fix(schema): allow null system_fingerprint in OpenAI response

[ayo6706]

The OpenAI API sometimes returns system_fingerprint: null in the response (observed with gpt-5.1-2025-11-13). Our Zod schema only allowed string | undefined, causing a validation error:

APIResponseError: Invalid OpenAI API response structure: [
{
"code": "invalid_type",
"expected": "string",
"received": "null",
"path": ["system_fingerprint"],
"message": "Expected string, received null"
}
]

Solution

Updated OPENAI_RESPONSE_SCHEMA in
src/schemas/openai-responses.ts
to use .nullable().optional():

This allows:

undefined (field missing)
null (field explicitly null)
string (field with value)

Summary by CodeRabbit

• Chores
  • Improved OpenAI API response handling to better manage edge cases in response validation and parsing.

[coderabbitai]

📝 Walkthrough

Walkthrough

A schema field in the OpenAI responses schema was modified to accept null values. The system_fingerprint field changed from z.string().optional() to z.string().nullable().optional(), allowing it to be null, undefined, or absent.

Changes

Cohort / File(s)	Summary
Schema Field Update src/schemas/openai-responses.ts	Modified system_fingerprint field in OPENAI_RESPONSE_SCHEMA to accept null values in addition to being optional, changing validation from z.string().optional() to z.string().nullable().optional().

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~2 minutes

Poem

🐰 A whisker twitch, a schema shift,
Null values dance, a gentle gift,
The fingerprint may now be naught,
In optional realms, so wisely wrought!
One line changed, the code takes flight! ✨

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title 'fix(schema): allow null system_fingerprint in OpenAI response' directly and clearly describes the main change: modifying the schema to accept null values for the system_fingerprint field.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

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✨ Finishing touches

• 📝 Generate docstrings

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch fix/openai

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