diff --git a/pkg/agentic/commands_session.go b/pkg/agentic/commands_session.go
index 21e260b..528c159 100644
--- a/pkg/agentic/commands_session.go
+++ b/pkg/agentic/commands_session.go
@@ -14,6 +14,8 @@ func (s *PrepSubsystem) registerSessionCommands() {
 	c.Command("agentic:session/end", core.Command{Description: "End a stored session with status, summary, and handoff notes", Action: s.cmdSessionEnd})
 	c.Command("session/complete", core.Command{Description: "Mark a stored session completed with status, summary, and handoff notes", Action: s.cmdSessionEnd})
 	c.Command("agentic:session/complete", core.Command{Description: "Mark a stored session completed with status, summary, and handoff notes", Action: s.cmdSessionEnd})
+	c.Command("session/log", core.Command{Description: "Add a work log entry to a stored session", Action: s.cmdSessionLog})
+	c.Command("agentic:session/log", core.Command{Description: "Add a work log entry to a stored session", Action: s.cmdSessionLog})
 	c.Command("session/resume", core.Command{Description: "Resume a paused or handed-off session from local cache", Action: s.cmdSessionResume})
 	c.Command("agentic:session/resume", core.Command{Description: "Resume a paused or handed-off session from local cache", Action: s.cmdSessionResume})
 	c.Command("session/replay", core.Command{Description: "Build replay context for a stored session", Action: s.cmdSessionReplay})
@@ -109,6 +111,48 @@ func (s *PrepSubsystem) cmdSessionEnd(options core.Options) core.Result {
 	return core.Result{Value: output, OK: true}
 }
 
+// core-agent session log ses-abc123 --message="Checked build" --type=checkpoint
+func (s *PrepSubsystem) cmdSessionLog(options core.Options) core.Result {
+	sessionID := optionStringValue(options, "session_id", "session-id", "id", "_arg")
+	message := optionStringValue(options, "message")
+	entryType := optionStringValue(options, "type")
+	if entryType == "" {
+		entryType = "info"
+	}
+	if sessionID == "" {
+		core.Print(nil, "usage: core-agent session log <session-id> --message=\"Checked build\" [--type=checkpoint] [--data='{\"key\":\"value\"}']")
+		return core.Result{Value: core.E("agentic.cmdSessionLog", "session_id is required", nil), OK: false}
+	}
+	if message == "" {
+		core.Print(nil, "usage: core-agent session log <session-id> --message=\"Checked build\" [--type=checkpoint] [--data='{\"key\":\"value\"}']")
+		return core.Result{Value: core.E("agentic.cmdSessionLog", "message is required", nil), OK: false}
+	}
+
+	result := s.handleSessionLog(s.commandContext(), core.NewOptions(
+		core.Option{Key: "session_id", Value: sessionID},
+		core.Option{Key: "message", Value: message},
+		core.Option{Key: "type", Value: entryType},
+		core.Option{Key: "data", Value: optionAnyMapValue(options, "data")},
+	))
+	if !result.OK {
+		err := commandResultError("agentic.cmdSessionLog", result)
+		core.Print(nil, "error: %v", err)
+		return core.Result{Value: err, OK: false}
+	}
+
+	output, ok := result.Value.(SessionLogOutput)
+	if !ok {
+		err := core.E("agentic.cmdSessionLog", "invalid session log output", nil)
+		core.Print(nil, "error: %v", err)
+		return core.Result{Value: err, OK: false}
+	}
+
+	core.Print(nil, "session: %s", sessionID)
+	core.Print(nil, "type:    %s", entryType)
+	core.Print(nil, "logged:  %s", output.Logged)
