must not be listed by fleet_list — "
+                        + "HerdrPeerLauncher never learns about it until a restart, so fleet_spawn on it "
+                        + "would fail with 'unknown worker profile' while fleet_list claimed it free");
+    }
+
+    @Test
+    @DisplayName("a profile present in the startup set IS listed")
+    void startupProfileIsListed(@TempDir Path dir) throws Exception {
+        Path file = dir.resolve("fleetd.yaml");
+        Files.writeString(file, STARTUP);
+        FleetConfig cfg = FleetConfig.load(file);
+        ConfigRef config = new ConfigRef(file, cfg);
+
+        FleetMcp.CapacitySource source = Fleetd.capacitySource(config, cfg, _ -> 0);
+
+        // fleetd #416, both-directions requirement: a test that only ever passes an empty/absent
+        // startup set (the case above) cannot tell a correct lookup from one that is permanently
+        // empty (e.g. a mutation replacing the supplier with Set::of). This is the direction that
+        // fails if the fix regresses to reporting nothing at all.
+        assertTrue(source.configuredProfiles().get().contains("terra"),
+                "a profile present in the startup snapshot must still be listed by fleet_list");
+    }
+
+    @Test
+    @DisplayName("a hot maxLoad edit still changes what fleet_list reports")
+    void reloadedMaxLoadStillChangesWhatFleetListReports(@TempDir Path dir) throws Exception {
+        Path file = dir.resolve("fleetd.yaml");
+        Files.writeString(file, STARTUP);
+        FleetConfig cfg = FleetConfig.load(file);
+        ConfigRef config = new ConfigRef(file, cfg);
+
+        FleetMcp.CapacitySource source = Fleetd.capacitySource(config, cfg, _ -> 0);
+        assertEquals(3, source.maxLoad().apply("terra"),
+                "sanity: maxLoad reads 3 from the startup config before any reload");
+
+        Files.writeString(file, WITH_CHANGED_MAX_LOAD);
+        assertTrue(config.reload().applied());
+
+        assertEquals(9, source.maxLoad().apply("terra"),
+                "maxLoad must stay hot — the SAME CapacitySource instance must reflect a reloaded "
+                        + "maxLoad without a restart, exactly like credentialId. Freezing the whole "
+                        + "CapacitySource against the startup snapshot (rather than only its "
+                        + "configuredProfiles set) would trade fleetd #416 for its mirror image.");
+    }
+}

fleetd/src/test/java/dev/ltms/fleet/FleetdPatternCoverageLineTest.java

@@ -0,0 +1,67 @@
+package dev.ltms.fleet;
+
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+
+import java.util.Set;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNotEquals;
+
+/**
+ * fleetd #415 (review follow-up): {@code CompletionResolverTest} proves {@code coverage()} words
+ * {@code UnsetMeaning.OFF} and {@code UnsetMeaning.BUILT_IN_DEFAULT} correctly — but every one of
+ * those tests supplies the meaning itself. That proves the enum's wording, never that {@code
+ * Fleetd} pairs the right meaning with the right pattern key. That pairing is #415's actual
+ * defect: {@code coverage()} had no way to know what unset meant for its key, so the fix moved
+ * the fact to the caller — and nothing yet proved the caller states it correctly.
+ *
+ * <p><b>Measured or it didn't happen:</b> swapping the two {@code UnsetMeaning} arguments at
+ * {@code Fleetd}'s two coverage call sites — giving {@code exhaustedPattern} the built-in-default
+ * wording and {@code errorPattern} the off wording, #415's exact defect with the keys exchanged —
+ * compiled with 0 errors and left all 1506 existing tests green. This class exists to turn that
+ * swap red.
+ *
+ * <p>It calls {@link Fleetd#exhaustedPatternCoverageLine} and {@link Fleetd#errorPatternCoverageLine}
+ * directly rather than reading {@code Fleetd.java} as source text (the shape {@code
+ * FleetdCompletionResolverWiringTest} uses for a different wiring gap): those two methods are the
+ * extracted call sites {@code main} actually invokes, following the same {@code static} factory +
+ * dedicated-test pattern as {@link Fleetd#capacitySource} and {@link Fleetd#worktreeBranchLookup}.
+ */
+class FleetdPatternCoverageLineTest {
+
+    private static final Set<String> PROFILES = Set.of("terra", "gx10");
+
+    @Test
+    @DisplayName("exhaustedPatternCoverageLine says off when no profile configures exhaustedPattern")
+    void exhaustedPatternCoverageLineSaysOffWhenNoProfileConfiguresIt() {
+        assertEquals("off (no profile has an exhaustedPattern configured; profiles: [gx10, terra])",
+                Fleetd.exhaustedPatternCoverageLine(PROFILES, Set.of()));
+    }
+
+    @Test
+    @DisplayName("errorPatternCoverageLine says built-in default when no profile configures errorPattern")
+    void errorPatternCoverageLineSaysBuiltInDefaultWhenNoProfileConfiguresIt() {
+        assertEquals("built-in default for all profiles (no profile customises errorPattern; "
+                        + "profiles: [gx10, terra])",
+                Fleetd.errorPatternCoverageLine(PROFILES, Set.of()));
+    }
+
+    @Test
+    @DisplayName("the two keys produce different wording for the identical empty-coverage input")
+    void theTwoKeysProduceDifferentWordingForTheSameEmptyInput() {
+        String exhaustedLine = Fleetd.exhaustedPatternCoverageLine(PROFILES, Set.of());
+        String errorLine = Fleetd.errorPatternCoverageLine(PROFILES, Set.of());
+
+        // Pinned individually above; restated here so this test alone still catches a swap even
+        // if one of the two tests above were ever deleted.
+        assertEquals("off (no profile has an exhaustedPattern configured; profiles: [gx10, terra])",
+                exhaustedLine);
+        assertEquals("built-in default for all profiles (no profile customises errorPattern; "
+                        + "profiles: [gx10, terra])", errorLine);
+        assertNotEquals(exhaustedLine, errorLine,
+                "swapping which UnsetMeaning pairs with which pattern key at Fleetd's call sites "
+                        + "must be caught here — that pairing, not coverage()'s own wording in isolation, "
+                        + "is fleetd #415's actual defect");
+    }
+}

