diff --git a/scripts/lib/skill-manifest.mjs b/scripts/lib/skill-manifest.mjs
index f00e3946..e7f084ca 100644
--- a/scripts/lib/skill-manifest.mjs
+++ b/scripts/lib/skill-manifest.mjs
@@ -253,21 +253,48 @@ export function validateEvalCases(skillName, cases) {
 export const PINNED_CLI_VERSION = "2.1.250";
 
 /**
- * Read a semver triple out of `claude --version` output ("2.1.250 (Claude Code)").
+ * Read the version out of `claude --version` output ("2.1.250 (Claude Code)").
+ *
+ * Returns the release triple **and** whether a prerelease/build suffix was
+ * attached, because the two callers want different things: the pin comparison
+ * must reject `2.1.250-beta.1` (a different validator schema that would compare
+ * equal to the stable pin while the log claimed an exact match — Copilot),
+ * while the eval's availability probe only needs *some* usable CLI.
  *
  * @param {string} text
- * @returns {number[] | null}
+ * @returns {{ parts: number[], prerelease: string | null } | null}
  */
 export function parseClaudeVersion(text) {
-  const m = /(\d+)\.(\d+)\.(\d+)/.exec(text);
-  return m === null ? null : [Number(m[1]), Number(m[2]), Number(m[3])];
+  const m =
+    /(\d+)\.(\d+)\.(\d+)(?:-([0-9A-Za-z.-]+))?(?:\+[0-9A-Za-z.-]+)?/.exec(text);
+  if (m === null) return null;
+  return {
+    parts: [Number(m[1]), Number(m[2]), Number(m[3])],
+    prerelease: m[4] ?? null,
+  };
+}
+
+/** A parsed version, formatted the way the CLI reports it. */
+export function formatClaudeVersion(version) {
+  if (version === null) return "(unreadable version)";
+  return (
+    version.parts.join(".") +
+    (version.prerelease ? `-${version.prerelease}` : "")
+  );
 }
 
 /**
- * @param {number[]} a
- * @param {number[]} b
- * @returns {number} negative if a < b, 0 if equal, positive if a > b.
+ * Whether a parsed version IS the pin — same triple and no prerelease.
+ *
+ * @param {{ parts: number[], prerelease: string | null } | null} version
+ * @param {string} pin e.g. `PINNED_CLI_VERSION`.
  */
+export function isPinnedVersion(version, pin) {
+  if (version === null || version.prerelease !== null) return false;
+  const pinned = parseClaudeVersion(pin);
+  return pinned !== null && compareVersions(version.parts, pinned.parts) === 0;
+}
+
 export function compareVersions(a, b) {
   for (let i = 0; i < Math.max(a.length, b.length); i++) {
     const diff = (a[i] ?? 0) - (b[i] ?? 0);
diff --git a/scripts/lib/skill-manifest.test.mjs b/scripts/lib/skill-manifest.test.mjs
index ff6c8830..a9bb3481 100644
--- a/scripts/lib/skill-manifest.test.mjs
+++ b/scripts/lib/skill-manifest.test.mjs
@@ -14,6 +14,8 @@ import {
   parseClaudeVersion,
   compareVersions,
   PINNED_CLI_VERSION,
+  isPinnedVersion,
+  formatClaudeVersion,
 } from "./skill-manifest.mjs";
 
 const fm = (body) => `---\n${body}\n---\n\n# Body\n`;
@@ -203,23 +205,47 @@ test("validateEvalCases rejects malformed cases", () => {
 });
 
 test("parseClaudeVersion reads the CLI's version banner", () => {
-  assert.deepEqual(parseClaudeVersion("2.1.250 (Claude Code)"), [2, 1, 250]);
-  assert.deepEqual(parseClaudeVersion("claude 10.0.4\n"), [10, 0, 4]);
+  assert.deepEqual(parseClaudeVersion("2.1.250 (Claude Code)"), {
+    parts: [2, 1, 250],
+    prerelease: null,
+  });
+  assert.deepEqual(parseClaudeVersion("claude 10.0.4\n"), {
+    parts: [10, 0, 4],
+    prerelease: null,
+  });
   assert.equal(parseClaudeVersion("no version here"), null);
 });
 
