diff --git a/.changeset/fn-7374-anthropic-sonnet-5-404.md b/.changeset/fn-7374-anthropic-sonnet-5-404.md
new file mode 100644
index 0000000000..4bbd6ed39b
--- /dev/null
+++ b/.changeset/fn-7374-anthropic-sonnet-5-404.md
@@ -0,0 +1,7 @@
+---
+"@runfusion/fusion": patch
+---
+
+summary: Stop force-advertising Anthropic Claude Sonnet 5 when account availability is unknown.
+category: fix
+dev: Removes static Sonnet 5 supplemental catalog/pricing metadata while preserving fallback handling for saved selections.
diff --git a/packages/core/src/__tests__/model-pricing.test.ts b/packages/core/src/__tests__/model-pricing.test.ts
index 02895052ac..4381bd7967 100644
--- a/packages/core/src/__tests__/model-pricing.test.ts
+++ b/packages/core/src/__tests__/model-pricing.test.ts
@@ -36,9 +36,7 @@ describe("model-pricing", () => {
     expect(result.usd).toBeCloseTo(10.0, 2);
   });
 
-  it("prices Claude Sonnet 5 for Anthropic and bare-model fallback", () => {
-    // claude-sonnet-5 introductory pricing: input $2/1M, output $10/1M,
-    // cache read $0.20/1M, 5m cache write $2.50/1M.
+  it("reports direct Anthropic Claude Sonnet 5 pricing as unavailable without a static catalog row", () => {
     const usage = {
       inputTokens: 1_000_000,
       outputTokens: 200_000,
@@ -47,12 +45,12 @@ describe("model-pricing", () => {
     };
 
     const anthropic = costFor(usage, { provider: "anthropic", model: "claude-sonnet-5" });
-    expect(anthropic.unavailable).toBe(false);
-    expect(anthropic.usd).toBeCloseTo(5.1, 3);
+    expect(anthropic.unavailable).toBe(true);
+    expect(anthropic.usd).toBeNull();
 
     const bare = costFor(usage, { model: "claude-sonnet-5" });
-    expect(bare.unavailable).toBe(false);
-    expect(bare.usd).toBeCloseTo(5.1, 3);
+    expect(bare.unavailable).toBe(true);
+    expect(bare.usd).toBeNull();
   });
 
   it("prices OpenAI Codex GPT-5 models instead of reporting unavailable", () => {
@@ -206,13 +204,11 @@ describe("model-pricing", () => {
       ).toBe(MODEL_PRICING["openai-codex:gpt-5-codex"]);
     });
 
-    it("resolves Claude Sonnet 5 by explicit provider and bare model", () => {
+    it("does not resolve static pricing for direct Anthropic Claude Sonnet 5", () => {
       expect(
         lookupPricing({ provider: " Anthropic ", model: " Claude-Sonnet-5 " }),
-      ).toBe(MODEL_PRICING["anthropic:claude-sonnet-5"]);
-      expect(lookupPricing({ model: "claude-sonnet-5" })).toBe(
-        MODEL_PRICING["anthropic:claude-sonnet-5"],
-      );
+      ).toBeUndefined();
+      expect(lookupPricing({ model: "claude-sonnet-5" })).toBeUndefined();
     });
 
     it("falls back to a bare model id when provider is unset", () => {
diff --git a/packages/core/src/anthropic-models.ts b/packages/core/src/anthropic-models.ts
index c46586736d..fa4e1b07d1 100644
--- a/packages/core/src/anthropic-models.ts
+++ b/packages/core/src/anthropic-models.ts
@@ -28,33 +28,15 @@ export interface AnthropicProviderRegistration {
 }
 
 /*
- * FNXC:ModelCatalog 2026-06-30-12:22:
- * Claude Sonnet 5 support must not depend on the installed pi-ai catalog version or on the Claude CLI provider. Keep this supplemental Anthropic registration shared by engine sessions and dashboard model routes, and dedupe by model id so upstream catalog catch-up does not create duplicate picker rows.
+ * FNXC:ModelCatalog 2026-07-01-18:05:
+ * Anthropic's official model overview lists `claude-sonnet-5` as a Claude API ID, but FN-7374 observed sparse provider `404 not_found_error` responses for direct Anthropic accounts after Fusion force-added that ID from static supplemental metadata. Fusion cannot encode per-account/model-surface availability from static docs, so direct Anthropic pickers must rely on the live/upstream registry for Sonnet 5 and only dedupe rows the registry already provides. Existing saved selections keep runtime fallback/actionable failure handling instead of being newly advertised here.
  */
 export const SUPPLEMENTAL_ANTHROPIC_PROVIDER_REGISTRATION: AnthropicProviderRegistration = {
   name: "Anthropic",
   baseUrl: "https://api.anthropic.com/v1",
   apiKey: "$ANTHROPIC_API_KEY",
   api: "anthropic-messages",
-  models: [
-    {
-      id: CLAUDE_SONNET_5_MODEL_ID,
-      name: "Claude Sonnet 5",
-      reasoning: true,
-      input: ["text", "image"],
-      cost: {
-        input: 2,
-        output: 10,
-        cacheRead: 0.2,
-        cacheWrite: 2.5,
-      },
-      contextWindow: 1_000_000,
-      maxTokens: 128_000,
-      compat: {
-        supportsDeveloperRole: false,
-      },
-    },
-  ],
+  models: [],
 };
 
