diff --git a/src/libcmd/installables.cc b/src/libcmd/installables.cc
index 415d63d876c..9ae24b44c45 100644
--- a/src/libcmd/installables.cc
+++ b/src/libcmd/installables.cc
@@ -583,16 +583,12 @@ static void throwBuildErrors(std::vector<KeyedBuildResult> & buildResults, const
     auto failedResult = failed.begin();
     if (failedResult != failed.end()) {
         if (failed.size() == 1) {
-            failedResult->second->rethrow();
+            throw *failedResult->second;
         } else {
             StringSet failedPaths;
             for (; failedResult != failed.end(); failedResult++) {
-                if (!failedResult->second->errorMsg.empty()) {
-                    logError(
-                        ErrorInfo{
-                            .level = lvlError,
-                            .msg = failedResult->second->errorMsg,
-                        });
+                if (!failedResult->second->message().empty()) {
+                    logError(failedResult->second->info());
                 }
                 failedPaths.insert(failedResult->first->path.to_string(store));
             }
diff --git a/src/libstore-c/nix_api_store.cc b/src/libstore-c/nix_api_store.cc
index d164efd596d..158c142836c 100644
--- a/src/libstore-c/nix_api_store.cc
+++ b/src/libstore-c/nix_api_store.cc
@@ -182,10 +182,8 @@ nix_err nix_store_realise(
         assert(results.size() == 1);
 
         // Check if any builds failed
-        for (auto & result : results) {
-            if (auto * failureP = result.tryGetFailure())
-                failureP->rethrow();
-        }
+        for (auto & result : results)
+            result.tryThrowBuildError();
 
         if (callback) {
             for (const auto & result : results) {
diff --git a/src/libstore-tests/build-result.cc b/src/libstore-tests/build-result.cc
index 85e799c2a73..b7e8f83f9e7 100644
--- a/src/libstore-tests/build-result.cc
+++ b/src/libstore-tests/build-result.cc
@@ -1,6 +1,7 @@
 #include <gtest/gtest.h>
 
 #include "nix/store/build-result.hh"
+#include "nix/util/tests/characterization.hh"
 #include "nix/util/tests/json-characterization.hh"
 
