Crafter.Review/implementations/Crafter.Review-SeatPool.cpp

// SPDX-License-Identifier: AGPL-3.0-only
// SPDX-FileCopyrightText: Copyright (C) 2026 Catcrafts®

module;
#include <cerrno>
#include <fcntl.h>
#include <unistd.h>

module Crafter.Review:SeatPool_impl;
import :SeatPool;
import :Json;
import :Text;
import :Crypto;
import :Platform;
import :Http;
import :Seats;
import std;

namespace fs = std::filesystem;

namespace Crafter::Review::SeatPool {
    const std::string_view ResumePrompt =
        "The previous attempt of this pass was interrupted by a limit on the account it ran on and continues here on "
        "another account with the same transcript. Do not repeat work already done: continue from where it stopped, "
        "finish the pass, and return the structured output exactly as the instructions require.\n";

    namespace {
        using Log = std::function<void(const std::string&)>;

        // A number as the files and the probes hold it, as a float.
        double AsDouble(const Json& value) {
            if (value.is_number_float()) return value.get<double>();
            if (value.is_boolean()) return value.get<bool>() ? 1.0 : 0.0;
            if (value.is_number_unsigned()) return static_cast<double>(value.get<std::uint64_t>());
            if (value.is_number_integer()) return static_cast<double>(value.get<std::int64_t>());
            if (value.is_string()) {
                if (const std::optional<double> parsed = Dyn::ParseFloat(value.get_ref<const std::string&>())) return *parsed;
                throw Dyn::Error("ValueError", Dyn::FloatError(value.get_ref<const std::string&>()));
            }
            throw Dyn::Error("TypeError", std::format("float() argument must be a string or a real number, not '{}'", Dyn::TypeName(value)));
        }

        // The value as a float, 0 when it is falsy.
        double Num(const Json& value) {
            return Dyn::Truthy(value) ? AsDouble(value) : 0.0;
        }

        // A float truncated toward zero, saturating at the ends of int64.
        std::int64_t Int(double value) {
            if (std::isinf(value)) throw Dyn::Error("OverflowError", "cannot convert float infinity to integer");
            if (std::isnan(value)) throw Dyn::Error("ValueError", "cannot convert float NaN to integer");
            if (value >= 9.2e18) return std::numeric_limits<std::int64_t>::max();
            if (value <= -9.2e18) return std::numeric_limits<std::int64_t>::min();
            return static_cast<std::int64_t>(value);
        }

        // `now or time.time()`
        double NowOr(std::optional<double> now) {
            return now && *now != 0 ? *now : Platform::Now();
        }

        // f'{value:g}'
        std::string G(double value) {
            return std::format("{:g}", value);
        }

        std::string Clock(double epoch) {
            return Platform::LocalTime("%H:%M:%S", epoch);
        }

        Json ZeroForeign() {
            return {{"count", 0}, {"cost5h", 0.0}, {"cost7d", 0.0}, {"costUsd", 0.0}};
        }

        std::string Kind(const Json& seat) {
            return Dyn::Str(Dyn::At(seat, "kind"));
        }

        std::string Id(const Json& seat) {
            return Dyn::Str(Dyn::At(seat, "id"));
        }

        std::int64_t Running(const Json& seat) {
            return Int(AsDouble(Dyn::At(seat, "running")));
        }

        const std::string& EnvOf(const std::map<std::string, std::string>& env, const std::string& key) {
            static const std::string none;
            const auto found = env.find(key);
            return found == env.end() ? none : found->second;
        }

        bool IsOpenRouter(const Json& seat) {
            return Kind(seat) == "openrouter";
        }

        double Budget(const Json& s, const Json& a) {
            return AsDouble(Dyn::At(a, IsOpenRouter(s) ? "orBudgetUsd" : "budgetUsd"));
        }

        const Json& LensCostValue(const Json& s, const Json& a) {
            return Dyn::At(a, IsOpenRouter(s) ? "orLensCostUsd" : "lensCostUsd");
        }

        double LensCost(const Json& s, const Json& a) {
            return AsDouble(LensCostValue(s, a));
        }

        std::int64_t Concurrency(const Json& s, const Json& a) {
            return Int(AsDouble(Dyn::At(a, IsOpenRouter(s) ? "orConcurrency" : "concurrency")));
        }

        // The windows a seat's utilisation is read from: all but the Fable
        // one, or all when that leaves none.
        void Reutil(Json& s) {
            Json own = Json::object();
            const Json& windows = s.at("windows");
            for (auto it = windows.begin(); it != windows.end(); ++it) {
                if (!Seats::IsFableWindow(it.key())) own[it.key()] = it.value();
            }
            const auto [util, binding] = Seats::SeatUtil(own.empty() ? windows : own);
            s["util"] = util;
            s["binding"] = binding;
        }

        bool LongOk(const Json& s) {
            const Json& windows = Dyn::At(s, "windows");
            for (auto it = windows.begin(); it != windows.end(); ++it) {
                if (it.key() == "five_hour" || Seats::IsFableWindow(it.key())) continue;
                if (Num(Dyn::Get(it.value(), "utilization")) >= Seats::LongWindowCutoff) return false;
            }
            return true;
        }

        bool ApiRoom(const Json& s, const Json& a) {
            return AsDouble(s.at("spentUsd")) + static_cast<double>(Running(s) + 1) * LensCost(s, a) + AsDouble(Foreign(s).at("costUsd")) <= Budget(s, a);
        }

        const Json& FiveHour(const Json& s) {
            return Dyn::Or(Dyn::Get(Dyn::At(s, "windows"), "five_hour"), Dyn::EmptyDict());
        }

        // ik.split('/', 1)[0]: the driver an in-flight entry belongs to.
        std::string Owner(std::string_view inflightKey) {
            return std::string(inflightKey.substr(0, inflightKey.find('/')));
        }

        // key.split(':')[0]
        std::string PidOf(std::string_view key) {
            return std::string(key.substr(0, key.find(':')));
        }

        // Board._key
        std::string KeyOf(const Json& seat) {
            const Json& key = Dyn::Get(seat, "boardKey");
            return Dyn::Truthy(key) ? Dyn::Str(key) : SeatKey(Kind(seat), Dyn::StrOr(Dyn::Get(seat, "secret"), ""));
        }

        // Per-token list prices when the catalogue cannot be fetched
        // (OpenRouter, 2026-10-12).
        const Json& BuiltInPrices() {
            static const Json prices = {{"xiaomi/mimo-v2.6-pro", {{"prompt", 0.435e-6}, {"completion", 0.87e-6}, {"cacheRead", 0.0036e-6}, {"cacheWrite", nullptr}}}};
            return prices;
        }

        // model -> prices, filled by FetchOpenRouterPrices.
        std::map<std::string, Json> Prices;
        std::mutex PricesLock;

        void WriteAll(std::int32_t fd, std::string_view text) {
            std::size_t written = 0;
            while (written < text.size()) {
                const ssize_t step = write(fd, text.data() + written, text.size() - written);
                if (step < 0) {
                    if (errno == EINTR) continue;
                    const std::int32_t failure = errno;
                    close(fd);
                    throw std::runtime_error(Dyn::ErrnoText(failure));
                }
                written += static_cast<std::size_t>(step);
            }
            close(fd);
        }

        // shutil.copyfile: the bytes only, the destination created as open()
        // creates it.
        void CopyContents(const fs::path& from, const fs::path& to) {
            const std::optional<std::string> bytes = Platform::ReadFile(from);
            if (!bytes) throw std::runtime_error(std::format("{}: {}", Dyn::ErrnoText(ENOENT), Dyn::Repr(from.string())));
            const std::int32_t fd = open(to.c_str(), O_WRONLY | O_CREAT | O_TRUNC | O_CLOEXEC, 0666);
            if (fd < 0) throw std::runtime_error(std::format("{}: {}", Dyn::ErrnoText(errno), Dyn::Repr(to.string())));
            WriteAll(fd, *bytes);
        }
    }

    bool IsPaid(const Json& seat) {
        return std::ranges::contains(Paid, Kind(seat));
    }

    Json ApiConfig(const std::map<std::string, std::string>& env) {
        auto num = [&](const std::string& key, double fallback) {
            const std::optional<double> v = Dyn::ParseFloat(EnvOf(env, key));
            return v && *v >= 0 ? *v : fallback;
        };
        return {
            {"budgetUsd", num("REVIEW_GATES_API_BUDGET_USD", 200.0)},
            {"lensCostUsd", num("REVIEW_GATES_API_LENS_COST_USD", 1.0)},
            {"concurrency", Int(num("REVIEW_GATES_API_CONCURRENCY", 8))},
            {"cycleDay", std::max<std::int64_t>(1, std::min<std::int64_t>(28, Int(num("REVIEW_GATES_API_CYCLE_DAY", 1))))},
            {"order", EnvOf(env, "REVIEW_GATES_SEAT_ORDER") == "oauth-first" ? "oauth-first" : "api-first"},
            // OpenRouter seats: a prepaid key, cheap models - a smaller reserve
            // per running process.
            {"orBudgetUsd", num("REVIEW_GATES_OPENROUTER_BUDGET_USD", 100.0)},
            {"orLensCostUsd", num("REVIEW_GATES_OPENROUTER_LENS_COST_USD", 0.1)},
            {"orConcurrency", Int(num("REVIEW_GATES_OPENROUTER_CONCURRENCY", 16))},
        };
    }

    Json Foreign(const Json& seat) {
        const Json& foreign = Dyn::Get(seat, "foreign");
        return Dyn::Truthy(foreign) ? foreign : ZeroForeign();
    }

    fs::path LedgerPath(const std::optional<fs::path>& scratchRoot) {
        fs::path root;
        if (scratchRoot && !scratchRoot->empty()) {
            root = *scratchRoot;
        } else if (const std::optional<std::string> configured = Platform::GetEnv("REVIEW_GATES_SCRATCH"); configured && !configured->empty()) {
            root = *configured;
        } else {
            root = fs::path(Platform::Home()) / ".cache" / "review-gates";
        }
        return root / "seat-ledger.json";
    }

    std::string CycleStart(double now, std::int32_t day) {
        using namespace std::chrono;
        const std::string today = Platform::LocalTime("%Y-%m-%d", now);
        const year_month_day date(year(std::stoi(today.substr(0, 4))), month(static_cast<unsigned>(std::stoi(today.substr(5, 2)))),
                                  std::chrono::day(static_cast<unsigned>(std::stoi(today.substr(8, 2)))));
        auto iso = [](const year_month_day& d) {
            return std::format("{:04d}-{:02d}-{:02d}", static_cast<std::int32_t>(d.year()), static_cast<std::uint32_t>(d.month()), static_cast<std::uint32_t>(d.day()));
        };
        if (static_cast<std::int32_t>(static_cast<std::uint32_t>(date.day())) >= day) {
            return iso(year_month_day(date.year(), date.month(), std::chrono::day(static_cast<std::uint32_t>(day))));
        }
        const year_month_day previous(sys_days(year_month_day(date.year(), date.month(), std::chrono::day(1))) - days(1));
        const auto last = static_cast<std::int32_t>(static_cast<std::uint32_t>(previous.day()));
        return iso(year_month_day(previous.year(), previous.month(), std::chrono::day(static_cast<std::uint32_t>(std::min(day, last)))));
    }

