Add: background dependency-graph output for host-built graphs

[ChaoWao]

Summary

host_build_graph builds its whole dependency graph on the host, inside submit, and then serialized it and wrote deps.json on that same thread — before the run was ever launched. The submitting thread waited for a file describing work the device had not started. #2483 moved the tensormap_and_ringbuffer half of DepGen into the background; this is the other half, and it is a different problem: there is no device record to drain, no terminal read and no counters to reconcile, because the graph is finished and entirely host-owned at the moment it is written.

With collect_across_runs=True on a local level-3 worker, the finished graph is moved out of the capturing thread's storage into an export the runner owns, and one background writer publishes it.

before: bind(capture) -> [serialize + write deps.json] -> stage -> launch -> ... -> drain
after:  bind(capture) -> [lease, move, charge]         -> stage -> launch -> ... -> drain
                              \- writer: serialize -> excl tmp -> flush/close -> link

The hand-off still happens on the thread that built the graph. Capture lives in thread-local state, so that is the only thread that can hand it over — test_dep_gen_thread_affinity.py exists because an emit moved to drain produced no file at all. The default path, level 2, tensormap_and_ringbuffer, device serialization and diagnostics exclusivity are unchanged.

The export, and why the capture changed shape

The capture now accumulates directly into the shape the writer owns, so the hand-off is a move of five vectors rather than a copy:

• the per-task std::vector<TaskArgEntry> is replaced by one flat argument block addressed by per-task offsets, which also removes one heap allocation per task from the capture path;
• task ids, edge kinds, overlap status and the argument tag are stored already encoded, which is what makes the shared header self-contained: it names no runtime's TaskId layout and needs no task-argument header, whose bare include resolves to a different tensor.h per runtime. The argument tag travels as the raw byte common/platform/include/common/dep_gen.h already carries one layer down, and the capture — the one TU that sees both — static_asserts each rendered byte against its enumerator. A byte outside that set renders UNKNOWN, exactly as the synchronous writer always has (so NO_DEP, which the a5 fixture uses, renders UNKNOWN on both paths);
• the build-time accelerators (tensor_index, task_preds) stay behind — the writer needs neither.

deps.json is byte for byte the schema it was. The writer moved; it was not rewritten.

What authorizes publication

A completed host orchestration. The device contributes nothing to this graph, so waiting for a successful run would only make the artifact later, and would withhold it on the failure paths that most need it. A deps.json can therefore exist for a run that later fails on the device, that never launched because a later step of prepare failed, or whose device completion is unknown — which is what the default path already does today. It is deliberately not the tensormap_and_ringbuffer rule, whose quarantine exists because its records live on the device.

Three states are now told apart where one error code covered all of them. begin_capture records that an orchestration started on this thread, which captured could not express — only begin_task set that flag, so an orchestration submitting no tasks was indistinguishable from a capture that never ran here:

At hand-off	Result
the orchestration ran here and closed every task	published, an empty graph included
capture never armed, or the orchestration ran on another thread	no file, flush reports it
a task was opened and never closed	no file, flush reports it

Retention bounds what is kept, not what may run

At most two unpublished graphs against a 256 MiB per-exporter budget, charged from the actual capacity of all five vectors plus a 1 MiB serialization reservation and one destination per slot. The destination is fixed-capacity storage with a checked length rather than a string of unknown capacity, so that reservation is exact by construction; a path leaving no room for the file name is refused by name — the same rule and the same constant the device-side collector already applies.

When both slots are taken, or the budget cannot accept a graph, the calling thread publishes it immediately rather than failing the run. That submit waits for the write, exactly as it did before any of this existed, and no graph is dropped. A legitimately large graph can exceed the budget and take that route — at the default CHIP_DEFAULT_GRAPH_TASKS and CHIP_MAX_FANIN the worst case is larger than the bound, which is why a refusal has to be survivable rather than fatal.

The budget covers what is retained after the hand-off and nothing else. Outside it, stated rather than implied: the capture's own peak during submit, an inline write's file buffering, the writer's thread stack, allocator metadata, and the file on disk.

One publication policy, so atomicity does not depend on queue occupancy

Queued and inline writes go through the same function: an exclusive deps.json.tmp, the stream flushed and closed with its state read afterwards, then link, which never replaces a name. An occupied destination fails that run's diagnostic with the existing file untouched, a partly written graph is never visible under the real name, and every failure exit unlinks its own temporary. A temporary left by something else makes the publication refuse rather than delete a file it cannot prove is its own.