 type AnthropicModelLike = Partial<Omit<AnthropicModelRegistration, "name" | "compat">> & {
diff --git a/packages/core/src/model-pricing.ts b/packages/core/src/model-pricing.ts
index 785363088c..664d15eb72 100644
--- a/packages/core/src/model-pricing.ts
+++ b/packages/core/src/model-pricing.ts
@@ -105,16 +105,9 @@ export const MODEL_PRICING: Readonly<Record<string, ModelPricing>> = {
   // ── Anthropic Claude ────────────────────────────────────────────────
   // input / output / cacheRead(0.1×) / cacheWrite(1.25×, 5-min TTL)
   /*
-   * FNXC:ModelCatalog 2026-06-30-12:10:
-   * Anthropic's docs publish Claude Sonnet 5 as the dateless pinned API ID `claude-sonnet-5`. Keep it in Fusion's hand-maintained support data before upstream pi-ai catalogs necessarily refresh so direct Anthropic runtime and cost surfaces can resolve it consistently.
+   * FNXC:ModelCatalog 2026-07-01-18:10:
+   * Do not maintain static pricing for `anthropic:claude-sonnet-5` while Fusion cannot prove that a direct Anthropic account can call the model. Saved selections that hit Anthropic's sparse `not_found_error` should be treated as unavailable/fallback candidates rather than receiving a confident cost from a model row Fusion no longer force-advertises.
    */
-  "anthropic:claude-sonnet-5": {
-    inputPer1M: 2,
-    outputPer1M: 10,
-    cacheReadPer1M: 0.2,
-    cacheWritePer1M: 2.5,
-    source: "platform.claude.com/docs/en/pricing#claude-sonnet-5-introductory-pricing",
-  },
   "anthropic:claude-opus-4-8": {
     inputPer1M: 5,
     outputPer1M: 25,
diff --git a/packages/dashboard/src/__tests__/routes-auth.test.ts b/packages/dashboard/src/__tests__/routes-auth.test.ts
index e930cc0425..43c6372282 100644
--- a/packages/dashboard/src/__tests__/routes-auth.test.ts
+++ b/packages/dashboard/src/__tests__/routes-auth.test.ts
@@ -398,7 +398,7 @@ describe("GET /models", () => {
     expect(res.body.models).toEqual([]);
   });
 
-  it("adds Claude Sonnet 5 for configured direct Anthropic users without relying on Claude CLI", async () => {
+  it("does not force-add Claude Sonnet 5 for configured direct Anthropic users", async () => {
     const modelRegistry = createMutableModelRegistry([
       { id: "claude-sonnet-4-5", name: "Claude Sonnet 4.5", provider: "anthropic", reasoning: true, contextWindow: 200000 },
       { id: "gpt-4o", name: "GPT-4o", provider: "openai", reasoning: false, contextWindow: 128000 },
@@ -408,9 +408,12 @@ describe("GET /models", () => {
 
     expect(res.status).toBe(200);
     expect(res.body.models).toEqual(expect.arrayContaining([
-      expect.objectContaining({ provider: "anthropic", id: "claude-sonnet-5", name: "Claude Sonnet 5", reasoning: true, contextWindow: 1_000_000 }),
+      expect.objectContaining({ provider: "anthropic", id: "claude-sonnet-4-5" }),
     ]));
-    expect(modelRegistry.registerProvider).toHaveBeenCalledWith("anthropic", expect.objectContaining({
+    expect(res.body.models).not.toEqual(expect.arrayContaining([
+      expect.objectContaining({ provider: "anthropic", id: "claude-sonnet-5" }),
+    ]));
+    expect(modelRegistry.registerProvider).not.toHaveBeenCalledWith("anthropic", expect.objectContaining({
       models: expect.arrayContaining([expect.objectContaining({ id: "claude-sonnet-5" })]),
     }));
   });
@@ -431,13 +434,13 @@ describe("GET /models", () => {
 
       expect(res.status).toBe(200);
       expect(res.body.models).toEqual([]);
-      expect(modelRegistry.models.some((model) => model.id === "claude-sonnet-5")).toBe(true);
+      expect(modelRegistry.models.some((model) => model.id === "claude-sonnet-5")).toBe(false);
     } finally {
       readFileSpy.mockRestore();
     }
   });
 
