Risk hotspots

Risk here is composed from two measured signals, because the one the default recipe reaches for is empty. Both gate-level static-analysis passes return zero findings on every file: cargo clippy --all-targets --message-format=json emits 0 diagnostics at warning or error level, and the semgrep pass the gate runs over all seven crates (mise.toml:112) reports 0 results. So severity is measured instead as test-tier reach, using CodeGraph’s covering-test relation over the 4,430-node index. A symbol counts once, and only if it carries at least one inbound calls/references/instantiates dependent and sits outside any #[cfg(test)] region. error means no test file reaches it and its containing file holds zero in-file #[test] functions — no test tier in this repository reaches that symbol through a source-level edge. warn means no test file reaches it but the file does carry an in-file #[cfg(test)] module, so a same-file unit test may while no cross-file tier does. Trend is cross-sectional over the 30-day window: 78 live source files were touched across 114 commits, per-file commit counts have median 4.0 and population σ 2.7928, so ↑ rising is 7 or more commits (19 files), → flat is 2 to 6 (58 files), and ↓ falling is 1 (1 file). The score is 2 × error + 0.5 × warn + 1 × (trend is rising), ties broken by commit count descending. Totals across the 75 scored files: 278 error-class and 654 warn-class findings.

Four limitations bound every number below. First, the repository’s whole history — 114 commits, 2026-08-05 to 2026-08-17 — fits inside the 30-day window, so there is no earlier baseline and the trend arrow compares a file against its peers, never against its own past. Second, the covering-test relation counts test files, and Rust’s dominant unit-test idiom here is an in-file #[cfg(test)] mod tests; 770 such tests exist across microvms-core (436), microvms-cli (172), agentd (130), protocol (17) and model (15), and none of them can satisfy a cross-file rule. A warn count is therefore a statement about tier reach, not about absence of testing — microvms-core/src/sandbox.rs returns an empty codegraph affected -d 1 result while holding 27 unit tests of its own. Third, and most consequential for reading the table: no source-level edge can cross the PyO3 or napi-rs FFI boundary, so the 159 pytest functions in microvms-py/tests/ and the 168 test( calls in microvms-js/__test__/ cannot register as covering tests for the Rust code they exercise, and CodeGraph does not classify a .mjs file as a test at all. Every error count in a bindings file measures Rust-tier reach only; the residual risk is narrower than “untested” and is named per file in the drill-down. The index also resolves references by name, so a declaration whose name is short or collides with a widely used external type absorbs mentions that are not references to it. Duration (microvms-js/src/cost.rs:60) is the clearest instance: it is the only node of that name in the index, so every Duration in the workspace resolves onto it, and it is credited with coverage from microvms-core/tests/turmoil_client.rs, a file containing zero references to microvms-js. live (microvms-js/src/session.rs:274) and data (microvms-py/src/exec.rs:236) are likewise sole holders of their names. So per-symbol dependent counts below are what the index records rather than verified call sites, and the direction of the bias on error counts is toward understating them. Fourth, ownership carries no bus-factor information: one human authors 87 of 114 commits under two identities and a bgagent bot the other 27, every file has one or two distinct authors, and a bgagent top-owner share marks a file that arrived inside a large squashed commit rather than one with a second maintainer. Two files are excluded from scoring because they are test code that lives under src/: microvms-cli/src/guards.rs (#![cfg(test)] at microvms-cli/src/guards.rs:20, declared at microvms-cli/src/main.rs:36-37) and microvms-core/src/control/fake.rs (declared at microvms-core/src/control/mod.rs:928-929). That exclusion matters: guards.rs is the joint-highest-churn source file in the repository at 13 commits, so a churn-only ranking puts a file that never ships in a binary at the top.

