feat: cohort segment detail view with CSV re-synchronisation

[Zaimwa9]

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• I have read the Contributing Guide.
• I have added information to docs/ if required so people know about the feature.
• I have filled in the "Changes" section below.
• I have filled in the "How did you test this code" section below.

Changes

Detail view for CSV cohort-managed segments, replacing the read-only rules editor:

• Sync status chip, progress bar and last-synchronisation time, polled while a synchronisation is in flight.
• Editable name and description via the new cohort PATCH endpoint.
• Re-upload flow reusing CsvUpload and the new shared CsvPreview, with a review summary before synchronising.
• SegmentSelect shows the CSV chip and hides segments pending deletion.
• Fixed double horizontal padding in the tabbed segment drawers.

Stacked on #8386.

How did you test this code?

Manually: created a CSV segment, re-uploaded a smaller file and verified the add/remove counts, progress and status against a running task processor; renamed the segment and checked list/breadcrumb refresh. Unit tests, eslint and typecheck (no new errors) pass.

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Project	Deployment	Actions	Updated (UTC)
flagsmith-frontend-preview	Ready	Preview	Aug 28, 2026 12:28pm
flagsmith-frontend-staging	Ready	Preview	Aug 28, 2026 12:28pm

1 Skipped Deployment

Project	Deployment	Actions	Updated (UTC)
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[coderabbitai]

📝 Walkthrough

Walkthrough

The API stores last_synced_at, returns membership counts, and supports cohort PATCH updates. The frontend adds cohort query and update hooks, expanded types, reusable CSV preview and upload controls, and a CSV cohort detail interface. Users can edit CSV cohort fields, upload replacement identifiers, monitor synchronisation progress, and update metadata. Segment selectors exclude cohorts pending deletion and show cohort source badges. Tests and OpenAPI documentation cover the new behaviour.

Estimated code review effort: 4 (Complex) | ~60 minutes

Merge Risk: 🟠 High · up to 34688

CSV re-synchronisation can change feature-targeting membership, but concurrent uploads may produce an unintended combined result and the new editing flow may bypass the existing approval process for segment changes. These high-impact correctness and authorization risks should be resolved or explicitly accepted before merging.

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[github-actions]

Docker builds report

Image	Build Status	Security report
ghcr.io/flagsmith/flagsmith-api-test:pr-8387	Finished ✅	Skipped
ghcr.io/flagsmith/flagsmith-e2e:pr-8387	Finished ✅	Skipped
ghcr.io/flagsmith/flagsmith-api:pr-8387	Finished ✅	Results ✅
ghcr.io/flagsmith/flagsmith:pr-8387	Finished ✅	Results ✅
ghcr.io/flagsmith/flagsmith-private-cloud:pr-8387	Finished ✅	Results ✅
ghcr.io/flagsmith/flagsmith-frontend:pr-8387	Finished ✅	Results ✅

[Zaimwa9]

@themis-blindfold review

[github-actions]

✅ private-cloud · depot-ubuntu-latest-arm-16 — run #19923 (attempt 1)

Playwright Test Results (private-cloud - depot-ubuntu-latest-arm-16)

 2 passed

Details

 2 tests across 2 suites
 38.2 seconds
 3468816
 🔄 Run: #19923 (attempt 1)

🗂️ Previous results

✅ private-cloud · depot-ubuntu-latest-16 — run #19923 (attempt 1)

Playwright Test Results (private-cloud - depot-ubuntu-latest-16)

 2 passed

Details

 2 tests across 2 suites
 32.7 seconds
 3468816
 🔄 Run: #19923 (attempt 1)

✅ oss · depot-ubuntu-latest-arm-16 — run #19923 (attempt 1)

Playwright Test Results (oss - depot-ubuntu-latest-arm-16)

 1 passed

Details

 1 test across 1 suite
 44.8 seconds
 3468816
 🔄 Run: #19923 (attempt 1)

✅ oss · depot-ubuntu-latest-16 — run #19923 (attempt 1)

Playwright Test Results (oss - depot-ubuntu-latest-16)

 1 passed

Details

 1 test across 1 suite
 40.2 seconds
 3468816
 🔄 Run: #19923 (attempt 1)

✅ private-cloud · depot-ubuntu-latest-arm-16 — run #19922 (attempt 1)

Playwright Test Results (private-cloud - depot-ubuntu-latest-arm-16)

 2 passed

Details

 2 tests across 2 suites
 1 minute, 3 seconds
 b43eb61
 🔄 Run: #19922 (attempt 1)

✅ private-cloud · depot-ubuntu-latest-16 — run #19922 (attempt 1)

Playwright Test Results (private-cloud - depot-ubuntu-latest-16)

 1 passed

Details

 1 test across 1 suite
 31.6 seconds
 b43eb61
 🔄 Run: #19922 (attempt 1)

✅ oss · depot-ubuntu-latest-arm-16 — run #19922 (attempt 1)

