diff --git a/docs/automation/cron-vs-heartbeat.md b/docs/automation/cron-vs-heartbeat.md
index 333a45d0b..325575602 100644
--- a/docs/automation/cron-vs-heartbeat.md
+++ b/docs/automation/cron-vs-heartbeat.md
@@ -201,7 +201,7 @@ For ad-hoc workflows, call Lobster directly.
 
 - Lobster runs as a **local subprocess** (`lobster` CLI) in tool mode and returns a **JSON envelope**.
 - If the tool returns `needs_approval`, you resume with a `resumeToken` and `approve` flag.
-- The tool is an **optional plugin**; you must allowlist `lobster` in `tools.allow`.
+- The tool is an **optional plugin**; enable it additively via `tools.alsoAllow: ["lobster"]` (recommended).
 - If you pass `lobsterPath`, it must be an **absolute path**.
 
 See [Lobster](/tools/lobster) for full usage and examples.
diff --git a/docs/tools/lobster.md b/docs/tools/lobster.md
index daf04fd39..f4718c4b5 100644
--- a/docs/tools/lobster.md
+++ b/docs/tools/lobster.md
@@ -158,7 +158,19 @@ If you want to use a custom binary location, pass an **absolute** `lobsterPath`
 
 ## Enable the tool
 
-Lobster is an **optional** plugin tool (not enabled by default). Allow it per agent:
+Lobster is an **optional** plugin tool (not enabled by default).
+
+Recommended (additive, safe):
+
+```json
+{
+  "tools": {
+    "alsoAllow": ["lobster"]
+  }
+}
+```
+
+Or per-agent:
 
 ```json
 {
@@ -167,7 +179,7 @@ Lobster is an **optional** plugin tool (not enabled by default). Allow it per ag
       {
         "id": "main",
         "tools": {
-          "allow": ["lobster"]
+          "alsoAllow": ["lobster"]
         }
       }
     ]
@@ -175,7 +187,7 @@ Lobster is an **optional** plugin tool (not enabled by default). Allow it per ag
 }
 ```
 
-You can also allow it globally with `tools.allow` if every agent should see it.
+Avoid using `tools.allow: ["lobster"]` unless you intend to run in restrictive allowlist mode.
 
 Note: allowlists are opt-in for optional plugins. If your allowlist only names
 plugin tools (like `lobster`), Clawdbot keeps core tools enabled. To restrict core
diff --git a/src/agents/pi-tools.policy.ts b/src/agents/pi-tools.policy.ts
index 98585ca9d..d6e125e33 100644
--- a/src/agents/pi-tools.policy.ts
+++ b/src/agents/pi-tools.policy.ts
@@ -96,13 +96,28 @@ export function filterToolsByPolicy(tools: AnyAgentTool[], policy?: SandboxToolP
 
 type ToolPolicyConfig = {
   allow?: string[];
+  alsoAllow?: string[];
   deny?: string[];
   profile?: string;
 };
 
+function unionAllow(base?: string[], extra?: string[]) {
+  if (!Array.isArray(extra) || extra.length === 0) return base;
+  // If the user is using alsoAllow without an allowlist, treat it as additive on top of
+  // an implicit allow-all policy.
+  if (!Array.isArray(base) || base.length === 0) {
+    return Array.from(new Set(["*", ...extra]));
+  }
+  return Array.from(new Set([...base, ...extra]));
+}
+
 function pickToolPolicy(config?: ToolPolicyConfig): SandboxToolPolicy | undefined {
   if (!config) return undefined;
-  const allow = Array.isArray(config.allow) ? config.allow : undefined;
+  const allow = Array.isArray(config.allow)
+    ? unionAllow(config.allow, config.alsoAllow)
+    : Array.isArray(config.alsoAllow) && config.alsoAllow.length > 0
+      ? unionAllow(undefined, config.alsoAllow)
+      : undefined;
   const deny = Array.isArray(config.deny) ? config.deny : undefined;
   if (!allow && !deny) return undefined;
   return { allow, deny };
@@ -195,6 +210,17 @@ export function resolveEffectiveToolPolicy(params: {
     agentProviderPolicy: pickToolPolicy(agentProviderPolicy),
     profile,
     providerProfile: agentProviderPolicy?.profile ?? providerPolicy?.profile,
+    // alsoAllow is applied at the profile stage (to avoid being filtered out early).
+    profileAlsoAllow: Array.isArray(agentTools?.alsoAllow)
+      ? agentTools?.alsoAllow
+      : Array.isArray(globalTools?.alsoAllow)
+        ? globalTools?.alsoAllow
+        : undefined,
+    providerProfileAlsoAllow: Array.isArray(agentProviderPolicy?.alsoAllow)
+      ? agentProviderPolicy?.alsoAllow
+      : Array.isArray(providerPolicy?.alsoAllow)
+        ? providerPolicy?.alsoAllow
+        : undefined,
   };
 }
 
