diff --git a/src/brainy.ts b/src/brainy.ts
index 2f6a5293..b90194d1 100644
--- a/src/brainy.ts
+++ b/src/brainy.ts
@@ -1708,95 +1708,162 @@ export class Brainy<T = any> implements BrainyInterface<T> {
     return entity
   }
 
-  /** One-shot registry for reserved-field drop warnings (per process, per method+field). */
+  /** One-shot registry for reserved-field warnings (per process, per method+field). */
   private static warnedReservedFields = new Set<string>()
 
   /**
-   * @description Warn once per process (per method+field) that a reserved
-   * field arrived inside a metadata bag and was dropped, naming the correct
-   * write path. Only dropped (system-managed) fields warn — user-settable
-   * fields are remapped to their dedicated param and honored silently.
+   * @description Resolve the human-readable "correct write path" guidance for a
+   * reserved field on a given write method. Single source of truth shared by the
+   * `'throw'` (Error message) and `'warn'` (one-shot warning) paths so the two
+   * never drift. The trio `confidence` / `weight` / `subtype` and the
+   * add()/relate()-time fields `service` / `createdBy` / `visibility` map to a
+   * dedicated param; everything else is system-managed.
    * @param method - The public write method the bag arrived through.
-   * @param field - The reserved field name that was dropped.
-   * @param rightPath - Human guidance naming the correct write path.
+   * @param field - The reserved field name found in the metadata bag.
+   * @returns Guidance naming the correct way to set the field.
    */
-  private warnDroppedReservedField(method: string, field: string, rightPath: string): void {
-    const key = `${method}:${field}`
-    if (Brainy.warnedReservedFields.has(key)) return
-    Brainy.warnedReservedFields.add(key)
-    prodLog.warn(
-      `[brainy] ${method}(): '${field}' is a reserved field and cannot be set ` +
-        `through the metadata bag — use ${rightPath}. The value was ignored. ` +
-        `(This warning is shown once per field per process.)`
-    )
+  private reservedWritePath(
+    method: 'add' | 'update' | 'relate' | 'updateRelation',
+    field: string
+  ): string {
+    const typeParam = "the top-level 'type' param"
+    switch (field) {
+      case 'noun':
+      case 'verb':
+        return typeParam
+      case 'data':
+        return "the top-level 'data' param"
+      case 'confidence':
+        return "the 'confidence' param"
+      case 'weight':
+        return "the 'weight' param"
+      case 'subtype':
+        return "the 'subtype' param"
+      case 'visibility':
+        return "the 'visibility' param ('public' | 'internal')"
+      case 'service':
+        return method === 'add'
+          ? "the 'service' param of add()"
+          : method === 'relate'
+            ? "the 'service' param of relate()"
+            : 'nothing — service is fixed at create time'
+      case 'createdBy':
+        return method === 'add'
+          ? "the 'createdBy' param of add()"
+          : 'nothing — createdBy is system-managed'
+      case 'createdAt':
+        return 'nothing — creation time is set automatically'
+      case 'updatedAt':
+        return 'nothing — set automatically on every write'
+      case '_rev':
+        return method === 'update'
+          ? "the 'ifRev' param for optimistic concurrency"
+          : 'nothing — revisions are system-managed'
+      default:
+        return 'a dedicated top-level param'
+    }
   }
 
   /**
-   * @description Emit the one-shot drop warnings for system-managed entity
-   * fields found in a metadata bag. Shared by the `add` and `update` remaps
-   * (live calls and their `transact()` mirrors).
-   * @param method - `'add'` or `'update'` (the contract is identical for the
-   *   matching `transact()` operation).
-   * @param reserved - The reserved half of the split metadata bag.
+   * @description Enforce {@link BrainyConfig.reservedFieldPolicy} for reserved
+   * fields found inside a metadata bag. Called by every write-path remap once
+   * the bag has been split and at least one reserved key is present.
+   *
+   * - `'throw'` (default): throw a clear Error naming every offending key and
+   *   its correct write path. The caller never reaches the remap.
+   * - `'warn'`: emit a ONE-SHOT (per method+field, per process) warning for
+   *   EVERY reserved key found — both the user-mutable fields that are about to
+   *   be remapped and the system-managed fields that are about to be dropped —
+   *   then fall through to the legacy remap.
+   * - `'remap'`: silent legacy remap, no warning.
+   *
+   * @param method - The public write method the bag arrived through.
+   * @param reserved - The reserved half of the split metadata bag (non-empty).
+   * @param reservedListName - `'RESERVED_ENTITY_FIELDS'` or
+   *   `'RESERVED_RELATION_FIELDS'` — named in the thrown Error for discoverability.
+   * @returns `true` when the caller should proceed with the legacy remap
+   *   (`'warn'` / `'remap'`); `'throw'` never returns (it throws first).
+   * @throws {Error} When the policy is `'throw'` and any reserved key is present.
    */
-  private warnDroppedReservedEntityFields(
-    method: 'add' | 'update',
-    reserved: Partial<Record<string, unknown>>
-  ): void {
-    if (reserved.noun !== undefined) {
-      this.warnDroppedReservedField(method, 'noun', "the top-level 'type' param")
-    }
-    if (reserved.data !== undefined) {
-      this.warnDroppedReservedField(method, 'data', "the top-level 'data' param")
-    }
-    if (reserved.createdAt !== undefined) {
-      this.warnDroppedReservedField(
-        method,
-        'createdAt',
-        method === 'add'
-          ? 'nothing — creation time is set automatically'
-          : 'nothing — creation time is immutable'
+  private enforceReservedPolicy(
+    method: 'add' | 'update' | 'relate' | 'updateRelation',
+    reserved: Partial<Record<string, unknown>>,
+    reservedListName: 'RESERVED_ENTITY_FIELDS' | 'RESERVED_RELATION_FIELDS'
+  ): boolean {
+    const policy = this.config.reservedFieldPolicy ?? 'throw'
+    const keys = Object.keys(reserved)
+    if (keys.length === 0) return true
+
+    if (policy === 'throw') {
+      const detail = keys
+        .map((k) => {
+          const path = this.reservedWritePath(method, k)
+          // System-managed fields resolve to a "nothing — …" sentinel; phrase
+          // those as "is system-managed" rather than "pass it as the nothing".
+          return path.startsWith('nothing')
+            ? `metadata.${k} is a reserved field (${path.replace(/^nothing\s*—\s*/, '')}) and cannot be set through ${method}()`
+            : `metadata.${k} is a reserved field — pass it as ${path} to ${method}()`
+        })
+        .join('; ')
+      throw new Error(
+        `${detail} (reserved: see ${reservedListName}). ` +
+          `Set reservedFieldPolicy:'remap' to opt into legacy remapping, ` +
+          `or reservedFieldPolicy:'warn' to remap with a warning.`
       )
     }
-    if (reserved.updatedAt !== undefined) {
-      this.warnDroppedReservedField(method, 'updatedAt', 'nothing — set automatically on every write')
-    }
-    if (reserved._rev !== undefined) {
-      this.warnDroppedReservedField(
-        method,
-        '_rev',
-        method === 'update'
-          ? "the 'ifRev' param for optimistic concurrency"
-          : 'nothing — revisions are system-managed'
-      )
-    }
-    // 'system' visibility is Brainy-only — a user bag cannot set it. (A 'public'/'internal'
-    // value IS user-settable and is silently remapped to the top-level param below.)
-    if (reserved.visibility === 'system') {
-      this.warnDroppedReservedField(method, 'visibility', "the 'visibility' param ('public' | 'internal')")
-    }
-    if (method === 'update') {
-      if (reserved.service !== undefined) {
-        this.warnDroppedReservedField(method, 'service', 'nothing — fixed at add() time')
-      }
-      if (reserved.createdBy !== undefined) {
-        this.warnDroppedReservedField(method, 'createdBy', 'nothing — fixed at add() time')
+
+    if (policy === 'warn') {
+      // One-shot warning for EVERY reserved key (today only system-managed ones
+      // warn — this closes that gap so user-mutable remaps are visible too).
+      for (const k of keys) {
+        this.warnReservedRemapped(method, k, this.reservedWritePath(method, k))
       }
     }
+
+    // 'warn' and 'remap' both fall through to the legacy remap.
+    return true
+  }
+
+  /**
+   * @description One-shot (per method+field, per process) warning that a
+   * reserved field arrived inside a metadata bag under the `'warn'` policy. The
+   * wording is neutral on "remapped vs dropped" — `reservedWritePath()` already
+   * tells the caller where the value goes (a dedicated param, or "nothing").
+   * @param method - The public write method the bag arrived through.
+   * @param field - The reserved field name found in the bag.
+   * @param rightPath - Guidance naming the correct write path.
+   */
+  private warnReservedRemapped(method: string, field: string, rightPath: string): void {
+    const key = `${method}:${field}`
+    if (Brainy.warnedReservedFields.has(key)) return
+    Brainy.warnedReservedFields.add(key)
+    // System-managed fields resolve to a "nothing — …" sentinel; phrase the
+    // guidance so it reads cleanly in both the remapped and dropped cases.
+    const guidance = rightPath.startsWith('nothing')
+      ? `it is ${rightPath.replace(/^nothing\s*—\s*/, '')} and was dropped`
+      : `set it via ${rightPath} instead`
+    prodLog.warn(
+      `[brainy] ${method}(): '${field}' is a reserved field and was found inside the ` +
+        `metadata bag — ${guidance}. (Legacy remap applied because ` +
+        `reservedFieldPolicy is 'warn'. This warning is shown once per field per process.)`
+    )
   }
 
