fix: remove unused Platform serialization code path

[maxday]

Issue #, if available:

Description of changes:

Target (OCI, Managed Runtime, both):

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 67.67%. Comparing base (e38423d) to head (efc77ff).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##               main     #648      +/-   ##
============================================
+ Coverage     66.03%   67.67%   +1.64%     
- Complexity      214      221       +7     
============================================
  Files            35       35              
  Lines           998      993       -5     
  Branches        143      139       -4     
============================================
+ Hits            659      672      +13     
+ Misses          287      271      -16     
+ Partials         52       50       -2     

Flag	Coverage Δ
aarch64	67.67% <100.00%> (+1.64%)	⬆️
x86_64	67.27% <100.00%> (+1.63%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[darklight3it]

Hey @maxday! 👋

I agree that simplifying this logic would be valuable.

However, I found a concrete compatibility concern that makes me hesitant to classify this path as unused: the AWS SDK for Android’s Lambda invoker automatically supplies the platform value that selects it.

Specifically:

• ClientContext sets env.platform to "Android".
• LambdaInvokerFactory constructs that client context, and LambdaInvocationHandler attaches it to the invocation.
• LambdaInvokerFactory uses LambdaJsonBinder by default, which uses Gson for request serialization and response deserialization.

This suggests that the runtime’s Gson path was intended to provide serialization semantics compatible with the Android client. I haven’t found an explicit statement confirming that intent. The AWS SDK for Android is now archived, and I couldn’t find this invoker or an equivalent direct-invocation API in the current Amplify Android repository. Existing applications may therefore still depend on the archived SDK and this behavior.

Since this PR changes both input deserialization and output serialization, I think we should treat it as potentially breaking for those callers. If you have additional information showing that this integration has been replaced, is no longer used, or that compatibility is otherwise covered, I’m happy to revisit that assessment.

If we decide to remove this path, I see three possible approaches:

• Merge this change, remove Gson as a dependency, and release new major versions of both Serialization and the RIC from a separate branch. These versions could initially be used only by OCI-based functions and a future managed Java runtime. However, this would require maintaining the existing versions and backporting changes, so I would not recommend this approach at the moment.

• Consolidate both paths on Jackson, while configuring and testing Jackson to preserve the serialization behavior expected by Android clients. If we can establish compatibility, we could remove Gson without introducing a breaking change.

• Follow the migration path I documented last year: use a service-provider design to decouple serialization from the RIC, preserve the existing behavior by default, and allow customers to opt into a new implementation. This could also support a future Jackson major-version upgrade, although I would keep that as a separate design discussion rather than a prerequisite for this PR.

For the last option, separating these concerns internally would not necessarily require publishing every resulting module. In general, I think we should publish fewer libraries to Maven Central, each with a clear customer use case. For example, I don’t see a compelling reason for customers to consume our serialization implementation independently of the RIC.

Overall, I support the cleanup; I’d just like us to understand the compatibility impact and agree on a migration strategy before shipping it.

[darklight3it]

We decided to continue with the changes since the Android AWS SDK is officially deprecated.

[darklight3it]

Ran a RIC test for the change. Results are here.

Android client context: RIC 2.12.1 vs this PR

Each handler echoes its input. Both images run the same handler jar and dependencies through the Runtime Interface Emulator and differ only in the RIC jar. Every handler is invoked with the client context the AWS Mobile SDK for Android sends, and without a client context as a control.

• Run: 2026-10-09T11:24:18Z, aarch64, public.ecr.aws/amazoncorretto/amazoncorretto:21-al2023-headless
• X-Amz-Client-Context (decoded): {"client":{"installation_id":"demo","app_title":"demo","app_version_name":"1.0","app_version_code":"1","app_package_name":"demo"},"custom":{},"env":{"platform":"Android","platform_version":"14","make":"Google","model":"Pixel","locale":"en_US"},"services":{}}

Summary

#	Handler	Request	RIC 2.12.1, Android	PR, Android	Same without client context
1	privateFields	{"name":"x"}	{"name":"x"}	{}	yes
2	prefixedField	{"mName":"x"}	{"mName":"x"}	{}	yes
3	booleanIsField	{"isActive":true}	{"isActive":true}	{"active":false}	yes
4	noDefaultConstructor	{"name":"x"}	{"name":"x"}	error: java.lang.RuntimeException: An error occurred during JSON parsing	yes
5	dateField	""	{"createdAt":"Jan 1, 2020, 12:00:00 AM"}	{"createdAt":1577836800000}	yes
6	computedGetter	{"name":"x"}	{"name":"x"}	{"name":"x","displayName":"Name: x"}	yes
7	readOnlyProperty	{"locked":true}	{"locked":true}	{"locked":false}	yes
8	transientField	{"name":"x"}	{"name":"x"}	{"name":"x","cache":"y"}	yes
9	untypedMap	{"attributes":{"count":1}}	{"attributes":{"count":1.0,"countType":"Double"}}	{"attributes":{"count":1,"countType":"Integer"}}	yes
10	nested	{"inner":{"name":"x"},"items":[{"name":"y"}]}	{"inner":{"name":"x"},"items":[{"name":"y"}]}	{"inner":{},"items":[{}]}	yes

"Same without client context" means RIC 2.12.1 and this PR return the same response without a client context, and it matches the PR's Android response: Android callers now get what every other caller already gets.

