diff --git a/.changeset/27660-skills-credential-presence-only.md b/.changeset/27660-skills-credential-presence-only.md
new file mode 100644
index 00000000000..802eb17bded
--- /dev/null
+++ b/.changeset/27660-skills-credential-presence-only.md
@@ -0,0 +1,12 @@
+---
+'@objectstack/skills': patch
+---
+
+docs(skills): objectstack-data teaches that a `secret` / `password` column is queried only for presence, with one eval
+
+Clause-②: no
+Metadata-protocol: none
+
+- **Before.** The engine refuses a credential column (`type: 'secret'` / `type: 'password'`) as a filter key, a sort key, a group-by or min/max key and an import `matchFields` key with `400 INVALID_FIELD`, and its search scan never reads one. `objectstack-data`'s `rules/security.md` taught the credential types but said nothing about querying them, so an agent following it could still write a view filter, sort, report or import mapping that the runtime refuses.
+- **Now.** `rules/security.md` states the rule next to the `secret` example: the only condition allowed on a credential column asks whether it has a value (`null`, `$null`, `$exists`, `$empty`); everything else is refused; search never scans it, so it does not belong in `searchableFields`. One eval asks for a list view filtered on a `secret` field and expects the redirect to the view's `is_not_null` rule.
+- The new text in `rules/security.md` is paid for by folding sentences the package already holds elsewhere (the `secret` type's purpose and encryption in `rules/field-types.md`, the queue parking rule in `SKILL.md`), and the remaining balance on it and on the eval file is raised by measurement, at zero headroom. The example shows the has-a-value check in both spellings: `where` / hook `query.filter`, and a list view's `filter` rule (`operator: 'is_not_null'`). No schema, key or runtime behaviour changes.
diff --git a/scripts/check-skills-token-ratchet.mjs b/scripts/check-skills-token-ratchet.mjs
index be6cade155b..c223c18ebf8 100644
--- a/scripts/check-skills-token-ratchet.mjs
+++ b/scripts/check-skills-token-ratchet.mjs
@@ -712,7 +712,24 @@ export const CEILINGS = new Map([
   // 3693 -> 3687 (#27016): RE-LOCK at the landed count. `queues` joins the
   // kernel names a membership key may not take (+3 tokens), paid by cutting
   // "not a stamp on every data row," from the membership-keys intro; net -6.
-  ['skills/objectstack-data/rules/security.md', 3687],
+  // 3687 -> 3698 (card #27660, the same Skills-docs follow-up): one rule
+  // beside the `secret` example — a `secret` / `password` column is never a
+  // filter, sort, group-by or import `matchFields` key (`400 INVALID_FIELD`),
+  // search never scans it, and the only condition is has-a-value, shown in
+  // both surfaces' spellings (`where` / hook `query.filter` and a list view's
+  // `filter` rule). Same standing ruling, 2026-10-27, decision card 「skills
+  // 修复卡的教学和 eval 都撞 token 天花板,怎么付?」, tap A, verbatim and
+  // untranslated: 「A:先削重复,余额按实测提高」. PAID DOWN FIRST: four passages
+  // the package holds elsewhere — the `secret` type's purpose, encryption and
+  // masking (`rules/field-types.md`, net 150 bytes), the queue-parking aside
+  // (`SKILL.md` § Ownership queues, 91), the `external` tier's mechanism list
+  // (the choice list above it, net 107) and `— NOT permissionSets` (the
+  // bullet below it, 25): 373 bytes = 93 units; the rule adds 442 bytes = 111
+  // units. On `origin/main` the file was 14722 bytes (3681 tokens, headroom
+  // 6); the LANDED file is 14791 bytes -> 3698 tokens, ceiling +11, pinned AT
+  // the measurement, zero headroom.
+  //   ceil($(wc -c < skills/objectstack-data/rules/security.md) / 4) == ceil(14791 / 4)
+  ['skills/objectstack-data/rules/security.md', 3698],
   // 3024 -> 3109 (2026-08-31 app-repo-principles raise, see the block above).
   // Severity Levels listed the three values and left the CHOICE unstated: a
   // block rests on a judgement a person made, so a machine-inferred signal — a
@@ -984,7 +1001,25 @@ export const CEILINGS = new Map([
   // -> 1573 tokens, ceiling +169, pinned AT the measurement, zero headroom.