Playwright Test Results (oss - depot-ubuntu-latest-arm-16)

 1 passed

Details

 1 test across 1 suite
 45.5 seconds
 b43eb61
 🔄 Run: #19922 (attempt 1)

✅ oss · depot-ubuntu-latest-16 — run #19922 (attempt 1)

Playwright Test Results (oss - depot-ubuntu-latest-16)

 1 passed

Details

 1 test across 1 suite
 33.5 seconds
 b43eb61
 🔄 Run: #19922 (attempt 1)

✅ private-cloud · depot-ubuntu-latest-16 — run #19904 (attempt 1)

Playwright Test Results (private-cloud - depot-ubuntu-latest-16)

 1 passed

Details

 1 test across 1 suite
 55.1 seconds
 2dff072
 🔄 Run: #19904 (attempt 1)

✅ private-cloud · depot-ubuntu-latest-arm-16 — run #19904 (attempt 1)

Playwright Test Results (private-cloud - depot-ubuntu-latest-arm-16)

 1 passed

Details

 1 test across 1 suite
 19.8 seconds
 2dff072
 🔄 Run: #19904 (attempt 1)

✅ oss · depot-ubuntu-latest-arm-16 — run #19904 (attempt 1)

Playwright Test Results (oss - depot-ubuntu-latest-arm-16)

 2 passed

Details

 2 tests across 2 suites
 39.6 seconds
 2dff072
 🔄 Run: #19904 (attempt 1)

✅ oss · depot-ubuntu-latest-16 — run #19904 (attempt 1)

Playwright Test Results (oss - depot-ubuntu-latest-16)

 2 passed

Details

 2 tests across 2 suites
 40.3 seconds
 2dff072
 🔄 Run: #19904 (attempt 1)

[github-actions]

Visual Regression

19 screenshots compared. See report for details.
View full report

[themis-blindfold]

⚖️ Themis review: 🟠 Fix before merge

The CSV cohort detail view needs two fixes before merge: preserve read-only access in the replacement view, and report synchronisation progress from stable work totals rather than mutable membership state. Completed unit, lint, UI, image, and preview checks passed; E2E jobs were still running.

Area	Score
🎯 Correctness	2/5
🧪 Test coverage	2/5
📐 Code quality	3/5
🚀 Product impact	3/5

🟠 Majors

• frontend/web/components/modals/CreateSegment.tsx:806 — CSV cohort details bypass the page's read-only mode.
• frontend/web/components/segments/CohortSegmentDetail/CohortSegmentDetail.tsx:64 — removal-only synchronisations display incorrect progress.

📝 Walkthrough

• Cohort API client - adds retrieve and PATCH endpoints with cache invalidation.
• CSV cohort detail - replaces the rules editor with editable metadata, sync state, and polling.
• Re-synchronisation - extracts the chosen CSV column, validates the generated upload, and submits it as a normalised CSV.
• Segment surfaces - marks cohort options, hides pending deletions, and shares the preview component.

🧪 How to verify

1. With Manage Segments, rename a CSV cohort segment and re-upload a CSV; verify the list and breadcrumb refresh.
2. Without Manage Segments, open a CSV cohort segment directly and verify all mutation controls are unavailable.
3. Re-sync a 1,000-member cohort to a 100-member CSV and verify progress advances meaningfully through removal work.
4. Run cd frontend && npm run test:unit -- --runInBand common/utils/__tests__/csv.test.ts.

Automate: add component tests for read-only controls and add-only, remove-only, and mixed synchronisation progress.

Local CSV utility tests could not be started because the checkout lacks frontend dependencies.

Product take: This is a solid operational improvement for cohort-managed segments, but misleading progress and unavailable permissions make the primary management flow unreliable until fixed.

🧭 Assumptions & unverified claims

No unverified assumptions or claims.

A resync button should know which way the members are heading · reviewed at d4e34f7

[Zaimwa9]

@themis-blindfold review

[themis-blindfold]

⚖️ Themis review: 🟠 Fix before merge

The new cohort detail screen bypasses the page's read-only permission and reports a fixed, misleading progress percentage for removal-only synchronisations; both active major findings remain unresolved. The completed CI suite is green. Local typecheck could not be rerun because the TypeScript compiler is not installed in this checkout.

Area	Score
🎯 Correctness	2/5
🧪 Test coverage	2/5
📐 Code quality	3/5
🚀 Product impact	4/5

🟠 Majors

• frontend/web/components/modals/CreateSegment.tsx: view-only users can submit cohort mutations.
• frontend/web/components/segments/CohortSegmentDetail/CohortSegmentDetail.tsx: removal-only synchronisations do not show advancing progress.

🧹 Nits

• frontend/common/types/responses.ts: Mixpanel is missing from the cohort source-type union.

📝 Walkthrough

• Cohort detail - replaces the rules editor for CSV-managed segments with metadata, status, and update controls.
• CSV synchronisation - reuses upload and preview components to send a normalised single-column CSV.
• Cohort service - adds retrieve and PATCH requests and cache invalidation for the detail view.

