Knowledge Base Architecture

This document describes the architecture for JP's knowledge base (KB) system. The KB provides a structured way to expose domain-specific knowledge to the assistant via topics and subjects, with a built-in learn tool for on-demand retrieval.

Related: Wasm Tools Architecture — describes the target Wasm plugin infrastructure that the learn tool will migrate to in v2. In v1, learn runs as native Rust in the jp_tool_learn crate.

Table of Contents

• Overview
• Design Goals
• Configuration Schema
• Subject Resolution
• System Prompt Injection
• The learn Tool
• CLI Integration
• File Format Handling
• Data Flow
• Crate Changes
• Migration Path

Overview

The knowledge base organizes reusable knowledge into topics and subjects. A topic is a named group (e.g., "project", "skills") that maps to a directory of text files. Each file is a subject.

The assistant discovers available topics through the system prompt and retrieves specific subjects on demand via the learn tool — JP's first built-in tool. Subjects can also be pre-loaded into the system prompt via the learned configuration field, or on-the-fly via the --knowledge (-k) CLI flag.

Design Goals

Goal	Description
Structured knowledge	Organize knowledge into topics with subjects
On-demand retrieval	Assistant fetches subjects via learn tool
Hidden subjects	.-prefixed paths excluded from listings
Pre-loaded subjects	Inject critical knowledge into system prompt
Glob support	Load multiple subjects with patterns

Configuration Schema

TOML Structure

kb is a top-level field on AppConfig, alongside assistant and conversation:

# All fields shown — only `subjects` is required.
[kb.topic.project]
enable = true
title = "General Project Knowledge"
introduction = "foo bar baz..."
description = "longer initial description talking about this"
subjects = ".jp/kb/project"
learned = []
disabled = []

# Minimal — just the title and subjects directory.
[kb.topic.skills]
title = "Learnable Assistant Skills"
subjects = ".jp/kb/skills"

Rust Types

// jp_config/src/kb.rs

/// Knowledge base configuration.
#[derive(Debug, Clone, PartialEq, Config)]
#[config(rename_all = "snake_case")]
pub struct KnowledgeBaseConfig {
    /// Map of topic ID → topic configuration.
    #[setting(nested, flatten, merge = merge_nested_indexmap)]
    pub topics: IndexMap<String, TopicConfig>,
}

/// A single knowledge base topic.
#[derive(Debug, Clone, PartialEq, Config)]
#[config(rename_all = "snake_case")]
pub struct TopicConfig {
    /// Whether this topic is active.
    #[setting(default = true)]
    pub enable: bool,

    /// Human-readable title. Replaces the topic ID in the system
    /// prompt and `learn` tool output when set.
    pub title: Option<String>,

    /// One-sentence summary for the `<knowledge>` system prompt
    /// section.
    pub introduction: Option<String>,

    /// Multi-paragraph description. Shown in `learn` output when
    /// no specific subjects are requested. Also included in the
    /// system prompt when one or more subjects are `learned`.
    pub description: Option<String>,

    /// Relative path from workspace root to the directory
    /// containing this topic's subject files.
    #[setting(required)]
    pub subjects: RelativePathBuf,

    /// Glob patterns for subjects to pre-load into the system
    /// prompt. Matched subjects are excluded from the `learn`
    /// tool to avoid duplication.
    #[setting(default = vec![])]
    pub learned: Vec<String>,

    /// Subject slugs to exclude entirely. Disabled subjects
    /// cannot be learned, even by exact reference. Overrides
    /// `learned`.
    #[setting(default = vec![])]
    pub disabled: Vec<String>,
}

Field Reference

Field	Required	Default	Description
enable	No	true	Set false to deactivate the topic
title	No	—	Display name shown to the assistant
introduction	No	—	One-line summary in system prompt
description	No	—	Extended description in learn output
subjects	Yes	—	Path to subject directory
learned	No	[]	Glob patterns for pre-loaded subjects
disabled	No	[]	Excluded subject slugs

---

Subject Resolution

A subject is a text file inside a topic's subjects directory. The slug is the file path relative to the topic directory, with the file extension stripped.

