diff --git a/src/__tests__/resource-monitor.test.ts b/src/__tests__/resource-monitor.test.ts
new file mode 100644
index 00000000..af39e45e
--- /dev/null
+++ b/src/__tests__/resource-monitor.test.ts
@@ -0,0 +1,101 @@
+import { afterEach, describe, expect, it, vi } from "vitest";
+import type { AutomatonDatabase, AutomatonIdentity, ConwayClient } from "../types.js";
+
+vi.mock("../conway/x402.js", () => ({
+  getUsdcBalance: vi.fn(),
+}));
+
+const { getUsdcBalance } = await import("../conway/x402.js");
+const { checkResources, formatResourceReport } = await import("../survival/monitor.js");
+
+describe("resource monitor diagnostics", () => {
+  afterEach(() => {
+    vi.clearAllMocks();
+  });
+
+  it("records diagnostics when balance checks fail instead of presenting confirmed zero balances", async () => {
+    vi.mocked(getUsdcBalance).mockRejectedValue(new Error("RPC unavailable"));
+
+    const status = await checkResources(
+      makeIdentity(),
+      makeConwayClient({
+        getCreditsBalance: vi.fn().mockRejectedValue(new Error("Conway API unavailable")),
+        exec: vi.fn().mockResolvedValue({ stdout: "ok\n", stderr: "", exitCode: 0 }),
+      }),
+      makeDb(),
+    );
+
+    expect(status.financial.creditsCents).toBe(0);
+    expect(status.financial.usdcBalance).toBe(0);
+    expect(status.diagnostics).toMatchObject({
+      creditsError: "Conway API unavailable",
+      usdcError: "RPC unavailable",
+    });
+
+    const report = formatResourceReport(status);
+    expect(report).toContain("Credits: unknown (Conway API unavailable)");
+    expect(report).toContain("USDC: unknown (RPC unavailable)");
+    expect(report).not.toContain("Credits: $0.00");
+    expect(report).not.toContain("USDC: 0.000000");
+  });
+
+  it("records sandbox diagnostics for failed health checks", async () => {
+    vi.mocked(getUsdcBalance).mockResolvedValue(1.25);
+
+    const status = await checkResources(
+      makeIdentity(),
+      makeConwayClient({
+        getCreditsBalance: vi.fn().mockResolvedValue(250),
+        exec: vi.fn().mockRejectedValue(new Error("sandbox exec timeout")),
+      }),
+      makeDb(),
+    );
+
+    expect(status.sandboxHealthy).toBe(false);
+    expect(status.diagnostics.sandboxError).toBe("sandbox exec timeout");
+    expect(formatResourceReport(status)).toContain("Sandbox: UNHEALTHY (sandbox exec timeout)");
+  });
+
+  it("records non-zero sandbox exit codes as diagnostics", async () => {
+    vi.mocked(getUsdcBalance).mockResolvedValue(1.25);
+
+    const status = await checkResources(
+      makeIdentity(),
+      makeConwayClient({
+        getCreditsBalance: vi.fn().mockResolvedValue(250),
+        exec: vi.fn().mockResolvedValue({ stdout: "", stderr: "boom", exitCode: 2 }),
+      }),
+      makeDb(),
+    );
+
+    expect(status.sandboxHealthy).toBe(false);
+    expect(status.diagnostics.sandboxError).toBe("health command exited 2");
+    expect(formatResourceReport(status)).toContain("Sandbox: UNHEALTHY (health command exited 2)");
+  });
+});
+
+function makeIdentity(): AutomatonIdentity {
+  return {
+    name: "Test Automaton",
+    address: "0x1234567890123456789012345678901234567890",
+    account: {} as AutomatonIdentity["account"],
+    creatorAddress: "0x0000000000000000000000000000000000000000",
+    sandboxId: "sandbox-1",
+    apiKey: "test-api-key",
+    createdAt: new Date(0).toISOString(),
+  };
+}
+
+function makeConwayClient(overrides: Partial<ConwayClient>): ConwayClient {
+  return overrides as ConwayClient;
+}
+
+function makeDb(): AutomatonDatabase {
+  const kv = new Map<string, string>();
+  return {
+    getKV: vi.fn((key: string) => kv.get(key)),
+    setKV: vi.fn((key: string, value: string) => {
+      kv.set(key, value);
+    }),
+  } as unknown as AutomatonDatabase;
+}
diff --git a/src/survival/monitor.ts b/src/survival/monitor.ts
index e1461f3f..5cc63644 100644
--- a/src/survival/monitor.ts
+++ b/src/survival/monitor.ts
@@ -22,6 +22,13 @@ export interface ResourceStatus {
   previousTier: SurvivalTier | null;
   tierChanged: boolean;
   sandboxHealthy: boolean;
+  diagnostics: ResourceDiagnostics;
+}
+
+export interface ResourceDiagnostics {
+  creditsError?: string;
+  usdcError?: string;
+  sandboxError?: string;
 }
 
