diff --git a/src/skills.mjs b/src/skills.mjs
index c1b3050..e87616a 100644
--- a/src/skills.mjs
+++ b/src/skills.mjs
@@ -46,9 +46,17 @@ export function skillInstallAction(key, spec) {
   }
 }
 
-/** Plan the fan-out: one entry per skills engine with its action or skip reason. */
+/**
+ * Plan the fan-out: one entry per engine with its action or skip reason.
+ * Every engine, not just SKILL_ENGINES — prd/0003 R8 requires the engines with
+ * no skills primitive to be *reported* as skipped, and an engine missing from
+ * the plan is missing from the summary. Derived from ENGINES the same way the
+ * /skill list matrix derives it, so an engine added later cannot quietly fall
+ * out of the fan-out while still showing up in the matrix.
+ */
 export function planSkillInstall(spec, { installedSet } = {}) {
-  return SKILL_ENGINES.map((key) => {
+  const rest = Object.keys(ENGINES).filter((key) => !SKILL_ENGINES.includes(key));
+  return [...SKILL_ENGINES, ...rest].map((key) => {
     const bin = ENGINES[key].bin;
     const installed = installedSet ? installedSet.has(key) : isInstalled(bin);
     return { key, bin, installed, ...skillInstallAction(key, spec) };
diff --git a/test/skill-install-fanout.test.mjs b/test/skill-install-fanout.test.mjs
new file mode 100644
index 0000000..f378649
--- /dev/null
+++ b/test/skill-install-fanout.test.mjs
@@ -0,0 +1,138 @@
+// prd/0003 R8: `/skill install` MUST report the engines that have no skills
+// primitive as skipped. The plan is what the summary prints, so an engine the
+// plan omits is an engine the user never hears about.
+import assert from "node:assert/strict";
+import path from "node:path";
+import test from "node:test";
+
+import { ENGINES } from "../src/engines.mjs";
+import {
+  SKILL_ENGINES, claudeSkillsDir, planSkillInstall, runSkillInstall,
+} from "../src/skills.mjs";
+
+const SPEC = { source: "https://github.com/acme/some-skill", name: "some-skill" };
+const NO_PRIMITIVE = Object.keys(ENGINES).filter((key) => !SKILL_ENGINES.includes(key));
+const byKey = (results) => Object.fromEntries(results.map((r) => [r.key, r]));
+
+// --- the bug -----------------------------------------------------------------
+
+test("the plan covers every engine, not just the ones with a primitive", () => {
+  const keys = planSkillInstall(SPEC, { installedSet: new Set() }).map((p) => p.key);
+  assert.deepEqual([...keys].sort(), Object.keys(ENGINES).sort());
+});
+
+test("every engine without a primitive carries the skip reason", () => {
+  const plan = byKey(planSkillInstall(SPEC, { installedSet: new Set() }));
+  for (const key of NO_PRIMITIVE) {
+    assert.equal(plan[key]?.skip, "no skills primitive", `${key} has no skip reason`);
+  }
+});
+
+test("the fan-out reports them as skipped, so the summary can print a line", async () => {
+  const plan = planSkillInstall(SPEC, { installedSet: new Set(["claude", "gemini"]) });
+  const results = byKey(await runSkillInstall(plan, { run: async () => ({ ok: true, code: 0 }) }));
+  for (const key of NO_PRIMITIVE) {
+    assert.equal(results[key]?.status, "skipped", `${key} missing from the summary`);
+    assert.equal(results[key]?.reason, "no skills primitive");
+  }
+});
+
+test("skipped beats not-installed: an absent engine still gets its reason", async () => {
+  // Nothing installed at all — the user must still learn *why* codex got
+  // nothing, rather than being told to go and install it.
