fix(guardrails): refuse an unscannable body only when a guardrail reads that side by jarvis9443 · Pull Request #1115 · api7/aisix

jarvis9443 · 2026-09-03T02:14:49Z

Problem

Two things were wrong with the unscannable_body refusals the gateway raises on the chain's behalf. Both come from the same gate: !chain.is_empty().

GuardrailIndex::resolve matches attachments on scope alone — env / model / mcp_server / api_key / team — and never filters by hook_point. A resolved chain is therefore non-empty whenever any attachment is in scope, including one attached on the output hook only. Each guardrail then no-ops on the hook it is not configured for, which makes !chain.is_empty() a correct gate for running the checks and a wrong one for refusing. So a guardrail configured for the output side alone caused a request-side refusal of a payload it would never have inspected.

The same gate also ignored fail_open. The refusal reports itself as guardrail_unavailable, and this project's standing rule is that a guardrail which cannot evaluate follows its configured failure policy — fail-closed by default, fail_open: true honoured when the operator sets it, with no class of cause carved out. A row explicitly set to fail open still refused the request, contradicting what the label promises.

The gate now

At the four sites listed below, a body the scanner cannot read is refused only if the resolved chain contains at least one guardrail that both reads that side of the exchange and is fail-closed on it. Both halves must hold on the same member.

The rule does not extend to the streamed-output path, and that is deliberate. Once an output-hook guardrail has held a streaming response back, a stream that leaves no scannable content at all is still refused regardless of fail_open — see "Deliberately not changed" below for why: honouring the setting there would not mean skipping a refusal, it would mean releasing already-buffered bytes that were never scanned. This is not a corner case reachable only by exotic configuration. keyword inherits the default hold-back streaming policy and pii sets its own, so any output-hook row on either kind necessarily takes that path. Anyone reading the rule as a statement about the gateway as a whole would be wrong about the response side.

The failure policy is per hook, mirroring how the kinds already read it: the row's fail_open on the input hook, each remote kind's <Kind>Config::output_fail_open on the output hook. keyword and pii never call out and so have no output_fail_open; their row-level fail_open governs both of their hooks, which is the only policy an operator of a local-only deployment can express.

Both halves on the same member is not pedantry: a chain of [output-only fail-closed, input-only fail-open] reads the request and contains a fail-closed row, yet nothing in it justifies refusing a request. Folding the two predicates independently gets that case wrong, which is why refuses_unevaluable_input / _output is one predicate rather than two you could &&.

Only a deployment that set hook_point or fail_open explicitly is affected — they default to both and false.

Behaviour change

POST /v1/files forwards an invalid-UTF-8 upload under a text purpose when no attachment in scope both reads the request and fails closed — exactly as it does for a deployment running no guardrails at all. A mixed chain folds to the strictest: one fail-closed request-side row restores the refusal.

Nothing else about the refusal moves: same text-purpose set (batch, fine-tune, evals), same 422, same content_filter / guardrail_unavailable / unscannable_body envelope, same handling of binary purposes, missing purposes and unconfigured deployments. This narrows the refusal introduced in #1113 and narrowed to the text purposes in #1114; all three land in the same release range and are meant to read together.

Upgrade risk

fail_open was documented as a no-op for keyword and pii, so existing rows may carry a fail_open: true that was set when it did nothing — copied from a template, left in a resources.yaml, or written by a form that renders the field for every kind. Those rows now take effect, so a deployment that upgrades only the data plane stops refusing bodies it refused before, with no operator action and no signal. Operators running keyword or pii rows should audit them for an unintended fail_open: true before upgrading. The DP rustdoc and the generated schemas/resources/guardrail.schema.json are corrected here; the matching cp-admin.yaml prose is a separate control-plane PR.

