[dependabot]

Bumps org.jetbrains.kotlinx:kotlinx-serialization-json from 1.11.0 to 1.12.0.

Release notes

Sourced from org.jetbrains.kotlinx:kotlinx-serialization-json's releases.

v1.12.0

This release is based on Kotlin 2.4.10 and contains all of the changes from 1.12.0-RC.

Additionally, it includes a fix removing unnecessary leading whitespaces from Proguard rules (#3270), and two changes stabilizing kotlin.uuid.Uuid serializer (#3263) and kotlin.time.Instant serializers (#3261).

For your convenience, the changelog for 1.12.0-RC is duplicated below:

API stabilization and deprecations

A big portion of the Json and Core APIs has been stabilized. Most important ones include: @KeepGeneratedSerializer and @SerialInfo annotations, JsonNamingStrategy, and ContextualSerializer. Additionally, various descriptor builders such as listDescriptor and JsonElementBuilder's addAll functions are also stable and can be freely used. There is also one deprecation: ChunkedDecoder interface. Since there is no demand for it, we plan to remove it in the future. See details in the #3238, #3239, and #3216.

Also, kotlin.time.Instant and kotlin.uuid.Uuid serializers are no longer annotated with experimental annotations from the Kotlin standard library (see #3261 and #3263)

Performance improvements

We also improved performance in various areas. ASCII-specific parser (#3225) brings performance of decoding from Okio and kotlinx-io sources closer to decoding performance from String. #3220 makes decoding significantly faster in case JsonElement present in your serializable classes. And #3248 should bring overall performance improvements (up to 30%) on large strings.

Exceptions rework

We continue to improve exception handling in Json encoders and decoders. #3235 makes a big change around custom serializers and @Serializable classes constructors: from now on, every exception thrown during deserialization is wrapped by decoder into a JsonException. This way, it is more predictable to write a catch and it is easier to understand what went wrong: JsonDecodingException also includes context information such as Json path and input. Besides that, #3246 limits maximum nesting depth of Json document, so you will get a proper JsonDecodingException instead of a random stack overflow error.

CBOR improvements

CBOR format also gets many improvements in this release. The most important one is memory optimization for definitely-sized collections (#3191, #3192).

The others include:

• Encode unsigned integer types as positive integers (#3194) (thanks to Eyüp Can Akman)
• Correctly decode CborLabel values (#3195)
• Include actual tag info into CborDecodingException (#3197)

Protobuf improvements

Protocol buffers format received a big new feature: support for unknown fields. Using a new ProtoUnknownFieldHolder class, you can now decode and store unknown fields in Protobuf messages to retransmit them back later. See documentation updates and #2860 for details.

... (truncated)

Changelog

Sourced from org.jetbrains.kotlinx:kotlinx-serialization-json's changelog.

1.12.0 / 2026-10-19

This release is based on Kotlin 2.4.10 and contains all of the changes from 1.12.0-RC.

Additionally, it includes a fix removing unnecessary leading whitespaces from Proguard rules (#3270), and two changes stabilizing kotlin.uuid.Uuid serializer (#3263) and kotlin.time.Instant serializers (#3261).

For your convenience, the changelog for 1.12.0-RC is duplicated below:

API stabilization and deprecations

A big portion of the Json and Core APIs has been stabilized. Most important ones include: @KeepGeneratedSerializer and @SerialInfo annotations, JsonNamingStrategy, and ContextualSerializer. Additionally, various descriptor builders such as listDescriptor and JsonElementBuilder's addAll functions are also stable and can be freely used. There is also one deprecation: ChunkedDecoder interface. Since there is no demand for it, we plan to remove it in the future. See details in the #3238, #3239, and #3216.

Also, kotlin.time.Instant and kotlin.uuid.Uuid serializers are no longer annotated with experimental annotations from the Kotlin standard library (see [#3261](Kotlin/kotlinx.serialization#3261 and #3263)

Performance improvements

We also improved performance in various areas. ASCII-specific parser (#3225) brings performance of decoding from Okio and kotlinx-io sources closer to decoding performance from String. #3220 makes decoding significantly faster in case JsonElement present in your serializable classes. And #3248 should bring overall performance improvements (up to 30%) on large strings.

Exceptions rework

We continue to improve exception handling in Json encoders and decoders. #3235 makes a big change around custom serializers and @Serializable classes constructors: from now on, every exception thrown during deserialization is wrapped by decoder into a JsonException. This way, it is more predictable to write a catch and it is easier to understand what went wrong: JsonDecodingException also includes context information such as Json path and input. Besides that, #3246 limits maximum nesting depth of Json document, so you will get a proper JsonDecodingException instead of a random stack overflow error.

CBOR improvements

CBOR format also gets many improvements in this release. The most important one is memory optimization for definitely-sized collections (#3191, #3192).

... (truncated)

Commits

• 4c28c3e 1.12.0 release (#3295)
• abe8a96 Merge remote-tracking branch 'origin/master' into dev
• 952d17a Added Gradle task to prepare release (#3279)
• 6f30025 Remove Play verification files (#3266)
• 89b23ca Workaround watchosArm32 removal (#3291)
• 53932a0 Update links to Okio site and its docs (#3292)
• 3a5db3b Reduce the number of input fields for bug report
• 9ede0e2 Added templates to the issue creation wizard
• 5d3f884 Update Dokka to version 2.3.0-Beta (#3286)
• 1fe9a49 Suppress deprecation of nodejs in wasmWasi configuration (#3287)
• Additional commits viewable in compare view

[jetbrains-air]

Looks good — happy to approve this one!

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[devcrocod]

@dependabot rebase

[jetbrains-air]

Looks good — happy to approve this one!

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Produced by Air Automations. Name: Code review / Run: https://air.jetbrains.cloud/org/05cf1a7f-6ab5-713b-abd3-29d0c8a05e2d/automations/409567ec-d3a7-40ac-ba95-8518ec577ac2?run=f468d2ad-f611-4c60-aab7-07af0c6e88bb

[devcrocod]

@dependabot rebase

[jetbrains-air]

Thanks — the bump looks good, approving.

[jetbrains-air]

Problem: this sample is watched by Dependabot (.github/dependabot.yml covers /samples/*) but is absent from both CI sample matrices — .github/workflows/samples.yml and the samples job in .github/workflows/build.yml both list only kotlin-mcp-client, kotlin-mcp-server, simple-streamable-server, weather-stdio-server. No check on this PR compiles or tests the module this line belongs to.

Failure scenario: ./gradlew build in samples/kotlinlang-mcp-server fails right now — KotlinlangServerTest > server registers both tools with correct schema and annotations fails with McpException: Request timed out on Initialize. I reproduced it identically with serialization = "1.11.0" and "1.12.0", so this bump is not the cause; the point is that a red build has been sitting on main unnoticed, and every future bump in this directory will merge on green checks that never built the sample.

Suggested fix: add kotlinlang-mcp-server to the matrix.sample lists in both workflows (and address the pre-existing test failure separately). If the sample is intentionally excluded from CI, exclude it from Dependabot as well, so bumps here don't arrive unverifiable.

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