Refuse an undeclared field a before-hook writes — the post-hook half of the declared-field door, one envelope on every driver

.changeset/post-hook-undeclared-field-door.md

@@ -0,0 +1,61 @@
+---
+'@objectstack/objectql': minor
+'@objectstack/lint': patch
+---
+
+Refuse an undeclared field a `before*` hook writes, identically on every driver
+
+**BREAKING** accept-set narrowing at the post-hook write door, shipped as `minor`
+under the repo's launch-window convention for breaking changes.
+
+**Bump level, argued**: `@objectstack/objectql` is `minor`, not `patch`. A
+`before*` hook or an L2 (`language:'js'`) body writing a key the object never
+declares **used to succeed** on the `memory` family — the value reached the
+store and persisted as a shadow column — and now **throws**, `INVALID_FIELD` /
+**400**, on every driver. That is a narrowing of the accept set on the record
+payload, a surface every hook body touches; it is not an instrument or a message
+fix, and a hook that relied on either driver-dependent outcome stops working at
+run time. The same-package sibling `.changeset/hook-input-symbol-key-refusal.md`
+argues exactly this shape — "used to succeed, and now throw. That is a narrowing
+of the accept set" — to `minor`, and the launch-window convention is what keeps
+it off `major` (pre-1.0 lockstep semantics: a breaking change does not burn a
+major version while the stack versions in lockstep — see
+`scripts/check-changeset-no-major.mjs`). `patch` would under-declare a change
+that turns a passing hook into a throwing one.
+
+`'@objectstack/lint': patch` is deliberate and stays. That half of the diff is
+message and comment prose only: `validateHookBodyWrites` reports the same
+findings on the same bodies at the same severity, with wording that now names
+the runtime refusal instead of the driver split this change retires.
+
+The declared-field door (#8682 on insert, #8738 on update) runs before the
+`before*` hooks — deliberately, so a payload about to be refused never consumes
+an autonumber (#8737). That left the payload the hooks themselves produce
+unjudged: a key a `beforeInsert` / `beforeUpdate` hook or an L2 (`language:'js'`)
+body wrote went straight to the driver, and the drivers disagreed. `memory`
+accepted it and stored a shadow column; `driver-sql` threw a raw `SQLITE_ERROR`
+with no `status` and the bound statement and its values quoted back in the
+message; `sqlite-wasm` threw a bare `Error` with neither. One app and one hook
+meant different things on two deployments, and nothing in the app could tell
+which one it was running on.
+
+The same check now runs a second time over the post-hook payload, before any
+statement is built, so a hook-written undeclared key is refused with the caller
+path's envelope — `INVALID_FIELD` / **400**, `Unknown field 'x' on object 'y'` —
+on every driver, because none of them is reached. The existing pre-hook door is
+unchanged and stays exactly where it is.
+
+This is a security fix as well as a consistency one: `fieldPermissions` is keyed
+by declared field name and reports only fields explicitly marked non-editable, so
+a key the object never declares can carry no entry and could never be gated by
+field-level security. On `memory`-family stores such a value was persisted where
+no view, formula, index or permission could name it.
+
+The platform's own stamps are unaffected. `created_at` / `updated_at` — the two
+the built-in audit hook writes unconditionally, because SQL drivers create them
+as built-in columns on every table — are already tolerated by this check
+alongside `id`; every other stamp (`created_by`, `updated_by`, `tenant_id`) is
+guarded by an explicit declaration test in the hook that writes it.
+
+<!-- adr-0087: not-required (no-migration-prescription) No metadata key, spec symbol, Zod schema, object definition or stored representation is added, removed or renamed. This narrows which run-time record payload the engine accepts after the `before*` hooks have run; an undeclared key was never a declarable metadata surface, so `objectstack migrate meta` has nothing in a stored source to rewrite. The remedy for an affected hook body is to declare the field on the object or stop writing it, which is authoring guidance, not a mechanical rewrite of stored metadata. -->
+

content/docs/automation/hook-bodies.mdx

@@ -204,19 +204,22 @@ A structured `writes` declaration was considered and dropped ([#3700](https://gi
 
 #### What still happens at runtime
 
-An unknown field is **not** caught at runtime, and it does not fail quietly either. The write-path validator walks the object's *declared* fields, so an undeclared key is neither rejected nor stripped, and the sandbox's mutations are copied back onto the payload verbatim. What happens next is the driver's call:
+An unknown field **is** caught at runtime, and the answer is the same on every driver. The sandbox's mutations are copied back onto the payload verbatim (`applyMutationsToInput` is a plain `Object.assign`) and the write-path validator still walks only the object's *declared* fields — but since [#13657](https://github.com/objectstack-ai/objectstack/issues/13657) the declared-field door runs a **second** time, over the payload the `before*` hooks produced, before any statement is built:
 
-- **SQL drivers** put the stray column into the statement, so the **whole write fails** with a driver-level error (`table deal has no column named stagee`) — nothing is stored, and the error surfaces far from the authoring mistake.
-- **Schemaless drivers** (memory, MongoDB) silently persist the stray key alongside the real ones.
+```
+INVALID_FIELD / 400 / Unknown field 'stagee' on object 'deal'
+```
+
+Identical on `memory`, `driver-sql` and `sqlite-wasm`, because none of them is reached. Before #13657 the driver decided instead, and the two families disagreed — SQL failed the whole write with an untyped `SQLITE_ERROR`, while schemaless drivers silently persisted the stray key as a column nothing downstream reads (and which field-level security, keyed by *declared* field name, could never gate). One app, one body, two meanings decided by which driver a deployment happened to run.
 
-Neither outcome is the one you wanted, and the advisory warning is the earliest signal you get.
+The runtime refusal is now the backstop; the advisory warning is still the earliest signal you get, and the one that names the mistake where it was made.
 
 Because the existence check is advisory, and every write-side check here is literal-only:
 
 - **Treat `hook-body-write-unknown-field` as a build failure by convention.** It does not gate, but the rule is tuned for near-zero false positives — in practice a warning is a real typo.
 - **Check by hand what the parser cannot see.** Computed keys, spreads, aliased input and dynamic object names are invisible to the rule; for an array or `"*"` hook, every field must exist on every target.
 - **Prefer a flow `update_record` node when the write set is fixed — and for *this* check most of all.** A flow node's writes are structured config: they diff field-by-field, render in the Console designer, and since [#4271](https://github.com/objectstack-ai/objectstack/issues/4271) the field-existence check gates there too — `flow-node-write-unknown-field` is an **error**, not the advisory warning a body gets, because a node's `fields` is a literal map next to a literal `objectName`: there is no parser in between that could have mis-extracted it, so a finding is a certainty rather than a best effort. (The *writability* check now has a hook-side counterpart — see [Writing a `readonly` field](#writing-a-readonly-field) below — but it covers only the `ctx.api` channel.)
-- **Exercise the hook against a real object before shipping** — on SQL drivers the mistake surfaces on the first write; schemaless drivers won't tell you.
+- **Exercise the hook against a real object before shipping** — the mistake surfaces on the first write, identically on every driver.
 
 ### Signature conventions
 

content/docs/permissions/system-context.mdx

@@ -109,18 +109,18 @@ that silently does not happen.
 
 | # | Behaviour when `isSystem` | Package | What you get / what you lose | Anchor |
 |:--|:---|:---|:---|:---|
-| 18 | **`readonly` strip bypassed — UPDATE, single row** | objectql | Get: a `readonly` field CAN be written. Lose: the protection that stops a caller seeding e.g. `approval_status` | `objectql/src/engine.ts:10787` |
-| 19 | **`readonly` strip bypassed — UPDATE, bulk/predicate** | objectql | Same, on the multi-row path | `objectql/src/engine.ts:10949` |
-| 20 | **`readonly` strip bypassed — INSERT (engine pass)** | objectql | Same, on create | `objectql/src/engine.ts:9680` |
+| 18 | **`readonly` strip bypassed — UPDATE, single row** | objectql | Get: a `readonly` field CAN be written. Lose: the protection that stops a caller seeding e.g. `approval_status` | `objectql/src/engine.ts:10882` |
+| 19 | **`readonly` strip bypassed — UPDATE, bulk/predicate** | objectql | Same, on the multi-row path | `objectql/src/engine.ts:11044` |
+| 20 | **`readonly` strip bypassed — INSERT (engine pass)** | objectql | Same, on create | `objectql/src/engine.ts:9747` |
 | 21 | **`readonly` strip bypassed — INSERT (protocol ingress)** | metadata-protocol | `isSystem` is the **only** exemption here. `preserveAudit` is deliberately not read on this path (#6640) — a non-system historical import is still stripped on create | `metadata-protocol/src/protocol.ts:1737` |
-| 22 | Strict-drop refusal never fires | objectql | Lose: a caller that opted into loud refusal gets **silence** — strict refuses exactly what the strip would have taken, and the strip took nothing | `objectql/src/engine.ts:9717`, `readonly-strict-errors.ts:66` |
+| 22 | Strict-drop refusal never fires | objectql | Lose: a caller that opted into loud refusal gets **silence** — strict refuses exactly what the strip would have taken, and the strip took nothing | `objectql/src/engine.ts:9784`, `readonly-strict-errors.ts:66` |
 | 23 | **Referential-integrity check skipped** | objectql | Get: writes proceed against unreachable/unresolvable targets. Lose: an `isSystem` caller can write a **dangling reference** | `objectql/src/engine.ts:5705` |
 | 24 | Tenant-audit warning silenced; `bypassTenantAudit` threaded to the driver | objectql | Get: unscoped system writes stop warning. Lose: the signal that would flag a genuine user-path scoping bug | `objectql/src/engine.ts:3574`, `:3584`, `:3611` |
 | 25 | Engine-owned / append-only write guard bypassed | plugin-security | Get: generic writes to `managedBy` engine-owned objects | `system-write-guard.ts:96`, `:120` |
 | 26 | Identity write guard bypassed (ADR-0092) | plugin-auth | Get: direct writes to identity tables through the generic data path | `identity-write-guard.ts:98` |
 | 27 | Search-companion column **kept** in a read's rows when it was explicitly requested | objectql | Get: the internal companion column is readable. Lose: nothing for app code — this is the engine reading its own index | `objectql/src/engine.ts:6403` |
-| 28 | Dependent-count disclosure on a blocked delete | objectql | Get: the count of blocking children. Nothing was elevated past the caller, so nothing is withheld | `objectql/src/engine.ts:11535` |
-| 29 | Reference-cleanup log attributes the write to `'system'` | objectql | Get: an honest actor label instead of `anonymous` when the context carries neither `userId` nor `actor` | `objectql/src/engine.ts:11464` |
+| 28 | Dependent-count disclosure on a blocked delete | objectql | Get: the count of blocking children. Nothing was elevated past the caller, so nothing is withheld | `objectql/src/engine.ts:11630` |
+| 29 | Reference-cleanup log attributes the write to `'system'` | objectql | Get: an honest actor label instead of `anonymous` when the context carries neither `userId` nor `actor` | `objectql/src/engine.ts:11559` |
 
 ### 3. Sharing (`plugin-sharing`)
 
@@ -180,7 +180,7 @@ a reader tracing where elevation travels needs them.
 | # | Site | Package | What it does |
 |:--|:---|:---|:---|
 | 62 | `objectql/src/engine.ts:3406` | objectql | Propagates `isSystem` into the hook session so hooks can tell engine self-writes from user writes |
-| 63 | `objectql/src/engine.ts:13876` | objectql | `ScopedContext.isSystem` getter — re-exposes the underlying execution context's flag |
+| 63 | `objectql/src/engine.ts:13971` | objectql | `ScopedContext.isSystem` getter — re-exposes the underlying execution context's flag |
 | 64 | `plugin-reports/src/report-service.ts:556` | plugin-reports | Threads the flag into the engine call that runs a report |
 | 65 | `body-runner.ts:279` | runtime | Rebuilds an `ExecutionContext` from a hook session, carrying the flag across |
 
@@ -195,7 +195,7 @@ assuming `isSystem` covers it is a documented source of bugs.
 |:---|:---|:---|
 | "It suppresses triggers / record-change automation" | **No.** Only `skipTriggers` does. A bare `{ isSystem: true }` on a seed write re-fired automation on freshly seeded rows and wedged first boot | `metadata-protocol/src/seed-loader.ts:1909` (rationale at `:1819`–`1821`, #3760), `flow.zod.ts:685` |
 | "It skips the state machine" | **No.** That is `skipStateMachine`, carried by seed replay and by `treatAsHistorical` imports | `objectql/src/engine.ts` FSM gate; see [State Machine](/docs/protocol/objectql/state-machine) |
-| "It skips validation rules" | **No.** Field shape, `format`, `script` and the rest still run. The `readonly` strip runs *before* validation precisely so a discarded value is not judged | `objectql/src/engine.ts:9663`–`9680` |
+| "It skips validation rules" | **No.** Field shape, `format`, `script` and the rest still run. The `readonly` strip runs *before* validation precisely so a discarded value is not judged | `objectql/src/engine.ts:9730`–`9747` |
 | "It preserves a supplied `updated_at` / `updated_by`" | **No.** That is `preserveAudit`, a separate opt-in — and an UPDATE-path exemption only | `field.zod.ts:1516` (#3493 / #6640) |
 | "It stamps `created_by`" | **No.** Audit stamping reads `userId` from the context. A user-less system write stamps nothing — that is today's behaviour, not an error | `runtime-identity.ts:280`–`281` |
 | "It bypasses every guard" | **No.** The last-admin guard applies to **every** context, `isSystem` included — the deprovision path that actually locks an org out is the system one | `last-admin-guard.ts:286` |

packages/lint/src/validate-hook-body-writes.ts

@@ -4,24 +4,30 @@
 //
 // An L2 body that writes a field the target object never declares —
 // `ctx.input.amout = 0`, `ctx.api.object('deal').update({ stag: 'won' })` —
-// runs clean in the QuickJS sandbox and reaches the driver UNFILTERED:
+// runs clean in the QuickJS sandbox and reaches the write path UNFILTERED:
 // `applyMutationsToInput` (runtime/src/sandbox/body-runner.ts) is a plain
 // `Object.assign`, and `validateRecord` walks declared fields on insert and
-// `continue`s past a key with no field def on update. What happens after that
-// is DRIVER-DEPENDENT, and neither half is acceptable:
+// `continue`s past a key with no field def on update.
 //
-// • SQL — the stray column enters the knex statement and the WHOLE write
-// fails with a driver-level error (`table deal has no column named
-// stagee`). The write is lost, and the error surfaces far from the
-// authoring mistake that caused it.
-// • Schemaless (memory, MongoDB) — the driver spreads the payload, so the
-// stray key IS persisted: an undeclared column nothing downstream reads.
+// [#13657] What happens after that used to be DRIVER-DEPENDENT, and neither
+// half was acceptable — SQL failed the whole write with an untyped
+// `SQLITE_ERROR` far from the authoring mistake, while schemaless drivers
+// (memory, MongoDB) spread the payload and PERSISTED the stray key as a column
+// nothing downstream reads. #13657 closed that: the declared-field door now
+// runs a second time over the payload the `before*` hooks produced, so the key
+// is refused `INVALID_FIELD` / 400 identically on every driver, before any
+// statement is built.
 //
-// Either way the mistake is invisible where it is MADE — the #4001 family, if
-// not literally its silent-no-op shape. Both runtime outcomes are pinned by
+// ⚠️ That does NOT retire this rule — it changes what it is worth. The runtime
+// refusal arrives at WRITE time, on whichever record first exercises the
+// branch; this rule arrives at AUTHOR time and names the field, the object and
+// the body. The mistake is still invisible where it is MADE, which is the
+// #4001 family and the whole reason for a build-time check.
+//
+// The runtime answer is pinned by
 // `runtime/src/sandbox/undeclared-field-write-driver-split.integration.test.ts`
-// so this rule's wording cannot drift from what the runtime does; the same
-// split is documented in `content/docs/automation/hook-bodies.mdx`.
+// so this rule's wording cannot drift from what the runtime does; the same is
+// documented in `content/docs/automation/hook-bodies.mdx`.
 //
 // The read side (`hook.condition`, ADR-0032) and the capability surface are
 // statically checked; until this rule, the write side was the one blind face
@@ -817,9 +823,12 @@ export function validateHookBodyWrites(stack: AnyRec): HookBodyWriteFinding[] {
  path,
  message:
  `body writes '${w.field}' to its input, but ${objDesc} ${declares}. The sandboxed script runs ` +
- `clean and the value is copied back onto the record payload unfiltered — on a SQL driver the ` +
- `stray column then fails the WHOLE write with a driver-level error far from here; on a ` +
- `schemaless driver (memory, MongoDB) it is persisted as an undeclared key (#4271).`,
+ // The post-hook declared-field door (#13657) is what refuses it; the
+ // id stays in this comment rather than in the string, which reaches
+ // authors and operators who cannot resolve a tracker number.
+ `clean and the value is copied back onto the record payload unfiltered, so the write is then ` +
+ `REFUSED at run time — INVALID_FIELD / 400, identically on every driver (#4271). The ` +
+ `record is never written, and the refusal names the field far from the body that wrote it.`,
  hint: fixHint(w.field, unionCandidates(targetSets)),
  });
  } else {

