diff --git a/apps/web/app/api/chat/_lib/request.ts b/apps/web/app/api/chat/_lib/request.ts
index ce67d5b..2a4af5c 100644
--- a/apps/web/app/api/chat/_lib/request.ts
+++ b/apps/web/app/api/chat/_lib/request.ts
@@ -1,10 +1,27 @@
+import { z } from "zod";
 import type { WebAgentUIMessage } from "@/app/types";
 
-export interface ChatRequestBody {
-  messages: WebAgentUIMessage[];
-  sessionId?: string;
-  chatId?: string;
-}
+const chatRequestBodySchema = z.object({
+  messages: z.custom<WebAgentUIMessage[]>((val) => Array.isArray(val), {
+    message: "messages must be an array",
+  }),
+  sessionId: z.string().optional(),
+  chatId: z.string().optional(),
+  /**
+   * Short-lived Recoupable access token (Privy JWT) for this prompt.
+   * Forwarded into the agent's `experimental_context` so tools making
+   * outbound calls to the Recoupable API authenticate as the user for
+   * the duration of this prompt only.
+   */
+  recoupAccessToken: z.string().min(1).max(8192).optional(),
+  context: z
+    .object({
+      contextLimit: z.number(),
+    })
+    .optional(),
+});
+
+export type ChatRequestBody = z.infer<typeof chatRequestBodySchema>;
 
 type ParseChatRequestResult =
   | {
@@ -30,15 +47,28 @@ type RequireChatIdentifiersResult =
 export async function parseChatRequestBody(
   req: Request,
 ): Promise<ParseChatRequestResult> {
+  let rawBody: unknown;
   try {
-    const body = (await req.json()) as ChatRequestBody;
-    return { ok: true, body };
+    rawBody = await req.json();
   } catch {
     return {
       ok: false,
       response: Response.json({ error: "Invalid JSON body" }, { status: 400 }),
     };
   }
+
+  const parsed = chatRequestBodySchema.safeParse(rawBody);
+  if (!parsed.success) {
+    return {
+      ok: false,
+      response: Response.json(
+        { error: "Invalid request body", issues: parsed.error.issues },
+        { status: 400 },
+      ),
+    };
+  }
+
+  return { ok: true, body: parsed.data };
 }
 
 export function requireChatIdentifiers(
diff --git a/apps/web/app/api/chat/route.ts b/apps/web/app/api/chat/route.ts
index 701facb..5d3a236 100644
--- a/apps/web/app/api/chat/route.ts
+++ b/apps/web/app/api/chat/route.ts
@@ -67,7 +67,7 @@ export async function POST(req: Request) {
     return parsedBody.response;
   }
 
-  const { messages } = parsedBody.body;
+  const { messages, recoupAccessToken } = parsedBody.body;
 
   // 2. Require sessionId and chatId to ensure sandbox ownership verification
   const chatIdentifiers = requireChatIdentifiers(parsedBody.body);
@@ -236,6 +236,7 @@ export async function POST(req: Request) {
           : {}),
         ...(skills.length > 0 && { skills }),
         customInstructions: assistantFileLinkPrompt,
+        ...(recoupAccessToken ? { recoupAccessToken } : {}),
       },
       ...(shouldAutoCommitPush &&
         sessionRecord.repoOwner &&
diff --git a/apps/web/app/sessions/[sessionId]/chats/[chatId]/hooks/use-session-chat-runtime.ts b/apps/web/app/sessions/[sessionId]/chats/[chatId]/hooks/use-session-chat-runtime.ts
index 9403238..24fac6b 100644
--- a/apps/web/app/sessions/[sessionId]/chats/[chatId]/hooks/use-session-chat-runtime.ts
+++ b/apps/web/app/sessions/[sessionId]/chats/[chatId]/hooks/use-session-chat-runtime.ts
@@ -1,6 +1,7 @@
 "use client";
 
 import { type UseChatHelpers, useChat } from "@ai-sdk/react";
+import { usePrivy } from "@privy-io/react-auth";
 import { isToolUIPart } from "ai";
 import { useCallback, useEffect, useMemo, useRef } from "react";
 import type { WebAgentUIMessage } from "@/app/types";
@@ -85,15 +86,28 @@ export function useSessionChatRuntime({
     contextLimitRef.current = contextLimit;
   }, [contextLimit]);
 
