Cost Tracking
affaan-m/ECC
Track and report Claude Code token usage, spending, and budgets from the local ECC cost-tracker metrics log.
CRITICAL: Use for generics, traits, zero-cost abstraction. An agent skill from fjrevoredo/mini-diarium.
MITAuto-check passed
Install M04 Zero Cost
$ npx skills add fjrevoredo/mini-diarium --skill m04-zero-cost -a claude-codeProject install by default; add -g for ~/.claude/skills/.
$ gh skill install fjrevoredo/mini-diarium m04-zero-cost --agent claude-codeProject scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).
$ git clone --depth 1 https://github.com/fjrevoredo/mini-diarium.git skills-src && mkdir -p .claude/skills && cp -r skills-src/.agents/skills/m04-zero-cost .claude/skills/m04-zero-cost && rm -rf skills-srcUse ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.
Claude Code skills documentation · loads skills from .claude/skills/
Install the "m04-zero-cost" agent skill from https://github.com/fjrevoredo/mini-diarium/tree/master/.agents/skills/m04-zero-cost into .claude/skills/m04-zero-cost/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "m04-zero-cost", then confirm the skill loads.Claude Code copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$skill-installer install https://github.com/fjrevoredo/mini-diarium/tree/master/.agents/skills/m04-zero-costType this inside Codex. $skill-installer <name> installs a curated skill from openai/skills. The installer writes to $CODEX_HOME/skills (default ~/.codex/skills). Restart Codex if the skill does not show up.
$ npx skills add fjrevoredo/mini-diarium --skill m04-zero-cost -a codexProject install goes to .agents/skills/; add -g for ~/.codex/skills/.
$ gh skill install fjrevoredo/mini-diarium m04-zero-cost --agent codexProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/fjrevoredo/mini-diarium.git skills-src && mkdir -p .agents/skills && cp -r skills-src/.agents/skills/m04-zero-cost .agents/skills/m04-zero-cost && rm -rf skills-srcUse ~/.agents/skills/ instead of .agents/skills for a personal install.
Codex skills documentation · loads skills from .agents/skills/
Install the "m04-zero-cost" agent skill from https://github.com/fjrevoredo/mini-diarium/tree/master/.agents/skills/m04-zero-cost into .agents/skills/m04-zero-cost/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "m04-zero-cost", then confirm the skill loads.Codex copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ npx skills add fjrevoredo/mini-diarium --skill m04-zero-cost -a cursorProject install goes to .agents/skills/; add -g for ~/.cursor/skills/.
$ gh skill install fjrevoredo/mini-diarium m04-zero-cost --agent cursorProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/fjrevoredo/mini-diarium.git skills-src && mkdir -p .cursor/skills && cp -r skills-src/.agents/skills/m04-zero-cost .cursor/skills/m04-zero-cost && rm -rf skills-srcUse ~/.cursor/skills/ instead of .cursor/skills for a personal install.
Cursor skills documentation · loads skills from .cursor/skills/, .agents/skills/, .claude/skills/, .codex/skills/
Install the "m04-zero-cost" agent skill from https://github.com/fjrevoredo/mini-diarium/tree/master/.agents/skills/m04-zero-cost into .cursor/skills/m04-zero-cost/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "m04-zero-cost", then confirm the skill loads.Cursor copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ gemini skills install https://github.com/fjrevoredo/mini-diarium.git --path .agents/skills/m04-zero-cost--scope user (default) or --scope workspace; --path is the subfolder of the repo that holds the skill; --consent skips the security confirmation prompt.
$ npx skills add fjrevoredo/mini-diarium --skill m04-zero-cost -a gemini-cliProject install goes to .agents/skills/; add -g for ~/.gemini/skills/.
$ gh skill install fjrevoredo/mini-diarium m04-zero-cost --agent gemini-cliProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/fjrevoredo/mini-diarium.git skills-src && mkdir -p .gemini/skills && cp -r skills-src/.agents/skills/m04-zero-cost .gemini/skills/m04-zero-cost && rm -rf skills-srcUse ~/.gemini/skills/ instead of .gemini/skills for a personal install, then run /skills reload.
Gemini CLI skills documentation · loads skills from .gemini/skills/, .agents/skills/
Install the "m04-zero-cost" agent skill from https://github.com/fjrevoredo/mini-diarium/tree/master/.agents/skills/m04-zero-cost into .gemini/skills/m04-zero-cost/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "m04-zero-cost", then confirm the skill loads.Gemini CLI copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ gh skill install fjrevoredo/mini-diarium m04-zero-costInstalls for Copilot at project scope by default; add --scope user for a personal install. Preview a skill first with gh skill preview. Needs GitHub CLI 2.90.0 or later (public preview).
