feat(#137): add doc-map input for path-scoped doc injection

- New --doc-map flag (DOC_MAP_FILE env var): path to YAML config mapping
  source path globs to governing design docs
- New --doc-map-max-bytes flag (DOC_MAP_MAX_BYTES env var): cap on total
  injected doc content, default 100KB
- review/docmap.go: DocMapConfig parsing, glob matching with ** support,
  doc loading via VCS with directory expansion and size guard
- budget.Sections: new DesignDocs field, trimmed after conventions
- budget.buildResult: injects DesignDocs under ## Design Documents heading
- action.yml: doc-map and doc-map-max-bytes inputs wired to env vars
- CHANGELOG.md: created with unreleased entry
- Tests: ParseDocMapConfig, MatchDocs, globMatch, LoadMatchingDocs

.gitea/actions/review/action.yml

@@ -130,6 +130,17 @@ inputs:
     description: 'Path to custom persona JSON file'
     required: false
     default: ''
+  doc-map:
+    description: >-
+      Path to a YAML file mapping source path globs to governing design docs.
+      review-bot intersects the map with changed PR paths and injects matching
+      docs as context alongside the diff.
+    required: false
+    default: ''
+  doc-map-max-bytes:
+    description: 'Maximum bytes of injected doc content from doc-map (default 102400 = 100KB)'
+    required: false
+    default: '102400'
 
 runs:
   using: 'composite'
@@ -493,6 +504,8 @@ runs:
         SYSTEM_PROMPT_FILE: ${{ inputs.system-prompt-file }}
         PERSONA: ${{ inputs.persona }}
         PERSONA_FILE: ${{ inputs.persona-file }}
+        DOC_MAP_FILE: ${{ inputs.doc-map }}
+        DOC_MAP_MAX_BYTES: ${{ inputs.doc-map-max-bytes }}
         AICORE_CLIENT_ID: ${{ inputs.aicore-client-id }}
         AICORE_CLIENT_SECRET: ${{ inputs.aicore-client-secret }}
         AICORE_AUTH_URL: ${{ inputs.aicore-auth-url }}

CHANGELOG.md

@@ -0,0 +1,33 @@
+# CHANGELOG
+
+## Unreleased
+
+### Added
+
+- **`doc-map` input** (`--doc-map` flag / `DOC_MAP_FILE` env var): Path to a YAML file mapping source path globs to governing design docs. review-bot intersects the map with changed PR paths and injects matching docs into the system prompt under a `## Design Documents` heading. ([#137](https://gitea.weiker.me/rodin/review-bot/issues/137))
+- **`doc-map-max-bytes` input** (`--doc-map-max-bytes` flag / `DOC_MAP_MAX_BYTES` env var): Cap on total injected design doc content in bytes. Default: 102400 (100 KB). Prevents accidental context overflow when a PR touches many modules.
+- **`DesignDocs` budget section**: Design docs are included in the context budget and trimmed after conventions, before file context, if the total exceeds the model's context limit.
+
+### Doc-map config format
+
+```yaml
+mappings:
+  - paths:
+      - "lib/gargoyle/engine/signal_risk/**"
+    docs:
+      - docs/domain/contexts/risk/risk-controls.md
+  - paths:
+      - "lib/gargoyle/trading/**"
+    docs:
+      - docs/domain/contexts/trading/
+```
+
+- `paths` — glob patterns (including `**`) matched against changed file paths in the PR
+- `docs` — local file paths or directories (all `.md` files under a directory) to inject
+- Multiple mappings can reference the same doc; docs are deduplicated
+- Missing doc files: warn and skip (review continues without them)
+- No matching paths: no docs injected, review runs normally
+
+## v0.3.2
+
+- Previous releases tracked in Gitea release notes.

