fix(responses): fail closed when a routed provider calls an undeclared tool - #1788
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…d tool The bridged paths already refuse a tool call the request never declared — `declaredToolNames` in src/bridge.ts turns it into a 502 naming the tool. The native Responses passthrough had no equivalent, so the same call was relayed verbatim. Codex then received a top-level `function_call(name=apply_patch)` for which it has no handler: under code mode `apply_patch` exists only as a nested `tools.apply_patch(...)` helper declared inside the `exec` description, never as a wire tool. The turn surfaced as a bare `aborted` with the target file unchanged, no `custom_tool_call_output`, and no error anywhere to explain it. Ground truth for the guard is the OUTBOUND body rather than the parsed internal tool list. The passthrough forwards wire shapes the internal list flattens or renames — namespaced MCP groups, `additional_tools` items carried inside `input`, the routed custom-tool rewrite — so only the wire names can be compared against what the provider echoes back. Namespaced tools are accepted under either coordinate system, since Codex routes MCP calls by an explicit `namespace` field. Scope: - Only client-executed items are checked (`function_call`, `custom_tool_call`). Hosted calls are run upstream or carry no name. - Forward auth is the canonical ChatGPT backend speaking Codex's own protocol rather than a routed provider, so it stays unguarded — the same line the routed custom-tool and image-gen rewrites already draw. - An unreadable or empty catalog disables the guard rather than failing every turn. - Both the streaming relay and the bounded-JSON answer are covered. Fixes lidge-jun#1700
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📝 WalkthroughWalkthroughThe Responses passthrough now collects declared tool names and rejects undeclared client-executed calls in streaming and non-streaming responses. SSE violations produce ChangesResponses tool declaration validation
Estimated code review effort: 4 (Complex) | ~45 minutes Sequence Diagram(s)sequenceDiagram
participant Client
participant ResponsesPipeline
participant ToolGuard
participant Upstream
Client->>ResponsesPipeline: submit Responses request
ResponsesPipeline->>ToolGuard: collect declared wire tool names
ResponsesPipeline->>Upstream: forward serialized request
Upstream-->>ResponsesPipeline: return SSE or JSON response
ResponsesPipeline->>ToolGuard: validate function_call or custom_tool_call
ToolGuard-->>ResponsesPipeline: pass response or undeclared-tool failure
ResponsesPipeline-->>Client: return response data, response.failed, or HTTP 502
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Actionable comments posted: 3
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Inline comments:
In `@src/server/responses/core.ts`:
- Around line 2895-2907: Move the rememberPassthroughResponse cache write to
after the undeclared-tool validation in the response handling flow, so rejected
responses are never stored. Preserve the existing cached raw upstream JSON
representation for any subsequent repair logic, and keep the 502 return behavior
for undeclared tool calls unchanged.
- Around line 2695-2699: The undeclared-tool guard currently affects only the
client relay while the inspection tee can still record response.completed.
Update the shared stream flow around createUndeclaredToolCallGuardBlockRewrite,
the stream split, and rememberPassthroughResponse so inspection consumes the
validated outcome before persistence/accounting, ensuring a rejected stream
cannot enter continuation state; add a regression covering an undeclared
streamed call followed by completion.
- Around line 2285-2294: In src/server/responses/core.ts lines 2285-2294, update
the outbound request parsing and undeclared-tool guard to preserve whether the
body was readable separately from the declared tool-name set, and enforce
rejection for readable requests whose catalog is empty, including no tools and
tools: []; keep unreadable-body handling distinct. In
tests/responses-undeclared-tool-guard.test.ts lines 98-101, add streaming and
JSON coverage for requests with no tools and with tools: [].
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src/server/responses-undeclared-tool-guard.tssrc/server/responses/core.tstests/responses-custom-tool-repair.test.tstests/responses-undeclared-tool-guard.test.ts
… turns out of replay
Three review findings on the undeclared-tool guard.
