diff --git a/packages/server/src/server/agent/providers/omp/agent.test.ts b/packages/server/src/server/agent/providers/omp/agent.test.ts
index 794dc41278..f31cb4d995 100644
--- a/packages/server/src/server/agent/providers/omp/agent.test.ts
+++ b/packages/server/src/server/agent/providers/omp/agent.test.ts
@@ -677,6 +677,35 @@ describe("OMP agent client and session", () => {
     expect(session.controls).toHaveLength(1);
   });
 
+  test("a Fast change OMP makes by itself replaces the held fast_mode option", async () => {
+    const omp = new OmpHarness();
+    await omp.start({ model: "openai/gpt-5" });
+    const session = omp.requireSession();
+    const events: AgentStreamEvent[] = [];
+    session.subscribe((event) => events.push(event));
+    omp.runtime().fastModeResult = { enabled: true, active: true };
+    await session.applyOptions?.({ fast_mode: true });
+
+    // Another model family has its own Fast tier, which is unset.
+    omp.runtime().setModelResult = { provider: "anthropic", id: "claude-x" };
+    omp.runtime().queueStateReports([
+      {
+        ...omp.runtime().state,
+        model: omp.runtime().setModelResult,
+        fastModeEnabled: false,
+        fastModeActive: false,
+      },
+    ]);
+    await session.setModel?.("anthropic/claude-x");
+
+    expect(events.filter((event) => event.type === "options_changed")).toEqual([
+      { type: "options_changed", provider: "omp", patch: { fast_mode: false } },
+    ]);
+    // The options the manager now holds leave the runtime alone.
+    await session.applyOptions?.({ fast_mode: false });
+    expect(omp.runtime().setFastModeRequests).toEqual([true]);
+  });
+
   test("switching model refreshes whether Fast applies", async () => {
     const omp = new OmpHarness();
     await omp.start({ model: "openrouter/google/gemini-3.8-flash" });
diff --git a/packages/server/src/server/agent/providers/omp/agent.ts b/packages/server/src/server/agent/providers/omp/agent.ts
index 1bcf34d7f3..974d56f8d4 100644
--- a/packages/server/src/server/agent/providers/omp/agent.ts
+++ b/packages/server/src/server/agent/providers/omp/agent.ts
@@ -2247,6 +2247,23 @@ export class OmpAgentSession implements AgentSession {
 
   private async refreshState(): Promise<void> {
     this.state = await this.runtimeSession.getState();
+    this.followRuntimeFastMode();
+  }
+
+  /**
+   * OMP tracks Fast per model family, so switching models can change it. A held `fast_mode`
+   * option follows what the runtime reports; with no option held, the control's default shows it.
+   */
+  private followRuntimeFastMode(): void {
+    const held = this.config.providerOptions?.fast_mode;
+    const reported = this.state.fastModeEnabled;
+    if (typeof held !== "boolean" || typeof reported !== "boolean" || held === reported) return;
+    this.config.providerOptions = { ...this.config.providerOptions, fast_mode: reported };
+    this.emit({
+      type: "options_changed",
+      provider: this.provider,
+      patch: { fast_mode: reported },
+    });
   }
 
   private async refreshAfterTurn(finalUsage: Promise<void>): Promise<void> {