Example Directory Layout

.jp/kb/project/
├── maintainers/
│   ├── jean.md          → slug: "maintainers/jean"
│   └── ryan.md          → slug: "maintainers/ryan"
├── code-quality.md      → slug: "code-quality"
└── .internal-notes.md   → slug: "internal-notes" (hidden)

.jp/kb/skills/
├── ast-grep.md          → slug: "ast-grep"
└── ast-grep/
    └── .rules.md        → slug: "ast-grep/rules" (hidden)

Hidden Subjects

A subject is hidden when any component of its path starts with .:

Path	Hidden?	Reason
.internal-notes.md	Yes	Filename starts with .
ast-grep/.rules.md	Yes	Nested filename starts with .
.hidden-dir/visible.md	Yes	Parent directory starts with .
maintainers/jean.md	No	No .-prefixed components

Hidden subjects:

• Not listed by learn (even with * or ** globs)
• Loadable only by exact slug: learn(topic, subjects: ["ast-grep/rules"])
• Discoverable only via external hints — e.g., a non-hidden subject mentions "read ast-grep/rules for full rule documentation"

Disabled Subjects

Subjects matching entries in the disabled array are fully excluded:

• Not listed by learn
• Not loadable, even by exact slug
• Override learned — a subject in both disabled and learned is disabled

Resolution Algorithm

resolve_subjects(topic_config, glob_patterns):
    base = workspace_root / topic_config.subjects

    # 1. Walk directory tree
    all_files = walk(base, recursive=true)

    # 2. Compute slugs (relative path, strip extension)
    all_slugs = [strip_ext(relative(f, base)) for f in all_files]

    # 3. Filter disabled
    available = [s for s in all_slugs if s not in disabled]

    # 4. If no patterns: return non-hidden available slugs
    if glob_patterns is None:
        return [s for s in available if not is_hidden(s)]

    # 5. Apply glob patterns
    matched = []
    for pattern in glob_patterns:
        for slug in available:
            if glob_match(pattern, slug):
                # Globs skip hidden subjects
                if not is_hidden(slug):
                    matched.append(slug)
            elif slug == pattern:
                # Exact match loads hidden subjects too
                matched.append(slug)

    return deduplicate(matched)

System Prompt Injection

Knowledge Section

When at least one topic has available (non-hidden, non-disabled) subjects, the system prompt includes a <knowledge> section:

<knowledge>
The following knowledge topics are available to learn:

- project (**General Project Knowledge**): foo bar baz...
- skills (**Learnable Assistant Skills**)

Use the `learn` tool to consume this knowledge.

(note: some topics may contain hidden subjects that are not listed via `learn`
by default, but can be loaded manually if you are made aware of their names via
other means, such as by reading non-hidden subjects first. This prevents
exposing too much irrelevant knowledge upfront)
</knowledge>

Generation rules:

1. Only list enabled topics with at least one non-hidden, non-disabled subject that is NOT already learned.
2. Show the title in bold after the topic ID, when present.
3. Append the introduction after the title, when present.
4. Omit topics where ALL subjects are pre-loaded via learned.

Pre-loaded Knowledge

When a topic has learned patterns matching subjects, those subjects are expanded inline in the system prompt:

<knowledge>
The following knowledge has been pre-loaded into your system prompt:

<topic "General Project Knowledge">

[[topic description here]]

<subject "maintainers/jean">
...file content...
</subject>

<subject "maintainers/ryan">
...file content...
</subject>
</topic>

The following knowledge topics are available to learn:

- skills (**Learnable Assistant Skills**)

Use the `learn` tool to consume this knowledge.

(note: some topics may contain hidden subjects that are not listed via `learn`
by default, but can be loaded manually if you are made aware of their names via
other means, such as by reading non-hidden subjects first. This prevents
exposing too much irrelevant knowledge upfront)
</knowledge>

Pre-loaded subjects do NOT appear in learn tool listings. They are shown in a separate "already learned" section when learn is called without subjects, so the assistant knows they exist.

Why Not Configurable Sections

The existing SectionConfig type (content, tag, position) is designed for user-controlled system prompt sections. The <knowledge> section is not user-configurable — its content is derived from KB config. It is built programmatically and injected directly into the system prompt string during thread construction.

