diff --git a/packages/opencode/src/session/llm.ts b/packages/opencode/src/session/llm.ts
index c5792c16dea..9cd40f30221 100644
--- a/packages/opencode/src/session/llm.ts
+++ b/packages/opencode/src/session/llm.ts
@@ -73,7 +73,7 @@ export namespace LLM {
 
     const header = system[0]
     const original = clone(system)
-    await Plugin.trigger("experimental.chat.system.transform", {}, { system })
+    await Plugin.trigger("experimental.chat.system.transform", { sessionID: input.sessionID }, { system })
     if (system.length === 0) {
       system.push(...original)
     }
diff --git a/packages/plugin/src/index.ts b/packages/plugin/src/index.ts
index 46ad8512c68..e57eff579e6 100644
--- a/packages/plugin/src/index.ts
+++ b/packages/plugin/src/index.ts
@@ -195,7 +195,7 @@ export interface Hooks {
     },
   ) => Promise<void>
   "experimental.chat.system.transform"?: (
-    input: {},
+    input: { sessionID: string },
     output: {
       system: string[]
     },