feat: add profiling regression proposal skill

CHANGELOG.md

@@ -9,6 +9,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Added
 
+- Add `performance/profiling-regression-proposal`: an evidence-only skill that proposes follow-up actions after MetaMask Mobile CI has already classified a Hermes CPU-profile regression.
 - Support explicit-only workflow skills through native invocation controls, preserve repository overlays, and prune managed retired skill names during sync.
 - Add `navigation` skill with a repo-agnostic base and a MetaMask Mobile overlay for `Routes` and `NavigationService`. Marked `base: true` so it installs even when its domain is filtered out.
 - Add `feature-flags` skill with a repo-agnostic base and a MetaMask Mobile overlay for version-gated remote flags. Marked `base: true` so it installs even when its domain is filtered out. ([#147](https://github.com/MetaMask/skills/pull/147))

domains/performance/skills/profiling-regression-proposal/references/evidence-schema.md

@@ -0,0 +1,58 @@
+# Evidence schema
+
+The caller provides a single JSON object. Field names may evolve, but the
+security boundary does not: only values present in this object may appear as
+facts in the proposal.
+
+```json
+{
+  "runId": "123",
+  "runUrl": "https://github.com/example/actions/runs/123",
+  "currentSha": "abc",
+  "previousRunId": "122",
+  "previousSha": "def",
+  "findings": [
+    {
+      "scenario": "Perps add funds",
+      "owner": "team-name",
+      "jsWorkMs": 12600,
+      "baselineMedianJsWorkMs": 3000,
+      "ratio": 4.2,
+      "baselineRuns": 3
+    }
+  ],
+  "frames": [
+    {
+      "scenario": "Perps add funds",
+      "name": "usePerpsOrderForm",
+      "url": "app/example.ts",
+      "line": 40,
+      "selfMs": 800
+    }
+  ],
+  "pullsOverlappingTheProfile": [
+    {
+      "number": 123,
+      "title": "Example",
+      "url": "https://github.com/example/pull/123",
+      "files": [
+        {
+          "path": "app/example.ts",
+          "patch": "+changed line"
+        }
+      ]
+    }
+  ],
+  "pullsMergedWithNoProfileFile": [
+    {
+      "number": 124,
+      "title": "Unrelated",
+      "url": "https://github.com/example/pull/124"
+    }
+  ]
+}
+```
+
+`pullsOverlappingTheProfile` is computed by deterministic tooling before model
+invocation. The model must not promote entries from
+`pullsMergedWithNoProfileFile` based on titles or prior knowledge.

domains/performance/skills/profiling-regression-proposal/skill.md

@@ -0,0 +1,76 @@
+---
+name: profiling-regression-proposal
+description: >-
+  Proposes follow-up actions for an already-classified Hermes CPU-profile
+  regression using only the profiling evidence supplied by the caller. Use
+  after deterministic tooling has identified a slow scenario and correlated
+  hot-frame paths with files from recently merged pull requests.
+maturity: stable
+---
+
+# Profiling Regression Proposal
+
+Produce a short, evidence-bound proposal after deterministic profiling tooling
+has already classified a run. This skill interprets evidence; it does not decide
+whether a regression exists.
+
+## When To Use
+
+Use this skill only when the caller supplies structured evidence containing:
+
+- findings produced by a deterministic threshold;
+- hot frames extracted from generated CPU-profile reports;
+- recently merged pull requests separated by whether their changed files
+  overlap those hot-frame paths.
+
+Do not use source-tree searches, repository knowledge, issue history, PR titles,
+or general performance heuristics as additional evidence.
+
+## Workflow
+
+1. Treat the supplied evidence object as the only source of truth.
+2. Do not change, second-guess, or reapply the caller's regression threshold.
+3. Mention a file, function, timing, ratio, run, or owner only when it appears
+   in the evidence.
+4. Connect a pull request to a finding only when the caller places it in the
+   profile-overlap collection. A title that mentions the affected feature is
+   not evidence.
+5. A changed file may be discussed only when its path already occurs in a hot
+   frame from the generated profile.
+6. Pull requests in the no-profile-overlap collection may be named only to say
+   the supplied profile cannot implicate them.
+7. Do not infer source files, behavior, ownership, causes, or fixes from
+   unsymbolicated frames.
+8. Several scenarios crossing the threshold in one run are one run-level
+   anomaly, not automatically several independent bugs.
+9. If no pull request overlaps a profiled path, say so and stop. Do not choose a
+   likely culprit.
+10. Describe every proposed action as a hypothesis to validate by rerunning the
+    same profile, never as a confirmed root cause.
+
+## Output
+
+Return Slack mrkdwn:
+
+- first line:
+  `*AI proposal (profiling evidence only; not a root cause)*`;
+- at most six bullets;
+- one sentence per bullet;
+- pull-request links formatted as `<url|#number>`;
+- no general disclaimer beyond the required first line.
+
+Good:
+
+> PR #123 changed a file that appears as a hot frame; rerun the same scenario
+> with that change isolated and compare the frame's self time.
+
+Not allowed:
+
+> PR #123 is the cause because its title mentions Perps.
+
+The title is routing context, not profiling evidence.
+
+## Failure behavior
+
+Return no proposal when the evidence is missing or malformed. Never fill gaps
+with repository knowledge or generic optimization advice.