feat: deterministic CV-to-job match score endpoint

New JobCvMatchService: a pure, AI-free keyword-coverage scorer that
returns a stable, reproducible 0-100 match score plus matched/missing
keyword lists and per-CV-section coverage. Unlike candidate-fit (AI
narrative), it makes no model calls, so results are instant and
identical for identical inputs - the Jobscan-style differentiator.

- GET /api/jobapplications/{id}/match-score
- keywords = curated SkillTagger tags (high weight) + salient posting
  terms (title terms boosted); word-boundary matching avoids false hits
- section coverage shows where CV evidence is concentrated
- fix(SkillTagger): punctuation-tolerant C#/.NET patterns; the old \b
  boundaries silently missed 'C#,' and '.NET,' everywhere they are used
- 7 unit tests on the pure scorer; full backend suite green (104)

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

JobTrackerApi.Tests/JobCvMatchServiceTests.cs

@@ -0,0 +1,105 @@
+using JobTrackerApi.Services;
+using Xunit;
+
+namespace JobTrackerApi.Tests;
+
+public sealed class JobCvMatchServiceTests
+{
+    private readonly JobCvMatchService _service = new();
+
+    private static Dictionary<string, string> Sections(params (string Name, string Text)[] items)
+        => items.ToDictionary(i => i.Name, i => i.Text, StringComparer.OrdinalIgnoreCase);
+
+    [Fact]
+    public void Strong_overlap_scores_high_and_lists_matched_keywords()
+    {
+        var result = _service.Evaluate(
+            jobTitle: "Senior C# Backend Developer",
+            jobText: "We need a backend engineer with strong C#, .NET, SQL and Docker experience building REST APIs.",
+            cvSections: Sections(
+                ("Skills", "C# .NET SQL Docker Kubernetes"),
+                ("Experience", "Built REST APIs in C# and .NET with SQL Server and Docker.")));
+
+        Assert.True(result.Score >= 75, $"expected strong score, got {result.Score}");
+        Assert.Equal("Strong", result.Band);
+        Assert.Contains("C#", result.MatchedKeywords);
+        Assert.Contains(".NET", result.MatchedKeywords);
+        Assert.True(result.HasEnoughSignal);
+    }
+
+    [Fact]
+    public void No_overlap_scores_low_and_surfaces_missing_keywords()
+    {
+        var result = _service.Evaluate(
+            jobTitle: "Kubernetes Platform Engineer",
+            jobText: "Deep Kubernetes, AWS, and Docker platform experience required. Terraform and CI/CD pipelines.",
+            cvSections: Sections(
+                ("Skills", "Graphic design, Adobe Photoshop, Illustrator, copywriting"),
+                ("Experience", "Ran marketing campaigns and brand design work.")));
+
+        Assert.True(result.Score < 50, $"expected low score, got {result.Score}");
+        Assert.Equal("Low", result.Band);
+        Assert.Contains("Kubernetes", result.MissingKeywords);
+        Assert.Contains("AWS", result.MissingKeywords);
+    }
+
+    [Fact]
+    public void Is_deterministic_for_identical_inputs()
+    {
+        var a = _service.Evaluate("Data Engineer", "Python, SQL, Spark, ETL pipelines and AWS.", Sections(("Skills", "Python SQL AWS")));
+        var b = _service.Evaluate("Data Engineer", "Python, SQL, Spark, ETL pipelines and AWS.", Sections(("Skills", "Python SQL AWS")));
+
+        Assert.Equal(a.Score, b.Score);
+        Assert.Equal(a.MatchedKeywords, b.MatchedKeywords);
+        Assert.Equal(a.MissingKeywords, b.MissingKeywords);
+    }
+
+    [Fact]
+    public void Word_boundary_prevents_false_substring_matches()
+    {
+        // "go" (the language) must not match inside "goals"/"ago".
+        var result = _service.Evaluate(
+            jobTitle: "Go Developer",
+            jobText: "Go programming language, goroutines, concurrency.",
+            cvSections: Sections(("Experience", "Achieved company goals two years ago in a great environment.")));
+
+        Assert.DoesNotContain("go", result.MatchedKeywords, StringComparer.OrdinalIgnoreCase);
+    }
+
+    [Fact]
+    public void Section_coverage_reports_where_matches_are_concentrated()
+    {
+        var result = _service.Evaluate(
+            jobTitle: "React Frontend Engineer",
+            jobText: "Build UIs with React, TypeScript and JavaScript. Strong testing culture.",
+            cvSections: Sections(
+                ("Skills", "React TypeScript JavaScript"),
+                ("Experience", "Wrote documentation and managed budgets.")));
+
+        var skills = Assert.Single(result.SectionCoverage, s => s.Section == "Skills");
+        var experience = Assert.Single(result.SectionCoverage, s => s.Section == "Experience");
+        Assert.True(skills.Matched > experience.Matched);
+    }
+
+    [Fact]
+    public void Empty_cv_reports_no_signal()
+    {
+        var result = _service.Evaluate("Anything", "Some role text with several words here.", Sections());
+        Assert.False(result.HasEnoughSignal);
+        Assert.Equal("Unknown", result.Band);
+        Assert.Equal(0, result.MatchedCount);
+    }
+
+    [Fact]
+    public void Title_keywords_are_weighted_and_missing_ones_rank_first()
+    {
+        // The title term "kubernetes" is absent from the CV; it should lead the missing list
+        // because title terms carry the title bonus weight.
+        var result = _service.Evaluate(
+            jobTitle: "Kubernetes Specialist",
+            jobText: "Kubernetes orchestration. Some familiarity with logging and monitoring dashboards.",
+            cvSections: Sections(("Skills", "logging monitoring dashboards")));
+
+        Assert.Equal("Kubernetes", result.MissingKeywords.First());
+    }
+}