 namespace nix {
@@ -44,22 +45,22 @@ INSTANTIATE_TEST_SUITE_P(
         std::pair{
             "not-deterministic",
             BuildResult{
-                .inner{BuildResult::Failure{
+                .inner{BuildResult::Failure{{
                     .status = BuildResult::Failure::NotDeterministic,
-                    .errorMsg = "no idea why",
+                    .msg = HintFmt("no idea why"),
                     .isNonDeterministic = false, // Note: This field is separate from the status
-                }},
+                }}},
                 .timesBuilt = 1,
             },
         },
         std::pair{
             "output-rejected",
             BuildResult{
-                .inner{BuildResult::Failure{
+                .inner{BuildResult::Failure{{
                     .status = BuildResult::Failure::OutputRejected,
-                    .errorMsg = "no idea why",
+                    .msg = HintFmt("no idea why"),
                     .isNonDeterministic = false,
-                }},
+                }}},
                 .timesBuilt = 3,
                 .startTime = 30,
                 .stopTime = 50,
diff --git a/src/libstore-tests/serve-protocol.cc b/src/libstore-tests/serve-protocol.cc
index 4be4b006015..b7be7b56d65 100644
--- a/src/libstore-tests/serve-protocol.cc
+++ b/src/libstore-tests/serve-protocol.cc
@@ -147,14 +147,14 @@ VERSIONED_READ_CHARACTERIZATION_TEST(
 VERSIONED_CHARACTERIZATION_TEST(ServeProtoTest, buildResult_2_2, "build-result-2.2", 2 << 8 | 2, ({
                                     using namespace std::literals::chrono_literals;
                                     std::tuple<BuildResult, BuildResult, BuildResult> t{
-                                        BuildResult{.inner{BuildResult::Failure{
+                                        BuildResult{.inner{BuildResult::Failure{{
                                             .status = BuildResult::Failure::OutputRejected,
-                                            .errorMsg = "no idea why",
-                                        }}},
-                                        BuildResult{.inner{BuildResult::Failure{
+                                            .msg = HintFmt("no idea why"),
+                                        }}}},
+                                        BuildResult{.inner{BuildResult::Failure{{
                                             .status = BuildResult::Failure::NotDeterministic,
-                                            .errorMsg = "no idea why",
-                                        }}},
+                                            .msg = HintFmt("no idea why"),
+                                        }}}},
                                         BuildResult{.inner{BuildResult::Success{
                                             .status = BuildResult::Success::Built,
                                         }}},
@@ -165,16 +165,16 @@ VERSIONED_CHARACTERIZATION_TEST(ServeProtoTest, buildResult_2_2, "build-result-2
 VERSIONED_CHARACTERIZATION_TEST(ServeProtoTest, buildResult_2_3, "build-result-2.3", 2 << 8 | 3, ({
                                     using namespace std::literals::chrono_literals;
                                     std::tuple<BuildResult, BuildResult, BuildResult> t{
-                                        BuildResult{.inner{BuildResult::Failure{
+                                        BuildResult{.inner{BuildResult::Failure{{
                                             .status = BuildResult::Failure::OutputRejected,
-                                            .errorMsg = "no idea why",
-                                        }}},
+                                            .msg = HintFmt("no idea why"),
+                                        }}}},
                                         BuildResult{
-                                            .inner{BuildResult::Failure{
+                                            .inner{BuildResult::Failure{{
                                                 .status = BuildResult::Failure::NotDeterministic,
-                                                .errorMsg = "no idea why",
+                                                .msg = HintFmt("no idea why"),
                                                 .isNonDeterministic = true,
-                                            }},
+                                            }}},
                                             .timesBuilt = 3,
                                             .startTime = 30,
                                             .stopTime = 50,
@@ -194,16 +194,16 @@ VERSIONED_CHARACTERIZATION_TEST(
     ServeProtoTest, buildResult_2_6, "build-result-2.6", 2 << 8 | 6, ({
         using namespace std::literals::chrono_literals;
         std::tuple<BuildResult, BuildResult, BuildResult> t{
-            BuildResult{.inner{BuildResult::Failure{
+            BuildResult{.inner{BuildResult::Failure{{
                 .status = BuildResult::Failure::OutputRejected,
-                .errorMsg = "no idea why",
-            }}},
+                .msg = HintFmt("no idea why"),
+            }}}},
             BuildResult{
-                .inner{BuildResult::Failure{
+                .inner{BuildResult::Failure{{
                     .status = BuildResult::Failure::NotDeterministic,
-                    .errorMsg = "no idea why",
+                    .msg = HintFmt("no idea why"),
                     .isNonDeterministic = true,
-                }},
+                }}},
                 .timesBuilt = 3,
                 .startTime = 30,
                 .stopTime = 50,
diff --git a/src/libstore-tests/worker-protocol.cc b/src/libstore-tests/worker-protocol.cc
index ac4aafe7bf3..ea3be80efc0 100644
--- a/src/libstore-tests/worker-protocol.cc
+++ b/src/libstore-tests/worker-protocol.cc
@@ -200,14 +200,14 @@ VERSIONED_READ_CHARACTERIZATION_TEST(
 VERSIONED_CHARACTERIZATION_TEST(WorkerProtoTest, buildResult_1_27, "build-result-1.27", 1 << 8 | 27, ({
                                     using namespace std::literals::chrono_literals;
                                     std::tuple<BuildResult, BuildResult, BuildResult> t{
-                                        BuildResult{.inner{BuildResult::Failure{
+                                        BuildResult{.inner{BuildResult::Failure{{
                                             .status = BuildResult::Failure::OutputRejected,
-                                            .errorMsg = "no idea why",
-                                        }}},
-                                        BuildResult{.inner{BuildResult::Failure{
+                                            .msg = HintFmt("no idea why"),
+                                        }}}},
+                                        BuildResult{.inner{BuildResult::Failure{{
                                             .status = BuildResult::Failure::NotDeterministic,
-                                            .errorMsg = "no idea why",
-                                        }}},
+                                            .msg = HintFmt("no idea why"),
+                                        }}}},
                                         BuildResult{.inner{BuildResult::Success{
                                             .status = BuildResult::Success::Built,
                                         }}},
@@ -219,14 +219,14 @@ VERSIONED_CHARACTERIZATION_TEST(
     WorkerProtoTest, buildResult_1_28, "build-result-1.28", 1 << 8 | 28, ({
         using namespace std::literals::chrono_literals;
         std::tuple<BuildResult, BuildResult, BuildResult> t{
-            BuildResult{.inner{BuildResult::Failure{
+            BuildResult{.inner{BuildResult::Failure{{
                 .status = BuildResult::Failure::OutputRejected,
-                .errorMsg = "no idea why",
-            }}},
-            BuildResult{.inner{BuildResult::Failure{
+                .msg = HintFmt("no idea why"),
+            }}}},
+            BuildResult{.inner{BuildResult::Failure{{
                 .status = BuildResult::Failure::NotDeterministic,
-                .errorMsg = "no idea why",
-            }}},
+                .msg = HintFmt("no idea why"),
+            }}}},
             BuildResult{.inner{BuildResult::Success{
                 .status = BuildResult::Success::Built,
                 .builtOutputs =
@@ -265,16 +265,16 @@ VERSIONED_CHARACTERIZATION_TEST(
     WorkerProtoTest, buildResult_1_29, "build-result-1.29", 1 << 8 | 29, ({
         using namespace std::literals::chrono_literals;
         std::tuple<BuildResult, BuildResult, BuildResult> t{
-            BuildResult{.inner{BuildResult::Failure{
+            BuildResult{.inner{BuildResult::Failure{{
                 .status = BuildResult::Failure::OutputRejected,
-                .errorMsg = "no idea why",
-            }}},
+                .msg = HintFmt("no idea why"),
+            }}}},
             BuildResult{
-                .inner{BuildResult::Failure{
+                .inner{BuildResult::Failure{{
                     .status = BuildResult::Failure::NotDeterministic,
-                    .errorMsg = "no idea why",
+                    .msg = HintFmt("no idea why"),
                     .isNonDeterministic = true,
-                }},
+                }}},
                 .timesBuilt = 3,
                 .startTime = 30,
                 .stopTime = 50,
@@ -324,16 +324,16 @@ VERSIONED_CHARACTERIZATION_TEST(
     WorkerProtoTest, buildResult_1_37, "build-result-1.37", 1 << 8 | 37, ({
         using namespace std::literals::chrono_literals;
         std::tuple<BuildResult, BuildResult, BuildResult> t{
-            BuildResult{.inner{BuildResult::Failure{
+            BuildResult{.inner{BuildResult::Failure{{
                 .status = BuildResult::Failure::OutputRejected,
-                .errorMsg = "no idea why",
-            }}},
+                .msg = HintFmt("no idea why"),
+            }}}},
             BuildResult{
-                .inner{BuildResult::Failure{
+                .inner{BuildResult::Failure{{
                     .status = BuildResult::Failure::NotDeterministic,
-                    .errorMsg = "no idea why",
+                    .msg = HintFmt("no idea why"),
                     .isNonDeterministic = true,
-                }},
+                }}},
                 .timesBuilt = 3,
                 .startTime = 30,
                 .stopTime = 50,
@@ -385,22 +385,22 @@ VERSIONED_CHARACTERIZATION_TEST(WorkerProtoTest, keyedBuildResult_1_29, "keyed-b
                                     using namespace std::literals::chrono_literals;
                                     std::tuple<KeyedBuildResult, KeyedBuildResult /*, KeyedBuildResult*/> t{
                                         KeyedBuildResult{
-                                            {.inner{BuildResult::Failure{
+                                            BuildResult{.inner{KeyedBuildResult::Failure{{
                                                 .status = KeyedBuildResult::Failure::OutputRejected,
-                                                .errorMsg = "no idea why",
-                                            }}},
+                                                .msg = HintFmt("no idea why"),
+                                            }}}},
                                             /* .path = */
                                             DerivedPath::Opaque{
                                                 StorePath{"g1w7hy3qg1w7hy3qg1w7hy3qg1w7hy3q-xxx"},
                                             },
                                         },
                                         KeyedBuildResult{
-                                            {
-                                                .inner{BuildResult::Failure{
+                                            BuildResult{
+                                                .inner{KeyedBuildResult::Failure{{
                                                     .status = KeyedBuildResult::Failure::NotDeterministic,
-                                                    .errorMsg = "no idea why",
+                                                    .msg = HintFmt("no idea why"),
                                                     .isNonDeterministic = true,
-                                                }},
+                                                }}},
                                                 .timesBuilt = 3,
                                                 .startTime = 30,
                                                 .stopTime = 50,
diff --git a/src/libstore/build-result.cc b/src/libstore/build-result.cc
index 19fb0024949..5abb451ac83 100644
--- a/src/libstore/build-result.cc
+++ b/src/libstore/build-result.cc
@@ -10,9 +10,6 @@ std::strong_ordering BuildResult::operator<=>(const BuildResult &) const noexcep
 bool BuildResult::Success::operator==(const BuildResult::Success &) const noexcept = default;
 std::strong_ordering BuildResult::Success::operator<=>(const BuildResult::Success &) const noexcept = default;
 
