fix(server): agents run in their own systemd scopes so an OOM kill spares the server

[t3dotgg]

On Linux, every agent and terminal runs inside t3code.service. systemd-oomd kills whole cgroups, so one greedy agent kills the server and every other agent. On BB-1 the kernel OOM killer took the server 6 times, and oomd killed the whole unit twice (296 and 167 processes). Fixes #5248.

Fix

• Own scope per agent. With a systemd user manager, each Claude, Codex, ACP, OpenCode, Pi, Muse, and terminal launch runs through systemd-run --user --scope in app-t3code-agents.slice. Every step execs, so the PID, stdio, and signals stay the agent's own. oomd only kills leaf cgroups, so it now picks the agent, not the server. A first-launch probe turns this off when there is no user manager (macOS, containers).
• oom_score_adj 800 for those processes, so the kernel kills agents first. Grok keeps its existing ACP cgroup lease (it is already its own leaf) and only gets the higher score.
• Slice limits: MemoryHigh = RAM − 6 GB and MemoryMax = RAM − 4 GB, set at runtime with systemctl --user set-property --runtime. On small machines agents get at least ½ and ¾ of RAM.
• Unit file: adds CPUWeight=1000, IOWeight=1000, and ManagedOOMPreference=avoid, and keeps OOMPolicy=continue and Restart=always. The agents slice sits in app.slice next to the server, so the weights compete with agents directly. Existing installs pick up the new unit on the next t3 service install. The scopes themselves work without a reinstall.
• Visible OOM: scopes use OOMPolicy=stop, so systemd records Result=oom-kill for both kernel and oomd kills. When a turn fails, ProviderEventIngestor checks the thread's newest scope and shows "Killed: out of memory." Only the thread's newest scope counts, and opening a new provider session clears it, so an OOM kill only labels failures of the session that launched it. That holds when the next session runs without a scope (Cursor, OpenCode, Claude script entries, the Grok cgroup lease). Past 500 tracked threads, scopes that have ended are dropped first. The answer stays the same until the thread launches its next agent, so a retried ingest reads the same. Failed units are reset, and scopes without a thread use --collect.
• Older systemd: scopes accept OOMPolicy from systemd 253. The probe tries it first and falls back to plain scopes (isolation without the OOM label) on Debian 12, Ubuntu 22.04, and similar.
• A command that does not resolve on PATH stays unwrapped, so a missing binary still fails at spawn. A Claude binaryPath that ends in .js, .mjs, .ts, .tsx, or .jsx also stays unwrapped, because the SDK runs those through node.

Findings

• ManagedOOMPreference does nothing in the reported case. Per systemd's docs and source (oomd-util.c), oomd honors it only when the cgroup is owned by root, or by the same user as the monitored ancestor. Distros monitor user-1000.slice, which root owns, while t3code.service is owned by uid 1000. I kept it because it helps when the monitored cgroup is user-owned. The scope split is what protects the server.
• oomd picks among leaf cgroups (or memory.oom.group=1 ones) with the most reclaim. Before this change, t3code.service was the leaf that held everything.
• Scopes cannot set OOMScoreAdjust, so a sh wrapper writes /proc/self/oom_score_adj before exec.
• Follow-ups: Grok keeps its existing ACP cgroup lease (a separate leaf, score 800), so it does not get slice limits or the OOM label yet.
• Not covered: Cursor runs its SDK inside the server process, so there is nothing to wrap. Server-spawned Chromium (previews, HTML render) also stays in the server unit. Both need a process split.
• Behavior change: t3 service stop no longer kills processes that agents started in the background (for example a dev server), because they now live in the agents slice. Agents themselves still exit when the server's pipes close.
• Codex has no handling for a process exit at all, so its turns do not get the OOM label. That is a separate bug (#16502).
• Prior art: #14338 used a busctl launcher. It targets V1 adapter files that no longer exist, and its CollectMode=inactive-or-failed makes the oom-kill result unreadable.

Cgroup tree (systemd-cgls --user)

Before (live service): agents live inside the server unit.

└─t3code.service
  ├─1529008 /home/theo/.t3/runtime/versions/0.0.46-nightly…/t3 serve
  ├─1529320 cloudflared tunnel …
  ├─1618514 muse-bin serve --trust-workspace …
  ├─1624596 claude --output-format stream-json …
  ├─1659450 claude --output-format stream-json …
  └─…

After (dev server from this branch): each agent and terminal has its own scope.

