feat(claude): add Fable 5.2 and Mythos 5.2 to the model catalog (#9233)

Adds Claude Fable 5.2 and Mythos 5.2, available from Claude Code 2.1.321, and defaults both to medium effort to match Claude Code.

Co-authored-by: Mohamed Boudra <boudra.moha@gmail.com>
Co-authored-by: gudcks <84506708+gudcks@users.noreply.github.com>

packages/cli/tests/15-provider.test.ts

@@ -62,10 +62,15 @@ const EXPECTED_CLAUDE_MODELS = [
     model: "Opus 5",
     descriptionFragment: "Previous release",
   },
+  {
+    id: "claude-fable-5-2",
+    model: "Fable 5.2",
+    descriptionFragment: "Most powerful",
+  },
   {
     id: "claude-fable-5-1",
     model: "Fable 5.1",
-    descriptionFragment: "Most powerful",
+    descriptionFragment: "Previous release",
   },
   {
     id: "claude-fable-5",
@@ -199,11 +204,10 @@ function assertClaudeModels(data: ProviderModel[]): void {
     );
   }
 
-  const fable51Index = data.findIndex((model) => model.id === "claude-fable-5-1");
-  const fable5Index = data.findIndex((model) => model.id === "claude-fable-5");
-  assert.strictEqual(
-    fable5Index,
-    fable51Index + 1,
+  const fable52Index = data.findIndex((model) => model.id === "claude-fable-5-2");
+  assert.deepStrictEqual(
+    data.slice(fable52Index, fable52Index + 3).map((model) => model.id),
+    ["claude-fable-5-2", "claude-fable-5-1", "claude-fable-5"],
     "Fable models should stay adjacent and newest-first",
   );
   assert(

packages/server/src/server/agent/providers/claude/agent.test.ts

@@ -1614,6 +1614,8 @@ describe("ClaudeAgentSession features", () => {
   test.each([
     ["supported model", "claude-opus-4-8", { type: "disabled" }, undefined],
     ["Mythos 5.1", "claude-mythos-5-1", { type: "adaptive", display: "summarized" }, "high"],
+    ["Fable 5.2", "claude-fable-5-2", { type: "adaptive", display: "summarized" }, "medium"],
+    ["Mythos 5.2", "claude-mythos-5-2", { type: "adaptive", display: "summarized" }, "medium"],
     ["Haiku 5.5", "claude-haiku-5-5", { type: "disabled" }, undefined],
     ["unsupported model", "claude-fable-5", { type: "adaptive", display: "summarized" }, "high"],
     ["custom model", "openrouter/anthropic/claude-opus-4-8", undefined, undefined],

packages/server/src/server/agent/providers/claude/feature-definitions.ts

@@ -5,7 +5,7 @@ export const CLAUDE_FAST_MODE_CONTROL: AgentOptionToggleControl = {
   type: "toggle",
   key: "fast_mode",
   label: "Fast",
-  description: "Lower latency Opus responses at higher token cost",
+  description: "Lower latency responses at higher token cost",
   tooltip: "Toggle fast mode",
   icon: "zap",
 };

packages/server/src/server/agent/providers/claude/model-manifest.ts

@@ -58,6 +58,17 @@ export const CLAUDE_MODEL_MANIFEST = [
     supportsThinkingDisabled: true,
     supportsFastMode: true,
   },
+  {
+    id: "claude-mythos-5-2",
+    label: "Mythos 5.2",
+    requiresDiscovery: true,
+    description: "Mythos 5.2 · Requires verified access",
+    minimumClaudeCodeVersion: "2.1.321",
+    defaultThinkingOptionId: "medium",
+    contextWindowMaxTokens: 1_000_000,
+    effortLevels: CLAUDE_EFFORT_LEVELS.xhigh,
+    supportsFastMode: true,
+  },
   {
     id: "claude-mythos-5-1",
     label: "Mythos 5.1",
@@ -66,10 +77,20 @@ export const CLAUDE_MODEL_MANIFEST = [
     contextWindowMaxTokens: 1_000_000,
     effortLevels: CLAUDE_EFFORT_LEVELS.xhigh,
   },
+  {
+    id: "claude-fable-5-2",
+    label: "Fable 5.2",
+    description: "Fable 5.2 · Most powerful model",
+    minimumClaudeCodeVersion: "2.1.321",
+    defaultThinkingOptionId: "medium",
+    contextWindowMaxTokens: 1_000_000,
+    effortLevels: CLAUDE_EFFORT_LEVELS.xhigh,
+    supportsFastMode: true,
+  },
   {
     id: "claude-fable-5-1",
     label: "Fable 5.1",
-    description: "Fable 5.1 · Most powerful model",
+    description: "Fable 5.1 · Previous release",
     contextWindowMaxTokens: 1_000_000,
     effortLevels: CLAUDE_EFFORT_LEVELS.xhigh,
   },

packages/server/src/server/agent/providers/claude/models.test.ts

@@ -61,17 +61,23 @@ async function createClaudeConfigDirWithRawSettings(settings: string): Promise<s
   return configDir;
 }
 
