9 changed files with 391 additions and 25 deletions
@@ -1075,7 +1075,33 @@ public final class Fleetd {
     */
    static FleetMcp.LeadConfigDirSource leadConfigDirSource(Supplier<Map<String, FleetConfig.Profile>> profiles,
            Map<String, FleetConfig.Leader> leaders) {
-        return new FleetMcp.LeadConfigDirSource(leadConfigDirLookup(profiles, leaders));
+        return new FleetMcp.LeadConfigDirSource(leadConfigDirLookup(profiles, leaders),
+                leadContextWindowLookup(profiles, leaders));
+    }
+
+    /**
+     * Per-lead-name factory for the effective auto-compact window {@link LeadContextGauge} scales
+     * its HIGH threshold against — the same {@code fleet.leaders.<name>.profile} link {@link
+     * #leadConfigDirLookup} already follows, one step further to that profile's own {@link
+     * FleetConfig.Profile#effectiveAutoCompactWindow()}. A lead entry that names no
+     * {@code profile:}, or whose named profile is not configured, or whose profile resolves no
+     * window at all, returns {@code null} — {@link LeadContextGauge} then falls back to its own
+     * fixed HIGH threshold.
+     */
+    static Function<String, Long> leadContextWindowLookup(Supplier<Map<String, FleetConfig.Profile>> profiles,
+            Map<String, FleetConfig.Leader> leaders) {
+        return leadName -> {
+            FleetConfig.Leader lead = leaders.get(leadName);
+            if (lead == null || lead.profile() == null || lead.profile().isBlank()) {
+                return null;
+            }
+            FleetConfig.Profile leadProfile = profiles.get().get(lead.profile());
+            if (leadProfile == null) {
+                return null;
+            }
+            Integer window = leadProfile.effectiveAutoCompactWindow();
+            return window == null ? null : window.longValue();
+        };
    }

    /**
@@ -1100,19 +1126,32 @@ public final class Fleetd {
     */
    static Function<String, LeadContextGauge.Reading> leadContextLookup(LeadContextGauge gauge, AgentControl agents,
            Supplier<Map<String, String>> liveLeadTerminals, Function<String, String> configDirForLeadName) {
+        return leadContextLookup(gauge, agents, liveLeadTerminals, configDirForLeadName, _ -> null);
+    }
+
+    /**
+     * As above, additionally resolving each lead's effective auto-compact window (normally {@link
+     * #leadContextWindowLookup}'s return) and passing it through to {@link LeadContextGauge#read},
+     * so the heartbeat's own HIGH reading scales with that lead's real window instead of always the
+     * gauge's fixed fallback.
+     */
+    static Function<String, LeadContextGauge.Reading> leadContextLookup(LeadContextGauge gauge, AgentControl agents,
+            Supplier<Map<String, String>> liveLeadTerminals, Function<String, String> configDirForLeadName,
+            Function<String, Long> windowForLeadName) {
        return terminal -> {
            String leadName = liveLeadTerminals.get().get(terminal);
            if (leadName == null) {
                return LeadContextGauge.Reading.unknown();
            }
            String configDir = configDirForLeadName.apply(leadName);
+            Long effectiveWindow = windowForLeadName.apply(leadName);
            Agent live;
            try {
                live = agents.get(terminal);
            } catch (RuntimeException e) {
                return LeadContextGauge.Reading.unknown();
            }
-            return gauge.read(configDir, live.sessionId(), live.agentType());
+            return gauge.read(configDir, live.sessionId(), live.agentType(), effectiveWindow);
        };
    }

@@ -1129,6 +1168,14 @@ public final class Fleetd {
                leadContextLookup(gauge, agents, liveLeadTerminals, configDirForLeadName));
    }

