get_pr_impact

Full risk assessment for a diff in one call. Walks every changed file, maps them to symbols, runs get_blast_radius on each, and layers on co-change history to surface files that historically change together but are missing from this PR.

Single-call convenience

This replaces running get_changed_symbols plus per-symbol get_blast_radius plus a history lookup. Use it before every merge.

Parameters

Name	Type	Required	Description
since	string	no	Git ref to diff against (default "HEAD~1")
maxFiles	integer	no	Cap on changed files analysed (default 50)
confidence	"confirmed" | "likely" | "potential"	no	Restrict blast radius results to a single tier

since accepts anything git diff accepts — a branch name (main), a tag, or a commit hash.

Example

Review the last commit:

{}

Review a feature branch against main:

{ "since": "main" }

Review a specific commit range, confirmed impacts only:

{ "since": "abc123", "confidence": "confirmed", "maxFiles": 20 }

Response

{
  "since": "HEAD~1",
  "changedFiles": 3,
  "changedSymbols": 7,
  "totalImpact": 42,
  "riskLevel": "high",
  "files": [
    {
      "file": "packages/cli/src/core/graph/graph.ts",
      "symbols": [
        {
          "symbolId": "packages/cli/src/core/graph/graph.ts::Graph::class",
          "name": "Graph",
          "kind": "class",
          "blast": {
            "impactScore": 31,
            "confirmedCount": 8,
            "likelyCount": 15,
            "potentialCount": 8,
            "riskScore": 0.88,
            "topImpacted": [ /* up to 10 highest-risk dependents */ ]
          }
        }
      ],
      "coChangedWith": [
        "packages/cli/src/core/graph/graph-builder.ts",
        "packages/cli/src/adapters/storage/sqlite.ts"
      ]
    }
  ],
  "summary": {
    "confirmedTotal": 12,
    "likelyTotal": 21,
    "potentialTotal": 9,
    "highRiskSymbols": [
      "packages/cli/src/core/graph/graph.ts::Graph::class"
    ]
  },
  "boundaryViolations": {
    "confidence": "medium",
    "snapshotsAvailable": 4,
    "violations": [
      {
        "from": { "symbolId": ".../CheckoutFlow::class", "communityId": 1, "label": "Billing" },
        "to":   { "symbolId": ".../UserPermissions::class", "communityId": 3, "label": "Auth" },
        "edgeKind": "calls",
        "historicalEdgesBetweenClusters": 0,
        "severity": "high"
      }
    ]
  },
  "clustersAffected": [
    { "id": 1, "label": "Billing", "symbolCount": 5 },
    { "id": 3, "label": "Auth", "symbolCount": 1 }
  ],
  "_meta": { "totalItems": 3, "returnedItems": 3, "truncated": false }
}

If the diff is empty:

{ "since": "HEAD~1", "changedFiles": 0, "changedSymbols": 0, "totalImpact": 0, "riskLevel": "low", "files": [], "summary": { "confirmedTotal": 0, "likelyTotal": 0, "potentialTotal": 0, "highRiskSymbols": [] } }

Reading the verdict

• riskLevel — high if any changed symbol has riskScore > 0.7, medium above 0.3, else low. Use it as the top-line gate for review depth.
• summary.highRiskSymbols — the symbols most likely to break something. Review these first.
• files[].coChangedWith — files that historically change together with this one but are not in the current diff. A strong signal that the PR may be incomplete.
• boundaryViolations.violations[] (v0.8) — edges introduced by this PR between clusters that had no edges between them historically. severity: "high" + historicalEdgesBetweenClusters: 0 is a first-ever layer crossing.
• clustersAffected[] (v0.8) — distinct clusters the PR touches. A PR spanning 3+ clusters is usually a cross-team change.

Killer example: the first-ever cluster crossing

A PR wires a direct call from CheckoutFlow (Billing cluster) to UserPermissions (Auth cluster). Typecheck passes. Tests pass. riskLevel from blast radius alone may even come back low — the affected set is tiny.

But the last 10 snapshots show zero edges between these two clusters. A senior reviewer would ask "why is Billing reaching into Auth internals?" Ctxo now hands that exact question to the AI reviewer before a human ever sees the PR:

"boundaryViolations": {
  "violations": [{
    "from": { "label": "Billing" },
    "to":   { "label": "Auth" },
    "historicalEdgesBetweenClusters": 0,
    "severity": "high"
  }]
}

This is architectural review from git history — no competitor MCP server has it.

When to use

• PR review and pre-merge sanity check
• CI gate on high-risk changes (parse riskLevel === "high" or boundaryViolations.violations.length > 0)
• "Did I forget a file?" check via coChangedWith
• "Should this span multiple teams?" check via clustersAffected

Related tools

• get_blast_radius — per-symbol deep dive
• get_changed_symbols — just the symbol list, no blast radius
• get_why_context — follow up on any high-risk symbol to read its history