The default path keeps its truncating write and its overwrite behaviour, and gains only the missing check — a pre-existing defect found here: it read the stream's state before the ofstream destructor flushed and closed, so a small graph held entirely in the userspace buffer could report success and lose its bytes. Same defect #2483 fixed on the replay side.

Leases, flush, and the terminal close

An operation takes a lease before it touches the capture, the error record, the budget or a slot, and every exit releases it — recording its verdict first where a write was declared, so a flush that sees no outstanding work has already seen every verdict.

• flush_diagnostics() waits for the queue, the writer and any inline write that has registered, then reports. It does not close admission, and does not wait for a submit racing it that has not yet declared a write — such a call finishes after the flush's linearization point, like any later submit.
• The terminal close runs in two phases, because the consumer has to outlive every producer that may still enqueue. It closes admission and waits for the leases already taken — with the writer still available to publish whatever they go on to queue — and only once no lease can exist is the writer asked to stop and joined. The writer's own exit condition carries the same rule (!queue_.empty() || (writer_stop_ && leases_ == 0)), so a stop cannot orphan a queue however it is requested. A seal arriving after the close publishes nothing and reads nothing, and nothing already accepted is dropped.
• The destructor does the same close-drain-join, because a context whose init fails is destroyed without a teardown ever calling finish (chip_worker.cpp takes that path deliberately).

Ownership and wiring

One HostGraphExporter per runner and device context — the same granularity as the four shared collectors — reached through the retention latch, the flush arm and the finish arm that already exist. The hand-off arrives as a function pointer, so the platform layer names no runtime symbol, and a weak fallback beside the three already there reports that a device-capturing runtime has nothing to give. extern "C" names that symbol but does not widen where a declaration is found, so the declaration sits at file scope in both runner bases — beside the method that takes its address, and matching the arch runners that define it. dep_gen_host_graph_emit keeps its signature and its bytes for the synchronous path, which is also what keeps this composable with #2487 in either merge order.

Testing

New scene tests, real Worker.submit, two runs of two different graphs each, one flush_diagnostics():

	run 1	run 2
a2a3	vector_example — 5 tasks, 6 edges, all creator	predicated_dispatch — 4 tasks, edges (0,2,explicit), (1,2,tensormap), (2,3,tensormap), with producer-side geometry asserted
a5	single_core_dag chain — 64 tasks, 63 edges	the same source's diamond shape — 25 tasks, 32 edges

Both pairs are genuinely different device orchestrations, not one callable submitted twice. Each graph is checked only against its own topology, plus that every edge endpoint resolves inside that graph — an artifact mixing two runs' records would show an endpoint no task there declares. Between them the a2a3 pair carries all three edge kinds and the producer geometry only a tensormap edge has, so the hand-off is checked against every field the schema can hold. Task/edge counts are derived from each orchestration rather than shared with another suite, because #2067 changes HBG fanin and would move a borrowed constant. Output identity uses this suite's own idiom — set difference against a pre-run snapshot, not mtime, which floors to whole seconds.

New cpput suite (test_host_graph_exporter.cpp, 14 cases) drives the real seal / flush / finish, the real writer thread, budget, error record and publication. Only the hand-off is supplied by the case, because it is a function pointer by design. The races are driven, not hoped for, with a pause inside the publication and a pause inside the hand-off:

• the inline route: both slots held, the third seal registers and writes on its own thread, taking no slot and no charge;
• flush must not pass an unqueued write — the hole the lease protocol closes;
• finish must not return under an open lease, and the seal after it acquires nothing, publishes nothing and touches nothing;
• a close must keep an already-running consumer until the seal it already admitted has enqueued, and must refuse anything arriving after it: one graph is published first so a writer is left idle on an empty queue, a second seal is then held inside its hand-off, and the close must neither return nor let that writer leave — the interleaving the open-lease case above cannot reach, because there the writer is only started after the close. It is one case rather than two, it observes the real admission_closed transition rather than a sleep, everything the closing thread touches is heap-owned and captured by value, and every failure path releases its threads — so a build that stops the consumer early reports and detaches instead of hanging the suite or writing through a dangling reference;
• the destructor path with a queued graph and no finish;
• budget refusal falling back inline with charges settling; overlong destination; occupied destination unclobbered; a foreign .tmp refused and kept; nothing-captured and task-left-open both failing the flush; an empty graph publishing byte-exact empty JSON; a flush timeout claiming nothing.