Sites

Both changes apply at all four sites that raise this refusal:


`POST /v1/files`	invalid-UTF-8 upload under a text purpose
`/v1/messages`	body the Anthropic scan parser rejects
`/v1/messages/count_tokens`	same
`/mcp` tool result	unparseable result — the mirror direction: it resolves one chain and uses it both ways, so an input-only row was refusing responses

Deliberately not changed

Left alone deliberately — confirmed, not an oversight — with the reason recorded in crates/aisix-proxy/AGENTS.md: the refusals that need a held-back stream (output_buffer_exceeded, mask_writeback_failed, and unscannable_body on a buffered SSE body, in messages.rs / responses.rs / passthrough_route.rs). Those already gate on runs_on_output(chain) && stream_output_policy().holds_back(), so the direction half is correct there; honouring fail_open would not mean skipping a refusal but releasing already-buffered bytes that were never scanned, which is a different decision. mcp.rs::moderate_selected_segments's collect-walk failure is gated on moderates_segments(chain), which is not hook-aware, but that arm is structurally unreachable — every caller's body has already parsed as JSON — so there is no fail-before test to write for it.

Implementation

Guardrail::runs_on_input mirrors the existing runs_on_output; fails_closed_on_input / _on_output expose the per-hook failure policy; refuses_unevaluable_input / _output combine them, with GuardrailChain overriding to any over members. All default to the secure-leaning value, so a kind that forgets to override keeps today's refusal. keyword and pii did not store the row's fail_open before and now do. GuardrailIndex::resolve is untouched and what a resolved chain means elsewhere is unchanged.

Tests

Unit (aisix-proxy, aisix-guardrails) plus the /v1/files e2e case. Every new case is mutation-checked against the specific gate it covers:

output-only guardrail + invalid-UTF-8 upload + text purpose → forwarded byte-for-byte
fail_open: true request-side row, same upload → forwarded
the two halves on different rows → forwarded (the case a naive fold refuses)
one fail-closed request-side row, alone or mixed in → still 422, envelope unchanged
both hooks attached → still 422
no guardrail → unchanged
the three sibling sites, each with its own direction and fail_open pair
GuardrailChain::runs_on_input and refuses_unevaluable_* across input-only / output-only / both / mixed / cross / empty

The e2e file grows output-only, input+output and fail_open: true environments. Two legs assert the premise rather than assuming it — the mock now echoes the uploaded filename, so an output-hook row can be shown to block the response, and the fail-open row can be shown to still scan. Without those, "forwarded" would be the same observation as the no-guardrail environment and would pass just as well if the row had never reached the chain.

Refs #1022, #1113, #1114.

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Summary by CodeRabbit

New Features
- Guardrails now apply input and output failure policies independently, including support for fail-open behavior when content cannot be evaluated.
- Keyword and PII guardrails support configurable failure handling.
- Guardrail chains accurately combine inspection and refusal policies across members.
Bug Fixes
- Unparseable requests, uploads, and tool results are forwarded when applicable guardrails allow fail-open handling, while strict input or output policies continue to block them.
Documentation
- Updated guidance and configuration descriptions to clarify failure-policy behavior across guardrail types.

…ds that side `GuardrailIndex::resolve` matches on scope alone — env / model / mcp_server / api_key / team — and never filters by `hook_point`. A chain is therefore non-empty whenever any attachment is in scope, including one attached on the output hook only. Each guardrail then no-ops on the hook it is not configured for, which makes `!chain.is_empty()` a correct gate for RUNNING the checks and a wrong one for REFUSING: the proxy-raised `unscannable_body` refusals fire before any member runs, so an output-side policy was refusing requests it would never have inspected. Behaviour change, narrowing the refusal #1113 introduced and #1114 narrowed to the text purposes: `POST /v1/files` now forwards an invalid-UTF-8 upload under a text purpose when every guardrail in scope is attached on the output hook alone, exactly as it does for a deployment running no guardrails at all. One input-side attachment is enough to restore the refusal, and nothing else about it moves — same text purposes, same 422, same `content_filter` / `guardrail_unavailable` / `unscannable_body` envelope, same handling of binary purposes, missing purposes and unconfigured deployments. Only a deployment that set `hook_point` explicitly is affected: the field defaults to `both`. The same gate shape was on three sibling refusal sites and is fixed with them: `/v1/messages` and `/v1/messages/count_tokens` refused a body their Anthropic scan parser rejects, and `/mcp` refused an unparseable tool RESULT on the strength of a request-side row (it resolves one chain and uses it in both directions). The streamed output refusals in `messages.rs` and `responses.rs` already sit behind `runs_on_output(chain) && holds_back()` and were correct. The gate is a new `Guardrail::runs_on_input`, the mirror of the existing `runs_on_output`: default `true`, overridden by every kind from its `hook_point`, folded over a chain with `any`. Nothing about what a resolved chain means changes, and `GuardrailIndex::resolve` is untouched.