PLAN-137.md

@@ -0,0 +1,194 @@
+# Plan: Issue #137 — doc-map input for path-scoped doc injection
+
+## Problem
+
+review-bot currently injects context via `patterns-repo` (external VCS repos) and `conventions-file` (a single file from the reviewed repo). There is no mechanism to inject local repo documentation files scoped to the paths changed in a PR.
+
+First consumer: `grgl/gargoyle#778` wants a "doc adherence" reviewer that checks code against the module's governing design doc, without injecting every doc in the tree.
+
+## Constraints
+
+- Must work with existing `budget.Fit` architecture (docs go into `SystemBase` section, never trimmed — or added as a new section below `Conventions`)
+- Must not fail the review if doc files are missing (warn + skip)
+- Context guard: default 100KB total injected doc content (configurable)
+- YAML parsing must use `github.com/goccy/go-yaml` (the only approved YAML library)
+- No new third-party dependencies (Go standard library + approved packages only)
+- Path security: doc files must be read via VCS API (not local filesystem), so they are always fetched from the PR head ref within the repo workspace — same path used by `conventions-file` loading
+
+Wait — re-reading the issue: the issue says "local repo files". In the CI action context, the action runner has the repo checked out. The design doc says "read each doc file from the local checkout". But review-bot has no local checkout — it runs as a binary and reads files via VCS API. Let me reconcile:
+
+- `conventions-file` uses `vcs.GetFileContent` (fetches from VCS API, default branch)
+- The doc-map docs should also be read via VCS API
+- The doc-map config file itself (`doc-map` input) is a local file in the workspace (like `system-prompt-file`)
+- The doc paths inside the config ARE relative to the repo root, to be fetched via VCS API
+
+**Conclusion:** The `doc-map` YAML file is read from local filesystem (like `system-prompt-file`). The doc files listed inside are fetched from the VCS API.
+
+Actually, re-reading more carefully: "Read each doc file (or all .md files under a directory) from the local checkout". But review-bot doesn't have a local checkout. Since `system-prompt-file` and `conventions-file` are both read locally, I should follow the same approach consistently.
+
+**Final decision:** The `doc-map` config file is local (passed via `--doc-map` flag, read with `os.ReadFile` after workspace validation). The listed doc paths (and directory expansion) are read via VCS `GetFileContent` / `GetAllFilesInPath` — matching the `conventions-file` pattern for consistency, and enabling it to work on any branch (not just the checked-out one).
+
+## Proposed Approach
+
+### New files
+
+1. `review/docmap.go` — `DocMap` type, YAML parsing, glob matching, doc loading logic
+2. `review/docmap_test.go` — unit tests
+
+### Modified files
+
+1. `cmd/review-bot/main.go` — add `--doc-map` flag, wire up in Step 6c
+2. `.gitea/actions/review/action.yml` — add `doc-map` input, pass as `DOC_MAP_FILE` env var
+3. `budget/budget.go` — add `DesignDocs` section (between `SystemBase`/`Conventions` and `Diff`)
+4. `CHANGELOG.md` — update
+
+### DocMap types (review/docmap.go)
+
+```go
+// DocMapping maps a set of path globs to doc files/directories.
+type DocMapping struct {
+    Paths []string `yaml:"paths"` // glob patterns
+    Docs  []string `yaml:"docs"`  // file paths or directories
+}
+
+// DocMapConfig is the top-level YAML structure.
+type DocMapConfig struct {
+    Mappings []DocMapping `yaml:"mappings"`
+}
+
+// DocMapOptions controls doc loading behavior.
+type DocMapOptions struct {
+    MaxBytes int // default 100*1024
+}
+```
+
+### Key functions
+
+```go
+// ParseDocMapConfig parses the YAML config file from a local path.
+func ParseDocMapConfig(path string) (*DocMapConfig, error)
+
+// MatchDocs returns deduplicated doc paths for the given changed files.
+func MatchDocs(cfg *DocMapConfig, changedFiles []string) []string
+
+// LoadMatchingDocs fetches doc content via VCS, respecting size limit.
+// Returns (content, error). Missing files are warned and skipped.
+func LoadMatchingDocs(ctx context.Context, fetcher DocFetcher, owner, repo string, docPaths []string, opts DocMapOptions) (string, error)
+```
+
+### DocFetcher interface
+
+```go
+// DocFetcher fetches files and directory listings from VCS.
+// Subset of vcsClient, defined here to keep review package free of cmd-level deps.
+type DocFetcher interface {
+    GetFileContent(ctx context.Context, owner, repo, filepath string) (string, error)
+    GetAllFilesInPath(ctx context.Context, owner, repo, path string) (map[string]string, error)
+}
+```
+
+### Glob matching
+
+Use `path.Match` from the Go standard library. It matches patterns like `lib/gargoyle/engine/signal_risk/**`. The `**` glob is NOT natively supported by `path.Match`, so we need either:
+
+a) Use `filepath.Match` which also doesn't support `**`
+b) Implement simple `**` support: `**` matches any number of path segments
+
+**Decision:** Implement minimal `**` support: split path on `/`, split pattern on `/`, match each segment with `filepath.Match`. When a pattern segment is `**`, it consumes any number of remaining segments. This covers the primary use case without a new dependency.
+
+### Budget integration
+
+Add `DesignDocs` field to `budget.Sections`. Position: after `Conventions`, before `FileContext` (trimming order: Patterns → Conventions → DesignDocs → FileContext → Diff). Inject under `## Design Documents` heading in system prompt.
+
+### Context size guard
+
+Accumulate doc content bytes. If total would exceed `MaxBytes`, truncate last doc with a notice and stop loading more.
+
+## State/Data Model
+
+```
+DocMapConfig
+  └── []DocMapping
+        ├── Paths []string  (glob patterns against changed file paths)
+        └── Docs  []string  (local doc paths or directories in target repo)
+
+Flow:
+  1. Parse doc-map YAML → DocMapConfig
+  2. GetPullRequestFiles → []string of changed paths
+  3. MatchDocs(cfg, changedPaths) → deduplicated []string doc paths
+  4. For each doc path:
+       - If path ends with "/" or is a "directory" → GetAllFilesInPath, filter .md
+       - Otherwise → GetFileContent
+  5. Accumulate, respect size limit
+  6. Inject into system prompt
+```
+
+## Error Cases
+
+| Situation | Behavior |
+|-----------|----------|
+| `--doc-map` file not found | Fatal error (like `--system-prompt-file`) |
+| `--doc-map` file invalid YAML | Fatal error with descriptive message |
+| Unknown keys in YAML | Log warning, continue |
+| Doc file not found in VCS | Log warning, skip |
+| Doc directory empty | Log debug, skip |
+| Total size exceeds limit | Truncate with notice, log warning |
+| No changed paths match | No docs injected, review runs normally |
+| `paths` list empty in a mapping | Skip that mapping (no match possible) |
+| `docs` list empty in a mapping | Skip that mapping (nothing to inject) |
+
+## Edge Cases
+
+- Empty `mappings` list → no docs injected, no error
+- Same doc matched by multiple mappings → deduplicate by path
+- Directory with no `.md` files → skip silently (log debug)
+- Very large single doc file → counts against limit, may truncate
+- Symlinks/special files in VCS → GetFileContent handles or errors (warn + skip)
+- `doc-map` path outside workspace → fatal error (validateWorkspacePath)
+- Directory path specified as `docs` entry without trailing `/` → check if it's a directory via ListContents or GetAllFilesInPath; if error, try GetFileContent
+
+## Testing Strategy
+
+### Unit tests (review/docmap_test.go)
+
+1. **ParseDocMapConfig** — valid YAML, invalid YAML, unknown keys (warning), empty file
+2. **MatchDocs** — no match, single match, multi-match, deduplication, `**` glob, exact match
+3. **LoadMatchingDocs** — with mock DocFetcher:
+   - file path → content returned
+   - missing file → warned + skipped
+   - directory path → expands .md files
+   - directory with no .md → empty
+   - size guard → truncation with notice
+   - deduplication in combined results
+
+### Integration coverage
+
+The existing `main_test.go` tests cover flag wiring — add a test for `--doc-map` flag parsing and workspace path validation.
+
+## Open Questions
+
+1. **Directory detection**: The issue says "directory paths expand to all .md files". But review-bot has no local filesystem. When a `docs` entry is `docs/domain/contexts/trading/`, we can call `GetAllFilesInPath`. But what if someone writes `docs/domain/contexts/trading` (no trailing slash)? We could try GetFileContent first, and if it fails with a 404 or "is directory" error, fall back to GetAllFilesInPath. OR we could just always call GetAllFilesInPath and if it returns content, use it; if it returns empty, try GetFileContent. 
+   **Decision**: Try GetAllFilesInPath first (always). If it returns ≥1 file, treat as directory. If it returns 0 files AND no error, try GetFileContent. If GetAllFilesInPath returns an error, try GetFileContent.
+
+2. **Budget section placement**: The issue says docs go in "system prompt after system-prompt-file content". That means docs are part of the system prompt. Current budget: SystemBase (includes additionalPrompt) → Patterns → Conventions. I'll add DesignDocs after Conventions (trim after Conventions). Docs are injected into system prompt via `buildResult`.
+   **Decision**: DesignDocs section in budget, trimmed after Conventions, before FileContext.
+
+3. **Configurable size limit**: The issue says "configurable". Add `--doc-map-max-bytes` flag (default 102400). Pass via `DocMapOptions`.
+   **Decision**: Add flag. Default 100KB (102400 bytes).
+
+## Completion Checklist
+
+1. `doc-map` input added to action.yml with correct env var passthrough
+2. `--doc-map` and `--doc-map-max-bytes` flags parsed in main.go
+3. `doc-map` file validated with `validateWorkspacePath` before reading
+4. YAML parsed with `go-yaml`, unknown keys warned not errored
+5. Glob matching handles `**` segments
+6. Changed files list from PR drives intersection (not hardcoded)
+7. Docs deduplicated before fetching
+8. Missing doc files: warn + skip, not fatal
+9. Context size guard truncates with notice, logs warning
+10. `DesignDocs` section added to `budget.Sections` and `buildResult`
+11. Tests cover: match, no-match, dedup, missing file, directory expansion, size guard, YAML parse error
+12. `go test ./...` passes
+13. `go vet ./...` passes
+14. CHANGELOG updated

