diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index ce92952..fd9e398 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -17,24 +17,24 @@ jobs:
       - name: checkout-code
         uses: actions/checkout@v4
       - name: cargo-check
-        run: nix develop --command cargo check
+        run: nix develop .#ci --command cargo check
       - name: cargo-test
-        run: nix develop --command cargo test --all-features
+        run: nix develop .#ci --command cargo test --all-features
       - name: cargo-clippy
-        run: nix develop --command cargo clippy
+        run: nix develop .#ci --command cargo clippy
       - name: cargo-bench
-        run: nix develop --command cargo bench --no-run # Just to make sure it compiles
+        run: nix develop .#ci --command cargo bench --no-run # Just to make sure it compiles
       - name: cargo-fmt
-        run: nix develop --command cargo fmt --check
+        run: nix develop .#ci --command cargo fmt --check
       - name: cargo-doc
-        run: nix develop --command cargo doc
+        run: nix develop .#ci --command cargo doc
       - name: nix-flake-check
         run: nix flake check
       - name: nix-deadnix
-        run: nix develop --command deadnix
+        run: nix develop .#ci --command deadnix
       - name: nix-statix
-        run: nix develop --command statix check
+        run: nix develop .#ci --command statix check
       - name: nix-alejandra
-        run: nix develop --command alejandra --check .
+        run: nix develop .#ci --command alejandra --check .
       - name: yamlfmt
-        run: nix develop --command yamlfmt -lint .
+        run: nix develop .#ci --command yamlfmt -lint --gitignore_excludes .
diff --git a/Cargo.lock b/Cargo.lock
index 95cf60a..2fd8f06 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1136,7 +1136,7 @@ checksum = "bbd2bcb4c963f2ddae06a2efc7e9f3591312473c50c6685e1f298068316e66fe"
 
 [[package]]
 name = "lfest"
-version = "0.138.3"
+version = "0.138.4"
 dependencies = [
  "assert2",
  "const-decimal",
diff --git a/Cargo.toml b/Cargo.toml
index 4ee9f00..6d6087e 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "lfest"
-version = "0.138.3"
+version = "0.138.4"
 authors = ["MathisWellmann <wellmannmathis@gmail.com>"]
 edition = "2024"
 license-file = "LICENSE"
diff --git a/flake.nix b/flake.nix
index 442655f..02f3c31 100644
--- a/flake.nix
+++ b/flake.nix
@@ -80,19 +80,29 @@
         ];
       in
         with pkgs; {
-          devShells.default = mkShell {
-            buildInputs = buildInputs ++ rust_tools ++ nix_tools ++ tools;
-            RUST_BACKTRACE = "1";
-          };
-          # Minimal shell for the AI PR review workflow
-          # (.github/workflows/review.yml). Kept tiny on purpose: `nix develop`
-          # builds this closure on the runner, so no rust/pythonEnv here.
-          devShells.review = mkShell {
-            buildInputs = with pkgs; [
-              llm-agents.packages.${pkgs.stdenv.hostPlatform.system}.pi
-              jq
-              curl
-            ];
+          devShells = {
+            # Minimal shell for .github/workflows/ci.yml: only the tools CI runs.
+            # The default shell also builds creusot, hongdown and the cargo-*
+            # tools, for which nix fetches crate tarballs from crates.io at
+            # build time; CI never uses them.
+            ci = mkShell {
+              buildInputs = [rust] ++ [deadnix statix alejandra yamlfmt];
+              RUST_BACKTRACE = "1";
+            };
+            default = mkShell {
+              buildInputs = buildInputs ++ rust_tools ++ nix_tools ++ tools;
+              RUST_BACKTRACE = "1";
+            };
+            # Minimal shell for the AI PR review workflow
+            # (.github/workflows/review.yml). Kept tiny on purpose: `nix develop`
+            # builds this closure on the runner, so no rust/pythonEnv here.
+            review = mkShell {
+              buildInputs = [
+                llm-agents.packages.${pkgs.stdenv.hostPlatform.system}.pi
+                jq
+                curl
+              ];
+            };
           };
         }
     );
diff --git a/src/account/position.rs b/src/account/position.rs
index 9a0c7fe..5098817 100644
--- a/src/account/position.rs
+++ b/src/account/position.rs
@@ -91,6 +91,27 @@ where
         }
     }
 
+    /// The signed position quantity as an `f64` (negative for a short position).
+    #[must_use]
+    #[inline(always)]
+    pub fn to_f64(&self) -> f64 {
+        self.quantity.into()
+    }
+
+    /// Whether the position is long (positive quantity).
+    #[must_use]
+    #[inline(always)]
+    pub fn is_long(&self) -> bool {
+        self.quantity.is_positive()
+    }
+
+    /// Whether the position is short (negative quantity).
+    #[must_use]
+    #[inline(always)]
+    pub fn is_short(&self) -> bool {
+        self.quantity.is_negative()
+    }
+
     /// Return the positions unrealized profit and loss.
     #[must_use]
     #[inline(always)]
@@ -332,6 +353,31 @@ mod tests {
         assert_eq!(size_of::<Position<i64, 5, BaseCurrency<_, 5>>>(), 16);
     }
 
+    #[test]
+    fn position_to_f64_and_side_predicates() {
+        let long = Position::new(
+            BaseCurrency::<i64, 5>::new(17, 2),
+            QuoteCurrency::new(100, 0),
+        )
+        .unwrap();
+        assert!(long.is_long());
+        assert!(!long.is_short());
+        assert_eq!(long.to_f64(), 0.17);
+
+        let short = Position::new(
+            -BaseCurrency::<i64, 5>::new(17, 2),
+            QuoteCurrency::new(100, 0),
+        )
+        .unwrap();
+        assert!(short.is_short());
+        assert!(!short.is_long());
+        assert_eq!(short.to_f64(), -0.17);
+
+        let neutral: Position<i64, 5, BaseCurrency<i64, 5>> = Position::default();
+        assert!(!neutral.is_long());
+        assert!(!neutral.is_short());
+    }
+
     #[test]
     fn position_side_invert() {
         use PositionSide::*;
diff --git a/src/market_state.rs b/src/market_state.rs
index 882c4e8..418bae9 100644
--- a/src/market_state.rs
+++ b/src/market_state.rs
@@ -82,6 +82,18 @@ where
         self.step += 1;
     }
 
+    /// The best (highest) bid price.
+    #[inline(always)]
+    pub fn best_bid(&self) -> QuoteCurrency<I, D> {
+        self.bid
+    }
+
+    /// The best (lowest) ask price.
+    #[inline(always)]
+    pub fn best_ask(&self) -> QuoteCurrency<I, D> {
+        self.ask
+    }
+
     /// Get the mid price
     #[inline(always)]
     pub fn mid_price(&self) -> QuoteCurrency<I, D> {
@@ -130,6 +142,22 @@ mod test {
         );
     }
 
+    #[test]
+    fn market_state_best_bid_and_ask() {
+        let mut state = MarketState::<i64, 1>::default();
+        let pf = PriceFilter::default();
+        state.update_state::<_, BaseCurrency<_, 1>>(
+            &Bba {
+                bid: QuoteCurrency::<i64, 1>::new(100, 0),
+                ask: QuoteCurrency::new(101, 0),
+                timestamp_exchange_ns: 1.into(),
+            },
+            &pf,
+        );
+        assert_eq!(state.best_bid(), QuoteCurrency::new(100, 0));
+        assert_eq!(state.best_ask(), QuoteCurrency::new(101, 0));
+    }
+
     #[test]
     fn market_state_mid_price() {
         let mut state = MarketState::<i64, 1>::default();