diff --git a/src/agents/pi-tools.ts b/src/agents/pi-tools.ts
index 9013f1e52..4a0bebed0 100644
--- a/src/agents/pi-tools.ts
+++ b/src/agents/pi-tools.ts
@@ -157,6 +157,8 @@ export function createClawdbotCodingTools(options?: {
     agentProviderPolicy,
     profile,
     providerProfile,
+    profileAlsoAllow,
+    providerProfileAlsoAllow,
   } = resolveEffectiveToolPolicy({
     config: options?.config,
     sessionKey: options?.sessionKey,
@@ -175,14 +177,25 @@ export function createClawdbotCodingTools(options?: {
   });
   const profilePolicy = resolveToolProfilePolicy(profile);
   const providerProfilePolicy = resolveToolProfilePolicy(providerProfile);
+
+  const mergeAlsoAllow = (policy: typeof profilePolicy, alsoAllow?: string[]) => {
+    if (!policy?.allow || !Array.isArray(alsoAllow) || alsoAllow.length === 0) return policy;
+    return { ...policy, allow: Array.from(new Set([...policy.allow, ...alsoAllow])) };
+  };
+
+  const profilePolicyWithAlsoAllow = mergeAlsoAllow(profilePolicy, profileAlsoAllow);
+  const providerProfilePolicyWithAlsoAllow = mergeAlsoAllow(
+    providerProfilePolicy,
+    providerProfileAlsoAllow,
+  );
   const scopeKey = options?.exec?.scopeKey ?? (agentId ? `agent:${agentId}` : undefined);
   const subagentPolicy =
     isSubagentSessionKey(options?.sessionKey) && options?.sessionKey
       ? resolveSubagentToolPolicy(options.config)
       : undefined;
   const allowBackground = isToolAllowedByPolicies("process", [
-    profilePolicy,
-    providerProfilePolicy,
+    profilePolicyWithAlsoAllow,
+    providerProfilePolicyWithAlsoAllow,
     globalPolicy,
     globalProviderPolicy,
     agentPolicy,
@@ -333,18 +346,18 @@ export function createClawdbotCodingTools(options?: {
     if (resolved.unknownAllowlist.length > 0) {
       const entries = resolved.unknownAllowlist.join(", ");
       const suffix = resolved.strippedAllowlist
-        ? "Ignoring allowlist so core tools remain available."
+        ? "Ignoring allowlist so core tools remain available. Use tools.alsoAllow for additive plugin tool enablement."
         : "These entries won't match any tool unless the plugin is enabled.";
       logWarn(`tools: ${label} allowlist contains unknown entries (${entries}). ${suffix}`);
     }
     return expandPolicyWithPluginGroups(resolved.policy, pluginGroups);
   };
   const profilePolicyExpanded = resolvePolicy(
-    profilePolicy,
+    profilePolicyWithAlsoAllow,
     profile ? `tools.profile (${profile})` : "tools.profile",
   );
   const providerProfileExpanded = resolvePolicy(
-    providerProfilePolicy,
+    providerProfilePolicyWithAlsoAllow,
     providerProfile ? `tools.byProvider.profile (${providerProfile})` : "tools.byProvider.profile",
   );
   const globalPolicyExpanded = resolvePolicy(globalPolicy, "tools.allow");
diff --git a/src/agents/tool-policy.ts b/src/agents/tool-policy.ts
index ac2b1a91c..85152069e 100644
--- a/src/agents/tool-policy.ts
+++ b/src/agents/tool-policy.ts
@@ -209,6 +209,12 @@ export function stripPluginOnlyAllowlist(
     if (!isCoreEntry && !isPluginEntry) unknownAllowlist.push(entry);
   }
   const strippedAllowlist = !hasCoreEntry;
+  // When an allowlist contains only plugin tools, we strip it to avoid accidentally
+  // disabling core tools. Users who want additive behavior should prefer `tools.alsoAllow`.
+  if (strippedAllowlist) {
+    // Note: logging happens in the caller (pi-tools/tools-invoke) after this function returns.
+    // We keep this note here for future maintainers.
+  }
   return {
     policy: strippedAllowlist ? { ...policy, allow: undefined } : policy,
     unknownAllowlist: Array.from(new Set(unknownAllowlist)),
diff --git a/src/config/config.tools-alsoAllow.test.ts b/src/config/config.tools-alsoAllow.test.ts
new file mode 100644
index 000000000..aea4f02d9
--- /dev/null
+++ b/src/config/config.tools-alsoAllow.test.ts
@@ -0,0 +1,53 @@
+import { describe, expect, it } from "vitest";
+
+import { validateConfigObject } from "./validation.js";
+
+// NOTE: These tests ensure allow + alsoAllow cannot be set in the same scope.
+
+describe("config: tools.alsoAllow", () => {
+  it("rejects tools.allow + tools.alsoAllow together", () => {
+    const res = validateConfigObject({
+      tools: {
+        allow: ["group:fs"],
+        alsoAllow: ["lobster"],
+      },
+    });
+
+    expect(res.ok).toBe(false);
+    if (!res.ok) {
+      expect(res.issues.some((i) => i.path === "tools")).toBe(true);
+    }
+  });
+
+  it("rejects agents.list[].tools.allow + alsoAllow together", () => {
+    const res = validateConfigObject({
+      agents: {
+        list: [
+          {
+            id: "main",
+            tools: {
+              allow: ["group:fs"],
+              alsoAllow: ["lobster"],
+            },
+          },
+        ],
+      },
+    });
+
+    expect(res.ok).toBe(false);
+    if (!res.ok) {
+      expect(res.issues.some((i) => i.path.includes("agents.list"))).toBe(true);
+    }
+  });
+
+  it("allows profile + alsoAllow", () => {
+    const res = validateConfigObject({
+      tools: {
+        profile: "coding",
+        alsoAllow: ["lobster"],
+      },
+    });
+
+    expect(res.ok).toBe(true);
+  });
+});
diff --git a/src/config/legacy.migrations.part-3.ts b/src/config/legacy.migrations.part-3.ts
index 9db9e3ede..21589e4fa 100644
--- a/src/config/legacy.migrations.part-3.ts
+++ b/src/config/legacy.migrations.part-3.ts
@@ -9,6 +9,10 @@ import {
   resolveDefaultAgentIdFromRaw,
 } from "./legacy.shared.js";
 