    // ---- the ledger -------------------------------------------------------------------
    Ledger::Ledger(fs::path path, Json apiConfig, Json data) : path(std::move(path)), apiConfig(std::move(apiConfig)), data(Dyn::Truthy(data) ? std::move(data) : Json::object()) {}

    Ledger Ledger::Load(const fs::path& path, const Json& apiConfig) {
        Json data;
        try {
            data = Dyn::LoadJsonFile(path);
        } catch (const std::exception&) {
            data = Json::object();
        }
        return Ledger(path, apiConfig, data.is_object() ? data : Json::object());
    }

    Json& Ledger::Entry(const std::string& seatId, std::optional<double> now) {
        const std::string cycle = CycleStart(NowOr(now), static_cast<std::int32_t>(Int(AsDouble(Dyn::At(apiConfig, "cycleDay")))));
        const Json& e = Dyn::Get(data, seatId);
        // Only a newer cycle starts over: an entry of a later one (another
        // driver's cycle day) is not wiped.
        if (!Dyn::Truthy(e) || cycle > Dyn::StrOr(Dyn::Get(e, "cycle"), "")) {
            data[seatId] = {{"cycle", cycle}, {"spentUsd", 0.0}, {"procs", 0}, {"outSince", nullptr}, {"outReason", nullptr}};
        }
        return data[seatId];
    }

    Json Ledger::Update(const std::string& seatId, const std::function<void(Json&)>& change, std::optional<double> now) {
        // The file is the record: re-read under its lock, this process only
        // ever adds to it (2026-10-15: each driver saved the copy it had loaded
        // and the last writer won - api4 reached the credit error with $157.54
        // recorded of the $199.66 its processes had cost).
        Json entry;
        Platform::LockedUpdate(path, [&](Json& file) {
            // The file wins where both have a seat.
            Json merged = data;
            for (auto it = file.begin(); it != file.end(); ++it) merged[it.key()] = it.value();
            data = std::move(merged);
            Json& e = Entry(seatId, now);
            change(e);
            entry = e;
            file = data;
            return true;
        }, data, 0600, {});
        return entry;
    }

    Json Ledger::Add(const std::string& seatId, double usd, std::optional<double> now) {
        return Update(seatId, [&](Json& e) {
            e["spentUsd"] = Dyn::Round(AsDouble(Dyn::At(e, "spentUsd")) + usd, 4);
            e["procs"] = Dyn::Add(Dyn::At(e, "procs"), Json(1));
        }, now);
    }

    Json Ledger::MarkOut(const std::string& seatId, std::string_view reason, std::optional<double> now) {
        return Update(seatId, [&](Json& e) {
            e["outSince"] = Platform::LocalTime("%Y-%m-%dT%H:%M:%S", NowOr(now));
            e["outReason"] = Dyn::Slice(reason, 0, 160);
        }, now);
    }

    void Ledger::Save() {
        try {
            Platform::WriteAtomic(path, DumpFile(data), 0600);
        } catch (const std::exception&) {
            // A record, never a dependency.
        }
    }

    const Json& Ledger::Data() const {
        return data;
    }

    const fs::path& Ledger::Path() const {
        return path;
    }

    // ---- the seats ---------------------------------------------------------------------
    Json NewSeat(const std::string& id, const std::string& kind, const std::string& secret) {
        return {
            {"id", id},
            {"kind", kind},
            {"secret", secret},
            {"state", "unknown"},
            {"windows", Json::object()},
            {"util", nullptr},
            {"binding", ""},
            {"resetsAt", nullptr},
            {"pauseUntil", 0.0},
            {"running", 0},
            {"procs", 0},
            {"spentUsd", 0.0},
            {"error", nullptr},
            {"probedWith", nullptr},
            {"foreign", ZeroForeign()},
            // The board's view of the seat.
            {"boardKey", SeatKey(kind, secret)},
            {"stateFrom", nullptr},
        };
    }

    std::vector<Json> LoadSeats(const std::map<std::string, std::string>& env, const std::optional<fs::path>& envFile, std::string_view specText, Ledger* ledger, const Json& apiConfig) {
        std::map<std::string, std::string> merged = env;
        if (envFile && !envFile->empty()) {
            for (const auto& [key, value] : Seats::SeatTokensFromEnvFile(Dyn::ReadText(*envFile))) merged[key] = value;
        }
        std::vector<std::pair<std::string, Json>> pool;
        for (const auto& [n, key] : Seats::ApiKeysFromEnv(merged)) pool.emplace_back(std::format("api{}", n), NewSeat(std::format("api{}", n), "api", key));
        for (const auto& [n, token] : Seats::SeatTokensFromEnv(merged)) pool.emplace_back(std::to_string(n), NewSeat(std::to_string(n), "oauth", token));
        for (const auto& [n, key] : Seats::OpenRouterKeysFromEnv(merged)) pool.emplace_back(std::format("or{}", n), NewSeat(std::format("or{}", n), "openrouter", key));
        pool.emplace_back("local", NewSeat("local", "local", ""));
        auto find = [&](std::string_view id) -> const Json* {
            for (const auto& [key, seat] : pool) {
                if (key == id) return &seat;
            }
            return nullptr;
        };
        const std::string spec = Dyn::Strip(specText.empty() ? std::string_view("auto") : specText);
        std::vector<std::string> ids;
        if (spec == "auto") {
            // Never an OpenRouter seat by default.
            for (const auto& [key, seat] : pool) {
                if (Kind(seat) == "api" || Kind(seat) == "oauth") ids.push_back(key);
            }
            if (ids.empty()) ids.emplace_back("local");
        } else if (spec == "local" || spec == "api" || spec == "oauth" || spec == "openrouter") {
            for (const auto& [key, seat] : pool) {
                if (Kind(seat) == spec) ids.push_back(key);
            }
        } else {
            std::vector<std::string> bad;
            for (const std::string& part : Dyn::Split(spec, ",")) {
                const std::string id = Dyn::Strip(part);
                if (id.empty()) continue;
                ids.push_back(id);
                if (!find(id)) bad.push_back(id);
            }
            if (!bad.empty()) {
                std::vector<std::string> configured;
                for (const auto& [key, seat] : pool) {
                    if (key != "local") configured.push_back(key);
                }
                throw std::invalid_argument(std::format("--seats names seat(s) not configured: {} (configured: {}, local)", Dyn::Join(bad, ", "), Dyn::Join(configured, ", ")));
            }
        }
        std::vector<Json> seats;
        for (const std::string& id : ids) seats.push_back(*find(id));
        if (std::ranges::any_of(seats, IsOpenRouter) && !std::ranges::all_of(seats, IsOpenRouter)) {
            throw std::invalid_argument("--seats: an OpenRouter seat cannot share a pool with Anthropic seats or the local login - a model name means a different model per endpoint");
        }
        if (ledger) {
            const double now = Platform::Now();
            for (Json& s : seats) {
                if (!IsPaid(s)) continue;
                const Json& e = ledger->Entry(Id(s), now);
                s["spentUsd"] = AsDouble(Dyn::At(e, "spentUsd"));
                if (Dyn::Truthy(Dyn::Get(e, "outSince"))) {
                    s["state"] = "out";
                    s["error"] = std::format("ledger: {} since {}", Dyn::StrOr(Dyn::Get(e, "outReason"), "out"), Dyn::Slice(Dyn::Str(e.at("outSince")), 0, 16));
                } else if (Dyn::Truthy(apiConfig) && AsDouble(s.at("spentUsd")) >= Budget(s, apiConfig)) {
                    s["state"] = "out";
                    s["error"] = std::format("ledger: ${:.2f} spent this cycle, budget ${}", AsDouble(s.at("spentUsd")), G(Budget(s, apiConfig)));
                }
            }
        }
        return seats;
    }

    void ApplyProbe(Json& s, const Json& r) {
        s["state"] = Dyn::Has(r, "state") ? r.at("state") : Json("unknown");
        s["windows"] = Dyn::Or(Dyn::Get(r, "windows"), Dyn::EmptyDict());
        s["util"] = Dyn::Get(r, "util");
        s["binding"] = Dyn::Truthy(Dyn::Get(r, "binding")) ? r.at("binding") : Json("");
        s["resetsAt"] = Dyn::Get(r, "resetsAt");
        s["error"] = Dyn::Get(r, "error");
        s["probedWith"] = Dyn::Get(r, "probedWith");
        if (Kind(s) == "oauth" && Dyn::Truthy(s.at("windows"))) Reutil(s);
        if (s.at("state") == "limited" && Dyn::Truthy(s.at("resetsAt"))) s["pauseUntil"] = AsDouble(s.at("resetsAt")) + 30;
    }

    std::string Describe(const Json& s) {
        if (IsPaid(s)) {
            std::string state = Dyn::Str(s.at("state"));
            if (Dyn::Truthy(Dyn::Get(s, "error")) && s.at("state") != "ok") state += std::format(" ({})", Dyn::Str(s.at("error")));
            const Json& remaining = Dyn::Get(s, "remainingUsd");
            return std::format("{}, ${:.2f} spent this cycle{}", state, AsDouble(s.at("spentUsd")), remaining.is_null() ? std::string() : std::format(", ${:.2f} left on the key", AsDouble(remaining)));
        }
        if (!Dyn::Truthy(s.at("windows"))) {
            return Dyn::Str(s.at("state")) + (Dyn::Truthy(Dyn::Get(s, "error")) ? std::format(" ({})", Dyn::Str(s.at("error"))) : std::string());
        }
        std::vector<std::string> parts;
        const Json& windows = s.at("windows");
        for (auto it = windows.begin(); it != windows.end(); ++it) {
            const Json& u = Dyn::Get(it.value(), "utilization");
            if (u.is_null()) continue;
            std::string label = it.key();
            if (it.key() == "five_hour") {
                label = "5h";
            } else if (it.key() == "seven_day") {
                label = "7d";
            } else if (it.key() == Seats::FableWindow || Seats::IsFableWindow(it.key())) {
                label = "fable";
            }
            parts.push_back(std::format("{} {}%", label, Seats::Fmt(u)));
        }
        const Json& binding = s.at("binding");
        return std::format("{}: {}{}", Dyn::Str(s.at("state")), Dyn::Join(parts, ", "), Dyn::Truthy(binding) ? std::format(" (binding {})", Dyn::Str(binding)) : std::string());
    }

