Feat/math validation agent (#6012)

Co-authored-by: James Brunton <[email protected]>
Co-authored-by: EthanHealy01 <[email protected]>

.pre-commit-config.yaml

@@ -16,7 +16,7 @@ repos:
     hooks:
       - id: codespell
         args:
-          - --ignore-words-list=thirdParty,tabEl,tabEls,Sie,ist
+          - --ignore-words-list=thirdParty,tabEl,tabEls,Sie,ist,fulfilment
           - --skip="./.*,*.csv,*.json,*.ambr"
           - --quiet-level=2
         files: \.(html|css|js|py|md)$

app/proprietary/build.gradle

@@ -59,6 +59,14 @@ dependencies {
     // https://mvnrepository.com/artifact/com.bucket4j/bucket4j_jdk17
     implementation "org.bouncycastle:bcprov-jdk18on:$bouncycastleVersion"
 
+    // Tabula table extraction — used by MathAuditorOrchestrator
+    implementation ('technology.tabula:tabula:1.0.5') {
+        exclude group: 'org.slf4j', module: 'slf4j-simple'
+        exclude group: 'org.bouncycastle', module: 'bcprov-jdk15on'
+        exclude group: 'com.google.code.gson', module: 'gson'
+    }
+    implementation 'com.google.code.gson:gson:2.13.2'
+
     api 'io.micrometer:micrometer-registry-prometheus'
 
     api "io.jsonwebtoken:jjwt-api:$jwtVersion"

app/proprietary/src/main/java/stirling/software/proprietary/controller/api/MathAuditorAgentController.java

@@ -0,0 +1,97 @@
+package stirling.software.proprietary.controller.api;
+
+import java.io.IOException;
+import java.math.BigDecimal;
+
+import org.springframework.http.HttpStatus;
+import org.springframework.http.MediaType;
+import org.springframework.http.ResponseEntity;
+import org.springframework.web.bind.annotation.PostMapping;
+import org.springframework.web.bind.annotation.RequestMapping;
+import org.springframework.web.bind.annotation.RequestParam;
+import org.springframework.web.bind.annotation.RestController;
+import org.springframework.web.multipart.MultipartFile;
+
+import io.swagger.v3.oas.annotations.Operation;
+import io.swagger.v3.oas.annotations.Parameter;
+import io.swagger.v3.oas.annotations.tags.Tag;
+
+import lombok.RequiredArgsConstructor;
+import lombok.extern.slf4j.Slf4j;
+
+import stirling.software.proprietary.model.api.ai.Verdict;
+import stirling.software.proprietary.service.MathAuditorOrchestrator;
+
+/**
+ * Public entry point for the Math Auditor Agent (mathAuditorAgent).
+ *
+ * <p>Accepts a PDF from the client, hands it to the {@link MathAuditorOrchestrator} which runs the
+ * multi-round Java-Python negotiation, and returns the Auditor's {@link Verdict}.
+ *
+ * <p>The raw PDF never leaves Java. Python receives only structured text and CSV data.
+ */
+@Slf4j
+@RestController
+@RequestMapping("/api/v1/ai")
+@RequiredArgsConstructor
+@Tag(name = "AI Engine", description = "AI-powered document analysis endpoints.")
+public class MathAuditorAgentController {
+
+    private final MathAuditorOrchestrator orchestrator;
+
+    @PostMapping(value = "/math-auditor-agent", consumes = MediaType.MULTIPART_FORM_DATA_VALUE)
+    @Operation(
+            summary = "Validate mathematical calculations in a PDF",
+            description =
+                    """
+                    Analyses a PDF document for mathematical errors using the Math Auditor Agent.
+
+                    The auditor checks:
+                    - Table row and column totals (tally errors)
+                    - Inline arithmetic expressions (e.g. "100 + 200 = 300")
+                    - Cross-page figure consistency (same figure cited differently on different pages)
+                    - Prose claims about percentages, growth rates, and comparisons
+
+                    The PDF is processed entirely on the Java side; only extracted text and table data
+                    are sent to the AI engine.
+
+                    Input: PDF  Output: JSON  Type: SISO
+                    """)
+    public ResponseEntity<Verdict> mathAuditorAgent(
+            @Parameter(description = "The PDF document to audit", required = true)
+                    @RequestParam("fileInput")
+                    MultipartFile fileInput,
+            @Parameter(
+                            description =
+                                    "Arithmetic tolerance — differences smaller than this are"
+                                            + " ignored (default: 0.01)")
+                    @RequestParam(value = "tolerance", defaultValue = "0.01")
+                    BigDecimal tolerance) {
+
+        String contentType = fileInput.getContentType();
+        if (contentType == null || !contentType.equals("application/pdf")) {
+            return ResponseEntity.badRequest().build();
+        }
+
+        if (tolerance.compareTo(BigDecimal.ZERO) < 0) {
+            return ResponseEntity.badRequest().build();
+        }
+
+        String safeName =
+                fileInput.getOriginalFilename() != null
+                        ? fileInput.getOriginalFilename().replaceAll("[\\r\\n]", "_")
+                        : "<unnamed>";
+        log.info("[math-auditor-agent] request file={} tolerance={}", safeName, tolerance);
+
+        try {
+            Verdict verdict = orchestrator.audit(fileInput, tolerance);
+            return ResponseEntity.ok(verdict);
+        } catch (IOException e) {
+            log.error("[math-auditor-agent] IO error during audit", e);
+            return ResponseEntity.status(HttpStatus.INTERNAL_SERVER_ERROR).build();
+        } catch (Exception e) {
+            log.error("[math-auditor-agent] unexpected error during audit", e);
+            return ResponseEntity.status(HttpStatus.INTERNAL_SERVER_ERROR).build();
+        }
+    }
+}

app/proprietary/src/main/java/stirling/software/proprietary/model/api/ai/AuditDiscrepancy.java

@@ -0,0 +1,21 @@
+package stirling.software.proprietary.model.api.ai;
+
+/**
+ * A single mathematical error found by the Python Auditor.
+ *
+ * @param page 0-indexed page number where the discrepancy appears.
+ * @param kind Category of the discrepancy.
+ * @param severity Whether this is a definite mistake or a possible ambiguity.
+ * @param description Human-readable explanation of the error.
+ * @param stated The value as it appears in the document.
+ * @param expected The value the Auditor calculated.
+ * @param context Surrounding text or table fragment for traceability.
+ */
+public record AuditDiscrepancy(
+        int page,
+        DiscrepancyKind kind,
+        AuditSeverity severity,
+        String description,
+        String stated,
+        String expected,
+        String context) {}

app/proprietary/src/main/java/stirling/software/proprietary/model/api/ai/AuditSeverity.java

@@ -0,0 +1,17 @@
+package stirling.software.proprietary.model.api.ai;
+
+import com.fasterxml.jackson.annotation.JsonValue;
+
+/**
+ * Severity of a mathematical discrepancy. Mirrors the Python {@code Severity} enum in {@code
+ * contracts/ledger.py}.
+ */
+public enum AuditSeverity {
+    ERROR,
+    WARNING;
+
+    @JsonValue
+    public String toJson() {
+        return name().toLowerCase();
+    }
+}

app/proprietary/src/main/java/stirling/software/proprietary/model/api/ai/DiscrepancyKind.java

@@ -0,0 +1,19 @@
+package stirling.software.proprietary.model.api.ai;
+
+import com.fasterxml.jackson.annotation.JsonValue;
+
+/**
+ * Category of a mathematical discrepancy found by the auditor. Mirrors the Python {@code
+ * DiscrepancyKind} enum in {@code contracts/ledger.py}.
+ */
+public enum DiscrepancyKind {
+    TALLY,
+    ARITHMETIC,
+    CONSISTENCY,
+    STATEMENT;
+
+    @JsonValue
+    public String toJson() {
+        return name().toLowerCase();
+    }
+}

app/proprietary/src/main/java/stirling/software/proprietary/model/api/ai/Evidence.java

@@ -0,0 +1,24 @@
+package stirling.software.proprietary.model.api.ai;
+
+import java.util.List;
+
+/**
+ * Java's fulfilment package: the extracted content the Python Auditor asked for.
+ *
+ * <p>Sent after Java has fulfilled a {@link Requisition}. When {@code finalRound} is {@code true},
+ * the Auditor must return a {@link Verdict} — Java will not honour further Requisitions.
+ *
+ * @param sessionId Matches the session opened by the original client request.
+ * @param folios The extracted page content for each page in the Requisition.
+ * @param round Which negotiation round this Evidence belongs to (1–3).
+ * @param finalRound When {@code true}, the Auditor must commit to a Verdict this round.
+ * @param unauditablePages Pages that were requested but could not be fulfilled — e.g. OCR was asked
+ *     for but is not yet wired. The Auditor echoes these into {@link Verdict#unauditablePages()} so
+ *     the client knows coverage is incomplete.
+ */
+public record Evidence(
+        String sessionId,
+        List<Folio> folios,
+        int round,
+        boolean finalRound,
+        List<Integer> unauditablePages) {}

app/proprietary/src/main/java/stirling/software/proprietary/model/api/ai/Folio.java

@@ -0,0 +1,17 @@
+package stirling.software.proprietary.model.api.ai;
+
+import java.util.List;
+
+/**
+ * One page's worth of extracted content, assembled by Java in response to a {@link Requisition}.
+ *
+ * <p>Only the fields explicitly requested will be populated; unused fields are {@code null}.
+ *
+ * @param page 0-indexed page number.
+ * @param text PDFBox plain-text extraction result (null if not requested).
+ * @param tables Tabula CSV strings, one per table found on the page (null if not requested).
+ * @param ocrText OCRmyPDF output text (null if not requested or OCR not available).
+ * @param ocrConfidence Mean character confidence from OCRmyPDF, 0.0–1.0 (null if OCR not run).
+ */
+public record Folio(
+        int page, String text, List<String> tables, String ocrText, Double ocrConfidence) {}

app/proprietary/src/main/java/stirling/software/proprietary/model/api/ai/FolioManifest.java

@@ -0,0 +1,18 @@
+package stirling.software.proprietary.model.api.ai;
+
+import java.util.List;
+
+/**
+ * Java's opening move in the audit negotiation.
+ *
+ * <p>Built from a cheap PDFBox scan (character count + image detection) with no OCR or Tabula
+ * involved. Sent to the Python Examiner, which replies with a {@link Requisition}.
+ *
+ * @param sessionId Opaque handle Java uses to locate the PDF on disk during this audit session.
+ * @param pageCount Total number of pages in the document.
+ * @param folioTypes One {@link FolioType} per page (0-indexed). {@code folioTypes.size() ==
+ *     pageCount}.
+ * @param round Which negotiation round this manifest belongs to (1–3).
+ */
+public record FolioManifest(
+        String sessionId, int pageCount, List<FolioType> folioTypes, int round) {}

app/proprietary/src/main/java/stirling/software/proprietary/model/api/ai/FolioType.java

@@ -0,0 +1,21 @@
+package stirling.software.proprietary.model.api.ai;
+
+import com.fasterxml.jackson.annotation.JsonValue;
+
+/**
+ * Java's classification of a single PDF page after a cheap PDFBox character-count scan. Mirrors the
+ * Python {@code FolioType} enum in {@code ledger/models.py}.
+ */
+public enum FolioType {
+    /** Selectable text layer is present — PDFBox can extract text directly. */
+    TEXT,
+    /** Image-only page — OCRmyPDF is required before any text is available. */
+    IMAGE,
+    /** Partial text layer plus embedded images — both PDFBox and OCRmyPDF may be useful. */
+    MIXED;
+
+    @JsonValue
+    public String toJson() {
+        return name().toLowerCase();
+    }
+}

app/proprietary/src/main/java/stirling/software/proprietary/model/api/ai/Requisition.java

@@ -0,0 +1,30 @@
+package stirling.software.proprietary.model.api.ai;
+
+import java.util.List;
+
+/**
+ * The Python Examiner's shopping list: which pages Java must extract before the Auditor can form an
+ * opinion.
+ *
+ * <p>Java parses this from the Examiner's response, fulfils it (text / tables / OCR), and sends the
+ * results back as an {@link Evidence} payload.
+ *
+ * @param type Discriminator — always {@code "requisition"}.
+ * @param needText 0-indexed page numbers requiring PDFBox plain-text extraction.
+ * @param needTables 0-indexed page numbers requiring Tabula CSV extraction.
+ * @param needOcr 0-indexed page numbers requiring OCRmyPDF.
+ * @param rationale Human-readable reason logged for observability.
+ */
+public record Requisition(
+        String type,
+        List<Integer> needText,
+        List<Integer> needTables,
+        List<Integer> needOcr,
+        String rationale) {
+
+    public boolean isEmpty() {
+        return (needText == null || needText.isEmpty())
+                && (needTables == null || needTables.isEmpty())
+                && (needOcr == null || needOcr.isEmpty());
+    }
+}

app/proprietary/src/main/java/stirling/software/proprietary/model/api/ai/Verdict.java

@@ -0,0 +1,43 @@
+package stirling.software.proprietary.model.api.ai;
+
+import java.util.List;
+
+/**
+ * The Auditor's final opinion on the document's mathematical integrity.
+ *
+ * <p>This is the terminal message in the audit negotiation; Java returns it to the client once
+ * received from Python.
+ *
+ * @param type Discriminator — always {@code "verdict"}.
+ * @param sessionId Matches the session opened by the original client request.
+ * @param discrepancies Every mathematical error found, sorted by page.
+ * @param pagesExamined 0-indexed page numbers the Auditor actually inspected.
+ * @param roundsTaken How many negotiation rounds were needed (1–3).
+ * @param summary One or two sentences suitable for the end user.
+ * @param clean {@code true} iff no errors were found (warnings are tolerated).
+ * @param unauditablePages Pages that could not be audited — typically image-only pages for which
+ *     OCR was requested but is not yet wired. The client should indicate that these pages were not
+ *     checked.
+ */
+public record Verdict(
+        String type,
+        String sessionId,
+        List<AuditDiscrepancy> discrepancies,
+        List<Integer> pagesExamined,
+        int roundsTaken,
+        String summary,
+        boolean clean,
+        List<Integer> unauditablePages) {
+
+    public long errorCount() {
+        return discrepancies == null
+                ? 0
+                : discrepancies.stream().filter(d -> d.severity() == AuditSeverity.ERROR).count();
+    }
+
+    public long warningCount() {
+        return discrepancies == null
+                ? 0
+                : discrepancies.stream().filter(d -> d.severity() == AuditSeverity.WARNING).count();
+    }
+}

app/proprietary/src/main/java/stirling/software/proprietary/pdf/FlexibleCSVWriter.java

@@ -0,0 +1,17 @@
+package stirling.software.proprietary.pdf;
+
+import org.apache.commons.csv.CSVFormat;
+
+import technology.tabula.writers.CSVWriter;
+
+/** Exposes Tabula's protected {@link CSVWriter#CSVWriter(CSVFormat)} constructor. */
+public class FlexibleCSVWriter extends CSVWriter {
+
+    public FlexibleCSVWriter() {
+        super();
+    }
+
+    public FlexibleCSVWriter(CSVFormat csvFormat) {
+        super(csvFormat);
+    }
+}

app/proprietary/src/main/java/stirling/software/proprietary/service/MathAuditorOrchestrator.java

