diff --git a/packages/context/src/ingest/adapters/historic-sql/evidence-tool.test.ts b/packages/context/src/ingest/adapters/historic-sql/evidence-tool.test.ts
new file mode 100644
index 00000000..a8219192
--- /dev/null
+++ b/packages/context/src/ingest/adapters/historic-sql/evidence-tool.test.ts
@@ -0,0 +1,80 @@
+import { describe, expect, it, vi } from 'vitest';
+import { createEmitHistoricSqlEvidenceTool } from './evidence-tool.js';
+
+describe('emit_historic_sql_evidence tool', () => {
+  it('writes table usage evidence to the ignored run evidence directory', async () => {
+    const writeFile = vi.fn(async () => ({ success: true, commitHash: null }));
+    const tool = createEmitHistoricSqlEvidenceTool();
+
+    const result = await tool.execute!(
+      {
+        kind: 'table_usage',
+        table: 'public.orders',
+        rawPath: 'tables/public.orders.json',
+        usage: {
+          narrative: 'Orders are repeatedly queried by paid status.',
+          frequencyTier: 'high',
+          commonFilters: ['status'],
+          commonJoins: [],
+          staleSince: null,
+        },
+      },
+      {
+        toolCallId: 'call-1',
+        messages: [],
+        abortSignal: new AbortController().signal,
+        experimental_context: {
+          connectionId: 'warehouse',
+          session: {
+            ingest: { runId: 'run-1', jobId: 'job-1', syncId: 'sync-1', sourceKey: 'historic-sql' },
+            configService: { writeFile },
+          },
+        },
+      } as never,
+    );
+
+    expect(result).toBe('Recorded historic-SQL table_usage evidence for public.orders.');
+    expect(writeFile).toHaveBeenCalledWith(
+      '.ktx/ingest-evidence/historic-sql/run-1/historic-sql-table-public-orders.json',
+      expect.stringContaining('"kind": "table_usage"'),
+      'System User',
+      'system@example.com',
+      'Record historic-SQL evidence: historic-sql-table-public-orders',
+      { skipLock: true },
+    );
+  });
+
+  it('rejects non-historic ingest sessions', async () => {
+    const tool = createEmitHistoricSqlEvidenceTool();
+
+    await expect(
+      tool.execute!(
+        {
+          kind: 'pattern',
+          rawPath: 'patterns-input.json',
+          pattern: {
+            slug: 'orders',
+            title: 'Orders',
+            narrative: 'Orders pattern.',
+            definitionSql: 'select * from public.orders',
+            tablesInvolved: ['public.orders'],
+            slRefs: ['orders'],
+            constituentTemplateIds: ['pg:1'],
+          },
+        },
+        {
+          toolCallId: 'call-1',
+          messages: [],
+          abortSignal: new AbortController().signal,
+          experimental_context: {
+            connectionId: 'warehouse',
+            session: {
+              ingest: { runId: 'run-1', jobId: 'job-1', syncId: 'sync-1', sourceKey: 'notion' },
+              configService: { writeFile: vi.fn() },
+            },
+          },
+        } as never,
+      ),
+    ).resolves.toContain('Error: emit_historic_sql_evidence is only available during historic-sql ingest');
+  });
+});
diff --git a/packages/context/src/ingest/adapters/historic-sql/evidence-tool.ts b/packages/context/src/ingest/adapters/historic-sql/evidence-tool.ts
new file mode 100644
index 00000000..634b7593
--- /dev/null
+++ b/packages/context/src/ingest/adapters/historic-sql/evidence-tool.ts
@@ -0,0 +1,72 @@
+import { tool } from 'ai';
+import { z } from 'zod';
+import { historicSqlEvidencePath, serializeHistoricSqlEvidence } from './evidence.js';
+import { patternOutputSchema, tableUsageOutputSchema } from './skill-schemas.js';
+
+const SYSTEM_AUTHOR = 'System User';
+const SYSTEM_EMAIL = 'system@example.com';
+
+function unitKeyForEvidence(input: { kind: string; table?: string; pattern?: { slug: string } }): string {
+  if (input.kind === 'table_usage') {
+    return `historic-sql-table-${String(input.table).replace(/[^a-zA-Z0-9]+/g, '-').replace(/^-+|-+$/g, '')}`;
+  }
+  return `historic-sql-pattern-${String(input.pattern?.slug).replace(/[^a-zA-Z0-9]+/g, '-').replace(/^-+|-+$/g, '')}`;
+}
+
+export function createEmitHistoricSqlEvidenceTool() {
+  return tool({
+    description:
+      'Record typed historic-SQL evidence for deterministic projection. Use this instead of wiki_write, sl_write_source, sl_edit_source, or context_candidate_write during historic-SQL WorkUnits.',
+    inputSchema: z.discriminatedUnion('kind', [
+      z.object({
+        kind: z.literal('table_usage'),
+        table: z.string().min(1),
+        rawPath: z.string().min(1),
+        usage: tableUsageOutputSchema,
+      }),
+      z.object({
+        kind: z.literal('pattern'),
+        rawPath: z.string().min(1),
+        pattern: patternOutputSchema,
+      }),
+    ]),
+    execute: async (input, options): Promise<string> => {
+      const context = options.experimental_context as
+        | {
+            connectionId?: string | null;
+            session?: {
+              ingest?: { runId: string; sourceKey: string };
+              configService?: {
+                writeFile(
+                  path: string,
+                  content: string,
+                  author: string,
+                  authorEmail: string,
+                  commitMessage: string,
+                  options?: { skipLock?: boolean },
+                ): Promise<unknown>;
+              };
+            };
+          }
+        | undefined;
+      const ingest = context?.session?.ingest;
+      const configService = context?.session?.configService;
+      if (!ingest || ingest.sourceKey !== 'historic-sql' || !configService || !context?.connectionId) {
+        return 'Error: emit_historic_sql_evidence is only available during historic-sql ingest.';
+      }
+
+      const unitKey = unitKeyForEvidence(input);
+      const content = serializeHistoricSqlEvidence({ ...input, connectionId: context.connectionId });
+      await configService.writeFile(
+        historicSqlEvidencePath(ingest.runId, unitKey),
+        content,
+        SYSTEM_AUTHOR,
+        SYSTEM_EMAIL,
+        `Record historic-SQL evidence: ${unitKey}`,
+        { skipLock: true },
+      );
+      const label = input.kind === 'table_usage' ? input.table : input.pattern.slug;
+      return `Recorded historic-SQL ${input.kind} evidence for ${label}.`;
+    },
+  });
+}
diff --git a/packages/context/src/ingest/adapters/historic-sql/evidence.test.ts b/packages/context/src/ingest/adapters/historic-sql/evidence.test.ts
new file mode 100644
index 00000000..2d6b7556
--- /dev/null
+++ b/packages/context/src/ingest/adapters/historic-sql/evidence.test.ts
@@ -0,0 +1,54 @@
+import { describe, expect, it } from 'vitest';
+import {
+  historicSqlEvidenceEnvelopeSchema,
+  historicSqlEvidencePath,
+  historicSqlTableUsageEvidenceSchema,
+} from './evidence.js';
+
+describe('historic-sql evidence contracts', () => {
+  it('validates table usage evidence emitted by table digest WorkUnits', () => {
+    const parsed = historicSqlTableUsageEvidenceSchema.parse({
+      kind: 'table_usage',
+      connectionId: 'warehouse',
+      table: 'public.orders',
+      rawPath: 'tables/public.orders.json',
+      usage: {
+        narrative: 'Orders are repeatedly queried for paid/refunded lifecycle analysis.',
+        frequencyTier: 'high',
+        commonFilters: ['status', 'created_at'],
+        commonGroupBys: ['status'],
+        commonJoins: [{ table: 'public.customers', on: ['customer_id'] }],
+        staleSince: null,
+      },
+    });
+
+    expect(parsed.table).toBe('public.orders');
+    expect(parsed.usage.frequencyTier).toBe('high');
+  });
+
+  it('validates pattern evidence emitted by the patterns WorkUnit', () => {
+    const parsed = historicSqlEvidenceEnvelopeSchema.parse({
+      kind: 'pattern',
+      connectionId: 'warehouse',
+      rawPath: 'patterns-input.json',
+      pattern: {
+        slug: 'order-lifecycle-analysis',
+        title: 'Order Lifecycle Analysis',
+        narrative: 'Analysts compare order status changes by customer segment.',
+        definitionSql: 'select status, count(*) from public.orders group by status',
+        tablesInvolved: ['public.orders', 'public.customers'],
+        slRefs: ['orders', 'customers'],
+        constituentTemplateIds: ['pg:1', 'pg:2'],
+      },
+    });
+
+    expect(parsed.kind).toBe('pattern');
+    expect(parsed.pattern.slug).toBe('order-lifecycle-analysis');
+  });
+
