feat: add projectToken and deprecate apiKey

[turnipdabeets]

💡 Motivation and Context

Add projectToken to PostHogConfig (core and server) and PostHogAndroidConfig, and deprecate apiKey. This is the Android part of the cross-SDK rename: posthog-ios #573, posthog-flutter #374, posthog-dotnet #183, posthog-kmp #91.

This is a minor release, not a breaking one. The first constructor parameter is renamed apiKey → projectToken. Parameter names are not part of JVM signatures, so the constructors and existing bytecode are unchanged.

Caller code	After this PR
PostHogAndroidConfig("phc_...") / new PostHogAndroidConfig("phc_...")	Compiles, no warning
PostHogAndroidConfig(projectToken = "phc_...")	New form
PostHogAndroidConfig(apiKey = "phc_...", ...)	Compiles with a deprecation warning (deprecated Companion.invoke with the same parameters)
config.apiKey / getApiKey()	Compiles with a deprecation warning (ReplaceWith("projectToken"))
PostHogConfig.builder("phc_...") (server)	Unchanged
Kotlin subclass calling super(apiKey = ...)	Breaks. A super call cannot resolve to a factory. Use projectToken = or a positional argument

The same rows apply to core com.posthog.PostHogConfig and server com.posthog.server.PostHogConfig.

• The deprecated factories are @JvmSynthetic, so Java callers never see them. Java callers never had named arguments anyway.
• The server builder(apiKey) / Builder(apiKey) parameter names stay the same. Renaming them would break Kotlin named calls such as builder(apiKey = ...), and a deprecated overload would clash with the new one.
• The deprecation message matches posthog-flutter and kmp: "Deprecated in favor of projectToken. This will be removed in the next major version."
• The setup and push-registration logs now say "project token". Trimming (fix: trim whitespace from API keys and host config #492), the blank-token no-op setup (fix: no-op setup without api key #503), and invalid-key push handling (fix: stop retrying push registration when the project API key is not valid #790) are unchanged.
• Storage paths and wire fields (api_key, token) still use the same value, so stored queues and preferences carry over.

External callers checked (origin/main):

• posthog-flutter: PostHogAndroidConfig(projectToken, host) is positional. No change needed.
• posthog-js RN plugin: PostHogAndroidConfig(apiKey, host) is positional. No change needed.
• posthog-kmp: PostHogAndroidConfig(apiKey = ...) and com.posthog.PostHogConfig(apiKey = ...) are named. Both still compile, with a deprecation warning, and switch to projectToken = on the next bump.
• None of these subclass the config classes.

Docs follow-up: posthog.com still uses apiKey = in contents/docs/libraries/android/index.mdx (lines 58, 181, 217, 269, 365, 380) and contents/docs/integrate/_snippets/install-android.mdx (line 43). Those need a separate posthog.com PR.

💚 How did you test it?

• Added a test for each config class (deprecated apiKey factory and getter alias projectToken). Each test checks that apiKey = trims into projectToken, that apiKey reads it back, and that the other named arguments are passed through. Existing tests now use projectToken.
• ./gradlew build :posthog-android-gradle-plugin:build --continue passed: spotlessCheck, apiCheck, lint, and unit tests (posthog 1013, posthog-server 568, posthog-android 1506 with 6 skipped, surveys-compose 75; 0 failures). The only failure was uploadPostHogProguardMappingsRelease in the sample app, because there are no PostHog CLI credentials locally.
• make testSurveyUI (49 passed), sample assembleDebug, Java and Spring sample builds, checkRelease with no lockfile diff, and sdk_compliance_adapter compile all passed.
• I compiled a probe file with -Werror and then removed it. It showed deprecation warnings only for apiKey = and .apiKey. Positional and projectToken = calls had no warnings. class X : PostHogAndroidConfig(apiKey = ...) failed to compile, as expected.
• The .api diff is additive only: getProjectToken() on core and server, plus the synthetic Companion.invoke entries (and a new PostHogAndroidConfig.Companion). getApiKey() and all <init> signatures are unchanged.

