blast-radius

name	blast-radius
description	Pre-flight protocol for missions that modify, remove, rename, or alter the semantics of existing symbols on fleet-generator. Documents call-site impact and required updates BEFORE code changes are made.
when_to_use	Mission renames or removes a symbol. Mission changes a function signature. Mission deprecates a method. Mission alters schema fields, enum cases, or shared constants. Trigger phrases: blast radius, MUST_UPDATE, INTENTIONALLY_LEFT, RESCOPE_REQUIRED, rename, signature change, symbol removal, deprecation, migration, orphan deprecation, bridge helper, partial migration, call sites.
status	active
tags	["skill"]
updated	2026-05-07T00:00:00.000Z

Blast Radius Discipline

Right the first time, every time. A partial migration is worse than a delayed migration.

When this skill applies

Before the worker makes any change to existing code that modifies, removes, renames, deprecates, or alters the semantics of a symbol that may be referenced elsewhere. Specifically, any of:

• Renaming a type, function, parameter, or field
• Changing a function signature (parameters, types, return)
• Removing a property, parameter, accessor, or case
• Adding deprecation annotations
• Changing semantics even when the signature is preserved
• Modifying schema, persistence, or canonical constants

Does NOT apply to purely additive changes: new files with no references yet, new private helpers, formatting, comment-only edits.

If uncertain whether a change triggers this skill — it does. Run the protocol.

The protocol — five steps

Step 0: Establish the baseline

Before writing any production code:

# Run the test suite. Capture the pass count.
<your-test-runner> 2>&1 | tail -5

If tests don't pass at mission start, STOP. Tests must pass at the baseline. Fix in a separate mission first.

Step 1: Identify every symbol being changed

For each symbol the mission will modify:

• Full path
• Change class: rename / signature / removal / deprecation / semantic
• Scope: public / internal / private

Step 2: Grep exhaustively

For each symbol, grep across all of: production code, tests, docs, configs, comments. See references/grep-recipes.md for language-specific patterns.

For renamed symbols, grep BOTH old and new names to confirm the old has no surviving references.

Step 3: Classify every hit

Every grep hit gets one of three classifications:

• MUST_UPDATE — uses the symbol; must change to match
• INTENTIONALLY_LEFT — false positive OR legitimate non-update. Requires written justification.
• RESCOPE_REQUIRED — must update, but doing so expands the mission beyond its sanctioned scope. The mission stops. Surface to the human with a rescope request.

The RESCOPE_REQUIRED classification is the escape valve. The wrong move is to silence the issue with a bridge or shim — see references/anti-patterns.md.

Step 4: Write the Blast Radius Report

Commit it to docs/blast_radius/<mission-id>_BLAST_RADIUS.md as the FIRST commit of the work, before any production change. Use the template in references/report-template.md.

Step 5: Implement — every MUST_UPDATE site must be touched

When implementation begins, every file listed as MUST_UPDATE must appear in the final diff. Garfield verifies this in post-flight.

The rule

If a change to symbol X has any effect on other code that reads or writes X, every such call site is in scope. There is no "pre-existing, out of scope" escape hatch for call sites of the SAME symbol.

If the mission cannot cover all call sites, the mission rescopes — it never ships partial.