tool_output config option is undocumented #45232

Description

tool_output has been a working config option since PR #23770 (merged 2026-04-22) and is not mentioned anywhere in the docs.

It is fully specified in both config schemas, with descriptions:

packages/core/src/v1/config/config.ts:

tool_output: Schema.optional(
  Schema.Struct({
    max_lines: Schema.optional(PositiveInt).annotate({
      description: "Maximum lines of tool output before it is truncated and saved to disk (default: 2000)",
    }),
    max_bytes: Schema.optional(PositiveInt).annotate({
      description: "Maximum bytes of tool output before it is truncated and saved to disk (default: 51200)",
    }),
  }),
)

and read at runtime in packages/opencode/src/tool/truncate.ts:

maxLines: cfg?.tool_output?.max_lines ?? MAX_LINES,
maxBytes: cfg?.tool_output?.max_bytes ?? MAX_BYTES,

Searching packages/web/src/content/docs/ for tool_output, max_lines or max_bytes returns nothing.

That matters because truncation is visible and often unwanted — a tool whose output crosses 2000 lines or 50 KB is replaced with a preview plus a file path, and #11313 is an example of users hitting it. The knob to raise it exists and is undiscoverable.

config.mdx has a dedicated section for nearly every other option (share, shell, subagent_depth, server, formatter, lsp, ...), so this looks like an oversight from when the feature landed rather than a deliberate omission.

For the record, config.mdx is also missing skills, references, enterprise, remote_config and username, plus the legacy autoshare/mode/layout keys. I kept the PR to tool_output since that is the one with a concrete user-facing consequence; happy to do the others separately if wanted.

Operating System

Windows 11 (documentation)