Context Mode Skill

Fix the two session killers that end most Claude Code sessions in under 30 minutes: context bloat from raw command output, and memory loss after a reset.

Context Mode runs three systems simultaneously to keep sessions alive:

Output Filtering — strips verbose command output before it enters context
Session Log — writes a running log of everything that happened
Auto-Resume — reads the log on reset and picks up exactly where you left off

Credit: Inspired by a skill from Nate Herk's YouTube channel — adapted and extended for this library.

Required Inputs

No inputs required. Context Mode activates on command.

Optional: user can specify a custom log file path if they don't want session.log in the project root.

How Context Mode Works

Part 1 — Output Filtering

The problem: every time Claude Code runs a command, the full raw output enters the context window. A single npm install can dump hundreds of lines. A test suite run? Thousands. Within 30 minutes, the context is full of noise and Claude resets.

The fix: before any command output enters context, filter it to the useful summary only.

What gets kept:

Last 10 lines of stdout
Every line containing error, warn, fail, exception, traceback, or fatal (case-insensitive)
The exit code
A one-line summary of what the command did and whether it succeeded

What gets discarded:

Middle section of long stdout (replaced with [... N lines of output truncated ...])
Progress bars, download indicators, verbose install logs
Repeated identical lines (deduplicated)

Filtering summary format:

COMMAND: [command run]
STATUS:  [exit code — success / failed]
SUMMARY: [one sentence: what happened]
ERRORS:  [any error/warn lines — or "none"]
TAIL:    [last 10 lines of stdout]

Part 2 — Session Log

Claude maintains a running log file at [project root]/session.log. This file is written after every significant action and is the source of truth for resuming after a reset.

Session log format:

SESSION LOG
===========
Started:    [timestamp]
Branch:     [current git branch]
Directory:  [working directory]

FILES EDITED
────────────
[timestamp] [file path] — [one-line description of what changed]

COMMANDS RUN
────────────
[timestamp] [command] — [outcome: success / failed — brief reason]

TASKS IN PROGRESS
─────────────────
[ ] [Task description — what's been done so far and what's left]
[x] [Completed task]

LAST USER PROMPT
────────────────
[The most recent instruction from the user, verbatim]

LAST ACTION TAKEN
─────────────────
[What Claude did last, in one sentence]

Log update rules:

Write to session.log after every file edit
Write to session.log after every command run
Update "Tasks in Progress" when a task is started, progressed, or completed
Always overwrite "Last User Prompt" and "Last Action Taken" with the current values — don't append, replace

Part 3 — Resume on Reset

When a new Claude session starts, the first action is:

Check for session.log in the project root
If found, read it and announce the resume:

Resuming session.

Branch:          [branch]
Last working on: [last task in progress]
Files edited:    [list from session log]
Tasks pending:   [incomplete tasks]
Last prompt:     "[last user prompt]"

Continuing from where we left off.

Continue with the next logical step — don't ask "what should I do?" — check the task list and carry on

If no session.log exists, start fresh and initialise the log.

Activation Response

When the user triggers Context Mode, respond with:

Context Mode active.

Session log initialised at: [absolute path to session.log]
Output filtering:           enabled
Auto-resume:                enabled

I'll maintain your session state across resets. Long sessions won't lose context.

Then immediately initialise session.log with the current timestamp, branch, and directory.

Output Structure

On activation

Context Mode active.
Session log initialised at: [path]
Output filtering: enabled
Auto-resume: enabled
I'll maintain your session state across resets. Long sessions won't lose context.

On command execution (filtered output format)

COMMAND: npm test
STATUS:  exit 1 — failed
SUMMARY: 47 tests passed, 3 failed in auth.test.ts
ERRORS:  Error: Expected 200, received 401 (line 84)
         Error: Token not found in response (line 112)
TAIL:
  ✓ login with valid credentials (23ms)
  ✓ logout clears session (11ms)
  ✗ refresh token after expiry
  ...

On reset / new session (resume announcement)

Resuming session.

Branch:          feature/auth-refresh
Last working on: Fixing token refresh logic in auth.service.ts
Files edited:    src/auth/auth.service.ts, src/auth/auth.test.ts
Tasks pending:   [ ] Fix failing test on line 112
                 [ ] Run full test suite once fix is applied
Last prompt:     "The refresh token test is still failing — look at the 401 handling"

Continuing from where we left off.

CLAUDE.md Installation Text

After activating Context Mode for the session, provide the user with the exact text to add to their CLAUDE.md to make it permanent across all sessions:

```
## Context Mode

Context Mode is always active in this project.

### Output Filtering
Before any command output enters context, filter it to:
- Last 10 lines of stdout
- Any lines containing: error, warn, fail, exception, traceback, fatal (case-insensitive)
- Exit code
- One-line summary of what the command did

Use this format for filtered output:
COMMAND: [command]
STATUS:  [exit code — success/failed]
SUMMARY: [one sentence]
ERRORS:  [error lines or "none"]
TAIL:    [last 10 lines]

### Session Log
Maintain a running session log at ./session.log. Write to it after every file edit and every command run. Track: files edited, commands run, tasks in progress, last user prompt, last action taken. Format defined in Context Mode skill.

### Auto-Resume
At the start of every new session, check for ./session.log. If it exists, read it and announce the resume state. Continue from the last task in progress without asking for instructions.
```

Tell the user: "Add this to your CLAUDE.md and Context Mode will be active permanently for this project — even after you close and reopen the session."

Quality Checks

session.log was initialised immediately on activation (not deferred)
Log path shown to user is the absolute path, not relative
Output filtering is applied on the very next command run — not just announced
Filtered output format includes: command, status, summary, errors, and tail — all five fields
Session log tracks all four categories: files edited, commands run, tasks in progress, last prompt
Resume announcement reads the actual log contents — not a generic template
On resume, Claude continues the work without prompting the user for instructions
CLAUDE.md installation text was offered after activation
Log update rule is clear: "Last User Prompt" and "Last Action Taken" replace previous values, not append

Example Trigger Phrases

"Enable context mode"
"Turn on context mode for this session"
"Activate long session mode"
"I keep losing context — fix it"
"Set up session logging"
"Keep track of what you've done so you can resume after a reset"
"Enable output filtering to save context"
"Set up auto-resume so we don't lose our place"

Context Mode