feat: wire CSV segments to the cohorts API

[Zaimwa9]

Thanks for submitting a PR! Please check the boxes below:

• 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

Wires the CSV segment drawer (#8283) to the cohorts API (#8294).

Create flow

• New useCohort service: createCohort, syncCohortCsv (multipart) and deleteCohort mutations, invalidating the segment list.
• The drawer submits in two steps: create the cohort, then sync the trimmed, headerless, single-column CSV built from the selected identifier column. Only the identifier column leaves the browser. If the sync fails, retrying reuses the created cohort instead of creating a duplicate segment.
• Success toast reports the added count from the API and stays visible for 10 seconds.
• Custom Fields (metadata) are sent with the create call.

Segment list

• CSV-backed segments show a CSV chip and a chip with the targeted environment's name, driven by the cohort summary on the segment payload.
• Removing a CSV segment routes through the cohort delete endpoint (the segment endpoint rejects cohort-managed segments); plain segments are unchanged.
• Deletion is drain-then-delete on the API side, so while a cohort is awaiting drain the row is greyed out, cannot be opened, and has no actions.
• Fixed the row action dropdown staying open under the confirm modal (it only closed on outside clicks).

Upload hardening

• CsvUpload takes a maxSizeBytes prop; the drawer passes 10MB to mirror the API cap, so oversized files are rejected client-side with a clear message.
• toParsedCsv no longer spreads every row into Math.max, which overflowed the call stack on large files.

How did you test this code?

• Unit tests for the CSV utilities (17 passing), including quoting and column extraction.
• Manual QA against a local API: happy path with multi-column and single-column files, count parity between the preview and the toast, metadata on create, oversized file rejection, CSV and plain segment deletion, the deleting state, and membership rows verified in the database.

[vercel]

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Project	Deployment	Actions	Updated (UTC)
flagsmith-frontend-preview	Ready	Preview	Aug 25, 2026 1:08pm
flagsmith-frontend-staging	Ready	Preview	Aug 25, 2026 1:08pm

1 Skipped Deployment

Project	Deployment	Actions	Updated (UTC)
docs	Ignored	Preview	Aug 25, 2026 1:08pm

[coderabbitai]

📝 Walkthrough

Walkthrough

Added typed cohort APIs and request and response contracts. Added UTF-8 identifier limits, CSV column serialisation, and upload size validation. Updated the CSV modal to create cohorts and synchronise identifier columns. Updated segment deletion and read-only editing for cohort-managed segments. Segment rows now show cohort details and deletion state.

Estimated code review effort: 4 (Complex) | ~45 minutes

Merge Risk: 🟠 High · up to 73abe

The CSV segment creation workflow can crash when users select a file or open Custom Fields because required UI components are missing imports, so the feature is not ready to merge until this is fixed. Cohort-managed segment metadata can also be edited locally despite being read-only, although those changes are not saved.

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[github-actions]

Docker builds report

Image	Build Status	Security report
ghcr.io/flagsmith/flagsmith-api-test:pr-8295	Finished ✅	Skipped
ghcr.io/flagsmith/flagsmith-e2e:pr-8295	Finished ✅	Skipped
ghcr.io/flagsmith/flagsmith-api:pr-8295	Finished ✅	Results ✅
ghcr.io/flagsmith/flagsmith:pr-8295	Finished ✅	Results ✅
ghcr.io/flagsmith/flagsmith-private-cloud:pr-8295	Finished ✅	Results ✅
ghcr.io/flagsmith/flagsmith-frontend:pr-8295	Finished ✅	Results ✅

[Zaimwa9]

@themis-blindfold review

[github-actions]

✅ private-cloud · depot-ubuntu-latest-arm-16 — run #19734 (attempt 1)

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

 1 passed

Details

 1 test across 1 suite
 38.5 seconds
 73abef4
 🔄 Run: #19734 (attempt 1)

🗂️ Previous results

✅ private-cloud · depot-ubuntu-latest-16 — run #19734 (attempt 1)

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

 3 passed

Details

 3 tests across 3 suites
 32.5 seconds
 73abef4
 🔄 Run: #19734 (attempt 1)

✅ oss · depot-ubuntu-latest-arm-16 — run #19734 (attempt 1)

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

 1 passed

Details

 1 test across 1 suite
 40.6 seconds
 73abef4
 🔄 Run: #19734 (attempt 1)

