feat(cli): replace ANTHROPIC_SMALL_FAST_MODEL with Fable default (#8343)

Claude Code retired ANTHROPIC_SMALL_FAST_MODEL; expose
ANTHROPIC_DEFAULT_FABLE_MODEL from the claude registry instead.

open-sse/config/providerRegistry.ts

@@ -258,11 +258,12 @@ export function getProviderCategory(provider: string): "oauth" | "apikey" {
 }
 
 /**
- * Derive the latest opus/sonnet/haiku model IDs from the `claude` registry entry.
+ * Derive the latest fable/opus/sonnet/haiku model IDs from the `claude` registry entry.
  * Picks the first model whose ID matches each family pattern — registry order
  * determines precedence, so newer models should be listed first.
  */
 export function getClaudeCodeDefaultModels(): {
+  fable: string;
   opus: string;
   sonnet: string;
   haiku: string;
@@ -270,6 +271,7 @@ export function getClaudeCodeDefaultModels(): {
   const models = REGISTRY.claude?.models ?? [];
   const find = (pattern: RegExp) => models.find((m) => pattern.test(m.id))?.id ?? "";
   return {
+    fable: find(/fable/i),
     opus: find(/opus/i),
     sonnet: find(/sonnet/i),
     haiku: find(/haiku/i),

src/shared/constants/cliTools.ts

@@ -23,11 +23,12 @@ export const CLI_TOOLS: Record<string, CliCatalogEntry> = {
     envVars: {
       baseUrl: "ANTHROPIC_BASE_URL",
       model: "ANTHROPIC_MODEL",
+      fableModel: "ANTHROPIC_DEFAULT_FABLE_MODEL",
       opusModel: "ANTHROPIC_DEFAULT_OPUS_MODEL",
       sonnetModel: "ANTHROPIC_DEFAULT_SONNET_MODEL",
       haikuModel: "ANTHROPIC_DEFAULT_HAIKU_MODEL",
     },
-    modelAliases: ["default", "sonnet", "opus", "haiku", "opusplan"],
+    modelAliases: ["default", "fable", "sonnet", "opus", "haiku", "opusplan"],
     settingsFile: "~/.claude/settings.json",
     defaultCommand: "claude",
     defaultModels: [
@@ -40,11 +41,11 @@ export const CLI_TOOLS: Record<string, CliCatalogEntry> = {
         isTopLevel: true,
       },
       {
-        id: "smallFast",
-        name: "Small Fast Model",
-        alias: "smallFast",
-        envKey: "ANTHROPIC_SMALL_FAST_MODEL",
-        defaultValue: _cc.haiku ? `cc/${_cc.haiku}` : "cc/claude-haiku-4-5-20251001",
+        id: "fable",
+        name: "Claude Fable",
+        alias: "fable",
+        envKey: "ANTHROPIC_DEFAULT_FABLE_MODEL",
+        defaultValue: _cc.fable ? `cc/${_cc.fable}` : "cc/claude-fable-5",
         isTopLevel: true,
       },
       {

tests/unit/claude-cli-defaults.test.ts

@@ -6,11 +6,15 @@ test("getClaudeCodeDefaultModels returns expected default models", () => {
   const models = getClaudeCodeDefaultModels();
 
   // They should be non-empty strings because providerRegistry is populated statically
+  assert.ok(typeof models.fable === "string");
   assert.ok(typeof models.opus === "string");
   assert.ok(typeof models.sonnet === "string");
   assert.ok(typeof models.haiku === "string");
 
   // Check that the returned IDs match the expected patterns
+  if (models.fable) {
+    assert.match(models.fable, /fable/i);
+  }
   if (models.opus) {
     assert.match(models.opus, /opus/i);
   }