fix(broker): catch a wrapped terminal delivery error, and de-flake its test - #1688
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Included review availability: Your plan provides up to 4 included reviews per hour; 1 remains after this review. 📝 WalkthroughWalkthroughThe changes make broker delivery-failure tests deterministic and add a RelayFlow proof case. The tests require retry-cap failure and exact write-error propagation. The proof case validates base and head outcomes with controlled source mutation. ChangesDelivery error fidelity
Estimated code review effort: 3 (Moderate) | ~25 minutes Merge Risk: ⚪ Minimal · up to This change makes broker delivery-retry testing deterministic and verifies that terminal write errors are preserved exactly. No current merge-blocking risk is identified. Sequence Diagram(s)sequenceDiagram
participant RelayFlow
participant BrokerSource
participant CargoTest
participant Evidence
RelayFlow->>BrokerSource: Validate provenance and inject wrapped write errors
RelayFlow->>CargoTest: Run targeted delivery retry test
CargoTest-->>RelayFlow: Return test output and status
RelayFlow->>Evidence: Classify outcome and write JSON evidence
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🚥 Pre-merge checks | ✅ 4 | ❌ 1❌ Failed checks (1 warning)
✅ Passed checks (4 passed)
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Inline comments:
In `@crates/broker/src/runtime/tests.rs`:
- Line 2828: Update the assertion around last_error in the relevant runtime test
to use assert_eq! against the complete expected terminal wire value, replacing
the current contains check while preserving the existing expected message text.
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Re-trigger cubic
added 2 commits
September 6, 2026 20:05
`delivery_retry_transient_blip_emits_failed_event_for_present_worker`
SIGKILLed a real `cat` child and then relied on the next write to its
stdin returning EPIPE. On macOS release builds under parallel load those
writes can keep SUCCEEDING, and the test then fails itself: the retry cap
gates on consecutive `failed_attempts`, which every successful write
resets to 0, while `attempts` only ever increments — so the loop marches
`attempts` past the cap and trips its own bound. That is relay#980, open
since 2026-05-25, which names this test.
Replace the fixture with a worker that is present in the registry but has
no stdin writer at all: `command_rx` is dropped, so the queue send fails
immediately and `deliver()` surfaces the same
`failed writing frame to worker '<name>'` error a live writer reports on
a write fault. No OS, timing, profile or load dependence remains. This
follows the existing `make_worker_registry_with_stalled_worker` idiom of
constructing a deterministic WorkerHandle rather than racing a real
process.
Every assertion is tightened, none relaxed, and the retry cap itself is
untouched:
- terminal failure must land on EXACTLY the capped attempt (was `>=`,
which existed only to tolerate the pipe race)
- `Attempted` is now unreachable and panics instead of asserting a bound
- the wire `lastError` must carry the real write error (the
`|| "max delivery retries exceeded"` alternative is gone)
- the fixture child is reaped via `cleanup_worker_registry`
`crates/broker/src/runtime/delivery.rs` is not modified and
MAX_DELIVERY_RETRIES is unchanged.
Tests bite. Mutating the guarded code in delivery.rs, both reverted:
1. cap boundary off-by-one, `failed_attempts >= MAX` -> `>`:
panicked at crates/broker/src/runtime/tests.rs:2775:17:
the final bounded retry should return a terminal failure
2. consecutive-failure counter stalls, `failed_attempts += 1` -> `= 0`:
panicked at crates/broker/src/runtime/tests.rs:2775:17:
the final bounded retry should return a terminal failure
Determinism, release profile (the one that flaked): 100/100 single-test
runs and 10/10 full broker suite runs clean.
Refs: relay#980
Refs: relay#1686
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_015LAYEYtXwYhV9MdfCPguQr
Session-Id: c60fc010-68bb-48be-bccd-1c9748e2b127
Session-Id: c60fc010-68bb-48be-bccd-1c9748e2b127
Both review threads applied.
cubic (P3, duplication): `make_worker_registry_with_unwritable_worker`
duplicated the whole process/registry/WorkerHandle construction from
`make_worker_registry_with_stalled_worker`, so a future WorkerHandle field
had to be added twice and could drift. Extract
`make_worker_registry_with_fixture_worker`, which builds both and hands the
command receiver back. What happens to that receiver is now the only axis
on which the two fixtures differ: the stalled one leaks it (sends succeed,
nothing drains), the unwritable one drops it (sends fail closed). Net -31
lines.
