fix(update): stop switch-to-configuration from restarting a harness-upgrade run in flight - #710
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📝 WalkthroughWalkthroughThe update flow now records an immutable nixpkgs pin, exposes a harness CLI, and upgrades each configured user’s installed agent harnesses after successful switches. New systemd units, wrappers, contracts, backend templates, and tests support the flow. ChangesHarness upgrade flow
Priority: ➖ Normal Estimated code review effort: 5 (Critical) | ~90 minutes Change: Feature · Severity of issue fixed: Medium Sequence Diagram(s)sequenceDiagram
participant UpdateService
participant Systemd
participant HarnessCLI
participant NixProfile
UpdateService->>Systemd: start per-user harness upgrade unit
Systemd->>HarnessCLI: run upgrade
HarnessCLI->>NixProfile: build, remove, and add pinned harness
NixProfile-->>HarnessCLI: report success or failure
Suggested reviewers: Merge Risk: 🟠 High · up to The intended update-loop fix may remain ineffective for active per-user upgrades, while transient failures and concurrent runs can leave harnesses stale or downgraded. These issues should be fixed before merge. 🚥 Pre-merge checks | ✅ 3 | ❌ 2❌ Failed checks (2 warnings)
✅ Passed checks (3 passed)
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In `@bin/agentbox`:
- Line 4859: Update the channel-resolution failure branches near the ref returns
to return a failure sentinel instead of the mutable channel URL, and make the
caller check that sentinel before invoking write_agent_pin. Preserve the
existing immutable pin whenever resolution fails, including the alternate branch
identified near the other return.
In `@modules/agent-box.nix`:
- Around line 14315-14338: Update the harness-upgrade service generation to add
a per-user agent-box-harness-upgrade@${name} entry using overrideStrategy =
"asDropin", with restartIfChanged = false and stopIfChanged = false on each
instantiated unit; retain the existing template-level settings.
In `@modules/src/lib/agents.sh`:
- Around line 295-300: Move the _jit_pin_file read and AGENT_BOX_NIXPKGS
equality check to after successful flock acquisition in the upgrade flow, so
concurrent upgrades revalidate the current pin while holding the lock before
removing or restoring anything. Preserve the existing already-pinned early
return behavior.
In `@modules/src/units/agent-box-harness-upgrade`@.service:
- Line 63: Update the service’s SuccessExitStatus configuration to accept only
exit code 0, so agent-box-harness upgrade failures propagate through the unit
status while preserving successful no-harness exits.
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bin/agentboxmodules/agent-box.nixmodules/agent-box.nix.inmodules/src/contract/agent-box-harness-upgrade.jsonmodules/src/contract/wrappers.jsonmodules/src/defang-cli.nixmodules/src/harness-cli.shmodules/src/lib/agents.shmodules/src/units/agent-box-harness-upgrade@.servicemodules/src/update.shnix/runtime.nixscripts/check_backend_parity.pytests/golden/DUPLICATEStests/golden/vm/payloads/agent-box-defang-cli-expr.nixtests/golden/vm/payloads/agent-box-harness/bin/agent-box-harnesstests/golden/vm/payloads/agent-box-supervisor/bin/agent-box-supervisortests/golden/vm/units/agent-box@agent.servicetests/golden/web/payloads/unit-script-agent-box-update-start/bin/agent-box-update-starttests/golden/web/units/agent-box-harness-upgrade@.servicetests/golden/web/units/agent-box-update.servicetests/golden/web/units/agent-box@agent.servicetests/golden/web/units/agent-box@robot.servicetests/native/expected-modes.jsontests/native/expected/etc/systemd/system/agent-box-harness-upgrade@.servicetests/native/expected/etc/systemd/system/agent-box-harness-upgrade@.service.d/execstart.conftests/native/expected/usr/local/bin/agent-box-harnesstests/test-jit-agents.sh
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…pgrade run in flight update.sh starts agent-box-harness-upgrade@<user> --no-block right after a successful switch, and a harness closure a few hundred MiB wide can still be downloading when the next update's switch-to-configuration runs. Every generation changes this unit's rendered definition (the ExecStart resolves through the whole system closure, like agent-box-update's own ExecStart does), so switch-to-configuration tries to stop-then-restart the still-running instance — which surfaced as it exiting 4 with "Failed to start agent-box-harness-upgrade@<user>.service: Unit ... not found" and rolling the whole update back (#707). agent-box-update.service hit the identical self-inflicted-restart shape and already carries restartIfChanged/stopIfChanged=false for exactly this reason; apply the same two lines here. Leaving an in-flight run alone costs nothing — the next trigger starts fresh from the new unit file anyway. Regenerated modules/agent-box.nix from the .nix.in source and refreshed the golden snapshot to match (X-RestartIfChanged/X-StopIfChanged now render in the drop-in). Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01MB26GQRXxhfGYoxWTsUp6M
… template-level CodeRabbit caught this on PR #710: a template-level `systemd.services."agent-box-harness-upgrade@"` drop-in is exactly the construct agent-box@ already proved (PR #295) never merges into an INSTANTIATED unit's config on a real boot, even right after a daemon-reload. restartIfChanged/stopIfChanged are switch-to-configuration's own read of a unit's properties, not something `systemctl start` merges at run time - so leaving the previous commit's fix at the template level would have left switch-to-configuration reading the default (true) for every real per-user instance and not actually fixed #707. Move to a per-user `agent-box-harness-upgrade@${name}` entry with overrideStrategy = "asDropin", mirroring agent-box@'s own per-instance pattern, with both restartIfChanged and stopIfChanged on each instance. Verified by evaluating a NixOS config with selfUpdate.enable = true: the four configured users now each render restartIfChanged = false; stopIfChanged = false on their own instance. Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01MB26GQRXxhfGYoxWTsUp6M
nix run .#update-golden after the per-instance restructure: the golden fixture's single template file becomes one per configured user (web/units/agent-box-harness-upgrade@agent.service, deduplicated against robot's identical copy via DUPLICATES, matching how agent-box@ already does this). Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01MB26GQRXxhfGYoxWTsUp6M
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Addressed in bc26286 (per-instance overrideStrategy fix, confirmed and resolved). The other 3 findings on this review were on pre-existing code that is no longer part of this PR after the branch was rebased cleanly onto master (see thread replies) - CodeRabbit itself acknowledged and withdrew them.