   /**
    * @description Normalize an `add()` params object with respect to
    * Brainy-reserved fields arriving inside `metadata` (untyped callers only —
    * the compile-time guard on `AddParams.metadata` stops TypeScript callers).
-   * Fields with a dedicated `add()` param (`confidence`, `weight`, `subtype`,
-   * `service`, `createdBy`) are remapped to that param unless the caller also
-   * passed it explicitly (top-level wins); system-managed fields (`noun`,
-   * `data`, `createdAt`, `updatedAt`, `_rev`) are dropped with a one-shot
-   * warning naming the correct write path. The remapped `subtype` flows
+   * Governed by {@link BrainyConfig.reservedFieldPolicy} (default `'throw'`):
+   * `'throw'` rejects the write naming the offending key(s); `'warn'`/`'remap'`
+   * fall through to the legacy remap, where fields with a dedicated `add()`
+   * param (`confidence`, `weight`, `subtype`, `visibility`, `service`,
+   * `createdBy`) are remapped to that param unless the caller also passed it
+   * explicitly (top-level wins) and system-managed fields (`noun`, `data`,
+   * `createdAt`, `updatedAt`, `_rev`) are dropped. A remapped `subtype` flows
    * through subtype-pairing enforcement exactly like a top-level one.
    * @param params - The caller's add params (not mutated).
    * @returns Params with reserved fields normalized out of `metadata`.
+   * @throws {Error} When `reservedFieldPolicy` is `'throw'` and the bag carries a reserved key.
    */
   private remapReservedAddMetadata(params: AddParams<T>): AddParams<T> {
     const bag = params.metadata as Record<string, unknown> | undefined
@@ -1804,7 +1871,9 @@ export class Brainy<T = any> implements BrainyInterface<T> {
     const { reserved, custom } = splitNounMetadataRecord(bag)
     if (Object.keys(reserved).length === 0) return params
 
-    this.warnDroppedReservedEntityFields('add', reserved)
+    // Policy gate: 'throw' (default) throws here; 'warn' warns once per key then
+    // remaps; 'remap' silently remaps. (Throw never returns.)
+    this.enforceReservedPolicy('add', reserved, 'RESERVED_ENTITY_FIELDS')
 
     const createdBy = reserved.createdBy as { augmentation?: unknown; version?: unknown } | undefined
     const createdByValid =
@@ -1841,13 +1910,15 @@ export class Brainy<T = any> implements BrainyInterface<T> {
    * `update({metadata:{confidence}})` silently dropped it (the patch value
    * survived the merge and was then clobbered by the preserve-existing
    * spread; a production consumer's confidence-evolution writes no-oped until
-   * read back). User-mutable fields (`confidence`, `weight`, `subtype`)
-   * remap to their dedicated param unless the caller also passed it
-   * (top-level wins); everything else (`noun`, `data`, `createdAt`,
-   * `updatedAt`, `service`, `createdBy`, `_rev`) is system-managed or fixed
-   * at `add()` time and is dropped with a one-shot warning.
+   * read back). Governed by {@link BrainyConfig.reservedFieldPolicy} (default
+   * `'throw'`): `'throw'` rejects the write; `'warn'`/`'remap'` remap
+   * user-mutable fields (`confidence`, `weight`, `subtype`) to their dedicated
+   * param unless the caller also passed it (top-level wins) and drop everything
+   * else (`noun`, `data`, `createdAt`, `updatedAt`, `service`, `createdBy`,
+   * `_rev`) as system-managed or fixed at `add()` time.
    * @param params - The caller's update params (not mutated).
    * @returns Params with reserved fields normalized out of `metadata`.
+   * @throws {Error} When `reservedFieldPolicy` is `'throw'` and the bag carries a reserved key.
    */
   private remapReservedUpdateMetadata(params: UpdateParams<T>): UpdateParams<T> {
     const bag = params.metadata as Record<string, unknown> | undefined
@@ -1855,7 +1926,9 @@ export class Brainy<T = any> implements BrainyInterface<T> {
     const { reserved, custom } = splitNounMetadataRecord(bag)
     if (Object.keys(reserved).length === 0) return params
 
-    this.warnDroppedReservedEntityFields('update', reserved)
+    // Policy gate: 'throw' (default) throws; 'warn' warns once per key then
+    // remaps; 'remap' silently remaps.
+    this.enforceReservedPolicy('update', reserved, 'RESERVED_ENTITY_FIELDS')
 
     return {
       ...params,
@@ -1869,61 +1942,18 @@ export class Brainy<T = any> implements BrainyInterface<T> {
     }
   }
 
