Resume inactive sessions

Session resume lets you continue an inactive Happier session by asking the provider backend to reopen the same provider session, then reconnecting that provider session to the same Happier session.

This is different from:

• Attach: reconnecting to a session that is still running locally through its live terminal/provider host
• Browse Direct sessions: opening a provider-native session that Happier does not own yet
• Resume ID: starting a new session by resuming an existing provider session id (see Resume a provider session (Resume ID))
• Starting a new session: creating a fresh provider session with no vendor resume

What “resume” means in Happier

In Happier, resume is a strict workflow:

1. Happier finds the existing Happier session
2. Happier checks whether that session is actually vendor-resumable
3. Happier asks the backend/provider to resume the same vendor session
4. If that vendor resume fails, Happier shows an error instead of silently starting a new session

That strict behavior matters because it keeps one session identity and one transcript source of truth.

When a synced Happier session resumes, Happier continues the existing session. It does not create a second imported-history pass just because you resumed it.

When a session is resumable

A session is resumable only when all of these are true:

• the session is a normal Happier-managed session
• it is currently inactive
• it is not archived
• Happier has a valid provider resume id stored in session metadata
• the selected backend/provider supports resume for that session
• your current settings do not disable that backend

If any of those checks fail, Happier treats the session as not resumable and shows that clearly in the UI or CLI.

App and web behavior

In the app or web UI, an inactive session can still accept input only if it is resumable.

Typical behavior:

• Inactive + resumable + machine reachable: you can send a message and Happier resumes the session first
• Inactive + not resumable: input is disabled
• Inactive + machine offline: input is disabled until the owning machine is reachable again

This is why some inactive sessions still look “ready”, while others show a blocked or offline state.

CLI behavior

Happier CLI exposes two main workflows for resume.

List sessions

happier session list

By default this prints a table with:

• shortened session id
• agent
• last updated time
• active state
• resume status
• title
• working directory path

Useful variants:

happier session list --resumable
happier session list --plain
happier session list --json

Use:

• --resumable to show only sessions that can currently be resumed
• --plain for the older one-line output format
• --json for scripting

Resume interactively

happier resume

In a real TTY, Happier opens an interactive selector and shows resumable inactive sessions sorted by recent activity.

If your terminal does not support the interactive selector, Happier tells you to use happier session list --resumable and then resume by id.

Resume by id

happier resume <session-id>

You can pass a full session id or an unambiguous prefix.

Happier then:

1. resolves the session
2. validates that it is inactive, not archived, and resumable
3. restores the session’s working directory
4. resumes the provider session
5. reconnects that provider session to the same Happier session

If the session is active already, archived, missing its working directory, or not vendor-resumable, the command fails with a clear error.

Resume status in the CLI table

The RESUME column is a quick summary:

• yes: resumable
• no(unsupported): that agent/backend does not support vendor resume
• no(missing-id): the session does not have the provider resume id Happier needs
• no(disabled): resume exists for that backend, but your current settings disable it
• no(off): account settings disabled that backend entirely

Codex-specific behavior

Codex resume in Happier normally uses the default App Server path. ACP resume is still available when you explicitly choose ACP.

Important points:

• Codex now defaults to App Server in Happier
• legacy mcp_resume behavior is gone
• if you opt Codex back to plain MCP, fresh sessions can still start there, but vendor resume is not available on that path
• for new Codex sessions, Happier does not silently fall back from the default App Server path; choose ACP or MCP explicitly if you want a different backend
• App Server is the default resumable path; ACP still works when you explicitly select it
• for an explicit resume, Happier stays strict and errors instead of falling back

So for Codex, “can I resume this session?” depends on the session metadata and on whether the current backend path supports resume for that session.

Resume vs attach

Use resume when the session is inactive and the provider supports reopening that provider session.

Use attach when the session is still running locally and you want to reconnect to the live process:

happier attach <session-id>

If you are unsure:

• use attach for a still-running local session
• use resume for an inactive session you want to continue

Attach can mean different things depending on how the session was started:

• tmux reattach,
• focusing an existing Windows Terminal or Console host,
• or using a provider-native attach flow when the provider supports it.

Resume vs Direct sessions

Direct sessions are provider-native sessions that Happier can inspect or follow, but that Happier does not fully own yet.

For those sessions:

• browsing/opening happens through the Direct sessions flow
• syncing/importing happens through Take over + Sync
• normal Happier resume applies after the session is a synced Happier session and has valid vendor-resume metadata

Things to check if resume is unavailable

If a session does not resume, check:

• is the session inactive rather than already running?
• is it archived?
• does it belong to the provider/backend you think it does?
• are you on the correct Happier server/account profile?
• for Codex, is the selected resume path available (App Server by default, or ACP when explicitly selected)?
• is the owning machine online and reachable from Happier?

Related guides

• Attach to a running session
• Synced and direct sessions
• Browse and import provider sessions
• CLI
• Codex
• Permissions