docs(research): add long-running posture axis to the sandbox landscape

Adds a "Long-running posture" row to the comparison table and an addendum
note contrasting the two models: E2B and CubeSandbox are ephemeral-per-task
(5-min default timeout, tier-capped continuous runtime, duration via
pause/resume + reconnect-by-id), while bot-bottle bottles are persistent,
named, and supervised by default. For agents that run for hours/days this
posture difference matters more than the isolation primitive.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01YBCHap11yGAKuKfsehNPaD

docs/research/agent-sandbox-landscape.md

@@ -220,6 +220,7 @@ claim that the monetization positioning leans on. See the addendum.
 | Agent target | Claude Code | Generic (demo) | Generic | Multi-agent wrapper | Generic (+ Claude/OpenAI SDKs) | Claude focus | Generic | Claude + Cursor (MCP/Skills) | Generic (AGENTS.md) | E2B-compatible (platform builders) |
 | Network policy | Default-deny via own egress scanner + per-bottle allowlist + content DLP + gitleaks on git push | Capability model only | Limited | Not addressed | Default-deny + allowlist + secret-injecting proxy | Default-deny + logging | Per-VM net (unverified) | Not documented | Off by default + allowlist | Default-deny allowlist + instant egress block + audit logs + per-sandbox tokens (eBPF) + credential vault |
 | Parallel agents | Yes (one bottle per agent) | n/a | Not addressed | One at a time | Multiple VMs | Yes (dashboard) | SDK-level | SDK-level | Architectural | Yes (2,000+/host claimed) |
+| Long-running posture | Persistent by default (named, supervised) | n/a (demo) | Session (up while in use) | Per-invocation | Ephemeral VM per run | Per-run (versioned) | Ephemeral + snapshot/fork | Ephemeral / on-demand | Named persistent by default | Ephemeral + auto pause/resume |
 | Config | JSON manifest (bottles + agents) | Programmatic refs | CLI wizard | Profile files / shell fns | CLI / SDK | DSL + CLI + SDK | SDK | CLI / SDK / MCP | TOML Smolfile | E2B-compatible SDK |
 | Maturity | Active May 2026 | Research (2022+) | Early (~66 ⭐) | Active (~1.4k ⭐) | Experimental (~574 ⭐) | Private preview | YC, ~4.7k ⭐ | YC, ~6k ⭐, beta | ~3.1k ⭐ | Tencent, prod, ~10.4k ⭐ |
 
@@ -333,6 +334,22 @@ distinctive:
   injected credentials (they can't leak if they were never present), but
   it is not a substitute for content inspection of everything else.
 
+**Long-running posture — a sharper axis than raw isolation.** E2B and
+CubeSandbox are *ephemeral-per-task* by design; a long-running agent is an
+architected pattern on top, not the default. E2B: 5-minute default
+timeout, continuous runtime tier-capped (~1h Hobby / ~24h Pro), duration
+achieved via **pause/resume** (preserves filesystem + memory + processes;
+reconnect by sandbox ID via `Sandbox.connect()`; resume resets the timeout
+to 5 min; auto-pause via `on_timeout: "pause"`). CubeSandbox mirrors this
+(E2B drop-in) with first-class auto pause/resume and hundred-ms
+checkpoint/fork — and, self-hosted, sets its own timeout policy with no
+vendor tier caps. bot-bottle inverts the model: a bottle is **persistent,
+named, and supervised by default** — long-running *is* the default, not a
+session-management loop over pause/resume. smolmachines is the other
+persistent-by-default project in this set. For anyone building agents that
+run for hours/days, this posture difference matters more than the
+isolation primitive.
+
 Why it still doesn't collide head-on:
 
 1. **Shape.** CubeSandbox is a *multi-tenant service for platform