.changeset/post-hook-undeclared-field-door.md

@@ -0,0 +1,61 @@
+---
+'@objectstack/objectql': minor
+'@objectstack/lint': patch
+---
+
+Refuse an undeclared field a `before*` hook writes, identically on every driver
+
+**BREAKING** accept-set narrowing at the post-hook write door, shipped as `minor`
+under the repo's launch-window convention for breaking changes.
+
+**Bump level, argued**: `@objectstack/objectql` is `minor`, not `patch`. A
+`before*` hook or an L2 (`language:'js'`) body writing a key the object never
+declares **used to succeed** on the `memory` family — the value reached the
+store and persisted as a shadow column — and now **throws**, `INVALID_FIELD` /
+**400**, on every driver. That is a narrowing of the accept set on the record
+payload, a surface every hook body touches; it is not an instrument or a message
+fix, and a hook that relied on either driver-dependent outcome stops working at
+run time. The same-package sibling `.changeset/hook-input-symbol-key-refusal.md`
+argues exactly this shape — "used to succeed, and now throw. That is a narrowing
+of the accept set" — to `minor`, and the launch-window convention is what keeps
+it off `major` (pre-1.0 lockstep semantics: a breaking change does not burn a
+major version while the stack versions in lockstep — see
+`scripts/check-changeset-no-major.mjs`). `patch` would under-declare a change
+that turns a passing hook into a throwing one.
+
+`'@objectstack/lint': patch` is deliberate and stays. That half of the diff is
+message and comment prose only: `validateHookBodyWrites` reports the same
+findings on the same bodies at the same severity, with wording that now names
+the runtime refusal instead of the driver split this change retires.
+
+The declared-field door (#8682 on insert, #8738 on update) runs before the
+`before*` hooks — deliberately, so a payload about to be refused never consumes
+an autonumber (#8737). That left the payload the hooks themselves produce
+unjudged: a key a `beforeInsert` / `beforeUpdate` hook or an L2 (`language:'js'`)
+body wrote went straight to the driver, and the drivers disagreed. `memory`
+accepted it and stored a shadow column; `driver-sql` threw a raw `SQLITE_ERROR`
+with no `status` and the bound statement and its values quoted back in the
+message; `sqlite-wasm` threw a bare `Error` with neither. One app and one hook
+meant different things on two deployments, and nothing in the app could tell
+which one it was running on.
+
+The same check now runs a second time over the post-hook payload, before any
+statement is built, so a hook-written undeclared key is refused with the caller
+path's envelope — `INVALID_FIELD` / **400**, `Unknown field 'x' on object 'y'` —
+on every driver, because none of them is reached. The existing pre-hook door is
+unchanged and stays exactly where it is.
+
+This is a security fix as well as a consistency one: `fieldPermissions` is keyed
+by declared field name and reports only fields explicitly marked non-editable, so
+a key the object never declares can carry no entry and could never be gated by
+field-level security. On `memory`-family stores such a value was persisted where
+no view, formula, index or permission could name it.
+
+The platform's own stamps are unaffected. `created_at` / `updated_at` — the two
+the built-in audit hook writes unconditionally, because SQL drivers create them
+as built-in columns on every table — are already tolerated by this check
+alongside `id`; every other stamp (`created_by`, `updated_by`, `tenant_id`) is
+guarded by an explicit declaration test in the hook that writes it.
+
+<!-- adr-0087: not-required (no-migration-prescription) No metadata key, spec symbol, Zod schema, object definition or stored representation is added, removed or renamed. This narrows which run-time record payload the engine accepts after the `before*` hooks have run; an undeclared key was never a declarable metadata surface, so `objectstack migrate meta` has nothing in a stored source to rewrite. The remedy for an affected hook body is to declare the field on the object or stop writing it, which is authoring guidance, not a mechanical rewrite of stored metadata. -->
+

content/docs/automation/hook-bodies.mdx

@@ -204,19 +204,22 @@ A structured `writes` declaration was considered and dropped ([#3700](https://gi
 
 #### What still happens at runtime
 
-An unknown field is **not** caught at runtime, and it does not fail quietly either. The write-path validator walks the object's *declared* fields, so an undeclared key is neither rejected nor stripped, and the sandbox's mutations are copied back onto the payload verbatim. What happens next is the driver's call:
+An unknown field **is** caught at runtime, and the answer is the same on every driver. The sandbox's mutations are copied back onto the payload verbatim (`applyMutationsToInput` is a plain `Object.assign`) and the write-path validator still walks only the object's *declared* fields — but since [#13657](https://github.com/objectstack-ai/objectstack/issues/13657) the declared-field door runs a **second** time, over the payload the `before*` hooks produced, before any statement is built:
 
-- **SQL drivers** put the stray column into the statement, so the **whole write fails** with a driver-level error (`table deal has no column named stagee`) — nothing is stored, and the error surfaces far from the authoring mistake.
-- **Schemaless drivers** (memory, MongoDB) silently persist the stray key alongside the real ones.
+```
+INVALID_FIELD / 400 / Unknown field 'stagee' on object 'deal'
+```
+
+Identical on `memory`, `driver-sql` and `sqlite-wasm`, because none of them is reached. Before #13657 the driver decided instead, and the two families disagreed — SQL failed the whole write with an untyped `SQLITE_ERROR`, while schemaless drivers silently persisted the stray key as a column nothing downstream reads (and which field-level security, keyed by *declared* field name, could never gate). One app, one body, two meanings decided by which driver a deployment happened to run.
 
-Neither outcome is the one you wanted, and the advisory warning is the earliest signal you get.
+The runtime refusal is now the backstop; the advisory warning is still the earliest signal you get, and the one that names the mistake where it was made.
 
 Because the existence check is advisory, and every write-side check here is literal-only:
 
 - **Treat `hook-body-write-unknown-field` as a build failure by convention.** It does not gate, but the rule is tuned for near-zero false positives — in practice a warning is a real typo.
 - **Check by hand what the parser cannot see.** Computed keys, spreads, aliased input and dynamic object names are invisible to the rule; for an array or `"*"` hook, every field must exist on every target.
 - **Prefer a flow `update_record` node when the write set is fixed — and for *this* check most of all.** A flow node's writes are structured config: they diff field-by-field, render in the Console designer, and since [#4271](https://github.com/objectstack-ai/objectstack/issues/4271) the field-existence check gates there too — `flow-node-write-unknown-field` is an **error**, not the advisory warning a body gets, because a node's `fields` is a literal map next to a literal `objectName`: there is no parser in between that could have mis-extracted it, so a finding is a certainty rather than a best effort. (The *writability* check now has a hook-side counterpart — see [Writing a `readonly` field](#writing-a-readonly-field) below — but it covers only the `ctx.api` channel.)
-- **Exercise the hook against a real object before shipping** — on SQL drivers the mistake surfaces on the first write; schemaless drivers won't tell you.
+- **Exercise the hook against a real object before shipping** — the mistake surfaces on the first write, identically on every driver.
 
 ### Signature conventions
 

content/docs/permissions/system-context.mdx

@@ -109,18 +109,18 @@ that silently does not happen.
 
 | # | Behaviour when `isSystem` | Package | What you get / what you lose | Anchor |
 |:--|:---|:---|:---|:---|
-| 18 | **`readonly` strip bypassed — UPDATE, single row** | objectql | Get: a `readonly` field CAN be written. Lose: the protection that stops a caller seeding e.g. `approval_status` | `objectql/src/engine.ts:10787` |
-| 19 | **`readonly` strip bypassed — UPDATE, bulk/predicate** | objectql | Same, on the multi-row path | `objectql/src/engine.ts:10949` |
-| 20 | **`readonly` strip bypassed — INSERT (engine pass)** | objectql | Same, on create | `objectql/src/engine.ts:9680` |
+| 18 | **`readonly` strip bypassed — UPDATE, single row** | objectql | Get: a `readonly` field CAN be written. Lose: the protection that stops a caller seeding e.g. `approval_status` | `objectql/src/engine.ts:10882` |
+| 19 | **`readonly` strip bypassed — UPDATE, bulk/predicate** | objectql | Same, on the multi-row path | `objectql/src/engine.ts:11044` |
+| 20 | **`readonly` strip bypassed — INSERT (engine pass)** | objectql | Same, on create | `objectql/src/engine.ts:9747` |
 | 21 | **`readonly` strip bypassed — INSERT (protocol ingress)** | metadata-protocol | `isSystem` is the **only** exemption here. `preserveAudit` is deliberately not read on this path (#6640) — a non-system historical import is still stripped on create | `metadata-protocol/src/protocol.ts:1737` |
-| 22 | Strict-drop refusal never fires | objectql | Lose: a caller that opted into loud refusal gets **silence** — strict refuses exactly what the strip would have taken, and the strip took nothing | `objectql/src/engine.ts:9717`, `readonly-strict-errors.ts:66` |
+| 22 | Strict-drop refusal never fires | objectql | Lose: a caller that opted into loud refusal gets **silence** — strict refuses exactly what the strip would have taken, and the strip took nothing | `objectql/src/engine.ts:9784`, `readonly-strict-errors.ts:66` |
 | 23 | **Referential-integrity check skipped** | objectql | Get: writes proceed against unreachable/unresolvable targets. Lose: an `isSystem` caller can write a **dangling reference** | `objectql/src/engine.ts:5705` |
 | 24 | Tenant-audit warning silenced; `bypassTenantAudit` threaded to the driver | objectql | Get: unscoped system writes stop warning. Lose: the signal that would flag a genuine user-path scoping bug | `objectql/src/engine.ts:3574`, `:3584`, `:3611` |
 | 25 | Engine-owned / append-only write guard bypassed | plugin-security | Get: generic writes to `managedBy` engine-owned objects | `system-write-guard.ts:96`, `:120` |
 | 26 | Identity write guard bypassed (ADR-0092) | plugin-auth | Get: direct writes to identity tables through the generic data path | `identity-write-guard.ts:98` |
 | 27 | Search-companion column **kept** in a read's rows when it was explicitly requested | objectql | Get: the internal companion column is readable. Lose: nothing for app code — this is the engine reading its own index | `objectql/src/engine.ts:6403` |
-| 28 | Dependent-count disclosure on a blocked delete | objectql | Get: the count of blocking children. Nothing was elevated past the caller, so nothing is withheld | `objectql/src/engine.ts:11535` |
-| 29 | Reference-cleanup log attributes the write to `'system'` | objectql | Get: an honest actor label instead of `anonymous` when the context carries neither `userId` nor `actor` | `objectql/src/engine.ts:11464` |
+| 28 | Dependent-count disclosure on a blocked delete | objectql | Get: the count of blocking children. Nothing was elevated past the caller, so nothing is withheld | `objectql/src/engine.ts:11630` |
+| 29 | Reference-cleanup log attributes the write to `'system'` | objectql | Get: an honest actor label instead of `anonymous` when the context carries neither `userId` nor `actor` | `objectql/src/engine.ts:11559` |
 
 ### 3. Sharing (`plugin-sharing`)
 
@@ -180,7 +180,7 @@ a reader tracing where elevation travels needs them.
 | # | Site | Package | What it does |
 |:--|:---|:---|:---|
 | 62 | `objectql/src/engine.ts:3406` | objectql | Propagates `isSystem` into the hook session so hooks can tell engine self-writes from user writes |
-| 63 | `objectql/src/engine.ts:13876` | objectql | `ScopedContext.isSystem` getter — re-exposes the underlying execution context's flag |
+| 63 | `objectql/src/engine.ts:13971` | objectql | `ScopedContext.isSystem` getter — re-exposes the underlying execution context's flag |
 | 64 | `plugin-reports/src/report-service.ts:556` | plugin-reports | Threads the flag into the engine call that runs a report |
 | 65 | `body-runner.ts:279` | runtime | Rebuilds an `ExecutionContext` from a hook session, carrying the flag across |
 
@@ -195,7 +195,7 @@ assuming `isSystem` covers it is a documented source of bugs.
 |:---|:---|:---|
 | "It suppresses triggers / record-change automation" | **No.** Only `skipTriggers` does. A bare `{ isSystem: true }` on a seed write re-fired automation on freshly seeded rows and wedged first boot | `metadata-protocol/src/seed-loader.ts:1909` (rationale at `:1819`–`1821`, #3760), `flow.zod.ts:685` |
 | "It skips the state machine" | **No.** That is `skipStateMachine`, carried by seed replay and by `treatAsHistorical` imports | `objectql/src/engine.ts` FSM gate; see [State Machine](/docs/protocol/objectql/state-machine) |
-| "It skips validation rules" | **No.** Field shape, `format`, `script` and the rest still run. The `readonly` strip runs *before* validation precisely so a discarded value is not judged | `objectql/src/engine.ts:9663`–`9680` |
+| "It skips validation rules" | **No.** Field shape, `format`, `script` and the rest still run. The `readonly` strip runs *before* validation precisely so a discarded value is not judged | `objectql/src/engine.ts:9730`–`9747` |
 | "It preserves a supplied `updated_at` / `updated_by`" | **No.** That is `preserveAudit`, a separate opt-in — and an UPDATE-path exemption only | `field.zod.ts:1516` (#3493 / #6640) |
 | "It stamps `created_by`" | **No.** Audit stamping reads `userId` from the context. A user-less system write stamps nothing — that is today's behaviour, not an error | `runtime-identity.ts:280`–`281` |
 | "It bypasses every guard" | **No.** The last-admin guard applies to **every** context, `isSystem` included — the deprovision path that actually locks an org out is the system one | `last-admin-guard.ts:286` |

packages/lint/src/validate-hook-body-writes.ts

@@ -4,24 +4,30 @@
 //
 // An L2 body that writes a field the target object never declares —
 // `ctx.input.amout = 0`, `ctx.api.object('deal').update({ stag: 'won' })` —
-// runs clean in the QuickJS sandbox and reaches the driver UNFILTERED:
+// runs clean in the QuickJS sandbox and reaches the write path UNFILTERED:
 // `applyMutationsToInput` (runtime/src/sandbox/body-runner.ts) is a plain
 // `Object.assign`, and `validateRecord` walks declared fields on insert and
-// `continue`s past a key with no field def on update. What happens after that
-// is DRIVER-DEPENDENT, and neither half is acceptable:
+// `continue`s past a key with no field def on update.
 //
-// • SQL — the stray column enters the knex statement and the WHOLE write
-// fails with a driver-level error (`table deal has no column named
-// stagee`). The write is lost, and the error surfaces far from the
-// authoring mistake that caused it.
-// • Schemaless (memory, MongoDB) — the driver spreads the payload, so the
-// stray key IS persisted: an undeclared column nothing downstream reads.
+// [#13657] What happens after that used to be DRIVER-DEPENDENT, and neither
+// half was acceptable — SQL failed the whole write with an untyped
+// `SQLITE_ERROR` far from the authoring mistake, while schemaless drivers
+// (memory, MongoDB) spread the payload and PERSISTED the stray key as a column
+// nothing downstream reads. #13657 closed that: the declared-field door now
+// runs a second time over the payload the `before*` hooks produced, so the key
+// is refused `INVALID_FIELD` / 400 identically on every driver, before any
+// statement is built.
 //
-// Either way the mistake is invisible where it is MADE — the #4001 family, if
-// not literally its silent-no-op shape. Both runtime outcomes are pinned by
+// ⚠️ That does NOT retire this rule — it changes what it is worth. The runtime
+// refusal arrives at WRITE time, on whichever record first exercises the
+// branch; this rule arrives at AUTHOR time and names the field, the object and
+// the body. The mistake is still invisible where it is MADE, which is the
+// #4001 family and the whole reason for a build-time check.
+//
+// The runtime answer is pinned by
 // `runtime/src/sandbox/undeclared-field-write-driver-split.integration.test.ts`
-// so this rule's wording cannot drift from what the runtime does; the same
-// split is documented in `content/docs/automation/hook-bodies.mdx`.
+// so this rule's wording cannot drift from what the runtime does; the same is
+// documented in `content/docs/automation/hook-bodies.mdx`.
 //
 // The read side (`hook.condition`, ADR-0032) and the capability surface are
 // statically checked; until this rule, the write side was the one blind face
@@ -817,9 +823,12 @@ export function validateHookBodyWrites(stack: AnyRec): HookBodyWriteFinding[] {
  path,
  message:
  `body writes '${w.field}' to its input, but ${objDesc} ${declares}. The sandboxed script runs ` +
- `clean and the value is copied back onto the record payload unfiltered — on a SQL driver the ` +
- `stray column then fails the WHOLE write with a driver-level error far from here; on a ` +
- `schemaless driver (memory, MongoDB) it is persisted as an undeclared key (#4271).`,
+ // The post-hook declared-field door (#13657) is what refuses it; the
+ // id stays in this comment rather than in the string, which reaches
+ // authors and operators who cannot resolve a tracker number.
+ `clean and the value is copied back onto the record payload unfiltered, so the write is then ` +
+ `REFUSED at run time — INVALID_FIELD / 400, identically on every driver (#4271). The ` +
+ `record is never written, and the refusal names the field far from the body that wrote it.`,
  hint: fixHint(w.field, unionCandidates(targetSets)),
  });
  } else {

