From bc12f1d33338c486c76dc3954031b1b1b3c7b0e2 Mon Sep 17 00:00:00 2001
From: Niklas Kahn <niklas@neatminds.se>
Date: Tue, 17 Feb 2026 21:47:47 +0100
Subject: [PATCH] fix: use chat.message hook instead of chat.params for context
 injection
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chat.params receives (input, output) where output only exposes
{temperature, topP, options} — no system prompt or message text.
The plugin was treating the first arg as a wrapper object and
accessing params.input.message.text, which was always undefined,
causing context injection to silently bail on every message.

Switch to chat.message hook which provides output.message.system
(the system prompt) and output.parts (user message TextParts),
matching the OpenCode plugin API contract.
---
 README.md         |  2 +-
 package-lock.json |  4 ++--
 package.json      |  2 +-
 src/index.ts      | 27 ++++++++++++++-------------
 4 files changed, 18 insertions(+), 17 deletions(-)

diff --git a/README.md b/README.md
index 6bab1f6..bb7ddaf 100644
--- a/README.md
+++ b/README.md
@@ -120,7 +120,7 @@ Restart OpenCode. The plugin will automatically load.
 │                                                      │
 │  Hooks:                                              │
 │  ┌─────────────────┐      ┌────────────────────┐     │
-│  │  chat.params    │─────▶│ Context Injection  │     │
+│  │  chat.message   │─────▶│ Context Injection  │     │
 │  │  (pre-LLM)      │      │ - Golden Rules     │     │
 │  │                 │      │ - Past Learnings   │     │
 │  │                 │      │ - Heuristics       │     │
diff --git a/package-lock.json b/package-lock.json
index 0e37efe..e049e66 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -1,12 +1,12 @@
 {
   "name": "opencode-elf",
-  "version": "0.5.3",
+  "version": "0.6.0",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "opencode-elf",
-      "version": "0.5.3",
+      "version": "0.6.0",
       "license": "MIT",
       "dependencies": {
         "@libsql/client": "^0.14.0",
diff --git a/package.json b/package.json
index cad4f94..f9fc39b 100644
--- a/package.json
+++ b/package.json
@@ -51,7 +51,7 @@
   "opencode": {
     "type": "plugin",
     "hooks": [
-      "chat.params",
+      "chat.message",
       "event"
     ]
   },
diff --git a/src/index.ts b/src/index.ts
index 6896333..34cacf7 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -75,18 +75,21 @@ export const ELFPlugin: Plugin = async ({ directory }: PluginInput) => {
   // 3. Return hooks immediately
   return {
     /**
-     * Chat params hook - Inject ELF context before the LLM processes the message
+     * Chat message hook - Inject ELF context into system prompt before LLM processing
      */
-    "chat.params": async (params: Record<string, unknown>) => {
+    "chat.message": async (input, output) => {
       const start = Date.now();
 
       try {
         // Wait for init to finish (only affects the very first message)
         await ensureReady();
 
-        const input = params.input as Record<string, unknown> | undefined;
-        const message = input?.message as Record<string, unknown> | undefined;
-        const userMessage = message?.text as string | undefined;
+        // Extract user text from message parts (TextParts have type "text" and a text field)
+        const userMessage = output.parts
+          .filter((p): p is Extract<typeof p, { type: "text" }> => p.type === "text")
+          .map(p => p.text)
+          .join("\n")
+          .trim();
 
         if (!userMessage) return;
 
@@ -110,13 +113,11 @@ export const ELFPlugin: Plugin = async ({ directory }: PluginInput) => {
           context.relevantLearnings.length > 0 ||
           context.heuristics.length > 0) {
 
-          // Inject into system prompt or prepend to user message
-          const systemPrompt = input?.systemPrompt as string | undefined;
-          if (systemPrompt && input) {
-            input.systemPrompt = `${systemPrompt}\n\n${elfMemory}`;
-          } else if (message) {
-            message.text = `${elfMemory}\n\n${userMessage}`;
-          }
+          // Inject into the system prompt via output.message.system
+          const currentSystem = output.message.system || "";
+          output.message.system = currentSystem
+            ? `${currentSystem}\n\n${elfMemory}`
+            : elfMemory;
 
           // Record metrics
           const duration = Date.now() - start;
@@ -129,7 +130,7 @@ export const ELFPlugin: Plugin = async ({ directory }: PluginInput) => {
         }
       } catch (error) {
         // Fail open: If ELF fails, log it but don't break the user's chat
-        console.error("ELF: Error in chat.params hook", error);
+        console.error("ELF: Error in chat.message hook", error);
       }
     },