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OpenAI: GPT-5.1 Chat

GPT-5.1 Chat (AKA Instant is the fast, lightweight member of the 5.1 family, optimized for low-latency chat while retaining strong general intelligence. It uses adaptive reasoning to selectively “think” on...

Anyone in the Space can @-mention OpenAI: GPT-5.1 Chat with the team's shared context - pooled credits, one chat, one memory.

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Verdict

GPT-5.1 Chat represents OpenAI's latest reasoning-focused architecture with a 128K context window and multimodal support across text, images, and files. At $1.25/$10 per Mtok, it sits in the premium tier—roughly 2.5× the cost of GPT-4o for output tokens. Without public benchmarks yet, early adopters report strong performance on complex reasoning chains and document analysis, but the price premium means you'll want to reserve it for tasks where GPT-4o falls short. Reach for this when you need the newest OpenAI capabilities and can justify the cost delta.

Best for

  • Complex multi-step reasoning tasks
  • Long-context document synthesis
  • Multimodal analysis combining text and images
  • Tasks requiring latest OpenAI architecture
  • High-stakes outputs justifying premium pricing

Strengths

The 128K context window handles substantial documents or conversation histories without truncation. Multimodal support lets you mix screenshots, PDFs, and text in a single request—useful for analyzing reports with embedded charts or debugging UI issues. Early testing suggests improved reasoning over GPT-4o on multi-hop logic problems, though we're waiting on independent benchmarks to quantify the gap. The model maintains OpenAI's typical instruction-following reliability.

Trade-offs

Output pricing at $10/Mtok makes this one of the more expensive frontier models—you'll pay roughly $10 for every million tokens generated, compared to $4 for GPT-4o or $15 for Claude Opus. Without published benchmarks, you're buying on trust in OpenAI's track record rather than verified performance deltas. The 128K window, while large, trails Gemini 1.5 Pro's 2M and Claude's 200K options for extreme long-context work. If GPT-4o already solves your use case, the cost jump is hard to justify.

Specifications

Provider
openai
Category
llm
Context length
128,000 tokens
Max output
32,000 tokens
Modalities
file, image, text
License
proprietary
Released
2025-11-13

Pricing

Input
$1.25/Mtok
Output
$10.00/Mtok
Model ID
openai/gpt-5.1-chat

Per-token prices show what the model costs upstream. On Switchy your team draws from one shared org credit pool - one plan, one balance for everyone.

Team cost calculator

Estimated monthly spend
$68.20
17.6M tokens / month
5 seats · 80 msgs/day

Switchy meters this against your org's shared credit pool - one plan, one balance for everyone.

Providers

ProviderContextInputOutputP50 latencyThroughput30d uptime
openai128k$1.25/Mtok$10.00/Mtok

Performance

Performance snapshots are collected daily. Check back after the next ingestion run.

Benchmarks

Public benchmark scores are not available yet for this model. Check back after the next ingestion run.

Works well with

Top MCPs

Compatibility data comes from first-party telemetry; once we have enough co-usage signal, top MCPs for this model will appear here.

How Switchy teams use it

Not enough Spaces have used this model yet to share anonymised team stats. We wait for at least 50 distinct Spaces per week before publishing any aggregate.

Starter prompts

Multi-Document Synthesis

I've uploaded three quarterly reports. Identify the top three strategic priorities mentioned across all documents, then flag any contradictions in how progress is described.
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Screenshot Debugging

Here's a screenshot of a broken layout and the relevant CSS file. Explain what's causing the alignment issue and provide the corrected CSS.
Open in a Space →

Complex Logic Chain

A train leaves Station A at 60 mph. Another leaves Station B (300 miles away) at 40 mph, departing 30 minutes later. When and where do they meet? Show each calculation step.
Open in a Space →

Contract Clause Analysis

Review this 80-page vendor agreement. List every clause that references data retention, then check if they're consistent with the definitions in Section 2.
Open in a Space →

Image-Text Reasoning

This flowchart shows our deployment process. Compare it to the written runbook I've pasted below and identify any steps that appear in one but not the other.
Open in a Space →

Example outputs

Illustrative - representative of the model's voice and quality, not literal recordings.

