add support for zod v4

[tkattkat]

Why

Adds support for zod 4 while maintaining backwards compatibility with zod 3

What changed

• Introduced a zodCompat layer so Stagehand speaks both Zod v3 and v4 natively. Every place that used to import zod/v3, zod-to-json-schema, or poke at schema internals now routes through the same helpers (StagehandZodSchema, InferStagehandSchema, toJsonSchema, etc.). That keeps existing apps on v3 working while letting us upgrade to the v4 ecosystem.
• Swapped all examples, eval tasks, tests, and LLM clients over to standard zod imports, updated dependencies to accept 3.25.76 || 4.1.8, and dropped zod-to-json-schema. Tool plumbing (Anthropic/Google CUA) and custom clients now produce the right JSON Schema regardless of which Zod flavor the user passes in.
• Tightened typings so structured LLM calls return { data, usage } directly no more as casts throughout inference or the samples.

Manual testing
To make sure nothing regressed, I ran:
Custom OpenAI client example (schema conversion + structured output).
Standard extract (including URL injection path).
Google computer-use agent with a custom tool.
Anthropic computer-use agent with a custom tool.
All behaved as before

[changeset-bot]

🦋 Changeset detected

Latest commit: d66a5d6

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

This PR includes changesets to release 2 packages

Name	Type
@browserbasehq/stagehand	Patch
@browserbasehq/stagehand-evals	Patch

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[seanmcguire12]

@greptileai

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[seanmcguire12]

@greptileai

[greptile-apps]

Greptile Summary

• Introduced zodCompat abstraction layer enabling dual support for Zod v3 (via zod-to-json-schema) and v4 (via built-in z.toJSONSchema()) with runtime version detection through _zod property inspection
• Updated all LLM clients (Anthropic, OpenAI, Cerebras, Groq) to use unified toJsonSchema() helper instead of direct zod-to-json-schema or zodResponseFormat calls, ensuring consistent schema conversion across providers
• Extended utils.ts schema introspection to handle both Zod v3 and v4 internal structures (_def vs _zod.def) for URL field transformation in extraction workflows

Confidence Score: 4/5

• This PR is safe to merge with thorough manual testing already completed across multiple scenarios
• The abstraction layer is well-designed with clear version detection logic, and the PR includes comprehensive manual testing of critical paths (OpenAI client, extract, Google/Anthropic CUA with custom tools). However, one point deducted because the implementation relies on runtime property detection (_zod) which is implementation-dependent and could be fragile if Zod internals change, and the fallback error path in toJsonSchema (line 48) could cause runtime failures if Zod v4.1+ assumptions don't hold
• packages/core/lib/v3/zodCompat.ts requires attention due to reliance on internal Zod properties for version detection

Important Files Changed

Filename	Overview
packages/core/lib/v3/zodCompat.ts	Introduces abstraction layer to support both Zod v3 and v4, with type guards and schema conversion utilities
packages/core/lib/utils.ts	Extended schema introspection helpers to support both Zod v3 and v4 internals for transformSchema operations
packages/core/package.json	Changed Zod peer dependency to accept "3.25.76

Sequence Diagram

sequenceDiagram
    participant User
    participant Stagehand
    participant zodCompat
    participant LLMClient
    participant LLM as "LLM Provider"

    User->>Stagehand: extract(instruction, zodSchema)
    Stagehand->>zodCompat: toJsonSchema(zodSchema)
    zodCompat->>zodCompat: isZod4Schema(schema)?
    alt Zod v4
        zodCompat->>zodCompat: z.toJSONSchema(schema)
    else Zod v3
        zodCompat->>zodCompat: zodToJsonSchema(schema)
    end
    zodCompat-->>Stagehand: jsonSchema
    Stagehand->>LLMClient: createChatCompletion(options)
    LLMClient->>LLM: API call with jsonSchema
    LLM-->>LLMClient: structured response
    LLMClient-->>Stagehand: {data, usage}
    Stagehand-->>User: extracted data

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