diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 04e256780..6263019a6 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -8,27 +8,40 @@ on:
 jobs:
   test:
     name: >
-      Test on ${{ matrix.os }}${{
-      matrix.extra_flags != 'NOT_A_PUZZLE' && format(' with --features {0}', matrix.extra_flags) || ''
-      }}
+      Test${{
+      matrix.state != 'NOT_A_PUZZLE' && format(' {0}', matrix.state) || ''
+      }} on ${{ matrix.target }}
     runs-on: ${{ matrix.os }}
-    continue-on-error: ${{ matrix.extra_flags != 'NOT_A_PUZZLE' }}
+    continue-on-error: ${{ matrix.state != 'NOT_A_PUZZLE' }}
     strategy:
       matrix:
-        os: [ubuntu-latest-8cores, windows-latest-8cores, macOS-latest]
-        extra_flags:
+        target:
+          - Linux
+          - macOS
+          - Windows
+        state:
           - NOT_A_PUZZLE
-          - orchard
-          - unstable-nu6
-          - zfuture
+          - Orchard
+          - NU6
+
         include:
-          - extra_flags: orchard
+          - target: Linux
+            os: ubuntu-latest-8cores
+          - target: macOS
+            os: macOS-latest
+          - target: Windows
+            os: windows-latest-8cores
+
+          - state: Orchard
+            extra_flags: orchard
             rustflags: '--cfg zcash_unstable="orchard"'
+          - state: NU6
+            rustflags: '--cfg zcash_unstable="nu6"'
+
         exclude:
-          - os: macOS-latest
-            extra_flags: unstable-nu6
-          - os: macOS-latest
-            extra_flags: zfuture
+          - target: macOS
+            state: NU6
+
     env:
       RUSTFLAGS: ${{ matrix.rustflags }}
       RUSTDOCFLAGS: ${{ matrix.rustflags }}
@@ -38,7 +51,7 @@ jobs:
       - id: prepare
         uses: ./.github/actions/prepare
         with:
-          extra-features: ${{ matrix.extra_flags != 'NOT_A_PUZZLE' && matrix.extra_flags || '' }}
+          extra-features: ${{ matrix.state != 'NOT_A_PUZZLE' && matrix.extra_flags || '' }}
       - uses: actions/cache@v4
         with:
           path: |
@@ -64,6 +77,63 @@ jobs:
       - name: Verify working directory is clean
         run: git diff --exit-code
 
+  # States that we want to ensure can be built, but that we don't actively run tests for.
+  check-msrv:
+    name: >
+      Check${{
+      matrix.state != 'NOT_A_PUZZLE' && format(' {0}', matrix.state) || ''
+      }} build on ${{ matrix.target }}
+    runs-on: ${{ matrix.os }}
+    continue-on-error: ${{ matrix.state != 'NOT_A_PUZZLE' }}
+    strategy:
+      matrix:
+        target:
+          - Linux
+          - macOS
+          - Windows
+        state:
+          - ZFuture
+
+        include:
+          - target: Linux
+            os: ubuntu-latest
+          - target: macOS
+            os: macOS-latest
+          - target: Windows
+            os: windows-latest
+
+          - state: ZFuture
+            rustflags: '--cfg zcash_unstable="zfuture"'
+
+    env:
+      RUSTFLAGS: ${{ matrix.rustflags }}
+      RUSTDOCFLAGS: ${{ matrix.rustflags }}
+
+    steps:
+      - uses: actions/checkout@v4
+      - id: prepare
+        uses: ./.github/actions/prepare
+        with:
+          extra-features: ${{ matrix.state != 'NOT_A_PUZZLE' && matrix.extra_flags || '' }}
+      - uses: actions/cache@v4
+        with:
+          path: |
+            ~/.cargo/bin/
+            ~/.cargo/registry/index/
+            ~/.cargo/registry/cache/
+            ~/.cargo/git/db/
+            target/
+          key: ${{ runner.os }}-cargo-msrv-${{ hashFiles('**/Cargo.lock') }}
+      - name: Run check
+        run: >
+          cargo check
+          --release
+          --workspace
+          --tests
+          ${{ steps.prepare.outputs.feature-flags }}
+      - name: Verify working directory is clean
+        run: git diff --exit-code
+
   build-latest:
     name: Latest build on ${{ matrix.os }}
     runs-on: ${{ matrix.os }}
diff --git a/Cargo.lock b/Cargo.lock
index 626fb840a..b671f7ebf 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -3102,6 +3102,21 @@ dependencies = [
  "nonempty",
 ]
 
+[[package]]
+name = "zcash_extensions"
+version = "0.0.0"
+dependencies = [
+ "blake2b_simd",
+ "ff",
+ "jubjub",
+ "orchard",
+ "rand_core",
+ "sapling-crypto",
+ "zcash_address",
+ "zcash_primitives",
+ "zcash_proofs",
+]
+
 [[package]]
 name = "zcash_history"
 version = "0.4.0"
diff --git a/Cargo.toml b/Cargo.toml
index a06d110e3..d90c6d3e0 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -7,8 +7,7 @@ members = [
     "components/zcash_protocol",
     "zcash_client_backend",
     "zcash_client_sqlite",
-    # Disabled until we replace the `zfutures` feature flag with a compiler flag.
-    # "zcash_extensions",
+    "zcash_extensions",
     "zcash_history",
     "zcash_keys",
     "zcash_primitives",
diff --git a/components/zcash_protocol/CHANGELOG.md b/components/zcash_protocol/CHANGELOG.md
index 2d20e03cc..362b92185 100644
--- a/components/zcash_protocol/CHANGELOG.md
+++ b/components/zcash_protocol/CHANGELOG.md
@@ -11,6 +11,11 @@ and this library adheres to Rust's notion of
 - `zcash_protocol::memo`:
   - `impl TryFrom<&MemoBytes> for Memo`
 
+### Removed
+- `unstable-nu6` and `zfuture` feature flags (use `--cfg zcash_unstable=\"nu6\"`
+  or `--cfg zcash_unstable=\"zfuture\"` in `RUSTFLAGS` and `RUSTDOCFLAGS`
+  instead).
+
 ## [0.1.0] - 2024-03-06
 The entries below are relative to the `zcash_primitives` crate as of the tag
 `zcash_primitives-0.14.0`.
diff --git a/components/zcash_protocol/Cargo.toml b/components/zcash_protocol/Cargo.toml
index 7a8114dad..e85b95834 100644
--- a/components/zcash_protocol/Cargo.toml
+++ b/components/zcash_protocol/Cargo.toml
@@ -45,14 +45,3 @@ test-dependencies = [
 
 ## Exposes support for working with a local consensus (e.g. regtest).
 local-consensus = []
-
-#! ### Experimental features
-#!
-#! ⚠️ Enabling these features will likely make your code incompatible with current Zcash
-#! consensus rules!
-
-## Exposes the in-development NU6 features.
-unstable-nu6 = []
-
-## Exposes early in-development features that are not yet planned for any network upgrade.
-zfuture = []
diff --git a/components/zcash_protocol/src/consensus.rs b/components/zcash_protocol/src/consensus.rs
index 7793b15f6..32af0be70 100644
--- a/components/zcash_protocol/src/consensus.rs
+++ b/components/zcash_protocol/src/consensus.rs
@@ -354,9 +354,9 @@ impl Parameters for MainNetwork {
             NetworkUpgrade::Heartwood => Some(BlockHeight(903_000)),
             NetworkUpgrade::Canopy => Some(BlockHeight(1_046_400)),
             NetworkUpgrade::Nu5 => Some(BlockHeight(1_687_104)),
-            #[cfg(feature = "unstable-nu6")]
+            #[cfg(zcash_unstable = "nu6")]
             NetworkUpgrade::Nu6 => None,
-            #[cfg(feature = "zfuture")]
+            #[cfg(zcash_unstable = "zfuture")]
             NetworkUpgrade::ZFuture => None,
         }
     }
@@ -384,9 +384,9 @@ impl Parameters for TestNetwork {
             NetworkUpgrade::Heartwood => Some(BlockHeight(903_800)),
             NetworkUpgrade::Canopy => Some(BlockHeight(1_028_500)),
             NetworkUpgrade::Nu5 => Some(BlockHeight(1_842_420)),
-            #[cfg(feature = "unstable-nu6")]
+            #[cfg(zcash_unstable = "nu6")]
             NetworkUpgrade::Nu6 => None,
-            #[cfg(feature = "zfuture")]
+            #[cfg(zcash_unstable = "zfuture")]
             NetworkUpgrade::ZFuture => None,
         }
     }
@@ -452,14 +452,14 @@ pub enum NetworkUpgrade {
     /// The [Nu6] network upgrade.
     ///
     /// [Nu6]: https://z.cash/upgrade/nu6/
-    #[cfg(feature = "unstable-nu6")]
+    #[cfg(zcash_unstable = "nu6")]
     Nu6,
     /// The ZFUTURE network upgrade.
     ///
     /// This upgrade is expected never to activate on mainnet;
     /// it is intended for use in integration testing of functionality
     /// that is a candidate for integration in a future network upgrade.
-    #[cfg(feature = "zfuture")]
+    #[cfg(zcash_unstable = "zfuture")]
     ZFuture,
 }
 
