diff --git a/CHANGELOG.md b/CHANGELOG.md
index cbbb28b8a4c..f1441754c4d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -256,6 +256,7 @@ Docs: https://docs.openclaw.ai
 - Exec approvals: treat bare allowlist `*` as a true wildcard for parsed executables, including unresolved PATH lookups, so global opt-in allowlists work as configured. (#25250) Thanks @widingmarcus-cyber.
 - Gateway/Auth: allow trusted-proxy authenticated Control UI websocket sessions to skip device pairing when device identity is absent, preventing false `pairing required` failures behind trusted reverse proxies. (#25428) Thanks @SidQin-cyber.
 - Agents/Tool dispatch: await block-reply flush before tool execution starts so buffered block replies preserve message ordering around tool calls. (#25427) Thanks @SidQin-cyber.
+- Agents/Compaction: harden summarization prompts to preserve opaque identifiers verbatim (UUIDs, IDs, tokens, host/IP/port, URLs), reducing post-compaction identifier drift and hallucinated identifier reconstruction.
 - iOS/Signing: improve `scripts/ios-team-id.sh` for Xcode 16+ by falling back to Xcode-managed provisioning profiles, add actionable guidance when an Apple account exists but no Team ID can be resolved, and ignore Xcode `xcodebuild` output directories (`apps/ios/build`, `apps/shared/OpenClawKit/build`, `Swabble/build`). (#22773) Thanks @brianleach.
 - macOS/Menu bar: stop reusing the injector delegate for the "Usage cost (30 days)" submenu to prevent recursive submenu injection loops when opening cost history. (#25341) Thanks @yingchunbai.
 - Control UI/Chat images: route image-click opens through a shared safe-open helper (allowing only safe URL schemes) and open new tabs with opener isolation to block tabnabbing. (#18685, #25444, #25847) Thanks @Mariana-Codebase and @shakkernerd.
diff --git a/src/agents/compaction.identifier-preservation.test.ts b/src/agents/compaction.identifier-preservation.test.ts
new file mode 100644
index 00000000000..f9667e3c800
--- /dev/null
+++ b/src/agents/compaction.identifier-preservation.test.ts
@@ -0,0 +1,107 @@
+import type { AgentMessage } from "@mariozechner/pi-agent-core";
+import type { ExtensionContext } from "@mariozechner/pi-coding-agent";
+import * as piCodingAgent from "@mariozechner/pi-coding-agent";
+import { beforeEach, describe, expect, it, vi } from "vitest";
+import { buildCompactionSummarizationInstructions, summarizeInStages } from "./compaction.js";
+
+vi.mock("@mariozechner/pi-coding-agent", async (importOriginal) => {
+  const actual = await importOriginal<typeof piCodingAgent>();
+  return {
+    ...actual,
+    generateSummary: vi.fn(),
+  };
+});
+
+const mockGenerateSummary = vi.mocked(piCodingAgent.generateSummary);
+
+function makeMessage(index: number, size = 1200): AgentMessage {
+  return {
+    role: "user",
+    content: `m${index}-${"x".repeat(size)}`,
+    timestamp: index,
+  };
+}
+
+describe("compaction identifier-preservation instructions", () => {
+  const testModel = {
+    provider: "anthropic",
+    model: "claude-3-opus",
+    contextWindow: 200_000,
+  } as unknown as NonNullable<ExtensionContext["model"]>;
+
+  beforeEach(() => {
+    mockGenerateSummary.mockReset();
+    mockGenerateSummary.mockResolvedValue("summary");
+  });
+
+  it("injects identifier-preservation guidance even without custom instructions", async () => {
+    await summarizeInStages({
+      messages: [makeMessage(1), makeMessage(2)],
+      model: testModel,
+      apiKey: "test-key",
+      signal: new AbortController().signal,
+      reserveTokens: 4000,
+      maxChunkTokens: 8000,
+      contextWindow: 200_000,
+    });
+
+    expect(mockGenerateSummary).toHaveBeenCalled();
+    const firstCall = mockGenerateSummary.mock.calls[0];
+    expect(firstCall?.[5]).toContain("Preserve all opaque identifiers exactly as written");
+    expect(firstCall?.[5]).toContain("UUIDs");
+    expect(firstCall?.[5]).toContain("IPs");
+    expect(firstCall?.[5]).toContain("ports");
