Merge bitcoin/bitcoin#29523: Wallet: Add `max_tx_weight` to transaction funding options (take 2)

734076c6de1781f957c8bc3bf7ed6951920cfcf6 [wallet, rpc]: add `max_tx_weight` to tx funding options (ismaelsadeeq)
b6fc5043c16c2467a2a6768a6ca9b18035fc400f [wallet]: update the data type of `change_output_size`, `change_spend_size` and `tx_noinputs_size` to `int` (ismaelsadeeq)
baab0d2d43049a71dc90176bc4d72062f7b2ce19 [doc]: update reason for deducting change output weight (ismaelsadeeq)
7f61d31a5cec8fc61328bee43f90d3f1dcb0a035 [refactor]: update coin selection algorithms input parameter `max_weight` name (ismaelsadeeq)

Pull request description:

  This PR taken over from #29264

  The PR added an option `max_tx_weight` to transaction funding RPC's that ensures the resulting transaction weight does not exceed the specified `max_tx_weight` limit.

  If `max_tx_weight` is not given `MAX_STANDARD_TX_WEIGHT` is used as the max threshold.

  This PR addressed outstanding review comments in #29264

  For more context and rationale behind this PR see https://delvingbitcoin.org/t/lightning-transactions-with-v3-and-ephemeral-anchors/418/11?u=instagibbs

ACKs for top commit:
  achow101:
    ACK 734076c6de1781f957c8bc3bf7ed6951920cfcf6
  furszy:
    utACK 734076c6de1781f957c8bc3bf7ed6951920cfcf6
  rkrux:
    reACK [734076c](https://github.com/bitcoin/bitcoin/pull/29523/commits/734076c6de1781f957c8bc3bf7ed6951920cfcf6)

Tree-SHA512: 013501aa443d239ee2ac01bccfc5296490c27b4edebe5cfca6b96c842375e895e5cfeb5424e82e359be581460f8be92095855763a62779a18ccd5bdfdd7ddce7

7 files changed, 129 insertions, 76 deletions

diff --git a/src/wallet/coincontrol.h b/src/wallet/coincontrol.h
index b2f813383d..d36314312a 100644
--- a/src/wallet/coincontrol.h
+++ b/src/wallet/coincontrol.h
@@ -115,6 +115,8 @@ public:
     std::optional<uint32_t> m_locktime;
     //! Version
     std::optional<uint32_t> m_version;
+    //! Caps weight of resulting tx
+    std::optional<int> m_max_tx_weight{std::nullopt};
 
     CCoinControl();
 
diff --git a/src/wallet/coinselection.cpp b/src/wallet/coinselection.cpp
index edde912ce0..b6fee37c95 100644
--- a/src/wallet/coinselection.cpp
+++ b/src/wallet/coinselection.cpp
@@ -84,14 +84,14 @@ struct {
  *        bound of the range.
  * @param const CAmount& cost_of_change This is the cost of creating and spending a change output.
  *        This plus selection_target is the upper bound of the range.
- * @param int max_weight The maximum weight available for the input set.
+ * @param int max_selection_weight The maximum allowed weight for a selection result to be valid.
  * @returns The result of this coin selection algorithm, or std::nullopt
  */
 
 static const size_t TOTAL_TRIES = 100000;
 
 util::Result<SelectionResult> SelectCoinsBnB(std::vector<OutputGroup>& utxo_pool, const CAmount& selection_target, const CAmount& cost_of_change,
-                                             int max_weight)
+                                             int max_selection_weight)
 {
     SelectionResult result(selection_target, SelectionAlgorithm::BNB);
     CAmount curr_value = 0;
@@ -128,7 +128,7 @@ util::Result<SelectionResult> SelectCoinsBnB(std::vector<OutputGroup>& utxo_pool
             curr_value > selection_target + cost_of_change || // Selected value is out of range, go back and try other branch
             (curr_waste > best_waste && is_feerate_high)) { // Don't select things which we know will be more wasteful if the waste is increasing
             backtrack = true;
-        } else if (curr_selection_weight > max_weight) { // Exceeding weight for standard tx, cannot find more solutions by adding more inputs
+        } else if (curr_selection_weight > max_selection_weight) { // Selected UTXOs weight exceeds the maximum weight allowed, cannot find more solutions by adding more inputs
             max_tx_weight_exceeded = true; // at least one selection attempt exceeded the max weight
             backtrack = true;
         } else if (curr_value >= selection_target) {       // Selected value is within range
@@ -319,10 +319,10 @@ util::Result<SelectionResult> SelectCoinsBnB(std::vector<OutputGroup>& utxo_pool
  *        group with multiple as a heavier UTXO with the combined amount here.)
  * @param const CAmount& selection_target This is the minimum amount that we need for the transaction without considering change.
  * @param const CAmount& change_target The minimum budget for creating a change output, by which we increase the selection_target.
- * @param int max_weight The maximum permitted weight for the input set.
+ * @param int max_selection_weight The maximum allowed weight for a selection result to be valid.
  * @returns The result of this coin selection algorithm, or std::nullopt
  */
-util::Result<SelectionResult> CoinGrinder(std::vector<OutputGroup>& utxo_pool, const CAmount& selection_target, CAmount change_target, int max_weight)
+util::Result<SelectionResult> CoinGrinder(std::vector<OutputGroup>& utxo_pool, const CAmount& selection_target, CAmount change_target, int max_selection_weight)
 {
     std::sort(utxo_pool.begin(), utxo_pool.end(), descending_effval_weight);
     // The sum of UTXO amounts after this UTXO index, e.g. lookahead[5] = Σ(UTXO[6+].amount)
@@ -359,7 +359,7 @@ util::Result<SelectionResult> CoinGrinder(std::vector<OutputGroup>& utxo_pool, c
 