$ npx skills add fjrevoredo/mini-diarium --skill m04-zero-cost -a github-copilotProject install goes to .agents/skills/; add -g for ~/.copilot/skills/.
$ git clone --depth 1 https://github.com/fjrevoredo/mini-diarium.git skills-src && mkdir -p .github/skills && cp -r skills-src/.agents/skills/m04-zero-cost .github/skills/m04-zero-cost && rm -rf skills-srcUse ~/.copilot/skills/ instead of .github/skills for a personal install. Commit .github/skills so cloud agent and code review can use it.
GitHub Copilot skills documentation · loads skills from .github/skills/, .claude/skills/, .agents/skills/
Install the "m04-zero-cost" agent skill from https://github.com/fjrevoredo/mini-diarium/tree/master/.agents/skills/m04-zero-cost into .github/skills/m04-zero-cost/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "m04-zero-cost", then confirm the skill loads.GitHub Copilot copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ npx skills add fjrevoredo/mini-diarium --skill m04-zero-cost -a opencodeOpenCode documents no install command of its own. Project install goes to .agents/skills/; add -g for ~/.config/opencode/skills/.
$ gh skill install fjrevoredo/mini-diarium m04-zero-cost --agent opencodeProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/fjrevoredo/mini-diarium.git skills-src && mkdir -p .opencode/skills && cp -r skills-src/.agents/skills/m04-zero-cost .opencode/skills/m04-zero-cost && rm -rf skills-srcUse ~/.config/opencode/skills/ instead of .opencode/skills for a personal install.
OpenCode skills documentation · loads skills from .opencode/skills/, .claude/skills/, .agents/skills/
Install the "m04-zero-cost" agent skill from https://github.com/fjrevoredo/mini-diarium/tree/master/.agents/skills/m04-zero-cost into .opencode/skills/m04-zero-cost/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "m04-zero-cost", then confirm the skill loads.OpenCode copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
Facts
- Skill name
m04-zero-cost- GitHub stars
- 308
- Used in
- 1 other repo
- Token cost
- ~1.2k tokens
- SKILL.md length
- 378 words
- Files
- 1
- Skills in repo
- 41
- Repo updated
- First seen
- Licence
- MIT
At a glance
CRITICAL: Use for generics, traits, zero-cost abstraction. An agent skill from fjrevoredo/mini-diarium.
- Works in 3 steps: What abstraction is needed? → When is type known? → What's the trade-off priority?
- Zero-cost abstraction
- SKILL.md covers Core Question, Error → Design Question, Thinking Prompt and Trace Up ↑, plus 8 more sections
- Instructions only: no scripts, shell commands, URLs or credentials in SKILL.md
What it does
M04 Zero Cost is an agent skill from fjrevoredo/mini-diarium. CRITICAL: Use for generics, traits, zero-cost abstraction. Triggers: E0277, E0308, E0599, generic, trait, impl, dyn, where, monomorphization, static dispatch, dynamic dispatch, impl Trait, trait bound not satisfied, 泛型, 特征, 零成本抽象, 单态化
Its SKILL.md is about 1.2k tokens, which your agent loads only when the skill is triggered. It is a single SKILL.md file with no bundled scripts.
The repository describes itself as: A local-only journal with serious encryption. Free, open source, and never touches the internet. The licence is MIT.
When your agent uses it
- Zero-cost abstraction
Example prompts
- “/m04-zero-cost”
Workflow steps
3 steps, taken from the first numbered list in SKILL.md.
- What abstraction is needed?
- When is type known?
- What's the trade-off priority?
What it can do on your machine
Read from SKILL.md and the folder at commit 3ddc537. It shows what the files ask for, not the result of running them.
Tool permissions
Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.
From allowed-tools in the SKILL.md frontmatter.
Runs code
No scripts in the folder and no shell commands in SKILL.md (its code samples are rust).
From the folder's file list and the shell code blocks in SKILL.md.
Network
No URLs in SKILL.md.
From URLs in SKILL.md, links to its own repository left out.
Credentials
Names no API keys, tokens, secrets or passwords.
From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.
Context cost
M04 Zero Cost loads about 1.2k tokens when it runs. Until then it costs about 62 tokens; SKILL.md has 378 words of instructions outside code blocks.
Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.
Safety
Auto-check passed
The automated check found no risky patterns in SKILL.md.
Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.