-bool BuildResult::Failure::operator==(const BuildResult::Failure &) const noexcept = default;
-std::strong_ordering BuildResult::Failure::operator<=>(const BuildResult::Failure &) const noexcept = default;
-
 static constexpr std::array<std::pair<BuildResult::Success::Status, std::string_view>, 4> successStatusStrings{{
 #define ENUM_ENTRY(e) {BuildResult::Success::e, #e}
     ENUM_ENTRY(Built),
@@ -75,9 +72,18 @@ static BuildResult::Failure::Status failureStatusFromString(std::string_view str
     throw Error("unknown built result failure status '%s'", str);
 }
 
-[[noreturn]] void BuildResult::Failure::rethrow() const
+bool BuildError::operator==(const BuildError & other) const noexcept
+{
+    return status == other.status && isNonDeterministic == other.isNonDeterministic && message() == other.message();
+}
+
+std::strong_ordering BuildError::operator<=>(const BuildError & other) const noexcept
 {
-    throw BuildError(status, "%s", errorMsg);
+    if (auto cmp = status <=> other.status; cmp != 0)
+        return cmp;
+    if (auto cmp = isNonDeterministic <=> other.isNonDeterministic; cmp != 0)
+        return cmp;
+    return message() <=> other.message();
 }
 
 } // namespace nix
@@ -113,7 +119,7 @@ void adl_serializer<BuildResult>::to_json(json & res, const BuildResult & br)
             [&](const BuildResult::Failure & failure) {
                 res["success"] = false;
                 res["status"] = failureStatusToString(failure.status);
-                res["errorMsg"] = failure.errorMsg;
+                res["errorMsg"] = failure.message();
                 res["isNonDeterministic"] = failure.isNonDeterministic;
             },
         },
@@ -148,11 +154,11 @@ BuildResult adl_serializer<BuildResult>::from_json(const json & _json)
         s.builtOutputs = valueAt(json, "builtOutputs");
         br.inner = std::move(s);
     } else {
-        BuildResult::Failure f;
-        f.status = failureStatusFromString(statusStr);
-        f.errorMsg = getString(valueAt(json, "errorMsg"));
-        f.isNonDeterministic = getBoolean(valueAt(json, "isNonDeterministic"));
-        br.inner = std::move(f);
+        br.inner = BuildResult::Failure{{
+            .status = failureStatusFromString(statusStr),
+            .msg = HintFmt(getString(valueAt(json, "errorMsg"))),
+            .isNonDeterministic = getBoolean(valueAt(json, "isNonDeterministic")),
+        }};
     }
 
     return br;
diff --git a/src/libstore/build/derivation-building-goal.cc b/src/libstore/build/derivation-building-goal.cc
index b161bfb9900..cca80feb49a 100644
--- a/src/libstore/build/derivation-building-goal.cc
+++ b/src/libstore/build/derivation-building-goal.cc
@@ -1210,13 +1210,7 @@ Goal::Done DerivationBuildingGoal::doneFailure(BuildError ex)
 
     worker.updateProgress();
 
-    return Goal::doneFailure(
-        ecFailed,
-        BuildResult::Failure{
-            .status = ex.status,
-            .errorMsg = fmt("%s", Uncolored(ex.info().msg)),
-        },
-        std::move(ex));
+    return Goal::doneFailure(ecFailed, std::move(ex));
 }
 
