fix(core): preserve explicit Gemini 3 Pro preview model IDs by FanouZeng-TT · Pull Request #29420 · google-gemini/gemini-cli

FanouZeng-TT · 2026-09-20T03:50:45Z

Summary

An explicit --model gemini-3-pro-preview is silently rewritten to gemini-3.1-pro-preview whenever the Gemini 3.1 rollout (useGemini3_1) is enabled. Only the auto/pro aliases should follow the rollout — a user who pins an explicit version should get that version.

Details

The rewrite happened on two independent paths, both fixed here:

Legacy resolver (resolveModel) grouped PREVIEW_GEMINI_MODEL into the same switch case as PREVIEW_GEMINI_MODEL_AUTO, so the explicit ID fell through into the 3.1 upgrade. It now has its own case that pins the ID; the existing hasAccessToPreview=false → gemini-2.5-pro downgrade is preserved.
Dynamic model configuration (defaultModelConfigs) remapped the explicit gemini-3-pro-preview key through useGemini3_1 contexts. Those contexts are removed from the explicit key, and the classifier pro tier gains an explicit requestedModels: ['gemini-3-pro-preview'] anchor so it stays pinned too.

Two call sites used the explicit model ID as an internal placeholder for "the current Pro rollout target" — they must keep following the rollout:

getModelPolicyChain (availability catalog) now derives the rollout Pro model inline from useGemini31/useCustomToolModel instead of calling resolveModel with the explicit ID.
The preview / auto-preview model chains select the pro alias (matching the existing lite chain's use of the flash-lite alias) rather than a hard-coded versioned ID.

Related Issues

Fixes #29417

How to Validate

npm ci
npm run build --workspace @google/gemini-cli-core
npm run test:ci --workspace @google/gemini-cli-core
npm run typecheck

Targeted regressions (red before the fix, green after):

cd packages/core
../../node_modules/.bin/vitest run \
  src/config/models.test.ts \
  src/core/geminiChat.test.ts \
  src/availability/policyCatalog.test.ts \
  src/availability/policyHelpers.test.ts

resolveModel/dynamic parity: explicit gemini-3-pro-preview (with and without custom tools) stays pinned when useGemini3_1=true; the auto/pro aliases still upgrade to gemini-3.1-pro-preview[-customtools]; hasAccessToPreview=false still downgrades to gemini-2.5-pro.
Request boundary: GeminiChat.sendMessageStream sends gemini-3-pro-preview unchanged with the rollout enabled.
Availability catalog/chain and classifier-tier parity remain intact.

Pre-Merge Checklist

Updated relevant documentation and README (if needed) — not needed (internal resolver behavior)
Added/updated tests (if needed)
Noted breaking changes (if any) — none; behavior only changes for the previously-broken explicit-ID case
Validated on required platforms/methods:
- MacOS
  - npm run

🤖 Generated with Claude Code

gemini-code-assist · 2026-09-20T03:50:55Z

Summary of Changes

Hello, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request addresses an issue where explicit requests for the 'gemini-3-pro-preview' model were being incorrectly rewritten to Gemini 3.1 versions when the rollout was enabled. By separating the handling of explicit model IDs from automatic aliases, the changes ensure that users who pin a specific model version maintain that selection, while general aliases continue to benefit from the intended rollout upgrades.

Highlights

Explicit Model Pinning: Modified the model resolver and configuration to ensure that explicit requests for 'gemini-3-pro-preview' remain pinned to that version, preventing them from being automatically upgraded to Gemini 3.1 during the rollout.
Rollout Logic Decoupling: Decoupled the Gemini 3.1 rollout logic from explicit model IDs, ensuring that only generic 'auto' or 'pro' aliases are subject to automatic version upgrades.
Availability Catalog Updates: Updated the availability catalog to derive rollout-specific models inline, ensuring consistent behavior for internal model chains while preserving user-requested model pinning.

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github-actions · 2026-09-20T03:50:56Z

📊 PR Size: size/M

Lines changed: 128
Additions: +106
Deletions: -22
Files changed: 5

google-cla · 2026-09-20T03:51:04Z

Thanks for your pull request! It looks like this may be your first contribution to a Google open source project. Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA).

View this failed invocation of the CLA check for more information.

