diff --git a/tests/web/pi-adapter.test.ts b/tests/web/pi-adapter.test.ts
index 60be746f..7a81cecd 100644
--- a/tests/web/pi-adapter.test.ts
+++ b/tests/web/pi-adapter.test.ts
@@ -28,6 +28,10 @@ function runtimeFor(
     workspaceSelected: true,
     sessionDirectory,
     sessionManager,
+    isSessionOwned: (sessionId, sessionPath) =>
+      sessionManager.getSessionId() === sessionId ||
+      (sessionPath !== undefined &&
+        sessionManager.getSessionFile() === sessionPath),
     isIdle: () => true,
     getActiveTurn: () => undefined,
     cancelTurn: async (options) => ({ ...options, state: "stale-turn" }),
@@ -259,6 +263,90 @@ test("first archive mutation preserves previously persisted archive metadata", a
   }
 });
 
+test("deletes a persisted non-active session and cleans derived metadata", async () => {
+  const root = await mkdtemp(join(tmpdir(), "openpi-web-session-delete-"));
+  const sessionDirectory = join(root, "sessions");
+  try {
+    await mkdir(sessionDirectory, { recursive: true });
+    const current = SessionManager.inMemory(root);
+    const candidate = SessionManager.create(root, sessionDirectory);
+    persistSession(candidate, "delete me", 2);
+    const candidatePath = candidate.getSessionFile();
+    assert.ok(candidatePath);
+    const adapter = new PiWebAdapter(
+      runtimeFor(root, sessionDirectory, current),
+    );
+    await adapter.archiveSession(candidatePath);
+    await adapter.removeWorkspace(root);
+
+    const deletedPath = await adapter.deleteSession(candidatePath);
+    assert.equal(deletedPath, candidatePath);
+    await assert.rejects(readFile(candidatePath));
+    const archived = JSON.parse(
+      await readFile(join(sessionDirectory, "archived-sessions.json"), "utf8"),
+    ) as string[];
+    assert.equal(archived.includes(candidatePath), false);
+    const workspaceState = JSON.parse(
+      await readFile(join(sessionDirectory, "workspace-state.json"), "utf8"),
+    ) as { ungroupedSessions: string[] };
+    assert.equal(
+      workspaceState.ungroupedSessions.includes(candidatePath),
+      false,
+    );
+    assert.equal(
+      (await adapter.listSessions()).some(
+        (session) => session.path === candidatePath,
+      ),
+      false,
+    );
+  } finally {
+    await rm(root, { recursive: true, force: true });
+  }
+});
+
+test("refuses to delete the active session", async () => {
+  const root = await mkdtemp(
+    join(tmpdir(), "openpi-web-session-delete-active-"),
+  );
+  const sessionDirectory = join(root, "sessions");
+  try {
+    await mkdir(sessionDirectory, { recursive: true });
+    const current = SessionManager.inMemory(root);
+    const adapter = new PiWebAdapter(
+      runtimeFor(root, sessionDirectory, current),
+    );
+    await assert.rejects(
+      adapter.deleteSession(`current:${current.getSessionId()}`),
+      /live Web runtime/u,
+    );
+  } finally {
+    await rm(root, { recursive: true, force: true });
+  }
+});
+
+test("refuses to delete a Session retained by a live runtime", async () => {
+  const root = await mkdtemp(join(tmpdir(), "openpi-web-session-delete-live-"));
+  const sessionDirectory = join(root, "sessions");
+  try {
+    await mkdir(sessionDirectory, { recursive: true });
+    const current = SessionManager.inMemory(root);
+    const candidate = SessionManager.create(root, sessionDirectory);
+    persistSession(candidate, "retained", 2);
+    const candidatePath = candidate.getSessionFile();
+    assert.ok(candidatePath);
+    const runtime = runtimeFor(root, sessionDirectory, current);
+    runtime.isSessionOwned = () => true;
+    const adapter = new PiWebAdapter(runtime);
+    await assert.rejects(
+      adapter.deleteSession(candidatePath),
+      /live Web runtime/u,
+    );
+    await readFile(candidatePath);
+  } finally {
+    await rm(root, { recursive: true, force: true });
+  }
+});
+
 test("corrupt package metadata fails closed without overwriting it", async () => {
