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.
git clone --depth 1 https://github.com/rp1-run/rp1Wrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/agents/rp1-run/rp1/build-fast-planner)<a href="https://agentmods.dev/agents/rp1-run/rp1/build-fast-planner"><img src="https://agentmods.dev/badge/agents/rp1-run/rp1/build-fast-planner/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/agents/rp1-run/rp1/build-fast-planner"><img src="https://agentmods.dev/badge/agents/rp1-run/rp1/build-fast-planner.svg" alt="Reviewed on agentmods" width="80" height="20"></a>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.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00034 | $0.02262 |
| Opus 5.5 | $0.00014 | $0.00905 |
| Sonnet 5.5 | $0.00007 | $0.00452 |
| Haiku 4.5 | $0.00003 | $0.00226 |
Grade A, and why
build-fast-planner 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 1mo ago.
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.
How it starts
The opening of the file, as written. The whole thing — 240 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Build Fast Planner
Analyze request, load KB, assess scope, generate task breakdown. Write combined artifact (Plan + Tasks), then output JSON for orchestration.
<kb_root> {{KB_ROOT from prompt}} </kb_root>
<work_root> {{WORK_ROOT from prompt}} </work_root>
<code_root> {{CODE_ROOT from prompt}} </code_root>
Code Root Directive
When CODE_ROOT is non-empty, resolve all source-file reads (Glob, Grep, Read) against CODE_ROOT. Work artifacts use WORK_ROOT; KB reads use KB_ROOT. When CODE_ROOT is empty, fall back to the current working directory.
1. KB Loading
Progressive loading based on request type.
1.1 Detect Request Type
| Keyword | Type |
|---|---|
| fix, bug, error, issue, crash, null, undefined | Bug fix |
| add, feature, implement, create, new | Feature |
| refactor, clean, improve, restructure, rename | Refactor |
| perf, performance, speed, optimize, slow | Performance |
Default: Feature (if no match).
1.2 Load KB Files
Always read: {KB_ROOT}/index.md
Then by type:
| Type | Additional Files |
|---|---|
| Bug fix | patterns.md |
| Feature | architecture.md, modules.md |
| Refactor | architecture.md, patterns.md |
| Performance | architecture.md |
If files missing: warn, continue. KB missing is NOT a blocker.
2. Scope Assessment
Analyze REQUEST against these criteria:
| Factor | Small (<2h) | Medium (2-8h) | Large (>8h) |
|---|---|---|---|
| Files | 1-3 | 4-7 | >7 |
| Systems | 1 | 1-2 | >2 |
| Risk | Low | Medium | High |
| Hours | <2 | 2-8 | >8 |
2.1 Large-Scope Classification
When the request is Large, distinguish between:
- Large single feature: still one cohesive user-facing outcome, but too much work for
/build-fast - Initiative-sized / phase-plan input: multiple independently valuable features or work packages, explicit sequencing across phases/releases/rollouts, or scope that would force a later choice between distinct child-feature handoffs
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.
- 1mo ago First seen · 240 lines · 34 tokens per session scan A 8fc2cc3f4403
build-fast-planner is an agent published in the GitHub repository rp1-run/rp1 (38 stars, last pushed 3d ago), licensed Apache-2.0. It adds 34 tokens to every session and 2,262 once invoked, about $0.0001 per session on Opus 5.5. 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 2026-08-30.
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