Prompt

Review this Python function for potential race conditions. It's meant to update a shared counter across threads, but we're seeing inconsistent totals in production.

Output

The function lacks thread synchronization around the read-modify-write sequence on `self.counter`. Between reading the current value and writing back `counter + 1`, another thread can interleave its own update, causing lost increments. You need either a threading.Lock around the entire operation, or switch to `threading.local()` for per-thread counters that you sum at the end. The 128K context window here means I can also analyze your entire codebase if you paste the related modules — I'll trace how this counter flows through your request handlers and identify whether the lock granularity should be finer or coarser based on your actual call patterns.

Notes

Demonstrates deep code reasoning with architectural advice that scales beyond the immediate bug. The 128K context window enables whole-repository analysis in one prompt, a key advantage over smaller-context models. Trade-off: at $10/Mtok output, verbose explanations get expensive fast for high-volume debugging workflows.

Prompt

Generate a product requirements document for a mobile app that lets users scan receipts, extract line items, and auto-categorize expenses. Target audience is freelancers who hate manual bookkeeping.

Output

**Product Requirements: ReceiptSnap** **Vision:** Eliminate manual expense entry for solo workers by turning phone photos into categorized ledger rows in under 5 seconds per receipt. **Core Features:** 1. OCR scan with line-item extraction (merchant, date, items, amounts) 2. ML-based category suggestion (meals, travel, supplies) with one-tap confirm 3. Export to CSV/QuickBooks/FreshBooks **User Flow:** Snap → Review extracted data → Confirm categories → Done. No account setup required for first 20 receipts. **Success Metrics:** <5s scan-to-save time, >90% OCR accuracy on crumpled receipts, 40% of users export within first week. **Out of Scope v1:** Multi-user teams, mileage tracking, tax-form generation.

Notes

Shows structured business-document generation with user empathy and scope discipline. The multimodal input support means you could attach competitor app screenshots or wireframe sketches directly in the prompt for richer context. Trade-off: no public benchmarks yet, so reasoning quality relative to GPT-4 or Claude 3.5 Sonnet remains unverified in head-to-head tests.

Prompt

I'm looking at this radiology report and the phrase 'ground-glass opacities in bilateral lower lobes' — what does that actually mean for my lungs, and should I be worried before my follow-up next week?

Output

Ground-glass opacities (GGOs) are hazy areas on a CT scan where your lung tissue looks slightly clouded, like frosted glass, but the underlying structures (blood vessels, airways) are still visible through it. In both lower lobes means it's affecting the bottom portions of each lung. This pattern shows up in many conditions — infections (viral pneumonia, COVID), inflammatory issues, early scarring, or even just transient changes from recent illness. The fact that your doctor scheduled a follow-up suggests they want to see if it resolves on its own (which infections often do) or persists (pointing toward something chronic). It's not an emergency finding, but it does warrant the monitoring you're already getting. Before your appointment, note any breathing changes, persistent cough, or fever — that context helps your doctor interpret whether the GGOs are resolving or need further workup.

Notes

Illustrates accessible medical explanation with appropriate caution and next-step framing. The image input modality means you could upload the actual scan for more specific interpretation. Trade-off: at $1.25/Mtok input, processing large image files or lengthy medical records adds cost compared to text-only models, though the 128K window absorbs that overhead better than smaller-context alternatives.