coderabbitai · 2026-09-03T02:15:59Z

📝 Walkthrough

Walkthrough

The Guardrail trait now reports input participation and separate input/output fail-closed policies. Guardrail chains and proxy endpoints use these predicates to handle unscannable request, upload, and tool-result bodies.

Changes

Guardrail failure-policy flow

Layer / File(s)	Summary
Guardrail policy contracts `crates/aisix-guardrails/src/lib.rs`, `crates/aisix-core/src/models/guardrail.rs`, `schemas/resources/guardrail.schema.json`	The trait exposes direction-specific failure predicates and refusal helpers. Documentation defines `fail_open` behavior for provider failures and unscannable bodies across guardrail kinds.
Guardrail implementation policies `crates/aisix-guardrails/src/{aliyun.rs,aliyun_ai_guardrail.rs,bedrock.rs,custom.rs,keyword.rs,lakera.rs,openai_moderation.rs,pii.rs,presidio.rs,prompt_shield.rs,semantic.rs,text_moderation.rs}`, `crates/aisix-guardrails/src/build.rs`	Guardrails report input participation and independent input/output failure policies. Keyword and PII guardrails receive row-level `fail_open` settings. Wrappers forward these policies.
Chain policy resolution `crates/aisix-guardrails/src/chain.rs`	Chains aggregate direction-specific policies and require input/output participation and fail-closed behavior on the same member before refusing unevaluable content.
Proxy unscannable-body handling `crates/aisix-proxy/src/{count_tokens.rs,jobs.rs,mcp.rs,messages.rs}`, `tests/e2e/src/cases/files-unscannable-upload-e2e.test.ts`, `crates/aisix-proxy/AGENTS.md`	Proxy paths forward unscannable bodies when no applicable guardrail refuses them. Tests cover output-only, fail-open, mixed, and fail-closed configurations.

Estimated code review effort: 4 (Complex) | ~45 minutes

Merge Risk: 🔵 Low · up to 584eb

Remote guardrail documentation can cause operators to configure fail-open behavior incorrectly for unreadable request bodies. Correct the model and generated schema descriptions before merge.

Sequence Diagram(s)

sequenceDiagram
  participant ProxyEndpoint
  participant LiveGuardrailChain
  participant GuardrailChain
  participant UpstreamProvider
  ProxyEndpoint->>LiveGuardrailChain: resolve current guardrail chain
  LiveGuardrailChain->>GuardrailChain: query direction and refusal policy
  GuardrailChain-->>LiveGuardrailChain: return applicable refusal status
  alt no applicable guardrail refuses unevaluable content
    ProxyEndpoint->>UpstreamProvider: forward original unscannable body
    UpstreamProvider-->>ProxyEndpoint: return upstream response
  else applicable guardrail refuses unevaluable content
    ProxyEndpoint-->>ProxyEndpoint: return unscannable-body refusal
  end

Suggested reviewers: membphis, moonming, nic-6443

🚥 Pre-merge checks | ✅ 5 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
E2e Test Quality Review	⚠️ Warning	The E2E additions introduce a hidden test-order dependency. The output-only test asserts `uploads` has length `1` at line 295, while a later test uses the same environment and mutates that array. If e…	Use an isolated environment per test, or capture `const before = outputOnly.upstream.uploads.length` and assert `before + 1` in every test. Add full E2E cases for the changed sibling endpoints, including output-only and fail-open unscannabl…

✅ Passed checks (5 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.
Security Check	✅ Passed	PASS. The PR introduces no finding in the stated security categories. 1. Sensitive data exposure: No new production log serializes credentials, headers, tokens, or guardrail configuration. The two new…
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly describes the main change: unscannable-body refusals now depend on whether a guardrail reads the relevant side. It omits the fail-closed requirement but remains concise and materiall…

Full details: E2e Test Quality Review

Explanation

The E2E additions introduce a hidden test-order dependency. The output-only test asserts uploads has length 1 at line 295, while a later test uses the same environment and mutates that array. If execution order changes, the assertion fails. The new gate is also tested through a real spawned gateway only for /v1/files; the changed /v1/messages, count_tokens, and /mcp paths use in-process tests instead of full E2E flows.

