diff --git a/docs/roadmap/implementation.md b/docs/roadmap/implementation.md
index 394918a..23a37a4 100644
--- a/docs/roadmap/implementation.md
+++ b/docs/roadmap/implementation.md
@@ -7,7 +7,7 @@ The eleven [audit reports](audit/) supply evidence and reproduction details;
 the target document owns the accepted outcomes and policy choices. This plan
 owns execution order, concrete implementation choices, and completion evidence.
 
-All stages are pending. Follow Stage 1 through Stage 19 in order as one
+Follow Stage 1 through Stage 19 in order as one
 end-to-end sprint. Stages separate work into units suitable for a Luna coding
 agent. Intermediate stages may leave related code or tests uncompilable;
 complete the dependencies before evaluating the final implementation. Run
@@ -37,7 +37,7 @@ the agent policy; an intermediate compilation dependency is recorded accurately.
 | Stage | Work items | Status |
 | --- | --- | --- |
 | 1 | A01; publication assertion portion of A19 | Complete — regression failed before the fix and passed afterward; focused publication and reconciliation tests passed. |
-| 2 | A02, A12: common Git mechanics | Pending |
+| 2 | A02, A12: common Git mechanics | Complete — focused Git, candidate, identity, and public build/publication/delivery tests passed; A02 regression evidence follows in Stage 3. |
 | 3 | A02: source identity regression evidence | Pending |
 | 4 | A03: buffered command teardown | Pending |
 | 5 | A03, A18: piped lifetime and queued cancellation | Pending |
diff --git a/internal/build/build.go b/internal/build/build.go
index af6f328..ef82a70 100644
--- a/internal/build/build.go
+++ b/internal/build/build.go
@@ -15,6 +15,7 @@ import (
 
 	"go.maximumdirect.net/releasekit/internal/artifact"
 	"go.maximumdirect.net/releasekit/internal/candidate"
+	"go.maximumdirect.net/releasekit/internal/git"
 	"go.maximumdirect.net/releasekit/internal/gotool"
 	"go.maximumdirect.net/releasekit/internal/releaseidentity"
 	"go.maximumdirect.net/releasekit/internal/tempdir"
@@ -102,14 +103,14 @@ func BuildResolved(ctx context.Context, request Request) (Result, error) {
 		return result, fmt.Errorf("resolve module directory: %w", err)
 	}
 	result.ModuleDir = moduleDir
-	commit, err := gitCommit(ctx, repositoryDir)
+	commit, err := git.CaptureHead(ctx, repositoryDir)
 	if err != nil {
-		return result, err
+		return result, fmt.Errorf("read source commit: %w", err)
 	}
 	result.CandidateCommit = commit
-	cleanBefore, err := cleanSource(ctx, repositoryDir)
+	statusBefore, err := git.WorktreeStatus(ctx, repositoryDir)
 	if err != nil {
-		return result, err
+		return result, fmt.Errorf("inspect build source: %w", err)
 	}
 
 	if len(result.Targets) == 0 {
@@ -192,30 +193,18 @@ func BuildResolved(ctx context.Context, request Request) (Result, error) {
 	if err := checkVersion(ctx, smokePath, settings.BinaryName, identity.Version); err != nil {
 		return result, err
 	}
-	commitAfter, err := gitCommit(ctx, repositoryDir)
+	commitAfter, err := git.CaptureHead(ctx, repositoryDir)
 	if err != nil {
-		return result, err
+		return result, fmt.Errorf("read source commit: %w", err)
 	}
-	cleanAfter, err := cleanSource(ctx, repositoryDir)
+	statusAfter, err := git.WorktreeStatus(ctx, repositoryDir)
 	if err != nil {
-		return result, err
+		return result, fmt.Errorf("inspect build source: %w", err)
 	}
-	result.SourceVerified = cleanBefore && cleanAfter && commitAfter == commit
+	result.SourceVerified = statusBefore == "" && statusAfter == "" && commitAfter == commit
 	return result, nil
 }
 
