Refresh live model catalog when a harness session becomes active

[stillNovice]

Problem

Opening the model picker for a fresh session showed only the built-in fallback model (e.g. just Default for Pi) instead of the live catalog from the CLI (pi --mode rpc reports ~70 models for a gateway-configured setup).

Root cause

Live model catalogs are loaded lazily — probing a CLI spawns a real process, so MonoCode deliberately avoids probing every harness at boot (see the comment in refreshHarnessCatalogs). But the boot-time refresh runs in a useEffect with [] deps that fires before restored sessions land in sessionsRef, so it sees an empty harness list and never probes anything.

The only remaining trigger was opening the model picker itself (ModelPicker.tsx). If the probe fails or hasn't run, a newly created session sits on the fallback list indefinitely.

Fix

Refresh the live catalog for the active session's harness whenever the active harness changes (App.tsx). This covers:

• creating a new session
• switching between sessions on different harnesses
• restoring sessions at boot (harness becomes active after restore)

No repeat spawns: refreshHarnessCatalogs is already idempotent — hasLiveCatalog skips harnesses whose catalog is loaded, and inflight dedupes concurrent probes.

Testing

• vitest run: 2121 passed, 0 failed
• Manual: fresh Pi session now loads the full live catalog without opening the picker

Summary by CodeRabbit

• Improvements
  • The live model catalog now refreshes automatically when the active harness changes, keeping available models current.
  • Catalog refreshes are skipped when no harness is selected or when the selected harness is not live.
  • Refresh requests are coordinated to avoid unnecessary duplicate updates.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

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Reviewing files that changed from the base of the PR and between 4ff1fa5 and cf733a4.

📒 Files selected for processing (1)

• src/App.tsx

🚧 Files skipped from review as they are similar to previous changes (1)

• src/App.tsx

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📝 Walkthrough

Walkthrough

Changes

Live harness catalog

Layer / File(s)	Summary
Refresh catalog on harness changes src/App.tsx	Comments clarify lazy probing, restored-session timing, live-harness checks, and refresh deduplication. Executable behavior is unchanged.

Priority: ⬇️ Low

Estimated code review effort: 1 (Trivial) | ~2 minutes

Change: Bug fix

Merge Risk: ⚪ Minimal · up to cf733

The documented catalog-refresh behavior has no identified merge-blocking risk in the supplied evidence.

🚥 Pre-merge checks | ✅ 4 | ❌ 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%. Docstring coverage is scoped to functions touched by this diff. Analyzed 1 functions across 1 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description check	✅ Passed	The description clearly explains the problem, root cause, fix, scope, and testing results. It does not use the template headings and omits the checklist, but it provides the required technical informa…
Title check	✅ Passed	The title is concise, specific, and accurately summarizes the main change: refreshing the live model catalog when a harness session becomes active.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

• Fix all pre-merge checks with AI

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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