@@ -474,9 +474,9 @@ impl fmt::Display for NetworkUpgrade {
             NetworkUpgrade::Heartwood => write!(f, "Heartwood"),
             NetworkUpgrade::Canopy => write!(f, "Canopy"),
             NetworkUpgrade::Nu5 => write!(f, "Nu5"),
-            #[cfg(feature = "unstable-nu6")]
+            #[cfg(zcash_unstable = "nu6")]
             NetworkUpgrade::Nu6 => write!(f, "Nu6"),
-            #[cfg(feature = "zfuture")]
+            #[cfg(zcash_unstable = "zfuture")]
             NetworkUpgrade::ZFuture => write!(f, "ZFUTURE"),
         }
     }
@@ -491,9 +491,9 @@ impl NetworkUpgrade {
             NetworkUpgrade::Heartwood => BranchId::Heartwood,
             NetworkUpgrade::Canopy => BranchId::Canopy,
             NetworkUpgrade::Nu5 => BranchId::Nu5,
-            #[cfg(feature = "unstable-nu6")]
+            #[cfg(zcash_unstable = "nu6")]
             NetworkUpgrade::Nu6 => BranchId::Nu6,
-            #[cfg(feature = "zfuture")]
+            #[cfg(zcash_unstable = "zfuture")]
             NetworkUpgrade::ZFuture => BranchId::ZFuture,
         }
     }
@@ -510,7 +510,7 @@ const UPGRADES_IN_ORDER: &[NetworkUpgrade] = &[
     NetworkUpgrade::Heartwood,
     NetworkUpgrade::Canopy,
     NetworkUpgrade::Nu5,
-    #[cfg(feature = "unstable-nu6")]
+    #[cfg(zcash_unstable = "nu6")]
     NetworkUpgrade::Nu6,
 ];
 
@@ -549,11 +549,11 @@ pub enum BranchId {
     /// The consensus rules deployed by [`NetworkUpgrade::Nu5`].
     Nu5,
     /// The consensus rules deployed by [`NetworkUpgrade::Nu6`].
-    #[cfg(feature = "unstable-nu6")]
+    #[cfg(zcash_unstable = "nu6")]
     Nu6,
     /// Candidates for future consensus rules; this branch will never
     /// activate on mainnet.
-    #[cfg(feature = "zfuture")]
+    #[cfg(zcash_unstable = "zfuture")]
     ZFuture,
 }
 
@@ -571,9 +571,9 @@ impl TryFrom<u32> for BranchId {
             0xf5b9_230b => Ok(BranchId::Heartwood),
             0xe9ff_75a6 => Ok(BranchId::Canopy),
             0xc2d6_d0b4 => Ok(BranchId::Nu5),
-            #[cfg(feature = "unstable-nu6")]
+            #[cfg(zcash_unstable = "nu6")]
             0xc8e7_1055 => Ok(BranchId::Nu6),
-            #[cfg(feature = "zfuture")]
+            #[cfg(zcash_unstable = "zfuture")]
             0xffff_ffff => Ok(BranchId::ZFuture),
             _ => Err("Unknown consensus branch ID"),
         }
@@ -590,9 +590,9 @@ impl From<BranchId> for u32 {
             BranchId::Heartwood => 0xf5b9_230b,
             BranchId::Canopy => 0xe9ff_75a6,
             BranchId::Nu5 => 0xc2d6_d0b4,
-            #[cfg(feature = "unstable-nu6")]
+            #[cfg(zcash_unstable = "nu6")]
             BranchId::Nu6 => 0xc8e7_1055,
-            #[cfg(feature = "zfuture")]
+            #[cfg(zcash_unstable = "zfuture")]
             BranchId::ZFuture => 0xffff_ffff,
         }
     }
@@ -658,15 +658,15 @@ impl BranchId {
                 .activation_height(NetworkUpgrade::Canopy)
                 .map(|lower| (lower, params.activation_height(NetworkUpgrade::Nu5))),
             BranchId::Nu5 => params.activation_height(NetworkUpgrade::Nu5).map(|lower| {
-                #[cfg(feature = "zfuture")]
+                #[cfg(zcash_unstable = "zfuture")]
                 let upper = params.activation_height(NetworkUpgrade::ZFuture);
-                #[cfg(not(feature = "zfuture"))]
+                #[cfg(not(zcash_unstable = "zfuture"))]
                 let upper = None;
                 (lower, upper)
             }),
-            #[cfg(feature = "unstable-nu6")]
+            #[cfg(zcash_unstable = "nu6")]
             BranchId::Nu6 => None,
-            #[cfg(feature = "zfuture")]
+            #[cfg(zcash_unstable = "zfuture")]
             BranchId::ZFuture => params
                 .activation_height(NetworkUpgrade::ZFuture)
                 .map(|lower| (lower, None)),
@@ -694,9 +694,9 @@ pub mod testing {
             BranchId::Heartwood,
             BranchId::Canopy,
             BranchId::Nu5,
-            #[cfg(feature = "unstable-nu6")]
+            #[cfg(zcash_unstable = "nu6")]
             BranchId::Nu6,
-            #[cfg(feature = "zfuture")]
+            #[cfg(zcash_unstable = "zfuture")]
             BranchId::ZFuture,
         ])
     }
diff --git a/components/zcash_protocol/src/local_consensus.rs b/components/zcash_protocol/src/local_consensus.rs
index 994154240..5d277cf1b 100644
--- a/components/zcash_protocol/src/local_consensus.rs
+++ b/components/zcash_protocol/src/local_consensus.rs
@@ -26,10 +26,6 @@ use crate::consensus::{BlockHeight, NetworkType, NetworkUpgrade, Parameters};
 ///         heartwood: Some(BlockHeight::from_u32(1)),
 ///         canopy: Some(BlockHeight::from_u32(1)),
 ///         nu5: Some(BlockHeight::from_u32(1)),
-///         #[cfg(feature = "unstable-nu6")]
-///         nu6: Some(BlockHeight::from_u32(1)),
-///         #[cfg(feature = "zfuture")]
-///         z_future: Some(BlockHeight::from_u32(1)),
 ///         };
 ///     ```
 ///     
@@ -41,9 +37,9 @@ pub struct LocalNetwork {
     pub heartwood: Option<BlockHeight>,
     pub canopy: Option<BlockHeight>,
     pub nu5: Option<BlockHeight>,
-    #[cfg(feature = "unstable-nu6")]
+    #[cfg(zcash_unstable = "nu6")]
     pub nu6: Option<BlockHeight>,
-    #[cfg(feature = "zfuture")]
+    #[cfg(zcash_unstable = "zfuture")]
     pub z_future: Option<BlockHeight>,
 }
 
@@ -61,9 +57,9 @@ impl Parameters for LocalNetwork {
             NetworkUpgrade::Heartwood => self.heartwood,
             NetworkUpgrade::Canopy => self.canopy,
             NetworkUpgrade::Nu5 => self.nu5,
-            #[cfg(feature = "unstable-nu6")]
+            #[cfg(zcash_unstable = "nu6")]
             NetworkUpgrade::Nu6 => self.nu6,
-            #[cfg(feature = "zfuture")]
+            #[cfg(zcash_unstable = "zfuture")]
             NetworkUpgrade::ZFuture => self.z_future,
         }
     }
@@ -85,9 +81,9 @@ mod tests {
         let expected_heartwood = BlockHeight::from_u32(4);
         let expected_canopy = BlockHeight::from_u32(5);
         let expected_nu5 = BlockHeight::from_u32(6);
-        #[cfg(feature = "unstable-nu6")]
+        #[cfg(zcash_unstable = "nu6")]
         let expected_nu6 = BlockHeight::from_u32(7);
-        #[cfg(feature = "zfuture")]
+        #[cfg(zcash_unstable = "zfuture")]
         let expected_z_future = BlockHeight::from_u32(7);
 
         let regtest = LocalNetwork {
@@ -97,9 +93,9 @@ mod tests {
             heartwood: Some(expected_heartwood),
             canopy: Some(expected_canopy),
             nu5: Some(expected_nu5),
-            #[cfg(feature = "unstable-nu6")]
+            #[cfg(zcash_unstable = "nu6")]
             nu6: Some(expected_nu6),
-            #[cfg(feature = "zfuture")]
+            #[cfg(zcash_unstable = "zfuture")]
             z_future: Some(expected_z_future),
         };
 
@@ -109,9 +105,9 @@ mod tests {
         assert!(regtest.is_nu_active(NetworkUpgrade::Heartwood, expected_heartwood));
         assert!(regtest.is_nu_active(NetworkUpgrade::Canopy, expected_canopy));
         assert!(regtest.is_nu_active(NetworkUpgrade::Nu5, expected_nu5));
-        #[cfg(feature = "unstable-nu6")]
+        #[cfg(zcash_unstable = "nu6")]
         assert!(regtest.is_nu_active(NetworkUpgrade::Nu6, expected_nu6));
-        #[cfg(feature = "zfuture")]
+        #[cfg(zcash_unstable = "zfuture")]
         assert!(!regtest.is_nu_active(NetworkUpgrade::ZFuture, expected_nu5));
     }
 
