diff --git a/.claude/commands/calibrate-loop.md b/.claude/commands/calibrate-loop.md
index 9fadb295..a1accf7d 100644
--- a/.claude/commands/calibrate-loop.md
+++ b/.claude/commands/calibrate-loop.md
@@ -108,7 +108,13 @@ Proceed to Step 4.
 
 After the Gap Analyzer returns, **you** write the JSON to `$RUN_DIR/gaps.json`.
 
-> **Note**: Discovery evidence from gap analysis is collected programmatically by the orchestrator during Step 4 (Evaluation). Do not manually append to `data/discovery-evidence.json`.
+Then collect uncovered actionable gaps into discovery evidence (deterministic CLI — no LLM):
+
+```bash
+npx canicode calibrate-collect-gap-evidence $RUN_DIR
+```
+
+This reads `gaps.json`, extracts gaps where `actionable: true` and `coveredByRule: null`, and appends them to `data/discovery-evidence.json` as `source: "gap-analysis"` entries.
 
 Append to `$RUN_DIR/activity.jsonl`:
 ```json
diff --git a/src/agents/evidence-collector.test.ts b/src/agents/evidence-collector.test.ts
index b2ced476..06fb3e15 100644
--- a/src/agents/evidence-collector.test.ts
+++ b/src/agents/evidence-collector.test.ts
@@ -336,7 +336,7 @@ describe("evidence-collector", () => {
       ], disPath);
 
       appendDiscoveryEvidence([
-        { description: "gap2", category: "color", impact: "moderate", fixture: "fx2", timestamp: "t2", source: "gap-analysis" },
+        { description: "gap2", category: "code-quality", impact: "moderate", fixture: "fx2", timestamp: "t2", source: "gap-analysis" },
       ], disPath);
 
       const raw = JSON.parse(readFileSync(disPath, "utf-8")) as { entries: DiscoveryEvidenceEntry[] };
@@ -415,7 +415,7 @@ describe("evidence-collector", () => {
       ]), "utf-8");
 
       appendDiscoveryEvidence([
-        { description: "new", category: "color", impact: "easy", fixture: "fx2", timestamp: "t1", source: "gap-analysis" },
+        { description: "new", category: "pixel-critical", impact: "easy", fixture: "fx2", timestamp: "t1", source: "gap-analysis" },
       ], disPath);
 
       const raw = JSON.parse(readFileSync(disPath, "utf-8")) as { schemaVersion: number; entries: DiscoveryEvidenceEntry[] };
@@ -435,6 +435,24 @@ describe("evidence-collector", () => {
       expect(after).toBe(before);
     });
 
+    it("warns on non-standard category", () => {
+      const spy = vi.spyOn(console, "warn").mockImplementation(() => {});
+      appendDiscoveryEvidence([
+        { description: "gap1", category: "old-structure", impact: "hard", fixture: "fx1", timestamp: "t1", source: "evaluation" },
+      ], disPath);
+      expect(spy).toHaveBeenCalledWith(expect.stringContaining('Non-standard category "old-structure"'));
+      spy.mockRestore();
+    });
+
+    it("does not warn on standard category", () => {
+      const spy = vi.spyOn(console, "warn").mockImplementation(() => {});
+      appendDiscoveryEvidence([
+        { description: "gap1", category: "pixel-critical", impact: "hard", fixture: "fx1", timestamp: "t1", source: "evaluation" },
+      ], disPath);
+      expect(spy).not.toHaveBeenCalled();
+      spy.mockRestore();
+    });
+
     it("throws when file has unsupported schemaVersion", () => {
       const file = { schemaVersion: 999, entries: [] };
       writeFileSync(disPath, JSON.stringify(file), "utf-8");
@@ -454,14 +472,14 @@ describe("evidence-collector", () => {
       appendDiscoveryEvidence([
         { description: "gap1", category: "Pixel-critical", impact: "hard", fixture: "fx1", timestamp: "t1", source: "evaluation" },
         { description: "gap2", category: "pixel-critical", impact: "hard", fixture: "fx2", timestamp: "t2", source: "gap-analysis" },
-        { description: "gap3", category: "color", impact: "moderate", fixture: "fx1", timestamp: "t1", source: "evaluation" },
+        { description: "gap3", category: "token-management", impact: "moderate", fixture: "fx1", timestamp: "t1", source: "evaluation" },
       ], disPath);
 
