fix(native): the spawn wrapper never had the env its payload demands - #500
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A standing watch on a native box stopped starting sessions. The receiver
logged, once per matching event:
local-webhook: spawn command exited 1 for defangdevs/agent-box:
agent-box-webhook-spawn: line 375: AGENT_BOX_ENVSTORE_BIN: the env-store
CLI is pinned by the generated wrapper; run this through the installed
command
and DROPPED the batch. GitHub does not retry, so the event is gone: an
@mention asking the box for work reached it and started nothing.
webhook-spawn.sh reads AGENT_BOX_ENVSTORE_BIN with ${...:?}, deliberately —
it parses the per-user env file with the store's own parser rather than a
fifth copy of the KEY=value loop (#212). The module exports it into
webhookSpawn's derivation. The native renderer's wrapper exported only
AGENT_BOX_HOOK_ARGS_OPTION_NAME, so the payload died before its first line
of work. Two more were missing beside it: AGENT_BOX_FLOCK_BIN, which
registry.sh takes the hook-session cap lock through and which is not on the
receiver unit's PATH, and AGENT_BOX_DEFAULT_AGENT, without which --preamble
reports "<the box default agent>" instead of naming it.
It only ever appeared to work because the receiver inherited the variable
from the `agentbox apply` process that started it. The box that found this
had been up for hours; a socket-activated restart at 23:48 gave the daemon a
clean environment and the watch went silent with nothing to show for it.
The three go in the spawn wrapper only, not in hook_env: the CLI wrapper's
payload reads none of them, and exporting a name into a wrapper that does not
need it is the same divergence pointing the other way.
Why no check caught it, and the one that does now: backend-parity compares
the names each backend supplies box-wide, and then per (unit, variable) —
which is the #426 lesson, that supplying a name somewhere is not supplying it
to the payload that reads it. A generated WRAPPER is a third place, and it
belongs to no unit: the webhook receiver and the settings daemon both run the
spawn wrapper, so its environment is the prologue the renderer writes above
the `exec`. Both backends write those prologues by hand in two languages —
the half of a shared payload that deduplicating modules/src/ never
deduplicated. Box-wide, AGENT_BOX_ENVSTORE_BIN looked supplied by both,
because the native session and profile CLIs export it. Just not the wrapper
that reads it.
So the check now runs a fourth time, keyed by (wrapper, variable), over the
six wrappers both backends render, with the same two staleness-checked tables
as the other three. Payload self-exports are subtracted: the module's wrapper
inlines the payload and the native one execs it, so a name the payload
exports for itself (AGENT_BOX_REGISTRY_LOCK_FD) would otherwise read as
module-only. Negative control: with the pre-fix fixture the new section fails
and names all three variables.
The one declared divergence is agent-box-webhook's own
AGENT_BOX_HOOK_ARGS_OPTION_NAME, native-side and correct — each backend has a
different home to name for the fleet-wide default.
Verified with the status of the build, not of a tail: NIX_BUILD_RC=0 over all
26 aarch64 checks, 85 native tests OK, PARITY_RC=0.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Rt3Sp5XwGZy1Uzto8qP4is
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Included review availability: Your plan provides up to 8 included reviews per hour; 5 remain after this review. 📝 WalkthroughWalkthroughThe webhook spawn wrapper now exports required locking, default-agent, and environment-store dependencies. Backend parity checking now compares exported variables across generated wrappers and reports wrapper-specific divergences. ChangesWebhook wrapper parity
Estimated code review effort: 3 (Moderate) | ~20 minutes Merge Risk: ⚪ Minimal · up to The change supplies the environment variables required by the native spawn wrapper and adds parity coverage to prevent this mismatch from recurring; no actionable merge-blocking risk remains after normal checks and review. 🚥 Pre-merge checks | ✅ 4 | ❌ 1❌ Failed checks (1 warning)
✅ Passed checks (4 passed)
✨ Finishing Touches 💡 1📝 Generate docstrings 💡
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Inline comments:
In `@scripts/check_backend_parity.py`:
- Line 673: Update the wrapper comparison flow around both so it first compares
the complete mod_wrappers and nat_wrappers name sets, reporting a parity failure
for every wrapper present on only one side; only then perform the intersection
comparison for shared wrappers.