CodeRabbit (functional correctness): the terminal `lastError` was compared
with `contains`, so a wrapped or substituted error could pass. Now
`assert_eq!` against the exact wire value.
That second one is not cosmetic. Wrapping the queue-send context in
worker.rs so the message still CONTAINS the fragment but no longer EQUALS
it — `"...worker 'worker-blip' (queue closed)"` — slips past every
remaining `contains` check in the test, including the Noop arm, and is
caught only by the new comparison:
panicked at crates/broker/src/runtime/tests.rs:2795:5:
assertion `left == right` failed: the terminal event must carry the
real write error verbatim, not a wrapped or substituted one
left: "failed writing frame to worker 'worker-blip' (queue closed)"
right: "failed writing frame to worker 'worker-blip'"
The two delivery.rs mutations still bite after the rebase and the
tightening, both at tests.rs:2743:
1. cap boundary off-by-one, `failed_attempts >= MAX` -> `>`
2. consecutive-failure counter stalls, `+= 1` -> `= 0`
delivery.rs and worker.rs are unmodified in this PR; MAX_DELIVERY_RETRIES
is unchanged. Full broker suite green: 1045 passed, 0 failed.
Rebased onto 5b1dc5c (#1667).
Refs: relay#980
Refs: relay#1686
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_015LAYEYtXwYhV9MdfCPguQr
Session-Id: c60fc010-68bb-48be-bccd-1c9748e2b127
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Inline comments:
In `@crates/broker/src/runtime/tests.rs`:
- Line 204: Remove the std::mem::forget(command_rx) call in the test setup and
ensure command_rx remains owned by the test scope or is returned to the
registry, so the queued WorkerWriteCommand and completion channel are dropped
when the test ends.
- Line 229: Configure the fixture command that spawns the `cat` child with
`kill_on_drop(true)`, ensuring the Tokio child process is terminated when
dropped during test unwinding. Preserve the existing cleanup flow.
After applying the fix, consider running `coderabbit review --agent` for local
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Re-trigger cubic
added 2 commits
September 6, 2026 20:33
Second review round, both findings valid.
CodeRabbit (stability): dropping a tokio `Child` does not kill the
process, so an assertion panicking before `cleanup_worker_registry` would
strand a live `cat` for the rest of the run. Add `.kill_on_drop(true)` to
the fixture command — the idiom already used in spawner.rs and
codex_session.rs. `cleanup_worker_registry` stays as the normal path.
CodeRabbit (stability): `std::mem::forget(command_rx)` permanently
retained the receiver, its queued frame and that frame's completion
channel. The receiver does have to stay alive — it is what makes the
stalled handoff hang instead of fail — but it only has to outlive the
test, not the process. The single caller now binds it for the test body
and drops it at scope end.
That leak predates this PR; it moved here in the previous commit's
deduplication, which is what surfaced it.
With the receiver bound at the call site,
`make_worker_registry_with_stalled_worker` became a pure passthrough to
`make_worker_registry_with_fixture_worker`, so it is folded away rather
than left as a second name for the same thing — the duplication cubic
flagged, one level up. Its semantics move onto the shared constructor,
which now documents both dispositions of the receiver: keep it bound for
a stalled handoff, drop it for an unwritable worker.
All three mutations still bite after the restructure:
1. cap boundary off-by-one (`>=` -> `>`) tests.rs:2747
2. failure counter stalls (`+= 1` -> `= 0`) tests.rs:2747
3. terminal wire error wrapped tests.rs:2799
assertion `left == right` failed
left: "...worker 'worker-blip' (queue closed)"
right: "...worker 'worker-blip'"
delivery.rs and worker.rs are unmodified; MAX_DELIVERY_RETRIES unchanged.
Full broker suite 3/3 clean at 1045 passed, 0 failed.