-  /**
-   * @description Emit the one-shot drop warnings for system-managed
-   * relationship fields found in a metadata bag. Shared by the `relate` and
-   * `updateRelation` remaps (live calls and the `transact()` relate mirror).
-   * @param method - `'relate'` or `'updateRelation'`.
-   * @param reserved - The reserved half of the split metadata bag.
-   */
-  private warnDroppedReservedRelationFields(
-    method: 'relate' | 'updateRelation',
-    reserved: Partial<Record<string, unknown>>
-  ): void {
-    if (reserved.verb !== undefined) {
-      this.warnDroppedReservedField(method, 'verb', "the top-level 'type' param")
-    }
-    if (reserved.data !== undefined) {
-      this.warnDroppedReservedField(method, 'data', "the top-level 'data' param")
-    }
-    if (reserved.createdAt !== undefined) {
-      this.warnDroppedReservedField(
-        method,
-        'createdAt',
-        method === 'relate'
-          ? 'nothing — creation time is set automatically'
-          : 'nothing — creation time is immutable'
-      )
-    }
-    if (reserved.updatedAt !== undefined) {
-      this.warnDroppedReservedField(method, 'updatedAt', 'nothing — set automatically on every write')
-    }
-    if (reserved.createdBy !== undefined) {
-      this.warnDroppedReservedField(method, 'createdBy', 'nothing — system-managed')
-    }
-    if (reserved._rev !== undefined) {
-      this.warnDroppedReservedField(method, '_rev', 'nothing — system-managed')
-    }
-    // 'system' visibility is Brainy-only — a user bag cannot set it. (A 'public'/'internal'
-    // value IS user-settable and is silently remapped to the top-level param below.)
-    if (reserved.visibility === 'system') {
-      this.warnDroppedReservedField(method, 'visibility', "the 'visibility' param ('public' | 'internal')")
-    }
-    if (method === 'updateRelation' && reserved.service !== undefined) {
-      this.warnDroppedReservedField(method, 'service', 'nothing — fixed at relate() time')
-    }
-  }
-
   /**
    * @description Normalize a `relate()` params object with respect to
    * Brainy-reserved fields arriving inside `metadata` — the relationship
-   * mirror of {@link remapReservedAddMetadata}. Fields with a dedicated
-   * `relate()` param (`confidence`, `weight`, `subtype`, `service`) remap to
-   * that param (top-level wins); system-managed fields (`verb`, `data`,
-   * `createdAt`, `updatedAt`, `createdBy`, `_rev`) are dropped with a
-   * one-shot warning.
+   * mirror of {@link remapReservedAddMetadata}. Governed by
+   * {@link BrainyConfig.reservedFieldPolicy} (default `'throw'`): `'throw'`
+   * rejects the write; `'warn'`/`'remap'` remap fields with a dedicated
+   * `relate()` param (`confidence`, `weight`, `subtype`, `visibility`,
+   * `service`) to that param (top-level wins) and drop system-managed fields
+   * (`verb`, `data`, `createdAt`, `updatedAt`, `createdBy`, `_rev`).
    * @param params - The caller's relate params (not mutated).
    * @returns Params with reserved fields normalized out of `metadata`.
+   * @throws {Error} When `reservedFieldPolicy` is `'throw'` and the bag carries a reserved key.
    */
   private remapReservedRelateMetadata(params: RelateParams<T>): RelateParams<T> {
     const bag = params.metadata as Record<string, unknown> | undefined
@@ -1931,7 +1961,9 @@ export class Brainy<T = any> implements BrainyInterface<T> {
     const { reserved, custom } = splitVerbMetadataRecord(bag)
     if (Object.keys(reserved).length === 0) return params
 
-    this.warnDroppedReservedRelationFields('relate', reserved)
+    // Policy gate: 'throw' (default) throws; 'warn' warns once per key then
+    // remaps; 'remap' silently remaps.
+    this.enforceReservedPolicy('relate', reserved, 'RESERVED_RELATION_FIELDS')
 
     return {
       ...params,
@@ -1954,12 +1986,14 @@ export class Brainy<T = any> implements BrainyInterface<T> {
   /**
    * @description Normalize an `updateRelation()` params object with respect
    * to Brainy-reserved fields arriving inside the metadata patch — the
-   * relationship mirror of {@link remapReservedUpdateMetadata}. User-mutable
-   * fields (`confidence`, `weight`, `subtype`) remap to their dedicated
-   * param (top-level wins); everything else is dropped with a one-shot
-   * warning.
+   * relationship mirror of {@link remapReservedUpdateMetadata}. Governed by
+   * {@link BrainyConfig.reservedFieldPolicy} (default `'throw'`): `'throw'`
+   * rejects the write; `'warn'`/`'remap'` remap user-mutable fields
+   * (`confidence`, `weight`, `subtype`, `visibility`) to their dedicated param
+   * (top-level wins) and drop everything else.
    * @param params - The caller's update-relation params (not mutated).
    * @returns Params with reserved fields normalized out of `metadata`.
+   * @throws {Error} When `reservedFieldPolicy` is `'throw'` and the bag carries a reserved key.
    */
   private remapReservedUpdateRelationMetadata(
     params: UpdateRelationParams<T>
@@ -1969,7 +2003,9 @@ export class Brainy<T = any> implements BrainyInterface<T> {
     const { reserved, custom } = splitVerbMetadataRecord(bag)
     if (Object.keys(reserved).length === 0) return params
 
-    this.warnDroppedReservedRelationFields('updateRelation', reserved)
+    // Policy gate: 'throw' (default) throws; 'warn' warns once per key then
+    // remaps; 'remap' silently remaps.
+    this.enforceReservedPolicy('updateRelation', reserved, 'RESERVED_RELATION_FIELDS')
 
     return {
       ...params,
@@ -11229,7 +11265,12 @@ export class Brainy<T = any> implements BrainyInterface<T> {
       requireSubtype: config?.requireSubtype ?? true,
       // Multi-process safety
       mode: config?.mode ?? 'writer',
-      force: config?.force ?? false
+      force: config?.force ?? false,
+      // Reserved-field-in-metadata-bag policy (8.0 — no silent failures).
+      // Default 'throw': an untyped caller that smuggles a reserved key past
+      // the compile guard gets a loud Error naming the correct write path.
+      // 'warn' = remap + one-shot warning per key; 'remap' = legacy silent remap.
+      reservedFieldPolicy: config?.reservedFieldPolicy ?? 'throw'
     }
   }
 
