NLP Lineage

12 November 2025 · Reasoning

GPT-5.1

GPT-5.1

OpenAI

Date
12 November 2025
What the date marks
Model release
Kind
Model
Organisation
OpenAI
Access
API only
Other dates
Codex-Max 2025-11-19
Threads
In the guided tour
Chapter 14. Where the threads meet now
Learning phases
3. API usage and prompting

A milestone: 1 later milestone descends directly from it, and its descendants reach 2 of the 10 threads. How levels are decided

Figures quoted here are reported by the organisation that built it, not independently verified.

Read the primary source (openai.com)

Full summary in progress. Until then, this page shows the milestone's record from the research data.

What it changed

Before it

GPT-5's router applied a fixed reasoning policy.

The problem

Reasoning effort should track problem difficulty more finely than a router decides.

What it introduced

Adaptive reasoning effort and a coding-specialised Codex-Max variant.

Why it matters

Part of the shift to rapid point releases as the competitive cadence.

What modern models inherit

Monthly-cadence frontier updates.

What came next

GPT-5.2 a month later, then the 2026 series.

Before and after

The milestones it descends from, and the milestones that descend from it. Work developed alongside it is not counted. Weak links are left out unless you include them.

Before: where it came from

GPT-5.1 has 44 documented ancestors across 11 chapters, reaching back to Recurrent networks in 1990. Showing its direct parents and the 18 turning points among them.

GPT-5.1 has 44 documented ancestors across 11 chapters, reaching back to Recurrent networks in 1990. Showing all of them.

GPT-5.1 has 57 recorded ancestors, including indirect ones, across 11 chapters, reaching back to Recurrent networks in 1990. Showing its direct parents and the 18 turning points among them.

GPT-5.1 has 57 recorded ancestors, including indirect ones, across 11 chapters, reaching back to Recurrent networks in 1990. Showing all of them.