-function createCatalogClient(claudeCodeVersion = "2.1.293"): ClaudeAgentClient {
+function createCatalogClient(claudeCodeVersion = "2.1.321"): ClaudeAgentClient {
   return new ClaudeAgentClient({
     logger: createTestLogger(),
     resolveVersion: async () => claudeCodeVersion,
     discoverModels: async () => [
       {
         value: "mythos",
-        resolvedModel: "claude-mythos-5-1",
+        resolvedModel: "claude-mythos-5-2",
         displayName: "Mythos",
         description: "",
       },
+      {
+        value: "claude-mythos-5-1",
+        resolvedModel: "claude-mythos-5-1",
+        displayName: "Mythos 5.1",
+        description: "",
+      },
     ],
   });
 }
@@ -82,7 +88,9 @@ describe("getClaudeModels", () => {
     expect(models.map((m) => m.id)).toEqual([
       "claude-opus-5-5",
       "claude-opus-5",
+      "claude-mythos-5-2",
       "claude-mythos-5-1",
+      "claude-fable-5-2",
       "claude-fable-5-1",
       "claude-fable-5",
       "claude-fable-5[1m]",
@@ -118,7 +126,9 @@ describe("getClaudeModels", () => {
       new Map([
         ["claude-opus-5-5", 1_000_000],
         ["claude-opus-5", 1_000_000],
+        ["claude-mythos-5-2", 1_000_000],
         ["claude-mythos-5-1", 1_000_000],
+        ["claude-fable-5-2", 1_000_000],
         ["claude-fable-5-1", 1_000_000],
         ["claude-fable-5", 1_000_000],
         ["claude-fable-5[1m]", 1_000_000],
@@ -163,6 +173,12 @@ describe("getClaudeModels", () => {
     expect(getClaudeModels("2.1.293").find((model) => model.isDefault)?.id).toBe("claude-opus-5-5");
   });
 
+  it("gates Fable 5.2 on Claude Code 2.1.321 without changing the default", () => {
+    expect(getClaudeModels("2.1.320").map((model) => model.id)).not.toContain("claude-fable-5-2");
+    expect(getClaudeModels("2.1.321").map((model) => model.id)).toContain("claude-fable-5-2");
+    expect(getClaudeModels("2.1.321").find((model) => model.isDefault)?.id).toBe("claude-opus-5-5");
+  });
+
   it("derives thinking options from model effort capabilities", () => {
     const models = new Map(getClaudeModels().map((model) => [model.id, model]));
 
@@ -232,6 +248,8 @@ describe("getClaudeModels", () => {
     ["claude-sonnet-5-20260101", true, "high"],
     ["claude-fable-5", false, "high"],
     ["claude-fable-5-1", false, "high"],
+    ["claude-fable-5-2", false, "medium"],
+    ["claude-mythos-5-2", false, "medium"],
     ["claude-haiku-5-5", true, "medium"],
     ["claude-haiku-5-5-20261007", true, "medium"],
     ["claude-haiku-4-5", false, undefined],
@@ -284,6 +302,31 @@ describe("ClaudeAgentClient.fetchCatalog", () => {
     },
   );
 
+  it("offers Mythos 5.2 in place of Mythos 5.1 when Claude Code resolves mythos to 5.2", async () => {
+    const configDir = await createClaudeConfigDir({});
+    const client = new ClaudeAgentClient({
+      logger: createTestLogger(),
+      resolveVersion: async () => "2.1.321",
+      runtimeSettings: { env: { CLAUDE_CONFIG_DIR: configDir } },
+      discoverModels: async () => [
+        {
+          value: "mythos",
+          resolvedModel: "claude-mythos-5-2",
+          displayName: "Mythos",
+          description: "",
+        },
+      ],
+    });
+    const { models } = await client.fetchCatalog({
+      scope: "workspace",
+      cwd: configDir,
+      force: false,
+    });
+    expect(models.filter((model) => model.id.startsWith("claude-mythos-"))).toEqual([
+      findClaudeModel("claude-mythos-5-2"),
+    ]);
+  });
+
   it("preserves the curated catalog and explicitly configured models after discovery failure", async () => {
     const configDir = await createClaudeConfigDir({ model: "claude-mythos-5-1" });
     const client = new ClaudeAgentClient({
@@ -299,8 +342,8 @@ describe("ClaudeAgentClient.fetchCatalog", () => {
       cwd: configDir,
       force: false,
     });
-    expect(models.filter((model) => model.id !== "claude-mythos-5-1")).toEqual(
-      getClaudeModels("2.1.293").filter((model) => model.id !== "claude-mythos-5-1"),
+    expect(models.filter((model) => !model.id.startsWith("claude-mythos-"))).toEqual(
+      getClaudeModels("2.1.293").filter((model) => !model.id.startsWith("claude-mythos-")),
     );
     expect(models.find((model) => model.id === "claude-mythos-5-1")).toEqual({
       ...findClaudeModel("claude-mythos-5-1"),
@@ -360,7 +403,7 @@ describe("ClaudeAgentClient.fetchCatalog", () => {
     });
     expect(models.map((model) => model.id)).toEqual(
       getClaudeModels("2.1.293")
-        .filter((model) => model.id !== "claude-mythos-5-1")
+        .filter((model) => !model.id.startsWith("claude-mythos-"))
         .map((model) => model.id),
     );
   });
@@ -785,6 +828,44 @@ describe("Claude Fable 5.1 catalog", () => {
   });
 });
 
