feat(mobile): fetch available model list from the LLM gateway

[oliverb123]

Problem

On mobile, the available model list was hardcoded in composer/options.ts, so newer models (e.g. 4.8 / 5) never showed up without shipping a new app build. The desktop app already downloads the list from the LLM gateway, so the two clients drifted.

Changes

• Moved the LLM gateway URL construction and the model fetch/format logic into @posthog/shared (zero-dependency, already a mobile dependency) as the single source of truth; packages/agent now re-exports from it so the desktop path is literally the same code.
• Mobile fetches the model list from the gateway's /v1/models endpoint via a new useModels hook backed by a persisted cache, mapping models exactly like the desktop app (Anthropic models, gateway-formatted names). A small built-in list remains only as a cold-start / offline fallback so the picker is never empty.

How did you test this?

• pnpm --filter @posthog/shared test (incl. new gateway URL + model tests) — pass
• Agent gateway tests (gateway-models, utils/gateway) — pass
• pnpm --filter agent typecheck and agent build — pass
• Mobile tsc on touched files (clean), biome on changed files (clean), and vitest run src/features/tasks (84 tests) — pass

Automatic notifications

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

---

Created with PostHog Code from a Slack thread

[github-actions]

React Doctor found no issues in the changed files. 🎉

_{Reviewed by React Doctor for commit cc47f46.}

[greptile-apps]

Comments Outside Diff (2)

1. apps/mobile/src/features/tasks/hooks/useModels.ts, line 323-328 (link)

   Query key missing cloudRegion — stale models served across region switches

   The query key ["models", "list"] is constant across regions. If a user switches from us to eu (or logs out and back in on a different region), TanStack Query sees the same key and treats the cached US models as fresh for the full 10-minute staleTime. During that window getAvailableModels is not called, so getLlmGatewayUrl(getBaseUrl()) points at the new region's gateway but the old region's model list is displayed. Including cloudRegion in the key fixes this: any region change immediately invalidates the cache and triggers a re-fetch.

   Prompt To Fix With AI

   This is a comment left during a code review.
   Path: apps/mobile/src/features/tasks/hooks/useModels.ts
   Line: 323-328
   
   Comment:
   **Query key missing `cloudRegion` — stale models served across region switches**
   
   The query key `["models", "list"]` is constant across regions. If a user switches from `us` to `eu` (or logs out and back in on a different region), TanStack Query sees the same key and treats the cached US models as fresh for the full 10-minute `staleTime`. During that window `getAvailableModels` is not called, so `getLlmGatewayUrl(getBaseUrl())` points at the new region's gateway but the old region's model list is displayed. Including `cloudRegion` in the key fixes this: any region change immediately invalidates the cache and triggers a re-fetch.
   
   How can I resolve this? If you propose a fix, please make it concise.

2. packages/shared/src/gateway-models.test.ts, line 736-746 (link)

   Non-parameterised tests for supportsReasoningEffort and isBlockedModelId

   The getLlmGatewayUrl test in gateway.test.ts already uses it.each (the preferred parameterised style for this repo). The supportsReasoningEffort and isBlockedModelId blocks below group multiple unrelated assertions inside a single it, making failures harder to attribute. Converting them to it.each tables would align with the team's convention and make each case independently named and reportable.

   Prompt To Fix With AI

   This is a comment left during a code review.
   Path: packages/shared/src/gateway-models.test.ts
   Line: 736-746
   
   Comment:
   **Non-parameterised tests for `supportsReasoningEffort` and `isBlockedModelId`**
   
   The `getLlmGatewayUrl` test in `gateway.test.ts` already uses `it.each` (the preferred parameterised style for this repo). The `supportsReasoningEffort` and `isBlockedModelId` blocks below group multiple unrelated assertions inside a single `it`, making failures harder to attribute. Converting them to `it.each` tables would align with the team's convention and make each case independently named and reportable.
   
