Fable Discover

Build the smallest reliable mental model of an unfamiliar code path before anyone commits to a design or edit.

Mission

Discovery is not "read a lot of files." It is uncertainty reduction.

The Skill should leave the next specialist with enough evidence to make a decision without rediscovering the repository, while stopping before exploration becomes archaeology.

Activate When

• entry points, ownership, or execution flow are not known;
• a request spans an unfamiliar package/subsystem;
• generated code, plugins, runtime configuration, queues, jobs, or dependency injection may change the real execution path;
• the user describes behavior but not where it is implemented;
• a previous assumption about the repository has been contradicted.

Do Not Activate When

• the exact bounded edit and target file are already known;
• the job is purely external API/version research (fable-research);
• the task is only to run existing checks (fable-verify).

Situation Classification

Classify the unknown before searching.

Discovery Protocol

Stage 1 — Frame the unknowns

Write 2-7 questions whose answers would materially change the plan. Mark each as load-bearing or nice-to-know.

Examples:

• Which process receives this request?
• Is the package source executed directly or from dist/?
• Where is this plugin registered?
• Which storage boundary commits the state?

Do not start broad search until the questions are explicit.

Stage 2 — Establish repository topology

Read project instructions and manifests first. Identify:

• workspace/package roots;
• build/test commands;
• generated directories;
• host/plugin manifests;
• source vs distribution entry points;
• configuration sources;
• relevant ownership boundaries.

Stage 3 — Trace a real path

Start from an observable entry point and follow concrete symbols/events toward the target behavior.

For every hop record:

• file/symbol;
• why this hop is reachable;
• input/output contract;
• side effect or state transition;
• certainty: [measured], [inferred], or [unresolved].

An import chain alone is not proof that code executes.

Stage 4 — Probe runtime only when static evidence is insufficient

Use safe read-only runtime observation to answer a named question: logs, help output, route listing, test discovery, build metadata, or a narrow reproduction.

Do not mutate production state just to satisfy curiosity.

Stage 5 — Resolve contradictions

When measured evidence contradicts the current model, update the model immediately. Do not preserve an old theory because it made the earlier search coherent.

Stage 6 — Stop deliberately

Stop when every load-bearing question is either:

• answered with evidence; or
• explicitly unresolved with a named consequence and next Skill.

Nice-to-know questions do not block handoff.

Decision Rules

• If the unknown is external and time-sensitive, hand that question to fable-research instead of inferring from model memory.
• If the exact edit becomes bounded and no design decision remains, hand off to fable-execute.
• If multiple components/risks must be coordinated, hand off to fable-plan.
• If search results suggest generated code, find the generator/source-of-truth before recommending edits.
• If direct imports disappear at a boundary, inspect registration tables, event buses, dependency injection, plugin discovery, reflection, codegen, and runtime configuration.
• If tests and runtime appear to disagree, record both paths; do not assume the test harness is authoritative.

Invariants

• Discovery is read-only unless the user explicitly changes the task.
• Every load-bearing conclusion has concrete repository/runtime evidence.
• Inference is labeled as inference.
• Search breadth is justified by an unresolved question.
• Generated output is not treated as canonical source without proving it is hand-maintained.

Failure Taxonomy

Search miss

A symbol cannot be located. Check aliases, generated names, dynamic loading, registries, event dispatch, reflection, compiled output, and package boundaries.

False path

Files look relevant but are not reachable from the real entry point. Return to a proven runtime/bootstrap boundary.

Environment ambiguity

Behavior depends on env/flags/config. Identify precedence and which configuration is active; do not report a default as runtime fact.

Source/artifact mismatch

Tests or commands execute built/stale artifacts rather than edited source. Record both paths and route to fable-recover if this caused repeated failure.

Unknown remains load-bearing

Do not paper over it. Hand off to research or report the unresolved decision explicitly.

Anti-Patterns

• reading every file in a package "for context";
• trusting filenames as architecture;
• treating grep frequency as importance;
• following imports without proving runtime reachability;
• ignoring build/codegen/plugin registration;
• reporting assumptions without [inferred] labels;
• continuing discovery after the planning decision is already safe.

Evidence Packet / Handoff

Produce a compact packet:

Target:
Load-bearing questions:
Measured facts: file:symbol → fact
Execution path: entry → ... → side effect
Configuration/runtime notes:
Generated/plugin boundaries:
Unresolved questions + consequence:
Recommended next Skill:

Completion Criteria

Discovery is complete when the next specialist can explain:

• where execution starts;
• which path reaches the behavior;
• which contracts/state boundaries matter;
• which facts are measured vs inferred;
• what remains unknown;
• why those remaining unknowns do or do not block the next action.

Progressive Resources

• Deep playbook: references/repository-investigation-playbook.md
• Existing evidence protocol: references/evidence-gathering-protocol.md
• Example: examples/codebase-inspection.md