File	Trend	Open findings	Top owner	Citation
microvms-py/src/cost.rs	↑ rising	0 warn, 66 error	Laith Al-Saadoon 57%	microvms-py/src/cost.rs (1,123 LOC)
microvms-js/src/cost.rs	→ flat	0 warn, 65 error	Laith Al-Saadoon 60%	microvms-js/src/cost.rs (1,038 LOC)
microvms-js/src/session.rs	→ flat	0 warn, 25 error	Laith Al-Saadoon 60%	microvms-js/src/session.rs (609 LOC)
microvms-core/src/cost.rs	↑ rising	93 warn, 0 error	bgagent 71%	microvms-core/src/cost.rs (4,127 LOC)
microvms-py/src/exec.rs	↑ rising	0 warn, 22 error	Laith Al-Saadoon 71%	microvms-py/src/exec.rs (631 LOC)
microvms-js/src/exec.rs	→ flat	0 warn, 19 error	Laith Al-Saadoon 60%	microvms-js/src/exec.rs (456 LOC)
microvms-js/src/sandbox.rs	→ flat	0 warn, 16 error	Laith Al-Saadoon 60%	microvms-js/src/sandbox.rs (623 LOC)
microvms-js/src/process.rs	↓ falling	0 warn, 12 error	Laith Al-Saadoon 100%	microvms-js/src/process.rs (541 LOC)
microvms-py/src/session.rs	→ flat	0 warn, 11 error	Laith Al-Saadoon 67%	microvms-py/src/session.rs (605 LOC)
microvms-core/src/sandbox.rs	↑ rising	40 warn, 0 error	Laith Al-Saadoon 73%	microvms-core/src/sandbox.rs (2,371 LOC)
agentd/src/fs.rs	↑ rising	38 warn, 0 error	bgagent 57%	agentd/src/fs.rs (2,628 LOC)
microvms-py/src/sandbox.rs	→ flat	0 warn, 10 error	Laith Al-Saadoon 67%	microvms-py/src/sandbox.rs (780 LOC)

The shape of that list is the finding. Nine of the twelve rows are binding files, and the reason is structural rather than per-file: all 18 files under microvms-py/src/ and microvms-js/src/ — 3,856 and 3,773 LOC respectively — contain zero #[cfg(test)] modules and zero #[test] functions, while the other five crates hold 770 between them — an average of 19 per file in microvms-core, 11 in microvms-cli, 10 in agentd. The three non-binding rows (microvms-core/src/cost.rs, microvms-core/src/sandbox.rs, agentd/src/fs.rs) are the opposite case: heavily unit-tested files whose churn is rising and whose public surface no cross-file tier reaches.

Per-file drill-down

1. microvms-py/src/cost.rs

What’s there. The PyO3 mirror of the cost engine, whose stated job is wrapping the core types “without loosening any of them (BIND-5)” by making the unsafe spellings absent rather than rejected — no __float__, __int__, __index__, __add__ or any numeric dunder on EstimatedUsd, no #[pyo3(transparent)], and no defaulting Duration constructor (microvms-py/src/cost.rs:2-24). Concretely it is 111 symbols of #[pyclass(frozen, from_py_object)] wrappers: PyDuration (microvms-py/src/cost.rs:89), PySizeClass (microvms-py/src/cost.rs:488), PyRateTable (microvms-py/src/cost.rs:576), PyLineItem (microvms-py/src/cost.rs:313) and PyCostReport (microvms-py/src/cost.rs:696).

Recent activity. 7 commits in the 30-day window, ↑ rising — at the rising threshold of 7 and joint-highest among all binding files.

Owners. Laith Al-Saadoon 57% (4 of 7 commits); bgagent 43% (3 of 7). Two identities, one of them a bot, so no second human reviewer is implied.

Findings. 66 error, 0 warn. All 66 of the file’s 66 symbols that carry inbound dependents are error-class, the highest count in the repository, and codegraph affected microvms-py/src/cost.rs -d 1 --json returns an empty affectedTests array against 2 dependents traversed in total. The most-depended-on uncovered symbols are PySizeClass (10 dependents, microvms-py/src/cost.rs:488), the seconds getter (6 dependents, microvms-py/src/cost.rs:126), PyDuration (5, microvms-py/src/cost.rs:89) and PyRateTable (5, microvms-py/src/cost.rs:576). The mitigation is real and it is dynamic: microvms-py/tests/test_cost.py holds 39 pytest functions over 753 lines, and the generated stubs are gated by stubs:check (mise.toml:179-195, listed in check at mise.toml:297). What no tier covers is a Rust-level refactor of the absences the module docs enumerate — a __float__ accidentally reintroduced on EstimatedUsd is caught only if a Python test happens to assert its absence, after a full native rebuild.

2. microvms-js/src/cost.rs

What’s there. The napi-rs mirror of the same engine, where the entire BIND-5 requirement reduces to one decision: every type is a #[napi] class and never #[napi(object)], because an object converts by structure and { amount: 1.5 } would satisfy an EstimatedUsd parameter (microvms-js/src/cost.rs:2-12). valueOf, toJSON, Symbol.toPrimitive and any add method are absent by design, so Number(usd) is NaN and the figure leaves only through .amount as a string (microvms-js/src/cost.rs:16-25).

Recent activity. 5 commits, → flat. It ranks second on score with no rising bonus, entirely on finding count.

