diff --git a/.craft.yml b/.craft.yml
index c0d5d6a..85a4021 100644
--- a/.craft.yml
+++ b/.craft.yml
@@ -7,7 +7,9 @@ targets:
     includeNames: /^vitest-evals-\d.*\.tgz$/
   - name: npm
     id: "@vitest-evals/harness-ai-sdk"
+    access: public
     includeNames: /^vitest-evals-harness-ai-sdk-\d.*\.tgz$/
   - name: npm
     id: "@vitest-evals/harness-pi-ai"
+    access: public
     includeNames: /^vitest-evals-harness-pi-ai-\d.*\.tgz$/
diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
index 55ba615..99d749e 100644
--- a/.github/workflows/release.yml
+++ b/.github/workflows/release.yml
@@ -11,6 +11,20 @@ on:
           - minor
           - patch
           - major
+      prerelease:
+        description: Prepare a prerelease instead of a stable release
+        required: false
+        type: boolean
+        default: false
+      prerelease_id:
+        description: Prerelease identifier
+        required: false
+        type: choice
+        default: beta
+        options:
+          - beta
+          - rc
+          - alpha
       force:
         description: Force release (bypass blockers)
         required: false
@@ -53,9 +67,13 @@ jobs:
       id: version
       env:
         BUMP: ${{ inputs.bump }}
+        PRERELEASE: ${{ inputs.prerelease }}
+        PRERELEASE_ID: ${{ inputs.prerelease_id }}
       run: |
+        set -euo pipefail
         CURRENT=$(node -p "require('./packages/vitest-evals/package.json').version")
-        NEW=$(npx semver -i "$BUMP" "$CURRENT")
+        NEW=$(node ./scripts/calculate-release-version.mjs \
+          "$CURRENT" "$BUMP" "$PRERELEASE" "$PRERELEASE_ID")
         echo "current=$CURRENT" >> "$GITHUB_OUTPUT"
         echo "new=$NEW" >> "$GITHUB_OUTPUT"
 
diff --git a/README.md b/README.md
index b2b041b..808a77b 100644
--- a/README.md
+++ b/README.md
@@ -51,6 +51,18 @@ tables.
 Pull request CI runs the same core safety checks: release config validation,
 lint, typecheck, the CI test suite, and the workspace build.
 
+## Releases
+
+Use the manual Release workflow for stable releases. Select `patch`, `minor`,
+or `major` for the normal version bump.
+
+For a preview release that should not become the main stable version, set
+`prerelease` to `true` and leave `prerelease_id` as `beta` unless you want an
+`rc` or `alpha` line. From `0.8.0`, `bump=minor` produces `0.9.0-beta.0` and
+`bump=major` produces `1.0.0-beta.0`; running prerelease again from
+`1.0.0-beta.0` produces `1.0.0-beta.1`. Craft publishes npm prereleases under a
+prerelease dist-tag so the stable `latest` line is not moved.
+
 ## Example
 
 The `apps/demo-pi` app shows the intended explicit-run flow:
diff --git a/packages/harness-ai-sdk/package.json b/packages/harness-ai-sdk/package.json
index 9645459..81a3277 100644
--- a/packages/harness-ai-sdk/package.json
+++ b/packages/harness-ai-sdk/package.json
@@ -6,6 +6,9 @@
   "main": "./dist/index.js",
   "module": "./dist/index.mjs",
   "files": ["dist"],
+  "publishConfig": {
+    "access": "public"
+  },
   "exports": {
     ".": {
       "source": "./src/index.ts",
diff --git a/packages/harness-pi-ai/package.json b/packages/harness-pi-ai/package.json
index 740ca9d..274878c 100644
--- a/packages/harness-pi-ai/package.json
+++ b/packages/harness-pi-ai/package.json
@@ -6,6 +6,9 @@
   "main": "./dist/index.js",
   "module": "./dist/index.mjs",
   "files": ["dist"],
+  "publishConfig": {
+    "access": "public"
+  },
   "exports": {
     ".": {
       "source": "./src/index.ts",
diff --git a/scripts/calculate-release-version.mjs b/scripts/calculate-release-version.mjs
new file mode 100644
index 0000000..5746075
--- /dev/null
+++ b/scripts/calculate-release-version.mjs
@@ -0,0 +1,103 @@
+#!/usr/bin/env node
+
+const current = process.argv[2];
+const bump = process.argv[3];
+const prerelease = process.argv[4] === "true";
+const prereleaseId = process.argv[5] || "beta";
+
+const allowedBumps = new Set(["patch", "minor", "major"]);
+const allowedPrereleaseIds = new Set(["beta", "rc", "alpha"]);
+
+if (!current || !bump) {
+  console.error(
+    "Usage: node scripts/calculate-release-version.mjs <current> <patch|minor|major> <true|false> [prerelease-id]",
+  );
+  process.exit(1);
+}
+
+if (!allowedBumps.has(bump)) {
+  console.error(`Invalid bump: ${bump}`);
+  process.exit(1);
+}
+
+if (!allowedPrereleaseIds.has(prereleaseId)) {
+  console.error(`Invalid prerelease id: ${prereleaseId}`);
+  process.exit(1);
+}
+
+const version = parseVersion(current);
+if (!version) {
+  console.error(`Invalid current version: ${current}`);
+  process.exit(1);
+}
+
+const next = prerelease
+  ? nextPrereleaseVersion(version, bump, prereleaseId)
+  : nextStableVersion(version, bump);
+
+console.log(next);
+
+function parseVersion(value) {
+  const match = value.match(
+    /^([0-9]+)\.([0-9]+)\.([0-9]+)(?:-([0-9A-Za-z-]+(?:\.[0-9A-Za-z-]+)*))?(?:\+[0-9A-Za-z-]+(?:\.[0-9A-Za-z-]+)*)?$/,
+  );
+
+  if (!match) {
+    return null;
+  }
+
+  return {
+    major: Number(match[1]),
+    minor: Number(match[2]),
+    patch: Number(match[3]),
+    prerelease: match[4]?.split(".") ?? [],
+  };
+}
+
+function formatVersion({ major, minor, patch }, prereleaseParts = []) {
+  const base = `${major}.${minor}.${patch}`;
+  return prereleaseParts.length > 0
+    ? `${base}-${prereleaseParts.join(".")}`
+    : base;
+}
+
+function bumpStableBase(version, bumpType) {
+  switch (bumpType) {
+    case "major":
+      return { major: version.major + 1, minor: 0, patch: 0 };
+    case "minor":
+      return { major: version.major, minor: version.minor + 1, patch: 0 };
+    case "patch":
+      return {
+        major: version.major,
+        minor: version.minor,
+        patch: version.patch + 1,
+      };
+  }
+}
+
+function nextStableVersion(version, bumpType) {
+  if (version.prerelease.length > 0) {
+    return formatVersion(version);
+  }
+
+  return formatVersion(bumpStableBase(version, bumpType));
+}
+
+function nextPrereleaseVersion(version, bumpType, id) {
+  if (version.prerelease.length === 0) {
+    return formatVersion(bumpStableBase(version, bumpType), [id, "0"]);
+  }
+
+  const [currentId] = version.prerelease;
+  const lastPart = version.prerelease.at(-1);
+
+  if (currentId !== id || !/^[0-9]+$/.test(lastPart)) {
+    return formatVersion(version, [id, "0"]);
+  }
+
+  return formatVersion(version, [
+    ...version.prerelease.slice(0, -1),
+    String(Number(lastPart) + 1),
+  ]);
+}