fix(claude): sanitize WebSearch domain filters for routed models

[Wibias]

Summary

• Sanitize Claude Code WebSearch / web_search* tool_use inputs from routed models: omit empty allowed_domains / blocked_domains, and if both are non-empty keep allowed_domains only.
• Apply on both JSON and SSE outbound paths (SSE buffers WebSearch args and emits one sanitized input_json_delta).

Fixes #381.

Test plan

• bun run typecheck
• bun test tests/claude-outbound.test.ts (25 pass)
• Manual: Claude Code + routed GPT (gpt-5.6-sol) asking for a domain-filtered web search no longer 400s on empty domain arrays

Summary by CodeRabbit

• Bug Fixes
  • Improved WebSearch domain filter handling for more reliable requests.
  • Removes empty or ambiguous domain filters and prioritizes allowed domains when conflicting filters are provided.
  • Applies consistent sanitization to both streamed and non-streamed WebSearch results.

[coderabbitai]

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ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: ASSERTIVE

Plan: Pro Plus

Run ID: 31e2c18a-7988-41ff-b034-63acabae3bce

📥 Commits

Reviewing files that changed from the base of the PR and between 9f953d8 and ed9e4ee.

📒 Files selected for processing (2)

• src/claude/outbound.ts
• tests/claude-outbound.test.ts

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📝 Walkthrough

Walkthrough

Adds WebSearch domain-filter sanitization to Claude JSON and SSE translation. Empty filters are omitted, conflicting non-empty filters favor allowed_domains, and streamed arguments are buffered before one sanitized delta is emitted.

Changes

WebSearch translation

Layer / File(s)	Summary
WebSearch sanitization and JSON translation src/claude/outbound.ts	Adds WebSearch name detection and input normalization, then applies it to constructed and JSON-translated tool inputs.
Buffered SSE WebSearch emission src/claude/outbound.ts	Buffers WebSearch argument deltas and emits one sanitized input_json_delta when the tool block closes.
Sanitization and translation tests tests/claude-outbound.test.ts	Tests empty-filter removal, conflicting-filter handling, JSON translation, and SSE buffering behavior.

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

Sequence Diagram(s)

sequenceDiagram
  participant OpenAIResponsesSSE
  participant SSETranslator
  participant closeOpenBlock
  participant AnthropicStream
  OpenAIResponsesSSE->>SSETranslator: function_call and argument delta frames
  SSETranslator->>SSETranslator: buffer WebSearch arguments
  OpenAIResponsesSSE->>SSETranslator: output_item.done
  SSETranslator->>closeOpenBlock: close buffered tool_use
  closeOpenBlock->>AnthropicStream: one sanitized input_json_delta

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Suggested reviewers: ingwannu, lidge-jun

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly matches the main change: sanitizing routed-model WebSearch domain filters.
Linked Issues check	✅ Passed	The changes satisfy #381 by omitting empty filters, enforcing one domain filter, and applying sanitization in both JSON and SSE paths.
Out of Scope Changes check	✅ Passed	No unrelated code changes are indicated beyond the WebSearch sanitization and its supporting test coverage.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/claude-websearch-domains

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[Ingwannu]

Verified against current dev. The reported Claude Code failure is real: routed WebSearch calls may contain empty or mutually exclusive domain filters, and this patch sanitizes both JSON and SSE translation paths without weakening terminal handling. I also reran the focused suite (25/25) and TypeScript typecheck at ed9e4ee; both passed, and required CI is green.