For the most up to date status, view the checks section at the bottom of the pull request.

gemini-code-assist

Code Review

This pull request modifies the model resolution logic to ensure that explicit requests for the gemini-3-pro-preview model remain pinned to that specific version instead of automatically upgrading to Gemini 3.1. The Gemini 3.1 rollout is now restricted to model aliases (such as pro and auto). This is implemented by updating resolveModel in models.ts, adjusting the default model configurations in defaultModelConfigs.ts to use the pro alias in preview chains, and updating the policy catalog. Corresponding unit tests have been added to verify the pinning behavior and alias rollouts. I have no further feedback to provide as the implementation is clean and well-tested.

An explicit `--model gemini-3-pro-preview` was silently rewritten to `gemini-3.1-pro-preview` while the Gemini 3.1 rollout was enabled, in both the legacy resolver and the dynamic model configuration. Only the `auto` and `pro` aliases should follow the rollout. - Pin the explicit Pro preview model ID in `resolveModel`, keeping the existing preview-access downgrade to `gemini-2.5-pro`. - Stop remapping the explicit model ID in `defaultModelConfigs` and keep the `useGemini3_1` contexts scoped to aliases and classifier tiers. - Select the Pro rollout default in the availability catalog and the model chains from the alias, so internal rollout selection stays separate from a user-pinned version. - Cover the request boundary so `GeminiChat` keeps sending the explicit ID. Fixes google-gemini#29417

FanouZeng-TT · 2026-09-23T03:57:14Z

Gentle follow-up: I've rebased this onto the latest main. The rebase had one conflict in packages/core/src/availability/policyCatalog.ts, where the rollout-default selection now resolves through resolveModel; I kept the catalog's own alias-based selection so that pinning the explicit ID inside resolveModel doesn't also suppress the Gemini 3.1 rollout for the auto/pro aliases.

Everything is green on the new head (fbcd441): check-changes, size-label and cla/google all pass, and the targeted suites are 293 passed. Would a maintainer have a moment to take a look?

gemini-cli · 2026-09-28T01:57:58Z

Hi there! Thank you for your interest in contributing to Gemini CLI.

To ensure we maintain high code quality and focus on our prioritized roadmap, we only guarantee review and consideration of pull requests for issues that are explicitly labeled as 'help wanted'.

This PR will be closed in 7 days if it remains without that designation. We encourage you to find and contribute to existing 'help wanted' issues in our backlog! Thank you for your understanding.

gemini-cli · 2026-10-05T02:02:09Z

This pull request is being closed as it has been open for 14 days without a 'help wanted' designation. We encourage you to find and contribute to existing 'help wanted' issues in our backlog! Thank you for your understanding.

FanouZeng-TT requested a review from a team as a code owner September 20, 2026 03:50

github-actions Bot added the size/m A medium sized PR label Sep 20, 2026

gemini-code-assist Bot reviewed Sep 20, 2026

View reviewed changes

gemini-cli Bot added priority/p2 Important but can be addressed in a future release. area/core Issues related to User Interface, OS Support, Core Functionality labels Sep 20, 2026

FanouZeng-TT force-pushed the fix-explicit-pro-preview-model branch from 2db5738 to 31b4a98 Compare September 20, 2026 03:53

github-actions Bot mentioned this pull request Sep 20, 2026

📊 AI CLI 工具社区动态日报 2026-09-20 96loveslife/big_model_radar#517

Open

gemini-cli Bot added the area/agent Issues related to Core Agent, Tools, Memory, Sub-Agents, Hooks, Agent Quality label Sep 20, 2026

github-actions Bot mentioned this pull request Sep 20, 2026

📊 AI CLI 工具社区动态日报 2026-09-21 litang9/big_model_radar#428

Open

FanouZeng-TT force-pushed the fix-explicit-pro-preview-model branch from 31b4a98 to fbcd441 Compare September 23, 2026 03:32

github-actions Bot mentioned this pull request Sep 23, 2026

📊 AI CLI 工具社区动态日报 2026-09-23 96loveslife/big_model_radar#533

Open

gemini-cli Bot added the status/pr-nudge-sent label Sep 28, 2026

github-actions Bot mentioned this pull request Sep 28, 2026

📊 AI CLI 工具社区动态日报 2026-09-28 96loveslife/big_model_radar#558

Open

gemini-cli Bot closed this Oct 5, 2026

github-actions Bot mentioned this pull request Oct 5, 2026

📊 AI CLI 工具社区动态日报 2026-10-05 96loveslife/big_model_radar#590

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fix(core): preserve explicit Gemini 3 Pro preview model IDs - #29420

fix(core): preserve explicit Gemini 3 Pro preview model IDs#29420
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FanouZeng-TT commented Sep 20, 2026

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