  1. 2025GPT-5.1This milestone.
  2. 2025GPT-5GPT-5.1 built directly on thisChapter 14. Where the threads meet now
  3. 2025o3 releasedGPT-5 built directly on thisChapter 12. Thinking longer
  4. 2024o3 announcedo3 released succeeded thisChapter 12. Thinking longer
  5. 2024o1 Turning pointo3 released built directly on thisChapter 12. Thinking longer
  6. 2024GPT-4oGPT-5 succeeded thisChapter 11. Seeing and hearing
  7. 2023GPT-4VGPT-4o built directly on thisChapter 11. Seeing and hearing
  8. 2023Function callingo3 released was influenced by thisChapter 13. Models that act
  9. 2023GPT-4 Turning pointGPT-4o built directly on thisChapter 7. The assistant goes public
  10. 2022GPT-3.5 Turning pointGPT-4 succeeded thisChapter 7. The assistant goes public
  11. 2022InstructGPT Turning pointGPT-4 built directly on thisChapter 6. Teaching models what people want
  12. 2022Chain of thought Turning pointo1 was influenced by thisChapter 12. Thinking longer
  13. 2021FLANInstructGPT was influenced by thisChapter 6. Teaching models what people want
  14. 2020RLHF for summarisation Turning pointInstructGPT built directly on thisChapter 6. Teaching models what people want
  15. 2020GPT-3 Turning pointChain of thought was influenced by this
    InstructGPT built directly on this
    GPT-3.5 built directly on this    Chapter 5. Scale becomes a science
  16. 2020Scaling laws Turning pointGPT-4 built directly on thisChapter 5. Scale becomes a science
  17. 2019T5 Turning pointFLAN was influenced by thisChapter 4. Pretrain once, use everywhere
  18. 2019C4 Turning pointT5 was influenced by thisChapter 4. Pretrain once, use everywhere
  19. 2019RLHF for LMsRLHF for summarisation built directly on thisChapter 6. Teaching models what people want
  20. 2019Sparse Transformer Turning pointGPT-3 built directly on thisChapter 4. Pretrain once, use everywhere
  21. 2019GPT-2 Turning pointScaling laws was influenced by thisChapter 4. Pretrain once, use everywhere
  22. 2019WebTextGPT-2 was influenced by thisChapter 4. Pretrain once, use everywhere
  23. 2018BERT Turning pointT5 was influenced by thisChapter 4. Pretrain once, use everywhere
  24. 2018SentencePieceT5 built directly on thisChapter 4. Pretrain once, use everywhere
  25. 2018GPT-1GPT-2 built directly on thisChapter 4. Pretrain once, use everywhere
  26. 2018ELMoBERT was influenced by thisChapter 4. Pretrain once, use everywhere
  27. 2018ULMFiTBERT was influenced by thisChapter 4. Pretrain once, use everywhere
  28. 2017CoVeELMo was influenced by thisChapter 3. Attention, then only attention
  29. 2017Transformer Turning pointScaling laws built directly on thisChapter 3. Attention, then only attention
  30. 2017RLHF originRLHF for summarisation built directly on thisChapter 6. Teaching models what people want
  31. 2016Layer normTransformer built directly on this
    GPT-2 built directly on this    Chapter 3. Attention, then only attention
  32. 2015Residual connectionsTransformer was influenced by thisChapter 3. Attention, then only attention
  33. 2015LM pretraining Turning pointGPT-1 was influenced by thisChapter 2. Words become vectors
  34. 2015BPE tokenizationGPT-2 built directly on thisChapter 2. Words become vectors
  35. 2015Luong attentionTransformer was influenced by thisChapter 3. Attention, then only attention
  36. 2014AdamTransformer was influenced by thisChapter 2. Words become vectors
  37. 2014GloVeELMo built directly on thisChapter 2. Words become vectors
  38. 2014Seq2seq Turning pointTransformer built directly on thisChapter 2. Words become vectors
  39. 2014Attention Turning pointTransformer built directly on thisChapter 3. Attention, then only attention
  40. 2014GRU / encoder-decoderAttention built directly on thisChapter 2. Words become vectors
  41. 2013word2vecELMo was influenced by thisChapter 2. Words become vectors
  42. 2011NLP from scratchELMo was influenced by thisChapter 1. Language as probability
  43. 2003Neural LMNLP from scratch was influenced by this
    word2vec was influenced by this    Chapter 1. Language as probability
  44. 1997LSTM Turning pointSeq2seq built directly on thisChapter 1. Language as probability
  45. 1990Recurrent networksLSTM was influenced by thisChapter 1. Language as probability
  1. 2025GPT-5.1This milestone.
  2. 2025GPT-5GPT-5.1 built directly on thisChapter 14. Where the threads meet now
  3. 2025o3 releasedGPT-5 built directly on thisChapter 12. Thinking longer
  4. 2024o3 announcedo3 released succeeded thisChapter 12. Thinking longer
  5. 2024o1 Turning pointo3 released built directly on thisChapter 12. Thinking longer
  6. 2024Test-time computeo3 announced was influenced by this (indirect influence)Chapter 12. Thinking longer
  7. 2024GPT-4oGPT-5 succeeded thisChapter 11. Seeing and hearing
  8. 2023GPT-4VGPT-4o built directly on thisChapter 11. Seeing and hearing
  9. 2023Function callingo3 released was influenced by thisChapter 13. Models that act
  10. 2023Process supervisiono1 was influenced by this (indirect influence)Chapter 12. Thinking longer
  11. 2023Tree of thoughtsTest-time compute was influenced by this (indirect influence)Chapter 12. Thinking longer
  12. 2023GPT-4 Turning pointGPT-4o built directly on thisChapter 7. The assistant goes public
  13. 2023ToolformerFunction calling was influenced by this (indirect influence)Chapter 13. Models that act
  14. 2022GPT-3.5 Turning pointGPT-4 succeeded thisChapter 7. The assistant goes public
  15. 2022ReActFunction calling was influenced by this (indirect influence)Chapter 13. Models that act
  16. 2022WhisperGPT-4o was influenced by this (indirect influence)Chapter 11. Seeing and hearing
  17. 2022STaRo1 was influenced by this (indirect influence)Chapter 12. Thinking longer
  18. 2022Self-consistencyTest-time compute built directly on thisChapter 12. Thinking longer
  19. 2022InstructGPT Turning pointGPT-4 built directly on thisChapter 6. Teaching models what people want
  20. 2022Chain of thought Turning pointo1 was influenced by thisChapter 12. Thinking longer
  21. 2021WebGPTReAct was influenced by this
    Toolformer was influenced by this    Chapter 13. Models that act
  22. 2021FLANInstructGPT was influenced by thisChapter 6. Teaching models what people want
  23. 2021CLIPGPT-4V was influenced by this (indirect influence)Chapter 11. Seeing and hearing
  24. 2020Vision TransformerCLIP built directly on thisChapter 11. Seeing and hearing
  25. 2020RLHF for summarisation Turning pointInstructGPT built directly on thisChapter 6. Teaching models what people want
  26. 2020GPT-3 Turning pointChain of thought was influenced by this
    InstructGPT built directly on this
    GPT-3.5 built directly on this    Chapter 5. Scale becomes a science
  27. 2020Scaling laws Turning pointGPT-4 built directly on thisChapter 5. Scale becomes a science
  28. 2019T5 Turning pointFLAN was influenced by thisChapter 4. Pretrain once, use everywhere
  29. 2019C4 Turning pointT5 was influenced by thisChapter 4. Pretrain once, use everywhere
  30. 2019RLHF for LMsRLHF for summarisation built directly on thisChapter 6. Teaching models what people want
  31. 2019Sparse Transformer Turning pointGPT-3 built directly on thisChapter 4. Pretrain once, use everywhere
  32. 2019GPT-2 Turning pointScaling laws was influenced by this
    CLIP built directly on this    Chapter 4. Pretrain once, use everywhere
  33. 2019WebTextGPT-2 was influenced by thisChapter 4. Pretrain once, use everywhere
  34. 2019Transformer-XLSparse Transformer was influenced by this (indirect influence)Chapter 4. Pretrain once, use everywhere
  35. 2018BERT Turning pointVision Transformer was influenced by thisChapter 4. Pretrain once, use everywhere
  36. 2018SentencePieceT5 built directly on thisChapter 4. Pretrain once, use everywhere
  37. 2018GPT-1GPT-2 built directly on thisChapter 4. Pretrain once, use everywhere
  38. 2018ELMoBERT was influenced by this
    GPT-1 was influenced by this (indirect influence)    Chapter 4. Pretrain once, use everywhere
  39. 2018ULMFiTBERT was influenced by this
    GPT-1 was influenced by this (indirect influence)    Chapter 4. Pretrain once, use everywhere
  40. 2017CoVeELMo was influenced by thisChapter 3. Attention, then only attention
  41. 2017RLHF origino1 was influenced by this (indirect influence)Chapter 6. Teaching models what people want
  42. 2017Transformer Turning pointWhisper built directly on thisChapter 3. Attention, then only attention
  43. 2017ConvS2STransformer was influenced by this (indirect influence)Chapter 3. Attention, then only attention
  44. 2016Layer normTransformer built directly on thisChapter 3. Attention, then only attention
  45. 2015Residual connectionsTransformer was influenced by thisChapter 3. Attention, then only attention
  46. 2015LM pretraining Turning pointBERT was influenced by this
    GPT-1 was influenced by this    Chapter 2. Words become vectors
  47. 2015BPE tokenizationGPT-2 built directly on thisChapter 2. Words become vectors
  48. 2015Luong attentionTransformer was influenced by thisChapter 3. Attention, then only attention
  49. 2014AdamTransformer was influenced by thisChapter 2. Words become vectors
  50. 2014GloVeELMo built directly on thisChapter 2. Words become vectors
  51. 2014Seq2seq Turning pointTransformer built directly on thisChapter 2. Words become vectors
  52. 2014Attention Turning pointTransformer built directly on thisChapter 3. Attention, then only attention
  53. 2014GRU / encoder-decoderAttention built directly on thisChapter 2. Words become vectors
  54. 2013word2vecELMo was influenced by thisChapter 2. Words become vectors
  55. 2011NLP from scratchELMo was influenced by thisChapter 1. Language as probability
  56. 2003Neural LMNLP from scratch was influenced by this
    word2vec was influenced by this    Chapter 1. Language as probability
  57. 1997LSTM Turning pointSeq2seq built directly on thisChapter 1. Language as probability
  58. 1990Recurrent networksLSTM was influenced by thisChapter 1. Language as probability