diff --git a/src/import/ImportCoordinator.ts b/src/import/ImportCoordinator.ts
index c2eaaef5..21d09410 100644
--- a/src/import/ImportCoordinator.ts
+++ b/src/import/ImportCoordinator.ts
@@ -23,6 +23,7 @@ import { SmartYAMLImporter } from '../importers/SmartYAMLImporter.js'
 import { SmartDOCXImporter } from '../importers/SmartDOCXImporter.js'
 import { VFSStructureGenerator } from '../importers/VFSStructureGenerator.js'
 import { NounType, VerbType } from '../types/graphTypes.js'
+import { splitNounMetadataRecord, splitVerbMetadataRecord } from '../types/reservedFields.js'
 import { v4 as uuidv4 } from '../universal/uuid.js'
 import * as fs from 'fs'
 import * as path from 'path'
@@ -834,7 +835,11 @@ export class ImportCoordinator {
               type: 'media',
               description: '',
               confidence: 1.0,
-              metadata: { subtype: 'image' }
+              // `subtype` is a reserved field — keep it top-level on the extractor
+              // entity (read into the `subtype` param at add() time), never inside
+              // the metadata bag that gets spread into add({ metadata }).
+              subtype: 'image',
+              metadata: {}
             },
             relatedEntities: [],
             relationships: []
@@ -843,7 +848,8 @@ export class ImportCoordinator {
             id: imageId,
             name: imageName,
             type: 'media',
-            metadata: { subtype: 'image' }
+            subtype: 'image',
+            metadata: {}
           }],
           relationships: [],
           metadata: {},
@@ -862,6 +868,38 @@ export class ImportCoordinator {
     }
   }
 
+  /**
+   * Strip Brainy-reserved entity keys out of an extractor-supplied metadata bag.
+   *
+   * Extractors (and consumer `customMetadata`) can carry reserved keys
+   * (`confidence`, `subtype`, `weight`, …) inside `metadata`. Brainy 8.0's
+   * default `reservedFieldPolicy` is `'throw'`, so spreading such a bag into
+   * `add({ metadata })` would reject the whole import. The import pipeline owns
+   * the correct write path: user-mutable reserved values are passed as dedicated
+   * `AddParams` params (see the call sites), so here we simply drop the reserved
+   * half of the bag and keep only the custom fields that belong in `metadata`.
+   *
+   * @param bag - The extractor/consumer metadata bag (may be undefined).
+   * @returns The custom-only metadata (reserved keys removed).
+   */
+  private stripReservedFromBag(bag: Record<string, any> | undefined | null): Record<string, any> {
+    if (!bag || typeof bag !== 'object') return {}
+    return splitNounMetadataRecord(bag).custom
+  }
+
+  /**
+   * Relationship mirror of {@link stripReservedFromBag} — strips reserved verb
+   * keys (`verb`, `confidence`, `weight`, `subtype`, …) out of an edge metadata
+   * bag so it carries only custom fields. Reserved values that have a dedicated
+   * `RelateParams` param are passed there by the call site instead.
+   * @param bag - The extractor/consumer edge metadata bag (may be undefined).
+   * @returns The custom-only edge metadata (reserved keys removed).
+   */
+  private stripReservedFromRelationBag(bag: Record<string, any> | undefined | null): Record<string, any> {
+    if (!bag || typeof bag !== 'object') return {}
+    return splitVerbMetadataRecord(bag).custom
+  }
+
   /**
    * Create entities and relationships in knowledge graph
    * Added sourceInfo parameter for document entity creation
@@ -977,7 +1015,7 @@ export class ImportCoordinator {
             importedAt: trackingContext.importedAt,
             importFormat: trackingContext.importFormat,
             importSource: trackingContext.importSource,
-            ...trackingContext.customMetadata
+            ...this.stripReservedFromBag(trackingContext.customMetadata)
           })
         }
       })
@@ -1005,10 +1043,14 @@ export class ImportCoordinator {
           data: entity.description || entity.name,
           type: entity.type,
           subtype: entity.subtype ?? options.defaultSubtype ?? 'imported',
+          // `confidence` is a reserved field — pass it as the dedicated param,
+          // never inside the metadata bag (8.0 reservedFieldPolicy defaults to 'throw').
+          confidence: entity.confidence,
           metadata: {
-            ...entity.metadata,
+            // Extractor/consumer bags may smuggle reserved keys — strip them so
+            // the bag carries only custom fields.
+            ...this.stripReservedFromBag(entity.metadata),
             name: entity.name,
-            confidence: entity.confidence,
             vfsPath: vfsFile?.path,
             importedFrom: 'import-coordinator',
             imports: [importSource],
@@ -1020,7 +1062,7 @@ export class ImportCoordinator {
               importSource: trackingContext.importSource,
               sourceRow: row.rowNumber,
               sourceSheet: row.sheet,
-              ...trackingContext.customMetadata
+              ...this.stripReservedFromBag(trackingContext.customMetadata)
             })
           }
         }
@@ -1101,7 +1143,7 @@ export class ImportCoordinator {
                 importIds: [trackingContext.importId],
                 projectId: trackingContext.projectId,
                 importFormat: trackingContext.importFormat,
-                ...trackingContext.customMetadata
+                ...this.stripReservedFromRelationBag(trackingContext.customMetadata)
               })
             }
           }
@@ -1132,10 +1174,12 @@ export class ImportCoordinator {
             data: entity.description || entity.name,
             type: entity.type,
             subtype: entity.subtype ?? options.defaultSubtype ?? 'imported',
+            // `confidence` is a reserved field — dedicated param, not metadata.
+            confidence: entity.confidence,
             metadata: {
-              ...entity.metadata,
+              // Strip any reserved keys an extractor smuggled into the bag.
+              ...this.stripReservedFromBag(entity.metadata),
               name: entity.name,
-              confidence: entity.confidence,
               vfsPath: vfsFile?.path,
               importedFrom: 'import-coordinator',
               // Import tracking metadata
@@ -1148,7 +1192,7 @@ export class ImportCoordinator {
                 importSource: trackingContext.importSource,
                 sourceRow: row.rowNumber,
                 sourceSheet: row.sheet,
-                ...trackingContext.customMetadata
+                ...this.stripReservedFromBag(trackingContext.customMetadata)
               })
             }
           })
@@ -1188,7 +1232,7 @@ export class ImportCoordinator {
                 importIds: [trackingContext.importId],
                 projectId: trackingContext.projectId,
                 importFormat: trackingContext.importFormat,
-                ...trackingContext.customMetadata
+                ...this.stripReservedFromRelationBag(trackingContext.customMetadata)
               })
             }
           })
@@ -1243,7 +1287,7 @@ export class ImportCoordinator {
                         projectId: trackingContext.projectId,
                         importedAt: trackingContext.importedAt,
                         importFormat: trackingContext.importFormat,
-                        ...trackingContext.customMetadata
+                        ...this.stripReservedFromBag(trackingContext.customMetadata)
                       })
                     }
                   })
@@ -1273,7 +1317,7 @@ export class ImportCoordinator {
                     projectId: trackingContext.projectId,
                     importedAt: trackingContext.importedAt,
                     importFormat: trackingContext.importFormat,
-                    ...trackingContext.customMetadata
+                    ...this.stripReservedFromRelationBag(trackingContext.customMetadata)
                   })
                 }
               })
@@ -1371,8 +1415,12 @@ export class ImportCoordinator {
             from: rel.from,
             to: rel.to,
             type: verbType,  // Enhanced type
+            // confidence/weight are reserved — carry them as dedicated params,
+            // never inside the bag (they were collected top-level on each rel).
+            ...(typeof (rel as any).confidence === 'number' && { confidence: (rel as any).confidence }),
+            ...(typeof (rel as any).weight === 'number' && { weight: (rel as any).weight }),
             metadata: {
-              ...(rel.metadata || {}),
+              ...this.stripReservedFromRelationBag(rel.metadata),
               relationshipType: 'semantic',  // Distinguish from VFS/provenance
               inferredType: verbType !== rel.type,  // Track if type was enhanced
               originalType: rel.type
diff --git a/src/importers/SmartImportOrchestrator.ts b/src/importers/SmartImportOrchestrator.ts
index d9157852..2084250d 100644
--- a/src/importers/SmartImportOrchestrator.ts
+++ b/src/importers/SmartImportOrchestrator.ts
@@ -12,6 +12,7 @@
 import { Brainy } from '../brainy.js'
 import { VirtualFileSystem } from '../vfs/VirtualFileSystem.js'
 import { NounType, VerbType } from '../types/graphTypes.js'
+import { splitNounMetadataRecord } from '../types/reservedFields.js'
 import { SmartExcelImporter, SmartExcelOptions, SmartExcelResult } from './SmartExcelImporter.js'
 import { SmartPDFImporter, SmartPDFOptions, SmartPDFResult } from './SmartPDFImporter.js'
 import { SmartCSVImporter, SmartCSVOptions, SmartCSVResult } from './SmartCSVImporter.js'
@@ -201,7 +202,9 @@ export class SmartImportOrchestrator {
                   .subtype ?? options.defaultSubtype ?? 'imported',
               confidence: extracted.entity.confidence, // reserved field — dedicated param, not metadata
               metadata: {
-                ...extracted.entity.metadata,
+                // Strip reserved keys an extractor may have smuggled into the bag
+                // (8.0 reservedFieldPolicy defaults to 'throw').
+                ...splitNounMetadataRecord(extracted.entity.metadata).custom,
                 name: extracted.entity.name,
                 importedFrom: 'smart-import'
               }
@@ -245,7 +248,7 @@ export class SmartImportOrchestrator {
         }
 
