diff --git a/CLAUDE.md b/CLAUDE.md
index e69efe1..3d39ce2 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -43,8 +43,12 @@ Coverage target: maintain ≥90.9%.
 
 - UK English throughout (colour, licence, initialise)
 - Explicit types on all function signatures and struct fields
+- Exported declarations must have Go doc comments beginning with the identifier name
 - `go test ./...` and `go vet ./...` must pass before commit
 - SPDX header on all source files: `// SPDX-Licence-Identifier: EUPL-1.2`
 - Error handling: all errors must use `coreerr.E(op, msg, err)` from `dappco.re/go/core/log`, never `fmt.Errorf` or `errors.New`
+- Banned imports in non-test Go files: `errors`, `github.com/pkg/errors`, and legacy `forge.lthn.ai/...` paths
 - Conventional commits: `type(scope): description`
 - Co-Author trailer: `Co-Authored-By: Virgil <virgil@lethean.io>`
+
+The conventions test suite enforces banned imports, exported usage comments, and test naming via `go test ./...`.
diff --git a/CODEX.md b/CODEX.md
new file mode 100644
index 0000000..b5ecf8e
--- /dev/null
+++ b/CODEX.md
@@ -0,0 +1,54 @@
+# CODEX.md
+
+This file provides guidance to Codex when working in this repository.
+
+Claude Code JSONL transcript parser, analytics engine, and HTML/video renderer. Module: `dappco.re/go/core/session`
+
+## Commands
+
+```bash
+go test ./...                              # Run all tests
+go test -v -run TestFunctionName_Context   # Run single test
+go test -race ./...                        # Race detector
+go test -bench=. -benchmem ./...           # Benchmarks
+go vet ./...                               # Vet
+golangci-lint run ./...                    # Lint (optional, config in .golangci.yml)
+```
+
+## Architecture
+
+Single-package library (`package session`) with five source files forming a pipeline:
+
+1. **parser.go** — Core JSONL parser. Reads Claude Code session files line-by-line (8 MiB scanner buffer), correlates `tool_use`/`tool_result` pairs via a `pendingTools` map keyed by tool ID, and produces `Session` with `[]Event`. Also handles session listing, fetching, and pruning.
+2. **analytics.go** — Pure computation over `[]Event`. `Analyse()` returns `SessionAnalytics` (per-tool counts, error rates, latency stats, token estimates). No I/O.
+3. **html.go** — `RenderHTML()` generates a self-contained HTML file (inline CSS/JS, dark theme, collapsible panels, client-side search). All user content is `html.EscapeString`-escaped.
+4. **video.go** — `RenderMP4()` generates a VHS `.tape` script and shells out to `vhs`. Requires `vhs` on PATH.
+5. **search.go** — `Search()`/`SearchSeq()` does cross-session case-insensitive substring search over tool event inputs and outputs.
+
+Both slice-returning and `iter.Seq` variants exist for `ListSessions`, `Search`, and `Session.EventsSeq`.
+
+### Adding a new tool type
+
+Touch all layers: add input struct in `parser.go` → case in `extractToolInput` → label in `html.go` `RenderHTML` → tape entry in `video.go` `generateTape` → tests in `parser_test.go`.
+
+## Testing
+
+Tests are white-box (`package session`). Test helpers in `parser_test.go` build synthetic JSONL in-memory — no fixture files. Use `writeJSONL(t, dir, name, lines...)` and the entry builders (`toolUseEntry`, `toolResultEntry`, `userTextEntry`, `assistantTextEntry`).
+
+Naming convention: `TestFunctionName_Context_Good/Bad/Ugly` (happy path / expected errors / extreme edge cases).
+
+Coverage target: maintain ≥90.9%.
+
+## Coding Standards
+
+- UK English throughout (colour, licence, initialise)
+- Explicit types on all function signatures and struct fields
+- Exported declarations must have Go doc comments beginning with the identifier name
+- `go test ./...` and `go vet ./...` must pass before commit
+- SPDX header on all source files: `// SPDX-Licence-Identifier: EUPL-1.2`
+- Error handling: all errors must use `coreerr.E(op, msg, err)` from `dappco.re/go/core/log`, never `fmt.Errorf` or `errors.New`
+- Banned imports in non-test Go files: `errors`, `github.com/pkg/errors`, and legacy `forge.lthn.ai/...` paths
+- Conventional commits: `type(scope): description`
+- Co-Author trailer: `Co-Authored-By: Virgil <virgil@lethean.io>`
+
+The conventions test suite enforces banned imports, exported usage comments, and test naming via `go test ./...`.
diff --git a/conventions_test.go b/conventions_test.go
new file mode 100644
index 0000000..9b8bdb3
--- /dev/null
+++ b/conventions_test.go
@@ -0,0 +1,213 @@
+// SPDX-Licence-Identifier: EUPL-1.2
+package session
+
+import (
+	"go/ast"
+	"go/parser"
+	"go/token"
+	"path/filepath"
+	"regexp"
+	"slices"
+	"strings"
+	"testing"
+)
+
+var testNamePattern = regexp.MustCompile(`^Test[A-Za-z0-9]+(?:_[A-Za-z0-9]+)+_(Good|Bad|Ugly)$`)
+
+func TestConventions_BannedImports_Good(t *testing.T) {
+	files := parsePackageFiles(t)
+
+	banned := map[string]string{
+		"errors":                "use coreerr.E(op, msg, err) for package errors",
+		"github.com/pkg/errors": "use coreerr.E(op, msg, err) for package errors",
+	}
+
+	for _, file := range files {
+		if strings.HasSuffix(file.path, "_test.go") {
+			continue
+		}
+
+		for _, spec := range file.ast.Imports {
+			path := strings.Trim(spec.Path.Value, `"`)
+			if strings.HasPrefix(path, "forge.lthn.ai/") {