   // The raising PR's body carries the same arithmetic.
   //   ceil($(wc -c < skills/objectstack-data/evals/hooks-security-seeds-datasources.json) / 4) == ceil(6292 / 4)
-  ['skills/objectstack-data/evals/hooks-security-seeds-datasources.json', 1573],
+  // 1573 -> 1674 (card #27660, the Skills-docs follow-up owed by the
+  // objectql PR that refuses a credential column as a filter or sort key):
+  // one case for a list view filtered on a `secret` field by prefix —
+  // expected the redirect to the view dialect's presence rule
+  // (`operator: 'is_not_null'`) and the `INVALID_FIELD` refusal named; NO
+  // `starts_with`. Seat decision on the card's open question, applying the
+  // standing maintainer ruling 2026-10-27 on the decision card 「skills 修复卡的
+  // 教学和 eval 都撞 token 天花板,怎么付?」, tap A, verbatim and untranslated:
+  // 「A:先削重复,余额按实测提高」. PAID DOWN FIRST: two clauses that restated
+  // their own case's `must_not_contain` — case 2's "Permission sets, not the
+  // object: " (restating `permissions: {`, 33 bytes) and case 8's " — no
+  // picklist, counter or insert hook" (restating `assigned_to` /
+  // `beforeInsert`, 40 bytes), 73 bytes = 18 units; the case adds 479 bytes =
+  // 120 units. On `origin/main` the file was 6289 bytes (1573 tokens, headroom
+  // 0); the LANDED file is 6695 bytes -> 1674 tokens, ceiling +101, pinned AT
+  // the measurement, zero headroom. The raising PR's thread carries the same
+  // arithmetic.
+  //   ceil($(wc -c < skills/objectstack-data/evals/hooks-security-seeds-datasources.json) / 4) == ceil(6695 / 4)
+  ['skills/objectstack-data/evals/hooks-security-seeds-datasources.json', 1674],
   // 946 -> 1050 (#26297): the invoice-line case gains the owner opt-in
   // (`ownerMayEdit` on the controlled_by_parent line) and pins `added_by` as
   // `type: 'user'`, never a lookup to a `user` object. +104 tokens at
diff --git a/skills/objectstack-data/evals/hooks-security-seeds-datasources.json b/skills/objectstack-data/evals/hooks-security-seeds-datasources.json
index 58f183b45d5..3bb4ee10e03 100644
--- a/skills/objectstack-data/evals/hooks-security-seeds-datasources.json
+++ b/skills/objectstack-data/evals/hooks-security-seeds-datasources.json
@@ -14,7 +14,7 @@
     {
       "id": 2,
       "prompt": "Sales reps see only their own leads, sales managers their unit and everything below it; every signed-in user reads the `product` catalog.",
-      "expected_output": "Permission sets, not the object: `lead` is `sharingModel: 'private'`; the rep grant carries `readScope: 'own'`, the manager grant `readScope: 'unit_and_below'` (`@objectstack/security-enterprise` + `requires: ['hierarchy-security']`, else fails closed to `own`); `product` is `sharingModel: 'public_read'`.",
+      "expected_output": "`lead` is `sharingModel: 'private'`; the rep grant carries `readScope: 'own'`, the manager grant `readScope: 'unit_and_below'` (`@objectstack/security-enterprise` + `requires: ['hierarchy-security']`, else fails closed to `own`); `product` is `sharingModel: 'public_read'`.",
       "files": [],
       "assertions": {
         "must_contain": ["sharingModel: 'private'", "readScope", "unit_and_below", "public_read", "hierarchy-security"],
@@ -74,12 +74,22 @@
     {
       "id": 8,
       "prompt": "Web-form leads arrive ownerless; inside sales holds them until a rep takes one, and two reps must never own the same lead.",
-      "expected_output": "`queues: [defineQueue({ name: 'inside_sales', label: 'Inside Sales', members: [{ type: 'position', value: 'inside_sales_rep' }] })]` and an `assignmentRules` entry `assignTo: { type: 'queue', value: 'inside_sales' }` with no `strategy` park each lead in the injected `queue` column — no picklist, counter or insert hook; a rep claims by an ordinary by-id `{ owner_id: <self> }` update, the loser gets `409 CONCURRENT_UPDATE`.",