An empty catalog is not an absent one. Disabling the guard whenever the declared
set was empty meant a request that declares no tools authorized every
client-executed call the provider cared to invent. Readability is the real
question, so the parse result and the name set are now separate state: an
unparseable body still stands down, a readable one enforces even at zero tools.
The outbound body alone turned out to be an incomplete record of the caller's
catalog. Hosted-tool preference REPLACES a client tool with its hosted form, so
a request declaring `image_gen.generate` ships `{type:"image_generation"}`
upstream and gets the client's own name back — which the guard would have
refused. The declared set is now the union of the outbound wire names and the
caller's own catalog. Widening only ever makes the guard fire less; a name
declared in neither place is still refused.
A refused turn must also not become continuation state. The passthrough records
completed responses so a later `previous_response_id` can expand from them, and
that write sat before the guard on the JSON path and on the untouched upstream
stream the inspection branch reads. Both now go through a wrapper that drops a
response carrying an undeclared call, and the JSON path records only after the
guard passes. The wrapper inspects the payload rather than sharing a flag with
the client relay, so tee ordering cannot race it.
Terminal-outcome recording still reports what upstream did: the request was
served and the tokens were spent, so quota and host health should account for
it even though the client received a failure.
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Thanks — all three were real. Pushed 1. Empty catalog vs unreadable catalog. You are right, and my original comment even said the wrong thing out loud: I wrote "an empty catalog disables the guard" and justified it with "a request whose tools this proxy could not read". Those are two different conditions and I collapsed them. A request that declares no tools authorizes none, so every client-executed call it gets back is undeclared. Readability and the name set are now separate state — an unparseable body still stands down, a readable one enforces even at zero tools. Covered for 2 and 3. Refused turns entering continuation state. Both correct, and the second is worse than I had it. My description called the inspection-tee divergence a "known limitation" and reasoned about it only as accounting. That was too narrow — Both writes now go through a wrapper that drops a response carrying an undeclared call, and the JSON path records only after the guard passes. I checked the payload inside the wrapper rather than sharing a trip flag with the client relay, because the inspection branch can run ahead of the client's pull — a flag would have been racy in exactly the case that matters. Regression is in One thing your fix surfaced that neither of us had. Making the empty catalog enforce broke One I did not apply. Terminal-outcome recording still reports what upstream did. The request was served and the tokens were spent, so quota and upstream-host health should account for it even though the client received a failure. Persisting the response was the actual defect and that is fixed; suppressing the accounting would make a real spend invisible. Happy to change it if the maintainers prefer the two to agree. Verification: |
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A note on the review-readiness checklist, since this PR is sitting at 0/4 and I would rather explain why than leave it looking abandoned. I have not ticked "All CI tests are green on my local testing", because on my Windows machine it is not true and I do not want to attest to something the gate cannot check. What I could do instead was run every test file in 16 batches of 50 through While chasing why those 164 exist I found the cause, and it is not this PR's business: So: boxes 2 and 4 I can tick honestly whenever you want them ticked, box 3 once CodeRabbit re-reviews the fixes I pushed in Separately, |
CI caught this: `c994d47e6` made the guard enforce on a readable request with an
empty tool catalog, and that broke six passthrough tests on macOS and three of
four test shards.
The reasoning behind that change sounded right in the abstract — a request that
declares no tools authorizes none — but it is wrong for the passthrough, and the
repository already had a test saying so. `github-copilot-stream-contract` sends
`{model, input, stream}` with no `tools` field at all, and Copilot answers with a
`custom_tool_call` for `apply_patch`. The client understands that call; the proxy
simply has no catalog to check it against. Enforcing there replaced the turn with
`response.failed` and the client never saw `response.completed`.
The same shape broke the DeepSeek terminal-repair and item-id-repair contracts.
So the activation condition goes back to "at least one declared name". An
unreadable body lands in the same place, since it also yields no names, which is
what the readable/empty distinction was reaching for.
