claude-code - 💡(How to fix) Fix [FEATURE] Built-in token optimization: read caching, test output filtering, large file blocking [2 comments, 3 participants]

Preflight Checklist

• I have searched existing requests and this feature hasn't been requested yet
• This is a single feature request (not multiple features)

Problem Statement

Claude Code consumes tokens every time it reads a file, runs a test, or checks logs. In a typical coding session, I observed several wasteful patterns:

1. Redundant file reads: The same file gets read 3-5 times per session (before edit, after edit, during review, when referencing). Each re-read consumes tokens for identical content that Claude already has in context.

2. Verbose test output: Running pytest or jest produces 200+ lines of output (progress dots, warnings, capture logs, fixture setup), but Claude only needs the session start, failures, and summary to make decisions.

3. Unbounded log output: Commands like cat app.log or docker logs dump entire files into the context when the last 100 lines would suffice.

4. Large file consumption: Files with 1000+ lines get read in full even when Claude only needs a specific section, consuming massive amounts of tokens unnecessarily.

These patterns compound in longer sessions and lead to faster context exhaustion and higher token costs.

Proposed Solution

I built a set of 6 hook scripts that solve these problems using Claude Code's existing hook system. The hooks work transparently without changing how the user interacts with Claude Code:

Read caching (pre-read.sh + post-file-cache.sh):

• First read: passes through normally, caches a snapshot
• Re-read (unchanged): blocked entirely with "File unchanged" message
• Re-read (after edit): returns only the unified diff, not the full file

Test output filtering (pre-bash.sh + pre-bash.helper.filter.sh):

• Detects test commands (pytest, jest, vitest, Django test)
• Pipes output through an awk filter that extracts only: session start, collected count, failures, errors, and final summary
• 200+ lines become ~8 lines

Log output limiting (pre-bash.sh):

• Detects log commands without existing truncation (cat *.log, docker logs, journalctl)
• Automatically appends | tail -100

Large file blocking (pre-read.sh):

• Files over 1000 lines are blocked unless offset/limit is specified
• Forces targeted reads instead of full-file consumption

Compaction awareness (post-compact.sh + session-start.sh):

• Clears read cache after context compaction (since Claude loses detailed file content)
• Cleans up stale caches older than 7 days

I'd love to see some form of these optimizations built into Claude Code natively, or at minimum, included as an official example/recipe in the docs.

Alternative Solutions

I'm currently using these hooks via a standalone repository with a one-command installer:

Repository: https://github.com/soonswan-study/claude-code-thrifty

The installer symlinks hooks to ~/.claude/hooks/ and merges config into ~/.claude/settings.json. It works well but requires manual installation and jq as a dependency.

Session Lifecycle:

Read Cache Flow:

Test Output Filter:

Large File Protection:

Priority

Medium - Would be very helpful

Feature Category

Performance and speed

Use Case Example

Example scenario:

1. I'm working on a Django backend with 50+ files
2. I ask Claude to fix a bug in services/payment.py (400 lines)
3. Claude reads the file, edits it, then reads it again to verify — that's 800 lines of tokens for one read of identical content
4. I then ask Claude to run tests: pytest tests/test_payment.py -v which outputs 150 lines, but only 8 lines matter (collected count + 1 failure + summary)
5. With read caching, the second read is blocked (0 tokens). With test filtering, 150 lines become 8 lines
6. Over a 30-minute session with multiple files and test runs, this compounds to significant token savings

Additional Context

• Repository with full implementation: https://github.com/soonswan-study/claude-code-thrifty
• Detailed per-hook documentation: https://github.com/soonswan-study/claude-code-thrifty/blob/main/docs/HOOKS.md
• Requirements: jq for JSON parsing, bash 4.0+
• The hooks are session-scoped (each session gets its own cache directory), so parallel sessions don't interfere
• All hooks are non-invasive: partial reads (offset/limit), binary files, and first reads always pass through unchanged