       pruneDiscoveryEvidence(["pixel-critical"], disPath);
 
       const raw = JSON.parse(readFileSync(disPath, "utf-8")) as { entries: DiscoveryEvidenceEntry[] };
       expect(raw.entries).toHaveLength(1);
-      expect(raw.entries[0]!.category).toBe("color");
+      expect(raw.entries[0]!.category).toBe("token-management");
     });
 
     it("writes versioned format after prune", () => {
diff --git a/src/agents/evidence-collector.ts b/src/agents/evidence-collector.ts
index 5f9e2d2f..24aef148 100644
--- a/src/agents/evidence-collector.ts
+++ b/src/agents/evidence-collector.ts
@@ -6,6 +6,7 @@ import {
   DiscoveryEvidenceFileSchema,
   DISCOVERY_EVIDENCE_SCHEMA_VERSION,
 } from "./contracts/evidence.js";
+import { CategorySchema } from "../core/contracts/category.js";
 import type {
   CalibrationEvidenceEntry,
   CrossRunEvidence,
@@ -293,6 +294,15 @@ export function appendDiscoveryEvidence(
   evidencePath: string = DEFAULT_DISCOVERY_PATH
 ): void {
   if (entries.length === 0) return;
+
+  // Warn on non-standard categories (safety net for converter typos/old labels)
+  for (const e of entries) {
+    const parsed = CategorySchema.safeParse(e.category);
+    if (!parsed.success) {
+      console.warn(`[evidence] Non-standard category "${e.category}" in discovery evidence (expected: ${CategorySchema.options.join(", ")})`);
+    }
+  }
+
   const existing = readDiscoveryEvidence(evidencePath);
 
   // Build map of existing entries keyed by dedupe key
diff --git a/src/cli/commands/internal/calibrate-debate.ts b/src/cli/commands/internal/calibrate-debate.ts
index 7a228e29..ddd94ce7 100644
--- a/src/cli/commands/internal/calibrate-debate.ts
+++ b/src/cli/commands/internal/calibrate-debate.ts
@@ -1,9 +1,10 @@
 import { existsSync, readFileSync, writeFileSync } from "node:fs";
-import { join, resolve } from "node:path";
+import { join } from "node:path";
 import type { CAC } from "cac";
 
 import { parseDebateResult } from "../../../agents/run-directory.js";
 import { loadCalibrationEvidence } from "../../../agents/evidence-collector.js";
+import { resolveRunDir } from "./cli-helpers.js";
 
 // ─── calibrate-gather-evidence ──────────────────────────────────────────────
 
@@ -103,11 +104,8 @@ export function registerGatherEvidence(cli: CAC): void {
       "Gather structured evidence for Critic from run artifacts + cross-run data"
     )
     .action((runDir: string) => {
-      const dir = resolve(runDir);
-      if (!existsSync(dir)) {
-        console.log(`Run directory not found: ${runDir}`);
-        return;
-      }
+      const dir = resolveRunDir(runDir);
+      if (!dir) return;
 
       const proposedRuleIds = loadProposedRuleIds(dir);
       const evidence = gatherEvidence(dir, proposedRuleIds);
@@ -134,11 +132,8 @@ export function registerFinalizeDebate(cli: CAC): void {
       "Check early-stop or determine stoppingReason after debate"
     )
     .action((runDir: string) => {
-      const dir = resolve(runDir);
-      if (!existsSync(dir)) {
-        console.log(`Run directory not found: ${runDir}`);
-        return;
-      }
+      const dir = resolveRunDir(runDir);
+      if (!dir) return;
 
       const debate = parseDebateResult(dir);
       if (!debate) {
diff --git a/src/cli/commands/internal/cli-helpers.ts b/src/cli/commands/internal/cli-helpers.ts
new file mode 100644
index 00000000..f59dae8e
--- /dev/null
+++ b/src/cli/commands/internal/cli-helpers.ts
@@ -0,0 +1,30 @@
+import { existsSync, statSync } from "node:fs";
+import { resolve } from "node:path";
+import { z } from "zod";
+
+export const RUN_DIR_ARG_SCHEMA = z.string().trim().min(1, "runDir is required");
+export const KEYWORD_ARG_SCHEMA = z.string().trim().min(1, "keyword is required");
+
+/**
+ * Validate and resolve a run directory path.
+ * Returns the resolved absolute path, or null if invalid/missing/not a directory.
+ * Logs to stdout and returns null on failure (internal CLI convention).