@@ -0,0 +1,226 @@
+package stirling.software.proprietary.service;
+
+import java.io.IOException;
+import java.math.BigDecimal;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+import java.util.UUID;
+
+import org.apache.pdfbox.pdmodel.PDDocument;
+import org.springframework.stereotype.Service;
+import org.springframework.web.multipart.MultipartFile;
+
+import lombok.RequiredArgsConstructor;
+import lombok.extern.slf4j.Slf4j;
+
+import stirling.software.common.service.CustomPDFDocumentFactory;
+import stirling.software.proprietary.model.api.ai.Evidence;
+import stirling.software.proprietary.model.api.ai.Folio;
+import stirling.software.proprietary.model.api.ai.FolioManifest;
+import stirling.software.proprietary.model.api.ai.FolioType;
+import stirling.software.proprietary.model.api.ai.Requisition;
+import stirling.software.proprietary.model.api.ai.Verdict;
+
+import tools.jackson.databind.ObjectMapper;
+
+/**
+ * Orchestrator for the Math Auditor Agent (mathAuditorAgent).
+ *
+ * <p>Manages a four-step Java-Python protocol:
+ *
+ * <ol>
+ *   <li>Classify all pages cheaply with PDFBox (no OCR or Tabula yet).
+ *   <li>Send the {@link FolioManifest} to the Python Examiner; receive a {@link Requisition}.
+ *   <li>Fulfil the Requisition (text / tables / OCR) for only the requested pages.
+ *   <li>Send the {@link Evidence} to the Python Auditor; receive a {@link Verdict}.
+ * </ol>
+ *
+ * <p>The raw PDF never leaves Java. Python only receives structured text and CSV data.
+ */
+@Slf4j
+@Service
+@RequiredArgsConstructor
+public class MathAuditorOrchestrator {
+
+    private static final String EXAMINE_PATH = "/api/v1/ai/math-auditor-agent/examine";
+    private static final String DELIBERATE_PATH = "/api/v1/ai/math-auditor-agent/deliberate";
+
+    private final AiEngineClient aiEngineClient;
+    private final CustomPDFDocumentFactory pdfDocumentFactory;
+    private final PdfContentExtractor pdfContentExtractor;
+    private final ObjectMapper objectMapper;
+
+    /**
+     * Run a full math audit against the supplied PDF file.
+     *
+     * @param pdfFile The uploaded PDF to audit.
+     * @param tolerance Arithmetic tolerance — differences smaller than this are ignored.
+     * @return The Auditor's final Verdict.
+     */
+    public Verdict audit(MultipartFile pdfFile, BigDecimal tolerance) throws IOException {
+        String sessionId = UUID.randomUUID().toString();
+        log.info(
+                "[math-auditor-agent] audit started session={} file={} tolerance={}",
+                sessionId,
+                pdfFile.getOriginalFilename(),
+                tolerance);
+
+        try (PDDocument document = pdfDocumentFactory.load(pdfFile)) {
+            // Round 1: classify pages cheaply; send manifest; get requisition
+            List<FolioType> folioTypes = classifyPages(document);
+            FolioManifest manifest =
+                    new FolioManifest(sessionId, document.getNumberOfPages(), folioTypes, 1);
+
+            Requisition requisition = callExamine(manifest);
+            log.info(
+                    "[math-auditor-agent] session={} requisition received: {}",
+                    sessionId,
+                    requisition.rationale());
+
+            // Round 2: fulfil the requisition and get verdict
+            Evidence evidence = fulfil(document, sessionId, requisition, 2, true);
+            Verdict verdict = callDeliberate(evidence, tolerance);
+
+            if (verdict == null) {
+                log.error(
+                        "[math-auditor-agent] session={} null Verdict from deliberate", sessionId);
+                throw new IllegalStateException("Math Auditor Agent returned null Verdict");
+            }
+
+            log.info(
+                    "[math-auditor-agent] session={} verdict: {} errors, {} warnings,"
+                            + " clean={}",
+                    sessionId,
+                    verdict.errorCount(),
+                    verdict.warningCount(),
+                    verdict.clean());
+            return verdict;
+        }
+    }
+
+    // -----------------------------------------------------------------------
+    // Python engine calls
+    // -----------------------------------------------------------------------
+
+    private Requisition callExamine(FolioManifest manifest) throws IOException {
+        String requestBody = objectMapper.writeValueAsString(manifest);
+        log.info(
+                "[math-auditor-agent] POST {} session={} round={}",
+                EXAMINE_PATH,
+                manifest.sessionId(),
+                manifest.round());
+        String responseBody = aiEngineClient.post(EXAMINE_PATH, requestBody);
+        return objectMapper.readValue(responseBody, Requisition.class);
+    }
+
+    private Verdict callDeliberate(Evidence evidence, BigDecimal tolerance) throws IOException {
+        String path = DELIBERATE_PATH + "?tolerance=" + tolerance.toPlainString();
+        String requestBody = objectMapper.writeValueAsString(evidence);
+        log.info(
+                "[math-auditor-agent] POST {} session={} round={} final={}",
+                path,
+                evidence.sessionId(),
+                evidence.round(),
+                evidence.finalRound());
+        String responseBody = aiEngineClient.post(path, requestBody);
+        return objectMapper.readValue(responseBody, Verdict.class);
+    }
+
+    // -----------------------------------------------------------------------
+    // Page classification
+    // -----------------------------------------------------------------------
+
+    private List<FolioType> classifyPages(PDDocument document) throws IOException {
+        List<FolioType> types = new ArrayList<>();
+        for (int page = 1; page <= document.getNumberOfPages(); page++) {
+            types.add(pdfContentExtractor.classifyPage(document, page));
+        }
+        return types;
+    }
+
+    // -----------------------------------------------------------------------
+    // Requisition fulfilment
+    // -----------------------------------------------------------------------
+
+    private Evidence fulfil(
+            PDDocument document,
+            String sessionId,
+            Requisition requisition,
+            int round,
+            boolean finalRound)
+            throws IOException {
+
+        List<Integer> allPages =
+                union(requisition.needText(), requisition.needTables(), requisition.needOcr());
+        int totalPages = document.getNumberOfPages();
+        allPages.removeIf(page -> page < 0 || page >= totalPages);
+        if (allPages.isEmpty()) {
+            log.warn(
+                    "[math-auditor-agent] session={} all requested pages are out of bounds",
+                    sessionId);
+        }
+        List<Folio> folios = new ArrayList<>();
+        List<Integer> unauditablePages = new ArrayList<>();
+
+        for (int page : allPages) {
+            // Page indices from Python are 0-based; PdfContentExtractor uses 1-based
+            int pageNumber = page + 1;
+            String text = null;
+            List<String> tables = null;
+            String ocrText = null;
+
+            if (contains(requisition.needText(), page)) {
+                text = pdfContentExtractor.extractPageTextRaw(document, pageNumber);
+            }
+            if (contains(requisition.needTables(), page)) {
+                tables = pdfContentExtractor.extractTablesAsCsv(document, pageNumber);
+            }
+            if (contains(requisition.needOcr(), page)) {
+                log.warn(
+                        "[math-auditor-agent] session={} OCR requested for page {} but not yet"
+                                + " wired - marking unauditable",
+                        sessionId,
+                        page);
+                unauditablePages.add(page);
+            }
+
+            if (text != null || tables != null) {
+                folios.add(new Folio(page, text, tables, ocrText, null));
+            }
+        }
+
+        log.info(
+                "[math-auditor-agent] session={} fulfilled round {} with {} folios, {}"
+                        + " unauditable pages",
+                sessionId,
+                round,
+                folios.size(),
+                unauditablePages.size());
+        return new Evidence(sessionId, folios, round, finalRound, unauditablePages);
+    }
+
+    // -----------------------------------------------------------------------
+    // Helpers
+    // -----------------------------------------------------------------------
+
+    @SafeVarargs
+    private static List<Integer> union(List<Integer>... lists) {
+        List<Integer> result = new ArrayList<>();
+        for (List<Integer> list : lists) {
+            if (list != null) {
+                for (int page : list) {
+                    if (!result.contains(page)) {
+                        result.add(page);
+                    }
+                }
+            }
+        }
+        Collections.sort(result);
+        return result;
+    }
+
+    private static boolean contains(List<Integer> list, int value) {
+        return list != null && list.contains(value);
+    }
+}

app/proprietary/src/main/java/stirling/software/proprietary/service/PdfContentExtractor.java

@@ -1,7 +1,9 @@
 package stirling.software.proprietary.service;
 
 import java.io.IOException;
+import java.io.StringWriter;
 import java.util.ArrayList;
+import java.util.Collections;
 import java.util.LinkedHashSet;
 import java.util.List;
 import java.util.Map;
@@ -9,6 +11,8 @@ import java.util.Optional;
 import java.util.Set;
 import java.util.stream.Collectors;
 
+import org.apache.commons.csv.CSVFormat;
+import org.apache.commons.csv.QuoteMode;
 import org.apache.pdfbox.pdmodel.PDDocument;
 import org.apache.pdfbox.text.PDFTextStripper;
 import org.springframework.stereotype.Service;
@@ -20,9 +24,17 @@ import lombok.Data;
 import lombok.extern.slf4j.Slf4j;
 
 import stirling.software.common.util.ExceptionUtils;
+import stirling.software.common.util.PdfUtils;
 import stirling.software.proprietary.model.api.ai.AiPdfContentType;
 import stirling.software.proprietary.model.api.ai.AiWorkflowFileRequest;
 import stirling.software.proprietary.model.api.ai.AiWorkflowTextSelection;
+import stirling.software.proprietary.model.api.ai.FolioType;
+import stirling.software.proprietary.pdf.FlexibleCSVWriter;
+
+import technology.tabula.ObjectExtractor;
+import technology.tabula.Page;
+import technology.tabula.Table;
+import technology.tabula.extractors.SpreadsheetExtractionAlgorithm;
 
 @Slf4j
 @Service
@@ -30,8 +42,84 @@ public class PdfContentExtractor {
 
     private static final int MAX_CHARACTERS_PER_PAGE = 4_000;
 
+    private static final int TEXT_PRESENCE_THRESHOLD = 20;
+
     record LoadedFile(String fileName, PDDocument document) {}
 
+    // -----------------------------------------------------------------------
+    // Low-level extraction methods (usable by any agent)
+    // -----------------------------------------------------------------------
+
+    /**
+     * Classify a single page as TEXT, IMAGE, or MIXED.
+     *
+     * @param document the open PDF
+     * @param pageNumber 1-based page number
+     */
+    public FolioType classifyPage(PDDocument document, int pageNumber) throws IOException {
+        PDFTextStripper stripper = new PDFTextStripper();
+        stripper.setStartPage(pageNumber);
+        stripper.setEndPage(pageNumber);
+        String text = stripper.getText(document).trim();
+
+        boolean hasText = text.length() > TEXT_PRESENCE_THRESHOLD;
+        boolean hasImages = PdfUtils.hasImagesOnPage(document.getPage(pageNumber - 1));
+
+        if (hasText && hasImages) {
+            return FolioType.MIXED;
+        } else if (hasText) {
+            return FolioType.TEXT;
+        } else {
+            return FolioType.IMAGE;
+        }
+    }
+
+    /**
+     * Extract plain text from a single page, clipped to {@link #MAX_CHARACTERS_PER_PAGE}.
+     *
+     * @param document the open PDF
+     * @param pageNumber 1-based page number
+     * @return trimmed text, or empty string if the page has no extractable text
+     */
+    public String extractPageTextRaw(PDDocument document, int pageNumber) throws IOException {
+        PDFTextStripper stripper = new PDFTextStripper();
+        stripper.setStartPage(pageNumber);
+        stripper.setEndPage(pageNumber);
+        String text = stripper.getText(document).trim();
+        return clip(text, MAX_CHARACTERS_PER_PAGE);
+    }
+
+    /**
+     * Extract all tables from a single page as CSV strings.
+     *
+     * @param document the open PDF
+     * @param pageNumber 1-based page number
+     * @return list of CSV strings (one per table), empty if no tables found
+     */
+    public List<String> extractTablesAsCsv(PDDocument document, int pageNumber) throws IOException {
+        SpreadsheetExtractionAlgorithm sea = new SpreadsheetExtractionAlgorithm();
+        CSVFormat format =
+                CSVFormat.EXCEL.builder().setEscape('"').setQuoteMode(QuoteMode.ALL).build();
+        List<String> csvStrings = new ArrayList<>();
+
+        try (ObjectExtractor extractor = new ObjectExtractor(document)) {
+            Page tabulaPage = extractor.extract(pageNumber);
+            List<Table> tables = sea.extract(tabulaPage);
+
+            for (Table table : tables) {
+                StringWriter sw = new StringWriter();
+                FlexibleCSVWriter csvWriter = new FlexibleCSVWriter(format);
+                csvWriter.write(sw, Collections.singletonList(table));
+                csvStrings.add(sw.toString());
+            }
+        }
+        return csvStrings;
+    }
+
+    // -----------------------------------------------------------------------
+    // Workflow extraction (used by AiWorkflowService)
+    // -----------------------------------------------------------------------
+
     /**
      * Extracts content from the loaded files according to the requested content types and budget
      * constraints.

engine/config/.env.example

@@ -12,3 +12,9 @@ STIRLING_FAST_MODEL_MAX_TOKENS=2048
 STIRLING_POSTHOG_ENABLED=false
 STIRLING_POSTHOG_API_KEY=phc_VOdeYnlevc2T63m3myFGjeBlRcIusRgmhfx6XL5a1iz
 STIRLING_POSTHOG_HOST=https://eu.i.posthog.com
+
+# Log level for the stirling logger hierarchy (DEBUG, INFO, WARNING, ERROR)
+STIRLING_LOG_LEVEL=INFO
+
+# Path to log file. Rolls daily, keeps 1 backup. Leave empty for console only.
+STIRLING_LOG_FILE=

engine/pyproject.toml

@@ -46,6 +46,7 @@ select = [
     "UP",
     "PYI",    # flake8-pyi: flags deprecated typing constructs
     "FA",     # flake8-future-annotations: flags missing future annotations imports
+    "BLE",    # flake8-blind-except: flags bare `except Exception`
 ]
 
 [tool.pyright]

engine/src/stirling/agents/ledger/__init__.py

@@ -0,0 +1,5 @@
+"""Math Auditor Agent (mathAuditorAgent) — AI-powered math validation for PDF documents."""
+
+from .agent import MathAuditorAgent
+
+__all__ = ["MathAuditorAgent"]

