docs(flutter): version 6 upgrade guide

[turnipdabeets]

Changes

Docs for posthog_flutter 6.0. Hold until 6.0 is released. It depends on PostHog/posthog-flutter#637 and PostHog/posthog-flutter#649, which wait on the posthog-ios 4.0 release (PostHog/posthog-ios#873). Several of these pages describe 6.0 requirements (iOS 15, Xcode 26, PROJECT_TOKEN only), which are wrong for 5.x users until then.

• New "Upgrading from version 5 to version 6" section at the end of /docs/libraries/flutter. It covers:
  • Platform requirements: iOS 15, macOS 11 and Xcode 26. Android stays at API 23.
  • A table of each removed API and what to use instead.
  • A before/after example for reading a flag payload.
  • Notes for custom platform implementations and test mocks.
  • Three iOS/macOS behavior changes that come from posthog-ios 4.0: malformed payloads become null, bootstrapped string payloads stay strings, and lifecycle events no longer include version/build.
• Opt-out section now uses optOut()/optIn(). Both shipped in 5.51.0; disable()/enable() are removed in 6.0.
• Install snippets and the Flutter surveys page: the minimum is now iOS 15.0 instead of 13.0, with a note that building requires Xcode 26.
• Flutter tutorials (analytics, A/B tests, feature flags, remote config):
  • com.posthog.posthog.API_KEY → PROJECT_TOKEN. 6.0 no longer reads API_KEY, while PROJECT_TOKEN already works on 5.x.
  • minSdkVersion 21 → 23. posthog-android already requires 23.
  • iOS 13 → 15.
• Cost-cutting page: the Flutter sample now uses sendFeatureFlagEvent instead of sendFeatureFlagEvents, which 6.0 removes.

Every claim was checked against the 6.0 branches and posthog-ios 4.0. Vale reports no alerts on the changed lines, apart from "Podfile" flagged as a misspelling on lines that already used the word.

Not in this PR:

• The in-app onboarding steps in the posthog monorepo (docs/onboarding/product-analytics/flutter.tsx and docs/onboarding/session-replay/flutter.tsx) still say iOS 13. They need a separate PR at release.
• session-replay/_snippets/flutter-installation.mdx and surveys/_snippets/flutter-surveys-installation.mdx also say iOS 13, but nothing imports them, so I left them unchanged.

Checklist

• I've read the docs and/or content style guides.
• Words are spelled using American English
• Use relative URLs for internal links
• I've checked the pages added or changed in the Vercel preview build
• If I moved a page, I added a redirect in vercel.json

🤖 Generated with Claude Code

[github-actions]

Deploy preview

Status	Details	Updated (UTC)
🟢 Ready	View preview	Oct 07, 2026 08:59PM

Changed pages

Page	Source
Cutting feature flag costs	contents/docs/feature-flags/cutting-costs.mdx
Flutter	contents/docs/libraries/flutter/index.mdx
Flutter Surveys installation	contents/docs/surveys/installation/flutter.mdx
How to set up A/B tests in Flutter	contents/tutorials/flutter-ab-tests.md
How to set up analytics in Flutter	contents/tutorials/flutter-analytics.md
How to set up feature flags in Flutter	contents/tutorials/flutter-feature-flags.md
How to set up Flutter remote config	contents/tutorials/flutter-remote-config.md

[github-actions]

Vale prose linter → found 4 errors, 73 warnings, 5 suggestions in your markdown

Full report → Copy the linter results into an LLM to batch-fix issues.

Linter being weird? Update the rules!

contents/docs/feature-flags/cutting-costs.mdx — 0 errors, 23 warnings, 0 suggestions