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… a JIT-upgrade race (#711) Two findings CodeRabbit raised on PR #710 (real, but unrelated to #707, since that PR's branch had been based on a stale pre-squash-merge history that made them look like part of its diff - they are not; the branch has since been corrected): - bin/agentbox's resolve_agent_pin() returned the mutable channel URL itself on a failed resolution (network error, or a redirect that did not land on a nixpkgs release). The caller wrote that straight into the pin file, silently downgrading a good immutable pin to the mutable channel URL on nothing worse than a transient blip - and that write survives an otherwise-successful update, since it is not part of what a failed update rolls back. resolve_agent_pin() now returns None on failure and the caller skips write_agent_pin() entirely, leaving the existing pin alone (matching what the OSError handler already did for a write that failed outright). - modules/src/lib/agents.sh's agent_upgrade() read the recorded pin and decided "already at this box's pin" BEFORE acquiring the per-harness flock, not after. Two concurrent upgrades for the same agent (the update service loops over every user; a person can run this by hand at the same moment) could both pass that check before either took the lock; if the second one's own `nix profile add` then failed, its recovery path restored what it still believed was the previous pin, silently undoing the first process's already-successful upgrade. Moved the pin read to right after the lock is acquired, matching how agent_install() already re-checks its own condition once it holds the lock ("The winner of the race installed it while we waited; nothing to do."). Both are one-line-of-logic fixes with no design trade-off, so this goes straight to a PR rather than an issue, per AGENTS.md. Claude-Session: https://claude.ai/code/session_01MB26GQRXxhfGYoxWTsUp6M Co-authored-by: defangdevs <defangdevs@users.noreply.github.com> Co-authored-by: Claude Sonnet 5 <noreply@anthropic.com>
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Summary
Fixes #707.
agent-box-update.servicestartsagent-box-harness-upgrade@<user>with--no-blockright after a successfulnixos-rebuild switch(issues #559,#590, #614). A harness closure is a few hundred MiB, so the per-user move can
still be running when the next update's
switch-to-configurationruns.Every generation re-renders this unit's definition (the
ExecStartresolvesthrough the whole system closure — exactly like
agent-box-update's ownExecStartdoes), soswitch-to-configurationtreats it as changed andtries to stop-then-restart the still-running instance. That's what surfaced
as:
with
switch-to-configurationexiting 4,nixos-rebuild switchfailing, andupdate.shrolling the whole update — source tree included — back, eventhough the new generation had already activated successfully.
agent-box-update.servicehit this identical self-inflicted-restart shapealready (see the comment a few lines below in the same file) and carries
restartIfChanged = false; stopIfChanged = false;for exactly this reason.This PR adds the same two lines to
agent-box-harness-upgrade@. Leaving anin-flight run alone costs nothing: the next trigger starts fresh from the new
unit file anyway.
Changes
modules/agent-box.nix.in: addrestartIfChanged = false; stopIfChanged = false;tosystemd.services."agent-box-harness-upgrade@".modules/agent-box.nix: regenerated (python3 bin/assemble-module.py).tests/golden/web/units/agent-box-harness-upgrade@.service: regenerated(
nix run .#update-golden) — the drop-in now rendersX-RestartIfChanged=false/X-StopIfChanged=false.Test plan
python3 scripts/check_backend_parity.py— OK, every divergencedeclared.
nix build .#checks.aarch64-linux.{module-generated-up-to-date,multi-user,backend-parity,module-single-file,phantom-unit-overrides,one-spec-both-backends,golden-snapshot,agentbox-render,assemble-module-escaping,checkout-bootstrap,checkout-options,connect-card,connect-install,download-route,envstore-format,fail2ban-jail,jit-agents,lease-protocol,portal-route,profile-panel,registry-protocol,runtime-profile,session-route,sessions-registry,socket-activated-restart,source-tree,upload-cli,vendor-integrity,webhook-backfill,webhook-claim,webhook-defer,webhook-panel-state,webhook-route,webhook-spawn-claim}— all green (28 checks + the earlier 7 = every aarch64-buildable check).checksare x86_64-only for the qemu-vmtests) were not run from this aarch64 box; CI will cover those.
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