     // The weight of the currently selected input set, and the weight of the best selection
     int curr_weight = 0;
-    int best_selection_weight = max_weight; // Tie is fine, because we prefer lower selection amount
+    int best_selection_weight = max_selection_weight; // Tie is fine, because we prefer lower selection amount
 
     // Whether the input sets generated during this search have exceeded the maximum transaction weight at any point
     bool max_tx_weight_exceeded = false;
@@ -436,8 +436,8 @@ util::Result<SelectionResult> CoinGrinder(std::vector<OutputGroup>& utxo_pool, c
             // Insufficient funds with lookahead: CUT
             should_cut = true;
         } else if (curr_weight > best_selection_weight) {
-            // best_selection_weight is initialized to max_weight
-            if (curr_weight > max_weight) max_tx_weight_exceeded = true;
+            // best_selection_weight is initialized to max_selection_weight
+            if (curr_weight > max_selection_weight) max_tx_weight_exceeded = true;
             // Worse weight than best solution. More UTXOs only increase weight:
             // CUT if last selected group had minimal weight, else SHIFT
             if (utxo_pool[curr_tail].m_weight <= min_tail_weight[curr_tail]) {
@@ -535,7 +535,7 @@ public:
 };
 
 util::Result<SelectionResult> SelectCoinsSRD(const std::vector<OutputGroup>& utxo_pool, CAmount target_value, CAmount change_fee, FastRandomContext& rng,
-                                             int max_weight)
+                                             int max_selection_weight)
 {
     SelectionResult result(target_value, SelectionAlgorithm::SRD);
     std::priority_queue<OutputGroup, std::vector<OutputGroup>, MinOutputGroupComparator> heap;
@@ -565,14 +565,14 @@ util::Result<SelectionResult> SelectCoinsSRD(const std::vector<OutputGroup>& utx
 
         // If the selection weight exceeds the maximum allowed size, remove the least valuable inputs until we
         // are below max weight.
-        if (weight > max_weight) {
+        if (weight > max_selection_weight) {
             max_tx_weight_exceeded = true; // mark it in case we don't find any useful result.
             do {
                 const OutputGroup& to_remove_group = heap.top();
                 selected_eff_value -= to_remove_group.GetSelectionAmount();
                 weight -= to_remove_group.m_weight;
                 heap.pop();
-            } while (!heap.empty() && weight > max_weight);
+            } while (!heap.empty() && weight > max_selection_weight);
         }
 
         // Now check if we are above the target
@@ -597,11 +597,12 @@ util::Result<SelectionResult> SelectCoinsSRD(const std::vector<OutputGroup>& utx
  *                              nTargetValue, with indices corresponding to groups. If the ith
  *                              entry is true, that means the ith group in groups was selected.
  * param@[out]  nBest           Total amount of subset chosen that is closest to nTargetValue.
+ * paramp[in]   max_selection_weight  The maximum allowed weight for a selection result to be valid.
  * param@[in]   iterations      Maximum number of tries.
  */
 static void ApproximateBestSubset(FastRandomContext& insecure_rand, const std::vector<OutputGroup>& groups,
                                   const CAmount& nTotalLower, const CAmount& nTargetValue,
-                                  std::vector<char>& vfBest, CAmount& nBest, int iterations = 1000)
+                                  std::vector<char>& vfBest, CAmount& nBest, int max_selection_weight, int iterations = 1000)
 {
     std::vector<char> vfIncluded;
 
@@ -613,6 +614,7 @@ static void ApproximateBestSubset(FastRandomContext& insecure_rand, const std::v
     {
         vfIncluded.assign(groups.size(), false);
         CAmount nTotal = 0;
+        int selected_coins_weight{0};
         bool fReachedTarget = false;
         for (int nPass = 0; nPass < 2 && !fReachedTarget; nPass++)
         {
@@ -627,9 +629,9 @@ static void ApproximateBestSubset(FastRandomContext& insecure_rand, const std::v
                 if (nPass == 0 ? insecure_rand.randbool() : !vfIncluded[i])
                 {
                     nTotal += groups[i].GetSelectionAmount();
+                    selected_coins_weight += groups[i].m_weight;
                     vfIncluded[i] = true;
-                    if (nTotal >= nTargetValue)
-                    {
+                    if (nTotal >= nTargetValue && selected_coins_weight <= max_selection_weight) {
                         fReachedTarget = true;
                         // If the total is between nTargetValue and nBest, it's our new best
                         // approximation.
@@ -639,6 +641,7 @@ static void ApproximateBestSubset(FastRandomContext& insecure_rand, const std::v
                             vfBest = vfIncluded;
                         }
                         nTotal -= groups[i].GetSelectionAmount();
+                        selected_coins_weight -= groups[i].m_weight;
                         vfIncluded[i] = false;
                     }
                 }
@@ -648,10 +651,11 @@ static void ApproximateBestSubset(FastRandomContext& insecure_rand, const std::v
 }
 
 util::Result<SelectionResult> KnapsackSolver(std::vector<OutputGroup>& groups, const CAmount& nTargetValue,
-                                             CAmount change_target, FastRandomContext& rng, int max_weight)
+                                             CAmount change_target, FastRandomContext& rng, int max_selection_weight)
 {
     SelectionResult result(nTargetValue, SelectionAlgorithm::KNAPSACK);
 
