Background sessions

Claude Code runs sessions in the background with agent view: claude agents to dispatch and watch them, claude --bg to start one from the shell, and ← on an empty prompt to send the one you are in there. A supervisor of Claude Code's own runs them, so they keep working after the terminal closes.

Every Claude Code session alc starts works there, on the provider alc gave it:

alc --codex claude agents
alc --codex claude --bg "fix the flaky test"
alc --openrouter claude agents

What a dispatched session answers on is the session's model, not a model fixed at launch: ← carries the conversation you are in, so one you send to the background after /model opus keeps the model you just picked. Under alc --codex claude every one of them is a Codex model either way.

How alc hands a session its provider

Claude Code keeps one thing for a background session: the flags it was launched with, which it reads again every time it restarts the session. So alc passes the provider as a settings file, --settings ~/.config/alc/claude/settings-<hash>.json, instead of the environment variables it used before, which the supervisor drops.

In the file	What it does
ANTHROPIC_BASE_URL	the provider's Anthropic endpoint, or alc's background bridge for Codex
model variables and modelPicker	the models Claude Code starts on and offers
apiKeyHelper	alc claude-credential …, which Claude Code runs for the credential

The file never contains a key. The helper prints the key alc already keeps - the profile's environment variable, or the key saved with alc config key - or, for Codex, the background bridge's token. A key that lives only in one shell's environment works in the sessions started from that shell; a background session started later may not see it, and then the helper says to save it with alc config key <profile>. It never falls back to your Claude login.

A background session keeps the settings alc merged at launch. If you pass your own --settings, alc merges it into the document it writes, yours winning, because Claude Code reads only one - so later edits to your file reach the sessions you launch afterwards, not the ones already running.

The background bridge

For Codex, the adapter now runs as a process of its own, because a background session outlives the alc that started it:

• one per alc configuration, on 127.0.0.1 only, on a port it picks once and keeps;
• every model request must carry its token;
• a session that needs it starts it, through the helper;
• it stops after an hour with nothing to do, or with alc bridge stop.

alc bridge          # running or not, pid, port, which alc started it
alc bridge stop     # the next session that needs it starts it again

alc doctor shows the same under Background sessions.

Every Claude model becomes a Codex model

Under alc --codex claude no request reaches a Claude model:

Where Claude Code picks a model	Under alc --codex claude
the model a session starts on, /model, the Default row	Codex models only
opus, fable, best	the most capable Codex model
sonnet, opusplan outside plan mode	the model the session started on
haiku, and Claude Code's background work (titles, summaries, agent view's rows)	the cheapest Codex model
a Claude model named in full: /model claude-opus-5, a subagent's model:, a fallback chain	the Codex model of the same tier
[1m] variants	sized like the plain model, at Codex's real window
fast mode, the advisor	off: they exist only on Claude models

claude ultrareview and cloud sessions run on Anthropic's servers; they stay Anthropic features.

Managing sessions

alc claude attach <id>, logs, stop, respawn and rm go straight to Claude Code. Plain claude attach <id> works just as well: the session already carries its settings file, and waking it starts the bridge if it needs one.

So do the Claude Code commands that never reach a model - mcp, doctor, plugin, update, auth and the like. They start no bridge, write no settings file and count no session in alc usage.

alc's own flags go before the agent's name and Claude Code's go after it. Where both want the same spelling - -p, --name - put Claude Code's after --:

alc --codex claude -- -p "fix the flaky test"
alc --codex claude -- --bg --name nightly "run the slow suite"

-- goes straight after the agent's name, before all of its flags. Later in the line it is passed to Claude Code as an argument of its own.

Limits

• A model you pick with /model in a background session you attached to with plain claude attach becomes Claude Code's default for new sessions, with no alc process around to put yours back. alc doctor reports it, and the next alc --codex claude clears it.
• If the bridge ever has to move to another port - another program took its port while it was down - sessions still running on the old one reconnect when they restart: claude respawn <id>, or claude respawn --all.