+	return core.Result{Value: output, OK: true}
+}
+
 func (s *PrepSubsystem) cmdSessionResume(options core.Options) core.Result {
 	sessionID := optionStringValue(options, "session_id", "session-id", "id", "_arg")
 	if sessionID == "" {
diff --git a/pkg/agentic/commands_session_test.go b/pkg/agentic/commands_session_test.go
index c1a008b..2c8047c 100644
--- a/pkg/agentic/commands_session_test.go
+++ b/pkg/agentic/commands_session_test.go
@@ -25,6 +25,8 @@ func TestCommandsSession_RegisterSessionCommands_Good(t *testing.T) {
 	assert.Contains(t, c.Commands(), "agentic:session/end")
 	assert.Contains(t, c.Commands(), "session/complete")
 	assert.Contains(t, c.Commands(), "agentic:session/complete")
+	assert.Contains(t, c.Commands(), "session/log")
+	assert.Contains(t, c.Commands(), "agentic:session/log")
 	assert.Contains(t, c.Commands(), "session/resume")
 	assert.Contains(t, c.Commands(), "agentic:session/resume")
 	assert.Contains(t, c.Commands(), "session/replay")
@@ -161,6 +163,69 @@ func TestCommandsSession_CmdSessionEnd_Ugly_InvalidResponse(t *testing.T) {
 	assert.False(t, result.OK)
 }
 
+func TestCommandsSession_CmdSessionLog_Good(t *testing.T) {
+	dir := t.TempDir()
+	t.Setenv("CORE_WORKSPACE", dir)
+
+	s := newTestPrep(t)
+	require.NoError(t, writeSessionCache(&Session{
+		SessionID: "ses-log",
+		AgentType: "codex",
+		Status:    "active",
+		WorkLog: []map[string]any{
+			{"type": "checkpoint", "message": "build passed"},
+		},
+	}))
+
+	result := s.cmdSessionLog(core.NewOptions(
+		core.Option{Key: "session_id", Value: "ses-log"},
+		core.Option{Key: "message", Value: "Checked build"},
+		core.Option{Key: "type", Value: "checkpoint"},
+		core.Option{Key: "data", Value: map[string]any{"repo": "go-io"}},
+	))
+	require.True(t, result.OK)
+
+	output, ok := result.Value.(SessionLogOutput)
+	require.True(t, ok)
+	assert.True(t, output.Success)
+	assert.Equal(t, "Checked build", output.Logged)
+
+	cached, err := readSessionCache("ses-log")
+	require.NoError(t, err)
+	require.NotNil(t, cached)
+	require.Len(t, cached.WorkLog, 2)
+	assert.Equal(t, "checkpoint", cached.WorkLog[1]["type"])
+	assert.Equal(t, "Checked build", cached.WorkLog[1]["message"])
+}
+
+func TestCommandsSession_CmdSessionLog_Bad_MissingMessage(t *testing.T) {
+	s := newTestPrep(t)
+
+	result := s.cmdSessionLog(core.NewOptions(core.Option{Key: "session_id", Value: "ses-log"}))
+
+	assert.False(t, result.OK)
+	require.Error(t, result.Value.(error))
+	assert.Contains(t, result.Value.(error).Error(), "message is required")
+}
+
+func TestCommandsSession_CmdSessionLog_Ugly_CorruptedCacheFallsBackToRemoteError(t *testing.T) {
+	dir := t.TempDir()
+	t.Setenv("CORE_WORKSPACE", dir)
+
+	s := newTestPrep(t)
+	require.True(t, fs.EnsureDir(sessionCacheRoot()).OK)
+	require.True(t, fs.WriteAtomic(sessionCachePath("ses-bad"), "{not-json").OK)
+
+	result := s.cmdSessionLog(core.NewOptions(
+		core.Option{Key: "session_id", Value: "ses-bad"},
+		core.Option{Key: "message", Value: "Checked build"},
+	))
+
+	assert.False(t, result.OK)
+	require.Error(t, result.Value.(error))
+	assert.Contains(t, result.Value.(error).Error(), "no platform API key configured")
+}
+
 func TestCommandsSession_CmdSessionResume_Good(t *testing.T) {
 	dir := t.TempDir()
 	t.Setenv("CORE_WORKSPACE", dir)