+  const plan = planSkillInstall(SPEC, { installedSet: new Set() });
+  const results = byKey(await runSkillInstall(plan, { run: async () => ({ ok: true, code: 0 }) }));
+  for (const key of NO_PRIMITIVE) {
+    assert.equal(results[key]?.status, "skipped", `${key} reported as ${results[key]?.status}`);
+  }
+});
+
+test("an installed engine without a primitive is skipped, never spawned", async () => {
+  const spawned = [];
+  const plan = planSkillInstall(SPEC, { installedSet: new Set(Object.keys(ENGINES)) });
+  const results = byKey(await runSkillInstall(plan, {
+    run: async (cmd, args) => { spawned.push([cmd, ...args]); return { ok: true, code: 0 }; },
+  }));
+
+  for (const key of NO_PRIMITIVE) assert.equal(results[key]?.status, "skipped");
+  assert.equal(spawned.length, SKILL_ENGINES.length);
+  for (const [cmd] of spawned) assert.ok(["git", "gemini"].includes(cmd), `spawned ${cmd}`);
+});
+
+test("privacycode — an engine added after SKILL_ENGINES was written — is reported", () => {
+  // The exact failure the /skill list matrix comment warns about: a hardcoded
+  // list silently drops any engine added later.
+  const plan = byKey(planSkillInstall(SPEC, { installedSet: new Set() }));
+  assert.equal(plan.privacycode?.skip, "no skills primitive");
+});
+
+test("the fan-out and the /skill list matrix name the same engines", async () => {
+  const results = await runSkillInstall(
+    planSkillInstall(SPEC, { installedSet: new Set() }),
+    { run: async () => ({ ok: true, code: 0 }) },
+  );
+  assert.deepEqual(results.map((r) => r.key).sort(), Object.keys(ENGINES).sort());
+});
+
+test("every planned engine carries a real bin, so the summary can name it", () => {
+  for (const item of planSkillInstall(SPEC, { installedSet: new Set() })) {
+    assert.equal(item.bin, ENGINES[item.key].bin);
+  }
+});
+
+// --- controls: the fix must not buy green by over-reporting -------------------
+
+test("the engines with a primitive still come first, in SKILL_ENGINES order", () => {
+  const keys = planSkillInstall(SPEC, { installedSet: new Set() }).map((p) => p.key);
+  assert.deepEqual(keys.slice(0, SKILL_ENGINES.length), SKILL_ENGINES);
+});
+
+test("SKILL_ENGINES is unchanged: no engine gained a primitive", () => {
+  assert.deepEqual(SKILL_ENGINES, ["claude", "gemini"]);
+});
+
+test("claude still clones the source into its skills dir, byte for byte", () => {
+  const claude = byKey(planSkillInstall(SPEC, { installedSet: new Set(["claude"]) })).claude;
+  assert.equal(claude.skip, undefined);
+  assert.equal(claude.cmd, "git");
+  assert.deepEqual(claude.args, [
+    "clone", "--depth", "1", SPEC.source, path.join(claudeSkillsDir(), "some-skill"),
+  ]);
+});
+
+test("gemini still installs natively, byte for byte", () => {
+  const gemini = byKey(planSkillInstall(SPEC, { installedSet: new Set(["gemini"]) })).gemini;
+  assert.equal(gemini.skip, undefined);
+  assert.equal(gemini.cmd, "gemini");
+  assert.deepEqual(gemini.args, ["skills", "install", SPEC.source, "--scope", "user"]);
+});
+
+test("installed / not-installed still decides the outcome for a real target", async () => {
+  const plan = planSkillInstall(SPEC, { installedSet: new Set(["gemini"]) });
+  const results = byKey(await runSkillInstall(plan, { run: async () => ({ ok: true, code: 0 }) }));
+  assert.equal(results.gemini.status, "installed");
+  assert.equal(results.claude.status, "not-installed");
+});
+
+test("a real install killed by a signal still reports failed", async () => {
+  const plan = planSkillInstall(SPEC, { installedSet: new Set(["gemini"]) });
+  const results = byKey(await runSkillInstall(plan, {
+    run: async () => ({ ok: true, code: null, signal: "SIGKILL" }),
+  }));
+  assert.equal(results.gemini.status, "failed");
+  assert.equal(results.gemini.signal, "SIGKILL");
+});
+
+test("a failing exit code is still a failure, not a skip", async () => {
+  const plan = planSkillInstall(SPEC, { installedSet: new Set(["gemini"]) });
+  const results = byKey(await runSkillInstall(plan, {
+    run: async () => ({ ok: true, code: 128, signal: null }),
+  }));
+  assert.equal(results.gemini.status, "failed");
+  assert.equal(results.gemini.code, 128);
+});
+
+test("no engine is planned twice", () => {
+  const keys = planSkillInstall(SPEC, { installedSet: new Set() }).map((p) => p.key);
+  assert.equal(new Set(keys).size, keys.length);
+});