JobTrackerApi/Controllers/JobApplicationsController.cs

@@ -23,8 +23,9 @@ namespace JobTrackerApi.Controllers
         private readonly ILogger<JobApplicationsController> _logger;
         private readonly ICvTemplateRenderer _cvTemplateRenderer;
         private readonly ICvPdfExporter _cvPdfExporter;
+        private readonly IJobCvMatchService _matchService;
 
-        public JobApplicationsController(JobTrackerContext db, ISummarizerService summarizer, IAppEmailSender email, UserManager<ApplicationUser> users, ILogger<JobApplicationsController> logger, ICvTemplateRenderer? cvTemplateRenderer = null, ICvPdfExporter? cvPdfExporter = null)
+        public JobApplicationsController(JobTrackerContext db, ISummarizerService summarizer, IAppEmailSender email, UserManager<ApplicationUser> users, ILogger<JobApplicationsController> logger, ICvTemplateRenderer? cvTemplateRenderer = null, ICvPdfExporter? cvPdfExporter = null, IJobCvMatchService? matchService = null)
         {
             _db = db;
             _summarizer = summarizer;
@@ -33,6 +34,7 @@ namespace JobTrackerApi.Controllers
             _logger = logger;
             _cvTemplateRenderer = cvTemplateRenderer ?? new CvTemplateRenderer();
             _cvPdfExporter = cvPdfExporter ?? new ThrowingCvPdfExporter();
+            _matchService = matchService ?? new JobCvMatchService();
         }
 
         private sealed class ThrowingCvPdfExporter : ICvPdfExporter
@@ -2107,6 +2109,89 @@ Canonical profile:
             };
         }
 
