Interactive --resume crashes with "JSON Parse error: Unexpected identifier" loading a large (~400MB+) session transcript

Version: 2.1.218 (Claude Code), Bun runtime, Windows 11

Update: the original title/body on this issue described the wrong cause (guessed it was --resume <value> argument parsing). Root cause is now isolated below — the crash is tied to session transcript file size, not the resume argument.

Actual behavior

Resuming a specific session via the interactive picker (claude --resume / claude -r, no argument, select from the list) loads the session, then immediately crashes, before any input is typed:

 ERROR  JSON Parse error: Unexpected identifier "..."

 -     at <parse> (:0)
 -     at parse (unknown)
 - Bt (B:/~BUN/root/src/entrypoints/cli.js:85:302)
 - kVp (B:/~BUN/root/src/entrypoints/cli.js:18086:51014)
 - Jn (B:/~BUN/root/src/entrypoints/cli.js:2101:21364)
 - fS (B:/~BUN/root/src/entrypoints/cli.js:2101:40461)
 - lO (B:/~BUN/root/src/entrypoints/cli.js:2101:51387)
 - iLe (B:/~BUN/root/src/entrypoints/cli.js:2101:89050)
 - oLe (B:/~BUN/root/src/entrypoints/cli.js:2101:88003)
 - cge (B:/~BUN/root/src/entrypoints/cli.js:2101:87823)
 - X9 (B:/~BUN/root/src/entrypoints/cli.js:2101:84476)

What's been ruled out

• Not the --resume <value> argument: the picker itself comes up fine, session is selected from the list (not typed), and the crash happens after the session finishes loading.
• Not file corruption: every line of the session's .jsonl transcript, and every subagent transcript/meta file under it, parses individually as valid JSON (checked with a script, zero failures).
• Not a local hook problem: this user has three SessionStart hooks configured (two PowerShell scripts, one Node CLI) that print plain, non-JSON text to stdout. Temporarily emptying hooks.SessionStart entirely in settings.json and retrying did not change the outcome — same crash, same stack.
• Not reproducible headless: claude --resume <session-id> --print "hi" against the same session completes normally and returns a response. The crash is specific to the interactive/TUI resume path.

What's confirmed

• The affected session's transcript file is ~434 MB (433,753,526 bytes) — one of the largest sessions in this project's history (166k+ JSONL lines, one very active session with dozens of subagent transcripts alongside it).
• Other, smaller sessions in the same project (tens of MB, tens of thousands of lines) resume without issue, both headless and (per user report) interactively.
• This strongly points at a bug in the interactive resume loader specifically for very large transcript files, e.g., a buffer/chunk-size limit being hit while reading or pre-processing the file, where the truncation boundary lands mid-string inside JSON content.

Steps to reproduce

1. Accumulate a single Claude Code session transcript in the multi-hundred-MB range (e.g., a long session with many large subagent transcripts).
2. Start a fresh claude process, run --resume/-r, and select that session from the interactive picker.
3. Session loads and displays history, then immediately crashes with the error above, before any further input.

Workaround

None found yet — headless resume (--resume <id> --print "...") works, but interactive resume of this specific large session does not.