+    /** As above, additionally threading the effective-window lookup through. */
+    static LeadHeartbeatLoop.LeadContextSource leadContextSource(LeadContextGauge gauge, AgentControl agents,
+            Supplier<Map<String, String>> liveLeadTerminals, Function<String, String> configDirForLeadName,
+            Function<String, Long> windowForLeadName) {
+        return new LeadHeartbeatLoop.LeadContextSource(
+                leadContextLookup(gauge, agents, liveLeadTerminals, configDirForLeadName, windowForLeadName));
+    }
+
    /**
     * fleetd #248 / fleetd#201 Unit 5: package-private factory for the per-target backend-error
     * pattern lookup {@link CompletionResolver} classifies a pane scrape against. Closes over the
@@ -405,7 +405,8 @@ final class FleetdAssembly {
                    TimeUnit.SECONDS.toNanos(hb.idleAfterSeconds()), hb.backoffMs(), hb.quietNudgeCap(),
                    metrics,
                    Fleetd.leadContextSource(leadContextGauge, router.leadAgents(), leads,
-                            Fleetd.leadConfigDirLookup(() -> config.get().profiles(), leaders)),
+                            Fleetd.leadConfigDirLookup(() -> config.get().profiles(), leaders),
+                            Fleetd.leadContextWindowLookup(() -> config.get().profiles(), leaders)),
                    Boolean.TRUE.equals(hb.contextHighNudge()), requireOperatorConfirm);
            heartbeat.start();
        } else {
@@ -798,6 +798,25 @@ public record FleetConfig(
            return isSubscription() ? SUBSCRIPTION_CREDENTIAL_ID : profile;
        }

+        /**
+         * The auto-compaction window a launched Claude Code session actually runs on: {@code env:
+         * CLAUDE_CODE_AUTO_COMPACT_WINDOW} when it parses as an integer, since that environment
+         * variable wins over the {@code --autocompact} flag {@link #autoCompactWindow} produces (see
+         * {@code ClaudeCodeArguments}); {@link #autoCompactWindow} otherwise. {@code null} when
+         * neither resolves to a usable number.
+         */
+        public Integer effectiveAutoCompactWindow() {
+            String envValue = env.get(CLAUDE_CODE_AUTO_COMPACT_WINDOW_ENV);
+            if (envValue == null) {
+                return autoCompactWindow;
+            }
+            try {
+                return Integer.valueOf(envValue.trim());
+            } catch (NumberFormatException e) {
+                return autoCompactWindow;
+            }
+        }
+
        /** 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();
@@ -2184,6 +2203,12 @@ public record FleetConfig(
    static final int AUTO_COMPACT_WINDOW_MIN = 100_000;
    /** Highest {@code autoCompactWindow} Claude Code's {@code --autocompact <tokens>} flag accepts. */
    static final int AUTO_COMPACT_WINDOW_MAX = 1_000_000;
+    /**
+     * The {@code env:} key a launched Claude Code session reads for its auto-compaction window,
+     * ahead of the {@code --autocompact} launch flag {@code autoCompactWindow} produces (see
+     * {@link Profile#effectiveAutoCompactWindow()}).
+     */
+    static final String CLAUDE_CODE_AUTO_COMPACT_WINDOW_ENV = "CLAUDE_CODE_AUTO_COMPACT_WINDOW";

    /**
     * Reject a profile whose {@code autoCompactWindow:} is set but outside the token band Claude
@@ -2265,13 +2290,13 @@ public record FleetConfig(
            if (!(entry.getValue() instanceof Map<?, ?> profile)
                    || !(profile.get("autoCompactWindow") instanceof Number window)
                    || !(profile.get("env") instanceof Map<?, ?> env)
-                    || !env.containsKey("CLAUDE_CODE_AUTO_COMPACT_WINDOW")) {
+                    || !env.containsKey(CLAUDE_CODE_AUTO_COMPACT_WINDOW_ENV)) {
                continue;
            }
            Object kind = profile.get("kind");
            boolean claudeCode = kind == null || String.valueOf(kind).isBlank()
                    || Profile.KIND_CLAUDE_CODE.equalsIgnoreCase(String.valueOf(kind));
-            Object envValue = env.get("CLAUDE_CODE_AUTO_COMPACT_WINDOW");
+            Object envValue = env.get(CLAUDE_CODE_AUTO_COMPACT_WINDOW_ENV);
            if (claudeCode && !String.valueOf(window).equals(String.valueOf(envValue))) {
                String name = String.valueOf(entry.getKey());
                names.add(name);
@@ -97,14 +97,19 @@ public final class LeadContextGauge {
    static final long DEFAULT_CACHE_TTL_MILLIS = 5_000;