Per case

1. privateFields

Request: {"name":"x"}

RIC	Client context	Response
2.12.1	Android	{"name":"x"}
2.12.1	none	{}
PR	Android	{}
PR	none	{}

2. prefixedField

Request: {"mName":"x"}

RIC	Client context	Response
2.12.1	Android	{"mName":"x"}
2.12.1	none	{}
PR	Android	{}
PR	none	{}

3. booleanIsField

Request: {"isActive":true}

RIC	Client context	Response
2.12.1	Android	{"isActive":true}
2.12.1	none	{"active":false}
PR	Android	{"active":false}
PR	none	{"active":false}

4. noDefaultConstructor

Request: {"name":"x"}

RIC	Client context	Response
2.12.1	Android	{"name":"x"}
2.12.1	none	{"errorMessage":"An error occurred during JSON parsing","errorType":"java.lang.RuntimeException","stackTrace":[]}
PR	Android	{"errorMessage":"An error occurred during JSON parsing","errorType":"java.lang.RuntimeException","stackTrace":[]}
PR	none	{"errorMessage":"An error occurred during JSON parsing","errorType":"java.lang.RuntimeException","stackTrace":[]}

Runtime output (2.12.1, none):

An error occurred during JSON parsing: java.lang.RuntimeException
java.lang.RuntimeException: An error occurred during JSON parsing
Caused by: java.io.UncheckedIOException: com.amazonaws.lambda.thirdparty.com.fasterxml.jackson.databind.exc.InvalidDefinitionException: Cannot construct instance of `demo.Handlers$NoDefaultConstructor` (no Creators, like default constructor, exist): cannot deserialize from Object value (no delegate- or property-based Creator)
Caused by: com.amazonaws.lambda.thirdparty.com.fasterxml.jackson.databind.exc.InvalidDefinitionException: Cannot construct instance of `demo.Handlers$NoDefaultConstructor` (no Creators, like default constructor, exist): cannot deserialize from Object value (no delegate- or property-based Creator)

5. dateField

Request: ""

RIC	Client context	Response
2.12.1	Android	{"createdAt":"Jan 1, 2020, 12:00:00 AM"}
2.12.1	none	{"createdAt":1577836800000}
PR	Android	{"createdAt":1577836800000}
PR	none	{"createdAt":1577836800000}

6. computedGetter

Request: {"name":"x"}

RIC	Client context	Response
2.12.1	Android	{"name":"x"}
2.12.1	none	{"name":"x","displayName":"Name: x"}
PR	Android	{"name":"x","displayName":"Name: x"}
PR	none	{"name":"x","displayName":"Name: x"}

7. readOnlyProperty

Request: {"locked":true}

RIC	Client context	Response
2.12.1	Android	{"locked":true}
2.12.1	none	{"locked":false}
PR	Android	{"locked":false}
PR	none	{"locked":false}

8. transientField

Request: {"name":"x"}

RIC	Client context	Response
2.12.1	Android	{"name":"x"}
2.12.1	none	{"name":"x","cache":"y"}
PR	Android	{"name":"x","cache":"y"}
PR	none	{"name":"x","cache":"y"}

9. untypedMap

Request: {"attributes":{"count":1}}

RIC	Client context	Response
2.12.1	Android	{"attributes":{"count":1.0,"countType":"Double"}}
2.12.1	none	{"attributes":{"count":1,"countType":"Integer"}}
PR	Android	{"attributes":{"count":1,"countType":"Integer"}}
PR	none	{"attributes":{"count":1,"countType":"Integer"}}

10. nested

Request: {"inner":{"name":"x"},"items":[{"name":"y"}]}

RIC	Client context	Response
2.12.1	Android	{"inner":{"name":"x"},"items":[{"name":"y"}]}
2.12.1	none	{"inner":{},"items":[{}]}
PR	Android	{"inner":{},"items":[{}]}
PR	none	{"inner":{},"items":[{}]}

Images and jars

ric-old

SHA-256	Jar
0d173520f1f3	android-gson-demo-1.0.jar
fafdcb55f4e5	annotations-2.34.0.jar
575c24393cc1	aws-lambda-java-core-1.4.0.jar
2e7b8120f104	aws-lambda-java-runtime-interface-client-2.12.1.jar
0ab04580117a	aws-lambda-java-serialization-1.4.1.jar
efaf784f07ae	utils-lite-2.34.0.jar

ric-new

SHA-256	Jar
0d173520f1f3	android-gson-demo-1.0.jar
fafdcb55f4e5	annotations-2.34.0.jar
575c24393cc1	aws-lambda-java-core-1.4.0.jar
5c8bbd0e8dc8	aws-lambda-java-runtime-interface-client-2.12.1-SNAPSHOT.jar
0ab04580117a	aws-lambda-java-serialization-1.4.1.jar
efaf784f07ae	utils-lite-2.34.0.jar