Resolution

Use an isolated environment per test, or capture const before = outputOnly.upstream.uploads.length and assert before + 1 in every test. Add full E2E cases for the changed sibling endpoints, including output-only and fail-open unscannable bodies, so configuration loading, routing, and upstream dispatch are verified end to end.

Full details: Security Check

Explanation

PASS. The PR introduces no finding in the stated security categories. 1. Sensitive data exposure: No new production log serializes credentials, headers, tokens, or guardrail configuration. The two new logs record only the model and AnthropicInboundError; its variants contain fixed messages or an untrusted role value. Credential-looking values occur only in test fixtures. 2. Plaintext database secrets: No database models, writes, or migrations changed. 3. Authorization bypass: No authorization checks or mutating control-plane handlers changed. The POST paths changed here are data-plane proxy screening paths. 4. Cross-resource access: GuardrailIndex::resolve and resource ownership checks are unchanged. 5. TLS or cryptography: No TLS or cryptographic configuration changed. 6. Shared-resource safety: No shared-resource binding, deletion, or cascade behavior changed. 7. Secret reference resolution: No secret-reference handling changed. The functional change allows forwarding of unscannable bodies for explicitly fail-open or non-applicable guardrails. That behavior is the stated PR objective and does not match any explicit failure condition in this check.

Full details: Title check

Explanation

The title clearly describes the main change: unscannable-body refusals now depend on whether a guardrail reads the relevant side. It omits the fail-closed requirement but remains concise and materially accurate.

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Pull request overview

This PR fixes an incorrect guardrail refusal gate by ensuring “unscannable body” refusals only trigger when at least one in-scope guardrail actually inspects that direction (input vs output), rather than when the resolved chain is merely non-empty (scope-only resolution).

Changes:

Add Guardrail::runs_on_input (mirror of runs_on_output) and implement it across guardrail kinds and GuardrailChain.
Update proxy refusal gates in /v1/files, /v1/messages, /v1/messages/count_tokens, and /mcp to key on runs_on_input / runs_on_output as appropriate.
Extend unit and e2e tests to cover output-only vs input+output guardrail attachment scenarios.

File summaries

File	Description
tests/e2e/src/cases/files-unscannable-upload-e2e.test.ts	Adds e2e legs to prove output-only guardrails don’t cause request-side unscannable refusals.
crates/aisix-proxy/src/jobs.rs	Gates `/v1/files` unscannable refusal on `runs_on_input(chain)` instead of chain non-emptiness.
crates/aisix-proxy/src/messages.rs	Ensures request-body parse refusal only happens when an input-reading guardrail is present; adds unit tests.
crates/aisix-proxy/src/count_tokens.rs	Mirrors `/v1/messages` gating behavior for count_tokens input screening; adds unit tests.
crates/aisix-proxy/src/mcp.rs	Avoids refusing unparseable tool results unless an output-reading guardrail exists; adds unit test.
crates/aisix-proxy/AGENTS.md	Documents the “direction-aware refusal gate” rule for future changes.
crates/aisix-guardrails/src/lib.rs	Introduces `Guardrail::runs_on_input` default behavior and documents its intent.
crates/aisix-guardrails/src/chain.rs	Implements `runs_on_input` folding across chain members; adds unit test coverage.
crates/aisix-guardrails/src/build.rs	Plumbs `runs_on_input` through wrapper guardrails (`MonitorGuardrail`, `LiveGuardrailChain`).
crates/aisix-guardrails/src/{keyword,custom,pii,lakera,presidio,prompt_shield,semantic,text_moderation,openai_moderation,bedrock,aliyun,aliyun_ai_guardrail}.rs	Implements `runs_on_input` per kind based on `hook_point` (or equivalent flags).