 } // namespace nix
diff --git a/src/libstore/build/derivation-goal.cc b/src/libstore/build/derivation-goal.cc
index 4c536bb1d90..2142c5e5b03 100644
--- a/src/libstore/build/derivation-goal.cc
+++ b/src/libstore/build/derivation-goal.cc
@@ -252,7 +252,7 @@ Goal::Co DerivationGoal::haveDerivation(bool storeDerivation)
     auto g = worker.makeDerivationBuildingGoal(drvPath, *drv, buildMode, storeDerivation);
 
     /* We will finish with it ourselves, as if we were the derivational goal. */
-    g->preserveException = true;
+    g->preserveFailure = true;
 
     {
         Goals waitees;
@@ -312,7 +312,7 @@ Goal::Co DerivationGoal::haveDerivation(bool storeDerivation)
         }
     }
 
-    co_return amDone(g->exitCode, g->ex);
+    co_return amDone(g->exitCode);
 }
 
 Goal::Co DerivationGoal::repairClosure()
@@ -501,13 +501,7 @@ Goal::Done DerivationGoal::doneFailure(BuildError ex)
 
     worker.updateProgress();
 
-    return Goal::doneFailure(
-        ecFailed,
-        BuildResult::Failure{
-            .status = ex.status,
-            .errorMsg = fmt("%s", Uncolored(ex.info().msg)),
-        },
-        std::move(ex));
+    return Goal::doneFailure(ecFailed, std::move(ex));
 }
 
 } // namespace nix
diff --git a/src/libstore/build/derivation-resolution-goal.cc b/src/libstore/build/derivation-resolution-goal.cc
index 6cb9702f4f6..e205fc774bb 100644
--- a/src/libstore/build/derivation-resolution-goal.cc
+++ b/src/libstore/build/derivation-resolution-goal.cc
@@ -90,7 +90,12 @@ Goal::Co DerivationResolutionGoal::resolveDerivation()
                 nrFailed,
                 nrFailed == 1 ? "dependency" : "dependencies");
         msg += showKnownOutputs(worker.store, *drv);
-        co_return amDone(ecFailed, {BuildError(BuildResult::Failure::DependencyFailed, msg)});
+        co_return doneFailure(
+            ecFailed,
+            BuildResult::Failure{{
+                .status = BuildResult::Failure::DependencyFailed,
+                .msg = HintFmt(msg),
+            }});
     }
 
     /* Gather information necessary for computing the closure and/or
@@ -185,7 +190,7 @@ Goal::Co DerivationResolutionGoal::resolveDerivation()
         }
     }
 
-    co_return amDone(ecSuccess, std::nullopt);
+    co_return amDone(ecSuccess);
 }
 
 } // namespace nix
diff --git a/src/libstore/build/derivation-trampoline-goal.cc b/src/libstore/build/derivation-trampoline-goal.cc
index cfa0c538f95..58a43c043a2 100644
--- a/src/libstore/build/derivation-trampoline-goal.cc
+++ b/src/libstore/build/derivation-trampoline-goal.cc
@@ -100,11 +100,10 @@ Goal::Co DerivationTrampolineGoal::init()
     if (nrFailed != 0) {
         co_return doneFailure(
             ecFailed,
-            BuildResult::Failure{
+            BuildResult::Failure{{
                 .status = BuildResult::Failure::DependencyFailed,
-                .errorMsg = fmt("failed to obtain derivation of '%s'", drvReq->to_string(worker.store)),
-            },
-            Error("failed to obtain derivation of '%s'", drvReq->to_string(worker.store)));
+                .msg = HintFmt("failed to obtain derivation of '%s'", drvReq->to_string(worker.store)),
+            }});
     }
 
     StorePath drvPath = resolveDerivedPath(worker.store, *drvReq);
@@ -152,7 +151,7 @@ Goal::Co DerivationTrampolineGoal::haveDerivation(StorePath drvPath, Derivation
 
     for (auto & output : resolvedWantedOutputs) {
         auto g = upcast_goal(worker.makeDerivationGoal(drvPath, drv, output, buildMode, false));
-        g->preserveException = true;
+        g->preserveFailure = true;
         /* We will finish with it ourselves, as if we were the derivational goal. */
         concreteDrvGoals.insert(std::move(g));
     }
@@ -170,7 +169,7 @@ Goal::Co DerivationTrampolineGoal::haveDerivation(StorePath drvPath, Derivation
                 for (auto && [x, y] : successP2->builtOutputs)
                     successP->builtOutputs.insert_or_assign(x, y);
 
-    co_return amDone(g->exitCode, g->ex);
+    co_return amDone(g->exitCode);
 }
 
 } // namespace nix
diff --git a/src/libstore/build/entry-points.cc b/src/libstore/build/entry-points.cc
index 04b16f5a8b1..774f00c0e83 100644
--- a/src/libstore/build/entry-points.cc
+++ b/src/libstore/build/entry-points.cc
@@ -18,13 +18,13 @@ void Store::buildPaths(const std::vector<DerivedPath> & reqs, BuildMode buildMod
     worker.run(goals);
 
     StringSet failed;
-    std::optional<Error> ex;
+    BuildResult::Failure * failure = nullptr;
     for (auto & i : goals) {
-        if (i->ex) {
-            if (ex)
-                logError(i->ex->info());
+        if (auto * f = i->buildResult.tryGetFailure()) {
+            if (failure)
+                logError(f->info());
             else
-                ex = std::move(i->ex);
+                failure = f;
         }
         if (i->exitCode != Goal::ecSuccess) {
             if (auto i2 = dynamic_cast<DerivationTrampolineGoal *>(i.get()))
@@ -34,12 +34,12 @@ void Store::buildPaths(const std::vector<DerivedPath> & reqs, BuildMode buildMod
         }
     }
 