Owners. Laith Al-Saadoon 60% (3 of 5); bgagent 40% (2 of 5).

Findings. 65 error, 0 warn, out of 66 symbols with inbound dependents — and the 66th is a measurement artifact, not a covered symbol. The one symbol credited with coverage is Duration (microvms-js/src/cost.rs:60), attributed to microvms-core/tests/turmoil_client.rs, which contains zero references to microvms-js in either spelling. Duration is the only node of that name in the entire index, so every Duration mention in the workspace — including every std::time::Duration — resolves onto this one napi class. The real figure for this file is 66 of 66. Highest-dependent uncovered symbols are SizeClass (27 dependents, microvms-js/src/cost.rs:422), Amount (5, microvms-js/src/cost.rs:187), the CostReport::wrap constructor (4, microvms-js/src/cost.rs:619), Total (3, microvms-js/src/cost.rs:383) and all (3, microvms-js/src/cost.rs:450). microvms-js/__test__/cost.mjs exercises this surface with 42 test( calls over 733 lines, but CodeGraph does not classify .mjs as a test file, so those never appear in affected output for any path. This crate’s index.d.ts is gitignored (.gitignore:29) and no drift gate for it appears anywhere in mise.toml, unlike its Python twin whose stubs are checked at mise.toml:179-195 — the one asymmetry on this list that is a gap in the gate rather than a limit of the measurement.

3. microvms-js/src/session.rs

What’s there. The control API of one running MicroVM on the Node side, where the binding inherits its exclusion guarantees from the core: Sandbox owns its Session by value, hands out only Option<&Session>, Session is not Clone, and no accessor exposes the agent token, so a second independent session against the same VM cannot be constructed (microvms-js/src/session.rs:4-12). The mutex is tokio’s rather than std’s because every method is async and holds the guard across an await, reproducing the &mut self exclusion that suspend/resume/terminate require (microvms-js/src/session.rs:14-18).

Recent activity. 5 commits, → flat.

Owners. Laith Al-Saadoon 60% (3 of 5); bgagent 40% (2 of 5).

Findings. 25 error, 0 warn, from 27 symbols with inbound dependents out of 33 total. The two the index ranks highest by dependent count are the lock-acquiring internals rather than the public methods — Live::session at 18 (microvms-js/src/session.rs:244) and the live() guard-taker at 17 (microvms-js/src/session.rs:274) — though both names are short enough that those counts are inflated by the name-resolution caveat above; into_request (3, microvms-js/src/session.rs:142), in_sandbox (3, microvms-js/src/session.rs:264) and port (3, microvms-js/src/session.rs:306) follow. Those two functions are where the “held for exactly one method call and no more” invariant in the doc comment at microvms-js/src/session.rs:272-273 actually lives, and a lock-scope regression in them is the class of defect a dynamic suite detects only as a hang. codegraph affected microvms-js/src/session.rs -d 1 does return two tests — agentd/tests/turmoil_transport.rs and microvms-core/tests/turmoil_client.rs — reached through the core types this file wraps, not through the binding surface itself.

4. microvms-core/src/cost.rs

What’s there. The cost engine proper, and the largest file in the workspace at 4,127 lines: rate data carried as types rather than prose because MicroVMs publishes no standalone pricing page, with two invariants enforced by shape instead of at runtime — “seconds are measured, dollars are estimated” via a DurationP enum whose every variant names its provenance (COST-1), and “unknown is not zero” via Amount::Unpriced as a distinct variant that forces a match arm (COST-3), promoting to Total::AtLeast so a floor cannot be read without its reasons (COST-4) (microvms-core/src/cost.rs:2-27). Central types are RateTable with its region/source_url/retrieved provenance fields (microvms-core/src/cost.rs:849), CalendarDate (microvms-core/src/cost.rs:209), LineItem (microvms-core/src/cost.rs:1440), CostReport (microvms-core/src/cost.rs:1478) and RunUsage (microvms-core/src/cost.rs:1730).

Recent activity. 7 commits, ↑ rising.

Owners. bgagent 71% (5 of 7); Laith Al-Saadoon 29% (2 of 7). The only top-5 file whose top owner is the bot, which means most of its 4,127 lines landed inside large squashed commits.

