[v1.x backport] fix(server): validate wrapped outputSchema

[lawrence3699]

Fixes #1308.

On v1.x, validateToolOutput() still assumes every outputSchema can be normalized to an object schema before validation. That holds for raw shapes and plain z.object(...), but wrapped schemas like .optional(), .nullable(), .nullish(), and top-level z.union(...) normalize to undefined, so tool calls fail with Cannot read properties of undefined (reading '_zod').

This keeps the existing normalization path for raw shapes / object schemas and falls back to the original schema when normalization does not return an object, matching how tool input validation already works on this branch. The regression test covers the wrapped schema variants across both Zod matrices.

Validation:

• npx vitest run test/server/mcp.test.ts -t 'should support wrapped outputSchema variants'
• npx vitest run test/server/mcp.test.ts -t 'outputSchema'
• npx eslint src/server/mcp.ts
• npx prettier --check src/server/mcp.ts test/server/mcp.test.ts

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commit: e2ce8d6

[Copilot]

Pull request overview

Backports a server-side fix to ensure validateToolOutput() can validate tool structuredContent when outputSchema is a wrapped/compound Zod schema (e.g., optional(), nullable(), nullish(), or top-level union()), preventing crashes when object-schema normalization returns undefined.

Changes:

• Update validateToolOutput() to attempt normalizeObjectSchema() but fall back to validating against the original outputSchema when normalization fails.
• Add a regression test covering wrapped outputSchema variants across the Zod test matrix.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
src/server/mcp.ts	Fixes output validation to handle non-normalizable (wrapped/compound) Zod schemas by falling back to the original schema.
test/server/mcp.test.ts	Adds a regression test ensuring tool calls succeed with wrapped outputSchema variants.

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