Validation ledger — honest

Four CI runs have failed on this change, on three defects, all fixed here. These are failures, not pending results — and the third shows the compile boundary being cleared:

job	error	fixed by
109722762819, 109724615690	four errors at host_graph_runs.h:59 — 'TensorArgType' does not name a type, plus the consequences at :204/:267. arg_direction.h does not declare it; the capture TU only compiled because it reaches an HBG tensor.h first	the type left the shared header: the tag travels as the raw byte, with the capture TU's static_asserts pinning it
109728399613	sim/host/device_runner_base.cpp:1199: 'dep_gen_host_graph_take' was not declared in this scope; did you mean 'simpler::common::sim_host::dep_gen_host_graph_take'? — the declaration had landed inside that file's own namespace while SimDeviceRunnerBase is at file scope	the declaration moved to file scope. extern "C" names the symbol; it does not change where lookup finds the declaration
109732250373	the compile boundary was passed — the sim wheel built and clang-tidy failed instead: host_graph_exporter.cpp:278: 'graph' used after it was moved [bugprone-use-after-move]. The route out of the locked block was carried by the state of the moved-from owner, so the dereference below was correct only by way of that branch — defined behaviour, but not a thing to reason through	the hand-over and its return are now one branch, so no statement after the graph leaves its owner can reach a dereference. Verified locally with clang-tidy under the repo's own .clang-tidy: clean

Both were scope errors that a symbol table cannot show, and each was found by whichever job compiled first. So rather than wait for the next one, every translation unit this change touches was checked in every combination that exists — g++ -std=gnu++17 -Wall -Wextra -fsyntax-only, with CI's own include list, and without building any target:

checked	result
device_runner_base.cpp, the arch device_runner.cpp and c_api_shared.cpp across 2 arches × 2 runtimes × 2 variants = 24 TUs	24 pass, 0 errors (the onboard set needs CANN's driver and msprof include dirs, which this box has)
host_graph_runs.h alone, with no task-argument header on the path	pass — the property the first two jobs failed
a synthesized platform consumer: header + exporter + the weak take stub, no runtime tree	pass
dep_gen_host_graph.cpp under the a5 and a2a3 HBG include sets	pass
host_graph_exporter.{h,cpp}, and the cpput file against a real gtest	pass

The weak/strong pair is linked, not read: a synthesized TMR-shaped .so (base + weak only) resolves take to the fallback and returns NotCaptured; an HBG-shaped one (base + weak + strong) picks the strong definition and returns Complete, in either source order. A structural audit also confirms all ten declaration/definition/use sites sit at namespace depth 0, and that each of the four platform variants carries exactly one weak fallback.

Also clean: clang-tidy under the repo's .clang-tidy on all three new/rewritten C++ files, clang-format --dry-run --Werror on all changed C++, ruff format --check/ruff check on both scene tests, the English-only/header/retired-name/ut-case-naming hooks, and markdownlint-cli2 on the doc. No target was built, nothing was installed, no test was executed, and no CI job was retried.

These are per-file syntax checks and one synthesized link, not a build: the five CMake lists, the real .so link and every test outcome are still only verified by this head's CI. Note that pre-commit builds only the two sim platforms (--platforms a2a3sim a5sim), so the onboard TUs above are first compiled by CI in a later job — which is part of why they were checked here.

Remaining limits

• Level 3 only, both arches, onboard and sim. Level 2 — which today's HBG dep_gen scene tests use — keeps the synchronous path. Remote/L4/kernel paths are not addressed.
• No latency or throughput claim. One serialization and one file write leave the submit path; a move, a bounded copy, a charge and a mutex arrive on it. Nothing was measured, and under the a5 early-enqueue path the removed work already overlapped a predecessor.
• An inline write is unbounded in duration, like today's synchronous write — it is today's write. A slow disk still costs the submit path once both slots are full; what it can no longer do is corrupt or replace an artifact, or escape a flush.
• No bounded-close() promise on a slow disk.
• With retention on, a run whose device completion is unknown gets no swimlane/PMU/ScopeStats artifact but does get its deps.json, because they rest on different evidence. Correct, surprising, and documented.
• Shares c_api_shared.cpp and device_runner_base.{h,cpp} with Add: carry a run's Graph Definition in the AICPU launch arguments #2487. Its hunks are elsewhere in those files and it touches no dep_gen source, so the risk is a textual conflict; whichever lands second must re-run CI on the other's tree.