Review details

Files reviewed: 21/21 changed files
Comments generated: 1
Review effort level: Lite

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Review follow-up. The three route-level "an output-only guardrail does not refuse" tests asserted only "200, and the upstream received it" — the same observation as the no-guardrail tests sitting beside them. They would therefore have passed just as well if the seeded row had never reached the chain at all, which is exactly the premise they exist to test. Each now resolves the chain from the same snapshot first and asserts it is non-empty AND not input-side, the anchor the `chain.rs` and `mcp.rs` tests already had. The e2e leg gets the equivalent, but end to end rather than by inspection: the `/v1/files` mock now echoes the uploaded filename, so the output hook has something under the caller's control to match on, and a new leg uploads a clean file named after the blocked term and asserts the output-only row blocks the RESPONSE with an ordinary policy 422. That proves the row is attached and running, not merely that nothing refused the request. Also: fold the `runs_on_input` chain walk into the match guard in `scan_input_blob`, so a decodable upload — the overwhelmingly common case — does not pay for it; give the `count_tokens` refusal test the same `unscannable_body` envelope assertion its three siblings make; and repoint a doc link left dangling when `GUARDRAIL` became the `guardrail(hook)` factory.

The refusal reports itself as `guardrail_unavailable`, and this project's standing rule is that a guardrail which cannot evaluate follows its configured failure policy — fail-closed by default, `fail_open: true` honoured when the operator sets it, with no class of cause carved out. This refusal ignored the setting, which contradicts what the label promises: a row explicitly set to fail open still refused the request. Behaviour change: a chain whose only request-side rows asked to fail open now forwards a body the scanner could not read, the same way an unconfigured deployment does. A mixed chain folds to the strictest — one fail-closed row that reads the request is enough. The policy is per hook, mirroring how the kinds already read it: the row's `fail_open` on the input hook, each remote kind's `<Kind>Config::output_fail_open` on the output hook. `keyword` and `pii` never call out and so have no `output_fail_open`; their row-level `fail_open` governs both hooks, which is the only policy an operator of a local-only deployment can express. Neither kind stored the field before — both now carry it. The gate is `refuses_unevaluable_input` / `_output`, folding direction and failure policy together per member. They are one predicate rather than two because both halves must hold on the SAME member: a chain of [output-only fail-closed, input-only fail-open] reads the request and contains a fail-closed row, yet nothing in it justifies refusing a request. That case is pinned by a test at both the chain and the route level. Applied at all four sites that raise the refusal — `/v1/files`, `/v1/messages`, `/v1/messages/count_tokens`, and the `/mcp` tool result. The refusals that need a held-back stream are deliberately left alone and the reason is recorded in `AGENTS.md`: honouring `fail_open` there would mean releasing already-buffered unscanned bytes, which is a different decision. Closes the coverage gap this change exposed — every fixture hardcoded `fail_open: false`, so the other half of the behaviour had none. Both values are now covered at the unit, route and e2e layers, each mutation-checked. Also documents, on `MonitorGuardrail`, why its hook predicates forward rather than return false: a monitor row still participates in these refusals (settled product decision — monitor mode downgrades a verdict, and these have none), and forcing them false would additionally disable the end-of-stream observation `responses.rs` gates on `runs_on_output`.

…e each premise Review follow-up on the fail_open work. `fails_closed_on_input` / `fails_closed_on_output` were asserted in exactly one place, on a `keyword` chain — where both read the same field by construction. None of the ten kinds that actually SPLIT the policy per hook were exercised, so swapping `fail_open` and `output_fail_open` in any of their overrides failed nothing. That is the failure mode this pairing most needs guarded, so it now has a table test: each split kind is built through `build_one` with the two values deliberately asymmetric, which a swapped pair cannot satisfy. Mutation-checked by swapping all nine at once. The new fail-open route tests asserted only "200, and the upstream received it", which a chain the row never reached satisfies just as well. Each now states its premise first: the row is in the chain and DOES read the request, and only the refusal is off. The cross case — the one a naive fold gets wrong — additionally pins the shape that makes it a cross case rather than a degenerate one, so dropping either seeded row fails it. Also: the e2e fail-open leg counted uploads from zero while sharing its environment with the leg after it; it uses the `before` snapshot its siblings use.

