diff --git a/packages/tools/src/claude-memory.test.ts b/packages/tools/src/claude-memory.test.ts
index ea9b5999..477b0481 100644
--- a/packages/tools/src/claude-memory.test.ts
+++ b/packages/tools/src/claude-memory.test.ts
@@ -26,7 +26,7 @@ vi.mock("supermemory", () => {
 	return { default: Supermemory, Supermemory, NotFoundError: sdk.NotFoundError }
 })
 
-import { ClaudeMemoryTool } from "./claude-memory"
+import { ClaudeMemoryTool, type MemoryCommand } from "./claude-memory"
 
 const FILE_PATH = "/memories/notes.txt"
 // 5 distinct lines so an off-by-one at either end is observable.
@@ -383,6 +383,97 @@ describe("ClaudeMemoryTool path IDs", () => {
 		)
 	})
 
+	it("never writes /memories/a into the legacy ID of /memories/s/a", async () => {
+		mockDocuments([
+			{ id: "memories_s_a", filePath: "/memories/s/a", content: "legacy" },
+		])
+
+		const result = await tool.handleCommand({
+			command: "create",
+			path: "/memories/a",
+			file_text: "new",
+		})
+
+		expect(result.success).toBe(true)
+		expect(updateMock).toHaveBeenCalledTimes(1)
+		expect(updateMock.mock.calls[0]?.[1]).toBe("cm_memories_s_a")
+	})
+
+	it("refuses to overwrite a foreign document holding the file's ID", async () => {
+		mockDocuments([
+			{ id: "cm_memories_s_a", filePath: "/memories/other", content: "x" },
+		])
+
+		const result = await tool.handleCommand({
+			command: "create",
+			path: "/memories/a",
+			file_text: "new",
+		})
+
+		expect(result.success).toBe(false)
+		expect(updateMock).not.toHaveBeenCalled()
+	})
+
+	it("renames onto a legacy destination in place", async () => {
+		mockDocuments([
+			{
+				id: "cm_memories_s_src_d_txt",
+				filePath: "/memories/src.txt",
+				content: "moved",
+			},
+			{
+				id: "memories_dst_txt",
+				filePath: "/memories/dst.txt",
+				content: "stale",
+			},
+		])
+		sdk.delete.mockResolvedValue({ count: 1 })
+
+		const result = await tool.handleCommand({
+			command: "rename",
+			old_path: "/memories/src.txt",
+			new_path: "/memories/dst.txt",
+		})
+
+		expect(result.success).toBe(true)
+		expect(updateMock).toHaveBeenCalledWith(
+			expect.anything(),
+			"memories_dst_txt",
+			expect.objectContaining({ content: "moved" }),
+		)
+		expect(sdk.delete).toHaveBeenCalledWith(expect.anything(), {
+			ids: ["cm_memories_s_src_d_txt"],
+		})
+	})
+
+	it("does not write when the lookup fails with a non-404 error", async () => {
+		documentsGetMock.mockRejectedValue(
+			Object.assign(new Error("upstream down"), { status: 500 }),
+		)
+
+		const result = await tool.handleCommand({
+			command: "create",
+			path: FILE_PATH,
+			file_text: "fresh",
+		})
+
+		expect(result.success).toBe(false)
+		expect(result.error).toContain("upstream down")
+		expect(updateMock).not.toHaveBeenCalled()
+		expect(sdk.add).not.toHaveBeenCalled()
+	})
+
+	it("keeps path required for every command except rename", () => {
+		// @ts-expect-error view needs a path
+		const view: MemoryCommand = { command: "view" }
+		const rename: MemoryCommand = {
+			command: "rename",
+			old_path: "/memories/a",
+			new_path: "/memories/b",
+		}
+		expect([view, rename]).toHaveLength(2)
+	})
+
 	it("ignores a legacy ID that belongs to a different path", async () => {
 		mockDocuments([
 			{ id: "memories_notes_txt", filePath: FILE_PATH, content: "other" },
diff --git a/packages/tools/src/claude-memory.ts b/packages/tools/src/claude-memory.ts
index f227eb1e..6ea73f6e 100644
--- a/packages/tools/src/claude-memory.ts
+++ b/packages/tools/src/claude-memory.ts
@@ -10,10 +10,7 @@ export type ClaudeMemoryConfig = SupermemoryToolsConfig
 
 export const CLAUDE_MEMORY_SOURCE = "claude-memory"
 