    /**
-     * Live tokens at or above this count report {@link State#HIGH}. On the host this was measured
-     * on, auto-compaction actually fires around 267,000–270,000 tokens, but the point of a HIGH
-     * state is to warn before that happens, not at it — 200,000 is the standard Claude context
-     * window size and a sensible built-in default: no config key is required to pick it, and a
-     * lead crossing it is already deep enough into its window that a compaction is foreseeable.
+     * Fallback HIGH threshold used when a caller resolves no effective auto-compact window for the
+     * lead being read (see {@link #read(String, String, String, Long)}) — the built-in default so
+     * no config key is required to get a warning at all.
     */
    static final long HIGH_THRESHOLD_TOKENS = 200_000;

+    /**
+     * The fraction of a resolved effective auto-compact window that HIGH warns at, so the warning
+     * margin scales with the window instead of only ever meaning something against the fixed
+     * {@link #HIGH_THRESHOLD_TOKENS} fallback.
+     */
+    static final double HIGH_THRESHOLD_FRACTION = 2.0 / 3.0;
+
    /** The only peer kind this reader understands ({@code Agent.agentType()}'s wire value). */
    private static final String CLAUDE_AGENT_TYPE = "claude";

@@ -167,6 +172,17 @@ public final class LeadContextGauge {
     *                  transcript format
     */
    public Reading read(String configDir, String sessionId, String agentType) {
+        return read(configDir, sessionId, agentType, null);
+    }
+
+    /**
+     * @param effectiveWindowTokens the caller's resolved effective auto-compact window for this
+     *                              lead's own profile, or {@code null} when it cannot be resolved.
+     *                              HIGH fires at {@link #HIGH_THRESHOLD_FRACTION} of this value;
+     *                              {@code null} (or a non-positive value) falls back to the fixed
+     *                              {@link #HIGH_THRESHOLD_TOKENS}
+     */
+    public Reading read(String configDir, String sessionId, String agentType, Long effectiveWindowTokens) {
        if (sessionId == null || sessionId.isBlank()) {
            return Reading.unknown();
        }
@@ -182,12 +198,20 @@ public final class LeadContextGauge {
        if (cached != null && now - cached.readAtMillis() < ttlMillis) {
            return cached.reading();
        }
-        Reading fresh = readUncached(base, sessionId);
+        Reading fresh = readUncached(base, sessionId, highThreshold(effectiveWindowTokens));
        cache.put(cacheKey, new CacheEntry(fresh, now));
        return fresh;
    }

-    private Reading readUncached(String base, String sessionId) {
+    /** {@link #HIGH_THRESHOLD_FRACTION} of {@code effectiveWindowTokens}, or the fixed fallback. */
+    private static long highThreshold(Long effectiveWindowTokens) {
+        if (effectiveWindowTokens == null || effectiveWindowTokens <= 0) {
+            return HIGH_THRESHOLD_TOKENS;
+        }
+        return (long) (effectiveWindowTokens * HIGH_THRESHOLD_FRACTION);
+    }
+
+    private Reading readUncached(String base, String sessionId, long highThreshold) {
        diskReads.incrementAndGet();
        Path file = findTranscript(base, sessionId);
        if (file == null) {
@@ -199,7 +223,7 @@ public final class LeadContextGauge {
        } catch (IOException e) {
            return Reading.unknown();
        }
-        return parse(tail);
+        return parse(tail, highThreshold);
    }

    /**
@@ -258,7 +282,7 @@ public final class LeadContextGauge {
     * read raced — see the "torn final line" section of the class javadoc) is skipped, not fatal.
     * Only when none of the remaining lines parse does this report {@link State#UNKNOWN}.
     */
-    private Reading parse(TailRead tail) {
+    private Reading parse(TailRead tail, long highThreshold) {
        String text = new String(tail.bytes(), StandardCharsets.UTF_8);
        List<String> lines = new ArrayList<>(List.of(text.split("\n", -1)));
        if (!lines.isEmpty() && lines.get(lines.size() - 1).isEmpty()) {
@@ -299,7 +323,7 @@ public final class LeadContextGauge {
        if (tokens == null) {
            return new Reading(State.UNKNOWN, null, compactions);
        }
-        State state = tokens >= HIGH_THRESHOLD_TOKENS ? State.HIGH : State.OK;
+        State state = tokens >= highThreshold ? State.HIGH : State.OK;
        return new Reading(state, tokens, compactions);
    }