-func gitCommit(ctx context.Context, repositoryDir string) (string, error) {
-	command := exec.CommandContext(ctx, "git", "-C", repositoryDir, "rev-parse", "--verify", "HEAD^{commit}")
-	output, err := command.Output()
-	if err != nil {
-		if ctx.Err() != nil {
-			return "", fmt.Errorf("read source commit: %w", ctx.Err())
-		}
-		return "", fmt.Errorf("read source commit: %w", err)
-	}
-	return strings.TrimSpace(string(output)), nil
-}
-
 func buildTarget(ctx context.Context, goTool *gotool.Tool, moduleDir, mainPackage, outputPath, version string, target Target) error {
 	ldflags := "-s -w -X " + versioncontract.InjectedVersionLinkerSymbol + "=" + version
 	err := goTool.Run(ctx, moduleDir, gotool.Static, gotool.Target{OS: target.OS, Arch: target.Arch}, nil,
@@ -252,15 +241,3 @@ func checkVersion(ctx context.Context, binaryPath, binaryName, version string) e
 	}
 	return nil
 }
-
-func cleanSource(ctx context.Context, repositoryDir string) (bool, error) {
-	command := exec.CommandContext(ctx, "git", "-C", repositoryDir, "status", "--porcelain", "--untracked-files=all")
-	output, err := command.Output()
-	if err != nil {
-		if ctx.Err() != nil {
-			return false, fmt.Errorf("inspect build source: %w", ctx.Err())
-		}
-		return false, fmt.Errorf("inspect build source: %w", err)
-	}
-	return len(output) == 0, nil
-}
diff --git a/internal/candidate/check.go b/internal/candidate/check.go
index 2a711a4..aa3dd45 100644
--- a/internal/candidate/check.go
+++ b/internal/candidate/check.go
@@ -194,18 +194,18 @@ func inspectLocalState(ctx context.Context, repositoryDir string) (localState, e
 	if err != nil {
 		return localState{}, fmt.Errorf("inspect current branch: %w", err)
 	}
-	commitOutput, err := gitOutput(ctx, repositoryDir, "rev-parse", "--verify", "HEAD^{commit}")
+	commit, err := git.CaptureHead(ctx, repositoryDir)
 	if err != nil {
 		return localState{}, fmt.Errorf("capture HEAD commit: %w", err)
 	}
-	statusOutput, err := gitOutput(ctx, repositoryDir, "status", "--porcelain=v1", "--untracked-files=all")
+	status, err := git.WorktreeStatus(ctx, repositoryDir)
 	if err != nil {
 		return localState{}, fmt.Errorf("inspect worktree and index: %w", err)
 	}
 	return localState{
 		branch: strings.TrimSpace(string(branchOutput)),
-		commit: strings.TrimSpace(string(commitOutput)),
-		status: strings.TrimSpace(string(statusOutput)),
+		commit: commit,
+		status: status,
 	}, nil
 }
 
