Add chat.messages.transform plugin hook

bun.lock

@@ -298,6 +298,7 @@
       "version": "1.0.120",
       "dependencies": {
         "@opencode-ai/sdk": "workspace:*",
+        "ai": "catalog:",
         "zod": "catalog:",
       },
       "devDependencies": {

nix/hashes.json

@@ -1,3 +1,3 @@
 {
-  "nodeModules": "sha256-4OrnnZy44edgShLMUrYFsO+07gAnL//pGKO/ehWu5P4="
+  "nodeModules": "sha256-YQs8rwprLClmuwEkS952jTvC7QCZtAnR9NmI2Azr9jA="
 }

packages/opencode/src/session/prompt.ts

@@ -513,6 +513,33 @@ export namespace SessionPrompt {
         })
       }
 
+      // Build messages array for the LLM request
+      const messages: ModelMessage[] = [
+        ...system.map(
+          (x): ModelMessage => ({
+            role: "system",
+            content: x,
+          }),
+        ),
+        ...MessageV2.toModelMessage(
+          msgs.filter((m) => {
+            if (m.info.role !== "assistant" || m.info.error === undefined) {
+              return true
+            }
+            if (
+              MessageV2.AbortedError.isInstance(m.info.error) &&
+              m.parts.some((part) => part.type !== "step-start" && part.type !== "reasoning")
+            ) {
+              return true
+            }
+
+            return false
+          }),
+        ),
+      ]
+
+      await Plugin.trigger("chat.messages.transform", {}, { messages })
+
       const result = await processor.process(() =>
         streamText({
           onError(error) {
@@ -564,29 +591,7 @@ export namespace SessionPrompt {
           stopWhen: stepCountIs(1),
           temperature: params.temperature,
           topP: params.topP,
-          messages: [
-            ...system.map(
-              (x): ModelMessage => ({
-                role: "system",
-                content: x,
-              }),
-            ),
-            ...MessageV2.toModelMessage(
-              msgs.filter((m) => {
-                if (m.info.role !== "assistant" || m.info.error === undefined) {
-                  return true
-                }
-                if (
-                  MessageV2.AbortedError.isInstance(m.info.error) &&
-                  m.parts.some((part) => part.type !== "step-start" && part.type !== "reasoning")
-                ) {
-                  return true
-                }
-
-                return false
-              }),
-            ),
-          ],
+          messages,
           tools: model.info.tool_call === false ? undefined : tools,
           model: wrapLanguageModel({
             model: model.language,

packages/plugin/package.json

@@ -16,6 +16,7 @@
   ],
   "dependencies": {
     "@opencode-ai/sdk": "workspace:*",
+    "ai": "catalog:",
     "zod": "catalog:"
   },
   "devDependencies": {

packages/plugin/src/index.ts

@@ -169,4 +169,10 @@ export interface Hooks {
       metadata: any
     },
   ) => Promise<void>
+  "chat.messages.transform"?: (
+    input: {},
+    output: {
+      messages: import("ai").ModelMessage[]
+    },
+  ) => Promise<void>
 }