fix(claude): default Fable and Mythos 5.2 to medium effort

Claude Code 2.1.321's model catalog declares default_effort "medium" for
both models, so Paseo's inherited "high" would start sessions above Claude
Code's own default and cost more.

Gate Mythos 5.2 on 2.1.321 as well: older Claude Code can advertise the
mythos alias without Paseo knowing its capabilities there.

The Fast control now applies beyond Opus, so its description no longer
names a model family.

Co-authored-by: gudcks <84506708+gudcks@users.noreply.github.com>

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

@@ -1614,7 +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" }, "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

@@ -63,6 +63,8 @@ export const CLAUDE_MODEL_MANIFEST = [
     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,
@@ -80,6 +82,7 @@ export const CLAUDE_MODEL_MANIFEST = [
     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,

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

@@ -248,8 +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, "high"],
-    ["claude-mythos-5-2", 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],
@@ -829,14 +829,14 @@ describe("Claude Fable 5.1 catalog", () => {
 });
 
 describe("Claude Fable 5.2 catalog", () => {
-  it("offers one 1M model with high default effort, always-on thinking, and fast mode", () => {
+  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: "high",
+      defaultThinkingOptionId: "medium",
     });
     expect(models[0].thinkingOptions?.map((option) => option.id)).toEqual([
       "low",
@@ -1047,14 +1047,39 @@ describe("Claude Mythos 5.1 catalog", () => {
 });
 
 describe("Claude Mythos 5.2 catalog", () => {
-  it("offers one 1M model with high default effort, always-on thinking, and fast mode", () => {
+  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: "high",
+      defaultThinkingOptionId: "medium",
     });
     expect(models[0].thinkingOptions?.map((option) => option.id)).toEqual([
       "low",