feat(parser): add aider session parser (#740)

## Summary

Adds an `aider` session parser. aider stores per-repo chat history as Markdown at `<repo>/.aider.chat.history.md`, where each file accumulates multiple `# aider chat started at ...` runs.

## What it does

- Splits a history file into one session per run, using the existing virtual-path fan-out (`<historyFile>#<runIdx>`) already used by the Shelley and Zed parsers, so a physical file maps to multiple sessions rather than one flattened blob.
- Parses `####` user prompts, assistant prose, and `> ` tool/edit lines. aider has no tool role in agentsview, so tool/edit lines surface as assistant transcript content (the `> Applied edit to ...` lines are preserved verbatim), mirroring the gptme parser.
- Discovers history files with a bounded, time-budgeted (2s) rootless walk under a configurable root — default `$HOME`, override via `AIDER_DIR` / `aider_dirs` — with a skip-set and a depth cap. The agent uses a shallow file watch so it does not recursively watch the whole home directory; new runs are picked up by the periodic sync.

## Identity and limitations

- Session IDs derive from the history-file path, the run's header timestamp, and an ordinal among same-header runs, so appends and different-header edits never re-key existing sessions. Residual: runs that share a byte-identical header timestamp (same repo, same second) disambiguate by position, so removing an earlier same-header run re-keys its later same-header siblings — rare given aider's 1-second header resolution, and pinned by a test.
- Per the multi-session-per-file model (same as Shelley/Zed), a run removed from a still-present file is reconciled on the next full resync rather than incrementally.

## Where to look

`internal/parser/aider.go` (parser + discovery), `internal/sync/engine.go` (`processAider` fan-out and the virtual-path stat resolution that lets a single session re-sync via the live watcher), `internal/parser/types.go` (registry entry, shallow watch).


Co-authored-by: KBS <youdie006@users.noreply.github.com>

Author: youdie006

README.md

@@ -270,6 +270,7 @@ agentsview auto-discovers sessions from all of these:
 
 | Agent                 | Session Directory                                                                                                                                                       |
 | --------------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
+| Aider                 | `<repo>/.aider.chat.history.md` (per repo; bounded scan of `~`, set `AIDER_DIR` to scope)                                                                               |
 | Amp                   | `~/.local/share/amp/threads/`                                                                                                                                           |
 | Antigravity           | `~/.gemini/antigravity/`                                                                                                                                                |
 | Antigravity CLI       | `~/.gemini/antigravity-cli/` (see note below)                                                                                                                           |
@@ -310,6 +311,29 @@ agentsview auto-discovers sessions from all of these:
 Each directory can be overridden with an environment variable. See the
 [configuration docs](https://agentsview.io/configuration/) for details.
 
+### Aider: per-repo Markdown logs
+
+Aider has no central session store; it writes one `.aider.chat.history.md`
+Markdown log per repository, and one log accumulates many runs (one per `aider`
+launch, delimited by `# aider chat started at ...` headers). agentsview indexes
+**each run as its own session**.
+
+Discovery is a bounded, symlink-safe walk of your home directory: it descends at
+most four levels below `~`, skips vendor/build/VCS directories by name
+(`node_modules`, `target`, `.git`, `Library`, `go`, `.cargo`, and similar), and
+stops after a two-second wall-clock budget so a large home tree cannot stall the
+scan. **A repository whose `.aider.chat.history.md` sits more than four levels
+under `~`, or outside your home directory, will not be found by the default
+scan.** Point `AIDER_DIR` (or the `aider_dirs` config key) at that code root to
+index it and to scope and speed up the walk. The live file watcher only watches
+the home root shallowly (registering it recursively would inotify the entire
+home tree); new repos are picked up by the periodic sync, which runs every 15
+minutes.
+
+Because the format is Markdown-derived, roles are reconstructed from line
+prefixes and there are no per-message timestamps; a run's start time comes from
+its `# aider chat started at ...` header (written in local time, assumed UTC).
+
 ### Antigravity CLI: high-resolution transcripts
 
 Antigravity CLI sessions now appear in two on-disk formats. Newer releases store

cmd/agentsview/session_export.go

@@ -8,6 +8,7 @@ import (
 	"fmt"
 	"io"
 	"os"
+	"strings"
 
