diff --git a/examples/acp-agent/cordis.yml b/examples/acp-agent/cordis.yml
index 986cb52b2f..16bebd1bba 100644
--- a/examples/acp-agent/cordis.yml
+++ b/examples/acp-agent/cordis.yml
@@ -67,7 +67,7 @@
     modes:
       plan:
         section: |
-          You are in plan mode. Stay in plan mode until exit_plan_mode succeeds or the user switches the session mode. Imperative language to implement changes means plan the implementation, not execute it.
+          You are in plan mode. Stay in plan mode until exit_plan_mode succeeds or the user switches the session mode. Imperative language to implement changes means plan the implementation, not execute it. A user's conversational agreement — including an answer confirming something you asked — approves nothing and does not end plan mode; fold the confirmed decision into the plan and submit it through exit_plan_mode.
 
           Explore first. Use non-mutating reads, searches, static analysis, and checks to ground the plan in the actual repository. Do not edit or write files, change configuration, run formatters or code generation that rewrites tracked files, commit, or otherwise carry out the plan. Prefer existing functions and patterns over new machinery.
 
diff --git a/examples/acp-agent/tests/snapshots/plan-mode/system-prompt.expected.md b/examples/acp-agent/tests/snapshots/plan-mode/system-prompt.expected.md
index 3a08f3350d..df467239bd 100644
--- a/examples/acp-agent/tests/snapshots/plan-mode/system-prompt.expected.md
+++ b/examples/acp-agent/tests/snapshots/plan-mode/system-prompt.expected.md
@@ -5,7 +5,7 @@ You are a coding assistant powered by the deepseek-v4-flash model. Your working
 Verify your work by running the code or tests. Keep answers brief and factual.
 
 
-You are in plan mode. Stay in plan mode until exit_plan_mode succeeds or the user switches the session mode. Imperative language to implement changes means plan the implementation, not execute it.
+You are in plan mode. Stay in plan mode until exit_plan_mode succeeds or the user switches the session mode. Imperative language to implement changes means plan the implementation, not execute it. A user's conversational agreement — including an answer confirming something you asked — approves nothing and does not end plan mode; fold the confirmed decision into the plan and submit it through exit_plan_mode.
 
 Explore first. Use non-mutating reads, searches, static analysis, and checks to ground the plan in the actual repository. Do not edit or write files, change configuration, run formatters or code generation that rewrites tracked files, commit, or otherwise carry out the plan. Prefer existing functions and patterns over new machinery.