-  it("does not duplicate Claude Sonnet 5 when upstream registry already includes it", async () => {
+  it("dedupes Claude Sonnet 5 when upstream registry already includes it", async () => {
     const modelRegistry = createMutableModelRegistry([
       { id: "claude-sonnet-5", name: "Claude Sonnet 5 Upstream", provider: "anthropic", reasoning: true, contextWindow: 1_000_000, maxTokens: 128_000 },
     ]);
diff --git a/packages/engine/src/__tests__/pi-create-fn-agent.test.ts b/packages/engine/src/__tests__/pi-create-fn-agent.test.ts
index b19db2d048..42ce606ed3 100644
--- a/packages/engine/src/__tests__/pi-create-fn-agent.test.ts
+++ b/packages/engine/src/__tests__/pi-create-fn-agent.test.ts
@@ -1625,42 +1625,28 @@ describe("createFnAgent", () => {
     });
   });
 
-  it("resolves direct Anthropic Claude Sonnet 5 when the mocked registry initially lacks it", async () => {
+  it("does not synthesize direct Anthropic Claude Sonnet 5 when the registry lacks it", async () => {
     getAllMock.mockReturnValueOnce([]);
     findMock.mockImplementation((provider: string, modelId: string) => {
       if (provider === "anthropic" && modelId === "claude-sonnet-5") {
-        const anthropicRegistration = registerProviderMock.mock.calls.find(([name]) => name === "anthropic")?.[1] as { models?: Array<{ id: string; name: string }> } | undefined;
-        const registeredModel = anthropicRegistration?.models?.find((model) => model.id === modelId);
-        return registeredModel ? { ...registeredModel, provider } : undefined;
+        return undefined;
       }
       return { provider, id: modelId };
     });
 
     const { createFnAgent } = await import("../pi.js");
-    const result = await createFnAgent({
+    await expect(createFnAgent({
       cwd: "/tmp",
       systemPrompt: "test",
       tools: "readonly",
       defaultProvider: "anthropic",
       defaultModelId: "claude-sonnet-5",
-    });
+    })).rejects.toThrow("Configured model anthropic/claude-sonnet-5 (primary selection) was not found in the pi model registry");
 
-    expect(registerProviderMock).toHaveBeenCalledWith("anthropic", expect.objectContaining({
-      api: "anthropic-messages",
-      models: expect.arrayContaining([expect.objectContaining({
-        id: "claude-sonnet-5",
-        name: "Claude Sonnet 5",
-        contextWindow: 1_000_000,
-        maxTokens: 128_000,
-      })]),
-    }));
-    expect(createAgentSessionMock).toHaveBeenCalledWith(expect.objectContaining({
-      model: expect.objectContaining({ provider: "anthropic", id: "claude-sonnet-5" }),
-    }));
-    expect((result.session as { model?: unknown }).model).toEqual(expect.objectContaining({
-      provider: "anthropic",
-      id: "claude-sonnet-5",
+    expect(registerProviderMock).not.toHaveBeenCalledWith("anthropic", expect.objectContaining({
+      models: expect.arrayContaining([expect.objectContaining({ id: "claude-sonnet-5" })]),
     }));
+    expect(createAgentSessionMock).not.toHaveBeenCalled();
   });
 
   it("does not duplicate Claude Sonnet 5 when the Anthropic registry already has it", async () => {
diff --git a/packages/engine/src/cli-agent/adapters/__tests__/pi.test.ts b/packages/engine/src/cli-agent/adapters/__tests__/pi.test.ts
index 6fa7b7551c..b9c7b8eeec 100644
--- a/packages/engine/src/cli-agent/adapters/__tests__/pi.test.ts
+++ b/packages/engine/src/cli-agent/adapters/__tests__/pi.test.ts
@@ -58,9 +58,9 @@ describe("piAdapter — buildLaunch", () => {
     ]);
   });
 
