diff --git a/src/muse-settings.ts b/src/muse-settings.ts
index 1e5bfc3..b970ab8 100644
--- a/src/muse-settings.ts
+++ b/src/muse-settings.ts
@@ -1,6 +1,7 @@
 import { readFileSync } from "node:fs";
 import { homedir } from "node:os";
 import { join } from "node:path";
+import { EFFORT_LEVELS, isReasoningEffort } from "./config-options.js";
 import { Logger } from "./logger.js";
 
 /**
@@ -36,10 +37,20 @@ export function readMuseSettings(
     return {};
   }
   const settings = raw as Record<string, unknown>;
+  const reasoningEffort =
+    typeof settings.reasoning_effort === "string" ? settings.reasoning_effort : undefined;
+  // The muse CLI documents efforts this adapter cannot carry (`max`), so a
+  // value copied from `muse exec --help` would otherwise fall back to the
+  // default with nothing said anywhere.
+  if (reasoningEffort !== undefined && !isReasoningEffort(reasoningEffort)) {
+    logger.log(
+      `muse settings at ${path}: unknown reasoning_effort "${reasoningEffort}"; ` +
+        `using the default (supported: ${EFFORT_LEVELS.join(", ")})`,
+    );
+  }
   return {
     provider: typeof settings.provider === "string" ? settings.provider : undefined,
     model: typeof settings.model === "string" ? settings.model : undefined,
-    reasoningEffort:
-      typeof settings.reasoning_effort === "string" ? settings.reasoning_effort : undefined,
+    reasoningEffort,
   };
 }
diff --git a/src/tests/muse-settings.test.ts b/src/tests/muse-settings.test.ts
index 12f6b7f..2d02806 100644
--- a/src/tests/muse-settings.test.ts
+++ b/src/tests/muse-settings.test.ts
@@ -31,6 +31,26 @@ describe("readMuseSettings edge cases", () => {
     expect(lines.some((line) => line.includes("is not an object"))).toBe(true);
   });
 
+  it("reports a reasoning_effort the adapter cannot carry", () => {
+    const lines: string[] = [];
+    expect(
+      readMuseSettings(
+        settingsEnv(JSON.stringify({ reasoning_effort: "max" })),
+        capturingLogger(lines),
+      ),
+    ).toEqual({ reasoningEffort: "max" });
+    expect(lines.some((line) => line.includes('unknown reasoning_effort "max"'))).toBe(true);
+  });
+
+  it("stays quiet on a reasoning_effort it supports", () => {
+    const lines: string[] = [];
+    readMuseSettings(
+      settingsEnv(JSON.stringify({ reasoning_effort: "xhigh" })),
+      capturingLogger(lines),
+    );
+    expect(lines.some((line) => line.includes("reasoning_effort"))).toBe(false);
+  });
+
   it("ignores non-string fields while keeping valid ones", () => {
     expect(
       readMuseSettings(