Refs: relay#980
Refs: relay#1686
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_015LAYEYtXwYhV9MdfCPguQr
Session-Id: c60fc010-68bb-48be-bccd-1c9748e2b127
Declares the RelayFlow case this PR was missing. The prior declaration of `non-functional` was rejected, correctly: `crates/broker/src/runtime/tests.rs` matches none of NON_RUNTIME_PATH_PATTERNS (`^tests/` is root-anchored), so a test file under crates/ is a runtime path regardless of how test-only the change is. The proven bug is real and is one this PR fixes. On a terminal delivery failure the broker emits `message_delivery_failed` carrying `lastError` — the only machine-readable account of what killed the delivery, and what reaches the dead-letter store and orchestrator. Base asserted only that it CONTAINS an expected fragment, so an error wrapped or substituted anywhere in the write path still satisfied it. Head compares it exactly. Shaped as mutation detection, deliberately. `runtime/tests.rs` is behind `#[cfg(test)]` (runtime/mod.rs:89), so it is compiled out of the shipped broker: base and head produce functionally identical binaries, and a case that merely runs the broker would prove nothing about this change whatever it observed. So both arms inject the same defect into the write path and ask the target's own test whether it notices. The defect is faithful rather than a strawman — the message still CONTAINS the fragment and only stops being EQUAL to it, which is exactly the class base could not see. All three write-error context sites are rewritten, not one: base surfaces this error from the completion path and head from the queue-send path, so mutating a single site leaves the defect inert on one arm. A first draft did exactly that and produced a base "pass" that proved nothing; the runner now asserts it finds all three and refuses to run otherwise. Fail-closed. Only two results are evidence: the target's test passing with the defect live (bug), or failing on that exact comparison (fixed). A missing toolchain, a compile error, a failure at any other assertion or an unparseable run throws — a crash must never be laundered into a proof. Both arms executed locally against real checkouts: base 5b1dc5c -> {"outcome":"bug","signature":"wrapped_delivery_error_undetected"} head 3412db6 -> {"outcome":"fixed","signature":"wrapped_delivery_error_detected"} NON_RUNTIME_PATH_PATTERNS and the proof workflow are untouched. Refs: relay#980 Refs: relay#1686 Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_015LAYEYtXwYhV9MdfCPguQr Session-Id: c60fc010-68bb-48be-bccd-1c9748e2b127
khaliqgant
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2 issues found across 2 files (changes from recent commits).
Prompt for AI agents (unresolved issues)
Check if these issues are valid — if so, understand the root cause of each and fix them. If appropriate, use sub-agents to investigate and fix each issue separately.
<file name="tests/relayflows/cases/1688-delivery-failure-error-fidelity/case.json">
<violation number="1" location="tests/relayflows/cases/1688-delivery-failure-error-fidelity/case.json:6">
P2: This case declares the `broker-linux-x64` requirement, but its runner (`run.mjs`) never reads `RELAY_PR_PROOF_BROKER_BINARY`: it runs `cargo test -p agent-relay-broker` directly against the target checkout. Declaring the requirement causes the dispatcher to perform wasted cold Rust builds of the broker for both SHAs. Drop the requirement since the runner does not use the supplied broker binary.</violation>
</file>
<file name="tests/relayflows/cases/1688-delivery-failure-error-fidelity/run.mjs">
<violation number="1" location="tests/relayflows/cases/1688-delivery-failure-error-fidelity/run.mjs:105">
P2: The case's only observable is a `#[cfg(test)]`-gated unit test (runtime::tests::delivery_retry_transient_blip_emits_failed_event_for_present_worker) run via `cargo test` against the target source. The README runner contract says cases must exercise public/production behavior, 'not head-only unit tests', and that 'test not found is not a valid observation'; broker cases are also expected to use the supplied binary rather than rebuild in Cloud. This case rebuilds the crate in Cloud and proves its fix only through the crate's internal test, so the proof never exercises a shipped artifact. The comments acknowledge this by design, but confirm the deviation from the documented contract is intended before shipping the case.</violation>
</file>
Tip: Review your code locally with the cubic CLI to iterate faster.
Re-trigger cubic
| "id": "1688-delivery-failure-error-fidelity", | ||
| "kind": "bugfix", | ||
| "title": "Terminal message_delivery_failed must carry the write error verbatim, not a wrapped or substituted one", | ||
| "requirements": ["broker-linux-x64"], |
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P2: This case declares the broker-linux-x64 requirement, but its runner (run.mjs) never reads RELAY_PR_PROOF_BROKER_BINARY: it runs cargo test -p agent-relay-broker directly against the target checkout. Declaring the requirement causes the dispatcher to perform wasted cold Rust builds of the broker for both SHAs. Drop the requirement since the runner does not use the supplied broker binary.
