fix(wake): probe with genuine Claude Code request shape so OAuth wakes succeed

The wake probe POSTed a bare { model, messages } body with no system[]
identity. Anthropic validates system[] on OAuth (Pro/Max) subscription
requests and rejects any that lack the verbatim Claude Code identity, so
every scheduled wake (and the manual Wake-now button) failed silently —
surfacing as a blank '— failed' status that then burned the retry budget.

- Add pure buildWakeProbeBody(model) in @dispatch/core mirroring a genuine
  Claude Code request (billing header block + identity block + 'hi'), with
  a unit test for its shape.
- wakeAllClaudeAccounts now sends that body plus the CLI session/request-id
  headers, and records 'HTTP <status>: <message>' on failure so the panel
  never shows a bare 'failed' and breakage stays debuggable.

3 files changed, 88 insertions, 0 deletions

diff --git a/packages/core/src/credentials/claude.ts b/packages/core/src/credentials/claude.ts
index 168d544..432e403 100644
--- a/packages/core/src/credentials/claude.ts
+++ b/packages/core/src/credentials/claude.ts
@@ -373,6 +373,44 @@ export function buildBillingHeaderValue(
 
 export const SYSTEM_IDENTITY = "You are Claude Code, Anthropic's official CLI for Claude.";
 
+/**
+ * Build the request body for a Claude "wake" probe — a tiny, cheap message
+ * whose only purpose is to keep the subscription's rate-limit window warm.
+ *
+ * This MUST mirror the shape of a genuine Claude Code CLI request, because
+ * Anthropic validates the `system[]` array on OAuth (Pro/Max) -authenticated,
+ * Claude-Code-billed requests. A bare `{ model, messages }` body (no system
+ * identity) is rejected (401/403) — which is exactly how the old probe silently
+ * failed. The valid shape is:
+ *
+ *   system: [
+ *     { type: "text", text: "x-anthropic-billing-header: ..." },  // billing, no cache_control
+ *     { type: "text", text: "You are Claude Code, Anthropic's official CLI for Claude." },
+ *   ]
+ *   messages: [ { role: "user", content: "hi" } ]
+ *
+ * Mirrors the runtime `transformClaudeOAuthBody` output for a single short user
+ * turn. Pure: deterministic given its inputs (the billing header samples only
+ * the user text), so it can be unit-tested without touching the network.
+ */
+export function buildWakeProbeBody(model: string): {
+	model: string;
+	max_tokens: number;
+	system: Array<{ type: "text"; text: string }>;
+	messages: Array<{ role: "user"; content: string }>;
+} {
+	const messages = [{ role: "user" as const, content: "hi" }];
+	return {
+		model,
+		max_tokens: 16,
+		system: [
+			{ type: "text", text: buildBillingHeaderValue(messages) },
+			{ type: "text", text: SYSTEM_IDENTITY },
+		],
+		messages,
+	};
+}
+
 // ─── Anthropic Request Headers ────────────────────────────────
 
 export function getAnthropicHeaders(accessToken: string): Record<string, string> {
diff --git a/packages/core/src/credentials/index.ts b/packages/core/src/credentials/index.ts
index ff7392b..46fa5b6 100644
--- a/packages/core/src/credentials/index.ts
+++ b/packages/core/src/credentials/index.ts
@@ -9,6 +9,7 @@ export {
 export {
 	ANTHROPIC_MODELS_FALLBACK,
 	buildBillingHeaderValue,
+	buildWakeProbeBody,
 	type ClaudeAccount,
 	type ClaudeCredentials,
 	type ClaudeProfile,
diff --git a/packages/core/tests/credentials/wake-probe.test.ts b/packages/core/tests/credentials/wake-probe.test.ts
new file mode 100644
index 0000000..253efec
--- /dev/null
+++ b/packages/core/tests/credentials/wake-probe.test.ts
@@ -0,0 +1,49 @@
+import { describe, expect, it, vi } from "vitest";
+
+// `claude.ts` transitively imports `db/index.js`, whose top-level
+// `import { Database } from "bun:sqlite"` can't resolve under vitest's Node
+// runtime. Stub the db module — `buildWakeProbeBody` never touches it.
+vi.mock("../../src/db/index.js", () => ({
+	getDatabase: vi.fn(() => {
+		throw new Error("db not available in this test");
+	}),
+}));
+
+const { buildWakeProbeBody } = await import("../../src/credentials/claude.js");
+
+const IDENTITY = "You are Claude Code, Anthropic's official CLI for Claude.";
+
+describe("buildWakeProbeBody", () => {
+	it("targets the requested model with a tiny token budget", () => {
+		const body = buildWakeProbeBody("claude-3-5-haiku-20241022");
+		expect(body.model).toBe("claude-3-5-haiku-20241022");
+		expect(body.max_tokens).toBe(16);
+	});
+
+	it("emits a Claude-Code-shaped system[]: billing first, identity second", () => {
+		const body = buildWakeProbeBody("claude-3-5-haiku-20241022");
+		expect(body.system).toHaveLength(2);
+
+		// system[0] is the billing header line (no cache_control on a probe).
+		expect(body.system[0]).toEqual({
+			type: "text",
+			text: expect.stringMatching(/^x-anthropic-billing-header: /),
+		});
+		expect(body.system[0]).not.toHaveProperty("cache_control");
+
+		// system[1] is the VERBATIM Claude Code identity string. Anthropic
+		// rejects OAuth (Pro/Max) requests whose system[] lacks this.
+		expect(body.system[1]).toEqual({ type: "text", text: IDENTITY });
+	});
+
+	it("carries a single short user message", () => {
+		const body = buildWakeProbeBody("claude-3-5-haiku-20241022");
+		expect(body.messages).toEqual([{ role: "user", content: "hi" }]);
+	});
+
+	it("is deterministic for a given model (pure)", () => {
+		const a = buildWakeProbeBody("claude-3-5-haiku-20241022");
+		const b = buildWakeProbeBody("claude-3-5-haiku-20241022");
+		expect(a).toEqual(b);
+	});
+});