-    if (failed.size() == 1 && ex) {
-        ex->withExitStatus(worker.failingExitStatus());
-        throw std::move(*ex);
+    if (failed.size() == 1 && failure) {
+        failure->withExitStatus(worker.failingExitStatus());
+        throw *failure;
     } else if (!failed.empty()) {
-        if (ex)
-            logError(ex->info());
+        if (failure)
+            logError(failure->info());
         throw Error(worker.failingExitStatus(), "build of %s failed", concatStringsSep(", ", quoteStrings(failed)));
     }
 }
@@ -88,10 +88,11 @@ BuildResult Store::buildDerivation(const StorePath & drvPath, const BasicDerivat
         worker.run(Goals{goal});
         return goal->buildResult;
     } catch (Error & e) {
-        return BuildResult{.inner{BuildResult::Failure{
-            .status = BuildResult::Failure::MiscFailure,
-            .errorMsg = e.msg(),
-        }}};
+        return BuildResult{
+            .inner = BuildResult::Failure{{
+                .status = BuildResult::Failure::MiscFailure,
+                .msg = e.msg(),
+            }}};
     };
 }
 
@@ -108,12 +109,8 @@ void Store::ensurePath(const StorePath & path)
     worker.run(goals);
 
     if (goal->exitCode != Goal::ecSuccess) {
-        if (goal->ex) {
-            goal->ex->withExitStatus(worker.failingExitStatus());
-            throw std::move(*goal->ex);
-        } else
-            throw Error(
-                worker.failingExitStatus(), "path '%s' does not exist and cannot be created", printStorePath(path));
+        goal->buildResult.tryThrowBuildError(worker.failingExitStatus());
+        throw Error(worker.failingExitStatus(), "path '%s' does not exist and cannot be created", printStorePath(path));
     }
 }
 
diff --git a/src/libstore/build/goal.cc b/src/libstore/build/goal.cc
index d119384da3f..618a7294cab 100644
--- a/src/libstore/build/goal.cc
+++ b/src/libstore/build/goal.cc
@@ -189,14 +189,14 @@ Goal::Done Goal::doneSuccess(BuildResult::Success success)
     return amDone(ecSuccess);
 }
 
-Goal::Done Goal::doneFailure(ExitCode result, BuildResult::Failure failure, std::optional<Error> ex)
+Goal::Done Goal::doneFailure(ExitCode result, BuildResult::Failure failure)
 {
     assert(result == ecFailed || result == ecNoSubstituters);
     buildResult.inner = std::move(failure);
-    return amDone(result, std::move(ex));
+    return amDone(result);
 }
 
-Goal::Done Goal::amDone(ExitCode result, std::optional<Error> ex)
+Goal::Done Goal::amDone(ExitCode result)
 {
     trace("done");
     assert(top_co);
@@ -204,11 +204,15 @@ Goal::Done Goal::amDone(ExitCode result, std::optional<Error> ex)
     assert(result == ecSuccess || result == ecFailed || result == ecNoSubstituters);
     exitCode = result;
 
-    if (ex) {
-        if (!preserveException && !waiters.empty())
-            logError(ex->info());
-        else
-            this->ex = std::move(*ex);
+    // Log the failure if we have one and shouldn't preserve it.
+    // Only log for actual failures (ecFailed), not for ecNoSubstituters
+    // which indicates "couldn't substitute, will try building" - that's
+    // expected behavior, not an error.
+    if (result == ecFailed) {
+        if (auto * failure = buildResult.tryGetFailure()) {
+            if (!preserveFailure && !waiters.empty())
+                logError(failure->info());
+        }
     }
 
     for (auto & i : waiters) {
diff --git a/src/libstore/build/substitution-goal.cc b/src/libstore/build/substitution-goal.cc
index e833f75c2ef..3ee6b898732 100644
--- a/src/libstore/build/substitution-goal.cc
+++ b/src/libstore/build/substitution-goal.cc
@@ -26,25 +26,6 @@ PathSubstitutionGoal::~PathSubstitutionGoal()
     cleanup();
 }
 
-Goal::Done PathSubstitutionGoal::doneSuccess(BuildResult::Success::Status status)
-{
-    return Goal::doneSuccess(
-        BuildResult::Success{
-            .status = status,
-        });
-}
-
-Goal::Done PathSubstitutionGoal::doneFailure(ExitCode result, BuildResult::Failure::Status status, std::string errorMsg)
-{
-    debug(errorMsg);
-    return Goal::doneFailure(
-        result,
-        BuildResult::Failure{
-            .status = status,
-            .errorMsg = std::move(errorMsg),
-        });
-}
-
 Goal::Co PathSubstitutionGoal::init()
 {
     trace("init");
@@ -53,7 +34,7 @@ Goal::Co PathSubstitutionGoal::init()
 
     /* If the path already exists we're done. */
     if (!repair && worker.store.isValidPath(storePath)) {
-        co_return doneSuccess(BuildResult::Success::AlreadyValid);
+        co_return doneSuccess(BuildResult::Success{.status = BuildResult::Success::AlreadyValid});
     }
 
     if (settings.readOnlyMode)
@@ -175,9 +156,12 @@ Goal::Co PathSubstitutionGoal::init()
        build. */
     co_return doneFailure(
         substituterFailed ? ecFailed : ecNoSubstituters,
-        BuildResult::Failure::NoSubstituters,
-        fmt("path '%s' is required, but there is no substituter that can build it",
-            worker.store.printStorePath(storePath)));
+        BuildResult::Failure{{
+            .status = BuildResult::Failure::NoSubstituters,
+            .msg = HintFmt(
+                "path '%s' is required, but there is no substituter that can build it",
+                worker.store.printStorePath(storePath)),
+        }});
 }
 