README.md

@@ -6,10 +6,11 @@ AI-powered code review bot for Gitea pull requests. Fetches diff + context, send
 
 - **Multi-provider**: OpenAI-compatible, Anthropic Messages API, and SAP AI Core
 - **Context-aware**: Fetches full file content, conventions, language patterns, CI status
+- **Path-scoped docs**: `doc-map` config injects only the governing design docs for changed paths
 - **Smart budget**: Automatically trims context to fit model token limits
 - **Idempotent reviews**: Posts new review, then cleans up stale ones (one review per bot)
 - **Custom prompts**: Load additional instructions from a file (e.g. security-focused review)
-- **Minimal dependencies**: Go stdlib + `gopkg.in/yaml.v3` only
+- **Minimal dependencies**: Go stdlib + `github.com/goccy/go-yaml` only
 
 ## Quick Start: Composite Action
 

budget/budget.go

@@ -63,7 +63,8 @@ type Sections struct {
 	SystemBase  string // Core instructions (never trimmed)
 	Patterns    string // Language patterns (trimmed first)
 	Conventions string // Repo conventions (trimmed second)
-	FileContext string // Full file content (trimmed third)
+	DesignDocs  string // Path-scoped design documents (trimmed third)
+	FileContext string // Full file content (trimmed fourth)
 	Diff        string // The actual diff (trimmed last, only truncated)
 	UserMeta    string // PR title, description, CI status (truncated only if base exceeds budget)
 }
@@ -103,6 +104,7 @@ func Fit(model string, sections Sections) Result {
 	entries := []entry{
 		{"patterns", &sections.Patterns},
 		{"conventions", &sections.Conventions},
+		{"design docs", &sections.DesignDocs},
 		{"file context", &sections.FileContext},
 	}
 
@@ -185,6 +187,10 @@ func buildResult(s Sections, trimmed []string, estTokens int) Result {
 		sys.WriteString("\n\n## Repository Conventions\n\nThe repository has the following coding conventions that must be respected:\n\n")
 		sys.WriteString(s.Conventions)
 	}
+	if s.DesignDocs != "" {
+		sys.WriteString("\n\n## Design Documents\n\nThe following design documents govern the changed code. Review the diff for adherence:\n\n")
+		sys.WriteString(s.DesignDocs)
+	}
 
 	var usr strings.Builder
 	usr.WriteString(s.UserMeta)

cmd/review-bot/main.go

@@ -97,6 +97,8 @@ func main() {
 	aicoreAuthURL := flag.String("aicore-auth-url", envOrDefault("AICORE_AUTH_URL", ""), "SAP AI Core auth URL (for provider=aicore)")
 	aicoreAPIURL := flag.String("aicore-api-url", envOrDefault("AICORE_API_URL", ""), "SAP AI Core API URL (for provider=aicore)")
 	aicoreResourceGroup := flag.String("aicore-resource-group", envOrDefault("AICORE_RESOURCE_GROUP", "default"), "SAP AI Core resource group (for provider=aicore)")
+	docMapFile := flag.String("doc-map", envOrDefault("DOC_MAP_FILE", ""), "Path to YAML file mapping source path globs to governing design docs")
+	docMapMaxBytes := flag.Int("doc-map-max-bytes", envOrDefaultInt("DOC_MAP_MAX_BYTES", review.DefaultDocMapMaxBytes), "Maximum bytes of injected doc content (default 102400)")
 
 	flag.Parse()
 
