Amazon Q is having trouble responding right now:

### Checks

- [x] I have searched [github.com/aws/amazon-q-developer-cli/issues](https://github.com/aws/amazon-q-developer-cli/issues?q=) and there are no duplicates of my issue
- [x] I have run `q doctor` in the affected terminal session
- [x] I have run `q restart` and replicated the issue again

### Operating system

macOS 15.5.0 (24F74)

### Expected behaviour

Amazon Q is having trouble responding right now:
0: Failed to send the request: unhandled error (ValidationException)
1: unhandled error (ValidationException)
2: service error
3: unhandled error (ValidationException)
4: Error { code: "ValidationException", message: "Improperly formed request.", aws_request_id: "e826a3ed-a2cd-4f6c-ae90-f5d1b30a7277" }

Location:
crates/chat-cli/src/cli/chat/mod.rs:993

Backtrace omitted. Run with RUST_BACKTRACE=1 environment variable to display it.
Run with RUST_BACKTRACE=full to include source snippets.

### Actual behaviour

Amazon Q is having trouble responding right now:
0: Failed to send the request: unhandled error (ValidationException)
1: unhandled error (ValidationException)
2: service error
3: unhandled error (ValidationException)
4: Error { code: "ValidationException", message: "Improperly formed request.", aws_request_id: "e826a3ed-a2cd-4f6c-ae90-f5d1b30a7277" }

Location:
crates/chat-cli/src/cli/chat/mod.rs:993

Backtrace omitted. Run with RUST_BACKTRACE=1 environment variable to display it.
Run with RUST_BACKTRACE=full to include source snippets.

### Steps to reproduce

_No response_

### Environment

```yaml

[q-details]
version = "1.13.1"
hash = "c658e9e187b6264a24821db3a3ddc591e3095d2f"
date = "2025-08-01T22:08:19.279481Z (11d ago)"

[system-info]
os = "macOS 15.5.0 (24F74)"
chip = "Apple M1 Max"
total-cores = 10
memory = "64.00 GB"

[environment]
cwd = "/Users/USER"
cli-path = "/Users/USER"
install-method = "unknown"

[env-vars]
PATH = "/Users/USER/.local/bin:/Users/USER/.local/share/mise/installs/node/22.17.1/bin:/Users/USER/.local/share/mise/installs/python/3.12.9/bin:/Users/USER/.local/share/mise/installs/python/3.11.11/bin:/Users/USER/.local/share/mise/installs/python/3.10.16/bin:/Users/USER/.local/share/mise/installs/python/3.9.21/bin:/Users/USER/.local/share/mise/installs/python/3.8.20/bin:/opt/homebrew/bin:/opt/homebrew/sbin:/Users/USER/.toolbox/bin:/Users/USER/.local/bin:/usr/local/bin:/System/Cryptexes/App/usr/bin:/usr/bin:/bin:/usr/sbin:/sbin:/var/run/com.apple.security.cryptexd/codex.system/bootstrap/usr/local/bin:/var/run/com.apple.security.cryptexd/codex.system/bootstrap/usr/bin:/var/run/com.apple.security.cryptexd/codex.system/bootstrap/usr/appleinternal/bin:/Library/Apple/usr/bin:/usr/local/share/dotnet:/Users/USER/.dotnet/tools:/Library/Frameworks/Mono.framework/Versions/Current/Commands:/Users/USER/.cargo/bin:/Applications/iTerm.app/Contents/Resources/utilities:/Users/USER/Library/Application Support/JetBrains/Toolbox/scripts"
QTERM_SESSION_ID = "965aed7026ba41ccb6d5349ed38e01b9"
Q_SET_PARENT_CHECK = "1"
Q_TERM = "1.13.0"
SHELL = "/bin/zsh"
TERM = "xterm-256color"
__CFBundleIdentifier = "com.googlecode.iterm2"
```

Beginne bei crates/chat-cli/src/cli/chat/mod.rs:993 und untersuche den Request-Pfad, der mit der ValidationException verbunden ist. Reproduziere den Fehler mit q doctor und q restart in der betroffenen macOS-Sitzung unter Verwendung der angegebenen Versions- und Umgebungsdetails; fertig ist die Arbeit, wenn Amazon Q ohne den Servicefehler antwortet.

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