diff --git a/packages/loopover-mcp/bin/loopover-mcp.js b/packages/loopover-mcp/bin/loopover-mcp.js
index 21bf14dfe7..0986eea09c 100755
--- a/packages/loopover-mcp/bin/loopover-mcp.js
+++ b/packages/loopover-mcp/bin/loopover-mcp.js
@@ -64,9 +64,24 @@ const CLI_COMMAND_SPEC = {
 };
 const COMPLETION_SHELLS = ["bash", "zsh", "fish", "powershell"];
 const AGENT_PROFILE_IDS = ["miner-planner", "miner-auto-dev", "maintainer-triage", "repo-owner-intake"];
-// #784 maintain set-level — the autonomy dial's action classes + levels (must mirror src/settings/autonomy.ts).
+// #784 maintain set-level — the autonomy dial's action classes + levels.
+//
+// Both are hand-synced literals, not imports: this file resolves @loopover/engine through the PUBLISHED package
+// (`^3.0.0`), whose export map exposes only `.` + a few `./scoring/*`/`./signals/*` subpaths — neither surfaces
+// AUTONOMY_LEVELS, so importing the canonical list would mean widening the engine's public API (#6153). The
+// drift this invites is real and has bitten once already, so test/unit/mcp-cli-maintain.test.ts pins LEVELS
+// against the live enum and fails the moment the two disagree.
+//
+// LEVELS mirrors AUTONOMY_LEVELS (src/settings/autonomy.ts -> packages/loopover-engine/src/settings/autonomy.ts)
+// exactly. #6153: it carried "suggest"/"propose" for the whole life of #4620, which dropped them server-side --
+// PUT /settings validates against the live enum (src/api/routes.ts), so every value this list accepted but the
+// server didn't turned an immediate, clear client-side error into a confusing 400 from the API.
+//
+// ACTION_CLASSES is deliberately NOT the engine's full AGENT_ACTION_CLASSES: it is the operator-settable subset
+// the maintain surface exposes, and src/mcp/server.ts's MAINTAIN_AUTONOMY_ACTION_CLASSES mirrors these six on
+// purpose. Do not "sync" it to the engine list.
 const MAINTAIN_ACTION_CLASSES = ["review", "request_changes", "approve", "merge", "close", "label"];
-const MAINTAIN_AUTONOMY_LEVELS = ["observe", "suggest", "propose", "auto_with_approval", "auto"];
+const MAINTAIN_AUTONOMY_LEVELS = ["observe", "auto_with_approval", "auto"];
 const AGENT_PROFILES = {
   "miner-planner": {
     id: "miner-planner",
diff --git a/src/mcp/server.ts b/src/mcp/server.ts
index ab0133605e..7665f6a0e6 100644
--- a/src/mcp/server.ts
+++ b/src/mcp/server.ts
@@ -551,11 +551,11 @@ const setAgentPausedOutputSchema = {
   agentPaused: z.boolean().optional(),
 };
 
-// `action` mirrors the CLI's MAINTAIN_ACTION_CLASSES exactly (loopover-mcp.js:65). `level` intentionally
-// validates against the LIVE AUTONOMY_LEVELS (src/settings/autonomy.ts), not the CLI's own stale
-// MAINTAIN_AUTONOMY_LEVELS -- that list still carries "suggest"/"propose", both removed server-side by #4620
-// and silently dropped by normalizeAutonomyPolicy on persist, so accepting them here would report success on a
-// write that never actually took effect.
+// `action` mirrors the CLI's MAINTAIN_ACTION_CLASSES exactly (loopover-mcp.js). `level` validates against the
+// LIVE AUTONOMY_LEVELS (src/settings/autonomy.ts) rather than restating one: "suggest"/"propose" were removed
+// server-side by #4620 and are silently dropped by normalizeAutonomyPolicy on persist, so accepting either here
+// would report success on a write that never actually took effect. (#6153: the CLI's own MAINTAIN_AUTONOMY_LEVELS
+// carried both until then -- binding to the live enum is what kept this surface correct while that one drifted.)
 const MAINTAIN_AUTONOMY_ACTION_CLASSES = ["review", "request_changes", "approve", "merge", "close", "label"] as const;
 
