feat: add fx provider

[t3-code]

what changed

• adds fx as an opt-in early-access provider across server, web, desktop, and mobile
• launches fx acp, reuses fx-managed gateway/codex/grok authentication, and discovers raw model ids from standard ACP config options
• supports sessions, resume, streaming, permissions, interruption, in-session model switching, attachments, and source-control text generation
• adds provider settings, icons, docs, health checks, and registry coverage

why

fx now supports eligible codex and grok subscriptions directly, so t3 code can use those subscription-backed tokens through one native ACP provider without proxying oauth credentials.

ui changes

adds fx to provider settings and model pickers on web/desktop and mobile.

before

after, light

after, dark

verification

• npx vp test run ...: 19 focused files, 199 tests passed
• npx vp run --filter t3 test --shard 2/3: 82 files, 944 tests passed
• contracts, shared, server, web, and mobile typechecks passed
• targeted lint and formatting checks passed
• installed and exercised fx 0.0.5; fx --version and fx acp --help passed
• exercised the real t3 web app in light and dark mode: configured the fx binary, enabled the provider, and verified its detected v0.0.5 plus expected unauthenticated ACP status
• live unauthenticated ACP probe returned fx's expected login error
• authenticated codex/grok live turns were not run because this environment has no fx subscription credentials; deterministic ACP integration tests cover startup, model discovery/selection, turns, permissions, events, interruption, and text generation

checklist

• this pr is focused on the fx provider
• i explained what changed and why
• focused tests, typechecks, lint, and formatting pass
• authenticated codex and grok live turns exercised
• ui screenshots attached

request provenance

• requested by: @maria-rcks

[github-actions]

Thread transfer impact

✅ Thread transfer remains within every enforced ceiling.

Provider	Metric	Main baseline	This PR	Impact	PR ceiling
Codex	Total thread wire	13.4 KiB	13.4 KiB	+2 B (+0.0%)	15.1 KiB	✅
Codex	Thread snapshot wire	6.9 KiB	6.9 KiB	−3 B (−0.0%)	7.3 KiB	✅
Codex	Live turn WebSocket wire	6.5 KiB	6.5 KiB	+5 B (+0.1%)	7.8 KiB	✅
Codex	Live turn WebSocket decoded	55.0 KiB	55.0 KiB	0 B (0.0%)	66.4 KiB	✅
Codex	Live turn messages	16	16	0 (0.0%)	21	✅
Claude	Total thread wire	13.5 KiB	13.4 KiB	−10 B (−0.1%)	15.1 KiB	✅
Claude	Thread snapshot wire	6.9 KiB	6.9 KiB	+1 B (+0.0%)	7.3 KiB	✅
Claude	Live turn WebSocket wire	6.6 KiB	6.6 KiB	−11 B (−0.2%)	7.8 KiB	✅
Claude	Live turn WebSocket decoded	55.8 KiB	55.8 KiB	0 B (0.0%)	66.4 KiB	✅
Claude	Live turn messages	16	16	0 (0.0%)	21	✅

Baseline: 592c598 · PR result: 04bd65c · 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: 109.4 KiB
• Claude decoded thread snapshot: 110.1 KiB

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

[macroscopeapp]

Two Effect service convention issues in the new fx provider code. Everything else (namespace subpath imports, Foo["Service"] usage, Effect.catchTags, structured tagged errors with preserved cause) looks consistent with the conventions.

^{Posted via Macroscope — Effect Service Conventions}

[macroscopeapp]

Approvability

Verdict: Not approved

Macroscope's review found this PR not approvable — This PR adds a new 'fx' provider integration with ~2000+ lines of new implementation code, including a new driver, adapter, ACP support, text generation, and UI components. New features introducing significant new capabilities and external integrations warrant human review.

^{You can add or adjust custom eligibility rules. Learn more.}

[cursor]

Cursor Bugbot has reviewed your changes using high effort and found 1 potential issue.

^{❌ Bugbot Autofix is OFF. To automatically fix reported issues with cloud agents, enable autofix in the Cursor dashboard.}

^{Reviewed by Cursor Bugbot for commit 0e97ae9. Configure here.}

[macroscopeapp]

One consistency finding on the new FxIcon brand glyph color plumbing. Everything else in the web scope (providerIconUtils.ts, providerDriverMeta.ts, session-logic.ts) matches the existing provider registration patterns.

^{Posted via Macroscope — UI Consistency}