.changeset/post-hook-undeclared-field-door.md

@@ -0,0 +1,61 @@
+---
+'@objectstack/objectql': minor
+'@objectstack/lint': patch
+---
+
+Refuse an undeclared field a `before*` hook writes, identically on every driver
+
+**BREAKING** accept-set narrowing at the post-hook write door, shipped as `minor`
+under the repo's launch-window convention for breaking changes.
+
+**Bump level, argued**: `@objectstack/objectql` is `minor`, not `patch`. A
+`before*` hook or an L2 (`language:'js'`) body writing a key the object never
+declares **used to succeed** on the `memory` family — the value reached the
+store and persisted as a shadow column — and now **throws**, `INVALID_FIELD` /
+**400**, on every driver. That is a narrowing of the accept set on the record
+payload, a surface every hook body touches; it is not an instrument or a message
+fix, and a hook that relied on either driver-dependent outcome stops working at
+run time. The same-package sibling `.changeset/hook-input-symbol-key-refusal.md`
+argues exactly this shape — "used to succeed, and now throw. That is a narrowing
+of the accept set" — to `minor`, and the launch-window convention is what keeps
+it off `major` (pre-1.0 lockstep semantics: a breaking change does not burn a
+major version while the stack versions in lockstep — see
+`scripts/check-changeset-no-major.mjs`). `patch` would under-declare a change
+that turns a passing hook into a throwing one.
+
+`'@objectstack/lint': patch` is deliberate and stays. That half of the diff is
+message and comment prose only: `validateHookBodyWrites` reports the same
+findings on the same bodies at the same severity, with wording that now names
+the runtime refusal instead of the driver split this change retires.
+
+The declared-field door (#8682 on insert, #8738 on update) runs before the
+`before*` hooks — deliberately, so a payload about to be refused never consumes
+an autonumber (#8737). That left the payload the hooks themselves produce
+unjudged: a key a `beforeInsert` / `beforeUpdate` hook or an L2 (`language:'js'`)
+body wrote went straight to the driver, and the drivers disagreed. `memory`
+accepted it and stored a shadow column; `driver-sql` threw a raw `SQLITE_ERROR`
+with no `status` and the bound statement and its values quoted back in the
+message; `sqlite-wasm` threw a bare `Error` with neither. One app and one hook
+meant different things on two deployments, and nothing in the app could tell
+which one it was running on.
+
+The same check now runs a second time over the post-hook payload, before any
+statement is built, so a hook-written undeclared key is refused with the caller
+path's envelope — `INVALID_FIELD` / **400**, `Unknown field 'x' on object 'y'` —
+on every driver, because none of them is reached. The existing pre-hook door is
+unchanged and stays exactly where it is.
+
+This is a security fix as well as a consistency one: `fieldPermissions` is keyed
+by declared field name and reports only fields explicitly marked non-editable, so
+a key the object never declares can carry no entry and could never be gated by
+field-level security. On `memory`-family stores such a value was persisted where
+no view, formula, index or permission could name it.
+
+The platform's own stamps are unaffected. `created_at` / `updated_at` — the two
+the built-in audit hook writes unconditionally, because SQL drivers create them
+as built-in columns on every table — are already tolerated by this check
+alongside `id`; every other stamp (`created_by`, `updated_by`, `tenant_id`) is
+guarded by an explicit declaration test in the hook that writes it.
+
+<!-- adr-0087: not-required (no-migration-prescription) No metadata key, spec symbol, Zod schema, object definition or stored representation is added, removed or renamed. This narrows which run-time record payload the engine accepts after the `before*` hooks have run; an undeclared key was never a declarable metadata surface, so `objectstack migrate meta` has nothing in a stored source to rewrite. The remedy for an affected hook body is to declare the field on the object or stop writing it, which is authoring guidance, not a mechanical rewrite of stored metadata. -->
+

content/docs/automation/hook-bodies.mdx

@@ -204,19 +204,22 @@ A structured `writes` declaration was considered and dropped ([#3700](https://gi
 
 #### What still happens at runtime
 
-An unknown field is **not** caught at runtime, and it does not fail quietly either. The write-path validator walks the object's *declared* fields, so an undeclared key is neither rejected nor stripped, and the sandbox's mutations are copied back onto the payload verbatim. What happens next is the driver's call:
+An unknown field **is** caught at runtime, and the answer is the same on every driver. The sandbox's mutations are copied back onto the payload verbatim (`applyMutationsToInput` is a plain `Object.assign`) and the write-path validator still walks only the object's *declared* fields — but since [#13657](https://github.com/objectstack-ai/objectstack/issues/13657) the declared-field door runs a **second** time, over the payload the `before*` hooks produced, before any statement is built:
 
-- **SQL drivers** put the stray column into the statement, so the **whole write fails** with a driver-level error (`table deal has no column named stagee`) — nothing is stored, and the error surfaces far from the authoring mistake.
-- **Schemaless drivers** (memory, MongoDB) silently persist the stray key alongside the real ones.
+```
+INVALID_FIELD / 400 / Unknown field 'stagee' on object 'deal'
+```
+
+Identical on `memory`, `driver-sql` and `sqlite-wasm`, because none of them is reached. Before #13657 the driver decided instead, and the two families disagreed — SQL failed the whole write with an untyped `SQLITE_ERROR`, while schemaless drivers silently persisted the stray key as a column nothing downstream reads (and which field-level security, keyed by *declared* field name, could never gate). One app, one body, two meanings decided by which driver a deployment happened to run.
 
-Neither outcome is the one you wanted, and the advisory warning is the earliest signal you get.
+The runtime refusal is now the backstop; the advisory warning is still the earliest signal you get, and the one that names the mistake where it was made.
 
 Because the existence check is advisory, and every write-side check here is literal-only:
 
 - **Treat `hook-body-write-unknown-field` as a build failure by convention.** It does not gate, but the rule is tuned for near-zero false positives — in practice a warning is a real typo.
 - **Check by hand what the parser cannot see.** Computed keys, spreads, aliased input and dynamic object names are invisible to the rule; for an array or `"*"` hook, every field must exist on every target.
 - **Prefer a flow `update_record` node when the write set is fixed — and for *this* check most of all.** A flow node's writes are structured config: they diff field-by-field, render in the Console designer, and since [#4271](https://github.com/objectstack-ai/objectstack/issues/4271) the field-existence check gates there too — `flow-node-write-unknown-field` is an **error**, not the advisory warning a body gets, because a node's `fields` is a literal map next to a literal `objectName`: there is no parser in between that could have mis-extracted it, so a finding is a certainty rather than a best effort. (The *writability* check now has a hook-side counterpart — see [Writing a `readonly` field](#writing-a-readonly-field) below — but it covers only the `ctx.api` channel.)
-- **Exercise the hook against a real object before shipping** — on SQL drivers the mistake surfaces on the first write; schemaless drivers won't tell you.
+- **Exercise the hook against a real object before shipping** — the mistake surfaces on the first write, identically on every driver.
 
 ### Signature conventions
 

content/docs/permissions/system-context.mdx

@@ -109,18 +109,18 @@ that silently does not happen.
 
 | # | Behaviour when `isSystem` | Package | What you get / what you lose | Anchor |
 |:--|:---|:---|:---|:---|
-| 18 | **`readonly` strip bypassed — UPDATE, single row** | objectql | Get: a `readonly` field CAN be written. Lose: the protection that stops a caller seeding e.g. `approval_status` | `objectql/src/engine.ts:10787` |
-| 19 | **`readonly` strip bypassed — UPDATE, bulk/predicate** | objectql | Same, on the multi-row path | `objectql/src/engine.ts:10949` |
-| 20 | **`readonly` strip bypassed — INSERT (engine pass)** | objectql | Same, on create | `objectql/src/engine.ts:9680` |
+| 18 | **`readonly` strip bypassed — UPDATE, single row** | objectql | Get: a `readonly` field CAN be written. Lose: the protection that stops a caller seeding e.g. `approval_status` | `objectql/src/engine.ts:10882` |
+| 19 | **`readonly` strip bypassed — UPDATE, bulk/predicate** | objectql | Same, on the multi-row path | `objectql/src/engine.ts:11044` |
+| 20 | **`readonly` strip bypassed — INSERT (engine pass)** | objectql | Same, on create | `objectql/src/engine.ts:9747` |
 | 21 | **`readonly` strip bypassed — INSERT (protocol ingress)** | metadata-protocol | `isSystem` is the **only** exemption here. `preserveAudit` is deliberately not read on this path (#6640) — a non-system historical import is still stripped on create | `metadata-protocol/src/protocol.ts:1737` |
-| 22 | Strict-drop refusal never fires | objectql | Lose: a caller that opted into loud refusal gets **silence** — strict refuses exactly what the strip would have taken, and the strip took nothing | `objectql/src/engine.ts:9717`, `readonly-strict-errors.ts:66` |
+| 22 | Strict-drop refusal never fires | objectql | Lose: a caller that opted into loud refusal gets **silence** — strict refuses exactly what the strip would have taken, and the strip took nothing | `objectql/src/engine.ts:9784`, `readonly-strict-errors.ts:66` |
 | 23 | **Referential-integrity check skipped** | objectql | Get: writes proceed against unreachable/unresolvable targets. Lose: an `isSystem` caller can write a **dangling reference** | `objectql/src/engine.ts:5705` |
 | 24 | Tenant-audit warning silenced; `bypassTenantAudit` threaded to the driver | objectql | Get: unscoped system writes stop warning. Lose: the signal that would flag a genuine user-path scoping bug | `objectql/src/engine.ts:3574`, `:3584`, `:3611` |
 | 25 | Engine-owned / append-only write guard bypassed | plugin-security | Get: generic writes to `managedBy` engine-owned objects | `system-write-guard.ts:96`, `:120` |
 | 26 | Identity write guard bypassed (ADR-0092) | plugin-auth | Get: direct writes to identity tables through the generic data path | `identity-write-guard.ts:98` |
 | 27 | Search-companion column **kept** in a read's rows when it was explicitly requested | objectql | Get: the internal companion column is readable. Lose: nothing for app code — this is the engine reading its own index | `objectql/src/engine.ts:6403` |
-| 28 | Dependent-count disclosure on a blocked delete | objectql | Get: the count of blocking children. Nothing was elevated past the caller, so nothing is withheld | `objectql/src/engine.ts:11535` |
-| 29 | Reference-cleanup log attributes the write to `'system'` | objectql | Get: an honest actor label instead of `anonymous` when the context carries neither `userId` nor `actor` | `objectql/src/engine.ts:11464` |
+| 28 | Dependent-count disclosure on a blocked delete | objectql | Get: the count of blocking children. Nothing was elevated past the caller, so nothing is withheld | `objectql/src/engine.ts:11630` |
+| 29 | Reference-cleanup log attributes the write to `'system'` | objectql | Get: an honest actor label instead of `anonymous` when the context carries neither `userId` nor `actor` | `objectql/src/engine.ts:11559` |
 
 ### 3. Sharing (`plugin-sharing`)
 
@@ -180,7 +180,7 @@ a reader tracing where elevation travels needs them.
 | # | Site | Package | What it does |
 |:--|:---|:---|:---|
 | 62 | `objectql/src/engine.ts:3406` | objectql | Propagates `isSystem` into the hook session so hooks can tell engine self-writes from user writes |
-| 63 | `objectql/src/engine.ts:13876` | objectql | `ScopedContext.isSystem` getter — re-exposes the underlying execution context's flag |
+| 63 | `objectql/src/engine.ts:13971` | objectql | `ScopedContext.isSystem` getter — re-exposes the underlying execution context's flag |
 | 64 | `plugin-reports/src/report-service.ts:556` | plugin-reports | Threads the flag into the engine call that runs a report |
 | 65 | `body-runner.ts:279` | runtime | Rebuilds an `ExecutionContext` from a hook session, carrying the flag across |
 
@@ -195,7 +195,7 @@ assuming `isSystem` covers it is a documented source of bugs.
 |:---|:---|:---|
 | "It suppresses triggers / record-change automation" | **No.** Only `skipTriggers` does. A bare `{ isSystem: true }` on a seed write re-fired automation on freshly seeded rows and wedged first boot | `metadata-protocol/src/seed-loader.ts:1909` (rationale at `:1819`–`1821`, #3760), `flow.zod.ts:685` |
 | "It skips the state machine" | **No.** That is `skipStateMachine`, carried by seed replay and by `treatAsHistorical` imports | `objectql/src/engine.ts` FSM gate; see [State Machine](/docs/protocol/objectql/state-machine) |
-| "It skips validation rules" | **No.** Field shape, `format`, `script` and the rest still run. The `readonly` strip runs *before* validation precisely so a discarded value is not judged | `objectql/src/engine.ts:9663`–`9680` |
+| "It skips validation rules" | **No.** Field shape, `format`, `script` and the rest still run. The `readonly` strip runs *before* validation precisely so a discarded value is not judged | `objectql/src/engine.ts:9730`–`9747` |
 | "It preserves a supplied `updated_at` / `updated_by`" | **No.** That is `preserveAudit`, a separate opt-in — and an UPDATE-path exemption only | `field.zod.ts:1516` (#3493 / #6640) |
 | "It stamps `created_by`" | **No.** Audit stamping reads `userId` from the context. A user-less system write stamps nothing — that is today's behaviour, not an error | `runtime-identity.ts:280`–`281` |
 | "It bypasses every guard" | **No.** The last-admin guard applies to **every** context, `isSystem` included — the deprovision path that actually locks an org out is the system one | `last-admin-guard.ts:286` |

packages/lint/src/validate-hook-body-writes.ts

@@ -4,24 +4,30 @@
 //
 // An L2 body that writes a field the target object never declares —
 // `ctx.input.amout = 0`, `ctx.api.object('deal').update({ stag: 'won' })` —
-// runs clean in the QuickJS sandbox and reaches the driver UNFILTERED:
+// runs clean in the QuickJS sandbox and reaches the write path UNFILTERED:
 // `applyMutationsToInput` (runtime/src/sandbox/body-runner.ts) is a plain
 // `Object.assign`, and `validateRecord` walks declared fields on insert and
-// `continue`s past a key with no field def on update. What happens after that
-// is DRIVER-DEPENDENT, and neither half is acceptable:
+// `continue`s past a key with no field def on update.
 //
-// • SQL — the stray column enters the knex statement and the WHOLE write
-// fails with a driver-level error (`table deal has no column named
-// stagee`). The write is lost, and the error surfaces far from the
-// authoring mistake that caused it.
-// • Schemaless (memory, MongoDB) — the driver spreads the payload, so the
-// stray key IS persisted: an undeclared column nothing downstream reads.
+// [#13657] What happens after that used to be DRIVER-DEPENDENT, and neither
+// half was acceptable — SQL failed the whole write with an untyped
+// `SQLITE_ERROR` far from the authoring mistake, while schemaless drivers
+// (memory, MongoDB) spread the payload and PERSISTED the stray key as a column
+// nothing downstream reads. #13657 closed that: the declared-field door now
+// runs a second time over the payload the `before*` hooks produced, so the key
+// is refused `INVALID_FIELD` / 400 identically on every driver, before any
+// statement is built.
 //
-// Either way the mistake is invisible where it is MADE — the #4001 family, if
-// not literally its silent-no-op shape. Both runtime outcomes are pinned by
+// ⚠️ That does NOT retire this rule — it changes what it is worth. The runtime
+// refusal arrives at WRITE time, on whichever record first exercises the
+// branch; this rule arrives at AUTHOR time and names the field, the object and
+// the body. The mistake is still invisible where it is MADE, which is the
+// #4001 family and the whole reason for a build-time check.
+//
+// The runtime answer is pinned by
 // `runtime/src/sandbox/undeclared-field-write-driver-split.integration.test.ts`
-// so this rule's wording cannot drift from what the runtime does; the same
-// split is documented in `content/docs/automation/hook-bodies.mdx`.
+// so this rule's wording cannot drift from what the runtime does; the same is
+// documented in `content/docs/automation/hook-bodies.mdx`.
 //
 // The read side (`hook.condition`, ADR-0032) and the capability surface are
 // statically checked; until this rule, the write side was the one blind face
@@ -817,9 +823,12 @@ export function validateHookBodyWrites(stack: AnyRec): HookBodyWriteFinding[] {
  path,
  message:
  `body writes '${w.field}' to its input, but ${objDesc} ${declares}. The sandboxed script runs ` +
- `clean and the value is copied back onto the record payload unfiltered — on a SQL driver the ` +
- `stray column then fails the WHOLE write with a driver-level error far from here; on a ` +
- `schemaless driver (memory, MongoDB) it is persisted as an undeclared key (#4271).`,
+ // The post-hook declared-field door (#13657) is what refuses it; the
+ // id stays in this comment rather than in the string, which reaches
+ // authors and operators who cannot resolve a tracker number.
+ `clean and the value is copied back onto the record payload unfiltered, so the write is then ` +
+ `REFUSED at run time — INVALID_FIELD / 400, identically on every driver (#4271). The ` +
+ `record is never written, and the refusal names the field far from the body that wrote it.`,
  hint: fixHint(w.field, unionCandidates(targetSets)),
  });
  } else {