         // Collect all relationship parameters
-        const relationshipParams: Array<{from: string; to: string; type: VerbType; subtype?: string; metadata?: any}> = []
+        const relationshipParams: Array<{from: string; to: string; type: VerbType; subtype?: string; confidence?: number; metadata?: any}> = []
 
         for (const extracted of result.extraction.rows) {
           for (const rel of extracted.relationships) {
@@ -288,8 +291,8 @@ export class SmartImportOrchestrator {
                 subtype:
                   (rel as typeof rel & { subtype?: string }).subtype ??
                   options.defaultSubtype ?? 'imported',
+                confidence: rel.confidence, // reserved field — dedicated param, not metadata
                 metadata: {
-                  confidence: rel.confidence,
                   evidence: rel.evidence
                 }
               })
@@ -615,7 +618,7 @@ export class SmartImportOrchestrator {
               (extracted.entity as typeof extracted.entity & { subtype?: string })
                 .subtype ?? options.defaultSubtype ?? 'imported',
             confidence: extracted.entity.confidence, // reserved field — dedicated param, not metadata
-            metadata: { ...extracted.entity.metadata, name: extracted.entity.name, importedFrom: 'smart-import' }
+            metadata: { ...splitNounMetadataRecord(extracted.entity.metadata).custom, name: extracted.entity.name, importedFrom: 'smart-import' }
           })
           result.entityIds.push(entityId)
           result.stats.entitiesCreated++
diff --git a/src/neural/neuralImport.ts b/src/neural/neuralImport.ts
index 8a2ba843..c8d19eb5 100644
--- a/src/neural/neuralImport.ts
+++ b/src/neural/neuralImport.ts
@@ -7,6 +7,7 @@
 
 import { Brainy } from '../brainy.js'
 import { NounType, VerbType } from '../types/graphTypes.js'
+import { splitNounMetadataRecord, splitVerbMetadataRecord } from '../types/reservedFields.js'
 import * as fs from '../universal/fs.js'
 import * as path from '../universal/path.js'
 // @ts-ignore
@@ -802,9 +803,12 @@ export class NeuralImport {
           data: this.extractMainText(entity.originalData),
           type: entity.nounType as NounType,
           subtype: entity.subtype ?? options.defaultSubtype ?? 'extracted',
+          // `confidence` is a reserved field — dedicated param, not metadata
+          // (8.0 reservedFieldPolicy defaults to 'throw').
+          confidence: entity.confidence,
           metadata: {
-            ...entity.originalData,
-            confidence: entity.confidence,
+            // Strip any reserved keys the source data smuggled into the bag.
+            ...splitNounMetadataRecord(entity.originalData).custom,
             id: entity.suggestedId
           }
         })
@@ -821,7 +825,8 @@ export class NeuralImport {
           confidence: relationship.confidence, // reserved field — dedicated param, not metadata
           metadata: {
             context: relationship.context,
-            ...relationship.metadata
+            // Strip any reserved keys smuggled into the edge metadata bag.
+            ...splitVerbMetadataRecord(relationship.metadata).custom
           }
         })
       }
diff --git a/src/types/brainy.types.ts b/src/types/brainy.types.ts
index 61e6a86a..5df12e11 100644
--- a/src/types/brainy.types.ts
+++ b/src/types/brainy.types.ts
@@ -1496,6 +1496,33 @@ export interface BrainyConfig {
    * (PID liveness + heartbeat) cannot prove it. Logs a warning regardless.
    */
   force?: boolean
+
+  /**
+   * How write paths react when an untyped (JavaScript) caller smuggles a
+   * Brainy-reserved field (`RESERVED_ENTITY_FIELDS` / `RESERVED_RELATION_FIELDS`
+   * — `confidence`, `weight`, `subtype`, `visibility`, `service`, `createdBy`,
+   * `noun`/`verb`, `data`, `createdAt`, `updatedAt`, `_rev`) **inside the
+   * `metadata` bag** of `add()` / `update()` / `relate()` / `updateRelation()`
+   * (and their `transact()` / `with()` mirrors). TypeScript callers can't write
+   * these shapes at all — the compile-time guard on the metadata param types
+   * (`NoReservedEntityKeys` / `NoReservedRelationKeys`) rejects a literal
+   * reserved key — so this policy only governs untyped callers that slip one
+   * past the compiler.
+   *
+   * - `'throw'` (**default, 8.0**): a reserved key in the bag throws a clear
+   *   `Error` naming the offending key(s) and the correct write path. No silent
+   *   remap, no data loss, no surprise. This is the 8.0 "no silent failures"
+   *   contract.
+   * - `'warn'`: legacy remapping with a loud, one-shot (per key, per process)
+   *   warning for EVERY reserved key found — user-mutable fields are remapped to
+   *   their dedicated top-level param (top-level wins when both are supplied),
+   *   system-managed fields are dropped. Use while migrating untyped call sites.
+   * - `'remap'`: the pre-8.0 silent remapping, no warning. Last-resort
+   *   compatibility hatch for code that intentionally relies on the bag path.
+   *
+   * @default 'throw'
+   */
+  reservedFieldPolicy?: 'throw' | 'warn' | 'remap'
 }
 