Use-case deep-dives

Multi-document legal synthesis

When 128K context beats RAG for contract cross-checks

A 4-person legal ops team needs to compare clauses across 12 vendor contracts before renewal season. GPT-5.1 Chat's 128K context window lets you load all contracts in one prompt—no chunking, no retrieval layer, no missed cross-references. At $1.25/Mtok input, a typical 80K-token batch costs ~$0.10 per analysis run. The model handles image uploads, so scanned signature pages and redlined PDFs go straight in. Output at $10/Mtok means a 4K summary costs $0.04. If you're running fewer than 200 analyses per month, this beats building a RAG pipeline. Above that volume, consider caching strategies or a cheaper model for the first-pass filter.

High-resolution design feedback

Why image + long context matters for iterative creative review

A 9-person brand studio reviews 30-50 mockups weekly, each with 6-10 prior revisions and a creative brief. GPT-5.1 Chat ingests the full revision history as images plus the 8-page brand guide in one context window, so feedback references both the brief and the design evolution without re-uploading. At $1.25 input, a 40K-token context (brief + chat history) costs $0.05; the image modality adds negligible cost but keeps the model grounded in actual pixels, not descriptions. Output runs $10/Mtok, so a 1K-token critique is $0.01. This works until you hit 500+ reviews/month—then the output cost ($5 per 500 reviews at 1K each) starts to justify a fine-tuned cheaper model.

Real-time customer support escalation

When to route live chats to GPT-5.1 instead of a faster model

A 12-person SaaS support team handles 300 chats/day; 40 escalate to a senior agent who needs full conversation context plus account notes. GPT-5.1 Chat's 128K window means the escalation prompt includes the entire 90-message thread, the user's 6-month ticket history, and the internal runbook—no summarization, no context loss. Input at $1.25/Mtok and output at $10/Mtok means each escalation costs ~$0.15 (assuming 10K input, 1K output). That's $6/day or $180/month for 40 escalations. If your escalation rate climbs above 100/day, the output cost ($10/day) justifies a two-tier system: a cheaper model for triage, GPT-5.1 for the complex 20%.

Frequently asked

Is GPT-5.1 Chat good for general conversation and chatbots?

Yes. GPT-5.1 Chat is optimized for conversational use cases with strong instruction-following and natural dialogue flow. The 128k token context window handles long conversations without losing thread. It supports text, image, and file inputs, making it versatile for customer support bots, assistants, and interactive applications where multi-turn coherence matters.

Is GPT-5.1 Chat cheaper than GPT-4o or Claude Sonnet?

No. At $1.25 input and $10.00 output per million tokens, GPT-5.1 Chat costs roughly 2-3x more than GPT-4o and Claude 3.5 Sonnet for output-heavy workloads. The premium pricing suggests OpenAI positions this as a higher-capability model, but without public benchmarks, you're paying for brand and incremental improvements over GPT-4 Turbo rather than proven performance gains.

Can GPT-5.1 Chat handle 128k tokens reliably in practice?

The 128k context window is supported, but real-world performance at maximum capacity depends on prompt structure and task complexity. Most production use cases stay under 32k tokens for cost and latency reasons. For document analysis or long transcripts, test with your actual data—context window size and retrieval accuracy at the edges aren't the same thing.

How does GPT-5.1 Chat compare to GPT-4 Turbo?

Without public benchmarks, the performance delta is unclear. OpenAI typically releases numbered versions for meaningful capability jumps, so expect improvements in reasoning, instruction-following, and refusal rates. The pricing is higher than GPT-4 Turbo, suggesting better quality, but you'll need to A/B test on your specific prompts to justify the cost difference for production workloads.

Should I use GPT-5.1 Chat for high-volume API applications?

Only if quality justifies the cost premium. At $10 per million output tokens, a chatbot generating 500-word responses costs $0.04 per conversation. For high-volume use cases, start with GPT-4o or Claude Sonnet and upgrade selectively for queries where GPT-5.1's capabilities—whatever they prove to be—deliver measurable value. Monitor your cost-per-interaction closely.

Data last verified 8 hours ago.Sources aggregated hourly to weekly. See docs/architecture/model-directory.md.