-export interface MemoryCommand {
-	command: "view" | "create" | "str_replace" | "insert" | "delete" | "rename"
-	// every command except rename addresses the file via path
-	path?: string
+interface MemoryCommandFields {
 	// view specific
 	view_range?: [number, number]
 	// create specific
@@ -30,6 +27,13 @@ export interface MemoryCommand {
 	new_path?: string
 }
 
+export type MemoryCommand =
+	| (MemoryCommandFields & {
+			command: "view" | "create" | "str_replace" | "insert" | "delete"
+			path: string
+	  })
+	| (MemoryCommandFields & { command: "rename"; path?: string })
+
 export interface MemoryResponse {
 	success: boolean
 	content?: string
@@ -56,13 +60,13 @@ export class ClaudeMemoryTool {
 	private client: Supermemory
 	private namespace: string
 
-	/** Reversible encoding so distinct paths never share an ID: /memories/a_b.txt -> memories_s_a__b_d_txt */
+	/** Reversible encoding; the `cm_` prefix keeps it disjoint from legacy IDs, which always start with `memories`: /memories/a_b.txt -> cm_memories_s_a__b_d_txt */
 	private normalizePathToId(path: string): string {
-		return path
+		return `cm_${path
 			.replace(/^\//, "")
 			.replace(/_/g, "__")
 			.replace(/\//g, "_s_")
-			.replace(/\./g, "_d_")
+			.replace(/\./g, "_d_")}`
 	}
 
 	/** Pre-3.1.2 IDs, where / and . both became _ */
@@ -334,13 +338,9 @@ export class ClaudeMemoryTool {
 		fileText: string,
 	): Promise<MemoryResponse> {
 		try {
-			// Overwrite a legacy-ID file in place instead of leaving a stale duplicate.
-			const existing = await this.getFileDocument(filePath)
-			const id =
-				existing.document?.documentId ??
-				existing.documentId ??
-				this.normalizePathToId(filePath)
-			await this.writeFile(id, fileText, {
+			const target = await this.resolveWriteId(filePath)
+			if ("error" in target) return { success: false, error: target.error }
+			await this.writeFile(target.id, fileText, {
 				source: CLAUDE_MEMORY_SOURCE,
 				claude_memory_type: "file",
 				file_path: filePath,
@@ -470,14 +470,16 @@ export class ClaudeMemoryTool {
 		try {
 			// Find the document first
 			const readResult = await this.getFileDocument(filePath)
-			if (!readResult.success || !readResult.document) {
+			const documentId =
+				readResult.document?.documentId ?? readResult.documentId
+			if (!documentId) {
 				return {
 					success: false,
 					error: readResult.error || "File not found",
 				}
 			}
 
-			await this.deleteFile(readResult.document.documentId)
+			await this.deleteFile(documentId)
 
 			return {
 				success: true,
@@ -516,17 +518,17 @@ export class ClaudeMemoryTool {
 				}
 			}
 
-			const originalContent = readResult.document.content
-			const newNormalizedId = this.normalizePathToId(newPath)
+			// Overwrite the destination's existing document (possibly a legacy ID) so no stale copy survives.
+			const target = await this.resolveWriteId(newPath)
+			if ("error" in target) return { success: false, error: target.error }
 
-			await this.writeFile(newNormalizedId, originalContent, {
+			await this.writeFile(target.id, readResult.document.content, {
 				...readResult.document.metadata,
 				file_path: newPath,
 				last_modified: new Date().toISOString(),
 			})
 
-			// Same normalized ID means the write above already replaced the file in place.
-			if (readResult.document.documentId !== newNormalizedId) {
+			if (readResult.document.documentId !== target.id) {
 				await this.deleteFile(readResult.document.documentId)
 			}
 