@@ -284,10 +284,23 @@ public final class FleetMcp {
     *                      no profile, or that profile sets no {@code configDir} override — either
     *                      way {@link LeadContextGauge} then falls back to its own built-in default,
     *                      exactly as before this ticket
+     * @param windowFor    lead name → that lead's profile's effective auto-compact window (see
+     *                      {@code dev.ltms.fleet.config.FleetConfig.Profile
+     *                      #effectiveAutoCompactWindow()}), or {@code null} when it cannot be
+     *                      resolved — either way {@link LeadContextGauge} falls back to its own
+     *                      fixed HIGH threshold
     */
-    public record LeadConfigDirSource(Function<String, String> configDirFor) {
-        /** Inert source — every lead reads {@link LeadContextGauge}'s built-in default {@code configDir}. */
-        public static LeadConfigDirSource none() { return new LeadConfigDirSource(_ -> null); }
+    public record LeadConfigDirSource(Function<String, String> configDirFor, Function<String, Long> windowFor) {
+        /** Inert source — every lead reads {@link LeadContextGauge}'s built-in defaults. */
+        public static LeadConfigDirSource none() { return new LeadConfigDirSource(_ -> null, _ -> null); }
+
+        /**
+         * Constructor that resolves no window — every lead this source answers for keeps
+         * {@link LeadContextGauge}'s fixed HIGH threshold.
+         */
+        public LeadConfigDirSource(Function<String, String> configDirFor) {
+            this(configDirFor, _ -> null);
+        }
    }

    /**
@@ -2153,7 +2166,8 @@ public final class FleetMcp {
            m.put("self", true);
        }
        String configDir = leadConfigDirs.configDirFor().apply(name);
-        m.put("context", contextView(contextGauge, live, configDir));
+        Long effectiveWindow = leadConfigDirs.windowFor().apply(name);
+        m.put("context", contextView(contextGauge, live, configDir, effectiveWindow));
        return m;
    }