+				t.Errorf("%s imports %q; use dappco.re/go/core/... paths instead", file.path, path)
+				continue
+			}
+			if reason, ok := banned[path]; ok {
+				t.Errorf("%s imports %q; %s", file.path, path, reason)
+			}
+		}
+	}
+}
+
+func TestConventions_TestNaming_Good(t *testing.T) {
+	files := parsePackageFiles(t)
+
+	for _, file := range files {
+		if !strings.HasSuffix(file.path, "_test.go") {
+			continue
+		}
+
+		for _, decl := range file.ast.Decls {
+			fn, ok := decl.(*ast.FuncDecl)
+			if !ok || fn.Recv != nil {
+				continue
+			}
+			if !strings.HasPrefix(fn.Name.Name, "Test") || fn.Name.Name == "TestMain" {
+				continue
+			}
+			if !isTestingTFunc(fn) {
+				continue
+			}
+			if !testNamePattern.MatchString(fn.Name.Name) {
+				t.Errorf("%s contains %s; expected TestFunctionName_Context_Good/Bad/Ugly", file.path, fn.Name.Name)
+			}
+		}
+	}
+}
+
+func TestConventions_UsageComments_Good(t *testing.T) {
+	files := parsePackageFiles(t)
+
+	for _, file := range files {
+		if strings.HasSuffix(file.path, "_test.go") {
+			continue
+		}
+
+		for _, decl := range file.ast.Decls {
+			switch d := decl.(type) {
+			case *ast.FuncDecl:
+				if d.Recv != nil || !d.Name.IsExported() {
+					continue
+				}
+				if !hasDocPrefix(commentText(d.Doc), d.Name.Name) {
+					t.Errorf("%s: exported function %s needs a usage comment starting with %s", file.path, d.Name.Name, d.Name.Name)
+				}
+			case *ast.GenDecl:
+				for i, spec := range d.Specs {
+					switch s := spec.(type) {
+					case *ast.TypeSpec:
+						if !s.Name.IsExported() {
+							continue
+						}
+						if !hasDocPrefix(commentText(typeDocGroup(d, s, i)), s.Name.Name) {
+							t.Errorf("%s: exported type %s needs a usage comment starting with %s", file.path, s.Name.Name, s.Name.Name)
+						}
+					case *ast.ValueSpec:
+						doc := valueDocGroup(d, s, i)
+						for _, name := range s.Names {
+							if !name.IsExported() {
+								continue
+							}
+							if !hasDocPrefix(commentText(doc), name.Name) {
+								t.Errorf("%s: exported declaration %s needs a usage comment starting with %s", file.path, name.Name, name.Name)
+							}
+						}
+					}
+				}
+			}
+		}
+	}
+}
+
+type parsedFile struct {
+	path string
+	ast  *ast.File
+}
+
+func parsePackageFiles(t *testing.T) []parsedFile {
+	t.Helper()
+
+	fset := token.NewFileSet()
+	pkgs, err := parser.ParseDir(fset, ".", nil, parser.ParseComments)
+	if err != nil {
+		t.Fatalf("parse package: %v", err)
+	}
+
+	pkg, ok := pkgs["session"]
+	if !ok {
+		t.Fatal("package session not found")
+	}
+
+	paths := filePaths(pkg.Files)
+	slices.Sort(paths)
+	files := make([]parsedFile, 0, len(paths))
+	for _, path := range paths {
+		files = append(files, parsedFile{
+			path: filepath.Base(path),
+			ast:  pkg.Files[path],
+		})
+	}
+	return files
+}
+
+func filePaths(files map[string]*ast.File) []string {
+	paths := make([]string, 0, len(files))
+	for path := range files {
+		paths = append(paths, path)
+	}
+	return paths
+}
+
+func isTestingTFunc(fn *ast.FuncDecl) bool {
+	if fn.Type == nil || fn.Type.Params == nil || len(fn.Type.Params.List) != 1 {
+		return false
+	}
+
+	param := fn.Type.Params.List[0]
+	star, ok := param.Type.(*ast.StarExpr)
+	if !ok {
+		return false
+	}
+
+	sel, ok := star.X.(*ast.SelectorExpr)
+	if !ok {
+		return false
+	}
+
+	pkg, ok := sel.X.(*ast.Ident)
+	if !ok {
+		return false
+	}
+
+	return pkg.Name == "testing" && sel.Sel.Name == "T"
+}
+
+func typeDocGroup(decl *ast.GenDecl, spec *ast.TypeSpec, index int) *ast.CommentGroup {
+	if spec.Doc != nil {
+		return spec.Doc
+	}
+	if len(decl.Specs) == 1 && index == 0 {
+		return decl.Doc
+	}
+	return nil
+}
+
+func valueDocGroup(decl *ast.GenDecl, spec *ast.ValueSpec, index int) *ast.CommentGroup {
+	if spec.Doc != nil {
+		return spec.Doc
+	}
+	if len(decl.Specs) == 1 && index == 0 {
+		return decl.Doc
+	}
+	return nil
+}
+
+func commentText(group *ast.CommentGroup) string {
+	if group == nil {
+		return ""
+	}
+	return strings.TrimSpace(group.Text())
+}
+
+func hasDocPrefix(text, name string) bool {
+	if text == "" || !strings.HasPrefix(text, name) {
+		return false
+	}
+	if len(text) == len(name) {
+		return true
+	}
+
+	next := text[len(name)]
+	return (next < 'A' || next > 'Z') && (next < 'a' || next > 'z') && (next < '0' || next > '9') && next != '_'
+}
diff --git a/docs/development.md b/docs/development.md
index f9cfc6f..747b694 100644
--- a/docs/development.md
+++ b/docs/development.md
@@ -138,6 +138,17 @@ Both `go vet ./...` and `golangci-lint run ./...` must be clean before committin
 - Use explicit types on struct fields and function signatures.
 - Avoid `interface{}` in public APIs; use typed parameters where possible.
 - Handle all errors explicitly; do not use blank `_` for error returns in non-test code.
+- Exported declarations must have Go doc comments beginning with the identifier name.
+
+### Imports and Error Handling
+
+- Do not import `errors` or `github.com/pkg/errors` in non-test Go files; use `coreerr.E(op, msg, err)` from `dappco.re/go/core/log`.
+- Do not reintroduce legacy `forge.lthn.ai/...` module paths; use `dappco.re/go/core/...` imports.
+
+### Test Naming
+
+Test functions should follow `TestFunctionName_Context_Good/Bad/Ugly`.
+The conventions test suite checks test naming, banned imports, and exported usage comments during `go test ./...`.
 