+        public sealed record MatchScoreDto(
+            int Score,
+            string Band,
+            int MatchedCount,
+            int TotalKeywords,
+            List<string> MatchedKeywords,
+            List<string> MissingKeywords,
+            List<MatchSectionCoverageDto> SectionCoverage,
+            bool HasEnoughSignal);
+
+        public sealed record MatchSectionCoverageDto(string Section, int Matched, int Total);
+
+        // Builds CV text grouped by section so match coverage can show *where* the evidence sits.
+        private static Dictionary<string, string> BuildCvSections(ApplicationUser? user)
+        {
+            var structured = StructuredCvProfileJson.Deserialize(user?.ProfileCvStructureJson);
+            var sections = new Dictionary<string, string>(StringComparer.OrdinalIgnoreCase);
+
+            void Add(string name, IEnumerable<string?> values)
+            {
+                var text = string.Join("\n", values.Where(v => !string.IsNullOrWhiteSpace(v)));
+                if (!string.IsNullOrWhiteSpace(text)) sections[name] = text;
+            }
+
+            Add("Summary", new[] { structured.Contact.Headline }.Concat(structured.Summary));
+            Add("Skills", structured.Skills);
+            Add("Experience", structured.Jobs.SelectMany(job =>
+                new[] { job.Title, job.Company }.Concat(job.Bullets).Concat(job.Skills)));
+            Add("Education", structured.Education.SelectMany(ed =>
+                new[] { ed.Qualification, ed.Institution }.Concat(ed.Details)));
+
+            // Always include raw profile text (covers users who only pasted plain CV text, and
+            // catches keywords the structured sections missed).
+            if (!string.IsNullOrWhiteSpace(user?.ProfileCvText))
+            {
+                sections["Profile"] = user!.ProfileCvText!;
+            }
+
+            return sections;
+        }
+
+        /// <summary>
+        /// Fast, deterministic CV↔job keyword coverage score. Unlike candidate-fit (AI narrative),
+        /// this makes no model calls, so it returns instantly and reproducibly.
+        /// </summary>
+        [HttpGet("{id:int}/match-score")]
+        public async Task<ActionResult<MatchScoreDto>> GetMatchScore([FromRoute] int id, CancellationToken cancellationToken)
+        {
+            var job = await _db.JobApplications
+                .Include(j => j.Company)
+                .FirstOrDefaultAsync(j => j.Id == id, cancellationToken);
+            if (job is null) return NotFound();
+
+            var userId = CurrentUserId;
+            if (string.IsNullOrWhiteSpace(userId)) return Unauthorized();
+
+            var user = await _db.Users.FirstOrDefaultAsync(x => x.Id == userId, cancellationToken);
+            var cvSections = BuildCvSections(user);
+            if (cvSections.Count == 0)
+            {
+                return BadRequest("Add your profile CV on the Profile page before running the match score.");
+            }
+
+            var jobText = string.Join("\n\n", new[] { job.Description, job.TranslatedDescription, job.Notes }
+                .Where(x => !string.IsNullOrWhiteSpace(x)));
+            if (string.IsNullOrWhiteSpace(jobText))
+            {
+                return BadRequest("This job does not have enough description or notes to compare against your CV.");
+            }
+
+            var result = _matchService.Evaluate(job.JobTitle, jobText, cvSections);
+
+            return Ok(new MatchScoreDto(
+                Score: result.Score,
+                Band: result.Band,
+                MatchedCount: result.MatchedCount,
+                TotalKeywords: result.TotalKeywords,
+                MatchedKeywords: result.MatchedKeywords.ToList(),
+                MissingKeywords: result.MissingKeywords.ToList(),
+                SectionCoverage: result.SectionCoverage.Select(s => new MatchSectionCoverageDto(s.Section, s.Matched, s.Total)).ToList(),
+                HasEnoughSignal: result.HasEnoughSignal));
+        }
+
         [HttpGet("{id:int}/candidate-fit")]
         public async Task<ActionResult<CandidateFitDto>> GetCandidateFit([FromRoute] int id, [FromQuery] string? attachmentIds, CancellationToken cancellationToken)
         {

JobTrackerApi/Program.cs

@@ -157,6 +157,7 @@ builder.Services.AddHttpClient("ai-service", client =>
 
 builder.Services.AddMemoryCache();
 builder.Services.AddSingleton<ISummarizerService, SummarizerService>();
+builder.Services.AddSingleton<IJobCvMatchService, JobCvMatchService>();
 builder.Services.AddSingleton<ICvAiClassifier, CvAiClassifier>();
 builder.Services.AddSingleton<ICvAiNormalizer, CvAiNormalizer>();
 builder.Services.AddSingleton<IGoogleTokenValidator, GoogleTokenValidator>();