    void Probe(std::vector<Json>& seats, const std::string& claudeBin, double timeout, const std::vector<std::string>& models, const Log& log, const ProbeFunction& probe) {
        const ProbeFunction run = probe ? probe : ProbeFunction([](std::int32_t seat, const std::string& token, const std::string& model, double t, const std::string& bin, bool local, bool api) {
            return Seats::ProbeSeat(seat, token, {.model = model, .timeoutS = t, .claudeBin = bin, .local = local, .api = api});
        });
        // OAuth seats probe on the lens model when that is Fable (its window
        // is seen only there), else on Haiku; API seats and the local login
        // on Haiku.
        std::optional<std::string> fable;
        for (const std::string& m : models) {
            if (Dyn::Lower(m).contains("fable")) {
                fable = m;
                break;
            }
        }
        if (std::ranges::any_of(seats, IsOpenRouter)) {
            const Json prices = FetchOpenRouterPrices(models, log);
            for (auto it = prices.begin(); it != prices.end(); ++it) {
                const Json& p = it.value();
                if (!Dyn::Truthy(p)) {
                    log(std::format("openrouter: NO PRICE for {} - its spend is not counted", it.key()));
                    continue;
                }
                log(std::format("openrouter: {} priced ${:.3f}/${:.3f} per M in/out, cache read {}", it.key(), AsDouble(p.at("prompt")) * 1e6, AsDouble(p.at("completion")) * 1e6,
                                Dyn::Get(p, "cacheRead").is_null() ? std::string("n/a") : std::format("${:.4f}", AsDouble(p.at("cacheRead")) * 1e6)));
            }
        }
        const std::string lensModel = fable.value_or(std::string(Seats::ProbeModel));
        for (Json& s : seats) {
            if (s.at("state") == "out") continue;
            const std::string kind = Kind(s);
            const std::string id = Id(s);
            const std::string secret = Dyn::StrOr(Dyn::Get(s, "secret"), "");
            if (kind == "openrouter") {
                const Json r = ProbeOpenRouter(secret, timeout);
                ApplyProbe(s, r);
                s["remainingUsd"] = Dyn::Get(r, "remaining");
                log(std::format("seat {} ({}): {}", id, kind, Describe(s)));
                continue;
            }
            const std::int32_t n = kind == "api" ? static_cast<std::int32_t>(Dyn::ParseInt(Dyn::Slice(id, 3)).value_or(0)) : (kind == "local" ? 0 : static_cast<std::int32_t>(Dyn::ParseInt(id).value_or(0)));
            Json r;
            if (kind == "api") {
                r = run(n, secret, std::string(Seats::ProbeModel), timeout, claudeBin, false, true);
            } else if (kind == "local") {
                r = run(n, "", lensModel, timeout, claudeBin, true, false);
            } else {
                r = run(n, secret, lensModel, timeout, claudeBin, false, false);
                if (fable && Seats::NeedsHaiku(r)) r = Seats::MergeFableProbe(run(n, secret, std::string(Seats::ProbeModel), timeout, claudeBin, false, false), r);
            }
            ApplyProbe(s, r);
            log(std::format("seat {} ({}): {}", id, kind, Describe(s)));
        }
    }

    // ---- placement -------------------------------------------------------------------------
    namespace {
        // A finite number >= 0 in Dyn::ParseFloat's syntax, else the default.
        double EnvNumber(const std::map<std::string, std::string>& env, const std::string& name, double fallback) {
            const std::string text = EnvOf(env, name);
            const std::optional<double> n = Dyn::ParseFloat(text);
            return n && !Dyn::Strip(text).empty() && std::isfinite(*n) && *n >= 0 ? *n : fallback;
        }

        // A pass's share of the weekly window, as measured: 0.04 at xhigh,
        // 0.125 at max and for any other effort.
        double Cost7d(const Json& config) {
            return Dyn::Has(config, "lensCost7dPct") ? AsDouble(config.at("lensCost7dPct")) : 0.125;
        }

        // The weekly window with the passes in flight and this one projected
        // on it stays under the cutoff: the room of an account whose burst
        // window is the weekly one.
        bool WeeklyRoom(const Json& s, const Json& config) {
            const double ahead = static_cast<double>(Running(s) + 1) * Cost7d(config) + Num(Dyn::Get(Foreign(s), "cost7d"));
            const Json& windows = Dyn::At(s, "windows");
            for (auto it = windows.begin(); it != windows.end(); ++it) {
                if (it.key() == "five_hour" || Seats::IsFableWindow(it.key())) continue;
                if (Num(Dyn::Get(it.value(), "utilization")) + ahead >= Seats::LongWindowCutoff) return false;
            }
            return true;
        }
    }

    Json PoolConfig(const std::map<std::string, std::string>& env, std::string_view effort) {
        Json config = Seats::ConfigFromEnv(env);
        if (Dyn::Strip(EnvOf(env, "REVIEW_GATES_LENS_COST_PCT")).empty()) config["lensCostPct"] = 0.25;
        config["lensCost7dPct"] = EnvNumber(env, "REVIEW_GATES_LENS_COST_7D_PCT", effort == "xhigh" ? 0.04 : 0.125);
        config["oauthConcurrency"] = static_cast<std::int64_t>(EnvNumber(env, "REVIEW_GATES_OAUTH_CONCURRENCY", static_cast<double>(OauthConcurrency)));
        return config;
    }

    double OauthProjected(const Json& s, const Json& config) {
        // Where the seat's burst window will be with its running processes -
        // this driver's at its projection, the other drivers' at theirs (the
        // board): the 5-hour window, or the weekly one on an account without
        // a 5-hour limit. Unknown = at the ceiling, ranked last.
        if (Seats::BurstWindow(Dyn::At(s, "windows")) == "seven_day") {
            return AsDouble(s.at("windows").at("seven_day").at("utilization")) + static_cast<double>(Running(s)) * Cost7d(config) + Num(Dyn::Get(Foreign(s), "cost7d"));
        }
        const Json& five = Dyn::Get(FiveHour(s), "utilization");
        const double base = five.is_null() ? AsDouble(config.at("maxUtil")) : AsDouble(five);
        return base + static_cast<double>(Running(s)) * AsDouble(config.at("lensCostPct")) + AsDouble(Foreign(s).at("cost5h"));
    }

    std::vector<std::string> ExpireWindows(Json& s, double now) {
        // 2026-10-13: S153 sat in a 30-second pause loop for 30 minutes after
        // the 20:20 resets - nothing was running, so no rate event ever
        // replaced the 83-89 % readings.
        std::vector<std::string> done;
        if (!Dyn::Truthy(Dyn::Get(s, "windows"))) return done;
        for (auto it = s["windows"].begin(); it != s["windows"].end(); ++it) {
            Json& w = it.value();
            if (Dyn::Truthy(Dyn::Get(w, "resetsAt")) && AsDouble(w.at("resetsAt")) + 30 <= now && Num(Dyn::Get(w, "utilization")) > 0) {
                w["utilization"] = 0;
                w["resetsAt"] = 0;
                done.push_back(it.key());
            }
        }
        return done;
    }

    bool Eligible(Json& s, double now, const Json& config, const Json& apiConfig) {
        if (s.at("state") == "out" || s.at("state") == "invalid" || now < AsDouble(s.at("pauseUntil"))) return false;
        if (IsPaid(s)) {
            // The cap counts every driver's processes.
            return Running(s) + Int(AsDouble(Foreign(s).at("count"))) < Concurrency(s, apiConfig) && ApiRoom(s, apiConfig);
        }
        ExpireWindows(s, now);
        // Its pause is over (checked above): back in placement, its windows
        // decide.
        if (s.at("state") == "limited") s["state"] = "ok";
        // So many passes per account at once, every driver's counted,
        // whatever its windows (2026-10-31).
        const std::int64_t cap = Dyn::Has(config, "oauthConcurrency") ? Int(AsDouble(config.at("oauthConcurrency"))) : OauthConcurrency;
        if (Running(s) + Int(AsDouble(Foreign(s).at("count"))) >= cap) return false;
        const std::optional<std::string> burst = Seats::BurstWindow(s.at("windows"));
        // No reading (no probe, or it failed): usable, ranked at the ceiling -
        // after every known seat.
        if (!burst) return true;
        // No 5-hour limit on the account: the weekly cutoff alone, with the
        // passes projected on it.
        if (*burst == "seven_day") return WeeklyRoom(s, config);
        return OauthProjected(s, config) + AsDouble(config.at("lensCostPct")) <= AsDouble(config.at("maxUtil")) && LongOk(s);
    }

    std::vector<Json*> Ranked(std::vector<Json>& seats, double now, const Json& config, const Json& apiConfig) {
        std::vector<Json*> api;
        std::vector<Json*> oauth;
        for (Json& s : seats) {
            if (!Eligible(s, now, config, apiConfig)) continue;
            (IsPaid(s) ? api : oauth).push_back(&s);
        }
        auto spend = [&](const Json* s) {
            return std::pair(AsDouble(s->at("spentUsd")) + static_cast<double>(Running(*s)) * LensCost(*s, apiConfig) + AsDouble(Foreign(*s).at("costUsd")), Id(*s));
        };
        std::ranges::stable_sort(api, [&](const Json* a, const Json* b) { return spend(a) < spend(b); });
        if (config.at("policy") == "pack") {
            std::ranges::stable_sort(oauth, [](const Json* a, const Json* b) { return std::pair(Kind(*a) != "oauth", Id(*a)) < std::pair(Kind(*b) != "oauth", Id(*b)); });
        } else {
            auto projected = [&](const Json* s) { return std::pair(Seats::Quantize(OauthProjected(*s, config)), Id(*s)); };
            std::ranges::stable_sort(oauth, [&](const Json* a, const Json* b) { return projected(a) < projected(b); });
        }
        const bool apiFirst = apiConfig.at("order") == "api-first";
        std::vector<Json*> out = apiFirst ? api : oauth;
        const std::vector<Json*>& rest = apiFirst ? oauth : api;
        out.insert(out.end(), rest.begin(), rest.end());
        return out;
    }

