diff --git a/packages/coding-agent/CHANGELOG.md b/packages/coding-agent/CHANGELOG.md
index e52f011e6..24ccd57a2 100644
--- a/packages/coding-agent/CHANGELOG.md
+++ b/packages/coding-agent/CHANGELOG.md
@@ -42,6 +42,9 @@
 ### Removed
 
 - Removed the bundled plan subagent from available task agents.
+### Fixed
+
+- Fixed advisor config preserving an explicit empty tool list so `/advisor config` can disable all advisor tools. ([#5155](https://github.com/can1357/oh-my-pi/issues/5155))
 
 ## [16.4.2] - 2026-07-10
 
diff --git a/packages/coding-agent/src/advisor/__tests__/advisor.test.ts b/packages/coding-agent/src/advisor/__tests__/advisor.test.ts
index 16911c00b..179756d80 100644
--- a/packages/coding-agent/src/advisor/__tests__/advisor.test.ts
+++ b/packages/coding-agent/src/advisor/__tests__/advisor.test.ts
@@ -1827,6 +1827,19 @@ describe("advisor", () => {
 			expect(text).toContain("read, grep, glob (default)");
 		});
 
+		it("renders an explicit no-tools advisor distinctly from the omitted default", async () => {
+			const uiTheme = await getThemeByName("dark");
+			if (!uiTheme) throw new Error("theme unavailable");
+			setThemeInstance(uiTheme);
+			const overlay = make({
+				advisors: [{ name: "Blank", tools: [] }],
+			});
+
+			const text = strip(overlay.render(200));
+			expect(text.toLowerCase()).toContain("no tools");
+			expect(text).not.toContain("read, grep, glob (default)");
+		});
+
 		it("moves the preview with keyboard selection and preserves an explicit tool set", async () => {
 			const uiTheme = await getThemeByName("dark");
 			if (!uiTheme) throw new Error("theme unavailable");
diff --git a/packages/coding-agent/src/advisor/__tests__/config.test.ts b/packages/coding-agent/src/advisor/__tests__/config.test.ts
index 44d14f936..2875d751f 100644
--- a/packages/coding-agent/src/advisor/__tests__/config.test.ts
+++ b/packages/coding-agent/src/advisor/__tests__/config.test.ts
@@ -56,6 +56,27 @@ describe("discoverAdvisorConfigs", () => {
 		expect(sharedInstructions).toBe("Shared baseline for all advisors.");
 	});
 
+	it("distinguishes omitted tools, explicit no-tools, and invalid-only lists", async () => {
+		const yaml = [
+			"advisors:",
+			"  - name: No Tools",
+			"    tools: []",
+			"  - name: Default Tools",
+			"  - name: Invalid Only",
+			"    tools: [reed]",
+		].join("\n");
+		await Bun.write(path.join(tmp, "WATCHDOG.yml"), yaml);
+
+		const { advisors } = await discoverAdvisorConfigs(tmp, agentDir);
+		const noTools = advisors.find(a => a.name === "No Tools");
+		const defaultTools = advisors.find(a => a.name === "Default Tools");
+		const invalidOnly = advisors.find(a => a.name === "Invalid Only");
+
+		expect(noTools?.tools).toEqual([]);
+		expect(defaultTools?.tools).toBeUndefined();
+		expect(invalidOnly?.tools).toBeUndefined();
+	});
+
 	it("ignores a malformed YAML file without throwing", async () => {
 		await Bun.write(path.join(tmp, "WATCHDOG.yml"), "advisors: [unclosed bracket");
 		const result = await discoverAdvisorConfigs(tmp, agentDir);
@@ -206,6 +227,21 @@ describe("WATCHDOG.yml file round-trip", () => {
 		expect(sharedInstructions).toContain("Shared baseline.");
 	});
 