Line	Severity	Message	Rule
21:1	warning	Capitalize 'Feature Flags' for PostHog's product. Use 'Feature flags' for the general industry concept.	PostHogBase.ProductNames
21:102	warning	Capitalize 'Feature Flags' for PostHog's product. Use 'feature flags' for the general industry concept.	PostHogBase.ProductNames
23:30	warning	Capitalize 'Feature Flags' for PostHog's product. Use 'feature flags' for the general industry concept.	PostHogBase.ProductNames
26:63	warning	Capitalize 'Feature Flags' for PostHog's product. Use 'feature flags' for the general industry concept.	PostHogBase.ProductNames
37:1	warning	Capitalize 'Feature Flags' for PostHog's product. Use 'Feature flags' for the general industry concept.	PostHogBase.ProductNames
61:127	warning	Capitalize 'Feature Flags' for PostHog's product. Use 'feature flags' for the general industry concept.	PostHogBase.ProductNames
65:118	warning	Capitalize 'Feature Flags' for PostHog's product. Use 'feature flags' for the general industry concept.	PostHogBase.ProductNames
67:96	warning	Capitalize 'Feature Flags' for PostHog's product. Use 'feature flags' for the general industry concept.	PostHogBase.ProductNames
69:99	warning	Capitalize 'Feature Flags' for PostHog's product. Use 'feature flags' for the general industry concept.	PostHogBase.ProductNames
69:195	warning	Capitalize 'Surveys' for PostHog's product. Use 'surveys' for the general industry concept.	PostHogBase.ProductNames
69:240	warning	Capitalize 'Feature Flags' for PostHog's product. Use 'feature flags' for the general industry concept.	PostHogBase.ProductNames
69:275	warning	Capitalize 'Surveys' for PostHog's product. Use 'surveys' for the general industry concept.	PostHogBase.ProductNames
75:17	warning	Capitalize 'Feature Flags' for PostHog's product. Use 'feature flags' for the general industry concept.	PostHogBase.ProductNames
75:95	warning	Capitalize 'Surveys' for PostHog's product. Use 'surveys' for the general industry concept.	PostHogBase.ProductNames
75:115	warning	Capitalize 'Surveys' for PostHog's product. Use 'surveys' for the general industry concept.	PostHogBase.ProductNames
92:36	warning	'ETags' is a possible misspelling.	PostHogBase.Spelling
92:151	warning	Use 'PostHog' instead of 'posthog'.	Vale.Terms
104:107	warning	Capitalize 'Feature Flags' for PostHog's product. Use 'feature flags' for the general industry concept.	PostHogBase.ProductNames
256:214	warning	Capitalize 'Feature Flags' for PostHog's product. Use 'feature flags' for the general industry concept.	PostHogBase.ProductNames
256:229	warning	Capitalize 'Session Replay' for PostHog's product. Use 'session replay' for the general industry concept.	PostHogBase.ProductNames
256:249	warning	Capitalize 'Surveys' for PostHog's product. Use 'surveys' for the general industry concept.	PostHogBase.ProductNames
272:42	warning	Capitalize 'Feature Flags' for PostHog's product. Use 'feature flags' for the general industry concept.	PostHogBase.ProductNames
272:69	warning	Capitalize 'Surveys' for PostHog's product. Use 'surveys' for the general industry concept.	PostHogBase.ProductNames

contents/docs/integrate/_snippets/install-flutter.mdx — 0 errors, 1 warnings, 0 suggestions

Line	Severity	Message	Rule
130:6	warning	'Dart setup (For manual step only)' heading should be in sentence case, and product names should be capitalized.	PostHogBase.SentenceCase

