[JustYannicc]

Problem

History discovery can occupy SQLite's synchronous writer while scanning retained events and receipts. This moves bounds and page discovery onto the existing reader worker and paces scheduled maintenance, while keeping offline doctor compaction free of background duty-cycle sleeps.

Change

Discovery processes 50 rows at a time; writer deletes, retention rules, descending cursors, and initial scan bounds remain in the existing compactor. The background caller rests for nine times the elapsed slice after at least 25 ms of active work. One-row lookahead avoids a terminal rest. Offline doctor uses the same operation without the pacing callback and retains its exclusive database lock.

Scope and approval

This continues @JustYannicc's contribution in #20877, preserving the author's commits and adding maintainer changes. The takeover removes shared pacing from the compactor because it also delayed offline repairs.

Maintainer direction and scope: Julius’s implementation takeover and his confirmation of reader discovery and background pacing scope. The broader issue remains open; this scope confirmation does not authorize merging.

Verification

Verification: the measured integrated head 2cc6fd9e69 includes the contributor’s concurrent main update and main through 08b1cbebf2. All seven compaction files are identical to the measured head c36020967f.

• Tests compared with the contributor head: 49 → 49 cases across 3 → 2 files. Replaced the standalone PR suite with two cases in FoundationPersistence and extended the existing offline-doctor case. Reader-routing and pacing mutations fail assertions; the pre-fix offline case records an unwanted 270 ms rest. All 49 now pass, plus 3 DatabaseStorage cases and 2 existing replay/caller cases: 54 focused tests initially; all 149 tests across the five affected suites also pass after integrating main.
• Scoped server typecheck, lint, formatting, and diff checks pass.
• Real isolated Linux app: scheduled maintenance removed 100,000 synthetic legacy receipts. All 450 authenticated shell HTTP requests succeeded; 113 fell within the observed removal window (p95 14 ms, max 18.3 ms). A separate post-compaction WebSocket check returned 80/80 pongs. These measurements use the real app/server at the measured head with a synthetic receipt workload; compaction sources are unchanged at the integrated head.
• Actual offline doctor on a stopped copy removed the receipts and shrank 18.3 MiB to 760 KiB; whole CLI wall time was 7.184 seconds. A second run with another connection open correctly refused repair with DatabaseInUseError.

Labeled workload, measurements, before/after tests, and verification limits.

This is a partial improvement related to #20203; it does not close that issue. A single synchronous DELETE, reader fallback, or checkpoint can still block. The live run did not simulate a busy disk or large JSON event payloads, and WebSocket pings were measured after compaction. Retention/replay and foreground writes during rests are covered by integration tests. macOS, Windows, Electron, iOS, Android, and relay/tunnel performance remain unverified. No visual behavior changed, so the proof is nonvisual.

Current verified head c2cd831294 includes main through 8f66e67de3. The merge preserves main's test pruning while keeping this PR's reader/writer routing, scheduled pacing, retention across pauses, fixed scan bounds, and completion-timestamp regression coverage. Both paused-reader cases still insert an event or receipt after bounds discovery and assert that its exact ID survives. Production compaction, scheduled storage, and the offline-doctor caller are unchanged from the preceding PR head.

Independent verification on c2cd831 passed all 44 tests across FoundationPersistence, DatabaseStorage, and DatabaseMaintenance, plus scoped server typecheck, targeted lint, formatting, and diff checks. Lint retains two unchanged upstream polling warnings. Two independent source-review axes returned no findings on an equivalent local merge; the two resolved test files differ only in import order, and the other six PR files are identical. The concurrent remote resolution was retained without pushing the duplicate local merge. Current-head CI remains separate evidence in the checks tab. Earlier test counts apply to their named revisions; the earlier live workload measurements predate main's SQLite checkpoint and locking changes. The earlier shared SQLite run passed 57 cases and failed one unchanged ArrayBuffer-binding case on Node 24.18; that suite was not rerun for this merge.

Earlier independent full-PR reviews: Sol and Opus each completed three full-diff rounds; neither found code blockers. The last round covered all seven compaction files plus the equivalent local fixture repair. The final main merge only selected main’s fixture value, leaving all seven reviewed files byte-identical; the parent checked that integration and confirmed the author’s concurrent resolution is byte-identical to the verified local merge.

Implementation: GPT-6.1 Sol; tests: GPT-6 Astra; reviews: Claude Opus 5.5 and GPT-6 Sol. Harnesses: Codex and Claude Code through T3 Code.

[macroscopeapp]

Approvability

Verdict: Approved at b523f2d

Macroscope's review found this PR approvable — This is a narrowly scoped maintenance fix that moves expensive history discovery off the SQLite writer and paces existing compaction work without changing retention rules, schemas, APIs, or product defaults. The accompanying tests directly cover connection routing, pacing, and state preservation.

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• apps/server/src/orchestration-v2/FoundationPersistence.test.ts
• apps/server/src/orchestration-v2/runtimeLayer.test.ts
• apps/server/src/persistence/DatabaseStorage.test.ts
• apps/server/src/ws.test.ts

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📝 Walkthrough

Event-store compaction now uses read-only discovery, bounded pages, and lookahead rows. DatabaseStorage supplies time-based pauses between pages. Tests cover query routing, deletion results, retained records, pacing, concurrent writes, and completion timing.