 Goal::Co PathSubstitutionGoal::tryToRun(
@@ -188,8 +172,11 @@ Goal::Co PathSubstitutionGoal::tryToRun(
     if (nrFailed > 0) {
         co_return doneFailure(
             nrNoSubstituters > 0 ? ecNoSubstituters : ecFailed,
-            BuildResult::Failure::DependencyFailed,
-            fmt("some references of path '%s' could not be realised", worker.store.printStorePath(storePath)));
+            BuildResult::Failure{{
+                .status = BuildResult::Failure::DependencyFailed,
+                .msg = HintFmt(
+                    "some references of path '%s' could not be realised", worker.store.printStorePath(storePath)),
+            }});
     }
 
     for (auto & i : info->references)
@@ -316,7 +303,7 @@ Goal::Co PathSubstitutionGoal::tryToRun(
 
     worker.updateProgress();
 
-    co_return doneSuccess(BuildResult::Success::Substituted);
+    co_return doneSuccess(BuildResult::Success{.status = BuildResult::Success::Substituted});
 }
 
 void PathSubstitutionGoal::cleanup()
diff --git a/src/libstore/include/nix/store/build-result.hh b/src/libstore/include/nix/store/build-result.hh
index 134a90abbc5..d3be9cc5065 100644
--- a/src/libstore/include/nix/store/build-result.hh
+++ b/src/libstore/include/nix/store/build-result.hh
@@ -7,6 +7,8 @@
 
 #include "nix/store/derived-path.hh"
 #include "nix/store/realisation.hh"
+#include "nix/util/error.hh"
+#include "nix/util/fmt.hh"
 #include "nix/util/json-impls.hh"
 
 namespace nix {
@@ -50,6 +52,70 @@ enum struct BuildResultFailureStatus : uint8_t {
     HashMismatch,
 };
 
+/**
+ * Denotes a permanent build failure.
+ *
+ * This is both an exception type (inherits from Error) and serves as
+ * the failure variant in BuildResult::inner.
+ */
+struct BuildError : public Error
+{
+    using Status = BuildResultFailureStatus;
+    using enum Status;
+
+    Status status = MiscFailure;
+
+    /**
+     * If timesBuilt > 1, whether some builds did not produce the same
+     * result. (Note that 'isNonDeterministic = false' does not mean
+     * the build is deterministic, just that we don't have evidence of
+     * non-determinism.)
+     */
+    bool isNonDeterministic = false;
+
+public:
+    /**
+     * Variadic constructor for throwing with format strings.
+     * Delegates to the string constructor after formatting.
+     */
+    template<typename... Args>
+    BuildError(Status status, const Args &... args)
+        : Error(args...)
+        , status{status}
+    {
+    }
+
+    struct Args
+    {
+        Status status;
+        HintFmt msg;
+        bool isNonDeterministic = false;
+    };
+
+    /**
+     * Constructor taking a pre-formatted error message.
+     * Also used for deserialization.
+     */
+    BuildError(Args args)
+        : Error(std::move(args.msg))
+        , status{args.status}
+        , isNonDeterministic{args.isNonDeterministic}
+
+    {
+    }
+
+    /**
+     * Default constructor for deserialization.
+     */
+    BuildError()
+        : Error("")
+    {
+    }
+
+    bool operator==(const BuildError &) const noexcept;
+    std::strong_ordering operator<=>(const BuildError &) const noexcept;
+};
+
 struct BuildResult
 {
     struct Success
@@ -68,33 +134,10 @@ struct BuildResult
         std::strong_ordering operator<=>(const BuildResult::Success &) const noexcept;
     };
 
-    struct Failure
-    {
-        using Status = enum BuildResultFailureStatus;
-        using enum Status;
-        Status status = MiscFailure;
-
-        /**
-         * Information about the error if the build failed.
-         *
-         * @todo This should be an entire ErrorInfo object, not just a
-         * string, for richer information.
-         */
-        std::string errorMsg;
-
-        /**
-         * If timesBuilt > 1, whether some builds did not produce the same
-         * result. (Note that 'isNonDeterministic = false' does not mean
-         * the build is deterministic, just that we don't have evidence of
-         * non-determinism.)
-         */
-        bool isNonDeterministic = false;
-
-        bool operator==(const BuildResult::Failure &) const noexcept;
-        std::strong_ordering operator<=>(const BuildResult::Failure &) const noexcept;
-
-        [[noreturn]] void rethrow() const;
-    };
+    /**
+     * Failure is now an alias for BuildError.
+     */
+    using Failure = BuildError;
 
     std::variant<Success, Failure> inner = Failure{};
 
@@ -118,6 +161,19 @@ struct BuildResult
         return std::get_if<Failure>(&self.inner);
     }
 
+    /**
+     * Throw the build error if this result represents a failure.
+     * Optionally set the exit status on the error before throwing.
+     */
+    void tryThrowBuildError(std::optional<unsigned int> exitStatus = std::nullopt)
+    {
+        if (auto * failure = tryGetFailure()) {
+            if (exitStatus)
+                failure->withExitStatus(*exitStatus);
+            throw *failure;
+        }
+    }
+
     /**
      * How many times this build was performed.
      */
@@ -138,20 +194,6 @@ struct BuildResult
     std::strong_ordering operator<=>(const BuildResult &) const noexcept;
 };
 