contents/docs/libraries/flutter/index.mdx — 4 errors, 27 warnings, 5 suggestions

Line	Severity	Message	Rule
6:18	warning	Use 'GitHub' instead of 'github'.	Vale.Terms
6:37	warning	Use 'PostHog' instead of 'posthog'.	Vale.Terms
134:49	suggestion	Address the reader directly. Use 'you' instead of 'the user'.	PostHogDocs.DirectAddress
136:66	suggestion	Address the reader directly. Use 'you' instead of 'the User'.	PostHogDocs.DirectAddress
136:131	suggestion	Address the reader directly. Use 'you' instead of 'the User'.	PostHogDocs.DirectAddress
150:69	warning	Avoid trivializing words. 'simply' can sound dismissive to the reader.	PostHogDocs.Trivializers
158:4	warning	Capitalize 'Feature Flags' for PostHog's product. Use 'Feature flags' for the general industry concept.	PostHogBase.ProductNames
158:4	warning	'Feature flags' heading should be in sentence case, and product names should be capitalized.	PostHogBase.SentenceCase
212:25	warning	Capitalize 'Feature Flags' for PostHog's product. Use 'feature flags' for the general industry concept.	PostHogBase.ProductNames
216:8	warning	Capitalize 'Experiments' for PostHog's product. Use 'experiments' for the general industry concept.	PostHogBase.ProductNames
216:55	warning	Capitalize 'Feature Flags' for PostHog's product. Use 'feature flags' for the general industry concept.	PostHogBase.ProductNames
216:128	warning	Capitalize 'Feature Flags' for PostHog's product. Use 'feature flags' for the general industry concept.	PostHogBase.ProductNames
218:28	warning	Capitalize 'Experiments' for PostHog's product. Use 'experiments' for the general industry concept.	PostHogBase.ProductNames
218:54	warning	Capitalize 'Feature Flags' for PostHog's product. Use 'feature flags' for the general industry concept.	PostHogBase.ProductNames
220:4	warning	Capitalize 'Error Tracking' for PostHog's product. Use 'Error tracking' for the general industry concept.	PostHogBase.ProductNames
220:4	warning	'Error tracking' heading should be in sentence case, and product names should be capitalized.	PostHogBase.SentenceCase
222:11	warning	Capitalize 'Error Tracking' for PostHog's product. Use 'error tracking' for the general industry concept.	PostHogBase.ProductNames
222:52	warning	Capitalize 'Error Tracking' for PostHog's product. Use 'error tracking' for the general industry concept.	PostHogBase.ProductNames
226:12	warning	Capitalize 'Logs' for PostHog's product. Use 'logs' for the general industry concept.	PostHogBase.ProductNames
228:4	warning	Capitalize 'Session Replay' for PostHog's product. Use 'Session replay' for the general industry concept.	PostHogBase.ProductNames
228:4	warning	'Session replay' heading should be in sentence case, and product names should be capitalized.	PostHogBase.SentenceCase
230:13	warning	Capitalize 'Session Replay' for PostHog's product. Use 'Session replay' for the general industry concept.	PostHogBase.ProductNames
232:12	warning	Capitalize 'Session Replay' for PostHog's product. Use 'session replay' for the general industry concept.	PostHogBase.ProductNames
232:65	warning	Capitalize 'Session Replay' for PostHog's product. Use 'session replay' for the general industry concept.	PostHogBase.ProductNames
232:127	warning	Avoid trivializing words. 'all you need to do' can sound dismissive to the reader.	PostHogDocs.Trivializers
237:111	error	Hi, Andy here... use an en dash ( – ) with spaces. On Mac, holding down the Option and hyphen key will give you an en dash.	PostHogBase.EnDash
237:276	warning	Use 'PostHog' instead of 'posthog'.	Vale.Terms
291:96	suggestion	Address the reader directly. Use 'you' instead of 'the user'.	PostHogDocs.DirectAddress
292:8	suggestion	Address the reader directly. Use 'you' instead of 'the user'.	PostHogDocs.DirectAddress
371:24	error	Hi, Andy here... use an en dash ( – ) with spaces. On Mac, holding down the Option and hyphen key will give you an en dash.	PostHogBase.EnDash
372:23	error	Hi, Andy here... use an en dash ( – ) with spaces. On Mac, holding down the Option and hyphen key will give you an en dash.	PostHogBase.EnDash
373:33	error	Hi, Andy here... use an en dash ( – ) with spaces. On Mac, holding down the Option and hyphen key will give you an en dash.	PostHogBase.EnDash
377:3	warning	Capitalize 'Session Replay' for PostHog's product. Use 'Session replay' for the general industry concept.	PostHogBase.ProductNames
384:62	warning	Capitalize 'Feature Flags' for PostHog's product. Use 'feature flags' for the general industry concept.	PostHogBase.ProductNames
384:100	warning	Capitalize 'Surveys' for PostHog's product. Use 'surveys' for the general industry concept.	PostHogBase.ProductNames
395:26	warning	Capitalize 'Logs' for PostHog's product. Use 'logs' for the general industry concept.	PostHogBase.ProductNames

contents/docs/surveys/installation/flutter.mdx — 0 errors, 2 warnings, 0 suggestions

Line	Severity	Message	Rule
13:64	warning	Capitalize 'Surveys' for PostHog's product. Use 'surveys' for the general industry concept.	PostHogBase.ProductNames
21:11	warning	Capitalize 'Surveys' for PostHog's product. Use 'surveys' for the general industry concept.	PostHogBase.ProductNames

contents/tutorials/flutter-ab-tests.md — 0 errors, 3 warnings, 0 suggestions

Line	Severity	Message	Rule
155:31	warning	'Cocoapods' is a possible misspelling.	PostHogBase.Spelling
175:71	warning	'Podfile' is a possible misspelling.	PostHogBase.Spelling
340:18	warning	Capitalize 'Feature Flags' for PostHog's product. Use 'feature flags' for the general industry concept.	PostHogBase.ProductNames

contents/tutorials/flutter-analytics.md — 0 errors, 8 warnings, 0 suggestions

Line	Severity	Message	Rule
19:2	warning	Capitalize 'Product Analytics' for PostHog's product. Use 'Product analytics' for the general industry concept.	PostHogBase.ProductNames
272:31	warning	'Cocoapods' is a possible misspelling.	PostHogBase.Spelling
292:71	warning	'Podfile' is a possible misspelling.	PostHogBase.Spelling
328:138	warning	Use 'PostHog' instead of 'Posthog'.	Vale.Terms
413:23	warning	Capitalize 'Logs' for PostHog's product. Use 'logs' for the general industry concept.	PostHogBase.ProductNames
454:18	warning	Capitalize 'Product Analytics' for PostHog's product. Use 'Product analytics' for the general industry concept.	PostHogBase.ProductNames
462:150	warning	'enabed' is a possible misspelling.	PostHogBase.Spelling
476:18	warning	Capitalize 'Feature Flags' for PostHog's product. Use 'feature flags' for the general industry concept.	PostHogBase.ProductNames

contents/tutorials/flutter-feature-flags.md — 0 errors, 5 warnings, 0 suggestions