Changes: Event-store compaction

Layer / File(s)	Summary
Read-only discovery and bounded paging apps/server/src/orchestration-v2/ProjectionMaintenance.ts	compactEventStore accepts an optional between-pages effect. Event and receipt discovery use read-only queries and lookahead rows to identify remaining pages. Error mapping occurs inside the compaction effect.
Scheduled compaction pacing and wiring apps/server/src/persistence/DatabaseStorage.ts, apps/server/src/persistence/DatabaseMaintenance.ts, apps/server/src/persistence/DatabaseMaintenance.test.ts, apps/server/src/persistence/DatabaseStorage.test.ts	DatabaseStorage checks elapsed slice time and sleeps for nine times the elapsed duration after 25 ms. DatabaseMaintenance invokes the compaction function. Tests validate pacing, deletion counts, and completion timestamp timing.
Compaction integration and call-site validation apps/server/src/orchestration-v2/FoundationPersistence.test.ts, apps/server/src/orchestration-v2/runtimeLayer.test.ts, apps/server/src/ws.test.ts	Integration tests validate reader and writer separation, bounded scans, concurrent writes, retained records, and updated compaction invocations.

Priority: ⬆️ High

Estimated code review effort: 3 (Moderate) | ~25 minutes

Change: Bug fix

Sequence Diagram(s)

sequenceDiagram
  participant DatabaseStorage
  participant compactEventStore
  participant ReadOnlySQLiteClient
  participant WriterSQLiteClient
  participant Clock
  DatabaseStorage->>compactEventStore: supply between-pages callback
  compactEventStore->>ReadOnlySQLiteClient: discover bounded event and receipt pages
  compactEventStore->>WriterSQLiteClient: delete discovered records
  compactEventStore->>DatabaseStorage: invoke callback when pages remain
  DatabaseStorage->>Clock: check elapsed time
  DatabaseStorage->>Clock: sleep after an over-budget page

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Suggested reviewers: juliusmarminge

Merge Risk: ⚪ Minimal · up to c2cd8

No actionable issue remains in the reviewed compaction changes; they appear ready to merge after normal checks.

Security architecture risk: 🔵 Low · up to c2cd8

The change stays within the existing local database boundary and retains offline repair protections. No new external access or privileges were identified. Residual uncertainty concerns concurrency and interruption behavior, which was assessed from source rather than executed.

Retained concerns
No architecture-level concerns identified.

Security review details

Security Blast Radius

• inferred — The reviewed authority is limited to history and receipt deletion in the configured server database, plus offline maintenance of the locally selected database. The pacing callback is supplied by internal code; it does not introduce client-selected SQL, credentials, or a new remote maintenance capability.

Security Findings and Attack Paths

• observed — Receipt discovery and deletion are not atomic, but that arrangement predates this PR: both base and head discover through the reader, yield, then delete by command ID. The new pacing occurs after the page deletion, not inside that interval. This does not establish an introduced stale-receipt attack path.

Trust Boundaries and Controls

• observed — Database storage exposes reclaim and status, while compaction remains a private scheduled operation using the orchestration maintenance service. Offline compaction keeps its separate exclusive-lock control. The signature change does not itself add a caller with greater authority.

Resilience and Maintainability Implications

• inferred — The implementation does not hold a compaction transaction across pacing. If interrupted after some deletes, those deletes can remain committed, but completion is not recorded before successful return. A later invocation starts with fresh bounds and retention state; failure containment therefore remains page-based rather than all-or-nothing.

Pre-merge checks: 4

Check name	Status	Explanation
Title check		The title clearly and concisely describes the primary changes: moving history discovery off the SQLite writer and pacing compaction.
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.
Description check		The pull request description includes all required sections: Problem, Change, Scope and approval, and Verification. It explains the affected behavior, implementation scope, maintainer approval, focuse…

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Explanation

The pull request description includes all required sections: Problem, Change, Scope and approval, and Verification. It explains the affected behavior, implementation scope, maintainer approval, focused tests, live checks, limitations, and agent details.

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Actionable comments posted: 1

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• 🪄 Fix comments: Fix CodeRabbit comments on this PR

🤖 Prompt to fix review comments

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Inline comments:
Review comments at @apps/server/src/orchestration-v2/ProjectionMaintenance.ts:
- Line 403: Update the terminal receipt pagination loop to fetch one extra row
and use the first COMPACTION_PAGE_SIZE rows for processing and advancing
throughReceiptRowId. Treat the extra row as evidence of another page: break
without pausing when none exists, and keep yield* pause for nonterminal pages.
Update the pause-count assertion to match.

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[JustYannicc]

[from Codex]: The Linked Issues warning evaluates the full scope of #20203. This PR addresses discovery-side blocking only, as stated in Scope and approval, and does not close that issue. Synchronous DELETEs, reader fallback, and the writer checkpoint path remain explicit limitations. Keeping those separate follows CONTRIBUTING.md's one-problem rule.

[juliusmarminge]

Taking over this one as maintainer for batch usage-billing-05. I will preserve the contributor commits, verify reader routing and retention behavior, and keep background pacing from slowing offline doctor compaction. Thanks @JustYannicc for the reproduction and worker-routing fix. This batch will not merge the PR.

[JustYannicc]

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