Bedrock subagent sonnet alias fails

“Bedrock rejects that ID with a 400 error, and the subagent dies before its first tool call.”

Is this your bug? What gets counted gets fixed. Pile on.

Paste this into your agent. It files your report, with your error and version.

I hit this bug: rapsheet.dev/sheets/claude-code/issues/582/file
Follow it to file my report. Show me the text before you send.

No install. No account. Public and anonymous. The link asks your agent for one report, nothing else. What it sends

Bedrock subagent sonnet alias ignores configured default model. Subagents with model: sonnet get the parent session's us. prefix instead of the configured global. profile and fail at first call.

Is this your bug?

File my report

Where: Subagents
Error text: API Error (us.anthropic.claude-sonnet-5-5): 400 The provided model identifier is invalid.. Try /model to switch to us.anthropic.claude-sonnet-5. (error type model_not_found, HTTP 400, model sent to the API: us.anthropic.claude-sonnet-5-5)
Versions: 2.1.284 to 2.1.286
Platforms: macOS, Windows
How bad: Breaks a normal workflow.

Part of: Subagent model not as requested5 bugs

Sub-agents silently run on Opus 4.83 people
Resumed custom subagent loses its type and model via SendMessage3 people
Subagent view shows parent model4 people
Subagents ignore session model2 people

Not quite your bug?

Auto mode ignores classifier model4 people

Original reports2, newest first

Sep 30, 2026Bedrock: subagent model alias resolved with the parent session's inference-profile prefix, ignoring ANTHROPIC_DEFAULT_<TIER>_MODEL#98516
Sep 29, 2026[bedrock] Subagent sonnet alias ignores ANTHROPIC_DEFAULT_SONNET_MODEL and sends an invalid us. profile ID (regression of / same as #73556)#98298