.changeset/post-hook-undeclared-field-door.md

@@ -0,0 +1,61 @@
+---
+'@objectstack/objectql': minor
+'@objectstack/lint': patch
+---
+
+Refuse an undeclared field a `before*` hook writes, identically on every driver
+
+**BREAKING** accept-set narrowing at the post-hook write door, shipped as `minor`
+under the repo's launch-window convention for breaking changes.
+
+**Bump level, argued**: `@objectstack/objectql` is `minor`, not `patch`. A
+`before*` hook or an L2 (`language:'js'`) body writing a key the object never
+declares **used to succeed** on the `memory` family — the value reached the
+store and persisted as a shadow column — and now **throws**, `INVALID_FIELD` /
+**400**, on every driver. That is a narrowing of the accept set on the record
+payload, a surface every hook body touches; it is not an instrument or a message
+fix, and a hook that relied on either driver-dependent outcome stops working at
+run time. The same-package sibling `.changeset/hook-input-symbol-key-refusal.md`
+argues exactly this shape — "used to succeed, and now throw. That is a narrowing
+of the accept set" — to `minor`, and the launch-window convention is what keeps
+it off `major` (pre-1.0 lockstep semantics: a breaking change does not burn a
+major version while the stack versions in lockstep — see
+`scripts/check-changeset-no-major.mjs`). `patch` would under-declare a change
+that turns a passing hook into a throwing one.
+
+`'@objectstack/lint': patch` is deliberate and stays. That half of the diff is
+message and comment prose only: `validateHookBodyWrites` reports the same
+findings on the same bodies at the same severity, with wording that now names
+the runtime refusal instead of the driver split this change retires.
+
+The declared-field door (#8682 on insert, #8738 on update) runs before the
+`before*` hooks — deliberately, so a payload about to be refused never consumes
+an autonumber (#8737). That left the payload the hooks themselves produce
+unjudged: a key a `beforeInsert` / `beforeUpdate` hook or an L2 (`language:'js'`)
+body wrote went straight to the driver, and the drivers disagreed. `memory`
+accepted it and stored a shadow column; `driver-sql` threw a raw `SQLITE_ERROR`
+with no `status` and the bound statement and its values quoted back in the
+message; `sqlite-wasm` threw a bare `Error` with neither. One app and one hook
+meant different things on two deployments, and nothing in the app could tell
+which one it was running on.
+
+The same check now runs a second time over the post-hook payload, before any
+statement is built, so a hook-written undeclared key is refused with the caller
+path's envelope — `INVALID_FIELD` / **400**, `Unknown field 'x' on object 'y'` —
+on every driver, because none of them is reached. The existing pre-hook door is
+unchanged and stays exactly where it is.
+
+This is a security fix as well as a consistency one: `fieldPermissions` is keyed
+by declared field name and reports only fields explicitly marked non-editable, so
+a key the object never declares can carry no entry and could never be gated by
+field-level security. On `memory`-family stores such a value was persisted where
+no view, formula, index or permission could name it.
+
+The platform's own stamps are unaffected. `created_at` / `updated_at` — the two
+the built-in audit hook writes unconditionally, because SQL drivers create them
+as built-in columns on every table — are already tolerated by this check
+alongside `id`; every other stamp (`created_by`, `updated_by`, `tenant_id`) is
+guarded by an explicit declaration test in the hook that writes it.
+
+<!-- adr-0087: not-required (no-migration-prescription) No metadata key, spec symbol, Zod schema, object definition or stored representation is added, removed or renamed. This narrows which run-time record payload the engine accepts after the `before*` hooks have run; an undeclared key was never a declarable metadata surface, so `objectstack migrate meta` has nothing in a stored source to rewrite. The remedy for an affected hook body is to declare the field on the object or stop writing it, which is authoring guidance, not a mechanical rewrite of stored metadata. -->
+

content/docs/automation/hook-bodies.mdx

@@ -204,19 +204,22 @@ A structured `writes` declaration was considered and dropped ([#3700](https://gi
 
 #### What still happens at runtime
 
-An unknown field is **not** caught at runtime, and it does not fail quietly either. The write-path validator walks the object's *declared* fields, so an undeclared key is neither rejected nor stripped, and the sandbox's mutations are copied back onto the payload verbatim. What happens next is the driver's call:
+An unknown field **is** caught at runtime, and the answer is the same on every driver. The sandbox's mutations are copied back onto the payload verbatim (`applyMutationsToInput` is a plain `Object.assign`) and the write-path validator still walks only the object's *declared* fields — but since [#13657](https://github.com/objectstack-ai/objectstack/issues/13657) the declared-field door runs a **second** time, over the payload the `before*` hooks produced, before any statement is built:
 
-- **SQL drivers** put the stray column into the statement, so the **whole write fails** with a driver-level error (`table deal has no column named stagee`) — nothing is stored, and the error surfaces far from the authoring mistake.
-- **Schemaless drivers** (memory, MongoDB) silently persist the stray key alongside the real ones.
+```
+INVALID_FIELD / 400 / Unknown field 'stagee' on object 'deal'
+```
+
+Identical on `memory`, `driver-sql` and `sqlite-wasm`, because none of them is reached. Before #13657 the driver decided instead, and the two families disagreed — SQL failed the whole write with an untyped `SQLITE_ERROR`, while schemaless drivers silently persisted the stray key as a column nothing downstream reads (and which field-level security, keyed by *declared* field name, could never gate). One app, one body, two meanings decided by which driver a deployment happened to run.
 
-Neither outcome is the one you wanted, and the advisory warning is the earliest signal you get.
+The runtime refusal is now the backstop; the advisory warning is still the earliest signal you get, and the one that names the mistake where it was made.
 
 Because the existence check is advisory, and every write-side check here is literal-only:
 
 - **Treat `hook-body-write-unknown-field` as a build failure by convention.** It does not gate, but the rule is tuned for near-zero false positives — in practice a warning is a real typo.
 - **Check by hand what the parser cannot see.** Computed keys, spreads, aliased input and dynamic object names are invisible to the rule; for an array or `"*"` hook, every field must exist on every target.
 - **Prefer a flow `update_record` node when the write set is fixed — and for *this* check most of all.** A flow node's writes are structured config: they diff field-by-field, render in the Console designer, and since [#4271](https://github.com/objectstack-ai/objectstack/issues/4271) the field-existence check gates there too — `flow-node-write-unknown-field` is an **error**, not the advisory warning a body gets, because a node's `fields` is a literal map next to a literal `objectName`: there is no parser in between that could have mis-extracted it, so a finding is a certainty rather than a best effort. (The *writability* check now has a hook-side counterpart — see [Writing a `readonly` field](#writing-a-readonly-field) below — but it covers only the `ctx.api` channel.)
-- **Exercise the hook against a real object before shipping** — on SQL drivers the mistake surfaces on the first write; schemaless drivers won't tell you.
+- **Exercise the hook against a real object before shipping** — the mistake surfaces on the first write, identically on every driver.
 
 ### Signature conventions
 

content/docs/permissions/system-context.mdx

@@ -109,18 +109,18 @@ that silently does not happen.
 
 | # | Behaviour when `isSystem` | Package | What you get / what you lose | Anchor |
 |:--|:---|:---|:---|:---|
-| 18 | **`readonly` strip bypassed — UPDATE, single row** | objectql | Get: a `readonly` field CAN be written. Lose: the protection that stops a caller seeding e.g. `approval_status` | `objectql/src/engine.ts:10787` |
-| 19 | **`readonly` strip bypassed — UPDATE, bulk/predicate** | objectql | Same, on the multi-row path | `objectql/src/engine.ts:10949` |
-| 20 | **`readonly` strip bypassed — INSERT (engine pass)** | objectql | Same, on create | `objectql/src/engine.ts:9680` |
+| 18 | **`readonly` strip bypassed — UPDATE, single row** | objectql | Get: a `readonly` field CAN be written. Lose: the protection that stops a caller seeding e.g. `approval_status` | `objectql/src/engine.ts:10882` |
+| 19 | **`readonly` strip bypassed — UPDATE, bulk/predicate** | objectql | Same, on the multi-row path | `objectql/src/engine.ts:11044` |
+| 20 | **`readonly` strip bypassed — INSERT (engine pass)** | objectql | Same, on create | `objectql/src/engine.ts:9747` |
 | 21 | **`readonly` strip bypassed — INSERT (protocol ingress)** | metadata-protocol | `isSystem` is the **only** exemption here. `preserveAudit` is deliberately not read on this path (#6640) — a non-system historical import is still stripped on create | `metadata-protocol/src/protocol.ts:1737` |
-| 22 | Strict-drop refusal never fires | objectql | Lose: a caller that opted into loud refusal gets **silence** — strict refuses exactly what the strip would have taken, and the strip took nothing | `objectql/src/engine.ts:9717`, `readonly-strict-errors.ts:66` |
+| 22 | Strict-drop refusal never fires | objectql | Lose: a caller that opted into loud refusal gets **silence** — strict refuses exactly what the strip would have taken, and the strip took nothing | `objectql/src/engine.ts:9784`, `readonly-strict-errors.ts:66` |
 | 23 | **Referential-integrity check skipped** | objectql | Get: writes proceed against unreachable/unresolvable targets. Lose: an `isSystem` caller can write a **dangling reference** | `objectql/src/engine.ts:5705` |
 | 24 | Tenant-audit warning silenced; `bypassTenantAudit` threaded to the driver | objectql | Get: unscoped system writes stop warning. Lose: the signal that would flag a genuine user-path scoping bug | `objectql/src/engine.ts:3574`, `:3584`, `:3611` |
 | 25 | Engine-owned / append-only write guard bypassed | plugin-security | Get: generic writes to `managedBy` engine-owned objects | `system-write-guard.ts:96`, `:120` |
 | 26 | Identity write guard bypassed (ADR-0092) | plugin-auth | Get: direct writes to identity tables through the generic data path | `identity-write-guard.ts:98` |
 | 27 | Search-companion column **kept** in a read's rows when it was explicitly requested | objectql | Get: the internal companion column is readable. Lose: nothing for app code — this is the engine reading its own index | `objectql/src/engine.ts:6403` |
-| 28 | Dependent-count disclosure on a blocked delete | objectql | Get: the count of blocking children. Nothing was elevated past the caller, so nothing is withheld | `objectql/src/engine.ts:11535` |
-| 29 | Reference-cleanup log attributes the write to `'system'` | objectql | Get: an honest actor label instead of `anonymous` when the context carries neither `userId` nor `actor` | `objectql/src/engine.ts:11464` |
+| 28 | Dependent-count disclosure on a blocked delete | objectql | Get: the count of blocking children. Nothing was elevated past the caller, so nothing is withheld | `objectql/src/engine.ts:11630` |
+| 29 | Reference-cleanup log attributes the write to `'system'` | objectql | Get: an honest actor label instead of `anonymous` when the context carries neither `userId` nor `actor` | `objectql/src/engine.ts:11559` |
 
 ### 3. Sharing (`plugin-sharing`)
 
@@ -180,7 +180,7 @@ a reader tracing where elevation travels needs them.
 | # | Site | Package | What it does |
 |:--|:---|:---|:---|
 | 62 | `objectql/src/engine.ts:3406` | objectql | Propagates `isSystem` into the hook session so hooks can tell engine self-writes from user writes |
-| 63 | `objectql/src/engine.ts:13876` | objectql | `ScopedContext.isSystem` getter — re-exposes the underlying execution context's flag |
+| 63 | `objectql/src/engine.ts:13971` | objectql | `ScopedContext.isSystem` getter — re-exposes the underlying execution context's flag |
 | 64 | `plugin-reports/src/report-service.ts:556` | plugin-reports | Threads the flag into the engine call that runs a report |
 | 65 | `body-runner.ts:279` | runtime | Rebuilds an `ExecutionContext` from a hook session, carrying the flag across |
 
@@ -195,7 +195,7 @@ assuming `isSystem` covers it is a documented source of bugs.
 |:---|:---|:---|
 | "It suppresses triggers / record-change automation" | **No.** Only `skipTriggers` does. A bare `{ isSystem: true }` on a seed write re-fired automation on freshly seeded rows and wedged first boot | `metadata-protocol/src/seed-loader.ts:1909` (rationale at `:1819`–`1821`, #3760), `flow.zod.ts:685` |
 | "It skips the state machine" | **No.** That is `skipStateMachine`, carried by seed replay and by `treatAsHistorical` imports | `objectql/src/engine.ts` FSM gate; see [State Machine](/docs/protocol/objectql/state-machine) |
-| "It skips validation rules" | **No.** Field shape, `format`, `script` and the rest still run. The `readonly` strip runs *before* validation precisely so a discarded value is not judged | `objectql/src/engine.ts:9663`–`9680` |
+| "It skips validation rules" | **No.** Field shape, `format`, `script` and the rest still run. The `readonly` strip runs *before* validation precisely so a discarded value is not judged | `objectql/src/engine.ts:9730`–`9747` |
 | "It preserves a supplied `updated_at` / `updated_by`" | **No.** That is `preserveAudit`, a separate opt-in — and an UPDATE-path exemption only | `field.zod.ts:1516` (#3493 / #6640) |
 | "It stamps `created_by`" | **No.** Audit stamping reads `userId` from the context. A user-less system write stamps nothing — that is today's behaviour, not an error | `runtime-identity.ts:280`–`281` |
 | "It bypasses every guard" | **No.** The last-admin guard applies to **every** context, `isSystem` included — the deprovision path that actually locks an org out is the system one | `last-admin-guard.ts:286` |

packages/lint/src/validate-hook-body-writes.ts

@@ -4,24 +4,30 @@
 //
 // An L2 body that writes a field the target object never declares —
 // `ctx.input.amout = 0`, `ctx.api.object('deal').update({ stag: 'won' })` —
-// runs clean in the QuickJS sandbox and reaches the driver UNFILTERED:
+// runs clean in the QuickJS sandbox and reaches the write path UNFILTERED:
 // `applyMutationsToInput` (runtime/src/sandbox/body-runner.ts) is a plain
 // `Object.assign`, and `validateRecord` walks declared fields on insert and
-// `continue`s past a key with no field def on update. What happens after that
-// is DRIVER-DEPENDENT, and neither half is acceptable:
+// `continue`s past a key with no field def on update.
 //
-// • SQL — the stray column enters the knex statement and the WHOLE write
-// fails with a driver-level error (`table deal has no column named
-// stagee`). The write is lost, and the error surfaces far from the
-// authoring mistake that caused it.
-// • Schemaless (memory, MongoDB) — the driver spreads the payload, so the
-// stray key IS persisted: an undeclared column nothing downstream reads.
+// [#13657] What happens after that used to be DRIVER-DEPENDENT, and neither
+// half was acceptable — SQL failed the whole write with an untyped
+// `SQLITE_ERROR` far from the authoring mistake, while schemaless drivers
+// (memory, MongoDB) spread the payload and PERSISTED the stray key as a column
+// nothing downstream reads. #13657 closed that: the declared-field door now
+// runs a second time over the payload the `before*` hooks produced, so the key
+// is refused `INVALID_FIELD` / 400 identically on every driver, before any
+// statement is built.
 //
-// Either way the mistake is invisible where it is MADE — the #4001 family, if
-// not literally its silent-no-op shape. Both runtime outcomes are pinned by
+// ⚠️ That does NOT retire this rule — it changes what it is worth. The runtime
+// refusal arrives at WRITE time, on whichever record first exercises the
+// branch; this rule arrives at AUTHOR time and names the field, the object and
+// the body. The mistake is still invisible where it is MADE, which is the
+// #4001 family and the whole reason for a build-time check.
+//
+// The runtime answer is pinned by
 // `runtime/src/sandbox/undeclared-field-write-driver-split.integration.test.ts`
-// so this rule's wording cannot drift from what the runtime does; the same
-// split is documented in `content/docs/automation/hook-bodies.mdx`.
+// so this rule's wording cannot drift from what the runtime does; the same is
+// documented in `content/docs/automation/hook-bodies.mdx`.
 //
 // The read side (`hook.condition`, ADR-0032) and the capability surface are
 // statically checked; until this rule, the write side was the one blind face
@@ -817,9 +823,12 @@ export function validateHookBodyWrites(stack: AnyRec): HookBodyWriteFinding[] {
  path,
  message:
  `body writes '${w.field}' to its input, but ${objDesc} ${declares}. The sandboxed script runs ` +
- `clean and the value is copied back onto the record payload unfiltered — on a SQL driver the ` +
- `stray column then fails the WHOLE write with a driver-level error far from here; on a ` +
- `schemaless driver (memory, MongoDB) it is persisted as an undeclared key (#4271).`,
+ // The post-hook declared-field door (#13657) is what refuses it; the
+ // id stays in this comment rather than in the string, which reaches
+ // authors and operators who cannot resolve a tracker number.
+ `clean and the value is copied back onto the record payload unfiltered, so the write is then ` +
+ `REFUSED at run time — INVALID_FIELD / 400, identically on every driver (#4271). The ` +
+ `record is never written, and the refusal names the field far from the body that wrote it.`,
  hint: fixHint(w.field, unionCandidates(targetSets)),
  });
  } else {