+  it('builds a stable ignored evidence path from run and WorkUnit identity', () => {
+    expect(historicSqlEvidencePath('run-1', 'historic-sql-table-public-orders')).toBe(
+      '.ktx/ingest-evidence/historic-sql/run-1/historic-sql-table-public-orders.json',
+    );
+  });
+});
diff --git a/packages/context/src/ingest/adapters/historic-sql/evidence.ts b/packages/context/src/ingest/adapters/historic-sql/evidence.ts
new file mode 100644
index 00000000..18c01a85
--- /dev/null
+++ b/packages/context/src/ingest/adapters/historic-sql/evidence.ts
@@ -0,0 +1,41 @@
+import { z } from 'zod';
+import { patternOutputSchema, tableUsageOutputSchema } from './skill-schemas.js';
+
+function safeEvidenceSegment(value: string): string {
+  const segment = value.replace(/[^a-zA-Z0-9._-]+/g, '-').replace(/^-+|-+$/g, '');
+  if (!segment) {
+    throw new Error(`Invalid historic-SQL evidence path segment: ${value}`);
+  }
+  return segment;
+}
+
+export const historicSqlTableUsageEvidenceSchema = z.object({
+  kind: z.literal('table_usage'),
+  connectionId: z.string().min(1),
+  table: z.string().min(1),
+  rawPath: z.string().min(1),
+  usage: tableUsageOutputSchema,
+});
+export type HistoricSqlTableUsageEvidence = z.infer<typeof historicSqlTableUsageEvidenceSchema>;
+
+export const historicSqlPatternEvidenceSchema = z.object({
+  kind: z.literal('pattern'),
+  connectionId: z.string().min(1),
+  rawPath: z.string().min(1),
+  pattern: patternOutputSchema,
+});
+export type HistoricSqlPatternEvidence = z.infer<typeof historicSqlPatternEvidenceSchema>;
+
+export const historicSqlEvidenceEnvelopeSchema = z.discriminatedUnion('kind', [
+  historicSqlTableUsageEvidenceSchema,
+  historicSqlPatternEvidenceSchema,
+]);
+export type HistoricSqlEvidenceEnvelope = z.infer<typeof historicSqlEvidenceEnvelopeSchema>;
+
+export function historicSqlEvidencePath(runId: string, unitKey: string): string {
+  return `.ktx/ingest-evidence/historic-sql/${safeEvidenceSegment(runId)}/${safeEvidenceSegment(unitKey)}.json`;
+}
+
+export function serializeHistoricSqlEvidence(evidence: HistoricSqlEvidenceEnvelope): string {
+  return `${JSON.stringify(historicSqlEvidenceEnvelopeSchema.parse(evidence), null, 2)}\n`;
+}
diff --git a/packages/context/src/ingest/index.ts b/packages/context/src/ingest/index.ts
index 352281d3..e3dc3899 100644
--- a/packages/context/src/ingest/index.ts
+++ b/packages/context/src/ingest/index.ts
@@ -334,6 +334,19 @@ export { PostgresPgssQueryHistoryReader } from './adapters/historic-sql/postgres
 export { SnowflakeHistoricSqlQueryHistoryReader } from './adapters/historic-sql/snowflake-query-history-reader.js';
 export { stageHistoricSqlAggregatedSnapshot } from './adapters/historic-sql/stage-unified.js';
 export { stageHistoricSqlTemplates } from './adapters/historic-sql/stage.js';
+export {
+  historicSqlEvidenceEnvelopeSchema,
+  historicSqlEvidencePath,
+  historicSqlPatternEvidenceSchema,
+  historicSqlTableUsageEvidenceSchema,
+  serializeHistoricSqlEvidence,
+} from './adapters/historic-sql/evidence.js';
+export type {
+  HistoricSqlEvidenceEnvelope,
+  HistoricSqlPatternEvidence,
+  HistoricSqlTableUsageEvidence,
+} from './adapters/historic-sql/evidence.js';
+export { createEmitHistoricSqlEvidenceTool } from './adapters/historic-sql/evidence-tool.js';
 export {
   patternOutputSchema,
   patternsArraySchema,
diff --git a/packages/context/src/package-exports.test.ts b/packages/context/src/package-exports.test.ts
index 40ed745f..25a3ddb1 100644
--- a/packages/context/src/package-exports.test.ts
+++ b/packages/context/src/package-exports.test.ts
@@ -243,6 +243,9 @@ describe('@ktx/context package exports', () => {
     expect(ingest.historicSqlUnifiedPullConfigSchema).toBeDefined();
     expect(ingest.aggregatedTemplateSchema).toBeDefined();
     expect(ingest.stagedTableInputSchema).toBeDefined();
+    expect(ingest.historicSqlEvidenceEnvelopeSchema).toBeDefined();
+    expect(ingest.historicSqlEvidencePath).toBeTypeOf('function');
+    expect(ingest.createEmitHistoricSqlEvidenceTool).toBeTypeOf('function');
     expect(ingest.SqliteContextEvidenceStore).toBeTypeOf('function');
     expect(ingest.SqliteBundleIngestStore).toBeTypeOf('function');
     expect(ingest.CuratorPaginationService).toBeTypeOf('function');