JobTrackerApi/Services/JobCvMatchService.cs

@@ -0,0 +1,208 @@
+using System.Globalization;
+using System.Text;
+using System.Text.RegularExpressions;
+using JobTrackerApi.Services.JobImport;
+
+namespace JobTrackerApi.Services
+{
+    /// <summary>One keyword drawn from the job posting and whether the CV covers it.</summary>
+    public sealed record MatchKeyword(string Keyword, int Weight, bool InTitle, bool Matched);
+
+    /// <summary>How many of the matched keywords appear in a given CV section.</summary>
+    public sealed record MatchSectionCoverage(string Section, int Matched, int Total);
+
+    public sealed record JobCvMatchResult(
+        int Score,
+        string Band,
+        int MatchedCount,
+        int TotalKeywords,
+        IReadOnlyList<string> MatchedKeywords,
+        IReadOnlyList<string> MissingKeywords,
+        IReadOnlyList<MatchSectionCoverage> SectionCoverage,
+        bool HasEnoughSignal);
+
+    public interface IJobCvMatchService
+    {
+        JobCvMatchResult Evaluate(string jobTitle, string jobText, IReadOnlyDictionary<string, string> cvSections);
+    }
+
+    /// <summary>
+    /// Deterministic CV↔job keyword coverage score. No AI: the same inputs always produce the
+    /// same number so users get a stable, reproducible signal (the Jobscan-style differentiator).
+    /// The AI narrative lives separately in the candidate-fit endpoint.
+    /// </summary>
+    public sealed class JobCvMatchService : IJobCvMatchService
+    {
+        // Weights: curated skill tags are high-signal; salient posting terms are the long tail.
+        private const int CuratedTagWeight = 3;
+        private const int TermWeight = 1;
+        private const int TitleBonus = 2;
+        private const int MaxKeywords = 28;
+
+        private static readonly Regex TokenPattern = new(@"[a-z0-9][a-z0-9+.#-]*", RegexOptions.Compiled);
+
+        private static readonly HashSet<string> StopWords = new(StringComparer.OrdinalIgnoreCase)
+        {
+            "the", "and", "for", "with", "you", "your", "our", "are", "will", "have", "has", "that",
+            "this", "from", "not", "but", "all", "can", "who", "how", "why", "what", "when", "who",
+            "job", "role", "work", "working", "team", "teams", "company", "years", "year", "experience",
+            "experienced", "skills", "skill", "ability", "able", "strong", "good", "great", "excellent",
+            "including", "include", "includes", "well", "using", "use", "used", "within", "across",
+            "into", "onto", "their", "them", "they", "were", "was", "would", "should", "could", "must",
+            "new", "also", "per", "via", "etc", "such", "any", "one", "two", "three", "day", "days",
+            "week", "weeks", "month", "months", "time", "full", "part", "based", "join", "looking",
+            "seeking", "candidate", "candidates", "applicant", "position", "positions", "opportunity",
+            "responsibilities", "requirements", "required", "preferred", "plus", "nice", "want", "need",
+            "needs", "help", "make", "made", "get", "got", "more", "most", "many", "much", "each",
+            "other", "others", "some", "than", "then", "there", "here", "about", "over", "under", "out",
+            "off", "its", "his", "her", "she", "him", "may", "might", "high", "low", "level", "levels",
+            "environment", "environments", "world", "people", "person", "customer", "customers", "client",
+            "clients", "product", "products", "service", "services", "business", "solution", "solutions",
+            "project", "projects", "process", "processes", "development", "develop", "developer",
+            // Seniority / role-title words: noise for CV keyword matching (the hard skills are what count).
+            "senior", "junior", "lead", "principal", "mid", "staff", "engineer", "engineers",
+            "engineering", "manager", "specialist", "analyst", "consultant", "administrator",
+            "coordinator", "associate", "intern", "officer", "director", "professional",
+        };
+
+        public JobCvMatchResult Evaluate(string jobTitle, string jobText, IReadOnlyDictionary<string, string> cvSections)
+        {
+            jobTitle ??= string.Empty;
+            jobText ??= string.Empty;
+            cvSections ??= new Dictionary<string, string>();
+
+            var titleTokens = Tokenize(jobTitle).ToHashSet(StringComparer.OrdinalIgnoreCase);
+            var keywords = BuildKeywords(jobTitle, jobText, titleTokens);
+
+            // Combine all CV sections into one searchable corpus, plus keep per-section text for coverage.
+            var sectionCorpora = cvSections
+                .Where(kvp => !string.IsNullOrWhiteSpace(kvp.Value))
+                .ToDictionary(kvp => kvp.Key, kvp => Normalize(kvp.Value), StringComparer.OrdinalIgnoreCase);
+            var fullCorpus = string.Join(" \n ", sectionCorpora.Values);
+
+            var evaluated = keywords
+                .Select(k => k with { Matched = CorpusContains(fullCorpus, k.Keyword) })
+                .ToList();
+
+            var totalWeight = evaluated.Sum(k => k.Weight);
+            var matchedWeight = evaluated.Where(k => k.Matched).Sum(k => k.Weight);
+            var hasEnoughSignal = evaluated.Count >= 3 && sectionCorpora.Count > 0;
+
+            var score = totalWeight == 0 ? 0 : (int)Math.Round(100.0 * matchedWeight / totalWeight, MidpointRounding.AwayFromZero);
