Add GLM 5.3 to the Z.AI Coding Plan catalogue

[byapparov]

Context

Z.AI released GLM 5.3 on 2026-08-14 and the live models.dev catalogue now lists it for zai-coding-plan. The CLI fallback catalogue and checked-in test fixture stop at GLM 5.2, so bundled or stale catalogue data cannot expose the new model with its supported reasoning efforts.

Goal

Make zai-coding-plan/glm-5.3 available with correct limits and request options.

Acceptance criteria

• The Coding Plan catalogue exposes GLM 5.3 with a 1M-token context window and 131,072-token output limit.
• Model variants match the native low, high, and max reasoning efforts.
• Streaming requests enable preserved thinking and send the selected reasoning effort.
• The checked-in model fixture and focused provider/session tests cover GLM 5.3.
• The model-only release uses a patch version bump.

Out of scope

• Adding GLM 5.3 to gateways that have not advertised availability.
• Porting unrelated OpenCode provider or OpenCode Go changes.

References

• https://z.ai/blog/glm-5.3

• packages/cli/src/provider/provider.ts

• packages/cli/src/provider/transform.ts

• Prior GLM 5.2 support: Add GLM-5.2 harness support #82

• I searched open and closed issues for an existing GLM 5.3 request.