    Json* Pick(std::vector<Json>& seats, double now, const Json& config, const Json& apiConfig) {
        const std::vector<Json*> ranked = Ranked(seats, now, config, apiConfig);
        return ranked.empty() ? nullptr : ranked.front();
    }

    // ---- resuming a pass on another seat ------------------------------------------------
    fs::path SeatDir(const fs::path& scratch, std::string_view seatId) {
        return scratch / std::format("seat-{}", seatId);
    }

    std::optional<fs::path> CarryTranscript(const fs::path& scratch, std::string_view fromSeat, std::string_view toSeat, std::string_view sessionId, const Log& log) {
        // The CLI keeps a session's transcript under
        // <CLAUDE_CONFIG_DIR>/projects/<cwd slug>/<session id>.jsonl, and
        // `claude --resume <id>` continues it; every process runs in the
        // repository, so the slug is the same on the other seat.
        if (fromSeat.empty() || toSeat.empty() || sessionId.empty() || fromSeat == toSeat) return std::nullopt;
        // glob(<seat>/projects/*/<session>.jsonl), whose * skips dot names.
        std::optional<fs::path> source;
        std::error_code error;
        for (fs::directory_iterator it(SeatDir(scratch, fromSeat) / "projects", error), end; !error && it != end; it.increment(error)) {
            if (it->path().filename().string().starts_with('.')) continue;
            const fs::path candidate = it->path() / std::format("{}.jsonl", sessionId);
            std::error_code missing;
            if (fs::exists(fs::symlink_status(candidate, missing))) {
                source = candidate;
                break;
            }
        }
        if (!source) return std::nullopt;
        const fs::path destination = SeatDir(scratch, toSeat) / "projects" / source->parent_path().filename() / source->filename();
        Platform::MakeDirs(destination.parent_path(), 0700);
        CopyContents(*source, destination);
        if (log) {
            log(std::format("seat {}: transcript of {} carried over from seat {} ({} bytes) - the pass resumes", toSeat, Dyn::Slice(sessionId, 0, 8), fromSeat, fs::file_size(destination)));
        }
        return destination;
    }

    bool AllOut(const std::vector<Json>& seats) {
        return std::ranges::all_of(seats, [](const Json& s) { return s.at("state") == "out" || s.at("state") == "invalid"; });
    }

    std::optional<double> EarliestResume(const std::vector<Json>& seats, double now, std::optional<double> recheck) {
        std::vector<double> times;
        for (const Json& s : seats) {
            if (s.at("state") == "out" || s.at("state") == "invalid") continue;
            if (AsDouble(s.at("pauseUntil")) > now) {
                times.push_back(AsDouble(s.at("pauseUntil")));
            } else if (Kind(s) != "api") {
                // The reset of the seat's burst window: the 5-hour one, the
                // weekly one on an account without it.
                const std::optional<std::string> burst = Seats::BurstWindow(s.at("windows"));
                const Json& window = burst ? Dyn::Get(s.at("windows"), *burst) : Dyn::EmptyDict();
                if (Dyn::Truthy(Dyn::Get(window, "resetsAt")) && AsDouble(window.at("resetsAt")) + 30 > now) times.push_back(AsDouble(window.at("resetsAt")) + 30);
            }
            if (recheck && AsDouble(Foreign(s).at("count")) > 0) times.push_back(now + *recheck);
        }
        if (times.empty()) return std::nullopt;
        return std::ranges::min(times);
    }

    double RetryAfter(std::string_view text, double fallback) {
        // re.search(r'retry[- ]after[^0-9]{0,12}(\d+)', text, re.I): the class
        // run is greedy, so the digits are the last \d that it leaves.
        const std::u32string t = Dyn::Decode(text);
        auto letters = [&](std::size_t at, std::string_view word) {
            for (std::size_t i = 0; i < word.size(); ++i) {
                if (Dyn::IgnoreCaseLetter(t[at + i]) != word[i]) return false;
            }
            return true;
        };
        for (std::size_t at = 0; at + 11 <= t.size(); ++at) {
            if (!letters(at, "retry") || (t[at + 5] != U'-' && t[at + 5] != U' ') || !letters(at + 6, "after")) continue;
            const std::size_t gap = at + 11;
            std::size_t run = 0;
            while (run < 12 && gap + run < t.size() && !(t[gap + run] >= U'0' && t[gap + run] <= U'9')) ++run;
            for (std::size_t k = run + 1; k-- > 0;) {
                std::size_t end = gap + k;
                std::int64_t seconds = 0;
                while (end < t.size() && Dyn::IsDecimal(t[end])) {
                    seconds = std::min<std::int64_t>(1'000'000, seconds * 10 + Dyn::DecimalValue(t[end]));
                    ++end;
                }
                if (end > gap + k) return static_cast<double>(std::min<std::int64_t>(900, std::max<std::int64_t>(30, seconds + 5)));
            }
        }
        return fallback;
    }

    bool Settle(Json& s, Json& record, double now, const Json& config, const Json& apiConfig, Ledger* ledger, const Log& log) {
        s["procs"] = Dyn::Add(s.at("procs"), Json(1));
        const Json& rate = Dyn::Or(Dyn::Get(record, "rateLimit"), Dyn::EmptyDict());
        if (Kind(s) != "api" && Dyn::Truthy(rate)) {
            Json windows = Json::object();
            for (auto it = rate.begin(); it != rate.end(); ++it) {
                const Json& u = Dyn::Get(it.value(), "utilization");
                const Json& r = Dyn::Get(it.value(), "resetsAt");
                windows[it.key()] = {{"utilization", Dyn::Truthy(u) ? u : Json(0)}, {"resetsAt", Dyn::Truthy(r) ? r : Json(0)}};
            }
            s["windows"] = std::move(windows);
            Reutil(s);
            const Json& five = FiveHour(s);
            if (Num(Dyn::Get(five, "utilization")) >= AsDouble(config.at("maxUtil")) && Dyn::Truthy(Dyn::Get(five, "resetsAt"))) {
                s["pauseUntil"] = std::max(AsDouble(s.at("pauseUntil")), AsDouble(five.at("resetsAt")) + 30);
                if (s.at("state") == "ok") log(std::format("seat {}: five_hour window at {}% - no new launches until its reset", Id(s), Seats::Fmt(five.at("utilization"))));
            }
        }
        if (IsPaid(s)) {
            if (IsOpenRouter(s)) {
                // The harness's own figure is wrong for a model it does not
                // know (the CLI) or is the catalogue's guess (OpenCode): the
                // seat's spend is tokens x OpenRouter's list prices, and that
                // is what the dump sums.
                record["costUsdHarness"] = Dyn::Get(record, "costUsd");
                record["costUsd"] = OpenRouterCost(Dyn::StrOr(Dyn::Get(record, "model"), ""), Dyn::Or(Dyn::Get(record, "usage"), Dyn::EmptyDict()));
            }
            const double usd = Num(Dyn::Get(record, "costUsd"));
            s["spentUsd"] = AsDouble(s.at("spentUsd")) + usd;
            if (ledger) ledger->Add(Id(s), usd, now);
            const double budget = Budget(s, apiConfig);
            const double spent = AsDouble(s.at("spentUsd"));
            if (spent >= budget && s.at("state") != "out" && s.at("state") != "invalid") {
                s["state"] = "out";
                s["error"] = std::format("budget: ${:.2f} spent this cycle, budget ${}", spent, G(budget));
                log(std::format("seat {}: {} - out for the rest of the cycle", Id(s), Dyn::Str(s.at("error"))));
            } else if (spent >= 0.8 * budget && spent - usd < 0.8 * budget) {
                log(std::format("seat {}: ${:.2f} of ${} spent this cycle", Id(s), spent, G(budget)));
            }
        }
        const Json& status = Dyn::Get(record, "status");
        const std::string reason = Dyn::StrOr(Dyn::Get(record, "reason"), "");
        if (status == "credits") {
            s["state"] = "out";
            s["error"] = std::format("credit balance exhausted ({})", Dyn::Slice(reason, 0, 80));
            if (ledger && IsPaid(s)) ledger->MarkOut(Id(s), "credit balance too low", now);
            log(std::format("seat {}: {} - out, the process is placed again", Id(s), Dyn::Str(s.at("error"))));
            return true;
        }
        if (status == "auth") {
            s["state"] = "invalid";
            s["error"] = std::format("authentication failure ({})", Dyn::Slice(reason, 0, 80));
            log(std::format("seat {}: {} - out, the process is placed again", Id(s), Dyn::Str(s.at("error"))));
            return true;
        }
        if (status == "limit") {
            if (IsPaid(s)) {
                s["pauseUntil"] = std::max(AsDouble(s.at("pauseUntil")), now + RetryAfter(reason, ApiBackoffS));
                log(std::format("seat {}: rate limited - paused {} s, the process is placed again", Id(s), Int(AsDouble(s.at("pauseUntil")) - now)));
                return true;
            }
            const std::string rateType = Dyn::StrOr(Dyn::Get(record, "rateType"), "");
            if (rateType == "concurrents") {
                // Not a window: the account had too many requests in flight
                // at once (a burst of passes released onto one seat when its
                // prompt prefix became cached). Seconds, not the window's
                // reset.
                s["pauseUntil"] = std::max(AsDouble(s.at("pauseUntil")), now + RetryAfter(reason, ConcurrentBackoffS));
                s["state"] = "limited";
                log(std::format("seat {}: too many requests at once ({}) - paused {} s, the process is placed again", Id(s), Dyn::Slice(reason, 0, 40), Int(AsDouble(s.at("pauseUntil")) - now)));
                return true;
            }
            const Json& binding = s.at("binding");
            if (rateType.starts_with("seven_day") || (Dyn::StrOr(binding, "").starts_with("seven_day") && Num(Dyn::Get(s, "util")) >= 100)) {
                s["state"] = "out";
                s["error"] = std::format("seven-day window rejected ({})", rateType.empty() ? Dyn::Str(binding) : rateType);
                log(std::format("seat {}: {} - out for the run, the process is placed again", Id(s), Dyn::Str(s.at("error"))));
                return true;
            }
            const Json& five = FiveHour(s);
            s["pauseUntil"] = std::max(AsDouble(s.at("pauseUntil")), Dyn::Truthy(Dyn::Get(five, "resetsAt")) ? AsDouble(five.at("resetsAt")) + 30 : now + OauthFallbackPauseS);
            s["state"] = "limited";
            log(std::format("seat {}: limit ({}) - paused until {}, the process is placed again", Id(s), Dyn::Slice(reason, 0, 60), Clock(AsDouble(s.at("pauseUntil")))));
            return true;
        }
        if (s.at("state") == "limited" && now >= AsDouble(s.at("pauseUntil"))) s["state"] = "ok";
        return false;
    }