Kept from that commit: the union with the caller's own catalog (hosted-tool
preference rewrites the outbound body, so it is not a complete record), and
keeping a refused turn out of `previous_response_id` replay state.
The empty-catalog cases in the guard's own test file asserted the behaviour this
reverts; they now pin the opposite, on both transports, with the Copilot contract
named as the reason.
Verified: github-copilot-stream-contract, deepseek-inbound-wire,
deepseek-responses-item-id-repair, responses-undeclared-tool-guard and
responses-custom-tool-repair all pass; `bun run typecheck` clean.
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CI caught a regression I introduced in What broke. One of the three review findings was that an empty tool catalog should still be enforced — a request that declares no tools authorizes none, so any client-executed call coming back is undeclared. That is a clean argument and I accepted it. It is also wrong for the passthrough, and this repository already had a test saying so.
So the activation condition is back to "at least one declared name". An unreadable body lands in the same place, since it also yields no names, which is what the readable-vs-empty distinction was reaching for. My mistake, and it is worth naming precisely. After changing the activation rule I only re-ran the suites adjacent to the change — the passthrough and rewrite files — and they were green. The tests that disprove the new rule live in provider-contract files I had no reason to associate with a tool-catalog condition. A broader run before pushing would have caught it, and CI is the only reason it did not reach a reviewer as a silent behaviour change. Kept from that commit, since both stand up: the union with the caller's own catalog (hosted-tool preference rewrites the outbound body, so it is not a complete record of what the caller declared), and keeping a refused turn out of The empty-catalog cases in the guard's own test file asserted the behaviour this reverts. They now pin the opposite on both transports, with the Copilot contract named as the reason, so this cannot be re-argued into the code without the counter-example showing up. Verified locally: |
Checking only the terminal snapshot left a hole. An upstream can announce the undeclared call in `response.output_item.added` — which trips the client guard and sends `response.failed` — and then close with a `response.completed` whose `output` is empty. The terminal check then sees nothing undeclared and the refused turn enters `previous_response_id` replay state anyway. Rejection is now sticky for the whole turn, set from every parsed payload on the inspection side rather than derived from the terminal snapshot. That required a seam: `SseInspectorHandlers` had no per-payload callback, so the flag could never have been set. `onParsedPayload` is added there, invoked in `scanPayload` before any terminal classification, and carried on `InspectionConsumerOptions` so both `consumeForInspection` and `consumeForResponseLogMetadata` wire it — adding it to the handler type alone would have left the tee path silently inert. The flag is gated on `undeclaredToolGuardActive`, the same condition as the guard. Without that gate a no-catalog or forward-auth stream would mark every call undeclared and stop recording continuation state for exactly the passthrough traffic the guard deliberately stands down for. Regression: a stream whose only undeclared item is in `output_item.added` and whose terminal `output` is empty must give the client `response.failed` and leave nothing for a follow-up to inherit. Driven red against the unfixed flag before landing.
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💡 Codex Review
Require the namespace for bare MCP tool names
When the request declares only a namespaced MCP tool such as linear/create_issue, this unconditional insertion also marks the bare create_issue name as declared. An upstream function_call containing only name: "create_issue" and no namespace therefore passes the guard, even though Codex routes MCP calls using the explicit namespace and will receive an unrouteable top-level call—the same silent-abort failure this change is intended to prevent. For namespace entries, retain only the flattened name; the existing namespace-aware check already accepts the valid {name: "create_issue", namespace: "linear"} form.
AGENTS.md reference: src/AGENTS.md:L10-L11
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Summary
Closes #1700.
