GAP-L1-P2-openai-codex-and-responses-api

Current state

• schema/examples/compute/models/gpt-5.yaml exists; gpt-5-codex, gpt-5-mini, o3, o4-mini absent.
• schema/examples/agent-stack/products/codex.yaml exists but no skills/plugins/hooks examples for Codex CLI.
• ModelTransportProtocol model-transport:openai-responses example is presumably present but Responses API features (streamed reasoning, tool-call grammar, function-calling-with-thinking) are not modeled as Capabilities.

Desired state

• Add ModelVersion examples: gpt-5-codex, gpt-5-mini, o3, o4-mini.
• Add Capability instances for Responses-API-specific features: cap:streamed-reasoning, cap:parallel-tool-calls, cap:strict-json-schema.
• Add Codex CLI skills/hooks examples (Codex now supports ~/.codex/agents.md, ~/.codex/skills/).

Evidence

• platform.openai.com/docs/api-reference/responses
• packages/agent-catalog evidence files referencing OpenAI

Propagation status

• Level 1: open
• Level 2: not-started

Propagation chain

• Level 1: 4 ModelVersion + 3 Capability + 2 Codex extension example files.
• Level 2: capabilities.md grows.

Notes

Lower priority than Anthropic gaps because Codex's surface evolves slower, but coverage parity matters.