 	"github.com/spf13/cobra"
 	"go.kenn.io/agentsview/internal/config"
@@ -63,6 +64,49 @@ func newSessionExportCommand() *cobra.Command {
 					"source file not found for session %s", id,
 				)
 			}
+			// Aider stores many repo runs in one Markdown history file,
+			// with sessions keyed by a <history>#<idx> virtual path.
+			// Export only the selected run, not sibling runs from the
+			// same repository.
+			if historyPath, idx, ok :=
+				parser.ParseAiderVirtualPath(storedPath); ok {
+				rawID, ok := rawAiderSessionID(id)
+				if !ok {
+					return fmt.Errorf(
+						"stale aider source for session %s: invalid aider session id",
+						id,
+					)
+				}
+				if got, ok := parser.AiderRawIDAt(historyPath, idx); !ok || got != rawID {
+					if _, statErr := os.Stat(historyPath); statErr != nil {
+						if os.IsNotExist(statErr) {
+							return fmt.Errorf(
+								"source file not found: %s", historyPath,
+							)
+						}
+						return statErr
+					}
+					resolved, found := parser.AiderVirtualPathForRawID(
+						historyPath, rawID,
+					)
+					if !found {
+						return fmt.Errorf(
+							"stale aider source for session %s: %s no longer contains the archived run",
+							id, historyPath,
+						)
+					}
+					historyPath, idx, _ = parser.ParseAiderVirtualPath(resolved)
+				}
+				err := parser.WriteAiderRunMarkdown(
+					cmd.OutOrStdout(), historyPath, idx,
+				)
+				if errors.Is(err, os.ErrNotExist) {
+					return fmt.Errorf(
+						"source file not found: %s", historyPath,
+					)
+				}
+				return err
+			}
 			// A Visual Studio Copilot trace file holds spans for several
 			// conversations, so streaming the whole file would disclose
 			// unrelated conversations. Filter to the requested conversation.
@@ -94,3 +138,13 @@ func newSessionExportCommand() *cobra.Command {
 		},
 	}
 }
+
+func rawAiderSessionID(sessionID string) (string, bool) {
+	def, ok := parser.AgentByPrefix(sessionID)
+	if !ok || def.Type != parser.AgentAider {
+		return "", false
+	}
+	_, rawID := parser.StripHostPrefix(sessionID)
+	rawID = strings.TrimPrefix(rawID, def.IDPrefix)
+	return rawID, rawID != ""
+}

cmd/agentsview/session_test.go

@@ -18,6 +18,7 @@ import (
 	"github.com/stretchr/testify/require"
 	"go.kenn.io/agentsview/internal/config"
 	"go.kenn.io/agentsview/internal/db"
+	"go.kenn.io/agentsview/internal/parser"
 )
 
 func TestSessionHelp_ShowsSubcommands(t *testing.T) {
@@ -673,6 +674,76 @@ func TestSessionExport_StreamsFromDisk(t *testing.T) {
 	assert.Equal(t, body, out)
 }
 
+func TestSessionExport_AiderVirtualPathStreamsOnlySelectedRun(t *testing.T) {
+	dataDir := t.TempDir()
+	t.Setenv("AGENTSVIEW_DATA_DIR", dataDir)
+
+	repo := filepath.Join(t.TempDir(), "repo")
+	require.NoError(t, os.MkdirAll(repo, 0o755))
+	history := filepath.Join(repo, parser.AiderHistoryFileName())
+	run0 := "# aider chat started at 2026-06-09 14:01:00\n" +
+		"#### first prompt\nanswer one\n"
+	run1 := "# aider chat started at 2026-06-09 15:30:00\n" +
+		"#### second prompt\nanswer two\n"
+	run2 := "# aider chat started at 2026-06-09 16:45:00\n" +
+		"#### third prompt\nanswer three\n"
+	require.NoError(t, os.WriteFile(
+		history, []byte("ignored preamble\n"+run0+run1+run2), 0o600,
+	))
+	rawID, ok := parser.AiderRawIDAt(history, 1)
+	require.True(t, ok, "run 1 raw ID")
+
+	seedSessionWithOpts(t, dataDir, "aider:"+rawID, "repo",
+		func(s *db.Session) {
+			s.Agent = string(parser.AgentAider)
+			vp := parser.AiderVirtualPath(history, 1)
+			s.FilePath = &vp
+		})
+
+	out, err := executeCommand(newRootCommand(),
+		"session", "export", "aider:"+rawID)
+	require.NoError(t, err)
+	assert.Equal(t, run1, out)
+	assert.NotContains(t, out, "first prompt")
+	assert.NotContains(t, out, "third prompt")
+}
+
+func TestSessionExport_AiderStaleIndexReResolvesBySessionID(t *testing.T) {
+	dataDir := t.TempDir()
+	t.Setenv("AGENTSVIEW_DATA_DIR", dataDir)
+
+	repo := filepath.Join(t.TempDir(), "repo")
+	require.NoError(t, os.MkdirAll(repo, 0o755))
+	history := filepath.Join(repo, parser.AiderHistoryFileName())
+	run0 := "# aider chat started at 2026-06-09 14:01:00\n" +
+		"#### first prompt\nanswer one\n"
+	run1 := "# aider chat started at 2026-06-09 15:30:00\n" +
+		"#### second prompt\nanswer two\n"
+	require.NoError(t, os.WriteFile(history, []byte(run0+run1), 0o600))
+	rawID, ok := parser.AiderRawIDAt(history, 1)
+	require.True(t, ok, "run 1 raw ID")
+
+	seedSessionWithOpts(t, dataDir, "aider:"+rawID, "repo",
+		func(s *db.Session) {
+			s.Agent = string(parser.AgentAider)
+			vp := parser.AiderVirtualPath(history, 1)
+			s.FilePath = &vp
+		})
+
+	inserted := "# aider chat started at 2026-06-09 13:00:00\n" +
+		"#### inserted prompt\ninserted answer\n"
+	require.NoError(t, os.WriteFile(
+		history, []byte(inserted+run0+run1), 0o600,
+	))
+
+	out, err := executeCommand(newRootCommand(),
+		"session", "export", "aider:"+rawID)
+	require.NoError(t, err)
+	assert.Equal(t, run1, out)
+	assert.NotContains(t, out, "inserted prompt")
+	assert.NotContains(t, out, "first prompt")
+}
+
 func TestSessionExport_FailsWhenSourceMissing(t *testing.T) {
 	dataDir := t.TempDir()
 	t.Setenv("AGENTSVIEW_DATA_DIR", dataDir)