GitHub Copilot CLI Slash Commands: Take Control of Long Sessions

GitHub shipped Copilot CLI v1.0.39 on April 28, adding four slash commands that solve the biggest problem with long agent sessions: running out of context window. If you have ever spent 90 minutes coding with an agent and watched it suddenly forget the early parts of the conversation, these commands are the fix.

The Four New Commands

All four are typed at the Copilot CLI prompt with a leading slash, and all four work in any active session. They are: /compact, /context, /usage, and /env.

/context — See How Much Window You Have Left

Type /context and Copilot CLI shows a visual breakdown of your current token usage: system overhead, conversation history, free space, and the buffer reserved for automatic context management. This is the first thing to check when you feel the agent getting forgetful.

/context

# Output:
# System / Tools:    8,500 tokens   (4%)
# Messages:         142,000 tokens  (71%)
# Free Space:        38,000 tokens  (19%)
# Buffer:            12,000 tokens   (6%)
# Total:            200,000 tokens

When messages hit roughly 80% of total, Copilot CLI starts compacting in the background. If /context shows you are already past 80% and the agent is acting drifty, do not wait for auto-compact. Run /compact yourself to clean things up before the next big request.

/compact — Free Up Window Space on Demand

Type /compact and Copilot CLI summarizes the older parts of your conversation, drops the original verbose history, and keeps only the summary plus the most recent few messages. You lose detail, but you gain back tens of thousands of tokens.

The smart use case is not waiting for it to fire automatically. Use /compact at planned breakpoints — right after you finish one feature and before you start the next. The summary preserves the high-level state without dragging every line of bash output and tool call into the next phase of work.

/usage — Track Your Premium Request Spend

GitHub's new token-billing model means premium model requests count against a quota. /usage shows how many premium requests you have used in the current session. Combine this with /context and you have the two numbers that actually matter when you are deciding whether to keep going or wrap up: how much window is left, and how much budget is left.

If you hit your quota mid-session, Copilot CLI falls back to the included model tier. The agent keeps working but loses some quality. /usage warns you before that switch happens.

/env — Show the Active Configuration

Type /env and Copilot CLI shows the environment variables and configuration values controlling the current session: the active model, permission mode, working directory, and any custom settings. Useful for debugging when the agent is behaving unexpectedly — most strange behavior turns out to be a config issue, not a model issue.

A Real Workflow Using These Together

Here is the pattern we now use on long Copilot CLI sessions:

# Start the session with /env to confirm config
> /env

# Work for 30-45 minutes on the first feature
> implement the new search endpoint
# ...agent does work...

# Before starting feature 2, compact and check
> /compact
> /context

# Work for another 30-45 minutes
> now add input validation to the search endpoint
# ...agent does work...

# Mid-session check on quota
> /usage

# Compact again before starting unrelated work
> /compact

The rhythm is: compact at natural breakpoints, check context before sensitive work, check usage before deciding to extend the session. Sessions that run for 3 to 4 hours stay coherent this way.

What These Commands Do Not Solve

These commands manage the conversation. They do not give the agent better long-term memory. If you close Copilot CLI, the next session starts fresh. For persistent context across sessions, you still need a separate mechanism — a project file the agent reads at startup, or a memory tool like the new Codex Chronicle feature.

Upgrade Path

If you are on Copilot CLI v1.0.38 or earlier, run npm update -g @github/copilot-cli to get the new version. Existing sessions started before the upgrade will not have the new commands available — you need to start a fresh session after upgrading.