@@ -123,9 +119,9 @@ mod tests {
         let expected_heartwood = BlockHeight::from_u32(4);
         let expected_canopy = BlockHeight::from_u32(5);
         let expected_nu5 = BlockHeight::from_u32(6);
-        #[cfg(feature = "unstable-nu6")]
+        #[cfg(zcash_unstable = "nu6")]
         let expected_nu6 = BlockHeight::from_u32(7);
-        #[cfg(feature = "zfuture")]
+        #[cfg(zcash_unstable = "zfuture")]
         let expected_z_future = BlockHeight::from_u32(7);
 
         let regtest = LocalNetwork {
@@ -135,9 +131,9 @@ mod tests {
             heartwood: Some(expected_heartwood),
             canopy: Some(expected_canopy),
             nu5: Some(expected_nu5),
-            #[cfg(feature = "unstable-nu6")]
+            #[cfg(zcash_unstable = "nu6")]
             nu6: Some(expected_nu6),
-            #[cfg(feature = "zfuture")]
+            #[cfg(zcash_unstable = "zfuture")]
             z_future: Some(expected_z_future),
         };
 
@@ -165,7 +161,7 @@ mod tests {
             regtest.activation_height(NetworkUpgrade::Nu5),
             Some(expected_nu5)
         );
-        #[cfg(feature = "zfuture")]
+        #[cfg(zcash_unstable = "zfuture")]
         assert_eq!(
             regtest.activation_height(NetworkUpgrade::ZFuture),
             Some(expected_z_future)
@@ -180,9 +176,9 @@ mod tests {
         let expected_heartwood = BlockHeight::from_u32(4);
         let expected_canopy = BlockHeight::from_u32(5);
         let expected_nu5 = BlockHeight::from_u32(6);
-        #[cfg(feature = "unstable-nu6")]
+        #[cfg(zcash_unstable = "nu6")]
         let expected_nu6 = BlockHeight::from_u32(7);
-        #[cfg(feature = "zfuture")]
+        #[cfg(zcash_unstable = "zfuture")]
         let expected_z_future = BlockHeight::from_u32(7);
 
         let regtest = LocalNetwork {
@@ -192,9 +188,9 @@ mod tests {
             heartwood: Some(expected_heartwood),
             canopy: Some(expected_canopy),
             nu5: Some(expected_nu5),
-            #[cfg(feature = "unstable-nu6")]
+            #[cfg(zcash_unstable = "nu6")]
             nu6: Some(expected_nu6),
-            #[cfg(feature = "zfuture")]
+            #[cfg(zcash_unstable = "zfuture")]
             z_future: Some(expected_z_future),
         };
 
diff --git a/zcash_client_sqlite/Cargo.toml b/zcash_client_sqlite/Cargo.toml
index d3a46eb32..b106fa5cc 100644
--- a/zcash_client_sqlite/Cargo.toml
+++ b/zcash_client_sqlite/Cargo.toml
@@ -97,8 +97,6 @@ zcash_address = { workspace = true, features = ["test-dependencies"] }
 
 [features]
 default = ["multicore"]
-unstable-nu6 = ["zcash_primitives/unstable-nu6"]
-zfuture = ["zcash_primitives/zfuture"]
 
 ## Enables multithreading support for creating proofs and building subtrees.
 multicore = ["maybe-rayon/threads", "zcash_primitives/multicore"]
diff --git a/zcash_client_sqlite/src/testing.rs b/zcash_client_sqlite/src/testing.rs
index 8c53b1769..7d63401a8 100644
--- a/zcash_client_sqlite/src/testing.rs
+++ b/zcash_client_sqlite/src/testing.rs
@@ -119,9 +119,9 @@ impl TestBuilder<()> {
                 heartwood: Some(BlockHeight::from_u32(100_000)),
                 canopy: Some(BlockHeight::from_u32(100_000)),
                 nu5: Some(BlockHeight::from_u32(100_000)),
-                #[cfg(feature = "unstable-nu6")]
+                #[cfg(zcash_unstable = "nu6")]
                 nu6: None,
-                #[cfg(feature = "zfuture")]
+                #[cfg(zcash_unstable = "zfuture")]
                 z_future: None,
             },
             cache: (),
diff --git a/zcash_extensions/Cargo.toml b/zcash_extensions/Cargo.toml
index d1bb69c45..009a16606 100644
--- a/zcash_extensions/Cargo.toml
+++ b/zcash_extensions/Cargo.toml
@@ -16,7 +16,7 @@ rustdoc-args = ["--cfg", "docsrs"]
 
 [dependencies]
 blake2b_simd.workspace = true
-zcash_primitives = { workspace = true, features = ["zfuture" ] }
+zcash_primitives.workspace = true
 
 [dev-dependencies]
 ff.workspace = true
@@ -29,7 +29,6 @@ zcash_proofs.workspace = true
 
 [features]
 transparent-inputs = []
-unstable-nu6 = ["zcash_primitives/unstable-nu6"]
 
 [lib]
 bench = false
diff --git a/zcash_extensions/src/lib.rs b/zcash_extensions/src/lib.rs
index 2b88fa20b..5dc0c812c 100644
--- a/zcash_extensions/src/lib.rs
+++ b/zcash_extensions/src/lib.rs
@@ -3,5 +3,10 @@
 // Catch documentation errors caused by code changes.
 #![deny(rustdoc::broken_intra_doc_links)]
 
+// For workspace compilation reasons, we have this crate in the workspace and just leave
+// it empty if `zfuture` is not enabled.
+
+#[cfg(zcash_unstable = "zfuture")]
 pub mod consensus;
+#[cfg(zcash_unstable = "zfuture")]
 pub mod transparent;
diff --git a/zcash_extensions/src/transparent/demo.rs b/zcash_extensions/src/transparent/demo.rs
index 6f2662993..40389cbb3 100644
--- a/zcash_extensions/src/transparent/demo.rs
+++ b/zcash_extensions/src/transparent/demo.rs
@@ -513,7 +513,7 @@ mod tests {
                 NetworkUpgrade::Heartwood => Some(BlockHeight::from_u32(903_800)),
                 NetworkUpgrade::Canopy => Some(BlockHeight::from_u32(1_028_500)),
                 NetworkUpgrade::Nu5 => Some(BlockHeight::from_u32(1_200_000)),
-                #[cfg(feature = "unstable-nu6")]
+                #[cfg(zcash_unstable = "nu6")]
                 NetworkUpgrade::Nu6 => Some(BlockHeight::from_u32(1_300_000)),
                 NetworkUpgrade::ZFuture => Some(BlockHeight::from_u32(1_400_000)),
             }
diff --git a/zcash_primitives/CHANGELOG.md b/zcash_primitives/CHANGELOG.md
index 35723435a..ffc62e899 100644
--- a/zcash_primitives/CHANGELOG.md
+++ b/zcash_primitives/CHANGELOG.md
@@ -33,6 +33,9 @@ and this library adheres to Rust's notion of
   - `impl From<NonNegativeAmount> for orchard::NoteValue`
 - The `local_consensus` module and feature flag have been removed; use the module
   from the `zcash_protocol` crate instead.
+- `unstable-nu6` and `zfuture` feature flags (use `--cfg zcash_unstable=\"nu6\"`
+  or `--cfg zcash_unstable=\"zfuture\"` in `RUSTFLAGS` and `RUSTDOCFLAGS`
+  instead).
 
 ## [0.14.0] - 2024-03-01
 ### Added
diff --git a/zcash_primitives/Cargo.toml b/zcash_primitives/Cargo.toml
index c34921560..7bbc788a0 100644
--- a/zcash_primitives/Cargo.toml
+++ b/zcash_primitives/Cargo.toml
@@ -123,16 +123,6 @@ test-dependencies = [
     "zcash_protocol/test-dependencies",
 ]
 
-#! ### Experimental features
-#!
-#! ⚠️ Enabling these features will likely make your code incompatible with current Zcash
-#! consensus rules!
-
-## Exposes the in-development NU6 features.
-unstable-nu6 = ["zcash_protocol/unstable-nu6"]
-
-## Exposes early in-development features that are not yet planned for any network upgrade.
-zfuture = ["zcash_protocol/zfuture"]
 [lib]
 bench = false
 
diff --git a/zcash_primitives/src/lib.rs b/zcash_primitives/src/lib.rs
index 37c37d653..f514fb177 100644
--- a/zcash_primitives/src/lib.rs
+++ b/zcash_primitives/src/lib.rs
@@ -26,6 +26,6 @@ pub mod merkle_tree;
 use sapling;
 pub mod transaction;
 pub use zip32;
-#[cfg(feature = "zfuture")]
+#[cfg(zcash_unstable = "zfuture")]
 pub mod extensions;
 pub mod zip339;
diff --git a/zcash_primitives/src/transaction/builder.rs b/zcash_primitives/src/transaction/builder.rs
index 2fc016bd8..ef352d7e0 100644
--- a/zcash_primitives/src/transaction/builder.rs
+++ b/zcash_primitives/src/transaction/builder.rs
@@ -35,7 +35,7 @@ use crate::transaction::components::transparent::builder::TransparentInputInfo;
 #[cfg(not(feature = "transparent-inputs"))]
 use std::convert::Infallible;
 
