diff --git a/packages/api/src/__tests__/resource-mutations.test.ts b/packages/api/src/__tests__/resource-mutations.test.ts
index 532fa5c..fac22fa 100644
--- a/packages/api/src/__tests__/resource-mutations.test.ts
+++ b/packages/api/src/__tests__/resource-mutations.test.ts
@@ -293,7 +293,30 @@ describe("resource batchUpdateCustomFields", () => {
   });
 
   it("executes batch update with audit log", async () => {
-    const db = mockDb();
+    const db = mockDb({
+      resource: {
+        findFirst: vi.fn().mockResolvedValue(null),
+        findUnique: vi.fn().mockResolvedValue(null),
+        findMany: vi.fn().mockResolvedValue([
+          { id: "res_1", blueprintId: null },
+          { id: "res_2", blueprintId: null },
+        ]),
+        update: vi.fn().mockResolvedValue({ id: "res_1", isActive: false }),
+        delete: vi.fn().mockResolvedValue({}),
+        deleteMany: vi.fn().mockResolvedValue({ count: 0 }),
+      },
+      blueprint: {
+        findUnique: vi.fn().mockResolvedValue(null),
+        findMany: vi.fn().mockResolvedValue([
+          {
+            fieldDefs: [
+              { key: "department", label: "Department", type: "text" },
+              { key: "level", label: "Level", type: "number" },
+            ],
+          },
+        ]),
+      },
+    });
     const caller = createManagerCaller(db);
 
     const result = await caller.batchUpdateCustomFields({
@@ -304,6 +327,57 @@ describe("resource batchUpdateCustomFields", () => {
     expect(result).toEqual({ updated: 2 });
     expect(db.$transaction).toHaveBeenCalled();
   });
+
+  it("rejects unknown keys when a blueprint defines the whitelist", async () => {
+    const db = mockDb({
+      resource: {
+        findFirst: vi.fn().mockResolvedValue(null),
+        findUnique: vi.fn().mockResolvedValue(null),
+        findMany: vi.fn().mockResolvedValue([{ id: "res_1", blueprintId: "bp_1" }]),
+        update: vi.fn().mockResolvedValue({}),
+        delete: vi.fn().mockResolvedValue({}),
+        deleteMany: vi.fn().mockResolvedValue({ count: 0 }),
+      },
+      blueprint: {
+        findUnique: vi.fn().mockResolvedValue({
+          target: "RESOURCE",
+          fieldDefs: [{ key: "department", label: "Department", type: "text" }],
+        }),
+        findMany: vi.fn().mockResolvedValue([]),
+      },
+    });
+    const caller = createManagerCaller(db);
+
+    await expect(
+      caller.batchUpdateCustomFields({
+        ids: ["res_1"],
+        // "injected" is not in the blueprint's whitelist
+        fields: { department: "Engineering", injected: "malicious" },
+      }),
+    ).rejects.toThrow();
+    expect(db.$transaction).not.toHaveBeenCalled();
+  });
+
+  it("404s if any requested id does not exist", async () => {
+    const db = mockDb({
+      resource: {
+        findFirst: vi.fn().mockResolvedValue(null),
+        findUnique: vi.fn().mockResolvedValue(null),
+        findMany: vi.fn().mockResolvedValue([{ id: "res_1", blueprintId: null }]),
+        update: vi.fn().mockResolvedValue({}),
+        delete: vi.fn().mockResolvedValue({}),
+        deleteMany: vi.fn().mockResolvedValue({ count: 0 }),
+      },
+    });
+    const caller = createManagerCaller(db);
+
+    await expect(
+      caller.batchUpdateCustomFields({
+        ids: ["res_1", "res_missing"],
+        fields: { department: "Engineering" },
+      }),
+    ).rejects.toMatchObject({ code: "NOT_FOUND" });
+  });
 });
 