 const setActionAutonomyShape = {
diff --git a/test/unit/mcp-cli-maintain.test.ts b/test/unit/mcp-cli-maintain.test.ts
index 401bf4860b..f80641974b 100644
--- a/test/unit/mcp-cli-maintain.test.ts
+++ b/test/unit/mcp-cli-maintain.test.ts
@@ -1,9 +1,22 @@
-import { mkdtempSync, rmSync } from "node:fs";
+import { mkdtempSync, readFileSync, rmSync } from "node:fs";
 import { tmpdir } from "node:os";
 import { join } from "node:path";
 import { afterEach, describe, expect, it } from "vitest";
+import { AUTONOMY_LEVELS } from "../../src/settings/autonomy";
 import { closeFixtureServer, runAsync, startFixtureServer } from "./support/mcp-cli-harness";
 
+// #6153: MAINTAIN_AUTONOMY_LEVELS is a hand-synced copy of the live enum (the CLI reaches @loopover/engine only
+// through its published export map, which doesn't surface AUTONOMY_LEVELS), so nothing but a test can catch the
+// two drifting apart. The source is parsed rather than imported because bin/loopover-mcp.js is an executable
+// entrypoint that starts a server on import.
+const CLI_SOURCE = readFileSync(join(process.cwd(), "packages/loopover-mcp/bin/loopover-mcp.js"), "utf8");
+
+/** The `maintain set-level` levels the committed CLI source really accepts. */
+function declaredLevels(): string[] {
+  const raw = /const MAINTAIN_AUTONOMY_LEVELS = \[([^\]]*)\];/.exec(CLI_SOURCE)?.[1] ?? "";
+  return [...raw.matchAll(/"([^"]+)"/g)].map((m) => m[1]!);
+}
+
 describe("loopover-mcp CLI — maintain (#784)", () => {
   let tempDir: string | null = null;
 
@@ -92,6 +105,31 @@ describe("loopover-mcp CLI — maintain (#784)", () => {
     await expect(runAsync(["maintain", "set-level", "merge", "bogus", "--repo", "owner/repo"], e)).rejects.toThrow(/Unknown level/);
   }, 45_000);
 
+  // Pins the INVARIANT (the two lists agree), not today's three values -- restating the literal here would just
+  // create a third hand-synced copy that rots alongside the one this guards.
+  it("set-level's levels stay in sync with the live autonomy enum (#6153)", () => {
+    expect(declaredLevels()).toEqual([...AUTONOMY_LEVELS]);
+  });
+
+  // #6153 regression: the CLI accepted "suggest"/"propose" for the whole life of #4620, which dropped them
+  // server-side. The fixture's PUT /settings echoes any autonomy body back as a success, exactly like a server
+  // with no enum -- so a rejection here can only have come from the CLI's own check, before any round-trip.
+  it("rejects levels #4620 removed server-side, client-side rather than via a 400 (#6153)", async () => {
+    const e = await env();
+    for (const removed of ["suggest", "propose"]) {
+      // Derived from the live enum for the same reason as above: the point is that the error names exactly the
+      // levels the server accepts, not that it names three particular strings.
+      await expect(runAsync(["maintain", "set-level", "review", removed, "--repo", "owner/repo"], e)).rejects.toThrow(
+        new RegExp(`Unknown level: ${removed}\\. Use ${AUTONOMY_LEVELS.join(", ")}\\.`),
+      );
+    }
+    // The dial still accepts every level the server does -- the fix narrowed the list, it didn't break it.
+    const json = JSON.parse(await runAsync(["maintain", "set-level", "review", "observe", "--repo", "owner/repo", "--json"], e)) as {
+      autonomy: Record<string, string>;
+    };
+    expect(json.autonomy).toMatchObject({ review: "observe" });
+  }, 45_000);
+
   it("prints help when invoked with no subcommand", async () => {
     const e = await env();
     const out = await runAsync(["maintain"], e);