+// NOTE: tools.alsoAllow was introduced after legacy migrations; no legacy migration needed.
+
+// tools.alsoAllow legacy migration intentionally omitted (field not shipped in prod).
+
 export const LEGACY_CONFIG_MIGRATIONS_PART_3: LegacyConfigMigration[] = [
   {
     id: "auth.anthropic-claude-cli-mode-oauth",
@@ -24,6 +28,7 @@ export const LEGACY_CONFIG_MIGRATIONS_PART_3: LegacyConfigMigration[] = [
       changes.push('Updated auth.profiles["anthropic:claude-cli"].mode → "oauth".');
     },
   },
+  // tools.alsoAllow migration removed (field not shipped in prod; enforce via schema instead).
   {
     id: "tools.bash->tools.exec",
     describe: "Move tools.bash to tools.exec",
diff --git a/src/config/schema.ts b/src/config/schema.ts
index 24d6bccfe..9627d64f3 100644
--- a/src/config/schema.ts
+++ b/src/config/schema.ts
@@ -165,7 +165,9 @@ const FIELD_LABELS: Record<string, string> = {
   "tools.links.models": "Link Understanding Models",
   "tools.links.scope": "Link Understanding Scope",
   "tools.profile": "Tool Profile",
+  "tools.alsoAllow": "Tool Allowlist Additions",
   "agents.list[].tools.profile": "Agent Tool Profile",
+  "agents.list[].tools.alsoAllow": "Agent Tool Allowlist Additions",
   "tools.byProvider": "Tool Policy by Provider",
   "agents.list[].tools.byProvider": "Agent Tool Policy by Provider",
   "tools.exec.applyPatch.enabled": "Enable apply_patch",
diff --git a/src/config/types.tools.ts b/src/config/types.tools.ts
index ad7f69d85..d84dd1aa7 100644
--- a/src/config/types.tools.ts
+++ b/src/config/types.tools.ts
@@ -140,12 +140,21 @@ export type ToolProfileId = "minimal" | "coding" | "messaging" | "full";
 