+    bool max_weight_exceeded{false};
     // List of values less than target
     std::optional<OutputGroup> lowest_larger;
     // Groups with selection amount smaller than the target and any change we might produce.
@@ -662,6 +666,10 @@ util::Result<SelectionResult> KnapsackSolver(std::vector<OutputGroup>& groups, c
     std::shuffle(groups.begin(), groups.end(), rng);
 
     for (const OutputGroup& group : groups) {
+        if (group.m_weight > max_selection_weight) {
+            max_weight_exceeded = true;
+            continue;
+        }
         if (group.GetSelectionAmount() == nTargetValue) {
             result.AddInput(group);
             return result;
@@ -677,11 +685,18 @@ util::Result<SelectionResult> KnapsackSolver(std::vector<OutputGroup>& groups, c
         for (const auto& group : applicable_groups) {
             result.AddInput(group);
         }
-        return result;
+        if (result.GetWeight() <= max_selection_weight) return result;
+        else max_weight_exceeded = true;
+
+        // Try something else
+        result.Clear();
     }
 
     if (nTotalLower < nTargetValue) {
-        if (!lowest_larger) return util::Error();
+        if (!lowest_larger) {
+            if (max_weight_exceeded) return ErrorMaxWeightExceeded();
+            return util::Error();
+        }
         result.AddInput(*lowest_larger);
         return result;
     }
@@ -691,9 +706,9 @@ util::Result<SelectionResult> KnapsackSolver(std::vector<OutputGroup>& groups, c
     std::vector<char> vfBest;
     CAmount nBest;
 
-    ApproximateBestSubset(rng, applicable_groups, nTotalLower, nTargetValue, vfBest, nBest);
+    ApproximateBestSubset(rng, applicable_groups, nTotalLower, nTargetValue, vfBest, nBest, max_selection_weight);
     if (nBest != nTargetValue && nTotalLower >= nTargetValue + change_target) {
-        ApproximateBestSubset(rng, applicable_groups, nTotalLower, nTargetValue + change_target, vfBest, nBest);
+        ApproximateBestSubset(rng, applicable_groups, nTotalLower, nTargetValue + change_target, vfBest, nBest, max_selection_weight);
     }
 
     // If we have a bigger coin and (either the stochastic approximation didn't find a good solution,
@@ -709,7 +724,7 @@ util::Result<SelectionResult> KnapsackSolver(std::vector<OutputGroup>& groups, c
         }
 
         // If the result exceeds the maximum allowed size, return closest UTXO above the target
-        if (result.GetWeight() > max_weight) {
+        if (result.GetWeight() > max_selection_weight) {
             // No coin above target, nothing to do.
             if (!lowest_larger) return ErrorMaxWeightExceeded();
 
@@ -728,7 +743,7 @@ util::Result<SelectionResult> KnapsackSolver(std::vector<OutputGroup>& groups, c
             LogPrint(BCLog::SELECTCOINS, "%stotal %s\n", log_message, FormatMoney(nBest));
         }
     }
-
+    Assume(result.GetWeight() <= max_selection_weight);
     return result;
 }
 
diff --git a/src/wallet/coinselection.h b/src/wallet/coinselection.h
index 416273be7a..08889c8e06 100644
--- a/src/wallet/coinselection.h
+++ b/src/wallet/coinselection.h
@@ -139,9 +139,9 @@ struct CoinSelectionParams {
     /** Randomness to use in the context of coin selection. */
     FastRandomContext& rng_fast;
     /** Size of a change output in bytes, determined by the output type. */
-    size_t change_output_size = 0;
+    int change_output_size = 0;
     /** Size of the input to spend a change output in virtual bytes. */
-    size_t change_spend_size = 0;
+    int change_spend_size = 0;
     /** Mininmum change to target in Knapsack solver and CoinGrinder:
      * select coins to cover the payment and at least this value of change. */
     CAmount m_min_change_target{0};
@@ -162,7 +162,7 @@ struct CoinSelectionParams {
     CFeeRate m_discard_feerate;
     /** Size of the transaction before coin selection, consisting of the header and recipient
      * output(s), excluding the inputs and change output(s). */
-    size_t tx_noinputs_size = 0;
+    int tx_noinputs_size = 0;
     /** Indicate that we are subtracting the fee from outputs */
     bool m_subtract_fee_outputs = false;
     /** When true, always spend all (up to OUTPUT_GROUP_MAX_ENTRIES) or none of the outputs
@@ -174,10 +174,13 @@ struct CoinSelectionParams {
      * 1) Received from other wallets, 2) replacing other txs, 3) that have been replaced.
      */
     bool m_include_unsafe_inputs = false;
+    /** The maximum weight for this transaction. */
+    std::optional<int> m_max_tx_weight{std::nullopt};
 
-    CoinSelectionParams(FastRandomContext& rng_fast, size_t change_output_size, size_t change_spend_size,
+    CoinSelectionParams(FastRandomContext& rng_fast, int change_output_size, int change_spend_size,
                         CAmount min_change_target, CFeeRate effective_feerate,
-                        CFeeRate long_term_feerate, CFeeRate discard_feerate, size_t tx_noinputs_size, bool avoid_partial)
+                        CFeeRate long_term_feerate, CFeeRate discard_feerate, int tx_noinputs_size, bool avoid_partial,
+                        std::optional<int> max_tx_weight = std::nullopt)
         : rng_fast{rng_fast},
           change_output_size(change_output_size),
           change_spend_size(change_spend_size),
@@ -186,7 +189,8 @@ struct CoinSelectionParams {
           m_long_term_feerate(long_term_feerate),
           m_discard_feerate(discard_feerate),
           tx_noinputs_size(tx_noinputs_size),
-          m_avoid_partial_spends(avoid_partial)
+          m_avoid_partial_spends(avoid_partial),
+          m_max_tx_weight(max_tx_weight)
     {
     }
     CoinSelectionParams(FastRandomContext& rng_fast)
@@ -440,9 +444,9 @@ public:
 };
 
 util::Result<SelectionResult> SelectCoinsBnB(std::vector<OutputGroup>& utxo_pool, const CAmount& selection_target, const CAmount& cost_of_change,
-                                             int max_weight);
+                                             int max_selection_weight);
 
