Add per-tab model persistence and selection functionality

[ferenci84]

Description

Persist agent/mode/model per session (not per tab), and load them when switching tabs. This replaces the previous per‑tab persistence so that a session’s settings travel with it, survive IDE restarts, and are consistent across views.

Original PR (for tabs only): #7617

Discussion: #7986

Key changes:

• Session persistence:
  • Added optional fields to the session payload: mode and chatModelTitle.
  • Persisted to disk in ~/.continue/sessions/<sessionId>.json alongside history/title/workspaceDirectory.
• Save/Load wiring:
  • When saving a session, the GUI includes mode and the selected chat chatModelTitle.
  • When loading a session, the GUI:
    • Restores session.mode into Redux.
    • Restores the selected chat model from session.chatModelTitle (when available).
• Tabs:
  • Removed per‑tab model and mode fields and their reducers (setTabModel, setTabMode).
  • Switching tabs now relies on the session’s persisted data; no more model/mode mirroring to tabs.
• Types and plumbing:
  • Extended Session type (core) with mode? and chatModelTitle?.
  • Updated Core history manager to write/read the new fields when present.

Why

• Keeps a conversation’s configuration together and makes it resilient to reloads.
• Eliminates flicker or divergence from tab-local model/mode.
• Paves the way for persisting additional session-level UI state when needed.

Backward compatibility

• Existing session files load normally (new fields are optional).
• Tabs continue to work; they just no longer store model/mode.

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Checklist

• I've read the contributing guide
• The relevant docs, if any, have been updated or created
• The relevant tests, if any, have been updated or created

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Tests

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---

Summary by cubic

Persist session-level chat mode and selected chat model. Switching tabs and loading sessions restore the session’s saved mode and model; new sessions start with the current selection.

• New Features
  • Added optional mode and chatModelTitle to Session and persisted them to disk.
  • Loading a session sets Redux mode and updates the selected chat model.
  • Saving a session writes mode and the selected chat model title.

^{Written for commit 4b330de. Summary will update automatically on new commits.}

[cubic-dev-ai]

1 issue found across 2 files

Prompt for AI agents (all 1 issues)

Understand the root cause of the following 1 issues and fix them.


<file name="gui/src/redux/slices/tabsSlice.ts">

<violation number="1" location="gui/src/redux/slices/tabsSlice.ts:46">
This PR&#39;s implementation contradicts its stated architectural goal. It re-introduces per-tab state management for model and mode (in `tabsSlice.ts`) instead of removing it, and the logic in `TabBar.tsx` incorrectly uses this tab-level state as the source of truth, overriding the intended session-level persistence.</violation>
</file>

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[cubic-dev-ai]

This PR's implementation contradicts its stated architectural goal. It re-introduces per-tab state management for model and mode (in tabsSlice.ts) instead of removing it, and the logic in TabBar.tsx incorrectly uses this tab-level state as the source of truth, overriding the intended session-level persistence.

Prompt for AI agents

Address the following comment on gui/src/redux/slices/tabsSlice.ts at line 46:

<comment>This PR&#39;s implementation contradicts its stated architectural goal. It re-introduces per-tab state management for model and mode (in `tabsSlice.ts`) instead of removing it, and the logic in `TabBar.tsx` incorrectly uses this tab-level state as the source of truth, overriding the intended session-level persistence.</comment>

<file context>
@@ -37,6 +42,26 @@ export const tabsSlice = createSlice({
       );
     },
+    // Set the model title for a specific tab
+    setTabModel: (
+      state,
+      action: PayloadAction&lt;{ id: string; modelTitle: string }&gt;,
</file context>

✅ Addressed in a3b5ee8

[RomneyDa]

@ferenci84 looks like it's still per-tab as opposed to per session, possible PR is on the wrong branch?

[ferenci84]

@ferenci84 looks like it's still per-tab as opposed to per session, possible PR is on the wrong branch?

@RomneyDa I just didn't push the latest commit. Corrected now.

[cubic-dev-ai]

No issues found across 6 files

[RomneyDa]

Great, will take a look!

[RomneyDa]

Clean implementation!

[RomneyDa]

Noticed the same logic is duplicated, could we move it to the newSession action instead?

[RomneyDa]

@ferenci84 I took forever to follow up on this so I went ahead and touched up. Appreciate the contribution!