diff --git a/src/resources/extensions/gsd/auto-model-selection.ts b/src/resources/extensions/gsd/auto-model-selection.ts
index c79ab55b2..60cca2663 100644
--- a/src/resources/extensions/gsd/auto-model-selection.ts
+++ b/src/resources/extensions/gsd/auto-model-selection.ts
@@ -222,9 +222,30 @@ export function resolveModelId<T extends { id: string; provider: string }>(
     );
   }
 
-  // Bare ID — prefer current provider, then first available
-  const exactProviderMatch = availableModels.find(
-    m => m.id === modelId && m.provider === currentProvider,
-  );
-  return exactProviderMatch ?? availableModels.find(m => m.id === modelId);
+  // Bare ID — resolve with provider precedence to avoid silent misrouting.
+  // Extension providers (e.g. claude-code) expose the same model IDs as their
+  // upstream API providers but route through a subprocess with different
+  // context, tool visibility, and cost characteristics (#2905).  Bare IDs in
+  // PREFERENCES.md must resolve to the canonical API provider, not to an
+  // extension wrapper that happens to be the current session provider.
+  const candidates = availableModels.filter(m => m.id === modelId);
+  if (candidates.length === 0) return undefined;
+  if (candidates.length === 1) return candidates[0];
+
+  // Extension / CLI-wrapper providers that should never win bare-ID resolution
+  // when a first-class API provider also offers the same model.
+  const EXTENSION_PROVIDERS = new Set(["claude-code"]);
+
+  // Prefer currentProvider only when it is a first-class API provider
+  if (currentProvider && !EXTENSION_PROVIDERS.has(currentProvider)) {
+    const providerMatch = candidates.find(m => m.provider === currentProvider);
+    if (providerMatch) return providerMatch;
+  }
+
+  // Prefer "anthropic" as the canonical provider for Anthropic models
+  const anthropicMatch = candidates.find(m => m.provider === "anthropic");
+  if (anthropicMatch) return anthropicMatch;
+
+  // Fall back to first non-extension candidate, or any candidate
+  return candidates.find(m => !EXTENSION_PROVIDERS.has(m.provider)) ?? candidates[0];
 }
diff --git a/src/resources/extensions/gsd/tests/auto-model-selection.test.ts b/src/resources/extensions/gsd/tests/auto-model-selection.test.ts
index 2bc41fa9e..4ea3245a3 100644
--- a/src/resources/extensions/gsd/tests/auto-model-selection.test.ts
+++ b/src/resources/extensions/gsd/tests/auto-model-selection.test.ts
@@ -4,7 +4,7 @@ import { mkdtempSync, mkdirSync, rmSync, writeFileSync } from "node:fs";
 import { join } from "node:path";
 import { tmpdir } from "node:os";
 
-import { resolvePreferredModelConfig } from "../auto-model-selection.js";
+import { resolvePreferredModelConfig, resolveModelId } from "../auto-model-selection.js";
 
 function makeTempDir(prefix: string): string {
   return mkdtempSync(join(tmpdir(), prefix));
@@ -137,3 +137,73 @@ test("resolvePreferredModelConfig keeps explicit phase models as the ceiling", (
     rmSync(tempGsdHome, { recursive: true, force: true });
   }
 });
+
+// ─── resolveModelId tests ─────────────────────────────────────────────────
+
+test("resolveModelId: bare ID resolves to anthropic over claude-code when session is claude-code (#2905)", () => {
+  const availableModels = [
+    { id: "claude-sonnet-4-6", provider: "anthropic" },
+    { id: "claude-sonnet-4-6", provider: "claude-code" },
+  ];
+
+  // Bug: when currentProvider is "claude-code", bare ID "claude-sonnet-4-6"
+  // resolves to claude-code/claude-sonnet-4-6 instead of anthropic/claude-sonnet-4-6
+  const result = resolveModelId("claude-sonnet-4-6", availableModels, "claude-code");
+  assert.ok(result, "should resolve a model");
+  assert.equal(result.provider, "anthropic", "bare ID must resolve to anthropic, not claude-code");
+});
+
+test("resolveModelId: bare ID still prefers current provider when it is a first-class API provider", () => {
+  const availableModels = [
+    { id: "claude-sonnet-4-6", provider: "anthropic" },
+    { id: "claude-sonnet-4-6", provider: "bedrock" },
+  ];
+
+  const result = resolveModelId("claude-sonnet-4-6", availableModels, "bedrock");
+  assert.ok(result, "should resolve a model");
+  assert.equal(result.provider, "bedrock", "bare ID should prefer current provider when it is a real API provider");
+});
+
+test("resolveModelId: explicit provider/model format still resolves to claude-code when specified", () => {
+  const availableModels = [
+    { id: "claude-sonnet-4-6", provider: "anthropic" },
+    { id: "claude-sonnet-4-6", provider: "claude-code" },
+  ];
+
+  const result = resolveModelId("claude-code/claude-sonnet-4-6", availableModels, "anthropic");
+  assert.ok(result, "should resolve a model");
+  assert.equal(result.provider, "claude-code", "explicit provider prefix must be respected");
+});
+
+test("resolveModelId: bare ID with only one provider works normally", () => {
+  const availableModels = [
+    { id: "claude-sonnet-4-6", provider: "anthropic" },
+  ];
+
+  const result = resolveModelId("claude-sonnet-4-6", availableModels, "anthropic");
+  assert.ok(result, "should resolve a model");
+  assert.equal(result.provider, "anthropic");
+});
+
+test("resolveModelId: bare ID with claude-code as only provider still resolves", () => {
+  const availableModels = [
+    { id: "claude-sonnet-4-6", provider: "claude-code" },
+  ];
+
+  // If claude-code is the ONLY provider for this model, it should still resolve
+  const result = resolveModelId("claude-sonnet-4-6", availableModels, "claude-code");
+  assert.ok(result, "should resolve even when only available via claude-code");
+  assert.equal(result.provider, "claude-code");
+});
+
+test("resolveModelId: anthropic wins over claude-code regardless of list order", () => {
+  const availableModels = [
+    { id: "claude-sonnet-4-6", provider: "claude-code" },
+    { id: "claude-sonnet-4-6", provider: "anthropic" },
+  ];
+
+  // Even when claude-code appears first in the list, anthropic should win
+  const result = resolveModelId("claude-sonnet-4-6", availableModels, "claude-code");
+  assert.ok(result, "should resolve a model");
+  assert.equal(result.provider, "anthropic", "anthropic must win over claude-code regardless of list order");
+});