├─app-t3code.slice
│ └─app-t3code-agents.slice
│   ├─t3code-terminal-9913306a.scope
│   │ └─1686527 /usr/bin/bash
│   └─t3code-claude-07e84ffb.scope
│     ├─1695657 /home/theo/.local/bin/claude --output-format stream-json …
│     ├─1695952 /usr/bin/bash -c …
│     └─1695954 sleep 45
└─t3code.service
  └─… (server only)

Test (cup2, Debian 13, systemd 257)

Two Claude threads on a dev server from this branch. Thread 1 runs sleep 45 while thread 2 runs stress-ng --vm 1 --vm-bytes 110% --timeout 60s. This box also runs a live T3 server that uses about 36 GB, so for the test I set the slice to MemoryMax=2G MemorySwapMax=0. stress-ng then hits a cgroup OOM (the same kernel kill path) and does not push the whole box into swap or a global OOM.

• t3code-claude-52a55f1d.scope: Failed with result 'oom-kill'. Only that scope died, and it was reset afterwards.
• Thread 1's scope kept running and finished ("Done").
• The dev server PID did not change.
• The thread shows the kill:

Also checked: agent oom_score_adj reads 800, the slice limits are 56.8 / 58.8 GiB on a 62.8 GiB box, and after a server restart the old agent and terminal scopes exit on their own (stdin EOF / PTY close). The oomd path was not run live (oomd is off on this box). It is covered by the systemd source reading above.

After the review fixes, I ran it again on the same box: a real OOM kill still shows the label. I also OOM-killed an idle agent and then killed the thread's next agent with SIGKILL. That turn shows "Provider turn failed.", not the OOM label, and the old failed scope was reset when the new agent started.

Tests: agentScope.test.ts (scope classification, slice limits, and the real service against a fake systemctl for the newest-scope and thread-cap rules), plus a ProviderSessionManager test that a new session does not inherit the last agent's OOM kill and AgentScope.test.ts (the wrapper keeps the PID and args, and raises the score). The existing tests for every touched adapter pass.

Reviewed with sol-loop: 7 rounds with GPT-6.1-Sol on high, approved on the final commit.

Made by Claude Opus 5.5 in Claude Code (via T3 Code).

🤖 Generated with Claude Code

[macroscopeapp]

Approvability

Verdict: Not approved

Macroscope's review found this PR not approvable — The PR adds a new Linux process-isolation subsystem and changes existing agent, terminal, provider, cgroup, and generated systemd-service behavior, including resource limits and OOM handling. Its default behavior changes and it adds static-analysis suppression directives, so the operational impact warrants human review.

No code changes detected at af217f2. Prior analysis still applies.

^{You can add or adjust custom eligibility rules. Learn more.}

[github-actions]

Thread transfer impact

✅ Thread transfer remains within every enforced ceiling.

Provider	Metric	Main baseline	This PR	Impact	PR ceiling
Codex	Total thread wire	5.0 KiB	4.9 KiB	−23 B (−0.5%)	6.8 KiB	✅
Codex	Thread snapshot wire	3.8 KiB	3.8 KiB	0 B (0.0%)	4.9 KiB	✅
Codex	Live turn WebSocket wire	1.2 KiB	1.2 KiB	−23 B (−1.9%)	2.0 KiB	✅
Codex	Live turn WebSocket decoded	20.9 KiB	20.8 KiB	−41 B (−0.2%)	29.3 KiB	✅
Codex	Live turn messages	2	1	−1 (−50.0%)	8	✅
Claude	Total thread wire	5.0 KiB	5.0 KiB	0 B (0.0%)	6.8 KiB	✅
Claude	Thread snapshot wire	3.8 KiB	3.8 KiB	0 B (0.0%)	4.9 KiB	✅
Claude	Live turn WebSocket wire	1.2 KiB	1.2 KiB	0 B (0.0%)	2.0 KiB	✅
Claude	Live turn WebSocket decoded	21.2 KiB	21.2 KiB	0 B (0.0%)	29.3 KiB	✅
Claude	Live turn messages	2	2	0 (0.0%)	8	✅

Baseline: 03bd839 · PR result: af217f2 · Source CI: success

Scenario and decoded snapshot size

10 historical turns, 5 command tools per turn, 878.9 KiB retained MCP result per historical turn, and a 1.05 MiB retained result in the measured turn.

• Codex decoded thread snapshot: 108.5 KiB
• Claude decoded thread snapshot: 108.8 KiB

Updated in place by a trusted workflow. PR artifacts are strictly validated and never executed.