-util::Result<SelectionResult> CoinGrinder(std::vector<OutputGroup>& utxo_pool, const CAmount& selection_target, CAmount change_target, int max_weight);
+util::Result<SelectionResult> CoinGrinder(std::vector<OutputGroup>& utxo_pool, const CAmount& selection_target, CAmount change_target, int max_selection_weight);
 
 /** Select coins by Single Random Draw. OutputGroups are selected randomly from the eligible
  * outputs until the target is satisfied
@@ -450,15 +454,15 @@ util::Result<SelectionResult> CoinGrinder(std::vector<OutputGroup>& utxo_pool, c
  * @param[in]  utxo_pool    The positive effective value OutputGroups eligible for selection
  * @param[in]  target_value The target value to select for
  * @param[in]  rng The randomness source to shuffle coins
- * @param[in]  max_weight The maximum allowed weight for a selection result to be valid
+ * @param[in]  max_selection_weight The maximum allowed weight for a selection result to be valid
  * @returns If successful, a valid SelectionResult, otherwise, util::Error
  */
 util::Result<SelectionResult> SelectCoinsSRD(const std::vector<OutputGroup>& utxo_pool, CAmount target_value, CAmount change_fee, FastRandomContext& rng,
-                                             int max_weight);
+                                             int max_selection_weight);
 
 // Original coin selection algorithm as a fallback
 util::Result<SelectionResult> KnapsackSolver(std::vector<OutputGroup>& groups, const CAmount& nTargetValue,
-                                             CAmount change_target, FastRandomContext& rng, int max_weight);
+                                             CAmount change_target, FastRandomContext& rng, int max_selection_weight);
 } // namespace wallet
 
 #endif // BITCOIN_WALLET_COINSELECTION_H
diff --git a/src/wallet/rpc/spend.cpp b/src/wallet/rpc/spend.cpp
index ac2a4826f0..8ea51e65c7 100644
--- a/src/wallet/rpc/spend.cpp
+++ b/src/wallet/rpc/spend.cpp
@@ -542,6 +542,7 @@ CreatedTransactionResult FundTransaction(CWallet& wallet, const CMutableTransact
                 {"minconf", UniValueType(UniValue::VNUM)},
                 {"maxconf", UniValueType(UniValue::VNUM)},
                 {"input_weights", UniValueType(UniValue::VARR)},
+                {"max_tx_weight", UniValueType(UniValue::VNUM)},
             },
             true, true);
 
@@ -701,6 +702,10 @@ CreatedTransactionResult FundTransaction(CWallet& wallet, const CMutableTransact
         }
     }
 
+    if (options.exists("max_tx_weight")) {
+        coinControl.m_max_tx_weight = options["max_tx_weight"].getInt<int>();
+    }
+
     if (recipients.empty())
         throw JSONRPCError(RPC_INVALID_PARAMETER, "TX must have at least one output");
 
@@ -786,6 +791,8 @@ RPCHelpMan fundrawtransaction()
                                     },
                                 },
                              },
+                            {"max_tx_weight", RPCArg::Type::NUM, RPCArg::Default{MAX_STANDARD_TX_WEIGHT}, "The maximum acceptable transaction weight.\n"
+                                                          "Transaction building will fail if this can not be satisfied."},
                         },
                         FundTxDoc()),
                         RPCArgOptions{
@@ -1240,6 +1247,8 @@ RPCHelpMan send()
                             {"vout_index", RPCArg::Type::NUM, RPCArg::Optional::OMITTED, "The zero-based output index, before a change output is added."},
                         },
                     },
+                    {"max_tx_weight", RPCArg::Type::NUM, RPCArg::Default{MAX_STANDARD_TX_WEIGHT}, "The maximum acceptable transaction weight.\n"
+                                                  "Transaction building will fail if this can not be satisfied."},
                 },
                 FundTxDoc()),
                 RPCArgOptions{.oneline_description="options"}},
@@ -1287,6 +1296,9 @@ RPCHelpMan send()
             // Automatically select coins, unless at least one is manually selected. Can
             // be overridden by options.add_inputs.
             coin_control.m_allow_other_inputs = rawTx.vin.size() == 0;
+            if (options.exists("max_tx_weight")) {
+                coin_control.m_max_tx_weight = options["max_tx_weight"].getInt<int>();
+            }
             SetOptionsInputWeights(options["inputs"], options);
             // Clear tx.vout since it is not meant to be used now that we are passing outputs directly.
             // This sets us up for a future PR to completely remove tx from the function signature in favor of passing inputs directly
@@ -1697,6 +1709,8 @@ RPCHelpMan walletcreatefundedpsbt()
                                     {"vout_index", RPCArg::Type::NUM, RPCArg::Optional::OMITTED, "The zero-based output index, before a change output is added."},
                                 },
                             },
+                            {"max_tx_weight", RPCArg::Type::NUM, RPCArg::Default{MAX_STANDARD_TX_WEIGHT}, "The maximum acceptable transaction weight.\n"
+                                                          "Transaction building will fail if this can not be satisfied."},
                         },
                         FundTxDoc()),
                         RPCArgOptions{.oneline_description="options"}},
diff --git a/src/wallet/spend.cpp b/src/wallet/spend.cpp
index 11a42eb469..7abf7f59c0 100644
--- a/src/wallet/spend.cpp
+++ b/src/wallet/spend.cpp
@@ -695,26 +695,35 @@ util::Result<SelectionResult> ChooseSelectionResult(interfaces::Chain& chain, co
         }
     };
 
