CLI not able to work with very large files - RangeError: Invalid string length

[jannikkraemer]

Describe the bug

Bug: Copilot CLI crashes with RangeError: Invalid string length when scanning large files

Describe the bug

Problem

When asking GitHub Copilot CLI to create a plan (no code changes requested), the CLI begins scanning project context and appears to attempt reading a very large .json file (~500+ MB).
During this scan, Copilot enters a failure loop and repeatedly prints:

RangeError: Invalid string length

The command never completes and the terminal becomes partially unresponsive due to the continuous error spam.

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Actual Behavior

• Copilot attempts to load the entire large JSON file into memory.
• The CLI loops with RangeError: Invalid string length.
• Error repeats indefinitely.
• No timeout or graceful abort.
• The terminal becomes partially unresponsive until restarted or task is aborted with Ctrl + c.

Affected version

0.0.365 Commit: 76d0881

Steps to reproduce the behavior

Steps to Reproduce

1. Run a Copilot CLI request similar to:

   Okay, the current script is only fetching data up to which date? How can I also get the November data? Right now, it has all projects cached, and I want to avoid the following:
   1. Re-running the script from scratch (it takes days)
   2. Losing any historic data (I fetched the last 12 months, but I would like to keep all that data and, from now on, only fetch the missing recent data).
   
   Don’t start working on anything yet — instead, create a plan with ideas that I can refine with you first.
   

2. Copilot starts collecting context:

   ✔ Glob "fetch_historic_data/**/*.go"
     └ No matches found
   ✔ Read fetch_historic.sh
     └ 63 lines read
   ✔ Read cache_status.sh
     └ 154 lines read
   ✔ Grep "AddDate"
     └ 12 lines found
   ✔ Read main.go:2300–2420
     └ 126 lines read
   ✔ Grep "cache/monthly"
     └ 1 line found
   ○ Grep "monthly"
   

3. Copilot attempts to read a very large JSON file (>500 MB).

4. The CLI enters a repeated error loop:

   ✘ RangeError: Invalid string length
   ✘ RangeError: Invalid string length
   ✘ RangeError: Invalid string length
   ...
   

Expected behavior

Expected Behavior

• Copilot should ignore extremely large non-code files (e.g., >50 MB),
  or
• limit the amount of context scanned,
  or
• fail once with a clear, actionable error message instead of looping.

Additional context

Additional Context

• The .json file is not relevant to the AI task but lives in a project subdirectory.
• The Copilot CLI currently has no mechanism to exclude or size-limit context scanning.

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Copilot CLI Version

0.0.365
Commit: 76d0881

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Environment

• OS: macOS
• Machine: Apple M4 Pro, 24 GB RAM
• Terminal: macOS built-in Terminal
• Project: Go-based hobby project with a cache/ directory containing large JSON files
• Largest file: ~500+ MB .json