…not evaluate UPGRADE RISK — read before shipping. `fail_open` was documented as a no-op for `keyword` and `pii` ("Keyword guardrails do not use this setting"), so existing rows may carry `fail_open: true` set at a time when it did nothing: copied from a template, left in a `resources.yaml`, or written by a form that renders the field for every kind. Those rows now take effect. A deployment that upgrades ONLY the data plane therefore stops refusing bodies it refused before — an undecodable `/v1/files` upload under a text purpose, an unparseable `/v1/messages` or `/v1/messages/count_tokens` body, an unparseable `/mcp` tool result — with no operator action, no configuration change, and no signal that enforcement weakened. Operators running `keyword` or `pii` rows should audit them for an unintended `fail_open: true` before upgrading. The DP-side statements that asserted otherwise are corrected here: the rustdoc on `Guardrail::fail_open`, and the thirteen copies of it that `dump-schema` generates into `schemas/resources/guardrail.schema.json`. The field now documents both causes it governs — a remote provider that cannot be reached, and a body the gateway could not give the guardrail at all — and says which kinds split the policy per hook (those with `output_fail_open`) versus which use the one value for both (`keyword`, `pii`, neither of which calls out). The matching control-plane prose is a separate PR: `cp-admin.yaml` still says "No-op for kind=keyword" and "this governs the INPUT hook only".

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Inline comments:
In `@crates/aisix-core/src/models/guardrail.rs`:
- Around line 1321-1325: The fail_open documentation near
Guardrail::refuses_unevaluable_input must describe that unreadable request
bodies use the remote guardrail’s fail_open value, allowing either
unscannable_body blocking or continuation without scanning; remove the “has only
the first cause” wording and regenerate every repeated fail_open description in
the guardrail schema.

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📥 Commits

Reviewing files that changed from the base of the PR and between 8955d6a and 584ebd8.

📒 Files selected for processing (23)

crates/aisix-core/src/models/guardrail.rs
crates/aisix-guardrails/src/aliyun.rs
crates/aisix-guardrails/src/aliyun_ai_guardrail.rs
crates/aisix-guardrails/src/bedrock.rs
crates/aisix-guardrails/src/build.rs
crates/aisix-guardrails/src/chain.rs
crates/aisix-guardrails/src/custom.rs
crates/aisix-guardrails/src/keyword.rs
crates/aisix-guardrails/src/lakera.rs
crates/aisix-guardrails/src/lib.rs
crates/aisix-guardrails/src/openai_moderation.rs
crates/aisix-guardrails/src/pii.rs
crates/aisix-guardrails/src/presidio.rs
crates/aisix-guardrails/src/prompt_shield.rs
crates/aisix-guardrails/src/semantic.rs
crates/aisix-guardrails/src/text_moderation.rs
crates/aisix-proxy/AGENTS.md
crates/aisix-proxy/src/count_tokens.rs
crates/aisix-proxy/src/jobs.rs
crates/aisix-proxy/src/mcp.rs
crates/aisix-proxy/src/messages.rs
schemas/resources/guardrail.schema.json
tests/e2e/src/cases/files-unscannable-upload-e2e.test.ts

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…e local ones The sentence added in the previous commit put the "only" on the wrong side: it said a kind that calls out meets only the provider-failure cause. It meets both. The second cause is the gateway failing to produce scannable text at all, which happens before any guardrail runs and so reaches every member of the chain — a lakera or presidio row on the input hook with `fail_open: true` stops refusing an unparseable body exactly as a keyword row does. What is actually one-sided is the other direction: `keyword` and `pii` never call out, so only the second cause can arise for them. Caught in review on #1115.