Internally, the implementation MAY use SectionConfig as a container (with a fixed tag of "knowledge" and a low position value), but this is an implementation detail, not a user-facing feature.

Injection Point

The knowledge section is built during Query::run, after config is resolved but before the LLM request is built:

// Pseudo-code
let kb_section = build_knowledge_section(
    &config.kb,
    &workspace_root,
)?;

if let Some(section) = kb_section {
    system_prompt_sections.push(section);
}

The learn Tool

Registration

learn is registered as a built-in tool via ToolSource::Builtin. Its definition is generated dynamically based on the KB configuration at query time.

// Pseudo-code for registration
if config.kb.has_learnable_topics() {
    let learn_definition = ToolDefinition {
        name: "learn".to_owned(),
        description: Some(
            "Learn about knowledge base topics and subjects."
                .to_owned(),
        ),
        parameters: build_learn_parameters(&config.kb),
    };

    tool_definitions.push(learn_definition);
}

The tool is only registered when at least one topic has subjects available to learn (not all pre-loaded or disabled).

JSON Schema

The topic parameter is a free-form string. The description lists available topics so the LLM knows what to pass. The schema itself is stable — it does not change when the KB configuration changes.

{
  "type": "object",
  "properties": {
    "topic": {
      "type": "string",
      "description": "The topic ID or title to learn about."
    },
    "subjects": {
      "type": [
        "string",
        "array",
        "null"
      ],
      "description": "Glob pattern(s) for subjects to load. Use * for current level, ** for recursive. Omit to list available subjects.",
      "items": {
        "type": "string"
      }
    }
  },
  "required": [
    "topic"
  ],
  "additionalProperties": false
}

The description is dynamically generated from the KB configuration (listing available topic IDs and titles). The schema structure remains constant. This avoids issues with providers caching stale tool schemas between turns.

Topic Resolution

When the assistant provides a topic value:

1. Exact match on topic ID → resolved
2. Case-insensitive match on title → resolved
3. No match → return error listing valid topics

Behavior: List Subjects (no subjects argument)

learn(topic: "skills")

# Topic: Learnable Assistant Skills

[[optional topic description]]

## Available subjects:

- ast-grep

Use the `learn` tool with the `subjects` argument to learn specific subjects.

When some subjects are pre-loaded:

# Topic: General Project Knowledge

[[optional topic description]]

## Available subjects:

- code-quality

Use the `learn` tool with the `subjects` argument to learn specific subjects.

## Already learned (in system prompt):

- maintainers/jean
- maintainers/ryan

Behavior: Load Subjects (with subjects argument)

Single subject:

learn(topic: "skills", subjects: ["ast-grep"])

Returns the raw file content of .jp/kb/skills/ast-grep.md (with format handling applied — see [File Format Handling]).

Multiple subjects (or glob):

learn(topic: "skills", subjects: ["**"])

Returns all matching non-hidden subjects, each wrapped in tags:

<subject "ast-grep">
...content...
</subject>

Glob Behavior

Standard glob semantics apply. * matches at one directory level. ** matches recursively across directories.

Pattern	Matches
*	Non-hidden subjects at the top level only
**	All non-hidden subjects, recursively
maintainers/*	Non-hidden subjects directly under maintainers/
maintainers/**	Non-hidden subjects under maintainers/, recursively
ast-grep/rules	Exact match — loads hidden subject
maintainers/j*	Non-hidden subjects starting with j under maintainers/

Key rules:

• * matches files at the current level (non-recursive)
• ** traverses directories recursively
• Globs never match hidden subjects
• Hidden subjects require an exact slug
• Disabled subjects are excluded from all matches, including exact

No De-duplication Across Calls

There is no mechanism to prevent the assistant from calling learn with the same subject twice. System prompt subjects (via learned) ARE excluded from the tool, because the system prompt is never compacted. But subjects learned via tool calls may have been compacted away from the context window, so re-learning them is valid.

