[WRONG BRANCH] fix(antigravity): preserve migrated default reasoning tier

[luvs01]

Motivation

• The model rename migration rewrote tier-specific retired Antigravity IDs (e.g. gemini-3.6-flash-high) to the bare gemini-3.7-flash, which dropped the tier encoded by the saved defaultModel and caused routed calls to fall back to the 3.7 default thinkingLevel.

Description

• Add an optional preserveDefaultModel flag to ModelRename to allow leaving a saved defaultModel untouched when the legacy id encodes request semantics the replacement cannot represent.
• Set preserveDefaultModel for tier-specific retired Antigravity Flash ids (but not the bare gemini-3.6-flash) so list/catalog fields are renamed while a tier-bearing saved default is retained.
• Change projectModelRenames to skip rewriting prov.defaultModel when rename.preserveDefaultModel is true.
• Update tests/gemini-37-flash-migration.test.ts to assert that a migrated gemini-3.6-flash-high remains the saved default and still resolves to gemini-3.7-flash with `thinkingLevel:

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Codex Task

Summary by CodeRabbit

• Bug Fixes
  • Improved retired-model migration for tiered Flash models.
  • Preserved saved tier-specific defaults where applicable, while still updating model selections and metadata.
  • Removed duplicate entries from migrated model lists.
  • Legacy tiered defaults now resolve to the current Flash model with the appropriate historical thinking level.

[github-actions]

✅ Deterministic PR hygiene checks passed.

[github-actions]

⏳ DRAFT

• wrong target branch (main); retarget to dev.

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• Retarget this PR to dev — all contributions go to dev.

Its title has been prefixed with [WRONG BRANCH].
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📥 Commits

Reviewing files that changed from the base of the PR and between f05ba75 and 8a4d261.

📒 Files selected for processing (2)

• src/providers/model-rename-migration.ts
• tests/gemini-37-flash-migration.test.ts

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📝 Walkthrough

Walkthrough

The migration adds conditional preservation for tier-specific legacy defaults. Antigravity Flash tier mappings retain their saved defaults while updating model lists and metadata. Tests verify deduplication and resolution to the new wire model with the historical thinking level.

Changes

Model default preservation

Layer / File(s)	Summary
Conditional default migration src/providers/model-rename-migration.ts, tests/gemini-37-flash-migration.test.ts	ModelRename supports preserveDefaultModel. Tiered Antigravity Flash mappings retain legacy defaults, while the base model default is still renamed. The migration test verifies the retained gemini-3.6-flash-high default and its resolution to gemini-3.7-flash with high thinking.

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

Merge Risk: ⚪ Minimal · up to 8a4d2

This localized migration fix preserves tier-specific saved defaults while continuing to rename the underlying model, and no actionable merge-blocking risk remains beyond normal checks and review.

Suggested reviewers: lidge-jun, ingwannu

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly identifies the Antigravity change to preserve the migrated default reasoning tier.
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.

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[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Preserve the tier through OAuth reconciliation

For the normal google-antigravity configuration with authMode: "oauth", this flag is undone during the same startup: startServer runs the rename migration and then reconcileOAuthProviders (src/server/index.ts:494-505), whose stale-default check replaces any default absent from the refreshed preset model list with gemini-3.7-flash (src/oauth/index.ts:935-942). Since the tier-bearing alias is deliberately removed from models, a saved gemini-3.6-flash-high therefore still becomes the medium default before requests are served. Preserve recognized compatibility aliases during OAuth reconciliation (or persist the tier separately), and cover the actual migration-plus-reconciliation sequence rather than testing the projection alone.

AGENTS.md reference: src/AGENTS.md:L24-L26

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