-#[cfg(feature = "zfuture")]
+#[cfg(zcash_unstable = "zfuture")]
 use crate::{
     extensions::transparent::{ExtensionTxBuilder, ToPayload},
     transaction::{
@@ -100,7 +100,7 @@ pub enum Error<FE> {
     /// spend or output was added.
     OrchardBuilderNotAvailable,
     /// An error occurred in constructing the TZE parts of a transaction.
-    #[cfg(feature = "zfuture")]
+    #[cfg(zcash_unstable = "zfuture")]
     TzeBuild(tze::builder::Error),
 }
 
@@ -132,7 +132,7 @@ impl<FE: fmt::Display> fmt::Display for Error<FE> {
                 f,
                 "Cannot create Orchard transactions without an Orchard anchor, or before NU5 activation"
             ),
-            #[cfg(feature = "zfuture")]
+            #[cfg(zcash_unstable = "zfuture")]
             Error::TzeBuild(err) => err.fmt(f),
         }
     }
@@ -284,9 +284,9 @@ pub struct Builder<'a, P, U: sapling::builder::ProverProgress> {
     // derivatives for proving and signing to complete transaction creation.
     sapling_asks: Vec<sapling::keys::SpendAuthorizingKey>,
     orchard_saks: Vec<orchard::keys::SpendAuthorizingKey>,
-    #[cfg(feature = "zfuture")]
+    #[cfg(zcash_unstable = "zfuture")]
     tze_builder: TzeBuilder<'a, TransactionData<Unauthorized>>,
-    #[cfg(not(feature = "zfuture"))]
+    #[cfg(not(zcash_unstable = "zfuture"))]
     tze_builder: std::marker::PhantomData<&'a ()>,
     progress_notifier: U,
 }
@@ -369,9 +369,9 @@ impl<'a, P: consensus::Parameters> Builder<'a, P, ()> {
             orchard_builder,
             sapling_asks: vec![],
             orchard_saks: Vec::new(),
-            #[cfg(feature = "zfuture")]
+            #[cfg(zcash_unstable = "zfuture")]
             tze_builder: TzeBuilder::empty(),
-            #[cfg(not(feature = "zfuture"))]
+            #[cfg(not(zcash_unstable = "zfuture"))]
             tze_builder: std::marker::PhantomData,
             progress_notifier: (),
         }
@@ -521,7 +521,7 @@ impl<'a, P: consensus::Parameters, U: sapling::builder::ProverProgress> Builder<
                         .map_err(|_| BalanceError::Overflow)
                 },
             )?,
-            #[cfg(feature = "zfuture")]
+            #[cfg(zcash_unstable = "zfuture")]
             self.tze_builder.value_balance()?,
         ];
 
@@ -577,7 +577,7 @@ impl<'a, P: consensus::Parameters, U: sapling::builder::ProverProgress> Builder<
             .map_err(FeeError::FeeRule)
     }
 
-    #[cfg(feature = "zfuture")]
+    #[cfg(zcash_unstable = "zfuture")]
     pub fn get_fee_zfuture<FR: FeeRule + FutureFeeRule>(
         &self,
         fee_rule: &FR,
@@ -641,7 +641,7 @@ impl<'a, P: consensus::Parameters, U: sapling::builder::ProverProgress> Builder<
     ///
     /// Upon success, returns a tuple containing the final transaction, and the
     /// [`SaplingMetadata`] generated during the build process.
-    #[cfg(feature = "zfuture")]
+    #[cfg(zcash_unstable = "zfuture")]
     pub fn build_zfuture<
         R: RngCore + CryptoRng,
         SP: SpendProver,
@@ -734,7 +734,7 @@ impl<'a, P: consensus::Parameters, U: sapling::builder::ProverProgress> Builder<
             None => (None, orchard::builder::BundleMetadata::empty()),
         };
 
-        #[cfg(feature = "zfuture")]
+        #[cfg(zcash_unstable = "zfuture")]
         let (tze_bundle, tze_signers) = self.tze_builder.build();
 
         let unauthed_tx: TransactionData<Unauthorized> = TransactionData {
@@ -746,7 +746,7 @@ impl<'a, P: consensus::Parameters, U: sapling::builder::ProverProgress> Builder<
             sprout_bundle: None,
             sapling_bundle,
             orchard_bundle,
-            #[cfg(feature = "zfuture")]
+            #[cfg(zcash_unstable = "zfuture")]
             tze_bundle,
         };
 
@@ -764,7 +764,7 @@ impl<'a, P: consensus::Parameters, U: sapling::builder::ProverProgress> Builder<
             )
         });
 
-        #[cfg(feature = "zfuture")]
+        #[cfg(zcash_unstable = "zfuture")]
         let tze_bundle = unauthed_tx
             .tze_bundle
             .clone()
@@ -814,7 +814,7 @@ impl<'a, P: consensus::Parameters, U: sapling::builder::ProverProgress> Builder<
             sprout_bundle: unauthed_tx.sprout_bundle,
             sapling_bundle,
             orchard_bundle,
-            #[cfg(feature = "zfuture")]
+            #[cfg(zcash_unstable = "zfuture")]
             tze_bundle,
         };
 
@@ -828,7 +828,7 @@ impl<'a, P: consensus::Parameters, U: sapling::builder::ProverProgress> Builder<
     }
 }
 
-#[cfg(feature = "zfuture")]
+#[cfg(zcash_unstable = "zfuture")]
 impl<'a, P: consensus::Parameters, U: sapling::builder::ProverProgress> ExtensionTxBuilder<'a>
     for Builder<'a, P, U>
 {
@@ -934,7 +934,7 @@ mod tests {
 
     use super::{Builder, Error};
 
-    #[cfg(feature = "zfuture")]
+    #[cfg(zcash_unstable = "zfuture")]
     #[cfg(feature = "transparent-inputs")]
     use super::TzeBuilder;
 
@@ -969,9 +969,9 @@ mod tests {
             expiry_height: sapling_activation_height + DEFAULT_TX_EXPIRY_DELTA,
             transparent_builder: TransparentBuilder::empty(),
             sapling_builder: None,
-            #[cfg(feature = "zfuture")]
+            #[cfg(zcash_unstable = "zfuture")]
             tze_builder: TzeBuilder::empty(),
-            #[cfg(not(feature = "zfuture"))]
+            #[cfg(not(zcash_unstable = "zfuture"))]
             tze_builder: std::marker::PhantomData,
             progress_notifier: (),
             orchard_builder: None,
diff --git a/zcash_primitives/src/transaction/components.rs b/zcash_primitives/src/transaction/components.rs
index bba5ddf95..f239b0ba0 100644
--- a/zcash_primitives/src/transaction/components.rs
+++ b/zcash_primitives/src/transaction/components.rs
@@ -16,6 +16,7 @@ pub mod orchard;
 pub mod sapling;
 pub mod sprout;
 pub mod transparent;
+#[cfg(zcash_unstable = "zfuture")]
 pub mod tze;
 
 pub use self::{
@@ -25,7 +26,7 @@ pub use self::{
 };
 pub use crate::sapling::bundle::{OutputDescription, SpendDescription};
 
-#[cfg(feature = "zfuture")]
+#[cfg(zcash_unstable = "zfuture")]
 pub use self::tze::{TzeIn, TzeOut};
 
 // π_A + π_B + π_C
diff --git a/zcash_primitives/src/transaction/components/tze.rs b/zcash_primitives/src/transaction/components/tze.rs
index 0e88d35d1..26e849cbc 100644
--- a/zcash_primitives/src/transaction/components/tze.rs
+++ b/zcash_primitives/src/transaction/components/tze.rs
@@ -1,5 +1,4 @@
 //! Structs representing the TZE components within Zcash transactions.
-#![cfg(feature = "zfuture")]
 
 use byteorder::{LittleEndian, ReadBytesExt, WriteBytesExt};
 use std::convert::TryFrom;
diff --git a/zcash_primitives/src/transaction/components/tze/builder.rs b/zcash_primitives/src/transaction/components/tze/builder.rs
index ff8ca49bf..974dac9ce 100644
--- a/zcash_primitives/src/transaction/components/tze/builder.rs
+++ b/zcash_primitives/src/transaction/components/tze/builder.rs
@@ -1,5 +1,4 @@
 //! Types and functions for building TZE transaction components
-#![cfg(feature = "zfuture")]
 
 use std::fmt;
 
diff --git a/zcash_primitives/src/transaction/fees.rs b/zcash_primitives/src/transaction/fees.rs
index 313391be6..0dc82acf2 100644
--- a/zcash_primitives/src/transaction/fees.rs
+++ b/zcash_primitives/src/transaction/fees.rs
@@ -9,7 +9,7 @@ pub mod fixed;
 pub mod transparent;
 pub mod zip317;
 
-#[cfg(feature = "zfuture")]
+#[cfg(zcash_unstable = "zfuture")]
 pub mod tze;
 
 /// A trait that represents the ability to compute the fees that must be paid
@@ -37,7 +37,7 @@ pub trait FeeRule {
 