+	it("round-trips an explicit empty tools list without collapsing it into the default", async () => {
+		const file = path.join(tmp, "WATCHDOG.yml");
+		const explicitNoToolsDoc: WatchdogConfigDoc = {
+			advisors: [{ name: "No Tools", tools: [] }, { name: "Default Tools" }],
+		};
+
+		await saveWatchdogConfigFile(file, explicitNoToolsDoc);
+		const serializedDoc = await loadWatchdogConfigFile(file);
+		expect(serializedDoc).toEqual(explicitNoToolsDoc);
+
+		const { advisors } = await discoverAdvisorConfigs(tmp, tmp);
+		expect(advisors.find(a => a.name === "No Tools")?.tools).toEqual([]);
+		expect(advisors.find(a => a.name === "Default Tools")?.tools).toBeUndefined();
+	});
+
 	it("removes the file when the doc is empty so legacy discovery resumes", async () => {
 		const file = path.join(tmp, "WATCHDOG.yml");
 		await saveWatchdogConfigFile(file, doc);
diff --git a/packages/coding-agent/src/advisor/config.ts b/packages/coding-agent/src/advisor/config.ts
index 1d0f15bb5..ae1633ed2 100644
--- a/packages/coding-agent/src/advisor/config.ts
+++ b/packages/coding-agent/src/advisor/config.ts
@@ -12,9 +12,10 @@ import { collectConfigCandidates } from "./watchdog";
  * with an optional `:level` thinking suffix (e.g. `x-ai/grok-code-fast:high`),
  * resolved exactly like any other model override; `tools` is a subset of
  * `BUILTIN_TOOL_NAMES` — any built-in name, including mutating tools such as
- * `edit`/`write`/`bash` (the advisor is a full agent). Omitted or empty falls
- * back to the default `read`/`grep`/`glob` subset. `instructions` is the
- * advisor's specialization, appended to the shared baseline.
+ * `edit`/`write`/`bash` (the advisor is a full agent). Omitted falls back to
+ * the default `read`/`grep`/`glob` subset; an explicit empty list grants no
+ * tools. `instructions` is the advisor's specialization, appended to the shared
+ * baseline.
  */
 export interface AdvisorConfig {
 	name: string;
@@ -93,11 +94,13 @@ const KNOWN_TOOL_NAMES = new Set<string>(BUILTIN_TOOL_NAMES);
 /**
  * Keep only valid tool names from an advisor's `tools` list, dropping unknowns
  * with a warning. The advisor is a full agent, so any built tool may be granted;
- * the runtime further filters to what's actually available this session. An empty
- * result (or no list) means "use the default subset" (read/grep/glob).
+ * the runtime further filters to what's actually available this session.
+ * `undefined` means "use the default subset" (read/grep/glob); only an explicit
+ * raw empty list means "no tools".
  */
 function filterAdvisorTools(tools: string[] | undefined, sourcePath: string): string[] | undefined {
-	if (!tools || tools.length === 0) return undefined;
+	if (tools === undefined) return undefined;
+	if (tools.length === 0) return [];
 	// Normalize legacy aliases (search→grep, find→glob) and dedupe before validating.
 	const filtered = normalizeToolNames(tools).filter(name => {
 		if (KNOWN_TOOL_NAMES.has(name)) return true;
@@ -238,7 +241,7 @@ export async function loadWatchdogConfigFile(filePath: string): Promise<Watchdog
 		advisors: (result.advisors ?? []).map(a => ({
 			name: a.name,
 			model: a.model?.trim() || undefined,
-			tools: a.tools?.length ? [...a.tools] : undefined,
+			tools: a.tools === undefined ? undefined : [...a.tools],
 			instructions: a.instructions?.trim() ? a.instructions : undefined,
 		})),
 	};
@@ -257,7 +260,7 @@ export function serializeWatchdogConfig(doc: WatchdogConfigDoc): string {
 		out.advisors = doc.advisors.map(a => {
 			const entry: AdvisorConfig = { name: a.name };
 			if (a.model?.trim()) entry.model = a.model;
-			if (a.tools?.length) entry.tools = [...a.tools];
+			if (a.tools !== undefined) entry.tools = [...a.tools];
 			if (a.instructions?.trim()) entry.instructions = a.instructions;
 			return entry;
 		});
diff --git a/packages/coding-agent/src/modes/components/advisor-config.ts b/packages/coding-agent/src/modes/components/advisor-config.ts
index 7f28bc4f9..34750b32f 100644
--- a/packages/coding-agent/src/modes/components/advisor-config.ts
+++ b/packages/coding-agent/src/modes/components/advisor-config.ts
@@ -82,9 +82,9 @@ function previewLine(text: string | undefined): string {
 	return first.length > PREVIEW_WIDTH ? `${first.slice(0, PREVIEW_WIDTH - 1)}…` : first;
 }
 
