Lesson 252: Spline Playtest Landing LCP Spot Receipt on BUILD_RECEIPT (2026)

Direct answer: Before July playtest signup links hit Discord, file spline_playtest_lcp_spot_receipt_v1.json proving idle baseline LCP ≤ 2.5 s, a documented concurrent load profile (parallel tabs or k6), LCP under load ≤ 3.5 s (team band), CTA click survival, and cousin spline_lcp_fest_receipt path linked—then promote BUILD_RECEIPT spline_playtest_lcp_spot_ok. Distinct from Lesson 233 (spline_lcp_fest fest-week) and LCP impact preflight (steady budget).

Lesson hero for Spline playtest landing LCP spot receipt

Why this matters now (July 2027 concurrent playtest traffic)

July 2026–2027 teams pass fest LCP spike preflight on a quiet laptop, then reuse the same Spline hero on a playtest hub—Tuesday evening brings 50+ facilitators hard-refreshing while CDN edges warm unevenly; mobile LCP jumps from 2.1 s to 4.8 s and the itch demo CTA feels frozen. Lesson 233 owns spline_lcp_fest on BUILD_RECEIPT for marketing fest URLs—252 owns spline_playtest_lcp_spot when concurrency, not cold traffic, is the stressor.

The playtest LCP spot under load preflight is the ninety-second gate—252 is the BUILD_RECEIPT milestone.

Beginner path (baseline → load → receipt)

Step	Action	Success check
1	Pin playtest URL in matrix	L1 pass
2	Confirm idle LCP ≤ 2.5 s	L2 pass
3	Run parallel-tab or k6 load	L3 profile logged
4	Lighthouse mobile under load	L4 ≤ 3.5 s band
5	Click primary CTA twice	L5 survival
6	File receipt + BUILD_RECEIPT	`lcp_playtest_spot_ok: true`

Time: ~62 minutes first playtest wave; ~15 minutes when load profile is pinned.

Developer path (gates L1–L6)

Gate	Check	Fail when
L1	`playtest-landing-url-matrix.md` row	URL drift vs prod
L2	Idle baseline LCP	> 2.5 s mobile lab
L3	Load profile	Missing `concurrent_sessions`
L4	LCP under load	> team band (default 3.5 s)
L5	CTA after load	Long task blocks handler
L6	Receipt + BUILD_RECEIPT	Promote before L3 GREEN

L2 — cousin receipt crosswalk

Field	Cousin (233)	This lesson (252)
Schema	`spline_lcp_fest_receipt_v1`	`spline_playtest_lcp_spot_receipt_v1`
Traffic	Fest marketing spike / cold visitors	Facilitator concurrent hammer
Path	`release-evidence/03-web/SPLINE_LCP_FEST_RECEIPT.json`	`release-evidence/03-web/SPLINE_PLAYTEST_LCP_SPOT_RECEIPT.json`
BUILD_RECEIPT column	`spline_lcp_fest`	`spline_playtest_lcp_spot`

Do not merge fest JSON into playtest spot receipt—reference cousin path only.

spline_playtest_lcp_spot_receipt_v1.json

{
  "schema": "spline_playtest_lcp_spot_receipt_v1",
  "build_label": "playtest-july-2027-rc1",
  "landing_url": "https://example.com/playtest-hub",
  "spline_scene_id": "SCENE_ID",
  "embed_policy": "poster_first_click_to_load",
  "load_profile": {
    "tool": "parallel_incognito_tabs",
    "concurrent_sessions": 10,
    "duration_seconds": 30
  },
  "baseline": {
    "cousin_receipt": "release-evidence/03-web/SPLINE_LCP_FEST_RECEIPT.json",
    "lab_lcp_seconds_mobile_idle": 2.1
  },
  "under_load": {
    "lab_lcp_seconds_mobile": 3.2,
    "long_tasks_gt_50ms_first_5s": 1,
    "cta_click_survival": true
  },
  "gates": {
    "L1_url_matrix": "pass",
    "L2_idle_baseline": "pass",
    "L3_load_profile": "pass",
    "L4_lcp_under_load": "pass",
    "L5_cta_click": "pass",
    "L6_build_receipt": "pass"
  },
  "lcp_playtest_spot_ok": true,
  "playtest_promotion_allowed": true
}

Pin under release-evidence/03-web/SPLINE_PLAYTEST_LCP_SPOT_RECEIPT.json.

BUILD_RECEIPT row (L6)

Column	Pass when
`spline_playtest_lcp_spot`	`lcp_playtest_spot_ok: true`
`spline_lcp_fest`	Cousin Lesson 233 independent column
`trailer_handoff`	Lesson 251 independent column

ALTER TABLE release_publish_gate ADD COLUMN IF NOT EXISTS
  spline_playtest_lcp_spot_blocked BOOLEAN NOT NULL DEFAULT false;

Thursday row review — playtest LCP spot line: load profile Y/N.

Key takeaways

Fest receipt ≠ playtest spot—233 and 252 are separate BUILD_RECEIPT columns.
Idle green ≠ concurrent green—run load ritual every playtest wave.
Poster-first policy must survive load test—no autoplay iframe “for realism.”
Lesson 233 — fest cousin path.
Phaser wasm heap cap — browser demo cousin, separate WebGL budget.
Forward: Lesson 253 Q4 capstone BUILD_RECEIPT.
Community playtest resources — facilitator ops, not LCP measurement.
Steam in-client browser may be worse than Chrome—re-spot if playtest links target Steam overlay.
playtest_promotion_allowed here ≠ Q4 capstone 253.
Pair Wednesday demo smoke before sharing hub URLs.

Common mistakes

Filing 252 while only desktop lab was measured.
Using spline_lcp_fest_receipt JSON for playtest week.
Load test enables autoplay iframe—invalidates L2 baseline.
Skipping L5—LCP OK but CTA handler blocked.
Different spline_scene_id in receipt vs live embed.

Troubleshooting

Symptom	Lane
Idle green, load red	Tighten poster; CDN-cache poster; shrink scene
CTA frozen under load	L5 long tasks—defer embed mount
TTFB spikes	L3 origin/CDN—warm cache
Fest GREEN, playtest RED	This lesson—concurrency not in fest receipt
Lab OK, Discord complaints	Re-spot mobile + Steam in-client

Mini exercise (55 minutes)

Document matrix row—confirm L1.
Run idle Lighthouse—log L2.
Ten parallel tabs + 11th Lighthouse—log L4.
Link cousin SPLINE_LCP_FEST_RECEIPT.json path.
File receipt; BUILD_RECEIPT GREEN.

Continuity — Q4 2027 July playtest scale (245–253)

Lesson	Receipt focus
251	DaVinci trailer handoff → OBS
252 (this)	Spline playtest LCP under load
253	Q4 capstone

Previous: Lesson 251 — DaVinci trailer handoff
Next: Lesson 253 — Q4 playtest scale capstone

FAQ

Same as Lesson 233?
233 = fest marketing spline_lcp_fest; 252 = concurrent playtest load spot.

Same as the Spline guide chapter?
Guide = L1–L6 checklist; 252 = BUILD_RECEIPT promotion.

Can I skip load test if fest receipt is GREEN?
No—fest idle does not prove facilitator pile-on behavior.

k6 required?
No—parallel incognito tabs are the indie default; name the tool in load_profile.tool.

Playtest hubs get hammered harder than fest day one—spot LCP under concurrent load, prove CTA survival, then spline_playtest_lcp_spot_ok on BUILD_RECEIPT before Lesson 253 capstone.