Performance budgets

Status: Soft render budgets on the living train (introduced in phase 0.8; still enforced). Phase 0.25 critical-path workloads (BUDGET-025 / W-025-*) have runnable CI evidence under tests/performance/test_w025_*.py.

Evidence: PERF-08-001, PERF-08-002, tests/performance/; BUDGET-025 / W-025-*.

Not product SLOs

These numbers are soft CI ceilings sized for GitHub-hosted runners. They catch gross regressions. They are not marketing latency claims, contractual SLOs, or 1.0 performance guarantees. Do not quote them in adopter SLAs. Measure with tests/performance/.

Live SSE/WebSocket load/proxy backpressure IDs (PERF-10-001 and related) were Superseded in 0.24 under disposition polling_only — prefer polling in production. See What’s ready, LIVE_DISPOSITION, and Performance guide.

Workloads

ID	Workload	Command
W-RENDER-200	Normalize + serialize 200 text nodes	pytest tests/performance -q
W-PAGE	Full RenderMode.PAGE for a small Page	same
W-FRAGMENT	Fragment render for a small tree	same
W-PAYLOAD	HTML payload size for 200-node stack	same

Phase 0.25 critical-path workloads (BUDGET-025)

Runnable CI evidence paths (soft ceilings in the named tests):

ID	Workload	evidence_path
W-025-FRAGMENT	Fragment latency under representative HTMX swap load	tests/performance/test_w025_fragment.py
W-025-JOB-POLL	Job status poll fanout	tests/performance/test_w025_job_poll.py
W-025-DATAEDITOR	DataEditor row-model smoke	tests/performance/test_w025_dataeditor.py

Checker: python scripts/check_budget_025.py.

Phase 0.26 critical-path workloads (CORE-026 / FASTAPI-026)

Budgets for the production-grade graduation packet (soft CI ceilings; extend 0.25):

ID	Workload	evidence_path
W-026-FRAGMENT	Fragment latency under Supported HTMX swap load	tests/performance/test_w025_fragment.py
W-026-JOB-POLL	Job status poll fanout (polling_only)	tests/performance/test_w025_job_poll.py
W-026-STARTUP	Flagship construct + min-deps import smoke	scripts/smoke_fastapi_026.py
W-026-INSTALL	Python 3.10–3.14 / pinned FastAPI–Pydantic matrix (COMPATIBILITY)	docs/COMPATIBILITY.md

Install matrix SSOT remains COMPATIBILITY.md (CPython 3.10–3.14; Supported FastAPI/Pydantic pins). Offline-wheel / min-deps smoke: python scripts/smoke_fastapi_026.py.

Budgets (CPython 3.12, ubuntu-latest)

Metric	Budget	Notes
Tree normalize (200 nodes)	≤ 250 ms	Soft CI ceiling
Serialize (200 nodes)	≤ 250 ms	Soft CI ceiling
Full render() (200 nodes)	≤ 500 ms	Includes normalize + serialize
Page HTML for small Page	≤ 200 KiB	Document shell + HTMX script tag allowed
Fragment HTML for 200-node stack	≤ 100 KiB	No document shell
Diagnostic JSON for ≤ 20 findings	≤ 256 KiB	SARIF/text exporters

Adapter / ops (reference)

Metric	Budget	Evidence location
Health endpoint	≤ 100 ms local	tests/ops/test_health.py
Job status poll JSON	≤ 64 KiB	job conformance
Chart SVG (Matplotlib smoke)	≤ 1.5 MiB	chart security corpus

Enforcement

tests/performance/test_budgets.py fails the suite when a budget is breached. Hosts that occasionally exceed soft ceilings should be investigated; do not silently raise budgets without an owning decision and changelog note. (There is no automatic CI retry for these tests.)