Silent stream truncation persisted as complete response + TUI desync after mid-stream provider errors #44210

Description

TUI responses get cut off mid-generation: mid-text, mid-reasoning, or before/during tool calls. UI stays blocked until I manually type "resume". Happens dozens of times per day.

Dug through ~/.local/share/opencode/log/opencode.log and SQLite storage (opencode.db). Provider fails in two ways; opencode's handling leaves the user stuck in both.

Failure mode 1: loud stream errors, then TUI desync

level=ERROR message="stream error" providerID=opencode modelID=x-preview-f-free
error.error="AI_APICallError: Upstream request failed: Endpoint is unavailable."
error.error="AI_APICallError: Service Unavailable"

Errors are logged and sometimes auto-retried (~3s retry observed). That part works. But in one incident the backend retried, completed every loop step, logged clean exiting loop, while the TUI stayed locked on a spinner for ~40 minutes (log silent between 15:36:47Z and 16:15:31Z, until I nudged it). The recovered response never rendered client-side either.

So: mid-stream error + successful server-side retry = TUI can stay desynced permanently even though the backend finished.

Failure mode 2: silent truncation persisted as complete response

Provider closes the SSE stream early, no error event. AI SDK seems to treat end-of-stream as normal completion. opencode then:

1. persists partial text to storage
2. logs nothing
3. exits the loop cleanly

Evidence from 2026-08-22:

Stored part ends mid-word:

part msg_02a466164001QEP4TCIt5B1QXx (session ses_fd5f975f3ffeGcbaIQY7uioPOj)
type=text, 1448 chars
tail: "...## Cosa fare\n\n- **Subito**: `/models` per passare a un modello stabile nelle"

No error reaches the user here either. Response stops mid-sentence; backend considers the turn complete; nothing gets retried. This is why the failures are invisible.

Expected behavior

• Detect incomplete generations (stream ends without a proper finish): show an error or retry instead of silently saving partial output.
• After error + successful auto-retry: unlock the TUI and render the completed response instead of staying stuck.

Environment

• opencode version: 1.18.18
• Platform: Windows 11, PowerShell 7.6 (pwsh), TUI
• Model/provider: opencode / x-preview-f-free
• Incidents date: 2026-08-22 (8x "Endpoint is unavailable", 3x "Service Unavailable", multiple silent truncations across several sessions)