🧪 How to verify

1. Open a CSV cohort segment as a user without Manage Segments and confirm no name, description, or upload mutation can be submitted.
2. Re-synchronise a 1,000-member cohort down to 100 members and confirm the progress bar advances through the removals to completion.
3. Fetch a Mixpanel-managed segment and confirm its cohort source type is accepted by the frontend API types.
4. Run cd frontend && npm run typecheck in a dependency-complete checkout.
   Automate: Add component tests for the read-only controls, polling/progress states, and source-type response fixtures.

Product take: A solid improvement to CSV cohort management, but view-only roles and removal-heavy synchronisations cannot be trusted until the two major issues are fixed.

🧭 Assumptions & unverified claims

No unverified assumptions or claims.

Two threads still need their cohort moment · reviewed at c385cad

The base branch was changed.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.81%. Comparing base (0f0e09a) to head (3468816).
⚠️ Report is 3 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #8387   +/-   ##
=======================================
  Coverage   98.81%   98.81%           
=======================================
  Files        1620     1621    +1     
  Lines       66018    66102   +84     
=======================================
+ Hits        65234    65318   +84     
  Misses        784      784           

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[coderabbitai]

Actionable comments posted: 3

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: ASSERTIVE

Plan: Pro Plus

Run ID: 1148b737-93ba-47d2-bf29-d2b685e491c9

📥 Commits

Reviewing files that changed from the base of the PR and between bbc4bd1 and b43eb61.

📒 Files selected for processing (25)

• api/cohorts/migrations/0005_cohort_last_synced_at.py
• api/cohorts/models.py
• api/cohorts/serializers.py
• api/cohorts/services.py
• api/cohorts/views.py
• api/tests/unit/cohorts/test_views.py
• docs/docs/deployment-self-hosting/observability/_events-catalogue.md
• frontend/common/services/useCohort.ts
• frontend/common/types/requests.ts
• frontend/common/types/responses.ts
• frontend/common/utils/csv.ts
• frontend/web/components/CsvPreview/CsvPreview.scss
• frontend/web/components/CsvPreview/CsvPreview.tsx
• frontend/web/components/CsvPreview/index.ts
• frontend/web/components/CsvUpload/CsvUpload.tsx
• frontend/web/components/SegmentSelect.tsx
• frontend/web/components/modals/CreateSegment.tsx
• frontend/web/components/modals/CreateSegmentFromCsv/CreateSegmentFromCsv.scss
• frontend/web/components/modals/CreateSegmentFromCsv/CreateSegmentFromCsv.tsx
• frontend/web/components/segments/CohortSegmentDetail/CohortCsvSync.tsx
• frontend/web/components/segments/CohortSegmentDetail/CohortSegmentDetail.scss
• frontend/web/components/segments/CohortSegmentDetail/CohortSegmentDetail.tsx
• frontend/web/components/segments/CohortSegmentDetail/index.ts
• frontend/web/components/segments/SegmentRow/SegmentRow.tsx
• openapi.yaml

💤 Files with no reviewable changes (2)

• frontend/web/components/modals/CreateSegmentFromCsv/CreateSegmentFromCsv.scss
• frontend/web/components/segments/SegmentRow/SegmentRow.tsx

Included review availability: Your plan provides up to 8 included reviews per hour; 7 remain after this review.

[coderabbitai]

Caution

Some comments are outside the diff and can’t be posted inline due to platform limitations.

⚠️ Outside diff range comments (2)

frontend/web/components/segments/CohortSegmentDetail/CohortSegmentDetail.tsx (2)

74-84: 🎯 Functional Correctness | 🟡 Minor | ⚡ Quick win

Reset synchronisation progress when the cohort changes.

When the same CohortSegmentDetail instance receives a new cohort, syncTotal remains from the previous cohort. A lower pendingCount does not replace it because the effect applies Math.max(total, pendingCount). Key the snapshot by cohort identity and initialise it from the new cohort’s pending work.

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86-89: 🗄️ Data Integrity & Integration | 🟡 Minor | ⚡ Quick win

Reset the form baseline when the segment identity changes.

When SegmentPage changes the route, the existing component can receive a different segment. If both segments have the same name and description, this effect does not reset the local form values. Include segment.id in the dependency list.

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: ASSERTIVE

Plan: Pro Plus

Run ID: 7c42fc81-f8c7-426f-ad51-71fa8d82118e

📥 Commits

Reviewing files that changed from the base of the PR and between b43eb61 and 3468816.

📒 Files selected for processing (3)

• frontend/web/components/modals/CreateSegment.tsx
• frontend/web/components/segments/CohortSegmentDetail/CohortSegmentDetail.scss
• frontend/web/components/segments/CohortSegmentDetail/CohortSegmentDetail.tsx

Included review availability: Your plan provides up to 8 included reviews per hour; 6 remain after this review.