 /**
@@ -32,25 +39,35 @@ export async function checkResources(
   conway: ConwayClient,
   db: AutomatonDatabase,
 ): Promise<ResourceStatus> {
+  const diagnostics: ResourceDiagnostics = {};
+
   // Check credits
   let creditsCents = 0;
   try {
     creditsCents = await conway.getCreditsBalance();
-  } catch {}
+  } catch (error) {
+    diagnostics.creditsError = toDiagnosticMessage(error);
+  }
 
   // Check USDC
   let usdcBalance = 0;
   try {
     usdcBalance = await getUsdcBalance(identity.address);
-  } catch {}
+  } catch (error) {
+    diagnostics.usdcError = toDiagnosticMessage(error);
+  }
 
   // Check sandbox health
   let sandboxHealthy = true;
   try {
     const result = await conway.exec("echo ok", 5000);
     sandboxHealthy = result.exitCode === 0;
-  } catch {
+    if (!sandboxHealthy) {
+      diagnostics.sandboxError = `health command exited ${result.exitCode}`;
+    }
+  } catch (error) {
     sandboxHealthy = false;
+    diagnostics.sandboxError = toDiagnosticMessage(error);
   }
 
   const financial: FinancialState = {
@@ -76,6 +93,7 @@ export async function checkResources(
     previousTier,
     tierChanged,
     sandboxHealthy,
+    diagnostics,
   };
 }
 
@@ -83,14 +101,31 @@ export async function checkResources(
  * Generate a human-readable resource report.
  */
 export function formatResourceReport(status: ResourceStatus): string {
+  const diagnostics = status.diagnostics || {};
+  const creditsLine = diagnostics.creditsError
+    ? `Credits: unknown (${diagnostics.creditsError})`
+    : `Credits: ${formatCredits(status.financial.creditsCents)}`;
+  const usdcLine = diagnostics.usdcError
+    ? `USDC: unknown (${diagnostics.usdcError})`
+    : `USDC: ${status.financial.usdcBalance.toFixed(6)}`;
+  const sandboxLine = diagnostics.sandboxError
+    ? `Sandbox: UNHEALTHY (${diagnostics.sandboxError})`
+    : `Sandbox: ${status.sandboxHealthy ? "healthy" : "UNHEALTHY"}`;
+
   const lines = [
     `=== RESOURCE STATUS ===`,
-    `Credits: ${formatCredits(status.financial.creditsCents)}`,
-    `USDC: ${status.financial.usdcBalance.toFixed(6)}`,
+    creditsLine,
+    usdcLine,
     `Tier: ${status.tier}${status.tierChanged ? ` (changed from ${status.previousTier})` : ""}`,
-    `Sandbox: ${status.sandboxHealthy ? "healthy" : "UNHEALTHY"}`,
+    sandboxLine,
     `Checked: ${status.financial.lastChecked}`,
     `========================`,
   ];
   return lines.join("\n");
 }
+
+function toDiagnosticMessage(error: unknown): string {
+  if (error instanceof Error) return error.message;
+  if (typeof error === "string") return error;
+  return "unknown error";
+}