The bridged paths already refuse a tool call the request never declared:
declaredToolNamesinsrc/bridge.tsturns it into a 502 that names the tool. The native Responses passthrough had no equivalent, so the same call was relayed to the client verbatim.Codex then received a top-level
function_call(name=apply_patch)it has no handler for. Under code modeapply_patchexists only as a nestedtools.apply_patch(...)helper declared inside theexecdescription, never as a wire tool — which is exactly why the reporter's request-visible catalog heldexec,wait, andrequest_user_inputand nothing else. The turn surfaced as a bareaborted: file unchanged, nocustom_tool_call_output, HTTP 200 upstream, and no error anywhere to explain it.This adds the missing guard to the passthrough. When a routed provider names a tool the request did not declare, the offending event is replaced with an explicit
response.failedcarryingcode: "undeclared_tool_call"and the same message the bridged paths use, and the rest of the turn is dropped so a laterresponse.completedcannot contradict the terminal already sent.This is a gap against an existing decision, not a new policy
The Responses decision log in
structure/04_transports-and-sidecars.mdalready settles this question. It records the alternatives that were rejected — prompt guidance alone, and auto-translating an undeclaredapply_patchinto Code Mode — and the one that was chosen:and states the resulting property as:
That property held on the bridged paths and not on the passthrough, which is the gap #1700 fell through. The change here makes the passthrough match the documented invariant rather than introduce a different one, so
structure/needs no correction — it simply becomes true.The log's adjusted-boundary line is about restoration, and stays intact: a native
apply_patchis still never restored into acustom_tool_call. When the request declares it, it passes through in its upstream form exactly as before; the guard only refuses names the catalog never carried.Why the outbound body is the source of truth
The guard reads the body that actually goes upstream rather than the parsed internal tool list. The passthrough forwards wire shapes that the internal list flattens or renames — namespaced MCP groups,
additional_toolsitems carried insideinput, the routed custom-tool rewrite — so only the wire names can be compared against what the provider echoes back. Namespaced tools are accepted under either coordinate system, since Codex routes MCP calls by an explicitnamespacefield rather than by parsing the name.Scope
function_callandcustom_tool_call. Hosted calls (web_search_call,image_generation_call,local_shell_call,tool_search_call) run upstream or carry no tool name.authMode: "forward"stays unguarded. That is the canonical ChatGPT backend speaking Codex's own protocol, not a routed provider — the same line the routed custom-tool and image-gen rewrites already draw a few lines above.stream: falseis not a way around it.One existing expectation changed
tests/responses-custom-tool-repair.test.tshas a policy matrix pinning that routed custom calls are not restored when request policy excludes them. Three of its four cases are unaffected — the tool is in the outbound body, so the guard never fires and the call is still relayed unrestored.The fourth case ("custom-looking metadata without a declared tool") declares only
ordinaryand has upstream callexec, where a{type: "custom", name: "exec"}shape sits inmetadata. That is an undeclared tool by any reading, so it is now refused instead of relayed. The original contract still holds either way: the call never becomes acustom_tool_call. I updated that one case and left the other three untouched.Worth noting the guard is deliberately narrower than
tool_choice: it asks only whether the name was sent upstream, not whether request policy currently authorizes it. That is why the threetool_choicecases are unaffected, and it keeps the guard from second-guessing a policy the restoration path already enforces.A refused turn does not become continuation state
The passthrough records completed responses so a later
previous_response_idcan expand from them. A refused turn must not be one of those, or the undeclared call comes back as history in the next request. Both write sites — the JSON path and the untouched upstream stream the inspection branch reads — go through a wrapper that drops a response carrying an undeclared call, and the JSON path records only after the guard passes.The wrapper inspects the payload rather than sharing a trip flag with the client relay, because the inspection branch can run ahead of the client's pull and a flag would be racy in exactly the case that matters.
Terminal-outcome recording still reports what upstream did. The request was served and the tokens were spent, so quota and upstream-host health should account for it even though the client received a failure. Say the word if you would rather the two agree.
Why the declared set is a union
The outbound body is not a complete record of the caller's catalog: hosted-tool preference replaces a client tool with its hosted form, so a request declaring
image_gen.generateships{type: "image_generation"}upstream and gets the client's own name back. The declared set is therefore the union of the outbound wire names and the caller's own catalog. Widening only ever makes the guard fire less, and a name declared in neither place — #1700'sapply_patch— is still refused.Readability, not size, decides whether the catalog is authoritative. A request that declares no tools authorizes none, so it enforces; only a body this proxy could not parse stands the guard down.