-/**
- * denotes a permanent build failure
- */
-struct BuildError : public Error
-{
-    BuildResult::Failure::Status status;
-
-    BuildError(BuildResult::Failure::Status status, auto &&... args)
-        : Error{args...}
-        , status{status}
-    {
-    }
-};
-
 /**
  * A `BuildResult` together with its "primary key".
  */
diff --git a/src/libstore/include/nix/store/build/goal.hh b/src/libstore/include/nix/store/build/goal.hh
index f1df869ec8f..6a92d282898 100644
--- a/src/libstore/include/nix/store/build/goal.hh
+++ b/src/libstore/include/nix/store/build/goal.hh
@@ -504,7 +504,7 @@ protected:
      * Prefer using `doneSuccess` or `doneFailure` instead, which ensure
      * `buildResult` is set correctly.
      */
-    Done amDone(ExitCode result, std::optional<Error> ex = {});
+    Done amDone(ExitCode result);
 
     /**
      * Signals successful completion of the goal.
@@ -518,15 +518,14 @@ protected:
      *
      * @param result The exit code (ecFailed or ecNoSubstituters)
      * @param failure The failure details including status and error message
-     * @param ex Optional exception to store/log
      */
-    Done doneFailure(ExitCode result, BuildResult::Failure failure, std::optional<Error> ex = {});
+    Done doneFailure(ExitCode result, BuildResult::Failure failure);
 
 public:
     virtual void cleanup() {}
 
     /**
-     * Hack to say that this goal should not log `ex`, but instead keep
+     * Hack to say that this goal should not log the failure, but instead keep
      * it around. Set by a waitee which sees itself as the designated
      * continuation of this goal, responsible for reporting its
      * successes or failures.
@@ -534,12 +533,7 @@ public:
      * @todo this is yet another not-nice hack in the goal system that
      * we ought to get rid of. See #11927
      */
-    bool preserveException = false;
-
-    /**
-     * Exception containing an error message, if any.
-     */
-    std::optional<Error> ex;
+    bool preserveFailure = false;
 
     Goal(Worker & worker, Co init)
         : worker(worker)
diff --git a/src/libstore/include/nix/store/build/substitution-goal.hh b/src/libstore/include/nix/store/build/substitution-goal.hh
index 9f5315b462b..7ce28d1deff 100644
--- a/src/libstore/include/nix/store/build/substitution-goal.hh
+++ b/src/libstore/include/nix/store/build/substitution-goal.hh
@@ -41,10 +41,6 @@ struct PathSubstitutionGoal : public Goal
      */
     std::optional<ContentAddress> ca;
 
-    Done doneSuccess(BuildResult::Success::Status status);
-
-    Done doneFailure(ExitCode result, BuildResult::Failure::Status status, std::string errorMsg);
-
 public:
     PathSubstitutionGoal(
         const StorePath & storePath,
diff --git a/src/libstore/restricted-store.cc b/src/libstore/restricted-store.cc
index c0bd273322f..15b2a3d049c 100644
--- a/src/libstore/restricted-store.cc
+++ b/src/libstore/restricted-store.cc
@@ -257,8 +257,7 @@ void RestrictedStore::buildPaths(
     const std::vector<DerivedPath> & paths, BuildMode buildMode, std::shared_ptr<Store> evalStore)
 {
     for (auto & result : buildPathsWithResults(paths, buildMode, evalStore))
-        if (auto * failureP = result.tryGetFailure())
-            failureP->rethrow();
+        result.tryThrowBuildError();
 }
 
 std::vector<KeyedBuildResult> RestrictedStore::buildPathsWithResults(
diff --git a/src/libstore/serve-protocol.cc b/src/libstore/serve-protocol.cc
index 74404233d27..a1250fee450 100644
--- a/src/libstore/serve-protocol.cc
+++ b/src/libstore/serve-protocol.cc
@@ -18,13 +18,16 @@ BuildResult ServeProto::Serialise<BuildResult>::read(const StoreDirConfig & stor
 {
     BuildResult res;
     BuildResult::Success success;
-    BuildResult::Failure failure;
+
+    // Temp variables for failure fields since BuildError uses methods
+    std::string errorMsg;
+    bool isNonDeterministic = false;
 
     auto status = ServeProto::Serialise<BuildResultStatus>::read(store, {conn.from});
-    conn.from >> failure.errorMsg;
+    conn.from >> errorMsg;
 
     if (GET_PROTOCOL_MINOR(conn.version) >= 3)
-        conn.from >> res.timesBuilt >> failure.isNonDeterministic >> res.startTime >> res.stopTime;
+        conn.from >> res.timesBuilt >> isNonDeterministic >> res.startTime >> res.stopTime;
     if (GET_PROTOCOL_MINOR(conn.version) >= 6) {
         auto builtOutputs = ServeProto::Serialise<DrvOutputs>::read(store, conn);
         for (auto && [output, realisation] : builtOutputs)
@@ -38,8 +41,11 @@ BuildResult ServeProto::Serialise<BuildResult>::read(const StoreDirConfig & stor
                 return std::move(success);
             },
             [&](BuildResult::Failure::Status s) -> decltype(res.inner) {
-                failure.status = s;
-                return std::move(failure);
+                return BuildResult::Failure{{
+                    .status = s,
+                    .msg = HintFmt(std::move(errorMsg)),
+                    .isNonDeterministic = isNonDeterministic,
+                }};
             },
         },
         status);
@@ -70,7 +76,7 @@ void ServeProto::Serialise<BuildResult>::write(
         overloaded{
             [&](const BuildResult::Failure & failure) {
                 ServeProto::write(store, {conn.to}, BuildResultStatus{failure.status});
-                common(failure.errorMsg, failure.isNonDeterministic, decltype(BuildResult::Success::builtOutputs){});
+                common(failure.message(), failure.isNonDeterministic, decltype(BuildResult::Success::builtOutputs){});
             },
             [&](const BuildResult::Success & success) {
                 ServeProto::write(store, {conn.to}, BuildResultStatus{success.status});
diff --git a/src/libstore/unix/build/derivation-builder.cc b/src/libstore/unix/build/derivation-builder.cc
index 83dfba7e097..ed8b41ca454 100644
--- a/src/libstore/unix/build/derivation-builder.cc
+++ b/src/libstore/unix/build/derivation-builder.cc
@@ -59,6 +59,7 @@ struct NotDeterministic : BuildError
     NotDeterministic(auto &&... args)
         : BuildError(BuildResult::Failure::NotDeterministic, args...)
     {
+        isNonDeterministic = true;
     }
 };
 
