Plan mode leave reminder becomes the final user turn after a tool-driven agent switch, models refuse #57013

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1. opencode-agent commented on Oct 19, 2026

   

   opencode-agentBot

   on Oct 19, 2026 – with OpenCode Agent

   Contributor

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   Thanks for the detailed report. I reproduced this on 2.0.32 and on the latest dev (ba06ff9e0b).

   To reproduce, I started a session in Plan and switched it to build through the server API while the first model request was still running, standing in for Plannotator's submit_plan. The model then made a tool call. The next request ended like this:

   ... user > assistant(tool_call) > tool(result) > user("<system-reminder> You are NO LONGER in Plan mode … </system-reminder>")

   It ends with a user turn that contains only the leave reminder, as you described. In this run, that message is the synthetic reminder saved by the plan plugin when the agent switches, not one added by the context hook, so a fix also has to move a reminder that is already saved at the end. Your patch says it handles that case.

   I used a simulated model, so I could not confirm the gpt-5.3-codex refusal itself, only the message order that causes it. The script below reproduces the problem.

   Reproduction script (drive.ts)

   // Repro for #57013: after a mid-turn switch from `plan` to `build` (as a plan-approval
   // plugin does from inside a tool call), the next model request ends with a user
   // message containing only the "NO LONGER in Plan mode" reminder.
   import { Effect, Stream } from "effect"
   import { Llm, OpenCodeDriver } from "opencode-drive"
   
   const bodies: unknown[] = []
   
   export default OpenCodeDriver.use(
     {
       ...(process.env.OC_DEV ? { opencode: { dev: process.env.OC_DEV } } : {}),
       tui: { recording: true },
       project: { git: true, files: { "PLAN.md": "1. do the thing\n" } },
     },
     ({ ui, llm, opencode }) =>
       Effect.gen(function* () {
         yield* llm.serve((request, index) => {
           bodies.push(request.body)
           if (index === 0)
             return Stream.unwrap(
               Effect.gen(function* () {
                 // Stand-in for Plannotator's submit_plan: switch plan -> build while the turn is running.
                 const list: any = yield* opencode.session.list()
                 const items = list.items ?? list.data ?? list
                 const id = items[0].id
                 yield* opencode.session.switchAgent({ sessionID: id, agent: "build" } as any)
                 yield* Effect.sleep("500 millis")
                 return Stream.make(
                   Llm.toolCall({ index: 0, id: "call_read", name: "read", input: { path: "PLAN.md" } }),
                   Llm.finish("tool-calls"),
                 )
               }).pipe(Effect.orDie),
             )
           return Stream.make(Llm.text("Implementing the approved plan now."))
         })
         yield* ui.press("tab", { shift: true }) // switch the TUI agent to Plan
         yield* Effect.sleep("500 millis")
         yield* ui.screenshot("plan-agent")
         yield* ui.submit("Read PLAN.md and get it approved")
         yield* ui.waitFor("Implementing the approved plan now.")
         yield* ui.screenshot("after")
         bodies.forEach((b: any, i) => console.log(`REQ ${i} roles:`, b.messages.map((m: any) => m.role + (JSON.stringify(m.content ?? "").includes("Plan mode") ? (JSON.stringify(m.content).includes("NO LONGER") ? "[LEAVE]" : "[ENTER]") : "")).join(" > ")))
         const last: any = bodies[1]
         const msgs = last.messages ?? last.input ?? last.contents
         console.log("REQUEST #2 URL-shaped body keys:", Object.keys(last))
         console.log("REQUEST #2 TAIL:", JSON.stringify(msgs.slice(-3), null, 2))
       }),
   )

   Run it with opencode-drive: opencode-drive run ./drive.ts. It drives opencode from your PATH; set OC_DEV to the path of an OpenCode checkout to run that from source instead.
2. opencode-agent

   added

   reproduced

   on Oct 19, 2026