@@ -577,6 +579,10 @@ export class ClaudeMemoryTool {
 		document?: ClaudeFileDocument
 		/** Set when the file exists, even if its content is still processing. */
 		documentId?: string
+		/** Only true for a confirmed 404, never for a failed lookup. */
+		notFound?: boolean
+		/** The file's own ID is held by a document that isn't this file. */
+		occupied?: boolean
 		error?: string
 	}> {
 		try {
@@ -585,6 +591,7 @@ export class ClaudeMemoryTool {
 				this.normalizePathToId(filePath),
 				this.legacyNormalizePathToId(filePath),
 			]
+			let occupied = false
 			for (const id of ids) {
 				let document: Awaited<ReturnType<Supermemory["documents"]["get"]>>
 				try {
@@ -599,6 +606,7 @@ export class ClaudeMemoryTool {
 					document.metadata?.source !== CLAUDE_MEMORY_SOURCE ||
 					this.getDocumentFilePath(document) !== filePath
 				) {
+					if (id === ids[0]) occupied = true
 					continue
 				}
 				if (typeof document.content !== "string") {
@@ -619,7 +627,12 @@ export class ClaudeMemoryTool {
 				}
 			}
 
-			return { success: false, error: `File not found: ${filePath}` }
+			return {
+				success: false,
+				notFound: true,
+				occupied,
+				error: `File not found: ${filePath}`,
+			}
 		} catch (error) {
 			return {
 				success: false,
@@ -628,6 +641,22 @@ export class ClaudeMemoryTool {
 		}
 	}
 
+	/** The ID a write to filePath must use; errors rather than guessing when the lookup fails. */
+	private async resolveWriteId(
+		filePath: string,
+	): Promise<{ id: string } | { error: string }> {
+		const existing = await this.getFileDocument(filePath)
+		const existingId = existing.document?.documentId ?? existing.documentId
+		if (existingId) return { id: existingId }
+		if (!existing.notFound) {
+			return { error: existing.error ?? `Failed to look up ${filePath}` }
+		}
+		if (existing.occupied) {
+			return { error: `Another document already uses the ID for ${filePath}` }
+		}
+		return { id: this.normalizePathToId(filePath) }
+	}
+
 	private getDocumentFilePath(document: {
 		metadata: unknown
 	}): string | undefined {
diff --git a/packages/tools/src/openai/tools.ts b/packages/tools/src/openai/tools.ts
index 9bc593b0..9655550b 100644
--- a/packages/tools/src/openai/tools.ts
+++ b/packages/tools/src/openai/tools.ts
@@ -332,6 +332,9 @@ export function createDocumentDeleteFunction(
 	}: {
 		documentId: string
 	}): Promise<DocumentDeleteResult> {
+		if (!documentId?.trim()) {
+			return { success: false, error: "documentId is required" }
+		}
 		try {
 			await deleteDocument(client, namespace, documentId)
 
@@ -497,6 +500,20 @@ export function createToolCallExecutor(
 		}
 		const args = parsed.value
 
+		// Blank arguments are only valid for tools with no required fields.
+		const schema =
+			memoryToolSchemas[functionName as keyof typeof memoryToolSchemas]
+		const missing = schema?.parameters.required.filter(
+			(field: string) =>
+				typeof args[field] !== "string" || args[field].trim() === "",
+		)
+		if (missing?.length) {
+			return JSON.stringify({
+				success: false,
+				error: `Missing required arguments for ${functionName}: ${missing.join(", ")}`,
+			})
+		}
+
 		switch (functionName) {
 			case "searchMemories":
 				return JSON.stringify(await tools.searchMemories(args))
diff --git a/packages/tools/src/tool-operations.test.ts b/packages/tools/src/tool-operations.test.ts
index 8059aa09..ca48d547 100644
--- a/packages/tools/src/tool-operations.test.ts
+++ b/packages/tools/src/tool-operations.test.ts
@@ -388,6 +388,22 @@ describe("openai executeToolCall argument parsing", () => {
 		expect(sdk.profile).not.toHaveBeenCalled()
 	})
 
