docs(spec-ssh-host-key-in-beacon): feat(minvmd): include SSH host public key in the ready beacon by gominimal-aw-bot[bot] · Pull Request #579 · gominimal/minimal

gominimal-aw-bot · 2026-06-26T04:35:24Z

Summary

This is the spec pull request for #467 — extending the minvmd ready-beacon protocol to carry the VM's SSH host public key, so the host can pre-populate known_hosts before the first SSH connection.

Demoable Units

Unit 1 — Beacon enrichment (minimald, guest side)

R1.1: emit_ready_marker() emits READY\n<openssh-pubkey>\n
R1.2: vsock boot path passes the host public key to emit_ready_marker()

Unit 2 — Key reception and known_hosts write (minvmd, host side)

R2.1: Both boot.rs and run.rs read the second beacon line
R2.2: Key is parsed and written to providers/local-0/known_hosts via learn_known_hosts_path
R2.3: Absent or malformed key logs a warning and does not abort boot
R2.4: providers/local-0/ directory hierarchy is created before the write
R2.5: russh promoted from dev-dep to production dep in minvmd/Cargo.toml

Files in scope

crates/minimald/src/guest.rs
crates/minimald/src/main.rs
crates/minvmd/src/cmd/boot.rs
crates/minvmd/src/cmd/run.rs
crates/minvmd/Cargo.toml

Next step

Merging this spec PR returns the tracking issue #467 from sdd:fastpath-review to sdd:fastpath. After the merge, comment /approve on the tracking issue to dispatch the implementation — or comment /approve now (while this PR is open) to record the approval and let the merge dispatch automatically. Merge and approve commute (ADR 0024).

Refs feat(minvmd): include SSH host public key in the ready beacon #467

Generated by sdd-spec for issue #467 · ◷

Closes #578

Summary by CodeRabbit

Documentation
- Added a new specification to extend the ready-beacon handshake with SSH host key information.
- Documented how the host should validate a second line after the READY marker and handle missing/invalid data non-fatally with warnings.
- Included guidance on where the key is stored, expected testing behavior, and backward-compatibility/security considerations.

Light spec for #467: extend the minvmd ready-beacon wire format from one line (READY\n) to two lines (READY\n<openssh-pubkey>\n) so minvmd can pre-populate known_hosts on the host before the first SSH connect. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

coderabbitai · 2026-06-26T04:35:37Z

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: 0ef56242-d113-4a14-8d54-9e3b0769f746

📥 Commits

Reviewing files that changed from the base of the PR and between f206024 and 3057c40.

📒 Files selected for processing (1)

docs/specs/06-spec-ssh-host-key-in-beacon/06-spec-ssh-host-key-in-beacon.md

✅ Files skipped from review due to trivial changes (1)

docs/specs/06-spec-ssh-host-key-in-beacon/06-spec-ssh-host-key-in-beacon.md

📝 Walkthrough

Walkthrough

Adds a spec for extending the READY beacon so minimald emits the SSH host public key, minvmd parses it, and the host writes it to known_hosts. The document also records compatibility, non-fatal error handling, security notes, and verification steps.

Changes

SSH host key beacon spec

Layer / File(s)	Summary
Front matter and goals `docs/specs/06-spec-ssh-host-key-in-beacon/06-spec-ssh-host-key-in-beacon.md`	Adds the spec metadata and describes the READY beacon extension that carries an SSH host public key.
Beacon emission and host write path `docs/specs/06-spec-ssh-host-key-in-beacon/06-spec-ssh-host-key-in-beacon.md`	Specifies two-line beacon emission, host parsing, `learn_known_hosts_path` writes, parent directory creation, and expected test coverage.
Constraints and verification notes `docs/specs/06-spec-ssh-host-key-in-beacon/06-spec-ssh-host-key-in-beacon.md`	Records non-goals, fixed host/port assumptions, non-fatal invalid-key handling, security considerations, and verification steps.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~5 minutes

Possibly related issues

#467: The spec directly matches the requested feature to include the SSH host public key in the ready beacon and write it into known_hosts.

Suggested labels

needs-human

Suggested reviewers

norrietaylor

Poem

A rabbit hopped by, ears all bright,
With READY and a key in sight.
The host wrote home, the path was tame,
And SSH greeted without a name. 🐰

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly describes the main change: adding the SSH host public key to the ready beacon spec.
Linked Issues check	✅ Passed	The spec change directly addresses `#578` by extending the ready beacon to carry the SSH host public key.
Out of Scope Changes check	✅ Passed	The changes stay within the requested spec work and do not introduce unrelated code or features.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

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coderabbitai

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@docs/specs/06-spec-ssh-host-key-in-beacon/06-spec-ssh-host-key-in-beacon.md`:
- Around line 43-45: The SSH host-key beacon flow needs an inverse compatibility
guarantee in the guest-side spec: if the host only waits for READY and does not
consume the second line, the guest must treat a failed second-line write as
best-effort and continue booting. Update the spec wording around the beacon
handshake to explicitly cover this additive-protocol case, alongside the
existing malformed-or-missing key behavior, so the guest-side write path never
turns compatibility into a boot failure.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

Push a commit to this branch (recommended)
Create a new PR with the fixes

ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: 2ba7ba92-3d0c-49fd-a671-ad2661b7d82a

📥 Commits

Reviewing files that changed from the base of the PR and between e14f4b6 and f206024.