+      "expected_output": "`queues: [defineQueue({ name: 'inside_sales', label: 'Inside Sales', members: [{ type: 'position', value: 'inside_sales_rep' }] })]` and an `assignmentRules` entry `assignTo: { type: 'queue', value: 'inside_sales' }` with no `strategy` park each lead in the injected `queue` column; a rep claims by an ordinary by-id `{ owner_id: <self> }` update, the loser gets `409 CONCURRENT_UPDATE`.",
       "files": [],
       "assertions": {
         "must_contain": ["defineQueue", "type: 'position'", "type: 'queue'", "CONCURRENT_UPDATE"],
         "must_not_contain": ["assigned_to", "beforeInsert"]
       }
+    },
+    {
+      "id": 9,
+      "prompt": "A `vendor` list view of the rows whose `api_key` (a `secret` field) starts with `sk_live`.",
+      "expected_output": "Redirects: a credential is filtered only by presence, `filter: [{ field: 'api_key', operator: 'is_not_null' }]`; any other filter or sort is `400 INVALID_FIELD`.",
+      "files": [],
+      "assertions": {
+        "must_contain": ["INVALID_FIELD", "is_not_null"],
+        "must_not_contain": ["starts_with"]
+      }
     }
   ]
 }
diff --git a/skills/objectstack-data/rules/security.md b/skills/objectstack-data/rules/security.md
index fcfd4a7a83b..dc6ade1c63d 100644
--- a/skills/objectstack-data/rules/security.md
+++ b/skills/objectstack-data/rules/security.md
@@ -16,7 +16,7 @@ export const salesUser = definePermissionSet({
   },
 });
 
-// Register it on the stack root under `permissions` — NOT `permissionSets`:
+// Register it on the stack root under `permissions`:
 // defineStack({ permissions: [salesUser], ... })
 ```
 
@@ -162,8 +162,7 @@ rowLevelSecurity: [
   position → `positions` on the policy; a named record → a membership key;
   one record, once → a sharing rule or a manual share; a team's records → a
   sharing rule whose `sharedWith: { type: 'queue', value: '<queue name>' }`
-  reaches an ownership queue's members (it shares the rule's rows, it parks
-  none — only the record's `queue` column does that; SKILL.md § Ownership queues).
+  reaches an ownership queue's members (SKILL.md § Ownership queues).
 
 ## Positions grant only what they name; portal users are `external`
 
@@ -177,9 +176,7 @@ rowLevelSecurity: [
   https://objectstack.ai/docs/permissions/authentication#membership-tiers-are-a-closed-list).
   The `everyone` baseline (`isDefault` sets) does not reach it, it sees no
   member directory and holds no business unit, and every org-wide default is
-  owner-only for it: rows reach it **only** through explicit grants — a
-  position or permission set whose row policies bound them (the key above),
-  a sharing rule or a manual share.
+  owner-only for it: rows reach it **only** through the explicit grants above.
 
 ## Field permissions — a row-conditioned edit lock (`when`)
 
@@ -214,16 +211,22 @@ fields: {
 
 `maskingRule` is **live** (FieldMasker). Two more channels:
 
-**Encrypted-at-rest values — `type: 'secret'` (ADR-0100).** For reversible
-machine credentials (DB passwords, API keys, tokens): encrypted on write via the
-registered `ICryptoProvider`, the ciphertext handle in `sys_secret` and only an
-opaque ref on the row, masked on read. **Fail-closed:** with no crypto provider,
-writes throw rather than persist cleartext.
+**Encrypted-at-rest values — `type: 'secret'` (ADR-0100).** Ciphertext lives in
+`sys_secret`, only an opaque ref on the row. **Fail-closed:** with no crypto
+provider, writes throw rather than persist cleartext.
+
+**Query a credential only for presence.** A `secret` / `password` column is
+never a filter, sort, group-by or import `matchFields` key (`400 INVALID_FIELD`;
+an import row naming it fails). Search never scans it: keep it out of
+`searchableFields`.
 
 ```typescript
 fields: {
   api_key: { type: 'secret', label: 'API Key' },
 }
+// also `null`, `$exists`, `$empty` / `is_not_empty`
+where: { api_key: { $null: false } }  // ObjectQL, hook `query.filter`
+filter: [{ field: 'api_key', operator: 'is_not_null' }]  // list view
 ```
 
 **Per-field access gating — `requiredPermissions` (ADR-0066 D3).** A field