diff --git a/.changeset/tidy-buckets-delete.md b/.changeset/tidy-buckets-delete.md
new file mode 100644
index 000000000..d16699638
--- /dev/null
+++ b/.changeset/tidy-buckets-delete.md
@@ -0,0 +1,7 @@
+---
+"deepagents": minor
+---
+
+feat(backends): add delete protocol support
+
+Adds a `DeleteResult` type and optional backend `delete` method, preserves delete through backend protocol adaptation, and implements StateBackend deletion through Pregel file-state updates.
diff --git a/libs/deepagents/src/backends/index.ts b/libs/deepagents/src/backends/index.ts
index 50116ae31..ee98d2d8e 100644
--- a/libs/deepagents/src/backends/index.ts
+++ b/libs/deepagents/src/backends/index.ts
@@ -22,6 +22,7 @@ export type {
   GlobResult,
   WriteResult,
   EditResult,
+  DeleteResult,
   StateAndStore,
   // Sandbox execution types
   ExecuteResponse,
diff --git a/libs/deepagents/src/backends/protocol.ts b/libs/deepagents/src/backends/protocol.ts
index 5ed3f6290..112f8454e 100644
--- a/libs/deepagents/src/backends/protocol.ts
+++ b/libs/deepagents/src/backends/protocol.ts
@@ -215,6 +215,16 @@ export interface EditResult {
   metadata?: Record<string, unknown>;
 }
 
+/**
+ * Result from backend delete operations.
+ */
+export interface DeleteResult {
+  /** Error message on failure, undefined on success */
+  error?: string;
+  /** File path of deleted file, undefined on failure */
+  path?: string;
+}
+
 /**
  * Result of code execution.
  * Simplified schema optimized for LLM consumption.
diff --git a/libs/deepagents/src/backends/state.test.ts b/libs/deepagents/src/backends/state.test.ts
index 5ad7eadba..871f2adfd 100644
--- a/libs/deepagents/src/backends/state.test.ts
+++ b/libs/deepagents/src/backends/state.test.ts
@@ -14,15 +14,17 @@ vi.mock("@langchain/langgraph", async (importOriginal) => {
 
 function makeConfig(files: Record<string, FileData> = {}) {
   const state = { messages: [], files: { ...files } };
-  const pendingFilesSends: Record<string, FileData>[] = [];
+  const pendingFilesSends: Record<string, FileData | null>[] = [];
 
   const sendSpy = vi
     .fn()
-    .mockImplementation((sends: [string, Record<string, FileData>][]) => {
-      for (const [channel, update] of sends) {
-        if (channel === "files") pendingFilesSends.push(update);
-      }
-    });
+    .mockImplementation(
+      (sends: [string, Record<string, FileData | null>][]) => {
+        for (const [channel, update] of sends) {
+          if (channel === "files") pendingFilesSends.push(update);
+        }
+      },
+    );
 
   const readSpy = vi
     .fn()
@@ -30,7 +32,15 @@ function makeConfig(files: Record<string, FileData> = {}) {
       if (channel !== "files") return undefined;
       if (!fresh || pendingFilesSends.length === 0) return state.files;
       const merged = { ...state.files };
-      for (const update of pendingFilesSends) Object.assign(merged, update);
+      for (const update of pendingFilesSends) {
+        for (const [path, fileData] of Object.entries(update)) {
+          if (fileData === null) {
+            delete merged[path];
+          } else {
+            merged[path] = fileData;
+          }
+        }
+      }
       return merged;
     });
 
@@ -40,7 +50,15 @@ function makeConfig(files: Record<string, FileData> = {}) {
 
   // Simulate Pregel committing task.writes to state and clearing the buffer.
   function commitSends() {
-    for (const update of pendingFilesSends) Object.assign(state.files, update);
+    for (const update of pendingFilesSends) {
+      for (const [path, fileData] of Object.entries(update)) {
+        if (fileData === null) {
+          delete state.files[path];
+        } else {
+          state.files[path] = fileData;
+        }
+      }
+    }
     pendingFilesSends.length = 0;
   }
 
@@ -109,6 +127,49 @@ describe("StateBackend", () => {
     expect(infos.files!.some((i) => i.path === "/notes.txt")).toBe(true);
   });
 
+  it("should delete files through Pregel send in zero-arg mode", () => {
+    const { sendSpy, commitSends } = makeConfig();
+    const backend = new StateBackend();
+
+    const writeRes = backend.write("/drop.txt", "bye");
+    expect(writeRes.error).toBeUndefined();
+    commitSends();
+    expect(backend.read("/drop.txt").error).toBeUndefined();
+
+    const deleteRes = backend.delete("/drop.txt");
+    expect(deleteRes.error).toBeUndefined();
+    expect(deleteRes.path).toBe("/drop.txt");
+    expect(sendSpy).toHaveBeenLastCalledWith([
+      ["files", { "/drop.txt": null }],
+    ]);
+
+    commitSends();
+    expect(backend.read("/drop.txt").error).toContain("not found");
+  });
+
+  it("should return an error when deleting a missing file", () => {
+    makeConfig();
+    const backend = new StateBackend();
+
+    const result = backend.delete("/missing.txt");
+
+    expect(result.path).toBeUndefined();
+    expect(result.error).toContain("not found");
+  });
+
+  it("should return an explicit error for delete in legacy mode", () => {
+    const { state, runtime } = makeConfig();
+    const backend = new StateBackend(runtime);
+    const writeRes = backend.write("/drop.txt", "bye");
+    Object.assign(state.files, writeRes.filesUpdate);
+
+    const result = backend.delete("/drop.txt");
+
+    expect(result.path).toBeUndefined();
+    expect(result.error).toContain("zero-argument StateBackend");
+    expect(backend.read("/drop.txt").error).toBeUndefined();
+  });
+
   it("should handle errors correctly", () => {
     const { state, runtime } = makeConfig();
     const backend = new StateBackend(runtime);
diff --git a/libs/deepagents/src/backends/state.ts b/libs/deepagents/src/backends/state.ts
index 4048ccd5c..efdad8914 100644
--- a/libs/deepagents/src/backends/state.ts
+++ b/libs/deepagents/src/backends/state.ts
@@ -3,6 +3,7 @@
  */
 