SKILL.md
The full file from fjrevoredo/mini-diarium at commit 3ddc537, republished under its MIT licence (© fjrevoredo). 378 words, ~1,164 tokens.
Download SKILL.mdSave it as
.claude/skills/m04-zero-cost/SKILL.md (or your agent's skills folder).- name
- m04-zero-cost
- description
- CRITICAL: Use for generics, traits, zero-cost abstraction. Triggers: E0277, E0308, E0599, generic, trait, impl, dyn, where, monomorphization, static dispatch, dynamic dispatch, impl Trait, trait bound not satisfied, 泛型, 特征, 零成本抽象, 单态化
- user-invocable
- false
Zero-Cost Abstraction
Layer 1: Language Mechanics
Core Question
Do we need compile-time or runtime polymorphism?
Before choosing between generics and trait objects:
- Is the type known at compile time?
- Is a heterogeneous collection needed?
- What's the performance priority?
Error → Design Question
| Error | Don't Just Say | Ask Instead |
|---|---|---|
| E0277 | "Add trait bound" | Is this abstraction at the right level? |
| E0308 | "Fix the type" | Should types be unified or distinct? |
| E0599 | "Import the trait" | Is the trait the right abstraction? |
| E0038 | "Make object-safe" | Do we really need dynamic dispatch? |
Thinking Prompt
Before adding trait bounds:
What abstraction is needed?
- Same behavior, different types → trait
- Different behavior, same type → enum
- No abstraction needed → concrete type
When is type known?
- Compile time → generics (static dispatch)
- Runtime → trait objects (dynamic dispatch)
What's the trade-off priority?
- Performance → generics
- Compile time → trait objects
- Flexibility → depends
Trace Up ↑
When type system fights back:
E0277 (trait bound not satisfied)
↑ Ask: Is the abstraction level correct?
↑ Check: m09-domain (what behavior is being abstracted?)
↑ Check: m05-type-driven (should use newtype?)| Persistent Error | Trace To | Question |
|---|---|---|
| Complex trait bounds | m09-domain | Is the abstraction right? |
| Object safety issues | m05-type-driven | Can typestate help? |
| Type explosion | m10-performance | Accept dyn overhead? |
Trace Down ↓
From design to implementation:
"Need to abstract over types with same behavior"
↓ Types known at compile time → impl Trait or generics
↓ Types determined at runtime → dyn Trait
"Need collection of different types"
↓ Closed set → enum
↓ Open set → Vec<Box<dyn Trait>>
"Need to return different types"
↓ Same type → impl Trait
↓ Different types → Box<dyn Trait>Quick Reference
| Pattern | Dispatch | Code Size | Runtime Cost |
|---|---|---|---|
fn foo<T: Trait>() | Static | +bloat | Zero |
fn foo(x: &dyn Trait) | Dynamic | Minimal | vtable lookup |
impl Trait return | Static | +bloat | Zero |
Box<dyn Trait> | Dynamic | Minimal | Allocation + vtable |
Syntax Comparison
// Static dispatch - type known at compile time
fn process(x: impl Display) { } // argument position
fn process<T: Display>(x: T) { } // explicit generic
fn get() -> impl Display { } // return position
// Dynamic dispatch - type determined at runtime
fn process(x: &dyn Display) { } // reference
fn process(x: Box<dyn Display>) { } // ownedShow full SKILL.md (162 more words)Show less
Error Code Reference
| Error | Cause | Quick Fix |
|---|---|---|
| E0277 | Type doesn't impl trait | Add impl or change bound |
| E0308 | Type mismatch | Check generic params |
| E0599 | No method found | Import trait with use |
| E0038 | Trait not object-safe | Use generics or redesign |
Decision Guide
| Scenario | Choose | Why |
|---|---|---|
| Performance critical | Generics | Zero runtime cost |
| Heterogeneous collection | dyn Trait | Different types at runtime |
| Plugin architecture | dyn Trait | Unknown types at compile |
| Reduce compile time | dyn Trait | Less monomorphization |
| Small, known type set | enum | No indirection |
Object Safety
A trait is object-safe if it:
- Doesn't have
Self: Sizedbound - Doesn't return
Self - Doesn't have generic methods
- Uses
where Self: Sizedfor non-object-safe methods
Anti-Patterns
| Anti-Pattern | Why Bad | Better |
|---|---|---|
| Over-generic everything | Compile time, complexity | Concrete types when possible |
dyn for known types | Unnecessary indirection | Generics |
| Complex trait hierarchies | Hard to understand | Simpler design |
| Ignore object safety | Limits flexibility | Plan for dyn if needed |
Related Skills
| When | See |
|---|---|
| Type-driven design | m05-type-driven |
| Domain abstraction | m09-domain |
| Performance concerns | m10-performance |
| Send/Sync bounds | m07-concurrency |
© fjrevoredo, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file
Files
Just SKILL.md in .agents/skills/m04-zero-cost of fjrevoredo/mini-diarium.
