Claude Haiku 4.5 vs R1 for Constrained Rewriting

Constrained Rewriting (per our benchmark definition) means compressing source text to fit hard character limits while preserving meaning and required elements. Key capabilities: faithful compression (preserve facts and intent), exact length control and format adherence (structured output), creative phrasing to retain meaning under tight limits, and the ability to handle long source contexts when the material to compress is large. Because no external benchmark is present for this task in the payload, the primary signal is our internal task score: Claude Haiku 4.5 = 3/5, R1 = 4/5. Supporting internal metrics: both models score 5/5 on faithfulness and 4/5 on structured_output, so loss of meaning and format compliance are unlikely differences. R1's edge on constrained_rewriting (4 vs 3) and its task rank (6 vs 31) indicate better practical compression strategies in our suite. Claude Haiku 4.5's strengths—very large context window (200,000 tokens) and top tool_calling (5 vs 4)—help when the source material is huge or when tool-assisted length checks are required, but they don't change the winner for standard hard-limit compression tasks.

Where R1 shines (choose R1):

• SMS/microcopy editing: compress a 600‑char product description to a 160‑char SMS while preserving CTA and SKU — R1 (4 vs 3) produced tighter, accurate compressions in our tests. R1's task rank (6/52) reflects consistent success on these tight-limit prompts.
• Marketing A/B variants: generate multiple strict-length headlines (e.g., <= 70 chars) with preserved claims — R1's higher constrained_rewriting score yields better adherence to the hard limit.

Where Claude Haiku 4.5 shines (choose Haiku 4.5):

• Large-document compression: extract and compress a relevant 100k‑token section down to a 500‑char abstract — Haiku's 200,000-token context window and long_context score (5 vs R1's 4) reduce context loss in our tests.
• Image-to-text compression workflows: Haiku supports text+image->text (payload) so if the source is a screenshot of text, Haiku can ingest that modality before compressing. Haiku also scored higher on tool_calling (5 vs 4), useful when integrating length-checking or validation tools into the pipeline.

Cost and tradeoffs:

• Output cost per mTok: Claude Haiku 4.5 = 5, R1 = 2.5. If you run high-volume compression, R1 is materially cheaper per output token. Use Haiku when its long-context or modality features are essential and you accept higher output cost.

For Constrained Rewriting, choose Claude Haiku 4.5 if you must compress text that lives inside very long contexts (up to 200,000 tokens), need image->text inputs, or will rely on tool-driven validation and can accept higher output cost. Choose R1 if your primary goal is compact, reliable compression under strict character limits at lower cost — R1 scored 4 vs 3 for this task in our testing and ranks 6 of 52 vs Haiku's 31 of 52.