 /// A trait that represents the ability to compute the fees that must be paid by a transaction
 /// having a specified set of inputs and outputs, for use when experimenting with the TZE feature.
-#[cfg(feature = "zfuture")]
+#[cfg(zcash_unstable = "zfuture")]
 pub trait FutureFeeRule: FeeRule {
     /// Computes the total fee required for a transaction given the provided inputs and outputs.
     ///
diff --git a/zcash_primitives/src/transaction/fees/fixed.rs b/zcash_primitives/src/transaction/fees/fixed.rs
index 660eb5f78..1bb1b3852 100644
--- a/zcash_primitives/src/transaction/fees/fixed.rs
+++ b/zcash_primitives/src/transaction/fees/fixed.rs
@@ -4,7 +4,7 @@ use crate::{
     transaction::fees::{transparent, zip317},
 };
 
-#[cfg(feature = "zfuture")]
+#[cfg(zcash_unstable = "zfuture")]
 use crate::transaction::fees::tze;
 
 /// A fee rule that always returns a fixed fee, irrespective of the structure of
@@ -62,7 +62,7 @@ impl super::FeeRule for FeeRule {
     }
 }
 
-#[cfg(feature = "zfuture")]
+#[cfg(zcash_unstable = "zfuture")]
 impl super::FutureFeeRule for FeeRule {
     fn fee_required_zfuture<P: consensus::Parameters>(
         &self,
diff --git a/zcash_primitives/src/transaction/mod.rs b/zcash_primitives/src/transaction/mod.rs
index 7e3802a18..b7e994329 100644
--- a/zcash_primitives/src/transaction/mod.rs
+++ b/zcash_primitives/src/transaction/mod.rs
@@ -38,7 +38,7 @@ use self::{
     util::sha256d::{HashReader, HashWriter},
 };
 
-#[cfg(feature = "zfuture")]
+#[cfg(zcash_unstable = "zfuture")]
 use self::components::tze::{self, TzeIn, TzeOut};
 
 const OVERWINTER_VERSION_GROUP_ID: u32 = 0x03C48270;
@@ -55,9 +55,9 @@ const V5_VERSION_GROUP_ID: u32 = 0x26A7270A;
 /// using these constants should be inspected, and use of these constants
 /// should be removed as appropriate in favor of the new consensus
 /// transaction version and group.
-#[cfg(feature = "zfuture")]
+#[cfg(zcash_unstable = "zfuture")]
 const ZFUTURE_VERSION_GROUP_ID: u32 = 0xFFFFFFFF;
-#[cfg(feature = "zfuture")]
+#[cfg(zcash_unstable = "zfuture")]
 const ZFUTURE_TX_VERSION: u32 = 0x0000FFFF;
 
 /// The identifier for a Zcash transaction.
@@ -131,7 +131,7 @@ pub enum TxVersion {
     Overwinter,
     Sapling,
     Zip225,
-    #[cfg(feature = "zfuture")]
+    #[cfg(zcash_unstable = "zfuture")]
     ZFuture,
 }
 
@@ -146,7 +146,7 @@ impl TxVersion {
                 (OVERWINTER_TX_VERSION, OVERWINTER_VERSION_GROUP_ID) => Ok(TxVersion::Overwinter),
                 (SAPLING_TX_VERSION, SAPLING_VERSION_GROUP_ID) => Ok(TxVersion::Sapling),
                 (V5_TX_VERSION, V5_VERSION_GROUP_ID) => Ok(TxVersion::Zip225),
-                #[cfg(feature = "zfuture")]
+                #[cfg(zcash_unstable = "zfuture")]
                 (ZFUTURE_TX_VERSION, ZFUTURE_VERSION_GROUP_ID) => Ok(TxVersion::ZFuture),
                 _ => Err(io::Error::new(
                     io::ErrorKind::InvalidInput,
@@ -176,7 +176,7 @@ impl TxVersion {
                 TxVersion::Overwinter => OVERWINTER_TX_VERSION,
                 TxVersion::Sapling => SAPLING_TX_VERSION,
                 TxVersion::Zip225 => V5_TX_VERSION,
-                #[cfg(feature = "zfuture")]
+                #[cfg(zcash_unstable = "zfuture")]
                 TxVersion::ZFuture => ZFUTURE_TX_VERSION,
             }
     }
@@ -187,7 +187,7 @@ impl TxVersion {
             TxVersion::Overwinter => OVERWINTER_VERSION_GROUP_ID,
             TxVersion::Sapling => SAPLING_VERSION_GROUP_ID,
             TxVersion::Zip225 => V5_VERSION_GROUP_ID,
-            #[cfg(feature = "zfuture")]
+            #[cfg(zcash_unstable = "zfuture")]
             TxVersion::ZFuture => ZFUTURE_VERSION_GROUP_ID,
         }
     }
@@ -206,7 +206,7 @@ impl TxVersion {
             TxVersion::Sprout(v) => *v >= 2u32,
             TxVersion::Overwinter | TxVersion::Sapling => true,
             TxVersion::Zip225 => false,
-            #[cfg(feature = "zfuture")]
+            #[cfg(zcash_unstable = "zfuture")]
             TxVersion::ZFuture => true,
         }
     }
@@ -221,7 +221,7 @@ impl TxVersion {
             TxVersion::Sprout(_) | TxVersion::Overwinter => false,
             TxVersion::Sapling => true,
             TxVersion::Zip225 => true,
-            #[cfg(feature = "zfuture")]
+            #[cfg(zcash_unstable = "zfuture")]
             TxVersion::ZFuture => true,
         }
     }
@@ -231,12 +231,12 @@ impl TxVersion {
         match self {
             TxVersion::Sprout(_) | TxVersion::Overwinter | TxVersion::Sapling => false,
             TxVersion::Zip225 => true,
-            #[cfg(feature = "zfuture")]
+            #[cfg(zcash_unstable = "zfuture")]
             TxVersion::ZFuture => true,
         }
     }
 
-    #[cfg(feature = "zfuture")]
+    #[cfg(zcash_unstable = "zfuture")]
     pub fn has_tze(&self) -> bool {
         matches!(self, TxVersion::ZFuture)
     }
@@ -250,9 +250,9 @@ impl TxVersion {
                 TxVersion::Sapling
             }
             BranchId::Nu5 => TxVersion::Zip225,
-            #[cfg(feature = "unstable-nu6")]
+            #[cfg(zcash_unstable = "nu6")]
             BranchId::Nu6 => TxVersion::Zip225,
-            #[cfg(feature = "zfuture")]
+            #[cfg(zcash_unstable = "zfuture")]
             BranchId::ZFuture => TxVersion::ZFuture,
         }
     }
@@ -264,7 +264,7 @@ pub trait Authorization {
     type SaplingAuth: sapling::bundle::Authorization;
     type OrchardAuth: orchard::bundle::Authorization;
 
-    #[cfg(feature = "zfuture")]
+    #[cfg(zcash_unstable = "zfuture")]
     type TzeAuth: tze::Authorization;
 }
 
@@ -277,7 +277,7 @@ impl Authorization for Authorized {
     type SaplingAuth = sapling::bundle::Authorized;
     type OrchardAuth = orchard::bundle::Authorized;
 
-    #[cfg(feature = "zfuture")]
+    #[cfg(zcash_unstable = "zfuture")]
     type TzeAuth = tze::Authorized;
 }
 
@@ -294,7 +294,7 @@ impl Authorization for Unauthorized {
     type OrchardAuth =
         orchard::builder::InProgress<orchard::builder::Unproven, orchard::builder::Unauthorized>;
 
-    #[cfg(feature = "zfuture")]
+    #[cfg(zcash_unstable = "zfuture")]
     type TzeAuth = tze::builder::Unauthorized;
 }
 
@@ -330,7 +330,7 @@ pub struct TransactionData<A: Authorization> {
     sprout_bundle: Option<sprout::Bundle>,
     sapling_bundle: Option<sapling::Bundle<A::SaplingAuth, Amount>>,
     orchard_bundle: Option<orchard::bundle::Bundle<A::OrchardAuth, Amount>>,
-    #[cfg(feature = "zfuture")]
+    #[cfg(zcash_unstable = "zfuture")]
     tze_bundle: Option<tze::Bundle<A::TzeAuth>>,
 }
 
@@ -356,14 +356,14 @@ impl<A: Authorization> TransactionData<A> {
             sprout_bundle,
             sapling_bundle,
             orchard_bundle,
-            #[cfg(feature = "zfuture")]
+            #[cfg(zcash_unstable = "zfuture")]
             tze_bundle: None,
         }
     }
 
     /// Constructs a `TransactionData` from its constituent parts, including speculative
     /// future parts that are not in the current Zcash consensus rules.
-    #[cfg(feature = "zfuture")]
+    #[cfg(zcash_unstable = "zfuture")]
     #[allow(clippy::too_many_arguments)]
     pub fn from_parts_zfuture(
         version: TxVersion,
@@ -423,7 +423,7 @@ impl<A: Authorization> TransactionData<A> {
         self.orchard_bundle.as_ref()
     }
 