    // ---- the child's credentials -----------------------------------------------------------
    fs::path WriteCredentials(const fs::path& configDir, std::string_view token) {
        // A setup-token is long-lived and never refreshed by the CLI: the
        // expiry only has to be far away.
        Platform::MakeDirs(configDir, 0700);
        const Json body = {{"claudeAiOauth", {{"accessToken", std::string(token)}, {"expiresAt", Int((Platform::Now() + 365 * 86400) * 1000)}, {"scopes", Json::array({"user:inference"})}}}};
        const fs::path path = configDir / ".credentials.json";
        // One temp name per writer: the pool's threads launch a fresh seat's
        // first passes in the same instant, each sees no credentials file yet
        // and each writes one - with a pid-only name one rename found the temp
        // file gone (S115, S116, S119 on 2026-10-10). The contents are
        // identical, so the last rename to win is fine.
        const fs::path temp = std::format("{}.{}.{}.tmp", path.string(), Platform::PublishedPid(), Uuid4().substr(0, 8));
        const std::int32_t fd = open(temp.c_str(), O_WRONLY | O_CREAT | O_EXCL | O_CLOEXEC, 0600);
        if (fd < 0) throw std::runtime_error(std::format("{}: {}", Dyn::ErrnoText(errno), Dyn::Repr(temp.string())));
        WriteAll(fd, std::format("{}\n", DumpSpaced(body)));
        fs::rename(temp, path);
        return path;
    }

    std::map<std::string, std::string> ChildEnv(const Json& seat, const std::map<std::string, std::string>& base, const fs::path& scratch) {
        // `local`: the driver's environment as it is (the machine's own
        // login). OAuth: the seat's config dir with its credentials file, no
        // token variable. API: the key in ANTHROPIC_API_KEY plus a config dir
        // of its own that approves that key, so no login on the machine is
        // picked up.
        std::map<std::string, std::string> env = base;
        // No Anthropic seat ever inherits another endpoint or credential from
        // the driver's environment.
        for (const std::string_view key : {"ANTHROPIC_API_KEY", "CLAUDE_CODE_OAUTH_TOKEN", "ANTHROPIC_AUTH_TOKEN", "ANTHROPIC_BASE_URL"}) env.erase(std::string(key));
        const std::string kind = Kind(seat);
        if (kind == "local") return env;
        const fs::path dir = scratch / std::format("seat-{}", Id(seat));
        Platform::MakeDirs(dir, 0700);
        env["CLAUDE_CONFIG_DIR"] = dir.string();
        const std::string secret = Dyn::StrOr(Dyn::Get(seat, "secret"), "");
        if (kind == "oauth") {
            if (!fs::exists(dir / ".credentials.json")) WriteCredentials(dir, secret);
        } else if (kind == "openrouter") {
            // The CLI against OpenRouter's Anthropic-format endpoint
            // (/api/v1/messages), the key as a bearer token. Verified
            // 2026-10-12 (CLI 2.1.296, xiaomi/mimo-v2.6-pro): tools, thinking,
            // cache reads and --json-schema all work; `--effort` does not
            // reach the model, and the CLI's total_cost_usd is wrong.
            env["ANTHROPIC_BASE_URL"] = std::string(OpenRouterBaseUrl);
            env["ANTHROPIC_AUTH_TOKEN"] = secret;
            env.erase("CLAUDE_CODE_ENTRYPOINT");
            // hasCompletedOnboarding, so --print asks nothing.
            Seats::WriteApiKeyApproval(dir, secret);
        } else {
            env["ANTHROPIC_API_KEY"] = secret;
            // The launcher's CLAUDE_CODE_ENTRYPOINT=claude-vscode is what broke
            // S111's API seats (2026-10-08, CLI 2.1.294): with it the key is
            // refused ("Not logged in") and, once approved, the subscriber
            // credits answer "Credit balance is too low". Bisected over every
            // CLAUDE_*/ANTHROPIC_* variable: only this one matters.
            env.erase("CLAUDE_CODE_ENTRYPOINT");
            Seats::WriteApiKeyApproval(dir, secret);
        }
        return env;
    }

    // ---- OpenRouter seats ------------------------------------------------------------------
    std::string ModelKey(std::string_view model) {
        return model.starts_with("openrouter/") ? std::string(model.substr(11)) : std::string(model);
    }

    Json FetchOpenRouterPrices(const std::vector<std::string>& models, const Log& log, double timeout) {
        std::set<std::string> want;
        for (const std::string& m : models) {
            if (!m.empty()) want.insert(ModelKey(m));
        }
        Json data = Json::array();
        try {
            const Json catalogue = Http::JsonBody(Http::UrlOpen(OpenRouterModelsUrl, {}, timeout));
            data = Dyn::Or(Dyn::Get(catalogue, "data"), Dyn::EmptyList());
        } catch (const std::exception& error) {
            if (log) log(std::format("openrouter: price catalogue not fetched ({}) - list prices from the built-in table", Dyn::Slice(error.what(), 0, 80)));
        }
        const std::lock_guard guard(PricesLock);
        for (const Json& m : data) {
            const Json& id = Dyn::Get(m, "id");
            if (!id.is_string() || !want.contains(id.get<std::string>())) continue;
            const Json& p = Dyn::Or(Dyn::Get(m, "pricing"), Dyn::EmptyDict());
            const Json& cacheRead = Dyn::Get(p, "input_cache_read");
            const Json& cacheWrite = Dyn::Get(p, "input_cache_write");
            Prices[id.get<std::string>()] = {
                {"prompt", Num(Dyn::Get(p, "prompt"))},
                {"completion", Num(Dyn::Get(p, "completion"))},
                {"cacheRead", cacheRead.is_null() ? Json() : Json(AsDouble(cacheRead))},
                {"cacheWrite", cacheWrite.is_null() ? Json() : Json(AsDouble(cacheWrite))},
            };
        }
        Json out = Json::object();
        for (const std::string& key : want) {
            if (!Prices.contains(key) && BuiltInPrices().contains(key)) Prices[key] = BuiltInPrices().at(key);
            out[key] = Prices.contains(key) ? Prices.at(key) : Json();
        }
        return out;
    }

    double OpenRouterCost(std::string_view model, const Json& usage) {
        // Uncached input and cache writes at the prompt price (a cache write
        // costs nothing extra on OpenRouter unless the catalogue says so),
        // cache reads and output at theirs. 0 for a model without a price.
        Json p;
        {
            const std::lock_guard guard(PricesLock);
            const auto found = Prices.find(ModelKey(model));
            if (found != Prices.end()) p = found->second;
        }
        if (!Dyn::Truthy(p)) p = Dyn::Get(BuiltInPrices(), ModelKey(model));
        if (!Dyn::Truthy(p)) return 0.0;
        const double prompt = AsDouble(p.at("prompt"));
        const double cacheRead = Dyn::Get(p, "cacheRead").is_null() ? prompt : AsDouble(p.at("cacheRead"));
        const double cacheWrite = Dyn::Get(p, "cacheWrite").is_null() ? prompt : AsDouble(p.at("cacheWrite"));
        const Json& u = Dyn::Or(usage, Dyn::EmptyDict());
        double total = Num(Dyn::Get(u, "input")) * prompt;
        total = total + Num(Dyn::Get(u, "cacheCreation")) * cacheWrite;
        total = total + Num(Dyn::Get(u, "cacheRead")) * cacheRead;
        total = total + Num(Dyn::Get(u, "output")) * AsDouble(p.at("completion"));
        return Dyn::Round(total, 6);
    }

    Json ProbeOpenRouter(const std::string& secret, double timeout) {
        Json d;
        try {
            const Json body = Http::JsonBody(Http::UrlOpen(OpenRouterKeyUrl, {{"Authorization", std::format("Bearer {}", secret)}}, timeout));
            d = Dyn::Or(Dyn::Get(body, "data"), Dyn::EmptyDict());
        } catch (const Http::HttpError& error) {
            return {{"state", error.Code() == 401 || error.Code() == 403 ? "invalid" : "unknown"}, {"error", std::format("HTTP {} from {}", error.Code(), OpenRouterKeyUrl)}};
        } catch (const std::exception& error) {
            return {{"state", "unknown"}, {"error", std::format("probe failed: {}", Dyn::Slice(error.what(), 0, 100))}};
        }
        const Json& remaining = Dyn::Get(d, "limit_remaining");
        if (!remaining.is_null() && AsDouble(remaining) <= 0) {
            return {{"state", "out"}, {"error", std::format("key limit reached (${:.2f} of ${} used)", Num(Dyn::Get(d, "usage")), G(Num(Dyn::Get(d, "limit"))))}, {"remaining", remaining}};
        }
        return {{"state", "ok"}, {"remaining", remaining}, {"usage", Dyn::Get(d, "usage")}, {"limit", Dyn::Get(d, "limit")}};
    }