fleetd/src/test/java/dev/ltms/fleet/inject/CompletionResolverTest.java

@@ -20,6 +20,7 @@ import java.util.regex.Pattern;
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertNotEquals;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 
 /** Unit behaviour of the CB-106 completion resolver in isolation from the injector. */
@@ -884,19 +885,22 @@ class CompletionResolverTest {
     @Test
     void coverageIsOffWhenNoProfileHasAPatternConfigured() {
         assertEquals("off (no profile has an exhaustedPattern configured; profiles: [terra])",
-                CompletionResolver.coverage("exhaustedPattern", Set.of("terra"), Set.of()));
+                CompletionResolver.coverage("exhaustedPattern", CompletionResolver.UnsetMeaning.OFF,
+                        Set.of("terra"), Set.of()));
     }
 
     @Test
     void coverageIsFullWhenEveryProfileHasAPatternConfigured() {
         assertEquals("full (all profiles configured: [gx10, terra])",
-                CompletionResolver.coverage("exhaustedPattern", Set.of("terra", "gx10"), Set.of("terra", "gx10")));
+                CompletionResolver.coverage("exhaustedPattern", CompletionResolver.UnsetMeaning.OFF,
+                        Set.of("terra", "gx10"), Set.of("terra", "gx10")));
     }
 
     @Test
     void coverageIsPartialAndNamesWhichProfilesAreConfigured() {
         assertEquals("partial (configured: [terra]; not configured: [gx10])",
-                CompletionResolver.coverage("exhaustedPattern", Set.of("terra", "gx10"), Set.of("terra")));
+                CompletionResolver.coverage("exhaustedPattern", CompletionResolver.UnsetMeaning.OFF,
+                        Set.of("terra", "gx10"), Set.of("terra")));
     }
 
     /**
@@ -910,11 +914,42 @@ class CompletionResolverTest {
      *
      * <p>Every earlier test here passed the exhaustion case only, so none of them could see it. This
      * one pins that the message names the key the caller actually meant.
+     *
+     * <p>fleetd#415: the expected wording changed here too. {@code errorPattern} has a built-in
+     * fallback ({@link CompletionResolver#BACKEND_ERROR}), so an empty {@code configuredProfiles}
+     * for it is not "off" — see {@link #coverageDistinguishesOffFromBuiltInDefaultForTheSameEmptyInput}
+     * for the test built specifically to pin that distinction.
      */
     @Test
     void coverageNamesTheConfigKeyItsCallerMeansRatherThanAlwaysSayingExhaustedPattern() {
-        assertEquals("off (no profile has an errorPattern configured; profiles: [gx10, terra])",
-                CompletionResolver.coverage("errorPattern", Set.of("terra", "gx10"), Set.of()));
+        assertEquals("built-in default for all profiles (no profile customises errorPattern; "
+                        + "profiles: [gx10, terra])",
+                CompletionResolver.coverage("errorPattern", CompletionResolver.UnsetMeaning.BUILT_IN_DEFAULT,
+                        Set.of("terra", "gx10"), Set.of()));
+    }
+
+    /**
+     * fleetd#415: {@code coverage()} measures pattern coverage (how many profiles set the key), but
+     * for {@code errorPattern} the empty case is not the feature-off state — a profile with no
+     * configured {@code errorPattern} still runs the classification against
+     * {@link CompletionResolver#BACKEND_ERROR}. For {@code exhaustedPattern} there is no fallback,
+     * so empty really is off. Same shape of input (empty {@code configuredProfiles}, one profile),
+     * different {@link CompletionResolver.UnsetMeaning} — the wording must differ, or this method is
+     * back to conflating pattern coverage with feature state for the one key where they disagree.
+     */
+    @Test
+    void coverageDistinguishesOffFromBuiltInDefaultForTheSameEmptyInput() {
+        String exhaustedLine = CompletionResolver.coverage("exhaustedPattern",
+                CompletionResolver.UnsetMeaning.OFF, Set.of("gx10", "terra"), Set.of());
+        String errorLine = CompletionResolver.coverage("errorPattern",
+                CompletionResolver.UnsetMeaning.BUILT_IN_DEFAULT, Set.of("gx10", "terra"), Set.of());
+
+        assertEquals("off (no profile has an exhaustedPattern configured; profiles: [gx10, terra])",
+                exhaustedLine);
+        assertEquals("built-in default for all profiles (no profile customises errorPattern; "
+                        + "profiles: [gx10, terra])", errorLine);
+        assertNotEquals(exhaustedLine, errorLine,
+                "the same empty-coverage input must not read as the same feature state for both keys");
     }
 
     // --- fleetd#201 Unit 1: target-keyed backend-error pattern + typed sink ----------------------