diff --git a/src/libstore/worker-protocol.cc b/src/libstore/worker-protocol.cc
index 9dc4bc8c98a..a78bb87bebe 100644
--- a/src/libstore/worker-protocol.cc
+++ b/src/libstore/worker-protocol.cc
@@ -208,13 +208,16 @@ BuildResult WorkerProto::Serialise<BuildResult>::read(const StoreDirConfig & sto
 {
     BuildResult res;
     BuildResult::Success success;
-    BuildResult::Failure failure;
+
+    // Temp variables for failure fields since BuildError uses methods
+    std::string errorMsg;
+    bool isNonDeterministic = false;
 
     auto status = WorkerProto::Serialise<BuildResultStatus>::read(store, {conn.from});
-    conn.from >> failure.errorMsg;
+    conn.from >> errorMsg;
 
     if (GET_PROTOCOL_MINOR(conn.version) >= 29) {
-        conn.from >> res.timesBuilt >> failure.isNonDeterministic >> res.startTime >> res.stopTime;
+        conn.from >> res.timesBuilt >> isNonDeterministic >> res.startTime >> res.stopTime;
     }
     if (GET_PROTOCOL_MINOR(conn.version) >= 37) {
         res.cpuUser = WorkerProto::Serialise<std::optional<std::chrono::microseconds>>::read(store, conn);
@@ -233,8 +236,11 @@ BuildResult WorkerProto::Serialise<BuildResult>::read(const StoreDirConfig & sto
                 return std::move(success);
             },
             [&](BuildResult::Failure::Status s) -> decltype(res.inner) {
-                failure.status = s;
-                return std::move(failure);
+                return BuildResult::Failure{{
+                    .status = s,
+                    .msg = HintFmt(std::move(errorMsg)),
+                    .isNonDeterministic = isNonDeterministic,
+                }};
             },
         },
         status);
@@ -270,7 +276,7 @@ void WorkerProto::Serialise<BuildResult>::write(
         overloaded{
             [&](const BuildResult::Failure & failure) {
                 WorkerProto::write(store, {conn.to}, BuildResultStatus{failure.status});
-                common(failure.errorMsg, failure.isNonDeterministic, decltype(BuildResult::Success::builtOutputs){});
+                common(failure.message(), failure.isNonDeterministic, decltype(BuildResult::Success::builtOutputs){});
             },
             [&](const BuildResult::Success & success) {
                 WorkerProto::write(store, {conn.to}, BuildResultStatus{success.status});
diff --git a/src/libutil/include/nix/util/error.hh b/src/libutil/include/nix/util/error.hh
index 17de21ce5bc..74bb3e4f46a 100644
--- a/src/libutil/include/nix/util/error.hh
+++ b/src/libutil/include/nix/util/error.hh
@@ -159,7 +159,7 @@ public:
     }
 
     /** The error message without "error: " prefixed to it. */
-    std::string message()
+    std::string message() const
     {
         return err.msg.str();
     }
diff --git a/src/nix/build-remote/build-remote.cc b/src/nix/build-remote/build-remote.cc
index 40502d19313..cc0baee327a 100644
--- a/src/nix/build-remote/build-remote.cc
+++ b/src/nix/build-remote/build-remote.cc
@@ -333,7 +333,7 @@ static int main_build_remote(int argc, char ** argv)
                             : "");
                 }
                 throw Error(
-                    "build of '%s' on '%s' failed: %s", store->printStorePath(*drvPath), storeUri, failureP->errorMsg);
+                    "build of '%s' on '%s' failed: %s", store->printStorePath(*drvPath), storeUri, failureP->message());
             }
         } else {
             copyClosure(*store, *sshStore, StorePathSet{*drvPath}, NoRepair, NoCheckSigs, substitute);
diff --git a/src/nix/flake.cc b/src/nix/flake.cc
index 32bd9124d12..07868c37933 100644
--- a/src/nix/flake.cc
+++ b/src/nix/flake.cc
@@ -824,12 +824,12 @@ struct CmdFlakeCheck : FlakeCommand
                                 "failed to build attribute '%s', build of '%s' failed: %s",
                                 attrPath.to_string(*state),
                                 result.path.to_string(*store),
-                                failure->errorMsg));
+                                failure->message()));
                         }
                     } else {
                         // Derivation has no attribute path (e.g., a build dependency)
                         reportError(
-                            Error("build of '%s' failed: %s", result.path.to_string(*store), failure->errorMsg));
+                            Error("build of '%s' failed: %s", result.path.to_string(*store), failure->message()));
                     }
                 }
             }