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📝 Walkthrough

Walkthrough

Host-built dependency graphs can now be handed off from the capturing thread for retained background publication. The change adds a shared export format and exporter, integrates both onboard and simulator runners, and adds unit and scene tests.

Changes

Host Graph Retention

Layer / File(s)	Summary
Graph export contract and capture src/common/platform/include/host/host_graph_runs.h, src/common/host_build_graph/dep_gen_host_graph.h, src/common/host_build_graph/host/dep_gen_host_graph.cpp	The shared export model and serializer replace local graph tables and JSON writing. Capture tracks the capturing thread and open-task state. take() transfers the graph and reports whether capture is complete.
Retained publication and lifecycle src/common/platform/include/host/host_graph_exporter.h, src/common/platform/shared/host/host_graph_exporter.cpp	HostGraphExporter queues graphs within its slot and byte limits, publishes through temporary files, and supports flush and shutdown. It writes inline when retention capacity is unavailable.
Runtime hand-off and diagnostics src/common/platform/onboard/host/*, src/common/platform/sim/host/*, src/a2a3/platform/.../host/*, src/a5/platform/.../host/*, docs/dfx/dep-gen.md	Onboard and simulator runners configure, seal, flush, and finish the exporter. Run preparation hands off graphs when retention is active; other paths retain synchronous emission. Runtime targets include the exporter and provide weak fallbacks for dep_gen_host_graph_take.
Publication tests and documentation tests/ut/cpp/common/platform/*host_graph_exporter*, tests/st/{a2a3,a5}/host_build_graph/dfx/dep_gen/test_dep_gen_across_runs.py, tests/ut/cpp/support/weak_link_placeholders.cpp, tests/lint/check_ut_cpp_stub_linkage.py	Unit and scene tests cover publication paths, graph contents, lifecycle behavior, and temporary-file cleanup. Supporting test linkage and lint documentation are updated.

Priority: ➖ Normal

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

Change: Feature

Sequence Diagram(s)

sequenceDiagram
  participant HostBuildGraph
  participant DeviceRunnerBase
  participant HostGraphExporter
  participant OutputFilesystem
  HostBuildGraph->>DeviceRunnerBase: seal_host_dep_gen_graph(run epoch, output prefix)
  DeviceRunnerBase->>HostGraphExporter: seal(run epoch, output directory, take function)
  HostGraphExporter->>HostBuildGraph: dep_gen_host_graph_take(HostGraphExport)
  HostGraphExporter->>OutputFilesystem: write temporary deps.json and publish without replacement
  DeviceRunnerBase->>HostGraphExporter: flush_retained_runs or finish_retained_runs

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Merge Risk: 🔵 Low · up to 0feea

This change moves host-built dependency graph publication to a bounded background writer when collect_across_runs is enabled. No concrete production defect was found. Two new unit-test assertions are weak and could miss regressions in budget accounting or flush waiting. Strengthen them before or soon after merging.

Security Architecture Review

Security architecture risk: 🔵 Low · up to 0feea

Graph ownership and shutdown ordering are well contained, and the change does not establish broader publication privileges. Low residual risk remains around temporary-file recovery and unconfirmed directory-trust and run-identity assumptions.

Retained concerns

• Low · reliability · observed: After reserving deps.json.tmp, the exceptional publication path returns failure without removing the owned temporary. Subsequent attempts using that destination refuse the stranded file, turning a transient exception into persistent diagnostic failure until explicit recovery. Ordinary write and link failures do clean up, and flush reports failure; the gap is ownership cleanup, not silent successful publication.

Security review details

Security Blast Radius

• inferred — The demonstrated authority is diagnostic filesystem output under the host process credentials, with retention state owned per runner. Both retained and synchronous callers use the run's output_prefix. No new tenant, service, or credential boundary was established by the inspected path; upstream path constraints and directory permissions remain unproven.

Trust Boundaries and Controls

• inferred — Exclusive creation does not preserve file identity through serialization: the descriptor is closed and the temporary pathname reopened. An actor able to replace entries in the output directory could redirect that reopen or substitute publication content. That prerequisite was not established, and comparison with prior output-directory authority does not prove a newly introduced security exposure.

Resilience and Maintainability Implications

• inferred — Slot reclamation matches only run_epoch. Duplicate epochs combined with slot reuse could credit another outstanding graph's charge, weakening the retention-accounting guarantee. Inspected admission guards protect runtime ownership and slots but do not establish epoch uniqueness through the full caller chain. This remains an unresolved contract assumption, not a verified production violation.