+            score = Math.Clamp(score, 0, 100);
+
+            var band = !hasEnoughSignal ? "Unknown" : score >= 75 ? "Strong" : score >= 50 ? "Partial" : "Low";
+
+            var matchedKeywords = evaluated.Where(k => k.Matched)
+                .OrderByDescending(k => k.Weight).ThenBy(k => k.Keyword, StringComparer.OrdinalIgnoreCase)
+                .Select(k => k.Keyword).ToList();
+            var missingKeywords = evaluated.Where(k => !k.Matched)
+                .OrderByDescending(k => k.Weight).ThenBy(k => k.Keyword, StringComparer.OrdinalIgnoreCase)
+                .Select(k => k.Keyword).ToList();
+
+            var sectionCoverage = sectionCorpora
+                .Select(section => new MatchSectionCoverage(
+                    section.Key,
+                    evaluated.Count(k => CorpusContains(section.Value, k.Keyword)),
+                    evaluated.Count))
+                .Where(sc => sc.Total > 0)
+                .OrderByDescending(sc => sc.Matched)
+                .ToList();
+
+            return new JobCvMatchResult(
+                Score: score,
+                Band: band,
+                MatchedCount: matchedKeywords.Count,
+                TotalKeywords: evaluated.Count,
+                MatchedKeywords: matchedKeywords,
+                MissingKeywords: missingKeywords,
+                SectionCoverage: sectionCoverage,
+                HasEnoughSignal: hasEnoughSignal);
+        }
+
+        private static List<MatchKeyword> BuildKeywords(string jobTitle, string jobText, HashSet<string> titleTokens)
+        {
+            var combined = $"{jobTitle}\n{jobText}";
+            var byKey = new Dictionary<string, MatchKeyword>(StringComparer.OrdinalIgnoreCase);
+
+            // 1) Curated skill tags: high-signal, canonical spelling.
+            foreach (var tag in SkillTagger.Detect(combined))
+            {
+                var inTitle = TitleContains(jobTitle, tag);
+                byKey[tag] = new MatchKeyword(tag, CuratedTagWeight + (inTitle ? TitleBonus : 0), inTitle, false);
+            }
+
+            // 2) Salient posting terms: frequency-ranked content words from the description.
+            var frequencies = new Dictionary<string, int>(StringComparer.OrdinalIgnoreCase);
+            foreach (var token in Tokenize(jobText))
+            {
+                if (token.Length < 3 || StopWords.Contains(token) || IsNumeric(token)) continue;
+                frequencies[token] = frequencies.TryGetValue(token, out var c) ? c + 1 : 1;
+            }
+
+            var rankedTerms = frequencies
+                .Where(kvp => kvp.Value >= 1)
+                .OrderByDescending(kvp => titleTokens.Contains(kvp.Key) ? 1 : 0)
+                .ThenByDescending(kvp => kvp.Value)
+                .ThenBy(kvp => kvp.Key, StringComparer.OrdinalIgnoreCase)
+                .Select(kvp => kvp.Key);
+
+            foreach (var term in rankedTerms)
+            {
+                if (byKey.Count >= MaxKeywords) break;
+                if (byKey.ContainsKey(term)) continue;
+                var inTitle = titleTokens.Contains(term);
+                byKey[term] = new MatchKeyword(term, TermWeight + (inTitle ? TitleBonus : 0), inTitle, false);
+            }
+
+            return byKey.Values
+                .OrderByDescending(k => k.Weight)
+                .ThenBy(k => k.Keyword, StringComparer.OrdinalIgnoreCase)
+                .Take(MaxKeywords)
+                .ToList();
+        }
+
+        private static bool TitleContains(string title, string phrase)
+            => Normalize(title).Contains(Normalize(phrase), StringComparison.Ordinal);
+
+        private static bool CorpusContains(string normalizedCorpus, string keyword)
+        {
+            var needle = Normalize(keyword);
+            if (needle.Length == 0) return false;
+            // Word-boundary-ish match to avoid "go" matching "goal".
+            var idx = normalizedCorpus.IndexOf(needle, StringComparison.Ordinal);
+            while (idx >= 0)
+            {
+                var beforeOk = idx == 0 || !char.IsLetterOrDigit(normalizedCorpus[idx - 1]);
+                var afterPos = idx + needle.Length;
+                var afterOk = afterPos >= normalizedCorpus.Length || !char.IsLetterOrDigit(normalizedCorpus[afterPos]);
+                if (beforeOk && afterOk) return true;
+                idx = normalizedCorpus.IndexOf(needle, idx + 1, StringComparison.Ordinal);
+            }
+            return false;
+        }
+
+        private static IEnumerable<string> Tokenize(string text)
+        {
+            if (string.IsNullOrWhiteSpace(text)) yield break;
+            foreach (Match m in TokenPattern.Matches(text.ToLowerInvariant()))
+            {
+                yield return m.Value.Trim('-', '.', '+', '#');
+            }
+        }
+
+        private static bool IsNumeric(string token)
+            => token.All(c => char.IsDigit(c) || c is '.' or '-' or '+');
+
+        private static string Normalize(string text)
+        {
+            if (string.IsNullOrWhiteSpace(text)) return string.Empty;
+            var sb = new StringBuilder(text.Length);
+            foreach (var ch in text.ToLowerInvariant())
+            {
+                sb.Append(char.IsWhiteSpace(ch) ? ' ' : ch);
+            }
+            return sb.ToString();
+        }
+    }
+}

