diff --git a/src/agents/pi-embedded-runner/run.overflow-compaction.test.ts b/src/agents/pi-embedded-runner/run.overflow-compaction.test.ts
new file mode 100644
index 0000000000..1a2c297917
--- /dev/null
+++ b/src/agents/pi-embedded-runner/run.overflow-compaction.test.ts
@@ -0,0 +1,240 @@
+import { beforeEach, describe, expect, it, vi } from "vitest";
+
+vi.mock("./run/attempt.js", () => ({
+  runEmbeddedAttempt: vi.fn(),
+}));
+
+vi.mock("./compact.js", () => ({
+  compactEmbeddedPiSessionDirect: vi.fn(),
+}));
+
+vi.mock("./model.js", () => ({
+  resolveModel: vi.fn(() => ({
+    model: {
+      id: "test-model",
+      provider: "anthropic",
+      contextWindow: 200000,
+      api: "messages",
+    },
+    error: null,
+    authStorage: {
+      setRuntimeApiKey: vi.fn(),
+    },
+    modelRegistry: {},
+  })),
+}));
+
+vi.mock("../model-auth.js", () => ({
+  ensureAuthProfileStore: vi.fn(() => ({})),
+  getApiKeyForModel: vi.fn(async () => ({
+    apiKey: "test-key",
+    profileId: "test-profile",
+    source: "test",
+  })),
+  resolveAuthProfileOrder: vi.fn(() => []),
+}));
+
+vi.mock("../models-config.js", () => ({
+  ensureOpenClawModelsJson: vi.fn(async () => {}),
+}));
+
+vi.mock("../context-window-guard.js", () => ({
+  CONTEXT_WINDOW_HARD_MIN_TOKENS: 1000,
+  CONTEXT_WINDOW_WARN_BELOW_TOKENS: 5000,
+  evaluateContextWindowGuard: vi.fn(() => ({
+    shouldWarn: false,
+    shouldBlock: false,
+    tokens: 200000,
+    source: "model",
+  })),
+  resolveContextWindowInfo: vi.fn(() => ({
+    tokens: 200000,
+    source: "model",
+  })),
+}));
+
+vi.mock("../../process/command-queue.js", () => ({
+  enqueueCommandInLane: vi.fn((_lane: string, task: () => unknown) => task()),
+}));
+
+vi.mock("../../utils/message-channel.js", () => ({
+  isMarkdownCapableMessageChannel: vi.fn(() => true),
+}));
+
+vi.mock("../agent-paths.js", () => ({
+  resolveOpenClawAgentDir: vi.fn(() => "/tmp/agent-dir"),
+}));
+
+vi.mock("../auth-profiles.js", () => ({
+  isProfileInCooldown: vi.fn(() => false),
+  markAuthProfileFailure: vi.fn(async () => {}),
+  markAuthProfileGood: vi.fn(async () => {}),
+  markAuthProfileUsed: vi.fn(async () => {}),
+}));
+
+vi.mock("../defaults.js", () => ({
+  DEFAULT_CONTEXT_TOKENS: 200000,
+  DEFAULT_MODEL: "test-model",
+  DEFAULT_PROVIDER: "anthropic",
+}));
+
+vi.mock("../failover-error.js", () => ({
+  FailoverError: class extends Error {},
+  resolveFailoverStatus: vi.fn(),
+}));
+
+vi.mock("../usage.js", () => ({
+  normalizeUsage: vi.fn((usage?: unknown) =>
+    usage && typeof usage === "object" ? usage : undefined,
+  ),
+  derivePromptTokens: vi.fn(
+    (usage?: { input?: number; cacheRead?: number; cacheWrite?: number }) => {
+      if (!usage) {
+        return undefined;
+      }
+      const input = usage.input ?? 0;
+      const cacheRead = usage.cacheRead ?? 0;
+      const cacheWrite = usage.cacheWrite ?? 0;
+      const sum = input + cacheRead + cacheWrite;
+      return sum > 0 ? sum : undefined;
+    },
+  ),
+}));
+
+vi.mock("../workspace-run.js", () => ({
+  resolveRunWorkspaceDir: vi.fn((params: { workspaceDir: string }) => ({
+    workspaceDir: params.workspaceDir,
+    usedFallback: false,
+    fallbackReason: undefined,
+    agentId: "main",
+  })),
+  redactRunIdentifier: vi.fn((value?: string) => value ?? ""),
+}));
+
+vi.mock("./lanes.js", () => ({
+  resolveSessionLane: vi.fn(() => "session-lane"),
+  resolveGlobalLane: vi.fn(() => "global-lane"),
+}));
+
+vi.mock("./logger.js", () => ({
+  log: {
+    debug: vi.fn(),
+    info: vi.fn(),
+    warn: vi.fn(),
+    error: vi.fn(),
+    isEnabled: vi.fn(() => false),
