Phase 0 — Instrumentation, Truth & Test Foundation

Authoritative spec. See also the phase index, perf-dod, and testing-strategy. Live issue numbers: pinned master #810.

Expansion: Phase 0 adds the testing/infra foundation (Docker CI, story gallery, alloc-budget gate, spec-test convention, E2E harness, determinism/fuzz fixtures, CI restructure) — see phase-specs-expansion.md §C. Total P0 issues = 19.

Phase 0 — Instrumentation & Truth (W0)

Goal: Measure before optimizing. Every later perf claim must be attributable to a non-zero phase counter and gated by a bench. Decision records for the two big redesigns are written here with fresh data. 12 issues.

Batch 0.1 — Instrumentation core (3 groups, parallel)

ID	Title	Grp	Effort	Blocked by
ENG2-P0-01	Add GPU timestamp queries (wgpu QuerySet) for shadow/render/submit phases	A	M	—
ENG2-P0-02	Fix always-zero CPU phase counters and surface both timing families via FFI + MCP	A	M	P0-01
ENG2-P0-03	Bench suite expansion: cull_scaling, primitive draw-call, real-GPU shadow benches	B	L	—
ENG2-P0-04	Feature-gated tracy/puffin profiler integration	C	M	—

P0-01: timestamp_writes: None at backend/wgpu_backend/frame.rs:148 and shadow_pass.rs:76,382 — no GPU timing exists; all phases are Instant::now() CPU record-time (frame.rs:18-127). Add QuerySet begin/end around shadow, main pass, submit; new gpu_shadow/gpu_render/gpu_submit phases distinct from CPU-record phases. This is why shadow_pass reports 0 µs while Metal stalls 300–600 ms (#677 evidence).
P0-02: Consumer profile shows uniform_upload, render_pass, gpu_submit, surface_present, shadow_build, bone_* all 0 µs (throne profile :44-52). Wire real values through frame_timing.rs → GetFramePhaseTimings FFI → MCP get_metrics_trace (tools/goudengine-mcp inherits the mis-attribution today).
P0-03: benches/helpers/scene3d.rs:81 force-disables frustum culling in every bench scene; renderer3d_frame_benchmarks.rs:29,35 scale only total count — bug #678 is structurally unmeasurable. Add: (a) cull_scaling group — fixed 5k visible, total 10k→100k, culling ON; (b) draw-call bench for CreatePlane/CreateCube (count-pinning test tests/renderer3d_frame_counts.rs already documents draw_calls == n); (c) opt-in real-wgpu shadow bench (NullBackend at helpers/null_backend.rs:46-53 no-ops everything, so shadow_record/casters_* measure the wrong thing).
P0-04: No tracy/puffin in any Cargo.toml. Feature-gate profiling crate spans in the frame path + ECS schedule so devs get flamegraphs beyond the 14 fixed counters.

Batch 0.2 — CI wiring & scene harness (4 groups, parallel)

ID	Title	Grp	Effort	Blocked by
ENG2-P0-05	Wire bench-gate.py into required CI; fix benchmarks.yml bench set; retire bench-gate.sh (absorbs #256)	A	M	P0-03
ENG2-P0-06	Promote curated GPU tests to a blocking lavapipe lane	B	M	—
ENG2-P0-07	Scripted consumer-scale scene harness: S1/S2/S3/S4/H1 + `scripts/perf-capture` + committed S1 baseline report	C	L	P0-01, P0-02
ENG2-P0-08	Move community-stats bot off protected main; revoke admin push token	D	S	—

P0-05: scripts/bench-gate.py (ratio-normalized, baselines at benches/baselines/criterion_baseline.json) has ZERO references in .github//.husky//verify.sh; benchmarks.yml:35 runs the wrong bench set, weekly-cron only, comparing nothing. Make it a required PR check over engine_tick + renderer3d_frame + the new P0-03 benches; delete redundant bench-gate.sh.
P0-06: 96 #[ignore] GPU tests run only in headless-gpu.yml with continue-on-error: true (line 25) — renderer is untested in gating CI (ci.yml:174-178 runs only null-named tests). Promote a curated subset to required.
P0-07: Builds the five named scenes (table above) as reproducible harness scenarios (headless + capture via MCP capture_frame/get_metrics_trace), documents the 3-run-median M-series procedure, and commits the S1 baseline numbers as the regression anchor for the Phase 2 gate.
P0-08: community-stats.yml:5-6,20-25,40-41 — daily cron force-pushes [skip ci] commits to protected main with an admin token (122 commits pollute blame/bisect for perf work). Move to a data branch/Pages; drop the token.

