[Regression]: Cursor subagents still receive no Responses exec bridge in v2.22.0 #1830

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1. coderabbitai commented on Aug 16, 2026

   

   coderabbitaibot

   on Aug 16, 2026 – with coderabbitai

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   ⚠️ Possible Duplicate Issue(s)

   • [Bug]: Cursor subagents drop Codex Desktop unified exec bridge #1661

   🔗 Related PRs

   #321 - docs(cursor): document exec policy and catalog troubleshooting [merged]
   #402 - fix(cursor): stop false shell blocked reports and cmd/command mismatch (#399) [merged]
   #1529 - fix(codex): keep direct MCP tools visible for routed models [merged]
   #1673 - fix(cursor): preserve unified exec in generic tool filtering [open]
   #1801 - fix(cursor): teach code-mode nested-helper contract in tool guidance [open]

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2. github-actions

   added

   bugSomething isn't workingSomething isn't working

   toolstool_calls, MCP, web-search / sidecar toolstool_calls, MCP, web-search / sidecar tools

   on Aug 16, 2026
3. Wibias commented on Aug 16, 2026

   

   Wibias

   on Aug 16, 2026 – with ChatGPT Codex Connector

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   Follow-up after reviewing #1661/#1673 and the current Cursor path: #1661's original defect is fixed. That bug was specifically exec being present in the parsed client catalog and then being removed by Cursor's second-stage generic-tool filter; #1673 corrected that filter and current dev still preserves a Responses-owned execution-path tool when one reaches the Cursor adapter.

   #1830 is a separate successor bug: the fresh Cursor child ends up with no Responses execution path in the advertised Cursor catalog, so #1673 has nothing to preserve. The later v2.18.2/v2.19.0/v2.22.0 reproductions should therefore be tracked here rather than treated as a regression of the #1673 filter itself.

   Current investigation is focused on where exec disappears before Cursor registration. The leading OpenCodex-local hypothesis is the interaction between Cursor's tool_mode = code_mode_only, supports_search_tool = false, and Cursor's exact 120,000-byte McpTools limit: current source comments/tests already document that disabling deferred discovery under Code Mode can inflate exec.description dramatically, and the Cursor budget intentionally drops an individually oversized exec and then drops wait with it. That would closely match the #1830 surface where small tools survive but exec/wait do not.

   I would not use the previously suggested bridge-less native-exec fallback as the fix: absence of a client bridge is not an authorization signal, and enabling Cursor-native fs/shell/fetch on that basis would weaken the existing server-local policy boundary. The safer fix should keep the Responses-owned execution path within Cursor's transport budget.
4. Wibias commented on Aug 16, 2026

   

   Wibias

   on Aug 16, 2026 – with ChatGPT Codex Connector

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   Draft fix is now in #1832.

   The patch addresses the catalog-projection seam rather than weakening Cursor execution policy: Cursor routed rows keep tool_mode = code_mode_only and now advertise Codex deferred tool exposure (supports_search_tool = true) in both template and template-less paths, while web_search_tool_type remains absent so Cursor still does not opt into the hosted-search sidecar.

   TDD was RED first: on current dev, the two focused Cursor catalog assertions failed exactly because both paths returned supports_search_tool = false. The production patch is now on clean head e93078ca694dcfaadeb72819552a98274871fe6b; React Doctor and typecheck are already green, with the full Cross-platform suite still running.

   The existing 120 KB Cursor tool-catalog limit, #1673/#1583 execution-path preservation, and fail-closed Cursor-native local-exec policy are unchanged. A credential-dependent live Cursor child re-probe is still desirable before treating the issue as fully closed.
5. lidge-jun commented on Aug 16, 2026

   

   lidge-jun

   on Aug 16, 2026

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   Fixed on dev by #1832 (merged as 0313716c2).

   Cursor routed catalog rows now enable deferred code-mode tool discovery (supports_search_tool: true) on both the template path and the template-less fallback. They still omit hosted web-search metadata, because the runTurn transport bypasses that separate sidecar — the two bits were being conflated, and turning the discovery bit off was what pushed the nested MCP catalog into exec.description.

   That inflation is the mechanism behind your symptom: once the whole catalog is inlined into one tool's description, the advertised catalog can exceed Cursor's 120KB serialized limit, and what gets trimmed is exactly the Responses execution bridge the child needed.

   Evidence added alongside the fix, measured on the real protobuf serializer rather than inferred from the flag:

   • a deferred catalog serializes inside CURSOR_TOOL_BYTES_LIMIT and keeps both exec and wait; the same two tools exceed the cap once the nested catalog is inlined into exec.description;
   • when the budget must trim, exec and wait are what survive, and the trimmed result fits — which is the direct inverse of the catalog you observed.

   One caveat worth stating plainly. This closes the mechanism we can prove from the code and the wire budget. Your report was from a fresh Cursor-routed child on Windows, and I have not reproduced that exact live child here. If a fresh cursor/grok-4.6 subagent still comes up with no Responses execution tool in its advertised catalog after this ships, please reopen with the observed catalog — that would point somewhere other than the byte budget, and I would rather reopen than have you work around it.

   Closing as completed. The change is on dev and ships with the next release; it is not in a published version yet.
6. lidge-jun

   closed this as completedon Aug 16, 2026
7. agentHits

   added a commit that references this issue on Sep 17, 2026

   test(cursor): prove the wire-budget consequence behind the search flag

   ...

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