+	it.each([
+		["documentDelete", "documentId"],
+		["searchMemories", "informationToGet"],
+		["addMemory", "memory"],
+	])("rejects blank arguments for %s, which requires %s", async (name, field) => {
+		const execute = openAi.createToolCallExecutor(API_KEY)
+
+		const result = JSON.parse(await execute(toolCall(name, "")))
+
+		expect(result.success).toBe(false)
+		expect(result.error).toContain(field)
+		expect(sdk.documentsDelete).not.toHaveBeenCalled()
+		expect(sdk.search).not.toHaveBeenCalled()
+		expect(sdk.add).not.toHaveBeenCalled()
+	})
+
 	it("still reports malformed JSON as a tool error", async () => {
 		const execute = openAi.createToolCallExecutor(API_KEY)
 
@@ -424,18 +440,25 @@ describe("openai executeToolCall argument parsing", () => {
 
 describe("ClaudeMemoryTool", () => {
 	const FILE_PATH = "/memories/prefs.txt"
-	const FILE_ID = "memories_s_prefs_d_txt"
+	const FILE_ID = "cm_memories_s_prefs_d_txt"
+
+	beforeEach(() => {
+		sdk.documentsGet.mockRejectedValue(new sdk.NotFoundError("missing"))
+	})
 
 	function mockFileDocument(content: string) {
-		sdk.documentsGet.mockResolvedValue({
-			id: "doc_file_1",
-			content,
-			metadata: {
-				source: "claude-memory",
-				claude_memory_type: "file",
-				file_path: FILE_PATH,
-			},
-			system: { status: "done" },
+		sdk.documentsGet.mockImplementation(async (_ns: string, id: string) => {
+			if (id !== FILE_ID) throw new sdk.NotFoundError("missing")
+			return {
+				id: "doc_file_1",
+				content,
+				metadata: {
+					source: "claude-memory",
+					claude_memory_type: "file",
+					file_path: FILE_PATH,
+				},
+				system: { status: "done" },
+			}
 		})
 	}
 
@@ -578,7 +601,7 @@ describe("ClaudeMemoryTool", () => {
 		expect(result.success).toBe(true)
 		expect(sdk.add).toHaveBeenCalledWith(
 			DEFAULT_NS,
-			expect.objectContaining({ id: "memories_s_renamed_d_txt" }),
+			expect.objectContaining({ id: "cm_memories_s_renamed_d_txt" }),
 		)
 		expect(sdk.documentsDelete).toHaveBeenCalledWith(DEFAULT_NS, {
 			ids: [FILE_ID],
diff --git a/packages/tools/test/claude-memory-commands.test.ts b/packages/tools/test/claude-memory-commands.test.ts
index 8764cd80..953a2bc3 100644
--- a/packages/tools/test/claude-memory-commands.test.ts
+++ b/packages/tools/test/claude-memory-commands.test.ts
@@ -25,15 +25,19 @@ vi.mock("supermemory", () => {
 import { createClaudeMemoryTool } from "../src/claude-memory"
 
 function stubFile(path: string, content: string) {
-	sdk.get.mockImplementation(async () => ({
-		id: "doc_src",
-		metadata: {
-			source: "claude-memory",
-			claude_memory_type: "file",
-			file_path: path,
-		},
-		content,
-	}))
+	const fileId = `cm_${path.slice(1).replace(/_/g, "__").replace(/\//g, "_s_").replace(/\./g, "_d_")}`
+	sdk.get.mockImplementation(async (_ns: string, id: string) => {
+		if (id !== fileId) throw new sdk.NotFoundError("missing")
+		return {
+			id: "doc_src",
+			metadata: {
+				source: "claude-memory",
+				claude_memory_type: "file",
+				file_path: path,
+			},
+			content,
+		}
+	})
 }
 
 describe("ClaudeMemoryTool rename", () => {