engine/src/stirling/agents/ledger/agent.py

@@ -0,0 +1,550 @@
+"""
+Math Auditor Agent (mathAuditorAgent) — pydantic-ai agents for PDF math validation.
+
+Examiner  (Round 1, /api/v1/ai/math-auditor-agent/examine)
+    Receives a FolioManifest and returns a Requisition declaring what
+    Java must extract before validation can begin.
+
+Audit pipeline  (Round 2, /api/v1/ai/math-auditor-agent/deliberate)
+    Processes Evidence per-page:
+      1. Deterministic pass — ArithmeticScanner on every folio
+      2. Fast-model pass  — extract named figures from each page
+      3. FigureTracker    — cross-page consistency check
+      4. Fast-model call  — generate human-readable summary
+      5. Assemble Verdict programmatically
+
+Neither agent ever touches a PDF file. All content arrives pre-extracted
+by Java, which owns the PDF from start to finish.
+"""
+
+from __future__ import annotations
+
+import asyncio
+import logging
+from collections.abc import Coroutine
+from decimal import Decimal, InvalidOperation
+from typing import Any
+
+from pydantic import BaseModel, Field
+from pydantic_ai import Agent
+from pydantic_ai.exceptions import AgentRunError
+
+from stirling.contracts.ledger import (
+    Discrepancy,
+    DiscrepancyKind,
+    Evidence,
+    Folio,
+    FolioManifest,
+    Requisition,
+    Severity,
+    Verdict,
+)
+from stirling.logging import Pretty
+from stirling.services import AppRuntime
+
+from .prompts import (
+    EXAMINER_SYSTEM_PROMPT,
+    FIGURE_EXTRACTOR_PROMPT,
+    STATEMENT_VERIFIER_PROMPT,
+    SUMMARY_PROMPT,
+    TABLE_FORMULA_PROMPT,
+)
+from .validators import ArithmeticScanner, FigureTracker, FormulaEvaluator
+
+logger = logging.getLogger(__name__)
+
+
+# ---------------------------------------------------------------------------
+# Structured output models for the per-page figure extractor
+# ---------------------------------------------------------------------------
+
+
+class ExtractedFigure(BaseModel):
+    """A single named figure found on a page."""
+
+    label: str = Field(description="Normalised name, e.g. 'Total Revenue', 'VAT'.")
+    value: str = Field(description="Numeric value as a string, e.g. '1200.00'.")
+    raw: str = Field(description="Original text from the document, e.g. '£1,200.00'.")
+
+
+class FigureExtractionResult(BaseModel):
+    """All named figures found on a single page."""
+
+    figures: list[ExtractedFigure] = Field(default_factory=list)
+
+
+class FormulaCheck(BaseModel):
+    """One verifiable mathematical relationship in a table."""
+
+    description: str = Field(description="Human-readable, e.g. 'Line Total = Qty × Unit Price'")
+    formula: str = Field(description="Expression: 'col3 = col1 * col2' or 'cell(4,3) = sum(col3, 1-3)'")
+    scope: str = Field(description="'each_row' | 'column_total' | 'single_cell'")
+    row_range: list[int] | None = Field(default=None, description="Data rows to check (for each_row scope)")
+    target_row: int | None = Field(default=None, description="Row index of total (for column_total/single_cell)")
+    target_col: int | None = Field(default=None, description="Column index (for column_total/single_cell)")
+
+
+class TableFormulas(BaseModel):
+    """All verifiable formulas found in one table."""
+
+    formulas: list[FormulaCheck] = Field(default_factory=list)
+
+
+class StatementCheck(BaseModel):
+    """One prose claim and its verification result."""
+
+    claim: str = Field(description="The exact text of the claim")
+    verification: str = Field(description="Type: percentage_change, comparison, ratio, trend, average, other")
+    values_referenced: list[str] = Field(default_factory=list, description="Numbers used in the check")
+    expected_result: str = Field(description="What the calculation actually yields")
+    actual_claim: str = Field(description="What the text claims")
+    is_valid: bool = Field(description="True if the claim is correct within tolerance")
+    explanation: str = Field(description="One-line working showing the calculation")
+
+
+class StatementsResult(BaseModel):
+    """All verifiable prose claims found on a page."""
+
+    statements: list[StatementCheck] = Field(default_factory=list)
+
+
+# ---------------------------------------------------------------------------
+# MathAuditorAgent — main entry point, instantiated once at startup
+# ---------------------------------------------------------------------------
+
+
+class MathAuditorAgent:
+    """
+    Encapsulates the Ledger Auditor pipeline.
+
+    Instantiated once at app startup with an AppRuntime, which provides
+    pre-built Model objects and ModelSettings.
+    """
+
+    def __init__(self, runtime: AppRuntime) -> None:
+        fast_model = runtime.fast_model
+        model_settings = runtime.fast_model_settings
+        self._runtime = runtime
+        self._examiner = Agent(
+            model=fast_model,
+            deps_type=FolioManifest,
+            output_type=Requisition,
+            system_prompt=EXAMINER_SYSTEM_PROMPT,
+            model_settings=model_settings,
+        )
+        self._figure_extractor = Agent(
+            model=fast_model,
+            output_type=FigureExtractionResult,
+            system_prompt=FIGURE_EXTRACTOR_PROMPT,
+            model_settings=model_settings,
+        )
+        self._table_analyser = Agent(
+            model=fast_model,
+            output_type=TableFormulas,
+            system_prompt=TABLE_FORMULA_PROMPT,
+            model_settings=model_settings,
+        )
+        self._statement_verifier = Agent(
+            model=fast_model,
+            output_type=StatementsResult,
+            system_prompt=STATEMENT_VERIFIER_PROMPT,
+            model_settings=model_settings,
+        )
+        self._summary_agent = Agent(
+            model=fast_model,
+            output_type=str,
+            system_prompt=SUMMARY_PROMPT,
+            model_settings=model_settings,
+        )
+        self._llm_semaphore = asyncio.Semaphore(10)
+
+    # ------------------------------------------------------------------
+    # Round 1: Examine
+    # ------------------------------------------------------------------
+
+    async def examine(self, manifest: FolioManifest) -> Requisition:
+        """Inspect a FolioManifest and declare the Requisition."""
+        logger.info(
+            "[math-auditor-agent] session=%s round=%d examining %d folios",
+            manifest.session_id,
+            manifest.round,
+            manifest.page_count,
+        )
+
+        user_prompt = "Examine this folio manifest and declare your requisition:\n" + manifest.model_dump_json()
+        logger.debug("REQUEST (examine)\n%s", Pretty({"user_prompt": user_prompt}))
+
+        result = await self._examiner.run(user_prompt, deps=manifest)
+        req = result.output
+
+        logger.debug("RESPONSE (examine)\n%s", Pretty(req.model_dump()))
+        logger.info(
+            "[math-auditor-agent] session=%s requisition: text=%s tables=%s ocr=%s",
+            manifest.session_id,
+            req.need_text,
+            req.need_tables,
+            req.need_ocr,
+        )
+        return req
+
+    # ------------------------------------------------------------------
+    # Round 2: Deliberate (deterministic-first pipeline)
+    # ------------------------------------------------------------------
+
+    async def audit(self, evidence: Evidence, tolerance: Decimal = Decimal("0.01")) -> Verdict:
+        """
+        Audit the evidence using a deterministic-first pipeline:
+
+        1. Run ArithmeticScanner on every folio (no LLM)
+        2. Extract named figures per-page with fast model
+        3. Run FigureTracker cross-page consistency check (no LLM)
+        4. Generate human summary with fast model
+        5. Assemble Verdict
+        """
+        return await self._audit_inner(evidence, tolerance)
+
+    async def _audit_inner(
+        self,
+        evidence: Evidence,
+        tolerance: Decimal,
+    ) -> Verdict:
+        logger.info(
+            "[math-auditor-agent] session=%s round=%d auditing %d folios (final=%s)",
+            evidence.session_id,
+            evidence.round,
+            len(evidence.folios),
+            evidence.final_round,
+        )
+
+        all_discrepancies: list[Discrepancy] = []
+        pages_examined: list[int] = []
+        figure_tracker = FigureTracker(tolerance=tolerance)
+
+        # Step 1: Arithmetic scanning (deterministic, instant)
+        arithmetic_scanner = ArithmeticScanner(tolerance=tolerance)
+        for folio in evidence.folios:
+            pages_examined.append(folio.page)
+            text = folio.readable_text
+            if text and text.strip():
+                results = arithmetic_scanner.scan(folio.page, text)
+                all_discrepancies.extend(results)
+                logger.debug(
+                    "TOOL (scan_arithmetic)\nArgs: %s\nResult: %s",
+                    Pretty({"page": folio.page, "text_length": len(text)}),
+                    Pretty([d.model_dump() for d in results]),
+                )
+
+        # Step 2: Parallel LLM calls — formula inference + figure extraction
+        # These are independent per-page so we fire them all concurrently.
+        formula_evaluator = FormulaEvaluator(tolerance=tolerance)
+        folios_with_text = [f for f in evidence.folios if f.readable_text.strip()]
+
+        # Collect all tables as (page, csv) pairs for formula inference
+        table_tasks: list[tuple[int, str]] = []
+        for folio in evidence.folios:
+            if folio.tables:
+                for table_csv in folio.tables:
+                    table_tasks.append((folio.page, table_csv))
+
+        logger.info(
+            "[math-auditor-agent] session=%s step 2: %d formula + %d figure LLM calls (parallel)",
+            evidence.session_id,
+            len(table_tasks),
+            len(folios_with_text),
+        )
+
+        # Fire all LLM calls concurrently (bounded by _llm_semaphore)
+        formula_coros = [self._throttled(self._infer_formulas(csv)) for _, csv in table_tasks]
+        figure_coros = [self._throttled(self._extract_figures_for_page(f)) for f in folios_with_text]
+        statement_coros = [self._throttled(self._verify_statements(f)) for f in folios_with_text]
+        all_results = await asyncio.gather(
+            *formula_coros,
+            *figure_coros,
+            *statement_coros,
+            return_exceptions=True,
+        )
+
+        n_formulas = len(table_tasks)
+        n_figures = len(folios_with_text)
+
+        # Process formula results
+        for i, (page, table_csv) in enumerate(table_tasks):
+            result = all_results[i]
+            if isinstance(result, BaseException):
+                logger.warning("[math-auditor-agent] formula inference failed for page %d: %s", page, result)
+                continue
+            assert isinstance(result, TableFormulas)
+            formulas = result
+            if not formulas.formulas:
+                logger.info("[math-auditor-agent] page %d: no verifiable formulas found", page)
+                continue
+            for fc in formulas.formulas:
+                checked = formula_evaluator.evaluate(
+                    page=page,
+                    table_csv=table_csv,
+                    formula=fc.formula,
+                    scope=fc.scope,
+                    description=fc.description,
+                    row_range=fc.row_range,
+                    target_row=fc.target_row,
+                    target_col=fc.target_col,
+                )
+                all_discrepancies.extend(checked)
+                logger.debug(
+                    "TOOL (check_formula)\nArgs: %s\nResult: %s",
+                    Pretty({"page": page, "formula": fc.formula, "scope": fc.scope, "description": fc.description}),
+                    Pretty([d.model_dump() for d in checked]),
+                )
+
+        # Process figure results
+        for i, folio in enumerate(folios_with_text):
+            result = all_results[n_formulas + i]
+            if isinstance(result, BaseException):
+                logger.warning("[math-auditor-agent] figure extraction failed for page %d: %s", folio.page, result)
+                continue
+            assert isinstance(result, list)
+            for fig, page in result:
+                try:
+                    decimal_value = Decimal(fig.value.replace(",", "").strip())
+                except (InvalidOperation, ValueError):
+                    logger.warning(
+                        "[math-auditor-agent] skipping figure %r on page %d: non-numeric value %r",
+                        fig.label,
+                        page,
+                        fig.value,
+                    )
+                    continue
+                figure_tracker.record(
+                    label=fig.label,
+                    value=decimal_value,
+                    page=page,
+                    raw=fig.raw,
+                )
+
+        # Process statement verification results
+        for i, folio in enumerate(folios_with_text):
+            result = all_results[n_formulas + n_figures + i]
+            if isinstance(result, BaseException):
+                logger.warning("[math-auditor-agent] statement verification failed for page %d: %s", folio.page, result)
+                continue
+            assert isinstance(result, StatementsResult)
+            stmts = result
+            for sc in stmts.statements:
+                if not sc.is_valid:
+                    all_discrepancies.append(
+                        Discrepancy(
+                            page=folio.page,
+                            kind=DiscrepancyKind.STATEMENT,
+                            severity=Severity.ERROR,
+                            description=f"{sc.claim}: {sc.explanation}",
+                            stated=sc.actual_claim,
+                            expected=sc.expected_result,
+                            context=sc.claim,
+                        )
+                    )
+                logger.debug(
+                    "TOOL (verify_statement)\nArgs: %s\nResult: %s",
+                    Pretty({"page": folio.page, "claim": sc.claim}),
+                    Pretty(sc.model_dump()),
+                )
+
+        logger.info(
+            "[math-auditor-agent] session=%s step 2 complete: %d figures registered",
+            evidence.session_id,
+            figure_tracker.entry_count,
+        )
+
+        # Step 3: Cross-page consistency — deterministic
+        consistency_discrepancies = figure_tracker.conflicts()
+        all_discrepancies.extend(consistency_discrepancies)
+        if consistency_discrepancies:
+            logger.debug(
+                "TOOL (check_figure_consistency)\nResult: %s",
+                Pretty([d.model_dump() for d in consistency_discrepancies]),
+            )
+
+        # Step 4: Summary — fast model, small payload
+        # Collect verification stats for the summary
+        total_tables = sum(len(f.tables) for f in evidence.folios if f.tables)
+        total_formulas_checked = sum(len(r.formulas) for r in all_results[:n_formulas] if isinstance(r, TableFormulas))
+        total_statements_checked = sum(
+            len(r.statements) for r in all_results[n_formulas + n_figures :] if isinstance(r, StatementsResult)
+        )
+        verification_stats = (
+            f"Verified: {len(pages_examined)} pages, {total_tables} tables "
+            f"({total_formulas_checked} formulas), "
+            f"{figure_tracker.entry_count} figures tracked, "
+            f"{total_statements_checked} prose claims checked."
+        )
+
+        logger.info(
+            "[math-auditor-agent] session=%s step 4: generating summary (%d discrepancies)",
+            evidence.session_id,
+            len(all_discrepancies),
+        )
+        pages_examined.sort()
+        summary = await self._generate_summary(
+            all_discrepancies,
+            pages_examined,
+            evidence.unauditable_pages,
+            verification_stats,
+        )
+
+        # Step 5: Assemble Verdict
+        error_count = sum(1 for d in all_discrepancies if d.severity == Severity.ERROR)
+        verdict = Verdict(
+            session_id=evidence.session_id,
+            discrepancies=all_discrepancies,
+            pages_examined=pages_examined,
+            rounds_taken=evidence.round,
+            summary=summary,
+            clean=error_count == 0,
+            unauditable_pages=evidence.unauditable_pages,
+        )
+
+        logger.debug("RESPONSE (deliberate)\n%s", Pretty(verdict.model_dump()))
+        logger.info(
+            "[math-auditor-agent] session=%s verdict: %d errors, %d warnings, clean=%s",
+            evidence.session_id,
+            verdict.error_count,
+            verdict.warning_count,
+            verdict.clean,
+        )
+        return verdict
+
+    # ------------------------------------------------------------------
+    # Internal helpers
+    # ------------------------------------------------------------------
+
+    async def _throttled[T](self, coro: Coroutine[Any, Any, T]) -> T:
+        """Wrap a coroutine with the LLM concurrency semaphore."""
+        async with self._llm_semaphore:
+            return await coro
+
+    async def _infer_formulas(self, table_csv: str) -> TableFormulas:
+        """Ask the fast model to infer verifiable formulas from a CSV table."""
+        try:
+            result = await self._table_analyser.run(f"CSV table:\n{table_csv}")
+            formulas = result.output
+        except AgentRunError:
+            logger.warning("[math-auditor-agent] formula inference failed, skipping table", exc_info=True)
+            formulas = TableFormulas(formulas=[])
+
+        logger.debug(
+            "TOOL (infer_formulas)\nArgs: %s\nResult: %s",
+            Pretty({"table_csv": table_csv[:300]}),
+            Pretty(formulas.model_dump()),
+        )
+        return formulas
+
+    async def _verify_statements(
+        self,
+        folio: Folio,
+    ) -> StatementsResult:
+        """Ask the fast model to find and verify prose claims on a page."""
+        text = folio.readable_text
+        if not text or not text.strip():
+            return StatementsResult(statements=[])
+
+        # Build context: page text + any table CSVs
+        prompt = f"Page {folio.page + 1} text:\n{text}"
+        if folio.tables:
+            prompt += "\n\nTable data on this page:\n"
+            for i, csv in enumerate(folio.tables):
+                prompt += f"\nTable {i + 1}:\n{csv}"
+
+        try:
+            result = await self._statement_verifier.run(prompt)
+            stmts = result.output
+        except AgentRunError:
+            logger.warning("[math-auditor-agent] statement verification failed for page %d", folio.page, exc_info=True)
+            stmts = StatementsResult(statements=[])
+
+        if stmts.statements:
+            logger.debug(
+                "TOOL (verify_statements)\nArgs: %s\nResult: %s",
+                Pretty({"page": folio.page, "text_length": len(text), "n_tables": len(folio.tables or [])}),
+                Pretty([s.model_dump() for s in stmts.statements]),
+            )
+        return stmts
+
+    async def _extract_figures_for_page(
+        self,
+        folio: Folio,
+    ) -> list[tuple[ExtractedFigure, int]]:
+        text = folio.readable_text
+        if not text or not text.strip():
+            return []
+
+        logger.info("[math-auditor-agent] extracting figures from page %d (%d chars)", folio.page, len(text))
+        prompt = f"Page {folio.page + 1} text:\n{text}"
+        try:
+            result = await self._figure_extractor.run(prompt)
+            figures = result.output.figures
+        except AgentRunError:
+            logger.warning(
+                "[math-auditor-agent] figure extraction failed for page %d, skipping",
+                folio.page,
+                exc_info=True,
+            )
+            figures = []
+
+        logger.debug(
+            "TOOL (extract_figures)\nArgs: %s\nResult: %s",
+            Pretty({"page": folio.page, "text_length": len(text)}),
+            Pretty([f.model_dump() for f in figures]),
+        )
+
+        return [(fig, folio.page) for fig in figures]
+
+    async def _generate_summary(
+        self,
+        discrepancies: list[Discrepancy],
+        pages_examined: list[int],
+        unauditable_pages: list[int],
+        verification_stats: str,
+    ) -> str:
+        error_count = sum(1 for d in discrepancies if d.severity == Severity.ERROR)
+        warning_count = sum(1 for d in discrepancies if d.severity == Severity.WARNING)
+
+        prompt = (
+            f"{verification_stats}\n"
+            f"Errors: {error_count}, Warnings: {warning_count}, "
+            f"Pages examined: {len(pages_examined)}, "
+            f"Unauditable pages: {unauditable_pages or 'none'}.\n"
+        )
+        if discrepancies:
+            prompt += "Discrepancies:\n"
+            for d in discrepancies:
+                prompt += f"  - [{d.severity}] p{d.page + 1}: {d.description}\n"
+
+        try:
+            result = await self._summary_agent.run(prompt)
+            summary = result.output
+        except AgentRunError:
+            logger.warning("[math-auditor-agent] summary generation failed, using fallback", exc_info=True)
+            summary = self._fallback_summary(error_count, warning_count, pages_examined, unauditable_pages)
+
+        logger.debug("RESPONSE (summary)\n%s", Pretty({"summary": summary}))
+        return summary
+
+    @staticmethod
+    def _fallback_summary(
+        error_count: int,
+        warning_count: int,
+        pages_examined: list[int],
+        unauditable_pages: list[int],
+    ) -> str:
+        parts = []
+        if error_count == 0 and warning_count == 0:
+            parts.append(f"No mathematical errors found across {len(pages_examined)} pages.")
+        else:
+            if error_count:
+                parts.append(f"Found {error_count} error{'s' if error_count != 1 else ''}.")
+            if warning_count:
+                parts.append(f"Found {warning_count} warning{'s' if warning_count != 1 else ''}.")
+        if unauditable_pages:
+            parts.append(
+                f"Pages {', '.join(str(p + 1) for p in unauditable_pages)} could not be audited (OCR unavailable)."
+            )
+        return " ".join(parts)

engine/src/stirling/agents/ledger/prompts.py

@@ -0,0 +1,147 @@
+"""
+Ledger Auditor — system prompts.
+
+One prompt per role; keep them short and directive. Each agent is a
+specialist with a narrow remit, not a general assistant.
+"""
+
+EXAMINER_SYSTEM_PROMPT = """\
+You are the Examiner, the first stage of the Ledger Auditor pipeline.
+
+You receive a FolioManifest: a list of page types (text / image / mixed) \
+for a PDF document. Your sole task is to declare exactly which pages you \
+need Java to extract content from so that the Auditor can verify the \
+document's mathematics.
+
+Rules:
+- Request BOTH text AND table extraction for every 'text' or 'mixed' page. \
+  Tables are critical — the Auditor cannot verify totals without them. \
+  Tabula extraction is cheap; missing a table is not.
+- Request OCR for any page classified as 'image' or 'mixed' (PDFBox cannot \
+  read image-only content).
+- Be conservative — if in doubt, request the page. False negatives \
+  (missed errors) are worse than false positives (wasted extraction).
+- Do not request pages that are clearly decorative (cover pages, blank pages) \
+  unless you cannot tell from the manifest alone.
+- Return a Requisition with your page lists and a plain-English rationale \
+  that will appear in server logs.
+"""
+
+FIGURE_EXTRACTOR_PROMPT = """\
+You are a figure extractor for financial document auditing.
+
+You receive the text content of a single PDF page. Your task is to \
+identify every significant named numeric figure on the page.
+
+A "named figure" is a labelled number that could appear elsewhere in \
+the document under the same name — for example:
+  "Total Revenue: £1,200,000"
+  "Net Profit  $45,000"
+  "VAT (20%): 240.00"
+  "Subtotal ......... 3,500"
+
+For each figure, return:
+- label: a normalised name (e.g. "Total Revenue", "Net Profit", "VAT")
+- value: the numeric value as a plain decimal string (e.g. "1200000")
+- raw: the original text as it appears in the document
+
+Rules:
+- Only extract figures that have a clear label/name attached.
+- Do not extract bare numbers without context.
+- Strip currency symbols and thousands separators from value.
+- If a figure appears multiple times on the same page, extract each.
+- Return an empty list if no named figures are found.
+- Be precise — do not invent figures that are not in the text.
+"""
+
+TABLE_FORMULA_PROMPT = """\
+You are a table formula analyser for financial document auditing.
+
+You receive a CSV table extracted from a PDF. Your task is to identify \
+every verifiable mathematical relationship between cells.
+
+Relationships fall into three scopes:
+
+1. "each_row" — a formula that should hold for every data row.
+   Example: "col3 = col1 * col2" (Line Total = Qty × Unit Price)
+
+2. "column_total" — a total row where cells = sum of the column above.
+   Example: a Subtotal row where each cell sums the column.
+
+3. "single_cell" — one specific cell computed from others.
+   Example: "cell(5,3) = cell(4,3) * 0.1" (Tax = Subtotal × 10%)
+
+Formula syntax (use exactly this):
+  - Column references: col0, col1, col2 ... (0-indexed)
+  - Cell references: cell(row, col) — 0-indexed, header is row 0
+  - Operators: + - * /
+  - sum(colN, start-end) — sum of colN from row start to row end inclusive
+  - Decimal numbers: 0.1, 100, etc.
+
+Rules:
+- Row 0 is the header. First data row is row 1.
+- Include the left-hand side: "col3 = col1 * col2" not just "col1 * col2"
+- For column_total scope, set target_row to the total row index. \
+  Set target_col to a specific column or null to check all numeric columns.
+- For each_row scope, set row_range to the data rows (exclude header \
+  and total rows).
+- Only return formulas you are confident about. Skip columns/rows \
+  where the relationship is unclear.
+- Return an empty list if the table has no verifiable math.
+"""
+
+STATEMENT_VERIFIER_PROMPT = """\
+You are a statement verifier for financial document auditing.
+
+You receive the text of a single PDF page, plus any table data from \
+that page. Your task is to find prose claims that make mathematical \
+assertions, and verify whether each claim is correct.
+
+A "verifiable claim" is a sentence that states a mathematical fact \
+about numbers present on the page or derivable from the data. Examples:
+  - "Revenue grew 15% year-over-year"
+  - "Costs decreased month on month"
+  - "Department A represents 40% of total spend"
+  - "Net margin improved to 12.4%"
+  - "Average transaction value was $250"
+
+For each claim you find:
+1. Identify the numbers referenced in the claim
+2. Perform the calculation yourself using the data on the page
+3. Compare your result to what the claim states
+4. Determine if the claim is valid (within reasonable rounding)
+
+Return:
+- claim: the exact text of the claim
+- verification: the type — "percentage_change", "comparison", \
+  "ratio", "trend", "average", or "other"
+- values_referenced: the specific numbers used in your check
+- expected_result: what the calculation actually yields
+- actual_claim: what the text claims
+- is_valid: true if the claim is correct within 1% tolerance
+- explanation: show your working, one line
+
+Rules:
+- Only check claims that can be verified from data on this page.
+- If a claim references data not on the page, skip it.
+- "Decreased month on month" means EVERY consecutive pair decreased.
+- Percentage claims allow 1% absolute tolerance (14.8% ≈ 15%).
+- Return an empty list if there are no verifiable claims.
+- Do not fabricate claims that are not in the text.
+"""
+
+SUMMARY_PROMPT = """\
+You are a summary writer for a PDF math audit tool.
+
+You receive a list of discrepancies (errors and warnings) found in a \
+document, plus coverage statistics and a breakdown of what was verified. \
+Write a two to three sentence summary suitable for an end user.
+
+Rules:
+- Start with what was verified: e.g. "Audited 6 pages: checked 4 tables \
+  (12 formulas), scanned 6 pages for arithmetic, extracted 20 figures \
+  for cross-page consistency, and verified 3 prose claims."
+- Then state the outcome: errors found or clean.
+- Mention unauditable pages if any exist.
+- Be concise and factual. Do not repeat individual discrepancy details.
+"""

