diff --git a/apps/api/src/common/guards/permission.guard.spec.ts b/apps/api/src/common/guards/permission.guard.spec.ts
index ab3ccd1..cce4442 100644
--- a/apps/api/src/common/guards/permission.guard.spec.ts
+++ b/apps/api/src/common/guards/permission.guard.spec.ts
@@ -1,11 +1,11 @@
 import { describe, it, expect, beforeEach, vi } from "vitest";
 import { Test, TestingModule } from "@nestjs/testing";
-import { ExecutionContext, ForbiddenException } from "@nestjs/common";
+import { ExecutionContext, ForbiddenException, InternalServerErrorException } from "@nestjs/common";
 import { Reflector } from "@nestjs/core";
+import { Prisma, WorkspaceMemberRole } from "@prisma/client";
 import { PermissionGuard } from "./permission.guard";
 import { PrismaService } from "../../prisma/prisma.service";
 import { Permission } from "../decorators/permissions.decorator";
-import { WorkspaceMemberRole } from "@prisma/client";
 
 describe("PermissionGuard", () => {
   let guard: PermissionGuard;
@@ -208,13 +208,67 @@ describe("PermissionGuard", () => {
       );
     });
 
-    it("should handle database errors gracefully", async () => {
+    it("should throw InternalServerErrorException on database connection errors", async () => {
       const context = createMockExecutionContext({ id: userId }, { id: workspaceId });
 
       mockReflector.getAllAndOverride.mockReturnValue(Permission.WORKSPACE_MEMBER);
-      mockPrismaService.workspaceMember.findUnique.mockRejectedValue(new Error("Database error"));
+      mockPrismaService.workspaceMember.findUnique.mockRejectedValue(
+        new Error("Database connection failed")
+      );
 
+      await expect(guard.canActivate(context)).rejects.toThrow(InternalServerErrorException);
+      await expect(guard.canActivate(context)).rejects.toThrow("Failed to verify permissions");
+    });
+
+    it("should throw InternalServerErrorException on Prisma connection timeout", async () => {
+      const context = createMockExecutionContext({ id: userId }, { id: workspaceId });
+
+      mockReflector.getAllAndOverride.mockReturnValue(Permission.WORKSPACE_MEMBER);
+
+      const prismaError = new Prisma.PrismaClientKnownRequestError("Connection timed out", {
+        code: "P1001", // Authentication failed (connection error)
+        clientVersion: "5.0.0",
+      });
+
+      mockPrismaService.workspaceMember.findUnique.mockRejectedValue(prismaError);
+
+      await expect(guard.canActivate(context)).rejects.toThrow(InternalServerErrorException);
+    });
+
+    it("should return null role for Prisma not found error (P2025)", async () => {
+      const context = createMockExecutionContext({ id: userId }, { id: workspaceId });
+
+      mockReflector.getAllAndOverride.mockReturnValue(Permission.WORKSPACE_MEMBER);
+
+      const prismaError = new Prisma.PrismaClientKnownRequestError("Record not found", {
+        code: "P2025", // Record not found
+        clientVersion: "5.0.0",
+      });
+
+      mockPrismaService.workspaceMember.findUnique.mockRejectedValue(prismaError);
+
+      // P2025 should be treated as "not a member" -> ForbiddenException
       await expect(guard.canActivate(context)).rejects.toThrow(ForbiddenException);
+      await expect(guard.canActivate(context)).rejects.toThrow(
+        "You are not a member of this workspace"
+      );
+    });
+
+    it("should NOT mask database pool exhaustion as permission denied", async () => {
+      const context = createMockExecutionContext({ id: userId }, { id: workspaceId });
+
+      mockReflector.getAllAndOverride.mockReturnValue(Permission.WORKSPACE_MEMBER);
+
+      const prismaError = new Prisma.PrismaClientKnownRequestError("Connection pool exhausted", {
+        code: "P2024", // Connection pool timeout
+        clientVersion: "5.0.0",
+      });
+
+      mockPrismaService.workspaceMember.findUnique.mockRejectedValue(prismaError);
+
+      // Should NOT throw ForbiddenException for DB errors
+      await expect(guard.canActivate(context)).rejects.toThrow(InternalServerErrorException);
+      await expect(guard.canActivate(context)).rejects.not.toThrow(ForbiddenException);
     });
   });
 });
diff --git a/apps/api/src/common/guards/permission.guard.ts b/apps/api/src/common/guards/permission.guard.ts
index c0dc7a5..6c4e43d 100644
--- a/apps/api/src/common/guards/permission.guard.ts
+++ b/apps/api/src/common/guards/permission.guard.ts
@@ -3,8 +3,10 @@ import {
   CanActivate,
   ExecutionContext,
   ForbiddenException,
+  InternalServerErrorException,
   Logger,
 } from "@nestjs/common";
+import { Prisma } from "@prisma/client";
 import { Reflector } from "@nestjs/core";
 import { PrismaService } from "../../prisma/prisma.service";
 import { PERMISSION_KEY, Permission } from "../decorators/permissions.decorator";
@@ -99,6 +101,10 @@ export class PermissionGuard implements CanActivate {
 