 // ============= Neural API Types =============
diff --git a/tests/api/performance-benchmarks.test.ts b/tests/api/performance-benchmarks.test.ts
index d26281d3..e83cebf2 100644
--- a/tests/api/performance-benchmarks.test.ts
+++ b/tests/api/performance-benchmarks.test.ts
@@ -201,7 +201,8 @@ describe('Performance Benchmarks - SLA Validation', () => {
         const start = performance.now()
         await brainy.update({
           id,
-          metadata: { version: 2, updatedAt: Date.now() }
+          // `updatedAt` is system-managed — Brainy sets it on every write.
+          metadata: { version: 2 }
         })
         const latency = performance.now() - start
         benchmark.recordOperation(latency)
diff --git a/tests/helpers/test-factory.ts b/tests/helpers/test-factory.ts
index 40bbe325..62dd53e6 100644
--- a/tests/helpers/test-factory.ts
+++ b/tests/helpers/test-factory.ts
@@ -39,17 +39,21 @@ export function generateTestVector(dimension = 384): Vector {
   return vector.map(val => val / magnitude)
 }
 
-// Generate realistic metadata
+// Generate realistic CUSTOM metadata.
+//
+// NOTE: this deliberately contains only custom (consumer-owned) fields. Reserved
+// Brainy fields (`createdAt`, `updatedAt`, `confidence`, `weight`, `subtype`,
+// `visibility`, `service`, `createdBy`, `data`, `_rev`) must NOT live in the
+// metadata bag — Brainy 8.0's default `reservedFieldPolicy: 'throw'` rejects any
+// reserved key passed through `metadata`. (Reserved values belong in their
+// dedicated top-level params, set by the add/relate factories below.)
 export function generateTestMetadata(overrides: any = {}): any {
   return {
     name: `Test Item ${generateTestId()}`,
     description: 'Test description',
     tags: ['test', 'automated'],
-    createdAt: Date.now(),
-    updatedAt: Date.now(),
     version: 1,
     source: 'test-factory',
-    confidence: 0.95,
     ...overrides,
   }
 }
diff --git a/tests/integration/batchImportWithRelations.test.ts b/tests/integration/batchImportWithRelations.test.ts
index 1594db88..7fe8e511 100644
--- a/tests/integration/batchImportWithRelations.test.ts
+++ b/tests/integration/batchImportWithRelations.test.ts
@@ -61,10 +61,12 @@ describe('Batch Import with Immediate Relations (v5.7.3 Fix)', () => {
     const entityParams = Array(372).fill(null).map((_, i) => ({
       data: `Extracted Entity ${i}`,
       type: NounType.Thing,
+      // `confidence` is a reserved field — pass it as the dedicated param, not
+      // inside the metadata bag (8.0 reservedFieldPolicy defaults to 'throw').
+      confidence: 0.9,
       metadata: {
         extractedFrom: 'TfT~Sapient Species.pdf',
-        entityNumber: i,
-        confidence: 0.9
+        entityNumber: i
       }
     }))
 
diff --git a/tests/integration/remaining-apis.test.ts b/tests/integration/remaining-apis.test.ts
index 5514bf17..12d60983 100644
--- a/tests/integration/remaining-apis.test.ts
+++ b/tests/integration/remaining-apis.test.ts
@@ -61,7 +61,9 @@ describe('Remaining APIs Comprehensive Test', () => {
       await brain.updateMany({
         items: ids.successful.map(id => ({
           id,
-          metadata: { status: 'published', updatedAt: Date.now() }
+          // `updatedAt` is system-managed (set automatically on every write) —
+          // only the custom `status` field belongs in the metadata bag.
+          metadata: { status: 'published' }
         }))
       })
 
