diff --git a/CHANGELOG.md b/CHANGELOG.md
index 9dd2338..9831ab3 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,7 +4,16 @@ All notable changes to OLP land here. Per `CLAUDE.md` release_kit overlay, this
 
 ## Unreleased
 
-(empty — Phase 4 entries land here once Phase 4 opens)
+### D56 — v1.x cleanup batch #1: AUTH_MISSING tuple test + `/health` activeSpawns (post-Phase-3)
+
+Post-Phase-3 cleanup batch. Resolves two small v1.x-roadmap deferrals into one D-day. No new user-facing feature; pins existing behaviour into tests + finally wires the ADR-documented `activeSpawns` field on `/health`.
+
+- **AUTH_MISSING tuple test** (v1.x roadmap #7 / D45 reviewer P3 deferral). New engine-level test in Suite D40 asserts that an `AUTH_MISSING` hop produces a `fallbackDetail` tuple with `trigger_type: 'auth_missing'` AND that the engine does NOT advance past the AUTH_MISSING hop (per ADR 0004 § Decision — `HARD_TRIGGER_CODES[AUTH_MISSING]=false`). Pre-D56 the behaviour was implicit through other engine-path tests; this commit makes it explicit so a future refactor that moves the tuple-push past the auth_missing branch fails this test directly.
+- **`/health` activeSpawns integration** (v1.x roadmap #4 / ADR 0002 Amendment 6 forward note). `handleHealth` now surfaces `providers.status.<name>.activeSpawns` (sourced from D38 `getActiveSpawnCount(name)`). The field is set BEFORE `healthCheck()` is awaited so it remains accessible even when `healthCheck()` throws (cheap in-memory counter read). New Suite 21c-extra test pins the field presence + non-negative value for every enabled provider. With no requests in flight: 0; under saturation: equals `hints.maxConcurrent`.
+- **Test count:** 601 → 603 (+2 D56 tests).
+- **Authority:** `docs/v1x-roadmap.md` #4 + #7; ADR 0002 Amendment 6 (concurrency observability forward note); ADR 0004 Amendment 5 (X-OLP-Fallback-Detail tuple shape the new test asserts).
+
+
 
 ## v0.3.0 — 2026-05-25
 
diff --git a/server.mjs b/server.mjs
index 304fff9..a71c570 100644
--- a/server.mjs
+++ b/server.mjs
@@ -577,10 +577,17 @@ async function handleHealth(req, res) {
   const available = listAllProviderNames().length;
   const providerStatuses = {};
   for (const [name, provider] of loadedProviders) {
+    // D56 / v1.x roadmap #4 (ADR 0002 Amendment 6 forward note): surface
+    // per-provider active spawn count for capacity-planning observability.
+    // D38 shipped getActiveSpawnCount; this is the /health integration.
+    // The field is set BEFORE healthCheck() in case healthCheck throws —
+    // activeSpawns is cheap (in-memory counter read) and useful even
+    // when healthCheck fails.
+    const activeSpawns = getActiveSpawnCount(name);
     try {
-      providerStatuses[name] = await provider.healthCheck();
+      providerStatuses[name] = { ...(await provider.healthCheck()), activeSpawns };
     } catch (e) {
-      providerStatuses[name] = { ok: false, error: e.message };
+      providerStatuses[name] = { ok: false, error: e.message, activeSpawns };
     }
   }
   sendJSON(res, 200, {
diff --git a/test-features.mjs b/test-features.mjs
index 5f61140..4831c8d 100644
--- a/test-features.mjs
+++ b/test-features.mjs
@@ -6247,6 +6247,30 @@ describe('D40 — X-OLP-Fallback-Detail header (issue #7)', () => {
     assert.equal(result.fallbackDetail[0].code, 'SPAWN_FAILED');
   });
 
+  it('engine: AUTH_MISSING terminates chain, fallbackDetail tuple records trigger_type:"auth_missing" (D56, v1.x roadmap #7)', async () => {
+    // v1.x roadmap #7 (D40 follow-up): explicit pin that the AUTH_MISSING
+    // path produces a fallbackDetail tuple with trigger_type:"auth_missing"
+    // BEFORE the engine's early-return at engine.mjs:486. Was implicit via
+    // other engine-path tests; D56 makes it explicit so any future refactor
+    // that moves the tuple-push past the auth_missing branch fails this.
+    const err = new ProviderError('No OAuth token found', 'AUTH_MISSING');
+    const chain = [
+      { provider: 'anthropic', model: 'claude-sonnet-4-6' },
+      { provider: 'openai', model: 'gpt-5.5' }, // present to verify AUTH_MISSING does NOT advance
+    ];
+    const hopFn = async () => { throw err; };
+    const result = await executeWithFallback(chain, makeIR({ model: 'claude-sonnet-4-6' }), hopFn);
+    // AUTH_MISSING is HARD_TRIGGER_CODES[AUTH_MISSING]=false (engine.mjs L52);
+    // chain stops at hop 0 instead of advancing to openai.
+    assert.equal(result.chunks, null, 'AUTH_MISSING terminates chain');
+    assert.equal(result.fallbackHops, 0, 'AUTH_MISSING does NOT advance — stays at hop 0');
+    assert.equal(result.fallbackDetail.length, 1, 'fallbackDetail has exactly 1 tuple (the AUTH_MISSING hop)');
+    assert.equal(result.fallbackDetail[0].code, 'AUTH_MISSING');
+    assert.equal(result.fallbackDetail[0].trigger_type, 'auth_missing');
+    assert.equal(result.fallbackDetail[0].provider, 'anthropic');
+    assert.equal(result.fallbackDetail[0].hop, 0);
+  });
+
   it('engine: non-ProviderError exception → tuple code is "UNKNOWN"', async () => {
     const err = new Error('Something unexpected'); // no .code field
     const chain = [{ provider: 'anthropic', model: 'claude-sonnet-4-6' }];
@@ -10522,6 +10546,29 @@ describe('Suite 21 — D46 owner-vs-guest gating (ADR 0007 §§ 7.1, 7.2)', () =
       assert.ok('status' in body.providers, 'owner /health providers.status must be present');
     });
 
+    it('21c-extra: owner /health each provider status carries activeSpawns field (D56, v1.x #4 / ADR 0002 Amendment 6)', async () => {
+      // ADR 0002 Amendment 6 forward note: when surfaced on /health, the
+      // per-provider concurrency counter lives at providers.status.<name>.
+      // activeSpawns. D56 wires it. With no requests in flight, the value
+      // is 0; under saturation it equals hints.maxConcurrent.
+      const { plaintext_token } = createKey({ name: '21c-extra', owner_tier: 'owner', providers_enabled: '*', olpHome: TMP });
+      const r = await fetch({
+        port, method: 'GET', path: '/health',
+        headers: { Authorization: `Bearer ${plaintext_token}` },
+      });
+      assert.equal(r.status, 200);
+      const body = JSON.parse(r.body);
+      // At least one provider must be enabled in the fixture
+      const statusEntries = Object.entries(body.providers.status);
+      assert.ok(statusEntries.length >= 1, 'fixture has at least one enabled provider');
+      for (const [name, status] of statusEntries) {
+        assert.ok('activeSpawns' in status,
+          `providers.status.${name}.activeSpawns MUST be present (ADR 0002 Amendment 6)`);
+        assert.equal(typeof status.activeSpawns, 'number');
+        assert.ok(status.activeSpawns >= 0, 'activeSpawns >= 0');
+      }
+    });
+
     it('21d: owner_only_endpoints config opt-out — empty list → guest gets full payload', async () => {
       __setAuthConfig({
         allow_anonymous: true,