JobTrackerApi/Services/JobImport/SkillTagger.cs

@@ -9,8 +9,10 @@ public static class SkillTagger
 {
     private static readonly (string Tag, Regex Pattern, int Weight)[] Patterns =
     {
-        ("C#", new Regex(@"\bC#\b|\bcsharp\b", RegexOptions.IgnoreCase | RegexOptions.Compiled), 6),
+        // Symbol skills need punctuation-tolerant boundaries: \b fails next to '#'/'.'
-        (".NET", new Regex(@"\b\.NET\b|\bASP\.NET\b|\bDOTNET\b|\bEntity Framework\b|\bEF Core\b", RegexOptions.IgnoreCase | RegexOptions.Compiled), 6),
+        // (both non-word chars), which previously left "C#," and ".NET," undetected.
+        ("C#", new Regex(@"(?<![A-Za-z0-9#])C#|\bc[-\s]?sharp\b", RegexOptions.IgnoreCase | RegexOptions.Compiled), 6),
+        (".NET", new Regex(@"(?<![A-Za-z0-9.])\.NET\b|\bASP\.NET\b|\bDOTNET\b|\bEntity Framework\b|\bEF Core\b", RegexOptions.IgnoreCase | RegexOptions.Compiled), 6),
         ("Python", new Regex(@"\bPython\b", RegexOptions.IgnoreCase | RegexOptions.Compiled), 6),
         ("Java", new Regex(@"\bJava\b", RegexOptions.IgnoreCase | RegexOptions.Compiled), 5),
         ("JavaScript", new Regex(@"\bJavaScript\b|\bJS\b", RegexOptions.IgnoreCase | RegexOptions.Compiled), 5),