@@ -350,6 +352,46 @@ func main() {
 		slog.Debug("loaded system prompt file", "file", *systemPromptFile, "bytes", len(additionalPrompt))
 	}
 
+	// Step 6c: Load path-scoped design docs if doc-map specified
+	designDocs := ""
+	if *docMapFile != "" {
+		resolvedDocMap, err := validateWorkspacePath(*docMapFile, "doc-map")
+		if err != nil {
+			slog.Error("invalid doc-map path", "error", err)
+			os.Exit(1)
+		}
+		docMapCfg, err := review.ParseDocMapConfig(resolvedDocMap)
+		if err != nil {
+			slog.Error("failed to parse doc-map file", "file", *docMapFile, "error", err)
+			os.Exit(1)
+		}
+
+		// Collect changed file paths from the PR for intersection.
+		var changedPaths []string
+		for _, f := range files {
+			changedPaths = append(changedPaths, f.Filename)
+		}
+
+		matchedDocs := review.MatchDocs(docMapCfg, changedPaths)
+		slog.Debug("doc-map: matched docs", "count", len(matchedDocs), "docs", matchedDocs)
+
+		if len(matchedDocs) > 0 {
+			docMapOpts := review.DocMapOptions{MaxBytes: *docMapMaxBytes}
+			designDocs, err = review.LoadMatchingDocs(ctx, vcs, owner, repoName, matchedDocs, docMapOpts)
+			if err != nil {
+				// Non-fatal: individual missing files are already warned; log and continue.
+				slog.Warn("doc-map: partial failure loading docs", "error", err)
+			}
+			if designDocs != "" {
+				slog.Info("doc-map: injected design docs", "matched", len(matchedDocs), "bytes", len(designDocs))
+			} else {
+				slog.Debug("doc-map: no doc content loaded (all files missing or empty)")
+			}
+		} else {
+			slog.Debug("doc-map: no changed paths matched any mapping")
+		}
+	}
+
 	// Step 7: Budget-aware prompt assembly
 	var systemBase string
 	if persona != nil {
@@ -365,6 +407,7 @@ func main() {
 		SystemBase:  systemBase,
 		Patterns:    patterns,
 		Conventions: conventions,
+		DesignDocs:  designDocs,
 		FileContext: fileContext,
 		Diff:        diff,
 		UserMeta:    review.BuildUserMeta(pr.Title, pr.Body, ciPassed, ciDetails),