@@ -2163,12 +2177,15 @@ public final class FleetMcp {
     * {@code fleet.leaders.<name>.profile} → that profile's own {@code configDir:} — or {@code null}
     * when the lead's entry names no profile, or that profile sets no override, in which case
     * {@link LeadContextGauge#read} falls back to its own built-in default
-     * ({@code <user.home>/.claude}).
+     * ({@code <user.home>/.claude}). {@code effectiveWindowTokens} is the same lead's resolved
+     * auto-compact window, or {@code null} when it cannot be resolved, in which case the gauge
+     * falls back to its own fixed HIGH threshold instead.
     */
-    private static Map<String, Object> contextView(LeadContextGauge contextGauge, Agent live, String configDir) {
+    private static Map<String, Object> contextView(LeadContextGauge contextGauge, Agent live, String configDir,
+                                                     Long effectiveWindowTokens) {
        String sessionId = live == null ? null : live.sessionId();
        String agentType = live == null ? null : live.agentType();
-        LeadContextGauge.Reading reading = contextGauge.read(configDir, sessionId, agentType);
+        LeadContextGauge.Reading reading = contextGauge.read(configDir, sessionId, agentType, effectiveWindowTokens);
        Map<String, Object> c = new LinkedHashMap<>();
        c.put("state", reading.state().name().toLowerCase());
        if (reading.tokens() != null) {
@@ -461,9 +461,9 @@ public final class LeadHeartbeatLoop {
                    .append(reading.compactions()).append(' ').append(compactionWord).append(" so far.");
        } else {
            // A HIGH reading always carries a non-null token count today: LeadContextGauge only
-            // reaches HIGH by comparing a number against HIGH_THRESHOLD_TOKENS. That invariant
-            // lives in another class and nothing asserts it, so this branch does not rely on it —
-            // it drops the token clause rather than printing "null tokens".
+            // reaches HIGH by comparing a number against a threshold. That invariant lives in
+            // another class and nothing asserts it, so this branch does not rely on it — it drops
+            // the token clause rather than printing "null tokens".
            sb.append(" (").append(reading.compactions()).append(' ').append(compactionWord)
                    .append(" so far).");
        }
@@ -0,0 +1,96 @@
+package dev.ltms.fleet;
+
+import dev.ltms.fleet.config.FleetConfig;
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+
+import java.util.Map;
+import java.util.function.Function;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNull;
+
+/**
+ * {@link Fleetd#leadContextWindowLookup} is the factory wired into {@code
+ * FleetMcp.LeadConfigDirSource} and {@code LeadHeartbeatLoop.LeadContextSource} so {@link
+ * dev.ltms.fleet.lead.LeadContextGauge} scales its HIGH threshold against a lead's own profile's
+ * effective auto-compact window instead of always the gauge's fixed fallback — the same {@code
+ * fleet.leaders.<name>.profile} link {@link Fleetd#leadConfigDirLookup} already follows, one step
+ * further to {@link FleetConfig.Profile#effectiveAutoCompactWindow()}.
+ */
+class FleetdLeadContextWindowLookupTest {
+
+    private static FleetConfig.Profile profileWithWindow(String name, Integer autoCompactWindow,
+            Map<String, String> env) {
+        return new FleetConfig.Profile(name, null, "claude-sonnet-5", null, null, null,
+                "tab", "fleet", "w #{n}", null, null, null, null, null, null, env,
+                null, null, true, null, null, null, null, null, autoCompactWindow, null);
+    }
+
+    private static FleetConfig.Leader leadOnProfile(String profile) {
+        return new FleetConfig.Leader(profile, "lead: primary", 1, "lead:", 10, "claude", "claude-sonnet-5");
+    }
+
+    @Test
+    @DisplayName("a lead on a profile that sets autoCompactWindow resolves to that window")
+    void leadOnAProfileWithAutoCompactWindowResolvesToIt() {
+        Map<String, FleetConfig.Profile> profiles =
+                Map.of("opus", profileWithWindow("opus", 250_000, Map.of()));
+        Map<String, FleetConfig.Leader> leaders = Map.of("primary", leadOnProfile("opus"));
+        Function<String, Long> lookup = Fleetd.leadContextWindowLookup(() -> profiles, leaders);
+
+        assertEquals(250_000L, lookup.apply("primary"));
+    }
+
+    @Test
+    @DisplayName("yaml and env disagree: the lookup resolves the env value, not the yaml one")
+    void yamlAndEnvDisagreeLookupResolvesTheEnvValue() {
+        Map<String, FleetConfig.Profile> profiles = Map.of("opus",
+                profileWithWindow("opus", 250_000, Map.of("CLAUDE_CODE_AUTO_COMPACT_WINDOW", "150000")));
