dgb: wire subsidy_func into embedded work source coinbasevalue (Phase B)

src/c2pool/main_dgb.cpp

@@ -277,7 +277,8 @@ int run_node(const core::CoinParams& params, bool testnet,
     // (declared just above, same scope). The StratumServer co-owns the work
     // source via shared_ptr.
     auto work_source = std::make_shared<dgb::stratum::DGBWorkSource>(
-        header_chain, mempool, testnet, std::move(stratum_submit_fn));
+        header_chain, mempool, testnet, std::move(stratum_submit_fn),
+        params.subsidy_func);
 
     if (stratum_port != 0) {
         stratum_server = std::make_unique<core::StratumServer>(

src/impl/dgb/stratum/work_source.cpp

@@ -17,6 +17,7 @@
 
 #include <impl/dgb/coin/header_chain.hpp>
 #include <impl/dgb/coin/mempool.hpp>
+#include <impl/dgb/coin/embedded_coinbase_value.hpp>
 
 #include <core/log.hpp>
 
@@ -26,23 +27,42 @@ DGBWorkSource::DGBWorkSource(c2pool::dgb::HeaderChain&     chain,
                              dgb::coin::Mempool&           mempool,
                              bool                          is_testnet,
                              SubmitBlockFn                 submit_fn,
+                             core::SubsidyFunc             subsidy_func,
                              core::stratum::StratumConfig  config)
     : chain_(chain)
     , mempool_(mempool)
     , is_testnet_(is_testnet)
     , submit_block_fn_(std::move(submit_fn))
+    , subsidy_func_(std::move(subsidy_func))
     , config_(std::move(config))
 {
     LOG_INFO << "[DGB-STRATUM] DGBWorkSource constructed"
              << " (testnet=" << is_testnet_
              << " min_diff=" << config_.min_difficulty
              << " max_diff=" << config_.max_difficulty
              << " target_time=" << config_.target_time
-             << "s vardiff=" << (config_.vardiff_enabled ? "on" : "off") << ")";
+             << "s vardiff=" << (config_.vardiff_enabled ? "on" : "off")
+             << " subsidy_func=" << (subsidy_func_ ? "wired" : "UNSET") << ")";
 }
 
 DGBWorkSource::~DGBWorkSource() = default;
 
+// ──────────────────────────────────────────────────────────────────
+// Embedded coinbasevalue — first PRODUCTION caller of CoinParams::subsidy_func.
+// Delegates to the dgb::coin SSOT (embedded_coinbase_value.hpp) so the embedded
+// TemplateBuilder coinbasevalue and the external-daemon GBT coinbasevalue are
+// computed from ONE definition and can never silently diverge. The GBT value,
+// when present, is authoritative and returned verbatim (external-daemon
+// fallback MUST PERSIST); otherwise subsidy_func(height)+fees is derived from
+// the DGB oracle decay schedule.
+// ──────────────────────────────────────────────────────────────────
+uint64_t DGBWorkSource::coinbase_value(uint32_t height, uint64_t total_fees,
+                                       std::optional<uint64_t> gbt_coinbasevalue) const
+{
+    return dgb::coin::resolve_coinbase_value(subsidy_func_, height, total_fees,
+                                             gbt_coinbasevalue);
+}
+
 // ─────────────────────────────────────────────────────────────────────────────
 // IWorkSource: config + read-only state — Stage 4b will fill these in.
 // ─────────────────────────────────────────────────────────────────────────────

src/impl/dgb/stratum/work_source.hpp

@@ -41,13 +41,15 @@
 
 #include <core/stratum_work_source.hpp>
 #include <core/uint256.hpp>
+#include <core/pow.hpp>       // core::SubsidyFunc — embedded coinbasevalue SSOT feed
 
 #include <atomic>
 #include <cstdint>
 #include <functional>
 #include <map>
 #include <memory>
 #include <mutex>
+#include <optional>
 #include <string>
 #include <utility>
 #include <vector>
@@ -83,6 +85,7 @@ class DGBWorkSource : public core::stratum::IWorkSource
                   dgb::coin::Mempool&           mempool,
                   bool                          is_testnet,
                   SubmitBlockFn                 submit_fn,
+                  core::SubsidyFunc             subsidy_func,
                   core::stratum::StratumConfig  config = {});
     ~DGBWorkSource() override;
 
@@ -160,6 +163,16 @@ class DGBWorkSource : public core::stratum::IWorkSource
     /// is constructed.
     void set_best_share_hash_fn(std::function<uint256()> fn);
 
+    /// Embedded-path coinbasevalue for the template builder (Stage 4c).
+    /// Routes through dgb::coin::resolve_coinbase_value: when the external
+    /// digibyted GBT supplied a coinbasevalue it is returned verbatim (the
+    /// external-daemon fallback that MUST PERSIST); otherwise the value is
+    /// derived locally as subsidy_func(height) + total_fees from the DGB
+    /// oracle decay schedule. First PRODUCTION invocation site of
+    /// CoinParams::subsidy_func (SSOT guarded by test_dgb_coinbase_value).
+    uint64_t coinbase_value(uint32_t height, uint64_t total_fees,
+                            std::optional<uint64_t> gbt_coinbasevalue) const;
+
 private:
     // External dependencies (non-owning references)
     c2pool::dgb::HeaderChain&   chain_;
@@ -169,6 +182,10 @@ class DGBWorkSource : public core::stratum::IWorkSource
     // Submission dispatch
     SubmitBlockFn               submit_block_fn_;
 