   How can I resolve this? If you propose a fix, please make it concise.

   Note: If this suggestion doesn't match your team's coding style, reply to this and let me know. I'll remember it for next time!

Prompt To Fix All With AI

Fix the following 3 code review issues. Work through them one at a time, proposing concise fixes.

---

### Issue 1 of 3
apps/mobile/src/features/tasks/hooks/useModels.ts:323-328
**Query key missing `cloudRegion` — stale models served across region switches**

The query key `["models", "list"]` is constant across regions. If a user switches from `us` to `eu` (or logs out and back in on a different region), TanStack Query sees the same key and treats the cached US models as fresh for the full 10-minute `staleTime`. During that window `getAvailableModels` is not called, so `getLlmGatewayUrl(getBaseUrl())` points at the new region's gateway but the old region's model list is displayed. Including `cloudRegion` in the key fixes this: any region change immediately invalidates the cache and triggers a re-fetch.

### Issue 2 of 3
packages/shared/src/gateway-models.ts:220-222
**Duplicated `MODELS_WITH_EFFORT` set — two sources of truth that must be kept in sync manually**

`supportsReasoningEffort` here and `supportsEffort` in `packages/agent/src/adapters/claude/session/models.ts` both maintain private copies of the same four-model set. The comment even says "keep in sync". Now that this logic lives in `@posthog/shared`, the agent's copy can be deleted and replaced with an import of `supportsReasoningEffort` — removing the manual sync requirement entirely.

```suggestion
// Models that expose a reasoning-effort control.
const MODELS_WITH_EFFORT = new Set([
```

### Issue 3 of 3
packages/shared/src/gateway-models.test.ts:736-746
**Non-parameterised tests for `supportsReasoningEffort` and `isBlockedModelId`**

The `getLlmGatewayUrl` test in `gateway.test.ts` already uses `it.each` (the preferred parameterised style for this repo). The `supportsReasoningEffort` and `isBlockedModelId` blocks below group multiple unrelated assertions inside a single `it`, making failures harder to attribute. Converting them to `it.each` tables would align with the team's convention and make each case independently named and reportable.

_{Reviews (1): Last reviewed commit: "feat(mobile): fetch available model list..." | Re-trigger Greptile}

[greptile-apps]

Duplicated MODELS_WITH_EFFORT set — two sources of truth that must be kept in sync manually

supportsReasoningEffort here and supportsEffort in packages/agent/src/adapters/claude/session/models.ts both maintain private copies of the same four-model set. The comment even says "keep in sync". Now that this logic lives in @posthog/shared, the agent's copy can be deleted and replaced with an import of supportsReasoningEffort — removing the manual sync requirement entirely.

Suggested change

	// Models that expose a reasoning-effort control. Mirrors `MODELS_WITH_EFFORT`
	// in packages/agent/src/adapters/claude/session/models.ts — keep in sync.
	const MODELS_WITH_EFFORT = new Set([
	// Models that expose a reasoning-effort control.
	const MODELS_WITH_EFFORT = new Set([

Prompt To Fix With AI

This is a comment left during a code review.
Path: packages/shared/src/gateway-models.ts
Line: 220-222

Comment:
**Duplicated `MODELS_WITH_EFFORT` set — two sources of truth that must be kept in sync manually**

`supportsReasoningEffort` here and `supportsEffort` in `packages/agent/src/adapters/claude/session/models.ts` both maintain private copies of the same four-model set. The comment even says "keep in sync". Now that this logic lives in `@posthog/shared`, the agent's copy can be deleted and replaced with an import of `supportsReasoningEffort` — removing the manual sync requirement entirely.

```suggestion
// Models that expose a reasoning-effort control.
const MODELS_WITH_EFFORT = new Set([
```

How can I resolve this? If you propose a fix, please make it concise.

Note: If this suggestion doesn't match your team's coding style, reply to this and let me know. I'll remember it for next time!