+        Map<String, FleetConfig.Leader> leaders = Map.of("primary", leadOnProfile("opus"));
+        Function<String, Long> lookup = Fleetd.leadContextWindowLookup(() -> profiles, leaders);
+
+        assertEquals(150_000L, lookup.apply("primary"));
+    }
+
+    @Test
+    @DisplayName("a lead entry with no `profile:` resolves to null, not a thrown exception")
+    void recogniseOnlyLeadWithNoProfileResolvesToNull() {
+        Map<String, FleetConfig.Profile> profiles =
+                Map.of("opus", profileWithWindow("opus", 250_000, Map.of()));
+        FleetConfig.Leader recogniseOnly = new FleetConfig.Leader(null, "lead: primary", 1, "lead:", 10,
+                "claude", "claude-sonnet-5");
+        Map<String, FleetConfig.Leader> leaders = Map.of("primary", recogniseOnly);
+        Function<String, Long> lookup = Fleetd.leadContextWindowLookup(() -> profiles, leaders);
+
+        assertNull(lookup.apply("primary"));
+    }
+
+    @Test
+    @DisplayName("a lead naming a profile that is not configured resolves to null, not a thrown exception")
+    void leadOnAnUnconfiguredProfileResolvesToNull() {
+        Map<String, FleetConfig.Leader> leaders = Map.of("primary", leadOnProfile("ghost-profile"));
+        Function<String, Long> lookup = Fleetd.leadContextWindowLookup(Map::of, leaders);
+
+        assertNull(lookup.apply("primary"));
+    }
+
+    @Test
+    @DisplayName("a lead on a profile that resolves no window at all resolves to null")
+    void leadOnAProfileWithNoWindowResolvesToNull() {
+        Map<String, FleetConfig.Profile> profiles =
+                Map.of("opus", profileWithWindow("opus", null, Map.of()));
+        Map<String, FleetConfig.Leader> leaders = Map.of("primary", leadOnProfile("opus"));
+        Function<String, Long> lookup = Fleetd.leadContextWindowLookup(() -> profiles, leaders);
+
+        assertNull(lookup.apply("primary"));
+    }
+
+    @Test
+    @DisplayName("an unrecognised lead name resolves to null, not a thrown exception")
+    void unrecognisedLeadNameResolvesToNull() {
+        Function<String, Long> lookup = Fleetd.leadContextWindowLookup(Map::of, Map.of());
+
+        assertNull(lookup.apply("ghost-lead"));
+    }
+}
@@ -0,0 +1,65 @@
+package dev.ltms.fleet.config;
+
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+
+import java.util.Map;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNull;
+
+/**
+ * {@link FleetConfig.Profile#effectiveAutoCompactWindow()} resolves the window a launched Claude
+ * Code session actually runs on, not just the {@code autoCompactWindow:} launch flag — {@code env:
+ * CLAUDE_CODE_AUTO_COMPACT_WINDOW} overrides that flag, so a profile setting both resolves from the
+ * environment variable.
+ */
+class FleetConfigProfileEffectiveAutoCompactWindowTest {
+
+    private static FleetConfig.Profile profile(Integer autoCompactWindow, Map<String, String> env) {
+        return new FleetConfig.Profile("sonnet", null, "claude-sonnet-5", null, null, null,
+                "tab", "fleet", "w #{n}", null, null, null, null, null, null, env,
+                null, null, true, null, null, null, null, null, autoCompactWindow, null);
+    }
+
+    @Test
+    @DisplayName("yaml and env disagree: the env var wins, not the yaml key")
+    void yamlAndEnvDisagreeEnvWins() {
+        FleetConfig.Profile p = profile(250_000, Map.of("CLAUDE_CODE_AUTO_COMPACT_WINDOW", "150000"));
+
+        assertEquals(150_000, p.effectiveAutoCompactWindow(),
+                "the two inputs must give DIFFERENT thresholds (150,000 vs 250,000) and the env value must win");
+    }
+
+    @Test
+    @DisplayName("only autoCompactWindow set: that value resolves")
+    void onlyAutoCompactWindowSetResolvesToIt() {
+        FleetConfig.Profile p = profile(250_000, Map.of());
+
+        assertEquals(250_000, p.effectiveAutoCompactWindow());
+    }
+
+    @Test
+    @DisplayName("only the env var set: that value resolves")
+    void onlyEnvVarSetResolvesToIt() {
+        FleetConfig.Profile p = profile(null, Map.of("CLAUDE_CODE_AUTO_COMPACT_WINDOW", "150000"));
+
+        assertEquals(150_000, p.effectiveAutoCompactWindow());
+    }
+
+    @Test
+    @DisplayName("neither set: resolves to null")
+    void neitherSetResolvesToNull() {
+        FleetConfig.Profile p = profile(null, Map.of());
+
+        assertNull(p.effectiveAutoCompactWindow());
+    }
+
+    @Test
+    @DisplayName("an unparseable env value falls back to autoCompactWindow rather than throwing")
+    void unparseableEnvValueFallsBackToAutoCompactWindow() {
+        FleetConfig.Profile p = profile(250_000, Map.of("CLAUDE_CODE_AUTO_COMPACT_WINDOW", "not-a-number"));
+
+        assertEquals(250_000, p.effectiveAutoCompactWindow());
+    }
+}
@@ -0,0 +1,91 @@
