Make passive memory context project-wide by default across clients

[oglenyaboss]

Problem

claude-mem stores Claude Code, Codex, OpenCode, and other client observations in the same project database, while some passive context paths automatically filter them by platform_source.

As a result, switching between Claude Code and Codex can make existing project memory appear unavailable even though it remains in the same database. Users effectively have to rediscover or restate project context after switching clients.

Proposed policy

Treat the project as the default memory namespace:

• passive context retrieval is project-wide by default;
• platform_source remains provenance and diagnostic metadata;
• explicit platformSource filters remain available for manual, diagnostic, and API queries;
• provide CLAUDE_MEM_CONTEXT_SCOPE=platform as a compatibility escape hatch;
• missing or invalid scope values fail open to project-wide context.

Affected passive paths

The proposed policy applies only to paths that already automatically scope reads by source:

1. SessionStart context injection;
2. semantic prompt injection;
3. legacy user-message injection;
4. transcript-generated AGENTS.md.

Manual search filters and unrelated integrations remain unchanged.

Compatibility

The database schema and stored attribution do not change.

Existing observations retain their original platform_source. Users who prefer the current isolation behavior can set:

CLAUDE_MEM_CONTEXT_SCOPE=platform

Validation performed

A local implementation has been tested with:

• 83 focused tests passing;
• 2,311 full-suite tests passing, 15 skipped, 0 failed;
• typecheck, hook lint, and build passing;
• isolated runtime smoke for both project and platform modes;
• shadow E2E against an online SQLite backup of a real database;
• real Claude Code and Codex sessions receiving identical project-wide passive context;
• explicit manual platformSource filters remaining isolated.

The installed plugin and original database were not modified.

Questions

1. Does project-wide passive context match the intended default behavior?
2. Is platform an acceptable compatibility mode?
3. Should the implementation target core-dev?
4. Would you prefer a separate implementation issue before a PR?

Related to #1472, #2081, #2389, and #3088.