 export type ToolPolicyConfig = {
   allow?: string[];
+  /**
+   * Additional allowlist entries merged into the effective allowlist.
+   *
+   * Intended for additive configuration (e.g., "also allow lobster") without forcing
+   * users to replace/duplicate an existing allowlist or profile.
+   */
+  alsoAllow?: string[];
   deny?: string[];
   profile?: ToolProfileId;
 };
 
 export type GroupToolPolicyConfig = {
   allow?: string[];
+  /** Additional allowlist entries merged into allow. */
+  alsoAllow?: string[];
   deny?: string[];
 };
 
@@ -188,6 +197,8 @@ export type AgentToolsConfig = {
   /** Base tool profile applied before allow/deny lists. */
   profile?: ToolProfileId;
   allow?: string[];
+  /** Additional allowlist entries merged into allow and/or profile allowlist. */
+  alsoAllow?: string[];
   deny?: string[];
   /** Optional tool policy overrides keyed by provider id or "provider/model". */
   byProvider?: Record<string, ToolPolicyConfig>;
@@ -312,6 +323,8 @@ export type ToolsConfig = {
   /** Base tool profile applied before allow/deny lists. */
   profile?: ToolProfileId;
   allow?: string[];
+  /** Additional allowlist entries merged into allow and/or profile allowlist. */
+  alsoAllow?: string[];
   deny?: string[];
   /** Optional tool policy overrides keyed by provider id or "provider/model". */
   byProvider?: Record<string, ToolPolicyConfig>;
diff --git a/src/config/zod-schema.agent-runtime.ts b/src/config/zod-schema.agent-runtime.ts
index c733dcfa9..99074c55e 100644
--- a/src/config/zod-schema.agent-runtime.ts
+++ b/src/config/zod-schema.agent-runtime.ts
@@ -147,13 +147,22 @@ export const SandboxPruneSchema = z
   .strict()
   .optional();
 
-export const ToolPolicySchema = z
+const ToolPolicyBaseSchema = z
   .object({
     allow: z.array(z.string()).optional(),
+    alsoAllow: z.array(z.string()).optional(),
     deny: z.array(z.string()).optional(),
   })
-  .strict()
-  .optional();
+  .strict();
+
+export const ToolPolicySchema = ToolPolicyBaseSchema.superRefine((value, ctx) => {
+  if (value.allow && value.allow.length > 0 && value.alsoAllow && value.alsoAllow.length > 0) {
+    ctx.addIssue({
+      code: z.ZodIssueCode.custom,
+      message: "tools policy cannot set both allow and alsoAllow in the same scope (merge alsoAllow into allow, or remove allow and use profile + alsoAllow)",
+    });
+  }
+}).optional();
 
 export const ToolsWebSearchSchema = z
   .object({
@@ -202,10 +211,20 @@ export const ToolProfileSchema = z
 export const ToolPolicyWithProfileSchema = z
   .object({
     allow: z.array(z.string()).optional(),
+    alsoAllow: z.array(z.string()).optional(),
     deny: z.array(z.string()).optional(),
     profile: ToolProfileSchema,
   })
-  .strict();
+  .strict()
+  .superRefine((value, ctx) => {
+    if (value.allow && value.allow.length > 0 && value.alsoAllow && value.alsoAllow.length > 0) {
+      ctx.addIssue({
+        code: z.ZodIssueCode.custom,
+        message:
+          "tools.byProvider policy cannot set both allow and alsoAllow in the same scope (merge alsoAllow into allow, or remove allow and use profile + alsoAllow)",
+      });
+    }
+  });
 
