headroom/wiki/learn.md

Headroom Learn

Offline failure learning for coding agents. Analyzes past conversations, finds what went wrong, correlates it with what eventually worked, and writes specific project-level learnings that prevent the same mistakes next session.

Quick Start

# See recommendations for current project (dry-run, no changes)
headroom learn

# Write recommendations to CLAUDE.local.md (gitignored, personal default)
headroom learn --apply

# Write to the shared team file instead
headroom learn --apply --target CLAUDE.md

# Analyze a specific project
headroom learn --project ~/my-project --apply

# Analyze all projects
headroom learn --all --apply

How It Works

Past Sessions → Plugin → Analyzer → Writer → Agent-native context file
                  │           │          │
                  │           │          └─ Writes marker-delimited sections
                  │           │             (replaced on re-run, not duplicated)
                  │           │
                  │           └─ LLM-based analysis: finds failure patterns,
                  │              success correlations, and actionable rules
                  │
                  └─ Plugin reads agent-specific logs:
                     • Claude Code: ~/.claude/projects/*.jsonl
                     • Codex:       ~/.codex/sessions/*.json
                     • Gemini CLI:  ~/.gemini/tmp/*/chats/session-*.json

Success Correlation

The core innovation. Instead of cataloging failures ("Read failed 5 times"), Headroom finds what the model did to fix each failure:

• Failed: Read axion-formats/src/main/java/.../FirstClassEntity.java
• Then succeeded: Read axion-scala-common/src/main/scala/.../FirstClassEntity.scala
• Learning: "FirstClassEntity is at axion-scala-common/, not axion-formats/"

This produces specific, actionable corrections — not generic advice.

What It Learns

1. Environment Facts → CLAUDE.md

Which runtime commands work vs fail.

### Environment
- **Python**: use `uv run python` (not `python3` — modules not available outside venv)

2. File Path Corrections → CLAUDE.md

Wrong paths the model keeps guessing, with the correct locations.

### File Path Corrections
- `axion-common/src/.../AxionSparkConstants.scala`
  → actually at `axion-spark-common/src/.../AxionSparkConstants.scala`

3. Search Scope → CLAUDE.md

Which directories to search in (narrow paths fail, broader ones work).

### Search Scope
- Don't search `axion-model/` → use `axion/` (the repo root)

4. Command Patterns → CLAUDE.md

How commands should (and shouldn't) be run.

### Command Patterns
- **user_prefers_manual**: User rejected gradle 18 times — show the command, don't execute
- **python_runtime**: Use `uv run python` not `python3` (ModuleNotFoundError)

5. Known Large Files → CLAUDE.md

Files that need offset/limit with Read.

### Known Large Files
- `proxy/server.py` (~8000 lines) — always use offset/limit

6. Retry Prevention → MEMORY.md

Specific suggestions derived from actual corrections.

7. Permission Notes → MEMORY.md

Commands repeatedly rejected — model should suggest them to the user instead.

Where Learnings Go

Pattern	Claude Code	Codex	Gemini CLI
Environment, paths, commands	CLAUDE.local.md (default) or CLAUDE.md (with --target CLAUDE.md)	AGENTS.md	GEMINI.md
Retry patterns, permissions	MEMORY.md	instructions.md	GEMINI.md

Output files are agent-native: Claude Code writes to CLAUDE.local.md by default (gitignored, personal); pass --target CLAUDE.md for the shared team file. Codex uses AGENTS.md, Gemini uses GEMINI.md. The same learnings, written to the format each agent reads.

Marker-Based Updates

Headroom manages a clearly-delimited section in each file:

<!-- headroom:learn:start -->
## Headroom Learned Patterns
*Auto-generated by `headroom learn` — do not edit manually*
...
<!-- headroom:learn:end -->

On re-run, only the content between markers is replaced. Your existing file content is preserved.