engine/src/stirling/agents/ledger/validators/__init__.py

@@ -0,0 +1,5 @@
+from .arithmetic import ArithmeticScanner
+from .figures import FigureTracker
+from .formula import FormulaEvaluator
+
+__all__ = ["ArithmeticScanner", "FigureTracker", "FormulaEvaluator"]

engine/src/stirling/agents/ledger/validators/_parsing.py

@@ -0,0 +1,31 @@
+"""Shared parsing helpers for ledger validators."""
+
+from __future__ import annotations
+
+import csv
+import io
+import re
+from decimal import Decimal, InvalidOperation
+
+# Strip common currency symbols and thousands separators before parsing.
+STRIP_PATTERN = re.compile(r"[£$€¥,\s]")
+
+
+def to_decimal(raw: str) -> Decimal | None:
+    """Parse a cell value to Decimal, returning None for non-numeric cells."""
+    cleaned = STRIP_PATTERN.sub("", raw.strip())
+    if not cleaned or cleaned in {"-", "—", "n/a", "N/A", "na", "NA"}:
+        return None
+    # Handle parenthesised negatives: (123.45) → -123.45
+    if cleaned.startswith("(") and cleaned.endswith(")"):
+        cleaned = "-" + cleaned[1:-1]
+    try:
+        return Decimal(cleaned)
+    except InvalidOperation:
+        return None
+
+
+def parse_csv(table_csv: str) -> list[list[str]]:
+    """Parse a CSV string into rows, dropping completely empty rows."""
+    reader = csv.reader(io.StringIO(table_csv.strip()))
+    return [row for row in reader if any(cell.strip() for cell in row)]

engine/src/stirling/agents/ledger/validators/arithmetic.py

@@ -0,0 +1,152 @@
+"""
+ArithmeticScanner — finds and verifies inline arithmetic expressions in text.
+
+Targets patterns commonly found in financial documents:
+  "100 + 200 + 150 = 450"
+  "Total: 1,250 (500 + 400 + 350)"
+  "Net profit of £1,200 (£2,000 revenue less £800 costs)"
+
+All arithmetic is performed in Decimal. The scanner does not use an LLM —
+it is a deterministic regex-and-eval pipeline.
+"""
+
+from __future__ import annotations
+
+import logging
+import re
+from decimal import Decimal
+
+from stirling.contracts.ledger import Discrepancy, DiscrepancyKind, Severity
+
+from ._parsing import STRIP_PATTERN as _STRIP
+from ._parsing import to_decimal as _to_decimal
+
+logger = logging.getLogger(__name__)
+
+# ---------------------------------------------------------------------------
+# Regex patterns
+# ---------------------------------------------------------------------------
+
+# Currency / number token: optional sign, optional currency symbol,
+# digits with optional thousands separator and decimal point.
+_NUM = r"[£$€¥]?-?[\d,]+(?:\.\d+)?"
+
+# "A + B + C = D" or "A + B + C = D" with arbitrary spacing
+_EQUALS_EXPR = re.compile(
+    rf"({_NUM}(?:\s*[+\-]\s*{_NUM})+)\s*=\s*({_NUM})",
+    re.IGNORECASE,
+)
+
+# "Total: X (A + B + C)" — the total comes before the addends
+_TOTAL_THEN_ADDENDS = re.compile(
+    rf"(?:total|sum|grand total|subtotal)\s*[:\-]?\s*({_NUM})\s*\(({_NUM}(?:\s*[+\-]\s*{_NUM})+)\)",
+    re.IGNORECASE,
+)
+
+
+def _parse(token: str) -> Decimal | None:
+    """Parse a regex-matched token to Decimal."""
+    return _to_decimal(token)
+
+
+def _eval_expression(expr: str) -> Decimal | None:
+    """
+    Evaluate a simple additive expression of the form  A +/- B +/- C ...
+    Returns None if the expression cannot be parsed.
+    """
+    # Tokenise: split on + or -, keep the operator.
+    tokens = re.split(r"([+\-])", _STRIP.sub("", expr.strip()))
+    result = Decimal(0)
+    operator = "+"
+    for token in tokens:
+        token = token.strip()
+        if not token:
+            continue  # skip empty tokens (e.g. from leading negative)
+        if token in ("+", "-"):
+            operator = token
+            continue
+        val = _parse(token)
+        if val is None:
+            return None
+        result = result + val if operator == "+" else result - val
+    return result
+
+
+class ArithmeticScanner:
+    """
+    Scans a block of text for arithmetic expressions and checks them.
+
+    Parameters
+    ----------
+    tolerance:
+        Maximum absolute difference before an expression is flagged as wrong.
+    """
+
+    def __init__(self, tolerance: Decimal = Decimal("0.01")) -> None:
+        self.tolerance = tolerance
+
+    def scan(self, page: int, text: str) -> list[Discrepancy]:
+        """
+        Find all verifiable arithmetic expressions in *text* and return
+        a Discrepancy for each one that does not balance within tolerance.
+        """
+        discrepancies: list[Discrepancy] = []
+        discrepancies.extend(self._check_equals_expressions(page, text))
+        discrepancies.extend(self._check_total_then_addends(page, text))
+        return discrepancies
+
+    # ------------------------------------------------------------------
+    # Internal helpers
+    # ------------------------------------------------------------------
+
+    def _check_equals_expressions(self, page: int, text: str) -> list[Discrepancy]:
+        """Handle patterns like '100 + 200 = 300'."""
+        found: list[Discrepancy] = []
+        for match in _EQUALS_EXPR.finditer(text):
+            expr_str = match.group(1)
+            stated_str = match.group(2)
+
+            computed = _eval_expression(expr_str)
+            stated = _parse(stated_str)
+            if computed is None or stated is None:
+                continue
+
+            if abs(computed - stated) > self.tolerance:
+                found.append(
+                    Discrepancy(
+                        page=page,
+                        kind=DiscrepancyKind.ARITHMETIC,
+                        severity=Severity.ERROR,
+                        description=f"Arithmetic error: {expr_str.strip()} should equal {computed}, not {stated}",
+                        stated=str(stated),
+                        expected=str(computed),
+                        context=match.group(0),
+                    )
+                )
+        return found
+
+    def _check_total_then_addends(self, page: int, text: str) -> list[Discrepancy]:
+        """Handle patterns like 'Total: 450 (100 + 200 + 150)'."""
+        found: list[Discrepancy] = []
+        for match in _TOTAL_THEN_ADDENDS.finditer(text):
+            stated_str = match.group(1)
+            expr_str = match.group(2)
+
+            stated = _parse(stated_str)
+            computed = _eval_expression(expr_str)
+            if stated is None or computed is None:
+                continue
+
+            if abs(computed - stated) > self.tolerance:
+                found.append(
+                    Discrepancy(
+                        page=page,
+                        kind=DiscrepancyKind.ARITHMETIC,
+                        severity=Severity.ERROR,
+                        description=f"Stated total {stated} does not match addends ({expr_str.strip()} = {computed})",
+                        stated=str(stated),
+                        expected=str(computed),
+                        context=match.group(0),
+                    )
+                )
+        return found

engine/src/stirling/agents/ledger/validators/figures.py

@@ -0,0 +1,98 @@
+"""
+FigureTracker — cross-page consistency checker for named figures.
+
+Collects named numeric figures as the auditor encounters them (e.g.
+"Total Revenue: £1,200,000") and surfaces any that appear under the same
+label but with a different value on another page — a classic symptom of
+copy-paste errors or stale data in executive summaries.
+
+The tracker is intentionally simple: normalise labels, compare values
+within tolerance, emit Discrepancy for each conflict.
+"""
+
+from __future__ import annotations
+
+import logging
+import re
+from decimal import Decimal
+
+from pydantic import BaseModel
+
+from stirling.contracts.ledger import Discrepancy, DiscrepancyKind, Severity
+
+logger = logging.getLogger(__name__)
+
+
+class FigureRecord(BaseModel):
+    """A named numeric figure seen on a specific page."""
+
+    label: str
+    value: Decimal
+    page: int
+    raw: str
+
+
+# Strip punctuation that varies between contexts ("revenue:" vs "revenue —")
+_LABEL_NOISE = re.compile(r"[:\-—\s]+")
+
+
+def _normalise_label(label: str) -> str:
+    return _LABEL_NOISE.sub(" ", label.lower()).strip()
+
+
+class FigureTracker:
+    """
+    Accumulates named figures during an audit and checks them for consistency.
+
+    Typical usage:
+        tracker = FigureTracker()
+        tracker.record("Net Profit", Decimal("1200.00"), page=3, raw="£1,200.00")
+        tracker.record("Net Profit", Decimal("1250.00"), page=7, raw="£1,250.00")
+        discrepancies = tracker.conflicts()  # returns one Discrepancy
+    """
+
+    def __init__(self, tolerance: Decimal = Decimal("0.01")) -> None:
+        self.tolerance = tolerance
+        self._ledger: dict[str, list[FigureRecord]] = {}
+
+    def record(self, label: str, value: Decimal, page: int, raw: str) -> None:
+        """Register a named figure sighting."""
+        key = _normalise_label(label)
+        self._ledger.setdefault(key, []).append(FigureRecord(label=key, value=value, page=page, raw=raw))
+
+    def conflicts(self) -> list[Discrepancy]:
+        """
+        Return a Discrepancy for every label that has sightings whose value
+        differs from the first-seen (canonical) value by more than tolerance.
+
+        O(n) per label — each record is compared against the canonical only.
+        """
+        discrepancies: list[Discrepancy] = []
+
+        for label, records in self._ledger.items():
+            if len(records) < 2:
+                continue
+            canonical = records[0]
+            for other in records[1:]:
+                if abs(canonical.value - other.value) > self.tolerance:
+                    discrepancies.append(
+                        Discrepancy(
+                            page=other.page,
+                            kind=DiscrepancyKind.CONSISTENCY,
+                            severity=Severity.WARNING,
+                            description=(
+                                f'"{label}" stated as {canonical.raw} on page'
+                                f" {canonical.page + 1}"
+                                f" but {other.raw} on page {other.page + 1}"
+                            ),
+                            stated=other.raw,
+                            expected=canonical.raw,
+                            context=(f"First seen: page {canonical.page + 1} | Later: page {other.page + 1}"),
+                        )
+                    )
+
+        return discrepancies
+
+    @property
+    def entry_count(self) -> int:
+        return sum(len(v) for v in self._ledger.values())