.changeset/post-hook-undeclared-field-door.md

@@ -0,0 +1,61 @@
+---
+'@objectstack/objectql': minor
+'@objectstack/lint': patch
+---
+
+Refuse an undeclared field a `before*` hook writes, identically on every driver
+
+**BREAKING** accept-set narrowing at the post-hook write door, shipped as `minor`
+under the repo's launch-window convention for breaking changes.
+
+**Bump level, argued**: `@objectstack/objectql` is `minor`, not `patch`. A
+`before*` hook or an L2 (`language:'js'`) body writing a key the object never
+declares **used to succeed** on the `memory` family — the value reached the
+store and persisted as a shadow column — and now **throws**, `INVALID_FIELD` /
+**400**, on every driver. That is a narrowing of the accept set on the record
+payload, a surface every hook body touches; it is not an instrument or a message
+fix, and a hook that relied on either driver-dependent outcome stops working at
+run time. The same-package sibling `.changeset/hook-input-symbol-key-refusal.md`
+argues exactly this shape — "used to succeed, and now throw. That is a narrowing
+of the accept set" — to `minor`, and the launch-window convention is what keeps
+it off `major` (pre-1.0 lockstep semantics: a breaking change does not burn a
+major version while the stack versions in lockstep — see
+`scripts/check-changeset-no-major.mjs`). `patch` would under-declare a change
+that turns a passing hook into a throwing one.
+
+`'@objectstack/lint': patch` is deliberate and stays. That half of the diff is
+message and comment prose only: `validateHookBodyWrites` reports the same
+findings on the same bodies at the same severity, with wording that now names
+the runtime refusal instead of the driver split this change retires.
+
+The declared-field door (#8682 on insert, #8738 on update) runs before the
+`before*` hooks — deliberately, so a payload about to be refused never consumes
+an autonumber (#8737). That left the payload the hooks themselves produce
+unjudged: a key a `beforeInsert` / `beforeUpdate` hook or an L2 (`language:'js'`)
+body wrote went straight to the driver, and the drivers disagreed. `memory`
+accepted it and stored a shadow column; `driver-sql` threw a raw `SQLITE_ERROR`
+with no `status` and the bound statement and its values quoted back in the
+message; `sqlite-wasm` threw a bare `Error` with neither. One app and one hook
+meant different things on two deployments, and nothing in the app could tell
+which one it was running on.
+
+The same check now runs a second time over the post-hook payload, before any
+statement is built, so a hook-written undeclared key is refused with the caller
+path's envelope — `INVALID_FIELD` / **400**, `Unknown field 'x' on object 'y'` —
+on every driver, because none of them is reached. The existing pre-hook door is
+unchanged and stays exactly where it is.
+
+This is a security fix as well as a consistency one: `fieldPermissions` is keyed
+by declared field name and reports only fields explicitly marked non-editable, so
+a key the object never declares can carry no entry and could never be gated by
+field-level security. On `memory`-family stores such a value was persisted where
+no view, formula, index or permission could name it.
+
+The platform's own stamps are unaffected. `created_at` / `updated_at` — the two
+the built-in audit hook writes unconditionally, because SQL drivers create them
+as built-in columns on every table — are already tolerated by this check
+alongside `id`; every other stamp (`created_by`, `updated_by`, `tenant_id`) is
+guarded by an explicit declaration test in the hook that writes it.
+
+<!-- adr-0087: not-required (no-migration-prescription) No metadata key, spec symbol, Zod schema, object definition or stored representation is added, removed or renamed. This narrows which run-time record payload the engine accepts after the `before*` hooks have run; an undeclared key was never a declarable metadata surface, so `objectstack migrate meta` has nothing in a stored source to rewrite. The remedy for an affected hook body is to declare the field on the object or stop writing it, which is authoring guidance, not a mechanical rewrite of stored metadata. -->
+

content/docs/automation/hook-bodies.mdx

@@ -204,19 +204,22 @@ A structured `writes` declaration was considered and dropped ([#3700](https://gi
 
 #### What still happens at runtime
 
-An unknown field is **not** caught at runtime, and it does not fail quietly either. The write-path validator walks the object's *declared* fields, so an undeclared key is neither rejected nor stripped, and the sandbox's mutations are copied back onto the payload verbatim. What happens next is the driver's call:
+An unknown field **is** caught at runtime, and the answer is the same on every driver. The sandbox's mutations are copied back onto the payload verbatim (`applyMutationsToInput` is a plain `Object.assign`) and the write-path validator still walks only the object's *declared* fields — but since [#13657](https://github.com/objectstack-ai/objectstack/issues/13657) the declared-field door runs a **second** time, over the payload the `before*` hooks produced, before any statement is built:
 
-- **SQL drivers** put the stray column into the statement, so the **whole write fails** with a driver-level error (`table deal has no column named stagee`) — nothing is stored, and the error surfaces far from the authoring mistake.
-- **Schemaless drivers** (memory, MongoDB) silently persist the stray key alongside the real ones.
+```
+INVALID_FIELD / 400 / Unknown field 'stagee' on object 'deal'
+```
+
+Identical on `memory`, `driver-sql` and `sqlite-wasm`, because none of them is reached. Before #13657 the driver decided instead, and the two families disagreed — SQL failed the whole write with an untyped `SQLITE_ERROR`, while schemaless drivers silently persisted the stray key as a column nothing downstream reads (and which field-level security, keyed by *declared* field name, could never gate). One app, one body, two meanings decided by which driver a deployment happened to run.
 
-Neither outcome is the one you wanted, and the advisory warning is the earliest signal you get.
+The runtime refusal is now the backstop; the advisory warning is still the earliest signal you get, and the one that names the mistake where it was made.
 
 Because the existence check is advisory, and every write-side check here is literal-only:
 
 - **Treat `hook-body-write-unknown-field` as a build failure by convention.** It does not gate, but the rule is tuned for near-zero false positives — in practice a warning is a real typo.
 - **Check by hand what the parser cannot see.** Computed keys, spreads, aliased input and dynamic object names are invisible to the rule; for an array or `"*"` hook, every field must exist on every target.
 - **Prefer a flow `update_record` node when the write set is fixed — and for *this* check most of all.** A flow node's writes are structured config: they diff field-by-field, render in the Console designer, and since [#4271](https://github.com/objectstack-ai/objectstack/issues/4271) the field-existence check gates there too — `flow-node-write-unknown-field` is an **error**, not the advisory warning a body gets, because a node's `fields` is a literal map next to a literal `objectName`: there is no parser in between that could have mis-extracted it, so a finding is a certainty rather than a best effort. (The *writability* check now has a hook-side counterpart — see [Writing a `readonly` field](#writing-a-readonly-field) below — but it covers only the `ctx.api` channel.)
-- **Exercise the hook against a real object before shipping** — on SQL drivers the mistake surfaces on the first write; schemaless drivers won't tell you.
+- **Exercise the hook against a real object before shipping** — the mistake surfaces on the first write, identically on every driver.
 
 ### Signature conventions
 

content/docs/permissions/system-context.mdx

@@ -109,18 +109,18 @@ that silently does not happen.
 
 | # | Behaviour when `isSystem` | Package | What you get / what you lose | Anchor |
 |:--|:---|:---|:---|:---|
-| 18 | **`readonly` strip bypassed — UPDATE, single row** | objectql | Get: a `readonly` field CAN be written. Lose: the protection that stops a caller seeding e.g. `approval_status` | `objectql/src/engine.ts:10787` |
-| 19 | **`readonly` strip bypassed — UPDATE, bulk/predicate** | objectql | Same, on the multi-row path | `objectql/src/engine.ts:10949` |
-| 20 | **`readonly` strip bypassed — INSERT (engine pass)** | objectql | Same, on create | `objectql/src/engine.ts:9680` |
+| 18 | **`readonly` strip bypassed — UPDATE, single row** | objectql | Get: a `readonly` field CAN be written. Lose: the protection that stops a caller seeding e.g. `approval_status` | `objectql/src/engine.ts:10882` |
+| 19 | **`readonly` strip bypassed — UPDATE, bulk/predicate** | objectql | Same, on the multi-row path | `objectql/src/engine.ts:11044` |
+| 20 | **`readonly` strip bypassed — INSERT (engine pass)** | objectql | Same, on create | `objectql/src/engine.ts:9747` |
 | 21 | **`readonly` strip bypassed — INSERT (protocol ingress)** | metadata-protocol | `isSystem` is the **only** exemption here. `preserveAudit` is deliberately not read on this path (#6640) — a non-system historical import is still stripped on create | `metadata-protocol/src/protocol.ts:1737` |
-| 22 | Strict-drop refusal never fires | objectql | Lose: a caller that opted into loud refusal gets **silence** — strict refuses exactly what the strip would have taken, and the strip took nothing | `objectql/src/engine.ts:9717`, `readonly-strict-errors.ts:66` |
+| 22 | Strict-drop refusal never fires | objectql | Lose: a caller that opted into loud refusal gets **silence** — strict refuses exactly what the strip would have taken, and the strip took nothing | `objectql/src/engine.ts:9784`, `readonly-strict-errors.ts:66` |
 | 23 | **Referential-integrity check skipped** | objectql | Get: writes proceed against unreachable/unresolvable targets. Lose: an `isSystem` caller can write a **dangling reference** | `objectql/src/engine.ts:5705` |
 | 24 | Tenant-audit warning silenced; `bypassTenantAudit` threaded to the driver | objectql | Get: unscoped system writes stop warning. Lose: the signal that would flag a genuine user-path scoping bug | `objectql/src/engine.ts:3574`, `:3584`, `:3611` |
 | 25 | Engine-owned / append-only write guard bypassed | plugin-security | Get: generic writes to `managedBy` engine-owned objects | `system-write-guard.ts:96`, `:120` |
 | 26 | Identity write guard bypassed (ADR-0092) | plugin-auth | Get: direct writes to identity tables through the generic data path | `identity-write-guard.ts:98` |
 | 27 | Search-companion column **kept** in a read's rows when it was explicitly requested | objectql | Get: the internal companion column is readable. Lose: nothing for app code — this is the engine reading its own index | `objectql/src/engine.ts:6403` |
-| 28 | Dependent-count disclosure on a blocked delete | objectql | Get: the count of blocking children. Nothing was elevated past the caller, so nothing is withheld | `objectql/src/engine.ts:11535` |
-| 29 | Reference-cleanup log attributes the write to `'system'` | objectql | Get: an honest actor label instead of `anonymous` when the context carries neither `userId` nor `actor` | `objectql/src/engine.ts:11464` |
+| 28 | Dependent-count disclosure on a blocked delete | objectql | Get: the count of blocking children. Nothing was elevated past the caller, so nothing is withheld | `objectql/src/engine.ts:11630` |
+| 29 | Reference-cleanup log attributes the write to `'system'` | objectql | Get: an honest actor label instead of `anonymous` when the context carries neither `userId` nor `actor` | `objectql/src/engine.ts:11559` |
 
 ### 3. Sharing (`plugin-sharing`)
 
@@ -180,7 +180,7 @@ a reader tracing where elevation travels needs them.
 | # | Site | Package | What it does |
 |:--|:---|:---|:---|
 | 62 | `objectql/src/engine.ts:3406` | objectql | Propagates `isSystem` into the hook session so hooks can tell engine self-writes from user writes |
-| 63 | `objectql/src/engine.ts:13876` | objectql | `ScopedContext.isSystem` getter — re-exposes the underlying execution context's flag |
+| 63 | `objectql/src/engine.ts:13971` | objectql | `ScopedContext.isSystem` getter — re-exposes the underlying execution context's flag |
 | 64 | `plugin-reports/src/report-service.ts:556` | plugin-reports | Threads the flag into the engine call that runs a report |
 | 65 | `body-runner.ts:279` | runtime | Rebuilds an `ExecutionContext` from a hook session, carrying the flag across |
 
@@ -195,7 +195,7 @@ assuming `isSystem` covers it is a documented source of bugs.
 |:---|:---|:---|
 | "It suppresses triggers / record-change automation" | **No.** Only `skipTriggers` does. A bare `{ isSystem: true }` on a seed write re-fired automation on freshly seeded rows and wedged first boot | `metadata-protocol/src/seed-loader.ts:1909` (rationale at `:1819`–`1821`, #3760), `flow.zod.ts:685` |
 | "It skips the state machine" | **No.** That is `skipStateMachine`, carried by seed replay and by `treatAsHistorical` imports | `objectql/src/engine.ts` FSM gate; see [State Machine](/docs/protocol/objectql/state-machine) |
-| "It skips validation rules" | **No.** Field shape, `format`, `script` and the rest still run. The `readonly` strip runs *before* validation precisely so a discarded value is not judged | `objectql/src/engine.ts:9663`–`9680` |
+| "It skips validation rules" | **No.** Field shape, `format`, `script` and the rest still run. The `readonly` strip runs *before* validation precisely so a discarded value is not judged | `objectql/src/engine.ts:9730`–`9747` |
 | "It preserves a supplied `updated_at` / `updated_by`" | **No.** That is `preserveAudit`, a separate opt-in — and an UPDATE-path exemption only | `field.zod.ts:1516` (#3493 / #6640) |
 | "It stamps `created_by`" | **No.** Audit stamping reads `userId` from the context. A user-less system write stamps nothing — that is today's behaviour, not an error | `runtime-identity.ts:280`–`281` |
 | "It bypasses every guard" | **No.** The last-admin guard applies to **every** context, `isSystem` included — the deprovision path that actually locks an org out is the system one | `last-admin-guard.ts:286` |

packages/lint/src/validate-hook-body-writes.ts

@@ -4,24 +4,30 @@
 //
 // An L2 body that writes a field the target object never declares —
 // `ctx.input.amout = 0`, `ctx.api.object('deal').update({ stag: 'won' })` —
-// runs clean in the QuickJS sandbox and reaches the driver UNFILTERED:
+// runs clean in the QuickJS sandbox and reaches the write path UNFILTERED:
 // `applyMutationsToInput` (runtime/src/sandbox/body-runner.ts) is a plain
 // `Object.assign`, and `validateRecord` walks declared fields on insert and
-// `continue`s past a key with no field def on update. What happens after that
-// is DRIVER-DEPENDENT, and neither half is acceptable:
+// `continue`s past a key with no field def on update.
 //
-// • SQL — the stray column enters the knex statement and the WHOLE write
-// fails with a driver-level error (`table deal has no column named
-// stagee`). The write is lost, and the error surfaces far from the
-// authoring mistake that caused it.
-// • Schemaless (memory, MongoDB) — the driver spreads the payload, so the
-// stray key IS persisted: an undeclared column nothing downstream reads.
+// [#13657] What happens after that used to be DRIVER-DEPENDENT, and neither
+// half was acceptable — SQL failed the whole write with an untyped
+// `SQLITE_ERROR` far from the authoring mistake, while schemaless drivers
+// (memory, MongoDB) spread the payload and PERSISTED the stray key as a column
+// nothing downstream reads. #13657 closed that: the declared-field door now
+// runs a second time over the payload the `before*` hooks produced, so the key
+// is refused `INVALID_FIELD` / 400 identically on every driver, before any
+// statement is built.
 //
-// Either way the mistake is invisible where it is MADE — the #4001 family, if
-// not literally its silent-no-op shape. Both runtime outcomes are pinned by
+// ⚠️ That does NOT retire this rule — it changes what it is worth. The runtime
+// refusal arrives at WRITE time, on whichever record first exercises the
+// branch; this rule arrives at AUTHOR time and names the field, the object and
+// the body. The mistake is still invisible where it is MADE, which is the
+// #4001 family and the whole reason for a build-time check.
+//
+// The runtime answer is pinned by
 // `runtime/src/sandbox/undeclared-field-write-driver-split.integration.test.ts`
-// so this rule's wording cannot drift from what the runtime does; the same
-// split is documented in `content/docs/automation/hook-bodies.mdx`.
+// so this rule's wording cannot drift from what the runtime does; the same is
+// documented in `content/docs/automation/hook-bodies.mdx`.
 //
 // The read side (`hook.condition`, ADR-0032) and the capability surface are
 // statically checked; until this rule, the write side was the one blind face
@@ -817,9 +823,12 @@ export function validateHookBodyWrites(stack: AnyRec): HookBodyWriteFinding[] {
  path,
  message:
  `body writes '${w.field}' to its input, but ${objDesc} ${declares}. The sandboxed script runs ` +
- `clean and the value is copied back onto the record payload unfiltered — on a SQL driver the ` +
- `stray column then fails the WHOLE write with a driver-level error far from here; on a ` +
- `schemaless driver (memory, MongoDB) it is persisted as an undeclared key (#4271).`,
+ // The post-hook declared-field door (#13657) is what refuses it; the
+ // id stays in this comment rather than in the string, which reaches
+ // authors and operators who cannot resolve a tracker number.
+ `clean and the value is copied back onto the record payload unfiltered, so the write is then ` +
+ `REFUSED at run time — INVALID_FIELD / 400, identically on every driver (#4271). The ` +
+ `record is never written, and the refusal names the field far from the body that wrote it.`,
  hint: fixHint(w.field, unionCandidates(targetSets)),
  });
  } else {