Findings. 93 warn, 0 error — the largest warn count in the repository, and every one of them is a tier-reach statement rather than an absence of tests: the file carries 65 in-file #[test] functions, so no symbol qualifies for the error class. Highest-dependent uncovered symbols are RateTable (15 dependents, microvms-core/src/cost.rs:849), CalendarDate (14, microvms-core/src/cost.rs:209), LineItem (13, microvms-core/src/cost.rs:1440), today_utc (12, microvms-core/src/cost.rs:251), CostReport (11, microvms-core/src/cost.rs:1478) and RunUsage (11, microvms-core/src/cost.rs:1730). codegraph affected microvms-core/src/cost.rs -d 1 reaches 8 test files, the broadest of any file on this list. Two specifics deserve attention: today_utc (microvms-core/src/cost.rs:251) reads the wall clock and floors on integer division, so it is the file’s one ambient-time dependency and cannot be exercised deterministically by a turmoil tier that controls virtual time only; and RateTable::retrieved (microvms-core/src/cost.rs:849) makes rate freshness a data property, which the separate scripts/check-live-rates.py --twin-only cross-check exists to verify (mise.toml:412-414) rather than any Rust test tier.

5. microvms-py/src/exec.rs

What’s there. One exec plus the SSE stream exposed as a Python iterator, which the module docs single out as the only shape on the surface that needed real work: ExecStream::new spawns a driver onto the shared runtime with an owned ExecHandle and a bounded mpsc sender, and __next__ blocks on recv (microvms-py/src/exec.rs:4-15). The channel bound is deliberately 1, because the daemon’s SSE body is the backpressure signal and an unbounded channel would buffer a fast producer’s whole output inside the binding — the failure the core’s byte-offset cursor exists to make unnecessary (microvms-py/src/exec.rs:11-15); dropping the iterator drops the receiver, the next send fails, and the drive ends on ControlFlow::Break (microvms-py/src/exec.rs:18-20).

Recent activity. 7 commits, ↑ rising — tied with microvms-py/src/cost.rs for the hottest binding file.

Owners. Laith Al-Saadoon 71% (5 of 7); bgagent 29% (2 of 7).

Findings. 22 error, 0 warn, covering all 22 of the file’s symbols that have inbound dependents (58 symbols total, so most of the surface has no recorded dependent at all). codegraph affected microvms-py/src/exec.rs -d 1 --json returns an empty affectedTests array. Ranked by dependents: PyExecResult (5, microvms-py/src/exec.rs:64), a wrap constructor (5, microvms-py/src/exec.rs:78), the seconds getter (3, microvms-py/src/exec.rs:629), PyStdinAck (2, microvms-py/src/exec.rs:173), data (2, microvms-py/src/exec.rs:236) and PyExecHandle (2, microvms-py/src/exec.rs:485). The drop-and-break lifecycle described at microvms-py/src/exec.rs:18-20 is the specific untested-at-Rust-tier surface worth attention, because a leaked driver task shows up as a hang or a stray thread rather than a failing assertion. microvms-py/tests/test_exec.py covers the behaviour dynamically with 29 pytest functions over 655 lines. PyExecResult keeping exit_code and signal as Option<i32> rather than sentinel integers (microvms-py/src/exec.rs:64-68) is the kind of distinction that a Python-only test can assert but no Rust tier here defends.

Reproduction

Every number above traces to one of these, run from the repository root at commit 5e6f752a4c2a75f88522a38ce40d0a444f23ebc4:

• Trend and ownership — git log --since=30.days.ago --name-only --pretty=format:'---%H|%an|%ae', keeping .rs/.py paths outside tests/, conformance/, scripts/, examples/, benches/ that still exist on disk (78 files; 15 touched paths have since been deleted, including the retired clients/python/ package).
• Static-analysis baseline — cargo clippy --all-targets --message-format=json (0 diagnostics) and the semgrep invocation at mise.toml:112 (0 results).
• Covering-test relation — reverse traversal of calls/references/instantiates edges in .codegraph/codegraph.db at depth 1. The rule was validated against 126 markers harvested from 33 codegraph explore calls: depth 1 agrees on 124 of 126, and the 2 disagreements are test-glob edge cases (microvms-js/__test__/*.mjs is not treated as a test; microvms-py/examples/typed_usage.py is). Aligning on those reproduces the tool at 126/126.
• In-file unit-test census — count of #[test] and tokio::test attributes per */src/**/*.rs.
• Per-file coverage cross-check — codegraph affected <path> -d 1 --json. Depth matters: at the default -d 5 every path returns the same saturated 19-file test set, so the default invocation is not a discriminator.

See also

• business logic — 6 shared source citations
• impact analysis — 6 shared source citations
• contract map — 5 shared source citations
• public api — 5 shared source citations
• dead code — 4 shared source citations