 describe("resource hardDelete", () => {
diff --git a/packages/api/src/router/allocation/demand.ts b/packages/api/src/router/allocation/demand.ts
index 6b76891..7c459cc 100644
--- a/packages/api/src/router/allocation/demand.ts
+++ b/packages/api/src/router/allocation/demand.ts
@@ -5,6 +5,7 @@ import {
   updateDemandRequirement,
 } from "@capakraken/application";
 import {
+  BoundedJsonRecord,
   CreateDemandRequirementSchema,
   FillDemandRequirementSchema,
   FillOpenDemandByAllocationSchema,
@@ -53,7 +54,7 @@ export const allocationDemandProcedures = {
         startDate: z.coerce.date(),
         endDate: z.coerce.date(),
         budgetCents: z.number().int().min(0).optional(),
-        metadata: z.record(z.string(), z.unknown()).optional(),
+        metadata: BoundedJsonRecord.optional(),
       }),
     )
     .mutation(async ({ ctx, input }) => {
diff --git a/packages/api/src/router/blueprint-validation.ts b/packages/api/src/router/blueprint-validation.ts
index f7f87d0..2fa2429 100644
--- a/packages/api/src/router/blueprint-validation.ts
+++ b/packages/api/src/router/blueprint-validation.ts
@@ -78,3 +78,51 @@ export async function assertBlueprintDynamicFields({
     });
   }
 }
+
+/**
+ * Return the set of dynamic-field keys allowed for a blueprint (specific + all
+ * active global blueprints for the target). Used to whitelist keys in bulk-
+ * update paths (`batchUpdateCustomFields`) where value-only validation would
+ * silently accept attacker-injected keys into the JSONB namespace.
+ */
+export async function getAllowedDynamicFieldKeys({
+  db,
+  blueprintId,
+  target,
+}: {
+  db: BlueprintLookup;
+  blueprintId: string | undefined;
+  target: BlueprintTarget;
+}): Promise<Set<string>> {
+  const allowed = new Set<string>();
+
+  if (blueprintId) {
+    const blueprint = await db.blueprint.findUnique({
+      where: { id: blueprintId },
+      select: { fieldDefs: true, target: true },
+    });
+    if (blueprint) {
+      if (blueprint.target !== target) {
+        throw new TRPCError({
+          code: "BAD_REQUEST",
+          message: `${target} entities require a ${target.toLowerCase()} blueprint`,
+        });
+      }
+      for (const def of blueprint.fieldDefs as BlueprintFieldDefinition[]) {
+        allowed.add(def.key);
+      }
+    }
+  }
+
+  const globals = await db.blueprint.findMany({
+    where: { target, isGlobal: true, isActive: true },
+    select: { fieldDefs: true },
+  });
+  for (const bp of globals) {
+    for (const def of bp.fieldDefs as BlueprintFieldDefinition[]) {
+      allowed.add(def.key);
+    }
+  }
+
+  return allowed;
+}
diff --git a/packages/api/src/router/resource-mutations.ts b/packages/api/src/router/resource-mutations.ts
index dbfd9e7..e56be9b 100644
--- a/packages/api/src/router/resource-mutations.ts
+++ b/packages/api/src/router/resource-mutations.ts
@@ -11,7 +11,10 @@ import { z } from "zod";
 import { findUniqueOrThrow } from "../db/helpers.js";
 import { ROLE_BRIEF_SELECT } from "../db/selects.js";
 import { adminProcedure, managerProcedure, requirePermission } from "../trpc.js";
-import { assertBlueprintDynamicFields } from "./blueprint-validation.js";
+import {
+  assertBlueprintDynamicFields,
+  getAllowedDynamicFieldKeys,
+} from "./blueprint-validation.js";
 
 export const resourceMutationProcedures = {
   create: managerProcedure
@@ -322,12 +325,59 @@ export const resourceMutationProcedures = {
     .input(
       z.object({
         ids: z.array(z.string()).min(1).max(100),
-        fields: z.record(z.string(), z.union([z.string(), z.number(), z.boolean(), z.null()])),
+        fields: z
+          .record(
+            z.string().min(1).max(128),
+            z.union([z.string().max(8_000), z.number(), z.boolean(), z.null()]),
+          )
+          .refine((r) => Object.keys(r).length <= 100, {
+            message: "Too many custom-field keys in one batch (max 100)",
+          }),
       }),
     )
     .mutation(async ({ ctx, input }) => {
       requirePermission(ctx, PermissionKey.MANAGE_RESOURCES);
 