.changeset/post-hook-undeclared-field-door.md

@@ -0,0 +1,61 @@
+---
+'@objectstack/objectql': minor
+'@objectstack/lint': patch
+---
+
+Refuse an undeclared field a `before*` hook writes, identically on every driver
+
+**BREAKING** accept-set narrowing at the post-hook write door, shipped as `minor`
+under the repo's launch-window convention for breaking changes.
+
+**Bump level, argued**: `@objectstack/objectql` is `minor`, not `patch`. A
+`before*` hook or an L2 (`language:'js'`) body writing a key the object never
+declares **used to succeed** on the `memory` family — the value reached the
+store and persisted as a shadow column — and now **throws**, `INVALID_FIELD` /
+**400**, on every driver. That is a narrowing of the accept set on the record
+payload, a surface every hook body touches; it is not an instrument or a message
+fix, and a hook that relied on either driver-dependent outcome stops working at
+run time. The same-package sibling `.changeset/hook-input-symbol-key-refusal.md`
+argues exactly this shape — "used to succeed, and now throw. That is a narrowing
+of the accept set" — to `minor`, and the launch-window convention is what keeps
+it off `major` (pre-1.0 lockstep semantics: a breaking change does not burn a
+major version while the stack versions in lockstep — see
+`scripts/check-changeset-no-major.mjs`). `patch` would under-declare a change
+that turns a passing hook into a throwing one.
+
+`'@objectstack/lint': patch` is deliberate and stays. That half of the diff is
+message and comment prose only: `validateHookBodyWrites` reports the same
+findings on the same bodies at the same severity, with wording that now names
+the runtime refusal instead of the driver split this change retires.
+
+The declared-field door (#8682 on insert, #8738 on update) runs before the
+`before*` hooks — deliberately, so a payload about to be refused never consumes
+an autonumber (#8737). That left the payload the hooks themselves produce
+unjudged: a key a `beforeInsert` / `beforeUpdate` hook or an L2 (`language:'js'`)
+body wrote went straight to the driver, and the drivers disagreed. `memory`
+accepted it and stored a shadow column; `driver-sql` threw a raw `SQLITE_ERROR`
+with no `status` and the bound statement and its values quoted back in the
+message; `sqlite-wasm` threw a bare `Error` with neither. One app and one hook
+meant different things on two deployments, and nothing in the app could tell
+which one it was running on.
+
+The same check now runs a second time over the post-hook payload, before any
+statement is built, so a hook-written undeclared key is refused with the caller
+path's envelope — `INVALID_FIELD` / **400**, `Unknown field 'x' on object 'y'` —
+on every driver, because none of them is reached. The existing pre-hook door is
+unchanged and stays exactly where it is.
+
+This is a security fix as well as a consistency one: `fieldPermissions` is keyed
+by declared field name and reports only fields explicitly marked non-editable, so
+a key the object never declares can carry no entry and could never be gated by
+field-level security. On `memory`-family stores such a value was persisted where
+no view, formula, index or permission could name it.
+
+The platform's own stamps are unaffected. `created_at` / `updated_at` — the two
+the built-in audit hook writes unconditionally, because SQL drivers create them
+as built-in columns on every table — are already tolerated by this check
+alongside `id`; every other stamp (`created_by`, `updated_by`, `tenant_id`) is
+guarded by an explicit declaration test in the hook that writes it.
+
+<!-- adr-0087: not-required (no-migration-prescription) No metadata key, spec symbol, Zod schema, object definition or stored representation is added, removed or renamed. This narrows which run-time record payload the engine accepts after the `before*` hooks have run; an undeclared key was never a declarable metadata surface, so `objectstack migrate meta` has nothing in a stored source to rewrite. The remedy for an affected hook body is to declare the field on the object or stop writing it, which is authoring guidance, not a mechanical rewrite of stored metadata. -->
+

content/docs/automation/hook-bodies.mdx

@@ -204,19 +204,22 @@ A structured `writes` declaration was considered and dropped ([#3700](https://gi
 
 #### What still happens at runtime
 
-An unknown field is **not** caught at runtime, and it does not fail quietly either. The write-path validator walks the object's *declared* fields, so an undeclared key is neither rejected nor stripped, and the sandbox's mutations are copied back onto the payload verbatim. What happens next is the driver's call:
+An unknown field **is** caught at runtime, and the answer is the same on every driver. The sandbox's mutations are copied back onto the payload verbatim (`applyMutationsToInput` is a plain `Object.assign`) and the write-path validator still walks only the object's *declared* fields — but since [#13657](https://github.com/objectstack-ai/objectstack/issues/13657) the declared-field door runs a **second** time, over the payload the `before*` hooks produced, before any statement is built:
 
-- **SQL drivers** put the stray column into the statement, so the **whole write fails** with a driver-level error (`table deal has no column named stagee`) — nothing is stored, and the error surfaces far from the authoring mistake.
-- **Schemaless drivers** (memory, MongoDB) silently persist the stray key alongside the real ones.
+```
+INVALID_FIELD / 400 / Unknown field 'stagee' on object 'deal'
+```
+
+Identical on `memory`, `driver-sql` and `sqlite-wasm`, because none of them is reached. Before #13657 the driver decided instead, and the two families disagreed — SQL failed the whole write with an untyped `SQLITE_ERROR`, while schemaless drivers silently persisted the stray key as a column nothing downstream reads (and which field-level security, keyed by *declared* field name, could never gate). One app, one body, two meanings decided by which driver a deployment happened to run.
 
-Neither outcome is the one you wanted, and the advisory warning is the earliest signal you get.
+The runtime refusal is now the backstop; the advisory warning is still the earliest signal you get, and the one that names the mistake where it was made.
 
 Because the existence check is advisory, and every write-side check here is literal-only:
 
 - **Treat `hook-body-write-unknown-field` as a build failure by convention.** It does not gate, but the rule is tuned for near-zero false positives — in practice a warning is a real typo.
 - **Check by hand what the parser cannot see.** Computed keys, spreads, aliased input and dynamic object names are invisible to the rule; for an array or `"*"` hook, every field must exist on every target.
 - **Prefer a flow `update_record` node when the write set is fixed — and for *this* check most of all.** A flow node's writes are structured config: they diff field-by-field, render in the Console designer, and since [#4271](https://github.com/objectstack-ai/objectstack/issues/4271) the field-existence check gates there too — `flow-node-write-unknown-field` is an **error**, not the advisory warning a body gets, because a node's `fields` is a literal map next to a literal `objectName`: there is no parser in between that could have mis-extracted it, so a finding is a certainty rather than a best effort. (The *writability* check now has a hook-side counterpart — see [Writing a `readonly` field](#writing-a-readonly-field) below — but it covers only the `ctx.api` channel.)
-- **Exercise the hook against a real object before shipping** — on SQL drivers the mistake surfaces on the first write; schemaless drivers won't tell you.
+- **Exercise the hook against a real object before shipping** — the mistake surfaces on the first write, identically on every driver.
 
 ### Signature conventions
 

content/docs/permissions/system-context.mdx

@@ -109,18 +109,18 @@ that silently does not happen.
 
 | # | Behaviour when `isSystem` | Package | What you get / what you lose | Anchor |
 |:--|:---|:---|:---|:---|
-| 18 | **`readonly` strip bypassed — UPDATE, single row** | objectql | Get: a `readonly` field CAN be written. Lose: the protection that stops a caller seeding e.g. `approval_status` | `objectql/src/engine.ts:10787` |
-| 19 | **`readonly` strip bypassed — UPDATE, bulk/predicate** | objectql | Same, on the multi-row path | `objectql/src/engine.ts:10949` |
-| 20 | **`readonly` strip bypassed — INSERT (engine pass)** | objectql | Same, on create | `objectql/src/engine.ts:9680` |
+| 18 | **`readonly` strip bypassed — UPDATE, single row** | objectql | Get: a `readonly` field CAN be written. Lose: the protection that stops a caller seeding e.g. `approval_status` | `objectql/src/engine.ts:10882` |
+| 19 | **`readonly` strip bypassed — UPDATE, bulk/predicate** | objectql | Same, on the multi-row path | `objectql/src/engine.ts:11044` |
+| 20 | **`readonly` strip bypassed — INSERT (engine pass)** | objectql | Same, on create | `objectql/src/engine.ts:9747` |
 | 21 | **`readonly` strip bypassed — INSERT (protocol ingress)** | metadata-protocol | `isSystem` is the **only** exemption here. `preserveAudit` is deliberately not read on this path (#6640) — a non-system historical import is still stripped on create | `metadata-protocol/src/protocol.ts:1737` |
-| 22 | Strict-drop refusal never fires | objectql | Lose: a caller that opted into loud refusal gets **silence** — strict refuses exactly what the strip would have taken, and the strip took nothing | `objectql/src/engine.ts:9717`, `readonly-strict-errors.ts:66` |
+| 22 | Strict-drop refusal never fires | objectql | Lose: a caller that opted into loud refusal gets **silence** — strict refuses exactly what the strip would have taken, and the strip took nothing | `objectql/src/engine.ts:9784`, `readonly-strict-errors.ts:66` |
 | 23 | **Referential-integrity check skipped** | objectql | Get: writes proceed against unreachable/unresolvable targets. Lose: an `isSystem` caller can write a **dangling reference** | `objectql/src/engine.ts:5705` |
 | 24 | Tenant-audit warning silenced; `bypassTenantAudit` threaded to the driver | objectql | Get: unscoped system writes stop warning. Lose: the signal that would flag a genuine user-path scoping bug | `objectql/src/engine.ts:3574`, `:3584`, `:3611` |
 | 25 | Engine-owned / append-only write guard bypassed | plugin-security | Get: generic writes to `managedBy` engine-owned objects | `system-write-guard.ts:96`, `:120` |
 | 26 | Identity write guard bypassed (ADR-0092) | plugin-auth | Get: direct writes to identity tables through the generic data path | `identity-write-guard.ts:98` |
 | 27 | Search-companion column **kept** in a read's rows when it was explicitly requested | objectql | Get: the internal companion column is readable. Lose: nothing for app code — this is the engine reading its own index | `objectql/src/engine.ts:6403` |
-| 28 | Dependent-count disclosure on a blocked delete | objectql | Get: the count of blocking children. Nothing was elevated past the caller, so nothing is withheld | `objectql/src/engine.ts:11535` |
-| 29 | Reference-cleanup log attributes the write to `'system'` | objectql | Get: an honest actor label instead of `anonymous` when the context carries neither `userId` nor `actor` | `objectql/src/engine.ts:11464` |
+| 28 | Dependent-count disclosure on a blocked delete | objectql | Get: the count of blocking children. Nothing was elevated past the caller, so nothing is withheld | `objectql/src/engine.ts:11630` |
+| 29 | Reference-cleanup log attributes the write to `'system'` | objectql | Get: an honest actor label instead of `anonymous` when the context carries neither `userId` nor `actor` | `objectql/src/engine.ts:11559` |
 
 ### 3. Sharing (`plugin-sharing`)
 
@@ -180,7 +180,7 @@ a reader tracing where elevation travels needs them.
 | # | Site | Package | What it does |
 |:--|:---|:---|:---|
 | 62 | `objectql/src/engine.ts:3406` | objectql | Propagates `isSystem` into the hook session so hooks can tell engine self-writes from user writes |
-| 63 | `objectql/src/engine.ts:13876` | objectql | `ScopedContext.isSystem` getter — re-exposes the underlying execution context's flag |
+| 63 | `objectql/src/engine.ts:13971` | objectql | `ScopedContext.isSystem` getter — re-exposes the underlying execution context's flag |
 | 64 | `plugin-reports/src/report-service.ts:556` | plugin-reports | Threads the flag into the engine call that runs a report |
 | 65 | `body-runner.ts:279` | runtime | Rebuilds an `ExecutionContext` from a hook session, carrying the flag across |
 
@@ -195,7 +195,7 @@ assuming `isSystem` covers it is a documented source of bugs.
 |:---|:---|:---|
 | "It suppresses triggers / record-change automation" | **No.** Only `skipTriggers` does. A bare `{ isSystem: true }` on a seed write re-fired automation on freshly seeded rows and wedged first boot | `metadata-protocol/src/seed-loader.ts:1909` (rationale at `:1819`–`1821`, #3760), `flow.zod.ts:685` |
 | "It skips the state machine" | **No.** That is `skipStateMachine`, carried by seed replay and by `treatAsHistorical` imports | `objectql/src/engine.ts` FSM gate; see [State Machine](/docs/protocol/objectql/state-machine) |
-| "It skips validation rules" | **No.** Field shape, `format`, `script` and the rest still run. The `readonly` strip runs *before* validation precisely so a discarded value is not judged | `objectql/src/engine.ts:9663`–`9680` |
+| "It skips validation rules" | **No.** Field shape, `format`, `script` and the rest still run. The `readonly` strip runs *before* validation precisely so a discarded value is not judged | `objectql/src/engine.ts:9730`–`9747` |
 | "It preserves a supplied `updated_at` / `updated_by`" | **No.** That is `preserveAudit`, a separate opt-in — and an UPDATE-path exemption only | `field.zod.ts:1516` (#3493 / #6640) |
 | "It stamps `created_by`" | **No.** Audit stamping reads `userId` from the context. A user-less system write stamps nothing — that is today's behaviour, not an error | `runtime-identity.ts:280`–`281` |
 | "It bypasses every guard" | **No.** The last-admin guard applies to **every** context, `isSystem` included — the deprovision path that actually locks an org out is the system one | `last-admin-guard.ts:286` |

packages/lint/src/validate-hook-body-writes.ts

@@ -4,24 +4,30 @@
 //
 // An L2 body that writes a field the target object never declares —
 // `ctx.input.amout = 0`, `ctx.api.object('deal').update({ stag: 'won' })` —
-// runs clean in the QuickJS sandbox and reaches the driver UNFILTERED:
+// runs clean in the QuickJS sandbox and reaches the write path UNFILTERED:
 // `applyMutationsToInput` (runtime/src/sandbox/body-runner.ts) is a plain
 // `Object.assign`, and `validateRecord` walks declared fields on insert and
-// `continue`s past a key with no field def on update. What happens after that
-// is DRIVER-DEPENDENT, and neither half is acceptable:
+// `continue`s past a key with no field def on update.
 //
-// • SQL — the stray column enters the knex statement and the WHOLE write
-// fails with a driver-level error (`table deal has no column named
-// stagee`). The write is lost, and the error surfaces far from the
-// authoring mistake that caused it.
-// • Schemaless (memory, MongoDB) — the driver spreads the payload, so the
-// stray key IS persisted: an undeclared column nothing downstream reads.
+// [#13657] What happens after that used to be DRIVER-DEPENDENT, and neither
+// half was acceptable — SQL failed the whole write with an untyped
+// `SQLITE_ERROR` far from the authoring mistake, while schemaless drivers
+// (memory, MongoDB) spread the payload and PERSISTED the stray key as a column
+// nothing downstream reads. #13657 closed that: the declared-field door now
+// runs a second time over the payload the `before*` hooks produced, so the key
+// is refused `INVALID_FIELD` / 400 identically on every driver, before any
+// statement is built.
 //
-// Either way the mistake is invisible where it is MADE — the #4001 family, if
-// not literally its silent-no-op shape. Both runtime outcomes are pinned by
+// ⚠️ That does NOT retire this rule — it changes what it is worth. The runtime
+// refusal arrives at WRITE time, on whichever record first exercises the
+// branch; this rule arrives at AUTHOR time and names the field, the object and
+// the body. The mistake is still invisible where it is MADE, which is the
+// #4001 family and the whole reason for a build-time check.
+//
+// The runtime answer is pinned by
 // `runtime/src/sandbox/undeclared-field-write-driver-split.integration.test.ts`
-// so this rule's wording cannot drift from what the runtime does; the same
-// split is documented in `content/docs/automation/hook-bodies.mdx`.
+// so this rule's wording cannot drift from what the runtime does; the same is
+// documented in `content/docs/automation/hook-bodies.mdx`.
 //
 // The read side (`hook.condition`, ADR-0032) and the capability surface are
 // statically checked; until this rule, the write side was the one blind face
@@ -817,9 +823,12 @@ export function validateHookBodyWrites(stack: AnyRec): HookBodyWriteFinding[] {
  path,
  message:
  `body writes '${w.field}' to its input, but ${objDesc} ${declares}. The sandboxed script runs ` +
- `clean and the value is copied back onto the record payload unfiltered — on a SQL driver the ` +
- `stray column then fails the WHOLE write with a driver-level error far from here; on a ` +
- `schemaless driver (memory, MongoDB) it is persisted as an undeclared key (#4271).`,
+ // The post-hook declared-field door (#13657) is what refuses it; the
+ // id stays in this comment rather than in the string, which reaches
+ // authors and operators who cannot resolve a tracker number.
+ `clean and the value is copied back onto the record payload unfiltered, so the write is then ` +
+ `REFUSED at run time — INVALID_FIELD / 400, identically on every driver (#4271). The ` +
+ `record is never written, and the refusal names the field far from the body that wrote it.`,
  hint: fixHint(w.field, unionCandidates(targetSets)),
  });
  } else {