-/** Default when the set is empty or exactly read/grep/glob; else the available-ordered subset. */
+/** Omitted means default read/grep/glob; an explicit empty set means no tools. */
 function commitTools(selected: ReadonlySet<string>, all: readonly string[]): string[] | undefined {
-	if (selected.size === 0) return undefined;
+	if (selected.size === 0) return [];
 	if (selected.size === ADVISOR_DEFAULT_TOOL_NAMES.size) {
 		let matchesDefault = true;
 		for (const name of ADVISOR_DEFAULT_TOOL_NAMES) {
@@ -98,6 +98,11 @@ function commitTools(selected: ReadonlySet<string>, all: readonly string[]): str
 	return all.filter(name => selected.has(name));
 }
 
+function formatAdvisorTools(tools: readonly string[] | undefined, emptyLabel: string): string {
+	if (tools === undefined) return "read, grep, glob (default)";
+	return tools.length > 0 ? tools.join(", ") : emptyLabel;
+}
+
 /** Soft-wrap plain text to `width`, returning at least one (possibly empty) line. */
 function wrap(text: string, width: number): string[] {
 	if (!text) return [""];
@@ -266,7 +271,7 @@ export class AdvisorConfigOverlayComponent implements Component {
 
 	#advisorPreview(advisor: AdvisorConfig, bodyWidth: number): string[] {
 		const model = advisor.model?.trim() || this.#defaultModelLabel || "advisor role default";
-		const tools = advisor.tools?.length ? advisor.tools.join(", ") : "read, grep, glob (default)";
+		const tools = formatAdvisorTools(advisor.tools, "no tools");
 		const lines = [
 			theme.bold(advisor.name || "(unnamed)"),
 			"",
@@ -303,13 +308,16 @@ export class AdvisorConfigOverlayComponent implements Component {
 		const advisor = doc.advisors[0];
 		if (!advisor) return false;
 		return (
-			advisor.name === "default" && !advisor.model?.trim() && !advisor.tools?.length && !advisor.instructions?.trim()
+			advisor.name === "default" &&
+			!advisor.model?.trim() &&
+			advisor.tools === undefined &&
+			!advisor.instructions?.trim()
 		);
 	}
 
 	#advisorSummary(advisor: AdvisorConfig): string {
 		const model = advisor.model?.trim() || this.#defaultModelLabel || "advisor role default";
-		const tools = advisor.tools?.length ? advisor.tools.join(", ") : "(default: read/grep/glob)";
+		const tools = formatAdvisorTools(advisor.tools, "no tools");
 		return `${model} · ${tools}`;
 	}
 
@@ -384,7 +392,7 @@ export class AdvisorConfigOverlayComponent implements Component {
 			return;
 		}
 		const modelDescription = advisor.model?.trim() || this.#defaultModelLabel || "advisor role default";
-		const toolsDescription = advisor.tools?.length ? advisor.tools.join(", ") : "(default: read/grep/glob)";
+		const toolsDescription = formatAdvisorTools(advisor.tools, "no tools");
 		const items: SelectItem[] = [
 			{ value: "name", label: "Name", description: advisor.name },
 			{ value: "model", label: "Model", description: modelDescription },
@@ -524,7 +532,7 @@ export class AdvisorConfigOverlayComponent implements Component {
 		this.#setScreen(
 			"tools",
 			list,
-			"Enter / click toggle · select Done or Esc to apply (empty or read/grep/glob = default)",
+			"Enter / click toggle · select Done or Esc to apply (empty = no tools; read/grep/glob = default)",
 		);
 	}
 
diff --git a/packages/coding-agent/src/session/agent-session.ts b/packages/coding-agent/src/session/agent-session.ts
index 11c739b5e..381b581f3 100644
--- a/packages/coding-agent/src/session/agent-session.ts
+++ b/packages/coding-agent/src/session/agent-session.ts
@@ -2509,7 +2509,7 @@ export class AgentSession {
 			if (this.#advisorSharedInstructions) systemPrompt.push(this.#advisorSharedInstructions);
 			if (config.instructions?.trim()) systemPrompt.push(config.instructions.trim());
 
-			const names = config.tools?.length ? new Set(config.tools) : ADVISOR_DEFAULT_TOOL_NAMES;
+			const names = config.tools === undefined ? ADVISOR_DEFAULT_TOOL_NAMES : new Set(config.tools);
 			const tools = (this.#advisorTools ?? []).filter(t => names.has(t.name));
 
 			const primaryProviderSessionId = this.sessionId;