   /**
    * Fetches the user's role in a workspace
+   *
+   * SEC-API-3 FIX: Database errors are no longer swallowed as null role.
+   * Connection timeouts, pool exhaustion, and other infrastructure errors
+   * are propagated as 500 errors to avoid masking operational issues.
    */
   private async getUserWorkspaceRole(
     userId: string,
@@ -119,11 +125,23 @@ export class PermissionGuard implements CanActivate {
 
       return member?.role ?? null;
     } catch (error) {
+      // Only handle Prisma "not found" errors (P2025) as expected cases
+      // All other database errors (connection, timeout, pool) should propagate
+      if (
+        error instanceof Prisma.PrismaClientKnownRequestError &&
+        error.code === "P2025" // Record not found
+      ) {
+        return null;
+      }
+
+      // Log the error before propagating
       this.logger.error(
-        `Failed to fetch user role: ${error instanceof Error ? error.message : "Unknown error"}`,
+        `Database error during permission check: ${error instanceof Error ? error.message : "Unknown error"}`,
         error instanceof Error ? error.stack : undefined
       );
-      return null;
+
+      // Propagate infrastructure errors as 500s, not permission denied
+      throw new InternalServerErrorException("Failed to verify permissions");
     }
   }
 
diff --git a/apps/api/src/common/guards/workspace.guard.spec.ts b/apps/api/src/common/guards/workspace.guard.spec.ts
index 8146ba6..5e1dea9 100644
--- a/apps/api/src/common/guards/workspace.guard.spec.ts
+++ b/apps/api/src/common/guards/workspace.guard.spec.ts
@@ -1,6 +1,12 @@
 import { describe, it, expect, beforeEach, vi } from "vitest";
 import { Test, TestingModule } from "@nestjs/testing";
-import { ExecutionContext, ForbiddenException, BadRequestException } from "@nestjs/common";
+import {
+  ExecutionContext,
+  ForbiddenException,
+  BadRequestException,
+  InternalServerErrorException,
+} from "@nestjs/common";
+import { Prisma } from "@prisma/client";
 import { WorkspaceGuard } from "./workspace.guard";
 import { PrismaService } from "../../prisma/prisma.service";
 
@@ -253,14 +259,60 @@ describe("WorkspaceGuard", () => {
       );
     });
 
-    it("should handle database errors gracefully", async () => {
+    it("should throw InternalServerErrorException on database connection errors", async () => {
       const context = createMockExecutionContext({ id: userId }, { "x-workspace-id": workspaceId });
 
       mockPrismaService.workspaceMember.findUnique.mockRejectedValue(
         new Error("Database connection failed")
       );
 