-  it("forwards direct Anthropic Claude Sonnet 5 without Claude CLI routing", () => {
+  it("forwards arbitrary direct Anthropic user-entered model ids without Claude CLI routing", () => {
     const spec = piAdapter.buildLaunch({
-      settings: { provider: "anthropic", model: "claude-sonnet-5", sessionDir: "/tmp/sess/pi" },
+      settings: { provider: "anthropic", model: "custom-anthropic-model", sessionDir: "/tmp/sess/pi" },
       posture: null,
     });
     expect(spec.command).toBe("pi");
@@ -68,7 +68,7 @@ describe("piAdapter — buildLaunch", () => {
       "--provider",
       "anthropic",
       "--model",
-      "claude-sonnet-5",
+      "custom-anthropic-model",
       "--session-dir",
       "/tmp/sess/pi",
     ]);
diff --git a/packages/pi-claude-cli/index.ts b/packages/pi-claude-cli/index.ts
index 99e719f585..a792509737 100644
--- a/packages/pi-claude-cli/index.ts
+++ b/packages/pi-claude-cli/index.ts
@@ -191,18 +191,9 @@ export default function (pi: ExtensionAPI) {
     // https://platform.claude.com/docs/en/about-claude/models/overview
     const extraModels: typeof catalogModels = [
       /*
-       * FNXC:ModelCatalog 2026-06-30-12:31:
-       * The vendored Claude CLI provider has its own model list because it exposes `pi-claude-cli` independently from direct `anthropic`. Add Claude Sonnet 5 here as supplemental metadata so Claude CLI users can select it before the upstream pi-ai catalog catches up, while the dedupe below prevents duplicate rows after it does.
+       * FNXC:ModelCatalog 2026-07-01-18:18:
+       * Keep Claude CLI supplemental metadata limited to models that Fusion can advertise without triggering the direct-Anthropic Sonnet 5 404 loop. `claude-sonnet-5` must come from the upstream/live registry before this provider shows it, because static metadata cannot prove the current account and CLI surface can call that model.
        */
-      {
-        id: "claude-sonnet-5",
-        name: "Claude Sonnet 5",
-        reasoning: true,
-        input: ["text", "image"],
-        cost: { input: 2, output: 10, cacheRead: 0.2, cacheWrite: 2.5 },
-        contextWindow: 1_000_000,
-        maxTokens: 128_000,
-      },
       {
         id: "claude-opus-4-7",
         name: "Claude Opus 4.7",
diff --git a/packages/pi-claude-cli/src/__tests__/process-manager.test.ts b/packages/pi-claude-cli/src/__tests__/process-manager.test.ts
index 101e1af846..f042b7c7c1 100644
--- a/packages/pi-claude-cli/src/__tests__/process-manager.test.ts
+++ b/packages/pi-claude-cli/src/__tests__/process-manager.test.ts
@@ -61,14 +61,14 @@ describe("buildClaudeSpawnArgs", () => {
   });
 
   it("builds args including model and optional session/mcp flags", () => {
-    const args = buildClaudeSpawnArgs("claude-sonnet-5", undefined, {
+    const args = buildClaudeSpawnArgs("claude-sonnet-4-6", undefined, {
       resumeSessionId: "sess-1",
       effort: "high",
       mcpConfigPath: "/tmp/mcp.json",
     });
 
     expect(args).toContain("--model");
-    expect(args[args.indexOf("--model") + 1]).toBe("claude-sonnet-5");
+    expect(args[args.indexOf("--model") + 1]).toBe("claude-sonnet-4-6");
     expect(args).toContain("--resume");
     expect(args).toContain("sess-1");
     expect(args).toContain("--effort");
diff --git a/packages/pi-claude-cli/src/__tests__/provider.test.ts b/packages/pi-claude-cli/src/__tests__/provider.test.ts
index 8916ccffbb..49d4a54ce4 100644
--- a/packages/pi-claude-cli/src/__tests__/provider.test.ts
+++ b/packages/pi-claude-cli/src/__tests__/provider.test.ts
@@ -116,7 +116,7 @@ describe("provider registration (default export)", () => {
     expect(firstModel.cost).toBeDefined();
   });
 
-  it("includes all extra Claude model entries", async () => {
+  it("includes supported extra Claude model entries without force-adding Sonnet 5", async () => {
     const registerProvider = vi.fn();
     const mockPi = { registerProvider, on: vi.fn() } as any;
 
@@ -127,7 +127,6 @@ describe("provider registration (default export)", () => {
     const modelIds = new Set(config.models.map((m: { id: string }) => m.id));
 
     for (const id of [
-      "claude-sonnet-5",
       "claude-opus-4-7",
       "claude-sonnet-4-6",
       "claude-sonnet-4-5",
@@ -136,14 +135,7 @@ describe("provider registration (default export)", () => {
       expect(modelIds.has(id)).toBe(true);
     }
 
-    expect(config.models.find((m: { id: string }) => m.id === "claude-sonnet-5")).toMatchObject({
-      name: "Claude Sonnet 5",
-      reasoning: true,
-      input: ["text", "image"],
-      cost: { input: 2, output: 10, cacheRead: 0.2, cacheWrite: 2.5 },
-      contextWindow: 1_000_000,
-      maxTokens: 128_000,
-    });
+    expect(modelIds.has("claude-sonnet-5")).toBe(false);
   });
 
   it("deduplicates extra models when catalog already includes them", async () => {