+ */
+export function resolveRunDir(runDir: string): string | null {
+  const parsed = RUN_DIR_ARG_SCHEMA.safeParse(runDir);
+  if (!parsed.success) {
+    console.log(`Invalid runDir: ${parsed.error.issues[0]?.message}`);
+    return null;
+  }
+  const dir = resolve(parsed.data);
+  try {
+    if (!existsSync(dir) || !statSync(dir).isDirectory()) {
+      console.log(`Run directory not found or is not a directory: ${runDir}`);
+      return null;
+    }
+  } catch {
+    console.log(`Run directory not accessible: ${runDir}`);
+    return null;
+  }
+  return dir;
+}
diff --git a/src/cli/commands/internal/fixture-management.ts b/src/cli/commands/internal/fixture-management.ts
index 85dfea03..12b73324 100644
--- a/src/cli/commands/internal/fixture-management.ts
+++ b/src/cli/commands/internal/fixture-management.ts
@@ -1,6 +1,6 @@
-import { existsSync } from "node:fs";
 import { basename, resolve } from "node:path";
 import type { CAC } from "cac";
+import { resolveRunDir } from "./cli-helpers.js";
 
 import {
   listActiveFixtures,
@@ -121,11 +121,8 @@ export function registerEvidenceEnrich(cli: CAC): void {
       "Enrich evidence with Critic's pro/con/confidence from debate.json"
     )
     .action((runDir: string) => {
-      const resolvedDir = resolve(runDir);
-      if (!existsSync(resolvedDir)) {
-        console.log(`Run directory not found: ${runDir}`);
-        return;
-      }
+      const resolvedDir = resolveRunDir(runDir);
+      if (!resolvedDir) return;
       const debate = parseDebateResult(resolvedDir);
       if (!debate?.critic) {
         console.log("No critic reviews in debate.json — nothing to enrich.");
@@ -161,11 +158,9 @@ export function registerEvidencePrune(cli: CAC): void {
       "Prune evidence for rules applied by the Arbitrator in the given run"
     )
     .action((runDir: string) => {
-      if (!existsSync(resolve(runDir))) {
-        console.log(`Run directory not found: ${runDir}`);
-        return;
-      }
-      const debate = parseDebateResult(resolve(runDir));
+      const resolvedDir = resolveRunDir(runDir);
+      if (!resolvedDir) return;
+      const debate = parseDebateResult(resolvedDir);
       if (!debate) {
         console.log("No debate.json found — nothing to prune.");
         return;
@@ -197,4 +192,4 @@ export function registerEvidencePrune(cli: CAC): void {
         process.exitCode = 1;
       }
     });
-}
+}
\ No newline at end of file
diff --git a/src/cli/commands/internal/rule-discovery.test.ts b/src/cli/commands/internal/rule-discovery.test.ts
index 3e6d6a25..5bb9d811 100644
--- a/src/cli/commands/internal/rule-discovery.test.ts
+++ b/src/cli/commands/internal/rule-discovery.test.ts
@@ -3,7 +3,7 @@ import { join } from "node:path";
 import { tmpdir } from "node:os";
 import { rm } from "node:fs/promises";
 
-import { filterDiscoveryEvidence, readDecision } from "./rule-discovery.js";
+import { filterDiscoveryEvidence, readDecision, collectGapEvidence } from "./rule-discovery.js";
 
 describe("filterDiscoveryEvidence", () => {
   it("returns empty array when no matching evidence exists", () => {
@@ -118,3 +118,63 @@ describe("readDecision", () => {
     expect(readDecision(runDir)).toBeNull();
   });
 });
+
+describe("collectGapEvidence", () => {
+  let runDir: string;
+
+  beforeEach(() => {
+    runDir = mkdtempSync(join(tmpdir(), "gap-evidence-test-"));
+  });
+
+  afterEach(async () => {
+    await rm(runDir, { recursive: true, force: true });
+  });
+
+  it("extracts uncovered actionable gaps", () => {
+    writeFileSync(join(runDir, "gaps.json"), JSON.stringify({
+      gaps: [
+        { category: "spacing", description: "padding off", actionable: true, coveredByRule: null },
+        { category: "color", description: "wrong shade", actionable: true, coveredByRule: null },
+        { category: "rendering", description: "font fallback", actionable: false },
+        { category: "layout", description: "flex gap", actionable: true, coveredByRule: "no-auto-layout" },
+      ],
+    }));
+
+    const entries = collectGapEvidence(runDir, "test-fixture");
+    expect(entries).toHaveLength(2);
+    expect(entries[0]!.category).toBe("spacing");
+    expect(entries[0]!.source).toBe("gap-analysis");
+    expect(entries[0]!.fixture).toBe("test-fixture");
+    expect(entries[1]!.category).toBe("color");
+  });
+