    // ---- the board -------------------------------------------------------------------------
    fs::path BoardPath() {
        if (const std::optional<std::string> configured = Platform::GetEnv("REVIEW_GATES_BOARD"); configured && !configured->empty()) return *configured;
        return fs::path(Platform::Home()) / ".cache" / "review-gates" / BoardFile;
    }

    std::string SeatKey(std::string_view kind, std::string_view secret) {
        if (kind == "local" || secret.empty()) return "local";
        return std::format("{}:{}", kind, Sha256Hex(secret).substr(0, 12));
    }

    std::string MyKey() {
        if (const std::optional<Platform::Identity> self = Platform::Self()) return self->Key();
        return std::format("{}:0", Platform::PublishedPid());
    }

    bool DriverAlive(std::string_view key, const fs::path& boardDir, bool reap) {
        const std::vector<std::string> parts = Dyn::Split(key, ":", 1);
        const std::optional<std::int64_t> pid = parts.size() == 2 ? Dyn::ParseInt(parts[0]) : std::nullopt;
        const std::optional<std::int64_t> start = parts.size() == 2 ? Dyn::ParseInt(parts[1]) : std::nullopt;
        if (!pid || !start) return false;
        const fs::path locks = boardDir / "drivers";
        if (const std::optional<bool> held = Platform::ProbeLifetimeLock(locks, *pid, *start)) {
            if (!*held && reap) {
                // Its driver died; nobody can take that name again.
                std::error_code error;
                fs::remove(Platform::LifetimeLockFile(locks, *pid, *start), error);
            }
            return *held;
        }
        // No lock file: a driver that takes none. In the sandbox a pid is
        // another namespace's and says nothing.
        if (Platform::InSandbox()) return true;
        const std::optional<std::int64_t> running = Platform::ProcStart(*pid);
        // No /proc at all: the deadline sweep is the backstop.
        if (!running) return !fs::is_directory(Platform::Paths().proc);
        return *running == *start;
    }

    bool ClaimScratch(const fs::path& path) {
        // 2026-10-18: two test runs launched seconds apart on one hash shared
        // `<hash8>-run-2` and its out/ files - the outputs rule alone saw an
        // empty out/ in the first seconds.
        fs::create_directories(path);
        const fs::path marker = path / ".driver";
        const std::string me = MyKey();
        std::int32_t fd = open(marker.c_str(), O_WRONLY | O_CREAT | O_EXCL | O_CLOEXEC, 0644);
        if (fd < 0) {
            if (errno != EEXIST) throw std::runtime_error(std::format("{}: {}", Dyn::ErrnoText(errno), Dyn::Repr(marker.string())));
            const std::vector<std::string> holder = Dyn::Split(Dyn::Strip(Platform::ReadFile(marker).value_or("")), ":", 1);
            const std::optional<std::int64_t> pid = holder.size() == 2 ? Dyn::ParseInt(holder[0]) : std::nullopt;
            const std::optional<std::int64_t> start = holder.size() == 2 ? Dyn::ParseInt(holder[1]) : std::nullopt;
            if (pid && start && *pid != 0 && *pid != Platform::PublishedPid() && DriverAlive(std::format("{}:{}", *pid, *start), BoardPath().parent_path())) return false;
            fd = open(marker.c_str(), O_WRONLY | O_CREAT | O_TRUNC | O_CLOEXEC, 0644);
            if (fd < 0) throw std::runtime_error(std::format("{}: {}", Dyn::ErrnoText(errno), Dyn::Repr(marker.string())));
        }
        WriteAll(fd, me);
        return true;
    }

    std::vector<std::string> MergeWindows(Json& into, const Json& other, double now) {
        // A window whose reset has passed is ignored on either side; of the
        // rest the newer resetsAt wins, and within one reset epoch the higher
        // utilization: utilization never falls inside an epoch (2026-10-18:
        // 1948 rate_limit_events of three runs, 942 rises, 0 falls), so the
        // merge is exact without a timestamp.
        std::vector<std::string> changed;
        const Json& readings = Dyn::Or(other, Dyn::EmptyDict());
        for (auto it = readings.begin(); it != readings.end(); ++it) {
            const Json& w = it.value();
            if (!w.is_object() || Dyn::Get(w, "utilization").is_null()) continue;
            const double r = Num(Dyn::Get(w, "resetsAt"));
            if (r + 30 <= now) continue;
            const Json& found = Dyn::Get(into, it.key());
            const Json* current = found.is_object() ? &found : nullptr;
            const double cr = current ? Num(Dyn::Get(*current, "resetsAt")) : 0.0;
            if (!current || Dyn::Get(*current, "utilization").is_null() || cr + 30 <= now || r > cr || (r == cr && AsDouble(w.at("utilization")) > AsDouble(current->at("utilization")))) {
                into[it.key()] = {{"utilization", w.at("utilization")}, {"resetsAt", Dyn::Get(w, "resetsAt")}};
                changed.push_back(it.key());
            }
        }
        return changed;
    }

    Board::Board(fs::path path, std::string me, std::optional<std::string> boot, Log log)
        : path(std::move(path)), me(me.empty() ? MyKey() : std::move(me)), boot(boot ? *boot : Platform::BootId()), log(log ? std::move(log) : Log([](const std::string&) {})) {
        data = {{"version", 1}, {"drivers", Json::object()}, {"seats", Json::object()}};
    }

    void Board::Warn(const std::string& message) {
        if (warned) return;
        warned = true;
        log(std::format("board: {} - placement continues on this driver's own view", message));
    }

    Json Board::Update(const std::function<bool(Json&)>& change) {
        data = Platform::LockedUpdate(path, [&](Json& d) {
            if (!Dyn::Has(d, "version")) d["version"] = 1;
            if (!Dyn::Has(d, "drivers")) d["drivers"] = Json::object();
            if (!Dyn::Has(d, "seats")) d["seats"] = Json::object();
            return change(d);
        }, data, 0600, [this](const std::string& message) { Warn(message); });
        return data;
    }

    bool Board::Alive(std::string_view key, const Json& drivers, bool reap) const {
        if (key == me) return true;
        const std::vector<std::string> parts = Dyn::Split(key, ":", 1);
        if (parts.size() != 2 || !Dyn::ParseInt(parts[0]) || !Dyn::ParseInt(parts[1])) return false;
        const Json& d = Dyn::Or(Dyn::Get(drivers, key), Dyn::EmptyDict());
        if (!boot.empty() && Dyn::Truthy(Dyn::Get(d, "boot")) && d.at("boot") != boot) return false;
        return DriverAlive(key, path.parent_path(), reap);
    }

    std::pair<bool, std::vector<std::string>> Board::Sweep(Json& d, double now, bool reap) const {
        std::vector<std::string> lines;
        bool changed = false;
        Json& drivers = d["drivers"];
        std::vector<std::string> dead;
        for (auto it = drivers.begin(); it != drivers.end(); ++it) {
            if (!Alive(it.key(), drivers, reap)) dead.push_back(it.key());
        }
        for (const std::string& key : dead) {
            drivers.erase(key);
            changed = true;
        }
        std::vector<std::string> gone;
        Json& seats = d["seats"];
        for (auto it = seats.begin(); it != seats.end(); ++it) {
            Json& s = it.value();
            if (!Dyn::Get(s, "inflight").is_object()) s["inflight"] = Json::object();
            Json& inflight = s["inflight"];
            // {owner: entries}, in the order they were met.
            std::vector<std::pair<std::string, std::int64_t>> deadOwners;
            std::vector<std::pair<std::string, std::int64_t>> lateOwners;
            auto count = [](std::vector<std::pair<std::string, std::int64_t>>& list, const std::string& owner) {
                for (auto& [o, n] : list) {
                    if (o == owner) {
                        ++n;
                        return;
                    }
                }
                list.emplace_back(owner, 1);
            };
            std::vector<std::string> drop;
            for (auto e = inflight.begin(); e != inflight.end(); ++e) {
                const std::string owner = Owner(e.key());
                if (owner != me && !drivers.contains(owner)) {
                    count(deadOwners, owner);
                    drop.push_back(e.key());
                } else if (Num(Dyn::Get(e.value(), "deadline")) <= now) {
                    count(lateOwners, owner);
                    drop.push_back(e.key());
                }
            }
            for (const std::string& key : drop) inflight.erase(key);
            const std::string name = Dyn::StrOr(Dyn::Get(s, "id"), it.key());
            for (const auto& [owner, n] : deadOwners) lines.push_back(std::format("swept pid {} (dead) with {} in-flight entr{} on seat {}", PidOf(owner), n, n == 1 ? "y" : "ies", name));
            for (const auto& [owner, n] : lateOwners) lines.push_back(std::format("swept {} in-flight entr{} of pid {} past their deadline on seat {}", n, n == 1 ? "y" : "ies", PidOf(owner), name));
            const Json& state = Dyn::Get(s, "state");
            if (Dyn::Truthy(state)) {
                const Json& until = Dyn::Get(state, "until");
                const Json& by = Dyn::Get(state, "by");
                if (!until.is_null() ? AsDouble(until) <= now : (by != me && !(by.is_string() && drivers.contains(by.get<std::string>())))) {
                    s["state"] = nullptr;
                    changed = true;
                }
            }
            bool liveWindow = false;
            for (const Json& w : Dyn::Or(Dyn::Get(s, "windows"), Dyn::EmptyDict())) liveWindow = liveWindow || (w.is_object() && Num(Dyn::Get(w, "resetsAt")) + 30 > now);
            if (inflight.empty() && !Dyn::Truthy(Dyn::Get(s, "state")) && !liveWindow && Num(Dyn::Get(s, "pauseUntil")) <= now) gone.push_back(it.key());
        }
        for (const std::string& key : gone) {
            seats.erase(key);
            changed = true;
        }
        return {changed || !lines.empty(), lines};
    }

    Json& Board::Record(Json& d, const Json& seat) const {
        const std::string key = KeyOf(seat);
        Json& seats = d["seats"];
        if (!seats.contains(key) || seats[key].is_null()) {
            seats[key] = {{"id", seat.at("id")}, {"kind", seat.at("kind")}, {"windows", Json::object()}, {"pauseUntil", 0.0}, {"state", nullptr}, {"inflight", Json::object()}};
        }
        return seats[key];
    }

    bool Board::StateHolds(const Json& state, const Json& d, double now) {
        const Json& until = Dyn::Get(state, "until");
        if (!until.is_null()) return AsDouble(until) > now;
        const Json& by = Dyn::Get(state, "by");
        return by.is_string() && d.at("drivers").contains(by.get<std::string>());
    }

