From 7b891bda66fe8d64f540b994c23af828f194116d Mon Sep 17 00:00:00 2001
From: Rauf Guliyev <rauf.guliyev@e2b.dev>
Date: Wed, 15 Jul 2026 00:02:09 +0000
Subject: [PATCH] fix: send max-steps instruction as user message, not
 assistant

When an agent hits its configured steps cap mid-turn, the loop appended
the "wrap up now" instruction as a role: assistant message, leaving the
outgoing request ending on an assistant turn. Providers that reject
assistant-message prefill bounce this immediately with "This model does
not support assistant message prefill." The instruction is directed at
the model, so it belongs on a user turn, not tacked onto the assistant
role.

Adds a regression test asserting the max-steps message is sent as
role: user.
---
 packages/opencode/src/session/prompt.ts       |  2 +-
 packages/opencode/test/session/prompt.test.ts | 32 +++++++++++++++++++
 2 files changed, 33 insertions(+), 1 deletion(-)

diff --git a/packages/opencode/src/session/prompt.ts b/packages/opencode/src/session/prompt.ts
index eb116f6b960f..88524a05ed56 100644
--- a/packages/opencode/src/session/prompt.ts
+++ b/packages/opencode/src/session/prompt.ts
@@ -1278,7 +1278,7 @@ const layer = Layer.effect(
               system,
               messages: [
                 ...modelMsgs,
-                ...(isLastStep ? [{ role: "assistant" as const, content: MAX_STEPS_PROMPT }] : []),
+                ...(isLastStep ? [{ role: "user" as const, content: MAX_STEPS_PROMPT }] : []),
               ],
               tools,
               model,
diff --git a/packages/opencode/test/session/prompt.test.ts b/packages/opencode/test/session/prompt.test.ts
index 491ad06aaf47..122f39085bbc 100644
--- a/packages/opencode/test/session/prompt.test.ts
+++ b/packages/opencode/test/session/prompt.test.ts
@@ -514,6 +514,38 @@ it.instance("loop calls LLM and returns assistant message", () =>
   }),
 )
 
+it.instance("loop sends max steps instruction as a user message", () =>
+  Effect.gen(function* () {
+    const { llm } = yield* useServerConfig((url) => ({
+      ...providerCfg(url),
+      agent: { build: { steps: 1 } },
+    }))
+    const prompt = yield* SessionPrompt.Service
+    const sessions = yield* Session.Service
+    const chat = yield* sessions.create({ title: "Pinned" })
+    yield* prompt.prompt({
+      sessionID: chat.id,
+      agent: "build",
+      noReply: true,
+      parts: [{ type: "text", text: "hello" }],
+    })
+    yield* llm.text("world")
+
+    yield* prompt.loop({ sessionID: chat.id })
+
+    const hits = yield* llm.hits
+    expect(hits).toHaveLength(1)
+    const messages = hits[0]?.body.messages
+    expect(messages).toBeArray()
+    if (!Array.isArray(messages)) return
+    const maxSteps = messages.find(
+      (message) => JSON.stringify(message).includes("CRITICAL - MAXIMUM STEPS REACHED"),
+    )
+    expect(maxSteps).toMatchObject({ role: "user" })
+  }),
+  30_000,
+)
+
 withMcpInstructions.instance(
   "loop includes MCP instructions in model system context",
   () =>