Capabilities

Capabilities were what an agent was allowed to do inside a sandbox: run commands, edit files, remember things, compact its own context. They were declared on BaseSandboxAgent, the subclassing entry point v1 offered for a sandboxed agent.

Sandboxing is not part of v3. BaseSandboxAgent and the machinery around it went with the v1 API, and the spec classes that described a sandboxed agent’s powers (CapabilitiesSpec, ShellSpec, FilesystemSpec, MemorySpec, CompactionSpec) have now been removed too — nothing in Agent/Deck ever constructed one, and there was no capabilities= argument to pass one to. Keeping unreachable scaffolding in the tree only made the feature look closer than it is.

It can come back: reintroducing a sandbox port and the declarations that feed it is additive, so nothing here is a one-way door.

Until then: Skills covers the deterministic, non-sandboxed half of the same picture (progressive disclosure of instructions and scripts into an agent’s own execution), and a plain Python tool= callable covers most of what shell/filesystem gave a sandboxed agent for a specific, narrower task.