feat(models): add Claude Sonnet 5 to available models

[richardsolomou]

Problem

We want Claude Sonnet 5 selectable as a model in PostHog Code.

Changes

• Add claude-sonnet-5 ("Claude Sonnet 5") to the mobile composer's static model picker, above Sonnet 4.6.
• Grant claude-sonnet-5 1M-context and effort support in the Claude adapter (MODELS_WITH_1M_CONTEXT, MODELS_WITH_EFFORT), mirroring Sonnet 4.6's capability profile — effort levels low/medium/high, no xhigh (Opus-tier only).
• Add a unit test documenting the new model's capability flags.

The desktop/web picker fetches models dynamically from the gateway's /v1/models and only filters a BLOCKED_MODELS set, so Sonnet 5 surfaces there automatically once the gateway serves it — no list edit required there. The gateway ID is inferred as claude-sonnet-5 (matching the claude-fable-5 convention); adjust if the real ID/capabilities differ.

Deliberately left alone: GATEWAY_TO_SDK_MODEL (the full ID passes through rather than aliasing to sonnet, which resolves to 4.6) and the useModelCatalog fallback / Storybook mocks (not load-bearing for availability).

How did you test this?

• vitest run packages/agent/.../models.test.ts — 32 passed, including the new claude-sonnet-5 capability test.

Automatic notifications

• Publish to changelog?
• Alert Sales and Marketing teams?

[github-actions]

React Doctor found no issues in the changed files. 🎉

_{Reviewed by React Doctor for commit 7c2015c.}

[greptile-apps]

Comments Outside Diff (1)

1. packages/agent/src/adapters/claude/session/models.test.ts, line 82-86 (link)

   The existing parameterized resolveEffortForModel table covers claude-sonnet-4-6 as an effort-capable model that falls back to "high", but the new claude-sonnet-5 isn't added there. Without this row the test suite doesn't verify that the new model's default effort resolves correctly, even though claude-sonnet-5 is now in MODELS_WITH_EFFORT.

_{Reviews (1): Last reviewed commit: "feat(models): add Claude Sonnet 5 to ava..." | Re-trigger Greptile}