.changeset/post-hook-undeclared-field-door.md

@@ -0,0 +1,61 @@
+---
+'@objectstack/objectql': minor
+'@objectstack/lint': patch
+---
+
+Refuse an undeclared field a `before*` hook writes, identically on every driver
+
+**BREAKING** accept-set narrowing at the post-hook write door, shipped as `minor`
+under the repo's launch-window convention for breaking changes.
+
+**Bump level, argued**: `@objectstack/objectql` is `minor`, not `patch`. A
+`before*` hook or an L2 (`language:'js'`) body writing a key the object never
+declares **used to succeed** on the `memory` family — the value reached the
+store and persisted as a shadow column — and now **throws**, `INVALID_FIELD` /
+**400**, on every driver. That is a narrowing of the accept set on the record
+payload, a surface every hook body touches; it is not an instrument or a message
+fix, and a hook that relied on either driver-dependent outcome stops working at
+run time. The same-package sibling `.changeset/hook-input-symbol-key-refusal.md`
+argues exactly this shape — "used to succeed, and now throw. That is a narrowing
+of the accept set" — to `minor`, and the launch-window convention is what keeps
+it off `major` (pre-1.0 lockstep semantics: a breaking change does not burn a
+major version while the stack versions in lockstep — see
+`scripts/check-changeset-no-major.mjs`). `patch` would under-declare a change
+that turns a passing hook into a throwing one.
+
+`'@objectstack/lint': patch` is deliberate and stays. That half of the diff is
+message and comment prose only: `validateHookBodyWrites` reports the same
+findings on the same bodies at the same severity, with wording that now names
+the runtime refusal instead of the driver split this change retires.
+
+The declared-field door (#8682 on insert, #8738 on update) runs before the
+`before*` hooks — deliberately, so a payload about to be refused never consumes
+an autonumber (#8737). That left the payload the hooks themselves produce
+unjudged: a key a `beforeInsert` / `beforeUpdate` hook or an L2 (`language:'js'`)
+body wrote went straight to the driver, and the drivers disagreed. `memory`
+accepted it and stored a shadow column; `driver-sql` threw a raw `SQLITE_ERROR`
+with no `status` and the bound statement and its values quoted back in the
+message; `sqlite-wasm` threw a bare `Error` with neither. One app and one hook
+meant different things on two deployments, and nothing in the app could tell
+which one it was running on.
+
+The same check now runs a second time over the post-hook payload, before any
+statement is built, so a hook-written undeclared key is refused with the caller
+path's envelope — `INVALID_FIELD` / **400**, `Unknown field 'x' on object 'y'` —
+on every driver, because none of them is reached. The existing pre-hook door is
+unchanged and stays exactly where it is.
+
+This is a security fix as well as a consistency one: `fieldPermissions` is keyed
+by declared field name and reports only fields explicitly marked non-editable, so
+a key the object never declares can carry no entry and could never be gated by
+field-level security. On `memory`-family stores such a value was persisted where
+no view, formula, index or permission could name it.
+
+The platform's own stamps are unaffected. `created_at` / `updated_at` — the two
+the built-in audit hook writes unconditionally, because SQL drivers create them
+as built-in columns on every table — are already tolerated by this check
+alongside `id`; every other stamp (`created_by`, `updated_by`, `tenant_id`) is
+guarded by an explicit declaration test in the hook that writes it.
+
+<!-- adr-0087: not-required (no-migration-prescription) No metadata key, spec symbol, Zod schema, object definition or stored representation is added, removed or renamed. This narrows which run-time record payload the engine accepts after the `before*` hooks have run; an undeclared key was never a declarable metadata surface, so `objectstack migrate meta` has nothing in a stored source to rewrite. The remedy for an affected hook body is to declare the field on the object or stop writing it, which is authoring guidance, not a mechanical rewrite of stored metadata. -->
+

content/docs/automation/hook-bodies.mdx

@@ -204,19 +204,22 @@ A structured `writes` declaration was considered and dropped ([#3700](https://gi
 
 #### What still happens at runtime
 
-An unknown field is **not** caught at runtime, and it does not fail quietly either. The write-path validator walks the object's *declared* fields, so an undeclared key is neither rejected nor stripped, and the sandbox's mutations are copied back onto the payload verbatim. What happens next is the driver's call:
+An unknown field **is** caught at runtime, and the answer is the same on every driver. The sandbox's mutations are copied back onto the payload verbatim (`applyMutationsToInput` is a plain `Object.assign`) and the write-path validator still walks only the object's *declared* fields — but since [#13657](https://github.com/objectstack-ai/objectstack/issues/13657) the declared-field door runs a **second** time, over the payload the `before*` hooks produced, before any statement is built:
 
-- **SQL drivers** put the stray column into the statement, so the **whole write fails** with a driver-level error (`table deal has no column named stagee`) — nothing is stored, and the error surfaces far from the authoring mistake.
-- **Schemaless drivers** (memory, MongoDB) silently persist the stray key alongside the real ones.
+```
+INVALID_FIELD / 400 / Unknown field 'stagee' on object 'deal'
+```
+
+Identical on `memory`, `driver-sql` and `sqlite-wasm`, because none of them is reached. Before #13657 the driver decided instead, and the two families disagreed — SQL failed the whole write with an untyped `SQLITE_ERROR`, while schemaless drivers silently persisted the stray key as a column nothing downstream reads (and which field-level security, keyed by *declared* field name, could never gate). One app, one body, two meanings decided by which driver a deployment happened to run.
 
-Neither outcome is the one you wanted, and the advisory warning is the earliest signal you get.
+The runtime refusal is now the backstop; the advisory warning is still the earliest signal you get, and the one that names the mistake where it was made.
 
 Because the existence check is advisory, and every write-side check here is literal-only:
 
 - **Treat `hook-body-write-unknown-field` as a build failure by convention.** It does not gate, but the rule is tuned for near-zero false positives — in practice a warning is a real typo.
 - **Check by hand what the parser cannot see.** Computed keys, spreads, aliased input and dynamic object names are invisible to the rule; for an array or `"*"` hook, every field must exist on every target.
 - **Prefer a flow `update_record` node when the write set is fixed — and for *this* check most of all.** A flow node's writes are structured config: they diff field-by-field, render in the Console designer, and since [#4271](https://github.com/objectstack-ai/objectstack/issues/4271) the field-existence check gates there too — `flow-node-write-unknown-field` is an **error**, not the advisory warning a body gets, because a node's `fields` is a literal map next to a literal `objectName`: there is no parser in between that could have mis-extracted it, so a finding is a certainty rather than a best effort. (The *writability* check now has a hook-side counterpart — see [Writing a `readonly` field](#writing-a-readonly-field) below — but it covers only the `ctx.api` channel.)
-- **Exercise the hook against a real object before shipping** — on SQL drivers the mistake surfaces on the first write; schemaless drivers won't tell you.
+- **Exercise the hook against a real object before shipping** — the mistake surfaces on the first write, identically on every driver.
 
 ### Signature conventions
 

content/docs/permissions/system-context.mdx

@@ -109,18 +109,18 @@ that silently does not happen.
 
 | # | Behaviour when `isSystem` | Package | What you get / what you lose | Anchor |
 |:--|:---|:---|:---|:---|
-| 18 | **`readonly` strip bypassed — UPDATE, single row** | objectql | Get: a `readonly` field CAN be written. Lose: the protection that stops a caller seeding e.g. `approval_status` | `objectql/src/engine.ts:10787` |
-| 19 | **`readonly` strip bypassed — UPDATE, bulk/predicate** | objectql | Same, on the multi-row path | `objectql/src/engine.ts:10949` |
-| 20 | **`readonly` strip bypassed — INSERT (engine pass)** | objectql | Same, on create | `objectql/src/engine.ts:9680` |
+| 18 | **`readonly` strip bypassed — UPDATE, single row** | objectql | Get: a `readonly` field CAN be written. Lose: the protection that stops a caller seeding e.g. `approval_status` | `objectql/src/engine.ts:10882` |
+| 19 | **`readonly` strip bypassed — UPDATE, bulk/predicate** | objectql | Same, on the multi-row path | `objectql/src/engine.ts:11044` |
+| 20 | **`readonly` strip bypassed — INSERT (engine pass)** | objectql | Same, on create | `objectql/src/engine.ts:9747` |
 | 21 | **`readonly` strip bypassed — INSERT (protocol ingress)** | metadata-protocol | `isSystem` is the **only** exemption here. `preserveAudit` is deliberately not read on this path (#6640) — a non-system historical import is still stripped on create | `metadata-protocol/src/protocol.ts:1737` |
-| 22 | Strict-drop refusal never fires | objectql | Lose: a caller that opted into loud refusal gets **silence** — strict refuses exactly what the strip would have taken, and the strip took nothing | `objectql/src/engine.ts:9717`, `readonly-strict-errors.ts:66` |
+| 22 | Strict-drop refusal never fires | objectql | Lose: a caller that opted into loud refusal gets **silence** — strict refuses exactly what the strip would have taken, and the strip took nothing | `objectql/src/engine.ts:9784`, `readonly-strict-errors.ts:66` |
 | 23 | **Referential-integrity check skipped** | objectql | Get: writes proceed against unreachable/unresolvable targets. Lose: an `isSystem` caller can write a **dangling reference** | `objectql/src/engine.ts:5705` |
 | 24 | Tenant-audit warning silenced; `bypassTenantAudit` threaded to the driver | objectql | Get: unscoped system writes stop warning. Lose: the signal that would flag a genuine user-path scoping bug | `objectql/src/engine.ts:3574`, `:3584`, `:3611` |
 | 25 | Engine-owned / append-only write guard bypassed | plugin-security | Get: generic writes to `managedBy` engine-owned objects | `system-write-guard.ts:96`, `:120` |
 | 26 | Identity write guard bypassed (ADR-0092) | plugin-auth | Get: direct writes to identity tables through the generic data path | `identity-write-guard.ts:98` |
 | 27 | Search-companion column **kept** in a read's rows when it was explicitly requested | objectql | Get: the internal companion column is readable. Lose: nothing for app code — this is the engine reading its own index | `objectql/src/engine.ts:6403` |
-| 28 | Dependent-count disclosure on a blocked delete | objectql | Get: the count of blocking children. Nothing was elevated past the caller, so nothing is withheld | `objectql/src/engine.ts:11535` |
-| 29 | Reference-cleanup log attributes the write to `'system'` | objectql | Get: an honest actor label instead of `anonymous` when the context carries neither `userId` nor `actor` | `objectql/src/engine.ts:11464` |
+| 28 | Dependent-count disclosure on a blocked delete | objectql | Get: the count of blocking children. Nothing was elevated past the caller, so nothing is withheld | `objectql/src/engine.ts:11630` |
+| 29 | Reference-cleanup log attributes the write to `'system'` | objectql | Get: an honest actor label instead of `anonymous` when the context carries neither `userId` nor `actor` | `objectql/src/engine.ts:11559` |
 
 ### 3. Sharing (`plugin-sharing`)
 
@@ -180,7 +180,7 @@ a reader tracing where elevation travels needs them.
 | # | Site | Package | What it does |
 |:--|:---|:---|:---|
 | 62 | `objectql/src/engine.ts:3406` | objectql | Propagates `isSystem` into the hook session so hooks can tell engine self-writes from user writes |
-| 63 | `objectql/src/engine.ts:13876` | objectql | `ScopedContext.isSystem` getter — re-exposes the underlying execution context's flag |
+| 63 | `objectql/src/engine.ts:13971` | objectql | `ScopedContext.isSystem` getter — re-exposes the underlying execution context's flag |
 | 64 | `plugin-reports/src/report-service.ts:556` | plugin-reports | Threads the flag into the engine call that runs a report |
 | 65 | `body-runner.ts:279` | runtime | Rebuilds an `ExecutionContext` from a hook session, carrying the flag across |
 
@@ -195,7 +195,7 @@ assuming `isSystem` covers it is a documented source of bugs.
 |:---|:---|:---|
 | "It suppresses triggers / record-change automation" | **No.** Only `skipTriggers` does. A bare `{ isSystem: true }` on a seed write re-fired automation on freshly seeded rows and wedged first boot | `metadata-protocol/src/seed-loader.ts:1909` (rationale at `:1819`–`1821`, #3760), `flow.zod.ts:685` |
 | "It skips the state machine" | **No.** That is `skipStateMachine`, carried by seed replay and by `treatAsHistorical` imports | `objectql/src/engine.ts` FSM gate; see [State Machine](/docs/protocol/objectql/state-machine) |
-| "It skips validation rules" | **No.** Field shape, `format`, `script` and the rest still run. The `readonly` strip runs *before* validation precisely so a discarded value is not judged | `objectql/src/engine.ts:9663`–`9680` |
+| "It skips validation rules" | **No.** Field shape, `format`, `script` and the rest still run. The `readonly` strip runs *before* validation precisely so a discarded value is not judged | `objectql/src/engine.ts:9730`–`9747` |
 | "It preserves a supplied `updated_at` / `updated_by`" | **No.** That is `preserveAudit`, a separate opt-in — and an UPDATE-path exemption only | `field.zod.ts:1516` (#3493 / #6640) |
 | "It stamps `created_by`" | **No.** Audit stamping reads `userId` from the context. A user-less system write stamps nothing — that is today's behaviour, not an error | `runtime-identity.ts:280`–`281` |
 | "It bypasses every guard" | **No.** The last-admin guard applies to **every** context, `isSystem` included — the deprovision path that actually locks an org out is the system one | `last-admin-guard.ts:286` |

packages/lint/src/validate-hook-body-writes.ts

@@ -4,24 +4,30 @@
 //
 // An L2 body that writes a field the target object never declares —
 // `ctx.input.amout = 0`, `ctx.api.object('deal').update({ stag: 'won' })` —
-// runs clean in the QuickJS sandbox and reaches the driver UNFILTERED:
+// runs clean in the QuickJS sandbox and reaches the write path UNFILTERED:
 // `applyMutationsToInput` (runtime/src/sandbox/body-runner.ts) is a plain
 // `Object.assign`, and `validateRecord` walks declared fields on insert and
-// `continue`s past a key with no field def on update. What happens after that
-// is DRIVER-DEPENDENT, and neither half is acceptable:
+// `continue`s past a key with no field def on update.
 //
-// • SQL — the stray column enters the knex statement and the WHOLE write
-// fails with a driver-level error (`table deal has no column named
-// stagee`). The write is lost, and the error surfaces far from the
-// authoring mistake that caused it.
-// • Schemaless (memory, MongoDB) — the driver spreads the payload, so the
-// stray key IS persisted: an undeclared column nothing downstream reads.
+// [#13657] What happens after that used to be DRIVER-DEPENDENT, and neither
+// half was acceptable — SQL failed the whole write with an untyped
+// `SQLITE_ERROR` far from the authoring mistake, while schemaless drivers
+// (memory, MongoDB) spread the payload and PERSISTED the stray key as a column
+// nothing downstream reads. #13657 closed that: the declared-field door now
+// runs a second time over the payload the `before*` hooks produced, so the key
+// is refused `INVALID_FIELD` / 400 identically on every driver, before any
+// statement is built.
 //
-// Either way the mistake is invisible where it is MADE — the #4001 family, if
-// not literally its silent-no-op shape. Both runtime outcomes are pinned by
+// ⚠️ That does NOT retire this rule — it changes what it is worth. The runtime
+// refusal arrives at WRITE time, on whichever record first exercises the
+// branch; this rule arrives at AUTHOR time and names the field, the object and
+// the body. The mistake is still invisible where it is MADE, which is the
+// #4001 family and the whole reason for a build-time check.
+//
+// The runtime answer is pinned by
 // `runtime/src/sandbox/undeclared-field-write-driver-split.integration.test.ts`
-// so this rule's wording cannot drift from what the runtime does; the same
-// split is documented in `content/docs/automation/hook-bodies.mdx`.
+// so this rule's wording cannot drift from what the runtime does; the same is
+// documented in `content/docs/automation/hook-bodies.mdx`.
 //
 // The read side (`hook.condition`, ADR-0032) and the capability surface are
 // statically checked; until this rule, the write side was the one blind face
@@ -817,9 +823,12 @@ export function validateHookBodyWrites(stack: AnyRec): HookBodyWriteFinding[] {
  path,
  message:
  `body writes '${w.field}' to its input, but ${objDesc} ${declares}. The sandboxed script runs ` +
- `clean and the value is copied back onto the record payload unfiltered — on a SQL driver the ` +
- `stray column then fails the WHOLE write with a driver-level error far from here; on a ` +
- `schemaless driver (memory, MongoDB) it is persisted as an undeclared key (#4271).`,
+ // The post-hook declared-field door (#13657) is what refuses it; the
+ // id stays in this comment rather than in the string, which reaches
+ // authors and operators who cannot resolve a tracker number.
+ `clean and the value is copied back onto the record payload unfiltered, so the write is then ` +
+ `REFUSED at run time — INVALID_FIELD / 400, identically on every driver (#4271). The ` +
+ `record is never written, and the refusal names the field far from the body that wrote it.`,
  hint: fixHint(w.field, unionCandidates(targetSets)),
  });
  } else {