   const root = await mkdtemp(join(tmpdir(), "openpi-web-corrupt-state-"));
   const imported = await mkdtemp(join(tmpdir(), "openpi-web-corrupt-import-"));
diff --git a/tests/web/web-host.test.ts b/tests/web/web-host.test.ts
index bddddbbb..1e0b6c5f 100644
--- a/tests/web/web-host.test.ts
+++ b/tests/web/web-host.test.ts
@@ -1,6 +1,6 @@
 import assert from "node:assert/strict";
 import { once } from "node:events";
-import { mkdtemp, rm } from "node:fs/promises";
+import { mkdir, mkdtemp, readFile, rm } from "node:fs/promises";
 import { request as httpRequest } from "node:http";
 import { createConnection } from "node:net";
 import { tmpdir } from "node:os";
@@ -111,6 +111,10 @@ test("serves workspaces through a runtime isolated from terminal sessions", asyn
     get sessionManager() {
       return sessionManager;
     },
+    isSessionOwned: (sessionId, sessionPath) =>
+      sessionManager.getSessionId() === sessionId ||
+      (sessionPath !== undefined &&
+        sessionManager.getSessionFile() === sessionPath),
     isIdle: () => false,
     getActiveTurn: () => undefined,
     cancelTurn: async (options) => ({ ...options, state: "stale-turn" }),
@@ -844,6 +848,10 @@ test("an unbound Host exposes no bootstrap Session and rejects prompt bypasses",
     workspaceSelected: false,
     sessionDirectory: root,
     sessionManager,
+    isSessionOwned: (sessionId, sessionPath) =>
+      sessionManager.getSessionId() === sessionId ||
+      (sessionPath !== undefined &&
+        sessionManager.getSessionFile() === sessionPath),
     isIdle: () => true,
     getActiveTurn: () => undefined,
     cancelTurn: async (options) => ({ ...options, state: "stale-turn" }),
@@ -943,6 +951,10 @@ test("returns accepted only after Pi admits the prompt", async () => {
     sessionDirectory: cwd,
     cwd,
     sessionManager,
+    isSessionOwned: (sessionId, sessionPath) =>
+      sessionManager.getSessionId() === sessionId ||
+      (sessionPath !== undefined &&
+        sessionManager.getSessionFile() === sessionPath),
     isIdle: () => false,
     getActiveTurn: () => undefined,
     cancelTurn: async (options) => ({ ...options, state: "stale-turn" }),
@@ -1070,13 +1082,18 @@ function testRuntime(
   sendPrompt: WebRuntimeController["sendPrompt"] = async () => ({
     pendingFollowUps: 0,
   }),
+  sessionDirectory = cwd,
 ) {
   const sessionManager = SessionManager.inMemory(cwd);
   const runtime: WebRuntimeController = {
     workspaceSelected: true,
-    sessionDirectory: cwd,
+    sessionDirectory,
     cwd,
     sessionManager,
+    isSessionOwned: (sessionId, sessionPath) =>
+      sessionManager.getSessionId() === sessionId ||
+      (sessionPath !== undefined &&
+        sessionManager.getSessionFile() === sessionPath),
     isIdle: () => true,
     getActiveTurn: () => undefined,
     cancelTurn: async (options) => ({ ...options, state: "stale-turn" }),
@@ -1132,7 +1149,7 @@ test("classifies invalid and oversized JSON bodies as client errors", async () =
     const oversizedBody = await fetch(`${launched.origin}/api/workspaces`, {
       method: "POST",
       headers: { ...headers, "Content-Type": "application/json" },
-      body: JSON.stringify({ path: "x".repeat(16 * 1024) }),
+      body: JSON.stringify({ path: "x".repeat(32 * 1024) }),
     });
     assert.equal(oversizedBody.status, 413);
     assert.deepEqual(await oversizedBody.json(), {
@@ -1146,6 +1163,64 @@ test("classifies invalid and oversized JSON bodies as client errors", async () =
   }
 });
 
+test("requires exact reviewed confirmation before deleting a persisted Session", async () => {
+  const cwd = await mkdtemp(join(tmpdir(), "openpi-web-session-delete-host-"));
+  const sessionDirectory = join(cwd, "sessions");
+  await mkdir(sessionDirectory);
+  const candidate = SessionManager.create(cwd, sessionDirectory);
+  candidate.appendMessage({ role: "user", content: "delete me", timestamp: 1 });
