fix(replay-vision): select Slack workspace for alerts

[Indira-kumar]

Problem

• Replay Vision users with multiple Slack workspaces cannot target the second workspace while creating an alert.
• Closes Can't change Slack Workspace while creating an alert #106294.

Changes

• Replay Vision alerts now pass the selected Slack workspace to the channel picker and notification payload.
• Changing workspaces clears the selected channel, preventing an invalid workspace-channel pair.
• Adds regression coverage for staging a notification from a second workspace.

Screenshots

Currently selected workspace A:

Switched to workspace B:

Selected channels from both workspaces:

How did you test this code?

• Manual local verification:
  1. Created a Replay Vision scanner.
  2. Opened Alerts and created a new alert.
  3. Selected Slack in the Notify step.
  4. Switched between two Slack workspaces.
  5. Confirmed each workspace loaded its own channel.
  6. Saved and reopened the alert.
  7. Confirmed the selected workspace and channel remained attached.
• Automated: hogli test products/replay_vision/frontend/replay_scanners/scannerAlertNotificationLogic.test.ts passed. The test verifies that workspace 2 is staged in the Slack notification payload.
• Automated: pnpm --filter=@posthog/frontend typescript:check passed.
• Automated: hogli ci:preflight --strict --against upstream/master reported zero strict failures.

Release status

• No feature flag controls this change
• This change is behind a feature flag and is not available to users
• This change makes a previously flagged feature available to everyone

Automatic notifications

• Publish to changelog?

Docs update

• No documentation update is needed for this bug fix.

🤖 Agent context

Autonomy: Human-driven (agent-assisted)

Agent: Codex, GPT-5

• The branch was rebased onto upstream/master and its focused regression test was added to cover the selected workspace payload.
• Skills invoked: /running-ci-preflight, /writing-pr-descriptions, /qa-frontend, /run-posthog, and /reviewing-with-coderabbit.
• CodeRabbit CLI was installed but unauthenticated, so this draft opened without a local CodeRabbit pass.
• A public open-PR search found no duplicate Replay Vision Slack-workspace fix.
• The committed fixture data is invented and contains no customer material.

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[coderabbitai]

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No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Repository: PostHog/posthog/.coderabbit.yaml

Review profile: QUIET

Plan: Enterprise

Run ID: f73239fa-4ca3-442d-b45d-dd5cf4bd7d3c

📥 Commits

Reviewing files that changed from the base of the PR and between d39c387 and 90f540f.

📒 Files selected for processing (3)

• products/replay_vision/frontend/replay_scanners/components/ScannerAlertNotifications.tsx
• products/replay_vision/frontend/replay_scanners/scannerAlertUtils.test.ts
• products/replay_vision/frontend/replay_scanners/scannerAlertUtils.ts

Included review availability: This review used your included allowance. Your plan provides up to 12 included reviews per hour; 11 remain after this review.

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📝 Walkthrough

Walkthrough

Scanner alerts now track the selected Slack workspace by integration ID. The component loads channels for the selected integration and passes workspace changes to the alert logic. The logic uses the resolved integration to validate and stage Slack notifications. A test covers default selection, switching workspaces, clearing the channel value, and staging a notification.

Priority: ➖ Normal

Severity of issue fixed: Medium

Merge Risk: ⚪ Minimal · up to 90f54

The reviewed workspace-selection and destination behavior has no identified issue requiring a fix before merge.

Security Architecture Review

Security architecture risk: 🔵 Low · up to 90f54

The editor now supports alerts in a second connected Slack workspace. The reviewed flow clears the old channel when workspaces change and saves the selected workspace with its channel. No introduced security issue was established, but server-side checks for those identifiers remain unverified.

Retained concerns
No architecture-level concerns identified.

Security review details

Security Blast Radius

• inferred — An alert creator can now choose a second available Slack integration as the destination workspace. Effective exposure beyond the integrations offered by the editor cannot be determined without the server-side ownership checks.

Trust Boundaries and Controls

• observed — Changing workspaces clears the selected channel, and integration-keyed Slack logic loads channels using the newly selected integration ID. The reviewed client path therefore preserves the workspace-channel association during a normal switch.

Hardening Proposals

• proposed — Confirm that the channel and destination endpoints enforce project ownership of the supplied integration and validate the workspace-channel association independently of the editor.

🚥 Pre-merge checks | ✅ 1

✅ Passed checks (1 passed)

Check name	Status	Explanation
Description check	✅ Passed	The description covers the problem, user-visible changes, screenshots, tests, release status, documentation, and agent context. The agent context does not include a session link or report patch-covera…

✨ Finishing Touches

🧪 Generate unit tests (beta)

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[TueHaulund]

🤖 Agent-drafted, reviewed by Tue.

Small follow-on: groupVisionAlertDestinations in scannerAlertUtils.ts groups Slack destinations by channel only. With a workspace picker, two workspaces can share a channel ID (Slack Connect), so they'd show up as one row. Adding the workspace to that key should fix it.

[Indira-kumar]

Addressed both points:

• Slack destinations are now grouped by workspace ID and channel ID.
• Pending destinations now display the Slack workspace and channel.

[Indira-kumar]

While testing, I noticed that saved destinations still display only “Slack” after reopening the alert. I’ve tracked that separately in #107955 so this PR can remain focused.

[arnohillen]

ScannerAlertNotifications.tsx:20: the pending row shows only #channel. Show the workspace name as InlineAlertNotifications.tsx:105 does.