diff --git a/packages/opencode/src/session/index.ts b/packages/opencode/src/session/index.ts
index a8586362..24cffdef 100644
--- a/packages/opencode/src/session/index.ts
+++ b/packages/opencode/src/session/index.ts
@@ -17,6 +17,7 @@ import {
 
 import PROMPT_INITIALIZE from "../session/prompt/initialize.txt"
 import PROMPT_PLAN from "../session/prompt/plan.txt"
+import BUILD_SWITCH from "../session/prompt/build-switch.txt"
 
 import { App } from "../app/app"
 import { Bus } from "../bus"
@@ -734,7 +735,7 @@ export namespace Session {
         messageID: userMsg.id,
         sessionID: input.sessionID,
         type: "text",
-        text: "You are now in build mode and are permitted to make edits",
+        text: BUILD_SWITCH,
         synthetic: true,
       })
     }
diff --git a/packages/opencode/src/session/prompt/build-switch.txt b/packages/opencode/src/session/prompt/build-switch.txt
new file mode 100644
index 00000000..0b70fa57
--- /dev/null
+++ b/packages/opencode/src/session/prompt/build-switch.txt
@@ -0,0 +1 @@
+Your operational mode has changed from plan to build. You are no longer in read-only mode. You are permitted to make file changes as necessary and utilize your arsenal of tools as needed.