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• apps/server/src/process/agentScope.test.ts
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📝 Walkthrough

📝 Walkthrough

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Walkthrough

This change adds Linux systemd scopes for agent and terminal processes, integrates scoped launches across providers, and reports detected scope OOM kills as provider failures. It also updates systemd service settings and adds tests for scope classification, memory limits, and command construction.

Changes

Linux agent scope isolation

Layer / File(s)	Summary
Shared scoped-launch contract packages/shared/src/AgentScope.ts, packages/shared/src/AgentScope.test.ts, packages/shared/package.json	Adds shared launch contracts and helpers for direct commands and systemd user scopes. The helper raises the process OOM score to 800; tests check process identity, score adjustment, and argument preservation.
Systemd scope lifecycle apps/server/src/process/agentScope.ts, apps/server/src/process/agentScope.test.ts, apps/server/src/cloud/bootService.ts	Adds systemd scope creation, memory limits, state and OOM-kill detection, and failed-scope cleanup. Adds CPU and I/O weights and ManagedOOMPreference=avoid to the service unit.
Scoped process-launch integrations apps/server/src/server.ts, apps/server/src/orchestration-v2/Adapters/*, apps/server/src/terminal/Manager.ts, packages/provider-acp/src/server/*, packages/provider-muse/src/server/*, packages/provider-opencode/src/server/OpenCodeRuntime.ts, packages/provider-pi/src/server/adapter.ts	Provides AgentScope to server services and uses it to wrap provider and terminal launches. ACP keeps its existing cgroup and shell launch paths. Muse adds optional launch arguments before its serve arguments.
OOM failure reporting apps/server/src/orchestration-v2/ProviderEventIngestor.ts	Checks tracked scopes when a turn fails. If a scope reports an OOM kill, the failure item uses the message Killed: out of memory. and code oom_kill; otherwise, it uses the provider failure.

Priority: ⬆️ High

Estimated code review effort: 4 (Complex) | ~50 minutes

Change: Bug fix · Severity of issue fixed: High

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Merge Risk: ⚪ Minimal · up to caf1a

This change runs agent processes in separate systemd scopes so an out-of-memory kill spares the server, and it falls back to the existing behavior when systemd is unavailable. No actionable merge-blocking risk remains in the reviewed changes.

Pre-merge checks | 3 | 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Linked Issues check		Issue [#5248] requires the existing spawn behavior when no user systemd manager is available. In apps/server/src/process/agentScope.ts, the no-manager path calls `agentScopeCommand({ command: resolv…	When the systemd probe returns no manager, return { command: resolved.value, args } without the shell wrapper. Add or update a test that verifies the fallback preserves the original command and arguments.

✅ Passed checks (3 passed)

Check name	Status	Explanation
Out of Scope Changes check		The agent slice limits, systemd scope wrapper, OOM score handling, launch integrations, OOM result tracking, user-facing OOM reporting, unit settings, and tests support the isolation and OOM-containme…
Title check		The title clearly and concisely describes the primary change: isolating agents in systemd scopes to protect the server from OOM kills.
Description check		The description is detailed and covers the problem, implementation, limitations, linked issue, verification, observed results, and agent attribution. It uses "Fix" instead of the template's "Change" h…

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Full details: Linked Issues check

Explanation

Issue [#5248] requires the existing spawn behavior when no user systemd manager is available. In apps/server/src/process/agentScope.ts, the no-manager path calls agentScopeCommand({ command: resolved.value, args }). That function changes the launch to /bin/sh and adds an oom_score_adj shell command. The scope isolation, scoped process-tree handling, OOM result tracking, and OOM reporting are implemented, but the fallback is not unchanged spawn behavior.

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Actionable comments posted: 3

🧹 Nitpick comments (1)

apps/server/src/orchestration-v2/ProviderEventIngestor.ts (1)

29-29: 📐 Maintainability & Code Quality | 🔵 Trivial | ⚡ Quick win

Use the service-module namespace import.

AgentScope is consumed as an Effect service at Line 320. Import the service module as a namespace and use its AgentScope export.

As per coding guidelines, “Consumers use a service module the same way: import * as Foo from "./Foo.ts", then yield* Foo.Foo and Foo.layer.”

Proposed import update

-import { AgentScope } from "@t3tools/shared/AgentScope";
+import * as AgentScope from "@t3tools/shared/AgentScope";
@@
-    const agentScope = yield* AgentScope;
+    const agentScope = yield* AgentScope.AgentScope;

Also applies to: 320-320

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Review comment at @apps/server/src/orchestration-v2/ProviderEventIngestor.ts at
line 29:
Update the import and service usage in ProviderEventIngestor to follow the
service-module namespace convention: import the AgentScope module as a namespace
and access its AgentScope export when yielding the Effect service.