+  // Attach a fresh Privy access token to each prompt so outbound calls
+  // from the sandbox to the Recoupable API authenticate as the user with
+  // a short-lived credential that dies with the prompt.
+  const { getAccessToken } = usePrivy();
+
   const transport = useMemo(
     () =>
       new AbortableChatTransport({
         api: "/api/chat",
-        body: () => {
+        body: async () => {
           const requestContextLimit = contextLimitRef.current;
+          const recoupAccessToken = await getAccessToken().catch((error) => {
+            console.error(
+              "[chat] failed to fetch Privy access token for prompt",
+              error,
+            );
+            return null;
+          });
           return {
             sessionId,
             chatId,
+            ...(recoupAccessToken ? { recoupAccessToken } : {}),
             ...(requestContextLimit !== null
               ? {
                   context: {
@@ -107,7 +121,7 @@ export function useSessionChatRuntime({
           api: `/api/chat/${id}/stream`,
         }),
       }),
-    [sessionId, chatId],
+    [sessionId, chatId, getAccessToken],
   );
 
   const { instance: chatInstance, alreadyExisted } = useMemo(
diff --git a/packages/agent/open-harness-agent.ts b/packages/agent/open-harness-agent.ts
index f66ce02..1ad86d9 100644
--- a/packages/agent/open-harness-agent.ts
+++ b/packages/agent/open-harness-agent.ts
@@ -44,6 +44,13 @@ const callOptionsSchema = z.object({
   subagentModel: z.custom<OpenHarnessAgentModelInput>().optional(),
   customInstructions: z.string().optional(),
   skills: z.custom<SkillMetadata[]>().optional(),
+  /**
+   * Short-lived Recoupable API access token forwarded by the caller on a
+   * per-prompt basis. Surfaced to tools via `experimental_context` so
+   * outbound calls to the Recoupable API can authenticate as the user
+   * without persisting a long-lived credential in the sandbox env.
+   */
+  recoupAccessToken: z.string().optional(),
 });
 
 export type OpenHarnessAgentCallOptions = z.infer<typeof callOptionsSchema>;
@@ -114,6 +121,7 @@ export const openHarnessAgent = new ToolLoopAgent({
     const customInstructions = options.customInstructions;
     const sandbox = options.sandbox;
     const skills = options.skills ?? [];
+    const recoupAccessToken = options.recoupAccessToken;
 
     const instructions = buildSystemPrompt({
       cwd: sandbox.workingDirectory,
@@ -137,6 +145,7 @@ export const openHarnessAgent = new ToolLoopAgent({
         skills,
         model: callModel,
         subagentModel,
+        ...(recoupAccessToken ? { recoupAccessToken } : {}),
       },
     };
   },
diff --git a/packages/agent/tools/bash.ts b/packages/agent/tools/bash.ts
index 07fad02..c3307ca 100644
--- a/packages/agent/tools/bash.ts
+++ b/packages/agent/tools/bash.ts
@@ -1,6 +1,7 @@
 import { tool } from "ai";
 import { z } from "zod";
 import * as path from "path";
+import { buildRecoupExecEnv } from "./build-recoup-exec-env";
 import { getSandbox } from "./utils";
 
 const TIMEOUT_MS = 120_000;
@@ -104,6 +105,7 @@ EXAMPLES:
     ) => {
       const sandbox = await getSandbox(experimental_context, "bash");
       const workingDirectory = sandbox.workingDirectory;
+      const recoupEnv = buildRecoupExecEnv(experimental_context);
 
       // Resolve the working directory
       const workingDir = cwd
@@ -125,6 +127,10 @@ EXAMPLES:
         }
 
         try {
+          // Detached processes outlive the prompt, so we deliberately do
+          // not inject RECOUP_ACCESS_TOKEN here — the token is scoped to
+          // foreground execs whose lifetime tracks the prompt. Long-
+          // running services must authenticate via their own mechanism.
           const { commandId } = await sandbox.execDetached(command, workingDir);
           return {
             success: true,
@@ -144,6 +150,7 @@ EXAMPLES:
 
       const result = await sandbox.exec(command, workingDir, TIMEOUT_MS, {
         signal: abortSignal,
+        ...(recoupEnv ? { env: recoupEnv } : {}),
       });
 
