Zeeg describes a Vercel sandbox harness that stores agent state separately

• Junior, Sentry’s agent harness, uses disposable Vercel sandboxes without persistent disks or on-device credentials, according to zeeg’s description.
• Durable state can live outside the worker: zeeg points to network disks and remote services as storage primitives.
• Parallel execution carries an infrastructure bill: zeeg says he can run hundreds of tasks without conflicts between them, at substantial infrastructure complexity.

Vercel’s credential brokering adds authentication headers outside the sandbox’s VM boundary. Its persistence documentation also says sandboxes preserve their filesystem by default, with an explicit opt-out for disposable workloads.

zeeg, who built Junior at Sentry, clarified that VMs can implement the same ephemeral model. Persistent disks remain compatible with his proposal, and he called state “already solved”.

A cloud service is optional in his explanation, which compares replaying machine configuration with Terraform rather than manual commands.

Replayability is the persuasive part of his pitch.

Junior keeps credentials off the machine using a man-in-the-middle proxy, zeeg said. Building this model generally requires owning the harness or adapting someone else’s, he added.

Vercel’s firewall documentation defines three egress modes that can change at runtime without restarting the process:

• allow-all: The default, with unrestricted access to the public internet.
• deny-all: Blocks all outbound traffic, including DNS.
• Custom: Denies traffic by default, then permits specified domains or address ranges.

Credential-transformation matchers select which requests receive rewritten headers. Unmatched requests to an allowed domain still reach it without the injected credential; those matchers do not block requests.

Disposable workers can start from a prepared environment. Vercel’s snapshots capture the filesystem and installed packages, skipping repeated setup and allowing child sandboxes to fork from a known checkpoint.

The documented opt-out from automatic filesystem persistence is persistent: false in Sandbox.create(). Vercel bills snapshot storage separately from compute, according to its persistence docs.

Shared work-in-progress has advocates: theo likes agents inspecting other threads and worktrees to make their jobs easier.

zeeg concedes that his approach targets enterprise scale and can be unnecessary or inefficient for many tasks. He has not adopted it for personal use, citing infrastructure complexity and cost.

For an agent creating a deployable artifact, zeeg described a conventional release path:

1. Create a branch.
2. Push the branch.
3. Deploy it to a preview environment.
4. QA it there.
5. Promote it to production.

Sentry’s observability product also surfaced in zeeg’s request for feedback. The Stack Overflow survey question covers observability, prompts and evals, with 2,277 respondents in the usage breakdown.