-    // Maximum allowed weight
-    int max_inputs_weight = MAX_STANDARD_TX_WEIGHT - (coin_selection_params.tx_noinputs_size * WITNESS_SCALE_FACTOR);
+    // Maximum allowed weight for selected coins.
+    int max_transaction_weight = coin_selection_params.m_max_tx_weight.value_or(MAX_STANDARD_TX_WEIGHT);
+    int tx_weight_no_input = coin_selection_params.tx_noinputs_size * WITNESS_SCALE_FACTOR;
+    int max_selection_weight = max_transaction_weight - tx_weight_no_input;
+    if (max_selection_weight <= 0) {
+        return util::Error{_("Maximum transaction weight is less than transaction weight without inputs")};
+    }
 
     // SFFO frequently causes issues in the context of changeless input sets: skip BnB when SFFO is active
     if (!coin_selection_params.m_subtract_fee_outputs) {
-        if (auto bnb_result{SelectCoinsBnB(groups.positive_group, nTargetValue, coin_selection_params.m_cost_of_change, max_inputs_weight)}) {
+        if (auto bnb_result{SelectCoinsBnB(groups.positive_group, nTargetValue, coin_selection_params.m_cost_of_change, max_selection_weight)}) {
             results.push_back(*bnb_result);
         } else append_error(std::move(bnb_result));
     }
 
-    // As Knapsack and SRD can create change, also deduce change weight.
-    max_inputs_weight -= (coin_selection_params.change_output_size * WITNESS_SCALE_FACTOR);
+    // Deduct change weight because remaining Coin Selection algorithms can create change output
+    int change_outputs_weight = coin_selection_params.change_output_size * WITNESS_SCALE_FACTOR;
+    max_selection_weight -= change_outputs_weight;
+    if (max_selection_weight < 0 && results.empty()) {
+        return util::Error{_("Maximum transaction weight is too low, can not accommodate change output")};
+    }
 
     // The knapsack solver has some legacy behavior where it will spend dust outputs. We retain this behavior, so don't filter for positive only here.
-    if (auto knapsack_result{KnapsackSolver(groups.mixed_group, nTargetValue, coin_selection_params.m_min_change_target, coin_selection_params.rng_fast, max_inputs_weight)}) {
+    if (auto knapsack_result{KnapsackSolver(groups.mixed_group, nTargetValue, coin_selection_params.m_min_change_target, coin_selection_params.rng_fast, max_selection_weight)}) {
         results.push_back(*knapsack_result);
     } else append_error(std::move(knapsack_result));
 
     if (coin_selection_params.m_effective_feerate > CFeeRate{3 * coin_selection_params.m_long_term_feerate}) { // Minimize input set for feerates of at least 3×LTFRE (default: 30 ṩ/vB+)
-        if (auto cg_result{CoinGrinder(groups.positive_group, nTargetValue, coin_selection_params.m_min_change_target, max_inputs_weight)}) {
+        if (auto cg_result{CoinGrinder(groups.positive_group, nTargetValue, coin_selection_params.m_min_change_target, max_selection_weight)}) {
             cg_result->RecalculateWaste(coin_selection_params.min_viable_change, coin_selection_params.m_cost_of_change, coin_selection_params.m_change_fee);
             results.push_back(*cg_result);
         } else {
@@ -722,7 +731,7 @@ util::Result<SelectionResult> ChooseSelectionResult(interfaces::Chain& chain, co
         }
     }
 
-    if (auto srd_result{SelectCoinsSRD(groups.positive_group, nTargetValue, coin_selection_params.m_change_fee, coin_selection_params.rng_fast, max_inputs_weight)}) {
+    if (auto srd_result{SelectCoinsSRD(groups.positive_group, nTargetValue, coin_selection_params.m_change_fee, coin_selection_params.rng_fast, max_selection_weight)}) {
         results.push_back(*srd_result);
     } else append_error(std::move(srd_result));
 
@@ -801,7 +810,7 @@ util::Result<SelectionResult> SelectCoins(const CWallet& wallet, CoinsResult& av
                                                 coin_selection_params.m_change_fee);
 
         // Verify we haven't exceeded the maximum allowed weight
-        int max_inputs_weight = MAX_STANDARD_TX_WEIGHT - (coin_selection_params.tx_noinputs_size * WITNESS_SCALE_FACTOR);
+        int max_inputs_weight = coin_selection_params.m_max_tx_weight.value_or(MAX_STANDARD_TX_WEIGHT) - (coin_selection_params.tx_noinputs_size * WITNESS_SCALE_FACTOR);
         if (op_selection_result->GetWeight() > max_inputs_weight) {
             return util::Error{_("The combination of the pre-selected inputs and the wallet automatic inputs selection exceeds the transaction maximum weight. "
                                  "Please try sending a smaller amount or manually consolidating your wallet's UTXOs")};
@@ -1012,7 +1021,11 @@ static util::Result<CreatedTransactionResult> CreateTransactionInternal(
     CoinSelectionParams coin_selection_params{rng_fast}; // Parameters for coin selection, init with dummy
     coin_selection_params.m_avoid_partial_spends = coin_control.m_avoid_partial_spends;
     coin_selection_params.m_include_unsafe_inputs = coin_control.m_include_unsafe_inputs;
-
+    coin_selection_params.m_max_tx_weight = coin_control.m_max_tx_weight.value_or(MAX_STANDARD_TX_WEIGHT);
+    int minimum_tx_weight = MIN_STANDARD_TX_NONWITNESS_SIZE * WITNESS_SCALE_FACTOR;
+    if (coin_selection_params.m_max_tx_weight.value() < minimum_tx_weight || coin_selection_params.m_max_tx_weight.value() > MAX_STANDARD_TX_WEIGHT) {
+        return util::Error{strprintf(_("Maximum transaction weight must be between %d and %d"), minimum_tx_weight, MAX_STANDARD_TX_WEIGHT)};
+    }
     // Set the long term feerate estimate to the wallet's consolidate feerate
     coin_selection_params.m_long_term_feerate = wallet.m_consolidate_feerate;
     // Static vsize overhead + outputs vsize. 4 nVersion, 4 nLocktime, 1 input count, 1 witness overhead (dummy, flag, stack size)
@@ -1077,7 +1090,7 @@ static util::Result<CreatedTransactionResult> CreateTransactionInternal(
     if (change_spend_size == -1) {
         coin_selection_params.change_spend_size = DUMMY_NESTED_P2WPKH_INPUT_SIZE;
     } else {
-        coin_selection_params.change_spend_size = (size_t)change_spend_size;
+        coin_selection_params.change_spend_size = change_spend_size;
     }
 
