Workflow orchestration / Microsoft Foundry hosted agents alternative

Microsoft Foundry hosted agents alternative

Microsoft Foundry hosted agents run custom-framework agent code in managed containers with scaling and governance. Each session has retained HOME data, while the sandbox root disk is ephemeral. Compare that session storage boundary with an agent’s installed system tools and complete writable RootFS.

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Reviewed 2026-10-19 · Published by the Sandbox0 team

When Microsoft Foundry hosted agents fits

Choose Foundry for its agent deployment, model/tool integrations, identity, observability and organizational controls. The managed agent platform does more than provide a Linux execution environment.

When to consider Sandbox0

Consider Sandbox0 for the compatible Linux execution layer and persistent whole RootFS. You still need agent orchestration, conversation services, model access and Foundry-specific governance or enterprise integrations you retain.

Capabilities

Microsoft Foundry hosted agents and Sandbox0: what persists?

Feature comparison with documentation and verification status
Environment and runtime lifetimeMicrosoft Foundry hosted agentsThe ephemeral root disk lasts up to twenty-four hours; retained session HOME has its separate thirty-day policy after idle cleanup.View evidence ↗Sandbox0ttl and hard_ttl default to 0 (disabled). Configure idle pause and deletion policies for the same persistent sandbox identity; an idle running sandbox still accrues compute charges.Read documentation →
Persistent filesMicrosoft Foundry hosted agentsPer-session HOME is retained under the documented 30-day policy after idle cleanup.View evidence ↗Sandbox0The writable RootFS survives successful checkpoints, including software, system configuration, dependencies, and user data.Read documentation →
Whole RootFSMicrosoft Foundry hosted agentsSandbox root disk is ephemeral; HOME has the separate persistent data lifecycle.View evidence ↗Sandbox0Persistence extends beyond /workspace to paths such as /usr/local, /etc, and /home. Runtime tmpfs and virtual filesystems are excluded.Read documentation →
Release compute, keep stateMicrosoft Foundry hosted agentsRetained HOME and recreated compute do not establish arbitrary machine checkpoint/resume.View evidence ↗Sandbox0Pause compute between tasks; resume on available capacity. Default resume starts fresh processes from the saved filesystem.Read documentation →
Memory and process stateMicrosoft Foundry hosted agentsSession state retention does not establish arbitrary process-memory recovery.View evidence ↗Sandbox0Experimental memory checkpoints can preserve compatible process state. Use memory: true on both pause and resume on a compatible deployment. A filesystem checkpoint alone does not preserve running processes.Read documentation →

Online RootFS growth

On growth-enabled images, Sandbox0 automatically expands the writable RootFS as free space runs low, within a configured sparse logical ceiling up to 64 TiB. Agent processes keep running. Growth is enabled in the qualified Cloud region; confirm activation for other regions. Existing images and snapshots retain their captured storage geometry. The ceiling is logical capacity, not preallocated host disk.

Foundry already retains per-session HOME. Its ephemeral root disk and separate retained directory do not establish whole-RootFS persistence or automatic online growth of system paths outside that directory.

Files while compute is paused

Sandbox0's Files API reads persistent files without resuming compute. Filesystem-only pauses also permit edits; retained-memory pauses are read-only and reject mutations with 409. SSH, SFTP, file watching, and runtime-only mounts require running compute.

Stored conversation/session data is distinct from a complete paused RootFS. The reviewed hosted-agent storage documentation does not establish arbitrary stopped-guest system-file reads or mutations without allocating compute.

See paused file operations →

HOME retention and the sandbox root disk differ

Microsoft documents an ephemeral sandbox root disk lasting up to 24 hours, with a persistent per-session HOME volume. After idle cleanup, HOME state is retained for 30 days unless the session is deleted. This protects selected user data, not every installed system path across compute replacement.

Source 1 ↗

Hosted agents have compute charges even when prompt agents do not

The pricing overview distinguishes Foundry-native prompt/workflow agents from custom-framework hosted agents. Hosted agents incur container CPU and memory charges. A no-additional-agent-fee statement for the prompt product does not mean hosted agent compute, model tokens or tools are free.

Source 1 ↗

Use an actual regional compute meter

The official East US USD retail catalog lists separate Hosted vCPU Usage and Hosted Memory Usage hourly meters. It also includes Skills Execution Container, which is a different SKU. Model consumption, code interpretation, search and licensed data connections remain separate scopes.

Source 1 ↗Source 2 ↗

Pricing

Compare billing models, then price your workload

CPU allocation, memory, billing minimums, disk, plan fees, and supported workload differ. These meters are not equal-performance machine quotes. Confirm region, resource units, and included allowances before estimating a total.

Microsoft Foundry hosted agents

Pricing reviewed 2026-10-19

Hosted CPU, East US USD
$0.0994 per vCPU-hour
Hosted vCPU Usage Consumption meter, effective February 1, 2026.
Rate source ↗
Hosted memory, East US USD
$0.0118 per GiB-hour
Hosted Memory Usage; preserve region and effective account terms.
Rate source ↗
Models, tools and connections
Separately metered or licensed
Prompt-agent base-fee wording does not waive model, hosted compute or tool charges.
Rate source ↗

Retail prices are references for East US, not negotiated rates or a universal regional offer. Skills Execution is not the Hosted CPU/memory meter. The documented hosted execution storage currently does not support customer-managed keys or bring-your-own storage for its HOME volume.

Check current Microsoft Foundry hosted agents pricing ↗

Sandbox0

$0.015/GiB-hour compute (billed by the second at approximately $0.000004167/GiB-second), plus $0.02/GiB-month of retained incremental RootFS and memory checkpoint data. Shared base images and platform recovery retention are excluded; paused sandboxes accrue storage charges only.

Compute / GiB-hour
$0.015
Retained data / GiB-month
$0.02
Paused compute
$0.00

A 4 GiB agent, 100 running hours

$6.00 compute

4 GiB × 100 hours, billed by the second. Keeping 20 GiB of billable incremental data for a full billing month adds $0.40. CPU is derived from memory by the platform; choose a tier that fits your workload.

Understand storage billing →

Before migrating from Microsoft Foundry hosted agents

  1. Inventory hosted versus prompt agents, session identities, HOME data, system-path changes, idle policy and model/tool integrations.
  2. Export required files and port compatible runtime setup to Sandbox0 while preserving necessary conversation and governance services.
  3. Test installed-system retention, growing outputs, paused files and the full compute, model, tool, storage and network bill.

Common questions

Is Sandbox0 a drop-in Microsoft Foundry hosted agents replacement?

Evaluate API compatibility and product scope. These products serve different core workflows, so a change may require a different architecture.

Does keeping files also keep a running agent?

Filesystem state and volatile process state are separate. Sandbox0 requires explicit compatible memory checkpoints to preserve running processes; its default filesystem resume starts fresh processes.

Sources and review scope

The Boat team's Battleships directory is the discovery source. References below describe the product and plan discussed on this page. Check current availability, regional terms and billing units before migrating. Where the cited material does not establish a capability or price, the comparison identifies that uncertainty.

Battleships research record ↗learn.microsoft.com/en-us/azure/foundry/concepts/customer-managed-keys ↗azure.microsoft.com/en-us/pricing/details/foundry-agent-service/ ↗prices.azure.com/api/retail/prices ↗Sandbox0 RootFS capacity →

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