review/docmap.go

@@ -0,0 +1,303 @@
+// Package review provides doc-map parsing and doc injection for path-scoped
+// design document context in AI code reviews.
+package review
+
+import (
+	"context"
+	"fmt"
+	"log/slog"
+	"os"
+	"path/filepath"
+	"strings"
+	"unicode/utf8"
+
+	"github.com/goccy/go-yaml"
+)
+
+const (
+	// DefaultDocMapMaxBytes is the default cap on total injected doc content.
+	DefaultDocMapMaxBytes = 100 * 1024 // 100 KB
+)
+
+// DocMapping maps a set of path glob patterns to governing doc files/directories.
+type DocMapping struct {
+	Paths []string `yaml:"paths"` // glob patterns matched against changed PR files
+	Docs  []string `yaml:"docs"`  // doc file paths or directories in the reviewed repo
+}
+
+// DocMapConfig is the top-level structure of a doc-map YAML file.
+type DocMapConfig struct {
+	Mappings []DocMapping `yaml:"mappings"`
+}
+
+// DocMapOptions configures behavior for doc loading.
+type DocMapOptions struct {
+	// MaxBytes caps the total size of injected doc content. Default: DefaultDocMapMaxBytes.
+	MaxBytes int
+}
+
+// DocFetcher reads file and directory content from a VCS repository.
+// It is a subset of vcsClient, defined here to keep the review package free
+// of cmd-level dependencies.
+type DocFetcher interface {
+	// GetFileContent returns the content of a single file at default branch.
+	GetFileContent(ctx context.Context, owner, repo, path string) (string, error)
+	// GetAllFilesInPath returns all files (path → content) under a directory.
+	GetAllFilesInPath(ctx context.Context, owner, repo, path string) (map[string]string, error)
+}
+
+// ParseDocMapConfig reads and parses a doc-map YAML file from a local path.
+// Unknown top-level keys produce a warning but are not fatal.
+func ParseDocMapConfig(localPath string) (*DocMapConfig, error) {
+	data, err := readFileBytes(localPath)
+	if err != nil {
+		return nil, fmt.Errorf("read doc-map file %q: %w", localPath, err)
+	}
+
+	var cfg DocMapConfig
+	if err := yaml.UnmarshalWithOptions(data, &cfg, yaml.Strict()); err != nil {
+		// Re-parse without strict mode to log which keys are unknown.
+		var relaxed DocMapConfig
+		if err2 := yaml.Unmarshal(data, &relaxed); err2 != nil {
+			return nil, fmt.Errorf("parse doc-map YAML %q: %w", localPath, err)
+		}
+		slog.Warn("doc-map YAML contains unknown keys (ignored)", "file", localPath, "error", err)
+		cfg = relaxed
+	}
+	return &cfg, nil
+}
+
+// MatchDocs returns deduplicated doc paths for the given changed file paths.
+// A mapping matches if any of its path globs matches any of the changed files.
+func MatchDocs(cfg *DocMapConfig, changedFiles []string) []string {
+	seen := make(map[string]struct{})
+	var result []string
+
+	for _, mapping := range cfg.Mappings {
+		if len(mapping.Paths) == 0 || len(mapping.Docs) == 0 {
+			continue
+		}
+		if mappingMatches(mapping.Paths, changedFiles) {
+			for _, doc := range mapping.Docs {
+				if doc == "" {
+					continue
+				}
+				if _, ok := seen[doc]; !ok {
+					seen[doc] = struct{}{}
+					result = append(result, doc)
+				}
+			}
+		}
+	}
+	return result
+}
+
+// mappingMatches returns true if any glob in patterns matches any file in files.
+func mappingMatches(patterns, files []string) bool {
+	for _, pat := range patterns {
+		for _, f := range files {
+			if globMatch(pat, f) {
+				return true
+			}
+		}
+	}
+	return false
+}
+
+// globMatch matches a path against a glob pattern that may contain **.
+// It supports:
+//   - Standard path.Match patterns (*, ?, [range])
+//   - ** as a path segment that matches zero or more segments
+//   - Trailing /** to match a directory and all its contents
+//
+// The pattern and path use forward slash as separator.
+func globMatch(pattern, path string) bool {
+	return globMatchParts(splitPath(pattern), splitPath(path))
+}
+
+// splitPath splits a slash-separated path into non-empty parts.
+func splitPath(p string) []string {
+	// Clean and split on "/"
+	parts := strings.Split(p, "/")
+	result := make([]string, 0, len(parts))
+	for _, part := range parts {
+		if part != "" {
+			result = append(result, part)
+		}
+	}
+	return result
+}
+
+// globMatchParts recursively matches pattern parts against path parts.
+func globMatchParts(patParts, pathParts []string) bool {
+	for len(patParts) > 0 {
+		pat := patParts[0]
+		if pat == "**" {
+			patParts = patParts[1:]
+			if len(patParts) == 0 {
+				// Trailing **: matches any remaining path (including empty).
+				return true
+			}
+			// ** in the middle: try matching the rest at every position.
+			for i := 0; i <= len(pathParts); i++ {
+				if globMatchParts(patParts, pathParts[i:]) {
+					return true
+				}
+			}
+			return false
