feat: expose max_output in /v1/models

[RATCHAW]

What

Surfaces per-model output-token limits in the public GET /v1/models catalogue:

• each providers[] entry carries its mapping's exact maxOutput as max_output
• the model level reports the minimum across still-servable mappings that declare one — the largest max_tokens value guaranteed to be accepted regardless of which provider serves the request (the gateway validates max_tokens against the routed mapping's limit and rejects anything above it with HTTP 400). Deactivated mappings can no longer serve, so their limits are excluded; deprecated mappings remain routable and stay in
• mappings that declare no limit accept any max_tokens, so they don't constrain the model-level bound; models where no mapping declares one omit the field

Why

Consumers currently have no way to discover the cap — they either guess low and truncate output or guess high and get 400s. The Pi coding-agent integration (earendil-works/pi#7480) reads this field to set per-model output limits (falling back to a conservative 4096 until this ships).

Testing

Extended models.spec.ts with a spot check (claude-haiku-4-5 → 64000 per-provider and model-level) plus an exhaustive assertion that every model's max_output equals the minimum across its still-servable declaring mappings (or is omitted), and a deepseek-v3.2 case pinning the bound to 65536 rather than its retired Nebius mapping's 32768. All 23 models endpoint tests pass; tsc and prettier clean.

🤖 Generated with Claude Code

Summary by CodeRabbit

• New Features

  • Model API responses now include maximum output limits for individual provider mappings.
  • Model-level responses show the lowest available limit across active mappings, while retaining deprecated mappings and excluding deactivated ones.
  • The limit is omitted when no applicable value is defined.

• Tests

  • Added coverage to verify maximum output limits are reported and calculated correctly.

[coderabbitai]

Walkthrough

The models API exposes optional max_output values for provider mappings and models. Model-level values use the minimum declared limit across eligible mappings. Deactivated mappings do not affect the result. Tests cover defined and omitted limits.

Changes

Model output limit metadata

Layer / File(s)	Summary
Limit contracts and provider output apps/gateway/src/models/models.ts	The provider-mapping and model response schemas define optional max_output fields. Provider mappings return provider.maxOutput.
Model limit aggregation apps/gateway/src/models/models.ts, apps/gateway/src/models/models.spec.ts	The model response computes the minimum declared limit across non-deactivated mappings. Tests cover active and deprecated mappings, deactivated mappings, and omitted limits.

Estimated code review effort: 2 (Simple) | ~10 minutes

Possibly related PRs

• theopenco/llmgateway#3191: Adds provider mapping output limits reported by this models API logic.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes the primary change: exposing max_output in the /v1/models endpoint.

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[coderabbitai]

🧹 Nitpick comments (1)

apps/gateway/src/models/models.spec.ts (1)

104-134: 🗄️ Data Integrity & Integration | 🔵 Trivial | ⚡ Quick win

Cover the omitted provider-level field.

This test verifies a mapping with max_output: 64000, but it does not verify the optional provider contract. Select a mapping whose source maxOutput is undefined and assert that the response object omits max_output. Otherwise, a provider-level serialization regression can pass this test.

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@apps/gateway/src/models/models.spec.ts` around lines 104 - 134, Extend the
GET /v1/models test to select a provider mapping from the response whose source
ProviderModelMapping.maxOutput is undefined, then assert that its serialized
provider object does not contain max_output. Keep the existing positive
max_output assertion and model-level minimum checks unchanged.

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Nitpick comments:
In `@apps/gateway/src/models/models.spec.ts`:
- Around line 104-134: Extend the GET /v1/models test to select a provider
mapping from the response whose source ProviderModelMapping.maxOutput is
undefined, then assert that its serialized provider object does not contain
max_output. Keep the existing positive max_output assertion and model-level
minimum checks unchanged.

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: Repository UI

Review profile: CHILL

Plan: Pro Plus

Run ID: 3fcf76f3-0025-4af1-9e72-ae75b6cf78fb

📥 Commits

Reviewing files that changed from the base of the PR and between 119b3c7 and 54f40d1.

📒 Files selected for processing (2)

• apps/gateway/src/models/models.spec.ts
• apps/gateway/src/models/models.ts

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Exclude deactivated mappings from the model-level limit

When a model retains both active and deactivated mappings, this minimum includes mappings that can no longer serve requests. For example, after 2026-06-22 the default GET /v1/models still includes deepseek-v3.2, but its deactivated Nebius mapping contributes 32768, so consumers such as the Pi integration cap output there even though every active mapping with a declared limit accepts at least 65536. Filter mappings whose deactivatedAt has passed before calculating the advertised serving bound, as pickPricingProvider already does for model-level pricing.

AGENTS.md reference: AGENTS.md:L229-L230

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