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Resuming the existing subagent preserves the expensive investigative context: files already inspected, data-flow relationships, hypotheses, and intermediate conclusions. Anthropic documents that session history contains prompts, tool calls, tool results, and responses, allowing an interrupted investigation to continue with its prior analysis intact. ( https://code.claude.com/docs/en/agent-sdk/sessions ) Subagent transcripts also persist within their parent session and can be resumed after an interruption or restart. ( https://code.claude.com/docs/en/agent-sdk/subagents?utm_source=chatgpt.com )

The engineer must nevertheless disclose the renamed utility functions. Anthropic explicitly distinguishes conversation persistence from filesystem persistence: resuming restores what the agent previously knew, but it does not freeze or snapshot the repository. ( https://code.claude.com/docs/en/agent-sdk/sessions ) Without the update, the subagent may search for obsolete symbols, misinterpret broken references, or rely on stale file paths.

Option A loses the detailed transcript and replaces it with a necessarily compressed summary. Option B preserves context but conceals a material repository change. Option D duplicates a large transcript inside a new context, increasing token consumption without providing any advantage over native resume functionality.

The resumed prompt should name the renamed functions, identify the merge or affected files, and instruct the subagent to re-read only the changed areas before continuing its broader exploration.

Official references/topics: Session Resume; Persistent Subagent Transcripts; Repository Drift; Targeted Context Refresh.