[BUG][Bedrock] Agent Teams teammates spawned with non-Bedrock model ID via --model flag, causing 400 errors

[boxp]

Preflight Checklist

• I have searched existing issues and this hasn't been reported yet
• This is a single bug report (please file separate reports for different bugs)
• I am using the latest version of Claude Code

What's Wrong?

When using Agent Teams with AWS Bedrock, teammates spawned via the Task tool always fail with 400 The provided model identifier is invalid.

The root cause: Claude Code spawns teammates in tmux panes with --model claude-opus-4-6 (Anthropic API format) instead of the Bedrock-qualified model ID us.anthropic.claude-opus-4-6-v1. The --model CLI flag is hardcoded from the team config's model field, which stores the API-format name regardless of the Bedrock environment.

Key observations:

• The parent/lead process correctly uses Bedrock with ANTHROPIC_MODEL=us.anthropic.claude-opus-4-6-v1
• The team config stores "model": "claude-opus-4-6" (API format) for each teammate
• The spawn command passes --model claude-opus-4-6 explicitly
• The child process shows claude-opus-4-6 · API Usage Billing (not Bedrock) despite CLAUDE_CODE_USE_BEDROCK=1 being available in the tmux global environment
• Setting tmux global environment variables (tmux set-environment -g) does not help because the --model CLI flag appears to take precedence over env vars

Note: The similar issue for regular Task subagents (#15907, #21235) was fixed, but Agent Teams uses a different code path for spawning teammates that still has this problem.

What Should Happen?

When CLAUDE_CODE_USE_BEDROCK=1 is set, Agent Teams should:

1. Store the Bedrock-qualified model ID in the team config (e.g., us.anthropic.claude-opus-4-6-v1 instead of claude-opus-4-6)
2. OR map the model alias (e.g., opus) to the Bedrock model ID using ANTHROPIC_DEFAULT_OPUS_MODEL when generating the --model flag for the spawn command
3. OR ensure the child process respects CLAUDE_CODE_USE_BEDROCK=1 from the environment even when --model is provided with an API-format name

Error Messages/Logs

API Error (claude-opus-4-6): 400 The provided model identifier is invalid.

Spawn command observed in tmux pane:

cd /path/to/repo && CLAUDECODE=1 CLAUDE_CODE_EXPERIMENTAL_AGENT_TEAMS=1 \
  /path/to/claude \
  --agent-id anime-otaku@team-name \
  --agent-name anime-otaku \
  --team-name team-name \
  --agent-color blue \
  --parent-session-id <uuid> \
  --agent-type general-purpose \
  --permission-mode acceptEdits \
  --model claude-opus-4-6

Team config showing API-format model:

{
  "agentId": "anime-otaku@team-name",
  "name": "anime-otaku",
  "model": "claude-opus-4-6",
  "backendType": "tmux"
}

Steps to Reproduce

1. Configure Claude Code for AWS Bedrock:

{
  "env": {
    "CLAUDE_CODE_USE_BEDROCK": "1",
    "AWS_REGION": "us-west-2",
    "ANTHROPIC_MODEL": "us.anthropic.claude-opus-4-6-v1",
    "ANTHROPIC_DEFAULT_OPUS_MODEL": "us.anthropic.claude-opus-4-6-v1",
    "AWS_PROFILE": "claude",
    "CLAUDE_CODE_EXPERIMENTAL_AGENT_TEAMS": "1"
  },
  "teammateMode": "tmux"
}

2. Create a team with TeamCreate
3. Spawn a teammate using the Task tool with team_name parameter
4. Observe the teammate's tmux pane showing claude-opus-4-6 · API Usage Billing and 400 The provided model identifier is invalid

Related Issues

• [BUG] Intermittent Task/subagents fail with API Error: 400 The provided model identifier is invalid while main agent succeeds (Bedrock) #15907 (closed) - Same model ID issue for regular Task subagents (fixed, but fix not applied to Agent Teams path)
• Task tool ignores model configuration when using AWS Bedrock #21235 (closed) - Task tool ignores model config on Bedrock (fixed, but not for Agent Teams)
• [BUG] in-process CLI flag and config file setting are ignored, claude always launches teammembers in tmux panes from tmux #23437 (open) - in-process mode ignored when running from tmux (blocks the workaround)
• [BUG][bedrock] Opus 4.6 [1m] selection writes invalid model id → 400 "The provided model identifier is invalid" #23499 (open) - Bedrock model ID issue with [1m] suffix

Claude Model

Opus

Is this a regression?

