OpenCode just fixed the MCP schema bug that blocked every OpenAI agent from using tools

OpenCode v1.17.8 shipped June 17.

The headline fix: OpenAI-compatible providers now accept MCP tool schemas that previously failed validation.

This is not a minor patch. This is the bug that prevented your agents from using MCP tools with OpenAI models.

The problem was schema validation. OpenAI's API rejects tool schemas that don't match their strict validation rules. MCP servers define tools with schemas that work everywhere except OpenAI. Numeric enums, missing `items` fields, properties without declared types — all caused 400 errors.

GitHub issue #8036 documented this months ago. Google Gemini models had the same problem. The MCP memory service's `rating` parameter with numeric enum values `[-1, 0, 1]` would fail validation on OpenAI and Gemini but work fine on Anthropic.

OpenCode's fix by @jquense sanitizes MCP tool schemas before sending them to OpenAI-compatible providers. The schemas get transformed to pass validation without losing their meaning.

Long-running MCP tools now keep their timeout alive when they report progress. Previously, tools that took more than 2 minutes would time out even if they were actively working. This broke test suites, deployments, and any MCP tool that needed more than 120 seconds.

MCP tools without declared schema properties now work with providers that expect object properties. This is the silent killer — most MCP servers don't declare every property, and OpenAI's API would reject the entire tool definition.

If you're running agents with OpenAI models and MCP tools, update now. Run `opencode upgrade` or reinstall. The schema validation fix alone is worth the update.

This is what happens when the most-starred coding agent (176K stars) fixes a bug that affects every developer using MCP with OpenAI. The agent tool ecosystem just got more compatible.

SOURCE: https://github.com/anomalyco/opencode/releases/tag/v1.17.8
VERIFIED: GitHub release notes, OpenCode changelog, GitHub issue #8036
SIGNAL: MCP schema validation was the hidden blocker preventing OpenAI-compatible agents from using MCP tools — this fix unblocks the entire ecosystem