fix(codex): keep Cursor code-mode exec within tool budget

[Wibias]

Problem

#1830 reports a fresh Cursor-routed Codex child with no Responses-owned execution path in its advertised Cursor catalog. #1661/#1673 fixed a different failure: exec was present and then removed by Cursor's generic-tool filter. Current dev still preserves exec when it reaches that layer.

The missing path is earlier catalog projection. Routed Cursor rows use tool_mode = code_mode_only but uniquely advertise supports_search_tool = false. In current codex-rs that capability controls deferred tool exposure, not the hosted web-search sidecar. With deferral disabled, Code Mode folds the nested tool catalog into unified exec guidance. OpenCodex's existing measurement records exec.description growing from 16,965 to 175,849 chars (turn-1 payload ~97K to ~259K), while Cursor enforces a 120,000-byte serialized McpTools ceiling and intentionally drops an individually oversized exec and then its companion wait. That matches the bridge-less #1830 surface.

Fix

• enable Codex deferred tool exposure for Cursor routed rows in both template and template-less catalog paths
• keep tool_mode = code_mode_only
• continue omitting Cursor web_search_tool_type; hosted search remains disabled because Cursor runTurn bypasses that sidecar
• leave Cursor's 120 KB transport guard unchanged
• leave Cursor-native local execution fail-closed; bridge absence never becomes execution authority
• leave fix(cursor): preserve unified exec in generic tool filtering #1673/fix(cursor): pin unified exec so wait cannot ship alone #1583 execution-path preservation unchanged
• update the catalog architecture decision record

TDD / verification

• RED first on base b81314cd29b78fecb447df882dc4fc1a987434b9: the two new Cursor expectations failed exactly because both catalog paths returned supports_search_tool = false (Cross-platform CI run 31941919912, shard 2/4: 145 pass / 2 fail in that batch)
• production patch changes only the two catalog projection seams, the focused regression test, and the architecture note
• clean implementation head: e93078ca694dcfaadeb72819552a98274871fe6b
• fresh CI on the production head is the GREEN gate; no credential-dependent live Cursor smoke is claimed yet

Security / compatibility

This does not raise Cursor's measured transport ceiling, synthesize undeclared client tools, or enable Cursor-native fs/shell/fetch. It fixes the catalog metadata that causes Code Mode to over-expand exec before the existing transport budget is applied.

Refs #1830

Summary by CodeRabbit

• New Features

  • Cursor catalog entries now support deferred search-tool discovery in code mode.
  • Search capabilities are available for normalized entries and fallback results without exposing hosted web search.

• Bug Fixes

  • Corrected catalog metadata so Cursor entries consistently advertise supported search functionality while preserving existing hosted-search limitations.

• Documentation

  • Clarified tool discovery behavior and search availability across routed catalog entries.

• Tests

  • Expanded coverage for deferred discovery, search support, and template-less fallback results.

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• tests/catalog-cursor-search.test.ts

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📝 Walkthrough

Walkthrough

The PR enables deferred search-tool discovery for Cursor routed catalog entries and fallback rows. Cursor entries use tool_mode: "code_mode_only" and supports_search_tool: true, while hosted web-search metadata remains absent.

Changes

Cursor deferred search behavior

Layer / File(s)	Summary
Enable deferred search in routed catalogs src/codex/catalog/parsing.ts, src/codex/catalog/sync.ts, structure/03_catalog-and-subagents.md	Routed entries and fallback rows now enable deferred search-tool discovery for Cursor. Cursor continues to omit web_search_tool_type; non-Cursor routes retain "text_and_image". The documentation records the updated policy and existing execution constraints.
Update Cursor search expectations tests/catalog-cursor-search.test.ts	Normalization and template-less fallback tests now require tool_mode: "code_mode_only" and supports_search_tool: true. Both cases continue to exclude hosted web search.

Estimated code review effort: 2 (Simple) | ~10 minutes

Merge Risk: ⚪ Minimal · up to 44241

The change adjusts Cursor catalog projection to keep execution within the existing tool budget without changing native execution permissions or transport limits; no actionable merge-blocking risk remains after normal checks and review.

Possibly related PRs

• lidge-jun/opencodex#1596: Modifies the same routed catalog capability flags and related tests.
• lidge-jun/opencodex#1606: Covers the routed tool-discovery behavior implemented and documented here.
• lidge-jun/opencodex#1529: Modifies the same catalog normalization, fallback, and test behavior for routed search support.

Suggested labels: documentation

Suggested reviewers: lidge-jun

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly summarizes the main change: keeping Cursor code-mode execution within the tool budget.

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Inline comments:
In `@tests/catalog-cursor-search.test.ts`:
- Around line 7-8: Update the Cursor-entry normalization logic in the parsing
code so supports_search_tool is true for Cursor rows, while preserving deletion
of entry.web_search_tool_type to keep deferred discovery separate from hosted
web search. Locate the change via the isCursorEntry handling in the catalog
parsing logic.

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only still-valid issues, skip the rest with a brief reason, keep changes
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Inline comments:
In `@tests/catalog-cursor-search.test.ts`:
- Around line 5-9: Strengthen the test for normalizeRoutedCatalogEntry by
initializing the Cursor fixture with web_search_tool_type set to
"text_and_image" before normalization, while preserving the existing
toBeUndefined assertion to verify inherited hosted-search metadata is removed.

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• src/codex/catalog/parsing.ts
• src/codex/catalog/sync.ts
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• tests/catalog-cursor-search.test.ts

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