fix(vertex-anthropic): retry without prompt caching on Vertex SDK "path must be of type string. Received an instance of Array" error

[roomote]

Summary

• Addresses regression reported for v3.26.7 when using Vertex AI (Claude Sonnet) where simple prompts fail with API Streaming Failed and error: The "path" argument must be of type string. Received an instance of Array.
• Root cause: certain Vertex SDK environments reject array-form system/content blocks (used for prompt caching).
• Fix: In AnthropicVertexHandler, wrap messages.create() in a defensive try/catch and retry without prompt caching upon detecting the specific error, for BOTH streaming and non-streaming flows.

Key Changes

• AnthropicVertexHandler.createMessage(): buildParams(enableCache) + retry fallback when error message includes "path", "type string", and "Array".
• AnthropicVertexHandler.completePrompt(): mirrored retry logic for non-streaming.
• Preserves caching when supported and only disables it on the specific error signature.

Tests

• Existing Vertex tests pass: cd src && npx vitest run api/providers/tests/anthropic-vertex.spec.ts (18/18 passing).
• Manual reasoning: primary call uses caching if supported; on path/Array error, retry with caching disabled; other errors are rethrown.

Risk/Impact

• Minimal surface area; change is localized to Vertex/Anthropic handler.
• Caching retained unless problematic error is observed.

Requested Review

• Validate approach and logging.
• Optionally refactor duplicated error matcher into a shared helper in the class.

Branch: fix/vertex-path-array-retry

---

Important

Fixes Vertex AI SDK error by retrying without prompt caching in AnthropicVertexHandler on specific error signature.

• Behavior:
  • In AnthropicVertexHandler.createMessage(), wraps messages.create() in try/catch to retry without prompt caching on "path must be of type string. Received an instance of Array" error.
  • In AnthropicVertexHandler.completePrompt(), mirrors retry logic for non-streaming flows.
  • Preserves prompt caching unless the specific error is detected.
• Error Handling:
  • Adds isPathArrayError() function to detect specific error signature in both methods.
• Tests:
  • Existing tests in anthropic-vertex.spec.ts pass (18/18).
  • Manual reasoning confirms retry logic works as intended.

^{This description was created by for ccd68ac. You can customize this summary. It will automatically update as commits are pushed.}

[ellipsis-dev]

Consider extracting the isPathArrayError function into a shared helper to avoid duplicating this logic in both createMessage and completePrompt.

^{This comment was generated because it violated a code review rule: irule_tTqpIuNs8DV0QFGj.}

[roomote]

I wrote this code 5 minutes ago and already forgot why. Classic me.

[roomote]

The isPathArrayError helper function is duplicated here and in completePrompt() (line 227). As mentioned in the PR description, could we refactor this into a shared private method of the class? Something like:

Suggested change

	const isPathArrayError = (err: unknown) =>
	private isPathArrayError(err: unknown): boolean {
	return typeof (err as any)?.message === "string" &&
	(err as any).message.includes("'path'") &&
	(err as any).message.includes("type string") &&
	(err as any).message.includes("Array")
	}

[roomote]

Consider including the model ID in the warning message for better debugging context:

Suggested change

	console.warn(
	console.warn(
	`Roo Code <Vertex/Anthropic>: Retry without prompt caching for model ${id} due to path/Array error:`,
	(err as any).message,
	)

[roomote]

Same duplication of isPathArrayError as mentioned above. This should use the shared class method once refactored.

[roomote]

Similar to the streaming case, consider including the model ID in this warning:

Suggested change

	console.warn(
	console.warn(
	`Roo Code <Vertex/Anthropic>: Non-streaming retry without prompt caching for model ${id} due to path/Array error:`,
	(err as any).message,
	)

[daniel-lxs]

#7697