Line	Severity	Message	Rule
2:22	warning	Capitalize 'Feature Flags' for PostHog's product. Use 'feature flags' for the general industry concept.	PostHogBase.ProductNames
16:2	warning	Capitalize 'Feature Flags' for PostHog's product. Use 'Feature flags' for the general industry concept.	PostHogBase.ProductNames
151:28	warning	'Cocoapods' is a possible misspelling.	PostHogBase.Spelling
171:71	warning	'Podfile' is a possible misspelling.	PostHogBase.Spelling
206:44	warning	Capitalize 'Feature Flags' for PostHog's product. Use 'feature flags' for the general industry concept.	PostHogBase.ProductNames

contents/tutorials/flutter-remote-config.md — 0 errors, 4 warnings, 0 suggestions

Line	Severity	Message	Rule
119:28	warning	'Cocoapods' is a possible misspelling.	PostHogBase.Spelling
139:63	warning	'Podfile' is a possible misspelling.	PostHogBase.Spelling
172:15	warning	Capitalize 'Feature Flags' for PostHog's product. Use 'feature flags' for the general industry concept.	PostHogBase.ProductNames
328:4	warning	Capitalize 'Feature Flags' for PostHog's product. Use 'Feature flags' for the general industry concept.	PostHogBase.ProductNames

[github-actions]

Bundle report

Total JS (gzip)

10.07 MiB (+0.0 KiB / +0.0%)

Eager graph (modules shipped in each entrypoint's initial chunks)

Entrypoint	Eager size	Budget	Modules
✅ app	19.36 MiB (+0.1 KiB / +0.0%)	report-only	2091

Largest modules in the app closure

Module	Size
./src/data/mcp-tools.json	1322.0 KiB
css ./node_modules/.pnpm/css-loader@5.2.7_webpack@5.101.3/node_modules/css-loader/dist/cjs.js??ruleSet[1].rules[8].oneOf[1].use[1]!./node_modules/.pnpm/postcss-loader@4.3.0_postcss@8.5.6_webpack@5.101.3/node_modules/postcss-loader/dist/cjs.js??ruleSet[1].rules[8].oneOf[1].use[2]!./src/styles/global.css	807.6 KiB
./src/components/Stickers/Stickers.tsx	696.4 KiB
./node_modules/.pnpm/@radix-ui+react-icons@1.3.2_react@18.3.1/node_modules/@radix-ui/react-icons/dist/react-icons.esm.js	481.4 KiB
./node_modules/.pnpm/@posthog+brand@0.13.0_react@18.3.1/node_modules/@posthog/brand/dist/generated/hoggies/svg/x-ray.mjs	481.2 KiB
./node_modules/.pnpm/@posthog+brand@0.13.0_react@18.3.1/node_modules/@posthog/brand/dist/generated/hoggies/svg/trenchcoat.mjs	450.8 KiB
./node_modules/.pnpm/rehype-raw@7.0.0/node_modules/rehype-raw/lib/index.js + 29 modules	395.1 KiB
./node_modules/.pnpm/@posthog+brand@0.13.0_react@18.3.1/node_modules/@posthog/brand/dist/generated/hoggies/svg/im-the-driver.mjs	385.8 KiB
./src/hooks/useCustomers.tsx + 59 modules	380.8 KiB
./node_modules/.pnpm/@posthog+icons@0.36.6_react-dom@18.3.1_react@18.3.1__react@18.3.1/node_modules/@posthog/icons/dist/posthog-icons.es.js	354.8 KiB
./node_modules/.pnpm/react-markdown@8.0.7_@types+react@16.14.66_react@18.3.1/node_modules/react-markdown/lib/react-markdown.js + 88 modules	351.4 KiB
./src/components/ProductComparisonTable/index.tsx + 127 modules	310.3 KiB
./node_modules/.pnpm/@posthog+brand@0.13.0_react@18.3.1/node_modules/@posthog/brand/dist/generated/hoggies/svg/doll-house.mjs	284.1 KiB
./node_modules/.pnpm/cloudinary-core@2.14.0_lodash@4.17.21/node_modules/cloudinary-core/cloudinary-core.js	281.9 KiB
./node_modules/.pnpm/@posthog+brand@0.13.0_react@18.3.1/node_modules/@posthog/brand/dist/generated/hoggies/svg/director.mjs	275.7 KiB

---

Eager-graph budgets are report-only until a baseline is established. Sizes are gzip of public/**/*.js; eager size is webpack module source bytes for the modules actually shipped in the entrypoint's initial chunks (post-tree-shake).