 ### File Headers
 
diff --git a/parser_test.go b/parser_test.go
index 2b3b06d..e8e6412 100644
--- a/parser_test.go
+++ b/parser_test.go
@@ -807,13 +807,13 @@ func TestTruncate_Empty_Good(t *testing.T) {
 
 // --- helper function tests ---
 
-func TestShortID_Good(t *testing.T) {
+func TestShortID_TruncatesAndPreservesLength_Good(t *testing.T) {
 	assert.Equal(t, "abcdefgh", shortID("abcdefghijklmnop"))
 	assert.Equal(t, "short", shortID("short"))
 	assert.Equal(t, "12345678", shortID("12345678"))
 }
 
-func TestFormatDuration_Good(t *testing.T) {
+func TestFormatDuration_CommonDurations_Good(t *testing.T) {
 	assert.Equal(t, "500ms", formatDuration(500*time.Millisecond))
 	assert.Equal(t, "1.5s", formatDuration(1500*time.Millisecond))
 	assert.Equal(t, "2m30s", formatDuration(2*time.Minute+30*time.Second))
@@ -1453,5 +1453,3 @@ func TestListSessions_TruncatedFile_Good(t *testing.T) {
 }
 
 // --- PruneSessions tests ---
-
-
diff --git a/video_test.go b/video_test.go
index 7a195ce..9be524c 100644
--- a/video_test.go
+++ b/video_test.go
@@ -174,7 +174,7 @@ func TestGenerateTape_BashEmptyCommand_Bad(t *testing.T) {
 	assert.NotContains(t, tape, `"$ "`)
 }
 
-func TestExtractCommand_Good(t *testing.T) {
+func TestExtractCommand_StripsDescriptionSuffix_Good(t *testing.T) {
 	assert.Equal(t, "ls -la", extractCommand("ls -la # list files"))
 	assert.Equal(t, "go test ./...", extractCommand("go test ./..."))
 	assert.Equal(t, "echo hello", extractCommand("echo hello"))