-    #[cfg(feature = "zfuture")]
+    #[cfg(zcash_unstable = "zfuture")]
     pub fn tze_bundle(&self) -> Option<&tze::Bundle<A::TzeAuth>> {
         self.tze_bundle.as_ref()
     }
@@ -469,7 +469,7 @@ impl<A: Authorization> TransactionData<A> {
             digester.digest_transparent(self.transparent_bundle.as_ref()),
             digester.digest_sapling(self.sapling_bundle.as_ref()),
             digester.digest_orchard(self.orchard_bundle.as_ref()),
-            #[cfg(feature = "zfuture")]
+            #[cfg(zcash_unstable = "zfuture")]
             digester.digest_tze(self.tze_bundle.as_ref()),
         )
     }
@@ -489,9 +489,10 @@ impl<A: Authorization> TransactionData<A> {
         f_orchard: impl FnOnce(
             Option<orchard::bundle::Bundle<A::OrchardAuth, Amount>>,
         ) -> Option<orchard::bundle::Bundle<B::OrchardAuth, Amount>>,
-        #[cfg(feature = "zfuture")] f_tze: impl FnOnce(
+        #[cfg(zcash_unstable = "zfuture")] f_tze: impl FnOnce(
             Option<tze::Bundle<A::TzeAuth>>,
-        ) -> Option<tze::Bundle<B::TzeAuth>>,
+        )
+            -> Option<tze::Bundle<B::TzeAuth>>,
     ) -> TransactionData<B> {
         TransactionData {
             version: self.version,
@@ -502,7 +503,7 @@ impl<A: Authorization> TransactionData<A> {
             sprout_bundle: self.sprout_bundle,
             sapling_bundle: f_sapling(self.sapling_bundle),
             orchard_bundle: f_orchard(self.orchard_bundle),
-            #[cfg(feature = "zfuture")]
+            #[cfg(zcash_unstable = "zfuture")]
             tze_bundle: f_tze(self.tze_bundle),
         }
     }
@@ -512,7 +513,7 @@ impl<A: Authorization> TransactionData<A> {
         f_transparent: impl transparent::MapAuth<A::TransparentAuth, B::TransparentAuth>,
         mut f_sapling: impl sapling_serialization::MapAuth<A::SaplingAuth, B::SaplingAuth>,
         mut f_orchard: impl orchard_serialization::MapAuth<A::OrchardAuth, B::OrchardAuth>,
-        #[cfg(feature = "zfuture")] f_tze: impl tze::MapAuth<A::TzeAuth, B::TzeAuth>,
+        #[cfg(zcash_unstable = "zfuture")] f_tze: impl tze::MapAuth<A::TzeAuth, B::TzeAuth>,
     ) -> TransactionData<B> {
         TransactionData {
             version: self.version,
@@ -539,7 +540,7 @@ impl<A: Authorization> TransactionData<A> {
                     |f, a| f.map_authorization(a),
                 )
             }),
-            #[cfg(feature = "zfuture")]
+            #[cfg(zcash_unstable = "zfuture")]
             tze_bundle: self.tze_bundle.map(|b| b.map_authorization(f_tze)),
         }
     }
@@ -566,7 +567,7 @@ impl Transaction {
                 Self::from_data_v4(data)
             }
             TxVersion::Zip225 => Ok(Self::from_data_v5(data)),
-            #[cfg(feature = "zfuture")]
+            #[cfg(zcash_unstable = "zfuture")]
             TxVersion::ZFuture => Ok(Self::from_data_v5(data)),
         }
     }
@@ -609,7 +610,7 @@ impl Transaction {
                 Self::read_v4(reader, version, consensus_branch_id)
             }
             TxVersion::Zip225 => Self::read_v5(reader.into_base_reader(), version),
-            #[cfg(feature = "zfuture")]
+            #[cfg(zcash_unstable = "zfuture")]
             TxVersion::ZFuture => Self::read_v5(reader.into_base_reader(), version),
         }
     }
@@ -685,7 +686,7 @@ impl Transaction {
                     )
                 }),
                 orchard_bundle: None,
-                #[cfg(feature = "zfuture")]
+                #[cfg(zcash_unstable = "zfuture")]
                 tze_bundle: None,
             },
         })
@@ -721,7 +722,7 @@ impl Transaction {
         let sapling_bundle = sapling_serialization::read_v5_bundle(&mut reader)?;
         let orchard_bundle = orchard_serialization::read_v5_bundle(&mut reader)?;
 
-        #[cfg(feature = "zfuture")]
+        #[cfg(zcash_unstable = "zfuture")]
         let tze_bundle = if version.has_tze() {
             Self::read_tze(&mut reader)?
         } else {
@@ -737,7 +738,7 @@ impl Transaction {
             sprout_bundle: None,
             sapling_bundle,
             orchard_bundle,
-            #[cfg(feature = "zfuture")]
+            #[cfg(zcash_unstable = "zfuture")]
             tze_bundle,
         };
 
@@ -765,7 +766,7 @@ impl Transaction {
         sapling_serialization::read_v5_bundle(reader)
     }
 
-    #[cfg(feature = "zfuture")]
+    #[cfg(zcash_unstable = "zfuture")]
     fn read_tze<R: Read>(mut reader: &mut R) -> io::Result<Option<tze::Bundle<tze::Authorized>>> {
         let vin = Vector::read(&mut reader, TzeIn::read)?;
         let vout = Vector::read(&mut reader, TzeOut::read)?;
@@ -786,7 +787,7 @@ impl Transaction {
                 self.write_v4(writer)
             }
             TxVersion::Zip225 => self.write_v5(writer),
-            #[cfg(feature = "zfuture")]
+            #[cfg(zcash_unstable = "zfuture")]
             TxVersion::ZFuture => self.write_v5(writer),
         }
     }
@@ -855,7 +856,7 @@ impl Transaction {
         self.write_transparent(&mut writer)?;
         self.write_v5_sapling(&mut writer)?;
         orchard_serialization::write_v5_bundle(self.orchard_bundle.as_ref(), &mut writer)?;
-        #[cfg(feature = "zfuture")]
+        #[cfg(zcash_unstable = "zfuture")]
         self.write_tze(&mut writer)?;
         Ok(())
     }
@@ -880,7 +881,7 @@ impl Transaction {
         sapling_serialization::write_v5_bundle(writer, self.sapling_bundle.as_ref())
     }
 
-    #[cfg(feature = "zfuture")]
+    #[cfg(zcash_unstable = "zfuture")]
     pub fn write_tze<W: Write>(&self, mut writer: W) -> io::Result<()> {
         if let Some(bundle) = &self.tze_bundle {
             Vector::write(&mut writer, &bundle.vin, |w, e| e.write(w))?;
@@ -919,7 +920,7 @@ pub struct TxDigests<A> {
     pub transparent_digests: Option<TransparentDigests<A>>,
     pub sapling_digest: Option<A>,
     pub orchard_digest: Option<A>,
-    #[cfg(feature = "zfuture")]
+    #[cfg(zcash_unstable = "zfuture")]
     pub tze_digests: Option<TzeDigests<A>>,
 }
 
@@ -929,7 +930,7 @@ pub trait TransactionDigest<A: Authorization> {
     type SaplingDigest;
     type OrchardDigest;
 
-    #[cfg(feature = "zfuture")]
+    #[cfg(zcash_unstable = "zfuture")]
     type TzeDigest;
 
     type Digest;
@@ -957,7 +958,7 @@ pub trait TransactionDigest<A: Authorization> {
         orchard_bundle: Option<&orchard::Bundle<A::OrchardAuth, Amount>>,
     ) -> Self::OrchardDigest;
 
-    #[cfg(feature = "zfuture")]
+    #[cfg(zcash_unstable = "zfuture")]
     fn digest_tze(&self, tze_bundle: Option<&tze::Bundle<A::TzeAuth>>) -> Self::TzeDigest;
 
     fn combine(
@@ -966,7 +967,7 @@ pub trait TransactionDigest<A: Authorization> {
         transparent_digest: Self::TransparentDigest,
         sapling_digest: Self::SaplingDigest,
         orchard_digest: Self::OrchardDigest,
-        #[cfg(feature = "zfuture")] tze_digest: Self::TzeDigest,
+        #[cfg(zcash_unstable = "zfuture")] tze_digest: Self::TzeDigest,
     ) -> Self::Digest;
 }
 
@@ -989,7 +990,7 @@ pub mod testing {
         Authorized, Transaction, TransactionData, TxId, TxVersion,
     };
 
-    #[cfg(feature = "zfuture")]
+    #[cfg(zcash_unstable = "zfuture")]
     use super::components::tze::testing::{self as tze};
 
     pub fn arb_txid() -> impl Strategy<Value = TxId> {
@@ -1004,14 +1005,14 @@ pub mod testing {
                 Just(TxVersion::Sapling).boxed()
             }
             BranchId::Nu5 => Just(TxVersion::Zip225).boxed(),
-            #[cfg(feature = "unstable-nu6")]
+            #[cfg(zcash_unstable = "nu6")]
             BranchId::Nu6 => Just(TxVersion::Zip225).boxed(),
-            #[cfg(feature = "zfuture")]
+            #[cfg(zcash_unstable = "zfuture")]
             BranchId::ZFuture => Just(TxVersion::ZFuture).boxed(),
         }
     }
 
-    #[cfg(not(feature = "zfuture"))]
+    #[cfg(not(zcash_unstable = "zfuture"))]
     prop_compose! {
         pub fn arb_txdata(consensus_branch_id: BranchId)(
             version in arb_tx_version(consensus_branch_id),
@@ -1036,7 +1037,7 @@ pub mod testing {
         }
     }
 