       return {
diff --git a/packages/agent/tools/build-recoup-exec-env.ts b/packages/agent/tools/build-recoup-exec-env.ts
new file mode 100644
index 0000000..3a3fd23
--- /dev/null
+++ b/packages/agent/tools/build-recoup-exec-env.ts
@@ -0,0 +1,17 @@
+import { getRecoupAccessToken } from "./get-recoup-access-token";
+
+/**
+ * Build a per-invocation env override carrying the Recoupable access
+ * token when one is available, so outbound shell commands (curl, scripts)
+ * can authenticate without the token persisting on the sandbox.
+ */
+export function buildRecoupExecEnv(
+  experimental_context: unknown,
+): { RECOUP_ACCESS_TOKEN: string } | undefined {
+  const token = getRecoupAccessToken(experimental_context);
+  if (!token) {
+    return undefined;
+  }
+
+  return { RECOUP_ACCESS_TOKEN: token };
+}
diff --git a/packages/agent/tools/fetch.ts b/packages/agent/tools/fetch.ts
index 8b15f0d..85faa2a 100644
--- a/packages/agent/tools/fetch.ts
+++ b/packages/agent/tools/fetch.ts
@@ -1,5 +1,6 @@
 import { tool } from "ai";
 import { z } from "zod";
+import { buildRecoupExecEnv } from "./build-recoup-exec-env";
 import { getSandbox, shellEscape } from "./utils";
 
 const TIMEOUT_MS = 30_000;
@@ -54,6 +55,7 @@ EXAMPLES:
   ) => {
     const sandbox = await getSandbox(experimental_context, "web_fetch");
     const workingDirectory = sandbox.workingDirectory;
+    const recoupEnv = buildRecoupExecEnv(experimental_context);
 
     const args: string[] = [
       "curl",
@@ -92,6 +94,7 @@ EXAMPLES:
     try {
       const result = await sandbox.exec(command, workingDirectory, TIMEOUT_MS, {
         signal: abortSignal,
+        ...(recoupEnv ? { env: recoupEnv } : {}),
       });
 
       if (result.exitCode !== 0 && result.exitCode !== 23) {
diff --git a/packages/agent/tools/get-recoup-access-token.ts b/packages/agent/tools/get-recoup-access-token.ts
new file mode 100644
index 0000000..43e7d8f
--- /dev/null
+++ b/packages/agent/tools/get-recoup-access-token.ts
@@ -0,0 +1,15 @@
+import { isAgentContext } from "./utils";
+
+/**
+ * Read the per-prompt Recoupable access token from agent context.
+ * Returns undefined when no token is present (e.g. callers that do not
+ * authenticate against the Recoupable API).
+ */
+export function getRecoupAccessToken(
+  experimental_context: unknown,
+): string | undefined {
+  const context = isAgentContext(experimental_context)
+    ? experimental_context
+    : undefined;
+  return context?.recoupAccessToken;
+}
diff --git a/packages/agent/tools/tools.test.ts b/packages/agent/tools/tools.test.ts
index cb3a2be..4fa0313 100644
--- a/packages/agent/tools/tools.test.ts
+++ b/packages/agent/tools/tools.test.ts
@@ -371,6 +371,88 @@ describe("tools execute behavior", () => {
     });
   });
 
+  test("bashTool forwards recoupAccessToken to foreground exec only, never detached", async () => {
+    const execCalls: Array<{
+      command: string;
+      cwd: string;
+      options?: { signal?: AbortSignal; env?: Record<string, string> };
+    }> = [];
+    const detachedCalls: Array<{ command: string; cwd: string }> = [];
+
+    const sandbox = {
+      workingDirectory: "/repo",
+      exec: async (
+        command: string,
+        cwd: string,
+        _timeoutMs: number,
+        options?: { signal?: AbortSignal; env?: Record<string, string> },
+      ) => {
+        execCalls.push({ command, cwd, options });
+        return {
+          success: true,
+          exitCode: 0,
+          stdout: "",
+          stderr: "",
+          truncated: false,
+        };
+      },
+      execDetached: async (command: string, cwd: string) => {
+        detachedCalls.push({ command, cwd });
+        return { commandId: "cmd-detached" };
+      },
+    };
+
+    const context = {
+      ...createContext(sandbox),
+      recoupAccessToken: "privy-jwt-abc",
+    };
+
+    await bashTool().execute?.(
+      { command: "curl https://developers.recoupable.com/ping" },
+      executionOptions(context),
+    );
+
+    expect(execCalls).toHaveLength(1);
+    expect(execCalls[0]?.options?.env).toEqual({
+      RECOUP_ACCESS_TOKEN: "privy-jwt-abc",
+    });
+
+    // Detached processes outlive the prompt — token must NOT be injected.
+    await bashTool().execute?.(
+      { command: "npm run dev", detached: true },
+      executionOptions(context),
+    );
+
+    expect(detachedCalls).toHaveLength(1);
+
+    const contextWithoutToken = createContext({
+      workingDirectory: "/repo",
+      exec: async (
+        command: string,
+        cwd: string,
+        _timeoutMs: number,
+        options?: { signal?: AbortSignal; env?: Record<string, string> },
+      ) => {
+        execCalls.push({ command, cwd, options });
+        return {
+          success: true,
+          exitCode: 0,
+          stdout: "",
+          stderr: "",
+          truncated: false,
+        };
+      },
+    });
+
+    await bashTool().execute?.(
+      { command: "ls" },
+      executionOptions(contextWithoutToken),
+    );
+
+    expect(execCalls).toHaveLength(2);
+    expect(execCalls[1]?.options?.env).toBeUndefined();
+  });
+
   test("commandNeedsApproval flags only rm -rf commands", () => {
     expect(commandNeedsApproval("ls -la")).toBe(false);
     expect(commandNeedsApproval("git status --short")).toBe(false);
diff --git a/packages/agent/tools/utils.ts b/packages/agent/tools/utils.ts
index a6d511e..3ff31f2 100644
--- a/packages/agent/tools/utils.ts
+++ b/packages/agent/tools/utils.ts
@@ -3,7 +3,7 @@ import type { LanguageModel, ModelMessage } from "ai";
 import * as path from "path";
 import type { AgentContext } from "../types";
 