Batch 0.3 — Decision records & repo truth (3 groups, parallel)

ID	Title	Grp	Effort	Blocked by
ENG2-P0-09	RFC-0005: Render submission redesign (spatial index, dense storage, instancing, uniform strategy)	A	M	P0-07
ENG2-P0-10	ADR: Remove legacy glfw/OpenGL backend; verify live backend; reconcile doc contradiction	A	S	—
ENG2-P0-11	Docs truth pass: archive ALPHA_ROADMAP.md, promote performance-roadmap.md, fix ARCHITECTURE.md, adopt perf definition-of-done	B	M	—
ENG2-P0-12	Issue/label/milestone hygiene + verify-close pass (#423, #670, #136, #114, #475; migrate #590–593)	C	M	—

P0-09: No RFC covers the redesign #677/#678/#679 require (docs/rfcs has only RFC-0001..0004). Must decide: grid vs BVH; dense-slot storage replacing FxHashMap<u32, Object3D> (renderer3d/core/mod.rs:54-93); dynamic-offset uniform slots; instancing-by-identity keying. Written with fresh P0-07 baseline numbers. Blocks Phase 2 Batch 2.1.
P0-10: ARCHITECTURE.md says wgpu default; ALPHA_ROADMAP.md:1246-1248 says wgpu incomplete/GL bypasses abstraction. User decision: “no legacy code kept” — record removal of the legacy-glfw-opengl path as an ADR (execution is ENG2-P2-03). Confirm the active Metal path in code first.
P0-11: ALPHA_ROADMAP.md:9 falsely claims “Phase 0 (v2) Core Performance — COMPLETE” while #677/#678/#679 are open. Archive it; promote docs/src/development/performance-roadmap.md (current, code-verified); write the perf definition-of-done (“closed only when the named scene hits the number AND the phase counter attributes the cost”) into CLAUDE.md/agents + PR template.
P0-12: Dedupe legacy labels (bug/enhancement/…) into type:*; add phase:v2-p*; close milestones 1–9 as superseded; retag #677-679 area:performance; verify-close: #423 (drawText EXISTS in wasm — wasm/rendering.rs:239, close invalid), #670 (sdks/csharp/build/GoudEngine.targets exists and packs — fix its repo-root path-preference fallback, then close), #136 (debugger substantially shipped — close, successor is P9-01), #114/#475 (superseded by new master issue); migrate #590–593 bodies to throne_ge and close GE-side.

Phase 0 Gate

S1 capture: gpu_shadow, gpu_render, gpu_submit report non-zero; CPU counters uniform_upload/render_pass/surface_present non-zero; MCP get_metrics_trace shows both families.
bench-gate.py is a required PR check over the tracked set (engine_tick, renderer3d_frame, cull_scaling, draw-call, ffi_component); baselines committed.
cull_scaling baseline recorded and documents the current O(total) defect (expected-fail documented, becomes gated in Phase 2).
Blocking lavapipe lane required on PRs; curated GPU tests pass.
S1 baseline report committed (re-measured post-#670-fix numbers).
RFC-0005 and the OpenGL-removal ADR merged; ALPHA_ROADMAP.md archived; zombie milestones closed.

Sync 0 (throne_ge, after gate): THR-S0-01 [S] — bump GoudEngine, delete the CopyGoudEngineNativeLib workaround (Throne.App.csproj:33-49), confirm the ~60x load-path overhead is gone, re-profile GameWorld with the fixed phase counters and post the report (this becomes Phase 2’s consumer-side “before” evidence). Maps throne_ge #1040 partially.