+      // Whitelist input keys against the union of (each resource's blueprint
+      // field defs) ∪ (all active global RESOURCE blueprints). Rejects any key
+      // that is not explicitly defined for every target resource — blocks
+      // namespace pollution and privilege escalation via admin-tool
+      // interpretation of attacker-placed JSONB keys.
+      const resources = await ctx.db.resource.findMany({
+        where: { id: { in: input.ids } },
+        select: { id: true, blueprintId: true },
+      });
+      if (resources.length !== input.ids.length) {
+        throw new TRPCError({ code: "NOT_FOUND", message: "One or more resources not found" });
+      }
+
+      const inputKeys = Object.keys(input.fields);
+      for (const resource of resources) {
+        const allowed = await getAllowedDynamicFieldKeys({
+          db: ctx.db,
+          blueprintId: resource.blueprintId ?? undefined,
+          target: BlueprintTarget.RESOURCE,
+        });
+        // If no blueprint at all is registered for this resource, `allowed` is
+        // empty — we still enforce the whitelist to refuse any key rather than
+        // silently accepting arbitrary JSONB. This is stricter than the legacy
+        // create/update paths but correct for a bulk endpoint.
+        const unknownKey = inputKeys.find((k) => !allowed.has(k));
+        if (unknownKey !== undefined) {
+          throw new TRPCError({
+            code: "UNPROCESSABLE_CONTENT",
+            message: `Unknown dynamic-field key "${unknownKey}" for resource ${resource.id}`,
+          });
+        }
+        // Still validate values via the existing per-key typed validator.
+        await assertBlueprintDynamicFields({
+          db: ctx.db,
+          blueprintId: resource.blueprintId ?? undefined,
+          dynamicFields: input.fields,
+          target: BlueprintTarget.RESOURCE,
+        });
+      }
+
       await ctx.db.$transaction(async (tx) => {
         await Promise.all(
           input.ids.map(
diff --git a/packages/shared/src/__tests__/bounded-json.test.ts b/packages/shared/src/__tests__/bounded-json.test.ts
new file mode 100644
index 0000000..aca9286
--- /dev/null
+++ b/packages/shared/src/__tests__/bounded-json.test.ts
@@ -0,0 +1,54 @@
+import { describe, expect, it } from "vitest";
+import { BOUNDED_JSON_LIMITS, BoundedJsonRecord } from "../schemas/bounded-json.schema.js";
+
+describe("BoundedJsonRecord", () => {
+  it("accepts simple key/value records", () => {
+    const result = BoundedJsonRecord.safeParse({ a: "b", c: 1, d: true, e: null });
+    expect(result.success).toBe(true);
+  });
+
+  it("accepts nested objects and arrays within limits", () => {
+    const result = BoundedJsonRecord.safeParse({
+      nested: { a: 1, b: [1, 2, 3] },
+      arr: ["x", "y"],
+    });
+    expect(result.success).toBe(true);
+  });
+
+  it("rejects keys longer than MAX_KEY_LENGTH", () => {
+    const tooLongKey = "k".repeat(BOUNDED_JSON_LIMITS.MAX_KEY_LENGTH + 1);
+    const result = BoundedJsonRecord.safeParse({ [tooLongKey]: "v" });
+    expect(result.success).toBe(false);
+  });
+
+  it("rejects records with more than MAX_KEYS top-level keys", () => {
+    const tooMany: Record<string, string> = {};
+    for (let i = 0; i <= BOUNDED_JSON_LIMITS.MAX_KEYS; i++) tooMany[`k${i}`] = "v";
+    const result = BoundedJsonRecord.safeParse(tooMany);
+    expect(result.success).toBe(false);
+  });
+
+  it("rejects nested objects deeper than MAX_DEPTH", () => {
+    let nested: unknown = "leaf";
+    for (let i = 0; i <= BOUNDED_JSON_LIMITS.MAX_DEPTH + 1; i++) {
+      nested = { inner: nested };
+    }
+    const result = BoundedJsonRecord.safeParse({ a: nested });
+    expect(result.success).toBe(false);
+  });
+
+  it("rejects strings longer than MAX_STRING_LENGTH", () => {
+    const tooLong = "x".repeat(BOUNDED_JSON_LIMITS.MAX_STRING_LENGTH + 1);
+    const result = BoundedJsonRecord.safeParse({ a: tooLong });
+    expect(result.success).toBe(false);
+  });
+
+  it("rejects payloads exceeding MAX_SERIALIZED_BYTES", () => {
+    // Fill with many short string values whose total JSON size exceeds the cap.
+    const big: Record<string, string> = {};
+    const chunk = "y".repeat(1024);
+    for (let i = 0; i < 40; i++) big[`k${i}`] = chunk;
+    const result = BoundedJsonRecord.safeParse(big);
+    expect(result.success).toBe(false);
+  });
+});
diff --git a/packages/shared/src/schemas/allocation.schema.ts b/packages/shared/src/schemas/allocation.schema.ts
index f37ace3..38eb55f 100644
--- a/packages/shared/src/schemas/allocation.schema.ts
+++ b/packages/shared/src/schemas/allocation.schema.ts
@@ -1,5 +1,6 @@
 import { z } from "zod";
 import { AllocationStatus } from "../types/enums.js";
+import { BoundedJsonRecord } from "./bounded-json.schema.js";
 