engine/src/stirling/agents/ledger/validators/formula.py

@@ -0,0 +1,375 @@
+"""
+FormulaEvaluator — verifies LLM-inferred formulas against CSV table data.
+
+Supports a safe expression syntax:
+  - Column refs:  col0, col1, col2 ...
+  - Cell refs:    cell(row, col)
+  - Operators:    +  -  *  /
+  - Functions:    sum(colN, rows start-end)
+
+All arithmetic is Decimal. No eval(), no arbitrary code execution.
+"""
+
+from __future__ import annotations
+
+import logging
+import re
+from decimal import Decimal, InvalidOperation
+
+from stirling.contracts.ledger import Discrepancy, DiscrepancyKind, Severity
+
+from ._parsing import parse_csv as _parse_csv
+from ._parsing import to_decimal as _to_decimal
+
+logger = logging.getLogger(__name__)
+
+
+class FormulaEvaluator:
+    """
+    Evaluates formula expressions against parsed CSV rows.
+
+    Formulas use a simple syntax:
+      "col3 = col1 * col2"           — per-row check
+      "cell(4,3) = sum(col3, 1-3)"   — single cell check
+    """
+
+    def __init__(self, tolerance: Decimal = Decimal("0.01")) -> None:
+        self.tolerance = tolerance
+
+    def evaluate(
+        self,
+        page: int,
+        table_csv: str,
+        formula: str,
+        scope: str,
+        description: str,
+        row_range: list[int] | None = None,
+        target_row: int | None = None,
+        target_col: int | None = None,
+    ) -> list[Discrepancy]:
+        """
+        Evaluate a formula against table data.
+
+        scope: "each_row" | "column_total" | "single_cell"
+        """
+        rows = _parse_csv(table_csv)
+        if len(rows) < 2:
+            return []
+
+        if scope == "each_row":
+            return self._check_each_row(page, rows, formula, description, row_range)
+        elif scope == "column_total":
+            return self._check_column_total(page, rows, formula, description, target_row, target_col)
+        elif scope == "single_cell":
+            return self._check_single_cell(page, rows, formula, description, target_row, target_col)
+        else:
+            logger.warning("[formula] unknown scope %r, skipping", scope)
+            return []
+
+    def _check_each_row(
+        self,
+        page: int,
+        rows: list[list[str]],
+        formula: str,
+        description: str,
+        row_range: list[int] | None,
+    ) -> list[Discrepancy]:
+        """Verify formula holds for each data row."""
+        discrepancies: list[Discrepancy] = []
+
+        # Parse "colX = expr" format
+        parts = formula.split("=", 1)
+        if len(parts) != 2:
+            return []
+        lhs = parts[0].strip()
+        rhs = parts[1].strip()
+
+        lhs_col = self._parse_col_ref(lhs)
+        if lhs_col is None:
+            return []
+
+        check_rows = row_range if row_range else list(range(1, len(rows)))
+
+        for row_idx in check_rows:
+            if row_idx >= len(rows):
+                continue
+            row = rows[row_idx]
+
+            stated = self._get_cell(row, lhs_col)
+            if stated is None:
+                continue
+
+            computed = self._eval_row_expr(rhs, row, rows)
+            if computed is None:
+                continue
+
+            if abs(stated - computed) > self.tolerance:
+                discrepancies.append(
+                    Discrepancy(
+                        page=page,
+                        kind=DiscrepancyKind.TALLY,
+                        severity=Severity.ERROR,
+                        description=f"{description}: row {row_idx} — stated {stated}, expected {computed}",
+                        stated=str(stated),
+                        expected=str(computed),
+                        context=f"row {row_idx}, {formula}",
+                    )
+                )
+
+        return discrepancies
+
+    def _check_column_total(
+        self,
+        page: int,
+        rows: list[list[str]],
+        formula: str,
+        description: str,
+        target_row: int | None,
+        target_col: int | None,
+    ) -> list[Discrepancy]:
+        """Verify that a total row contains correct column sums."""
+        if target_row is None or target_row >= len(rows):
+            return []
+
+        discrepancies: list[Discrepancy] = []
+        total_row = rows[target_row]
+
+        # Determine which columns to check
+        cols_to_check: list[int] = []
+        if target_col is not None:
+            cols_to_check = [target_col]
+        else:
+            # Check all numeric columns in the total row
+            cols_to_check = list(range(len(total_row)))
+
+        # Determine addend rows (all rows between header and total row)
+        addend_rows = list(range(1, target_row))
+
+        for col in cols_to_check:
+            stated = self._get_cell(total_row, col)
+            if stated is None:
+                continue
+
+            computed = Decimal(0)
+            has_addends = False
+            for r_idx in addend_rows:
+                if r_idx >= len(rows):
+                    continue
+                val = self._get_cell(rows[r_idx], col)
+                if val is not None:
+                    computed += val
+                    has_addends = True
+
+            if not has_addends:
+                continue
+
+            if abs(stated - computed) > self.tolerance:
+                discrepancies.append(
+                    Discrepancy(
+                        page=page,
+                        kind=DiscrepancyKind.TALLY,
+                        severity=Severity.ERROR,
+                        description=f"{description}: column {col} — stated {stated}, expected {computed}",
+                        stated=str(stated),
+                        expected=str(computed),
+                        context=f"column {col}, total row {target_row}",
+                    )
+                )
+
+        return discrepancies
+
+    def _check_single_cell(
+        self,
+        page: int,
+        rows: list[list[str]],
+        formula: str,
+        description: str,
+        target_row: int | None,
+        target_col: int | None,
+    ) -> list[Discrepancy]:
+        """Verify a single cell formula (e.g. Grand Total = Subtotal + Tax)."""
+        parts = formula.split("=", 1)
+        if len(parts) != 2:
+            return []
+
+        # Parse target from LHS cell(r,c) if not provided explicitly
+        if target_row is None or target_col is None:
+            lhs_match = re.match(r"cell\(\s*(\d+)\s*,\s*(\d+)\s*\)", parts[0].strip())
+            if lhs_match:
+                target_row = int(lhs_match.group(1))
+                target_col = int(lhs_match.group(2))
+            else:
+                return []
+
+        if target_row >= len(rows):
+            return []
+
+        rhs = parts[1].strip()
+
+        stated = self._get_cell(rows[target_row], target_col)
+        if stated is None:
+            return []
+
+        computed = self._eval_row_expr(rhs, rows[target_row], rows)
+        if computed is None:
+            return []
+
+        if abs(stated - computed) > self.tolerance:
+            return [
+                Discrepancy(
+                    page=page,
+                    kind=DiscrepancyKind.TALLY,
+                    severity=Severity.ERROR,
+                    description=f"{description}: stated {stated}, expected {computed}",
+                    stated=str(stated),
+                    expected=str(computed),
+                    context=f"cell({target_row},{target_col}), {formula}",
+                )
+            ]
+        return []
+
+    # ------------------------------------------------------------------
+    # Expression evaluation
+    # ------------------------------------------------------------------
+
+    def _eval_row_expr(self, expr: str, row: list[str], all_rows: list[list[str]]) -> Decimal | None:
+        """
+        Evaluate an expression in the context of a specific row.
+        Supports: colN refs, cell(r,c) refs, +, -, *, /
+        Also supports: sum(colN, start-end)
+        """
+        # Handle sum() function first
+        sum_pattern = re.compile(r"sum\(\s*col(\d+)\s*,\s*(\d+)\s*-\s*(\d+)\s*\)")
+        resolved = expr
+        for match in sum_pattern.finditer(expr):
+            col = int(match.group(1))
+            start = int(match.group(2))
+            end = int(match.group(3))
+            total = Decimal(0)
+            for r_idx in range(start, end + 1):
+                if r_idx < len(all_rows):
+                    val = self._get_cell(all_rows[r_idx], col)
+                    if val is not None:
+                        total += val
+            resolved = resolved.replace(match.group(0), str(total))
+
+        # Handle cell(r, c) references
+        cell_pattern = re.compile(r"cell\(\s*(\d+)\s*,\s*(\d+)\s*\)")
+        for match in cell_pattern.finditer(resolved):
+            r = int(match.group(1))
+            c = int(match.group(2))
+            if r < len(all_rows):
+                val = self._get_cell(all_rows[r], c)
+                if val is not None:
+                    resolved = resolved.replace(match.group(0), str(val))
+                else:
+                    return None
+            else:
+                return None
+
+        # Replace colN references with values from the current row.
+        # Use re.sub with word boundaries to avoid col1 corrupting col12.
+        _failed = False
+
+        def _col_replacer(m: re.Match[str]) -> str:
+            nonlocal _failed
+            col_idx = int(m.group(1))
+            val = self._get_cell(row, col_idx)
+            if val is None:
+                _failed = True
+                return m.group(0)
+            return str(val)
+
+        resolved = re.sub(r"\bcol(\d+)\b", _col_replacer, resolved)
+        if _failed:
+            return None
+
+        # Evaluate the resulting arithmetic expression safely
+        return self._safe_eval(resolved)
+
+    def _safe_eval(self, expr: str) -> Decimal | None:
+        """
+        Evaluate a simple arithmetic expression containing only
+        numbers and +, -, *, / operators.  Respects standard operator
+        precedence (* and / bind tighter than + and -).  No eval().
+        """
+        try:
+            raw = re.findall(r"\d+(?:\.\d+)?|[+\-*/]", expr.strip())
+            if not raw:
+                return None
+
+            # Build (values, ops) lists, merging a leading '-' or an
+            # operator-adjacent '-' into the next number token.
+            values: list[Decimal] = []
+            ops: list[str] = []
+            i = 0
+            while i < len(raw):
+                tok = raw[i]
+                if tok in "+-*/" and not values and tok == "-":
+                    # Leading negative: merge with next number
+                    i += 1
+                    if i >= len(raw):
+                        return None
+                    values.append(Decimal("-" + raw[i]))
+                elif tok in "+-*/":
+                    # Operator followed by '-' → negative operand
+                    if (
+                        tok in "+-*/"
+                        and i + 1 < len(raw)
+                        and raw[i + 1] == "-"
+                        and i + 2 < len(raw)
+                        and raw[i + 2] not in "+-*/"
+                    ):
+                        ops.append(tok)
+                        values.append(Decimal("-" + raw[i + 2]))
+                        i += 2  # skip the '-' and the number
+                    else:
+                        ops.append(tok)
+                else:
+                    values.append(Decimal(tok))
+                i += 1
+
+            if not values:
+                return None
+
+            # Pass 1: evaluate * and /
+            j = 0
+            while j < len(ops):
+                if ops[j] in ("*", "/"):
+                    if ops[j] == "*":
+                        values[j] = values[j] * values[j + 1]
+                    else:
+                        if values[j + 1] == 0:
+                            return None
+                        values[j] = values[j] / values[j + 1]
+                    values.pop(j + 1)
+                    ops.pop(j)
+                else:
+                    j += 1
+
+            # Pass 2: evaluate + and -
+            result = values[0]
+            for j, op in enumerate(ops):
+                if op == "+":
+                    result += values[j + 1]
+                elif op == "-":
+                    result -= values[j + 1]
+
+            return result
+        except (InvalidOperation, IndexError, ValueError):
+            return None
+
+    # ------------------------------------------------------------------
+    # Helpers
+    # ------------------------------------------------------------------
+
+    @staticmethod
+    def _parse_col_ref(ref: str) -> int | None:
+        match = re.match(r"col(\d+)", ref.strip())
+        return int(match.group(1)) if match else None
+
+    @staticmethod
+    def _get_cell(row: list[str], col: int) -> Decimal | None:
+        if col >= len(row):
+            return None
+        return _to_decimal(row[col])

engine/src/stirling/agents/orchestrator.py

@@ -21,8 +21,11 @@ from stirling.contracts import (
     PdfQuestionRequest,
     PdfQuestionResponse,
     SupportedCapability,
+    ToolOperationStep,
     UnsupportedCapabilityResponse,
 )
+from stirling.contracts.pdf_edit import EditPlanResponse
+from stirling.models.agent_tool_models import AgentToolId, MathAuditorAgentParams
 from stirling.services import AppRuntime
 
 
@@ -53,6 +56,14 @@ class OrchestratorAgent:
                     name="delegate_user_spec",
                     description="Delegate requests to create or revise a user agent spec and return the draft result.",
                 ),
+                ToolOutput(
+                    self.math_auditor_agent,
+                    name="math_auditor_agent",
+                    description=(
+                        "Delegate requests to check arithmetic, validate table totals, "
+                        "audit financial calculations, or verify mathematical accuracy in PDFs."
+                    ),
+                ),
                 ToolOutput(
                     self.unsupported_capability,
                     name="unsupported_capability",
@@ -66,6 +77,8 @@ class OrchestratorAgent:
                 "Use delegate_pdf_edit for requested PDF modifications. "
                 "Use delegate_pdf_question for questions about PDF contents. "
                 "Use delegate_user_spec for requests to create or define an agent spec. "
+                "Use math_auditor_agent for requests to check arithmetic, validate "
+                "table totals, audit financial calculations, or verify math in PDFs. "
                 "Use unsupported_capability only when none of the other outputs fit."
             ),
             model_settings=runtime.fast_model_settings,
@@ -93,6 +106,7 @@ class OrchestratorAgent:
                 SupportedCapability.ORCHESTRATE
                 | SupportedCapability.AGENT_REVISE
                 | SupportedCapability.AGENT_NEXT_ACTION
+                | SupportedCapability.MATH_AUDITOR_AGENT
             ):
                 raise ValueError(f"Cannot resume orchestrator with capability: {capability}")
             case _ as unreachable:
@@ -123,6 +137,17 @@ class OrchestratorAgent:
     async def _run_agent_draft(self, request: OrchestratorRequest) -> AgentDraftWorkflowResponse:
         return await UserSpecAgent(self.runtime).draft(AgentDraftRequest(user_message=request.user_message))
 
+    async def math_auditor_agent(self, ctx: RunContext[OrchestratorDeps]) -> EditPlanResponse:
+        return EditPlanResponse(
+            summary="Validate mathematical calculations in the document.",
+            steps=[
+                ToolOperationStep(
+                    tool=AgentToolId.MATH_AUDITOR_AGENT,
+                    parameters=MathAuditorAgentParams(),
+                )
+            ],
+        )
+
     async def unsupported_capability(
         self,
         ctx: RunContext[OrchestratorDeps],

engine/src/stirling/api/app.py

@@ -8,10 +8,12 @@ from pydantic_ai import Agent
 from pydantic_ai.models.instrumented import InstrumentationSettings
 
 from stirling.agents import ExecutionPlanningAgent, OrchestratorAgent, PdfEditAgent, PdfQuestionAgent, UserSpecAgent
+from stirling.agents.ledger import MathAuditorAgent
 from stirling.api.middleware import UserIdMiddleware
 from stirling.api.routes import (
     agent_draft_router,
     execution_router,
+    ledger_router,
     orchestrator_router,
     pdf_edit_router,
     pdf_question_router,
@@ -40,6 +42,7 @@ async def lifespan(fast_api: FastAPI):
     fast_api.state.pdf_question_agent = PdfQuestionAgent(runtime)
     fast_api.state.user_spec_agent = UserSpecAgent(runtime)
     fast_api.state.execution_planning_agent = ExecutionPlanningAgent(runtime)
+    fast_api.state.math_auditor_agent = MathAuditorAgent(runtime)
     tracer_provider = setup_posthog_tracking(settings)
     if tracer_provider:
         Agent.instrument_all(InstrumentationSettings(tracer_provider=tracer_provider))
@@ -55,6 +58,7 @@ app.include_router(pdf_edit_router)
 app.include_router(pdf_question_router)
 app.include_router(agent_draft_router)
 app.include_router(execution_router)
+app.include_router(ledger_router)
 
 
 @app.get("/health", response_model=HealthResponse)

engine/src/stirling/api/dependencies.py

@@ -3,6 +3,7 @@ from __future__ import annotations
 from fastapi import Request
 
 from stirling.agents import ExecutionPlanningAgent, OrchestratorAgent, PdfEditAgent, PdfQuestionAgent, UserSpecAgent
+from stirling.agents.ledger import MathAuditorAgent
 from stirling.services import AppRuntime
 
 
@@ -28,3 +29,7 @@ def get_user_spec_agent(request: Request) -> UserSpecAgent:
 
 def get_execution_planning_agent(request: Request) -> ExecutionPlanningAgent:
     return request.app.state.execution_planning_agent
+
+
+def get_math_auditor_agent(request: Request) -> MathAuditorAgent:
+    return request.app.state.math_auditor_agent

engine/src/stirling/api/routes/__init__.py

@@ -1,5 +1,6 @@
 from .agent_drafts import router as agent_draft_router
 from .execution import router as execution_router
+from .ledger import router as ledger_router
 from .orchestrator import router as orchestrator_router
 from .pdf_edit import router as pdf_edit_router
 from .pdf_questions import router as pdf_question_router
@@ -7,6 +8,7 @@ from .pdf_questions import router as pdf_question_router
 __all__ = [
     "agent_draft_router",
     "execution_router",
+    "ledger_router",
     "orchestrator_router",
     "pdf_edit_router",
     "pdf_question_router",

engine/src/stirling/api/routes/ledger.py

@@ -0,0 +1,60 @@
+"""
+Math Auditor Agent (mathAuditorAgent) — FastAPI routes.
+
+Two internal endpoints, called only by the Java MathAuditorOrchestrator:
+
+  POST /api/v1/ai/math-auditor-agent/examine
+      Java sends a FolioManifest (cheap page classification).
+      Python returns a Requisition (what Java must extract).
+
+  POST /api/v1/ai/math-auditor-agent/deliberate
+      Java sends Evidence (fulfilled extraction results).
+      Python returns a Verdict directly.
+"""
+
+from __future__ import annotations
+
+import logging
+from decimal import Decimal, InvalidOperation
+from typing import Annotated
+
+from fastapi import APIRouter, Depends, HTTPException, Query
+
+from stirling.agents.ledger import MathAuditorAgent
+from stirling.api.dependencies import get_math_auditor_agent
+from stirling.contracts.ledger import (
+    Evidence,
+    FolioManifest,
+    Requisition,
+    Verdict,
+)
+
+logger = logging.getLogger(__name__)
+
+router = APIRouter(prefix="/api/v1/ai/math-auditor-agent", tags=["math-auditor-agent"])
+
+
+@router.post("/examine", response_model=Requisition)
+async def examine_endpoint(
+    manifest: FolioManifest,
+    agent: Annotated[MathAuditorAgent, Depends(get_math_auditor_agent)],
+) -> Requisition:
+    """Round 1: Java presents a FolioManifest; Python declares its Requisition."""
+    return await agent.examine(manifest)
+
+
+@router.post("/deliberate", response_model=Verdict)
+async def deliberate_endpoint(
+    evidence: Evidence,
+    agent: Annotated[MathAuditorAgent, Depends(get_math_auditor_agent)],
+    tolerance: str = Query(default="0.01"),
+) -> Verdict:
+    """Round 2: Java presents fulfilled Evidence; Python returns a Verdict."""
+    try:
+        tol = Decimal(tolerance)
+        if tol < 0:
+            raise HTTPException(status_code=400, detail="tolerance must be non-negative")
+    except InvalidOperation:
+        raise HTTPException(status_code=400, detail=f"Invalid tolerance value: {tolerance!r}")
+
+    return await agent.audit(evidence, tol)

engine/src/stirling/config/settings.py

@@ -1,5 +1,7 @@
 from __future__ import annotations
 
+import logging
+import logging.handlers
 from functools import lru_cache
 from pathlib import Path
 
@@ -19,12 +21,44 @@ class AppSettings(BaseSettings):
     smart_model_max_tokens: int = Field(validation_alias="STIRLING_SMART_MODEL_MAX_TOKENS")
     fast_model_max_tokens: int = Field(validation_alias="STIRLING_FAST_MODEL_MAX_TOKENS")
 
+    log_level: str = Field(default="INFO", validation_alias="STIRLING_LOG_LEVEL")
+    log_file: str = Field(default="", validation_alias="STIRLING_LOG_FILE")
+
     posthog_enabled: bool = Field(validation_alias="STIRLING_POSTHOG_ENABLED")
     posthog_api_key: str = Field(validation_alias="STIRLING_POSTHOG_API_KEY")
     posthog_host: str = Field(validation_alias="STIRLING_POSTHOG_HOST")
 
 
+def _configure_logging(level_name: str, log_file: str) -> None:
+    """Configure the ``stirling`` logger hierarchy."""
+    level = logging.getLevelNamesMapping().get(level_name.upper())
+    if level is None:
+        logging.getLogger("stirling").warning(
+            "Unknown STIRLING_LOG_LEVEL %r, defaulting to INFO",
+            level_name,
+        )
+        level = logging.INFO
+
+    root = logging.getLogger("stirling")
+    root.setLevel(level)
+
+    if log_file:
+        log_path = Path(log_file)
+        log_path.parent.mkdir(parents=True, exist_ok=True)
+        fh = logging.handlers.TimedRotatingFileHandler(
+            log_path,
+            when="midnight",
+            backupCount=1,
+            encoding="utf-8",
+        )
+        fh.setFormatter(logging.Formatter("%(asctime)s %(levelname)s %(name)s [%(funcName)s] %(message)s"))
+        fh.setLevel(level)
+        root.addHandler(fh)
+
+
 @lru_cache(maxsize=1)
 def load_settings() -> AppSettings:
     load_dotenv(ENV_FILE)
-    return AppSettings.model_validate({})
+    settings = AppSettings.model_validate({})
+    _configure_logging(settings.log_level, settings.log_file)
+    return settings

engine/src/stirling/contracts/__init__.py

@@ -29,6 +29,17 @@ from .execution import (
     ToolCallExecutionAction,
 )
 from .health import HealthResponse
+from .ledger import (
+    Discrepancy,
+    DiscrepancyKind,
+    Evidence,
+    Folio,
+    FolioManifest,
+    FolioType,
+    Requisition,
+    Severity,
+    Verdict,
+)
 from .orchestrator import (
     ExtractedTextArtifact,
     OrchestratorRequest,
@@ -53,7 +64,6 @@ from .pdf_questions import (
 )
 
