GPT-5.1 Codex
Coding-agent specialization of GPT-5.1: 400K context, tool calling and structured output for SWE agents.
- name
- GPT-5.1 Codex
- vendor
- OpenAI
- model_id
- gpt-5.1-codex
- context_window
- 400K
- max_output
- 128K
- input_per_mtok
- $1.25
- output_per_mtok
- $10.00
- strengths
- Coding-agent specialization of GPT-5.1: 400K context, tool calling and structured output for SWE agents.
- provider
- OpenAI
- family
- GPT-5
- release_date
- 2025-11-13 source
- last_updated
- 2026-06-15
- open_weights
- false source
- license
- proprietary source
- params_total
- — verify-against-primary-at-build ↗ https://models.dev/models/openai/gpt-5.1-codex/ — total parameter count not published for this model.
- params_active
- — verify-against-primary-at-build ↗ https://models.dev/models/openai/gpt-5.1-codex/ — active (MoE) parameter count not published for this model.
- tool_call
- true source
- reasoning
- always source
- structured_output
- true source
- attachment
- — verify-against-primary-at-build ↗ https://models.dev/models/openai/gpt-5.1-codex/ — accepted attachment/file modalities not enumerated on the fetched entry; confirm at build.
- temperature
- false source
- knowledge_cutoff
- 2024-09 source
- context_advertised
- 400K source
- context_effective
- — verify-against-primary-at-build ↗ No published measured long-context recall benchmark for this model; do not derive effective context from advertised.
- price_input
- $1.25 source
- price_output
- $10.00 source
- price_cache_read
- — verify-against-primary-at-build ↗ https://models.dev/models/openai/gpt-5.1-codex/ — cache-read rate not captured numerically from a primary source in this pass.
- price_cache_write
- — verify-against-primary-at-build ↗ https://models.dev/models/openai/gpt-5.1-codex/ — cache-write rate not captured numerically from a primary source in this pass.
- cost_per_full_window
- — verify-against-primary-at-build ↗ Derived at build from price_input x advertised context once confirmed.
- cost_per_agent_task
- — verify-against-primary-at-build ↗ Derived at build from the cache-aware agent-task model once cache rates are confirmed.
- modalities
- text-in,text-out source
- gpqa_diamond
- — verify-against-primary-at-build ↗ https://artificialanalysis.ai/ — GPQA-Diamond for this model to confirm at build.
- swe_bench_verified
- — verify-against-primary-at-build ↗ https://www.swebench.com/ — SWE-bench Verified score for this model to confirm at build.
- terminal_bench
- — verify-against-primary-at-build ↗ https://www.tbench.ai/ — Terminal-Bench score for this model to confirm at build.
- tau2_bench
- — verify-against-primary-at-build ↗ Primary tau2-Bench leaderboard — score for this model to confirm at build.
- bfcl_tool_use
- — verify-against-primary-at-build ↗ https://gorilla.cs.berkeley.edu/leaderboard.html — BFCL tool-use score for this model to confirm at build.
- aa_index
- — verify-against-primary-at-build ↗ https://artificialanalysis.ai/ — Intelligence Index for this model to confirm at build.
- lmarena_elo
- — verify-against-primary-at-build ↗ https://lmarena.ai/leaderboard — human-preference Elo for this model to confirm at build.
- tokens_per_sec
- — verify-against-primary-at-build ↗ https://artificialanalysis.ai/ — measured throughput for this model to confirm at build.
- ttft
- — verify-against-primary-at-build ↗ https://artificialanalysis.ai/ — measured time-to-first-token for this model to confirm at build.
- hallucination_rate
- — verify-against-primary-at-build ↗ No primary hallucination benchmark captured for this model in this pass.
- agent_readiness_score
- — verify-against-primary-at-build ↗ Score withheld: R_tool (BFCL/tau2-Bench), R_ctx (effective context), R_cost (cache rates) and R_latency inputs are not yet sourced. Compute per /models/agent-readiness-score once inputs confirmed.
- score_confidence
- partial
- source_url
- https://models.dev/models/openai/gpt-5.1-codex/
- source_type
- models.dev
- last_verified
- 2026-06-15