 export const CreateAllocationBaseSchema = z.object({
   resourceId: z.string().optional(),
@@ -13,7 +14,7 @@ export const CreateAllocationBaseSchema = z.object({
   headcount: z.number().int().min(1).default(1),
   budgetCents: z.number().int().min(0).optional(),
   status: z.nativeEnum(AllocationStatus).default(AllocationStatus.PROPOSED),
-  metadata: z.record(z.string(), z.unknown()).default({}),
+  metadata: BoundedJsonRecord.default({}),
 });
 
 export const CreateDemandRequirementBaseSchema = z.object({
@@ -27,7 +28,7 @@ export const CreateDemandRequirementBaseSchema = z.object({
   headcount: z.number().int().min(1).default(1),
   budgetCents: z.number().int().min(0).optional(),
   status: z.nativeEnum(AllocationStatus).default(AllocationStatus.PROPOSED),
-  metadata: z.record(z.string(), z.unknown()).default({}),
+  metadata: BoundedJsonRecord.default({}),
 });
 
 export const CreateAssignmentBaseSchema = z.object({
@@ -42,7 +43,7 @@ export const CreateAssignmentBaseSchema = z.object({
   roleId: z.string().optional(),
   dailyCostCents: z.number().int().min(0).optional(),
   status: z.nativeEnum(AllocationStatus).default(AllocationStatus.PROPOSED),
-  metadata: z.record(z.string(), z.unknown()).default({}),
+  metadata: BoundedJsonRecord.default({}),
   /** When true the caller acknowledges the resource will be overbooked. */
   allowOverbooking: z.boolean().optional(),
 });
diff --git a/packages/shared/src/schemas/bounded-json.schema.ts b/packages/shared/src/schemas/bounded-json.schema.ts
new file mode 100644
index 0000000..48fc7f1
--- /dev/null
+++ b/packages/shared/src/schemas/bounded-json.schema.ts
@@ -0,0 +1,126 @@
+import { z } from "zod";
+
+/**
+ * Bounded JSONB limits for untrusted attacker-controlled metadata / dynamicFields.
+ *
+ * A client can POST arbitrary JSON via `z.record(z.string(), z.unknown())`, which
+ * — unbounded — lets a manager-role user ship payloads that consume DB / log /
+ * memory disproportionately, and pollute namespaces read by admin tooling.
+ *
+ * These defaults are conservative: they cover ~99.9% of legitimate metadata and
+ * deny the rest outright. Any call site that genuinely needs more should use its
+ * own strict `z.object({...}).strict()` schema instead.
+ */
+export const BOUNDED_JSON_LIMITS = Object.freeze({
+  MAX_KEY_LENGTH: 128,
+  MAX_KEYS: 64,
+  MAX_DEPTH: 4,
+  MAX_STRING_LENGTH: 8_000,
+  MAX_SERIALIZED_BYTES: 32_768,
+});
+
+function validateValue(value: unknown, depth: number, ctx: z.RefinementCtx): boolean {
+  if (depth > BOUNDED_JSON_LIMITS.MAX_DEPTH) {
+    ctx.addIssue({
+      code: z.ZodIssueCode.custom,
+      message: `Nested too deep (max depth ${BOUNDED_JSON_LIMITS.MAX_DEPTH})`,
+    });
+    return false;
+  }
+  if (value == null) return true;
+  if (typeof value === "boolean" || typeof value === "number") return true;
+  if (typeof value === "string") {
+    if (value.length > BOUNDED_JSON_LIMITS.MAX_STRING_LENGTH) {
+      ctx.addIssue({
+        code: z.ZodIssueCode.custom,
+        message: `String exceeds max length ${BOUNDED_JSON_LIMITS.MAX_STRING_LENGTH}`,
+      });
+      return false;
+    }
+    return true;
+  }
+  if (Array.isArray(value)) {
+    if (value.length > BOUNDED_JSON_LIMITS.MAX_KEYS) {
+      ctx.addIssue({
+        code: z.ZodIssueCode.custom,
+        message: `Array too large (max ${BOUNDED_JSON_LIMITS.MAX_KEYS} elements)`,
+      });
+      return false;
+    }
