# Parameter :: 13. `session::`
Session identifier parameter — acts as substring filter in listing commands, as exact identifier in counting/search commands.
**Type:** [`SessionFilter`](../type/08_session_filter.md) (in `.list`, `.projects`) / [`SessionId`](../type/09_session_id.md) (in `.count`, `.search`)
**Fundamental Type:** String
**Constraints:**
- Non-empty string expected
- In `.list` and `.projects`: case-insensitive substring match against session filename stem
- In `.count` and `.search`: exact match (used to scope to a specific session)
**Default:** unset (no filter / no scope restriction)
**Commands:** `.list`, `.count`, `.search`, `.projects`
**Per-command semantics:**
| `.list` | SessionFilter | Substring filter — shows sessions whose ID contains this string |
| `.projects` | SessionFilter | Substring filter — shows sessions whose ID contains this string |
| `.count` | SessionId | Exact scope — counts entries within this specific session |
| `.search` | SessionId | Exact scope — restricts search to this specific session |
**Purpose:** Narrows results by session identity. In listing contexts (`.list`, `.projects`), acts as a substring filter for discovery. In counting/search contexts (`.count`, `.search`), acts as an exact scope pin to a specific session.
**Side effect:** Auto-enables `sessions::1` in `.list`.
**Examples:**
```bash
# Listing: substring filter
session::commit # Matches -commit.jsonl, auto-commit.jsonl
session::default # Matches -default_topic.jsonl
# Counting/search: exact scope
.count target::entries project::abc session::-default_topic
.search query::error session::-default_topic
```
**Group (listing context):** [Session Filter](../param_group/04_session_filter.md) — applies to `.list` and `.projects` only where `session::` acts as a substring filter alongside `agent::` and `min_entries::`.
### Referenced Type
| [`SessionFilter`](../type/08_session_filter.md) | String | String | In `.list`/`.projects`: case-insensitive substring |
| [`SessionId`](../type/09_session_id.md) | String (filename stem) | String | In `.count`/`.search`: exact match |
### Referenced Parameter Groups
| 4 | [Session Filter](../param_group/04_session_filter.md) | Full | `agent::`, `min_entries::` |
### Referenced Commands
| 2 | [`.list`](../command/02_list.md) | unset | SessionFilter: substring filter; auto-enables `sessions::1` |
| 4 | [`.count`](../command/04_count.md) | unset | SessionId: exact scope pin to a specific session |
| 5 | [`.search`](../command/05_search.md) | unset | SessionId: exact scope pin to a specific session |
| 7 | [`.projects`](../command/07_projects.md) | unset | SessionFilter: substring filter |
### Referenced User Stories
| 2 | [Find Past Conversation](../user_story/002_find_past_conversation.md) | developer |