+  it("returns empty for no gaps.json", () => {
+    expect(collectGapEvidence(runDir, "fx")).toHaveLength(0);
+  });
+
+  it("returns empty when all gaps are covered or non-actionable", () => {
+    writeFileSync(join(runDir, "gaps.json"), JSON.stringify({
+      gaps: [
+        { category: "spacing", description: "x", actionable: false },
+        { category: "color", description: "y", actionable: true, coveredByRule: "raw-value" },
+      ],
+    }));
+
+    expect(collectGapEvidence(runDir, "fx")).toHaveLength(0);
+  });
+
+  it("skips actionable gap when coveredByRule is empty string", () => {
+    writeFileSync(join(runDir, "gaps.json"), JSON.stringify({
+      gaps: [
+        { category: "spacing", description: "x", actionable: true, coveredByRule: "" },
+      ],
+    }));
+
+    expect(collectGapEvidence(runDir, "fx")).toHaveLength(0);
+  });
+
+  it("returns empty for malformed gaps.json", () => {
+    writeFileSync(join(runDir, "gaps.json"), "not json");
+    expect(collectGapEvidence(runDir, "fx")).toHaveLength(0);
+  });
+});
diff --git a/src/cli/commands/internal/rule-discovery.ts b/src/cli/commands/internal/rule-discovery.ts
index 717379b5..a8c16081 100644
--- a/src/cli/commands/internal/rule-discovery.ts
+++ b/src/cli/commands/internal/rule-discovery.ts
@@ -1,9 +1,11 @@
-import { existsSync, readFileSync, statSync, writeFileSync } from "node:fs";
-import { join, resolve } from "node:path";
+import { existsSync, readFileSync, writeFileSync } from "node:fs";
+import { join } from "node:path";
 import type { CAC } from "cac";
-import { loadDiscoveryEvidence } from "../../../agents/evidence-collector.js";
+import { z } from "zod";
+import { loadDiscoveryEvidence, appendDiscoveryEvidence } from "../../../agents/evidence-collector.js";
 import type { DiscoveryEvidenceEntry } from "../../../agents/evidence-collector.js";
 import { DecisionFileSchema } from "../../../agents/contracts/evidence.js";
+import { resolveRunDir, KEYWORD_ARG_SCHEMA } from "./cli-helpers.js";
 
 // ─── discovery-filter-evidence ──────────────────────────────────────────────
 
@@ -39,15 +41,14 @@ export function registerFilterDiscoveryEvidence(cli: CAC): void {
     )
     .option("--run-dir <path>", "Write filtered evidence to run directory")
     .action((keyword: string, options: { runDir?: string }) => {
+      const kParsed = KEYWORD_ARG_SCHEMA.safeParse(keyword);
+      if (!kParsed.success) { console.log(`Invalid keyword: ${kParsed.error.issues[0]?.message}`); return; }
       try {
-        const filtered = filterDiscoveryEvidence(keyword);
+        const filtered = filterDiscoveryEvidence(kParsed.data);
 
         if (options.runDir) {
-          const dir = resolve(options.runDir);
-          if (!existsSync(dir) || !statSync(dir).isDirectory()) {
-            console.log(`Run directory not found or is not a directory: ${options.runDir}`);
-            return;
-          }
+          const dir = resolveRunDir(options.runDir);
+          if (!dir) return;
           const outPath = join(dir, "prior-evidence.json");
           writeFileSync(outPath, JSON.stringify(filtered, null, 2) + "\n", "utf-8");
           console.log(`Filtered ${filtered.length} entries for "${keyword}" → ${outPath}`);
@@ -110,11 +111,8 @@ export function registerApplyDecision(cli: CAC): void {
       "Read decision.json and output the action (commit/revert/adjust)"
     )
     .action((runDir: string) => {
-      const dir = resolve(runDir);
-      if (!existsSync(dir) || !statSync(dir).isDirectory()) {
-        console.log(`Run directory not found or is not a directory: ${runDir}`);
-        return;
-      }
+      const dir = resolveRunDir(runDir);
+      if (!dir) return;
 
       const result = readDecision(dir);
       if (!result) {
@@ -125,3 +123,86 @@ export function registerApplyDecision(cli: CAC): void {
       console.log(JSON.stringify(result));
     });
 }
+
+// ─── calibrate-collect-gap-evidence ─────────────────────────────────────────
+
+const GapSchema = z.object({
+  category: z.string(),
+  description: z.string(),
+  actionable: z.boolean(),
+  coveredByRule: z.unknown().default(null),
+}).passthrough();
+
+const GapsFileSchema = z.object({
+  fixture: z.string().optional(),
+  gaps: z.array(GapSchema),
+}).passthrough();
+
+/**
+ * Extract uncovered actionable gaps from gaps.json and append to discovery evidence.