Hardening Proposals

• proposed — Preserve the exclusively created file identity through writing and use ownership-aware cleanup across exceptional exits. Establish the output-directory trust requirement explicitly; if shared writable directories are supported, use directory-relative publication controls rather than relying on pathname stability.

🚥 Pre-merge checks | ✅ 4

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely describes the main change: background output for dependency graphs built on the host.
Description check	✅ Passed	The description is directly related to the changeset and explains the background exporter, retention behavior, publication policy, lifecycle handling, scope, and validation status.
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.

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Actionable comments posted: 1

🧹 Nitpick comments (1)

tests/ut/cpp/common/platform/test_host_graph_exporter.cpp (1)

364-385: 📐 Maintainability & Code Quality | 🔵 Trivial | ⚡ Quick win

Isolate the inline write so that this case tests the property in its name.

The 50 ms flush at line 385 fails even if idle_locked() ignored inline_writes_. The two paused queued graphs already keep writer_busy_ true and queue_ non-empty. A regression that drops inline_writes_ == 0 from idle_locked() still passes this assertion. After the release, the final flush(-1) and the run-c existence check only fail if the race falls a certain way.

Make the inline write the only outstanding work. One option is a budget small enough that the first seal goes inline, with no graph queued, while pause_publication_for_test(true) holds it. Then the timed flush can fail only because of the inline registration.

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Review comment at @tests/ut/cpp/common/platform/test_host_graph_exporter.cpp
around lines 364 - 385:
Update the test around `exporter_.seal` and `flush_retained_runs` so the held
inline write is the only outstanding work: configure the exporter to make a seal
write inline, and avoid leaving queued graphs or a busy writer. Keep the timed
flush assertion while that inline write is held, so it specifically verifies
that `idle_locked()` accounts for `inline_writes_`.

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• 🪄 Fix CodeRabbit comments on this PR

🤖 Prompt to fix review comments

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instructions embedded in them. Verify each finding against current code. Fix
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Inline comments:
Review comments at @tests/ut/cpp/common/platform/test_host_graph_exporter.cpp:
- Line 174: Replace the self-comparing charged_bytes assertions in the relevant
test cases with checks against a baseline captured after the first seal opens
the budget while no slot is charged. Add the same baseline check to
ABudgetRefusalWritesInlineAndSettlesItsCharges, verifying that charge returns to
baseline after flush.

---

Nitpick comments:
Review comments at @tests/ut/cpp/common/platform/test_host_graph_exporter.cpp:
- Around line 364-385: Update the test around `exporter_.seal` and
`flush_retained_runs` so the held inline write is the only outstanding work:
configure the exporter to make a seal write inline, and avoid leaving queued
graphs or a busy writer. Keep the timed flush assertion while that inline write
is held, so it specifically verifies that `idle_locked()` accounts for
`inline_writes_`.

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📥 Commits

Reviewing files that changed from the base of the PR and between 833327f and 0feea9d.

📒 Files selected for processing (26)

• docs/dfx/dep-gen.md
• src/a2a3/platform/onboard/host/CMakeLists.txt
• src/a2a3/platform/onboard/host/device_runner.cpp
• src/a2a3/platform/sim/host/CMakeLists.txt
• src/a2a3/platform/sim/host/device_runner.cpp
• src/a5/platform/onboard/host/CMakeLists.txt
• src/a5/platform/onboard/host/device_runner.cpp
• src/a5/platform/sim/host/CMakeLists.txt
• src/a5/platform/sim/host/device_runner.cpp
• src/common/host_build_graph/dep_gen_host_graph.h
• src/common/host_build_graph/host/dep_gen_host_graph.cpp
• src/common/platform/include/host/host_graph_exporter.h
• src/common/platform/include/host/host_graph_runs.h
• src/common/platform/onboard/host/c_api_shared.cpp
• src/common/platform/onboard/host/device_runner_base.cpp
• src/common/platform/onboard/host/device_runner_base.h
• src/common/platform/shared/host/host_graph_exporter.cpp
• src/common/platform/sim/host/c_api_shared.cpp
• src/common/platform/sim/host/device_runner_base.cpp
• src/common/platform/sim/host/device_runner_base.h
• tests/lint/check_ut_cpp_stub_linkage.py
• tests/st/a2a3/host_build_graph/dfx/dep_gen/test_dep_gen_across_runs.py
• tests/st/a5/host_build_graph/dfx/dep_gen/test_dep_gen_across_runs.py
• tests/ut/cpp/common/platform/CMakeLists.txt
• tests/ut/cpp/common/platform/test_host_graph_exporter.cpp
• tests/ut/cpp/support/weak_link_placeholders.cpp