+		}
+		// Non-** segment: path must have a segment here.
+		if len(pathParts) == 0 {
+			return false
+		}
+		matched, err := filepath.Match(pat, pathParts[0])
+		if err != nil || !matched {
+			return false
+		}
+		patParts = patParts[1:]
+		pathParts = pathParts[1:]
+	}
+	// All pattern parts consumed; path must also be consumed.
+	return len(pathParts) == 0
+}
+
+// LoadMatchingDocs fetches content for the given doc paths via VCS and returns
+// a formatted string suitable for injection into the system prompt.
+//
+// Behavior:
+//   - Paths that look like directories (end with /, or GetAllFilesInPath returns files)
+//     are expanded to all .md files under them.
+//   - Missing files are logged as warnings and skipped.
+//   - Total content is capped at opts.MaxBytes; truncation is noted inline.
+func LoadMatchingDocs(ctx context.Context, fetcher DocFetcher, owner, repo string, docPaths []string, opts DocMapOptions) (string, error) {
+	if opts.MaxBytes <= 0 {
+		opts.MaxBytes = DefaultDocMapMaxBytes
+	}
+
+	var sb strings.Builder
+	totalBytes := 0
+	limitReached := false
+
+	for _, docPath := range docPaths {
+		if ctx.Err() != nil {
+			break
+		}
+		if limitReached {
+			slog.Warn("doc-map: context size limit reached, skipping remaining docs",
+				"remaining_path", docPath, "limit_bytes", opts.MaxBytes)
+			break
+		}
+
+		entries, err := loadDocEntries(ctx, fetcher, owner, repo, docPath)
+		if err != nil {
+			slog.Warn("doc-map: could not load doc, skipping", "path", docPath, "error", err)
+			continue
+		}
+		if len(entries) == 0 {
+			slog.Debug("doc-map: no .md files found under path", "path", docPath)
+			continue
+		}
+
+		for _, entry := range entries {
+			if limitReached {
+				break
+			}
+			available := opts.MaxBytes - totalBytes
+			if available <= 0 {
+				limitReached = true
+				sb.WriteString("\n\n> ⚠️ Design document context truncated — size limit reached.\n")
+				break
+			}
+
+			content := entry.content
+			truncated := false
+			if len(content) > available {
+				content = truncateUTF8(content, available)
+				truncated = true
+				limitReached = true
+			}
+
+			sb.WriteString("### ")
+			sb.WriteString(entry.path)
+			sb.WriteString("\n\n")
+			sb.WriteString(content)
+			sb.WriteString("\n")
+			if truncated {
+				sb.WriteString("\n> ⚠️ (truncated — size limit reached)\n")
+			}
+			totalBytes += len(content)
+			slog.Debug("doc-map: injected doc", "path", entry.path, "bytes", len(content))
+		}
+	}
+
+	if sb.Len() == 0 {
+		return "", nil
+	}
+	return sb.String(), nil
+}
+
+// docEntry holds a single doc file path and content.
+type docEntry struct {
+	path    string
+	content string
+}
+
+// loadDocEntries returns the doc content for a given path.
+// If the path is a directory, all .md files under it are returned.
+// If it's a file, a single entry is returned.
+func loadDocEntries(ctx context.Context, fetcher DocFetcher, owner, repo, docPath string) ([]docEntry, error) {
+	// Try directory expansion first.
+	files, err := fetcher.GetAllFilesInPath(ctx, owner, repo, docPath)
+	if err == nil && len(files) > 0 {
+		// Filter for .md files only.
+		var entries []docEntry
+		for path, content := range files {
+			if isMDFile(path) {
+				entries = append(entries, docEntry{path: path, content: content})
+			}
+		}
+		// Sort for deterministic output.
+		sortDocEntries(entries)
+		return entries, nil
+	}
+
+	// Try as a single file.
+	content, fileErr := fetcher.GetFileContent(ctx, owner, repo, docPath)
+	if fileErr != nil {
+		// Return the file error (more specific than directory error).
+		return nil, fmt.Errorf("fetch doc %q: %w", docPath, fileErr)
+	}
+	return []docEntry{{path: docPath, content: content}}, nil
+}
+
+// isMDFile returns true if the file has a .md extension.
+func isMDFile(path string) bool {
+	return strings.HasSuffix(strings.ToLower(path), ".md")
+}
+
+// sortDocEntries sorts entries by path for deterministic output.
+func sortDocEntries(entries []docEntry) {
+	// Simple insertion sort (doc lists are small).
+	for i := 1; i < len(entries); i++ {
+		for j := i; j > 0 && entries[j].path < entries[j-1].path; j-- {
+			entries[j], entries[j-1] = entries[j-1], entries[j]
+		}
+	}
+}
+
+// readFileBytes reads the contents of a local file.
+func readFileBytes(path string) ([]byte, error) {
+	return os.ReadFile(path)
+}
+
+// truncateUTF8 truncates s to at most maxBytes without splitting multi-byte
+// UTF-8 characters. Returns a valid UTF-8 string of at most maxBytes bytes.
+func truncateUTF8(s string, maxBytes int) string {
+	if len(s) <= maxBytes {
+		return s
+	}
+	for maxBytes > 0 && !utf8.RuneStart(s[maxBytes]) {
+		maxBytes--
+	}
+	return s[:maxBytes]
+}

