perf(mobile): skip showcase subscriptions in normal builds

[juliusmarminge]

Normal mobile builds mounted the showcase capture coordinator even when EXPO_PUBLIC_SHOWCASE was disabled. Its hooks subscribed to workspace, projects and thread shells, causing renders and a full thread-list search during streaming.

Gate the hook-bearing component before it mounts. Showcase-enabled builds retain the same behavior; redundant internal flag guards are removed. This adds no cache, timer or dependency.

Release profile

Same optimized native Release binary, Hermes -O, dev=false, no Metro. Before is bab9fdb; source maps confirm only this component differs after. The same 1,210-shell server fixture was restored for each run. Navigate from Home to a settled 40-turn history with large tool output while one other chat streams at 20 Hz and four at 2 Hz for 15 seconds. Both runs emitted 300 + 120 events and displayed populated history.

Inclusive sampled stacks	Before	After
Showcase coordinator	26	0
Showcase coordinator after navigation, seconds 7–18	17	0
Active JS / total samples	1,023 / 14,918	1,241 / 17,357
GC samples	76	174
Capture span	22.90 s	23.01 s

Measurement details · Before Hermes trace · After Hermes trace

This single pair proves removal of the targeted work, not an overall speedup or battery improvement. Total active samples increased, with more GC; sampling, batching and generated text vary. Aggregate thread-list work remains present from other consumers. There is no visual change or claimed navigation-latency change; the evidence is the sampled work, not a video timing comparison.

Repeated measurement follow-up

Two additional alternating pairs restore both the server fixture and the same saved app cache before every run. Before process CPU: 3.16 s and 3.55 s. After: 3.42 s and 3.25 s. Mean: 3.36 s before versus 3.34 s after, effectively unchanged at this sample size. Process CPU includes native threads as well as JS.

Showcase sampled stacks: 22 and 39 before, zero in both after runs. GC samples: 87 and 104 before, 87 and 98 after. The initial GC increase did not repeat. This remains a small removal of unnecessary work, with no demonstrated net CPU, latency or battery improvement.

Repeat measurements

Verification and scope

Targeted lint and formatting passed. Mobile typechecking passed. The three existing lint warnings are unchanged from the parent. Reviewed the complete diff and sole mount in Stack.tsx: the exported wrapper has no hooks, and enabled builds run the original hook body. Full showcase capture was not exercised. No wiring-only test was added.

Both iOS and Android use this component; runtime profiling was on the iOS 27 simulator only. Web, desktop, providers, contracts and connection modes are unchanged. Unrelated widget edits are excluded.

Julius requested this performance audit and one PR per measured hotspot in the maintainer session. There is no separate public approval issue. This is one small removal of unnecessary subscriptions, stacked with the audit fixes.

Implementation: Claude Opus 5.5 through T3 Code. Integration, review and release profiling: GPT-6 Astra through the Codex harness.

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[macroscopeapp]

Approvability

Verdict: Approved at 4a0c6b2

Macroscope's review found this PR approvable — This is a focused one-file optimization that prevents disabled showcase code from mounting and subscribing in normal mobile builds, while preserving showcase-enabled behavior. It introduces no product-default, schema, security, or static-analysis changes.

No code changes detected at eb57c3c. Prior analysis still applies.

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[github-actions]

Thread transfer impact

✅ Thread transfer remains within every enforced ceiling.

ℹ️ No successful main baseline artifact is available yet. This run establishes the initial measurement.

Provider	Metric	Main baseline	This PR	Impact	PR ceiling
Codex	Total thread wire	—	5.0 KiB	—	6.8 KiB	✅
Codex	Thread snapshot wire	—	3.8 KiB	—	4.9 KiB	✅
Codex	Live turn WebSocket wire	—	1.2 KiB	—	2.0 KiB	✅
Codex	Live turn WebSocket decoded	—	20.9 KiB	—	29.3 KiB	✅
Codex	Live turn messages	—	2	—	8	✅
Claude	Total thread wire	—	5.0 KiB	—	6.8 KiB	✅
Claude	Thread snapshot wire	—	3.8 KiB	—	4.9 KiB	✅
Claude	Live turn WebSocket wire	—	1.2 KiB	—	2.0 KiB	✅
Claude	Live turn WebSocket decoded	—	21.2 KiB	—	29.3 KiB	✅
Claude	Live turn messages	—	1	—	8	✅

Baseline: unavailable · PR result: eb57c3c · Source CI: success

Scenario and decoded snapshot size

10 historical turns, 5 command tools per turn, 878.9 KiB retained MCP result per historical turn, and a 1.05 MiB retained result in the measured turn.

• Codex decoded thread snapshot: 108.5 KiB
• Claude decoded thread snapshot: 108.8 KiB

Updated in place by a trusted workflow. PR artifacts are strictly validated and never executed.

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📥 Commits

Reviewing files that changed from the base of the PR and between bab9fdb and 4a0c6b2.

📒 Files selected for processing (1)

• apps/mobile/src/features/showcase/ShowcaseCaptureCoordinator.tsx

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📝 Walkthrough

Walkthrough

The showcase capture coordinator now checks whether showcase mode is enabled before mounting the capture logic. The inner coordinator no longer repeats that check in its effects or readiness rendering.

Changes

Showcase capture

Layer / File(s)	Summary
Gate showcase capture at mount apps/mobile/src/features/showcase/ShowcaseCaptureCoordinator.tsx	The outer coordinator returns null when showcase mode is disabled. The inner coordinator retains its existing capture conditions without repeated enabled-mode checks.

Priority: ⬇️ Low

Estimated code review effort: 2 (Simple) | ~8 minutes

Change: Bug fix

Merge Risk: ⚪ Minimal · up to 4a0c6

Normal builds no longer mount the showcase capture coordinator. No actionable merge-blocking risk was identified in the reviewed change.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 33.33% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 3 functions across 1 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Title check	✅ Passed	The title clearly summarizes the main change: showcase subscriptions are skipped in normal builds.
Description check	✅ Passed	The description explains the problem and change, provides scope and approval context, and reports focused verification and measurement limits. It does not use all template headings, but the required i…

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[juliusmarminge]

Reviewed the CodeRabbit docstring-coverage warning. No additional docstrings are needed: the wrapper already explains why it prevents subscriptions, and the remaining functions retain their existing behavior. Adding comments solely to meet a coverage percentage would conflict with the repository guidance to avoid narrating code. CodeRabbit reported no actionable code findings; its host check passed.

The transfer report passes all enforced ceilings. Its missing main baseline means it is not evidence of a before/after transfer improvement; the PR makes no such claim.