Background remote refresh on the new-thread composer triggers an ssh passphrase prompt

[noih]

Summary

Opening the new-thread composer (new thread or new project) starts a background git fetch --all --prune on the project source. With a passphrase-protected ssh key that is not loaded in an agent and SSH_ASKPASS configured, that fetch pops a GUI passphrase dialog on every composer visit, without any user action behind it. I expected a background refresh to never surface a credential prompt; prompts should come only from explicit actions such as opening the branch picker.

Versions and environment

• bb 0.40.0 (desktop app), macOS 26 (Darwin 25.5.0)
• ssh key protected by a passphrase, deliberately not persisted to the agent; SSH_ASKPASS points at a GUI helper, SSH_ASKPASS_REQUIRE=force
• Project source is a local checkout whose origin is an ssh remote

Steps to reproduce

1. Configure git to reach origin over ssh with a passphrase-protected key that is not loaded in ssh-agent, and set SSH_ASKPASS to a GUI helper.
2. Create a bb project from that checkout.
3. Open the new-thread composer for the project (or create a new project and land on its composer).
4. A passphrase dialog appears immediately, before touching the branch picker or any other control.

Repeats on every composer visit once the daemon's 30-second fetch throttle has expired. Did not reproduce with the key loaded in the agent (fetch succeeds silently), which is what hides this from most setups.

Expected vs actual

Actual: GUI passphrase prompt on composer load, no user action behind it. Dismissing it leaves the refs unrefreshed; the composer otherwise works.

Expected: no credential prompt from a background refresh. Fetching (and prompting) only when I ask for fresh refs, e.g. opening the branch picker or `bb project branches --refresh`.

Note the failure mode is environment-dependent, which is why this is rarely seen:

- Desktop-app-launched daemon without `SSH_ASKPASS` (no controlling tty, stdin ignored): ssh cannot open `/dev/tty`; the background fetch already fails silently today.
- Terminal-launched daemon: ssh reads the passphrase from that terminal's `/dev/tty`; git blocks until the 5s refresh timeout kills it.
- `SSH_ASKPASS` set in the daemon's environment (mine is system-wide, so the desktop-launched daemon inherits it): the GUI dialog reported here.

The background refresh cannot succeed for this key setup in any of these cases — its result is already discarded and errors swallowed — so the prompt buys nothing.

Evidence

Call path, at f4bbc2fe8:

• Composer mounts the branches query with refresh=background on load: https://github.com/get-bb/bb/blob/f4bbc2fe8/apps/app/src/hooks/queries/project-queries.ts#L111-L116 (mounted from NewThreadComposer: https://github.com/get-bb/bb/blob/f4bbc2fe8/apps/app/src/components/promptbox/NewThreadComposer.tsx#L660)
• Server maps it to host.inspect_git_source { remoteRefresh: "background" }: https://github.com/get-bb/bb/blob/f4bbc2fe8/apps/server/src/routes/projects.ts#L837-L846
• Daemon starts the throttled refresh for both background and blocking: https://github.com/get-bb/bb/blob/f4bbc2fe8/apps/host-daemon/src/command-handlers/host-branches.ts#L253-L260
• The fetch runs with the daemon's interactive git/ssh environment: https://github.com/get-bb/bb/blob/f4bbc2fe8/packages/host-workspace/src/git.ts#L1286

fetchRemoteBranches is the only network-touching git call on this path; every other read is local (for-each-ref, symbolic-ref, rev-parse). The worktree provisioning fetch sets GIT_TERMINAL_PROMPT=0 (https://github.com/get-bb/bb/blob/f4bbc2fe8/packages/host-workspace/src/provisioning.ts#L406), but that only suppresses git's own credential prompt, not the ssh passphrase, and the branch-refresh fetch sets neither.

What you ruled out

• Not the provisioning fetch (Fetch remote base before creating worktree #244): the prompt appears before any worktree is created, on plain composer load.
• Not a misread of the semantics: remoteRefresh: "background" means "do not wait for the fetch", not "do not fetch" — the enum has no non-fetching value for host.inspect_git_source (https://github.com/get-bb/bb/blob/f4bbc2fe8/packages/host-daemon-contract/src/commands.ts#L754).
• No existing issue found for prompts from the background refresh; --base-branch resolves against the stale local ref, so spawned worktrees silently start behind #1770/Resolve a named default base branch against origin when spawning #2152 cover stale-ref freshness, Avoid unsolicited local network prompt in bb connect #1608 covers the browser's local-network prompt (same principle, different surface).

AGENT GENERATED — drafted by Claude Code in a local session; no public report link. Reproduction and code-path verification reviewed by the reporter.

Suggested priority and effort (optional)

Low: hits passphrase-key-without-agent setups only, but each composer visit costs a prompt or a 5s stall with no workaround short of changing key management; fix is small and daemon-local, PR ready.

Checks

• I reproduced this on the latest release or on main, or I say above that I could not.
• I searched open and closed issues for the same problem.
• If an agent wrote this, the body ends with > AGENT GENERATED and links the thread or report.

[bb-slop-cop]

🚨 SLOP COP 🚨 · new-issue-autopilot

• Classification: Bug · Priority Low · Effort Medium
• Labels: host, workspaces, confirmed-repro
• Report: https://get-bb.github.io/reports/issues/2737.html
• Verdict: REPRODUCED · confidence high
• Root cause: The background branch refresh starts an interactive remote fetch with inherited SSH askpass settings.
• Reproduction label: confirmed-repro
• Pull request: No new pull request was safe because Keep background remote refreshes from prompting for credentials #2738 already addresses the root cause.