review/docmap_test.go

@@ -0,0 +1,394 @@
+package review
+
+import (
+	"context"
+	"errors"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+)
+
+// fakeDocFetcher is a mock DocFetcher for tests.
+type fakeDocFetcher struct {
+	files map[string]string // path -> content
+	dirs  map[string]map[string]string // dir path -> (file path -> content)
+}
+
+func (f *fakeDocFetcher) GetFileContent(_ context.Context, _, _, path string) (string, error) {
+	if content, ok := f.files[path]; ok {
+		return content, nil
+	}
+	return "", errors.New("file not found: " + path)
+}
+
+func (f *fakeDocFetcher) GetAllFilesInPath(_ context.Context, _, _, path string) (map[string]string, error) {
+	if files, ok := f.dirs[path]; ok {
+		return files, nil
+	}
+	// Return empty (not an error) for unknown directories.
+	return nil, nil
+}
+
+// ============================================================
+// ParseDocMapConfig
+// ============================================================
+
+func TestParseDocMapConfig_Valid(t *testing.T) {
+	yaml := `
+mappings:
+  - paths:
+      - "lib/foo/**"
+    docs:
+      - docs/foo.md
+  - paths:
+      - "lib/bar/**"
+      - "lib/baz.go"
+    docs:
+      - docs/bar.md
+      - docs/shared/
+`
+	f := writeTempYAML(t, yaml)
+	cfg, err := ParseDocMapConfig(f)
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if len(cfg.Mappings) != 2 {
+		t.Fatalf("expected 2 mappings, got %d", len(cfg.Mappings))
+	}
+	if cfg.Mappings[0].Paths[0] != "lib/foo/**" {
+		t.Errorf("unexpected path: %q", cfg.Mappings[0].Paths[0])
+	}
+	if cfg.Mappings[1].Docs[1] != "docs/shared/" {
+		t.Errorf("unexpected doc: %q", cfg.Mappings[1].Docs[1])
+	}
+}
+
+func TestParseDocMapConfig_InvalidYAML(t *testing.T) {
+	f := writeTempYAML(t, "mappings: [{{invalid")
+	_, err := ParseDocMapConfig(f)
+	if err == nil {
+		t.Fatal("expected error for invalid YAML, got nil")
+	}
+}
+
+func TestParseDocMapConfig_EmptyMappings(t *testing.T) {
+	f := writeTempYAML(t, "mappings: []\n")
+	cfg, err := ParseDocMapConfig(f)
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if len(cfg.Mappings) != 0 {
+		t.Errorf("expected 0 mappings, got %d", len(cfg.Mappings))
+	}
+}
+
+func TestParseDocMapConfig_UnknownKeys(t *testing.T) {
+	// Unknown keys should produce a warning but not fail.
+	yaml := `
+mappings:
+  - paths: ["lib/foo/**"]
+    docs: ["docs/foo.md"]
+extra_key: ignored
+`
+	f := writeTempYAML(t, yaml)
+	// Should succeed (lenient parsing).
+	cfg, err := ParseDocMapConfig(f)
+	if err != nil {
+		t.Fatalf("unexpected error for unknown keys: %v", err)
+	}
+	if len(cfg.Mappings) != 1 {
+		t.Errorf("expected 1 mapping, got %d", len(cfg.Mappings))
+	}
+}
+
+func TestParseDocMapConfig_FileNotFound(t *testing.T) {
+	_, err := ParseDocMapConfig("/nonexistent/path/doc-map.yml")
+	if err == nil {
+		t.Fatal("expected error for missing file, got nil")
+	}
+}
+
+// ============================================================
+// MatchDocs
+// ============================================================
+
+func TestMatchDocs_NoMatch(t *testing.T) {
+	cfg := &DocMapConfig{
+		Mappings: []DocMapping{
+			{Paths: []string{"lib/foo/**"}, Docs: []string{"docs/foo.md"}},
+		},
+	}
+	got := MatchDocs(cfg, []string{"lib/bar/baz.go"})
+	if len(got) != 0 {
+		t.Errorf("expected no matches, got %v", got)
+	}
+}
+
+func TestMatchDocs_SingleMatch(t *testing.T) {
+	cfg := &DocMapConfig{
+		Mappings: []DocMapping{
+			{Paths: []string{"lib/foo/**"}, Docs: []string{"docs/foo.md"}},
+		},
+	}
+	got := MatchDocs(cfg, []string{"lib/foo/bar.go"})
+	if len(got) != 1 || got[0] != "docs/foo.md" {
+		t.Errorf("expected [docs/foo.md], got %v", got)
+	}
+}
+
+func TestMatchDocs_MultipleMatchesDeduplicated(t *testing.T) {
+	cfg := &DocMapConfig{
+		Mappings: []DocMapping{
+			{Paths: []string{"lib/foo/**"}, Docs: []string{"docs/shared.md", "docs/foo.md"}},
+			{Paths: []string{"lib/bar/**"}, Docs: []string{"docs/shared.md", "docs/bar.md"}},
+		},
+	}
+	got := MatchDocs(cfg, []string{"lib/foo/a.go", "lib/bar/b.go"})
+	// Both match; docs/shared.md should appear only once.
+	wantSet := map[string]bool{
+		"docs/shared.md": true,
+		"docs/foo.md":    true,
+		"docs/bar.md":    true,
+	}
+	if len(got) != 3 {
+		t.Errorf("expected 3 docs, got %d: %v", len(got), got)
+	}
+	for _, d := range got {
+		if !wantSet[d] {
+			t.Errorf("unexpected doc: %q", d)
+		}
+	}
+}
+
+func TestMatchDocs_EmptyPaths(t *testing.T) {
+	// Mapping with empty paths list should not match anything.
+	cfg := &DocMapConfig{
+		Mappings: []DocMapping{
+			{Paths: []string{}, Docs: []string{"docs/foo.md"}},
+		},
+	}
+	got := MatchDocs(cfg, []string{"lib/foo/bar.go"})
+	if len(got) != 0 {
+		t.Errorf("expected no matches for empty paths, got %v", got)
+	}
+}
+
+func TestMatchDocs_EmptyDocs(t *testing.T) {
+	// Mapping with empty docs list should produce nothing.
+	cfg := &DocMapConfig{
+		Mappings: []DocMapping{
+			{Paths: []string{"lib/foo/**"}, Docs: []string{}},
+		},
+	}
+	got := MatchDocs(cfg, []string{"lib/foo/bar.go"})
+	if len(got) != 0 {
+		t.Errorf("expected no docs for empty docs list, got %v", got)
+	}
+}
+
+func TestMatchDocs_ExactMatch(t *testing.T) {
+	cfg := &DocMapConfig{
+		Mappings: []DocMapping{
+			{Paths: []string{"lib/baz.go"}, Docs: []string{"docs/baz.md"}},
+		},
+	}
+	got := MatchDocs(cfg, []string{"lib/baz.go"})
+	if len(got) != 1 || got[0] != "docs/baz.md" {
+		t.Errorf("expected [docs/baz.md], got %v", got)
+	}
+}
+
+// ============================================================
+// globMatch
+// ============================================================
+
+func TestGlobMatch(t *testing.T) {
+	tests := []struct {
+		name    string
+		pattern string
+		path    string
+		want    bool
+	}{
+		{"exact match", "lib/foo/bar.go", "lib/foo/bar.go", true},
+		{"exact no match", "lib/foo/bar.go", "lib/foo/baz.go", false},
+		{"star wildcard", "lib/foo/*.go", "lib/foo/bar.go", true},
+		{"star no match cross-dir", "lib/foo/*.go", "lib/foo/sub/bar.go", false},
+		{"trailing doublestar", "lib/foo/**", "lib/foo/bar.go", true},