📒 Files selected for processing (1)

docs/specs/06-spec-ssh-host-key-in-beacon/06-spec-ssh-host-key-in-beacon.md

norrietaylor · 2026-06-26T05:59:58Z

/revise address code rabbit concerns

… R-IDs Move function names, file paths, and Rust API calls out of requirement bodies; each R-ID now states the observable behavior only. The specific implementation details (emit_ready_marker signature, from_openssh call, learn_known_hosts_path invocation, create_dir_all, tracing::warn!) are preserved in the Design Considerations section where they belong. Addresses the gate 2 (implementation leakage) warnings from sdd-validate and the CodeRabbit review noting that R-IDs contained code-level detail.

gominimal-aw-bot · 2026-06-26T06:08:43Z

Commit pushed: 3057c40

Generated by sdd-spec

gominimal-aw-bot · 2026-06-26T06:16:37Z

sdd-validate findings — spec boundary

Resolved boundary: Spec (file added: docs/specs/06-spec-ssh-host-key-in-beacon/06-spec-ssh-host-key-in-beacon.md)
Fast-path: yes (light spec, ADR 0024 — no architecture record required)

Gate 1 — Acceptance criteria testable ✅

All R-IDs (R1.1, R1.2, R2.1–R2.5) state observable outcomes. No finding.

Gate 2 — No implementation leakage ⚠️ Warning

docs/specs/06-spec-ssh-host-key-in-beacon/06-spec-ssh-host-key-in-beacon.md:85–87

R2.5 — russh is promoted from [dev-dependencies] to [dependencies] in minvmd/Cargo.toml so the production code can call russh::keys::known_hosts::learn_known_hosts_path.

This R-ID names a specific build file (minvmd/Cargo.toml), specific Cargo manifest sections ([dev-dependencies] → [dependencies]), and a fully-qualified function path. Where a behavioral statement belongs — e.g. "the SSH key-parsing library is available to production code in minvmd" — the R-ID instead prescribes the mechanism. Warning per spec gate 2.

All other R-IDs are clean. R2.2's "using the same known-hosts API path" is a consistency constraint whose primary content is behavioral; below the 80% confidence floor for a Warning.

Gate 3 — Assumptions explicit ✅

The instance-0 assumption, the marker socket as the sole synchronization point, the XDG_STATE_HOME path derivation, and the port-22 / local-0 hostname mapping are all stated in Context or Design Considerations. No finding.

Gate 4 — Proof artifacts present and behavioral ✅

Unit 1: one Test artifact. States "does not pass against the current single-line implementation" — passes the empty-PR rule.
Unit 2: one Test artifact ("cannot pass against the current single-line reader") and one File artifact (known_hosts would not exist on the current code). Both pass the empty-PR rule.

Gate 5 — Demoable unit sized to a reviewable PR ✅

Unit 1 (guest-side beacon emission) and Unit 2 (host-side key reception) are separated by a real producer/consumer dependency edge — Unit 2 reads what Unit 1 emits. This exempts the pair from the under-sizing check. No finding.

Summary: 1 Warning, 0 Blockers. Spec boundary passes clean; no needs-human hand-off required.

Generated by sdd-validate for issue #579 · ◷

gominimal-aw-bot Bot mentioned this pull request Jun 26, 2026

feat(minvmd): include SSH host public key in the ready beacon #467

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github-actions Bot mentioned this pull request Jun 26, 2026

spec: feat(minvmd): include SSH host public key in the ready beacon #578

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coderabbitai Bot reviewed Jun 26, 2026

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norrietaylor enabled auto-merge (squash) June 26, 2026 06:13

norrietaylor approved these changes Jun 26, 2026

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norrietaylor merged commit bf05ff4 into main Jun 26, 2026
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norrietaylor deleted the spec/ssh-host-key-in-beacon-3c4d22af94a3a068 branch June 26, 2026 06:13

coderabbitai Bot mentioned this pull request Jun 26, 2026

feat(minimald,minvmd): include SSH host key in the ready beacon #582

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gominimal-aw-bot Bot commented Jun 26, 2026

sdd-validate findings — spec boundary

Gate 1 — Acceptance criteria testable ✅

Gate 2 — No implementation leakage ⚠️ Warning

Gate 3 — Assumptions explicit ✅

Gate 4 — Proof artifacts present and behavioral ✅

Gate 5 — Demoable unit sized to a reviewable PR ✅

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