From beeb2873d0d6f3efc46614eebbb8f56235f263e2 Mon Sep 17 00:00:00 2001
From: Sawyer Cutler <sawyer@dirtroad.dev>
Date: Sat, 8 Aug 2026 11:37:16 -0700
Subject: [PATCH] Extract a shared resolveDefaultModel helper for the
 default-model fallback

The defaultModel-or-first-model precedence was hand-rolled at three call
sites (providers.ts:86, inference-sources.ts:43, settings.ts:1074), so a
rule change at one site wouldn't apply at the others and the active and
backup model for the same provider could diverge.
---
 src/config/inference-sources.ts |  3 ++-
 src/config/providers.test.ts    | 26 +++++++++++++++++++++++++-
 src/config/providers.ts         | 12 +++++++++++-
 src/config/settings.ts          |  3 ++-
 4 files changed, 40 insertions(+), 4 deletions(-)

diff --git a/src/config/inference-sources.ts b/src/config/inference-sources.ts
index 374a5d04f..9a378d29d 100644
--- a/src/config/inference-sources.ts
+++ b/src/config/inference-sources.ts
@@ -13,6 +13,7 @@ import type { Settings } from "./settings.js";
 import type { ReasoningEffort } from "../provider/reasoning-effort.js";
 import { SOURCE_MAX_TOKENS } from "./index.js";
 import { isOpenCodeGoProvider } from "../../packages/opencode-go/src/index.js";
+import { resolveDefaultModel } from "./providers.js";
 
 export type BuildSourceContext = {
   sessionId: string;
@@ -40,7 +41,7 @@ function backupRefsFromSettings(
   const tail: ProviderRef[] = [];
   for (const [provider, p] of Object.entries(settings.providers)) {
     if (seenProviders.has(provider)) continue;
-    const model = p.defaultModel ?? p.models[0];
+    const model = resolveDefaultModel(p);
     if (model === undefined || model.length === 0) continue;
     seenProviders.add(provider);
     tail.push({ provider, model });
diff --git a/src/config/providers.test.ts b/src/config/providers.test.ts
index 877e0d295..b6a14d8e6 100644
--- a/src/config/providers.test.ts
+++ b/src/config/providers.test.ts
@@ -2,7 +2,7 @@ import { describe, expect, test } from "bun:test";
 
 import { OPENCODE_GO_BASE_URL } from "../../packages/opencode-go/src/index.js";
 import type { ProviderCatalogEntry } from "./index.js";
-import { buildProviderEntry } from "./providers.js";
+import { buildProviderEntry, resolveDefaultModel } from "./providers.js";
 
 const baseCatalog: ProviderCatalogEntry[] = [
   {
@@ -269,3 +269,27 @@ describe("buildProviderEntry OpenCode Go baseURL pin", () => {
     expect(result.entry.opencodeGo).toBe(true);
   });
 });
+
+describe("resolveDefaultModel", () => {
+  test("returns defaultModel when present and non-empty", () => {
+    expect(resolveDefaultModel({ defaultModel: "gpt-4o", models: ["gpt-4o", "gpt-4o-mini"] })).toBe(
+      "gpt-4o",
+    );
+  });
+
+  test("falls back to models[0] when defaultModel is absent", () => {
+    expect(resolveDefaultModel({ models: ["gpt-4o", "gpt-4o-mini"] })).toBe("gpt-4o");
+  });
+
+  test("falls back to models[0] when defaultModel is empty", () => {
+    expect(resolveDefaultModel({ defaultModel: "", models: ["gpt-4o"] })).toBe("gpt-4o");
+  });
+
+  test("returns undefined for an undefined entry", () => {
+    expect(resolveDefaultModel(undefined)).toBeUndefined();
+  });
+
+  test("returns undefined when entry has no models and no defaultModel", () => {
+    expect(resolveDefaultModel({ models: [] })).toBeUndefined();
+  });
+});
diff --git a/src/config/providers.ts b/src/config/providers.ts
index 638baf67f..f762adf9d 100644
--- a/src/config/providers.ts
+++ b/src/config/providers.ts
@@ -19,6 +19,16 @@ export type ProviderSubmission = {
   opencodeGo?: boolean;
 };
 
+// Precedence for the active/backup model of a provider: defaultModel wins
+// when present and non-empty, otherwise the first configured model.
+export function resolveDefaultModel(
+  entry: { defaultModel?: string; models: readonly string[] } | undefined,
+): string | undefined {
+  const defaultModel = entry?.defaultModel;
+  if (defaultModel !== undefined && defaultModel.length > 0) return defaultModel;
+  return entry?.models[0];
+}
+
 export type ProviderEntryResult =
   | { ok: true; entry: ProviderCatalogEntry; catalog: ProviderCatalogEntry[]; selectedModel: string }
   | { ok: false; error: string };
@@ -83,7 +93,7 @@ export function buildProviderEntry(
   const catalog = currentCatalog
     .filter((p) => p.name !== submission.name && p.name !== submission.originalName)
     .concat(entry);
-  const selectedModel = entry.defaultModel ?? entry.models[0];
+  const selectedModel = resolveDefaultModel(entry);
   if (selectedModel === undefined) {
     return { ok: false, error: "Provider must include at least one model" };
   }
diff --git a/src/config/settings.ts b/src/config/settings.ts
index ef78c4428..9c9ab0677 100644
--- a/src/config/settings.ts
+++ b/src/config/settings.ts
@@ -8,6 +8,7 @@ import { type } from "arktype";
 import { SETTINGS_DIR_NAME } from "../branding.js";
 import { REASONING_EFFORTS, isReasoningEffort, type ReasoningEffort } from "../provider/reasoning-effort.js";
 import { isSessionMode, type SessionMode } from "./session-mode.js";
+import { resolveDefaultModel } from "./providers.js";
 import {
   OPENCODE_GO_BASE_URL,
   isOpenCodeGoProvider,
@@ -1071,7 +1072,7 @@ export function resolveProvider(input: ResolveInput): ResolvedProvider {
   const baseURL = go ? OPENCODE_GO_BASE_URL : selected?.baseURL;
   const apiKey = selected?.apiKey;
   const keyless = selected?.keyless === true;
-  const model = cli.model ?? local?.model ?? selected?.defaultModel ?? selected?.models[0];
+  const model = cli.model ?? local?.model ?? resolveDefaultModel(selected);
 
   // A provider name was selected (from local file or defaultProvider) but is not
   // actually configured — distinguish this from "nothing configured at all" so