fix(cursor): budget buffered textual tool calls to prevent pre-finalization memory growth

[luvs01]

Motivation

• Close a memory-accounting hole where complete textual [TOOL_CALL]... markers were retained in bufferedTextToolCalls without charging the translator budget, allowing an upstream Cursor provider to accumulate many large argument strings before finalizeTurnEvents enforced limits.

Description

• Immediately budget complete textual fallbacks when parsed by mapCursorProtobufServerMessage by opening a synthetic call id, reserving transient tool_args bytes, and committing the reservation before pushing into bufferedTextToolCalls (see src/adapters/cursor/protobuf-events.ts).
• Ensure buffered fallback charges are released whenever a real client-tool frame wins or when buffered calls are dropped by adding discardBufferedTextToolCalls and closing the synthetic call leases in recordRealToolCall, the synthetic exec path, and finalizeTurnEvents.
• Update the buffered structure to track a callId per retained entry so reservations map to the normal translator accounting, and adjust promotion to use the retained callId during recordToolCall/commitToolCall paths.
• Add a regression test that asserts oversized fallback arguments are rejected immediately and that charges are released when a real tool frame supersedes the fallback, and update structure/providers/cursor.md to document the budget behavior.

Testing

• Ran the focused Cursor suite with bun test tests/providers/cursor/cursor-protobuf-events.test.ts, which passed 63/63 tests after the change.
• Ran bun run typecheck, bun run structure:check, and bun run privacy:scan, all of which completed successfully for the modified code.
• The full repository bun run test was exercised but encountered existing, unrelated environment/concurrency failures in other suites; the focused Cursor coverage and privacy/type checks that verify this change passed.

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[chatgpt-codex-connector]

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-09-20T06:20:26.500263Z	755d50b	PR opened

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[github-actions]

✅ Deterministic PR hygiene checks passed.

[devin-ai-integration]

✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no bugs or issues to report.

[luvs01]

Consolidated into lidge-jun#5533 as a single related-function aggregate.

Source head: 755d50b139f7ecda576e0ce5617ac8b29a419418. Replacement head: 799ebc5d5d6a8c75eeb99f358db5c64906117584.

Source and carried commit 799ebc5 have identical stable Git patch IDs; original author and cherry-pick provenance are retained. Combined-head focused tests: 141 passed / 648 assertions, plus typecheck, structure and file-size checks. POSIX branches, full suite and hosted cross-platform CI remain unverified. Maintainer-owned lidge-jun#5507 is independent and was not changed or placed into a dependent chain.

Closing this duplicate standalone review entry at the author's request after verifying migration. This is not a merge or release claim; remaining integration checks and reviews are tracked on the draft replacement. Original branches are retained.