…ent (#1117) `usage_events.guardrail_bypassed_reason` was written by `/v1/chat/completions` and nowhere else, so on every other route a guardrail that failed open left no trace: the caller got a normal 200 and the usage row was byte-identical to a request the chain actually decided. An operator can now see, on the usage event, that a request was let past a guardrail that did not evaluate it — and which one — on `/v1/chat/completions`, `/v1/completions`, `/v1/responses`, `/v1/messages`, `/v1/messages/count_tokens`, `/v1/embeddings`, `/v1/rerank`, `/v1/audio/{transcriptions,translations,speech}`, `/v1/images/{generations,edits}`, `/v1/videos`, `/v1/realtime`, `/mcp`, `/a2a/:agent`, the jobs surface (`/v1/files`, `/v1/batches`, `/v1/fine_tuning/jobs`) and the passthrough routes. Both the success and the error event carry it, so a request that failed open and then hit a dead upstream is still visible. Two causes reach the field. A guardrail that could not evaluate on a `fail_open: true` row reports the kind's existing bounded tag (`lakera_timeout`, `bedrock_5xx`, `custom_script_error`, …). A body the scanner could not read reports `unscannable_body` — the same tag the fail-closed direction already puts in its refusal envelope — and only where a chain that reads that side let it through, never where nothing was going to screen it. Three cases were previously invisible even on chat: its failed-attempt events and its pre-dispatch failure event both dropped the reason, and on the unbilled paths a bypass suppressed the whole event, because it leaves no enforced hit and no score for the attribution gate to find. Observability only — what is refused, released or masked is unchanged, and the field stays free-form, so no control-plane change is required. Deliberately not covered, and recorded in `crates/aisix-proxy/AGENTS.md`: the sites that scan a lossy copy unconditionally with no failure policy involved (`jobs::scan_output_blob`, the binary-purpose upload arm, the non-UTF-8 multipart prompt parts dropped in `audio.rs` / `images_edits.rs`, `passthrough_route`'s lossy body). A fail-closed row does not refuse at any of them either; that asymmetry is #1022's open product decision. Refs #1115.

…1121) `/v1/files` decoded an uploaded file with `String::from_utf8_lossy` and checked the result as one synthetic user message, while `create_file` forwarded the ORIGINAL bytes to the provider. That scan cannot do its job: it feeds JSON syntax to keyword matchers, answers a file holding thousands of independent requests with a single verdict, can rewrite nothing, and on a binary upload inspects a run of replacement characters. The download side had the same shape. Nothing narrower repairs it — screening a batch file means decomposing it per JSONL record and running the ordinary per-record request chain, which is #1120. Removed: the input blob scan on `POST /v1/files`, the output blob scan on its response and on every `/v1/files*` read, and the `unscannable_body` refusal built on the input scan (added by #1113, narrowed by #1114, gated by #1115) together with the purpose classification it keyed on. `forward_simple` skips the output chain for the files surface alone. `/v1/files` is now `Posture::Unscreened` in the guardrail coverage census, which says what the surface does rather than claiming enforcement it no longer has. Behaviour change: an upload that began answering `422` with the `unscannable_body` tag after #1113 is forwarded again, under every declared `purpose`. Capability narrowing: guardrails no longer apply to the files surface at all. An upload or a download that a keyword, PII or remote guardrail would previously have blocked on a policy match now reaches the provider and the caller respectively. The published documentation says input and output guardrails cover Files request and response payloads; that coverage is gone until #1120 lands. Unchanged: `/v1/batches` and `/v1/fine_tuning/jobs` still scan their serialised JSON request bodies and their responses — a serialised request body is not a caller-uploaded blob — and the `unscannable_body` gate stays on `/v1/messages`, `/v1/messages/count_tokens` and `/mcp` tool results, with `fail_open` governing every guardrail kind as before. Three statements elsewhere in the crate that described the files surface as screened are corrected, and the two job surfaces that still screen are promoted to `Posture::Enforced` with census fixtures, since this change's own tests disproved the premise that kept them out. Refs #1120, #1022

