Claude Opus 4.7 vs GPT-5.4 vs Gemini 3.1: 6 Real Tasks, 3 Different Winners (2026)

Task 1 — Long-document synthesis (100+ pages)

Use when: A 60-page 10-K, white paper, or RFP. You need the thesis, the contradictions, the unstated implications — not a summary.

You are a senior research analyst. Synthesize this 100+ page document for a founder.

Document: "[PASTE FULL TEXT]"

Output:
1. Thesis in ONE sentence (the author's, not mine)
2. 5 claims the author actually makes, with page cites
3. 3 claims the author IMPLIES but never states — and whether evidence holds
4. The 2 places where the document contradicts itself (cite both)
5. 3 questions this document doesn't answer

Rules:
- If a cite is missing, SAY "no cite found" — never fabricate.
- Flag any claim where confidence <70% with [LOW CONFIDENCE].

Why this winner: The "contradicts itself" and "implies but never states" slots force the model to read against the text. Gemini 3.1 has the longest context (1M tokens), but on this prompt it summarized obediently — it did not interrogate. GPT-5.4 lost the thread past page 40.

When the runner-up wins instead: If your doc is over 200k tokens, Opus rejects it. Gemini 3.1 is the only path. Accept the slightly weaker reasoning.

Task 2 — Code review with refactor proposal

Use when: Paste a 300-line file. Get back a review that names the worst smell, proposes a refactor, and writes the diff with self-review.

You are a senior staff engineer. Review this file with NO sycophancy.

[PASTE FILE]

Output:
- Worst code smell, with line number and explanation
- Refactor proposal (architecture, not nits)
- Diff in unified format
- Self-review: 3 things your own diff might break in production
- 1 question you'd ask the author before merging

Why this winner: The self-review slot. Opus 4.7 writes a refactor and then attacks it. GPT-5.4 writes the refactor and stops. Gemini 3.1 writes a refactor with a long preamble you have to scroll past.

When the runner-up wins instead: If you are inside Cursor or Copilot and you want the change applied directly, GPT-5.4 tool integration is unbeaten. Opus is for review; GPT for execution.

Task 3 — Fast comparison with fresh web data

Use when: "Compare the top 5 [X] tools as of this week." Anything time-sensitive.

You are a product analyst. Compare the top 5 [CATEGORY] tools as of [TODAY].

For each tool:
- Pricing (current, with date checked)
- One concrete strength a competitor lacks
- One concrete weakness
- Best fit ICP

Cite the source URL for every pricing claim.

Why this winner: Native, real, current browsing. GPT-5.4 Browse mode works but is slower and limits source count. Opus 4.7 has no browsing — it will make up pricing from training data and you will embarrass yourself in a board meeting.

When the runner-up wins instead: This is the one task where the answer is not Opus.

Task 4 — Voice agent or heavy tool density

Use when: Real-time voice, function calling against 8+ tools, low-latency back-and-forth.

(Architectural choice — no single prompt. Default to GPT-5.4 Realtime API.)

Why this winner: GPT-5.4 voice mode and the Realtime API have no real competition in 2026. Opus has voice in the API but the latency penalty is brutal. Gemini has voice through AI Studio but the tool ecosystem is thinner.

When the runner-up wins instead: If you are building a voice agent in 2026, default to GPT-5.4 unless you have a strong reason not to.

Task 5 — Bulk writing under 800 words

Use when: Blog intros, emails, ad copy, product descriptions, short-form prose.

(Any standard prose prompt — Sonnet matches Opus blind 80% of the time at a fraction of cost.)

Why this winner: Opus 4.7 only earns its premium when the job has long context, deep reasoning, or self-verification. None apply to a 600-word blog intro.

When the runner-up wins instead: If you are batching short outputs (>50 in a session), the cost gap to Opus becomes the entire decision. Pick Sonnet.

Task 6 — Agent harness with self-verification

Use when: An agent that runs autonomously for 20+ steps, has to back off when uncertain, and produces a final report with citations.

You are an autonomous research agent.

Goal: [GOAL]
Tools available: [LIST]
Budget: 20 steps max

After each step:
- State what you learned
- State your confidence (0-100)
- If confidence <70, narrow scope and try again before continuing
- If confidence >70, proceed

Final report must include:
- Findings (with cites)
- 2 places you might be wrong
- The single question whose answer would most change the conclusion

Why this winner: GPT-5.4 will execute. Gemini 3.1 will execute. Opus will execute, and then push back on its own conclusion. If "confidence calibration" matters in your application — research, due diligence, code review, anything reversible-but-expensive — Opus is the only model worth trusting unsupervised.

When the runner-up wins instead: If the agent must call >10 different tools per step, GPT-5.4 function-calling is more reliable in practice. Use Opus for planning, GPT-5.4 for execution.