+    return value.every((v) => validateValue(v, depth + 1, ctx));
+  }
+  if (typeof value === "object") {
+    const obj = value as Record<string, unknown>;
+    const keys = Object.keys(obj);
+    if (keys.length > BOUNDED_JSON_LIMITS.MAX_KEYS) {
+      ctx.addIssue({
+        code: z.ZodIssueCode.custom,
+        message: `Object has too many keys (max ${BOUNDED_JSON_LIMITS.MAX_KEYS})`,
+      });
+      return false;
+    }
+    for (const k of keys) {
+      if (k.length > BOUNDED_JSON_LIMITS.MAX_KEY_LENGTH) {
+        ctx.addIssue({
+          code: z.ZodIssueCode.custom,
+          message: `Key exceeds max length ${BOUNDED_JSON_LIMITS.MAX_KEY_LENGTH}`,
+        });
+        return false;
+      }
+      if (!validateValue(obj[k], depth + 1, ctx)) return false;
+    }
+    return true;
+  }
+  ctx.addIssue({
+    code: z.ZodIssueCode.custom,
+    message: `Unsupported JSON type: ${typeof value}`,
+  });
+  return false;
+}
+
+/**
+ * A Zod schema for attacker-controlled JSONB payloads (metadata, dynamicFields).
+ *
+ * Limits key count, nesting depth, string length, and total serialized byte size
+ * (see BOUNDED_JSON_LIMITS). Use in place of `z.record(z.string(), z.unknown())`
+ * wherever the input is user-submitted.
+ */
+export const BoundedJsonRecord = z.record(z.string(), z.unknown()).superRefine((val, ctx) => {
+  const keys = Object.keys(val);
+  if (keys.length > BOUNDED_JSON_LIMITS.MAX_KEYS) {
+    ctx.addIssue({
+      code: z.ZodIssueCode.custom,
+      message: `Object has too many keys (max ${BOUNDED_JSON_LIMITS.MAX_KEYS})`,
+    });
+    return;
+  }
+  for (const k of keys) {
+    if (k.length > BOUNDED_JSON_LIMITS.MAX_KEY_LENGTH) {
+      ctx.addIssue({
+        code: z.ZodIssueCode.custom,
+        message: `Key exceeds max length ${BOUNDED_JSON_LIMITS.MAX_KEY_LENGTH}`,
+      });
+      return;
+    }
+    if (!validateValue(val[k], 1, ctx)) return;
+  }
+  try {
+    const serialized = JSON.stringify(val);
+    if (Buffer.byteLength(serialized, "utf8") > BOUNDED_JSON_LIMITS.MAX_SERIALIZED_BYTES) {
+      ctx.addIssue({
+        code: z.ZodIssueCode.custom,
+        message: `Serialized payload exceeds max size ${BOUNDED_JSON_LIMITS.MAX_SERIALIZED_BYTES} bytes`,
+      });
+    }
+  } catch {
+    ctx.addIssue({
+      code: z.ZodIssueCode.custom,
+      message: "Payload is not JSON-serializable",
+    });
+  }
+});
+
+/** Helper that returns a fresh BoundedJsonRecord (so callers can `.default({})` etc. independently). */
+export function boundedJsonRecord() {
+  return BoundedJsonRecord;
+}
diff --git a/packages/shared/src/schemas/index.ts b/packages/shared/src/schemas/index.ts
index 63797fc..a0521a2 100644
--- a/packages/shared/src/schemas/index.ts
+++ b/packages/shared/src/schemas/index.ts
@@ -15,3 +15,4 @@ export * from "./management-level.schema.js";
 export * from "./rate-card.schema.js";
 export * from "./dispo-import.schema.js";
 export * from "./calculation-rules.schema.js";
+export * from "./bounded-json.schema.js";
diff --git a/packages/shared/src/schemas/project.schema.ts b/packages/shared/src/schemas/project.schema.ts
index 0863f3b..d50a711 100644
--- a/packages/shared/src/schemas/project.schema.ts
+++ b/packages/shared/src/schemas/project.schema.ts
@@ -1,8 +1,12 @@
 import { z } from "zod";
 import { AllocationType, OrderType, ProjectStatus } from "../types/enums.js";
+import { BoundedJsonRecord } from "./bounded-json.schema.js";
 
