diff --git a/packages/opencode/src/session/llm.ts b/packages/opencode/src/session/llm.ts
index 565d037f4..f95690420 100644
--- a/packages/opencode/src/session/llm.ts
+++ b/packages/opencode/src/session/llm.ts
@@ -80,6 +80,7 @@ export namespace LLM {
           ? (input.agent.temperature ?? ProviderTransform.temperature(input.model))
           : undefined,
         topP: input.agent.topP ?? ProviderTransform.topP(input.model),
+        topK: ProviderTransform.topK(input.model),
         options: pipe(
           {},
           mergeDeep(ProviderTransform.options(input.model, input.sessionID)),
@@ -132,6 +133,7 @@ export namespace LLM {
       },
       temperature: params.temperature,
       topP: params.topP,
+      topK: params.topK,
       providerOptions: ProviderTransform.providerOptions(input.model, params.options),
       activeTools: Object.keys(tools).filter((x) => x !== "invalid"),
       tools,
diff --git a/packages/plugin/src/index.ts b/packages/plugin/src/index.ts
index 9dd4820b9..ef06a4d8b 100644
--- a/packages/plugin/src/index.ts
+++ b/packages/plugin/src/index.ts
@@ -161,7 +161,7 @@ export interface Hooks {
    */
   "chat.params"?: (
     input: { sessionID: string; agent: string; model: Model; provider: ProviderContext; message: UserMessage },
-    output: { temperature: number; topP: number; options: Record<string, any> },
+    output: { temperature: number; topP: number; topK: number; options: Record<string, any> },
   ) => Promise<void>
   "permission.ask"?: (input: Permission, output: { status: "ask" | "deny" | "allow" }) => Promise<void>
   "tool.execute.before"?: (