-function isAgentContext(value: unknown): value is AgentContext {
+export function isAgentContext(value: unknown): value is AgentContext {
   return (
     typeof value === "object" &&
     value !== null &&
diff --git a/packages/agent/types.ts b/packages/agent/types.ts
index 6ce53ab..2af799d 100644
--- a/packages/agent/types.ts
+++ b/packages/agent/types.ts
@@ -21,6 +21,12 @@ export interface AgentContext {
   skills?: SkillMetadata[];
   model: LanguageModel;
   subagentModel?: LanguageModel;
+  /**
+   * Short-lived Recoupable API access token (Privy JWT) scoped to the
+   * current prompt. Tools that call out to the Recoupable API should
+   * forward this as a Bearer token instead of holding a long-lived key.
+   */
+  recoupAccessToken?: string;
 }
 
 export interface SandboxExecutionContext {
diff --git a/packages/sandbox/interface.ts b/packages/sandbox/interface.ts
index 0bfed68..8c9062b 100644
--- a/packages/sandbox/interface.ts
+++ b/packages/sandbox/interface.ts
@@ -132,7 +132,7 @@ export interface Sandbox {
     command: string,
     cwd: string,
     timeoutMs: number,
-    options?: { signal?: AbortSignal },
+    options?: { signal?: AbortSignal; env?: Record<string, string> },
   ): Promise<ExecResult>;
 
   /**
diff --git a/packages/sandbox/vercel/sandbox.ts b/packages/sandbox/vercel/sandbox.ts
index b8c0d51..fb564ae 100644
--- a/packages/sandbox/vercel/sandbox.ts
+++ b/packages/sandbox/vercel/sandbox.ts
@@ -471,15 +471,23 @@ ${hostLine}${portLines}${runtimeEnvLine}`;
     return runtimeEnv;
   }
 
-  private getCommandEnv(): Record<string, string> | undefined {
+  private getCommandEnv(
+    perCallEnv?: Record<string, string>,
+  ): Record<string, string> | undefined {
     const runtimePreviewEnv = this.getRuntimePreviewEnv();
-    if (!this.env && Object.keys(runtimePreviewEnv).length === 0) {
+    const hasPerCall = perCallEnv && Object.keys(perCallEnv).length > 0;
+    if (
+      !this.env &&
+      Object.keys(runtimePreviewEnv).length === 0 &&
+      !hasPerCall
+    ) {
       return undefined;
     }
 
     return {
       ...this.env,
       ...runtimePreviewEnv,
+      ...perCallEnv,
     };
   }
 
@@ -923,7 +931,7 @@ ${hostLine}${portLines}${runtimeEnvLine}`;
     command: string,
     cwd: string,
     timeoutMs: number,
-    options?: { signal?: AbortSignal },
+    options?: { signal?: AbortSignal; env?: Record<string, string> },
   ): Promise<ExecResult> {
     try {
       const timeoutSignal = AbortSignal.timeout(timeoutMs);
@@ -934,7 +942,7 @@ ${hostLine}${portLines}${runtimeEnvLine}`;
       const result = await this.session.runCommand({
         cmd: "bash",
         args: ["-c", `cd "${cwd}" && ${command}`],
-        env: this.getCommandEnv(),
+        env: this.getCommandEnv(options?.env),
         signal,
       });