diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index f278749..74c8637 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -9,7 +9,7 @@ on:
 permissions:
   contents: read
 
-# z-engine tracks one PHP minor per release line; the "8.4.x-dev || 8.5.x-dev"
+# z-engine tracks one PHP minor per release line; the "~8.4.2 || ~8.5.0"
 # constraint lets Composer resolve the line matching each runner's PHP, so the
 # suite runs on PHP 8.4 and 8.5 in parallel.
 jobs:
diff --git a/AGENTS.md b/AGENTS.md
index 67fdf4d..d86fddf 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -311,7 +311,7 @@ in every process.
 ### z-engine's line must match the running PHP minor
 
 z-engine reads engine structures by byte offset and those offsets change on every PHP minor, so the
-constraint is `8.4.x-dev || 8.5.x-dev` — Composer resolves the line matching the running PHP.
+constraint is `~8.4.2 || ~8.5.0` — Composer resolves the stable line matching the running PHP.
 `ZEngine\Core::init()` enforces the exact match and refuses to boot on a mismatch. **Never loosen the
 constraint, skip `Core::init()`, or defeat the guard to make a failure go away.** A refusal is the
 guard working.
diff --git a/README.md b/README.md
index dab6052..be208e3 100644
--- a/README.md
+++ b/README.md
@@ -24,10 +24,11 @@ fork-shared `mmap` arena and travel as addresses.
 composer require lisachenko/native-php-coroutines
 ```
 
-z-engine is required as `8.4.x-dev || 8.5.x-dev` — one development line per supported PHP minor,
-resolved by Composer to match the running PHP — so a consuming project needs
-`"minimum-stability": "dev"` with `"prefer-stable": true` at its root, as Composer only resolves
-development stability there.
+z-engine is required as `~8.4.2 || ~8.5.0` — one stable release line per supported PHP minor,
+resolved by Composer to match the running PHP. `lisachenko/php-shared-data-extension` is still
+consumed from `dev-main` (it has no tags yet), so this package keeps `"minimum-stability": "dev"`
+with `"prefer-stable": true` at its root, and a consuming project needs the same pair until that
+dependency is tagged — Composer only resolves development stability at the root level.
 
 ## Quick start
 
@@ -528,8 +529,9 @@ z-engine requires it, and z-engine is a hard dependency of this package.
 - PHP **8.4** or **8.5**, NTS.
 - `ext-ffi` with `ffi.enable=1`, and `opcache.jit=off` — the JIT rewrites the executor internals the
   engine hooks depend on.
-- `lisachenko/z-engine`, resolved per PHP minor (`8.4.x-dev` on 8.4, `8.5.x-dev` on 8.5) — engine
-  structures are read by byte offset, so the line must match the running minor. `ZEngine\Core::init()`
+- `lisachenko/z-engine`, resolved per PHP minor (`8.4.x` on 8.4, `8.5.x` on 8.5, from the
+  `~8.4.2 || ~8.5.0` constraint) — engine structures are read by byte offset, so the line must
+  match the running minor. `ZEngine\Core::init()`
   enforces it and refuses to boot on a mismatch.
 - `ext-pcntl` and `ext-posix` for the parallel and preemption layers (suggested, not required).
   Preemption needs `ext-pcntl` specifically: the slice timer is delivered as `SIGALRM`.
diff --git a/composer.json b/composer.json
index f6de7b4..6b82f6f 100644
--- a/composer.json
+++ b/composer.json
@@ -14,7 +14,7 @@
         "php": "^8.4",
         "ext-ffi": "*",
         "lisachenko/php-shared-data-extension": "dev-main",
-        "lisachenko/z-engine": "8.4.x-dev || 8.5.x-dev"
+        "lisachenko/z-engine": "~8.4.2 || ~8.5.0"
     },
     "minimum-stability": "dev",
     "prefer-stable": true,
diff --git a/spikes/README.md b/spikes/README.md
index 09b0b6d..481a0fe 100644
--- a/spikes/README.md
+++ b/spikes/README.md
@@ -51,9 +51,7 @@ for v in 8.4:ze84 8.5:ze85; do
   php="php${v%%:*}"; dir="${v##*:}"
   mkdir -p "$dir" && (cd "$dir" \
     && "$php" $(command -v composer) init -n --name=spikes/preemption \
-    && "$php" $(command -v composer) config minimum-stability dev \
-    && "$php" $(command -v composer) config prefer-stable true \
-    && "$php" $(command -v composer) require lisachenko/z-engine:"8.4.x-dev || 8.5.x-dev" -n)
+    && "$php" $(command -v composer) require lisachenko/z-engine:"~8.4.2 || ~8.5.0" -n)
 done
 ```