diff --git a/.version-determinate b/.version-determinate
index d15b8b06f..4f2c1d15f 100644
--- a/.version-determinate
+++ b/.version-determinate
@@ -1 +1 @@
-3.6.5
+3.6.6
diff --git a/doc/manual/source/SUMMARY.md.in b/doc/manual/source/SUMMARY.md.in
index 374aacb59..dd3218d2f 100644
--- a/doc/manual/source/SUMMARY.md.in
+++ b/doc/manual/source/SUMMARY.md.in
@@ -129,6 +129,7 @@
   - [Contributing](development/contributing.md)
 - [Determinate Nix Release Notes](release-notes-determinate/index.md)
   - [Changes between Nix and Determinate Nix](release-notes-determinate/changes.md)<!-- next -->
+  - [Release 3.6.6 (2025-06-17)](release-notes-determinate/rl-3.6.6.md)
   - [Release 3.6.5 (2025-06-16)](release-notes-determinate/rl-3.6.5.md)
   - [Release 3.6.2 (2025-06-02)](release-notes-determinate/rl-3.6.2.md)
   - [Release 3.6.1 (2025-05-24)](release-notes-determinate/rl-3.6.1.md)
diff --git a/doc/manual/source/release-notes-determinate/changes.md b/doc/manual/source/release-notes-determinate/changes.md
index 30a68f6e9..6f27f7f6b 100644
--- a/doc/manual/source/release-notes-determinate/changes.md
+++ b/doc/manual/source/release-notes-determinate/changes.md
@@ -1,6 +1,6 @@
 # Changes between Nix and Determinate Nix
 
-This section lists the differences between upstream Nix 2.29 and Determinate Nix 3.6.5.<!-- differences -->
+This section lists the differences between upstream Nix 2.29 and Determinate Nix 3.6.6.<!-- differences -->
 
 * In Determinate Nix, flakes are stable. You no longer need to enable the `flakes` experimental feature.
 
@@ -72,3 +72,5 @@ This section lists the differences between upstream Nix 2.29 and Determinate Nix
 * Improve error messages that use the hypothetical future tense of "will" by @lucperkins in [DeterminateSystems/nix-src#92](https://github.com/DeterminateSystems/nix-src/pull/92)
 
 * Improve caching of inputs in dry-run mode by @edolstra in [DeterminateSystems/nix-src#98](https://github.com/DeterminateSystems/nix-src/pull/98)
+
+<!-- Determinate Nix version 3.6.6 -->
diff --git a/doc/manual/source/release-notes-determinate/rl-3.6.6.md b/doc/manual/source/release-notes-determinate/rl-3.6.6.md
new file mode 100644
index 000000000..bf4e3690a
--- /dev/null
+++ b/doc/manual/source/release-notes-determinate/rl-3.6.6.md
@@ -0,0 +1,7 @@
+# Release 3.6.6 (2025-06-17)
+
+* Based on [upstream Nix 2.29.0](../release-notes/rl-2.29.md).
+
+## What's Changed
+
+* No-op release on the nix-src side, due to a regression on nix-darwin in determinate-nixd.