    Others Board::OthersOf(const Json& d) const {
        // Memory and stacks are the machine's, not a seat's: every other
        // driver's pass counts, whatever account it runs on.
        Others o;
        for (const Json& b : d.at("seats")) {
            const Json& inflight = Dyn::Or(Dyn::Get(b, "inflight"), Dyn::EmptyDict());
            for (auto it = inflight.begin(); it != inflight.end(); ++it) {
                if (Owner(it.key()) == me) continue;
                ++o.count;
                if (Dyn::Get(it.value(), "mb").is_null()) ++o.unmeasured;
                o.mb += Num(Dyn::Get(it.value(), "mb"));
                if (Dyn::Truthy(Dyn::Get(it.value(), "stack"))) o.stacks.insert(Dyn::Str(it.value().at("stack")));
            }
        }
        o.mb = Dyn::Round(o.mb, 1);
        return o;
    }

    std::pair<bool, std::vector<std::string>> Board::FoldInto(std::vector<Json>& seats, double now, Json& d) {
        auto [changed, lines] = Sweep(d, now);
        others = OthersOf(d);
        for (Json& s : seats) {
            Json f = ZeroForeign();
            f["drivers"] = Json::object();
            const Json& b = Dyn::Get(d.at("seats"), KeyOf(s));
            if (Dyn::Truthy(b)) {
                const Json& inflight = Dyn::Or(Dyn::Get(b, "inflight"), Dyn::EmptyDict());
                std::int64_t count = 0;
                double cost5h = 0.0;
                double cost7d = 0.0;
                double costUsd = 0.0;
                for (auto it = inflight.begin(); it != inflight.end(); ++it) {
                    const std::string owner = Owner(it.key());
                    if (owner == me) continue;
                    ++count;
                    cost5h += Num(Dyn::Get(it.value(), "cost5h"));
                    cost7d += Num(Dyn::Get(it.value(), "cost7d"));
                    costUsd += Num(Dyn::Get(it.value(), "costUsd"));
                    f["drivers"][owner] = Dyn::Has(f["drivers"], owner) ? f["drivers"][owner].get<std::int64_t>() + 1 : 1;
                }
                f["count"] = count;
                f["cost5h"] = cost5h;
                f["cost7d"] = cost7d;
                f["costUsd"] = costUsd;
                if (!IsPaid(s) && !MergeWindows(s["windows"], Dyn::Get(b, "windows"), now).empty()) Reutil(s);
                const double pause = Num(Dyn::Get(b, "pauseUntil"));
                if (pause > Num(Dyn::Get(s, "pauseUntil"))) {
                    s["pauseUntil"] = pause;
                    if (pause > now) lines.push_back(std::format("seat {}: paused until {} - another driver's limit", Id(s), Clock(pause)));
                }
                const Json& st = Dyn::Get(b, "state");
                if (Dyn::Truthy(st) && std::ranges::contains(StateShared, Kind(s)) && s.at("state") != "out" && s.at("state") != "invalid" && StateHolds(st, d, now)) {
                    s["state"] = Dyn::At(st, "state");
                    s["stateFrom"] = Dyn::Get(st, "by");
                    const Json& error = Dyn::Get(st, "error");
                    s["error"] = std::format("{} (seen by pid {})", Dyn::Truthy(error) ? Dyn::Str(error) : Dyn::Str(st.at("state")), PidOf(Dyn::StrOr(Dyn::Get(st, "by"), "?")));
                    lines.push_back(std::format("seat {}: {} - {}", Id(s), Dyn::Str(s.at("state")), Dyn::Str(s.at("error"))));
                }
            }
            f["cost5h"] = Dyn::Round(AsDouble(f.at("cost5h")), 4);
            f["cost7d"] = Dyn::Round(AsDouble(f.at("cost7d")), 4);
            f["costUsd"] = Dyn::Round(AsDouble(f.at("costUsd")), 4);
            s["foreign"] = std::move(f);
        }
        return {changed, lines};
    }

    bool Board::PublishSeat(Json& d, const Json& s, double now, bool probed) const {
        // Readings merged, pause raised, an out/invalid verdict of our own
        // written (OAuth and local seats; a paid seat's credit-out is the
        // ledger's, its budget-out this driver's alone); a seat our own probe
        // read ok clears a verdict another driver left.
        Json& b = Record(d, s);
        bool changed = !Dyn::Equal(Dyn::Get(b, "id"), s.at("id"));
        b["id"] = s.at("id");
        if (!IsPaid(s)) {
            if (!Dyn::Has(b, "windows")) b["windows"] = Json::object();
            if (!MergeWindows(b["windows"], Dyn::Get(s, "windows"), now).empty()) changed = true;
        }
        if (Num(Dyn::Get(s, "pauseUntil")) > Num(Dyn::Get(b, "pauseUntil"))) {
            b["pauseUntil"] = AsDouble(s.at("pauseUntil"));
            changed = true;
        }
        if (std::ranges::contains(StateShared, Kind(s))) {
            const Json& state = s.at("state");
            const Json& held = Dyn::Get(b, "state");
            if ((state == "out" || state == "invalid") && !Dyn::Truthy(Dyn::Get(s, "stateFrom")) && (!Dyn::Truthy(held) || Dyn::Get(held, "by") == me)) {
                Json until;
                if (state == "out") {
                    // A seven-day rejection stands until that window resets.
                    const Json& seven = Dyn::Or(Dyn::Get(Dyn::Or(Dyn::Get(s, "windows"), Dyn::EmptyDict()), "seven_day"), Dyn::EmptyDict());
                    if (Dyn::Truthy(Dyn::Get(seven, "resetsAt"))) until = AsDouble(seven.at("resetsAt")) + 30;
                }
                const Json record = {{"state", state}, {"error", Dyn::Slice(Dyn::StrOr(Dyn::Get(s, "error"), ""), 0, 160)}, {"until", until}, {"by", me}};
                if (!Dyn::Equal(held, record)) {
                    b["state"] = record;
                    changed = true;
                }
            } else if (probed && state == "ok" && Dyn::Truthy(held)) {
                b["state"] = nullptr;
                changed = true;
            }
        }
        return changed;
    }

    void Board::Join(const Json& info, double now) {
        Update([&](Json& d) {
            Sweep(d, now);
            Json entry = info;
            entry["since"] = now;
            entry["boot"] = boot;
            d["drivers"][me] = std::move(entry);
            return true;
        });
    }

    void Board::Leave() {
        try {
            Update([&](Json& d) {
                bool changed = d["drivers"].erase(me) > 0;
                for (auto it = d["seats"].begin(); it != d["seats"].end(); ++it) {
                    if (!Dyn::Get(it.value(), "inflight").is_object()) continue;
                    Json& inflight = it.value()["inflight"];
                    std::vector<std::string> mine;
                    for (auto e = inflight.begin(); e != inflight.end(); ++e) {
                        if (e.key().starts_with(std::format("{}/", me))) mine.push_back(e.key());
                    }
                    for (const std::string& key : mine) {
                        inflight.erase(key);
                        changed = true;
                    }
                }
                return changed;
            });
        } catch (const std::exception& error) {
            Warn(std::format("leave failed ({})", error.what()));
        }
    }

    void Board::Publish(const std::vector<Json>& seats, double now, bool probed) {
        Update([&](Json& d) {
            bool changed = Sweep(d, now).first;
            for (const Json& s : seats) changed = PublishSeat(d, s, now, probed) || changed;
            return changed;
        });
    }

    std::vector<std::string> Board::Fold(std::vector<Json>& seats, double now) {
        std::vector<std::string> lines;
        Update([&](Json& d) {
            auto [changed, folded] = FoldInto(seats, now, d);
            lines = std::move(folded);
            return changed;
        });
        for (const std::string& line : lines) log(std::format("board: {}", line));
        return lines;
    }

    std::int64_t Board::TotalInflight(const Json& d) {
        std::int64_t total = 0;
        for (const Json& s : Dyn::Or(Dyn::Get(d, "seats"), Dyn::EmptyDict())) total += static_cast<std::int64_t>(Dyn::Or(Dyn::Get(s, "inflight"), Dyn::EmptyDict()).size());
        return total;
    }

    std::pair<double, std::string> Board::MemoryBase(std::int64_t free, double now) {
        // MemAvailable as it was with no pass in flight on the machine. With
        // other drivers' passes in flight the recorded reading stands: those
        // passes are in the budget at what they were admitted at, and the
        // reading of now has their use taken off already - it would count
        // them twice. With no record, or a pass in flight that records no
        // memory, `free` - the safe side.
        std::optional<std::pair<double, std::string>> result;
        Update([&](Json& d) {
            const bool changed = Sweep(d, now).first;
            std::vector<const Json*> entries;
            for (const Json& s : d.at("seats")) {
                for (const Json& e : Dyn::Or(Dyn::Get(s, "inflight"), Dyn::EmptyDict())) entries.push_back(&e);
            }
            const Json memory = Dyn::Get(d, "memory").is_object() ? d.at("memory") : Json::object();
            if (entries.empty()) {
                d["memory"] = {{"freeMb", free}, {"at", now}, {"by", me}};
                result = {static_cast<double>(free), "no pass in flight on this machine"};
                return true;
            }
            std::vector<double> held;
            for (const Json* e : entries) held.push_back(Num(Dyn::Get(*e, "mb")));
            const double mb = Dyn::Sum(held);
            const std::size_t n = entries.size();
            const std::string plural = n != 1 ? "es" : "";
            if (!Dyn::Get(memory, "freeMb").is_null() && std::ranges::all_of(entries, [](const Json* e) { return !Dyn::Get(*e, "mb").is_null(); })) {
                result = {AsDouble(memory.at("freeMb")), std::format("the board's reading of {} with no pass in flight; {} pass{} of other drivers in flight hold{} {:.0f} MB of it",
                                                                     Clock(Num(Dyn::Get(memory, "at"))), n, plural, n == 1 ? "s" : "", mb)};
            } else {
                const std::string why = Dyn::Get(memory, "freeMb").is_null()
                                            ? std::string("no reading on the board")
                                            : std::format("{} of them record no memory", std::ranges::count_if(entries, [](const Json* e) { return Dyn::Get(*e, "mb").is_null(); }));
                result = {static_cast<double>(free), std::format("read now with {} pass{} of other drivers in flight ({}): their {:.0f} MB counted again, on the safe side", n, plural, why, mb)};
            }
            return changed;
        });
        return result.value_or(std::pair<double, std::string>{static_cast<double>(free), "read now"});
    }