 // Provider docking: allowlists keyed by provider id (no schema updates when adding providers).
 export const ElevatedAllowFromSchema = z
@@ -231,6 +250,7 @@ export const AgentToolsSchema = z
   .object({
     profile: ToolProfileSchema,
     allow: z.array(z.string()).optional(),
+    alsoAllow: z.array(z.string()).optional(),
     deny: z.array(z.string()).optional(),
     byProvider: z.record(z.string(), ToolPolicyWithProfileSchema).optional(),
     elevated: z
@@ -271,6 +291,15 @@ export const AgentToolsSchema = z
       .optional(),
   })
   .strict()
+  .superRefine((value, ctx) => {
+    if (value.allow && value.allow.length > 0 && value.alsoAllow && value.alsoAllow.length > 0) {
+      ctx.addIssue({
+        code: z.ZodIssueCode.custom,
+        message:
+          "agent tools cannot set both allow and alsoAllow in the same scope (merge alsoAllow into allow, or remove allow and use profile + alsoAllow)",
+      });
+    }
+  })
   .optional();
 
 export const MemorySearchSchema = z
@@ -425,6 +454,7 @@ export const ToolsSchema = z
   .object({
     profile: ToolProfileSchema,
     allow: z.array(z.string()).optional(),
+    alsoAllow: z.array(z.string()).optional(),
     deny: z.array(z.string()).optional(),
     byProvider: z.record(z.string(), ToolPolicyWithProfileSchema).optional(),
     web: ToolsWebSchema,
@@ -507,4 +537,13 @@ export const ToolsSchema = z
       .optional(),
   })
   .strict()
+  .superRefine((value, ctx) => {
+    if (value.allow && value.allow.length > 0 && value.alsoAllow && value.alsoAllow.length > 0) {
+      ctx.addIssue({
+        code: z.ZodIssueCode.custom,
+        message:
+          "tools cannot set both allow and alsoAllow in the same scope (merge alsoAllow into allow, or remove allow and use profile + alsoAllow)",
+      });
+    }
+  })
   .optional();
diff --git a/src/gateway/tools-invoke-http.test.ts b/src/gateway/tools-invoke-http.test.ts
index 18c23692d..f08035885 100644
--- a/src/gateway/tools-invoke-http.test.ts
+++ b/src/gateway/tools-invoke-http.test.ts
@@ -1,12 +1,19 @@
-import { describe, expect, it, vi } from "vitest";
+import { beforeEach, describe, expect, it, vi } from "vitest";
 
 import type { IncomingMessage, ServerResponse } from "node:http";
+
 import { installGatewayTestHooks, getFreePort, startGatewayServer } from "./test-helpers.server.js";
 import { resetTestPluginRegistry, setTestPluginRegistry, testState } from "./test-helpers.mocks.js";
 import { createTestRegistry } from "../test-utils/channel-plugins.js";
 
 installGatewayTestHooks({ scope: "suite" });
 
+beforeEach(() => {
+  // Ensure these tests are not affected by host env vars.
+  delete process.env.CLAWDBOT_GATEWAY_TOKEN;
+  delete process.env.CLAWDBOT_GATEWAY_PASSWORD;
+});
+
 const resolveGatewayToken = (): string => {
   const token = (testState.gatewayAuth as { token?: string } | undefined)?.token;
   if (!token) throw new Error("test gateway token missing");
@@ -47,6 +54,63 @@ describe("POST /tools/invoke", () => {
     await server.close();
   });
 