📝 Checklist

• I reviewed the submitted code.
• I added tests to verify the changes.
• I updated the docs if needed. (posthog.com follow-up listed above)
• No breaking change or entry added to the changelog.

If releasing new changes

• Ran pnpm changeset to generate a changeset file (written by hand: .changeset/project-token-rename.md)

🤖 Generated with Claude Code

[greptile-apps]

[Medium risk] Renames apiKey parameter to projectToken across SDK configuration.

The PR appears safe to merge within its explicitly acknowledged compatibility limits.

_{Reviews (1) · Last reviewed commit: "feat: add projectToken and deprecate api..."}

[github-actions]

posthog-android Compliance Report

Date: 2026-10-03 00:00:04 UTC
Duration: 117841ms

✅ All Tests Passed!

46/46 tests passed

---

Capture Tests

✅ 29/29 tests passed

View Details

Test	Status	Duration
Format Validation.Event Has Required Fields	✅	272ms
Format Validation.Event Has Uuid	✅	24ms
Format Validation.Event Has Lib Properties	✅	22ms
Format Validation.Distinct Id Is String	✅	21ms
Format Validation.Token Is Present	✅	21ms
Format Validation.Custom Properties Preserved	✅	22ms
Format Validation.Event Has Timestamp	✅	19ms
Retry Behavior.Retries On 503	✅	7033ms
Retry Behavior.Does Not Retry On 400	✅	4022ms
Retry Behavior.Does Not Retry On 401	✅	4023ms
Retry Behavior.Respects Retry After Header	✅	7024ms
Retry Behavior.Implements Backoff	✅	17019ms
Retry Behavior.Retries On 500	✅	7018ms
Retry Behavior.Retries On 502	✅	7017ms
Retry Behavior.Retries On 504	✅	7019ms
Retry Behavior.Max Retries Respected	✅	17033ms
Deduplication.Generates Unique Uuids	✅	26ms
Deduplication.Preserves Uuid On Retry	✅	7012ms
Deduplication.Preserves Uuid And Timestamp On Retry	✅	12019ms
Deduplication.Preserves Uuid And Timestamp On Batch Retry	✅	7015ms
Deduplication.No Duplicate Events In Batch	✅	26ms
Deduplication.Different Events Have Different Uuids	✅	17ms
Compression.Sends Gzip When Enabled	✅	11ms
Batch Format.Uses Proper Batch Structure	✅	12ms
Batch Format.Flush With No Events Sends Nothing	✅	7ms
Batch Format.Multiple Events Batched Together	✅	27ms
Error Handling.Does Not Retry On 403	✅	4013ms
Error Handling.Does Not Retry On 413	✅	4015ms
Error Handling.Retries On 408	✅	5020ms

Feature_Flags Tests

✅ 17/17 tests passed

View Details

Test	Status	Duration
Request Payload.Request With Person Properties Device Id	✅	22ms
Request Payload.Flags Request Uses V2 Query Param	✅	14ms
Request Payload.Flags Request Hits Flags Path Not Decide	✅	15ms
Request Payload.Flags Request Omits Authorization Header	✅	16ms
Request Payload.Token In Flags Body Matches Init	✅	22ms
Request Payload.Groups Round Trip	✅	16ms
Request Payload.Groups Default To Empty Object	✅	15ms
Request Payload.Disable Geoip False Propagates As Geoip Disable False	✅	12ms
Request Payload.Disable Geoip Omitted Defaults To False	✅	12ms
Request Payload.Flag Keys To Evaluate Contains Only Requested Key	✅	12ms
Request Lifecycle.No Flags Request On Init Alone	✅	4ms
Request Lifecycle.No Flags Request On Normal Capture	✅	12ms
Request Lifecycle.Two Flag Calls Produce Two Remote Requests	✅	26ms
Request Lifecycle.Mock Response Value Is Returned To Caller	✅	13ms
Retry Behavior.Retries Flags On 502	✅	317ms
Retry Behavior.Retries Flags On 504	✅	314ms
Side Effect Events.Get Feature Flag Captures Feature Flag Called Event	✅	13ms

[turnipdabeets]

@marandaneto looks like this didn't make it to a few PRs. OK to continue? It seems like parity is useful.