     // Set discard feerate
diff --git a/src/wallet/test/coinselector_tests.cpp b/src/wallet/test/coinselector_tests.cpp
index 7bd92b471c..eb9c349c22 100644
--- a/src/wallet/test/coinselector_tests.cpp
+++ b/src/wallet/test/coinselector_tests.cpp
@@ -1097,13 +1097,13 @@ BOOST_AUTO_TEST_CASE(effective_value_test)
 static util::Result<SelectionResult> CoinGrinder(const CAmount& target,
                                                     const CoinSelectionParams& cs_params,
                                                     const node::NodeContext& m_node,
-                                                    int max_weight,
+                                                    int max_selection_weight,
                                                     std::function<CoinsResult(CWallet&)> coin_setup)
 {
     std::unique_ptr<CWallet> wallet = NewWallet(m_node);
     CoinEligibilityFilter filter(0, 0, 0); // accept all coins without ancestors
     Groups group = GroupOutputs(*wallet, coin_setup(*wallet), cs_params, {{filter}})[filter].all_groups;
-    return CoinGrinder(group.positive_group, target, cs_params.m_min_change_target, max_weight);
+    return CoinGrinder(group.positive_group, target, cs_params.m_min_change_target, max_selection_weight);
 }
 
 BOOST_AUTO_TEST_CASE(coin_grinder_tests)
@@ -1135,8 +1135,8 @@ BOOST_AUTO_TEST_CASE(coin_grinder_tests)
         // 1) Insufficient funds, select all provided coins and fail
         // #########################################################
         CAmount target = 49.5L * COIN;
-        int max_weight = 10'000; // high enough to not fail for this reason.
-        const auto& res = CoinGrinder(target, dummy_params, m_node, max_weight, [&](CWallet& wallet) {
+        int max_selection_weight = 10'000; // high enough to not fail for this reason.
+        const auto& res = CoinGrinder(target, dummy_params, m_node, max_selection_weight, [&](CWallet& wallet) {
             CoinsResult available_coins;
             for (int j = 0; j < 10; ++j) {
                 add_coin(available_coins, wallet, CAmount(1 * COIN));
@@ -1153,8 +1153,8 @@ BOOST_AUTO_TEST_CASE(coin_grinder_tests)
         // 2) Test max weight exceeded
         // ###########################
         CAmount target = 29.5L * COIN;
-        int max_weight = 3000;
-        const auto& res = CoinGrinder(target, dummy_params, m_node, max_weight, [&](CWallet& wallet) {
+        int max_selection_weight = 3000;
+        const auto& res = CoinGrinder(target, dummy_params, m_node, max_selection_weight, [&](CWallet& wallet) {
             CoinsResult available_coins;
             for (int j = 0; j < 10; ++j) {
                 add_coin(available_coins, wallet, CAmount(1 * COIN), CFeeRate(5000), 144, false, 0, true);
@@ -1171,8 +1171,8 @@ BOOST_AUTO_TEST_CASE(coin_grinder_tests)
         // 3) Test selection when some coins surpass the max allowed weight while others not. --> must find a good solution
         // ################################################################################################################
         CAmount target = 25.33L * COIN;
-        int max_weight = 10'000; // WU
-        const auto& res = CoinGrinder(target, dummy_params, m_node, max_weight, [&](CWallet& wallet) {
+        int max_selection_weight = 10'000; // WU
+        const auto& res = CoinGrinder(target, dummy_params, m_node, max_selection_weight, [&](CWallet& wallet) {
             CoinsResult available_coins;
             for (int j = 0; j < 60; ++j) { // 60 UTXO --> 19,8 BTC total --> 60 × 272 WU = 16320 WU
                 add_coin(available_coins, wallet, CAmount(0.33 * COIN), CFeeRate(5000), 144, false, 0, true);
@@ -1193,8 +1193,8 @@ BOOST_AUTO_TEST_CASE(coin_grinder_tests)
         // 4) Test that two less valuable UTXOs with a combined lower weight are preferred over a more valuable heavier UTXO
         // #################################################################################################################
         CAmount target =  1.9L * COIN;
-        int max_weight = 400'000; // WU
-        const auto& res = CoinGrinder(target, dummy_params, m_node, max_weight, [&](CWallet& wallet) {
+        int max_selection_weight = 400'000; // WU
+        const auto& res = CoinGrinder(target, dummy_params, m_node, max_selection_weight, [&](CWallet& wallet) {
             CoinsResult available_coins;
             add_coin(available_coins, wallet, CAmount(2 * COIN), CFeeRate(5000), 144, false, 0, true, 148);
             add_coin(available_coins, wallet, CAmount(1 * COIN), CFeeRate(5000), 144, false, 0, true, 68);
@@ -1215,8 +1215,8 @@ BOOST_AUTO_TEST_CASE(coin_grinder_tests)
         // 5) Test finding a solution in a UTXO pool with mixed weights
         // ################################################################################################################
         CAmount target = 30L * COIN;
-        int max_weight = 400'000; // WU
-        const auto& res = CoinGrinder(target, dummy_params, m_node, max_weight, [&](CWallet& wallet) {
+        int max_selection_weight = 400'000; // WU
+        const auto& res = CoinGrinder(target, dummy_params, m_node, max_selection_weight, [&](CWallet& wallet) {
             CoinsResult available_coins;
             for (int j = 0; j < 5; ++j) {
                 // Add heavy coins {3, 6, 9, 12, 15}
@@ -1244,8 +1244,8 @@ BOOST_AUTO_TEST_CASE(coin_grinder_tests)
         // 6) Test that the lightest solution among many clones is found
         // #################################################################################################################
         CAmount target =  9.9L * COIN;
-        int max_weight = 400'000; // WU
-        const auto& res = CoinGrinder(target, dummy_params, m_node, max_weight, [&](CWallet& wallet) {
+        int max_selection_weight = 400'000; // WU
+        const auto& res = CoinGrinder(target, dummy_params, m_node, max_selection_weight, [&](CWallet& wallet) {
             CoinsResult available_coins;
             // Expected Result: 4 + 3 + 2 + 1 = 10 BTC at 400 vB
             add_coin(available_coins, wallet, CAmount(4 * COIN), CFeeRate(5000), 144, false, 0, true, 100);
@@ -1283,8 +1283,8 @@ BOOST_AUTO_TEST_CASE(coin_grinder_tests)
         // 7) Test that lots of tiny UTXOs can be skipped if they are too heavy while there are enough funds in lookahead
         // #################################################################################################################
         CAmount target =  1.9L * COIN;
-        int max_weight = 40000; // WU
-        const auto& res = CoinGrinder(target, dummy_params, m_node, max_weight, [&](CWallet& wallet) {
+        int max_selection_weight = 40000; // WU
+        const auto& res = CoinGrinder(target, dummy_params, m_node, max_selection_weight, [&](CWallet& wallet) {
             CoinsResult available_coins;
             add_coin(available_coins, wallet, CAmount(1.8 * COIN), CFeeRate(5000), 144, false, 0, true, 2500);
             add_coin(available_coins, wallet, CAmount(1 * COIN), CFeeRate(5000), 144, false, 0, true, 1000);
@@ -1308,13 +1308,13 @@ BOOST_AUTO_TEST_CASE(coin_grinder_tests)
 static util::Result<SelectionResult> SelectCoinsSRD(const CAmount& target,
                                                     const CoinSelectionParams& cs_params,
                                                     const node::NodeContext& m_node,
-                                                    int max_weight,
+                                                    int max_selection_weight,
                                                     std::function<CoinsResult(CWallet&)> coin_setup)
 {
     std::unique_ptr<CWallet> wallet = NewWallet(m_node);
     CoinEligibilityFilter filter(0, 0, 0); // accept all coins without ancestors
     Groups group = GroupOutputs(*wallet, coin_setup(*wallet), cs_params, {{filter}})[filter].all_groups;
-    return SelectCoinsSRD(group.positive_group, target, cs_params.m_change_fee, cs_params.rng_fast, max_weight);
+    return SelectCoinsSRD(group.positive_group, target, cs_params.m_change_fee, cs_params.rng_fast, max_selection_weight);
 }
 