… policy (#1123) `transcription_output_text` fell back to `String::from_utf8_lossy` for the plain-text response formats (`text` / `srt` / `vtt`) and then relayed the original bytes. It consulted neither `refuses_unevaluable_output` nor `record_unevaluable_output_bypass`, so a guardrail attached to the response side was handed a text the caller never receives, and nothing recorded the gap. BEHAVIOUR CHANGE: a transcription or translation response the gateway cannot decode is now refused when a guardrail in scope both reads the response side and fails closed on it. The caller gets 422 `content_filter` with code `guardrail_unavailable` and the message "response rejected: a guardrail could not evaluate it (unscannable_body)", where the bytes were previously relayed. A row that fails open on the response side relays them as before, and its usage event now carries `guardrail_bypassed_reason: unscannable_body`. Same predicate, tag and envelope as `/mcp`'s tool-result arm; the response-side mirror of the gate #1115 put on `/v1/messages` and `/v1/messages/count_tokens`. Unlike those, the lossy text is still scanned when the chain does not refuse: a transcript is prose the caller reads, so only the bytes `from_utf8_lossy` replaced go unread. That is why this site is gated rather than removed the way the files surface was in #1121. Also corrects rustdoc that had gone stale and had already propagated into the published documentation. `SemanticConfig::deny_threshold` claimed `/a2a` attaches no guardrail attribution to its usage event and that `rerank` emits no usage event when the upstream reports no parsable usage. `/a2a` sets all six guardrail fields, and `rerank` emits whenever a guardrail attributed the request, which a semantic score alone does; two `rerank.rs` comments were wrong for the same reason. The replacement enumerates the input-hook-only surfaces, `/v1/audio/speech` among them.

…s_total `aisix_guardrail_bypasses_total` only ever counted bypasses a guardrail member reported: the increment hangs off the per-execution record, and an unscannable body has no execution by construction — the body could not be decoded, so no member ran. The chain recorded that pass-through to the audit log (and so to `UsageEvent.guardrail_bypassed_reason`) and to nothing else. The sibling counter is the other way round: `aisix_guardrail_blocks_total` deliberately includes the fail-closed paths that happen before a member executes. So one situation — the body could not be scanned — was counted when the chain refused and counted nowhere when it let the request through, which is the direction an operator reads `bypasses_total` to find. #1115 widened exactly that fail-open half, so the traffic newly passing through was the traffic the counter could not see. `GuardrailMetricsSink` gains `record_guardrail_bypass(reason)` and `GuardrailChain::record_bypass` now feeds both receivers. Deliberately a second method rather than a synthetic execution: there is no member, kind or duration to report, and inventing them would put a phantom row in the per-execution latency histogram. It is required rather than defaulted so a sink cannot silently drop these. Which pass-throughs count is unchanged and is still decided in one place. `record_unevaluable_{input,output}_bypass` already distinguishes a chain whose members all fail open on that side (a bypass) from one where no member reads that side (never offered to screen it, so not a bypass), off the same member set the refusal gate uses. The counter reads that decision rather than deriving its own. Tests: the chain unit test that pins the distinction now asserts both sinks, so the usage field and the counter cannot disagree about which pass-through was a bypass. All three assertions were verified to go red under mutation — dropping the sink forwarding, counting every pass-through, and letting the counter derive its own predicate. The bypass-reason e2e additionally asserts the `reason="unscannable_body"` delta in `GET /metrics` after driving a real unscannable request.

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jarvis9443 merged commit a889c8a into main Sep 3, 2026
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jarvis9443 deleted the fix/files-unscannable-input-hook-gate branch September 3, 2026 04:11

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feat(guardrails): record a fail-open bypass on every route's usage event #1117

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docs(proxy): correct a stale unscannable-body claim in the proxy AGENTS.md #1119

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fix(guardrails): remove the whole-blob scan from the files surface #1121

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jarvis9443 mentioned this pull request Sep 3, 2026

fix(guardrails): gate the audio transcript output scan on the failure policy #1123

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fix(security): AWS SigV4 headers are credential slots; full-version image tags only; count unscannable-body bypasses #1126

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fix(guardrails): refuse an unscannable body only when a guardrail reads that side - #1115

fix(guardrails): refuse an unscannable body only when a guardrail reads that side#1115
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fix/files-unscannable-input-hook-gate

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