diff --git a/packages/coding-agent/src/tools/index.ts b/packages/coding-agent/src/tools/index.ts
index 2a29c605c..a96477dac 100644
--- a/packages/coding-agent/src/tools/index.ts
+++ b/packages/coding-agent/src/tools/index.ts
@@ -11,7 +11,7 @@ import type { HindsightSessionState } from "../hindsight/state";
 import type { InternalUrlRouter } from "../internal-urls";
 import { LspTool } from "../lsp";
 import type { PlanModeState } from "../plan-mode/state";
-import type { AgentRegistry } from "../registry/agent-registry";
+import { type AgentRegistry, MAIN_AGENT_ID } from "../registry/agent-registry";
 import type { CustomMessage } from "../session/messages";
 import type { ToolChoiceQueue } from "../session/tool-choice-queue";
 import { TaskTool } from "../task";
@@ -443,7 +443,13 @@ export async function createTools(session: ToolSession, toolNames?: string[]): P
 		if (name === "calc") return session.settings.get("calc.enabled");
 		if (name === "browser") return session.settings.get("browser.enabled");
 		if (name === "checkpoint" || name === "rewind") return session.settings.get("checkpoint.enabled");
-		if (name === "irc") return session.settings.get("irc.enabled");
+		if (name === "irc") {
+			if (!session.settings.get("irc.enabled")) return false;
+			// Main agent only needs `irc` when subagents may run concurrently (async).
+			// In sync mode main blocks on `task`, so peer messaging from main is dead weight.
+			if (!session.settings.get("async.enabled") && session.getAgentId?.() === MAIN_AGENT_ID) return false;
+			return true;
+		}
 		if (name === "recipe") return session.settings.get("recipe.enabled");
 		if (name === "retain" || name === "recall" || name === "reflect") {
 			return session.settings.get("memory.backend") === "hindsight";