GPT 5.2 Codex - Compaction happens way too early and context limit is wrong #11086

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1. Simplereally

   added

   bugSomething isn't workingSomething isn't working

   on Jan 29, 2026
2. github-actions

   assigned

   rekram1-node

   on Jan 29, 2026
3. github-actions

   added

   windows

   on Jan 29, 2026
4. github-actions commented on Jan 29, 2026

   

   github-actionsBot

   on Jan 29, 2026 – with GitHub Actions

   Contributor

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   This issue might be a duplicate of existing issues. Please check:

   • Default Codex context length not matching Pro plan #7705: Default Codex context length not matching Pro plan - Reports that GPT 5.2 Codex shows 400k but Pro plan actually has 250-260k, causing early compaction
   • GitHub Copilot GPT-5 throwing "invalid_request_body" on requests after compaction #10650: GitHub Copilot GPT-5 throwing "invalid_request_body" on requests after compaction - Reports context compaction failures with GitHub Copilot GPT-5
   • github copilot: 2x token (counts total=total+cached) compacts at 64k, instead of 128k #3314: github copilot: 2x token (counts total=total+cached) compacts at 64k, instead of 128k - Reports incorrect token counting and premature compaction with GitHub Copilot models
   • Compaction overflow check doesn't account for large tool outputs until the next step, causing context overflow #10634: Compaction overflow check doesn't account for large tool outputs until the next step, causing context overflow - Reports compaction being triggered too early due to incomplete overflow checks

   Feel free to ignore if none of these address your specific case.
5. Deftera186 commented on Jan 29, 2026

   

   Deftera186

   on Jan 29, 2026

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   This is probably related to a problem in models.dev that was fixed 2 weeks ago:
   anomalyco/models.dev@b0e5b91

   maybe you still have the old cache for some reason? try to remove your ~/.cache/opencode/models.json and update if it helps
6. Waishnav commented on Jan 29, 2026

   

   Waishnav

   on Jan 29, 2026

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   Yup, they have fixed this issue. It is working all fine
7. dlukt

   marked GPT-5.2 context limit for Github Copilot is too low #12247 as a duplicate of this issue on Feb 5, 2026
8. dlukt commented on Feb 5, 2026

   

   dlukt

   on Feb 5, 2026

   Last edited by dlukt

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   Nope. Deleting ~/.cache/opencode/models.json does not fix it.

   49,590  39% ($0.00)
   v1.1.51
   

   50k tokens and already 39% context used.

   grep github-copilot/gpt-5.2 ~/.cache/opencode/models.json
   

   No results.

   The search for github-copilot in this repo reveals no results either.

   How can you greatly announce your partnership when you don't even do the basics?
9. dlukt commented on Feb 5, 2026

   

   dlukt

   on Feb 5, 2026

   Last edited by dlukt

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   The issue is most likely because you source https://models.dev/api.json
   which incorrectly states the limits for context and output to 128k and 64k

   I'm letting OpenAI/gpt-5.2 now fix this issue and will send a PR
10. dlukt commented on Feb 5, 2026

    

    dlukt

    on Feb 5, 2026

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    "provider": {
        "github-copilot": {
          "models": {
            "gpt-5.2": {
              "limit": {
                "context": 400000,
                "input": 272000,
                "output": 128000
              }
            },
            "gpt-5.2-codex": {
              "limit": {
                "context": 400000,
                "input": 272000,
                "output": 128000
              }
            }
          }
        },
        "github-copilot-enterprise": {
          "models": {
            "gpt-5.2": {
              "limit": {
                "context": 400000,
                "input": 272000,
                "output": 128000
              }
            },
            "gpt-5.2-codex": {
              "limit": {
                "context": 400000,
                "input": 272000,
                "output": 128000
              }
            }
          }
        }
      }
    }
    
11. lightsofapollo

    added a commit that references this issue on Feb 10, 2026

    test(compaction): add failing tests for missing headroom when limit.i…

    ...

    ce54d70
12. github-actions commented on Apr 7, 2026

    

    github-actionsBot

    on Apr 7, 2026 – with GitHub Actions

    Contributor

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    To stay organized issues are automatically closed after 90 days of no activity. If the issue is still relevant please open a new one.
13. github-actions

    closed this as completedon Apr 7, 2026