reference: fabro-sandbox-forkd JSON-RPC plugin (feedback on the provider-plugin sketch) - #20
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zenprocess wants to merge 4 commits into
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reference: fabro-sandbox-forkd JSON-RPC plugin (feedback on the provider-plugin sketch)#20zenprocess wants to merge 4 commits into
zenprocess wants to merge 4 commits into
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WIP commit before adding the protocol dispatcher, main.rs, and tests. Includes: Cargo.toml, lib.rs (JSON-RPC envelope + Plugin + PluginState), capabilities.rs (honest initialize payload), gaps.rs (gap 1/2/3 prose), forkd.rs (async ForkdClient trait + reqwest-backed HttpClient). Not yet wired into the workspace; not yet buildable.
JSON-RPC 2.0 stdio plugin subprocess for the forkd microVM controller. Implements initialize (honest capabilities: exec streaming false, fs native false, snapshots dockerfile false) plus the create/exec/delete handlers. sandbox/delete is idempotent on unknown id (test covers it). Unsupported capabilities return the spec's literal error string. The three capability gaps that forkd's microVM shape exposes (vs the container-centric sketch) are marked in code at the friction site: - GAP 1 src/capabilities.rs:71 (SnapshotCapability::dockerfile) + src/protocol.rs:90 (sandbox_create) — microVM snapshot/COW-branch - GAP 2 src/protocol.rs:97 (sandbox_create) — guest RAM/vCPU sizing - GAP 3 src/protocol.rs:266 (exec result) — ran/infra outcome distinction Verified: cargo build, cargo nextest (7/7), cargo fmt --check, and clippy -p fabro-sandbox-forkd --no-deps --tests -D warnings are all clean for this crate alone. No live forkd calls in tests; mock HTTP responder only.
No internal hostnames, tokens, or private URLs. Every method/field name verified against the design doc rather than paraphrased. Three proposals: - GAP 1: snapshots.dockerfile is too narrow; add microvm/branch/register - GAP 2: SandboxSpec has no memory/cpu knob; add resources block - GAP 3: termination cannot carry ran/infra; add outcomeKind + stage Drafted for public posting; operator reviews before upstream contact.
zenprocess
marked this pull request as draft
July 25, 2026 19:53
PR #20 added `httpmock 0.8` as a dev-dependency of the new fabro-sandbox-forkd crate but never committed the resulting root Cargo.lock update (+40 lines). Found during the adversarial review pass: running the crate's tests dirties Cargo.lock, which means every contributor and every CI run would regenerate it as an uncommitted change. No source change — lockfile only. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
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Closes fabro-sh#567
Reference implementation + concrete feedback on the provider-plugin sketch
This PR ships a reference implementation of the JSON-RPC 2.0 over stdio provider-plugin half of the upstream sketch (PR #567), built against a genuinely different sandbox shape (a Firecracker microVM, via forkd). Its purpose is to validate the design against a non-container backend and to surface three concrete capability gaps the container-centric sketch misses.
The plugin is the subprocess half only — the upstream
Sandboxtrait split /PluginProviderhost-side wiring is deliberately out of scope (separate concern, separate PR). The reference is wired into a workingfabro-sandbox-forkdcrate, the wire protocol is end-to-end with the host, and all tests pass against a mock HTTP responder — no live forkd controller call.Resources
~/.ao/data/aofactory/UPSTREAM-SANDBOX-PLUGIN-DESIGN.mddocs/internal/upstream-proposal-pr567.mdWhat the implementation demonstrates
initializereturns the honest forkd capability payload:exec.streaming: false(forkd is buffered),fs.native: false(host derives from exec),snapshots.dockerfile: false,network.modes: [allow_all, block, cidr_allow_list],clone.github: true.sandbox/create→POST /v1/sandboxes,sandbox/delete→DELETE(idempotent on unknown id, per spec),exec→POST /v1/sandboxes/{id}/exec.streaming:false),sandbox/deleteidempotency on unknown id, and the unsupported-method error shape.Three capability gaps the microVM shape exposes (each marked in code)
snapshots: { dockerfile }; forkd needsregister-snapshot/branch-from-snapshot(copy-on-write reflink off a read-only golden rootfs). Marker:lib/components/fabro-sandbox-forkd/src/capabilities.rs:73andlib/components/fabro-sandbox-forkd/src/protocol.rs:96.SandboxSpec. forkd needs--mem-size-miband vCPU count at create time. A 512 MiB guest silently OOM-killed our test suites; the fix was a host-side resize the wire protocol cannot currently express. Marker:lib/components/fabro-sandbox-forkd/src/protocol.rs:103.{termination}. forkd distinguishesran(real code verdict) frominfra(sandbox could not be created/reached/exec'd/torn down) with astage: boot | exec | teardown. Conflating them turns infrastructure faults into code failures, which are sticky and poison downstream labels. Marker:lib/components/fabro-sandbox-forkd/src/protocol.rs:236.What is NOT implemented (and why)
Sandboxtrait split /SandboxProviderRegistrywiring /PluginProviderhost side. That is the other half of the sketch and a prerequisite refactor; this PR is deliberately just the plugin subprocess half.exec/stream,exec/outputnotifications). forkd is buffered; the plugin declaresstreaming:falseand returns the spec's unsupported error if asked.fs/*handlers. Declarednative:false; the host derives read/write/list/grep/glob from exec (base64 cat/tee + POSIX grep/find).Verification (scoped to this crate, not the full workspace)
The full-workspace
cargo buildis intentionally not run on the development Mac (a hook blocks it because it pins the machine); the authoritative build runs in PR CI. This crate alone passes the four gates above.Tone
This is a collaborative PR. The sketch works for our needs modulo the three gaps above; the diff is small; the test suite is honest; the gap markers are the actual code path of friction, not prose. Reviewer feedback welcome — happy to iterate.
🤖 Generated with Claude Code