[BUG] Agent Teams unavailable in Claude Code on the web despite CLAUDE_CODE_EXPERIMENTAL_AGENT_TEAMS=1

Summary

When running a cloud session in Claude Code on the web with CLAUDE_CODE_EXPERIMENTAL_AGENT_TEAMS=1 set in committed project-level .claude/settings.json, the team tools (TeamCreate, SendMessage, spawnTeam, TeammateTool) are not injected. Asking the agent to create a team produces the standard "Agent Teams feature is not available on this plan" message. Task tools (TaskCreate, TaskUpdate, etc.) work correctly in the same session, indicating the env var is being read but team-tool gating has additional non-honored conditions in the cloud runtime.

Repro

1. On the default branch of a repo, add to .claude/settings.json:

``json
{
"env": {
"CLAUDE_CODE_EXPERIMENTAL_AGENT_TEAMS": "1",
"CLAUDE_CODE_ENABLE_TASKS": "1"
}
}
``

1. Commit and push.
2. Start a fresh Claude Code on the web session against that branch.
3. In the session, confirm the env var is present in the runtime shell (e.g., echo $CLAUDE_CODE_EXPERIMENTAL_AGENT_TEAMS → 1). Verified set.
4. Observe available tools:

• Task tools (TaskCreate, TaskUpdate, TaskList, TaskGet) are available.
• Team tools (TeamCreate, SendMessage, spawnTeam, TeammateTool) are not available.

1. Asking the agent to create a team returns "Agent Teams feature is not available on this plan."

Expected

With CLAUDE_CODE_EXPERIMENTAL_AGENT_TEAMS=1 correctly plumbed through to the cloud runtime, team tools should be injected — matching CLI behavior. At minimum, if there is a cloud-specific incompatibility, the user-facing message should be accurate ("not supported in cloud sessions") rather than "not available on this plan."

Environment

• Claude Code on the web (cloud session, default branch)
• Env var confirmed set in cloud runtime
• Same flag works correctly on local CLI

Related

• #23420 — misleading "not available on this plan" gate; root-cause discussion shows several telemetry/Bedrock flags silently disable team tools. None of those flags are set in this case (cloud uses Anthropic API, not Bedrock; env var is confirmed live).
• #23874 — decompiled-binary analysis showing TTY-based gating (process.stdout.isTTY) for both task and team tools in non-CLI hosts. Tasks now work in cloud, suggesting that gate has been lifted for tasks but not for teams.
• #28048 — same symptom in the VS Code extension (closed as dup of #23874).

Notes

The agent-teams docs cover display modes (in-process / tmux / iTerm2) but do not document cloud as supported or unsupported. Either supporting team tools in cloud sessions, or explicitly documenting cloud as unsupported with an accurate user-facing message, would resolve the confusion.