fix(sessions): an unreadable sessions.json is not an empty one (#279) - #538
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Both halves of the box read "cannot parse" as "there are no sessions".
`read_sessions` returned `{}` on any OSError/ValueError, and all three
settings-daemon mutation routes wrote that back plus their own edit. One
click on "Add session" therefore republished the registry with a SINGLE
entry: every other session delisted for good, with its `hasRun`,
`boxSessionId` and `stopped` gone. Running panes survived as unmanaged tmux
sessions nothing respawns, and re-adding a name started a fresh
conversation. Reproduced against the shipped daemon before the fix.
The supervisor could not repair it either: the reconcile loop sent jq's
error to /dev/null, so it iterated over nothing, logged nothing and left
the unit `active (running)` -- a box that looks idle -- and
`registry_ensure` re-seeds only a MISSING OR EMPTY file, which a corrupt
one is neither.
- `load_sessions()` distinguishes the two and raises `RegistryUnreadable`;
add, delete and restart refuse on it, say so in the journal, and put a
banner in front of the operator instead of rewriting the file. A MISSING
registry is still a first boot, and `read_sessions()` still answers `{}`
for the read-only paths, so a corrupt file renders an empty list rather
than a 500 on every route that mentions a session.
- `registry_selfheal()` joins the shared write protocol: the supervisor
calls it at startup and on every tick, so a registry that does not parse
is moved aside as `sessions.json.corrupt-<ts>` (kept, never deleted) and
re-seeded, with one journal line naming the file. A read-only home warns
once per transition rather than every two seconds.
- Its jq check is `-s` (slurped) so it agrees with the daemon's
`json.load`: bare jq reads a STREAM, so a registry with garbage appended
yielded the first document's session names to the loop while python
refused the same file outright.
- `write_sessions` preserves an unknown `version` instead of stamping 1
over a document a newer box wrote, and `load_sessions` keeps an entry
whose value is not an object rather than silently dropping it into a
write that would delete it.
Coverage, natively on every architecture plus one VM assertion:
- `tests/test-sessions-registry.py` (new check `sessions-registry`): the
three routes against five ways the file can break, the banner, the
version, and the negative control that a healthy registry still works.
- `tests/test-registry.py`: quarantine-and-reseed, trailing garbage, two
documents, the `.sessions`-as-a-list shape from #356, a healthy tick
touching nothing, first boot with no directory, an unwritable directory
warning once, and a heal waiting for a writer that holds the lock.
- `tests/sessions.nix`: corrupt the registry on a live box and assert the
declared session comes back on its own, the bad file is kept and the
journal names it.
Fixes #279
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01YZxFZERYWS1ynz9T8HnnPa
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Important Approval pendingCodeRabbit has no unresolved comments, but it could not review the latest commit because the review limit was reached. Follow the review guidance in this comment to continue. 📝 WalkthroughWalkthroughThe change adds strict session registry validation, supervisor self-healing, version-preserving mutation routes, visible refusal handling, generated payload updates, integration tests, and a native Nix check. ChangesSession registry integrity
Estimated code review effort: 4 (Complex) | ~45 minutes Merge Risk: 🟡 Moderate · up to Concurrent registry activity during recovery can leave declared sessions unseeded. Keep the lock through reseeding before merging. Sequence Diagram(s)sequenceDiagram
participant agent-box-supervisor
participant sessions.json
participant registry_selfheal
participant settings-daemon
agent-box-supervisor->>registry_selfheal: Validate registry
registry_selfheal->>sessions.json: Lock and revalidate
registry_selfheal->>sessions.json: Quarantine and reseed corrupt file
settings-daemon->>sessions.json: Load registry for mutation
settings-daemon->>settings-daemon: Refuse mutation if unreadable
settings-daemon->>sessions.json: Write preserved version and entries
Suggested reviewers: 🚥 Pre-merge checks | ✅ 4 | ❌ 1❌ Failed checks (1 warning)
✅ Passed checks (4 passed)
Full details: Linked Issues checkExplanation The changes satisfy issue Full details: Out of Scope Changes checkExplanation The changes remain within the linked issue scope. The added implementation, generated payloads, tests, and flake check support registry validation, safe mutation, self-healing, and regression coverage. Full details: Docstring CoverageExplanation Docstring coverage is 42.22% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 45 functions across 5 files. (9 skipped: 9 unsupported.) ✨ Finishing Touches 💡 1📝 Generate docstrings 💡
🧪 Generate unit tests (beta)
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Inline comments:
In
`@tests/golden/web/payloads/agent-box-webhook-spawn/bin/agent-box-webhook-spawn`:
- Around line 299-301: Update registry_selfheal in registry.sh to retain the
outer registry lock through the registry_ensure call, removing the unlock before
re-seeding while preserving nested _registry_depth deadlock handling. Regenerate
the affected payloads after applying the change.