+  it("supports tools.alsoAllow as additive allowlist (profile stage)", async () => {
+    // No explicit tool allowlist; rely on profile + alsoAllow.
+    testState.agentsConfig = {
+      list: [{ id: "main" }],
+    } as any;
+
+    // minimal profile does NOT include sessions_list, but alsoAllow should.
+    const { writeConfigFile } = await import("../config/config.js");
+    await writeConfigFile({
+      tools: { profile: "minimal", alsoAllow: ["sessions_list"] },
+    } as any);
+
+    const port = await getFreePort();
+    const server = await startGatewayServer(port, { bind: "loopback" });
+    const token = resolveGatewayToken();
+
+    const res = await fetch(`http://127.0.0.1:${port}/tools/invoke`, {
+      method: "POST",
+      headers: { "content-type": "application/json", authorization: `Bearer ${token}` },
+      body: JSON.stringify({ tool: "sessions_list", action: "json", args: {}, sessionKey: "main" }),
+    });
+
+    expect(res.status).toBe(200);
+    const body = await res.json();
+    expect(body.ok).toBe(true);
+
+    await server.close();
+  });
+
+  it("supports tools.alsoAllow without allow/profile (implicit allow-all)", async () => {
+    testState.agentsConfig = {
+      list: [{ id: "main" }],
+    } as any;
+
+    await fs.mkdir(path.dirname(CONFIG_PATH_CLAWDBOT), { recursive: true });
+    await fs.writeFile(
+      CONFIG_PATH_CLAWDBOT,
+      JSON.stringify({ tools: { alsoAllow: ["sessions_list"] } }, null, 2),
+      "utf-8",
+    );
+
+    const port = await getFreePort();
+    const server = await startGatewayServer(port, { bind: "loopback" });
+
+    const res = await fetch(`http://127.0.0.1:${port}/tools/invoke`, {
+      method: "POST",
+      headers: { "content-type": "application/json" },
+      body: JSON.stringify({ tool: "sessions_list", action: "json", args: {}, sessionKey: "main" }),
+    });
+
+    expect(res.status).toBe(200);
+    const body = await res.json();
+    expect(body.ok).toBe(true);
+
+    await server.close();
+  });
+
   it("accepts password auth when bearer token matches", async () => {
     testState.agentsConfig = {
       list: [
diff --git a/src/gateway/tools-invoke-http.ts b/src/gateway/tools-invoke-http.ts
index 80e2f295e..b747e2561 100644
--- a/src/gateway/tools-invoke-http.ts
+++ b/src/gateway/tools-invoke-http.ts
@@ -130,9 +130,22 @@ export async function handleToolsInvokeHttpRequest(
     agentProviderPolicy,
     profile,
     providerProfile,
+    profileAlsoAllow,
+    providerProfileAlsoAllow,
   } = resolveEffectiveToolPolicy({ config: cfg, sessionKey });
   const profilePolicy = resolveToolProfilePolicy(profile);
   const providerProfilePolicy = resolveToolProfilePolicy(providerProfile);
+
+  const mergeAlsoAllow = (policy: typeof profilePolicy, alsoAllow?: string[]) => {
+    if (!policy?.allow || !Array.isArray(alsoAllow) || alsoAllow.length === 0) return policy;
+    return { ...policy, allow: Array.from(new Set([...policy.allow, ...alsoAllow])) };
+  };
+
+  const profilePolicyWithAlsoAllow = mergeAlsoAllow(profilePolicy, profileAlsoAllow);
+  const providerProfilePolicyWithAlsoAllow = mergeAlsoAllow(
+    providerProfilePolicy,
+    providerProfileAlsoAllow,
+  );
   const groupPolicy = resolveGroupToolPolicy({
     config: cfg,
     sessionKey,
@@ -176,18 +189,18 @@ export async function handleToolsInvokeHttpRequest(
     if (resolved.unknownAllowlist.length > 0) {
       const entries = resolved.unknownAllowlist.join(", ");
       const suffix = resolved.strippedAllowlist
-        ? "Ignoring allowlist so core tools remain available."
+        ? "Ignoring allowlist so core tools remain available. Use tools.alsoAllow for additive plugin tool enablement."
         : "These entries won't match any tool unless the plugin is enabled.";
       logWarn(`tools: ${label} allowlist contains unknown entries (${entries}). ${suffix}`);
     }
     return expandPolicyWithPluginGroups(resolved.policy, pluginGroups);
   };
   const profilePolicyExpanded = resolvePolicy(
-    profilePolicy,
+    profilePolicyWithAlsoAllow,
     profile ? `tools.profile (${profile})` : "tools.profile",
   );
   const providerProfileExpanded = resolvePolicy(
-    providerProfilePolicy,
+    providerProfilePolicyWithAlsoAllow,
     providerProfile ? `tools.byProvider.profile (${providerProfile})` : "tools.byProvider.profile",
   );
   const globalPolicyExpanded = resolvePolicy(globalPolicy, "tools.allow");