+  candidate.appendMessage({
+    role: "assistant",
+    content: [],
+    api: "openai-responses",
+    provider: "fixture",
+    model: "fixture",
+    usage: {
+      input: 0,
+      output: 0,
+      cacheRead: 0,
+      cacheWrite: 0,
+      totalTokens: 0,
+      cost: { input: 0, output: 0, cacheRead: 0, cacheWrite: 0, total: 0 },
+    },
+    stopReason: "stop",
+    timestamp: 1,
+  });
+  const sessionPath = candidate.getSessionFile();
+  assert.ok(sessionPath);
+  const { host, launched, headers } = await startTestHost(
+    testRuntime(cwd, undefined, sessionDirectory),
+  );
+  try {
+    const target = `${launched.origin}/api/sessions?path=${encodeURIComponent(sessionPath)}`;
+    const bare = await fetch(target, { method: "DELETE", headers });
+    assert.equal(bare.status, 400);
+    assert.deepEqual(await bare.json(), {
+      code: "CONFIRMATION_REQUIRED",
+      error: "Confirm the exact canonical Session path before deletion",
+      path: sessionPath,
+    });
+    await readFile(sessionPath);
+    const wrong = await fetch(`${target}&confirm=wrong`, {
+      method: "DELETE",
+      headers,
+    });
+    assert.equal(wrong.status, 400);
+    const confirmed = await fetch(
+      `${target}&confirm=${encodeURIComponent(sessionPath)}`,
+      { method: "DELETE", headers },
+    );
+    assert.equal(confirmed.status, 200);
+    assert.deepEqual(await confirmed.json(), {
+      path: sessionPath,
+      deleted: true,
+    });
+  } finally {
+    await host.stop();
+    await rm(cwd, { recursive: true, force: true });
+  }
+});
+
 test("classifies an oversized body sent in multiple chunks as a client error", async () => {
   const cwd = await mkdtemp(join(tmpdir(), "openpi-web-request-chunks-"));
   const { host, launched, headers } = await startTestHost(testRuntime(cwd));
diff --git a/web/adapter/pi-adapter.ts b/web/adapter/pi-adapter.ts
index 68a5175a..90793eea 100644
--- a/web/adapter/pi-adapter.ts
+++ b/web/adapter/pi-adapter.ts
@@ -1,5 +1,5 @@
 import { readFile, realpath, rename, rm, stat, writeFile } from "node:fs/promises";
-import { basename, join, resolve } from "node:path";
+import { basename, isAbsolute, join, relative, resolve, sep } from "node:path";
 import { SessionManager } from "@earendil-works/pi-coding-agent";
 import { webCapabilitySnapshot } from "../../extensions/shared/web-observer-registry.ts";
 import {
@@ -19,6 +19,16 @@ import {
 } from "../protocol/types.ts";
 import type { WebRuntimeController } from "../runtime/types.ts";
 
+export class WebSessionDeletionError extends Error {
+  readonly code = "SESSION_CONFLICT" as const;
+  readonly statusCode = 409 as const;
+
+  constructor(message: string) {
+    super(message);
+    this.name = "WebSessionDeletionError";
+  }
+}
+
 type WorkspaceStateSnapshot = {
   importedWorkspaces: Set<string>;
   hiddenWorkspaces: Set<string>;
@@ -292,6 +302,37 @@ export class PiWebAdapter {
     });
   }
 
+  async deleteSession(path: string) {
+    await this.ensureWorkspaceStateLoaded();
+    await this.ensureArchivesLoaded();
+    const session = await this.requireSession(path);
+    const canonical = resolve(session.path);
+    if (this.runtime.isSessionOwned(session.id, canonical)) {
+      throw new WebSessionDeletionError(
+        "Cannot delete a Session owned by a live Web runtime",
+      );
+    }
+    const sessionDirectory = resolve(this.runtime.sessionDirectory);
+    const relativePath = relative(sessionDirectory, canonical);
+    if (
+      !relativePath ||
+      isAbsolute(relativePath) ||
+      relativePath === ".." ||
+      relativePath.startsWith(`..${sep}`) ||
+      !canonical.endsWith(".jsonl")
+    ) {
+      throw new Error("Session target is outside the Web Session directory");
+    }
+    await rm(canonical);
+    await this.enqueueArchiveMutation((draft) => {
+      draft.delete(canonical);
+    });
+    await this.enqueueWorkspaceMutation((draft) => {
+      draft.ungroupedSessions.delete(canonical);
