RepoPrompt CE Concurrency Fix

Resolve the requested diagnostics with the smallest semantic change that makes the runtime ownership explicit. Do not treat an annotation-only compile as proof of safety.

Required context

1. Read references/diagnostic-playbook.md, classify the boundary, then load the matching detailed reference below. Load another only if the traced boundary spans families:
   • references/isolation-sendability-samples.md for actor isolation, Sendable crossings, global state, isolated conformances, reentrancy, or escape-hatch repairs;
   • references/tasks-cancellation-continuations-samples.md for task ownership, detached work, continuation races, streams, or deterministic concurrency tests;
   • references/synchronization-interop-samples.md for locks, queues, @unchecked Sendable, Objective-C/C callbacks, runtime assertions, or @preconcurrency.
2. Read references/repository-patterns.md before changing an existing RepoPrompt task, continuation, synchronization, UI-publication, or concurrency-utility pattern.
3. For Swift 6.2 settings or execution semantics, read ../rpce-swift-6-concurrency-migration/references/official-swift-6-2.md and its linked local samples.
4. Inspect the owning target's actual manifest settings before interpreting a diagnostic.
5. Before running builds or tests, read root AGENTS.md and the applicable section of ../rpce-swift-6-concurrency-migration/references/validation-matrix.md.

Workflow

1. Capture the failure

Record:

• exact diagnostic text;
• package, target, file, and declaration;
• compiler and Swift language mode;
• strict checking, default isolation, and upcoming-feature settings;
• whether the issue is first-party, imported, generated, or dependency code.

2. Trace the boundary

Follow the value, closure, or mutable state through its real execution path. Identify:

• source and destination isolation domains;
• owning actor, task, lock, queue, or immutable value;
• suspension and reentrancy points;
• task lifetime and cancellation owner;
• callback/continuation completion paths;
• public API or interoperability constraints.

State the runtime invariant the compiler cannot see. If it is unknown, investigate rather than selecting an escape hatch.

3. Choose the smallest semantic fix

Prefer, in order:

1. express the correct actor or global-actor isolation;
2. keep non-Sendable state within one isolation domain;
3. transfer immutable or genuinely Sendable snapshots;
4. give unstructured work an explicit owner or replace it with structured concurrency;
5. protect short synchronous mutable state using an established actor/lock/queue invariant;
6. adjust a boundary API when the existing contract is the root cause.

Use @concurrent only for intentional off-actor async work after verifying Swift 6.2 settings and sendability crossings.

4. Verify immediately

After reading the repository validation instructions, recompile the smallest supported affected product through conductor, then run focused tests for the changed contract. Use $rpce-test-quality before adding timing-sensitive concurrency tests.

Stop when the requested diagnostic family is resolved. Record causally unrelated diagnostics for the migration inventory rather than expanding the change.

Escape-hatch gate

Do not add @unchecked Sendable, nonisolated(unsafe), @preconcurrency, MainActor.assumeIsolated, Task.detached, or a new manual lock merely to silence the compiler.

If no checked design is practical, document:

• protected state and allowed operations;
• synchronization or ownership mechanism;
• why it prevents concurrent invalid access;
• cancellation, lifetime, and reentrancy behavior;
• why checked alternatives are impractical;
• focused verification;
• audit or removal condition.

Anti-refactor rules

• Do not rename, reorganize, or broadly reformat adjacent code.
• Do not modernize unrelated async APIs.
• Do not convert neighboring types to actors without a traced invariant requiring it.
• Do not replace established synchronization without a demonstrated defect.
• Do not blanket-apply @MainActor.
• Do not assume all GCD, locks, or detached work is wrong; prove whether the ownership is valid.
• Do not use sleeps as deterministic concurrency verification.

Handoff

Summarize the diagnostic, confirmed boundary, invariant, minimal fix, escape-hatch decision, focused build/test evidence, and deferred unrelated findings.