 __all__ = [
-    "ArtifactKind",
     "AgentDraft",
     "AgentDraftRequest",
     "AgentDraftResponse",
@@ -65,35 +75,45 @@ __all__ = [
     "AgentSpec",
     "AgentSpecStep",
     "AiToolAgentStep",
+    "ArtifactKind",
     "CannotContinueExecutionAction",
-    "ConversationMessage",
-    "ExtractedFileText",
     "CompletedExecutionAction",
+    "ConversationMessage",
+    "Discrepancy",
+    "DiscrepancyKind",
     "EditCannotDoResponse",
     "EditClarificationRequest",
     "EditPlanResponse",
+    "Evidence",
     "ExecutionContext",
     "ExecutionStepResult",
+    "ExtractedFileText",
+    "ExtractedTextArtifact",
+    "Folio",
+    "FolioManifest",
+    "FolioType",
     "HealthResponse",
     "NeedContentFileRequest",
     "NextExecutionAction",
-    "ExtractedTextArtifact",
     "OrchestratorRequest",
     "OrchestratorResponse",
+    "PdfContentType",
     "PdfEditRequest",
     "PdfEditResponse",
     "PdfQuestionAnswerResponse",
-    "PdfQuestionNotFoundResponse",
-    "PdfContentType",
     "PdfQuestionNeedContentResponse",
+    "PdfQuestionNotFoundResponse",
     "PdfQuestionRequest",
     "PdfQuestionResponse",
     "PdfTextSelection",
+    "Requisition",
+    "Severity",
     "StepKind",
     "SupportedCapability",
-    "ToolOperationStep",
     "ToolCallExecutionAction",
-    "WorkflowOutcome",
+    "ToolOperationStep",
     "UnsupportedCapabilityResponse",
+    "Verdict",
     "WorkflowArtifact",
+    "WorkflowOutcome",
 ]

engine/src/stirling/contracts/common.py

@@ -1,11 +1,12 @@
 from __future__ import annotations
 
 from enum import StrEnum
-from typing import Literal
+from typing import Literal, assert_never
 
 from pydantic import Field, model_validator
 
-from stirling.models import OPERATIONS, ApiModel, OperationId, ParamToolModel
+from stirling.models import OPERATIONS, ApiModel, OperationId
+from stirling.models.agent_tool_models import AGENT_OPERATIONS, AgentToolId, AnyParamModel, AnyToolId
 
 
 class PdfContentType(StrEnum):
@@ -82,6 +83,7 @@ class SupportedCapability(StrEnum):
     AGENT_DRAFT = "agent_draft"
     AGENT_REVISE = "agent_revise"
     AGENT_NEXT_ACTION = "agent_next_action"
+    MATH_AUDITOR_AGENT = "math_auditor_agent"
 
 
 class ConversationMessage(ApiModel):
@@ -101,14 +103,19 @@ class ExtractedFileText(ApiModel):
 
 class ToolOperationStep(ApiModel):
     kind: Literal[StepKind.TOOL] = StepKind.TOOL
-    tool: OperationId
-    parameters: ParamToolModel
+    tool: AnyToolId
+    parameters: AnyParamModel
 
     @model_validator(mode="after")
     def validate_tool_parameter_pairing(self) -> ToolOperationStep:
-        expected_type = OPERATIONS[self.tool]
+        if isinstance(self.tool, AgentToolId):
+            expected_type = AGENT_OPERATIONS[self.tool]
+        elif isinstance(self.tool, OperationId):
+            expected_type = OPERATIONS[self.tool]
+        else:
+            assert_never(self.tool)
+
         if not isinstance(self.parameters, expected_type):
             actual_type = type(self.parameters).__name__
-            expected_type_name = expected_type.__name__
-            raise ValueError(f"Parameters for tool {self.tool.value} must be {expected_type_name}, got {actual_type}.")
+            raise ValueError(f"Parameters for tool {self.tool} must be {expected_type.__name__}, got {actual_type}.")
         return self

engine/src/stirling/contracts/ledger.py

@@ -0,0 +1,196 @@
+"""
+Ledger Auditor — shared models for the Java-Python protocol.
+
+Every struct that crosses the wire lives here so the contract is
+impossible to miss or partially implement.
+"""
+
+from __future__ import annotations
+
+from enum import StrEnum
+from typing import Literal
+
+from pydantic import Field
+
+from stirling.models import ApiModel
+
+# ---------------------------------------------------------------------------
+# Page classification — Java's side of the conversation
+# ---------------------------------------------------------------------------
+
+
+class FolioType(StrEnum):
+    """How Java classifies each page after a cheap PDFBox scan.
+
+    Java counterpart: FolioType.java - values must stay in sync.
+    """
+
+    TEXT = "text"  # selectable text layer present
+    IMAGE = "image"  # image-only, will need OCR
+    MIXED = "mixed"  # partial text layer + embedded images
+
+
+class FolioManifest(ApiModel):
+    """
+    Java's opening move: a fast, cheap page classification with no OCR or
+    table extraction — just PDFBox character counts and image detection.
+
+    Python inspects this and returns a Requisition declaring what it needs.
+    """
+
+    session_id: str = Field(description="Opaque handle Java uses to find the PDF on disk.")
+    page_count: int = Field(ge=1)
+    folio_types: list[FolioType] = Field(description="One entry per page (0-indexed). len(folio_types) == page_count.")
+    round: int = Field(default=1, ge=1, le=3, description="Which negotiation round this is.")
+
+
+# ---------------------------------------------------------------------------
+# Requisition — Python's declaration of what it needs
+# ---------------------------------------------------------------------------
+
+
+class Requisition(ApiModel):
+    """
+    Python's reply to a FolioManifest: a precise shopping list of what Java
+    must extract before the auditor can form an opinion.
+
+    Java fulfils this and sends back an Evidence payload.
+    """
+
+    type: Literal["requisition"] = "requisition"
+    need_text: list[int] = Field(
+        default_factory=list,
+        description="0-indexed page numbers. Java runs PDFBox text extraction on these.",
+    )
+    need_tables: list[int] = Field(
+        default_factory=list,
+        description="0-indexed page numbers. Java runs Tabula CSV extraction on these.",
+    )
+    need_ocr: list[int] = Field(
+        default_factory=list,
+        description="0-indexed page numbers. Java runs OCRmyPDF on these.",
+    )
+    rationale: str = Field(description="Plain-language reason, written for log readability, not the client.")
+
+
+# ---------------------------------------------------------------------------
+# Evidence — Java's fulfilment of a Requisition
+# ---------------------------------------------------------------------------
+
+
+class Folio(ApiModel):
+    """
+    One page's worth of extracted content — whatever Java was able to provide
+    in response to the Requisition for that page.
+    """
+
+    page: int = Field(ge=0, description="0-indexed page number.")
+    text: str | None = Field(default=None, description="PDFBox plain-text extraction.")
+    tables: list[str] | None = Field(default=None, description="Tabula CSV strings, one per table found on the page.")
+    ocr_text: str | None = Field(default=None, description="OCRmyPDF output text.")
+    ocr_confidence: float | None = Field(
+        default=None, ge=0.0, le=1.0, description="Mean character confidence from OCRmyPDF."
+    )
+
+    @property
+    def readable_text(self) -> str:
+        """Best available text for this folio — OCR wins over digital when present."""
+        return self.ocr_text or self.text or ""
+
+
+class Evidence(ApiModel):
+    """
+    Java's fulfilment package: the extracted content Python asked for.
+    Java may also set final_round=True on the last allowable round to signal
+    that the auditor must return a Verdict regardless of remaining questions.
+    """
+
+    session_id: str
+    folios: list[Folio]
+    round: int = Field(ge=1, le=3)
+    final_round: bool = Field(
+        default=False,
+        description="When True, Java will not honour further Requisitions. "
+        "The auditor must return a Verdict this round.",
+    )
+    unauditable_pages: list[int] = Field(
+        default_factory=list,
+        description=(
+            "Pages that were requested in the Requisition but could not be fulfilled — "
+            "e.g. OCR was asked for but is not wired. The Auditor echoes these into "
+            "Verdict.unauditable_pages so the client knows coverage is incomplete."
+        ),
+    )
+
+
+# ---------------------------------------------------------------------------
+# Findings — what the auditor discovers
+# ---------------------------------------------------------------------------
+
+
+class DiscrepancyKind(StrEnum):
+    """Java counterpart: DiscrepancyKind.java - values must stay in sync."""
+
+    TALLY = "tally"  # a row/column sum is wrong
+    ARITHMETIC = "arithmetic"  # an inline calculation is wrong
+    CONSISTENCY = "consistency"  # the same figure is stated differently elsewhere
+    STATEMENT = "statement"  # a prose claim contradicts the numbers
+
+
+class Severity(StrEnum):
+    """Java counterpart: AuditSeverity.java - values must stay in sync."""
+
+    ERROR = "error"  # definite arithmetic mistake
+    WARNING = "warning"  # possible rounding or ambiguity
+
+
+class Discrepancy(ApiModel):
+    """A single mathematical error found in the document."""
+
+    page: int = Field(ge=0)
+    kind: DiscrepancyKind
+    severity: Severity
+    description: str = Field(description="Human-readable explanation of the error.")
+    stated: str = Field(description="The value as it appears in the document.")
+    expected: str = Field(description="The value the auditor calculated.")
+    context: str = Field(
+        default="",
+        description="Surrounding text or table fragment for traceability.",
+    )
+
+
+# ---------------------------------------------------------------------------
+# Verdict — the final report
+# ---------------------------------------------------------------------------
+
+
+class Verdict(ApiModel):
+    """
+    The auditor's final opinion on the document's mathematical integrity.
+    Returned to Java as the terminal message in the negotiation.
+    """
+
+    type: Literal["verdict"] = "verdict"
+    session_id: str
+    discrepancies: list[Discrepancy] = Field(default_factory=list)
+    pages_examined: list[int] = Field(description="0-indexed page numbers the auditor actually inspected.")
+    rounds_taken: int = Field(ge=1, le=3)
+    summary: str = Field(description="One or two sentences summarising the audit outcome for the client.")
+    clean: bool = Field(description="True iff no errors were found (warnings are tolerated).")
+    unauditable_pages: list[int] = Field(
+        default_factory=list,
+        description=(
+            "0-indexed pages that could not be audited — typically because OCR was "
+            "requested but is not yet wired. Java populates this by omitting the folio "
+            "and the Auditor echoes the page number here so the client knows coverage "
+            "is incomplete."
+        ),
+    )
+
+    @property
+    def error_count(self) -> int:
+        return sum(1 for d in self.discrepancies if d.severity == Severity.ERROR)
+
+    @property
+    def warning_count(self) -> int:
+        return sum(1 for d in self.discrepancies if d.severity == Severity.WARNING)

engine/src/stirling/logging.py

@@ -0,0 +1,22 @@
+"""Shared logging utilities for the Stirling AI engine."""
+
+from __future__ import annotations
+
+import json
+
+
+class Pretty:
+    """Lazy JSON formatter — only serialises when ``str()`` is called.
+
+    Designed for use with ``logging``'s ``%s`` formatting so that the
+    JSON serialisation is skipped entirely when the log message is
+    never emitted.
+    """
+
+    __slots__ = ("_obj",)
+
+    def __init__(self, obj: object) -> None:
+        self._obj = obj
+
+    def __str__(self) -> str:
+        return json.dumps(self._obj, indent=2, default=str, ensure_ascii=True)

engine/src/stirling/models/agent_tool_models.py

@@ -0,0 +1,30 @@
+"""Agent tool IDs, parameter models, and registry.
+
+tool_models.py is auto-generated from the frontend. This file is its
+manually-maintained counterpart for tools backed by AI agent pipelines.
+"""
+
+from __future__ import annotations
+
+from enum import StrEnum
+
+from stirling.models.base import ApiModel
+from stirling.models.tool_models import OperationId, ParamToolModel
+
+
+class AgentToolId(StrEnum):
+    MATH_AUDITOR_AGENT = "mathAuditorAgent"
+
+
+class MathAuditorAgentParams(ApiModel):
+    tolerance: str = "0.01"
+
+
+type AgentParamModel = MathAuditorAgentParams
+
+type AnyToolId = OperationId | AgentToolId
+type AnyParamModel = ParamToolModel | AgentParamModel
+
+AGENT_OPERATIONS: dict[AgentToolId, type[AgentParamModel]] = {
+    AgentToolId.MATH_AUDITOR_AGENT: MathAuditorAgentParams,
+}

engine/tests/ledger/test_arithmetic_scanner.py

@@ -0,0 +1,133 @@
+"""
+ArithmeticScanner — unit tests.
+
+Tests cover the two inline arithmetic patterns the scanner targets:
+  1. Equals expressions:        A + B = C
+  2. Total-then-addends:        Total: C (A + B)
+"""
+
+from decimal import Decimal
+
+import pytest
+
+from stirling.agents.ledger.validators.arithmetic import ArithmeticScanner
+
+
+@pytest.fixture
+def scanner() -> ArithmeticScanner:
+    return ArithmeticScanner(tolerance=Decimal("0.01"))
+
+
+# ---------------------------------------------------------------------------
+# Equals expressions: A + B + C = D
+# ---------------------------------------------------------------------------
+
+
+def test_correct_equals_expression(scanner: ArithmeticScanner) -> None:
+    """A correct sum should produce no findings."""
+    text = "The total cost is 100 + 200 + 150 = 450."
+    assert scanner.scan(page=0, text=text) == []
+
+
+def test_wrong_equals_expression(scanner: ArithmeticScanner) -> None:
+    """An incorrect sum should produce one error discrepancy."""
+    text = "Revenue: 500 + 300 = 900"  # should be 800
+    discrepancies = scanner.scan(page=3, text=text)
+    assert len(discrepancies) == 1
+    d = discrepancies[0]
+    assert d.page == 3
+    assert d.kind == "arithmetic"
+    assert d.severity == "error"
+    assert d.stated == "900"
+    assert d.expected == "800"
+
+
+def test_subtraction_expression(scanner: ArithmeticScanner) -> None:
+    """Subtraction in expressions should be evaluated correctly."""
+    text = "Net: 1000 - 250 = 750"
+    assert scanner.scan(page=0, text=text) == []
+
+
+def test_wrong_subtraction(scanner: ArithmeticScanner) -> None:
+    text = "Net: 1000 - 250 = 800"  # should be 750
+    discrepancies = scanner.scan(page=0, text=text)
+    assert len(discrepancies) == 1
+    assert discrepancies[0].expected == "750"
+
+
+def test_currency_symbols_stripped(scanner: ArithmeticScanner) -> None:
+    """Currency symbols and thousand separators must not break parsing."""
+    text = "Total: £1,000 + £500 = £1,500"
+    assert scanner.scan(page=0, text=text) == []
+
+
+def test_multiple_expressions_in_text(scanner: ArithmeticScanner) -> None:
+    """Multiple expressions in the same text should each be evaluated."""
+    text = (
+        "Q1 revenue: 100 + 200 = 300. "
+        "Q2 revenue: 150 + 100 = 350. "  # wrong: should be 250
+    )
+    discrepancies = scanner.scan(page=0, text=text)
+    assert len(discrepancies) == 1
+    assert discrepancies[0].expected == "250"
+
+
+# ---------------------------------------------------------------------------
+# Total-then-addends: "Total: X (A + B + C)"
+# ---------------------------------------------------------------------------
+
+
+def test_correct_total_then_addends(scanner: ArithmeticScanner) -> None:
+    text = "Grand Total: 750 (300 + 250 + 200)"
+    assert scanner.scan(page=0, text=text) == []
+
+
+def test_wrong_total_then_addends(scanner: ArithmeticScanner) -> None:
+    text = "Grand Total: 900 (300 + 250 + 200)"  # addends sum to 750
+    discrepancies = scanner.scan(page=0, text=text)
+    assert len(discrepancies) == 1
+    d = discrepancies[0]
+    assert d.stated == "900"
+    assert d.expected == "750"
+
+
+def test_total_keyword_variations(scanner: ArithmeticScanner) -> None:
+    """The pattern must work for 'Sum', 'Subtotal', 'Grand Total' etc."""
+    cases = [
+        ("Sum: 600 (200 + 200 + 200)", True),
+        ("Subtotal: 600 (200 + 200 + 200)", True),
+        ("Total: 999 (200 + 200 + 200)", False),  # wrong
+    ]
+    for text, should_be_clean in cases:
+        result = scanner.scan(page=0, text=text)
+        if should_be_clean:
+            assert result == [], f"Expected clean for: {text!r}"
+        else:
+            assert len(result) == 1, f"Expected error for: {text!r}"
+
+
+# ---------------------------------------------------------------------------
+# Edge cases
+# ---------------------------------------------------------------------------
+
+
+def test_no_expressions_in_text(scanner: ArithmeticScanner) -> None:
+    text = "This paragraph discusses revenue trends but contains no arithmetic."
+    assert scanner.scan(page=0, text=text) == []
+
+
+def test_empty_text(scanner: ArithmeticScanner) -> None:
+    assert scanner.scan(page=0, text="") == []
+
+
+def test_leading_negative_expression(scanner: ArithmeticScanner) -> None:
+    """Expressions starting with a negative number should evaluate correctly."""
+    text = "Adjustment: -100 + 250 = 150"
+    assert scanner.scan(page=0, text=text) == []
+
+
+def test_leading_negative_wrong(scanner: ArithmeticScanner) -> None:
+    text = "Adjustment: -100 + 250 = 200"  # should be 150
+    discrepancies = scanner.scan(page=0, text=text)
+    assert len(discrepancies) == 1
+    assert discrepancies[0].expected == "150"

