diff --git a/flake.lock b/flake.lock
index 52fabf4e2..90a157f69 100644
--- a/flake.lock
+++ b/flake.lock
@@ -1,5 +1,26 @@
 {
   "nodes": {
+    "fenix": {
+      "inputs": {
+        "nixpkgs": [
+          "nixpkgs"
+        ],
+        "rust-analyzer-src": "rust-analyzer-src"
+      },
+      "locked": {
+        "lastModified": 1786348189,
+        "narHash": "sha256-tnTpFky6/GeXVMBO+hLJK2jWS4J8TYloL+rqRME9gAk=",
+        "owner": "nix-community",
+        "repo": "fenix",
+        "rev": "a0b1aef63d7e9c5568958e0d90f6fe48f0f4a7a2",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nix-community",
+        "repo": "fenix",
+        "type": "github"
+      }
+    },
     "flake-utils": {
       "inputs": {
         "systems": "systems"
@@ -20,16 +41,16 @@
     },
     "nixpkgs": {
       "locked": {
-        "lastModified": 1764521362,
-        "narHash": "sha256-M101xMtWdF1eSD0xhiR8nG8CXRlHmv6V+VoY65Smwf4=",
-        "owner": "nixos",
+        "lastModified": 1786313170,
+        "narHash": "sha256-9BG7OgUWdu0ONDO5X2q6+K4bsuBITkX/3W4nNJu1Ito=",
+        "owner": "NixOS",
         "repo": "nixpkgs",
-        "rev": "871b9fd269ff6246794583ce4ee1031e1da71895",
+        "rev": "fcb8fcd6bf2d0adecae5bd491afaaaf8311b758d",
         "type": "github"
       },
       "original": {
-        "owner": "nixos",
-        "ref": "25.11",
+        "owner": "NixOS",
+        "ref": "nixos-26.05",
         "repo": "nixpkgs",
         "type": "github"
       }
@@ -50,45 +71,28 @@
         "type": "github"
       }
     },
-    "nixpkgs_2": {
-      "locked": {
-        "lastModified": 1744536153,
-        "narHash": "sha256-awS2zRgF4uTwrOKwwiJcByDzDOdo3Q1rPZbiHQg/N38=",
-        "owner": "NixOS",
-        "repo": "nixpkgs",
-        "rev": "18dd725c29603f582cf1900e0d25f9f1063dbf11",
-        "type": "github"
-      },
-      "original": {
-        "owner": "NixOS",
-        "ref": "nixpkgs-unstable",
-        "repo": "nixpkgs",
-        "type": "github"
-      }
-    },
     "root": {
       "inputs": {
+        "fenix": "fenix",
         "flake-utils": "flake-utils",
         "nixpkgs": "nixpkgs",
-        "nixpkgs-bitcoind": "nixpkgs-bitcoind",
-        "rust-overlay": "rust-overlay"
+        "nixpkgs-bitcoind": "nixpkgs-bitcoind"
       }
     },
-    "rust-overlay": {
-      "inputs": {
-        "nixpkgs": "nixpkgs_2"
-      },
+    "rust-analyzer-src": {
+      "flake": false,
       "locked": {
-        "lastModified": 1777950921,
-        "narHash": "sha256-NpOgt8ISaHTDNJZjNUfwFfbieKfRXzab4WKM31gZCGA=",
-        "owner": "oxalica",
-        "repo": "rust-overlay",
-        "rev": "366ea19e0e55b768f74b7a0b2a20f847e7ae828d",
+        "lastModified": 1786285255,
+        "narHash": "sha256-zJukKxGKLxcO7E6+P49Qe6XaSbbyGG44kFvQYLWaD3M=",
+        "owner": "rust-lang",
+        "repo": "rust-analyzer",
+        "rev": "57411b3a0fb0181ed5965f6541d5ed39a9d79d4c",
         "type": "github"
       },
       "original": {
-        "owner": "oxalica",
-        "repo": "rust-overlay",
+        "owner": "rust-lang",
+        "ref": "nightly",
+        "repo": "rust-analyzer",
         "type": "github"
       }
     },
diff --git a/flake.nix b/flake.nix
index 4d6435815..d887d0ebe 100644
--- a/flake.nix
+++ b/flake.nix
@@ -3,16 +3,19 @@
 