    Board::Placed Board::Place(std::vector<Json>& seats, double now, const Json& config, const Json& apiConfig, const Chooser& chooser, std::optional<std::int64_t> cap) {
        // Two drivers polling in the same instant cannot both take the last
        // slot, the last stack or the last of the memory. `cap` is the pool
        // width, enforced across every driver on the machine (Jorijn,
        // 2026-10-18).
        Placed placed;
        std::vector<std::string> lines;
        Update([&](Json& d) {
            auto [changed, folded] = FoldInto(seats, now, d);
            lines = std::move(folded);
            placed.ranked = Ranked(seats, now, config, apiConfig);
            const std::int64_t total = TotalInflight(d);
            if (cap && total >= *cap) {
                placed.full = total;
                return changed;
            }
            placed.picked = placed.ranked.empty() ? std::nullopt : chooser(placed.ranked, others);
            if (placed.picked) {
                const Json& seat = *placed.picked->first;
                const Json& job = *placed.picked->second;
                const bool paid = IsPaid(seat);
                const Json& timeout = Dyn::Get(job, "timeoutMin");
                Json entry = {
                    {"since", now},
                    {"deadline", now + 60 * (Dyn::Truthy(timeout) ? AsDouble(timeout) : 20.0) * 1.5 + InflightGraceS},
                    {"cost5h", paid ? Json(0) : config.at("lensCostPct")},
                    {"cost7d", paid ? Json(0) : Json(Cost7d(config))},
                    {"costUsd", paid ? LensCostValue(seat, apiConfig) : Json(0)},
                };
                if (!Dyn::Get(job, "_admitted").is_null()) entry["mb"] = Dyn::Round(AsDouble(job.at("_admitted")), 1);
                if (Dyn::Truthy(Dyn::Get(job, "stackKey"))) entry["stack"] = job.at("stackKey");
                Record(d, seat)["inflight"][std::format("{}/{}", me, Dyn::Str(Dyn::At(job, "label")))] = std::move(entry);
                changed = true;
            }
            return changed;
        });
        for (const std::string& line : lines) log(std::format("board: {}", line));
        return placed;
    }

    void Board::Finish(const Json& seat, std::string_view label, double now) {
        // Off the board whether or not it is placed again, and the seat's
        // settled state onto it.
        Update([&](Json& d) {
            bool changed = Sweep(d, now).first;
            const std::string key = KeyOf(seat);
            if (Dyn::Truthy(Dyn::Get(d.at("seats"), key))) {
                Json& b = d["seats"][key];
                if (Dyn::Get(b, "inflight").is_object() && b["inflight"].erase(std::format("{}/{}", me, label)) > 0) changed = true;
            }
            return PublishSeat(d, seat, now, false) || changed;
        });
    }

    Json Board::View(double now) const {
        Json d;
        try {
            d = Dyn::LoadJsonFile(path);
        } catch (const std::exception&) {
            d = Json::object();
        }
        if (!d.is_object()) d = Json::object();
        if (!Dyn::Has(d, "drivers")) d["drivers"] = Json::object();
        if (!Dyn::Has(d, "seats")) d["seats"] = Json::object();
        // Nothing written, not even a dead driver's lock file taken away.
        Sweep(d, now, false);
        Json drivers = Json::object();
        for (auto it = d.at("drivers").begin(); it != d.at("drivers").end(); ++it) {
            Json driver = it.value();
            driver["inflight"] = 0;
            driver["mb"] = 0.0;
            driver["stacks"] = Json::array();
            drivers[it.key()] = std::move(driver);
        }
        Json seats = Json::object();
        for (auto it = d.at("seats").begin(); it != d.at("seats").end(); ++it) {
            const Json& s = it.value();
            Json by = Json::object();
            std::int64_t count = 0;
            double cost5h = 0.0;
            double cost7d = 0.0;
            double costUsd = 0.0;
            Json oldest;
            const Json& inflight = Dyn::Or(Dyn::Get(s, "inflight"), Dyn::EmptyDict());
            for (auto e = inflight.begin(); e != inflight.end(); ++e) {
                const std::string owner = Owner(e.key());
                by[owner] = Dyn::Has(by, owner) ? by[owner].get<std::int64_t>() + 1 : 1;
                ++count;
                cost5h += Num(Dyn::Get(e.value(), "cost5h"));
                cost7d += Num(Dyn::Get(e.value(), "cost7d"));
                costUsd += Num(Dyn::Get(e.value(), "costUsd"));
                const double since = Num(Dyn::Get(e.value(), "since"));
                if (oldest.is_null() || since < oldest.get<double>()) oldest = since;
                if (drivers.contains(owner)) {
                    Json& driver = drivers[owner];
                    driver["inflight"] = driver.at("inflight").get<std::int64_t>() + 1;
                    driver["mb"] = Dyn::Round(AsDouble(driver.at("mb")) + Num(Dyn::Get(e.value(), "mb")), 1);
                    if (Dyn::Truthy(Dyn::Get(e.value(), "stack"))) driver["stacks"].push_back(e.value().at("stack"));
                }
            }
            const Json& pause = Dyn::Get(s, "pauseUntil");
            seats[it.key()] = {
                {"id", Dyn::Get(s, "id")},
                {"kind", Dyn::Get(s, "kind")},
                {"inflight", count},
                {"cost5h", Dyn::Round(cost5h, 4)},
                {"cost7d", Dyn::Round(cost7d, 4)},
                {"costUsd", Dyn::Round(costUsd, 4)},
                {"by", by},
                {"oldest", oldest},
                {"windows", Dyn::Or(Dyn::Get(s, "windows"), Dyn::EmptyDict())},
                {"pauseUntil", Dyn::Truthy(pause) ? pause : Json(0)},
                {"state", Dyn::Get(s, "state")},
            };
        }
        return {{"path", path.string()}, {"drivers", drivers}, {"seats", seats}, {"memory", Dyn::Get(d, "memory")}};
    }

    std::vector<std::string> Board::OthersLines(const std::vector<Json>& seats, double, const Json& config, const Json& apiConfig, std::optional<std::int64_t> cap) const {
        Json drivers = Json::object();
        const Json& all = Dyn::Or(Dyn::Get(data, "drivers"), Dyn::EmptyDict());
        for (auto it = all.begin(); it != all.end(); ++it) {
            if (it.key() != me) drivers[it.key()] = it.value();
        }
        const std::string width = cap ? std::format("; {} in flight on this machine, the cap is {}", TotalInflight(data), *cap) : std::string();
        if (drivers.empty()) return {std::format("board: {}; no other driver running{}", path.string(), width)};
        std::vector<std::string> each;
        for (auto it = drivers.begin(); it != drivers.end(); ++it) {
            std::int64_t n = 0;
            for (const Json& s : seats) {
                const Json f = Foreign(s);
                const Json& by = Dyn::Or(Dyn::Get(f, "drivers"), Dyn::EmptyDict());
                if (Dyn::Has(by, it.key())) n += Int(AsDouble(by.at(it.key())));
            }
            const Json& d = it.value();
            each.push_back(std::format("pid {} ({}, {}) since {}, {} in flight on our seats", PidOf(it.key()), Dyn::Has(d, "run") ? Dyn::Str(d.at("run")) : std::string("?"),
                                       Dyn::Has(d, "effort") ? Dyn::Str(d.at("effort")) : std::string("?"), Platform::LocalTime("%H:%M", Num(Dyn::Get(d, "since"))), n));
        }
        std::string held;
        if (others.count) {
            held = std::format("; theirs hold {:.0f} MB of memory", others.mb);
            if (!others.stacks.empty()) {
                held += std::format(" and {} stack(s) ({})", others.stacks.size(), Dyn::Join(std::vector<std::string>(others.stacks.begin(), others.stacks.end()), ", "));
            }
        }
        std::vector<std::string> lines = {std::format("board: {}; {} other driver(s) running: {}{}{}", path.string(), drivers.size(), Dyn::Join(each, "; "), width, held)};
        for (const Json& s : seats) {
            const Json f = Foreign(s);
            if (!Dyn::Truthy(f.at("count"))) continue;
            std::vector<std::string> who;
            const Json& by = Dyn::Or(Dyn::Get(f, "drivers"), Dyn::EmptyDict());
            for (auto it = by.begin(); it != by.end(); ++it) who.push_back(std::format("{} from pid {}", Dyn::Str(it.value()), PidOf(it.key())));
            const std::int64_t count = Int(AsDouble(f.at("count")));
            if (IsPaid(s)) {
                const std::int64_t c = Concurrency(s, apiConfig);
                lines.push_back(std::format("  seat {}: {} in flight ({}) - {} of {} slots free, ${:.2f} reserved", Id(s), count, Dyn::Join(who, ", "), std::max<std::int64_t>(0, c - count - Running(s)), c,
                                            AsDouble(f.at("costUsd"))));
            } else if (Seats::BurstWindow(s.at("windows")) == "seven_day") {
                lines.push_back(std::format("  seat {}: {} passes in flight ({}) - projected 7d {:.1f} %, no 5-hour limit", Id(s), count, Dyn::Join(who, ", "), OauthProjected(s, config)));
            } else {
                lines.push_back(std::format("  seat {}: {} passes in flight ({}) - projected 5h {:.1f} %", Id(s), count, Dyn::Join(who, ", "), OauthProjected(s, config)));
            }
        }
        return lines;
    }

    const Others& Board::OthersNow() const {
        return others;
    }

    const std::string& Board::Me() const {
        return me;
    }

    const fs::path& Board::Path() const {
        return path;
    }

    const Json& Board::Data() const {
        return data;
    }

    // ---- reporting -----------------------------------------------------------------------------
    Json Summary(const std::vector<Json>& seats) {
        Json out = Json::array();
        for (const Json& s : seats) {
            Json copy = s;
            copy.erase("secret");
            out.push_back(std::move(copy));
        }
        return out;
    }

    std::string Table(const std::vector<Json>& seats, std::optional<double> nowGiven) {
        const double now = NowOr(nowGiven);
        std::vector<std::vector<std::string>> rows = {{"seat", "kind", "state", "5h", "7d", "fable", "running", "foreign", "done", "spent", "note"}};
        for (const Json& s : seats) {
            const Json& windows = s.at("windows");
            auto w = [&](std::string_view k) { return Seats::WindowCell(windows, k); };
            std::string fable = "—";
            for (auto it = windows.begin(); it != windows.end(); ++it) {
                if (Seats::IsFableWindow(it.key()) && !Dyn::Get(it.value(), "utilization").is_null()) {
                    fable = std::format("{}%", Seats::Fmt(it.value().at("utilization")));
                    break;
                }
            }
            std::string note;
            if (s.at("state") != "ok") {
                note = Dyn::Slice(Dyn::StrOr(s.at("error"), ""), 0, 60);
            } else if (AsDouble(s.at("pauseUntil")) > now) {
                note = std::format("paused until {}", Platform::LocalTime("%H:%M", AsDouble(s.at("pauseUntil"))));
            }
            const Json f = Foreign(s);
            rows.push_back({Id(s), Kind(s), Dyn::Str(s.at("state")), w("five_hour"), w("seven_day"), fable, Dyn::Str(s.at("running")),
                            Dyn::Truthy(f.at("count")) ? Dyn::Str(f.at("count")) : std::string("—"), Dyn::Str(s.at("procs")),
                            IsPaid(s) ? std::format("${:.2f}", AsDouble(s.at("spentUsd"))) : std::string("—"), note});
        }
        return Seats::RenderTable(rows);
    }
}