diff --git a/docs/tools/subagents.md b/docs/tools/subagents.md
index f2554e1be..7d0545c18 100644
--- a/docs/tools/subagents.md
+++ b/docs/tools/subagents.md
@@ -30,6 +30,9 @@ Cost note: each sub-agent has its **own** context and token usage. For heavy or
 tasks, set a cheaper model for sub-agents and keep your main agent on a higher-quality model.
 You can configure this via `agents.defaults.subagents.model` or per-agent overrides.
 
+Thinking level: sub-agents inherit the caller's thinking level by default. Override globally
+via `agents.defaults.subagents.thinking` or per-spawn via the `thinking` tool param.
+
 ## Tool
 
 Use `sessions_spawn`:
@@ -102,7 +105,9 @@ Override via config:
   agents: {
     defaults: {
       subagents: {
-        maxConcurrent: 1
+        maxConcurrent: 1,
+        model: "anthropic/claude-haiku-4",
+        thinking: "low"
       }
     }
   },
diff --git a/src/agents/clawdbot-tools.subagents.sessions-spawn-applies-model-child-session.test.ts b/src/agents/clawdbot-tools.subagents.sessions-spawn-applies-model-child-session.test.ts
index 1f27a6530..d4a734c70 100644
--- a/src/agents/clawdbot-tools.subagents.sessions-spawn-applies-model-child-session.test.ts
+++ b/src/agents/clawdbot-tools.subagents.sessions-spawn-applies-model-child-session.test.ts
@@ -195,4 +195,79 @@ describe("moltbot-tools: subagents", () => {
       model: "minimax/MiniMax-M2.1",
     });
   });
+
+  it("sessions_spawn applies default subagent thinking from defaults config", async () => {
+    resetSubagentRegistryForTests();
+    callGatewayMock.mockReset();
+    configOverride = {
+      session: { mainKey: "main", scope: "per-sender" },
+      agents: { defaults: { subagents: { thinking: "medium" } } },
+    };
+    const calls: Array<{ method?: string; params?: unknown }> = [];
+
+    callGatewayMock.mockImplementation(async (opts: unknown) => {
+      const request = opts as { method?: string; params?: unknown };
+      calls.push(request);
+      if (request.method === "agent") {
+        return { runId: "run-default-thinking", status: "accepted" };
+      }
+      return {};
+    });
+
+    const tool = createMoltbotTools({
+      agentSessionKey: "agent:main:main",
+      agentChannel: "discord",
+    }).find((candidate) => candidate.name === "sessions_spawn");
+    if (!tool) throw new Error("missing sessions_spawn tool");
+
+    const result = await tool.execute("call-default-thinking", {
+      task: "do thing",
+    });
+    expect(result.details).toMatchObject({
+      status: "accepted",
+    });
+
+    const agentCall = calls.find((call) => call.method === "agent");
+    expect(agentCall?.params).toMatchObject({
+      thinking: "medium",
+    });
+  });
+
+  it("sessions_spawn tool param thinking overrides config default", async () => {
+    resetSubagentRegistryForTests();
+    callGatewayMock.mockReset();
+    configOverride = {
+      session: { mainKey: "main", scope: "per-sender" },
+      agents: { defaults: { subagents: { thinking: "low" } } },
+    };
+    const calls: Array<{ method?: string; params?: unknown }> = [];
+
+    callGatewayMock.mockImplementation(async (opts: unknown) => {
+      const request = opts as { method?: string; params?: unknown };
+      calls.push(request);
+      if (request.method === "agent") {
+        return { runId: "run-override-thinking", status: "accepted" };
+      }
+      return {};
+    });
+
+    const tool = createMoltbotTools({
+      agentSessionKey: "agent:main:main",
+      agentChannel: "discord",
+    }).find((candidate) => candidate.name === "sessions_spawn");
+    if (!tool) throw new Error("missing sessions_spawn tool");
+
+    const result = await tool.execute("call-override-thinking", {
+      task: "do thing",
+      thinking: "high",
+    });
+    expect(result.details).toMatchObject({
+      status: "accepted",
+    });
+
+    const agentCall = calls.find((call) => call.method === "agent");
+    expect(agentCall?.params).toMatchObject({
+      thinking: "high",
+    });
+  });
 });
diff --git a/src/agents/tools/sessions-spawn-tool.ts b/src/agents/tools/sessions-spawn-tool.ts
index e5e1391d1..19a9ee85b 100644
--- a/src/agents/tools/sessions-spawn-tool.ts
+++ b/src/agents/tools/sessions-spawn-tool.ts
@@ -176,6 +176,10 @@ export function createSessionsSpawnTool(opts?: {
           });
         }
         thinkingOverride = normalized;
+      } else {
+        // Fall back to config defaults if no explicit override
+        thinkingOverride =
+          targetAgentConfig?.subagents?.thinking ?? cfg.agents?.defaults?.subagents?.thinking;
       }
       if (resolvedModel) {
         try {
diff --git a/src/config/types.agent-defaults.ts b/src/config/types.agent-defaults.ts
index 9c6ce0211..ea224869a 100644
--- a/src/config/types.agent-defaults.ts
+++ b/src/config/types.agent-defaults.ts
@@ -204,6 +204,8 @@ export type AgentDefaultsConfig = {
     archiveAfterMinutes?: number;
     /** Default model selection for spawned sub-agents (string or {primary,fallbacks}). */
     model?: string | { primary?: string; fallbacks?: string[] };
+    /** Default thinking level for spawned sub-agents. */
+    thinking?: "off" | "minimal" | "low" | "medium" | "high" | "xhigh";
   };
   /** Optional sandbox settings for non-main sessions. */
   sandbox?: {
diff --git a/src/config/types.tools.ts b/src/config/types.tools.ts
index bb1d45bf0..bb7896fe7 100644
--- a/src/config/types.tools.ts
+++ b/src/config/types.tools.ts
@@ -433,6 +433,8 @@ export type ToolsConfig = {
   subagents?: {
     /** Default model selection for spawned sub-agents (string or {primary,fallbacks}). */
     model?: string | { primary?: string; fallbacks?: string[] };
+    /** Default thinking level for spawned sub-agents. */
+    thinking?: "off" | "minimal" | "low" | "medium" | "high" | "xhigh";
     tools?: {
       allow?: string[];
       deny?: string[];
diff --git a/src/config/zod-schema.agent-defaults.ts b/src/config/zod-schema.agent-defaults.ts
index a849078ed..6f13c7784 100644
--- a/src/config/zod-schema.agent-defaults.ts
+++ b/src/config/zod-schema.agent-defaults.ts
@@ -150,6 +150,16 @@ export const AgentDefaultsSchema = z
               .strict(),
           ])
           .optional(),
+        thinking: z
+          .union([
+            z.literal("off"),
+            z.literal("minimal"),
+            z.literal("low"),
+            z.literal("medium"),
+            z.literal("high"),
+            z.literal("xhigh"),
+          ])
+          .optional(),
       })
       .strict()
       .optional(),