---

CLI Integration

The -k / --knowledge Flag

A convenience flag on the query command for pre-loading subjects into the system prompt:

jp query -k "project/maintainers/*" "Review this PR"

Equivalent to:

jp query --cfg kb.topic.project.learned+="maintainers/*" "Review this PR"

Behavior:

• Format: topic_id/glob_pattern
• Repeatable: -k "project/*" -k "skills/ast-grep"
• Merges with existing learned patterns (does not replace)
• Affects the current conversation going forward

Config Load Paths

Pre-loading can also be configured via config_load_paths:

# .jp/config.d/kb/maintainers.toml
[kb.topic.project]
learned = ["maintainers/*"]

jp query --cfg kb/maintainers "Review this PR"

This leverages the existing configuration loading system without any new infrastructure.

Implementation

// In Query CLI args (jp_cli)
/// Pre-load knowledge base subjects into the system prompt.
///
/// Format: `<topic>/<subject glob pattern>`. Repeatable.
#[arg(short = 'k', long = "knowledge")]
knowledge: Vec<String>,

Each value is split on the first / into (topic_id, pattern) and converted to a config merge on kb.topic.<id>.learned.

File Format Handling

Subject files are read as UTF-8 text. The file extension determines presentation format.

Pass-through Formats

Included as-is in tool output:

Extension	Format
.md	Markdown
.txt	Plain text
.text	Plain text
(none)	Plain text

Fenced Code Block Formats

Wrapped in fenced code blocks with the extension as language:

Extension	Language tag
.toml	toml
.json	json
.yaml / .yml	yaml
.rs	rust
.py	python
.js	javascript
.ts	typescript
(other)	extension name

Example: a .toml file is returned as:

```toml
[package]
name = "example"
```

Binary File Detection

If the first 8192 bytes of a file contain a null byte, the file is treated as binary and skipped. The learn tool returns a message indicating the file was skipped.

---

Data Flow

System Prompt Construction

Config Loading (layered merge)
     │
     │ AppConfig { kb: KnowledgeBaseConfig { topics } }
     │
     ▼
Query::run
     │
     ├─── For each enabled topic:
     │    ├── Scan subjects directory
     │    ├── Filter disabled subjects
     │    ├── Identify hidden subjects
     │    ├── Match `learned` glob patterns
     │    └── Read learned subject files
     │
     ├─── Build <knowledge> section
     │    ├── Pre-loaded subjects (expanded content)
     │    └── Available topics list (for `learn` tool)
     │
     ├─── Append <knowledge> to system prompt
     │
     ├─── Generate `learn` tool definition
     │    └── Dynamic description from topic IDs/titles
     │
     └─── Register `learn` as builtin tool

learn Tool Execution

Assistant calls: learn(topic: "skills", subjects: ["ast-grep"])
     │
     ▼
ToolSource::Builtin
     │
     ├── Host resolves topic "skills" → TopicConfig
     │
     ├── Host calls jp_tool_learn::execute():
     │   ├── Passes topic config (subjects path, disabled, learned)
     │   └── Passes tool arguments (subjects: ["ast-grep"])
     │
     ▼
jp_tool_learn (native Rust, v1)
     │
     ├── Resolve subjects directory from topic config
     │
     ├── Match glob "ast-grep" against directory contents
     │   ├── Exclude hidden (unless exact match)
     │   └── Exclude disabled
     │
     ├── Read matched file(s)
     │   └── Apply format handling
     │
     └── Return Outcome::Success(formatted content)
     │
     ▼
Host returns tool result to LLM

v2 (Wasm): The same jp_tool_learn crate compiles to wasm32-wasip2 and runs in a Wasm sandbox with a preopened subjects directory. See Wasm Tools Architecture.

---

Crate Changes

jp_config

New module src/kb.rs:

• KnowledgeBaseConfig, TopicConfig
• Partial variants with AssignKeyValue, PartialConfigDelta, ToPartial implementations
• Config field names, environment variables, CLI assignment

New field on AppConfig:

pub struct AppConfig {
    // ...existing fields...

    /// Knowledge base configuration.
    #[setting(nested)]
    pub kb: KnowledgeBaseConfig,
}

jp_tool

No changes to existing types. Context, Outcome, and Question are sufficient for the learn tool.