engine/tests/ledger/test_figure_tracker.py

@@ -0,0 +1,100 @@
+"""
+FigureTracker — unit tests.
+
+Tests that named figures are correctly accumulated and that conflicting
+sightings (same label, different value) are surfaced as consistency warnings.
+"""
+
+from decimal import Decimal
+
+import pytest
+
+from stirling.agents.ledger.validators.figures import FigureTracker
+
+
+@pytest.fixture
+def tracker() -> FigureTracker:
+    return FigureTracker(tolerance=Decimal("0.01"))
+
+
+# ---------------------------------------------------------------------------
+# No conflicts
+# ---------------------------------------------------------------------------
+
+
+def test_no_conflicts_single_figure(tracker: FigureTracker) -> None:
+    tracker.record("Net Profit", Decimal("1200.00"), page=3, raw="£1,200.00")
+    assert tracker.conflicts() == []
+
+
+def test_no_conflicts_consistent_figure(tracker: FigureTracker) -> None:
+    """The same figure cited identically on two pages must not raise a conflict."""
+    tracker.record("Total Revenue", Decimal("5000.00"), page=1, raw="£5,000")
+    tracker.record("Total Revenue", Decimal("5000.00"), page=8, raw="£5,000")
+    assert tracker.conflicts() == []
+
+
+def test_no_conflicts_within_tolerance(tracker: FigureTracker) -> None:
+    """A difference within tolerance must not be flagged."""
+    tracker.record("VAT", Decimal("100.00"), page=2, raw="£100.00")
+    tracker.record("VAT", Decimal("100.005"), page=5, raw="£100.005")
+    assert tracker.conflicts() == []
+
+
+# ---------------------------------------------------------------------------
+# Conflicts
+# ---------------------------------------------------------------------------
+
+
+def test_conflict_different_values(tracker: FigureTracker) -> None:
+    """Same label, different value on two pages → one consistency warning."""
+    tracker.record("Net Profit", Decimal("1200.00"), page=3, raw="£1,200")
+    tracker.record("Net Profit", Decimal("1250.00"), page=7, raw="£1,250")
+    conflicts = tracker.conflicts()
+    assert len(conflicts) == 1
+    d = conflicts[0]
+    assert d.kind == "consistency"
+    assert d.severity == "warning"
+    assert d.page == 7  # later occurrence is flagged
+
+
+def test_conflict_three_sightings_two_values(tracker: FigureTracker) -> None:
+    """Three sightings where one differs from canonical → 1 conflict."""
+    tracker.record("Revenue", Decimal("1000"), page=1, raw="£1,000")
+    tracker.record("Revenue", Decimal("1000"), page=3, raw="£1,000")
+    tracker.record("Revenue", Decimal("999"), page=5, raw="£999")
+    conflicts = tracker.conflicts()
+    # Canonical=p1 (1000). p3 matches, p5 differs → 1 conflict
+    assert len(conflicts) == 1
+    assert conflicts[0].page == 5
+
+
+# ---------------------------------------------------------------------------
+# Label normalisation
+# ---------------------------------------------------------------------------
+
+
+def test_label_normalisation_case_insensitive(tracker: FigureTracker) -> None:
+    """Labels must be compared case-insensitively."""
+    tracker.record("Net Profit", Decimal("1200"), page=2, raw="1200")
+    tracker.record("net profit", Decimal("1100"), page=4, raw="1100")
+    assert len(tracker.conflicts()) == 1
+
+
+def test_label_normalisation_punctuation(tracker: FigureTracker) -> None:
+    """Colons and dashes in labels must be normalised before comparison."""
+    tracker.record("Total Revenue:", Decimal("5000"), page=1, raw="5000")
+    tracker.record("Total Revenue —", Decimal("4000"), page=9, raw="4000")
+    assert len(tracker.conflicts()) == 1
+
+
+# ---------------------------------------------------------------------------
+# Entry count
+# ---------------------------------------------------------------------------
+
+
+def test_entry_count(tracker: FigureTracker) -> None:
+    tracker.record("A", Decimal("1"), page=0, raw="1")
+    tracker.record("A", Decimal("1"), page=1, raw="1")
+    tracker.record("B", Decimal("2"), page=2, raw="2")
+    assert tracker.entry_count == 3

engine/tests/ledger/test_formula_evaluator.py

@@ -0,0 +1,205 @@
+"""
+FormulaEvaluator — unit tests.
+
+Tests cover:
+  - Operator precedence (* / before + -)
+  - Column reference replacement (colN with word boundaries)
+  - Negative number handling
+  - each_row, column_total, and single_cell scopes
+"""
+
+from decimal import Decimal
+
+import pytest
+
+from stirling.agents.ledger.validators.formula import FormulaEvaluator
+
+
+@pytest.fixture
+def evaluator() -> FormulaEvaluator:
+    return FormulaEvaluator(tolerance=Decimal("0.01"))
+
+
+# ---------------------------------------------------------------------------
+# _safe_eval — operator precedence
+# ---------------------------------------------------------------------------
+
+
+def test_safe_eval_addition(evaluator: FormulaEvaluator) -> None:
+    assert evaluator._safe_eval("2 + 3") == Decimal("5")
+
+
+def test_safe_eval_multiplication_before_addition(evaluator: FormulaEvaluator) -> None:
+    """2 + 3 * 4 should be 14, not 20."""
+    assert evaluator._safe_eval("2 + 3 * 4") == Decimal("14")
+
+
+def test_safe_eval_division_before_subtraction(evaluator: FormulaEvaluator) -> None:
+    """10 - 6 / 2 should be 7, not 2."""
+    assert evaluator._safe_eval("10 - 6 / 2") == Decimal("7")
+
+
+def test_safe_eval_mixed_precedence(evaluator: FormulaEvaluator) -> None:
+    """1 + 2 * 3 - 4 / 2 should be 1 + 6 - 2 = 5."""
+    assert evaluator._safe_eval("1 + 2 * 3 - 4 / 2") == Decimal("5")
+
+
+def test_safe_eval_all_multiplication(evaluator: FormulaEvaluator) -> None:
+    assert evaluator._safe_eval("2 * 3 * 4") == Decimal("24")
+
+
+def test_safe_eval_division_by_zero(evaluator: FormulaEvaluator) -> None:
+    assert evaluator._safe_eval("10 / 0") is None
+
+
+def test_safe_eval_negative_result(evaluator: FormulaEvaluator) -> None:
+    assert evaluator._safe_eval("3 - 5") == Decimal("-2")
+
+
+def test_safe_eval_leading_negative(evaluator: FormulaEvaluator) -> None:
+    """Expressions starting with a negative number should work."""
+    result = evaluator._safe_eval("-100 + 200")
+    assert result == Decimal("100")
+
+
+def test_safe_eval_empty(evaluator: FormulaEvaluator) -> None:
+    assert evaluator._safe_eval("") is None
+
+
+def test_safe_eval_single_number(evaluator: FormulaEvaluator) -> None:
+    assert evaluator._safe_eval("42") == Decimal("42")
+
+
+def test_safe_eval_decimal_numbers(evaluator: FormulaEvaluator) -> None:
+    result = evaluator._safe_eval("1.5 * 2 + 0.5")
+    assert result == Decimal("3.5")
+
+
+# ---------------------------------------------------------------------------
+# colN replacement — word boundary safety
+# ---------------------------------------------------------------------------
+
+
+def test_col1_does_not_corrupt_col12(evaluator: FormulaEvaluator) -> None:
+    """col1 replacement must not alter col12."""
+    csv = "a,b,c,d,e,f,g,h,i,j,k,l,m\n0,10,0,0,0,0,0,0,0,0,0,0,120\n"
+    # col1=10, col12=120 → col12 - col1 should be 110
+    result = evaluator.evaluate(
+        page=0,
+        table_csv=csv,
+        formula="col0 = col12 - col1",
+        scope="each_row",
+        description="test",
+    )
+    # row 1: col0=0, expected=120-10=110 → discrepancy
+    assert len(result) == 1
+    assert result[0].expected == "110"
+
+
+def test_col_replacement_adjacent_columns(evaluator: FormulaEvaluator) -> None:
+    """col1 and col10 should both be replaced correctly."""
+    csv = "a,b,c,d,e,f,g,h,i,j,k\n55,5,0,0,0,0,0,0,0,0,50\n"
+    # col0=55, col1=5, col10=50 → col1 + col10 = 55
+    result = evaluator.evaluate(
+        page=0,
+        table_csv=csv,
+        formula="col0 = col1 + col10",
+        scope="each_row",
+        description="test",
+    )
+    assert result == []  # 5 + 50 = 55, matches col0
+
+
+# ---------------------------------------------------------------------------
+# each_row scope
+# ---------------------------------------------------------------------------
+
+
+def test_each_row_correct(evaluator: FormulaEvaluator) -> None:
+    csv = "Item,Qty,Price,Total\nWidget,10,5,50\nGadget,3,20,60\n"
+    result = evaluator.evaluate(
+        page=0,
+        table_csv=csv,
+        formula="col3 = col1 * col2",
+        scope="each_row",
+        description="unit price check",
+    )
+    assert result == []
+
+
+def test_each_row_error(evaluator: FormulaEvaluator) -> None:
+    csv = "Item,Qty,Price,Total\nWidget,10,5,50\nGadget,3,20,99\n"
+    result = evaluator.evaluate(
+        page=0,
+        table_csv=csv,
+        formula="col3 = col1 * col2",
+        scope="each_row",
+        description="unit price check",
+    )
+    assert len(result) == 1
+    assert result[0].expected == "60"
+    assert result[0].stated == "99"
+
+
+# ---------------------------------------------------------------------------
+# column_total scope
+# ---------------------------------------------------------------------------
+
+
+def test_column_total_correct(evaluator: FormulaEvaluator) -> None:
+    csv = "Name,Amount\nA,100\nB,200\nTotal,300\n"
+    result = evaluator.evaluate(
+        page=0,
+        table_csv=csv,
+        formula="sum",
+        scope="column_total",
+        description="total check",
+        target_row=3,
+        target_col=1,
+    )
+    assert result == []
+
+
+def test_column_total_error(evaluator: FormulaEvaluator) -> None:
+    csv = "Name,Amount\nA,100\nB,200\nTotal,400\n"
+    result = evaluator.evaluate(
+        page=0,
+        table_csv=csv,
+        formula="sum",
+        scope="column_total",
+        description="total check",
+        target_row=3,
+        target_col=1,
+    )
+    assert len(result) == 1
+    assert result[0].expected == "300"
+
+
+# ---------------------------------------------------------------------------
+# single_cell scope
+# ---------------------------------------------------------------------------
+
+
+def test_single_cell_correct(evaluator: FormulaEvaluator) -> None:
+    csv = "A,B,C\n10,20,30\n5,15,20\n15,35,50\n"
+    result = evaluator.evaluate(
+        page=0,
+        table_csv=csv,
+        formula="cell(3,2) = cell(1,2) + cell(2,2)",
+        scope="single_cell",
+        description="grand total",
+    )
+    assert result == []
+
+
+def test_single_cell_error(evaluator: FormulaEvaluator) -> None:
+    csv = "A,B,C\n10,20,30\n5,15,20\n15,35,99\n"
+    result = evaluator.evaluate(
+        page=0,
+        table_csv=csv,
+        formula="cell(3,2) = cell(1,2) + cell(2,2)",
+        scope="single_cell",
+        description="grand total",
+    )
+    assert len(result) == 1
+    assert result[0].expected == "50"

engine/tests/ledger/test_models.py

@@ -0,0 +1,144 @@
+"""
+Ledger models — unit tests for serialisation and business logic.
+
+These tests confirm the wire contract: models round-trip through JSON
+correctly and their helper properties behave as documented.
+"""
+
+import pytest
+from pydantic import ValidationError
+
+from stirling.contracts.ledger import (
+    Discrepancy,
+    DiscrepancyKind,
+    Evidence,
+    Folio,
+    FolioManifest,
+    FolioType,
+    Requisition,
+    Severity,
+    Verdict,
+)
+
+# ---------------------------------------------------------------------------
+# FolioManifest
+# ---------------------------------------------------------------------------
+
+
+def test_folio_manifest_round_trip() -> None:
+    manifest = FolioManifest(
+        session_id="abc-123",
+        page_count=3,
+        folio_types=[FolioType.TEXT, FolioType.IMAGE, FolioType.MIXED],
+    )
+    reloaded = FolioManifest.model_validate_json(manifest.model_dump_json())
+    assert reloaded == manifest
+
+
+def test_folio_manifest_round_bounds() -> None:
+    with pytest.raises(ValidationError):
+        FolioManifest(session_id="x", page_count=1, folio_types=[FolioType.TEXT], round=0)
+    with pytest.raises(ValidationError):
+        FolioManifest(session_id="x", page_count=1, folio_types=[FolioType.TEXT], round=4)
+
+
+# ---------------------------------------------------------------------------
+# Requisition
+# ---------------------------------------------------------------------------
+
+
+def test_requisition_empty() -> None:
+    req = Requisition(rationale="nothing needed")
+    assert req.need_text == []
+    assert req.need_tables == []
+    assert req.need_ocr == []
+
+
+def test_requisition_type_discriminator() -> None:
+    req = Requisition(need_text=[0, 1], rationale="needs text")
+    assert req.type == "requisition"
+
+
+# ---------------------------------------------------------------------------
+# Folio.readable_text
+# ---------------------------------------------------------------------------
+
+
+def test_folio_readable_text_prefers_ocr() -> None:
+    folio = Folio(page=0, text="digital text", ocr_text="ocr text")
+    assert folio.readable_text == "ocr text"
+
+
+def test_folio_readable_text_falls_back_to_text() -> None:
+    folio = Folio(page=0, text="digital text")
+    assert folio.readable_text == "digital text"
+
+
+def test_folio_readable_text_empty_when_none() -> None:
+    folio = Folio(page=0)
+    assert folio.readable_text == ""
+
+
+# ---------------------------------------------------------------------------
+# Verdict
+# ---------------------------------------------------------------------------
+
+
+def test_verdict_clean_flag() -> None:
+    verdict = Verdict(
+        session_id="s1",
+        discrepancies=[],
+        pages_examined=[0, 1],
+        rounds_taken=2,
+        summary="All figures balance.",
+        clean=True,
+    )
+    assert verdict.error_count == 0
+    assert verdict.warning_count == 0
+    assert verdict.clean is True
+
+
+def test_verdict_error_and_warning_counts() -> None:
+    discrepancies = [
+        Discrepancy(
+            page=0,
+            kind=DiscrepancyKind.TALLY,
+            severity=Severity.ERROR,
+            description="bad sum",
+            stated="100",
+            expected="110",
+        ),
+        Discrepancy(
+            page=1,
+            kind=DiscrepancyKind.CONSISTENCY,
+            severity=Severity.WARNING,
+            description="mismatched figure",
+            stated="500",
+            expected="550",
+        ),
+    ]
+    verdict = Verdict(
+        session_id="s1",
+        discrepancies=discrepancies,
+        pages_examined=[0, 1],
+        rounds_taken=1,
+        summary="Issues found.",
+        clean=False,
+    )
+    assert verdict.error_count == 1
+    assert verdict.warning_count == 1
+
+
+# ---------------------------------------------------------------------------
+# Evidence.final_round
+# ---------------------------------------------------------------------------
+
+
+def test_evidence_final_round() -> None:
+    evidence = Evidence(
+        session_id="s",
+        folios=[Folio(page=0, text="hello")],
+        round=3,
+        final_round=True,
+    )
+    assert evidence.final_round is True

