feat(core): thread agent and thread identity through the processor surface

[CalebBarnes]

Summary

Processors today have no first-class way to learn which agent, thread, or resource a run belongs to. Consumers that need this (for example the channels output processor) are forced to depend on request-scoped side channels that are not always populated. This PR adds agentId, agentName, threadId, and resourceId as flat optional fields on ProcessorContext, so every processor method receives them directly.

The fields are optional and undefined for non-agent or threadless pipelines, so existing processors keep working unchanged.

const myProcessor: Processor = {
  id: 'my-processor',
  processOutputStream: async ({ part, agentId, threadId, resourceId }) => {
    // agentId, threadId, resourceId now available here
    return part;
  },
};

What changed

• Added the four identity fields to ProcessorContext (propagates to all method arg types).
• Added agentId to the ProcessorRunner constructor alongside agentName; threadId/resourceId are passed per-call into the public entry methods.
• Injected the identity fields into every hand-built processor args object — both the in-process regular-processor objects and the workflow-as-processor inline objects.
• Added the identity fields to the workflow step schemas and types so they survive the workflow serialization boundary, and spread them into baseContext in both the default and evented workflow executors.
• Wired agentId (and proper agentName/threadId/resourceId where available) into all non-test ProcessorRunner construction sites.

All four fields are plain strings, so they cross the workflow step serialization boundary safely. No live handles or closures were added to any step schema.

Test plan

• New cross-path symmetry test in runner.test.ts: a processor receives identical agentId/agentName/threadId/resourceId whether it runs in-process or as a workflow.
• pnpm build:core — passing.
• pnpm --filter ./packages/core check (typecheck) — passing.
• Focused processor tests (src/processors/, 38 files) — passing.
• Loop, agent, and workflow tests (125 files) — passing.

This is PR #1 of a stack. It is independently useful and unblocks a follow-up that makes the channels output processor self-sufficient.

[changeset-bot]

🦋 Changeset detected

Latest commit: 95c066b

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 22 packages

Name	Type
@mastra/core	Minor
mastracode	Patch
@mastra/mcp-docs-server	Patch
@internal/playground	Patch
@mastra/client-js	Patch
@mastra/opencode	Patch
@mastra/longmemeval	Patch
mastra	Patch
@mastra/deployer-cloud	Minor
@mastra/react	Patch
@mastra/playground-ui	Patch
@mastra/server	Minor
@mastra/deployer	Minor
create-mastra	Patch
@mastra/express	Patch
@mastra/fastify	Patch
@mastra/hono	Patch
@mastra/koa	Patch
@mastra/nestjs	Patch
@mastra/next	Patch
@mastra/tanstack-start	Patch
@mastra/temporal	Patch

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[CalebBarnes]

Superseded by #18630. The self-sufficient channels output processor (the only consumer of this identity work) instead sources the run's threadId from the framework-populated MastraMemory request-context key via parseMemoryRequestContext, so threading agentId/agentName/threadId/resourceId through the entire processor surface is no longer required for this work. Closing to avoid a stale stack.