iOS snapshot backend convergence and fast Simulator observation

[thymikee]

Outcome

Converge iOS snapshot acquisition behind one host presentation interface while adding a fast local
Simulator observation path. Every producer reports facts; one engine owns projection, geometry,
scope, depth, actionability narrowing, semantic compaction, invariants, and publication.

This tracker deliberately separates issues (durable outcomes) from PRs (narrow review slices).
Children may use stacked PRs, but every PR must preserve the dependency and proof requirements of
its owning issue.

What success changes

• Local Simulator observation no longer waits for XCTest runner readiness when the bridge is eligible.
• XCTest remains the interaction and typed-fallback path.
• Simulator bridge, XCTest, Appium/WebDriver, and Limrun use one meaning for regular/raw,
  interactive-only, depth, and scope to the extent their declared acquisition evidence permits.
• Swift and TypeScript geometric presentation stay consistent through independent goldens,
  differential fuzzing, and structural invariants.
• agent-device proxy performs acquisition and presentation on the daemon host and transfers only
  the published response, with explicit remote latency and lease-isolation acceptance.
• Superseded backend-name policy and duplicate orchestration become deletion-ready.

Non-goals

• Physical-iPhone startup, signing, installation, transport, or runner retention.
• Replacing XCTest interactions or custom-action invocation.
• Redesigning Android acquisition.
• A generated presentation-rule language, shared C++/Rust/WASM implementation, or new public
  backend-selection flag.
• Closing or silently absorbing iOS: skip private-AX deep extension on observation-only captures (settle, stabilization, corroboration) #1626 before its separate product decision.

Invariants

1. Acquisition and presentation remain separate concepts.
2. Geometric presentation occurs exactly once.
3. interactive ⊆ regular ⊆ raw is asserted over one acquisition.
4. Raw depth is acquisition traversal depth; regular depth is the presented frontier.
5. Missing evidence is never upgraded, especially hittability and viewport evidence.
6. Producer differences enter through typed capabilities and residue, never producer-name branches.
7. Bridge fallback is typed, attempted at most once, and shares the original request deadline.
8. Runner-presented output still crosses implementation-independent host invariants.
9. Internal stage, hint, lineage, generation, and quality contracts do not become required RPC fields.
10. Physical-device behavior and performance remain unchanged.

Related work

• iOS snapshot backends: make interpretation divergence impossible by construction (acquire/present split) #1797 is closed architectural groundwork; this tracker does not reopen it.
• iOS: skip private-AX deep extension on observation-only captures (settle, stabilization, corroboration) #1626 remains held and separate. Its deep-button false-failure reproduction becomes permanent
  evidence without changing that issue's status or proposed product behavior.
• refactor(daemon): establish the interaction application facade #2177 → refactor(daemon): move interaction and find routes behind the interaction facade #2178 is a hard prerequisite chain for the later comparison/re-baselining work. No child
  may recreate the retired src/daemon/handlers/interaction-* paths from an older base.
• App-mount race on fast/cold opens: first capture can see an unreadable or empty tree (cross-platform) #1571 is related cold-open evidence, not automatically a blocker; benchmark and bridge work must
  distinguish app-mount unreadability from bridge failure.

Children and dependency graph

Foundation

• test(ios): establish snapshot convergence baselines and permanent evidence #2189 — reproducible local/proxy/package baselines and permanent regression evidence
• refactor(ios): define snapshot acquisition and presentation contracts #2190 — acquisition/presentation vocabulary, capabilities, intent, residue, and engine interface

Convergence and bridge decision

• refactor(ios): build and prove the converged snapshot engine #2191 — Swift/TypeScript engine implementation, independent conformance, current-runner
  integration, and ADR 0004 amendment
• refactor(ios): converge Appium and Limrun acquisition adapters #2195 — Appium/WebDriver and Limrun acquisition-adapter convergence
• perf(ios): decide Simulator AX bridge viability with a bounded spike #2192 — bounded Simulator AX bridge spike with explicit GO/NO-GO
• feat(ios): productionize the selected Simulator snapshot bridge #2196 — production native bridge plus private Apple host adapter/lifecycle

Routing, latency, remote acceptance, and deletion

• feat(ios): route Simulator snapshots through the bridge with bounded fallback #2197 — bridge routing, generation circuit, shared-deadline fallback, and comparison re-baseline
• perf(ios): optimize observation lifecycle and prove proxy parity #2198 — runner-demand/open/relaunch optimization plus proxy acceptance
• refactor(ios): prune converged snapshot paths and close release gates #2199 — final pruning, no-regrowth enforcement, size report, and release evidence

#2189 ─────────► #2192
└──────────────────────────────► #2198

#2190 ─► #2191 ─► #2195 ─────────────────► #2199
│          └──────────────► #2197
└──────► #2192 ─► #2196 ─► #2197 ─► #2198 ─► #2199

#2177 ─► #2178 ─────────────────────► #2197

Only #2189 and #2190 are initially unblocked and ready-for-agent. Blocked children remain
needs-triage until every Blocked by: prerequisite lands and the issue is re-audited against its
exact head. #2196 additionally requires #2192 to close with GO; a NO-GO stops the bridge branch.

Tracker acceptance

Close this tracker only after every child is closed and the exact implementation heads prove:

• local cold-cold, cold, warm, and relaunch targets;
• Swift/TypeScript conformance with reproducible failures and planted-red proof;
• provider option consistency and typed fidelity residue;
• stale-generation, cancellation, crash, timeout, and fallback behavior;
• direct-daemon/proxy semantic parity, lease isolation, supported version skew, and controlled-RTT
  measurements;
• packed, installed, and bundled package-size deltas;
• final provider, macOS, Simulator, affected, and structural gates.

[thymikee]

Maintainer triage: this is a coherent, actionable dependency program, so the parent tracker is accepted and needs-triage is removed here. The execution frontier is intentionally only #2189 and #2190, which are fully specified and already ready-for-agent. Blocked children #2191, #2192, #2195, #2196, #2197, #2198, and #2199 remain needs-triage by the tracker’s explicit gate: re-audit each against the landed prerequisite heads before promoting it; #2196 additionally requires a GO outcome from #2192. Preserve the #2177 → #2178 stack constraint, and keep #1626/#1571 separate as specified.