## Thinking Path
> - Paperclip orchestrates AI agents for zero-human companies
> - Agents execute in sandboxed remote environments served by pluggable
sandbox
> providers (E2B today, more later)
> - Today every sandbox command runs under `sh -lc` regardless of what
the
> provider's container actually ships
> - That misses bash-only shell init on E2B (which ships bash) and
prevents
> future providers from declaring a different default — there's no way
for a
> provider to say "I have bash, use it"
> - This PR adds a `shellCommand` field to sandbox execution targets so
providers
> can declare their preferred shell ("bash" for E2B), threads it through
the
> sandbox-managed-runtime client, callback bridge, and execution-target
shell
> helper, and validates the value at the lease-metadata boundary
> - The benefit is that sandbox commands run under the right shell on
the right
> provider, and adding new sandbox providers only needs to declare a
shell
> preference
## What Changed
- Added `packages/adapter-utils/src/sandbox-shell.ts` exporting
`preferredShellForSandbox(shellCommand)` (returns `"bash"` if input is
`"bash"`,
else `"sh"`)
- Added `shellCommand?: "bash" | "sh" | null` to
`AdapterSandboxExecutionTarget`
and `CommandManagedRuntimeSpec`; threaded it through
`runAdapterExecutionTargetShellCommand`,
`prepareAdapterExecutionTargetRuntime`,
and `startAdapterExecutionTargetPaperclipBridge`
- `createCommandManagedRuntimeClient`, `prepareCommandManagedRuntime`,
and
`createCommandManagedSandboxCallbackBridgeQueueClient` now take an
optional
`shellCommand` and use `preferredShellForSandbox` to pick the shell
- `startSandboxCallbackBridgeServer` accepts a `shellCommand` for its
server
startup, readiness probe, and stop hook
- E2B sandbox plugin declares `shellCommand: "bash"` in `leaseMetadata`
- `resolveEnvironmentExecutionTarget` reads `shellCommand` from lease
metadata
(validating against `"bash" | "sh" | null`)
- `environment-runtime.ts` adds `"shellCommand"` to
`INTERNAL_PLUGIN_SANDBOX_CONFIG_KEYS`
so the field round-trips through internal plugin config without leaking
to
external plugin metadata
- Updated tests in `command-managed-runtime.test.ts`,
`execution-target-sandbox.test.ts`, `sandbox-callback-bridge.test.ts`,
`environment-execution-target.test.ts`
## Verification
- `pnpm --filter @paperclipai/adapter-utils test`
- `pnpm --filter @paperclipai/server test --
environment-execution-target`
- `pnpm --filter @paperclipai/sandbox-providers-e2b test`
- Manual QA: boot a Paperclip instance, create an E2B-backed
environment, run a
claude_local agent against it, and confirm the run completes (verifies
bash
shell semantics flow through the callback bridge end-to-end)
## Risks
- E2B sandbox commands now run under `bash -lc` instead of `sh -lc`.
Bash is a
strict superset for the commands we issue (no busybox-only flags in our
shell
scripts), so risk is low. The shellCommand field is opt-in via lease
metadata —
providers that don't declare it stay on `sh`.
- New optional field on `CommandManagedRuntimeSpec` and
`AdapterSandboxExecutionTarget`.
Consumers ignoring the field retain previous behaviour (sh).
- Lease metadata now carries an additional field. Existing leases
without
`shellCommand` resolve to `null` and fall back to sh — backwards
compatible.
## Model Used
- OpenAI GPT-5.4 (reasoning effort: high) via Codex CLI
- Provider: OpenAI
- Used to author the code changes in this PR
## Checklist
- [x] I have included a thinking path that traces from project context
to this change
- [x] I have specified the model used (with version and capability
details)
- [x] I have checked ROADMAP.md and confirmed this PR does not duplicate
planned core work
- [x] I have run tests locally and they pass
- [x] I have added or updated tests where applicable
- [ ] If this change affects the UI, I have included before/after
screenshots — N/A (no UI changes)
- [ ] I have updated relevant documentation to reflect my changes — N/A
- [x] I have considered and documented any risks above
- [x] I will address all Greptile and reviewer comments before
requesting merge
Devin Foley
a7b45938b7