After: what it led to

GPT-5.1 has 5 documented descendants across 2 chapters, reaching forward to GPT-5.6 Sol in 2026. Showing its direct descendants.

GPT-5.1 has 5 documented descendants across 2 chapters, reaching forward to GPT-5.6 Sol in 2026. Showing all of them.

GPT-5.1 has 5 recorded descendants, including indirect ones, across 2 chapters, reaching forward to GPT-5.6 Sol in 2026. Showing its direct descendants.

GPT-5.1 has 5 recorded descendants, including indirect ones, across 2 chapters, reaching forward to GPT-5.6 Sol in 2026. Showing all of them.

  1. 2025GPT-5.1This milestone.
  2. 2025GPT-5.2built directly on GPT-5.1Chapter 14. Where the threads meet now
  3. 2026GPT-5.3-Codexbuilt directly on GPT-5.2Chapter 13. Models that act
  4. 2026GPT-5.4built directly on GPT-5.3-CodexChapter 14. Where the threads meet now
  5. 2026GPT-5.5built directly on GPT-5.4Chapter 14. Where the threads meet now
  6. 2026GPT-5.6 Solbuilt directly on GPT-5.5Chapter 14. Where the threads meet now
  1. 2025GPT-5.1This milestone.
  2. 2025GPT-5.2built directly on GPT-5.1Chapter 14. Where the threads meet now
  3. 2026GPT-5.3-Codexbuilt directly on GPT-5.2Chapter 13. Models that act
  4. 2026GPT-5.4built directly on GPT-5.3-CodexChapter 14. Where the threads meet now
  5. 2026GPT-5.5built directly on GPT-5.4Chapter 14. Where the threads meet now
  6. 2026GPT-5.6 Solbuilt directly on GPT-5.5Chapter 14. Where the threads meet now

Direct links and their sources

Where it came from

Built directly on

What it led to

Built on directly by