docs(agents): "Before You Push (Rust)" guidance + REQ-202 (minimal build) — issues #438, #456

[avrabe]

From the hourly dogfooding + issue-triage loop. Two AI-agent friction reports, triaged and acted on.

#438 — fmt/clippy not guarded in the default agent workflow

Assessment: valid, with one nuance. The report names the .claude/settings.json hook (provenance stamp only) and the pre-commit framework (.pre-commit-config.yaml, not active in fresh clones). What it missed: scripts/install-hooks.sh now installs a git pre-commit that runs cargo fmt --all -- --check on staged .rs — so the fmt gap is closed if you install hooks. The residual, real gap: the default Claude Code workflow has no fast fmt/clippy guard unless hooks are manually installed, and clippy is never checked per-commit.

Fix (this PR): #438's own second suggestion — surface the exact CI gates in AGENTS.md under a "Before You Push (Rust)" heading, with the verbatim one-liners and the three traps that actually bite agents (the grep '^error' blind spot vs -D warnings; -p <crate> skipping --all-targets test lints; the commit-msg hook rejecting Word: body lines).

A stronger fix — a .claude/settings.json PostToolUse hook that auto-runs cargo fmt --all on every .rs edit (making fmt drift impossible, not just documented) — was attempted but is gated as self-modification of agent config and needs maintainer authorization. Flagged on the issue.

#456 — no minimal --no-default-features build

Assessment: valid (verified against rivet-cli/Cargo.toml). [features] is default = []; axum/tower-http/notify (serve), lsp-server/lsp-types (LSP) and rmcp (full MCP server) are unconditional deps, so every from-source build compiles the entire web/MCP/LSP tree even for the validate/list hot path. rivet-core already gates its heavy deps; the coupling is rivet-cli-specific.

Action (this PR): filed REQ-202 (draft) capturing the additive fix — serve/mcp/lsp cargo features kept in default so the published binary is byte-for-byte unchanged, enabling cargo build -p rivet-cli --no-default-features for hooks/CI/dogfooding. The #[cfg] gating across the command dispatch is the real work and the default-feature set is a maintainer call, so it's filed draft rather than implemented here.

Verification

rivet validate PASS (257 warnings, 0 errors). Docs + draft-artifact only; no rivet-core/src or rivet-cli/src code change.

🤖 Generated with Claude Code

[github-actions]

📐 Rivet artifact delta

Change	Count
Added	1
Removed	0
Modified	0
Downstream impacted (depth ≤ 5)	0

Graph

graph LR
  REQ_202["REQ-202"]:::added
  classDef added fill:#d4edda,stroke:#28a745,color:#155724
  classDef removed fill:#f8d7da,stroke:#dc3545,color:#721c24
  classDef modified fill:#fff3cd,stroke:#ffc107,color:#856404
  classDef overflow fill:#e2e3e5,stroke:#6c757d,color:#495057,stroke-dasharray: 3 3

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Added

• REQ-202

📎 Full HTML dashboard attached as workflow artifact rivet-delta-pr-475 — download from the workflow run.

_{Posted by rivet-delta workflow. The graph shows only changed artifacts; open the HTML dashboard (above) for full context.}

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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