tui: model switch races session creation and gets a Session not found toast #57354

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1. opencode-agent commented on Oct 20, 2026

   

   opencode-agentBot

   on Oct 20, 2026 – with OpenCode Agent

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   Thanks for the detailed report! I reproduced this on 2.1.0, and it still happens on the latest dev (d30e990).

   Steps:

   1. From the home route, send a prompt. This creates a new session and opens it in a tab.
   2. About 150 ms later, while the create request is still in flight, press Enter with the composer empty in that tab.
   3. The red toast Failed to prepare session / Failed to switch model: Session not found: ses_… appears.

   On Linux the create is normally too fast to hit this. To widen the window, the script below adds random network delay between the TUI and the server, so the model switch can reach the server before the create. The race only shows some of the time, so the script may need a few runs. The recording and screenshots below show the toast.

   As you pointed out, prompts already wait for the in-flight create (sendAdmission in packages/client/src/solid/data.ts). The composer's agent/model commit in packages/tui/src/component/prompt/index.tsx calls switchAgent/switchModel directly, without waiting.

   recording.mp4

   

   

   Reproduction script (drive.ts)

   // Reproduces anomalyco/opencode#57354: an empty Enter in a freshly created
   // session tab sends POST /api/session/:id/model before the session create has
   // been committed, and the TUI shows "Failed to switch model: Session not found".
   import { Effect } from "effect"
   import { Llm, OpenCodeDriver } from "opencode-drive"
   // The report takes as given that the server stores the new session a little
   // after the TUI fires the model switch (152 ms in the author's log on
   // Windows). Locally both are near-instant, so the TUI<->server link is routed
   // through opencode-drive's chaos proxy with per-chunk jitter: requests on
   // different connections can then reach the server in either order. The race
   // is probabilistic: the toast appeared in 1 of 1 runs on 2.1.0 and 1 of 8 on
   // dev, so re-run a few times if waitFor times out.
   
   
   export default OpenCodeDriver.use(
     {
       ...(process.env.OC_DEV ? { opencode: { dev: process.env.OC_DEV } } : {}),
       network: true,
       tui: { recording: true, keypressOverlay: true },
     },
     ({ ui, llm, network }) =>
       Effect.gen(function* () {
         yield* llm.queue(Llm.text("Hello from the simulated model."))
         yield* ui.screenshot("01-home")
         yield* Effect.sleep(3000) // let the TUI finish loading over the proxy
         yield* network.set({ jitterMs: 1500 })
         // Send a prompt from home: this creates a new session and opens it.
         yield* ui.submit("Say hello")
         // Immediately press Enter with an empty composer in the new session,
         // which commits the composer's model selection (switchModel).
         yield* Effect.sleep(150)
         yield* ui.screenshot("02a-session-tab")
         yield* ui.enter()
         yield* Effect.sleep(1500)
         yield* ui.screenshot("02-after-empty-enter")
         yield* ui.waitFor("Session not found", { timeout: 8000 })
         yield* ui.screenshot("03-toast")
         yield* Effect.sleep(1500)
       }),
   )

   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 20, 2026
3. Bearmancer commented on Oct 20, 2026

   

   Bearmancer

   on Oct 20, 2026

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   This was generated by AI during triage.

   Fix PR: #57361