engine/tests/ledger/test_routes.py

@@ -0,0 +1,249 @@
+"""
+Ledger Auditor — FastAPI route tests.
+
+Uses FastAPI's TestClient with dependency overrides. All LLM calls are
+mocked out; these tests exercise HTTP parsing, serialisation, and response
+enveloping only — not the agent's reasoning.
+"""
+
+from __future__ import annotations
+
+from collections.abc import Iterator
+from decimal import Decimal
+
+import pytest
+from fastapi.testclient import TestClient
+
+from stirling.api import app
+from stirling.api.dependencies import get_math_auditor_agent
+from stirling.config import AppSettings, load_settings
+from stirling.contracts.ledger import (
+    Discrepancy,
+    DiscrepancyKind,
+    Evidence,
+    FolioManifest,
+    Requisition,
+    Severity,
+    Verdict,
+)
+
+# ---------------------------------------------------------------------------
+# Stubs
+# ---------------------------------------------------------------------------
+
+
+class StubSettingsProvider:
+    def __call__(self) -> AppSettings:
+        return AppSettings(
+            smart_model_name="test",
+            fast_model_name="test",
+            smart_model_max_tokens=8192,
+            fast_model_max_tokens=2048,
+            posthog_enabled=False,
+            posthog_api_key="",
+            posthog_host="https://eu.i.posthog.com",
+        )
+
+
+class StubLedgerAgent:
+    """Stub that returns canned responses without touching any model."""
+
+    def __init__(
+        self,
+        requisition: Requisition | None = None,
+        verdict: Verdict | None = None,
+    ) -> None:
+        self._requisition = requisition or _stub_requisition()
+        self._verdict = verdict or _stub_verdict()
+        self.examine_calls: list[FolioManifest] = []
+        self.audit_calls: list[tuple[Evidence, Decimal]] = []
+
+    async def examine(self, manifest: FolioManifest) -> Requisition:
+        self.examine_calls.append(manifest)
+        return self._requisition
+
+    async def audit(self, evidence: Evidence, tolerance: Decimal = Decimal("0.01")) -> Verdict:
+        self.audit_calls.append((evidence, tolerance))
+        return self._verdict
+
+
+# ---------------------------------------------------------------------------
+# Helpers
+# ---------------------------------------------------------------------------
+
+
+def _stub_requisition() -> Requisition:
+    return Requisition(
+        need_text=[0, 2],
+        need_tables=[0],
+        need_ocr=[1],
+        rationale="Page 1 is image-only; pages 0 and 2 have financial text.",
+    )
+
+
+def _stub_verdict(
+    clean: bool = True,
+    discrepancies: list[Discrepancy] | None = None,
+) -> Verdict:
+    return Verdict(
+        session_id="test-session",
+        discrepancies=discrepancies or [],
+        pages_examined=[0, 2],
+        rounds_taken=2,
+        summary="No errors found." if clean else "1 tally error found.",
+        clean=clean,
+    )
+
+
+def _manifest_body(**overrides: object) -> dict[str, object]:
+    base: dict[str, object] = {
+        "sessionId": "test-session",
+        "pageCount": 3,
+        "folioTypes": ["text", "image", "mixed"],
+        "round": 1,
+    }
+    return {**base, **overrides}
+
+
+def _evidence_body(**overrides: object) -> dict[str, object]:
+    base: dict[str, object] = {
+        "sessionId": "test-session",
+        "folios": [
+            {"page": 0, "text": "Fee: £100\nTax: £20\nTotal: £120"},
+            {"page": 2, "text": "Summary: all tallies correct"},
+        ],
+        "round": 2,
+        "finalRound": False,
+    }
+    return {**base, **overrides}
+
+
+# ---------------------------------------------------------------------------
+# Fixtures
+# ---------------------------------------------------------------------------
+
+
+@pytest.fixture
+def stub_agent() -> StubLedgerAgent:
+    return StubLedgerAgent()
+
+
+@pytest.fixture
+def client(stub_agent: StubLedgerAgent) -> Iterator[TestClient]:
+    app.dependency_overrides[load_settings] = StubSettingsProvider()
+    app.dependency_overrides[get_math_auditor_agent] = lambda: stub_agent
+    yield TestClient(app, raise_server_exceptions=False)
+    app.dependency_overrides.pop(load_settings, None)
+    app.dependency_overrides.pop(get_math_auditor_agent, None)
+
+
+# ---------------------------------------------------------------------------
+# POST /api/v1/ai/math-auditor-agent/examine
+# ---------------------------------------------------------------------------
+
+
+class TestExamineEndpoint:
+    """Tests for POST /api/v1/ai/math-auditor-agent/examine."""
+
+    def test_returns_200(self, client: TestClient) -> None:
+        resp = client.post("/api/v1/ai/math-auditor-agent/examine", json=_manifest_body())
+        assert resp.status_code == 200
+
+    def test_response_is_requisition(self, client: TestClient) -> None:
+        resp = client.post("/api/v1/ai/math-auditor-agent/examine", json=_manifest_body())
+        body = resp.json()
+        assert body["type"] == "requisition"
+        assert body["needText"] == [0, 2]
+        assert body["needTables"] == [0]
+        assert body["needOcr"] == [1]
+        assert "rationale" in body
+
+    def test_examine_called_with_parsed_manifest(
+        self,
+        client: TestClient,
+        stub_agent: StubLedgerAgent,
+    ) -> None:
+        client.post("/api/v1/ai/math-auditor-agent/examine", json=_manifest_body(sessionId="my-session", pageCount=3))
+        assert len(stub_agent.examine_calls) == 1
+        manifest = stub_agent.examine_calls[0]
+        assert manifest.session_id == "my-session"
+        assert manifest.page_count == 3
+
+    def test_content_type_is_json(self, client: TestClient) -> None:
+        resp = client.post("/api/v1/ai/math-auditor-agent/examine", json=_manifest_body())
+        assert "application/json" in resp.headers["content-type"]
+
+
+# ---------------------------------------------------------------------------
+# POST /api/v1/ai/math-auditor-agent/deliberate
+# ---------------------------------------------------------------------------
+
+
+class TestDeliberateEndpoint:
+    """Tests for POST /api/v1/ai/math-auditor-agent/deliberate."""
+
+    def test_returns_200_clean(self, client: TestClient) -> None:
+        resp = client.post("/api/v1/ai/math-auditor-agent/deliberate", json=_evidence_body())
+        assert resp.status_code == 200
+
+    def test_response_is_verdict(self, client: TestClient) -> None:
+        resp = client.post("/api/v1/ai/math-auditor-agent/deliberate", json=_evidence_body())
+        body = resp.json()
+        assert body["type"] == "verdict"
+        assert body["clean"] is True
+
+    def test_discrepancies_serialised(self, client: TestClient) -> None:
+        d = Discrepancy(
+            page=0,
+            kind=DiscrepancyKind.TALLY,
+            severity=Severity.ERROR,
+            description="Column total wrong",
+            stated="250",
+            expected="300",
+        )
+        stub = StubLedgerAgent(verdict=_stub_verdict(clean=False, discrepancies=[d]))
+        app.dependency_overrides[get_math_auditor_agent] = lambda: stub
+        resp = client.post("/api/v1/ai/math-auditor-agent/deliberate", json=_evidence_body())
+        body = resp.json()
+        discrepancies = body["discrepancies"]
+        assert len(discrepancies) == 1
+        assert discrepancies[0]["kind"] == "tally"
+        assert discrepancies[0]["severity"] == "error"
+        assert discrepancies[0]["stated"] == "250"
+        assert discrepancies[0]["expected"] == "300"
+
+    def test_tolerance_query_param_forwarded(
+        self,
+        client: TestClient,
+        stub_agent: StubLedgerAgent,
+    ) -> None:
+        client.post("/api/v1/ai/math-auditor-agent/deliberate?tolerance=0.05", json=_evidence_body())
+        assert len(stub_agent.audit_calls) == 1
+        _, tolerance = stub_agent.audit_calls[0]
+        assert tolerance == Decimal("0.05")
+
+    def test_default_tolerance_when_omitted(
+        self,
+        client: TestClient,
+        stub_agent: StubLedgerAgent,
+    ) -> None:
+        client.post("/api/v1/ai/math-auditor-agent/deliberate", json=_evidence_body())
+        _, tolerance = stub_agent.audit_calls[0]
+        assert tolerance == Decimal("0.01")
+
+    def test_invalid_tolerance_returns_400(
+        self,
+        client: TestClient,
+        stub_agent: StubLedgerAgent,
+    ) -> None:
+        resp = client.post("/api/v1/ai/math-auditor-agent/deliberate?tolerance=notanumber", json=_evidence_body())
+        assert resp.status_code == 400
+
+    def test_final_round_flag_parsed(
+        self,
+        client: TestClient,
+        stub_agent: StubLedgerAgent,
+    ) -> None:
+        client.post("/api/v1/ai/math-auditor-agent/deliberate", json=_evidence_body(finalRound=True))
+        evidence, _ = stub_agent.audit_calls[0]
+        assert evidence.final_round is True

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testing/ledger/generate_test_pdfs.py

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+"""
+Generate test PDFs for the Ledger Auditor math validation agent.
+
+Run:  uv run python testing/ledger/generate_test_pdfs.py
+Outputs PDFs into testing/ledger/
+"""
+
+from fpdf import FPDF
+
+
+def _new_pdf() -> FPDF:
+    pdf = FPDF()
+    pdf.set_auto_page_break(auto=True, margin=15)
+    return pdf
+
+
+def _heading(pdf: FPDF, text: str) -> None:
+    pdf.set_font("Helvetica", "B", 16)
+    pdf.cell(0, 12, text, new_x="LMARGIN", new_y="NEXT")
+    pdf.ln(2)
+
+
+def _body(pdf: FPDF) -> None:
+    pdf.set_font("Helvetica", "", 11)
+
+
+def _table_row(pdf: FPDF, cells: list[str], bold: bool = False) -> None:
+    style = "B" if bold else ""
+    pdf.set_font("Helvetica", style, 10)
+    col_w = (pdf.w - 2 * pdf.l_margin) / len(cells)
+    for c in cells:
+        pdf.cell(col_w, 8, c, border=1, align="C")
+    pdf.ln()
+
+
+# ─────────────────────────────────────────────────────────────────────────────
+# 1. Clean invoice — all math is correct
+# ─────────────────────────────────────────────────────────────────────────────
+def create_clean_invoice():
+    pdf = _new_pdf()
+    pdf.add_page()
+
+    _heading(pdf, "INVOICE #1001 - Acme Corp")
+    _body(pdf)
+    pdf.cell(0, 8, "Date: 2026-03-15", new_x="LMARGIN", new_y="NEXT")
+    pdf.cell(0, 8, "Bill To: Widget Industries", new_x="LMARGIN", new_y="NEXT")
+    pdf.ln(5)
+
+    _table_row(pdf, ["Item", "Qty", "Unit Price", "Line Total"], bold=True)
+    _table_row(pdf, ["Consulting Hours", "40", "$150.00", "$6,000.00"])
+    _table_row(pdf, ["Software License", "5", "$200.00", "$1,000.00"])
+    _table_row(pdf, ["Travel Expenses", "1", "$450.00", "$450.00"])
+    _table_row(pdf, ["", "", "Subtotal", "$7,450.00"], bold=True)
+
+    pdf.ln(5)
+    pdf.cell(0, 8, "Tax (10%): $745.00", new_x="LMARGIN", new_y="NEXT")
+    pdf.cell(0, 8, "Grand Total: $8,195.00", new_x="LMARGIN", new_y="NEXT")
+    pdf.ln(3)
+    pdf.cell(
+        0, 8,
+        "Breakdown: $6,000.00 + $1,000.00 + $450.00 = $7,450.00",
+        new_x="LMARGIN", new_y="NEXT",
+    )
+
+    pdf.output("testing/ledger/clean_invoice.pdf")
+    print("  clean_invoice.pdf")
+
+
+# ─────────────────────────────────────────────────────────────────────────────
+# 2. Tally error — column total is wrong
+# ─────────────────────────────────────────────────────────────────────────────
+def create_tally_error():
+    pdf = _new_pdf()
+    pdf.add_page()
+
+    _heading(pdf, "Q1 2026 Expense Report")
+    _body(pdf)
+    pdf.cell(0, 8, "Department: Engineering", new_x="LMARGIN", new_y="NEXT")
+    pdf.ln(5)
+
+    _table_row(pdf, ["Category", "Jan", "Feb", "Mar", "Total"], bold=True)
+    _table_row(pdf, ["Salaries", "$50,000", "$50,000", "$52,000", "$152,000"])
+    _table_row(pdf, ["Cloud Infra", "$12,000", "$13,500", "$14,200", "$39,700"])
+    _table_row(pdf, ["Equipment", "$8,000", "$2,500", "$5,000", "$15,500"])
+    # BUG: column totals are wrong — Jan should be 70,000, Grand should be 207,200
+    _table_row(pdf, ["Total", "$68,000", "$66,000", "$71,200", "$205,200"], bold=True)
+
+    pdf.ln(5)
+    pdf.cell(
+        0, 8,
+        "Total Q1 spend: $68,000 + $66,000 + $71,200 = $205,200",
+        new_x="LMARGIN", new_y="NEXT",
+    )
+
+    pdf.output("testing/ledger/tally_error.pdf")
+    print("  tally_error.pdf")
+
+
+# ─────────────────────────────────────────────────────────────────────────────
+# 3. Arithmetic error — inline expression is wrong
+# ─────────────────────────────────────────────────────────────────────────────
+def create_arithmetic_error():
+    pdf = _new_pdf()
+    pdf.add_page()
+
+    _heading(pdf, "Project Budget Summary")
+    _body(pdf)
+
+    lines = [
+        "Phase 1 (Design):       $45,000",
+        "Phase 2 (Development):  $120,000",
+        "Phase 3 (Testing):      $35,000",
+        "Phase 4 (Deployment):   $18,000",
+        "",
+        # BUG: 45000 + 120000 + 35000 + 18000 = 218,000, NOT 215,000
+        "Total project cost: $45,000 + $120,000 + $35,000 + $18,000 = $215,000",
+        "",
+        "Contingency (15%): $32,250",
+        # This one is also wrong: 215000 + 32250 = 247250, but the real total
+        # should be 218000 + 32700 = 250700. Either way 247,250 is stated.
+        "Grand total with contingency: $215,000 + $32,250 = $247,250",
+    ]
+    for line in lines:
+        pdf.cell(0, 8, line, new_x="LMARGIN", new_y="NEXT")
+
+    pdf.output("testing/ledger/arithmetic_error.pdf")
+    print("  arithmetic_error.pdf")
+
+
+# ─────────────────────────────────────────────────────────────────────────────
+# 4. Cross-page consistency error — same figure, different values
+# ─────────────────────────────────────────────────────────────────────────────
+def create_consistency_error():
+    pdf = _new_pdf()
+
+    # Page 1: Executive Summary
+    pdf.add_page()
+    _heading(pdf, "Annual Report 2025 - Executive Summary")
+    _body(pdf)
+    lines_p1 = [
+        "FY2025 was a strong year for GlobalTech Inc.",
+        "",
+        "Total Revenue: $24,500,000",
+        "Total Expenses: $18,200,000",
+        "Net Profit: $6,300,000",
+        "",
+        "Headcount grew from 142 to 187 employees.",
+        "Customer acquisition cost fell to $1,250 per customer.",
+    ]
+    for line in lines_p1:
+        pdf.cell(0, 8, line, new_x="LMARGIN", new_y="NEXT")
+
+    # Page 2: Financial Detail
+    pdf.add_page()
+    _heading(pdf, "Financial Detail")
+    _body(pdf)
+
+    _table_row(pdf, ["Metric", "Q1", "Q2", "Q3", "Q4", "FY2025"], bold=True)
+    _table_row(pdf, ["Revenue", "$5,100,000", "$5,800,000", "$6,200,000",
+                      "$7,200,000", "$24,300,000"])
+    _table_row(pdf, ["Expenses", "$4,300,000", "$4,400,000", "$4,600,000",
+                      "$4,900,000", "$18,200,000"])
+    _table_row(pdf, ["Profit", "$800,000", "$1,400,000", "$1,600,000",
+                      "$2,300,000", "$6,100,000"])
+
+    pdf.ln(5)
+    # BUG: Page 1 says Total Revenue = $24,500,000
+    #      Page 2 table says Revenue FY2025 = $24,300,000
+    #      Page 1 says Net Profit = $6,300,000
+    #      Page 2 table says Profit FY2025 = $6,100,000
+    pdf.cell(
+        0, 8,
+        "Full-year revenue of $24,300,000 exceeded targets by 8%.",
+        new_x="LMARGIN", new_y="NEXT",
+    )
+
+    pdf.output("testing/ledger/consistency_error.pdf")
+    print("  consistency_error.pdf")
+
+
+# ─────────────────────────────────────────────────────────────────────────────
+# 5. Mixed errors — has both tally and arithmetic problems
+# ─────────────────────────────────────────────────────────────────────────────
+def create_mixed_errors():
+    pdf = _new_pdf()
+    pdf.add_page()
+
+    _heading(pdf, "Monthly Sales Report - March 2026")
+    _body(pdf)
+
+    _table_row(pdf, ["Region", "Units Sold", "Revenue", "Commission"], bold=True)
+    _table_row(pdf, ["North", "340", "$51,000", "$5,100"])
+    _table_row(pdf, ["South", "280", "$42,000", "$4,200"])
+    _table_row(pdf, ["East", "195", "$29,250", "$2,925"])
+    _table_row(pdf, ["West", "410", "$61,500", "$6,150"])
+    # BUG: Units should be 1225 not 1220, Revenue should be $183,750 not $182,750
+    _table_row(pdf, ["Total", "1,220", "$182,750", "$18,375"], bold=True)
+
+    pdf.ln(5)
+    # BUG: 51000 + 42000 + 29250 + 61500 = 183,750, NOT 182,750
+    pdf.cell(
+        0, 8,
+        "Total revenue: $51,000 + $42,000 + $29,250 + $61,500 = $182,750",
+        new_x="LMARGIN", new_y="NEXT",
+    )
+    pdf.ln(3)
+    pdf.cell(
+        0, 8,
+        "Commission rate: 10% across all regions.",
+        new_x="LMARGIN", new_y="NEXT",
+    )
+
+    pdf.output("testing/ledger/mixed_errors.pdf")
+    print("  mixed_errors.pdf")
+
+
+# ─────────────────────────────────────────────────────────────────────────────
+# 6. Statement errors — prose claims that contradict the numbers
+# ─────────────────────────────────────────────────────────────────────────────
+def create_statement_errors():
+    pdf = _new_pdf()
+    pdf.add_page()
+
+    _heading(pdf, "FY2025 Annual Review - Statement Errors")
+    _body(pdf)
+
+    # Table with correct numbers
+    _table_row(pdf, ["Metric", "FY2024", "FY2025"], bold=True)
+    _table_row(pdf, ["Revenue", "$10,000,000", "$11,200,000"])
+    _table_row(pdf, ["Expenses", "$7,500,000", "$8,100,000"])
+    _table_row(pdf, ["Profit", "$2,500,000", "$3,100,000"])
+    _table_row(pdf, ["Headcount", "142", "187"])
+
+    pdf.ln(5)
+
+    # Correct claim: profit grew from 2.5M to 3.1M = 24% growth
+    pdf.cell(
+        0, 8,
+        "Profit grew 24% year-over-year, from $2,500,000 to $3,100,000.",
+        new_x="LMARGIN", new_y="NEXT",
+    )
+
+    # BUG: Revenue grew from 10M to 11.2M = 12% growth, NOT 15%
+    pdf.cell(
+        0, 8,
+        "Revenue increased 15% compared to the prior year.",
+        new_x="LMARGIN", new_y="NEXT",
+    )
+
+    # BUG: Expenses went UP from 7.5M to 8.1M, NOT decreased
+    pdf.cell(
+        0, 8,
+        "Operating expenses decreased year-over-year.",
+        new_x="LMARGIN", new_y="NEXT",
+    )
+
+    # BUG: Headcount grew from 142 to 187 = 31.7%, NOT 25%
+    pdf.cell(
+        0, 8,
+        "The team expanded by 25%, growing from 142 to 187 employees.",
+        new_x="LMARGIN", new_y="NEXT",
+    )
+
+    # Correct claim: profit margin = 3.1M / 11.2M = 27.68%
+    pdf.cell(
+        0, 8,
+        "Net profit margin reached approximately 28%.",
+        new_x="LMARGIN", new_y="NEXT",
+    )
+
+    pdf.output("testing/ledger/statement_errors.pdf")
+    print("  statement_errors.pdf")
+
+
+if __name__ == "__main__":
+    import os
+    os.makedirs("testing/ledger", exist_ok=True)
+    print("Generating test PDFs:")
+    create_clean_invoice()
+    create_tally_error()
+    create_arithmetic_error()
+    create_consistency_error()
+    create_mixed_errors()
+    create_statement_errors()
+    print("Done!")

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