✅ oss · depot-ubuntu-latest-16 — run #19734 (attempt 1)

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

 1 passed

Details

 1 test across 1 suite
 41.2 seconds
 73abef4
 🔄 Run: #19734 (attempt 1)

✅ private-cloud · depot-ubuntu-latest-arm-16 — run #19719 (attempt 1)

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

 3 passed

Details

 3 tests across 3 suites
 1 minute, 4 seconds
 290b0c1
 🔄 Run: #19719 (attempt 1)

✅ private-cloud · depot-ubuntu-latest-16 — run #19719 (attempt 1)

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

 4 passed

Details

 4 tests across 4 suites
 32.6 seconds
 290b0c1
 🔄 Run: #19719 (attempt 1)

✅ oss · depot-ubuntu-latest-arm-16 — run #19719 (attempt 1)

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

 1 passed

Details

 1 test across 1 suite
 38.5 seconds
 290b0c1
 🔄 Run: #19719 (attempt 1)

✅ oss · depot-ubuntu-latest-16 — run #19719 (attempt 1)

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

 1 passed

Details

 1 test across 1 suite
 36.6 seconds
 290b0c1
 🔄 Run: #19719 (attempt 1)

✅ private-cloud · depot-ubuntu-latest-arm-16 — run #19710 (attempt 1)

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

 2 passed

Details

 2 tests across 2 suites
 38.1 seconds
 b2ed327
 🔄 Run: #19710 (attempt 1)

✅ private-cloud · depot-ubuntu-latest-16 — run #19710 (attempt 1)

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

 2 passed

Details

 2 tests across 2 suites
 32.1 seconds
 b2ed327
 🔄 Run: #19710 (attempt 1)

✅ oss · depot-ubuntu-latest-arm-16 — run #19710 (attempt 1)

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

 1 passed

Details

 1 test across 1 suite
 44.5 seconds
 b2ed327
 🔄 Run: #19710 (attempt 1)

✅ oss · depot-ubuntu-latest-16 — run #19710 (attempt 1)

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

 1 passed

Details

 1 test across 1 suite
 36.7 seconds
 b2ed327
 🔄 Run: #19710 (attempt 1)

[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: 8b480a4e-0382-4485-8041-aa747fe926f9

📥 Commits

Reviewing files that changed from the base of the PR and between aa61a35 and f5c68a3.

📒 Files selected for processing (10)

• frontend/common/services/useCohort.ts
• frontend/common/types/requests.ts
• frontend/common/types/responses.ts
• frontend/common/utils/__tests__/csv.test.ts
• frontend/common/utils/csv.ts
• frontend/web/components/CsvUpload/CsvUpload.tsx
• frontend/web/components/modals/ConfirmRemoveSegment.tsx
• frontend/web/components/modals/CreateSegmentFromCsv/CreateSegmentFromCsv.tsx
• frontend/web/components/segments/SegmentRow/SegmentRow.tsx
• frontend/web/components/segments/SegmentRow/components/SegmentAction.tsx

[github-actions]

Visual Regression

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

[coderabbitai]

Actionable comments posted: 1

Caution

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

⚠️ Outside diff range comments (1)

frontend/web/components/modals/CreateSegmentFromCsv/CreateSegmentFromCsv.tsx (1)

1-2: 🩺 Stability & Availability | 🟠 Major | ⚡ Quick win

Import the JSX components before use.

Select on Line 244 and FormGroup on Line 378 have no binding in this module. Selecting a CSV or opening Custom Fields throws a ReferenceError.

Proposed fix

 import React, { FC, FormEvent, useMemo, useState } from 'react'
 import classNames from 'classnames'
+import Select from 'react-select'
+import { FormGroup } from 'reactstrap'

Also applies to: 244-261, 378-390

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: ASSERTIVE

Plan: Pro Plus

Run ID: 4c190586-88c5-49af-9b90-fcbc2e78c96c

📥 Commits

Reviewing files that changed from the base of the PR and between ecb0485 and 73abef4.

📒 Files selected for processing (4)

• frontend/common/types/requests.ts
• frontend/common/types/responses.ts
• frontend/web/components/modals/CreateSegment.tsx
• frontend/web/components/modals/CreateSegmentFromCsv/CreateSegmentFromCsv.tsx

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

[talissoncosta]

Looks pretty good, just some non-blocking comments.

What about the name input, is it intentional to be narrow ?