Prompt for AI agents
Check if this issue is valid — if so, understand the root cause and fix it. At tests/relayflows/cases/1688-delivery-failure-error-fidelity/case.json, line 6:
<comment>This case declares the `broker-linux-x64` requirement, but its runner (`run.mjs`) never reads `RELAY_PR_PROOF_BROKER_BINARY`: it runs `cargo test -p agent-relay-broker` directly against the target checkout. Declaring the requirement causes the dispatcher to perform wasted cold Rust builds of the broker for both SHAs. Drop the requirement since the runner does not use the supplied broker binary.</comment>
<file context>
@@ -0,0 +1,21 @@
+ "id": "1688-delivery-failure-error-fidelity",
+ "kind": "bugfix",
+ "title": "Terminal message_delivery_failed must carry the write error verbatim, not a wrapped or substituted one",
+ "requirements": ["broker-linux-x64"],
+ "runner": {
+ "command": ["node", "tests/relayflows/cases/1688-delivery-failure-error-fidelity/run.mjs"]
</file context>
| try { | ||
| const { stdout, stderr } = await execFileAsync( | ||
| 'cargo', | ||
| ['test', '-p', 'agent-relay-broker', '--lib', TEST_NAME, '--', '--exact'], |
Contributor
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P2: The case's only observable is a #[cfg(test)]-gated unit test (runtime::tests::delivery_retry_transient_blip_emits_failed_event_for_present_worker) run via cargo test against the target source. The README runner contract says cases must exercise public/production behavior, 'not head-only unit tests', and that 'test not found is not a valid observation'; broker cases are also expected to use the supplied binary rather than rebuild in Cloud. This case rebuilds the crate in Cloud and proves its fix only through the crate's internal test, so the proof never exercises a shipped artifact. The comments acknowledge this by design, but confirm the deviation from the documented contract is intended before shipping the case.
Prompt for AI agents
Check if this issue is valid — if so, understand the root cause and fix it. At tests/relayflows/cases/1688-delivery-failure-error-fidelity/run.mjs, line 105:
<comment>The case's only observable is a `#[cfg(test)]`-gated unit test (runtime::tests::delivery_retry_transient_blip_emits_failed_event_for_present_worker) run via `cargo test` against the target source. The README runner contract says cases must exercise public/production behavior, 'not head-only unit tests', and that 'test not found is not a valid observation'; broker cases are also expected to use the supplied binary rather than rebuild in Cloud. This case rebuilds the crate in Cloud and proves its fix only through the crate's internal test, so the proof never exercises a shipped artifact. The comments acknowledge this by design, but confirm the deviation from the documented contract is intended before shipping the case.</comment>
<file context>
@@ -0,0 +1,164 @@
+ try {
+ const { stdout, stderr } = await execFileAsync(
+ 'cargo',
+ ['test', '-p', 'agent-relay-broker', '--lib', TEST_NAME, '--', '--exact'],
+ {
+ cwd: targetDir,
</file context>
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Closes the test-fixture half of #980.
bugfix1688-delivery-failure-error-fidelityWhat was wrong
delivery_retry_transient_blip_emits_failed_event_for_present_workerSIGKILLed areal
catchild and then relied on the next write to its stdin returning EPIPE.On macOS release builds under parallel load, those writes can keep succeeding.
When they do, the test fails itself. The retry cap gates on consecutive
failed_attempts, which every successful write resets to0, whileattemptsonly ever increments. Once any write fails the writer task breaks and every later
send fails too — so for the
Attemptedarm to be reached on the final iteration,all 11 writes must have succeeded, marching
attemptsto 11 against a cap of10 and tripping the test's own bound.
This is #980, open since 2026-05-25, which names this test by name. It fired
four times on 2026-09-06 alone, across three unrelated branches:
021f7f572chore/relay-cleanroom-verification(#1665)79d0fbf6cfix/relay-1671-release69f0504035chore/relay-cleanroom-verification(#1665)27ab0d726fix/broker-node-delivery-introspectionIt is release-profile only — in each case the plain
cargo teststep passedand only
cargo test --releasefailed.What this changes
A new fixture,
make_worker_registry_with_unwritable_worker: the worker ispresent in the registry but has no stdin writer at all.
command_rxis dropped,so the queue send fails immediately and
deliver()surfaces the samefailed writing frame to worker '<name>'error a live writer reports on a writefault. No OS, timing, profile or load dependence remains.
This follows the existing
make_worker_registry_with_stalled_workeridiom in thesame file — construct a deterministic
WorkerHandlerather than race a realprocess.
