diff --git a/.changeset/empty-hoops-tie.md b/.changeset/empty-hoops-tie.md
new file mode 100644
index 0000000..93c3abe
--- /dev/null
+++ b/.changeset/empty-hoops-tie.md
@@ -0,0 +1,5 @@
+---
+"opencode-adaptive-thinking": patch
+---
+
+Preserve the active agent when synthetic prompts adjust reasoning effort and when temporary overrides reset after a session becomes idle. This prevents OpenCode from routing follow-up work to the default agent instead of the agent that initiated the change.
diff --git a/src/index.test.ts b/src/index.test.ts
index a059845..7c13359 100644
--- a/src/index.test.ts
+++ b/src/index.test.ts
@@ -117,6 +117,21 @@ describe("AdaptiveThinkingPlugin", () => {
     expect(system[0]).toContain("set_reasoning_effort");
   });
 
+  test("preserves the calling agent when setting reasoning effort", async () => {
+    const sessionID = "preserve-agent";
+    const { client, toolContext } = createClient(sessionID, [createMessage("medium")]);
+    toolContext.agent = "custom-worker";
+    const plugin = await AdaptiveThinkingPlugin({ client } as never);
+
+    await setReasoningEffort(plugin, { level: "high", persist: true }, toolContext);
+
+    expect(client.session.promptAsync).toHaveBeenCalledWith(
+      expect.objectContaining({
+        body: expect.objectContaining({ agent: "custom-worker", variant: "high" }),
+      }),
+    );
+  });
+
   test("returns no hooks when disabled", async () => {
     const { client } = createClient("disabled-plugin");
     const plugin = await AdaptiveThinkingPlugin({ client } as never, { enabled: false });
@@ -298,6 +313,7 @@ describe("AdaptiveThinkingPlugin", () => {
     const secondPrompt = promptCalls[1]?.[0];
     expect(secondPrompt).toMatchObject({
       body: {
+        agent: "agent",
         variant: "medium",
         parts: [{ ignored: true, synthetic: true }],
       },
diff --git a/src/index.ts b/src/index.ts
index ec6cc14..48ae69b 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -11,6 +11,7 @@ type SessionState = {
   currentVariant?: string;
   persistedVariant?: string;
   temporaryResetVariant?: string;
+  temporaryResetAgent?: string;
 };
 
 class SessionStateCache {
@@ -83,6 +84,7 @@ export const AdaptiveThinkingPlugin: Plugin = async ({ client }, options) => {
     sessionID: string,
     variant: string,
     text: string,
+    agent: string,
     ignored = true,
   ) => {
     const body: PromptAsyncBody = {
@@ -95,6 +97,7 @@ export const AdaptiveThinkingPlugin: Plugin = async ({ client }, options) => {
           ignored,
         },
       ],
+      agent,
       variant,
     };
 
@@ -212,7 +215,7 @@ export const AdaptiveThinkingPlugin: Plugin = async ({ client }, options) => {
               "Whether to persist the setting for this session, otherwise it will only apply for the remainder of the current turn",
             ),
         },
-        execute: async ({ level, persist }, { sessionID }) => {
+        execute: async ({ level, persist }, { sessionID, agent }) => {
           const validVariants = await resolveValidVariants(sessionID);
           if (validVariants.length === 0) {
             return "Failed to set reasoning effort: no valid reasoning effort levels are available for this session";
@@ -230,6 +233,7 @@ export const AdaptiveThinkingPlugin: Plugin = async ({ client }, options) => {
             sessionID,
             level,
             `Reasoning effort set to ${level}`,
+            agent,
           );
           if (promptResponse.error) {
             return `Failed to set reasoning effort: ${JSON.stringify(promptResponse.error.data)}`;
@@ -240,10 +244,13 @@ export const AdaptiveThinkingPlugin: Plugin = async ({ client }, options) => {
             if (persist) {
               entry.persistedVariant = level;
               delete entry.temporaryResetVariant;
+              delete entry.temporaryResetAgent;
             } else if (resetVariant && resetVariant !== level) {
               entry.temporaryResetVariant = resetVariant;
+              entry.temporaryResetAgent = agent;
             } else {
               delete entry.temporaryResetVariant;
+              delete entry.temporaryResetAgent;
             }
           });
 
@@ -256,12 +263,14 @@ export const AdaptiveThinkingPlugin: Plugin = async ({ client }, options) => {
         const sessionID = event.properties.sessionID;
         const sessionState = state.get(sessionID);
         const resetVariant = sessionState?.temporaryResetVariant;
-        if (!resetVariant) return;
+        const resetAgent = sessionState?.temporaryResetAgent;
+        if (!resetVariant || !resetAgent) return;
 
         const promptResponse = await sendVariantPrompt(
           sessionID,
           resetVariant,
           `Reasoning effort reset to ${resetVariant}.`,
+          resetAgent,
         );
         if (promptResponse.error) {
           client.app.log({
@@ -277,6 +286,7 @@ export const AdaptiveThinkingPlugin: Plugin = async ({ client }, options) => {
         state.update(sessionID, (entry) => {
           entry.currentVariant = resetVariant;
           delete entry.temporaryResetVariant;
+          delete entry.temporaryResetAgent;
         });
         return;
       }