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Fix all unresolved CodeRabbit comments on this PR:
- Push a commit to this branch (recommended)
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bin/agentboxscripts/check_backend_parity.pytests/native/expected/etc/agent-box/bin/agent-box-webhook-spawn
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The per-wrapper comparison intersected the two name sets, so a wrapper only one backend renders was never compared — and renaming native's agent-box-webhook-spawn would have quietly dropped it out of the intersection without failing anything. Absence and intent look identical again, which is the thing this check exists to refuse. The comparison cannot be the raw name sets. The module wraps every payload it packages (one writeShellScriptBin bin/ per payload) while native ships those flat in the profile and generates a wrapper only where per-box config must be baked in, so thirteen module-only names are packaging rather than divergence, and a table of them would say one sentence thirteen times. So what is compared is a one-sided wrapper that EXPORTS a contract variable — the shape with consequences, since the variable is why the wrapper exists. One entry today: agent-box-attach carries AGENT_BOX_SESSION_BIN, the same divergence the agent-web-terminal@.service entry already explains from the unit side, cross-referenced rather than restated. Negative control: rename the native spawn wrapper in the fixture and the run fails twice — the module's goes one-sided carrying AGENT_BOX_ENVSTORE_BIN, and the renamed native one is undeclared. NIX_BUILD_RC=0 over all 26 aarch64 checks, 85 native tests OK, PARITY_RC=0. CodeRabbit on PR #500. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01Rt3Sp5XwGZy1Uzto8qP4is
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Sep 2, 2026
…#488) A standing watch can now name the agent profile its own sessions start on: `agent-box-webhook subscribe --profile NAME` writes a spawnConfig onto the dispatch entry, the receiver hands it to the spawn command in LOCAL_WEBHOOK_SPAWN_CONFIG, and webhook-spawn.sh resolves it. Two watches on one repo can therefore start different workers, and local-webhook queues dispatch batches per (key, spawnConfig) so they cannot coalesce into one spawn that hands one watch's events to the other's worker. AGENT_BOX_HOOK_PROFILE stays the box-wide fallback. --preamble reports which worker a match starts, and both of its guards are exercised through the dispatch file. jq is pinned for the --preamble caller (the settings daemon, whose PATH does not carry it) on both backends, which is the same wrapper-prologue parity the check added in #500 now covers. Rebased onto #500: the native jq export folded into that PR's spawn_env, so the native wrapper's prologue is line-for-line parallel to the module's.
defangdevs
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Sep 2, 2026
…lists (#502) #500 added a parity comparison because a wrapper prologue COULD diverge. This removes the ability to diverge: modules/src/contract/wrappers.json declares each generated wrapper's environment once — the export and the reason it exists — and both renderers render it, so neither backend writes a prologue any more. The mechanism is issue #451's contract, one level over. It already carries a UNIT's bindings as data both backends read; a wrapper belongs to no unit, which is why it fell through — the webhook receiver and the settings daemon both run agent-box-webhook-spawn, so what its payload gets is the block above the `exec`. Entries are 'bin' (names a PROGRAM, resolved by each backend the way it already resolves a unit contract's) or 'config' (names a per-box VALUE by key, because the two backends may legitimately resolve one to different text — a diagnostic naming where a default LIVES has to name a NixOS option on one and config.yaml on the other). omitWhenEmpty keeps "nothing set" distinguishable from "set to nothing". The per-export prose moves into the manifest too: it was maintained twice, once in Nix and once in Python, which is how the two drift. Two divergences died on the way, both invisible box-wide because each name was supplied SOMEWHERE by both backends: the module's CLI wrapper never exported AGENT_BOX_HOOK_ARGS_OPTION_NAME and now does, so #500's by-design entry for it is deleted; and native's CLI wrapper exported AGENT_BOX_HOOK_SESSION_ARGS, which nothing reads, and now does not. Scope is the two webhook wrappers. Session, profile, password and attach are a follow-up; #500's comparisons stay as the backstop until they migrate.
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A standing watch on a native box stops starting sessions. Every matching event dies here, and the batch is dropped — GitHub does not retry, so the event is gone:
Found on this box when an
@mentionasking it for work reached it and started nothing.What is wrong
modules/src/webhook-spawn.shreadsAGENT_BOX_ENVSTORE_BINwith${...:?}, deliberately (#212). The module exports it intowebhookSpawn's derivation. The native renderer's generated wrapper exported onlyAGENT_BOX_HOOK_ARGS_OPTION_NAME:Two more were missing beside it:
AGENT_BOX_FLOCK_BIN, whichregistry.shtakes the hook-session cap lock through and which is not on the receiver unit's PATH, andAGENT_BOX_DEFAULT_AGENT, without which--preamblereports<the box default agent>instead of naming it.It only ever appeared to work because the receiver inherited the variable from the
agentbox applyprocess that started it. A socket-activated restart hands the daemon a clean environment, and the watch goes silent with nothing to show for it.Why no check caught it
backend-paritycompares the names each backend supplies box-wide, then per(unit, variable)— the #426 lesson, that supplying a name somewhere is not supplying it to the payload that reads it. A generated wrapper is a third place, and it belongs to no unit: the webhook receiver and the settings daemon both run the spawn wrapper, so its environment is the prologue the renderer writes above theexec. Both backends write those prologues by hand, in two languages — the half of a shared payload that deduplicatingmodules/src/never deduplicated.Box-wide,
AGENT_BOX_ENVSTORE_BINlooked supplied by both backends, because the native session and profile CLIs export it. Just not the wrapper that reads it.What this changes
bin/agentboxexports the three names into the spawn wrapper — and only there. The CLI wrapper's payload reads none of them, and exporting a name into a wrapper that does not need it is the same divergence pointing the other way.scripts/check_backend_parity.pyruns a fourth comparison, keyed by(wrapper, variable), over the six wrappers both backends render, with the same two staleness-checked tables as the other three. Payload self-exports are subtracted, since the module inlines the payload and native execs it.agent-box-webhook's ownAGENT_BOX_HOOK_ARGS_OPTION_NAME, native-side and correct.Negative control: with the pre-fix fixture, the new section fails and names all three variables.
Verification
Read from the status of the build, not of a tail:
NIX_BUILD_RC=0over all 26 aarch64 checks, 85 native tests OK,PARITY_RC=0.Note for #488, which is mine: it adds
AGENT_BOX_JQ_BINto both sides of the same wrapper. Once this lands I rebase that branch, and the new check covers its variable too.🤖 Generated with Claude Code
https://claude.ai/code/session_01Rt3Sp5XwGZy1Uzto8qP4is