Verification
All run on Windows against
devat4b950101a:bun run typecheck— clean.bun test tests/responses-undeclared-tool-guard.test.ts— 26 pass, 0 fail (new file).bun test tests/responses-custom-tool-repair.test.ts tests/openai-responses-passthrough.test.ts tests/sse-payload-rewrite.test.ts tests/github-copilot-sse-rewrite.test.ts— 113 pass, 0 fail.bun run privacy:scan— passed.On the full suite I would rather give you the real picture than a green tick, because
bun run testdoes not complete on my Windows machine: Bun 1.3.14 panics partway through withpanic(main thread): index out of bounds: index 0, len 0. It does that on a cleandevcheckout too, so it is not this PR.I know from
devlog/_plan/260815_roadmap_closeout/110_release_readiness.mdthat the same command is 0 fail across 789 files on the Linux validation host at this exact commit, with CI green on all three platforms — so what follows is my environment, not the repository's state. I am reporting it rather than hiding it because a bare tick from a machine that cannot run the command would not mean anything.To get a comparable answer I ran every test file in 16 batches of 50 through
bun scripts/test.ts <files>— the same wrapper, so stillbun test --isolatewith the sandboxed home, just chunked so one panic cannot truncate the rest. Twice, identical batching, nothing else running: once ondevat4b950101awith a clean tree, once on this branch.devcleanThe two failing sets are identical —
commin both directions is empty — so this branch adds no failure and fixes none. That is the claim I can actually support.The 164 are Codex-home, catalog, SQLite, and filesystem tests (
codex-inject-*,codex-catalog-*,Codex SQLite home resolution, and similar); none touch the Responses path. They are not the cross-fileOPENCODEX_HOMEbleed from devlog 110 either — I checked after reading it:bun test tests/codex-inject-integration.test.tsalone gives 7 pass / 16 fail, andbun test --isolateon that one file gives exactly the same, withrunInject's child process returningsuccess: false. Something about spawning that helper is broken on my box.The clean-
devrun also hit one extra unnamed failure this branch did not: an unhandledCannot find package 'react'from the dashboard workspace, whosenode_modulesI have not installed.The Responses-path suites — the ones this change could plausibly break — are green here, and they are listed above.
New coverage in
tests/responses-undeclared-tool-guard.test.ts. Three cases go end to end throughhandleResponseswith the report's own setup — a model pinned to theopenai-responsesadapter and a catalog ofexec,wait,request_user_input:apply_patchbecomes a named failure and the client never seesresponse.completed;execcall still completes normally and comes back restored, so the supportedexec -> tools.apply_patch(...)editing path in the report is unaffected.Continuation state has its own pair, with a control so the negative cannot pass vacuously: an accepted turn is asserted to expand on a follow-up naming its
previous_response_id, and a refused turn is asserted not to.A readable request that declares nothing is covered on both transports, for
toolsabsent and fortools: [].The rest are unit-level:
apply_patchinresponse.output_item.addedbecomesresponse.failedplus[DONE], and the followingresponse.completedis dropped;response.completed;apply_patchis never blocked, including thecustom_tool_callshape it comes back as;namespacefield is accepted;[DONE], and unparseable payloads pass through untouched;Checklist
src/server/responses/core.tsand the one policy-matrix case described above.docs-site/to correct.bun run privacy:scanpasses.Review readiness checklist
This PR stays in draft until every box below is ticked. Tick all four boxes once the requirements are met:
All CI tests are green on my local testing.
I pushed my PR to the latest dev commit.
I resolved all correct Codex and CodeRabbit findings.
My PR is ready for review.
Summary by CodeRabbit
Bug Fixes
Tests