Every assertion is tightened, none relaxed:
>=, whichexisted only to tolerate the pipe race)
Attemptedarm is now unreachable and panics, instead of asserting a boundlastErrormust carry the real write error — the|| "max delivery retries exceeded"alternative is gonecleanup_worker_registrycrates/broker/src/runtime/delivery.rsis not modified andMAX_DELIVERY_RETRIESis unchanged. The cap was never the problem; it doesexactly what it says on the consecutive-failure path.
Tests bite
Mutating the guarded code in
delivery.rs(both reverted;delivery.rsispristine in this PR):
1. Cap boundary off-by-one —
failed_attempts >= MAX→>:2. Consecutive-failure counter stalls —
failed_attempts += 1→= 0:3. Terminal wire error wrapped —
worker.rsqueue-send context gains asuffix, so the message still contains the expected fragment but no longer
equals it. This slips past every
containscheck left in the test, includingthe one in the
Nooparm, and is caught only by the exact comparison added inreview:
worker.rsis unmodified in this PR; the mutation was reverted.Determinism evidence, and its limits
Release profile, the one that flaked:
Stated honestly: these numbers do not prove the flake is gone, because I was
never able to reproduce it locally in the first place — 35 release full-suite runs
on the old fixture at
69f0504035produced 0 occurrences. An idle Apple Siliconbox is faster and far less contended than a GitHub macOS runner. The argument for
this fix is structural, not statistical: the write now fails at an in-process
channel with no file descriptor, no signal delivery and no scheduler involved, so
there is no longer a timing-dependent branch to lose. The runs are consistency
evidence on top of that, not the proof.
Trade-off a reviewer should weigh: this removes an accidental detector
The flaky assertion was, on the runs where it tripped, observing a real defect:
a delivery whose writes succeed but which is never ACKed does march
attemptspast the cap, forever, and is never dead-lettered. Making the fixture deterministic
means that behaviour is no longer detected by anything.
That is filed separately as #1686, with the reasoning and the reason it may
bear on the Monday "idle agent stops receiving" risk. It needs its own
deterministic test whichever way it is fixed — it must not be assumed covered
because this test used to trip on it by accident. I did not add a characterisation
test for it here, because pinning the current behaviour would cement the bug.
RelayFlow proof case
Earlier revisions of this PR declared
non-functional/n/a. That was rejected,and correctly:
crates/broker/src/runtime/tests.rsmatches none ofNON_RUNTIME_PATH_PATTERNS(^tests/is anchored at the repo root), so a testfile under
crates/counts as a runtime path however test-only the change is.Verified by running the classifier directly —
runtimeSurfaceChanged()returnstruefor this file list.Now declared
bugfixwith case1688-delivery-failure-error-fidelity.The proven bug is real and is one this PR fixes. On a terminal delivery failure
the broker emits
message_delivery_failedcarryinglastError— the onlymachine-readable account of what killed the delivery, and what reaches the
dead-letter store and the orchestrator. Base asserted only that it contains an
expected fragment, so an error wrapped or substituted anywhere in the write path
still satisfied it. Head compares it exactly.
Why it is shaped as mutation detection.
runtime/tests.rsis behind#[cfg(test)](runtime/mod.rs:89), so it is compiled out of the shippedbroker. Base and head produce functionally identical binaries, and a case that
merely runs the broker would prove nothing about this change whatever it
observed. So both arms inject the same defect into the write path and ask the
target's own test whether it notices. The defect is faithful rather than a
strawman: the message still CONTAINS the fragment and only stops being EQUAL to
it — exactly the class base could not see.
All three write-error context sites are rewritten, not one. Base surfaces this
error from the completion path and head from the queue-send path, so mutating a
single site leaves the defect inert on one arm. A first draft did exactly that
and produced a base "pass" that proved nothing; the runner now asserts it finds
all three and refuses to run otherwise.
Fail-closed. Only two results count as evidence — the target's test passing
with the defect live (
bug), or failing on that exact comparison (fixed). Amissing toolchain, a compile error, a failure at any other assertion, or an
unparseable run throws instead. A crash must never be laundered into a proof.
Both arms were executed locally against real checkouts before pushing:
NON_RUNTIME_PATH_PATTERNSand the proof workflow are untouched.Not in the changelog
Deliberate. Per
CLAUDE.mdthe root changelog is the user-facing releasenarrative; a test-fixture determinism fix changes nothing a user of
agent-relaycan observe.
Refs #980
Refs #1686
🤖 Generated with Claude Code
https://claude.ai/code/session_015LAYEYtXwYhV9MdfCPguQr