+describe("Claude Fable 5.2 catalog", () => {
+  it("offers one 1M model with medium default effort, always-on thinking, and fast mode", () => {
+    const models = getClaudeModels().filter((model) => model.id.startsWith("claude-fable-5-2"));
+    expect(models).toHaveLength(1);
+    expect(models[0]).toMatchObject({
+      id: "claude-fable-5-2",
+      label: "Fable 5.2",
+      contextWindowMaxTokens: 1_000_000,
+      defaultThinkingOptionId: "medium",
+    });
+    expect(models[0].thinkingOptions?.map((option) => option.id)).toEqual([
+      "low",
+      "medium",
+      "high",
+      "xhigh",
+      "max",
+      CLAUDE_ULTRACODE_THINKING_OPTION_ID,
+    ]);
+    expect(claudeManifestModelSupportsFastMode("claude-fable-5-2")).toBe(true);
+  });
+
+  it.each([
+    "claude-fable-5-2[1m]",
+    "claude-fable-5-2-20261110",
+    "claude-fable-5-2-20261110[1m]",
+    "Fable 5.2",
+  ])("resolves %s to the single catalog entry", (id) => {
+    expect(findClaudeModel(id)?.id).toBe("claude-fable-5-2");
+  });
+
+  it.each(["claude-fable-5-2", "anthropic/claude-fable-5-2", "us.anthropic.claude-fable-5-2-v1:0"])(
+    "keeps runtime model %s from collapsing onto Fable 5",
+    (id) => {
+      expect(normalizeClaudeRuntimeModelId(id)).toBe("claude-fable-5-2");
+    },
+  );
+});
+
 describe("Claude Opus 5.5 catalog", () => {
   it("offers one Opus 5.5 entry with a 1M context window", () => {
     const opus55Models = getClaudeModels()
@@ -920,7 +1001,7 @@ describe("claudeManifestModelSupportsFastMode", () => {
 
 describe("Claude Mythos 5.1 catalog", () => {
   it("offers one 1M model with high default effort and always-on thinking", () => {
-    const models = getClaudeModels().filter((model) => model.id.startsWith("claude-mythos"));
+    const models = getClaudeModels().filter((model) => model.id.startsWith("claude-mythos-5-1"));
     expect(models).toHaveLength(1);
     expect(models[0]).toMatchObject({
       id: "claude-mythos-5-1",
@@ -965,6 +1046,61 @@ describe("Claude Mythos 5.1 catalog", () => {
   );
 });
 
+describe("Claude Mythos 5.2 catalog", () => {
+  it("stays hidden on Claude Code older than 2.1.321 even when advertised", async () => {
+    const configDir = await createClaudeConfigDir({});
+    const client = new ClaudeAgentClient({
+      logger: createTestLogger(),
+      resolveVersion: async () => "2.1.320",
+      runtimeSettings: { env: { CLAUDE_CONFIG_DIR: configDir } },
+      discoverModels: async () => [
+        {
+          value: "mythos",
+          resolvedModel: "claude-mythos-5-2",
+          displayName: "Mythos",
+          description: "",
+        },
+      ],
+    });
+
+    const { models } = await client.fetchCatalog({
+      scope: "workspace",
+      cwd: configDir,
+      force: false,
+    });
+
+    expect(models.some((model) => model.id === "claude-mythos-5-2")).toBe(false);
+  });
+
+  it("offers one 1M model with medium default effort, always-on thinking, and fast mode", () => {
+    const models = getClaudeModels().filter((model) => model.id.startsWith("claude-mythos-5-2"));
+    expect(models).toHaveLength(1);
+    expect(models[0]).toMatchObject({
+      id: "claude-mythos-5-2",
+      label: "Mythos 5.2",
+      contextWindowMaxTokens: 1_000_000,
+      defaultThinkingOptionId: "medium",
+    });
+    expect(models[0].thinkingOptions?.map((option) => option.id)).toEqual([
+      "low",
+      "medium",
+      "high",
+      "xhigh",
+      "max",
+      CLAUDE_ULTRACODE_THINKING_OPTION_ID,
+    ]);
+    expect(claudeManifestModelSupportsFastMode("claude-mythos-5-2")).toBe(true);
+  });
+
+  it.each(["anthropic/claude-mythos-5-2", "us.anthropic.claude-mythos-5-2-v1:0"])(
+    "normalizes runtime identity without granting first-party capabilities: %s",
+    (id) => {
+      expect(normalizeClaudeRuntimeModelId(id)).toBe("claude-mythos-5-2");
+      expect(normalizeClaudeManifestModelId(id)).toBeNull();
+    },
+  );
+});
+
 describe("Claude model discovery process", () => {
   it("does not send a prompt or persist a session and closes after discovery", async () => {
     let closed = false;