-test("compareVersions can decide exact equality with the pin", () => {
-  // Both validators require the EXACT pinned version, so what matters is that
-  // "equal" is distinguishable from newer as well as older — a floor would let a
-  // newer local CLI validate against a different schema than CI's.
-  const pin = parseClaudeVersion(PINNED_CLI_VERSION);
-  assert.equal(compareVersions(pin, pin), 0);
-  assert.ok(compareVersions([pin[0], pin[1], pin[2] - 1], pin) < 0);
-  assert.ok(compareVersions([pin[0], pin[1], pin[2] + 1], pin) > 0);
-  assert.ok(compareVersions([pin[0] + 1, 0, 0], pin) > 0);
-  // Shorter and longer triples still order sanely.
-  assert.ok(compareVersions([pin[0]], pin) < 0);
-  assert.equal(compareVersions([...pin, 0], pin), 0);
+test("parseClaudeVersion keeps a prerelease suffix rather than dropping it", () => {
+  // Dropping it made `2.1.250-beta.1` compare EQUAL to the stable pin — a
+  // different validator schema running while the log claimed an exact match.
+  assert.deepEqual(parseClaudeVersion("2.1.250-beta.1 (Claude Code)"), {
+    parts: [2, 1, 250],
+    prerelease: "beta.1",
+  });
+  assert.equal(
+    formatClaudeVersion(parseClaudeVersion("2.1.250-beta.1")),
+    "2.1.250-beta.1",
+  );
+  assert.equal(formatClaudeVersion(null), "(unreadable version)");
+});
+
+test("isPinnedVersion accepts only the exact stable pin", () => {
+  const pin = PINNED_CLI_VERSION;
+  assert.equal(isPinnedVersion(parseClaudeVersion(pin), pin), true);
+  // Build metadata is ignored for precedence by SemVer, so it still matches.
+  assert.equal(
+    isPinnedVersion(parseClaudeVersion(`${pin}+build.7`), pin),
+    true,
+  );
+  // A prerelease of the same triple is NOT the pin.
+  assert.equal(
+    isPinnedVersion(parseClaudeVersion(`${pin}-beta.1`), pin),
+    false,
+  );
+  assert.equal(isPinnedVersion(parseClaudeVersion("2.1.249"), pin), false);
+  assert.equal(isPinnedVersion(parseClaudeVersion("99.0.0"), pin), false);
+  assert.equal(isPinnedVersion(null, pin), false);
 });
 
 test("the listing-entry cap covers description AND when_to_use together", () => {
diff --git a/scripts/verify-skills-cli.mjs b/scripts/verify-skills-cli.mjs
index 7bfb85cf..ee01b247 100644
--- a/scripts/verify-skills-cli.mjs
+++ b/scripts/verify-skills-cli.mjs
@@ -25,14 +25,12 @@ import { fileURLToPath } from "node:url";
 import { probeClaudeVersion } from "./lib/claude-cli.mjs";
 import { winShellArgs } from "./lib/win-shell-args.mjs";
 import {
-  compareVersions,
+  formatClaudeVersion,
+  isPinnedVersion,
   parseClaudeVersion,
   PINNED_CLI_VERSION,
 } from "./lib/skill-manifest.mjs";
 
-/** `PINNED_CLI_VERSION` as a comparable triple. */
-const PINNED_VERSION_PARTS = parseClaudeVersion(PINNED_CLI_VERSION) ?? [];
-
 const ROOT = path.resolve(path.dirname(fileURLToPath(import.meta.url)), "..");
 const SKILLS_DIR = ".claude/skills";
 
@@ -49,20 +47,17 @@ const SKILLS_DIR = ".claude/skills";
  * @returns {{ command: string, args: string[], via: string }}
  */
 export function validatorCommand({ version }) {
-  if (
-    version !== null &&
-    compareVersions(version, PINNED_VERSION_PARTS) === 0
-  ) {
+  if (isPinnedVersion(version, PINNED_CLI_VERSION)) {
     return {
       command: "claude",
       args: ["plugin", "validate", SKILLS_DIR],
-      via: `local claude ${version.join(".")} (matches the pin)`,
+      via: `local claude ${formatClaudeVersion(version)} (matches the pin)`,
     };
   }
   const why =
     version === null
       ? "no local CLI"
-      : `local CLI is ${version.join(".")}, not the pinned ${PINNED_CLI_VERSION}`;
+      : `local CLI is ${formatClaudeVersion(version)}, not the pinned ${PINNED_CLI_VERSION}`;
   return {
     command: "npx",
     args: [
diff --git a/scripts/verify-skills-cli.test.mjs b/scripts/verify-skills-cli.test.mjs
index 816a8196..2c93a77d 100644
--- a/scripts/verify-skills-cli.test.mjs
+++ b/scripts/verify-skills-cli.test.mjs
@@ -14,9 +14,13 @@
 import { test } from "node:test";
 import assert from "node:assert/strict";
 import { validatorCommand, runValidator } from "./verify-skills-cli.mjs";
-import { PINNED_CLI_VERSION } from "./lib/skill-manifest.mjs";
+import {
+  PINNED_CLI_VERSION,
+  parseClaudeVersion,
+} from "./lib/skill-manifest.mjs";
 