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📒 Files selected for processing (14)
flake.nixmodules/agent-box.nixmodules/src/lib/registry.shmodules/src/settings-daemon.pymodules/src/supervisor.shtests/golden/vm/payloads/agent-box-agent-mark-stoppedtests/golden/vm/payloads/agent-box-session/bin/agent-box-sessiontests/golden/vm/payloads/agent-box-supervisor/bin/agent-box-supervisortests/golden/web/payloads/agent-box-robot-mark-stoppedtests/golden/web/payloads/agent-box-settings/bin/agent-box-settingstests/golden/web/payloads/agent-box-webhook-spawn/bin/agent-box-webhook-spawntests/sessions.nixtests/test-registry.pytests/test-sessions-registry.py
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Two follow-ups on the same change. registry_selfheal released the lock between moving the unreadable file aside and calling registry_ensure. In that gap `agent-box-session add` can create the registry, and registry_ensure never clobbers a file that exists -- so the declared sessions would stay unseeded on that boot and every later one, which is the outcome the function exists to prevent. The two steps are now one critical section; the lock nests, so registry_ensure taking it again does not deadlock. Reported by CodeRabbit on #538. The new test asks the library directly, standing in for registry_ensure and reading REGISTRY_HELD/_registry_depth at the call: timing a window that small from outside would prove nothing on a loaded runner. Verified against the pre-fix shape, which reports held=0 depth=0. And the VM subtest named a local `log`, which the test driver already binds to its own AbstractLogger -- the driver's type check refuses the shadowing at BUILD time, before any VM boots, and that is the only thing that failed CI on bf37a2a. Renamed to `journal`. The kill that goes with it is now tolerant: main can be the last session left by that point in the file, and killing the last one ends the tmux server, which tmux may report back as a failure. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01YZxFZERYWS1ynz9T8HnnPa
defangdevs
dismissed
coderabbitai[bot]’s stale review
September 3, 2026 02:37
addressed in 9f17969 (lock now held across quarantine + re-seed, with a regression test)
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Closes #279.
The symptom
Both halves of the box read "cannot parse" as "there are no sessions".
The web half acted on it.
read_sessionsreturned{}on anyOSError/ValueError, and all three settings-daemon mutation routes wrotethat back plus their own edit. One click on Add session republished the
registry with a SINGLE entry: every other session delisted for good, with its
hasRun,boxSessionIdandstoppedgone. Running panes survived asunmanaged tmux sessions nothing respawns, and re-adding a name started a fresh
conversation.
Reproduced against the shipped daemon (
tests/golden/.../agent-box-settings)before touching anything. A registry holding
claude(withhasRunand aboxSessionId) andcodex, with a line of garbage appended, plus one POST to/sessions/add:The supervisor could not repair it.
supervisor.shsent jq's error to/dev/null, so the reconcile loop iterated over nothing, logged nothing andleft the unit
active (running)-- a box that looks idle. Andregistry_ensurere-seeds only a MISSING OR EMPTY file, which a corrupt one isneither.
Worth naming, because it is why this hid so well: bare jq reads a stream of
values, so
{...}\nnot jsonparses far enough to yield the first document'ssession names (the loop printed
claudeand then exited 5) while python'sjson.loadrefuses the same file outright. The two halves did not even agreeon which files were broken.
The fix
load_sessions()distinguishes "unreadable" from "no sessions" andraises
RegistryUnreadable. Add, delete and restart refuse on it, write oneline to the journal, and put a banner in front of the operator instead of
rewriting the file. A MISSING registry is still a first boot, so an add on a
box that has never had one still creates it.
read_sessions()still answers{}for the read-only paths. A page thatrenders an empty list beats a 500 on every route that mentions a session, and
the empty list is now transient.
registry_selfheal()joins the shared write protocol inmodules/src/lib/registry.sh. The supervisor calls it at startup and onevery tick, so a registry that does not parse is moved aside as
sessions.json.corrupt-<ts>(kept, never deleted -- it is the only record ofwhat the operator asked for) and re-seeded, with one journal line naming the
file. It re-checks under the lock, because every writer publishes by rename
and quarantining a document that landed mid-check would throw away a good
registry. A read-only home warns once per transition, not every two seconds.
Its jq check is
-s(slurped) precisely so the two halves agree on what"corrupt" means.
write_sessionspreserves an unknownversionrather than stamping 1over a document a newer box wrote, and
load_sessionskeeps an entry whosevalue is not an object rather than silently dropping it into a write that
would delete it.
User-visible and security effects
banner: "The session list could not be read, so nothing was changed. The box
moves the unreadable file aside and rebuilds the list within a few seconds --
reload this page and try again." Carried on the existing
ok=channel, likewebhook_kept. An operator here has no shell, so the page has to say boththat nothing changed and that the box repairs itself.
declared seed. Sessions added at runtime that were only in the corrupt
file are not restored automatically -- the quarantined file is what they can
be read back from. Losing them to a fresh start is worse than losing none,
and better than a box that silently runs nothing.
jqper 2s supervisor tick. No new file, socket, privilege orsudo grant; the quarantined file is written by the same user, in the same
directory, and the registry is re-created 0600 as before.
Checks run
Native, on this aarch64 box:
The VM checks are
x86_64-linux-only, sotests/sessions.nix(the newself-heal subtest) and
testscript-fitsrun in CI, not here.Coverage added
tests/test-sessions-registry.py(new flake checksessions-registry,same shape and same subject as
profile-panel): the three mutation routesdriven over HTTP against the golden payload, each against five ways the file
can break; the banner; version preservation; a non-object entry surviving a
write; and the negative control that a healthy registry is still added to,
deleted from and started.
tests/test-registry.py: quarantine-and-reseed, trailing garbage, twodocuments (valid to jq, fatal to python), the
.sessions-as-a-list shapefrom Two native-backend bugs from the live Lightsail launch have NixOS-side twins (#154 Phase 5) #356, a healthy tick touching nothing and saying nothing, a first boot
with no directory, an unwritable directory warning once across three calls,
and a heal that waits for a writer holding the lock and then finds the
document it published.
tests/sessions.nix: corrupt the registry on a live box with the unit leftrunning, and assert the declared session comes back on its own, the bad file
is kept, and the journal names it. Last in that file, deliberately: healing
re-seeds the declared set.
🤖 Generated with Claude Code
https://claude.ai/code/session_01YZxFZERYWS1ynz9T8HnnPa