   inputs = {
     # Nixpkgs channel. New channels are released every 6 months.
-    # See: https://github.com/NixOS/nixpkgs/tags
-    nixpkgs.url = "github:nixos/nixpkgs/25.11";
+    # See: https://github.com/NixOS/nixpkgs/branches
+    nixpkgs.url = "github:NixOS/nixpkgs/nixos-26.05";
 
     # This makes it easy for the flake to be multi-platform.
     # See: https://github.com/numtide/flake-utils
     flake-utils.url = "github:numtide/flake-utils";
 
-    # Provides Rust toolchains.
-    # See: https://github.com/oxalica/rust-overlay
-    rust-overlay.url = "github:oxalica/rust-overlay";
+    # Provides pinned Rust toolchains.
+    # See: https://github.com/nix-community/fenix
+    fenix = {
+      url = "github:nix-community/fenix";
+      inputs.nixpkgs.follows = "nixpkgs";
+    };
 
     # Pinned nixpkgs that ships bitcoind 27.1. The integration tests' bundled
     # `corepc-node` deserializes the 27.x `getblockchaininfo` schema, so newer
@@ -25,25 +28,20 @@
       self,
       nixpkgs,
       flake-utils,
-      rust-overlay,
+      fenix,
       nixpkgs-bitcoind,
     }:
     flake-utils.lib.eachDefaultSystem (
       system:
       let
-        # Overlays provide additional packages not available in the channels.
-        overlays = [
-          # Provides the rust-bin package; a set of pre-built Rust toolchains.
-          (import rust-overlay)
-        ];
-
         # The final set of packages.
         pkgs = import nixpkgs {
           # Inheriting from system is what makes this multi-platform.
-          # We also inherit the overlays that we want to use.
-          inherit system overlays;
+          inherit system;
         };
 
+        fenixPkgs = fenix.packages.${system};
+
         # bitcoind 27.1 from the pinned input (see inputs above).
         bitcoind = nixpkgs-bitcoind.legacyPackages.${system}.bitcoind;
 
@@ -53,17 +51,23 @@
         # deliberately exclude `rustfmt`: this repo's `rustfmt.toml` relies on
         # nightly-only options, so formatting is supplied by `rustfmt-nightly`
         # below to keep `just fmt`/`just check` consistent with CI's nightly job.
-        rust-toolchain = pkgs.rust-bin.stable."1.85.1".minimal.override {
-          extensions = [
-            "rust-src" # Needed for the rust-analyzer extension to work.
-            "clippy" # Linter used by `just check`.
-          ];
-        };
+        rust-toolchain =
+          (fenixPkgs.toolchainOf {
+            channel = "1.85.1";
+            sha256 = "sha256-Hn2uaQzRLidAWpfmRwSRdImifGUCAb9HeAqTYFXWeQk=";
+          }).withComponents
+            [
+              "rustc"
+              "cargo"
+              "rust-std"
+              "rust-src" # Needed for the rust-analyzer extension to work.
+              "clippy" # Linter used by `just check`.
+            ];
 
         # Nightly rustfmt only. `cargo fmt` shells out to whichever `rustfmt` is
         # on PATH, so a nightly rustfmt lets the nightly-only options in
         # `rustfmt.toml` apply even though cargo/rustc are pinned to stable.
-        rustfmt-nightly = pkgs.rust-bin.nightly.latest.rustfmt;
+        rustfmt-nightly = fenixPkgs.latest.rustfmt;
 
         # Esplora/HTTP electrs for the integration tests' Esplora chain source.
         #