fix(lightspeed): disable model selector during active chat sessions

[its-mitesh-kumar]

Summary

Fixes RHDHBUGS-3313

Bug: Switching the model in an active conversation incorrectly opens a new chat instead of staying in the current session.

Root cause: The model selector's onSelect handler in LightSpeedChat.tsx unconditionally called onNewChat(), creating a new conversation every time the model was changed — even mid-conversation.

Fix:

• Disable the model selector once a chat session has messages (messages.length > 0)
• Show a localized tooltip explaining why: "Each chat session supports only one model. To switch models, open a new chat."
• Remove the spurious onNewChat() call from the model selector's onSelect handler
• Apply the same logic to both the footer and header model selectors for consistency

Changes

File	What changed
LightSpeedChat.tsx	Disable model selector when messages.length > 0; remove onNewChat() from onSelect; pass disabledTooltip prop
MessageBarModelSelector.tsx	Accept disabledTooltip prop; wrap dropdown in <Tooltip> when disabled
ref.ts	Add modelSelector.disabledTooltip translation key
de.ts, es.ts, fr.ts, it.ts, ja.ts	Add translated tooltip strings
report-alpha.api.md	Auto-generated API report update

UI before changes

The model selector is clickable mid-conversation and switching models creates a new chat

UI after changes

The model selector is disabled once a message is sent, showing a tooltip on hover

Test plan

• Reproduction test confirms model selector becomes disabled after sending a message
• yarn tsc:full passes with no errors
• yarn build passes
• Lint-staged hooks pass on commit
• Manual verification: open Lightspeed, send a message, confirm model selector is disabled with tooltip
• Manual verification: start a new chat, confirm model selector is enabled again

[rhdh-gh-app]

Changed Packages

Package Name	Package Path	Changeset Bump	Current Version
@red-hat-developer-hub/backstage-plugin-lightspeed	workspaces/lightspeed/plugins/lightspeed	patch	v2.9.1

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 54.29%. Comparing base (12b0c0b) to head (409ac7b).
⚠️ Report is 1 commits behind head on main.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3690   +/-   ##
=======================================
  Coverage   54.28%   54.29%           
=======================================
  Files        2347     2347           
  Lines       89650    89644    -6     
  Branches    25062    25068    +6     
=======================================
+ Hits        48666    48670    +4     
+ Misses      40724    40714   -10     
  Partials      260      260           

Flag	Coverage Δ		*Carryforward flag
adoption-insights	83.70% <ø> (ø)		Carriedforward from 1bd1997
ai-integrations	68.35% <ø> (ø)		Carriedforward from 1bd1997
app-defaults	69.79% <ø> (ø)		Carriedforward from 1bd1997
augment	46.39% <ø> (ø)		Carriedforward from 1bd1997
boost	74.68% <ø> (ø)		Carriedforward from 1bd1997
bulk-import	72.46% <ø> (ø)		Carriedforward from 1bd1997
cost-management	14.10% <ø> (ø)		Carriedforward from 1bd1997
dcm	61.81% <ø> (ø)		Carriedforward from 1bd1997
extensions	61.53% <ø> (ø)		Carriedforward from 1bd1997
global-floating-action-button	71.18% <ø> (ø)		Carriedforward from 1bd1997
global-header	59.71% <ø> (ø)		Carriedforward from 1bd1997
homepage	50.23% <ø> (ø)		Carriedforward from 1bd1997
install-dynamic-plugins	56.77% <ø> (ø)		Carriedforward from 1bd1997
konflux	91.49% <ø> (ø)		Carriedforward from 1bd1997
lightspeed	68.96% <100.00%> (+0.14%)	⬆️
mcp-integrations	85.46% <ø> (ø)		Carriedforward from 1bd1997
orchestrator	39.47% <ø> (ø)		Carriedforward from 1bd1997
quickstart	65.63% <ø> (ø)		Carriedforward from 1bd1997
sandbox	79.56% <ø> (ø)		Carriedforward from 1bd1997
scorecard	82.67% <ø> (ø)		Carriedforward from 1bd1997
theme	61.26% <ø> (ø)		Carriedforward from 1bd1997
translations	7.25% <ø> (ø)		Carriedforward from 1bd1997
x2a	78.68% <ø> (ø)		Carriedforward from 1bd1997

*This pull request uses carry forward flags. Click here to find out more.

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[its-mitesh-kumar]

Cc: @HusneShabbir if you get time please check if atleast functionality is working properly. As it is first pr by bug-fix skill.

[HusneShabbir]

@its-mitesh-kumar I agree that this is an edge-case scenario, but I think it's worth addressing as well.

When the model dropdown is open and a message is sent, it's still possible to change the model mid-conversation. Please refer to the recording below.

It would be great if we could handle this case too and prevent the model from being changed while a conversation is in progress.

cc: @karthikjeeyar / @rohitkrai03

Screen.Recording.2026-07-06.at.8.37.29.PM.mov