Source: Coding guidelines

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• 🪄 Fix CodeRabbit comments on this PR

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Inline comments:
Review comments at @apps/server/src/orchestration-v2/ProviderEventIngestor.ts:
- Around line 659-661: Update the OOM classification flow around
agentScope.takeOomKill so a failed event-sink write cannot lose the
classification before the event is published. Retain the marker until
publication succeeds or make the failure classification idempotent across
retries, ensuring reprocessing still publishes the OOM failure.

Review comments at @apps/server/src/process/agentScope.ts:
- Around line 241-246: Update the unit tracking in wrap so unitsByThread does
not retain completed scopes indefinitely; remove each unit when its scope ends,
or prune stale scopes when adding a new unit, while preserving takeOomKill
behavior for active scopes.
- Line 25: Remove the export modifiers from AGENT_SLICE and make in the
agent-scope module, keeping both symbols private because no other module imports
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---

Nitpick comments:
Review comments at @apps/server/src/orchestration-v2/ProviderEventIngestor.ts:
- Line 29: Update the import and service usage in ProviderEventIngestor to
follow the service-module namespace convention: import the AgentScope module as
a namespace and access its AgentScope export when yielding the Effect service.

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• apps/server/src/cloud/bootService.ts
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• apps/server/src/orchestration-v2/Adapters/CodexAdapterV2.ts
• apps/server/src/orchestration-v2/ProviderEventIngestor.ts
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• apps/server/src/process/agentScope.ts
• apps/server/src/server.ts
• apps/server/src/terminal/Manager.ts
• packages/provider-acp/src/server/AcpSessionRuntime.ts
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• packages/provider-muse/src/server/adapter.ts
• packages/provider-muse/src/server/sdk.ts
• packages/provider-opencode/src/server/OpenCodeRuntime.ts
• packages/provider-pi/src/server/adapter.ts
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Actionable comments posted: 1

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• 🪄 Fix CodeRabbit comments on this PR

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Inline comments:
Review comments at @apps/server/src/process/agentScope.ts:
- Around line 42-71: Update classifyScope to check whether oomKills is positive
before the terminal-state checks that return "gone", classifying it as
"oom-killed" even when the scope is inactive or failed. Remove the now-redundant
oomKills condition from the later "stopping" check while preserving the existing
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🧹 Nitpick comments (1)

apps/server/src/orchestration-v2/Adapters/ClaudeAdapterV2.ts (1)

634-662: 📐 Maintainability & Code Quality | 🔵 Trivial | 💤 Low value

Log the effective Claude launch path.

When AgentScope wraps a native binary, query receives the derived options, but query.open logs loggedClaudeQueryOptions(input.options). The native protocol log therefore records the requested Claude binary instead of /bin/sh, which is the wrapper used for scoped launches.

Pass options to the logger. This identifies whether the launch was wrapped. The logger omits executableArgs, so this change does not record the systemd unit or scope flags.

Suggested fix

-            options: loggedClaudeQueryOptions(input.options),
+            options: loggedClaudeQueryOptions(options),

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Review comment at @apps/server/src/orchestration-v2/Adapters/ClaudeAdapterV2.ts
around lines 634 - 662:
Update the `query.open` logging to call `loggedClaudeQueryOptions` with the
derived `options` passed to `query`, rather than `input.options`, so the log
records the effective launch path after AgentScope wrapping.

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Nitpick comments:
Review comments at
@apps/server/src/orchestration-v2/Adapters/ClaudeAdapterV2.ts:
- Around line 634-662: Update the `query.open` logging to call
`loggedClaudeQueryOptions` with the derived `options` passed to `query`, rather
than `input.options`, so the log records the effective launch path after
AgentScope wrapping.

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[t3dotgg]

Note

Claude Opus 5.5 responding on behalf of Theo

Re the CodeRabbit nit on logging the effective Claude launch path: declined. The logger drops executableArgs, so the derived options would only log /bin/sh for every scoped launch and hide which Claude binary was asked for. The requested path is the useful one when debugging, and the scope itself appears in the "Agent scopes are on" log and in systemctl --user list-units 't3code-*'.

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Actionable comments posted: 1

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• 🪄 Fix CodeRabbit comments on this PR

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Inline comments:
Review comments at @apps/server/src/process/agentScope.ts:
- Around line 229-258: Update evictOldest to scan tracked scopes until it finds
and removes an ended entry, preserving live entries; have track add the new
scope only when capacity is available, and leave existing records unchanged if
all tracked scopes are live. Update the 600-launch test so every fake unit is
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