 import type {
+  DeleteResult,
   EditResult,
   FileData,
   FileDownloadResponse,
@@ -118,9 +119,10 @@ export class StateBackend implements BackendProtocolV2 {
    * In legacy mode, this is a no-op — the caller uses `filesUpdate`
    * from the return value instead.
    *
-   * @param update - Map of file paths to their updated {@link FileData}
+   * @param update - Map of file paths to their updated {@link FileData},
+   *   or null deletion markers.
    */
-  private sendFilesUpdate(update: Record<string, FileData>): void {
+  private sendFilesUpdate(update: Record<string, FileData | null>): void {
     if (this.isLegacy) {
       return;
     }
@@ -325,6 +327,27 @@ export class StateBackend implements BackendProtocolV2 {
     };
   }
 
+  /**
+   * Delete a file from state by sending a null deletion marker through Pregel.
+   */
+  delete(filePath: string): DeleteResult {
+    const files = this.files;
+
+    if (!(filePath in files)) {
+      return { error: `Error: File '${filePath}' not found` };
+    }
+
+    if (this.isLegacy) {
+      return {
+        error:
+          "StateBackend.delete requires a zero-argument StateBackend in a LangGraph execution context.",
+      };
+    }
+
+    this.sendFilesUpdate({ [filePath]: null });
+    return { path: filePath };
+  }
+
   /**
    * Search file contents for a literal text pattern.
    * Binary files are skipped.
diff --git a/libs/deepagents/src/backends/utils.ts b/libs/deepagents/src/backends/utils.ts
index 26e2c5560..ebabb382a 100644
--- a/libs/deepagents/src/backends/utils.ts
+++ b/libs/deepagents/src/backends/utils.ts
@@ -930,6 +930,7 @@ export function adaptBackendProtocol(
     write: (filePath, content) => backend.write(filePath, content),
     edit: (filePath, oldString, newString, replaceAll) =>
       backend.edit(filePath, oldString, newString, replaceAll),
+    delete: backend.delete?.bind(backend),
     uploadFiles: backend.uploadFiles
       ? (files) => backend.uploadFiles!(files)
       : undefined,
diff --git a/libs/deepagents/src/backends/v1/protocol.ts b/libs/deepagents/src/backends/v1/protocol.ts
index f0d237dad..0f77a458c 100644
--- a/libs/deepagents/src/backends/v1/protocol.ts
+++ b/libs/deepagents/src/backends/v1/protocol.ts
@@ -7,6 +7,7 @@
  */
 
 import type {
+  DeleteResult,
   EditResult,
   ExecuteResponse,
   FileData,
@@ -111,6 +112,14 @@ export interface BackendProtocolV1 {
     replaceAll?: boolean,
   ): MaybePromise<EditResult>;
 
+  /**
+   * Delete a single file.
+   *
+   * @param filePath - Absolute path to the file to delete
+   * @returns DeleteResult with path on success or error on failure
+   */
+  delete?(filePath: string): MaybePromise<DeleteResult>;
+
   /**
    * Upload multiple files.
    * Optional - backends that don't support file upload can omit this.
diff --git a/libs/deepagents/src/backends/v2/protocol.ts b/libs/deepagents/src/backends/v2/protocol.ts
index 68de11fbb..23ba351a9 100644
--- a/libs/deepagents/src/backends/v2/protocol.ts
+++ b/libs/deepagents/src/backends/v2/protocol.ts
@@ -7,6 +7,7 @@
 
 import type { BackendProtocolV1 } from "../v1/protocol.js";
 import type {
+  DeleteResult,
   ExecuteResponse,
   GlobResult,
   GrepResult,
@@ -93,6 +94,15 @@ export interface BackendProtocolV2 extends Omit<
    * @returns GlobResult with list of FileInfo objects matching the pattern on success or error on failure
    */
   glob(pattern: string, path?: string): MaybePromise<GlobResult>;
+
+  /**
+   * Delete a single file.
+   * Optional - backends that don't support file deletion can omit this.
+   *
+   * @param filePath - Absolute path to the file to delete
+   * @returns DeleteResult with path on success or error on failure
+   */
+  delete?(filePath: string): MaybePromise<DeleteResult>;
 }
 
 /**
diff --git a/libs/deepagents/src/browser.ts b/libs/deepagents/src/browser.ts
index aafd59ab0..4cb4e575d 100644
--- a/libs/deepagents/src/browser.ts
+++ b/libs/deepagents/src/browser.ts
@@ -117,6 +117,7 @@ export type {
   GlobResult,
   WriteResult,
   EditResult,
+  DeleteResult,
   StateAndStore,
   // Sandbox execution types
   ExecuteResponse,
diff --git a/libs/deepagents/src/index.ts b/libs/deepagents/src/index.ts
index 7b4467367..92915cc4b 100644
--- a/libs/deepagents/src/index.ts
+++ b/libs/deepagents/src/index.ts
@@ -148,6 +148,7 @@ export {
   type ReadRawResult,
   type WriteResult,
   type EditResult,
+  type DeleteResult,
   // Sandbox execution types
   type ExecuteResponse,
   type FileData,