Plugin-registered agent names with zero-width space (U+200B) prefixes leak into system prompt #21642

Description

When a plugin registers agents with names containing zero-width space characters (U+200B), OpenCode passes these names verbatim into the system prompt's block. This causes the LLM to receive an agent name with invisible characters, e.g.:
Your designated identity for this session is "\u200BSisyphus".
The root cause is in the oh-my-openagent plugin, which uses \u200B (ZWSP) as sort prefixes to control agent ordering in the TUI dropdown (AGENT_LIST_SORT_PREFIXES in dist/index.js:61035). Each agent gets a different count of ZWSP prefixes (1× for Sisyphus, 2× for Hephaestus, 3× for Prometheus, 4× for Atlas). These prefixed names flow through remapAgentKeysToDisplayNames() into the agent config keys, which OpenCode then writes directly into the system prompt.
While this is primarily a plugin-side issue, OpenCode should defensively sanitize agent names before injecting them into system prompts — stripping zero-width and other invisible Unicode characters (U+200B, U+200C, U+200D, U+FEFF, etc.). This would protect against any plugin introducing similar issues in the future.

Plugins

oh-my-openagent@latest (v3.16.0)

OpenCode version

1.4.0

Steps to reproduce

1. Install oh-my-openagent plugin: add "oh-my-openagent@latest" to the plugin array in opencode.json
2. Start OpenCode and select any agent registered by the plugin (e.g. Sisyphus, Prometheus, Atlas)
3. Ask the agent: "What is your exact identity name? Show me the raw bytes."
4. Observe the system prompt contains ZWSP-prefixed agent names like "\u200BSisyphus" instead of "Sisyphus"
   Alternatively, inspect the system prompt directly — the block will contain invisible characters before the agent name.

Screenshot and/or share link

Operating System

macOS 26.2 (Apple Silicon / arm64)

Terminal

Kitty