+ * Deterministic — no LLM needed.
+ */
+export function collectGapEvidence(runDir: string, fixture: string): DiscoveryEvidenceEntry[] {
+  const gapsPath = join(runDir, "gaps.json");
+  if (!existsSync(gapsPath)) return [];
+
+  let raw: unknown;
+  try {
+    raw = JSON.parse(readFileSync(gapsPath, "utf-8"));
+  } catch {
+    return [];
+  }
+  const parsed = GapsFileSchema.safeParse(raw);
+  if (!parsed.success) return [];
+
+  const timestamp = new Date().toISOString();
+  const entries: DiscoveryEvidenceEntry[] = [];
+
+  for (const gap of parsed.data.gaps) {
+    // Only actionable gaps not covered by existing rules
+    if (!gap.actionable) continue;
+    // Skip when coveredByRule is present (non-nullish); empty string counts as "marked covered"
+    if (gap.coveredByRule != null) continue;
+
+    entries.push({
+      description: gap.description,
+      category: gap.category,
+      impact: "medium",
+      fixture,
+      timestamp,
+      source: "gap-analysis",
+    });
+  }
+
+  return entries;
+}
+
+export function registerCollectGapEvidence(cli: CAC): void {
+  cli
+    .command(
+      "calibrate-collect-gap-evidence <runDir>",
+      "Collect uncovered actionable gaps from gaps.json into discovery evidence"
+    )
+    .action((runDir: string) => {
+      const dir = resolveRunDir(runDir);
+      if (!dir) return;
+
+      // Extract fixture name from run dir
+      const dirName = dir.split(/[/\\]/).pop() ?? "";
+      const idx = dirName.lastIndexOf("--");
+      const fixture = idx === -1 ? dirName : dirName.slice(0, idx);
+
+      try {
+        const entries = collectGapEvidence(dir, fixture);
+        if (entries.length === 0) {
+          console.log("No uncovered actionable gaps found");
+          return;
+        }
+
+        appendDiscoveryEvidence(entries);
+        console.log(`Collected ${entries.length} gap evidence entries for fixture "${fixture}"`);
+      } catch (err) {
+        console.log(`Failed to collect gap evidence: ${err instanceof Error ? err.message : String(err)}`);
+      }
+    });
+}
diff --git a/src/cli/index.ts b/src/cli/index.ts
index 940ac521..b29b7203 100644
--- a/src/cli/index.ts
+++ b/src/cli/index.ts
@@ -33,7 +33,7 @@ import { registerCalibrateEvaluate } from "./commands/internal/calibrate-evaluat
 import { registerCalibrateGapReport } from "./commands/internal/calibrate-gap-report.js";
 import { registerCalibrateRun } from "./commands/internal/calibrate-run.js";
 import { registerGatherEvidence, registerFinalizeDebate } from "./commands/internal/calibrate-debate.js";
-import { registerFilterDiscoveryEvidence, registerApplyDecision } from "./commands/internal/rule-discovery.js";
+import { registerFilterDiscoveryEvidence, registerApplyDecision, registerCollectGapEvidence } from "./commands/internal/rule-discovery.js";
 import { registerFixtureManagement, registerEvidenceEnrich, registerEvidencePrune } from "./commands/internal/fixture-management.js";
 
 const require = createRequire(import.meta.url);
@@ -87,6 +87,7 @@ registerEvidenceEnrich(cli);
 registerEvidencePrune(cli);
 registerFilterDiscoveryEvidence(cli);
 registerApplyDecision(cli);
+registerCollectGapEvidence(cli);
 
 // ============================================
 // Documentation command