-    #[cfg(feature = "zfuture")]
+    #[cfg(zcash_unstable = "zfuture")]
     prop_compose! {
         pub fn arb_txdata(consensus_branch_id: BranchId)(
             version in arb_tx_version(consensus_branch_id),
diff --git a/zcash_primitives/src/transaction/sighash.rs b/zcash_primitives/src/transaction/sighash.rs
index 93ca0eef2..702ed1757 100644
--- a/zcash_primitives/src/transaction/sighash.rs
+++ b/zcash_primitives/src/transaction/sighash.rs
@@ -11,7 +11,7 @@ use crate::{
     sapling::{self, bundle::GrothProofBytes},
 };
 
-#[cfg(feature = "zfuture")]
+#[cfg(zcash_unstable = "zfuture")]
 use {super::components::Amount, crate::extensions::transparent::Precondition};
 
 pub const SIGHASH_ALL: u8 = 0x01;
@@ -29,7 +29,7 @@ pub enum SignableInput<'a> {
         script_pubkey: &'a Script,
         value: NonNegativeAmount,
     },
-    #[cfg(feature = "zfuture")]
+    #[cfg(zcash_unstable = "zfuture")]
     Tze {
         index: usize,
         precondition: &'a Precondition,
@@ -42,7 +42,7 @@ impl<'a> SignableInput<'a> {
         match self {
             SignableInput::Shielded => SIGHASH_ALL,
             SignableInput::Transparent { hash_type, .. } => *hash_type,
-            #[cfg(feature = "zfuture")]
+            #[cfg(zcash_unstable = "zfuture")]
             SignableInput::Tze { .. } => SIGHASH_ALL,
         }
     }
@@ -92,7 +92,7 @@ pub fn signature_hash<
 
         TxVersion::Zip225 => v5_signature_hash(tx, signable_input, txid_parts),
 
-        #[cfg(feature = "zfuture")]
+        #[cfg(zcash_unstable = "zfuture")]
         TxVersion::ZFuture => v5_signature_hash(tx, signable_input, txid_parts),
     })
 }
diff --git a/zcash_primitives/src/transaction/sighash_v4.rs b/zcash_primitives/src/transaction/sighash_v4.rs
index e50c6902f..ad136e5f8 100644
--- a/zcash_primitives/src/transaction/sighash_v4.rs
+++ b/zcash_primitives/src/transaction/sighash_v4.rs
@@ -255,7 +255,7 @@ pub fn v4_signature_hash<
                 }
             }
 
-            #[cfg(feature = "zfuture")]
+            #[cfg(zcash_unstable = "zfuture")]
             SignableInput::Tze { .. } => {
                 panic!("A request has been made to sign a TZE input, but the transaction version is not ZFuture");
             }
diff --git a/zcash_primitives/src/transaction/sighash_v5.rs b/zcash_primitives/src/transaction/sighash_v5.rs
index 72d15d94f..60b02b8b7 100644
--- a/zcash_primitives/src/transaction/sighash_v5.rs
+++ b/zcash_primitives/src/transaction/sighash_v5.rs
@@ -16,20 +16,18 @@ use crate::transaction::{
     Authorization, TransactionData, TransparentDigests, TxDigests,
 };
 
-#[cfg(feature = "zfuture")]
-use byteorder::WriteBytesExt;
-
-#[cfg(feature = "zfuture")]
-use zcash_encoding::{CompactSize, Vector};
-
-#[cfg(feature = "zfuture")]
-use crate::transaction::{components::tze, TzeDigests};
+#[cfg(zcash_unstable = "zfuture")]
+use {
+    crate::transaction::{components::tze, TzeDigests},
+    byteorder::WriteBytesExt,
+    zcash_encoding::{CompactSize, Vector},
+};
 
 const ZCASH_TRANSPARENT_INPUT_HASH_PERSONALIZATION: &[u8; 16] = b"Zcash___TxInHash";
 const ZCASH_TRANSPARENT_AMOUNTS_HASH_PERSONALIZATION: &[u8; 16] = b"ZTxTrAmountsHash";
 const ZCASH_TRANSPARENT_SCRIPTS_HASH_PERSONALIZATION: &[u8; 16] = b"ZTxTrScriptsHash";
 
-#[cfg(feature = "zfuture")]
+#[cfg(zcash_unstable = "zfuture")]
 const ZCASH_TZE_INPUT_HASH_PERSONALIZATION: &[u8; 16] = b"Zcash__TzeInHash";
 
 fn hasher(personal: &[u8; 16]) -> State {
@@ -140,7 +138,7 @@ fn transparent_sig_digest<A: TransparentAuthorizingContext>(
     }
 }
 
-#[cfg(feature = "zfuture")]
+#[cfg(zcash_unstable = "zfuture")]
 fn tze_input_sigdigests<A: tze::Authorization>(
     bundle: &tze::Bundle<A>,
     input: &SignableInput<'_>,
@@ -197,7 +195,7 @@ pub fn v5_signature_hash<
         ),
         txid_parts.sapling_digest,
         txid_parts.orchard_digest,
-        #[cfg(feature = "zfuture")]
+        #[cfg(zcash_unstable = "zfuture")]
         tx.tze_bundle
             .as_ref()
             .zip(txid_parts.tze_digests.as_ref())
diff --git a/zcash_primitives/src/transaction/tests.rs b/zcash_primitives/src/transaction/tests.rs
index e74fe6370..09552226e 100644
--- a/zcash_primitives/src/transaction/tests.rs
+++ b/zcash_primitives/src/transaction/tests.rs
@@ -21,7 +21,7 @@ use super::{
     Authorization, Transaction, TransactionData, TxDigests, TxIn,
 };
 
-#[cfg(feature = "zfuture")]
+#[cfg(zcash_unstable = "zfuture")]
 use super::components::tze;
 
 #[test]
@@ -44,7 +44,7 @@ fn check_roundtrip(tx: Transaction) -> Result<(), TestCaseError> {
     let txo = Transaction::read(&txn_bytes[..], tx.consensus_branch_id).unwrap();
 
     prop_assert_eq!(tx.version, txo.version);
-    #[cfg(feature = "zfuture")]
+    #[cfg(zcash_unstable = "zfuture")]
     prop_assert_eq!(tx.tze_bundle.as_ref(), txo.tze_bundle.as_ref());
     prop_assert_eq!(tx.lock_time, txo.lock_time);
     prop_assert_eq!(
@@ -115,7 +115,7 @@ proptest! {
     }
 }
 
-#[cfg(feature = "zfuture")]
+#[cfg(zcash_unstable = "zfuture")]
 proptest! {
     #[test]
     #[ignore]
@@ -196,7 +196,7 @@ impl Authorization for TestUnauthorized {
     type SaplingAuth = sapling::bundle::Authorized;
     type OrchardAuth = orchard::bundle::Authorized;
 
-    #[cfg(feature = "zfuture")]
+    #[cfg(zcash_unstable = "zfuture")]
     type TzeAuth = tze::Authorized;
 }
 
@@ -246,7 +246,7 @@ fn zip_0244() {
                 },
             });
 
-        #[cfg(not(feature = "zfuture"))]
+        #[cfg(not(zcash_unstable = "zfuture"))]
         let tdata = TransactionData::from_parts(
             txdata.version(),
             txdata.consensus_branch_id(),
@@ -257,7 +257,7 @@ fn zip_0244() {
             txdata.sapling_bundle().cloned(),
             txdata.orchard_bundle().cloned(),
         );
-        #[cfg(feature = "zfuture")]
+        #[cfg(zcash_unstable = "zfuture")]
         let tdata = TransactionData::from_parts_zfuture(
             txdata.version(),
             txdata.consensus_branch_id(),
diff --git a/zcash_primitives/src/transaction/txid.rs b/zcash_primitives/src/transaction/txid.rs
index ba3b45d37..84941271c 100644
--- a/zcash_primitives/src/transaction/txid.rs
+++ b/zcash_primitives/src/transaction/txid.rs
@@ -23,7 +23,7 @@ use super::{
     Authorization, Authorized, TransactionDigest, TransparentDigests, TxDigests, TxId, TxVersion,
 };
 
-#[cfg(feature = "zfuture")]
+#[cfg(zcash_unstable = "zfuture")]
 use super::{
     components::tze::{self, TzeIn, TzeOut},
     TzeDigests,
@@ -36,7 +36,7 @@ const ZCASH_TX_PERSONALIZATION_PREFIX: &[u8; 12] = b"ZcashTxHash_";
 const ZCASH_HEADERS_HASH_PERSONALIZATION: &[u8; 16] = b"ZTxIdHeadersHash";
 pub(crate) const ZCASH_TRANSPARENT_HASH_PERSONALIZATION: &[u8; 16] = b"ZTxIdTranspaHash";
 const ZCASH_SAPLING_HASH_PERSONALIZATION: &[u8; 16] = b"ZTxIdSaplingHash";
-#[cfg(feature = "zfuture")]
+#[cfg(zcash_unstable = "zfuture")]
 const ZCASH_TZE_HASH_PERSONALIZATION: &[u8; 16] = b"ZTxIdTZE____Hash";
 