+    });
+    return canonical;
+  }
+
   async removeWorkspace(path: string) {
     await this.ensureWorkspaceStateLoaded();
     const canonical = resolve(path);
diff --git a/web/host/web-host.ts b/web/host/web-host.ts
index ee49fa04..8ff7fe7d 100644
--- a/web/host/web-host.ts
+++ b/web/host/web-host.ts
@@ -8,6 +8,7 @@ import {
   type ServerResponse,
 } from "node:http";
 import { URL } from "node:url";
+import { resolve } from "node:path";
 import { promisify } from "node:util";
 import {
   subscribeWebCapabilities,
@@ -15,7 +16,10 @@ import {
   webCapabilitySnapshot,
 } from "../../extensions/shared/web-observer-registry.ts";
 import { loadSetupConfig } from "../../extensions/shared/setup-config.ts";
-import { PiWebAdapter } from "../adapter/pi-adapter.ts";
+import {
+  PiWebAdapter,
+  WebSessionDeletionError,
+} from "../adapter/pi-adapter.ts";
 import {
   jsonByteLength,
   WEB_MAX_EVENT_BYTES,
@@ -520,6 +524,34 @@ export class WebHost {
       this.publish("session_unarchived", { sessionPath: path });
       return this.json(response, 200, { path, archived: false });
     }
+    if (url.pathname === "/api/sessions" && request.method === "DELETE") {
+      const path = url.searchParams.get("path");
+      const confirmation = url.searchParams.get("confirm");
+      if (!path)
+        return this.json(response, 400, { error: "session path is required" });
+      try {
+        const session = await this.adapter.requireSession(path);
+        const canonical = resolve(session.path);
+        if (confirmation !== canonical) {
+          return this.json(response, 400, {
+            code: "CONFIRMATION_REQUIRED",
+            error: "Confirm the exact canonical Session path before deletion",
+            path: canonical,
+          });
+        }
+        const deletedPath = await this.adapter.deleteSession(canonical);
+        this.publish("session_deleted", { sessionPath: deletedPath });
+        return this.json(response, 200, { path: deletedPath, deleted: true });
+      } catch (error) {
+        if (error instanceof WebSessionDeletionError) {
+          return this.json(response, error.statusCode, {
+            code: error.code,
+            error: error.message,
+          });
+        }
+        throw error;
+      }
+    }
     if (url.pathname === "/api/sessions/select" && request.method === "POST") {
       const body = await this.readJson(request);
       if (typeof body.path !== "string" || body.path.trim().length === 0) {
diff --git a/web/runtime/pi-runtime.ts b/web/runtime/pi-runtime.ts
index c9d5cdee..80390d69 100644
--- a/web/runtime/pi-runtime.ts
+++ b/web/runtime/pi-runtime.ts
@@ -702,6 +702,24 @@ export class PiWebRuntime implements WebRuntimeController {
     );
   }
 
+  isSessionOwned(sessionId: string, sessionPath?: string) {
+    const runtimes = new Set([
+      this.runtime,
+      ...this.retainedRuntimes,
+      ...this.candidateRuntimes,
+    ]);
+    return [...runtimes].some((runtime) => {
+      const manager = runtime.session.sessionManager;
+      if (manager.getSessionId() === sessionId) return true;
+      const ownedPath = manager.getSessionFile();
+      return (
+        sessionPath !== undefined &&
+        ownedPath !== undefined &&
+        resolve(ownedPath) === resolve(sessionPath)
+      );
+    });
+  }
+
   private async createNewSession(
     workspacePath: string,
     options?: WebSessionCreationOptions,
diff --git a/web/runtime/types.ts b/web/runtime/types.ts
index 8c60e5c0..f73d0eff 100644
--- a/web/runtime/types.ts
+++ b/web/runtime/types.ts
@@ -106,6 +106,7 @@ export interface WebRuntimeController {
   readonly workspaceSelected: boolean;
   readonly sessionDirectory: string;
   readonly sessionManager: SessionManager;
+  isSessionOwned(sessionId: string, sessionPath?: string): boolean;
   getProjectTrustStatus?(): WebProjectTrustStatus;
   isIdle(): boolean;
   getActiveTurn(): WebActiveTurn | undefined;