fix(billing): let a slow ledger read finish instead of blocking execution at the singleflight default

[waleedlatif1]

Summary

• Execution admission goes through the usage-gate cache, which coalesces concurrent misses with coalesceLocally. That helper's default settle deadline is 30 s and exists to bound a hung producer. The gate's producer is a ledger sum over the payer's billing period; for a large organization that is millions of rows and, from a cold cache or under heavy I/O, legitimately takes longer than 30 s
• When the deadline fired, every caller coalesced on that key got CoalesceSettleTimeoutError, the preprocessing step could not determine limits and blocked the run ("Unable to determine usage limits. Execution blocked for security"), while the timed-out read kept running detached and the next caller started a second read of the same ledger alongside it
• The gate now passes its own settle deadline, USAGE_GATE_SETTLE_TIMEOUT_MS (120 s), above any statement ceiling the deployment applies: a slow read waits and finishes, the database's own statement timeout still ends a stuck one and that failure is reported as before, and only a connection that never answers is given up on by the gate
• No change to the cache policy: admissions cached for the TTL, refusals re-read, failed reads never cached, writes on the value the caller received

Type of Change

• Bug fix

Testing

• Two new tests: a ledger read that takes 45 s resolves instead of rejecting (fails on the previous default), and a read that never answers is rejected at the gate deadline and re-read fresh afterwards
• bun run lint, check:audits (47 audits), docs-manifest:check, type-check pass

Checklist

• Code follows project style guidelines
• Self-reviewed my changes
• Tests added/updated and passing
• No new warnings introduced
• I confirm that I have read and agree to the terms outlined in the Contributor License Agreement (CLA)

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1 Skipped Deployment

Project	Deployment	Actions	Updated
docs	Skipped		Sep 22, 2026 6:36pm UTC

[greptile-apps]

Confidence Score: 5/5

The PR appears safe to merge; the previous deadline and delay-helper findings are resolved, and no new actionable issue was found.

Summary

This PR prevents legitimate slow billing-ledger reads from being abandoned by the usage gate while ensuring that PostgreSQL terminates reads that exceed the configured ceiling.

• Adds a transaction-local 60-second statement timeout around billing-period ledger sums.
• Derives the usage-gate coalescing deadline from that database timeout with a 15-second margin.
• Tests slow, hung, and statement-bounded reads and updates affected provisioning fixtures.
• Moves the shared timeout constant into the billing constants module.

Diagram

sequenceDiagram
    participant Caller
    participant Gate as Usage gate
    participant Flight as Local singleflight
    participant DB as PostgreSQL

    Caller->>Gate: Check usage limits
    Gate->>Flight: Coalesce cache miss (75s deadline)
    Flight->>DB: Begin transaction
    Flight->>DB: "SET LOCAL statement_timeout = 60s"
    Flight->>DB: Sum billing-period ledger
    alt Query completes within 60s
        DB-->>Flight: Usage total
        Flight-->>Gate: Limit result
        Gate-->>Caller: Admission decision
    else Query exceeds 60s
        DB-->>Flight: Statement timeout error
        Flight-->>Gate: Read failure
        Gate-->>Caller: Fail closed
    else Connection never responds
        Flight-->>Gate: Coalescing timeout after 75s
        Gate-->>Caller: Read failure
    end

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_{Reviews (4) · Last reviewed commit: "fix(billing): keep the ledger statement ..."}

[cubic-dev-ai]

All reported issues were addressed across 2 files

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[waleedlatif1]

@greptile

[waleedlatif1]

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[cubic-dev-ai]

@cubic-dev-ai review this PR

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[cubic-dev-ai]

No issues found across 5 files

Confidence score: 5/5

• Automated review surfaced no issues in the provided summaries.
• No files require special attention.

_{Re-trigger cubic}

[waleedlatif1]

@greptile

[waleedlatif1]

@cubic-dev-ai review this PR

[cubic-dev-ai]

@cubic-dev-ai review this PR

@waleedlatif1 I have started the AI code review. It will take a few minutes to complete.

[waleedlatif1]

@greptile

[waleedlatif1]

@cubic-dev-ai review this PR

[cubic-dev-ai]

@cubic-dev-ai review this PR

@waleedlatif1 I have started the AI code review. It will take a few minutes to complete.

[cubic-dev-ai]

No issues found across 6 files

Confidence score: 5/5

• Automated review surfaced no issues in the provided summaries.
• No files require special attention.

_{Re-trigger cubic}