From ec20a82b4eb68813429137e066247dffff2ab2d5 Mon Sep 17 00:00:00 2001
From: Ravi Tharuma <RaviTharuma@users.noreply.github.com>
Date: Wed, 25 Mar 2026 22:19:51 +0100
Subject: [PATCH] fix(model-capabilities): align gemini aliases and alias
 lookup

---
 src/shared/model-capabilities.test.ts          |  6 +++---
 src/shared/model-capability-aliases.test.ts    | 12 +++++++++++-
 src/shared/model-capability-aliases.ts         |  8 ++++----
 src/shared/model-capability-guardrails.test.ts |  8 ++++----
 4 files changed, 22 insertions(+), 12 deletions(-)

diff --git a/src/shared/model-capabilities.test.ts b/src/shared/model-capabilities.test.ts
index 4a97002f9..35dc40f8b 100644
--- a/src/shared/model-capabilities.test.ts
+++ b/src/shared/model-capabilities.test.ts
@@ -27,8 +27,8 @@ describe("getModelCapabilities", () => {
         },
         toolCall: true,
       },
-      "gemini-3.1-pro-preview": {
-        id: "gemini-3.1-pro-preview",
+      "gemini-3.1-pro": {
+        id: "gemini-3.1-pro",
         family: "gemini",
         reasoning: true,
         temperature: true,
@@ -193,7 +193,7 @@ describe("getModelCapabilities", () => {
     })
 
     expect(result).toMatchObject({
-      canonicalModelID: "gemini-3.1-pro-preview",
+      canonicalModelID: "gemini-3.1-pro",
       family: "gemini",
       supportsThinking: true,
       supportsTemperature: true,
diff --git a/src/shared/model-capability-aliases.test.ts b/src/shared/model-capability-aliases.test.ts
index a164ffb60..9e563fc02 100644
--- a/src/shared/model-capability-aliases.test.ts
+++ b/src/shared/model-capability-aliases.test.ts
@@ -18,12 +18,22 @@ describe("model-capability-aliases", () => {
 
     expect(result).toEqual({
       requestedModelID: "gemini-3.1-pro-high",
-      canonicalModelID: "gemini-3.1-pro-preview",
+      canonicalModelID: "gemini-3.1-pro",
       source: "exact-alias",
       ruleID: "gemini-3.1-pro-tier-alias",
     })
   })
 
+  test("does not resolve prototype keys as aliases", () => {
+    const result = resolveModelIDAlias("constructor")
+
+    expect(result).toEqual({
+      requestedModelID: "constructor",
+      canonicalModelID: "constructor",
+      source: "canonical",
+    })
+  })
+
   test("normalizes legacy Claude thinking aliases through a named exact rule", () => {
     const result = resolveModelIDAlias("claude-opus-4-6-thinking")
 
diff --git a/src/shared/model-capability-aliases.ts b/src/shared/model-capability-aliases.ts
index 523755d61..953b5a300 100644
--- a/src/shared/model-capability-aliases.ts
+++ b/src/shared/model-capability-aliases.ts
@@ -23,13 +23,13 @@ const EXACT_ALIAS_RULES: ReadonlyArray<ExactAliasRule> = [
   {
     aliasModelID: "gemini-3.1-pro-high",
     ruleID: "gemini-3.1-pro-tier-alias",
-    canonicalModelID: "gemini-3.1-pro-preview",
+    canonicalModelID: "gemini-3.1-pro",
     rationale: "OmO historically encoded Gemini tier selection in the model name instead of variant metadata.",
   },
   {
     aliasModelID: "gemini-3.1-pro-low",
     ruleID: "gemini-3.1-pro-tier-alias",
-    canonicalModelID: "gemini-3.1-pro-preview",
+    canonicalModelID: "gemini-3.1-pro",
     rationale: "OmO historically encoded Gemini tier selection in the model name instead of variant metadata.",
   },
   {
@@ -52,7 +52,7 @@ const EXACT_ALIAS_RULES: ReadonlyArray<ExactAliasRule> = [
   },
 ]
 
-const EXACT_ALIAS_RULES_BY_MODEL: Readonly<Record<string, ExactAliasRule>> = Object.fromEntries(
+const EXACT_ALIAS_RULES_BY_MODEL: ReadonlyMap<string, ExactAliasRule> = new Map(
   EXACT_ALIAS_RULES.map((rule) => [rule.aliasModelID, rule]),
 )
 
@@ -64,7 +64,7 @@ function normalizeLookupModelID(modelID: string): string {
 
 export function resolveModelIDAlias(modelID: string): ModelIDAliasResolution {
   const normalizedModelID = normalizeLookupModelID(modelID)
-  const exactRule = EXACT_ALIAS_RULES_BY_MODEL[normalizedModelID]
+  const exactRule = EXACT_ALIAS_RULES_BY_MODEL.get(normalizedModelID)
   if (exactRule) {
     return {
       requestedModelID: normalizedModelID,
diff --git a/src/shared/model-capability-guardrails.test.ts b/src/shared/model-capability-guardrails.test.ts
index c5e7c54fc..06a9c07eb 100644
--- a/src/shared/model-capability-guardrails.test.ts
+++ b/src/shared/model-capability-guardrails.test.ts
@@ -29,7 +29,7 @@ describe("model-capability-guardrails", () => {
     const brokenSnapshot: ModelCapabilitiesSnapshot = {
       ...bundledSnapshot,
       models: Object.fromEntries(
-        Object.entries(bundledSnapshot.models).filter(([modelID]) => modelID !== "gemini-3.1-pro-preview"),
+        Object.entries(bundledSnapshot.models).filter(([modelID]) => modelID !== "gemini-3.1-pro"),
       ),
     }
 
@@ -42,7 +42,7 @@ describe("model-capability-guardrails", () => {
       expect.objectContaining({
         kind: "alias-target-missing-from-snapshot",
         aliasModelID: "gemini-3.1-pro-high",
-        canonicalModelID: "gemini-3.1-pro-preview",
+        canonicalModelID: "gemini-3.1-pro",
       }),
     )
   })
@@ -70,7 +70,7 @@ describe("model-capability-guardrails", () => {
       expect.objectContaining({
         kind: "exact-alias-collides-with-snapshot",
         aliasModelID: "gemini-3.1-pro-high",
-        canonicalModelID: "gemini-3.1-pro-preview",
+        canonicalModelID: "gemini-3.1-pro",
       }),
     )
   })
@@ -84,7 +84,7 @@ describe("model-capability-guardrails", () => {
       expect.objectContaining({
         kind: "built-in-model-relies-on-alias",
         modelID: "gemini-3.1-pro-high",
-        canonicalModelID: "gemini-3.1-pro-preview",
+        canonicalModelID: "gemini-3.1-pro",
         ruleID: "gemini-3.1-pro-tier-alias",
       }),
     )