[BUG] Date() tool parameters show up as empty objects in Braintrust #11024
Description
Describe the Bug
Date() objects as passed to tools used to be coerced to strings in Braintrust traces, now the show up as empty objects.
Steps To Reproduce
Create an agent with a tool that takes a native Date as a parameter.
Observe the tool calls in Braintrust.
Link to Minimal Reproducible Example
N/A
Expected Behavior
Should see ISO date strings for Dates in tool calls in Braintrust.
Environment Information
System:
OS: macOS 15.7.2
CPU: (12) arm64 Apple M4 Pro
Memory: 493.33 MB / 48.00 GB
Shell: 5.9 - /bin/zsh
Binaries:
Node: 24.11.1 - /Users/guincho/.nvm/versions/node/v24.11.1/bin/node
npm: 11.6.2 - /Users/guincho/.nvm/versions/node/v24.11.1/bin/npm
Browsers:
Chrome: 143.0.7499.41
Safari: 26.1
npmPackages:
@ai-sdk/openai: ^2.0.80 => 2.0.80
@bufbuild/protobuf: ^1.10.1 => 1.10.1
@connectrpc/connect: ^1.4.0 => 1.7.0
@connectrpc/connect-node: ^1.4.0 => 1.7.0
@eslint-community/eslint-plugin-eslint-comments: ^4.5.0 => 4.5.0
@eslint/compat: ^1.3.0 => 1.4.1
@eslint/eslintrc: ^3.3.1 => 3.3.1
@eslint/js: ^9.29.0 => 9.39.1
@faker-js/faker: ^9.9.0 => 9.9.0
@glossgenius/applications: ^11.1.2 => 11.3.0
@glossgenius/core-protos: ^10.317.0 => 10.329.0
@glossgenius/eslint-config-gg-linting: ^2.0.0 => 2.0.0
@glossgenius/loggers: ^9.6.0 => 9.6.0
@koa/router: ^13.1.0 => 13.1.1
@langfuse/client: ^4.0.1 => 4.4.2
@langfuse/core: ^4.0.1 => 4.4.2
@mastra/braintrust: ^1.0.0-beta.3 => 1.0.0-beta.3
@mastra/core: ^1.0.0-beta.7 => 1.0.0-beta.7
@mastra/langfuse: ^1.0.0-beta.3 => 1.0.0-beta.3
@mastra/langsmith: ^1.0.0-beta.3 => 1.0.0-beta.3
@mastra/memory: ^1.0.0-beta.3 => 1.0.0-beta.4
@mastra/observability: ^1.0.0-beta.1 => 1.0.0-beta.3
@mastra/pg: ^1.0.0-beta.4 => 1.0.0-beta.4
@types/js-yaml: ^4.0.9 => 4.0.9
@types/koa: ^2.15.0 => 2.15.0
@types/koa__router: ^12.0.4 => 12.0.5
@types/node: ^24.0.4 => 24.10.1
@types/supertest: ^6.0.3 => 6.0.3
@typescript-eslint/eslint-plugin: ^8.35.0 => 8.48.0
@typescript-eslint/parser: ^8.35.0 => 8.48.0
@vitest/coverage-v8: ^2.1.8 => 2.1.9
@vitest/ui: ^2.1.8 => 2.1.9
ai: ^5.0.102 => 5.0.102
axios: ^1.12.0 => 1.13.2
braintrust: ^1.0.1 => 1.0.1
commander: ^14.0.1 => 14.0.2
dayjs: ^1.11.18 => 1.11.19
dd-trace: ^5.65.0 => 5.80.0
dotenv: ^17.2.1 => 17.2.3
eslint: ^9.29.0 => 9.39.1
eslint-import-resolver-alias: ^1.1.2 => 1.1.2
eslint-import-resolver-typescript: ^4.4.3 => 4.4.4
eslint-plugin-diff: ^2.0.3 => 2.0.3
eslint-plugin-functional: ^9.0.2 => 9.0.2
eslint-plugin-jsdoc: ^51.2.3 => 51.4.1
eslint-plugin-vitest: ^0.5.4 => 0.5.4
globals: ^16.2.0 => 16.5.0
http-graceful-shutdown: ^3.1.14 => 3.1.14
js-yaml: ^4.1.1 => 4.1.1
koa: ^3.0.3 => 3.1.1
langsmith: ^0.3.47 => 0.3.81
lefthook: ^1.11.14 => 1.13.6
lockfile-lint: ^4.14.1 => 4.14.1
mastra: ^1.0.0-beta.6 => 1.0.0-beta.6
msw: ^2.12.3 => 2.12.3
prettier: ^3.6.0 => 3.6.2
supertest: ^7.1.1 => 7.1.4
ts-node: ^10.9.2 => 10.9.2
tsconfig-paths: ^4.2.0 => 4.2.0
tsx: ^4.21.0 => 4.21.0
typescript: ^5.8.3 => 5.9.3
vite: ^6.0.3 => 6.4.1
vitest: ^2.1.8 => 2.1.9
winston: ^3.18.3 => 3.18.3
zod: ^3.25.67 => 3.25.76
npmGlobalPackages:
corepack: 0.34.2
Verification
- I have searched the existing issues to make sure this is not a duplicate
- I have included sufficient information for the team to reproduce and understand the issue