+      await expect(guard.canActivate(context)).rejects.toThrow(InternalServerErrorException);
+      await expect(guard.canActivate(context)).rejects.toThrow("Failed to verify workspace access");
+    });
+
+    it("should throw InternalServerErrorException on Prisma connection timeout", async () => {
+      const context = createMockExecutionContext({ id: userId }, { "x-workspace-id": workspaceId });
+
+      const prismaError = new Prisma.PrismaClientKnownRequestError("Connection timed out", {
+        code: "P1001", // Authentication failed (connection error)
+        clientVersion: "5.0.0",
+      });
+
+      mockPrismaService.workspaceMember.findUnique.mockRejectedValue(prismaError);
+
+      await expect(guard.canActivate(context)).rejects.toThrow(InternalServerErrorException);
+    });
+
+    it("should return false for Prisma not found error (P2025)", async () => {
+      const context = createMockExecutionContext({ id: userId }, { "x-workspace-id": workspaceId });
+
+      const prismaError = new Prisma.PrismaClientKnownRequestError("Record not found", {
+        code: "P2025", // Record not found
+        clientVersion: "5.0.0",
+      });
+
+      mockPrismaService.workspaceMember.findUnique.mockRejectedValue(prismaError);
+
+      // P2025 should be treated as "not a member" -> ForbiddenException
       await expect(guard.canActivate(context)).rejects.toThrow(ForbiddenException);
+      await expect(guard.canActivate(context)).rejects.toThrow(
+        "You do not have access to this workspace"
+      );
+    });
+
+    it("should NOT mask database pool exhaustion as access denied", async () => {
+      const context = createMockExecutionContext({ id: userId }, { "x-workspace-id": workspaceId });
+
+      const prismaError = new Prisma.PrismaClientKnownRequestError("Connection pool exhausted", {
+        code: "P2024", // Connection pool timeout
+        clientVersion: "5.0.0",
+      });
+
+      mockPrismaService.workspaceMember.findUnique.mockRejectedValue(prismaError);
+
+      // Should NOT throw ForbiddenException for DB errors
+      await expect(guard.canActivate(context)).rejects.toThrow(InternalServerErrorException);
+      await expect(guard.canActivate(context)).rejects.not.toThrow(ForbiddenException);
     });
   });
 });
diff --git a/apps/api/src/common/guards/workspace.guard.ts b/apps/api/src/common/guards/workspace.guard.ts
index d0f9dab..75d065f 100644
--- a/apps/api/src/common/guards/workspace.guard.ts
+++ b/apps/api/src/common/guards/workspace.guard.ts
@@ -4,8 +4,10 @@ import {
   ExecutionContext,
   ForbiddenException,
   BadRequestException,
+  InternalServerErrorException,
   Logger,
 } from "@nestjs/common";
+import { Prisma } from "@prisma/client";
 import { PrismaService } from "../../prisma/prisma.service";
 import type { AuthenticatedRequest } from "../types/user.types";
 
@@ -127,6 +129,10 @@ export class WorkspaceGuard implements CanActivate {
 
   /**
    * Verifies that a user is a member of the specified workspace
+   *
+   * SEC-API-2 FIX: Database errors are no longer swallowed as "access denied".
+   * Connection timeouts, pool exhaustion, and other infrastructure errors
+   * are propagated as 500 errors to avoid masking operational issues.
    */
   private async verifyWorkspaceMembership(userId: string, workspaceId: string): Promise<boolean> {
     try {
@@ -141,11 +147,23 @@ export class WorkspaceGuard implements CanActivate {
 
       return member !== null;
     } catch (error) {
+      // Only handle Prisma "not found" errors (P2025) as expected cases
+      // All other database errors (connection, timeout, pool) should propagate
+      if (
+        error instanceof Prisma.PrismaClientKnownRequestError &&
+        error.code === "P2025" // Record not found
+      ) {
+        return false;
+      }
+
+      // Log the error before propagating
       this.logger.error(
-        `Failed to verify workspace membership: ${error instanceof Error ? error.message : "Unknown error"}`,
+        `Database error during workspace membership check: ${error instanceof Error ? error.message : "Unknown error"}`,
         error instanceof Error ? error.stack : undefined
       );
-      return false;
+
+      // Propagate infrastructure errors as 500s, not access denied
+      throw new InternalServerErrorException("Failed to verify workspace access");
     }
   }
 }