.changeset/post-hook-undeclared-field-door.md

@@ -0,0 +1,61 @@
+---
+'@objectstack/objectql': minor
+'@objectstack/lint': patch
+---
+
+Refuse an undeclared field a `before*` hook writes, identically on every driver
+
+**BREAKING** accept-set narrowing at the post-hook write door, shipped as `minor`
+under the repo's launch-window convention for breaking changes.
+
+**Bump level, argued**: `@objectstack/objectql` is `minor`, not `patch`. A
+`before*` hook or an L2 (`language:'js'`) body writing a key the object never
+declares **used to succeed** on the `memory` family — the value reached the
+store and persisted as a shadow column — and now **throws**, `INVALID_FIELD` /
+**400**, on every driver. That is a narrowing of the accept set on the record
+payload, a surface every hook body touches; it is not an instrument or a message
+fix, and a hook that relied on either driver-dependent outcome stops working at
+run time. The same-package sibling `.changeset/hook-input-symbol-key-refusal.md`
+argues exactly this shape — "used to succeed, and now throw. That is a narrowing
+of the accept set" — to `minor`, and the launch-window convention is what keeps
+it off `major` (pre-1.0 lockstep semantics: a breaking change does not burn a
+major version while the stack versions in lockstep — see
+`scripts/check-changeset-no-major.mjs`). `patch` would under-declare a change
+that turns a passing hook into a throwing one.
+
+`'@objectstack/lint': patch` is deliberate and stays. That half of the diff is
+message and comment prose only: `validateHookBodyWrites` reports the same
+findings on the same bodies at the same severity, with wording that now names
+the runtime refusal instead of the driver split this change retires.
+
+The declared-field door (#8682 on insert, #8738 on update) runs before the
+`before*` hooks — deliberately, so a payload about to be refused never consumes
+an autonumber (#8737). That left the payload the hooks themselves produce
+unjudged: a key a `beforeInsert` / `beforeUpdate` hook or an L2 (`language:'js'`)
+body wrote went straight to the driver, and the drivers disagreed. `memory`
+accepted it and stored a shadow column; `driver-sql` threw a raw `SQLITE_ERROR`
+with no `status` and the bound statement and its values quoted back in the
+message; `sqlite-wasm` threw a bare `Error` with neither. One app and one hook
+meant different things on two deployments, and nothing in the app could tell
+which one it was running on.
+
+The same check now runs a second time over the post-hook payload, before any
+statement is built, so a hook-written undeclared key is refused with the caller
+path's envelope — `INVALID_FIELD` / **400**, `Unknown field 'x' on object 'y'` —
+on every driver, because none of them is reached. The existing pre-hook door is
+unchanged and stays exactly where it is.
+
+This is a security fix as well as a consistency one: `fieldPermissions` is keyed
+by declared field name and reports only fields explicitly marked non-editable, so
+a key the object never declares can carry no entry and could never be gated by
+field-level security. On `memory`-family stores such a value was persisted where
+no view, formula, index or permission could name it.
+
+The platform's own stamps are unaffected. `created_at` / `updated_at` — the two
+the built-in audit hook writes unconditionally, because SQL drivers create them
+as built-in columns on every table — are already tolerated by this check
+alongside `id`; every other stamp (`created_by`, `updated_by`, `tenant_id`) is
+guarded by an explicit declaration test in the hook that writes it.
+
+<!-- adr-0087: not-required (no-migration-prescription) No metadata key, spec symbol, Zod schema, object definition or stored representation is added, removed or renamed. This narrows which run-time record payload the engine accepts after the `before*` hooks have run; an undeclared key was never a declarable metadata surface, so `objectstack migrate meta` has nothing in a stored source to rewrite. The remedy for an affected hook body is to declare the field on the object or stop writing it, which is authoring guidance, not a mechanical rewrite of stored metadata. -->
+

content/docs/automation/hook-bodies.mdx

@@ -204,19 +204,22 @@ A structured `writes` declaration was considered and dropped ([#3700](https://gi
 
 #### What still happens at runtime
 
-An unknown field is **not** caught at runtime, and it does not fail quietly either. The write-path validator walks the object's *declared* fields, so an undeclared key is neither rejected nor stripped, and the sandbox's mutations are copied back onto the payload verbatim. What happens next is the driver's call:
+An unknown field **is** caught at runtime, and the answer is the same on every driver. The sandbox's mutations are copied back onto the payload verbatim (`applyMutationsToInput` is a plain `Object.assign`) and the write-path validator still walks only the object's *declared* fields — but since [#13657](https://github.com/objectstack-ai/objectstack/issues/13657) the declared-field door runs a **second** time, over the payload the `before*` hooks produced, before any statement is built:
 
-- **SQL drivers** put the stray column into the statement, so the **whole write fails** with a driver-level error (`table deal has no column named stagee`) — nothing is stored, and the error surfaces far from the authoring mistake.
-- **Schemaless drivers** (memory, MongoDB) silently persist the stray key alongside the real ones.
+```
+INVALID_FIELD / 400 / Unknown field 'stagee' on object 'deal'
+```
+
+Identical on `memory`, `driver-sql` and `sqlite-wasm`, because none of them is reached. Before #13657 the driver decided instead, and the two families disagreed — SQL failed the whole write with an untyped `SQLITE_ERROR`, while schemaless drivers silently persisted the stray key as a column nothing downstream reads (and which field-level security, keyed by *declared* field name, could never gate). One app, one body, two meanings decided by which driver a deployment happened to run.
 
-Neither outcome is the one you wanted, and the advisory warning is the earliest signal you get.
+The runtime refusal is now the backstop; the advisory warning is still the earliest signal you get, and the one that names the mistake where it was made.
 
 Because the existence check is advisory, and every write-side check here is literal-only:
 
 - **Treat `hook-body-write-unknown-field` as a build failure by convention.** It does not gate, but the rule is tuned for near-zero false positives — in practice a warning is a real typo.
 - **Check by hand what the parser cannot see.** Computed keys, spreads, aliased input and dynamic object names are invisible to the rule; for an array or `"*"` hook, every field must exist on every target.
 - **Prefer a flow `update_record` node when the write set is fixed — and for *this* check most of all.** A flow node's writes are structured config: they diff field-by-field, render in the Console designer, and since [#4271](https://github.com/objectstack-ai/objectstack/issues/4271) the field-existence check gates there too — `flow-node-write-unknown-field` is an **error**, not the advisory warning a body gets, because a node's `fields` is a literal map next to a literal `objectName`: there is no parser in between that could have mis-extracted it, so a finding is a certainty rather than a best effort. (The *writability* check now has a hook-side counterpart — see [Writing a `readonly` field](#writing-a-readonly-field) below — but it covers only the `ctx.api` channel.)
-- **Exercise the hook against a real object before shipping** — on SQL drivers the mistake surfaces on the first write; schemaless drivers won't tell you.
+- **Exercise the hook against a real object before shipping** — the mistake surfaces on the first write, identically on every driver.
 
 ### Signature conventions
 

content/docs/permissions/system-context.mdx

@@ -109,18 +109,18 @@ that silently does not happen.
 
 | # | Behaviour when `isSystem` | Package | What you get / what you lose | Anchor |
 |:--|:---|:---|:---|:---|
-| 18 | **`readonly` strip bypassed — UPDATE, single row** | objectql | Get: a `readonly` field CAN be written. Lose: the protection that stops a caller seeding e.g. `approval_status` | `objectql/src/engine.ts:10787` |
-| 19 | **`readonly` strip bypassed — UPDATE, bulk/predicate** | objectql | Same, on the multi-row path | `objectql/src/engine.ts:10949` |
-| 20 | **`readonly` strip bypassed — INSERT (engine pass)** | objectql | Same, on create | `objectql/src/engine.ts:9680` |
+| 18 | **`readonly` strip bypassed — UPDATE, single row** | objectql | Get: a `readonly` field CAN be written. Lose: the protection that stops a caller seeding e.g. `approval_status` | `objectql/src/engine.ts:10882` |
+| 19 | **`readonly` strip bypassed — UPDATE, bulk/predicate** | objectql | Same, on the multi-row path | `objectql/src/engine.ts:11044` |
+| 20 | **`readonly` strip bypassed — INSERT (engine pass)** | objectql | Same, on create | `objectql/src/engine.ts:9747` |
 | 21 | **`readonly` strip bypassed — INSERT (protocol ingress)** | metadata-protocol | `isSystem` is the **only** exemption here. `preserveAudit` is deliberately not read on this path (#6640) — a non-system historical import is still stripped on create | `metadata-protocol/src/protocol.ts:1737` |
-| 22 | Strict-drop refusal never fires | objectql | Lose: a caller that opted into loud refusal gets **silence** — strict refuses exactly what the strip would have taken, and the strip took nothing | `objectql/src/engine.ts:9717`, `readonly-strict-errors.ts:66` |
+| 22 | Strict-drop refusal never fires | objectql | Lose: a caller that opted into loud refusal gets **silence** — strict refuses exactly what the strip would have taken, and the strip took nothing | `objectql/src/engine.ts:9784`, `readonly-strict-errors.ts:66` |
 | 23 | **Referential-integrity check skipped** | objectql | Get: writes proceed against unreachable/unresolvable targets. Lose: an `isSystem` caller can write a **dangling reference** | `objectql/src/engine.ts:5705` |
 | 24 | Tenant-audit warning silenced; `bypassTenantAudit` threaded to the driver | objectql | Get: unscoped system writes stop warning. Lose: the signal that would flag a genuine user-path scoping bug | `objectql/src/engine.ts:3574`, `:3584`, `:3611` |
 | 25 | Engine-owned / append-only write guard bypassed | plugin-security | Get: generic writes to `managedBy` engine-owned objects | `system-write-guard.ts:96`, `:120` |
 | 26 | Identity write guard bypassed (ADR-0092) | plugin-auth | Get: direct writes to identity tables through the generic data path | `identity-write-guard.ts:98` |
 | 27 | Search-companion column **kept** in a read's rows when it was explicitly requested | objectql | Get: the internal companion column is readable. Lose: nothing for app code — this is the engine reading its own index | `objectql/src/engine.ts:6403` |
-| 28 | Dependent-count disclosure on a blocked delete | objectql | Get: the count of blocking children. Nothing was elevated past the caller, so nothing is withheld | `objectql/src/engine.ts:11535` |
-| 29 | Reference-cleanup log attributes the write to `'system'` | objectql | Get: an honest actor label instead of `anonymous` when the context carries neither `userId` nor `actor` | `objectql/src/engine.ts:11464` |
+| 28 | Dependent-count disclosure on a blocked delete | objectql | Get: the count of blocking children. Nothing was elevated past the caller, so nothing is withheld | `objectql/src/engine.ts:11630` |
+| 29 | Reference-cleanup log attributes the write to `'system'` | objectql | Get: an honest actor label instead of `anonymous` when the context carries neither `userId` nor `actor` | `objectql/src/engine.ts:11559` |
 
 ### 3. Sharing (`plugin-sharing`)
 
@@ -180,7 +180,7 @@ a reader tracing where elevation travels needs them.
 | # | Site | Package | What it does |
 |:--|:---|:---|:---|
 | 62 | `objectql/src/engine.ts:3406` | objectql | Propagates `isSystem` into the hook session so hooks can tell engine self-writes from user writes |
-| 63 | `objectql/src/engine.ts:13876` | objectql | `ScopedContext.isSystem` getter — re-exposes the underlying execution context's flag |
+| 63 | `objectql/src/engine.ts:13971` | objectql | `ScopedContext.isSystem` getter — re-exposes the underlying execution context's flag |
 | 64 | `plugin-reports/src/report-service.ts:556` | plugin-reports | Threads the flag into the engine call that runs a report |
 | 65 | `body-runner.ts:279` | runtime | Rebuilds an `ExecutionContext` from a hook session, carrying the flag across |
 
@@ -195,7 +195,7 @@ assuming `isSystem` covers it is a documented source of bugs.
 |:---|:---|:---|
 | "It suppresses triggers / record-change automation" | **No.** Only `skipTriggers` does. A bare `{ isSystem: true }` on a seed write re-fired automation on freshly seeded rows and wedged first boot | `metadata-protocol/src/seed-loader.ts:1909` (rationale at `:1819`–`1821`, #3760), `flow.zod.ts:685` |
 | "It skips the state machine" | **No.** That is `skipStateMachine`, carried by seed replay and by `treatAsHistorical` imports | `objectql/src/engine.ts` FSM gate; see [State Machine](/docs/protocol/objectql/state-machine) |
-| "It skips validation rules" | **No.** Field shape, `format`, `script` and the rest still run. The `readonly` strip runs *before* validation precisely so a discarded value is not judged | `objectql/src/engine.ts:9663`–`9680` |
+| "It skips validation rules" | **No.** Field shape, `format`, `script` and the rest still run. The `readonly` strip runs *before* validation precisely so a discarded value is not judged | `objectql/src/engine.ts:9730`–`9747` |
 | "It preserves a supplied `updated_at` / `updated_by`" | **No.** That is `preserveAudit`, a separate opt-in — and an UPDATE-path exemption only | `field.zod.ts:1516` (#3493 / #6640) |
 | "It stamps `created_by`" | **No.** Audit stamping reads `userId` from the context. A user-less system write stamps nothing — that is today's behaviour, not an error | `runtime-identity.ts:280`–`281` |
 | "It bypasses every guard" | **No.** The last-admin guard applies to **every** context, `isSystem` included — the deprovision path that actually locks an org out is the system one | `last-admin-guard.ts:286` |

packages/lint/src/validate-hook-body-writes.ts

@@ -4,24 +4,30 @@
 //
 // An L2 body that writes a field the target object never declares —
 // `ctx.input.amout = 0`, `ctx.api.object('deal').update({ stag: 'won' })` —
-// runs clean in the QuickJS sandbox and reaches the driver UNFILTERED:
+// runs clean in the QuickJS sandbox and reaches the write path UNFILTERED:
 // `applyMutationsToInput` (runtime/src/sandbox/body-runner.ts) is a plain
 // `Object.assign`, and `validateRecord` walks declared fields on insert and
-// `continue`s past a key with no field def on update. What happens after that
-// is DRIVER-DEPENDENT, and neither half is acceptable:
+// `continue`s past a key with no field def on update.
 //
-// • SQL — the stray column enters the knex statement and the WHOLE write
-// fails with a driver-level error (`table deal has no column named
-// stagee`). The write is lost, and the error surfaces far from the
-// authoring mistake that caused it.
-// • Schemaless (memory, MongoDB) — the driver spreads the payload, so the
-// stray key IS persisted: an undeclared column nothing downstream reads.
+// [#13657] What happens after that used to be DRIVER-DEPENDENT, and neither
+// half was acceptable — SQL failed the whole write with an untyped
+// `SQLITE_ERROR` far from the authoring mistake, while schemaless drivers
+// (memory, MongoDB) spread the payload and PERSISTED the stray key as a column
+// nothing downstream reads. #13657 closed that: the declared-field door now
+// runs a second time over the payload the `before*` hooks produced, so the key
+// is refused `INVALID_FIELD` / 400 identically on every driver, before any
+// statement is built.
 //
-// Either way the mistake is invisible where it is MADE — the #4001 family, if
-// not literally its silent-no-op shape. Both runtime outcomes are pinned by
+// ⚠️ That does NOT retire this rule — it changes what it is worth. The runtime
+// refusal arrives at WRITE time, on whichever record first exercises the
+// branch; this rule arrives at AUTHOR time and names the field, the object and
+// the body. The mistake is still invisible where it is MADE, which is the
+// #4001 family and the whole reason for a build-time check.
+//
+// The runtime answer is pinned by
 // `runtime/src/sandbox/undeclared-field-write-driver-split.integration.test.ts`
-// so this rule's wording cannot drift from what the runtime does; the same
-// split is documented in `content/docs/automation/hook-bodies.mdx`.
+// so this rule's wording cannot drift from what the runtime does; the same is
+// documented in `content/docs/automation/hook-bodies.mdx`.
 //
 // The read side (`hook.condition`, ADR-0032) and the capability surface are
 // statically checked; until this rule, the write side was the one blind face
@@ -817,9 +823,12 @@ export function validateHookBodyWrites(stack: AnyRec): HookBodyWriteFinding[] {
  path,
  message:
  `body writes '${w.field}' to its input, but ${objDesc} ${declares}. The sandboxed script runs ` +
- `clean and the value is copied back onto the record payload unfiltered — on a SQL driver the ` +
- `stray column then fails the WHOLE write with a driver-level error far from here; on a ` +
- `schemaless driver (memory, MongoDB) it is persisted as an undeclared key (#4271).`,
+ // The post-hook declared-field door (#13657) is what refuses it; the
+ // id stays in this comment rather than in the string, which reaches
+ // authors and operators who cannot resolve a tracker number.
+ `clean and the value is copied back onto the record payload unfiltered, so the write is then ` +
+ `REFUSED at run time — INVALID_FIELD / 400, identically on every driver (#4271). The ` +
+ `record is never written, and the refusal names the field far from the body that wrote it.`,
  hint: fixHint(w.field, unionCandidates(targetSets)),
  });
  } else {