fix: distinguish model options with duplicate labels (#1286)

Fixes #1246.

When `availableModels` includes aliases and pinned IDs that inherit the
same SDK display name, name-only model pickers show indistinguishable
rows. Append the selectable model ID to names that remain duplicated
after the existing version-label normalization. For example, the four
`Opus 5.5` rows become `Opus 5.5 (opus)`, `Opus 5.5 (opus[1m])`, and
their explicit-ID equivalents.

Keep every option and its ID, description, selection, and recommendation
behavior. Existing distinct labels stay unchanged. Regression tests
exercise the real allowlist transformation and cover duplicate custom
labels too.

Validation:

- Linux, locked dependencies and the repository's `lts/*` Node
configuration: `npm run check`, `npm run build`, and the full test suite
passed at ba37dd8: **2,491 passed, 30 skipped** ([fix
job](https://github.com/jipeng6036-del/claude-agent-acp/actions/runs/37923655565/job/113797353655)).
- Exact baseline 908c994: **2,489 passed, 30 skipped**; both new
regression tests fail against the original implementation. All existing
test outcomes match ([baseline
verification](https://github.com/jipeng6036-del/claude-agent-acp/actions/runs/37923859076)).
- Windows/Node 24: build and 105 focused tests passed. The full suite
has the same 48 failures on baseline and fix; only the two new tests add
passes. Authenticated SDK and JetBrains UI integration were not run.

Signed-off-by: Jasper <241105014+jipeng6036-del@users.noreply.github.com>
Co-authored-by: Jasper <241105014+jipeng6036-del@users.noreply.github.com>

src/session-model.ts

@@ -595,12 +595,20 @@ export async function getAvailableModels(
   for (const name of displayNames) {
     displayNameCounts.set(name, (displayNameCounts.get(name) ?? 0) + 1);
   }
+  const names = models.map((model, index) =>
+    displayNameCounts.get(displayNames[index]) === 1 ? displayNames[index] : model.displayName,
+  );
+  const nameCounts = new Map<string, number>();
+  for (const name of names) {
+    nameCounts.set(name, (nameCounts.get(name) ?? 0) + 1);
+  }
 
   return {
     availableModels: models.map((model, index) => ({
       modelId: model.value,
-      name:
+      // Allowlisted aliases can inherit the same SDK label. Keep every ID
-        displayNameCounts.get(displayNames[index]) === 1 ? displayNames[index] : model.displayName,
+      // selectable, but distinguish the rows for clients that show only names.
+      name: nameCounts.get(names[index]) === 1 ? names[index] : `${names[index]} (${model.value})`,
       description: model.description,
     })),
     currentModelId: currentModel.value,

src/tests/model-presentation.test.ts

@@ -1,6 +1,10 @@
 import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
 import { query, type ModelInfo, type Query } from "@anthropic-ai/claude-agent-sdk";
-import { buildModelConfigOption, getAvailableModels } from "../session-model.js";
+import {
+  applyAvailableModelsAllowlist,
+  buildModelConfigOption,
+  getAvailableModels,
+} from "../session-model.js";
 
 const OPUS: ModelInfo = {
   value: "opus[1m]",
@@ -151,6 +155,68 @@ describe("versioned model display names", () => {
     );
     expect(state.availableModels.map((model) => model.name)).toEqual(["Opus (1M context)", "Opus"]);
   });
+
+  it("distinguishes allowlisted aliases and pins that inherit the same SDK label", async () => {
+    const sdkModels: ModelInfo[] = [
+      { value: "default", displayName: "Default (recommended)", description: "" },
+      {
+        value: "opus",
+        resolvedModel: "claude-opus-5-5",
+        displayName: "Opus 5.5",
+        description: "For complex work and everyday tasks",
+      },
+      { value: "haiku", displayName: "Haiku", description: "Fast" },
+    ];
+    const ids = ["claude-opus-5-5[1m]", "claude-opus-5-5", "opus[1m]", "opus", "haiku"];
+    const models = applyAvailableModelsAllowlist(sdkModels, ids);
+    const setModel = vi.fn();
+    const state = await getAvailableModels(
+      { setModel } as unknown as Query,
+      models,
+      sdkModels,
+      { getSettings: () => ({}) },
+      { log: vi.fn(), error: vi.fn() },
+      false,
+      "model-presentation-test",
+    );
+
+    const expected = [
+      "Default (recommended)",
+      ...ids.slice(0, 4).map((id) => `Opus 5.5 (${id})`),
+      "Haiku",
+    ];
+    expect(state.availableModels.map((model) => model.name)).toEqual(expected);
+    expect(state.availableModels.map((model) => model.modelId)).toEqual(["default", ...ids]);
+    expect(state.currentModelId).toBe("default");
+    expect(state.availableModels.slice(1, 5).map((model) => model.description)).toEqual(
+      Array(4).fill(sdkModels[1].description),
+    );
+    const option = buildModelConfigOption(state, models, false);
+    expect(option).toMatchObject({ currentValue: "default" });
+    expect(option.type === "select" && option.options.map((model) => model.name)).toEqual(expected);
+    expect(sdkModels[1].displayName).toBe("Opus 5.5");
+    expect(setModel).not.toHaveBeenCalled();
+  });
+
+  it("distinguishes identical custom labels without changing their model IDs", async () => {
+    const models: ModelInfo[] = [
+      { value: "provider-a", displayName: "My model", description: "First endpoint" },
+      { value: "provider-b", displayName: "My model", description: "Second endpoint" },
+    ];
+    const state = await getAvailableModels(
+      {} as Query,
+      models,
+      models,
+      { getSettings: () => ({}) },
+      { log: vi.fn(), error: vi.fn() },
+      false,
+      "model-presentation-test",
+    );
+    expect(state.availableModels).toEqual([
+      { modelId: "provider-a", name: "My model (provider-a)", description: "First endpoint" },
+      { modelId: "provider-b", name: "My model (provider-b)", description: "Second endpoint" },
+    ]);
+  });
 });
 
 // Account-dependent model availability requires the same authenticated environment