diff --git a/tests/unit/brainy/reserved-field-policy.test.ts b/tests/unit/brainy/reserved-field-policy.test.ts
new file mode 100644
index 00000000..c5f37af4
--- /dev/null
+++ b/tests/unit/brainy/reserved-field-policy.test.ts
@@ -0,0 +1,251 @@
+/**
+ * @module tests/unit/brainy/reserved-field-policy
+ * @description The 8.0 `reservedFieldPolicy` matrix — what happens when an
+ * untyped (JavaScript) caller smuggles a Brainy-reserved field INSIDE the
+ * `metadata` bag of a write call, past the compile-time guard.
+ *
+ * 8.0 is a clean break with no silent failures. The decided contract:
+ * - `'throw'` (DEFAULT): a reserved key in the bag throws a clear Error naming
+ *   the offending key(s) and the correct write path. No remap, no data loss.
+ * - `'warn'`: legacy remap PLUS a one-shot (per method+field, per process)
+ *   warning for EVERY reserved key found.
+ * - `'remap'`: the pre-8.0 silent remap, no warning.
+ *
+ * The deep correctness of the remap itself (top-level precedence, system-managed
+ * drops, transact()/with() mirrors, read-side splitting) lives in
+ * tests/unit/brainy/update-reserved-metadata-remap.test.ts (which now runs under
+ * `reservedFieldPolicy: 'remap'`). This file pins the POLICY SELECTION and the
+ * throw/warn behaviors.
+ *
+ * Compile-time callers can't write these shapes at all (see
+ * tests/unit/types/reserved-metadata-keys.test-d.ts); the `as object` widenings
+ * below simulate untyped callers.
+ */
+
+import { describe, it, expect, beforeEach, afterEach, vi } from 'vitest'
+import { Brainy } from '../../../src/index.js'
+import { NounType, VerbType } from '../../../src/types/graphTypes.js'
+import { createTestConfig } from '../../helpers/test-factory.js'
+import { prodLog } from '../../../src/utils/logger.js'
+
+describe('reservedFieldPolicy', () => {
+  describe("default policy is 'throw'", () => {
+    let brain: Brainy
+
+    beforeEach(async () => {
+      // No reservedFieldPolicy override → resolves to 'throw'.
+      brain = new Brainy(createTestConfig())
+      await brain.init()
+    })
+
+    afterEach(async () => {
+      await brain.close()
+    })
+
+    it('add() throws naming the offending key and the correct write path', async () => {
+      await expect(
+        brain.add({
+          type: NounType.Concept,
+          subtype: 'general',
+          data: 'x',
+          metadata: { confidence: 0.8 } as object
+        })
+      ).rejects.toThrow(/metadata\.confidence is a reserved field/)
+
+      // The error names the right param and the reserved list for discoverability.
+      await expect(
+        brain.add({
+          type: NounType.Concept,
+          subtype: 'general',
+          data: 'x',
+          metadata: { confidence: 0.8 } as object
+        })
+      ).rejects.toThrow(/'confidence' param.*RESERVED_ENTITY_FIELDS/s)
+    })
+
+    it('add() lists EVERY offending key when several are present', async () => {
+      const err = await brain
+        .add({
+          type: NounType.Person,
+          data: 'multi',
+          metadata: { confidence: 0.5, weight: 0.6, subtype: 'employee' } as object
+        })
+        .catch((e) => e as Error)
+      expect(err).toBeInstanceOf(Error)
+      expect(err.message).toMatch(/confidence/)
+      expect(err.message).toMatch(/weight/)
+      expect(err.message).toMatch(/subtype/)
+    })
+
+    it('update() throws on a reserved key in the patch', async () => {
+      const id = await brain.add({ type: NounType.Concept, subtype: 'general', data: 'y' })
+      await expect(
+        brain.update({ id, metadata: { confidence: 0.3 } as object })
+      ).rejects.toThrow(/metadata\.confidence is a reserved field/)
+    })
+
+    it('relate() throws on a reserved key in the bag', async () => {
+      const a = await brain.add({ type: NounType.Person, subtype: 'employee', data: 'A' })
+      const b = await brain.add({ type: NounType.Person, subtype: 'employee', data: 'B' })
+      await expect(
+        brain.relate({
+          from: a,
+          to: b,
+          type: VerbType.RelatedTo,
+          subtype: 'colleague',
+          metadata: { confidence: 0.4 } as object
+        })
+      ).rejects.toThrow(/metadata\.confidence is a reserved field.*RESERVED_RELATION_FIELDS/s)
+    })
+
+    it('updateRelation() throws on a reserved key in the patch', async () => {
+      const a = await brain.add({ type: NounType.Person, subtype: 'employee', data: 'A' })
+      const b = await brain.add({ type: NounType.Person, subtype: 'employee', data: 'B' })
+      const relId = await brain.relate({
+        from: a,
+        to: b,
+        type: VerbType.ReportsTo,
+        subtype: 'direct'
+      })
+      await expect(
+        brain.updateRelation({ id: relId, metadata: { weight: 0.2 } as object })
+      ).rejects.toThrow(/metadata\.weight is a reserved field/)
+    })
+
+    it('transact() add op throws on a reserved key in the bag', async () => {
+      await expect(
+        brain.transact([
+          {
+            op: 'add',
+            type: NounType.Concept,
+            subtype: 'general',
+            data: 'tx',
+            metadata: { confidence: 0.7 } as object
+          }
+        ])
+      ).rejects.toThrow(/metadata\.confidence is a reserved field/)
+    })
+
+    it('a custom (non-reserved) key in the bag does NOT throw', async () => {
+      const id = await brain.add({
+        type: NounType.Concept,
+        subtype: 'general',
+        data: 'ok',
+        metadata: { status: 'draft', rating: 4 }
+      })
+      const entity = await brain.get(id)
+      expect(entity?.metadata).toEqual({ status: 'draft', rating: 4 })
+    })
+  })
+
+  describe("'remap' policy remaps silently (no warning)", () => {
+    let brain: Brainy
+    let warnSpy: ReturnType<typeof vi.spyOn>
+
+    beforeEach(async () => {
+      warnSpy = vi.spyOn(prodLog, 'warn').mockImplementation(() => {})
+      brain = new Brainy(createTestConfig({ reservedFieldPolicy: 'remap' }))
+      await brain.init()
+    })
+
+    afterEach(async () => {
+      await brain.close()
+      warnSpy.mockRestore()
+    })
+
+    it('lifts user-mutable reserved fields to top-level without warning', async () => {
+      const id = await brain.add({
+        type: NounType.Person,
+        data: 'remap lift',
+        metadata: { confidence: 0.8, weight: 0.6, subtype: 'employee', dept: 'eng' } as object
+      })
+      const entity = await brain.get(id)
+      expect(entity?.confidence).toBe(0.8)
+      expect(entity?.weight).toBe(0.6)
+      expect(entity?.subtype).toBe('employee')
+      expect(entity?.metadata).toEqual({ dept: 'eng' })
+      // 'remap' is silent about reserved fields (unrelated storage logs may fire,
+      // so assert specifically that no reserved-field warning was emitted).
+      const reservedWarned = warnSpy.mock.calls.some((c) =>
+        String(c[0]).includes('reserved field')
+      )
+      expect(reservedWarned).toBe(false)
+    })
+
+    it('preserves _originalId on natural-key ids through the remap path', async () => {
+      // A speculative view applies the same normalization and maps a natural-key
+      // id to a stable UUID, preserving the caller's original string.
+      const base = await brain.now()
+      const speculative = await base.with([
+        {
+          op: 'add',
+          id: 'remap-spec-entity',
+          type: NounType.Concept,
+          subtype: 'general',
+          data: 'spec',
+          metadata: { confidence: 0.65, custom: 'spec' } as object
+        }
+      ])
+      const entity = await speculative.get('remap-spec-entity')
+      expect(entity?.confidence).toBe(0.65)
+      expect(entity?.metadata).toEqual({ custom: 'spec', _originalId: 'remap-spec-entity' })
+      await speculative.release()
+      await base.release()
+    })
+  })
+
+  describe("'warn' policy remaps AND warns once per key", () => {
+    let brain: Brainy
+    let warnSpy: ReturnType<typeof vi.spyOn>
+
+    beforeEach(async () => {
+      warnSpy = vi.spyOn(prodLog, 'warn').mockImplementation(() => {})
+      brain = new Brainy(createTestConfig({ reservedFieldPolicy: 'warn' }))
+      await brain.init()
+    })
+
+    afterEach(async () => {
+      await brain.close()
+      warnSpy.mockRestore()
+    })
+
+    it('remaps the value (same as remap) and emits a warning naming the field', async () => {
+      // Use a method+field combo unique to this test so the per-process one-shot
+      // registry has not already consumed it.
+      const id = await brain.add({
+        type: NounType.Person,
+        data: 'warn lift',
+        // weight is user-mutable → remapped; this is the only 'warn'-policy
+        // add({ weight }) in the suite, so the one-shot warning fires here.
+        metadata: { weight: 0.42, dept: 'eng' } as object
+      })
+      const entity = await brain.get(id)
+      // Value is honored (remap still happens under 'warn').
+      expect(entity?.weight).toBe(0.42)
+      expect(entity?.metadata).toEqual({ dept: 'eng' })
+      // And a warning was emitted naming the reserved field.
+      expect(warnSpy).toHaveBeenCalled()
+      const warned = warnSpy.mock.calls.some((c) =>
+        String(c[0]).includes("'weight'")
+      )
+      expect(warned).toBe(true)
+    })
+
+    it('warns for system-managed keys too (closes the historical gap)', async () => {
+      // Pre-8.0 only system-managed fields warned; 'warn' warns for every key.
+      // 'createdBy' (system-managed on update) is unique to this test.
+      const id = await brain.add({ type: NounType.Concept, subtype: 'general', data: 'sys' })
+      warnSpy.mockClear()
+      await brain.update({ id, metadata: { createdBy: 'nope', keep: 'me' } as object })
+      const entity = await brain.get(id)
+      // System-managed key dropped; custom field merged.
+      expect((entity?.metadata as Record<string, unknown>)?.createdBy).toBeUndefined()
+      expect((entity?.metadata as Record<string, unknown>)?.keep).toBe('me')
+      // A warning was emitted for the dropped system-managed key.
+      const warned = warnSpy.mock.calls.some((c) =>
+        String(c[0]).includes("'createdBy'")
+      )
+      expect(warned).toBe(true)
+    })
+  })
+})
diff --git a/tests/unit/brainy/update-reserved-metadata-remap.test.ts b/tests/unit/brainy/update-reserved-metadata-remap.test.ts
index 8e1a97c3..31713f99 100644
--- a/tests/unit/brainy/update-reserved-metadata-remap.test.ts
+++ b/tests/unit/brainy/update-reserved-metadata-remap.test.ts
@@ -10,13 +10,19 @@
  * consumer's confidence-evolution writes no-oped for weeks before being
  * caught by reading values back.
  *
- * 8.0 contract under test (every write path, entities AND relationships):
+ * These tests pin the LEGACY REMAP behavior, which in 8.0 is opt-in via
+ * `reservedFieldPolicy: 'remap'` (the default is `'throw'` — see the policy
+ * matrix in tests/unit/brainy/reserved-field-policy.test.ts). The brain in
+ * every test below is constructed with `reservedFieldPolicy: 'remap'` so these
+ * deep correctness assertions about the remap path stay exercised.
+ *
+ * Remap contract under test (every write path, entities AND relationships):
  * - user-mutable reserved fields (`confidence`, `weight`, `subtype` — plus
  *   `service`/`createdBy` at add()/relate() time) remap from the metadata
  *   bag to their dedicated top-level param, with top-level winning when both
  *   are present;
  * - system-managed reserved fields (`createdAt`, `_rev`, `noun`/`verb`,
- *   `data`, …) are dropped from the bag (one-shot warning);
+ *   `data`, …) are dropped from the bag;
  * - the same normalization applies to `transact()` operations and `with()`
  *   speculative views;
  * - reads NEVER echo a reserved field inside `metadata`.
@@ -32,11 +38,12 @@ import { Brainy } from '../../../src/index.js'
 import { NounType, VerbType } from '../../../src/types/graphTypes.js'
 import { createTestConfig } from '../../helpers/test-factory.js'
 