+  },
+}));
+
+vi.mock("./run/payloads.js", () => ({
+  buildEmbeddedRunPayloads: vi.fn(() => []),
+}));
+
+vi.mock("./tool-result-truncation.js", () => ({
+  truncateOversizedToolResultsInSession: vi.fn(async () => ({
+    truncated: false,
+    truncatedCount: 0,
+    reason: "no oversized tool results",
+  })),
+  sessionLikelyHasOversizedToolResults: vi.fn(() => false),
+}));
+
+vi.mock("./utils.js", () => ({
+  describeUnknownError: vi.fn((err: unknown) => {
+    if (err instanceof Error) {
+      return err.message;
+    }
+    return String(err);
+  }),
+}));
+
+vi.mock("../pi-embedded-helpers.js", () => ({
+  formatBillingErrorMessage: vi.fn(() => ""),
+  classifyFailoverReason: vi.fn(() => null),
+  formatAssistantErrorText: vi.fn(() => ""),
+  isAuthAssistantError: vi.fn(() => false),
+  isBillingAssistantError: vi.fn(() => false),
+  isCompactionFailureError: vi.fn(() => false),
+  isLikelyContextOverflowError: vi.fn((msg?: string) => {
+    const lower = (msg ?? "").toLowerCase();
+    return lower.includes("request_too_large") || lower.includes("context window exceeded");
+  }),
+  isFailoverAssistantError: vi.fn(() => false),
+  isFailoverErrorMessage: vi.fn(() => false),
+  parseImageSizeError: vi.fn(() => null),
+  parseImageDimensionError: vi.fn(() => null),
+  isRateLimitAssistantError: vi.fn(() => false),
+  isTimeoutErrorMessage: vi.fn(() => false),
+  pickFallbackThinkingLevel: vi.fn(() => null),
+}));
+
+import type { EmbeddedRunAttemptResult } from "./run/types.js";
+import { compactEmbeddedPiSessionDirect } from "./compact.js";
+import { runEmbeddedPiAgent } from "./run.js";
+import { runEmbeddedAttempt } from "./run/attempt.js";
+
+const mockedRunEmbeddedAttempt = vi.mocked(runEmbeddedAttempt);
+const mockedCompactDirect = vi.mocked(compactEmbeddedPiSessionDirect);
+
+function makeAttemptResult(
+  overrides: Partial<EmbeddedRunAttemptResult> = {},
+): EmbeddedRunAttemptResult {
+  return {
+    aborted: false,
+    timedOut: false,
+    timedOutDuringCompaction: false,
+    promptError: null,
+    sessionIdUsed: "test-session",
+    assistantTexts: ["Hello!"],
+    toolMetas: [],
+    lastAssistant: undefined,
+    messagesSnapshot: [],
+    didSendViaMessagingTool: false,
+    messagingToolSentTexts: [],
+    messagingToolSentTargets: [],
+    cloudCodeAssistFormatError: false,
+    ...overrides,
+  };
+}
+
+describe("runEmbeddedPiAgent overflow compaction trigger routing", () => {
+  beforeEach(() => {
+    vi.clearAllMocks();
+  });
+
+  it("passes trigger=overflow when retrying compaction after context overflow", async () => {
+    const overflowError = new Error("request_too_large: Request size exceeds model context window");
+
+    mockedRunEmbeddedAttempt
+      .mockResolvedValueOnce(makeAttemptResult({ promptError: overflowError }))
+      .mockResolvedValueOnce(makeAttemptResult({ promptError: null }));
+
+    mockedCompactDirect.mockResolvedValueOnce({
+      ok: true,
+      compacted: true,
+      result: {
+        summary: "Compacted session",
+        firstKeptEntryId: "entry-5",
+        tokensBefore: 150000,
+      },
+    });
+
+    await runEmbeddedPiAgent({
+      sessionId: "test-session",
+      sessionKey: "test-key",
+      sessionFile: "/tmp/session.json",
+      workspaceDir: "/tmp/workspace",
+      prompt: "hello",
+      timeoutMs: 30000,
+      runId: "run-1",
+    });
+
+    expect(mockedCompactDirect).toHaveBeenCalledTimes(1);
+    expect(mockedCompactDirect).toHaveBeenCalledWith(
+      expect.objectContaining({
+        trigger: "overflow",
+        authProfileId: "test-profile",
+      }),
+    );
+  });
+});