+    // Embedded coinbasevalue SSOT feed (CoinParams::subsidy_func). Drives the
+    // template builder's coinbasevalue when no external-daemon GBT value.
+    core::SubsidyFunc           subsidy_func_;
+
     // Config (held by value; const after construction in MVP)
     core::stratum::StratumConfig config_;
 

src/impl/dgb/test/work_source_test.cpp

@@ -16,15 +16,23 @@
 #include <impl/dgb/stratum/work_source.hpp>
 #include <impl/dgb/coin/header_chain.hpp>
 #include <impl/dgb/coin/mempool.hpp>
+#include <impl/dgb/config_coin.hpp>   // dgb::CoinParams::subsidy (oracle SSOT)
+
+#include <core/pow.hpp>                 // core::SubsidyFunc
 
 #include <core/stratum_work_source.hpp>
 
 #include <gtest/gtest.h>
 
 #include <memory>
+#include <optional>
 
 namespace {
 
+// IDENTICAL to params.hpp `p.subsidy_func` — the live CoinParams indirection.
+const core::SubsidyFunc kSubsidyFunc =
+    [](uint32_t height) -> uint64_t { return dgb::CoinParams::subsidy(height); };
+
 // Construct a DGBWorkSource over default-constructed coin deps. The submit
 // callback records whether it was invoked (it must NOT be in the 4a skeleton).
 struct Fixture {
@@ -39,7 +47,7 @@ struct Fixture {
             return false;
         };
         return std::make_unique<dgb::stratum::DGBWorkSource>(
-            chain, mempool, /*is_testnet=*/false, fn);
+            chain, mempool, /*is_testnet=*/false, fn, kSubsidyFunc);
     }
 };
 
@@ -166,4 +174,55 @@ TEST(DgbWorkSource, ComputeShareDifficultyReturnsNotYetSentinel)
     EXPECT_DOUBLE_EQ(diff, 0.0);
 }
 
+// ── Embedded coinbasevalue: first production caller of subsidy_func ──────────
+// One pin on each side of every DGB reward-era boundary (p2pool-dgb-scrypt
+// oracle vectors, test_dgb_subsidy.cpp).
+namespace {
+struct EraVec { uint32_t height; uint64_t subsidy; const char* era; };
+constexpr EraVec kEraBoundaries[] = {
+    {67199,   8000000000ULL, "phase1-fixed last"},
+    {67200,   7960000000ULL, "phase2 -0.5%/wk first"},
+    {399999,  6746441103ULL, "phase2 last"},
+    {400000,  2434410000ULL, "phase3 -1%/wk first"},
+    {1429999, 2157824200ULL, "phase3 last"},
+    {1430000, 1078500000ULL, "phase4 monthly-decay first"},
+};
+}  // namespace
+
+// No external GBT (embedded path): coinbasevalue is derived THROUGH the work
+// source's subsidy_func at every era boundary, zero fees -> oracle subsidy.
+TEST(DgbWorkSource, CoinbaseValueDerivesViaSubsidyFuncWhenNoGbt)
+{
+    Fixture fx;
+    auto ws = fx.make();
+    for (const auto& v : kEraBoundaries) {
+        EXPECT_EQ(ws->coinbase_value(v.height, /*fees=*/0, std::nullopt), v.subsidy)
+            << "embedded coinbasevalue diverged from oracle subsidy at " << v.era;
+    }
+}
+
+// Fees compose additively on the embedded path: subsidy + total_fees.
+TEST(DgbWorkSource, CoinbaseValueAddsFeesOnEmbeddedPath)
+{
+    Fixture fx;
+    auto ws = fx.make();
+    constexpr uint64_t kFees = 1234567ULL;
+    for (const auto& v : kEraBoundaries) {
+        EXPECT_EQ(ws->coinbase_value(v.height, kFees, std::nullopt), v.subsidy + kFees)
+            << "fee addition wrong at " << v.era;
+    }
+}
+
+// External-daemon fallback PERSISTS: a present GBT coinbasevalue is authoritative
+// and returned verbatim through the work source, bypassing local derivation.
+TEST(DgbWorkSource, CoinbaseValueHonorsGbtVerbatim)
+{
+    Fixture fx;
+    auto ws = fx.make();
+    constexpr uint64_t kGbt = 99999999999ULL;  // deliberately != subsidy+fees
+    EXPECT_EQ(ws->coinbase_value(/*height=*/400000, /*fees=*/500,
+                                 std::optional<uint64_t>{kGbt}),
+              kGbt);
+}
+
 }  // namespace