Open the folder on GitHubat commit 3ddc537
Used in 1 other repository
We found 1 copy of this SKILL.md (exact, near-identical or edited) in other folders, from 1 other GitHub owner. This page covers the copy in fjrevoredo/mini-diarium, which our catalogue first saw on October 7, 2026.
Compare with similar skills
M04 Zero Cost next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.
| Skill | Stars | Used in | Tokens | Auto-check | Licence | Repo updated |
|---|---|---|---|---|---|---|
| M04 Zero Cost this skillfjrevoredo/mini-diarium | 308 | 1 repos | ~1.2k | Automated safety check: Pass | MIT | |
| Cost Trackingaffaan-m/ECC | 275k | 1 repos | ~1.3k | Automated safety check: Pass | MIT | |
| Cost Conversationruvnet/ruflo | 74k | — | ~407 | Automated safety check: Notes | MIT | |
| Cost Reportruvnet/ruflo | 74k | 1 repos | ~830 | Automated safety check: Notes | MIT | |
| Cost Optimizeruvnet/ruflo | 74k | 1 repos | ~997 | Automated safety check: Notes | MIT | |
| Cost Trackruvnet/ruflo | 74k | — | ~773 | Automated safety check: Notes | MIT |
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Analyze token usage patterns and recommend cost optimizations with estimated savings
Cost Track
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Auto-capture per-session token usage from the Claude Code session jsonl and persist to the cost-tracking namespace
Cost Export
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Questions about M04 Zero Cost
What does M04 Zero Cost do?
CRITICAL: Use for generics, traits, zero-cost abstraction. An agent skill from fjrevoredo/mini-diarium. M04 Zero Cost is an agent skill from fjrevoredo/mini-diarium. CRITICAL: Use for generics, traits, zero-cost abstraction.
When should I use M04 Zero Cost?
M04 Zero Cost fits situations like: zero-cost abstraction.
How do I install M04 Zero Cost in Claude Code?
Run `npx skills add fjrevoredo/mini-diarium --skill m04-zero-cost -a claude-code`. Or copy the skill folder (.agents/skills/m04-zero-cost in fjrevoredo/mini-diarium) into .claude/skills/m04-zero-cost in your project. Claude Code loads it when a task matches its description.
How do I install M04 Zero Cost in Codex?
Run `npx skills add fjrevoredo/mini-diarium --skill m04-zero-cost -a codex`. Or copy the skill folder (.agents/skills/m04-zero-cost in fjrevoredo/mini-diarium) into .agents/skills/m04-zero-cost in your project. Codex loads it when a task matches its description.
Can I use M04 Zero Cost in Cursor, Gemini CLI or GitHub Copilot?
Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add fjrevoredo/mini-diarium --skill m04-zero-cost -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/m04-zero-cost, .gemini/skills/m04-zero-cost, .github/skills/m04-zero-cost and .opencode/skills/m04-zero-cost in your project.
What does M04 Zero Cost need to run?
SKILL.md names no scripts, command-line tools or credentials: M04 Zero Cost is instructions for the agent only.
Does M04 Zero Cost access the network?
SKILL.md contains no URLs. Any network use would come from the scripts or tools the agent runs. This is read from the text; nothing was executed.
Is M04 Zero Cost safe to install?
Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. Review the folder before installing.
What licence does M04 Zero Cost use?
M04 Zero Cost is published under the MIT licence (the repository's licence). It allows redistribution, so the full SKILL.md is shown on this page.
How many tokens does M04 Zero Cost use?
About 1.2k tokens (SKILL.md is roughly 4.7k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full.
What are the alternatives to M04 Zero Cost?
Skills that share tags, products or a category with M04 Zero Cost: Cost Tracking (affaan-m/ECC, 275k stars), Cost Conversation (ruvnet/ruflo, 74k stars), Cost Report (ruvnet/ruflo, 74k stars) and Cost Optimize (ruvnet/ruflo, 74k stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.
Who maintains M04 Zero Cost?
fjrevoredo (a GitHub user) maintains it in fjrevoredo/mini-diarium, which has 308 GitHub stars. The repository holds 41 skills in this directory. The repository was last updated on October 7, 2026.
Source: fjrevoredo/mini-diarium on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.