-describe('reserved-field metadata remap (8.0 contract)', () => {
+describe('reserved-field metadata remap (8.0 legacy remap path)', () => {
   let brain: Brainy
 
   beforeEach(async () => {
-    brain = new Brainy(createTestConfig())
+    // The remap path is opt-in in 8.0 (default policy is 'throw').
+    brain = new Brainy(createTestConfig({ reservedFieldPolicy: 'remap' }))
     await brain.init()
   })
 
diff --git a/tests/unit/brainy/visibility.test.ts b/tests/unit/brainy/visibility.test.ts
index 8bd37ebd..a5a02422 100644
--- a/tests/unit/brainy/visibility.test.ts
+++ b/tests/unit/brainy/visibility.test.ts
@@ -198,36 +198,60 @@ describe('visibility (8.0 reserved field)', () => {
       expect(entity?.visibility).toBeUndefined()
     })
 
-    it('an untyped caller passing visibility inside metadata is normalized (lifted to top-level)', async () => {
+    it('an untyped caller passing visibility inside metadata is normalized under reservedFieldPolicy:"remap" (lifted to top-level)', async () => {
       // Simulate a JavaScript caller smuggling the reserved key past the compile-time guard.
-      const id = await brain.add({
-        type: NounType.Concept,
-        data: 'y',
-        metadata: { visibility: 'internal', tag: 't' } as object
-      })
-      const entity = await brain.get(id)
-      // Lifted to the top-level field…
-      expect(entity?.visibility).toBe('internal')
-      // …and stripped from the metadata bag.
-      expect((entity?.metadata as Record<string, unknown>)?.visibility).toBeUndefined()
-      expect((entity?.metadata as Record<string, unknown>)?.tag).toBe('t')
-      // It is excluded from the default count, exactly like a top-level internal write.
-      expect(await brain.getNounCount()).toBe(0)
+      // The legacy remap behavior is now opt-in (8.0 default is 'throw').
+      const remapBrain = new Brainy(createTestConfig({ reservedFieldPolicy: 'remap' }))
+      await remapBrain.init()
+      try {
+        const id = await remapBrain.add({
+          type: NounType.Concept,
+          data: 'y',
+          metadata: { visibility: 'internal', tag: 't' } as object
+        })
+        const entity = await remapBrain.get(id)
+        // Lifted to the top-level field…
+        expect(entity?.visibility).toBe('internal')
+        // …and stripped from the metadata bag.
+        expect((entity?.metadata as Record<string, unknown>)?.visibility).toBeUndefined()
+        expect((entity?.metadata as Record<string, unknown>)?.tag).toBe('t')
+        // It is excluded from the default count, exactly like a top-level internal write.
+        expect(await remapBrain.getNounCount()).toBe(0)
+      } finally {
+        await remapBrain.close()
+      }
     })
 
-    it('a "system" value smuggled through metadata is dropped, not honored', async () => {
+    it('a "system" value smuggled through metadata is dropped under reservedFieldPolicy:"remap", not honored', async () => {
       // 'system' is Brainy-only; an untyped caller must not be able to set it.
-      const id = await brain.add({
-        type: NounType.Concept,
-        data: 'z',
-        metadata: { visibility: 'system' } as object
-      })
-      const entity = await brain.get(id)
-      // The smuggled 'system' was dropped → entity stays public (counted, visible).
-      expect(entity?.visibility).toBeUndefined()
-      expect(await brain.getNounCount()).toBe(1)
-      const found = await brain.find({ type: NounType.Concept, limit: 10 })
-      expect(found.map((r) => r.id)).toContain(id)
+      const remapBrain = new Brainy(createTestConfig({ reservedFieldPolicy: 'remap' }))
+      await remapBrain.init()
+      try {
+        const id = await remapBrain.add({
+          type: NounType.Concept,
+          data: 'z',
+          metadata: { visibility: 'system' } as object
+        })
+        const entity = await remapBrain.get(id)
+        // The smuggled 'system' was dropped → entity stays public (counted, visible).
+        expect(entity?.visibility).toBeUndefined()
+        expect(await remapBrain.getNounCount()).toBe(1)
+        const found = await remapBrain.find({ type: NounType.Concept, limit: 10 })
+        expect(found.map((r) => r.id)).toContain(id)
+      } finally {
+        await remapBrain.close()
+      }
+    })
+
+    it('an untyped caller passing visibility inside metadata throws under the default policy', async () => {
+      // 8.0 default: no silent remap — a reserved key in the bag is a loud error.
+      await expect(
+        brain.add({
+          type: NounType.Concept,
+          data: 'throws',
+          metadata: { visibility: 'internal', tag: 't' } as object
+        })
+      ).rejects.toThrow(/visibility.*reserved field/)
     })
   })
 })