No, this never worked

Last Working Version

No response

Claude Code Version

v2.1.33

Platform

AWS Bedrock

Operating System

macOS

Terminal/Shell

Other

Additional Information

The in-process teammate mode workaround is also blocked by #23437 (in-process setting is ignored when running from tmux, always falls back to tmux panes).

[github-actions]

Found 2 possible duplicate issues:

1. [BUG] Task Tool Fails to Spawn Agents in AWS GovCloud #22742
2. [BUG] model: opus alias resolves to Opus 4.1 instead of available Opus 4.5 on Bedrock #22587

This issue will be automatically closed as a duplicate in 3 days.

• If your issue is a duplicate, please close it and 👍 the existing issue instead
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🤖 Generated with Claude Code

[yhan1-godaddy]

Same issue, and also even if parent is 4.5, the children are using --model claude-opus-4-6

This only happens when you are in tmux and the children are another tmux pane. If you run them within parent (without tmux, etc), then no issues.

[Ahacad]

It's a bug you can patch yourself, I asked claude code to fix itself and it did, for me needed to:

file: @anthropic-ai/claude-code/cli.js, replace XvA=aA1.firstParty with XvA="opus", the variable name could be very different on your machine but that's a hint.

[cjpeterein]

Not specific to CLAUDE_CODE_USE_BEDROCK=1. The same issue happens when ANTHROPIC_BASE_URL and ANTHROPIC_AUTH_TOKEN are set. The team agents don't respect the ANTHROPIC_DEFAULT_OPUS_MODEL value.

[christianvuerings]

Reproducing this with Agent Teams split panes via tmux + iTerm2 on macOS

I'm hitting a similar issue. When Agent Teams spawns teammates in tmux panes, the Bedrock-related environment variables are not propagated, causing teammates to fail with Not logged in · Please run /login.

Setup:

• macOS, iTerm2 with Python API enabled
• tmux installed via Homebrew
• CLAUDE_CODE_EXPERIMENTAL_AGENT_TEAMS=1
• Using AWS Bedrock via a custom proxy (ANTHROPIC_BEDROCK_BASE_URL, CLAUDE_CODE_USE_BEDROCK=1, etc.)

What I observed:

The spawned teammate command looks like this:

cd /Users/.../project && \
CLAUDECODE=1 \
CLAUDE_CODE_EXPERIMENTAL_AGENT_TEAMS=1 \
/path/to/bin/claude_code_latest \
  --agent-id infra-inspector@tech-debt-investigation \
  --agent-name infra-inspector \
  --team-name tech-debt-investigation \
  --agent-color orange \
  --parent-session-id ... \
  --agent-type general-purpose \
  --settings /private/var/folders/.../claude-settings-....json \
  --model claude-opus-4-6

Note that:

1. --model claude-opus-4-6 is the Anthropic API format, not the Bedrock model ID
2. CLAUDE_CODE_USE_BEDROCK, ANTHROPIC_BEDROCK_BASE_URL, and ANTHROPIC_AUTH_TOKEN are missing from the spawned process environment — only CLAUDECODE=1 and CLAUDE_CODE_EXPERIMENTAL_AGENT_TEAMS=1 are set

This results in every teammate pane showing "Not logged in" since the child process has no way to authenticate against Bedrock without those env vars.

Expected behavior: All authentication-related environment variables from the parent session should be propagated to spawned teammate processes, and the model ID should be resolved to the Bedrock-qualified format when CLAUDE_CODE_USE_BEDROCK=1 is active.