 BOOST_AUTO_TEST_CASE(srd_tests)
@@ -1342,8 +1342,8 @@ BOOST_AUTO_TEST_CASE(srd_tests)
         // 1) Insufficient funds, select all provided coins and fail
         // #########################################################
         CAmount target = 49.5L * COIN;
-        int max_weight = 10000; // high enough to not fail for this reason.
-        const auto& res = SelectCoinsSRD(target, dummy_params, m_node, max_weight, [&](CWallet& wallet) {
+        int max_selection_weight = 10000; // high enough to not fail for this reason.
+        const auto& res = SelectCoinsSRD(target, dummy_params, m_node, max_selection_weight, [&](CWallet& wallet) {
             CoinsResult available_coins;
             for (int j = 0; j < 10; ++j) {
                 add_coin(available_coins, wallet, CAmount(1 * COIN));
@@ -1360,8 +1360,8 @@ BOOST_AUTO_TEST_CASE(srd_tests)
         // 2) Test max weight exceeded
         // ###########################
         CAmount target = 49.5L * COIN;
-        int max_weight = 3000;
-        const auto& res = SelectCoinsSRD(target, dummy_params, m_node, max_weight, [&](CWallet& wallet) {
+        int max_selection_weight = 3000;
+        const auto& res = SelectCoinsSRD(target, dummy_params, m_node, max_selection_weight, [&](CWallet& wallet) {
             CoinsResult available_coins;
             for (int j = 0; j < 10; ++j) {
                 /* 10 × 1 BTC + 10 × 2 BTC = 30 BTC. 20 × 272 WU = 5440 WU */
@@ -1379,8 +1379,8 @@ BOOST_AUTO_TEST_CASE(srd_tests)
         // 3) Test selection when some coins surpass the max allowed weight while others not. --> must find a good solution
         // ################################################################################################################
         CAmount target = 25.33L * COIN;
-        int max_weight = 10000; // WU
-        const auto& res = SelectCoinsSRD(target, dummy_params, m_node, max_weight, [&](CWallet& wallet) {
+        int max_selection_weight = 10000; // WU
+        const auto& res = SelectCoinsSRD(target, dummy_params, m_node, max_selection_weight, [&](CWallet& wallet) {
             CoinsResult available_coins;
             for (int j = 0; j < 60; ++j) { // 60 UTXO --> 19,8 BTC total --> 60 × 272 WU = 16320 WU
                 add_coin(available_coins, wallet, CAmount(0.33 * COIN), CFeeRate(0), 144, false, 0, true);
@@ -1415,7 +1415,7 @@ static bool has_coin(const CoinSet& set, CAmount amount)
     return std::any_of(set.begin(), set.end(), [&](const auto& coin) { return coin->GetEffectiveValue() == amount; });
 }
 