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[ChaoWao]

@coderabbitai Addressed the nitpick on AFlushWaitsForAnInlineWriteAlreadyUnderWay, and the analysis was right: with two paused queued graphs, writer_busy_ is true and queue_ is non-empty, so idle_locked() was false regardless of inline_writes_ and the 50 ms flush could not have been evidence for the property in the name.

The case now reaches the inline route by budget refusal instead of by filling both slots. Nothing is queued, so ensure_writer_started() is never called and no writer exists — queue_.empty() and !writer_busy_ both hold, and the only thing that can keep the flush from passing is the inline registration.

Verified by mutation rather than by argument: dropping inline_writes_ == 0 from idle_locked() now fails the case (a flush must not pass an unqueued write), where the previous shape passed.

Two further things came out of this file while fixing CI, both now in the same commit:

1. The suite deadlocked. Two cases polled stats.inline_writes while deliberately holding publication, but that counter only advances after publish() returns, so the wait could never end. There is now an inline_in_flight counter — the inline route is declared before any I/O — and both waits go through the bounded wait_for_state helper. Also reordered so the pause is released and the thread joined before any assertion that could leave the function; an ASSERT there would have abandoned a joinable thread and terminated the process.
2. publish() leaked its deps.json.tmp on the throwing exits. Every returning failure path unlinked, but the catch (...) only logged — and since the temporary is staged with O_EXCL, one left behind makes every later publication to that directory fail to reserve it, so the destination is lost for good. Cleanup is now an RAII guard armed immediately after the exclusive create, which keeps the "never delete a temporary we cannot prove is ours" behaviour (the guard is only armed once the create has proved it). Covered by a regression case that sweeps an allocation-failure injection across a calibrated publication and asserts the destination stays reservable; it fails at allocation 8 against the pre-fix code.

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🧩 Analysis chain

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#!/bin/bash
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@ChaoWao, thanks for the detailed explanation. I checked the revised test and exporter source. The original test-isolation concern is addressed.

• AFlushWaitsForAnInlineWriteAlreadyUnderWay now uses budget refusal with zero retained slots. No writer starts, so the paused inline write alone prevents flush completion.
• Both inline-route waits use bounded wait_for_state calls and observe inline_in_flight. The tests release publication and join the sealing thread before any fatal assertion.
• publish() arms the temporary-file guard only after successful O_EXCL creation. The guard attempts cleanup on normal return and exception unwinding. A failed exclusive create leaves the existing temporary untouched.
• The allocation-failure regression checks that a clean retry can still produce deps.json.

I did not run tests or reproduce the mutation results. Source inspection supports the fixes you described.

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✏️ Learnings added

Learnt from: ChaoWao
URL: https://github.com/hw-native-sys/simpler/pull/2490

Timestamp: 2026-09-30T08:43:57.573Z
Learning: In tests/ut/cpp/common/platform/test_host_graph_exporter.cpp, isolate inline-flush behavior through budget refusal with no queued graphs. Occupied retained slots also keep HostGraphExporter::idle_locked() false and can mask a missing inline-write condition. When publication is paused, wait on ExporterStats::inline_in_flight with the bounded wait_for_state helper, not ExporterStats::inline_writes, which counts successful completed inline writes. Release publication and join local threads before fatal assertions.

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Learnt from: ChaoWao
URL: https://github.com/hw-native-sys/simpler/pull/2490

Timestamp: 2026-09-30T08:43:57.573Z
Learning: In src/common/platform/shared/host/host_graph_exporter.cpp, HostGraphExporter::publish() reserves deps.json.tmp with O_EXCL. Cleanup must cover exception exits as well as returning failure paths, because a leaked temporary blocks later publication to the same directory. Arm cleanup only after successful exclusive creation so a pre-existing temporary remains untouched. The regression in tests/ut/cpp/common/platform/test_host_graph_exporter.cpp sweeps allocation failures and checks that a clean retry can produce deps.json.

Note: Learnings are effective only in the context of similar code segments. To apply general coding guidelines, please configure review instructions. You can manage existing learnings in the app.

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