google/gemini-3-pro-preview output formatting went off the rails

[jdanbrown]

Description

No idea if this is a model error or opencode error, but I figured I'd file it in case it indicates anything helpful for opencode folks. I had a handful of roundtrips with google/gemini-3-pro-preview, and then its output stopped showing any formatting, and eventually the model itself went into a brain-damage loop. 🤷

• https://opencode.ai/s/b7Ka03T9

Config

$ opencode debug config
{
  "$schema": "https://opencode.ai/config.json",
  "theme": "jdanbrown",
  "keybinds": {
    "leader": "ctrl+o",
    "app_exit": "ctrl+d,<leader>q",
    "editor_open": "<leader>e",
    "theme_list": "<leader>t",
    "sidebar_toggle": "<leader>b",
    "status_view": "<leader>s",
    "session_export": "<leader>x",
    "session_new": "<leader>n",
    "session_list": "<leader>l",
    "session_timeline": "<leader>g",
    "session_share": "none",
    "session_unshare": "none",
    "session_interrupt": "ctrl+c",
    "session_compact": "<leader>c",
    "messages_page_up": "pageup",
    "messages_page_down": "pagedown",
    "messages_half_page_up": "ctrl+alt+u",
    "messages_half_page_down": "ctrl+alt+d",
    "messages_first": "ctrl+alt+a",
    "messages_last": "ctrl+alt+e",
    "messages_copy": "<leader>y",
    "messages_undo": "<leader>u",
    "messages_redo": "<leader>r",
    "messages_toggle_conceal": "<leader>h",
    "model_list": "<leader>m,ctrl+j",
    "model_cycle_recent": "f2",
    "model_cycle_recent_reverse": "shift+f2",
    "command_list": "ctrl+_",
    "agent_list": "<leader>a",
    "agent_cycle": "tab",
    "agent_cycle_reverse": "shift+tab",
    "input_clear": "ctrl+c",
    "input_forward_delete": "ctrl+d",
    "input_paste": "ctrl+v",
    "input_submit": "return",
    "input_newline": "alt+enter,shift+enter,shift+return",
    "history_previous": "up,ctrl+p",
    "history_next": "down,ctrl+n",
    "session_child_cycle": "<leader>right",
    "session_child_cycle_reverse": "<leader>left",
    "terminal_suspend": "ctrl+z"
  },
  "tui": {
    "scroll_acceleration": {
      "enabled": true
    },
    "diff_style": "stacked"
  },
  "share": "manual",
  "autoupdate": false,
  "model": "openrouter/anthropic/claude-haiku-4.5",
  "small_model": "openrouter/google/gemini-2.5-flash",
  "provider": {
    "openrouter": {
      "models": {
        "anthropic/claude-sonnet-4.5@thinking-32k": {
          "id": "anthropic/claude-sonnet-4.5",
          "options": {
            "reasoning": {
              "effort": "high"
            }
          }
        }
      }
    }
  },
  "mcp": {
    "context7": {
      "type": "remote",
      "url": "https://mcp.context7.com/mcp",
      "headers": {
        "CONTEXT7_API_KEY": ...
      }
    }
  },
  "formatter": {
    "swiftformat": {
      "command": [
        "swiftformat",
        "$FILE"
      ],
      "extensions": [
        ".swift"
      ]
    }
  },
  "instructions": [],
  "permission": {
    "bash": "allow",
    "external_directory": "allow"
  },
  "agent": {},
  "mode": {},
  "plugin": [],
  "command": {},
  "username": "danb"
}

OpenCode version

1.0.126

Steps to reproduce

No response

Screenshot and/or share link

No response

Operating System

macOS 15.5

Terminal

VS Code terminal

[github-actions[bot]]

This issue might be a duplicate of or related to existing issues. Please check:

• #4953: openrouter/google/gemini-3-pro-preview stops responding
• #4912: Lots of REDACTED with openrouter/google/gemini-3-pro-preview
• #4632: Gemini 3 pro preview issues (plan mode and general behavioral issues)
• #4346: Gemini models hang waiting endlessly

Feel free to ignore if this specific formatting/brain-damage loop issue is distinct from these.

[Shinobu-Kazahana]

experiencing the same, highly annoying

[rekram1-node]

It looks like the model misbehaving, I mean maybe the openrouter people are having more problems/bugs gemini seems to be a constant issue over there.

Now if this isn't related to openrouter then we can try to make some prompts more "gemini friendly" but gemini models have always had looping problems

[jdanbrown]

Yeah, I wonder if the output formatting and looping are two separate problems. Surely the looping is (at least partially) a gemini model problem, but the output formatting I'm hoping is an opencode/~~openrouter~~ tool bug that's fixable.

[jdanbrown]

Oh wait! — this isn't openrouter's gemini, this is normal google gemini. My bad. 🤦

• I've edited the title and description with openrouter/google/gemini-3-pro-preview → google/gemini-3-pro-preview
• The screenshot is correct: Google Gemini 3 Pro Preview (not OpenRouter Gemini 3 Pro Preview)
• The config is says haiku/flash, but that's spurious, since I set my models with shell aliases that aren't reflected in opencode debug config