Hierarchical session filter from #24849 has no exact-match mode; -c from parent dir picks wrong child session and widens permission scope #26099

Description

Problem 1: No exact directory matching for sessions

The session list filter (added in #24849) uses a hierarchical prefix match on path:

eq(path, input.path) OR like(path, input.path + "/%")

When launching opencode at /root/opencode, all sessions from child subdirectories appear in /sessions. The KV flag session_directory_filter_enabled only offers two modes:

No option for exact directory matching, which was the behavior before #24849:

if (input?.directory) { conditions.push(eq(SessionTable.directory, input.directory)) }

Problem 2: Selecting a child-directory session leaves CWD unchanged

Selecting a session whose directory differs from where opencode was launched keeps the TUI CWD at the launch directory (directory.ts:10 reads project.instance.path().directory, not the session's directory). No warning is shown. When the sidebar is collapsed, the parent CWD isn't visible at all — making it even harder to realize you're in the wrong session. (Related fix discussed in #23507.)

Problem 3: opencode -c from a parent path lands in the wrong session

Running opencode -c from /root/opencode picks up the most recent session across all child subdirectories due to the hierarchical path filter. The user lands in a session from a different directory, at the wrong CWD, unaware of the mismatch.

Problem 4: external_directory boundary evaluated against launch directory, not session directory

external_directory uses containsPath(filepath, ctx) (instance-context.ts:18) which checks if the path is inside ctx.directory (the instance's launch directory). When -c lands you in a child-directory session but the CWD stays at the parent:

1. User works in /root/opencode/orca, finishes a session, exits
2. User navigates to /root/opencode and runs opencode -c
3. Due to hierarchical session filtering, -c picks up the orca session
4. ctx.directory is /root/opencode (launch dir), NOT /root/opencode/orca (session dir)
5. Everything under /root/opencode/ is now considered "internal" — including sibling directories like /root/opencode/northerner/
6. If the user had "external_directory": "ask" or "deny", tool calls to sibling directories would pass the check since they're still under /root/opencode. The user unknowingly has a wider boundary than intended.
7. For non-git projects where worktree = "/", the worktree fallback at instance-context.ts:22 returns false, so ctx.directory is the only boundary — making this even more impactful.
8. With the sidebar collapsed and the parent CWD invisible, the user has no indication that the permission boundary is broader than expected.

Related issues

• Sessions from different non-git directories are mixed when using --continue #18890 — Sessions from different non-git directories mixed with --continue
• --continue resumes latest session across root-level git worktrees instead of current worktree #25963 — --continue resumes latest session across root-level git worktrees
• session list is showing all sessions not only the ones scopes to the curent dir #8836 — Session list showing all sessions not scoped to current dir
• feat: move sidebar footer directory path to status bar at the bottom #23507 — Collapsed sidebar CWD visibility

Proposed fixes

1. Add an exact-match mode for session filtering (scope: "directory" or three-value KV flag)
2. When selecting a session whose directory differs from the active CWD, warn the user or offer to switch
3. Scope opencode -c to the current directory
4. Ensure external_directory boundary considers the session's original directory

Plugins

No response

OpenCode version

No response

Steps to reproduce

No response

Screenshot and/or share link

No response

Operating System

No response

Terminal

No response