fix: use valid model ID for default LLM settings

[Gkrumbach07]

Summary

• Default model was "sonnet" which isn't a valid model manifest ID
• Changed to "claude-sonnet-4-5" which matches the manifest
• Fixes 400 errors when creating sessions without an explicit model (e.g. CI workflows via ambient-action)

Test plan

• Create a session without specifying a model — should default to claude-sonnet-4-5
• Verify PR fixer CI workflow can create sessions successfully

🤖 Generated with Claude Code

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: ASSERTIVE

Plan: Pro

Run ID: b6b948b5-618d-410b-a2dd-27877bf7ed32

📥 Commits

Reviewing files that changed from the base of the PR and between 42f7927 and 376a419.

📒 Files selected for processing (1)

• components/backend/handlers/sessions.go

---

Walkthrough

A one-line configuration change updates the default LLM model identifier in session creation from "sonnet" to "claude-sonnet-4-5". No functional logic or control flow modifications are introduced.

Changes

Cohort / File(s)	Summary
LLM Default Configuration components/backend/handlers/sessions.go	Updated default LLM model identifier in CreateSession from "sonnet" to "claude-sonnet-4-5".

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~2 minutes

🚥 Pre-merge checks | ✅ 2 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and accurately summarizes the main change: updating the default LLM model ID from an invalid value to a valid one.
Description check	✅ Passed	The description directly relates to the changeset, explaining why the change was made, what was changed, and how to verify it.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing Touches

• 📝 Generate docstrings (stacked PR)
• 📝 Generate docstrings (commit on current branch)

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch fix/default-model-name

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands and usage tips.}

[mergify]

🧪 CI Insights

Here's what we observed from your CI run for 376a419.

🟢 All jobs passed!

But CI Insights is watching 👀

[ambient-code]

Test comment from Claude Code to verify GitHub token permissions.