[thatswiftdev]

Closes #15.

What's in this PR (all generic — no consumer vocabulary)

1. Cause-based failure classification (src/loop.ts) — LoopError carries an explicit cause (budget-hop|wall|token, caller-abort, provider, tool-invalid) and a widened code union. Provider failures keep their own codes (PROVIDER_BAD_REQUEST etc. pass through; unattributed timeouts → PROVIDER_TIMEOUT; unknown → PROVIDER_FAILED) instead of being relabeled BUDGET_EXCEEDED, which the transport treats as a resumable pause. The loop-owned wall is a separate signal; explicit Stop beats a concurrent wall expiry. Only genuine budget outcomes create a resume stash.

2. Execution authority (src/orchestrate/execution-authority.ts, new) — one executor per canonical agent DB, elected by a lifetime BEGIN IMMEDIATE on a separate <agent>.execution-control.db. Atomic durable admission (epoch check, session-active check, request idempotence via stored fingerprint, turn.request events + receipt + ledger row in one sink-connection commit, requiring the intended turn.started — queue decisions and storage failures roll back entirely). Stash peek + exact CAS consume at the execution boundary. Truthful dead-owner recovery (ONE EXECUTION_INTERRUPTED, idempotent re-recovery, ledger-only reconcile when already terminal). Durable worker rows with operator-evidenced quarantine for unproven survivors. readSession common read: legacy active folds are uncertain/legacy_owner, never silently idle.

3. Transport wiring (src/transport/conversation.ts) — additive ConversationDeps.execution: authority-driven message POST (409 busy / REQUEST_ALREADY_ADMITTED with original turnId / REQUEST_ID_REUSE / 503 quarantine-drain-recovery with no acceptance; optional clientRequestId body field), attempt-fenced durable writes, execution-boundary stash consumption, Stop-before-start as honest ABORTED, /abort with optional expectedTurnId (stale → 409), session GET with the common execution snapshot (liveTurn only for positively-known local ownership). Legacy no-authority hosts keep the process-local path unchanged. Ownership release is once and identity-guarded; the disconnect hook can no longer abort a released turn on either path.

4. Runtime tool durability + per-invocation identity (src/loop.ts) — ordinary registry tools emit per-invocation onTool call/result callbacks carrying the provider-NATIVE call id; the transport keys durable calls by invocation (tc_<turn>_i_<nativeId>), so repeated same-name invocations are distinct durable calls with their own args/results (previously: zero durable events; name-derived identity collapsed repeats). Failures record isError, never silent success.

5. Text block lifecycle durability (NEW src/provider/activity.ts + loop/turn-engine/transport) — the glued-narration fix: streamed text persists with block identity. createBlockTracker emits text.start/delta/end per assistant block; deltas forward bytes exactly (de+velop=develop, never whitespace injection); text.end carries the full streamed block text. The turn.chunk command/event gains optional additive block {id, phase, native?, text?} metadata (scalar delta always kept); legacy readers are unaffected. Multiple narration blocks in one turn stay distinct — a renderer can finally recover the boundaries the flat stream destroyed.

6. Claude CLI parser fidelity (src/provider/claude-cli.ts) — completed snapshots replace-or-complete the streamed block (no duplicated partial+full text; a cut stream gets exactly the missing tail), native tool_use ids preserved into invocationId, full results (no 160-char/first-line reduction), empty results emitted honestly.

7. Owned atomic finalization (finalizeOwned) — terminal event, projections, session token accounting, budget-stash write and ledger settle commit in ONE sink-connection transaction (Storage gains optional sync in-transaction hooks applyAccountingSync/stashPartialSync). Duplicate finalize is a no-op; a storage failure rolls back everything, leaves the attempt reserved for an idempotent retry, and the transport reports 503 FINALIZATION_PENDING — success is never reported for an uncommitted terminal. All three terminal paths route through it under an authority.

8. Drainable host tails — afterTurn may return a Promise: the POST never awaits it, but under an authority it registers as a tracked worker; the provider root run is itself tracked, so normal shutdown (drain) awaits real provider work AND host tails before releasing the control lock.

9. EventSink / Storage (additive) — passive constructors ({ passive: true } skips the boot sweep; recovery is authority-gated), handleInTransaction (caller ledger writes join the event commit; rollback discards the poisoned state cache), withTransaction (ledger writes on the sink's own connection — two connections to one file must never nest transactions), readSnapshot (one consistent state+events+lastSeq boundary), Storage.peekPartial/consumePartialExact/sync hooks.

Verification

• pnpm run check: tsc clean, 47 files / 275 passed / 5 skipped / 0 failed at head 4cb897c (49 new tests across classification matrix, admission race, authority groups on real disk SQLite, authority-transport integration over real HTTP, tool durability/identity, finalizeOwned atomicity, drainable tails, block lifecycle, claude parser fidelity).
• Key behaviors proven over real HTTP + real disk SQLite: concurrent same-session sends → one 200/one 409, single provider run, no phantom user row; provider 400 → envelope PROVIDER_BAD_REQUEST, no budget stash, session error; duplicate clientRequestId → 409 without re-execution; mid-turn Stop → ABORTED and session back to ready; second executor fails election; died owner → exactly one interruption terminal, re-recovery no-op; same-name double invocation → two distinct durable calls; duplicate finalize → no second terminal; budget stash commits inside the finalization transaction; afterTurn tail returns after the envelope and is awaited by drain; two-hop stream → distinct block ids with byte-exact per-block concatenation; claude fake-binary → no duplicate snapshot text, native ids preserved, empty results recorded, long results untruncated.
• Loop wall test updated to the corrected cause/message contract; no other existing test changed.

All planned work for this PR is in. Consumer pin (Lionidas) follows this PR's exact merged SHA — merge stays operator-owned.