What is the specific context size of Github Copilot, is it only 128K?

[tlerbao]

Question

As the title says, I'm considering purchasing GitHub Copilot.

May I ask if GitHub Copilot's Claude model only has a 128K context size (whether used in VSCode or OpenCode)?

If it only has a 128K context, does that mean the model's capabilities are severely limited?

[github-actions]

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

• Is there a way to increase Context limit for Github Copilot Provider? #5993: Same question about GitHub Copilot context limit being capped at 128K tokens in OpenCode
• Github Copliot provider allows only 128k token conversations. #2317: Earlier report of GitHub Copilot provider only allowing 128K token conversations (closed with discussion)
• github copilot: 2x token (counts total=total+cached) compacts at 64k, instead of 128k #3314: Related bug about token counting causing compaction to trigger early at 64K instead of 128K

These issues cover the same underlying question about GitHub Copilot's context window limitations in OpenCode.

[jeroenev]

1. Github copilot has custom limits for different models, usually 128k but not always. 4o only has 64k, and some codex models get 272k, this is basically only visible in the model picker in the VScode extension of Copilot
2. This does impact the model, but less than you would think.
   Usually the performance degrades rapidly after about 100k - 120k context used. I have both an anthropic key and Copilot, and using Opus through both I find that I usually compact / restart sessions before 128k context is filled anyway

[tlerbao]

@jeroenev
I don't have a Copilot subscription, so I can only test the following two models. Haiku should have 200K, and GPT-5-mini should have 272K, but when I run /context in the Copilot CLI, both only show 160K. Could it be that they increased the context size? Is the maximum now 160K? Can you test what the total context size shows when running /context with Sonnet or Opus?

[jeroenev]

Seems like they increased the context recently, just 2 weeks ago this was 128k for most models:

[tlerbao]

@jeroenev May I ask which software this screenshot is from or where you saw it? Thank you.

[jeroenev]

That is in VS-code, in the Agent Chat panel from Github Copilot
Click the model selector -> More models -> Manage models

[tlerbao]

@jeroenev Thank you, this makes it more transparent. It seems the 1M model won't be available for Copilot pricing in the near future.

[hjnnjh]

Seems like they increased the context recently, just 2 weeks ago this was 128k for most models:

Will the context size in OpenCode be increased as well? I' m using OMO plugin, the auto compaction will be triggered frequently if the task is complex with 128K context size.

[TomLucidor]

Similar problem on OpenCode failing to "phone home" to check provider context size #16709

[d4rky-pl]

If you don't feel like waiting keep in mind the context size limit can be adjusted in opencode.json:

  "provider": {
    "github-copilot": {
      "models": {
        "claude-haiku-4.5": {
          "limit": { "context": 160000, "output": 32000 }
        },
        "claude-opus-4.5": {
          "limit": { "context": 160000, "output": 32000 }
        },
        "claude-opus-4.6": {
          "limit": { "context": 192000, "output": 64000 }
        },
        "claude-sonnet-4": {
          "limit": { "context": 144000, "output": 16000 }
        },
        "claude-sonnet-4.5": {
          "limit": { "context": 160000, "output": 32000 }
        },
        "claude-sonnet-4.6": {
          "limit": { "context": 160000, "output": 32000 }
        },
        "gemini-2.5-pro": {
          "limit": { "context": 173000, "output": 64000 }
        },
        "gemini-3-flash-preview": {
          "limit": { "context": 173000, "output": 64000 }
        },
        "gemini-3-pro-preview": {
          "limit": { "context": 173000, "output": 64000 }
        },
        "gemini-3.1-pro-preview": {
          "limit": { "context": 173000, "output": 64000 }
        },
        "gpt-4.1": {
          "limit": { "context": 128000, "output": 16384 }
        },
        "gpt-4o": {
          "limit": { "context": 68000, "output": 16384 }
        },
        "gpt-5-mini": {
          "limit": { "context": 192000, "output": 64000 }
        },
        "gpt-5.1": {
          "limit": { "context": 192000, "output": 64000 }
        },
        "gpt-5.1-codex": {
          "limit": { "context": 256000, "output": 128000 }
        },
        "gpt-5.1-codex-max": {
          "limit": { "context": 256000, "output": 128000 }
        },
        "gpt-5.1-codex-mini": {
          "limit": { "context": 256000, "output": 128000 }
        },
        "gpt-5.2": {
          "limit": { "context": 192000, "output": 64000 }
        },
        "gpt-5.2-codex": {
          "limit": { "context": 400000, "output": 128000 }
        },
        "grok-code-fast-1": {
          "limit": { "context": 173000, "output": 64000 }
        }
      }
    },

I give no guarantees this will work correctly and that the values are right, I just mapped what I saw in vscode and I'm dogfooding it right now.

[tlerbao]

@d4rky-pl Looking forward to the results of your test.