-const pinned = PINNED_CLI_VERSION.split(".").map(Number);
+const pinned = parseClaudeVersion(PINNED_CLI_VERSION);
+const at = (text) => parseClaudeVersion(text);
 const npxArgs = [
   "-y",
   `@anthropic-ai/claude-code@${PINNED_CLI_VERSION}`,
@@ -35,14 +39,18 @@ test("uses a local CLI only when it matches the pin exactly", () => {
 test("falls back to the pinned package for any other local version", () => {
   // Newer as well as older: a newer CLI is a DIFFERENT schema from CI's, which
   // is exactly the cross-machine disagreement the pin exists to prevent.
-  for (const version of [
-    [pinned[0], pinned[1], pinned[2] + 1],
-    [pinned[0], pinned[1], pinned[2] - 1],
-    [pinned[0] + 1, 0, 0],
-    [2, 1, 232],
+  const [maj, min, patch] = pinned.parts;
+  for (const banner of [
+    `${maj}.${min}.${patch + 1}`,
+    `${maj}.${min}.${patch - 1}`,
+    `${maj + 1}.0.0`,
+    "2.1.232",
+    // A prerelease of the pinned triple is a DIFFERENT validator schema, and
+    // dropping the suffix made it compare equal (Copilot).
+    `${maj}.${min}.${patch}-beta.1`,
   ]) {
-    const cmd = validatorCommand({ version });
-    assert.equal(cmd.command, "npx", `expected npx for ${version.join(".")}`);
+    const cmd = validatorCommand({ version: at(banner) });
+    assert.equal(cmd.command, "npx", `expected npx for ${banner}`);
     assert.deepEqual(cmd.args, npxArgs);
     assert.match(cmd.via, /not the pinned/);
   }
@@ -72,7 +80,7 @@ function harness({ probe, spawnResult }) {
   return { code, spawned, logs, errors };
 }
 
-const okProbe = PINNED_CLI_VERSION.split(".").map(Number);
+const okProbe = parseClaudeVersion(PINNED_CLI_VERSION);
 
 test("runs the local CLI and succeeds when the validator accepts", () => {
   const r = harness({ probe: okProbe, spawnResult: { status: 0 } });
diff --git a/scripts/verify-skills.mjs b/scripts/verify-skills.mjs
index f298624c..b3ffee50 100755
--- a/scripts/verify-skills.mjs
+++ b/scripts/verify-skills.mjs
@@ -34,7 +34,8 @@ import { claudeSpawnArgs, probeClaudeVersion } from "./lib/claude-cli.mjs";
 import { reachableScripts, rootReachesScript } from "./lib/npm-scripts.mjs";
 import { parse as parseYaml } from "yaml";
 import {
-  compareVersions,
+  formatClaudeVersion,
+  isPinnedVersion,
   parseClaudeVersion,
   PINNED_CLI_VERSION,
   parseSkill,
@@ -46,9 +47,6 @@ import {
 const ROOT = path.resolve(path.dirname(fileURLToPath(import.meta.url)), "..");
 const DEFAULT_SKILLS_DIR = path.join(ROOT, ".claude", "skills");
 
-/** `PINNED_CLI_VERSION` as a comparable triple. */
-const PINNED_VERSION_PARTS = parseClaudeVersion(PINNED_CLI_VERSION) ?? [];
-
 /** Directory names under `.claude/skills` that contain a SKILL.md. */
 export function skillDirs(
   dir,
@@ -273,16 +271,10 @@ function main(argv = process.argv.slice(2)) {
   // would reintroduce exactly the cross-machine schema drift the pin removes.
   // Anything else is left to `verify:skills:cli`, which fetches the pin.
   const version = probeClaudeVersion(parseClaudeVersion);
-  if (version === null) {
+  if (!isPinnedVersion(version, PINNED_CLI_VERSION)) {
     console.log(
-      "verify:skills — no usable `claude` CLI here; `verify:skills:cli` runs the pinned validator.",
-    );
-    return;
-  }
-  if (compareVersions(version, PINNED_VERSION_PARTS) !== 0) {
-    console.log(
-      `verify:skills — local \`claude\` is ${version.join(".")}, not the pinned ` +
-        `${PINNED_CLI_VERSION}; \`verify:skills:cli\` runs the pinned validator.`,
+      `verify:skills — local \`claude\` is ${formatClaudeVersion(version)}, not the ` +
+        `pinned ${PINNED_CLI_VERSION}; \`verify:skills:cli\` runs the pinned validator.`,
     );
     return;
   }