Architecture (Plugin System)

Headroom Learn uses a plugin architecture where each agent is a self-contained plugin:

Plugin Registry (auto-discovered)
├── ClaudeCodePlugin  →  Analyzer (LLM)  →  ClaudeCodeWriter  →  CLAUDE.md / MEMORY.md
├── CodexPlugin       →  Analyzer (LLM)  →  CodexWriter       →  AGENTS.md / instructions.md
├── GeminiPlugin      →  Analyzer (LLM)  →  GeminiWriter      →  GEMINI.md
└── (your plugin)     →  Analyzer (LLM)  →  (your writer)     →  (your file)

Plugins bundle scanning, detection, and writing for one agent. Built-in plugins are auto-discovered from headroom.learn.plugins.*. External plugins register via the headroom.learn_plugin entry point.

The Analyzer is shared — it uses an LLM (Sonnet, GPT-4o, or Gemini Flash) to find patterns. Same analysis for any agent.

Adding Support for a New Agent

1. Create headroom/learn/plugins/myagent.py
2. Implement LearnPlugin + ConversationScanner (scanner + writer + detection)
3. Add plugin = MyAgentPlugin() at module scope
4. Done — headroom learn --agent myagent works automatically

Or install an external plugin: pip install headroom-learn-cursor (registers via entry point).

CLI Reference

headroom learn [OPTIONS]

Options:
  --project PATH               Project directory (default: current directory)
  --all                        Analyze all discovered projects (mutually exclusive with --project)
  --apply                      Write recommendations (default: dry-run)
  --target TEXT                Context file to write (default: CLAUDE.local.md for Claude Code)
  --main-only                  Write only to the main context file, skip MEMORY.md
  --agent [auto|claude|codex|gemini]
                               Which agent to analyze (default: auto-detect)
  --model TEXT                 LLM for analysis (default: auto from API keys or CLI)
  --workers / -j INTEGER       Parallel analysis workers (min 1, default: auto)
  --verbosity                  Analyze verbosity level instead of failure patterns
  --llm-judge                  Use an LLM to score verbosity quality (requires --verbosity)

Verbosity learning (--verbosity)

headroom learn --verbosity analyzes past sessions to infer the ideal output verbosity level for your project and writes a verbosity.json profile.

Important: the output shaper is off by default and requires the beta runtime rollout channel. Running --verbosity --apply will either:

• Hot-enable the output shaper on an eligible running proxy (POST /admin/runtime-env), OR
• Print instructions to set HEADROOM_ROLLOUT_CHANNEL=beta and HEADROOM_OUTPUT_SHAPER=1 before headroom wrap ...

To keep the shaper on across proxy restarts, export both variables before starting the proxy.

Flag interactions:

• --all and --project are mutually exclusive
• --llm-judge requires --verbosity
• --verbosity --all --apply is rejected (verbosity persists a single global level)

Supported Agents

Agent	Scanner	Writer	Output Files
Claude Code	Reads ~/.claude/projects/*.jsonl	ClaudeCodeWriter	CLAUDE.md, MEMORY.md
OpenAI Codex	Reads ~/.codex/sessions/*.json	CodexWriter	AGENTS.md, instructions.md
Gemini CLI	Reads ~/.gemini/tmp/*/chats/session-*.json	GeminiWriter	GEMINI.md

LLM Backend Selection

headroom learn needs an LLM to analyze your sessions. It picks one automatically using this priority:

Priority	Source	Example
1	--model flag	headroom learn --model gpt-4o
2	API key env var	ANTHROPIC_API_KEY, OPENAI_API_KEY, GEMINI_API_KEY
3	HEADROOM_LEARN_CLI env var	export HEADROOM_LEARN_CLI=gemini
4	Auto-detect installed CLIs	Checks PATH for claude, gemini, codex

Using without an API key

If you use Claude Code, Gemini CLI, or Codex via subscription (no raw API key), headroom learn can call them directly:

# Auto-detects claude in PATH — no API key needed
headroom learn

# Explicitly select a CLI backend
headroom learn --model gemini-cli

# Pin a CLI via environment variable
export HEADROOM_LEARN_CLI=codex
headroom learn

Valid values for HEADROOM_LEARN_CLI: claude, gemini, codex.

Real-World Results

Tested on 67,583 tool calls across 23 projects:

Metric	Value
Failure rate	7.5% (5,066 failures)
Corrections extracted	164 per project (avg)
Specific path corrections	22 (axion project)
Search scope corrections	24 (axion project)
Command patterns learned	5 (axion project)
Estimated preventable waste	~27 MB across corpus