+package dev.ltms.fleet.lead;
+
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.io.TempDir;
+
+import java.io.IOException;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
+import java.nio.file.Path;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+/**
+ * {@code LeadContextGauge}'s HIGH threshold scales with the caller's resolved effective
+ * auto-compact window, so the margin it warns at makes sense against a window that can legally sit
+ * as low as {@code 100_000}, not only against the fixed fallback. These properties pin that
+ * scaling, its boundary, and the fallback used when no window is resolvable.
+ */
+class LeadContextGaugeHighThresholdTest {
+
+    private static final String SESSION_ID = "55555555-5555-5555-5555-555555555555";
+
+    private static String usageLine(long tokens) {
+        return "{\"type\":\"assistant\",\"message\":{\"role\":\"assistant\",\"usage\":{"
+                + "\"input_tokens\":" + tokens + ",\"cache_read_input_tokens\":0,\"cache_creation_input_tokens\":0}}}";
+    }
+
+    private static String writeTranscript(Path configDir, String sessionId, long tokens) throws IOException {
+        Path projectDir = configDir.resolve("projects").resolve("some-project-slug");
+        Files.createDirectories(projectDir);
+        Files.writeString(projectDir.resolve(sessionId + ".jsonl"), usageLine(tokens) + "\n", StandardCharsets.UTF_8);
+        return configDir.toString();
+    }
+
+    @Test
+    @DisplayName("an effective window of 100000 reports HIGH strictly below 100000")
+    void effectiveWindowOf100000ReportsHighStrictlyBelow100000(@TempDir Path tmp) throws IOException {
+        // 90,000 is below the 100,000 window itself, but above a fixed 200,000 fallback would ever
+        // reach — only a threshold that scales with the window can report HIGH here.
+        String configDir = writeTranscript(tmp, SESSION_ID, 90_000);
+        LeadContextGauge gauge = new LeadContextGauge();
+
+        LeadContextGauge.Reading reading = gauge.read(configDir, SESSION_ID, "claude", 100_000L);
+
+        assertEquals(LeadContextGauge.State.HIGH, reading.state(),
+                "90,000 tokens against a 100,000 effective window must already be HIGH, with margin to spare "
+                        + "before a compaction at the window itself");
+    }
+
+    @Test
+    @DisplayName("the boundary sits strictly between OK and HIGH on both sides")
+    void boundarySitsStrictlyBetweenOkAndHighOnBothSides(@TempDir Path tmp) throws IOException {
+        long window = 100_000L;
+        long threshold = (long) (window * (2.0 / 3.0)); // 66,666
+
+        String belowConfigDir = writeTranscript(tmp.resolve("below"), SESSION_ID, threshold - 1);
+        LeadContextGauge belowGauge = new LeadContextGauge();
+        assertEquals(LeadContextGauge.State.OK,
+                belowGauge.read(belowConfigDir, SESSION_ID, "claude", window).state(),
+                "one token short of the threshold must stay OK");
+
+        String atConfigDir = writeTranscript(tmp.resolve("at"), SESSION_ID, threshold);
+        LeadContextGauge atGauge = new LeadContextGauge();
+        assertEquals(LeadContextGauge.State.HIGH,
+                atGauge.read(atConfigDir, SESSION_ID, "claude", window).state(),
+                "exactly at the threshold must already be HIGH");
+    }
+
+    @Test
+    @DisplayName("with no effective window resolvable, the threshold is still the fixed 200000 default")
+    void noEffectiveWindowFallsBackToTheFixed200000Default(@TempDir Path tmp) throws IOException {
+        String belowConfigDir = writeTranscript(tmp.resolve("below"), SESSION_ID, 199_999);
+        LeadContextGauge belowGauge = new LeadContextGauge();
+        assertEquals(LeadContextGauge.State.OK,
+                belowGauge.read(belowConfigDir, SESSION_ID, "claude", null).state(),
+                "one token short of the fixed default must stay OK when no window is resolvable");
+
+        String atConfigDir = writeTranscript(tmp.resolve("at"), SESSION_ID, 200_000);
+        LeadContextGauge atGauge = new LeadContextGauge();
+        assertEquals(LeadContextGauge.State.HIGH,
+                atGauge.read(atConfigDir, SESSION_ID, "claude", null).state(),
+                "the fixed default must still be 200,000 when no window is resolvable");
+
+        String legacyConfigDir = writeTranscript(tmp.resolve("legacy"), SESSION_ID, 200_000);
+        LeadContextGauge legacyGauge = new LeadContextGauge();
+        assertEquals(LeadContextGauge.State.HIGH,
+                legacyGauge.read(legacyConfigDir, SESSION_ID, "claude").state(),
+                "the 3-arg read() (no window argument at all) must behave exactly like passing a null window");
+    }
+}