The Wasm-specific contract (WIT interface) is defined in the jp_tool crate but is part of the Wasm tools architecture — see Wasm Tools Architecture.

jp_tool_learn

New crate at crates/jp_tool_learn/. In v1, this is a regular Rust library crate called from the host. In v2, it compiles to wasm32-wasip2 and runs in a Wasm sandbox (see Wasm Tools Architecture).

Contains the learn tool logic:

• Topic listing (directory scan, hidden/disabled filtering)
• Subject loading (glob matching, file reading, format handling)
• Output formatting (markdown with <subject> tags)

The crate's public API is designed to be portable across both native and Wasm targets:

// crates/jp_tool_learn/src/lib.rs

pub struct LearnInput {
    /// Absolute path to the topic's subjects directory.
    pub subjects_dir: PathBuf,
    /// Topic metadata.
    pub title: Option<String>,
    pub description: Option<String>,
    pub disabled: Vec<String>,
    pub learned: Vec<String>,
    /// Tool arguments from the LLM.
    pub topic: String,
    pub subjects: Option<Vec<String>>,
}

pub fn execute(input: LearnInput) -> jp_tool::Outcome {
    // Pure function: reads files, returns formatted content.
    // No dependency on jp_config, jp_llm, or jp_cli.
}

The host (jp_llm) constructs LearnInput from the resolved TopicConfig and the LLM's tool arguments, then calls execute().

jp_cli

• Build <knowledge> section during Query::run
• Generate and register learn tool definition (dynamic description)
• Add -k / --knowledge CLI flag to Query args
• Parse -k values into config overrides on kb.topic.<id>.learned

jp_llm

• Implement ToolSource::Builtin in ToolDefinition::new() and ToolDefinition::execute() (currently todo!())
• v1: Call jp_tool_learn::execute() directly (native Rust)
• v2: Delegate to Wasm runtime (see Wasm Tools Architecture)

jp_conversation

No changes. The learn tool produces standard ToolCallRequest / ToolCallResponse events in the conversation stream.

---

Migration Path

Phase 1: Configuration

1. Create jp_config/src/kb.rs with KnowledgeBaseConfig and TopicConfig
2. Add partial config types, merging, and CLI assignment
3. Add kb field to AppConfig
4. Add config snapshot tests

Phase 2: System Prompt Injection

1. Implement subject directory scanning and slug computation
2. Implement hidden/disabled filtering
3. Implement learned glob matching and file reading
4. Implement file format handling (pass-through vs fenced)
5. Build <knowledge> section generator
6. Integrate into Query::run system prompt construction
7. Add unit tests for section generation

Phase 3: learn Tool Definition

1. Implement schema generation with dynamic description
2. Implement topic resolution (ID and title matching)
3. Register learn as a builtin tool (conditional on KB config)
4. Add -k / --knowledge flag to Query CLI args
5. Add unit tests for schema generation and topic resolution

Phase 4: learn Tool Execution (v1 — native Rust)

1. Create jp_tool_learn crate as a regular Rust library
2. Implement LearnInput and execute() as a pure function
3. Implement listing logic (directory scan, hidden/disabled filter)
4. Implement loading logic (glob matching, file reading, format handling)
5. Implement ToolSource::Builtin in jp_llm — construct LearnInput from TopicConfig + LLM arguments, call jp_tool_learn::execute()
6. Add integration tests (tool call → file content)

Phase 5: Testing

1. Unit tests: config parsing, slug resolution, glob matching, format handling, section generation, schema generation
2. Integration tests: full learn tool call (native execution)
3. Edge cases: empty topics, all-learned topics, all-disabled subjects, binary files, deeply nested directories

Phase 6: Wasm Migration (v2)

See Wasm Tools Architecture.

1. Add wasm32-wasip2 target support to jp_tool_learn
2. Implement WIT exports via wit-bindgen
3. Embed compiled Wasm binary in jp via include_bytes!
4. Update ToolSource::Builtin to use jp_wasm::execute()
5. Verify identical behavior between native and Wasm execution

SummaryA design for a workspace knowledge base of topics and subjects, retrieved through a built-in learn tool and injected into the system prompt.

AuthorsJean Mertz

Date2026-03-05