-BOOST_AUTO_TEST_CASE(check_max_weight)
+BOOST_AUTO_TEST_CASE(check_max_selection_weight)
 {
     const CAmount target = 49.5L * COIN;
     CCoinControl cc;
diff --git a/src/wallet/test/fuzz/coinselection.cpp b/src/wallet/test/fuzz/coinselection.cpp
index 644a8dd7ad..209c87fd42 100644
--- a/src/wallet/test/fuzz/coinselection.cpp
+++ b/src/wallet/test/fuzz/coinselection.cpp
@@ -195,11 +195,11 @@ FUZZ_TARGET(coin_grinder_is_optimal)
 
     if (best_weight < std::numeric_limits<int>::max()) {
         // Sufficient funds and acceptable weight: CoinGrinder should find at least one solution
-        int high_max_weight = fuzzed_data_provider.ConsumeIntegralInRange<int>(best_weight, std::numeric_limits<int>::max());
+        int high_max_selection_weight = fuzzed_data_provider.ConsumeIntegralInRange<int>(best_weight, std::numeric_limits<int>::max());
 
-        auto result_cg = CoinGrinder(group_pos, target, coin_params.m_min_change_target, high_max_weight);
+        auto result_cg = CoinGrinder(group_pos, target, coin_params.m_min_change_target, high_max_selection_weight);
         assert(result_cg);
-        assert(result_cg->GetWeight() <= high_max_weight);
+        assert(result_cg->GetWeight() <= high_max_selection_weight);
         assert(result_cg->GetSelectedEffectiveValue() >= target + coin_params.m_min_change_target);
         assert(best_weight < result_cg->GetWeight() || (best_weight == result_cg->GetWeight() && best_amount <= result_cg->GetSelectedEffectiveValue()));
         if (result_cg->GetAlgoCompleted()) {
@@ -210,8 +210,8 @@ FUZZ_TARGET(coin_grinder_is_optimal)
     }
 
     // CoinGrinder cannot ever find a better solution than the brute-forced best, or there is none in the first place
-    int low_max_weight = fuzzed_data_provider.ConsumeIntegralInRange<int>(0, best_weight - 1);
-    auto result_cg = CoinGrinder(group_pos, target, coin_params.m_min_change_target, low_max_weight);
+    int low_max_selection_weight = fuzzed_data_provider.ConsumeIntegralInRange<int>(0, best_weight - 1);
+    auto result_cg = CoinGrinder(group_pos, target, coin_params.m_min_change_target, low_max_selection_weight);
     // Max_weight should have been exceeded, or there were insufficient funds
     assert(!result_cg);
 }
@@ -256,29 +256,34 @@ FUZZ_TARGET(coinselection)
         (void)group.EligibleForSpending(filter);
     }
 
+    int max_selection_weight = fuzzed_data_provider.ConsumeIntegralInRange<int>(0, std::numeric_limits<int>::max());
+
     // Run coinselection algorithms
     auto result_bnb = coin_params.m_subtract_fee_outputs ? util::Error{Untranslated("BnB disabled when SFFO is enabled")} :
-                      SelectCoinsBnB(group_pos, target, coin_params.m_cost_of_change, MAX_STANDARD_TX_WEIGHT);
+                      SelectCoinsBnB(group_pos, target, coin_params.m_cost_of_change, max_selection_weight);
     if (result_bnb) {
         assert(result_bnb->GetChange(coin_params.min_viable_change, coin_params.m_change_fee) == 0);
         assert(result_bnb->GetSelectedValue() >= target);
+        assert(result_bnb->GetWeight() <= max_selection_weight);
         (void)result_bnb->GetShuffledInputVector();
         (void)result_bnb->GetInputSet();
     }
 
-    auto result_srd = SelectCoinsSRD(group_pos, target, coin_params.m_change_fee, fast_random_context, MAX_STANDARD_TX_WEIGHT);
+    auto result_srd = SelectCoinsSRD(group_pos, target, coin_params.m_change_fee, fast_random_context, max_selection_weight);
     if (result_srd) {
         assert(result_srd->GetSelectedValue() >= target);
         assert(result_srd->GetChange(CHANGE_LOWER, coin_params.m_change_fee) > 0); // Demonstrate that SRD creates change of at least CHANGE_LOWER
+        assert(result_srd->GetWeight() <= max_selection_weight);
         result_srd->RecalculateWaste(coin_params.min_viable_change, coin_params.m_cost_of_change, coin_params.m_change_fee);
         (void)result_srd->GetShuffledInputVector();
         (void)result_srd->GetInputSet();
     }
 
     CAmount change_target{GenerateChangeTarget(target, coin_params.m_change_fee, fast_random_context)};
-    auto result_knapsack = KnapsackSolver(group_all, target, change_target, fast_random_context, MAX_STANDARD_TX_WEIGHT);
+    auto result_knapsack = KnapsackSolver(group_all, target, change_target, fast_random_context, max_selection_weight);
     if (result_knapsack) {
         assert(result_knapsack->GetSelectedValue() >= target);
+        assert(result_knapsack->GetWeight() <= max_selection_weight);
         result_knapsack->RecalculateWaste(coin_params.min_viable_change, coin_params.m_cost_of_change, coin_params.m_change_fee);
         (void)result_knapsack->GetShuffledInputVector();
         (void)result_knapsack->GetInputSet();