core

A step-by-step workflow for carrying out small, planned code changes and checking each one before committing it. A commit is a saved checkpoint in a version-controlled project.

In plain words
What is it for?
Use it when implementing plan steps, handling code changes at commit boundaries, and verifying progress through tests or other automated checks.
Why use it?
It gives each implementation step a defined check, such as a test, compiler, or linter, so problems are found before the change is recorded.

Skill for Claude CodeCodex

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add skills/nrdxp/predicate/core
Any agent
npx skills add nrdxp/predicate --skill core
Clone the repo
git clone --depth 1 https://github.com/nrdxp/predicate

Made for: Claude Code, Codex.

Per session 76 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 3,086 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00076 $0.03086
Opus 5 $0.00038 $0.01543
Sonnet 5 $0.00015 $0.00617
Haiku 4.5 $0.00008 $0.00309

Measured yesterday against content hash ff3ac74eabe0, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

core scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured yesterday.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

skills/core/SKILL.md · 183 lines

How it starts

The opening of the file, as written. The whole thing — 183 lines — stays where its author put it; the contents beside it link to each section on GitHub.

C.O.R.E. Protocol: Micro-Execution under the Verification Dual

Context → Obstacles → Resolution → Execution

This workflow defines the C.O.R.E. micro-execution phase. It guides a localized plan segment through a series of discrete state transitions (Context, Obstacles, Resolution, Execution), closing each step against the Verification Dual before committing: every step carries a deterministic evaluator (the symbolic path — test, compiler, linter) that must reach $\Delta E = 0$, and each commit boundary meets the Commit Gate (§3). C.O.R.E. is the task-scale instance of the Dual's symbolic path: drive a candidate edit to its evaluator's fixed point, then authorize the change through the ledger gate.


Scope

[!IMPORTANT] C.O.R.E. maps a localized plan segment (typically 2-3 commit boundaries) and manages the execution trajectory. It is execution, not strategy: high-level planning and the exploration of design alternatives are standing dispositions — the Planning Invariants and the Sketch Principle — not steps inside this workflow. If the sequence begins exploring design alternatives or modifying the architecture, it has exited C.O.R.E. space; the walk must immediately halt.

Grammar

# 1. TRAJECTORY METADATA
STATUS: [ABSORB | CLARIFY | PLAN | EXECUTE]
CONTROL_MODE: [MANUAL | AUTOMATIC] # MANUAL: halt at boundaries; AUTOMATIC: autocommit and continue if tests pass.
 
# 2. CONTEXT (The Initial Boundary Condition)
CTX:
  GOAL: "User's objective (quoted verbatim)"
  CONSTRAINTS:
    - "Boundary condition 1"
  FILES:
    - path/to/target/file
 
# 3. OBSTACLES (Divergence Vectors)
# Populated in CLARIFY status; forces sequence freeze
OBSTACLES:
  - "Uncertainty / contradiction 1"
 
# 4. TRAJECTORY PLAN (Discrete TDD Optimization Steps)
# Populated in PLAN/EXECUTE status
PLAN:
  RATIONALE: "Mathematical / control rationale for this trajectory"
  STEPS:
    - ID: 1
      INVARIANT: "Test assertion or property contract (TDD constraint)"
      TEST_TARGET: "tests/test_file.py::test_name"
      IMPL_TARGET: "src/file.py::function_name"
      IMPL_DELTA: "Implementation edit to satisfy the invariant"
      VALIDATOR: "pytest tests/test_file.py"
      COMMIT: true # Marks a commit boundary

Read the full file on GitHub · 183 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. yesterday First seen · 183 lines · 76 tokens per session scan A ff3ac74eabe0

Subscribe to this mod's changes

core is a skill published in the GitHub repository nrdxp/predicate (10 stars, last pushed 8d ago), licensed MIT. It adds 76 tokens to every session and 3,086 once invoked, about $0.0004 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.

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