[grabbou]

Stacked on #319.

Only context overflow and rate limits had their own codes; every other Foundation Models failure was GENERATION_ERROR, so apps couldn't tell a guardrail hit from a missing download.

New public codes, mapped from LanguageModelSession.GenerationError (iOS 26), LanguageModelError and PrivateCloudComputeLanguageModel.Error (iOS 27):

Code	From
GUARDRAIL_VIOLATION	guardrailViolation
REFUSAL	refusal
UNSUPPORTED_LANGUAGE	unsupportedLanguageOrLocale
ASSETS_UNAVAILABLE	assetsUnavailable
CONCURRENT_REQUESTS	concurrentRequests
DECODING_FAILURE	decodingFailure
TIMEOUT	timeout (iOS 27)
NETWORK_FAILURE, SERVICE_UNAVAILABLE	Private Cloud Compute (iOS 27)

unsupportedGuide / unsupportedGenerationGuide now map to the existing INVALID_SCHEMA. The error docs list every code with its meaning.

Added a harness test where a harmful prompt rejects with GUARDRAIL_VIOLATION (was GENERATION_ERROR). Generate tests pass on the iPhone 18 Pro simulator (iOS 27).

🤖 Generated with Claude Code

Summary by CodeRabbit

• New Features
  • Apple LLM integrations now report additional error types, including guardrail violations, refusals, unsupported languages, unavailable assets, concurrent requests, decoding failures, timeouts, and network or service issues. Each error includes a corresponding code and message.
  • Invalid JSON in tool-call input now returns an invalid-message error that identifies the tool.
• Documentation
  • Updated Apple LLM error-code descriptions and iOS version support information.
• Tests
  • Added coverage for guardrail violations and invalid tool-call input.

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Walkthrough

The PR adds nine Apple LLM error codes and maps additional iOS language model and Private Cloud Compute errors. It adds tests for guardrail rejection and invalid tool-call JSON. Apple documentation now describes the error codes and their iOS version support.

Changes: Apple LLM error mapping

Layer / File(s)	Summary
Define Apple LLM error codes packages/apple-llm/ios/AppleLLMError.swift, packages/apple-llm/src/errors.ts, website/src/docs/apple/generating.md, website/src/docs/apple/ios-versions.md	AppleLLMError and AppleLLMErrorCodes add nine error codes. The documentation describes the codes and their supported iOS versions.
Map native errors packages/apple-llm/ios/AppleLLMImpl.swift, harness/apple/generate.harness.ts	The iOS mapper handles additional language model and Private Cloud Compute errors. The harness checks guardrail rejection and invalid tool-call JSON handling.

Priority: Normal

Estimated code review effort: 3 (Moderate) | ~20 minutes

Change: Feature

Possibly related PRs

• callstackincubator/ai#321: The AI SDK adapter consumes the guardrail and refusal codes added here.
• callstackincubator/ai#323: Prewarming calls the native implementation, which uses the expanded error mapper.
• callstackincubator/ai#329: This PR also covers Private Cloud Compute quota failures and RATE_LIMITED behavior.

Suggested reviewers: jkobrynski

Merge Risk: Low · up to adbf9

Truncated tool-call input may enter the transcript instead of returning INVALID_MESSAGE. This is a bounded edge case that should be fixed or accepted before merging.

Security architecture risk: Low · up to adbf9

The change primarily improves error reporting without changing tool permissions or guardrail settings. No introduced security issue was identified. Applications may nevertheless need to accommodate newly specific error codes; native runtime behavior and external applications’ recovery policies were not independently validated.

Retained concerns
No architecture-level concerns identified.

Security review details

Security Blast Radius

• inferred — The demonstrated exposure is the calling application's generation and streaming error handling. More failures become distinguishable to those existing callers; the inspected changes do not establish increased tool authority or a new cross-service access path. Effects on external applications' recovery policies remain unverified.

Trust Boundaries and Controls

• observed — Caller-provided tool history still requires string identifiers, a tool name, and input passed through GeneratedContent before a tool-call entry is appended. The parser and successful-input path are unchanged; only thrown failures are relabeled. Neither version adds an explicit completeness check, so this PR should not be interpreted as establishing strict rejection of every incomplete JSON prefix. Existing orphan tool-output filtering remains in place.

Resilience and Maintainability Implications

• observed — Transcript entries remain local until construction returns, and parsing failure prevents session construction. Error classification does not change native task registration, cancellation, or cleanup. The inspected TypeScript consumer retains finally-based tool cleanup for generation and listener/tool cleanup for stream completion, errors, and cancellation.

Pre-merge checks: 4 · 1

Failed checks: 1 warning

Check name	Status	Explanation	Resolution
Docstring Coverage		Docstring coverage is 0.00% which is insufficient. The required threshold is 50.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 3 functions across 4 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

Passed checks: 4 passed

Check name	Status	Explanation
Description Check		Check skipped - CodeRabbit’s high-level summary is enabled.
Title check		The title clearly and concisely describes the main change: adding distinct error codes for Apple Foundation Models failures.
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.

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Inline comments:
Review comments at @packages/apple-llm/ios/AppleLLMImpl.swift:
- Around line 983-988: Add iOS 27 error mappings before the GenerationError cast
in both generation and streaming paths, mapping
SystemLanguageModel.Error.assetsUnavailable,
LanguageModelSession.Error.concurrentRequests, and GeneratedContent.ParsingError
to their corresponding specific error codes. Preserve the existing
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- Around line 960-961: At the tool-input parsing site using
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Inline comments:
Review comments at @packages/apple-llm/ios/AppleLLMImpl.swift:
- Around line 1227-1233: Check `arguments.isComplete` after
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