diff --git a/client.ts b/client.ts
index 47d32d1..e900175 100644
--- a/client.ts
+++ b/client.ts
@@ -6,6 +6,7 @@ import {
 } from "./lib/validate.js"
 import { log } from "./logger.ts"
 import { clampEntityContext } from "./memory.ts"
+import { buildAddMemoryMetadata } from "./metadata.ts"
 
 export type SearchResult = {
 	id: string
@@ -72,14 +73,7 @@ export class SupermemoryClient {
 		const cleaned = sanitizeContent(content)
 		const tag = containerTag ?? this.containerTag
 
-		// Always stamp `sm_source` so mono's `document.source` column attributes
-		// these writes to the OpenClaw plugin. Existing callers can still pass
-		// extra metadata (e.g. `source: "openclaw_tool"`) and it is preserved
-		// underneath the canonical `sm_source` key.
-		const mergedMetadata: Record<string, string | number | boolean> = {
-			sm_source: "openclaw",
-			...(metadata ?? {}),
-		}
+		const mergedMetadata = buildAddMemoryMetadata(metadata)
 
 		log.debugRequest("add", {
 			contentLength: cleaned.length,
diff --git a/hooks/capture.ts b/hooks/capture.ts
index d89d949..0fa2f9b 100644
--- a/hooks/capture.ts
+++ b/hooks/capture.ts
@@ -115,7 +115,7 @@ export function buildCaptureHandler(
 		try {
 			await client.addMemory(
 				content,
-				{ source: "openclaw", timestamp: new Date().toISOString() },
+				{ source: "openclaw" },
 				customId,
 				undefined,
 				cfg.entityContext,
diff --git a/metadata.test.ts b/metadata.test.ts
new file mode 100644
index 0000000..4889678
--- /dev/null
+++ b/metadata.test.ts
@@ -0,0 +1,46 @@
+import { describe, expect, test } from "bun:test"
+import { buildAddMemoryMetadata } from "./metadata.ts"
+
+const FIXED = new Date("2026-08-13T15:30:00.000Z")
+
+describe("buildAddMemoryMetadata", () => {
+	test("stamps sm_source and captured_at when metadata is omitted", () => {
+		expect(buildAddMemoryMetadata(undefined, () => FIXED)).toEqual({
+			sm_source: "openclaw",
+			captured_at: "2026-08-13T15:30:00.000Z",
+		})
+	})
+
+	test("preserves caller fields and fills missing captured_at", () => {
+		expect(
+			buildAddMemoryMetadata(
+				{ type: "preference", source: "openclaw_command" },
+				() => FIXED,
+			),
+		).toEqual({
+			sm_source: "openclaw",
+			type: "preference",
+			source: "openclaw_command",
+			captured_at: "2026-08-13T15:30:00.000Z",
+		})
+	})
+
+	test("keeps an explicit captured_at", () => {
+		expect(
+			buildAddMemoryMetadata(
+				{ captured_at: "2026-07-01T00:00:00.000Z" },
+				() => FIXED,
+			),
+		).toEqual({
+			sm_source: "openclaw",
+			captured_at: "2026-07-01T00:00:00.000Z",
+		})
+	})
+
+	test("replaces blank captured_at", () => {
+		expect(buildAddMemoryMetadata({ captured_at: "  " }, () => FIXED)).toEqual({
+			sm_source: "openclaw",
+			captured_at: "2026-08-13T15:30:00.000Z",
+		})
+	})
+})
diff --git a/metadata.ts b/metadata.ts
new file mode 100644
index 0000000..aeae7de
--- /dev/null
+++ b/metadata.ts
@@ -0,0 +1,21 @@
+export type MemoryMetadata = Record<string, string | number | boolean>
+
+/** Merge caller metadata with OpenClaw defaults for `add()`. */
+export function buildAddMemoryMetadata(
+	metadata?: MemoryMetadata,
+	now: () => Date = () => new Date(),
+): MemoryMetadata {
+	const merged: MemoryMetadata = {
+		sm_source: "openclaw",
+		...(metadata ?? {}),
+	}
+
+	// Give extraction a real capture-time anchor (issue #61). Callers can still
+	// pass an explicit `captured_at` (e.g. when replaying older events).
+	const existing = merged.captured_at
+	if (typeof existing !== "string" || !existing.trim()) {
+		merged.captured_at = now().toISOString()
+	}
+
+	return merged
+}
diff --git a/package.json b/package.json
index 4cd2553..97c2275 100644
--- a/package.json
+++ b/package.json
@@ -19,6 +19,7 @@
 		"config.ts",
 		"logger.ts",
 		"memory.ts",
+		"metadata.ts",
 		"runtime.ts",
 		"types",
 		"lib/version-check.ts",
@@ -32,6 +33,7 @@
 		"check-types": "tsc --noEmit",
 		"lint": "bunx @biomejs/biome ci .",
 		"lint:fix": "bunx @biomejs/biome check --write .",
+		"test": "bun test",
 		"build:lib": "node -e \"const fs=require('node:fs'); fs.accessSync('lib/validate.js'); fs.accessSync('lib/validate.d.ts')\"",
 		"prepack": "npm run build"
 	},
diff --git a/tsconfig.json b/tsconfig.json
index 852bfd0..cb687ac 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -21,5 +21,5 @@
 		"lib/*.ts",
 		"lib/*.d.ts"
 	],
-	"exclude": ["node_modules", "dist"]
+	"exclude": ["node_modules", "dist", "**/*.test.ts"]
 }