---
name: memtrace-change-impact-analysis
description: "Compute what a planned source-code change will break — blast radius, affected processes, cross-repo callers, temporal stability, and Cortex decision-memory constraints — and produce a risk-rated change plan. Use for multi-symbol or multi-part edits, refactors, API changes, renames, removals, PR reviews, or risk assessments that need a plan; for one symbol's raw blast radius, call get_impact directly. Do not manually grep references or browse files for impact; use Memtrace graph context, change history, and decision recall/provenance."
---

## Overview

Pre-change risk assessment workflow. Before modifying code, this workflow maps the full blast radius, identifies affected processes, checks recent change history for instability signals, checks Cortex decision memory for recorded decisions/bans/contracts, and produces a risk-rated change plan.

Use this workflow when the change spans multiple symbols or needs a risk-rated plan. For a quick raw upstream/downstream radius around one known symbol, call `get_impact` directly.

## Steps

### 1. Identify what's being changed

Find the target symbol(s):
- Use `find_symbol` if the user named specific functions/classes
- Use `find_code` if the user described behaviour ("the authentication middleware")

Collect symbol **names** (`name`, `scope_path`, `file_path`) for all targets — graph tools use names, not internal IDs.

### 2. Get 360° context for each target

For each symbol, call `get_symbol_context` (`repo_id`, `symbol`, `file_path`):
- Direct callers and callees
- Community membership (which module is this in?)
- Process membership (which execution flows does this participate in?)
- Cross-repo API callers (is this an endpoint called by other services?)

**Decision:** If cross-repo API callers exist, this change requires coordination with other teams. Flag this immediately.

### 3. Compute blast radius

For each target, call `get_impact` (`repo_id`, `target`) with `direction: "both"`, `depth: 5`:
- Upstream impact: what depends on this symbol
- Downstream impact: what this symbol depends on
- Risk rating: Low / Medium / High / Critical

**Decision:**
| Risk | Action |
|------|--------|
| Low | Proceed with standard testing |
| Medium | Review all direct callers; test affected processes |
| High | Plan incremental migration; consider feature flags |
| Critical | Full migration strategy; backward-compatible changes required |

### 4. Check Cortex decision memory

For each target or subsystem, call `recall_decision("<target/subsystem/approach>")`.
If the graph result exposes a numeric `symbol_id`, also call
`why_is_this_here(symbol_id)` and `governing_contracts(symbol_id)`.

- Matching decision/ban/convention → include it in the plan before recommending a change.
- Decision you intend to rely on → run `verify_intent(decision_id)` first.
- CannotProve → record "no decision proven"; do not treat it as approval.

### 5. Check temporal stability

Call `get_evolution` (`repo_id`, `from: "30d ago"`, `mode: "compound"`), then `get_timeline` on each target symbol (requires `scope_path` + `file_path` from `find_symbol`):
- Sparse timeline history + you're about to change it → structurally surprising; extra scrutiny warranted.
- Target appears in `top_touched_symbols` → high churn + high impact = volatile hotspot.

### 6. Map affected execution flows

From step 2, you already know which processes are affected. For critical changes, use `analyze_relationships` (`repo_id`, `target`) with `query_type: "find_callers"` at `depth: 3` to trace the full transitive caller chain.

`depth: 3` is a JSON number, not a string — the validator rejects `"3"`.
Full parameter spec for every Memtrace tool: `references/mcp-parameters.md` (bundled at the memtrace-skills plugin root).

### 7. Produce the risk assessment

Synthesize into a change plan:

1. **Target(s)** — what's being changed and where
2. **Blast Radius** — number of direct/transitive dependents, risk rating
3. **Affected Processes** — which execution flows will be impacted
4. **Cross-Service Impact** — any external callers or consumers
5. **Stability Signal** — sparse `get_timeline` history (stable) vs frequent appearance in `top_touched_symbols` (volatile)
6. **Decision Memory** — relevant decisions/bans/contracts, or CannotProve as unknown
7. **Recommended Approach** — based on risk and decision constraints: direct change, incremental migration, or backward-compatible evolution
8. **Test Coverage** — which callers/processes to verify after the change

## Decision Points

| Condition | Action |
|-----------|--------|
| Risk = Critical | Recommend backward-compatible change + deprecation path |
| Cross-repo callers exist | Flag as requiring multi-service coordination |
| Symbol has sparse timeline but high impact | Extra review — this rarely changes; make sure the change is intentional |
| Multiple processes affected | List each affected flow; recommend testing each one |
| Symbol is a bridge point | Change may disconnect parts of the architecture — verify alternative paths exist |
| Cortex returns a held ban/contract | Do not recommend contradicting it without explicit user sign-off |

## Output

The workflow's artifact is the step-6 risk-rated change plan. Compact example:

```text
Target: AuthService::validateToken (src/auth/service.ts)
Blast Radius: 4 direct / 23 transitive dependents — Risk: High
Affected Processes: login-flow, session-refresh
Cross-Service Impact: 2 cross-repo API callers — needs multi-service coordination
Stability Signal: appears in top_touched_symbols (volatile hotspot)
Recommended Approach: incremental migration behind a feature flag
Test Coverage: all 4 direct callers + both affected processes
```