@@ -215,6 +215,7 @@ func gitOutput(ctx context.Context, repositoryDir string, args ...string) ([]byt
 	err := process.Run(ctx, process.Invocation{
 		Args:   commandArgs,
 		Dir:    repositoryDir,
+		Env:    map[string]string{"GIT_NO_REPLACE_OBJECTS": "1"},
 		Stdout: &stdout,
 		Stderr: &stderr,
 	})
@@ -233,6 +234,7 @@ func hasLocalTag(ctx context.Context, repositoryDir, tag string) (bool, error) {
 	err := process.Run(ctx, process.Invocation{
 		Args:   []string{"git", "show-ref", "--verify", "--quiet", "refs/tags/" + tag},
 		Dir:    repositoryDir,
+		Env:    map[string]string{"GIT_NO_REPLACE_OBJECTS": "1"},
 		Stderr: &stderr,
 	})
 	if err == nil {
diff --git a/internal/git/blob_reader.go b/internal/git/blob_reader.go
index 01fa29a..f455fe4 100644
--- a/internal/git/blob_reader.go
+++ b/internal/git/blob_reader.go
@@ -128,8 +128,9 @@ func (reader *BlobReader) startLocked() error {
 		Args: []string{"git", "cat-file", "--batch"},
 		Dir:  reader.repositoryDir,
 		Env: map[string]string{
-			"GIT_NO_LAZY_FETCH":  "1",
-			"GIT_ALLOW_PROTOCOL": "",
+			"GIT_NO_LAZY_FETCH":      "1",
+			"GIT_ALLOW_PROTOCOL":     "",
+			"GIT_NO_REPLACE_OBJECTS": "1",
 		},
 		Stderr: &reader.stderr,
 	})
diff --git a/internal/git/remote.go b/internal/git/remote.go
index ccd9834..631a135 100644
--- a/internal/git/remote.go
+++ b/internal/git/remote.go
@@ -234,6 +234,7 @@ func run(ctx context.Context, dir string, config []string, args ...string) (stri
 	err := process.Run(ctx, process.Invocation{
 		Args:   append([]string{"git"}, commandArgs...),
 		Dir:    dir,
+		Env:    map[string]string{"GIT_NO_REPLACE_OBJECTS": "1"},
 		Stdout: &stdout,
 		Stderr: &stderr,
 	})
diff --git a/internal/git/source.go b/internal/git/source.go
index 68340bf..48df854 100644
--- a/internal/git/source.go
+++ b/internal/git/source.go
@@ -64,7 +64,7 @@ func DiscoverRepositoryRoot(ctx context.Context, directory string) (string, bool
 	var stdout, stderr strings.Builder
 	err := process.Run(ctx, process.Invocation{
 		Args: []string{"git", "rev-parse", "--show-toplevel"}, Dir: directory,
-		Env: map[string]string{"LC_ALL": "C"}, Stdout: &stdout, Stderr: &stderr,
+		Env: map[string]string{"LC_ALL": "C", "GIT_NO_REPLACE_OBJECTS": "1"}, Stdout: &stdout, Stderr: &stderr,
 	})
 	if err == nil {
 		root, err := normalizeRepositoryRoot(stdout.String())
@@ -199,6 +199,15 @@ func CaptureHead(ctx context.Context, repositoryDir string) (string, error) {
 	return head, nil
 }
 
+// WorktreeStatus observes repository-wide worktree and index changes.
+func WorktreeStatus(ctx context.Context, repositoryDir string) (string, error) {
+	status, err := run(ctx, repositoryDir, nil, "status", "--porcelain=v1", "--untracked-files=all")
+	if err != nil {
+		return "", err
+	}
+	return strings.TrimSpace(status), nil
+}
+
 // InspectTaggedSource reads the local HEAD, worktree state, and selected tag.
 // Both lightweight historical tags and annotated tags are supported.
 func InspectTaggedSource(ctx context.Context, repositoryDir, tag string) (TaggedSource, error) {
@@ -206,15 +215,12 @@ func InspectTaggedSource(ctx context.Context, repositoryDir, tag string) (Tagged
 		return TaggedSource{}, err
 	}
 	var source TaggedSource
-	head, err := run(ctx, repositoryDir, nil, "rev-parse", "--verify", "HEAD^{commit}")
+	head, err := CaptureHead(ctx, repositoryDir)
 	if err != nil {
-		return TaggedSource{}, fmt.Errorf("read checkout HEAD: %w", err)
+		return TaggedSource{}, err
 	}
-	source.Head = strings.TrimSpace(head)
-	if !validObjectID(source.Head) {
-		return TaggedSource{}, fmt.Errorf("Git returned an invalid checkout commit %q", source.Head)
-	}
-	status, err := run(ctx, repositoryDir, nil, "status", "--porcelain", "--untracked-files=all")
+	source.Head = head
+	status, err := WorktreeStatus(ctx, repositoryDir)
 	if err != nil {
 		return TaggedSource{}, fmt.Errorf("inspect tagged checkout state: %w", err)
 	}
@@ -411,7 +417,7 @@ func readLocalObjects(ctx context.Context, repositoryDir string, input io.Reader
 		Args: append([]string{"git"}, args...),
 		Dir:  repositoryDir,
 		// Disable transports as well for Git versions predating lazy-fetch control.
-		Env:    map[string]string{"GIT_NO_LAZY_FETCH": "1", "GIT_ALLOW_PROTOCOL": ""},
+		Env:    map[string]string{"GIT_NO_LAZY_FETCH": "1", "GIT_ALLOW_PROTOCOL": "", "GIT_NO_REPLACE_OBJECTS": "1"},
 		Stdin:  input,
 		Stdout: &stdout,
 		Stderr: &stderr,