+  });
+
+  it("keeps identifier-preservation guidance when custom instructions are provided", async () => {
+    await summarizeInStages({
+      messages: [makeMessage(1), makeMessage(2)],
+      model: testModel,
+      apiKey: "test-key",
+      signal: new AbortController().signal,
+      reserveTokens: 4000,
+      maxChunkTokens: 8000,
+      contextWindow: 200_000,
+      customInstructions: "Focus on release-impacting bugs.",
+    });
+
+    const firstCall = mockGenerateSummary.mock.calls[0];
+    expect(firstCall?.[5]).toContain("Preserve all opaque identifiers exactly as written");
+    expect(firstCall?.[5]).toContain("Additional focus:");
+    expect(firstCall?.[5]).toContain("Focus on release-impacting bugs.");
+  });
+
+  it("applies identifier-preservation guidance on staged split + merge summarization", async () => {
+    await summarizeInStages({
+      messages: [makeMessage(1), makeMessage(2), makeMessage(3), makeMessage(4)],
+      model: testModel,
+      apiKey: "test-key",
+      signal: new AbortController().signal,
+      reserveTokens: 4000,
+      maxChunkTokens: 1000,
+      contextWindow: 200_000,
+      parts: 2,
+      minMessagesForSplit: 4,
+    });
+
+    expect(mockGenerateSummary.mock.calls.length).toBeGreaterThan(1);
+    for (const call of mockGenerateSummary.mock.calls) {
+      expect(call[5]).toContain("Preserve all opaque identifiers exactly as written");
+    }
+  });
+});
+
+describe("buildCompactionSummarizationInstructions", () => {
+  it("returns base instructions when no custom text is provided", () => {
+    const result = buildCompactionSummarizationInstructions();
+    expect(result).toContain("Preserve all opaque identifiers exactly as written");
+    expect(result).not.toContain("Additional focus:");
+  });
+
+  it("appends custom instructions in a stable format", () => {
+    const result = buildCompactionSummarizationInstructions("Keep deployment details.");
+    expect(result).toContain("Preserve all opaque identifiers exactly as written");
+    expect(result).toContain("Additional focus:");
+    expect(result).toContain("Keep deployment details.");
+  });
+});
diff --git a/src/agents/compaction.ts b/src/agents/compaction.ts
index 25163471839..f2c56286b6d 100644
--- a/src/agents/compaction.ts
+++ b/src/agents/compaction.ts
@@ -16,6 +16,16 @@ const DEFAULT_PARTS = 2;
 const MERGE_SUMMARIES_INSTRUCTIONS =
   "Merge these partial summaries into a single cohesive summary. Preserve decisions," +
   " TODOs, open questions, and any constraints.";
+const IDENTIFIER_PRESERVATION_INSTRUCTIONS =
+  "Preserve all opaque identifiers exactly as written (no shortening or reconstruction), " +
+  "including UUIDs, hashes, IDs, tokens, API keys, hostnames, IPs, ports, URLs, and file names.";
+
+export function buildCompactionSummarizationInstructions(customInstructions?: string): string {
+  if (!customInstructions || customInstructions.trim().length === 0) {
+    return IDENTIFIER_PRESERVATION_INSTRUCTIONS;
+  }
+  return `${IDENTIFIER_PRESERVATION_INSTRUCTIONS}\n\nAdditional focus:\n${customInstructions}`;
+}
 
 export function estimateMessagesTokens(messages: AgentMessage[]): number {
   // SECURITY: toolResult.details can contain untrusted/verbose payloads; never include in LLM-facing compaction.
@@ -174,7 +184,7 @@ async function summarizeChunks(params: {
   const safeMessages = stripToolResultDetails(params.messages);
   const chunks = chunkMessagesByMaxTokens(safeMessages, params.maxChunkTokens);
   let summary = params.previousSummary;
-
+  const effectiveInstructions = buildCompactionSummarizationInstructions(params.customInstructions);
   for (const chunk of chunks) {
     summary = await retryAsync(
       () =>
@@ -184,7 +194,7 @@ async function summarizeChunks(params: {
           params.reserveTokens,
           params.apiKey,
           params.signal,
-          params.customInstructions,
+          effectiveInstructions,
           summary,
         ),
       {