Claude Sonnet 4.6 vs Grok 4 for Long Context

What Long Context demands: retrieval accuracy at 30K+ tokens, stable reference resolution across many document spans, resisting hallucination when sources are far apart, and the ability to coordinate tools and structured outputs across iterative retrieval steps. With no external benchmark provided for this task in the payload, our winner call relies on internal results and model properties. Both models achieve 5/5 on our long_context test (tie), so supporting capabilities decide the practical winner. Important capabilities: (1) context window size — larger windows let you avoid chunking and preserve global state (Sonnet 4.6: 1,000,000 tokens; Grok 4: 256,000); (2) tool calling — selecting and sequencing functions against long documents (Sonnet 4.6 tool_calling 5 vs Grok 4 tool_calling 4 in our testing); (3) safety and faithfulness — ensuring refusals and source fidelity over long retrieval chains (Sonnet safety_calibration 5 vs Grok 4 at 2; both tie on faithfulness at 5); (4) multi-step agentic planning — breaking large tasks into retrievable subtasks (Sonnet agentic_planning 5 vs Grok 4 at 3). Grok 4’s strengths include constrained_rewriting (4 vs Sonnet’s 3) and multimodal file input support (text+image+file), which can be important when the long corpus includes many file types.

1. Large codebase triage (500k+ token repo + docs): Sonnet 4.6 — 1,000,000-token window avoids chunking; tool_calling 5 in our tests helps reliably select and call refactoring or search functions. Grok 4 — still 5/5 for retrieval but requires more chunking and benefits from its file input support. 2) Litigation document review (multi-hundred-page bundles): Sonnet 4.6 — higher safety_calibration (5 vs 2) and agentic_planning (5 vs 3) reduce risky hallucinations and make multi-step review workflows safer in our testing. 3) Manuscript or book-level editing: Both models hit 5/5 on long_context retrieval, but Sonnet’s 128,000 max_output_tokens supports longer summarization outputs; Grok 4 shines when constrained rewriting is needed (constrained_rewriting 4 vs Sonnet 3). 4) Mixed-format research corpus (PDFs, images, spreadsheets): Grok 4’s modality (text+image+file) is advantageous for ingesting files directly; Sonnet 4.6 supports text+image->text but not explicit file input in the payload. 5) Agent-driven data extraction across large corpora: Sonnet’s combination of large window and superior tool_calling and planning scores in our testing makes it better for orchestrating many sequential or parallel retrieval steps.

For Long Context, choose Claude Sonnet 4.6 if you need the largest working window (1,000,000 tokens), longer max outputs (128,000 tokens), stronger tool calling (5 vs 4), and higher safety and planning in our testing. Choose Grok 4 if you need built-in file+image ingestion and stronger constrained_rewriting (4 vs 3) while still getting a top-tier long_context score (both are 5/5 in our tests).