codegraph/docs/benchmarks/explore-factory-closure-cg27.md

Deterministic measurement — the factory-closure envelope (task CG-27)

Date: 2026-08-06 · Baseline: feature/CG-24 @ dc4fd75 · Harness: scripts/agent-eval/probe-factory-closure.mjs against a hermetic fixture (__tests__/fixtures/factory-closure-ts/, copied to a temp dir and indexed per run, so two runs on one build give identical numbers). No agent A/B: the claim under test is which SYMBOLS get selected inside one file, and the agent runs are far too noisy to see that.

Verdict: the premise does not survive measurement. CG-27 is closed as obsolete, CG-30 credited. The literal change the issue proposes is a large REGRESSION, and a more careful mechanism reaching the same intent is noise (69 vs 68 inner definitions delivered across nine query shapes).

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The claim

ENVELOPE_KINDS in src/mcp/tools.ts drops a node covering >50% of its file from the cluster ranges, so the granular symbols inside form their own clusters instead of merging into one blob. It lists container kinds — class, struct, interface, enum, … — and not function or method. A factory closure (createFoo() returning an object of closures) therefore survives as a file-spanning range. That shape is common, not a one-repo quirk: Svelte 5 .svelte.ts rune stores, React custom-hook modules, IIFE/module-pattern JS, and Zustand's create((set, get) => ({ … })).

CG-30 already bounds the BYTES such a member may spend, so what remained was a ranking claim: a file-spanning range merges every inner symbol into one cluster, so selection cannot rank and pick the relevant closures independently. The issue required that claim be measured before any fix.

The fixture

__tests__/fixtures/factory-closure-ts/ — a dashboard app with three stores written as factory closures, two stateless services and a UI consumer competing for one envelope.

file	lines	shape
src/stores/dashboard-store.ts	385	createDashboardStore spans 15–376 (94%), 11 closures inside; a tail type alias + helper at file scope
src/stores/alerts-store.ts	141	createAlertsStore spans 19–138 (85%), 9 closures inside
src/stores/session-store.ts	148	a factory and NOTHING else at file scope — no companion type, no tail helper
src/services/metric-service.ts, src/services/filter-parser.ts	105, 62	ordinary top-level functions — the control

Both factory files are past WHOLE_FILE_MAX_LINES where it matters, so they render through the cluster path and the envelope actually bites.

Result 1 — the envelope is almost never selected in the first place

shrinkCluster orders a cluster's members by (importance desc, size ASC) and refuses any member that overruns the cap once something is kept. A file-spanning member is therefore only ever selected when it is the FIRST candidate — which requires it to be the sole member of the top importance tier. In eight of the nine query shapes measured, some smaller member shared that tier (a one-line type alias, a tail helper, another closure), so the factory sorted last and was never kept. The envelope was inert.

Result 2 — the proposed change is a large regression

Making the >50% drop kind-independent, measured on the primary query ("how does the dashboard store refresh its metrics and apply a filter"):

	baseline	drop the range
dashboard-store.ts (rank #1) delivered	7,539 chars	397
inner closure definitions delivered	7 of 11	0 of 11
its own reservation left unspent	0	~5,200 of 5,601

The mechanism, from the cluster dump: dropping the range splits the file into two clusters — 378-384 (a one-line type alias plus a four-line helper, score 15, span 7) and 4-362 (every closure, score 116, span 359). Cluster ranking breaks the maxImportance tie on density, so the trivial cluster wins, is taken first, and is the only one that may be shrunk. The answer-bearing cluster then does not fit the remainder and is dropped whole — later clusters are never shrunk, by design.

The enclosing range is what was holding the file together as one cluster, inside which shrinkCluster was already doing exactly the per-symbol ranking the issue asked for.

Result 3 — the careful version of the same intent is noise

Deferring the envelope MEMBER inside shrinkCluster (leaving clustering granularity untouched, so Result 2's split never happens) reaches the issue's intent by a better mechanism. Nine query shapes, same fixture, same indexes — inner closure definitions delivered:

query	target	baseline	deferred
how does the dashboard store refresh its metrics and apply a filter	dashboard	7/11	8/11
createDashboardStore	dashboard	8/11	8/11
how is the dashboard store created and wired up	dashboard	9/11	8/11
createDashboardStore exportCsv summarize	dashboard	9/11	9/11
where is the dashboard store constructed	dashboard	7/11	7/11
how are widgets loaded and the layout reconciled	dashboard	4/11	4/11
createSessionStore (adverse: the factory IS the sole top-tier member)	alerts	6/9	7/9
how are alerts refreshed and acknowledged	alerts	9/9	9/9
createAlertsStore	alerts	9/9	9/9
total		68	69

One better, one worse, seven unchanged — on a fixture built specifically to make this pattern maximally visible. That is not a measurable selection improvement, so nothing shipped.

Where the envelope DOES get selected, and why CG-30 already covers it

The adverse row above is the one configuration the ordering cannot neutralise: createAlertsStore was the sole importance-10 member, so it was kept first at 3,939 chars against a 2,468 cap and every closure was skipped. CG-30 then windowed it on whole lines rather than emitting it whole or dropping the file — the response carried lines 16–108, a contiguous, readable head of the factory carrying 6 of its 9 closure definitions. Bounded, sufficient, never empty. That is the symptom this issue was filed against, already absorbed.

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Byproduct — a real defect this measurement exposed (filed separately)

Result 2's mechanism is not confined to the hypothetical change. Instrumenting the epic tip across the deterministic 6-repo suite for files that drop a cluster while leaving most of their reservation unspent:

file	budget	spent	unspent	kept cluster	dropped cluster
django/db/models/sql/query.py	10,135	1,923	8,212 (81%)	1379–1400, score 14	306–929, score 290
okhttp .../RealInterceptorChain.kt	6,058	1,474	4,584 (76%)	16–44, score 44	113–373, score 171
okhttp .../Interceptor.kt	4,697	2,027	2,670 (57%)	85–138, score 21	154–257, score 10
gin/routergroup.go	5,782	3,273	2,509 (43%)	33–91, score 116	103–188, score 128

A file whose top cluster by density is trivial keeps that one, drops the cluster carrying 20x the score, and leaves most of its own reservation unspent — because only the first-chosen cluster may be shrunk. query.py is the file CLAUDE.md already names as the _fetch_all case.

Reproducing

npm run build
node scripts/agent-eval/probe-factory-closure.mjs                      # primary query
node scripts/agent-eval/probe-factory-closure.mjs \
  --target src/stores/alerts-store.ts --factory createAlertsStore \
  --query "createSessionStore"                                          # the adverse configuration
npx vitest run __tests__/explore-factory-closure.test.ts                # the standing gate