+		{"trailing doublestar nested", "lib/foo/**", "lib/foo/sub/deep/bar.go", true},
+		// Note: trailing ** matches the parent path too; PR file lists contain file paths
+		// (not directories), so this corner case does not arise in practice.
+		{"trailing doublestar matches parent", "lib/foo/**", "lib/foo", true},
+		{"doublestar in middle", "lib/**/bar.go", "lib/foo/sub/bar.go", true},
+		{"doublestar in middle no match", "lib/**/bar.go", "lib/foo/sub/baz.go", false},
+		{"leading doublestar", "**/bar.go", "lib/foo/bar.go", true},
+		{"leading doublestar top-level", "**/bar.go", "bar.go", true},
+		{"question mark", "lib/foo/ba?.go", "lib/foo/bar.go", true},
+		{"question mark no match", "lib/foo/ba?.go", "lib/foo/ba.go", false},
+		{"star matches none in segment", "lib/*/bar.go", "lib/bar.go", false},
+		{"star single segment", "lib/*/bar.go", "lib/foo/bar.go", true},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			got := globMatch(tc.pattern, tc.path)
+			if got != tc.want {
+				t.Errorf("globMatch(%q, %q) = %v, want %v", tc.pattern, tc.path, got, tc.want)
+			}
+		})
+	}
+}
+
+// ============================================================
+// LoadMatchingDocs
+// ============================================================
+
+func TestLoadMatchingDocs_FileInjection(t *testing.T) {
+	fetcher := &fakeDocFetcher{
+		files: map[string]string{
+			"docs/foo.md": "# Foo Design\n\nThis is the foo doc.",
+		},
+	}
+	content, err := LoadMatchingDocs(context.Background(), fetcher, "owner", "repo",
+		[]string{"docs/foo.md"}, DocMapOptions{MaxBytes: DefaultDocMapMaxBytes})
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if !strings.Contains(content, "# Foo Design") {
+		t.Errorf("expected doc content, got: %q", content)
+	}
+	if !strings.Contains(content, "### docs/foo.md") {
+		t.Errorf("expected heading with path, got: %q", content)
+	}
+}
+
+func TestLoadMatchingDocs_MissingFileSkipped(t *testing.T) {
+	fetcher := &fakeDocFetcher{
+		files: map[string]string{
+			"docs/present.md": "present",
+		},
+	}
+	content, err := LoadMatchingDocs(context.Background(), fetcher, "owner", "repo",
+		[]string{"docs/missing.md", "docs/present.md"}, DocMapOptions{MaxBytes: DefaultDocMapMaxBytes})
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if !strings.Contains(content, "present") {
+		t.Errorf("expected present doc content, got: %q", content)
+	}
+	// Missing file should be skipped, not cause a failure.
+}
+
+func TestLoadMatchingDocs_DirectoryExpansion(t *testing.T) {
+	fetcher := &fakeDocFetcher{
+		dirs: map[string]map[string]string{
+			"docs/domain/": {
+				"docs/domain/a.md": "# A",
+				"docs/domain/b.md": "# B",
+				"docs/domain/c.go": "package domain", // should be skipped (not .md)
+			},
+		},
+	}
+	content, err := LoadMatchingDocs(context.Background(), fetcher, "owner", "repo",
+		[]string{"docs/domain/"}, DocMapOptions{MaxBytes: DefaultDocMapMaxBytes})
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if !strings.Contains(content, "# A") {
+		t.Errorf("expected doc A content, got: %q", content)
+	}
+	if !strings.Contains(content, "# B") {
+		t.Errorf("expected doc B content, got: %q", content)
+	}
+	if strings.Contains(content, "package domain") {
+		t.Errorf("non-.md file should not be injected, got: %q", content)
+	}
+}
+
+func TestLoadMatchingDocs_DirectoryNoMDFiles(t *testing.T) {
+	fetcher := &fakeDocFetcher{
+		dirs: map[string]map[string]string{
+			"src/": {
+				"src/main.go": "package main",
+			},
+		},
+	}
+	content, err := LoadMatchingDocs(context.Background(), fetcher, "owner", "repo",
+		[]string{"src/"}, DocMapOptions{MaxBytes: DefaultDocMapMaxBytes})
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if content != "" {
+		t.Errorf("expected empty content for dir with no .md files, got: %q", content)
+	}
+}
+
+func TestLoadMatchingDocs_NoMatchingPaths(t *testing.T) {
+	fetcher := &fakeDocFetcher{}
+	content, err := LoadMatchingDocs(context.Background(), fetcher, "owner", "repo",
+		[]string{}, DocMapOptions{MaxBytes: DefaultDocMapMaxBytes})
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if content != "" {
+		t.Errorf("expected empty content for no paths, got: %q", content)
+	}
+}
+
+func TestLoadMatchingDocs_ContextSizeGuard(t *testing.T) {
+	bigContent := strings.Repeat("x", 200)
+	fetcher := &fakeDocFetcher{
+		files: map[string]string{
+			"docs/a.md": bigContent,
+			"docs/b.md": bigContent,
+			"docs/c.md": bigContent,
+		},
+	}
+	// Limit to 350 bytes — enough for a.md fully and part of b.md.
+	content, err := LoadMatchingDocs(context.Background(), fetcher, "owner", "repo",
+		[]string{"docs/a.md", "docs/b.md", "docs/c.md"}, DocMapOptions{MaxBytes: 350})
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if len(content) > 600 {
+		t.Errorf("content too large, expected ≤600 bytes total, got %d", len(content))
+	}
+	if !strings.Contains(content, "truncated") {
+		t.Errorf("expected truncation notice, got: %q", content)
+	}
+}
+
+func TestLoadMatchingDocs_Deduplication(t *testing.T) {
+	fetcher := &fakeDocFetcher{
+		files: map[string]string{
+			"docs/shared.md": "shared content",
+		},
+	}
+	// MatchDocs deduplicates before calling LoadMatchingDocs, but test it with
+	// duplicates in input too.
+	content, err := LoadMatchingDocs(context.Background(), fetcher, "owner", "repo",
+		[]string{"docs/shared.md"}, DocMapOptions{MaxBytes: DefaultDocMapMaxBytes})
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if !strings.Contains(content, "shared content") {
+		t.Errorf("expected shared content, got: %q", content)
+	}
+}
+
+// ============================================================
+// Helpers
+// ============================================================
+
+func writeTempYAML(t *testing.T, content string) string {
+	t.Helper()
+	f, err := os.CreateTemp(t.TempDir(), "doc-map-*.yml")
+	if err != nil {
+		t.Fatalf("failed to create temp file: %v", err)
+	}
+	defer f.Close()
+	if _, err := f.WriteString(content); err != nil {
+		t.Fatalf("failed to write temp file: %v", err)
+	}
+	return filepath.Clean(f.Name())
+}