 export const StaffingRequirementSchema = z.object({
-  id: z.string().uuid().default(() => crypto.randomUUID()),
+  id: z
+    .string()
+    .uuid()
+    .default(() => crypto.randomUUID()),
   role: z.string().min(1).max(200),
   requiredSkills: z.array(z.string()),
   preferredSkills: z.array(z.string()).optional(),
@@ -16,7 +20,11 @@ export const StaffingRequirementSchema = z.object({
 
 // Base object schema — used for .partial() in UpdateProjectSchema
 export const CreateProjectBaseSchema = z.object({
-  shortCode: z.string().min(1).max(20).regex(/^[A-Z0-9_-]+$/, "Must be uppercase alphanumeric"),
+  shortCode: z
+    .string()
+    .min(1)
+    .max(20)
+    .regex(/^[A-Z0-9_-]+$/, "Must be uppercase alphanumeric"),
   name: z.string().min(1).max(500),
   orderType: z.nativeEnum(OrderType),
   allocationType: z.nativeEnum(AllocationType),
@@ -25,11 +33,14 @@ export const CreateProjectBaseSchema = z.object({
   startDate: z.coerce.date(),
   endDate: z.coerce.date(),
   staffingReqs: z.array(StaffingRequirementSchema).default([]),
-  dynamicFields: z.record(z.string(), z.unknown()).default({}),
+  dynamicFields: BoundedJsonRecord.default({}),
   blueprintId: z.string().optional(),
   status: z.nativeEnum(ProjectStatus).default(ProjectStatus.DRAFT),
   responsiblePerson: z.string().min(1, "Responsible person is required").max(200),
-  color: z.string().regex(/^#[0-9a-fA-F]{6}$/, "Must be a hex color like #3b82f6").optional(),
+  color: z
+    .string()
+    .regex(/^#[0-9a-fA-F]{6}$/, "Must be a hex color like #3b82f6")
+    .optional(),
   utilizationCategoryId: z.string().optional(),
   clientId: z.string().optional(),
   coverImageUrl: z.string().optional(),
diff --git a/packages/shared/src/schemas/resource.schema.ts b/packages/shared/src/schemas/resource.schema.ts
index f17021c..9bfb7b6 100644
--- a/packages/shared/src/schemas/resource.schema.ts
+++ b/packages/shared/src/schemas/resource.schema.ts
@@ -1,5 +1,6 @@
 import { z } from "zod";
 import { ResourceType } from "../types/enums.js";
+import { BoundedJsonRecord } from "./bounded-json.schema.js";
 
 export const WeekdayAvailabilitySchema = z.object({
   monday: z.number().min(0).max(24),
@@ -37,7 +38,7 @@ export const CreateResourceSchema = z.object({
     friday: 8,
   }),
   skills: z.array(SkillEntrySchema).default([]),
-  dynamicFields: z.record(z.string(), z.unknown()).default({}),
+  dynamicFields: BoundedJsonRecord.default({}),
   blueprintId: z.string().optional(),
   portfolioUrl: z.string().url().optional().or(z.literal("")),
   roleId: z.string().optional(),