Summary

Fixes #4019 and #4088 — clicking "New Session" (or the "+" tab button) in the desktop app created a blank tab with hardcoded defaults instead of carrying over the current session's model, effort, collaboration mode, and tool-approval posture.

Problem

When a user had model=deepseek-v4-pro, effort=max, and YOLO enabled in the current tab, clicking "New Session" would create a blank tab that did not inherit any of those settings:

Root Cause

EnsureBlankTab() in desktop/tabs.go created the WorkspaceTab struct with hardcoded defaults and zero-value fields:

mode:             "normal",              // hardcoded
toolApprovalMode: control.ToolApprovalAsk, // hardcoded
// model and effort left as zero values

No settings were carried over from the currently active tab. Additionally, Fork() was missing toolApprovalMode from its carry-over set — every forked session silently reverted to "ask" approval.

Changes

desktop/tabs.go — EnsureBlankTab (main fix)

• Inherit model, effort, mode, toolApprovalMode, disabledMCP, and mcpOrder from the active tab before constructing the blank WorkspaceTab. Falls back to the previous hardcoded defaults only when no active tab exists (first launch).
• Fallback path (reusing a previously-indexed blank topic) now builds the tab inline instead of delegating to OpenProjectTab / OpenGlobalTab, which had their own hardcoded defaults. Both code paths share the same inherited variables, so the reuse path is no longer a gap.

desktop/app.go — Fork

• Added toolApprovalMode to the carry-over set (model, effort, mode, disabledMCP, and mcpOrder were already inherited).

Affected code paths

Verification

• go build ./... passes.
• Three rounds of code review addressed — the initial implementation, an external review identifying a bypass path and MCP asymmetry, and a final symptom-by-symptom verification against the issue's reproduction steps.
• No new dependencies, no public API changes, mutex discipline unchanged.