From 32e4beffd9fd1a00b5d84ae5020ea6c7f5257585 Mon Sep 17 00:00:00 2001
From: Kailigithub <12250313+Kailigithub@users.noreply.github.com>
Date: Fri, 31 Jul 2026 03:08:12 +0800
Subject: [PATCH] fix(agent_loop): apply agent_before hook return value to
 context (closes #537)
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plugins/hooks.py::trigger() already supports returning a dict to mutate
agent context, but agent_runner_loop() discarded the return value of
_hook('agent_before', ...). Plugins returning updated system_prompt,
user_input, or initial_user_content had their changes silently dropped.

When the hook returns a dict, apply system_prompt to messages[0] and
user_input (or initial_user_content when set) to messages[1]. Backward
compatible: hooks returning None or non-dict values leave messages
unchanged, so existing read-only hooks (logging, telemetry, langfuse)
keep working without modification.

Verification: /tmp/test_issue_537.py — 4 cases (system_prompt override,
legacy None-return, non-dict return, user_input override). All pass on
the fixed code, Test 1 fails on main (messages[0] == 'ORIGINAL prompt'
without '[AUGMENTED]' suffix).
---
 agent_loop.py | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/agent_loop.py b/agent_loop.py
index a744f0d26..494db9f5c 100644
--- a/agent_loop.py
+++ b/agent_loop.py
@@ -46,7 +46,14 @@ def agent_runner_loop(client, system_prompt, user_input, handler, tools_schema,
         {"role": "user", "content": initial_user_content if initial_user_content is not None else user_input}
     ]
     turn = 0;  handler.max_turns = max_turns
-    _hook('agent_before', locals())
+    _ctx = _hook('agent_before', locals())
+    if isinstance(_ctx, dict):
+        if 'system_prompt' in _ctx:
+            messages[0]['content'] = _ctx['system_prompt']
+        if _ctx.get('initial_user_content') is not None:
+            messages[1]['content'] = _ctx['initial_user_content']
+        elif 'user_input' in _ctx and initial_user_content is None:
+            messages[1]['content'] = _ctx['user_input']
     while turn < handler.max_turns:
         turn += 1; turnstr = f'LLM Running (Turn {turn}) ...'
         if handler.parent.task_dir: turnstr = f'Turn {turn} ...'