 // TxId transparent level 2 node personalization
@@ -45,9 +45,9 @@ const ZCASH_SEQUENCE_HASH_PERSONALIZATION: &[u8; 16] = b"ZTxIdSequencHash";
 const ZCASH_OUTPUTS_HASH_PERSONALIZATION: &[u8; 16] = b"ZTxIdOutputsHash";
 
 // TxId tze level 2 node personalization
-#[cfg(feature = "zfuture")]
+#[cfg(zcash_unstable = "zfuture")]
 const ZCASH_TZE_INPUTS_HASH_PERSONALIZATION: &[u8; 16] = b"ZTxIdTZEIns_Hash";
-#[cfg(feature = "zfuture")]
+#[cfg(zcash_unstable = "zfuture")]
 const ZCASH_TZE_OUTPUTS_HASH_PERSONALIZATION: &[u8; 16] = b"ZTxIdTZEOutsHash";
 
 // TxId sapling level 2 node personalization
@@ -63,7 +63,7 @@ const ZCASH_SAPLING_OUTPUTS_NONCOMPACT_HASH_PERSONALIZATION: &[u8; 16] = b"ZTxId
 const ZCASH_AUTH_PERSONALIZATION_PREFIX: &[u8; 12] = b"ZTxAuthHash_";
 const ZCASH_TRANSPARENT_SCRIPTS_HASH_PERSONALIZATION: &[u8; 16] = b"ZTxAuthTransHash";
 const ZCASH_SAPLING_SIGS_HASH_PERSONALIZATION: &[u8; 16] = b"ZTxAuthSapliHash";
-#[cfg(feature = "zfuture")]
+#[cfg(zcash_unstable = "zfuture")]
 const ZCASH_TZE_WITNESSES_HASH_PERSONALIZATION: &[u8; 16] = b"ZTxAuthTZE__Hash";
 
 fn hasher(personal: &[u8; 16]) -> State {
@@ -112,7 +112,7 @@ pub(crate) fn transparent_outputs_hash<T: Borrow<TxOut>>(vout: &[T]) -> Blake2bH
 /// witness data, to a hash personalized by ZCASH_TZE_INPUTS_HASH_PERSONALIZATION.
 /// In the case that no inputs are provided, this produces a default
 /// hash from just the personalization string.
-#[cfg(feature = "zfuture")]
+#[cfg(zcash_unstable = "zfuture")]
 pub(crate) fn hash_tze_inputs<A>(tze_inputs: &[TzeIn<A>]) -> Blake2bHash {
     let mut h = hasher(ZCASH_TZE_INPUTS_HASH_PERSONALIZATION);
     for tzein in tze_inputs {
@@ -125,7 +125,7 @@ pub(crate) fn hash_tze_inputs<A>(tze_inputs: &[TzeIn<A>]) -> Blake2bHash {
 /// to a hash personalized by ZCASH_TZE_OUTPUTS_HASH_PERSONALIZATION.
 /// In the case that no outputs are provided, this produces a default
 /// hash from just the personalization string.
-#[cfg(feature = "zfuture")]
+#[cfg(zcash_unstable = "zfuture")]
 pub(crate) fn hash_tze_outputs(tze_outputs: &[TzeOut]) -> Blake2bHash {
     let mut h = hasher(ZCASH_TZE_OUTPUTS_HASH_PERSONALIZATION);
     for tzeout in tze_outputs {
@@ -210,7 +210,7 @@ fn transparent_digests<A: transparent::Authorization>(
     }
 }
 
-#[cfg(feature = "zfuture")]
+#[cfg(zcash_unstable = "zfuture")]
 fn tze_digests<A: tze::Authorization>(bundle: &tze::Bundle<A>) -> TzeDigests<Blake2bHash> {
     // The txid commits to the hash for all outputs.
     TzeDigests {
@@ -276,7 +276,7 @@ fn hash_sapling_txid_empty() -> Blake2bHash {
     hasher(ZCASH_SAPLING_HASH_PERSONALIZATION).finalize()
 }
 
-#[cfg(feature = "zfuture")]
+#[cfg(zcash_unstable = "zfuture")]
 fn hash_tze_txid_data(tze_digests: Option<&TzeDigests<Blake2bHash>>) -> Blake2bHash {
     let mut h = hasher(ZCASH_TZE_HASH_PERSONALIZATION);
     if let Some(d) = tze_digests {
@@ -304,7 +304,7 @@ impl<A: Authorization> TransactionDigest<A> for TxIdDigester {
     type SaplingDigest = Option<Blake2bHash>;
     type OrchardDigest = Option<Blake2bHash>;
 
-    #[cfg(feature = "zfuture")]
+    #[cfg(zcash_unstable = "zfuture")]
     type TzeDigest = Option<TzeDigests<Blake2bHash>>;
 
     type Digest = TxDigests<Blake2bHash>;
@@ -340,7 +340,7 @@ impl<A: Authorization> TransactionDigest<A> for TxIdDigester {
         orchard_bundle.map(|b| b.commitment().0)
     }
 
-    #[cfg(feature = "zfuture")]
+    #[cfg(zcash_unstable = "zfuture")]
     fn digest_tze(&self, tze_bundle: Option<&tze::Bundle<A::TzeAuth>>) -> Self::TzeDigest {
         tze_bundle.map(tze_digests)
     }
@@ -351,14 +351,14 @@ impl<A: Authorization> TransactionDigest<A> for TxIdDigester {
         transparent_digests: Self::TransparentDigest,
         sapling_digest: Self::SaplingDigest,
         orchard_digest: Self::OrchardDigest,
-        #[cfg(feature = "zfuture")] tze_digests: Self::TzeDigest,
+        #[cfg(zcash_unstable = "zfuture")] tze_digests: Self::TzeDigest,
     ) -> Self::Digest {
         TxDigests {
             header_digest,
             transparent_digests,
             sapling_digest,
             orchard_digest,
-            #[cfg(feature = "zfuture")]
+            #[cfg(zcash_unstable = "zfuture")]
             tze_digests,
         }
     }
@@ -371,7 +371,7 @@ pub(crate) fn to_hash(
     transparent_digest: Blake2bHash,
     sapling_digest: Option<Blake2bHash>,
     orchard_digest: Option<Blake2bHash>,
-    #[cfg(feature = "zfuture")] tze_digests: Option<&TzeDigests<Blake2bHash>>,
+    #[cfg(zcash_unstable = "zfuture")] tze_digests: Option<&TzeDigests<Blake2bHash>>,
 ) -> Blake2bHash {
     let mut personal = [0; 16];
     personal[..12].copy_from_slice(ZCASH_TX_PERSONALIZATION_PREFIX);
@@ -395,7 +395,7 @@ pub(crate) fn to_hash(
     )
     .unwrap();
 
-    #[cfg(feature = "zfuture")]
+    #[cfg(zcash_unstable = "zfuture")]
     if _txversion.has_tze() {
         h.write_all(hash_tze_txid_data(tze_digests).as_bytes())
             .unwrap();
@@ -416,7 +416,7 @@ pub fn to_txid(
         hash_transparent_txid_data(digests.transparent_digests.as_ref()),
         digests.sapling_digest,
         digests.orchard_digest,
-        #[cfg(feature = "zfuture")]
+        #[cfg(zcash_unstable = "zfuture")]
         digests.tze_digests.as_ref(),
     );
 
@@ -437,7 +437,7 @@ impl TransactionDigest<Authorized> for BlockTxCommitmentDigester {
     type SaplingDigest = Blake2bHash;
     type OrchardDigest = Blake2bHash;
 
-    #[cfg(feature = "zfuture")]
+    #[cfg(zcash_unstable = "zfuture")]
     type TzeDigest = Blake2bHash;
 
     type Digest = Blake2bHash;
@@ -499,7 +499,7 @@ impl TransactionDigest<Authorized> for BlockTxCommitmentDigester {
         })
     }
 
-    #[cfg(feature = "zfuture")]
+    #[cfg(zcash_unstable = "zfuture")]
     fn digest_tze(&self, tze_bundle: Option<&tze::Bundle<tze::Authorized>>) -> Blake2bHash {
         let mut h = hasher(ZCASH_TZE_WITNESSES_HASH_PERSONALIZATION);
         if let Some(bundle) = tze_bundle {
@@ -516,7 +516,7 @@ impl TransactionDigest<Authorized> for BlockTxCommitmentDigester {
         transparent_digest: Self::TransparentDigest,
         sapling_digest: Self::SaplingDigest,
         orchard_digest: Self::OrchardDigest,
-        #[cfg(feature = "zfuture")] tze_digest: Self::TzeDigest,
+        #[cfg(zcash_unstable = "zfuture")] tze_digest: Self::TzeDigest,
     ) -> Self::Digest {
         let digests = [transparent_digest, sapling_digest, orchard_digest];
 
@@ -531,7 +531,7 @@ impl TransactionDigest<Authorized> for BlockTxCommitmentDigester {
             h.write_all(digest.as_bytes()).unwrap();
         }
 
-        #[cfg(feature = "zfuture")]
+        #[cfg(zcash_unstable = "zfuture")]
         if TxVersion::suggested_for_branch(consensus_branch_id).has_tze() {
             h.write_all(tze_digest.as_bytes()).unwrap();
         }