Add _is_system_injected() filter to conversation.py that drops user
messages starting with known system-injected prefixes. These messages
(hook outputs, system reminders, teammate notifications) appear in
JSONL session logs as type: "user" with string content but are not
human-typed input.
Filtered prefixes:
- <system-reminder> — Claude Code system context injection
- <local-command-caveat> — local command hook output
- <available-deferred-tools> — deferred tool discovery messages
- <teammate-message — team agent message delivery (no closing >
because tag has attributes)
This brings Claude parsing to parity with the Codex parser, which
already filters system-injected content via SKIP_PREFIXES (line 222).
The filter uses str.startswith(tuple) with lstrip() to handle leading
whitespace. Applied at line 75 in the existing content-type guard chain.
Affects both chat display and input history navigation — system noise
is removed at the source so all consumers benefit.
tests/test_conversation.py:
- TestIsSystemInjected: 10 unit tests for the filter function covering
each prefix, leading whitespace, normal messages, mid-string tags,
empty strings, slash commands, and multiline content
- TestClaudeSystemInjectedFiltering: 5 integration tests through the
full parser verifying exclusion, sequential ID preservation after
filtering, and all-system-message edge case
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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